CN107721819B - Method for reducing energy consumption and water consumption of system for preparing methanol from synthesis gas and system for preparing methanol from synthesis gas - Google Patents
Method for reducing energy consumption and water consumption of system for preparing methanol from synthesis gas and system for preparing methanol from synthesis gas Download PDFInfo
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- CN107721819B CN107721819B CN201610665653.0A CN201610665653A CN107721819B CN 107721819 B CN107721819 B CN 107721819B CN 201610665653 A CN201610665653 A CN 201610665653A CN 107721819 B CN107721819 B CN 107721819B
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- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 title claims abstract description 138
- 238000003786 synthesis reaction Methods 0.000 title claims abstract description 85
- 230000015572 biosynthetic process Effects 0.000 title claims abstract description 84
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 44
- 238000000034 method Methods 0.000 title claims abstract description 32
- 238000005265 energy consumption Methods 0.000 title claims abstract description 18
- 239000007795 chemical reaction product Substances 0.000 claims abstract description 116
- 239000007788 liquid Substances 0.000 claims abstract description 111
- 239000000047 product Substances 0.000 claims abstract description 98
- 238000001816 cooling Methods 0.000 claims abstract description 90
- 238000000926 separation method Methods 0.000 claims abstract description 64
- 239000002994 raw material Substances 0.000 claims abstract description 55
- 239000007791 liquid phase Substances 0.000 claims abstract description 50
- 239000012071 phase Substances 0.000 claims abstract description 42
- 238000001704 evaporation Methods 0.000 claims abstract description 31
- 230000008020 evaporation Effects 0.000 claims abstract description 31
- 239000002826 coolant Substances 0.000 claims abstract description 29
- 238000002360 preparation method Methods 0.000 claims abstract description 5
- 239000000463 material Substances 0.000 claims description 19
- 238000006243 chemical reaction Methods 0.000 claims description 17
- 230000008569 process Effects 0.000 claims description 12
- 239000007789 gas Substances 0.000 description 102
- 230000000052 comparative effect Effects 0.000 description 11
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 9
- 239000003054 catalyst Substances 0.000 description 9
- 238000009833 condensation Methods 0.000 description 9
- 230000005494 condensation Effects 0.000 description 9
- 229910002092 carbon dioxide Inorganic materials 0.000 description 7
- 239000002737 fuel gas Substances 0.000 description 7
- 229910052739 hydrogen Inorganic materials 0.000 description 7
- 239000001257 hydrogen Substances 0.000 description 7
- 238000010992 reflux Methods 0.000 description 6
- 238000002156 mixing Methods 0.000 description 5
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 4
- 239000001569 carbon dioxide Substances 0.000 description 4
- 229910002091 carbon monoxide Inorganic materials 0.000 description 4
- 150000002431 hydrogen Chemical class 0.000 description 4
- 239000010949 copper Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000010926 purge Methods 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 241000183024 Populus tremula Species 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 229910052593 corundum Inorganic materials 0.000 description 1
- 230000006837 decompression Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006356 dehydrogenation reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 229910001845 yogo sapphire Inorganic materials 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
- C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
Abstract
The invention relates to the field of industrial methanol preparation, and discloses a method for reducing energy consumption and water consumption of a system for preparing methanol from synthesis gas and a system for preparing methanol from synthesis gas. The method comprises the steps of reacting a synthesis gas raw material to obtain a reaction product containing methanol, sequentially carrying out primary cooling, secondary cooling and gas-liquid separation on the reaction product, carrying out flash evaporation on a liquid-phase product obtained by the gas-liquid separation, and condensing a gas-phase product after the flash evaporation, wherein the primary cooling mode comprises the following steps: the reaction product exchanges heat with the synthesis gas raw material and a liquid-phase product obtained by gas-liquid separation respectively; the condensed cooling medium is provided by the gas-phase product obtained by gas-liquid separation. The system comprises a reactor, a primary cooling unit, a secondary cooling unit, a gas-liquid separator, a flash tower and a condenser which are sequentially connected, wherein the primary cooling unit comprises a first heat exchanger and a second heat exchanger, and a gas-phase product outlet of the gas-liquid separator is connected with a cooling medium inlet of the condenser. The invention can save the consumption of steam and circulating water.
Description
Technical Field
The invention relates to the field of methanol preparation from industrial synthesis gas, in particular to a method for reducing energy consumption of a system for preparing methanol from synthesis gas and a system for preparing methanol from synthesis gas.
