EP1942088A1 - Hydrocracking start-up system and process - Google Patents
Hydrocracking start-up system and process Download PDFInfo
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- EP1942088A1 EP1942088A1 EP07100004A EP07100004A EP1942088A1 EP 1942088 A1 EP1942088 A1 EP 1942088A1 EP 07100004 A EP07100004 A EP 07100004A EP 07100004 A EP07100004 A EP 07100004A EP 1942088 A1 EP1942088 A1 EP 1942088A1
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- Prior art keywords
- feed material
- hydrocarbon
- hydrocracking
- facilities
- units
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G65/00—Treatment of hydrocarbon oils by two or more hydrotreatment processes only
- C10G65/02—Treatment of hydrocarbon oils by two or more hydrotreatment processes only plural serial stages only
- C10G65/12—Treatment of hydrocarbon oils by two or more hydrotreatment processes only plural serial stages only including cracking steps and other hydrotreatment steps
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G2/00—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon
- C10G2/30—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen
- C10G2/32—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G47/00—Cracking of hydrocarbon oils, in the presence of hydrogen or hydrogen- generating compounds, to obtain lower boiling fractions
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G49/00—Treatment of hydrocarbon oils, in the presence of hydrogen or hydrogen-generating compounds, not provided for in a single one of groups C10G45/02, C10G45/32, C10G45/44, C10G45/58 or C10G47/00
- C10G49/24—Starting-up hydrotreatment operations
Definitions
- the present invention relates to a system or process for starting up a hydrocracking system and process.
- Petroleum refiners produce desirable products, such as gasoline and turbine fuel, by catalytically hydrocracking high boiling hydrocarbons into product hydrocarbons of lower average molecular weight and boiling point.
- Hydrocracking is generally accomplished by contacting, in an appropriate reactor vessel, a gas oil or other hydrocarbon feedstock with molecular hydrogen in the presence of a suitable hydrocracking catalyst under appropriate conditions, including an elevated temperature and an elevated pressure, such that hydrocarbon products are obtained containing a substantial proportion of a desired product or products boiling in a specified range.
- One source of hydrocarbon feedstock is from the Fischer-Tropsch ("FT") process.
- the Fischer-Tropsch process can be used as part of the conversion of hydrocarbonaceous feed stocks into liquid and/or solid FT hydrocarbons.
- the feed stock e.g. natural gas, associated gas and/or coal-bed methane, residual (crude) oil fractions or coal
- a gasifier optionally in combination with a reforming unit, into a mixture of hydrogen and carbon monoxide (this mixture is often referred to as synthesis gas or syngas).
- the synthesis gas is then fed into a Fischer-Tropsch reactor where it is converted in one or more steps over a suitable catalyst at elevated temperature and pressure into paraffinic compounds ranging from methane to high molecular weight molecules comprising up to 200 carbon atoms, or, under particular circumstances, even more.
- the hydrocarbons formed in the Fischer-Tropsch reactor then proceed to a hydrogenation unit, preferably a hydroisomerisation/hydrocracking unit, and thereafter to a distillation unit, to form final hydrocarbon products.
- a hydrogenation unit preferably a hydroisomerisation/hydrocracking unit
- a hydrocracking unit is most efficient and efficacious when it is operating at its designed operating parameters, which include an expected minimum rate of feed material. That is, efficiency is dependent on providing a sufficient (usually 'full') supply of material into the hydrocracking unit. Where this is not possible, the unit will be less efficient, or may not even be able to operate.
- Hydrocracking units can range in any size of capacity, but are generally determined according to the volume of products produced. Such product outflows can be measured in barrels per day (bbl/day), and hydrocracking units can have capacities from under 1000 bbl/day, up to 70-100,000 bbl/day. Naturally, the greater the capacity of the hydrocracking unit, the greater amount of feed material required to achieve the design operating conditions for the hydrocracking unit.
- the feed material for the hydrocracking unit is supplied by one or more prior chemical operations, such as the hydrocarbon synthesis of the Fischer-Tropsch reaction, (providing 'FT hydrocarbons'), or by distillation of crude oil fractions.
- the hydrocarbon synthesis of the Fischer-Tropsch reaction providing 'FT hydrocarbons'
- distillation of crude oil fractions it may be that there is insufficient feed material from the previous (chemical) operation(s) to allow the hydrocarbon unit to immediately start at full operating design capacity.
- a hydrocracking system comprising:
- the storage facility or facilities are able to store and hold hydrocarbon feed material until there is a sufficient amount of feed material to be able to supply the hydrocracking unit(s) under favourable start up conditions.
- the storage facility or facilities are filled up for at least 50% of their volume, more preferably at least 75%, still more preferably 90%, before start up of the hydrocracking unit(s).
- a storage facility may have any suitable shape, design or size, and may be in any suitable form.
- One suitable facility is a holding or accumulator tank. Such tanks are generally symmetrical, and may have a generally circular cross section, although the invention is not limited thereto.
- each storage facility may be the same or different in terms of size, shape and design. That is, it may be desired to have one or more storage facilities that are smaller than one or more other storage facilities.
- the storage facilities could be arranged in parallel or series or a combination of same, and may have any suitable arrangement to supply more than one hydrocracking unit.
- the storage capacity of the storage facility or facilities could be such as to be able to supply as low as 1,000-10,000 bbl/day, or in the range 10,000-100,000 bbl/day over at least one day, preferably more than one day, more preferably 2 to 5 days.
- the storage facility of facilities have a capacity for supplying hydrocarbon feedstock to the hydrocracking unit(s) at 80% of their design capacity for at least 0.5 days, preferably 1-6 days.
- the capacity of the storage facility or facilities may also need to account for any variation in the volume, rate or flow supply of feed material thereto. Where the supply of feed material is already wholly or substantially constant, and/or the hydrocracking units are receiving feed material from one or more other sources (such as directly from the feed material production) the capacity of the storage facility or facilities may be different, e.g. less, than a situation where the supply of feed material to the storage facility of facilities and/or the supply of feed material directly to the hydrocracking unit(s) is changing, in particular where the supply is increasing.
- a hydrocracking unit(s) has been wholly or partially stopped or taken out of service due to the desire for regeneration or replacement of the catalyst in the hydrocracking unit.
- the intention is to re-start the hydrocracking unit(s) whilst there continues to be production of the feed material during the regeneration period.
- the hydrocracking unit(s) are being started in line with the start of the arrangement for production of the feed material, such that as the feed material production increases from its start, there is an increasing amount of feed material available to be provided to the hydrocarbon unit(s).
- the storage facility or facilities can be heated, preferably by one or more heating means.
- Such hating means are known in the art, and are intended to maintain the feed material stored in the storage facility or facilities at a temperature or range of temperatures which allow their properties and/or state to be maintained, and/or allow the feed material to be maintained in a manner suitable for direct passage and use in the hydrocarbon unit(s).
- One suitable temperature range is 50-150 °C, preferably 70-130 °C.
- the storage facility or facilities may also be used at any suitable pressure, e.g. in the range 1-50 bar, commonly at an ambient pressure or slightly above, such as 1.5 bar.
- the material stored in the storage facility or facilities may also be kept under a particular atmosphere, such as under a nitrogen blanket.
- One or more of the hydrocracking units may also receive hydrocarbon feed material from one or more sources other than the storage facility or facilities.
- hydrocracking as used herein includes hydroisomerism/hydroisomerisation.
