CN114806624A - Method and system for preparing hydrocarbons from synthesis gas - Google Patents
Method and system for preparing hydrocarbons from synthesis gas Download PDFInfo
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- CN114806624A CN114806624A CN202110113520.3A CN202110113520A CN114806624A CN 114806624 A CN114806624 A CN 114806624A CN 202110113520 A CN202110113520 A CN 202110113520A CN 114806624 A CN114806624 A CN 114806624A
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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
- C10G2/34—Apparatus, reactors
Abstract
The invention relates to hydrocarbon synthesis reaction, and discloses a method for preparing hydrocarbons by synthesis gas, which comprises the following steps: (1) in the presence of a catalyst-I, mixing raw material synthesis gas with recycle gas A and then carrying out primary reaction; (2) performing first separation on a product obtained by the first-stage reaction to obtain a first gas phase material and a first hydrocarbon product; (3) after supplementing hydrogen into the first gas phase material, mixing the first gas phase material with optional circulating gas B, and carrying out secondary reaction in the presence of a catalyst-II; (4) performing second separation on the product obtained by the second-stage reaction to obtain a second gas-phase material and a second hydrocarbon product; (5) and (3) taking part of the second gas-phase material as a circulating gas, and taking the whole circulating gas as the circulating gas A for the step (1), or dividing the circulating gas into the circulating gas A and the circulating gas B for the step (1) and the step (3) respectively. Process for preparing hydrocarbons with the synthesis gas according to the invention, C 5 + The overall selectivity of the hydrocarbons can reach 95% and the overall conversion of CO can be greater than 95%.
Description
Technical Field
The invention relates to hydrocarbon synthesis reaction, in particular to a method and a system for preparing hydrocarbons by synthesis gas.
Background
The Fischer-Tropsch synthesis reaction refers to synthesis gas (H) 2 + CO) is converted to hydrocarbons and other chemicals over a catalyst at a temperature and pressure. The fixed bed Fischer-Tropsch synthesis technology adopting the cobalt-based catalyst has the advantages of high yield of high-melting-point wax, low equipment investment and the like, and is widely applied to industry. The Fischer-Tropsch synthesis reaction is a strong exothermic reaction, so how to efficiently remove the reaction heat is a great challenge facing the fixed bed cobalt-based Fischer-Tropsch synthesis technology.
CN1662476A adopts the mode that multistage reactor is established ties to synthetic hydrocarbon, in order to realize the effective heat removal of reactor, adds cooling fluidum to each stage reactor, makes the reaction heat in the reactor partly be taken away by cooling fluidum.
CN1611565A discloses a process for the synthesis of hydrocarbons using two fischer-tropsch synthesis units in series, each stage of the fischer-tropsch synthesis unit having its own tail gas recycle system.
CN101085930A discloses a fischer-tropsch synthesis process consisting of two groups of fixed beds connected end to end, each group of fixed beds comprising a reactor, a heater, a casing, a heat exchanger and a three-phase distributor. The reaction synthesis gas enters the reactor from bottom to top and exchanges heat with circulating water from top to bottom in the reactor, the circulating water absorbs heat at the lower part of the reactor, releases heat at the upper part, the liquid product generated by the reaction verifies that the wall of the reactor flows out, and the unreacted gas enters the next-stage reactor.
The series-parallel connection of the fixed bed reactors is an important means for realizing the effective heat transfer of the fixed bed Fischer-Tropsch reactors. The simple parallel system can not realize the effective heat transfer of the system and the high conversion rate of the reaction gas. The series process results in large system pressure difference and high energy consumption of the circulating compressor.
Disclosure of Invention
The invention aims to solve the problems of large system pressure difference and high energy consumption in the Fischer-Tropsch synthesis process in the prior art, and provides a method and a system for preparing hydrocarbons by using synthesis gas.
In order to achieve the above object, a first aspect of the present invention provides a method for producing hydrocarbons from synthesis gas, the method comprising the steps of:
(1) in the presence of a catalyst-I, mixing raw material synthesis gas with recycle gas A and then carrying out primary reaction;
(2) performing first separation on a product obtained by the first-stage reaction to obtain a first gas phase material and a first hydrocarbon product;
(3) after supplementing hydrogen into the first gas phase material, mixing the first gas phase material with optional circulating gas B, and carrying out secondary reaction in the presence of a catalyst-II;
(4) performing second separation on the product obtained by the second-stage reaction to obtain a second gas-phase material and a second hydrocarbon product;
(5) and (3) taking part of the second gas-phase material as a circulating gas, and taking the whole circulating gas as the circulating gas A for the step (1), or dividing the circulating gas into the circulating gas A and the circulating gas B for the step (1) and the step (3) respectively.
Preferably, the amount of the recycle gas A is 50-100 vol%, and the amount of the recycle gas B is 0-50 vol%, based on the total volume of the recycle gas.