Background
The industrial methanol is prepared by reacting synthesis gas containing carbon monoxide, carbon dioxide and hydrogen under the action of a certain temperature, pressure and catalyst, cooling, gas-liquid separation, filtering, washing, rectification and the like, reaction products are obtained, although the prior methanol preparation process also properly recovers reaction heat, the energy consumption and water consumption of cooling and rectification are still large for a large-scale methanol synthesis device (a large amount of electric energy (accounting for 30 percent of the total energy consumption of the device) is still consumed after preheating inlet gas at an outlet of a reactor), meanwhile, during flash evaporation, about 0.15t of steam is consumed for producing one ton of methanol, the steam needs to be further reduced, and the circulating water consumption for condensing the gas after flash evaporation is also large.
Disclosure of Invention
The invention aims to overcome the defects of high energy consumption and water consumption in the prior art, and provides a method and a system for preparing methanol from synthesis gas, which can improve the energy efficiency of the system and reduce the water consumption.
In order to achieve the above object, the present invention provides a method for reducing energy consumption and water consumption of a system for preparing methanol from synthesis gas, comprising: reacting a synthesis gas raw material to obtain a reaction product containing methanol, sequentially carrying out primary cooling, secondary cooling and gas-liquid separation on the reaction product, carrying out flash evaporation on a liquid-phase product obtained by gas-liquid separation of the reaction product, and condensing a gas-phase product after the flash evaporation, wherein the primary cooling mode is as follows: the reaction product is divided into two parts to respectively exchange heat with the synthesis gas raw material and the liquid phase product obtained by gas-liquid separation of the reaction product, so that the temperature of the liquid phase product obtained by gas-liquid separation of the synthesis gas raw material and the reaction product is increased and the temperature of the reaction product is reduced; the cooling medium used for condensing the gas-phase product after the flash evaporation is partially or completely provided by the gas-phase product obtained by gas-liquid separation of the reaction product.
The invention further provides a system for preparing methanol from synthesis gas, which comprises a reactor, a primary cooling unit, a secondary cooling unit, a gas-liquid separator, a flash tower and a condenser which are sequentially connected, wherein the primary cooling unit comprises a first heat exchanger and a second heat exchanger which are used for respectively exchanging heat between reaction products sent out by the reactor and materials entering the reactor and liquid-phase products sent out by the gas-liquid separator, a gas-phase product outlet of the gas-liquid separator is connected with a cooling medium inlet of the condenser, and the reaction products are divided into two parts to respectively exchange heat with synthesis gas raw materials and the liquid-phase products of the gas-liquid separator so as to increase the temperature of the synthesis gas raw materials and the liquid-phase products of the gas-liquid separator and reduce the temperature of the reaction products; the cooling medium used by the condenser is partially or completely provided by the gas-phase product of the gas-liquid separator.
Through the technical scheme, the heat released by the reaction of preparing the methanol from the synthesis gas is recycled and used in the working section needing to be heated (namely the synthesis gas raw material and the liquid-phase product obtained by gas-liquid separation), so that the self-generated heat of the system is effectively recycled, the energy consumption for heating the synthesis gas raw material is saved, the temperature of the gas at the outlet of the reactor needing to be cooled is further reduced due to the heat exchange with the synthesis gas raw material and the liquid-phase product of the gas-liquid separator, the load and the strength of secondary cooling (including air cooling and water cooling) are reduced, and the electricity consumption or the water consumption for the secondary cooling is saved; in addition, the gas-phase product obtained by gas-liquid separation of the reaction product is used as a cooling medium of the condenser, the gas-phase product discharged from the top of the flash tower is condensed, and water is partially or completely replaced by the cooling medium of the condenser, so that the water consumption of the system is further reduced. Therefore, the method or the system can save the consumption of steam and circulating water and reduce energy consumption, thereby improving the energy efficiency of the system as a whole.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic block diagram of a system according to one embodiment of the present invention.
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
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.
The method for reducing the energy consumption and the water consumption of the system for preparing the methanol from the synthesis gas comprises the following steps: reacting a synthesis gas raw material to obtain a reaction product containing methanol, sequentially carrying out primary cooling, secondary cooling and gas-liquid separation on the reaction product, carrying out flash evaporation on a liquid-phase product obtained by gas-liquid separation of the reaction product, and condensing a gas-phase product after the flash evaporation, wherein the primary cooling mode is as follows: the reaction product is divided into two parts to respectively exchange heat with the synthesis gas raw material and the liquid phase product obtained by gas-liquid separation of the reaction product, so that the temperature of the liquid phase product obtained by gas-liquid separation of the synthesis gas raw material and the reaction product is increased and the temperature of the reaction product is reduced; the cooling medium used for condensing the gas-phase product after the flash evaporation is partially or completely provided by the gas-phase product obtained by gas-liquid separation of the reaction product.