- the hydrocarbon feed material is produced in a hydrocarbon synthesis process.
- a hydrocarbon synthesis process is the Fischer-Tropsch process.
- Such a process may be designed to produce normally gaseous, normally liquid and optionally normally solid hydrocarbons from synthesis gas.
- a hydrocarbon production facility comprising:
- a process for producing hydrocarbons from a feed material by hydrocracking which comprises the steps of:
- a process for producing hydrocarbons from synthesis gas which comprises the steps of:
- the present invention encompasses the provision of hydrocarbon feed material stored in one or more storage facilities, and the direct supply of hydrocarbon feed material from reactor(s) producing same, to the hydrocracking unit(s), to be in any arrangement or combination.
- all the hydrocarbon feed material desired for the start up of a hydrocracking unit(s) could be provided by the storage facility or facilities once there has been sufficient material.
- the reactor(s) providing the hydrocarbon feed material is creating more feed material, and indeed there may be one or more other hydrocarbon feed material reactors being started, available or otherwise coming on stream.
- the present invention provides the user with the flexibility to consider how best to arrange the increasing provision of hydrocarbon feed material by one or more reactors as they are started, and how best to supply some or all of the hydrocarbon feed material directly to the hydrocracking unit(s) and/or still supply hydrocarbon feed material into the storage facility or facilities.
- the or all hydrocracking unit(s) are on-line, it may be desirable for them to be fed directly from the hydrocarbon feed material reactors, and to keep the storage facility or facilities in reserve, or maintain the passage of some feed material through the storage facility or facilities as a reserve or in case of an emergency.
- This flexibility also allows the user to be flexible as to how long to use the storage facility or facilities during a start up procedure, and how soon to start the direct passage of hydrocarbon feed material from the reactors to the hydrocracking unit(s).
- the feed suitably is methane, natural gas, associated gas or a mixture of C 1-4 hydrocarbons.
- the feed comprises mainly, i.e. more than 90 v/v%, especially more than 94%, C 1-4 hydrocarbons, especially comprises at least 60 v/v percent methane, preferably at least 75 percent, more preferably 90 percent.
- Very suitably natural gas or associated gas is used.
- any sulphur in the feedstock is removed.
- Catalysts for use in the Fischer-Tropsch hydrocarbon synthesis process frequently comprise, as the catalytically active component, a metal from Group VIII of the previous IUPAC version of the Periodic Table of Elements such as that described in the 68th Edition of the Handbook of Chemistry and Physics (CPC Press).
- Particular catalytically active metals include ruthenium, iron, cobalt and nickel. Cobalt is a preferred catalytically active metal.
- hydrocarbons produced in the process and mentioned in the present description are suitably C 3-200 hydrocarbons, more suitably C 4-150 hydrocarbons, especially C 5-100 hydrocarbons, or mixtures thereof.
- These hydrocarbons or mixtures thereof are liquid or solid at temperatures between 5 and 30 °C (1 bar), especially at about 20 °C (1 bar), and usually are paraffinic of nature, while up to 30 wt%, preferably up to 15 wt%, of either olefins or oxygenated compounds may be present.
- Hydrocarbons normally liquid hydrocarbons and optionally normally solid hydrocarbons are obtained. It is often preferred to obtain a large fraction of normally solid hydrocarbons. These solid hydrocarbons may be obtained up to 85 wt% based on total hydrocarbons, usually between 50 and 75 wt%.
- the oxygen containing gas for the partial oxidation can be air (containing about 21 vol. percent of oxygen), oxygen enriched air, suitably containing up to 70 percent, or substantially pure oxygen, containing typically at least 95 vol.%, usually at least 98 vol.%, oxygen.
- Oxygen or oxygen enriched air may be produced via cryogenic techniques, but could also be produced by a membrane based process, e.g. the process as described in WO 93/06041 .
- a gas turbine can provide the power for driving at least one air compressor or separator of the air compression/separating unit. If necessary, an additional compressing unit may be used between the separation process and step (i), and the gas turbine in that case may also provide at the (re)start power for this compressor.
- the compressor may also be started at a later point in time, e.g. after a full start, using steam generated in steps (i) and/or (ii).
- carbon dioxide and/or steam may be introduced into the partial oxidation process.
- Water produced in the hydrocarbon synthesis may be used to generate the steam.
- carbon dioxide from the effluent gasses of the expanding/combustion step may be used.
- the H 2 /CO ratio of the syngas is suitably between 1.5 and 2.3, preferably between 1.6 and 2.0.
- additional amounts of hydrogen may be made by steam methane reforming, preferably in combination with the water gas shift reaction. Any carbon monoxide and carbon dioxide produced together with the hydrogen may be used in the hydrocarbon synthesis reaction or recycled to increase the carbon efficiency. Hydrogen from other sources, for example hydrogen itself, may be an option.
- the gaseous mixture comprising predominantly hydrogen, carbon monoxide and optionally nitrogen, is contacted with a suitable catalyst in the catalytic conversion stage, in which FT hydrocarbons are formed.
- a suitable catalyst in the catalytic conversion stage, in which FT hydrocarbons are formed.
- at least 70 v/v% of the syngas is contacted with the catalyst, preferably at least 80%, more preferably at least 90%, still more preferably all the syngas.
- the catalytically active metal is preferably supported on a porous carrier.
- the porous carrier may be selected from any of the suitable refractory metal oxides or silicates or combinations thereof known in the art. Particular examples of preferred porous carriers include silica, alumina, titania, zirconia, ceria, gallia and mixtures thereof, especially silica and titania.
- the amount of catalytically active metal on the carrier is preferably in the range of from 3 to 300 pbw per 100 pbw of carrier material, more preferably from 5 to 60 pbw, especially from 10 to 40 pbw.
- the catalyst may also comprise one or more metals or metal oxides as promoters.
- Suitable metal oxide promoters may be selected from Groups IIA, IIIB, IVB, VB, VIB and VIIB and VIIIB of the (same) Periodic Table of Elements, or the actinides and lanthanides.
- oxides of magnesium, calcium, strontium, barium, scandium, yttrium. lanthanum, cerium, titanium, zirconium, hafnium, thorium, uranium, vanadium, chromium and manganese are most suitable promoters.
- Particularly preferred metal oxide promoters for the catalyst used to prepare the waxes for use in the present invention are manganese and zirconium oxide.
- Suitable metal promoters may be selected from Groups VIIB or VIII of the (same) Periodic Table. Manganese, iron, rhenium and Group VIII noble metals are particularly suitable, with platinum and palladium being especially preferred.
- the amount of promoter present in the catalyst is suitably in the range of from 0.001 to 100 pbw, preferably 0.05 to 20, more preferably 0.1 to 15 pbw, per 100 pbw of carrier.
- the catalytically active metal and the promoter may be deposited on the carrier material by any suitable treatment, such as impregnation, kneading and extrusion.
- the loaded carrier is typically subjected to calcination at a temperature of generally from 350 to 750 °C, preferably a temperature in the range of from 450 to 550 °C.
- the effect of the calcination treatment is to remove crystal water, to decompose volatile decomposition products and to convert organic and inorganic compounds to their respective oxides.
- the resulting catalyst may be activated by contacting the catalyst with hydrogen or a hydrogen-containing gas, typically at temperatures of about 200 to 350 °C.
- the steady state catalytic conversion process may be performed under conventional synthesis conditions known in the art.