Preferably, the amount of the recycle gas A is 60-99 vol%, and the amount of the recycle gas B is 1-40 vol%, based on the total volume of the recycle gas.
Preferably, the amount of the recycle gas A is 60-90 vol% and the amount of the recycle gas B is 10-40 vol% based on the total volume of the recycle gas.
In a second aspect, the present invention provides a system for producing hydrocarbons from synthesis gas, the system comprising: the first-stage reaction unit, the second-stage reaction unit and the gas circulation unit are sequentially communicated through pipelines;
the first-stage reaction unit is used for carrying out first-stage reaction and a first separation device on the mixed gas of the raw material synthesis gas and the circulating gas A to obtain a first gas-phase material and a first hydrocarbon product;
the second-stage reaction unit is used for carrying out a second-stage reaction and a second separation device on the supplemented hydrogen, the first gas-phase material and the mixed gas of the circulating gas B to obtain a second gas-phase material and a second hydrocarbon product;
the gas circulation unit is used for taking part of the second gas-phase material as circulation gas, the whole circulation gas is taken as the circulation gas A and introduced into the first-stage reaction unit, or the circulation gas is divided into the circulation gas A and the circulation gas B and respectively introduced into the first-stage reaction unit and the second-stage reaction unit.
Preferably, the first stage reaction unit comprises a first stage reaction device and a first separation device; the second-stage reaction unit comprises a second reaction device and a second separation device; the gas circulation unit includes a circulation compressor.
Through the technical scheme, the method for preparing hydrocarbons by using the synthesis gas provided by the invention has the advantages that the circulating gas is divided between the first-stage reaction device and the second-stage reaction device, the high pressure drop defect of the serial reactors is reduced, the pressure difference between the front and the back of the circulating compressor can be reduced, and the energy consumption is reduced. In addition, a plurality of reactors connected in parallel are arranged in the first-stage reaction device, when one reactor in the first-stage reaction device has a problem and needs to be stopped, the circulating gas distribution ratio entering the second-stage reaction device can be increased, and therefore the system is guaranteed to still maintain high-load operation without stopping.
Drawings
FIG. 1 is a schematic flow diagram of a system for producing hydrocarbons from syngas in accordance with one embodiment of the present invention.
Description of the reference numerals
R1, a first fixed bed reactor R2, a second fixed bed reactor R3 and a third fixed bed reactor
S1, a first separation tank S2, a second separation tank S3 and a third separation tank
S4, fourth separation tank P and circulating compressor
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
In a first aspect the present invention provides a process for the production of hydrocarbons from synthesis gas, the process comprising the steps of:
(1) in the presence of a catalyst-I, mixing raw material synthesis gas with recycle gas A and then carrying out primary reaction;
(2) performing first separation on a product obtained by the first-stage reaction to obtain a first gas phase material and a first hydrocarbon product;
(3) after supplementing hydrogen into the first gas phase material, mixing the first gas phase material with optional circulating gas B, and carrying out secondary reaction in the presence of a catalyst-II;
(4) performing second separation on the product obtained by the second-stage reaction to obtain a second gas-phase material and a second hydrocarbon product;
(5) and (3) taking part of the second gas-phase material as a circulating gas, and taking the whole circulating gas as the circulating gas A for the step (1), or dividing the circulating gas into the circulating gas A and the circulating gas B for the step (1) and the step (3) respectively.
The two-stage reaction is simply connected in series, so that the reaction load of the first-stage reaction can be effectively reduced, the heat release of the first-stage reaction is reduced, and the temperature runaway phenomenon is avoided; the concentration of the synthesis gas in the secondary reaction is low, and the temperature runaway phenomenon can not occur, so that the system can stably run. However, if two-stage reactions are connected in series, the pressure difference of the system is large, the work of the circulating compressor is increased, and the energy consumption is increased. The inventor of the invention finds that the circulating gas is divided and then enters the first-stage reaction and the second-stage reaction respectively, the first-stage reaction is mainly carried out, and a small amount of circulating gas enters the second-stage reaction, so that heat in the first-stage reaction can be effectively brought out, the pressure difference of a system is reduced, and the energy consumption of the system is reduced.
H consumed in the Fischer-Tropsch reaction of cobalt based 2 The volume ratio of the carbon to the CO is more than 2.0, so as the reaction is carried out, the hydrogen-carbon ratio of the gas in the system is lower, the final CO total conversion rate of the system is higher, and the hydrogen-carbon ratio of the outlet gas of the system is lower. For the cobalt-based Fischer-Tropsch synthesis reaction, the catalyst has low activity and is easy to generate carbon deposition inactivation under a low hydrogen-carbon ratio, and in order to ensure that the catalyst does not generate carbon deposition inactivation, the total conversion rate of CO is generally maintained below 90%, which causes the utilization efficiency of CO in the whole system to be low. In the invention, the inventor connects two stages of reactors in series, divides the circulating gas and supplements a certain amount of H at the inlet of the two stages of reactors 2 The process solves the problems. The invention not only realizes high total conversion rate of CO, but also avoids carbon deposition inactivation of the catalyst under low hydrogen-carbon ratio. In the present invention, the overall CO conversion of the entire system is greater than 95% with only one recycle compressor.