In the present invention, the temperature of the reaction product is usually 280-290 ℃, the primary cooling of the reaction product is heat exchange, and the temperature of the reaction product after the primary cooling heat exchange (if the reaction product is divided into a plurality of portions to be respectively heat exchanged with different materials, the temperature refers to the temperature after the reaction products of each portion are mixed after the heat exchange) is reduced by at least 130-160 ℃ (for example, 190-200 ℃ reduction). The heat released by the methanol synthesis reaction can be effectively recovered by primary cooling in a heat exchange mode, so that the strength and load of secondary cooling are reduced, and the energy consumption and water consumption of the system are saved. And (4) the reaction product after heat exchange enters a secondary cooling step.
In a preferred embodiment of the present invention, the primary cooling method is: exchanging heat between one part of the reaction product and the synthesis gas raw material at 70-80 ℃ to increase the temperature of the synthesis gas raw material to the temperature required by the reaction, exchanging heat between the other part of the reaction product and the liquid phase product obtained by gas-liquid separation of the reaction product to increase the temperature of the liquid phase product obtained by gas-liquid separation of the reaction product to 155-165 ℃, mixing the two parts of the reaction products again after heat exchange, wherein the temperature after mixing is 90-100 ℃.
Wherein, generally, the synthesis gas raw material for carrying out the reaction is obtained by mixing a fresh synthesis gas raw material and a synthesis gas raw material circulated in the system. The temperature of the fresh synthesis gas feed is typically 140-160 ℃ and the temperature of the recycle synthesis gas feed to the system is typically 40-55 ℃.
In the present invention, the synthesis gas feed temperature to the reactor is preferably 233-. The reaction pressure is preferably 7 to 8 MPa. The reaction temperature is usually 275 ℃ and 285 ℃.
In the present invention, the manner of the secondary cooling is not particularly limited as long as the temperature of the reaction product can be further lowered so that the temperature of the reaction product is lowered to a temperature particularly suitable for gas-liquid separation (e.g., 40 to 55 ℃), and for example, the secondary cooling may be performed by air cooling and/or water cooling.
Preferably, when the temperature of the reaction product after heat exchange (primary cooling) is 90 to 100 ℃, the secondary cooling is performed by sequentially performing air cooling and water cooling. Wherein, the air cooling can reduce the temperature of the reaction product to 60-70 ℃, has no special requirement on the specific operation of the air cooling, and can be implemented by an air cooler. The water cooling can further reduce the temperature of the reaction product to 40-55 ℃, has no special requirement on the specific operation of water cooling, and can be implemented by a water cooler.
In the present invention, the conditions for the gas-liquid separation of the reaction product are not particularly limited, and for example, high-pressure gas-liquid separation may be employed, and therefore, it is preferable that the conditions for the gas-liquid separation include a temperature of 40 to 55 ℃ and a pressure of 7.2 to 7.9 MPa. More preferably, the gas-liquid separation conditions include a temperature of 40 to 45 ℃ and the gas-liquid separation temperature is controlled within the range so as to condense as much methanol as possible, and further reduce the amount of circulating water for condensation at the top of the flash column (the cooling medium may be substantially entirely supplied from the gas-phase product obtained by gas-liquid separation of the reaction product having a temperature of preferably 40 to 45 ℃). Generally, in the prior art, a part of the gas phase product (mainly unreacted synthesis gas) obtained by gas-liquid separation of the reaction product (which may be compressed) is recycled as the synthesis gas raw material (usually, a certain amount of fresh synthesis gas raw material needs to be mixed with the gas to reduce the partial pressure of inert gas in the recycle gas and ensure the carbon-hydrogen ratio of the synthesis gas raw material undergoing reaction), and a part of the gas phase product is recovered as purge gas for dehydrogenation.
However, in the present invention, the gas phase product (mainly unreacted synthesis gas) obtained by gas-liquid separation of these reaction products is used at least partially or entirely as a cooling medium in a condenser connected to a flash tower before being used for circulating synthesis gas, and the gas phase product after being used as a cooling medium in the condenser is increased in temperature and then pressurized or mixed with a portion not used as a cooling medium and then pressurized and mixed with a fresh synthesis gas raw material to be used as a synthesis gas raw material.