- the catalytic conversion may be effected at a temperature in the range of from 100 to 600 °C, preferably from 150 to 350 °C, more preferably from 180 to 270 °C.
- Typical total pressures for the catalytic conversion process are in the range of from 1 to 200 bar absolute, more preferably from 10 to 70 bar absolute.
- the catalytic conversion process mainly (at least 70 wt%, preferably 90 wt%) of C 5 + hydrocarbons are formed, based on the total weight of hydrocarbonaceous products formed.
- a Fischer-Tropsch catalyst which yields substantial quantities of paraffins, more preferably substantially unbranched paraffins.
- a part may boil above the boiling point range of the so-called middle distillates, to normally solid hydrocarbons.
- a most suitable catalyst for this purpose is a cobalt-containing Fischer-Tropsch catalyst.
- middle distillates is a reference to hydrocarbon mixtures of which the boiling point range corresponds substantially to that of kerosene and gas oil fractions obtained in a conventional atmospheric distillation of crude mineral oil.
- the boiling point range of middle distillates generally lies within the range of about 150 to about 360 °C.
- paraffinic hydrocarbons if present, may be isolated and subjected to catalytic hydrocracking to yield the desired middle distillates.
- the catalytic hydro-cracking can be carried out by contacting the FT hydrocarbons at elevated temperature and pressure and in the presence of hydrogen with a catalyst containing one or more metals having hydrogenation activity, and supported on a carrier.
- Suitable hydrocracking catalysts include catalysts comprising metals selected from Groups VIB and VIII of the (same) Periodic Table of Elements.
- the hydrocracking catalysts contain one or more noble metals from Group VIII.
- Preferred noble metals are platinum, palladium, rhodium, ruthenium, iridium and osmium.
- Most preferred catalysts for use in the hydro-cracking stage are those comprising platinum.
- the amount of catalytically active metal present in the hydrocracking catalyst may vary within wide limits and is typically in the range of from about 0.05 to about 5 parts by weight per 100 parts by weight of the carrier material.
- Suitable conditions for the hydrocracking/isomerisation step of the FT hydrocarbon mixture are a temperature of 280-400 °C, preferably 290-375 °C, more preferably 300-350 °C, a pressure between 15 and 200 bar, preferably 20-100 bar, more preferably between 30-80 bar, an hourly space velocity of 0.2-20 kg of hydrocarbon feed per litre of catalyst per hour, preferably between 0.5 and 3 kg/1/h, more preferably between 0.7 and 2.5 kg/1/h, and a hydrogen/hydrocarbon feed molar ratio of 1-50.
- hydrocracking products or effluents could be recycled, optionally after separation from other products and effluents, for example by distillation such as flash distillation.
- At least part of the effluent of the isomerisation/hydrocracking step could be passed to a separation step in which a hydrogen-containing gas and a hydrocarbon effluent are separated from each other.
- a hydrogen-containing gas and a hydrocarbon effluent are separated off by flash distillation.
- the flash distillation is carried out at a temperature between -20 and 100 °C and a pressure between 1 and 50 bar.
- the hydrocarbon effluent is separated into a fraction boiling above 370 °C and one or more fractions boiling below 370 °C, e.g. two or three fractions boiling in the (light and heavy) gasoil range and a kerosene fraction.
- At least part of the heavy fraction obtained in the first hydrocracking/hydroisomerisation reaction could be introduced in the second hydrocracking/hyroisomerisation reaction.
- a substantial part of the 370 °C fraction could be introduced in the second reaction, but also substantial parts of the kerosene/gasoil fraction may be introduced into this second step.
- at least 50 wt%, of the 370 °C fraction is introduced into the second hydrocracking/ hydroisomerisation step, preferably 70 wt%, more preferably at least 90 wt%, especially the total 370 °C plus fraction could be introduced into the second step.
- the conditions (catalyst, temperature, pressure, WHSV etc.) of the second hydrocracking/ hydroisomerisation reaction are suitable similar to the first reaction, although this is not necessarily the case.
- the conditions and the preferred conditions are described above for the first reaction. In a preferred situation the conditions in the first and the second hydrocracking/hydroisomerisation are the same.
- the product of the FT hydrocarbon synthesis and consequent hydrocracking suitably comprises mainly normally liquid hydrocarbons, beside water and normally gaseous hydrocarbons.
- the catalyst and the process conditions in such a way that especially normally liquid hydrocarbons are obtained, the product obtained (“syncrude”) may transported in the liquid form or be mixed with any stream of crude oil without creating any problems as to solidification and or crystallization of the mixture. It is observed in this respect that the production of heavy hydrocarbons, comprising large amounts of solid wax, are less suitable for mixing with crude oil while transport in the liquid form has to be done at elevated temperatures, which is less desired.
- the off gas of the FT hydrocarbon synthesis may comprise normally gaseous hydrocarbons produced in the synthesis process, nitrogen, unconverted methane and other feedstock hydrocarbons, unconverted carbon monoxide, carbon dioxide, hydrogen and water.
- the normally gaseous hydrocarbons are suitably C 1-5 hydrocarbons, preferably C 1-4 hydrocarbons, more preferably C 1-3 hydrocarbons. These hydrocarbons, or mixtures thereof, are gaseous at temperatures of 5-30 °C (1 bar), especially at 20 °C (1 bar).
- oxygenated compounds e.g. methanol, dimethyl ether, may be present in the off gas.
- the off gas may be utilized for the production of electrical power, in an expanding/combustion process such as in a gas turbine described herein, or recycled to the process.
- the energy generated in the process may be used for own use or for export to local customers. Part of an energy could be used for the compression of the oxygen containing gas.
- hydrogen may be separated from the synthesis gas provided for the first step.
- the hydrogen is preferably separated after quenching/cooling, and may be separated by techniques well known in the art, as pressure swing adsorption, or, preferably, by means of membrane separation techniques.
- the hydrogen may be used in a second heavy paraffin synthesis step after the first reactor (provided that a two stage hydrocarbon synthesis is used), or for other purposes, e.g. hydrotreating and/or hydrocracking of the FT hydrocarbons produced in the paraffin synthesis. In this way a further product optimization is obtained (for instance by fine tuning the H 2 /CO ratios in the first and second hydrocarbon synthesis step), while also the carbon efficiency can be improved.
- the product quality may be improved by e.g. hydrogenation and/or hydrocracking.
- Steam generated by any start-up gas turbine and/or steam generated in step (i) may also be used to preheat the reactor to be used in step (ii) and/or may be used to create fluidization in the case that a fluidized bed reactor or slurry bubble column is used in step (ii).
- Figure 2 is a simplistic illustration of a portion of the process line whereby hydrocarbon products are obtained.
- a Fischer-Tropsch stage 10 involving one or more process reactors, Fischer-Tropsch hydrocarbon products are obtained. These products can then be stored in a storage facility 12 such as a holding tank. Such stored material can then be passed to one or more hydrocracking units 14, wherefrom desired hydrocarbon products are obtained.
- the Fisher-Tropsch stage involves a number of Fischer-Tropsch process reactors, possibly 2-15 reactors, which may be arranged in two or more stages so as to be able to achieve high conversion of synthesis gas into desired Fischer-Tropsch (FT) hydrocarbon product material.
- a standard Fischer-Tropsch reactor can produce approximately 2000-20,000 bbl/day of FT products, such that the steady state production of FT products can be anywhere in the range 20,000-100,000 bbl/day.