In some embodiments of the present invention, preferably, the amount of the recycle gas a is 50 to 100 vol% and the amount of the recycle gas B is 0 to 50 vol%, based on the total volume of the recycle gas.
In some embodiments of the present invention, in order to make the system pressure difference smaller, it is preferable that the amount of the recycle gas a is 60 to 99 vol% and the amount of the recycle gas B is 1 to 40 vol%, based on the total volume of the recycle gas; further preferably, the amount of the recycle gas A is 60-90 vol%, and the amount of the recycle gas B is 10-40 vol%.
In some embodiments of the invention, the conditions of the first stage reaction may include: the pressure-I is 1-6.5MPa, and the temperature-I is 190-; preferably, the conditions of the first-order reaction include: the pressure-I is 1.5-4.5MPa, and the temperature-I is 200-.
In some embodiments of the invention, the conditions of the secondary reaction may include: the pressure-II is 1.5-5.5MPa, and the temperature-II is 200-.
In some embodiments of the present invention, in order to make full use of CO, it is preferred that the CO conversion in the first stage reaction is higher than 80%.
In some embodiments of the present invention, the amount of the raw syngas is not particularly limited as long as it can satisfy the amount of the syngas used to prepare hydrocarbons. Preferably, the space velocity of the raw material synthesis gas is 400-1500h -1 。
In some embodiments of the present invention, the volume ratio of the raw syngas to the recycle gas a is not particularly limited; preferably, the volume ratio of recycle gas a to feed synthesis gas is >1.5: 1.
In some embodiments of the invention, to further increase the CO conversion and improve the catalyst stability, the amount of hydrogen make-up in the first gas phase feed is 1-15% of the amount of the raw syngas.
In some embodiments of the present invention, the hydrogen supplying manner is not particularly limited, and the hydrogen may be supplied by supplying pure hydrogen or by supplying hydrogen-rich synthesis gas.
In some embodiments of the invention, the first separation serves to separate heavy hydrocarbons (solid hydrocarbons), light hydrocarbons (liquid hydrocarbons), gaseous hydrocarbons and water, and unconverted syngas, from the products of the first stage reaction. Wherein heavy hydrocarbons and light hydrocarbons are exported as a first hydrocarbon product; wherein the unconverted synthesis gas and the gaseous hydrocarbon are used as the first gas phase material to enter the second-stage reaction.
In some embodiments of the present invention, it is preferred that the first hydrocarbon product comprises: a first solid hydrocarbon product and a first liquid hydrocarbon product.
In some embodiments of the invention, it is preferred that the first solid hydrocarbon product has a number of carbon atoms in the range of C8 to C135.
In some embodiments of the invention, it is preferred that the first liquid hydrocarbon product has a carbon number of from C4 to C30.
In some embodiments of the invention, it is preferred that the first hydrocarbon product also contains a small amount of water.
In some embodiments of the invention, preferably, the first separation comprises a first solid hydrocarbon product separation and a first liquid hydrocarbon product separation.
In some embodiments of the present invention, it is preferred that the temperature of the first solid hydrocarbon product separation is 100-210 ℃.
In some embodiments of the invention, preferably, the temperature of the first liquid hydrocarbon product separation is from-10 ℃ to 100 ℃.
In some embodiments of the invention, the second separation serves to separate heavy hydrocarbons (solid hydrocarbons), light hydrocarbons (liquid hydrocarbons), gaseous hydrocarbons and water, and unconverted syngas, from the products of the second stage reaction. Wherein heavy hydrocarbons and light hydrocarbons are exported as a second hydrocarbon product; wherein unconverted synthesis gas and gaseous hydrocarbon are taken as second gas phase materials, part of the second gas phase materials are taken as circulating gas, and the rest of the second gas phase materials are taken as purge gas and discharged out of the system.
In some embodiments of the present invention, it is preferred that the second hydrocarbon product comprises: a second solid hydrocarbon product and a second liquid hydrocarbon product.
In some embodiments of the present invention, preferably, the second solid hydrocarbon product is a solid hydrocarbon having a carbon number of C8-C135.
In some embodiments of the present invention, preferably, the second liquid hydrocarbon product is a liquid hydrocarbon having a carbon number of C4-C30.
In some embodiments of the invention, it is preferred that the second hydrocarbon product also contains a small amount of water.
In some embodiments of the invention, preferably, the second separation comprises a second solid hydrocarbon product separation and a second liquid hydrocarbon product separation.