In the present invention, there is no particular requirement for the flash conditions, for example, flash conditions include: the temperature is 93-96 deg.C, and the pressure is 0.25-0.35 MPa. When high-pressure gas-liquid separation is adopted, the pressure of a liquid-phase product obtained by gas-liquid separation is higher, and the liquid-phase product is subjected to pressure reduction operation before flash evaporation so as to enable the material to be at a pressure more suitable for flash evaporation. Therefore, in order to perform the flash evaporation more efficiently, the method further comprises a step of decompressing (which may be performed by means of a decompression valve) the liquid-phase product obtained by the gas-liquid separation before the flash evaporation. The pressure reduction is carried out to reduce the pressure of the liquid phase product obtained by gas-liquid separation to 0.25-0.35MPa (the temperature is about 93-96 ℃). The reduced pressure followed by flash evaporation is particularly advantageous for removing impurities (e.g., H) from methanol-containing materials2、CO2CO and CH4Etc.). Through heat exchange, flash evaporation is not neededAdditional steam is provided.
In the invention, the liquid phase obtained by flash evaporation is the methanol product, the gas phase can be further condensed, the condensed liquid is used as reflux liquid to return to flash evaporation, and the gas phase discharged after condensation can be used as fuel gas. As described above, the cooling medium used for condensation is a gas-phase product obtained by gas-liquid separation of the reaction product (i.e., the cooling medium is partially or entirely supplied from the gas-phase product obtained by gas-liquid separation of the reaction product).
Therefore, the gas-phase product obtained by gas-liquid separation of the reaction product is used as the cooling medium of the condenser, the gas-phase product coming out from the top of the flash tower is condensed, and the water is partially or completely replaced by the cooling medium which is usually used as the condenser, so that the water consumption of the system is further reduced.
In the present invention, the synthesis gas feedstock may be conventionally used synthesis gas containing hydrogen, carbon monoxide and carbon dioxide, for example, the molar ratio of the three may be (25-30): (10-12): 1. carbon to hydrogen ratio (H)2-CO2)/(CO+CO2) It may be 2.05 to 2.15 (molar ratio). Furthermore, the reaction is carried out in the presence of a catalyst, which may be any of the conventional catalysts, which the skilled person is able to select, such as copper-based catalysts (Cu/Zn/Al)2O3) And will not be described herein.
As shown in fig. 1, the present invention provides a system for preparing methanol from synthesis gas, comprising: reactor 1, primary cooling unit, secondary cooling unit, vapour and liquid separator 4, flash column 5 and the condenser 7 that connects gradually, wherein, primary cooling unit includes: the reaction product at the outlet of the reactor 1 is respectively subjected to heat exchange with the material entering the reactor and the liquid-phase product at the bottom of the gas-liquid separator 4 by the first heat exchanger 2a and the second heat exchanger 2b, and the gas-phase product outlet of the gas-liquid separator 4 is connected with the cooling medium inlet of the condenser 7 (so that the gas-phase product of the gas-liquid separator 4 is introduced into the condenser 7 as the cooling medium). Wherein, the connection in sequence means that the material outlet of the previous unit is connected with the material inlet of the next unit, for example, the material outlet of the gas-liquid separator 4 is connected with the material inlet of the flash tower 5.
Wherein, the reaction product is divided into two parts to respectively exchange heat with the synthesis gas raw material and the liquid phase product of the gas-liquid separator 4, so that the temperature of the synthesis gas raw material and the liquid phase product of the gas-liquid separator 4 is increased and the temperature of the reaction product is reduced; the cooling medium used by the condenser 7 is partly or wholly supplied by the gas-phase product of the gas-liquid separator 4.
According to a preferred embodiment of the present invention, the secondary cooling unit includes an air cooler 3a and a water cooler 3b connected in series. The second heat exchanger 2b is preferably a high pressure heat exchanger.
According to a preferred embodiment of the present invention, the gas-liquid separator may be a high-pressure gas-liquid separator. Generally, a part of the gaseous product discharged from the gas-liquid separator is recycled as a synthesis gas raw material (which may be compressed by the recycle gas compressor 8) and a part is recovered as purge gas to remove hydrogen, and therefore, the system may further comprise a pipe for recycling the gaseous product discharged from the gas-liquid separator to the reactor and the recycle gas compressor 8 for compressing the recycle gas. The cooling medium used in the condenser 7 is partly or entirely supplied from the gaseous product discharged from the gas-liquid separator, and the gaseous product after condensation, the temperature of which is raised, can be recycled to be mixed with fresh synthesis gas raw material as synthesis gas raw material, and therefore, the gaseous product in the condenser 7 can be recycled as synthesis gas raw material.
According to the present invention, in order to more efficiently perform the flash evaporation and thus more efficiently remove impurities from the material, the system may further comprise a pressure reducing valve 6 disposed between the gas-liquid separator and the flash tower (specifically, disposed downstream of the second heat exchanger 2b, i.e., between the second heat exchanger 2b and the flash tower 5) for reducing the pressure of the liquid-phase product sent out from the gas-liquid separator.