- a typical example of a hydrocracking unit would be one that is able to convert very approximately 70,000 bbl/day FT products.
- the holding tank 12 can be any suitable size and design.
- large storage tanks such as 'strategic storage tanks' that occur at oil refineries, and are generally in the size 40-50,000 m 3 .
- storage tanks are known to come in many other shapes and sizes, and have capacities to match.
- the FT reactors of stage 10 involve a number of reactors, which are being started at different times. Such timing may be wholly sequential, or may involve two or more reactors starting simultaneously, either with or more expectantly after the sequential start up of some of the FT reactors.
- Such FT product may be provided at a constant rate, or may be provided at a variable rate, i.e. in an increasing manner over the start up period.
- a typical example could be the provision of approximately 10,000 bbl/day from each of a number of FT reactors, which are started in sequentially, each one after an approximate two week period from the other. Thus, every two weeks, there is the increased provision of 10,000 bbl/day of FT product available to the hydrocracking unit 14.
- a hydrocracking unit 14 can act to convert FT product into suitable hydrocarbon products under less than 100% full conversion capacity. By careful metering and consideration of the operating conditions, a hydrocracking unit can run at 50%, more usually at least 60-70%, of its possible conversion capacity. Thus, assuming that the hydrocracking unit 14 has a capacity of approximately 70,000 bbl/day, it is possible to operate the hydrocracking unit 14 if there is available at least 35-40,000 bbl/day of FT product.
- a constant supply of at least 35-40,000 bbl/day may not be available to the hydrocracking unit 14 due to the staggered nature of the start up of the FT reactors 10, but by storing the FT products in the holding tank 12, a volume of FT products is built up such that the hydrocracking unit 14 can be started for a period of time to use up the FT products stored. Whilst this is occurring, the FT reactors 10 will be providing further FT product, which can then be stored, expectantly over a shorter time period as more FT reactors are started up and brought on stream.
- the periods when the hydrocracking unit 14 is not in use, (possibly on 'hot standby'), will be less and less frequent, and will occur for shorter periods, as time progresses, until a point is reached wherein at least 35-40,000 bbl/day are able to be supplied either through the holding tank 12, or directly by the FT reactors 10 (through line 16), or in a combination of same, with the proportion of product provided by the holding tank 12 expectantly to reduce over time until the FT reactors 10 are able to solely supply at least 35-40,000 bbl/day to the hydrocracking unit 14 directly.
- the holding tank 12 is redundant in relation to the start up phase.
- the holding tank 12 may still be required at certain periods when the hydrocracking unit 14 is not able to operate at full operating conditions or conversion capacity. This may be due to a need for routine maintenance or catalyst regeneration, or due to unexpected conditions, in the hydrocracking unit 14.
- Figure 3 illustrates a graph of operation of the hydrocracking unit 14 (based on FT products conversion percentage) over time, and can be directly compared with the graph of figure 1 , which shows the prior art start up procedure of a hydrocracking unit relying only an direct supply of FT hydrocarbons. It can be seen that there are less periods when the hydrocracking unit 14 is transient between operating and 'stand-by', resulting in significantly less time and effort involved. Once the hydrocracking unit 14 has sufficient supply to be able to run continuously, at least in a reduced conversion percentage state, the increased volume of FT products from the starting FT reactors will allow the conversion percentage to be increased to 100% conversion capacity.
- the present invention is not limited to operation with FT reactors, or FT products, but is suitable for use in starting up a hydrocracking unit for other hydrocarbon feed materials provided by other processes known in the art.
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Abstract
A hydrocracking system comprising:
(a) one or more hydrocracking units, preferably 1 or 2, more preferably 1 unit, adapted to convert hydrocarbon feed material into one or more hydrocarbon products, and
(b) one or more hydrocarbon feed material storage facilities upstream of the one or more hydrocarbon units to supply hydrocarbon feed material to the one or more hydrocracking units.
(a) one or more hydrocracking units, preferably 1 or 2, more preferably 1 unit, adapted to convert hydrocarbon feed material into one or more hydrocarbon products, and
(b) one or more hydrocarbon feed material storage facilities upstream of the one or more hydrocarbon units to supply hydrocarbon feed material to the one or more hydrocracking units.
Thus, the storage facility or facilities are able to store and hold hydrocarbon feed material until there is a sufficient amount of feed material to be able to supply the hydrocracking unit(s) under favourable start up conditions.
Description
- The present invention relates to a system or process for starting up a hydrocracking system and process.
- Petroleum refiners produce desirable products, such as gasoline and turbine fuel, by catalytically hydrocracking high boiling hydrocarbons into product hydrocarbons of lower average molecular weight and boiling point. Hydrocracking is generally accomplished by contacting, in an appropriate reactor vessel, a gas oil or other hydrocarbon feedstock with molecular hydrogen in the presence of a suitable hydrocracking catalyst under appropriate conditions, including an elevated temperature and an elevated pressure, such that hydrocarbon products are obtained containing a substantial proportion of a desired product or products boiling in a specified range.
- One source of hydrocarbon feedstock is from the Fischer-Tropsch ("FT") process. The Fischer-Tropsch process can be used as part of the conversion of hydrocarbonaceous feed stocks into liquid and/or solid FT hydrocarbons. The feed stock (e.g. natural gas, associated gas and/or coal-bed methane, residual (crude) oil fractions or coal) is converted in a gasifier, optionally in combination with a reforming unit, into a mixture of hydrogen and carbon monoxide (this mixture is often referred to as synthesis gas or syngas).
- The synthesis gas is then fed into a Fischer-Tropsch reactor where it is converted in one or more steps over a suitable catalyst at elevated temperature and pressure into paraffinic compounds ranging from methane to high molecular weight molecules comprising up to 200 carbon atoms, or, under particular circumstances, even more.
- The hydrocarbons formed in the Fischer-Tropsch reactor then proceed to a hydrogenation unit, preferably a hydroisomerisation/hydrocracking unit, and thereafter to a distillation unit, to form final hydrocarbon products.
- Naturally, a hydrocracking unit is most efficient and efficacious when it is operating at its designed operating parameters, which include an expected minimum rate of feed material. That is, efficiency is dependent on providing a sufficient (usually 'full') supply of material into the hydrocracking unit. Where this is not possible, the unit will be less efficient, or may not even be able to operate.
- Hydrocracking units can range in any size of capacity, but are generally determined according to the volume of products produced. Such product outflows can be measured in barrels per day (bbl/day), and hydrocracking units can have capacities from under 1000 bbl/day, up to 70-100,000 bbl/day. Naturally, the greater the capacity of the hydrocracking unit, the greater amount of feed material required to achieve the design operating conditions for the hydrocracking unit.
- In most situations, the feed material for the hydrocracking unit is supplied by one or more prior chemical operations, such as the hydrocarbon synthesis of the Fischer-Tropsch reaction, (providing 'FT hydrocarbons'), or by distillation of crude oil fractions. In a situation where a hydrocracking unit is being started, it may be that there is insufficient feed material from the previous (chemical) operation(s) to allow the hydrocarbon unit to immediately start at full operating design capacity.