In some embodiments of the present invention, it is preferred that the temperature of the second solid hydrocarbon product separation is 100-210 ℃.
In some embodiments of the invention, preferably, the temperature of the second liquid hydrocarbon product separation is from-10 ℃ to 50 ℃.
Some implementations of the inventionIn the mode, H in the raw material synthesis gas 2 The molar ratio to CO is not particularly limited as long as it meets the requirements of synthesis gas to produce hydrocarbons. Preferably, in the raw syngas, H 2 The molar ratio to CO is 1.5-2.5: 1; preferably 1.7-2.2: 1; more preferably 1.7 to 2.1:1, still more preferably 1.7 to 2.05: 1.
In some embodiments of the present invention, in order to improve the stability of the reaction, the method may further include preheating the mixed gas of the raw syngas and the recycle gas a before the first-stage reaction; preferably, the temperature of the preheating is 180-.
In some embodiments of the present invention, the catalyst-I and the catalyst-II may be the same catalyst or different catalysts, and the catalyst-I and the catalyst-II are fischer-tropsch synthesis catalysts conventional in the art.
In some embodiments of the invention, preferably, the catalyst-I is a cobalt-based catalyst and the support of the catalyst-I is TiO 2 、ZrO 2 And SiO 2 The active component of the catalyst-I is metallic cobalt; more preferably, the content of metallic cobalt in the catalyst-I is 10-50 wt% and the content of the carrier in the catalyst-I is 50-90 wt% based on the total weight of the catalyst-I.
In some embodiments of the present invention, it is preferred that the specific surface area of the catalyst-I is from 20 to 100m 2 (ii)/g, pore size distribution of 10-40 nm.
In some embodiments of the invention, it is preferred that the catalyst-II is a cobalt-based catalyst and the support of the catalyst-II is TiO 2 And/or ZrO 2 The active component of the catalyst-II is metallic cobalt; more preferably, the content of the metallic cobalt in the catalyst-II is 10-50 wt% and the content of the carrier in the catalyst-II is 50-90 wt% based on the total weight of the catalyst-II.
In some embodiments of the present invention, it is preferred that the specific surface area of the catalyst-II is from 20 to 100m 2 (ii)/g, pore size distribution of 10-40 nm.
In some embodiments of the present invention, the source of the catalyst used in the present invention is not particularly limited, and the catalyst used in the present invention may be obtained by purchase or may be prepared according to a literature method. Generally, the catalyst of the present invention is prepared by at least one of impregnation, coprecipitation, and kneading.
In some embodiments of the present invention, preferably, the first gas phase material contains: h 2 、CH 4 、 C 2 H 6 、C 2 H 4 、C 3 H 8 、C 3 H 6 、C 4 H 10 、C 4 H 8 、C 5 H 12 、C 5 H 10 、CO 2 And CO.
In some embodiments of the present invention, preferably, the second gas-phase material contains: h 2 、CH 4 、 C 2 H 6 、C 2 H 4 、C 3 H 8 、C 3 H 6 、C 4 H 10 、C 4 H 8 、C 5 H 12 、C 5 H 10 、CO 2 And CO.
In a second aspect, the present invention provides a system for producing hydrocarbons from synthesis gas, as shown in fig. 1, the system comprising: the first-stage reaction unit, the second-stage reaction unit and the gas circulation unit are sequentially communicated through pipelines; the first-stage reaction unit is used for carrying out first-stage reaction and first separation on the mixed gas of the raw material synthesis gas and the circulating gas A to obtain a first gas phase material and a first hydrocarbon product; the second-stage reaction unit is used for carrying out second-stage reaction and second separation on the supplemented hydrogen, the first gas-phase material and the mixed gas of the circulating gas B to obtain a second gas-phase material and a second hydrocarbon product; the gas circulation unit is used for taking part of the second gas-phase material as circulation gas, and the circulation gas is completely taken as the circulation gas A and introduced into the first-stage reaction unit, or the circulation gas is divided into the circulation gas A and the circulation gas B and respectively introduced into the first-stage reaction unit and the second-stage reaction unit.
Preferably, the first stage reaction unit comprises a first stage reaction device and a first separation device.
Preferably, the second stage reaction unit comprises a second reaction device and a second separation device.
Preferably, the gas circulation unit comprises a circulation compressor.
Preferably, the first stage reaction device is a fixed bed reactor.
Preferably, the second stage reaction device is a fixed bed reactor.
Preferably, the first separation means comprises 2-3 separation tanks in series.
Preferably, the second separation means comprises 2-3 separation tanks in series.
Preferably, the first stage reaction device comprises 1-4 fixed bed reactors connected in parallel.
Preferably, the second stage reaction device comprises 1-2 fixed bed reactors connected in parallel.
Preferably, the fixed bed reactor is a tubular fixed bed reactor.