According to the invention, the system comprises a condenser 7 for condensing the gas coming out of the flash column. The methanol product is discharged from the bottom outlet of the flash column, the gas at the top of the flash column can be condensed by the condenser 7 to be used as fuel gas, and the condensed liquid is returned to the flash column as reflux.
According to the invention, internal heat extraction and steam generation can be obtained from the reactor by arranging the tubes and can be used for other purposes.
The use method of the system of the invention can be as follows: reacting a synthesis gas raw material in a reactor 1 to obtain a reaction product containing methanol, introducing the reaction product into a primary cooling unit, a secondary cooling unit (such as an air cooler 3a and a water cooler 3b) and a gas-liquid separator 4 in sequence, reducing the pressure of a liquid phase product discharged from the gas-liquid separator through a pressure reducing valve 6, introducing the reduced pressure material into a flash tower 5 for flash evaporation, condensing gas discharged from the top of the flash tower through a condenser 7 (introducing a gas phase product discharged from the gas-liquid separator into the condenser as a cooling medium), returning the condensed liquid serving as reflux liquid to the flash tower, and taking the gas discharged from the condenser as fuel gas, wherein, part or all of the reaction products exchange heat with the synthesis gas raw material and the liquid phase products through the first heat exchanger 2a and the second heat exchanger 2b respectively, so that the temperature of the synthesis gas raw material and the liquid phase products is increased and the temperature of the reaction products is reduced.
The method or system of the present invention is particularly suitable for the synthesis gas preparation of MTO grade methanol, and may further comprise a purification step or unit for further purification of methanol, which is not described in detail herein.
The present invention will be described in detail below by way of examples. In the following examples, the synthesis gas feedstock is a mixed gas of hydrogen, carbon monoxide and carbon dioxide, wherein the molar ratio of hydrogen, carbon monoxide and carbon dioxide is 27:11: 1; the volume of the reactor was 280m3(annual yield of methanol is about 120 ten thousand tons); the catalyst is Cu/Zn/Al2O3From Johnson Mamley, UK, CatALCOJM51-9, the amount of catalyst used is 1 ton per 200 tons of methanol produced.
Example 1
The process is shown in fig. 1, wherein,
(1) reaction: preheating (heat exchange) a synthesis gas raw material to 234 ℃, continuously introducing the synthesis gas raw material into a reactor according to a flow of 167t/h, and reacting in the presence of a catalyst, wherein the reaction pressure is 7.6 MPa;
(2) primary cooling: exchanging heat of the reaction product (285 ℃) obtained in the step (1) by a heat exchanger;
(3) secondary cooling: cooling the reaction product subjected to primary cooling and heat exchange to 65 ℃ by an air cooler, and then cooling to 53 ℃ by a water cooler;
(4) gas-liquid separation: the product after secondary cooling enters a gas-liquid separator for gas-liquid separation (7.7MPa) to obtain a liquid phase product and a gas phase product;
(5) and (3) reducing pressure: reducing the pressure of the liquid phase product to 0.32MPa through a pressure reducing valve;
(6) flash evaporation: introducing the decompressed material into a flash tower for flash evaporation, wherein the temperature of the material entering the flash tower is 94 ℃, the temperature at the top of the flash tower is 50 ℃, the pressure is 0.27MPa, MTO-grade methanol (the content of the methanol is 95 weight percent) is arranged at the bottom of the flash tower, the temperature is 96 ℃, and the flow of 150t/h is led out of the flash tower;
(7) condensation: gas phase products (53 ℃) obtained by gas-liquid separation are used as part of cooling media (meanwhile, part of circulating water is used for condensing gas (89 ℃) discharged from the top of the flash tower, liquid (50 ℃) obtained after condensation is used as reflux liquid to return to flash, and gas phase discharged after condensation is used as fuel gas;
wherein, the mode of once cooling heat transfer does: a part of the reaction products (84.8 wt% of the total reaction products) and the synthesis gas raw material with the temperature of 77 ℃ are subjected to heat exchange (BEM type heat exchanger, the same is applied hereinafter) so that the temperature of the synthesis gas raw material introduced into the reactor is increased to 234 ℃ and the temperature of the part of the reaction products is reduced to 95 ℃, the other part of the reaction products (15.2 wt% of the total reaction products) and the liquid phase product of gas-liquid separation are subjected to heat exchange (BEM type high pressure heat exchanger, the same is applied hereinafter) so that the temperature of the liquid phase product of gas-liquid separation is increased to 163 ℃ and the temperature of the part of the reaction products is reduced to 62 ℃, and the two parts of the reaction products after heat exchange are mixed (the temperature is 91 ℃) and.