- Hitherto, such hydrocracking units have therefore been started by a series of 'stop-start' stages over time, until the supply of feed material is such that it is possible to have continuous running of the hydrocracking unit, albeit at a reduced conversion efficiency. Such an arrangement is diagrammatically shown in
figure 1 herewith. - However, this 'start-stop' arrangement is inefficient, as it requires a number of transient operations, high operational attention, and in the transient periods there will be created, conversion material that is not of sufficient quality for subsequent use as intended.
- It is an object of the present invention to improve the start-up procedure for a hydrocracking unit.
- Thus, according to one aspect of the present invention, there is provided a hydrocracking system comprising:
- (a) one or more hydrocracking units, preferably 1 or 2 units, more preferably 1 unit, adapted to convert hydrocarbon feed material into one or more hydrocarbon products, and
- (b) one or more hydrocarbon feed material storage facilities upstream of the one or more hydrocarbon units to supply hydrocarbon feed material to the one or more hydrocracking units.
- Thus, the storage facility or facilities are able to store and hold hydrocarbon feed material until there is a sufficient amount of feed material to be able to supply the hydrocracking unit(s) under favourable start up conditions. Preferably the storage facility or facilities are filled up for at least 50% of their volume, more preferably at least 75%, still more preferably 90%, before start up of the hydrocracking unit(s).
- A storage facility may have any suitable shape, design or size, and may be in any suitable form. One suitable facility is a holding or accumulator tank. Such tanks are generally symmetrical, and may have a generally circular cross section, although the invention is not limited thereto.
- Where the invention involves the use of more than one storage facility, each storage facility may be the same or different in terms of size, shape and design. That is, it may be desired to have one or more storage facilities that are smaller than one or more other storage facilities.
- Where the invention involves the use of more than one storage facility, the storage facilities could be arranged in parallel or series or a combination of same, and may have any suitable arrangement to supply more than one hydrocracking unit.
- The storage capacity of the storage facility or facilities could be such as to be able to supply as low as 1,000-10,000 bbl/day, or in the range 10,000-100,000 bbl/day over at least one day, preferably more than one day, more preferably 2 to 5 days. In another embodiment, the storage facility of facilities have a capacity for supplying hydrocarbon feedstock to the hydrocracking unit(s) at 80% of their design capacity for at least 0.5 days, preferably 1-6 days.
- The capacity of the storage facility or facilities may also need to account for any variation in the volume, rate or flow supply of feed material thereto. Where the supply of feed material is already wholly or substantially constant, and/or the hydrocracking units are receiving feed material from one or more other sources (such as directly from the feed material production) the capacity of the storage facility or facilities may be different, e.g. less, than a situation where the supply of feed material to the storage facility of facilities and/or the supply of feed material directly to the hydrocracking unit(s) is changing, in particular where the supply is increasing.
- In the first above circumstance, it may be that a hydrocracking unit(s) has been wholly or partially stopped or taken out of service due to the desire for regeneration or replacement of the catalyst in the hydrocracking unit. Thus, the intention is to re-start the hydrocracking unit(s) whilst there continues to be production of the feed material during the regeneration period.
- In the second circumstance described above, it may be that the hydrocracking unit(s) are being started in line with the start of the arrangement for production of the feed material, such that as the feed material production increases from its start, there is an increasing amount of feed material available to be provided to the hydrocarbon unit(s).
- In one embodiment of the present invention, the storage facility or facilities can be heated, preferably by one or more heating means. Such hating means are known in the art, and are intended to maintain the feed material stored in the storage facility or facilities at a temperature or range of temperatures which allow their properties and/or state to be maintained, and/or allow the feed material to be maintained in a manner suitable for direct passage and use in the hydrocarbon unit(s). One suitable temperature range is 50-150 °C, preferably 70-130 °C.
- The storage facility or facilities may also be used at any suitable pressure, e.g. in the range 1-50 bar, commonly at an ambient pressure or slightly above, such as 1.5 bar. The material stored in the storage facility or facilities may also be kept under a particular atmosphere, such as under a nitrogen blanket.
- In a second aspect of the present invention, there is provided a method to start a process for converting a hydrocarbon feed material into one or more hydrocarbon products in one or more hydrocracking units, wherein the feed material is partly, substantially or wholly provided by one or more storage facilities.
- One or more of the hydrocracking units may also receive hydrocarbon feed material from one or more sources other than the storage facility or facilities.
- The term "hydrocracking" as used herein includes hydroisomerism/hydroisomerisation.
- In one embodiment of the present invention, the hydrocarbon feed material is produced in a hydrocarbon synthesis process. One such process is the Fischer-Tropsch process. Such a process may be designed to produce normally gaseous, normally liquid and optionally normally solid hydrocarbons from synthesis gas.
- Thus, according to a third aspect of the present invention, there is provided a hydrocarbon production facility comprising:
- (a) means for providing synthesis gas;
- (b) means for catalytically converting the synthesis gas of step (a) to obtain gaseous, liquid and optionally solid hydrocarbon feed material, preferably FT hydrocarbons;
- (c) one or more storage facilities to partly, substantially or wholly store the hydrocarbon feed material of step (b); and
- (d) one or more hydrocracking units able to convert the hydrocarbon feed material of step (c) into one or more hydrocarbon products.
- According to a fourth aspect of the present invention, there is provided a process for producing hydrocarbons from a feed material by hydrocracking, which comprises the steps of:
- (a) providing at least some of the feed material from one or more hydrocarbon feed material storage facilities; and
- (b) hydrocracking said feed material in one or more hydrocracking units to convert the hydrocarbon feed material into one or more hydrocarbon products.
- According to a fifth aspect of the present invention, there is provided a process for producing hydrocarbons from synthesis gas which comprises the steps of:
- (a) providing the synthesis gas;
- (b) catalytically converting the synthesis gas of step (a) at an elevated temperature and pressure to obtain a hydrocarbon feed material, preferably FT hydrocarbons;
- (c) partly, substantially or wholly storing the hydrocarbon feed material of step (b) in one or more storage facilities; and
- (d) converting the stored feed material of step (d) in one or more hydrocracking units into hydrocarbon products.
- The present invention encompasses the provision of hydrocarbon feed material stored in one or more storage facilities, and the direct supply of hydrocarbon feed material from reactor(s) producing same, to the hydrocracking unit(s), to be in any arrangement or combination. Naturally, upon start up of a first hydrocarbon feed material reactor(s), all the hydrocarbon feed material desired for the start up of a hydrocracking unit(s) could be provided by the storage facility or facilities once there has been sufficient material. As the hydrocracking unit(s) is being provided by the storage facility or facilities, the reactor(s) providing the hydrocarbon feed material is creating more feed material, and indeed there may be one or more other hydrocarbon feed material reactors being started, available or otherwise coming on stream.
- The present invention provides the user with the flexibility to consider how best to arrange the increasing provision of hydrocarbon feed material by one or more reactors as they are started, and how best to supply some or all of the hydrocarbon feed material directly to the hydrocracking unit(s) and/or still supply hydrocarbon feed material into the storage facility or facilities. Once the or all hydrocracking unit(s) are on-line, it may be desirable for them to be fed directly from the hydrocarbon feed material reactors, and to keep the storage facility or facilities in reserve, or maintain the passage of some feed material through the storage facility or facilities as a reserve or in case of an emergency.
- This flexibility also allows the user to be flexible as to how long to use the storage facility or facilities during a start up procedure, and how soon to start the direct passage of hydrocarbon feed material from the reactors to the hydrocracking unit(s).