According to the invention, in the first-stage reaction device, because the concentration of the synthesis gas is high, the released heat is much in the reaction process, and the temperature runaway phenomenon is easy to occur; therefore, in order to further avoid the temperature runaway phenomenon and reduce the influence of the reaction heat release on the system stability and the catalyst activity, a heat extraction device is provided in the fixed bed reactor of the primary reaction device. Preferably, a heat exchange system device is arranged in the fixed bed reactor of the first-stage reaction device.
The operation of the system for producing hydrocarbons from synthesis gas is described below with reference to the schematic flow diagram of the system for producing hydrocarbons from synthesis gas according to the present invention shown in fig. 1.
Mixing the purified synthesis gas with a circulating gas A, preheating, dividing into two parts, respectively feeding into a first fixed bed reactor R1 and a second fixed bed reactor R2 in a first-stage reaction device, and sequentially feeding the products obtained after the first-stage reaction into a first separation tank S1 and a second separation tank S2 of the first separation device; separating by a first separation tank S1 to obtain a first solid hydrocarbon product, and separating by a second separation tank S2 to obtain a first liquid hydrocarbon product, wherein the first solid hydrocarbon product and the first liquid hydrocarbon product are output as the first hydrocarbon product, a certain amount of hydrogen is supplemented to the separated residual first gas-phase material, and then the separated residual first gas-phase material is mixed with the circulating gas B and then enters a third fixed bed reactor R3 in a second-stage reaction device, and the product after the second-stage reaction enters a third separation tank S3 and a fourth separation tank S4 of the second separation device; and separating by a third separation tank S3 to obtain a second solid hydrocarbon product, and separating by a fourth separation tank S4 to obtain a second liquid hydrocarbon product, wherein the second solid hydrocarbon product and the second liquid hydrocarbon product are output as the second hydrocarbon product, the separated residual second gas phase material is compressed by a circulating compressor to be used as circulating gas, and the circulating gas is divided into two streams, namely circulating gas A and circulating gas B.
The present invention will be described in detail below by way of examples.
The catalyst used in the following examples was a cobalt-based catalyst, the composition of which comprised 70% by weight of TiO 2 A support and 30 wt% metallic cobalt; the specific surface area of the catalyst was 35m 2 (ii)/g, pore size 26 nm; the adopted fixed bed reactor is a tubular fixed bed reactor, wherein heat exchange medium steam is introduced outside the tubes of the first fixed bed reactor R1 and the second fixed bed reactor R2 in the first stage reaction device and is used for removing heat released by the reaction.
The analysis of the composition of the hydrocarbon products from synthesis gas is carried out by means of a gas chromatograph equipped with a TCD detector and a FID detector.
The mole number of CO in the feeding is respectively measured through the inlets of the first-stage reaction device and the second-stage reaction device, the mole number of CO in the discharging and the mole number of CO in the circulating gas B are respectively measured through the outlets of the first separation device and the second separation device, and the percent conversion rate of CO is calculated as follows:
the percent conversion of CO in the first stage reactor is (mole of CO at the inlet of the first stage reactor-mole of CO at the outlet of the first separation device)/(mole of CO at the inlet of the first stage reactor) × 100%;
the percent conversion of CO in the second stage reactor is (mole of CO at the outlet of the first stage reactor-mole of CO at the outlet of the second separation device)/(mole of CO at the inlet of the first stage reactor) × 100%;
the total conversion rate of CO is (the mole number of CO at the inlet of the first-stage reaction device-the mole number of CO at the outlet of the second separation device)/the mole number of CO at the inlet of the first-stage reaction device multiplied by 100 percent;
for C in the product 5 + The% selectivity was calculated as:
C 5 + selectivity [% selectivity ] - ] is the number of moles of hydrocarbons with carbon numbers greater than or equal to 5 produced per total number of moles of CO reacted to convert to hydrocarbons.