In this process, the amount of preheated steam at 0.46MPa (calculated from Aspen Plus, the same below), the amount of circulating water used in the system and the unit energy efficiency (calculated with reference to standard GBT2589-2008, the same below) are shown in Table 1, respectively.
Example 2
The process is shown in fig. 1, wherein,
(1) reaction: heating (exchanging heat) a synthesis gas raw material to 233 ℃, continuously introducing the synthesis gas raw material into a reactor according to a flow of 167t/h, and reacting in the presence of a catalyst, wherein the reaction pressure is 8 MPa;
(2) primary cooling: exchanging heat of the reaction product (284 ℃) obtained in the step (1) by means of a heat exchanger;
(3) secondary cooling: cooling the reaction product subjected to primary cooling and heat exchange to 60 ℃ by an air cooler, and then cooling to 45 ℃ by a water cooler;
(4) gas-liquid separation: the product after secondary cooling enters a gas-liquid separator for gas-liquid separation (7.2MPa) to obtain a liquid phase product and a gas phase product;
(5) and (3) reducing pressure: reducing the pressure of the liquid phase product to 0.35MPa through a pressure reducing valve;
(6) flash evaporation: introducing the decompressed material into a flash tower for flash evaporation, wherein the temperature of the material entering the flash tower is 93 ℃, the temperature at the top of the tower is 50 ℃, the pressure is 0.3MPa, MTO-grade methanol (the content of the methanol is 95 weight percent) is arranged at the bottom of the tower, the temperature is 96 ℃, and the flow of 150t/h is led out of the flash tower;
(7) condensation: condensing gas (89 ℃) discharged from the top of the flash tower by taking a gas-phase product (45 ℃) obtained by gas-liquid separation as a cooling medium, returning the condensed liquid (50 ℃) to flash evaporation as reflux liquid, and using the condensed discharged gas as fuel gas;
wherein, the mode of once cooling heat transfer does: heat exchange is carried out between part of reaction products (accounting for 86 weight percent of the total reaction products) and the synthesis gas raw material with the temperature of 70 ℃ so that the temperature of the synthesis gas raw material introduced into the reactor is increased to 233 ℃ and the temperature of the part of reaction products is reduced to 94 ℃, heat exchange is carried out between the other part of reaction products (accounting for 14 weight percent of the total reaction products) and the liquid-phase product of gas-liquid separation so that the temperature of the liquid-phase product of gas-liquid separation is increased to 155 ℃ and the temperature of the part of reaction products is reduced to 64 ℃, and the two parts of reaction products after heat exchange are mixed (the temperature is 90 ℃) and enter secondary cooling.
In the process, the amount of preheated steam at 0.46MPa, the amount of circulating water used in the system, and the unit energy efficiency are shown in Table 1, respectively.
Example 3
The process is shown in fig. 1, wherein,
(1) reaction: heating (exchanging heat) a synthesis gas raw material to 237 ℃, continuously introducing the synthesis gas raw material into a reactor according to a flow of 167t/h, and reacting in the presence of a catalyst, wherein the reaction pressure is 7 MPa;
(2) primary cooling: exchanging heat of the reaction product (286 ℃) obtained in the step (1) by a heat exchanger;
(3) secondary cooling: cooling the reaction product subjected to primary cooling and heat exchange to 70 ℃ by an air cooler, and then cooling to 40 ℃ by a water cooler;
(4) gas-liquid separation: the product after secondary cooling enters a gas-liquid separator for gas-liquid separation (7.9MPa) to obtain a liquid phase product and a gas phase product;
(5) and (3) reducing pressure: reducing the pressure of the liquid phase product to 0.3MPa through a pressure reducing valve;
(6) flash evaporation: introducing the decompressed material into a flash tower for flash evaporation, wherein the temperature of the material entering the flash tower is 96 ℃, the temperature of the tower top (fuel gas) is 50 ℃, the pressure is 0.25MPa, the tower bottom is MTO-grade methanol (the content of the methanol is 95 weight percent), the temperature is 96 ℃, and the material is led out of the flash tower at the flow rate of 150 t/h;
(7) condensation: condensing gas (89 ℃) discharged from the top of the flash tower by taking a gas-phase product (40 ℃) obtained by gas-liquid separation as a cooling medium, returning the condensed liquid (50 ℃) to flash evaporation as reflux liquid, and using the condensed discharged gas as fuel gas;
wherein, the mode of once cooling heat transfer does: heat exchange is carried out between part of reaction products (accounting for 84 weight percent of the total reaction products) and the synthesis gas raw material with the temperature of 80 ℃ so that the temperature of the synthesis gas raw material introduced into the reactor is increased to 237 ℃ and the temperature of the part of reaction products is reduced to 98 ℃, heat exchange is carried out between the other part of reaction products (accounting for 16 weight percent of the total reaction products) and the liquid-phase product of gas-liquid separation so that the temperature of the liquid-phase product of gas-liquid separation is increased to 165 ℃ and the temperature of the part of reaction products is reduced to 61 ℃, and the two parts of reaction products after heat exchange are mixed (the temperature is 96 ℃) and enter secondary cooling.