- An example of the present invention will now be described by way of example only and with reference to the accompanying drawings in which:
-
Figure 1 is a diagramatic graph of a prior art start up procedure for hydrocracking unit; -
Figure 2 is a schematic drawing of a part of a hydrocarbon production plant according to one embodiment of the present invention; -
Figure 3 is a diagramatic graph of a start up procedure of a hydrocracking unit according to the present invention. - For a hydrocarbon synthesis process, the feed suitably is methane, natural gas, associated gas or a mixture of C1-4 hydrocarbons. The feed comprises mainly, i.e. more than 90 v/v%, especially more than 94%, C1-4 hydrocarbons, especially comprises at least 60 v/v percent methane, preferably at least 75 percent, more preferably 90 percent. Very suitably natural gas or associated gas is used. Suitably, any sulphur in the feedstock is removed.
- In the steady state process the catalysts used for the catalytic conversion of the mixture comprising hydrogen and carbon monoxide into hydrocarbons are known in the art and are usually referred to as Fischer-Tropsch catalysts. Catalysts for use in the Fischer-Tropsch hydrocarbon synthesis process frequently comprise, as the catalytically active component, a metal from Group VIII of the previous IUPAC version of the Periodic Table of Elements such as that described in the 68th Edition of the Handbook of Chemistry and Physics (CPC Press). Particular catalytically active metals include ruthenium, iron, cobalt and nickel. Cobalt is a preferred catalytically active metal.
- The hydrocarbons produced in the process and mentioned in the present description are suitably C3-200 hydrocarbons, more suitably C4-150 hydrocarbons, especially C5-100 hydrocarbons, or mixtures thereof. These hydrocarbons or mixtures thereof are liquid or solid at temperatures between 5 and 30 °C (1 bar), especially at about 20 °C (1 bar), and usually are paraffinic of nature, while up to 30 wt%, preferably up to 15 wt%, of either olefins or oxygenated compounds may be present.
- Hydrocarbons, normally liquid hydrocarbons and optionally normally solid hydrocarbons are obtained. It is often preferred to obtain a large fraction of normally solid hydrocarbons. These solid hydrocarbons may be obtained up to 85 wt% based on total hydrocarbons, usually between 50 and 75 wt%.
- The partial oxidation of gaseous feedstocks, producing mixtures of especially carbon monoxide and hydrogen, can take place according to various established processes. These processes include the Shell Gasification Process. A comprehensive survey of this process can be found in the Oil and Gas Journal, September 6, 1971, pp 86-90.
- The oxygen containing gas for the partial oxidation can be air (containing about 21 vol. percent of oxygen), oxygen enriched air, suitably containing up to 70 percent, or substantially pure oxygen, containing typically at least 95 vol.%, usually at least 98 vol.%, oxygen. Oxygen or oxygen enriched air may be produced via cryogenic techniques, but could also be produced by a membrane based process, e.g. the process as described in
WO 93/06041 - To adjust the H2/CO ratio in the syngas, carbon dioxide and/or steam may be introduced into the partial oxidation process. Preferably up to 15% volume based on the amount of syngas, preferably up to 8% volume, more preferable up to 4% volume, of either carbon dioxide or steam is added to the feed. Water produced in the hydrocarbon synthesis may be used to generate the steam. As a suitable carbon dioxide source, carbon dioxide from the effluent gasses of the expanding/combustion step may be used. The H2/CO ratio of the syngas is suitably between 1.5 and 2.3, preferably between 1.6 and 2.0. If desired, (small) additional amounts of hydrogen may be made by steam methane reforming, preferably in combination with the water gas shift reaction. Any carbon monoxide and carbon dioxide produced together with the hydrogen may be used in the hydrocarbon synthesis reaction or recycled to increase the carbon efficiency. Hydrogen from other sources, for example hydrogen itself, may be an option.
- The gaseous mixture, comprising predominantly hydrogen, carbon monoxide and optionally nitrogen, is contacted with a suitable catalyst in the catalytic conversion stage, in which FT hydrocarbons are formed. Suitably at least 70 v/v% of the syngas is contacted with the catalyst, preferably at least 80%, more preferably at least 90%, still more preferably all the syngas.
- The catalytically active metal is preferably supported on a porous carrier. The porous carrier may be selected from any of the suitable refractory metal oxides or silicates or combinations thereof known in the art. Particular examples of preferred porous carriers include silica, alumina, titania, zirconia, ceria, gallia and mixtures thereof, especially silica and titania.
- The amount of catalytically active metal on the carrier is preferably in the range of from 3 to 300 pbw per 100 pbw of carrier material, more preferably from 5 to 60 pbw, especially from 10 to 40 pbw.
- If desired, the catalyst may also comprise one or more metals or metal oxides as promoters. Suitable metal oxide promoters may be selected from Groups IIA, IIIB, IVB, VB, VIB and VIIB and VIIIB of the (same) Periodic Table of Elements, or the actinides and lanthanides. In particular, oxides of magnesium, calcium, strontium, barium, scandium, yttrium. lanthanum, cerium, titanium, zirconium, hafnium, thorium, uranium, vanadium, chromium and manganese are most suitable promoters. Particularly preferred metal oxide promoters for the catalyst used to prepare the waxes for use in the present invention are manganese and zirconium oxide.
- Suitable metal promoters may be selected from Groups VIIB or VIII of the (same) Periodic Table. Manganese, iron, rhenium and Group VIII noble metals are particularly suitable, with platinum and palladium being especially preferred. The amount of promoter present in the catalyst is suitably in the range of from 0.001 to 100 pbw, preferably 0.05 to 20, more preferably 0.1 to 15 pbw, per 100 pbw of carrier.
- The catalytically active metal and the promoter, if present, may be deposited on the carrier material by any suitable treatment, such as impregnation, kneading and extrusion. After deposition of the metal and, if appropriate, the promoter on the carrier material, the loaded carrier is typically subjected to calcination at a temperature of generally from 350 to 750 °C, preferably a temperature in the range of from 450 to 550 °C. The effect of the calcination treatment is to remove crystal water, to decompose volatile decomposition products and to convert organic and inorganic compounds to their respective oxides. After calcination, the resulting catalyst may be activated by contacting the catalyst with hydrogen or a hydrogen-containing gas, typically at temperatures of about 200 to 350 °C.
- The steady state catalytic conversion process may be performed under conventional synthesis conditions known in the art. Typically, the catalytic conversion may be effected at a temperature in the range of from 100 to 600 °C, preferably from 150 to 350 °C, more preferably from 180 to 270 °C. Typical total pressures for the catalytic conversion process are in the range of from 1 to 200 bar absolute, more preferably from 10 to 70 bar absolute. In the catalytic conversion process mainly (at least 70 wt%, preferably 90 wt%) of C5+ hydrocarbons are formed, based on the total weight of hydrocarbonaceous products formed.
- Preferably, a Fischer-Tropsch catalyst is used which yields substantial quantities of paraffins, more preferably substantially unbranched paraffins. A part may boil above the boiling point range of the so-called middle distillates, to normally solid hydrocarbons. A most suitable catalyst for this purpose is a cobalt-containing Fischer-Tropsch catalyst. The term "middle distillates", as used herein, is a reference to hydrocarbon mixtures of which the boiling point range corresponds substantially to that of kerosene and gas oil fractions obtained in a conventional atmospheric distillation of crude mineral oil. The boiling point range of middle distillates generally lies within the range of about 150 to about 360 °C.