Example 1
This example illustrates the preparation of hydrocarbons from synthesis gas
After being mixed with the circulating gas A, the raw material-purified synthesis gas is preheated to 200 ℃ by a preheater, then is divided into two parts which respectively enter from the upper parts of a first fixed bed reactor R1 and a second fixed bed reactor R2, and under the action of a cobalt-based catalyst, the synthesis gas and the circulating gas A undergo Fischer-Tropsch synthesis reaction, and the reaction conditions of the first fixed bed reactor R1 and the second fixed bed reactor R2 are as follows: the pressure-I is 4.5MPa, and the maximum temperature-I is 215 ℃. Unreacted gas and reaction products are led out from the lower parts of the first fixed bed reactor R1 and the second fixed bed reactor R2 and enter a first separating tank S1 and a second separating tank S2 of a first separating device in sequence, and the separating conditions of the first separating tank S1 are as follows: the separation temperature is 160 ℃, and the separation conditions of the second separation tank S2 are: the separation temperature was 5 ℃. The first separation tank S1 separates to obtain a first solid hydrocarbon product, and the second separation tank S2 separates to obtain a first liquid hydrocarbon product, wherein the first solid hydrocarbon product and the first liquid hydrocarbon product are output as a first hydrocarbon product; separating the residual first gas phase material, supplementing hydrogen and mixing with the recycle gas B, wherein the amount of the supplemented hydrogen is 5% of the amount of the purified synthesis gas; then preheating the mixture to 200 ℃ by a preheater, entering the third fixed bed reactor from the upper part of R3, and carrying out Fischer-Tropsch synthesis reaction under the action of a cobalt-based catalyst, wherein the reaction conditions of the third fixed bed reactor R3 are as follows: the pressure-II was 4.45MPa, and the temperature-II was 219 ℃. Unreacted gas and reaction products are led out from the lower part of the third fixed bed reactor R3 and enter a third separating tank S3 and a fourth separating tank S4 of a second separating device in sequence; the separation conditions of the third separation tank S3 were: the separation temperature was 160 ℃ and the separation conditions of the fourth separation tank S4 were: the separation temperature is 2 ℃, a second solid hydrocarbon product is obtained by separation in a third separation tank S3, a second liquid hydrocarbon product is obtained by separation in a fourth separation tank S4, wherein the second solid hydrocarbon product and the second liquid hydrocarbon product are output as a second hydrocarbon product; and compressing the separated and residual second gas-phase material by a circulating compressor to be used as circulating gas, wherein the circulating gas is divided into circulating gas A and circulating gas B.
The space velocity of the raw material synthesis gas is 900h -1 (ii) a H in synthesis gas 2 And CO in a molar ratio of 1.9; the volume ratio of the recycle gas A to the raw material synthesis gas is 3: 1; the volume ratio of the circulating gas A to the circulating gas B in the circulating gas is 70: 30.
The CO conversion rate of the first-stage reaction device is 85 percent, the CO conversion rate of the second-stage reaction device is 12 percent, the total CO conversion rate is 97 percent, and C 5 + The hydrocarbon selectivity was 95%.
Example 2
This example illustrates the preparation of hydrocarbons from synthesis gas
After being mixed with the circulating gas A, the raw material-purified synthesis gas is preheated to 180 ℃ by a preheater, then is divided into two parts which respectively enter from the upper parts of a first fixed bed reactor R1 and a second fixed bed reactor R2, and under the action of a cobalt-based catalyst, the synthesis gas and the circulating gas A undergo Fischer-Tropsch synthesis reaction, and the reaction conditions of the first fixed bed reactor R1 and the second fixed bed reactor R2 are as follows: the pressure-I is 2.0MPa, and the maximum temperature-I is 235 ℃. Unreacted gas and reaction products are led out from the lower parts of the first fixed bed reactor R1 and the second fixed bed reactor R2 and enter a first separating tank S1 and a second separating tank S2 of a first separating device in sequence, and the separating conditions of the first separating tank S1 are as follows: the separation temperature is 120 ℃, and the separation conditions of the second separation tank S2 are as follows: the separation temperature was 10 ℃. The first separation tank S1 separates to obtain a first solid hydrocarbon product, and the second separation tank S2 separates to obtain a first liquid hydrocarbon product, wherein the first solid hydrocarbon product and the first liquid hydrocarbon product are output as a first hydrocarbon product; separating the residual first gas phase material, supplementing hydrogen and mixing with the recycle gas B, wherein the amount of the supplemented hydrogen is 10% of the amount of the purified synthesis gas; then preheating the mixture to 180 ℃ by a preheater, entering the third fixed bed reactor from the upper part of R3, and carrying out Fischer-Tropsch synthesis reaction under the action of a cobalt-based catalyst, wherein the reaction conditions of the third fixed bed reactor R3 are as follows: the pressure-II was 1.5MPa, and the temperature-II was 210 ℃. Unreacted gas and reaction products are led out from the lower part of the third fixed bed reactor R3 and enter a third separating tank S3 and a fourth separating tank S4 of a second separating device in sequence; the separation conditions of the third separation tank S3 were: the separation temperature was 110 ℃ and the separation conditions of the fourth separation tank S4 were: the separation temperature is 10 ℃, a second solid hydrocarbon product is obtained by separation in a third separation tank S3, a second liquid hydrocarbon product is obtained by separation in a fourth separation tank S4, wherein the second solid hydrocarbon product and the second liquid hydrocarbon product are output as a second hydrocarbon product; and compressing the separated and residual second gas-phase material by a circulating compressor to be used as circulating gas, wherein the circulating gas is divided into circulating gas A and circulating gas B.
The space velocity of the synthesis gas is 600h -1 (ii) a H in synthesis gas 2 And CO in a molar ratio of 1.8; the volume ratio of the recycle gas A to the raw material synthesis gas is 3.5: 1; the volume ratio of the circulating gas A to the circulating gas B in the circulating gas is 60: 40.