In the process, the amount of preheated steam at 0.46MPa, the amount of circulating water used in the system, and the unit energy efficiency are shown in Table 1, respectively.
Example 4
Methanol was prepared according to the method of example 1, except that: the primary cooling heat exchange mode is as follows: heat exchange is carried out between part of reaction products (accounting for 85 weight percent of the total reaction products) and the synthesis gas raw material with the temperature of 69 ℃ so that the temperature of the synthesis gas raw material introduced into the reactor is increased to 234 ℃ and the temperature of the part of reaction products is reduced to 92 ℃, heat exchange is carried out between the other part of reaction products (accounting for 15 weight percent of the total reaction products) and the liquid-phase product of gas-liquid separation so that the temperature of the liquid-phase product of gas-liquid separation is increased to 153 ℃ and the temperature of the part of reaction products is reduced to 70 ℃, and the two parts of reaction products after primary cooling and heat exchange are mixed (the temperature is 88 ℃) and enter secondary cooling. In the process, the amount of preheated steam of 0.46MPa, the amount of circulating water used in the system and the unit energy consumption are shown in Table 1.
Comparative example 1
Methanol was prepared according to the method of example 1, except that: the primary cooling heat exchange mode is as follows: the heat exchange between part of the reaction product (95 wt% of the total reaction product) and the synthesis gas raw material with the temperature of 77 deg.C makes the temperature of the synthesis gas raw material introduced into the reactor raise to 234 deg.C and the temperature of the part of the reaction product lower to 106 deg.C, and after mixing the part of the reaction product with another part of the reaction product (with the temperature of 102 deg.C), the mixture enters into secondary cooling, at this time, 0.46MPa of preheating steam is additionally consumed in the flash evaporation. In the process, the amount of preheated steam of 0.46MPa, the amount of circulating water used in the system and the unit energy consumption are shown in Table 1.
Comparative example 2
Methanol was prepared according to the method of example 1, except that: the primary cooling heat exchange mode is as follows: and (3) exchanging heat between part of reaction products (accounting for 50 wt% of the total reaction products) and the liquid-phase products subjected to gas-liquid separation to increase the temperature of the liquid-phase products subjected to gas-liquid separation to 165 ℃ and reduce the temperature of the part of reaction products to 199 ℃, mixing the part of reaction products with the other part of reaction products (the temperature is 197 ℃) and then carrying out secondary cooling. In the process, the amount of the preheated steam of 1.7MPa, the amount of the circulating water used in the system and the unit energy consumption are respectively shown in Table 1.
Comparative example 3
Methanol was prepared according to the method of example 1, except that: and (2) directly carrying out secondary cooling on the reaction product obtained in the step (1) without primary cooling, condensing gas discharged from the top of the flash tower without using a gas-phase product obtained by gas-liquid separation as a cooling medium, and completely using circulating water as the cooling medium. In the process, the amount of the preheated steam of 1.7MPa, the amount of the circulating water used in the system and the unit energy consumption are respectively shown in Table 1.