- The higher boiling range paraffinic hydrocarbons, if present, may be isolated and subjected to catalytic hydrocracking to yield the desired middle distillates.
- In the present invention, the catalytic hydro-cracking can be carried out by contacting the FT hydrocarbons at elevated temperature and pressure and in the presence of hydrogen with a catalyst containing one or more metals having hydrogenation activity, and supported on a carrier.
- Suitable hydrocracking catalysts include catalysts comprising metals selected from Groups VIB and VIII of the (same) Periodic Table of Elements. Preferably, the hydrocracking catalysts contain one or more noble metals from Group VIII. Preferred noble metals are platinum, palladium, rhodium, ruthenium, iridium and osmium. Most preferred catalysts for use in the hydro-cracking stage are those comprising platinum.
- The amount of catalytically active metal present in the hydrocracking catalyst may vary within wide limits and is typically in the range of from about 0.05 to about 5 parts by weight per 100 parts by weight of the carrier material.
- Suitable conditions for the hydrocracking/isomerisation step of the FT hydrocarbon mixture are a temperature of 280-400 °C, preferably 290-375 °C, more preferably 300-350 °C, a pressure between 15 and 200 bar, preferably 20-100 bar, more preferably between 30-80 bar, an hourly space velocity of 0.2-20 kg of hydrocarbon feed per litre of catalyst per hour, preferably between 0.5 and 3 kg/1/h, more preferably between 0.7 and 2.5 kg/1/h, and a hydrogen/hydrocarbon feed molar ratio of 1-50.
- One or more of the hydrocracking products or effluents could be recycled, optionally after separation from other products and effluents, for example by distillation such as flash distillation.
- At least part of the effluent of the isomerisation/hydrocracking step could be passed to a separation step in which a hydrogen-containing gas and a hydrocarbon effluent are separated from each other. Suitably, in this separation step a hydrogen-containing gas and a hydrocarbon effluent are separated off by flash distillation. Suitably the flash distillation is carried out at a temperature between -20 and 100 °C and a pressure between 1 and 50 bar. Suitably the hydrocarbon effluent is separated into a fraction boiling above 370 °C and one or more fractions boiling below 370 °C, e.g. two or three fractions boiling in the (light and heavy) gasoil range and a kerosene fraction. At least part of the heavy fraction obtained in the first hydrocracking/hydroisomerisation reaction could be introduced in the second hydrocracking/hyroisomerisation reaction. Especially, a substantial part of the 370 °C fraction could be introduced in the second reaction, but also substantial parts of the kerosene/gasoil fraction may be introduced into this second step. Suitably at least 50 wt%, of the 370 °C fraction is introduced into the second hydrocracking/ hydroisomerisation step, preferably 70 wt%, more preferably at least 90 wt%, especially the total 370 °C plus fraction could be introduced into the second step.
- The conditions (catalyst, temperature, pressure, WHSV etc.) of the second hydrocracking/ hydroisomerisation reaction are suitable similar to the first reaction, although this is not necessarily the case. The conditions and the preferred conditions are described above for the first reaction. In a preferred situation the conditions in the first and the second hydrocracking/hydroisomerisation are the same.
- The product of the FT hydrocarbon synthesis and consequent hydrocracking suitably comprises mainly normally liquid hydrocarbons, beside water and normally gaseous hydrocarbons. By selecting the catalyst and the process conditions in such a way that especially normally liquid hydrocarbons are obtained, the product obtained ("syncrude") may transported in the liquid form or be mixed with any stream of crude oil without creating any problems as to solidification and or crystallization of the mixture. It is observed in this respect that the production of heavy hydrocarbons, comprising large amounts of solid wax, are less suitable for mixing with crude oil while transport in the liquid form has to be done at elevated temperatures, which is less desired.
- The off gas of the FT hydrocarbon synthesis may comprise normally gaseous hydrocarbons produced in the synthesis process, nitrogen, unconverted methane and other feedstock hydrocarbons, unconverted carbon monoxide, carbon dioxide, hydrogen and water. The normally gaseous hydrocarbons are suitably C1-5 hydrocarbons, preferably C1-4 hydrocarbons, more preferably C1-3 hydrocarbons. These hydrocarbons, or mixtures thereof, are gaseous at temperatures of 5-30 °C (1 bar), especially at 20 °C (1 bar). Further, oxygenated compounds, e.g. methanol, dimethyl ether, may be present in the off gas. The off gas may be utilized for the production of electrical power, in an expanding/combustion process such as in a gas turbine described herein, or recycled to the process. The energy generated in the process may be used for own use or for export to local customers. Part of an energy could be used for the compression of the oxygen containing gas.
- The process as just described may be combined with all possible embodiments as described in this specification.
- In the process of the invention, hydrogen may be separated from the synthesis gas provided for the first step. The hydrogen is preferably separated after quenching/cooling, and may be separated by techniques well known in the art, as pressure swing adsorption, or, preferably, by means of membrane separation techniques. The hydrogen may be used in a second heavy paraffin synthesis step after the first reactor (provided that a two stage hydrocarbon synthesis is used), or for other purposes, e.g. hydrotreating and/or hydrocracking of the FT hydrocarbons produced in the paraffin synthesis. In this way a further product optimization is obtained (for instance by fine tuning the H2/CO ratios in the first and second hydrocarbon synthesis step), while also the carbon efficiency can be improved. In addition, the product quality may be improved by e.g. hydrogenation and/or hydrocracking.
- Steam generated by any start-up gas turbine and/or steam generated in step (i) may also be used to preheat the reactor to be used in step (ii) and/or may be used to create fluidization in the case that a fluidized bed reactor or slurry bubble column is used in step (ii).
- Any percentage mentioned in this description is calculated on total weight or volume of the composition, unless indicated differently. When not mentioned, percentages are considered to be weight percentages. Pressures are indicated in bar absolute, unless indicated differently.
-
Figure 2 is a simplistic illustration of a portion of the process line whereby hydrocarbon products are obtained. In a Fischer-Tropsch stage 10, involving one or more process reactors, Fischer-Tropsch hydrocarbon products are obtained. These products can then be stored in astorage facility 12 such as a holding tank. Such stored material can then be passed to one ormore hydrocracking units 14, wherefrom desired hydrocarbon products are obtained. - In one situation, the Fisher-Tropsch stage involves a number of Fischer-Tropsch process reactors, possibly 2-15 reactors, which may be arranged in two or more stages so as to be able to achieve high conversion of synthesis gas into desired Fischer-Tropsch (FT) hydrocarbon product material. A standard Fischer-Tropsch reactor can produce approximately 2000-20,000 bbl/day of FT products, such that the steady state production of FT products can be anywhere in the range 20,000-100,000 bbl/day. A typical example of a hydrocracking unit would be one that is able to convert very approximately 70,000 bbl/day FT products.
- The holding
tank 12 can be any suitable size and design. There already exists known large storage tanks, such as 'strategic storage tanks' that occur at oil refineries, and are generally in the size 40-50,000 m3. However, such storage tanks are known to come in many other shapes and sizes, and have capacities to match. - In one situation, the FT reactors of
stage 10 involve a number of reactors, which are being started at different times. Such timing may be wholly sequential, or may involve two or more reactors starting simultaneously, either with or more expectantly after the sequential start up of some of the FT reactors. - As each FT reactor starts up, it will provide FT hydrocarbon feed material product. Such FT product may be provided at a constant rate, or may be provided at a variable rate, i.e. in an increasing manner over the start up period.