The CO conversion rate of the first-stage reaction device is 90 percent, the CO conversion rate of the second-stage reaction device is 6 percent, the total CO conversion rate is 96 percent, and C 5 + The hydrocarbon selectivity was 93%.
Example 3
This example illustrates the preparation of hydrocarbons from synthesis gas
After being mixed with the circulating gas A, the raw material-purified synthesis gas is preheated to 210 ℃ by a preheater, then is divided into two parts which respectively enter from the upper parts of a first fixed bed reactor R1 and a second fixed bed reactor R2, and under the action of a cobalt-based catalyst, the synthesis gas and the circulating gas A undergo Fischer-Tropsch synthesis reaction, and the reaction conditions of the first fixed bed reactor R1 and the second fixed bed reactor R2 are as follows: the pressure-I is 3.5MPa, and the maximum temperature-I is 210 ℃. Unreacted gas and reaction products are led out from the lower parts of the first fixed bed reactor R1 and the second fixed bed reactor R2 and enter a first separating tank S1 and a second separating tank S2 of a first separating device in sequence, and the separating conditions of the first separating tank S1 are as follows: the separation temperature was 190 ℃ and the separation conditions of the second separation tank S2 were: the separation temperature was 65 ℃. The first separation tank S1 separates to obtain a first solid hydrocarbon product, and the second separation tank S2 separates to obtain a first liquid hydrocarbon product, wherein the first solid hydrocarbon product and the first liquid hydrocarbon product are output as a first hydrocarbon product; separating the residual first gas phase material, supplementing hydrogen and mixing with the recycle gas B, wherein the amount of the supplemented hydrogen is 8% of the amount of the purified synthesis gas; then preheating the mixture to 210 ℃ by a preheater, entering the third fixed bed reactor from the upper part of R3, and carrying out Fischer-Tropsch synthesis reaction under the action of a cobalt-based catalyst, wherein the reaction conditions of the third fixed bed reactor R3 are as follows: the pressure-II was 3.4MPa, and the temperature-II was 240 ℃. Unreacted gas and reaction products are led out from the lower part of the third fixed bed reactor R3 and enter a third separating tank S3 and a fourth separating tank S4 of a second separating device in sequence; the separation conditions of the third separation tank S3 were: the separation temperature was 190 ℃ and the separation conditions of the fourth separation tank S4 were: the separation temperature is 5 ℃, a second solid hydrocarbon product is obtained by separation in a third separation tank S3, a second liquid hydrocarbon product is obtained by separation in a fourth separation tank S4, wherein the second solid hydrocarbon product and the second liquid hydrocarbon product are output as a second hydrocarbon product; and compressing the separated and residual second gas-phase material by a circulating compressor to be used as circulating gas, wherein the circulating gas is divided into circulating gas A and circulating gas B.
The space velocity of the synthetic gas is 800h -1 (ii) a H in synthesis gas 2 And a CO molar ratio of 2.05; the volume ratio of the recycle gas A to the raw material synthesis gas is 4: 1; the volume ratio of the circulating gas A to the circulating gas B in the circulating gas is 85: 15.
The CO conversion rate of the first-stage reaction device is 87 percent, the CO conversion rate of the second-stage reaction device is 11 percent, the total CO conversion rate is 98 percent, and C is 5 + The hydrocarbon selectivity was 91%.
Example 4
This example illustrates the preparation of hydrocarbons from synthesis gas
Synthesis gas to hydrocarbons was carried out as in example 1 except that only recycle gas a was included and no recycle gas B was included.
The CO conversion rate of the first-stage reaction device is 85 percent, the CO conversion rate of the second-stage reaction device is 5 percent, the total CO conversion rate is 90 percent, and C is 5 + The hydrocarbon selectivity was 88%.
Comparative example 1
This example illustrates the preparation of hydrocarbons from synthesis gas
Synthesis gas to hydrocarbons was carried out as in example 1, except that the remaining first gaseous feed was separated and mixed directly with recycle gas B without make-up of hydrogen.
The CO conversion rate of the first-stage reaction device is 84 percent, the CO conversion rate of the second-stage reaction device is 3 percent, the total CO conversion rate is 87 percent, and C is 5 + The hydrocarbon selectivity was 86%.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (12)
1. A process for the production of hydrocarbons from synthesis gas, the process comprising the steps of:
(1) in the presence of a catalyst-I, mixing raw material synthesis gas with recycle gas A and then carrying out primary reaction;
(2) performing first separation on a product obtained by the first-stage reaction to obtain a first gas phase material and a first hydrocarbon product;
(3) after supplementing hydrogen into the first gas phase material, mixing the first gas phase material with optional circulating gas B, and carrying out secondary reaction in the presence of a catalyst-II;
(4) performing second separation on the product obtained by the second-stage reaction to obtain a second gas-phase material and a second hydrocarbon product;
(5) and (3) taking part of the second gas-phase material as a circulating gas, and taking the whole circulating gas as the circulating gas A for the step (1), or dividing the circulating gas into the circulating gas A and the circulating gas B for the step (1) and the step (3) respectively.