TABLE 1
| Example numbering | Preheating steam dosage (t/h) | Circulating water volume (t/h) | Unit energy efficiency (%) |
| Example 1 | 0 | 5672 | 76％ |
| Example 2 | 0 | 5966 | 75.9％ |
| Example 3 | 0 | 5666 | 76％ |
| Example 4 | 0 | 6780 | 74.8％ |
| Comparative example 1 | 19 | 7550 | 71.5％ |
| Comparative example 2 | 134(1.7MPa) | 12000 | 54％ |
| Comparative example 3 | 256(1.7MPa) | 12000 | 37％ |
As can be seen from the above embodiments, the method or system of the present invention can effectively improve the energy efficiency of the system and reduce the water consumption. In particular, example 1 performs primary cooling (i.e., heat exchange) according to the preferred embodiment of the present invention, while example 4 does not perform according to the preferred embodiment, and it can be seen from the results of comparing example 1 and example 4 that performing primary cooling according to the preferred embodiment of the present invention can further improve the energy efficiency of the system; in addition, the comparative example 1 only exchanges heat between the reaction product and the raw material of the synthesis gas, while the comparative example 2 only exchanges heat between the reaction product and the liquid phase product of the gas-liquid separation, and the results of the comparative example 1 and the comparative examples 1-2 show that only partial heat exchange can not effectively improve the energy efficiency of the system. Comparative example 3 does not perform heat exchange or uses a gas-phase product produced by gas-liquid separation as a cooling medium, so that the energy consumption and the amount of circulating water are significantly higher than those of example 1, and the system energy efficiency is low.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (8)
1. A method for reducing energy consumption and water consumption of a device for preparing methanol from synthesis gas is characterized by comprising the following steps: reacting a synthesis gas raw material to obtain a reaction product containing methanol, sequentially carrying out primary cooling, secondary cooling and gas-liquid separation on the reaction product, carrying out flash evaporation on a liquid-phase product obtained by gas-liquid separation of the reaction product, and condensing a gas-phase product after the flash evaporation, wherein the primary cooling mode is as follows: exchanging heat between part of reaction products and the synthesis gas raw material at 70-80 ℃ so as to increase the preheating temperature of the synthesis gas raw material to the temperature required by the reaction; the other part of the reaction product exchanges heat with the liquid phase product obtained by gas-liquid separation of the reaction product, so that the temperature of the liquid phase product obtained by gas-liquid separation of the reaction product is raised to 155-165 ℃, and the two parts of the reaction product are mixed after heat exchange, and the mixed temperature is 90-100 ℃; the cooling medium used for condensing the flash-evaporated gas-phase product is partially or completely provided by the gas-phase product obtained by gas-liquid separation of the reaction product;
wherein the temperature of the synthesis gas raw material entering the reactor is 233-237 ℃; the reaction temperature is 275-285 ℃; the gas-liquid separation temperature of the reaction product is 40-55 ℃; the flash conditions include: the temperature is 93-96 deg.C, and the pressure is 0.25-0.35 MPa.
2. The method as claimed in claim 1, wherein the temperature of the reaction product is 280-290 ℃.
3. The process according to claim 1, wherein the reaction pressure is 7 to 8 MPa.
4. The method of claim 1, wherein the secondary cooling is performed by sequentially performing air cooling and water cooling.
5. The process as claimed in claim 1, wherein the gas-liquid separation conditions of the reaction product include a pressure of 7.2 to 7.9 MPa.
6. An apparatus for the preparation of methanol from synthesis gas according to any of the claims 1 to 5, characterized in that it comprises a reactor (1), a primary cooling unit, a secondary cooling unit, a gas-liquid separator (4), a flash column (5) and a condenser (7) connected in series, wherein the primary cooling unit comprises: a first heat exchanger (2 a) and a second heat exchanger (2 b) which respectively exchange heat between reaction products at the outlet of the reactor (1) and materials entering the reactor and liquid phase products at the bottom of the gas-liquid separator (4), wherein the gas phase product outlet of the gas-liquid separator (4) is connected with a cooling medium inlet of the condenser (7),
wherein, the reaction product is divided into two parts to respectively exchange heat with the synthesis gas raw material and the liquid phase product of the gas-liquid separator (4), so that the temperature of the synthesis gas raw material and the liquid phase product of the gas-liquid separator (4) is increased and the temperature of the reaction product is reduced; the cooling medium used by the condenser (7) is partially or completely provided by the gas-phase product of the gas-liquid separator (4).
7. The apparatus of claim 6, wherein the secondary cooling unit comprises an air cooler (3 a) and a water cooler (3 b) connected in series.
8. The device according to claim 6 or 7, wherein the second heat exchanger (2 b) is a high pressure heat exchanger, the device further comprising a pressure reducing valve (6) arranged downstream of the second heat exchanger (2 b).
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1144214A (en) * | 1995-08-25 | 1997-03-05 | 中国科学院山西煤炭化学研究所 | Method for synthesizing methyl alcohol |
| CN102433169A (en) * | 2011-08-30 | 2012-05-02 | 中国石油化工股份有限公司 | Low temperature methanol washing technology |
| CN105481646A (en) * | 2014-09-15 | 2016-04-13 | 中国石油天然气股份有限公司 | Refrigeration method for methanol synthesis and separation |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1144214A (en) * | 1995-08-25 | 1997-03-05 | 中国科学院山西煤炭化学研究所 | Method for synthesizing methyl alcohol |
| CN102433169A (en) * | 2011-08-30 | 2012-05-02 | 中国石油化工股份有限公司 | Low temperature methanol washing technology |
| CN105481646A (en) * | 2014-09-15 | 2016-04-13 | 中国石油天然气股份有限公司 | Refrigeration method for methanol synthesis and separation |
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