- A typical example could be the provision of approximately 10,000 bbl/day from each of a number of FT reactors, which are started in sequentially, each one after an approximate two week period from the other. Thus, every two weeks, there is the increased provision of 10,000 bbl/day of FT product available to the
hydrocracking unit 14. - Generally, a
hydrocracking unit 14 can act to convert FT product into suitable hydrocarbon products under less than 100% full conversion capacity. By careful metering and consideration of the operating conditions, a hydrocracking unit can run at 50%, more usually at least 60-70%, of its possible conversion capacity. Thus, assuming that thehydrocracking unit 14 has a capacity of approximately 70,000 bbl/day, it is possible to operate thehydrocracking unit 14 if there is available at least 35-40,000 bbl/day of FT product. - However, a constant supply of at least 35-40,000 bbl/day may not be available to the
hydrocracking unit 14 due to the staggered nature of the start up of theFT reactors 10, but by storing the FT products in theholding tank 12, a volume of FT products is built up such that thehydrocracking unit 14 can be started for a period of time to use up the FT products stored. Whilst this is occurring, theFT reactors 10 will be providing further FT product, which can then be stored, expectantly over a shorter time period as more FT reactors are started up and brought on stream. - Thus, the periods when the
hydrocracking unit 14 is not in use, (possibly on 'hot standby'), will be less and less frequent, and will occur for shorter periods, as time progresses, until a point is reached wherein at least 35-40,000 bbl/day are able to be supplied either through the holdingtank 12, or directly by the FT reactors 10 (through line 16), or in a combination of same, with the proportion of product provided by the holdingtank 12 expectantly to reduce over time until theFT reactors 10 are able to solely supply at least 35-40,000 bbl/day to thehydrocracking unit 14 directly. Thereafter, the holdingtank 12 is redundant in relation to the start up phase. The holdingtank 12 may still be required at certain periods when thehydrocracking unit 14 is not able to operate at full operating conditions or conversion capacity. This may be due to a need for routine maintenance or catalyst regeneration, or due to unexpected conditions, in thehydrocracking unit 14. -
Figure 3 illustrates a graph of operation of the hydrocracking unit 14 (based on FT products conversion percentage) over time, and can be directly compared with the graph offigure 1 , which shows the prior art start up procedure of a hydrocracking unit relying only an direct supply of FT hydrocarbons. It can be seen that there are less periods when thehydrocracking unit 14 is transient between operating and 'stand-by', resulting in significantly less time and effort involved. Once thehydrocracking unit 14 has sufficient supply to be able to run continuously, at least in a reduced conversion percentage state, the increased volume of FT products from the starting FT reactors will allow the conversion percentage to be increased to 100% conversion capacity. - The present invention is not limited to operation with FT reactors, or FT products, but is suitable for use in starting up a hydrocracking unit for other hydrocarbon feed materials provided by other processes known in the art.
Claims (18)
- A hydrocracking system comprising:(a) one or more hydrocracking units, preferably 1 or 2 units, more preferably 1 unit, adapted to convert hydrocarbon feed material into one or more hydrocarbon products, and(b) one or more hydrocarbon feed material storage facilities upstream of the one or more hydrocarbon units to supply hydrocarbon feed material to the one or more hydrocracking units.
- A system as claimed in claim 1 wherein at least one storage facility is a holding or accumulator tank.
- A system as claimed in claim 1 or claim 2 wherein the storage facility of facilities can supply between 1,000-100,000 bbl/day for at least one day, preferably more than one day, and more preferably 2-5 days, and preferably between 10,000-100,000 bbl/day.
- A system as claimed in any one of the preceding claims wherein at least one of the hydrocracking units is directly supplied by one or more sources other than the storage facility or facilities.
- A system as claimed in claim 4 wherein one other source is a means for providing hydrocarbon feed material.
- A system as claimed in any one of the preceding claims wherein the hydrocarbon feed material is provided by one or more hydrocarbon synthesis reactors, preferably 2-40 reactors, more preferably 4-20 reactors, especially 6-16 reactors.
- A system as claimed in claim 6 wherein the hydrocarbon synthesis reactor(s) includes one or more Fischer-Tropsch reactors, preferably all the hydrocarbon synthesis reactors are Fischer-Tropsch reactors.
- A system as claimed in any one of the preceding claims wherein the storage facility or facilities are heated, preferably by one or more heating means.
- A system as claimed in claim 8 wherein the storage facility or facilities are heated in the range 50-150 °C, preferably in the range 70-130 °C.
- A system as claimed in any one of the preceding claims wherein the hydrocracking unit or units are solely supplied by the storage facilities during the start up of the hydrocracking unit or units.
- A system as claimed in any one of the preceding claims, wherein after their start up, the hydrocracking unit or units are supplied by the storage facility or facilities and one or more other sources of hydrocarbon feed material, preferably as defined on claim 6 or claim 7.
- A method to start a process for converting a hydrocarbon feed material into one or more hydrocarbon products in one or more hydrocracking units, wherein the feed material is partly, substantially or wholly provided by one or more storage facilities.
- A method as claimed in claim 12 wherein one or more of the hydrocracking units also receive hydrocarbon feed material from one or more sources other than the storage facility or facilities.
- A hydrocarbon production facility comprising:(a) means for providing synthesis gas;(b) means for catalytically converting the synthesis gas of step (a) to obtain gaseous, liquid and optionally solid hydrocarbon feed material, preferably FT hydrocarbons;(c) one or more storage facilities to partly, substantially or wholly store the hydrocarbon feed material of step (b); and(d) one or more hydrocracking units able to convert the hydrocarbon feed material of step (c) into one or more hydrocarbon products.
- A process for producing hydrocarbons from a feed material by hydrocracking, which comprises the steps of:(a) providing at least some of the feed material from one or more hydrocarbon feed material storage facilities; and(b) hydrocracking said feed material in one or more hydrocracking units to convert the hydrocarbon feed material into one or more hydrocarbon products.
- A process for producing hydrocarbons from synthesis gas which comprises the steps of:(a) providing the synthesis gas;(b) catalytically converting the synthesis gas of step (a) at an elevated temperature and pressure to obtain a hydrocarbon feed material, preferably FT hydrocarbons;(c) partly, substantially or wholly storing the hydrocarbon feed material of step (b) in one or more storage facilities; and(d) converting the stored feed material of step (c) in one or more hydrocracking units into hydrocarbon products.
- A process for producing normally gaseous, normally liquid and optionally normally solid hydrocarbons from a hydrocarbonaceous feed, which process includes a system as described in any one of claims 1 to 11.
- Hydrocarbons whenever provided by a process as claimed in any one of claims 15-17.
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2007
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US5866751A (en) * | 1996-10-01 | 1999-02-02 | Mcdermott Technology, Inc. | Energy recovery and transport system |
WO2003004586A1 (en) * | 2001-07-06 | 2003-01-16 | Institut Francais Du Petrole | Method for production of medium distillates by hydroisomerisation and hydrocracking of a heavy fraction from the residue obtained by the fischer-tropsch process |
WO2003099961A2 (en) * | 2002-05-28 | 2003-12-04 | Fmc Technologies, Inc. | Portable gas-to-liquids unit and method for capturing natural gas at remote locations |
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