2. The method according to claim 1, wherein the amount of the recycle gas A is 50-100 vol%, and the amount of the recycle gas B is 0-50 vol%;
preferably, the amount of the recycle gas A is 60-99 vol%, and the amount of the recycle gas B is 1-40 vol%, based on the total volume of the recycle gas.
3. The process according to claim 1, wherein the volume ratio of recycle gas a to raw syngas is >1.5: 1; the amount of the hydrogen supplemented into the first gas phase material is 1-15% of the amount of the raw material synthesis gas.
4. The process of any one of claims 1-3, wherein the conditions of the primary reaction comprise: the pressure-I is 1-6.5MPa, and the temperature-I is 190-; preferably the pressure-I is 1.5-4.5MPa and the temperature-I is 200-;
preferably, the conditions of the secondary reaction include: the pressure-II is 1.5-5.5MPa, and the temperature-II is 200-240 ℃;
preferably, the CO conversion in the first stage reaction is higher than 80%.
5. The method of any of claims 1-4, wherein the first separation comprises a first solid hydrocarbon product separation and a first liquid hydrocarbon product separation;
wherein the second separation comprises a second solid hydrocarbon product separation and a second liquid hydrocarbon product separation;
preferably, the temperature of the first solid hydrocarbon product separation is 100-210 ℃;
preferably, the temperature of the first liquid hydrocarbon product separation is from-10 ℃ to 100 ℃;
preferably, the temperature of the second solid hydrocarbon product separation is 100-210 ℃;
preferably, the temperature of the second liquid hydrocarbon product separation is from-10 ℃ to 50 ℃.
6. The process according to any one of claims 1-5, wherein in the raw syngas, H 2 The molar ratio to CO is 1.5-2.5: 1; preferably 1.7 to 2.2:1, more preferably 1.7 to 2.1:1, and still more preferably 1.7 to 2.05: 1.
7. The method according to any one of claims 1 to 6, wherein the method further comprises preheating the mixture of the raw synthesis gas and the recycle gas A before the primary reaction;
preferably, the temperature of the preheating is 180-.
8. The process of any one of claims 1-7, wherein the catalyst-I is a cobalt-based catalyst and the support of the catalyst-I is TiO 2 、ZrO 2 And SiO 2 The active component of the catalyst-I is metallic cobalt;
wherein the catalyst-II is a cobalt-based catalyst, and the carrier of the catalyst-II is TiO 2 And/or ZrO 2 The active component of the catalyst-II is metallic cobalt;
preferably, the content of the metallic cobalt in the catalyst-I is 10-50 wt%, and the content of the carrier in the catalyst-I is 50-90 wt%;
preferably, the content of the metal cobalt in the catalyst-II is 10-50 wt%, and the content of the carrier in the catalyst-II is 50-90 wt%, based on the total weight of the catalyst-II.
9. A system for producing hydrocarbons from synthesis gas, the system comprising: the first-stage reaction unit, the second-stage reaction unit and the gas circulation unit are sequentially communicated through pipelines;
the first-stage reaction unit is used for carrying out first-stage reaction and first separation on the mixed gas of the raw material synthesis gas and the circulating gas A to obtain a first gas phase material and a first hydrocarbon product;
the second-stage reaction unit is used for carrying out second-stage reaction and second separation on the supplemented mixed gas of the hydrogen, the first gas-phase material and the circulating gas B to obtain a second gas-phase material and a second hydrocarbon product;
the gas circulation unit is used for taking part of the second gas-phase material as circulation gas, and the circulation gas is completely taken as the circulation gas A and introduced into the first-stage reaction unit, or the circulation gas is divided into the circulation gas A and the circulation gas B and respectively introduced into the first-stage reaction unit and the second-stage reaction unit.
10. The system of claim 9, wherein the first stage reaction unit comprises a first stage reaction device and a first separation device; the second-stage reaction unit comprises a second reaction device and a second separation device; the gas circulation unit includes a circulation compressor.
11. The system of claim 10, wherein the first stage reaction device is a fixed bed reactor;
and/or the second-stage reaction device is a fixed bed reactor;
and/or the first separation device comprises 2-3 separation tanks connected in series;
and/or the second separation device comprises 2-3 separation tanks connected in series;
preferably, the first-stage reaction device comprises 1-4 fixed bed reactors connected in parallel;
preferably, the second-stage reaction device comprises 1-2 fixed bed reactors connected in parallel.
12. The system of claim 11, wherein the fixed bed reactor is a tubular fixed bed reactor;
preferably, a heat exchange device is arranged in the fixed bed reactor of the first-stage reaction device.
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