阅读说明：本技术 一种集成余热制冷的煤制天然气和甲醇多联产系统及方法 (Coal-based natural gas and methanol poly-generation system and method integrating waste heat refrigeration ) 是由 钱宇 刘兆利 史克年 杨思宇 于 2021-07-26 设计创作，主要内容包括：本发明公开了一种集成余热制冷的煤制天然气和甲醇多联产系统,包括依次连接的鲁奇气化单元、酸性气体脱除单元、深冷分离单元、甲烷化单元、甲醇合成单元、甲醇精馏单元,溴化锂余热制冷单元；所述甲烷化单元的空冷高温物流与溴化锂余热制冷单元的余热入口连接,所述溴化锂余热制冷单元的冷水出口与酸性气体脱除单元的冷却水进口连接；或所述溴化锂余热制冷单元的冷水出口同时与深冷分离单元的冷却水进口、酸性气体脱除单元的冷却水进口连接。本发明还公开了一种集成余热制冷的煤制天然气和甲醇多联产方法。本发明减少了废热的排放和额外冷却水的消耗以及余热制冷所需的电耗。(The invention discloses a coal-based natural gas and methanol poly-generation system integrating waste heat refrigeration, which comprises a Lurgi gasification unit, an acid gas removal unit, a cryogenic separation unit, a methanation unit, a methanol synthesis unit, a methanol rectification unit and a lithium bromide waste heat refrigeration unit which are sequentially connected; the air-cooled high-temperature material flow of the methanation unit is connected with a waste heat inlet of a lithium bromide waste heat refrigerating unit, and a cold water outlet of the lithium bromide waste heat refrigerating unit is connected with a cooling water inlet of an acid gas removal unit; or a cold water outlet of the lithium bromide waste heat refrigerating unit is simultaneously connected with a cooling water inlet of the deep cooling separation unit and a cooling water inlet of the acid gas removing unit. The invention also discloses a coal-based natural gas and methanol poly-generation method integrating waste heat refrigeration. The invention reduces the discharge of waste heat, the consumption of extra cooling water and the power consumption required by waste heat refrigeration.)

1. A coal-based natural gas and methanol poly-generation system integrating waste heat refrigeration comprises a Lurgi gasification unit, an acid gas removal unit, a cryogenic separation unit, a methanation unit, a methanol synthesis unit and a methanol rectification unit which are connected in sequence, and is characterized by further comprising a lithium bromide waste heat refrigeration unit;

the air-cooled high-temperature material flow of the methanation unit is connected with a waste heat inlet of a lithium bromide waste heat refrigerating unit, and a cold water outlet of the lithium bromide waste heat refrigerating unit is connected with a cooling water inlet of an acid gas removal unit; or a cold water outlet of the lithium bromide waste heat refrigerating unit is simultaneously connected with a cooling water inlet of the cryogenic separation unit and a cooling water inlet of the acid gas removal unit;

the lithium bromide waste heat refrigerating unit comprises a generator, a condenser, an evaporator, an absorber, a solution heat exchanger and a solvent pump;

a water vapor outlet of the generator is connected with a water vapor inlet of the condenser, a condensed water outlet of the condenser is connected with a condensed water inlet of the evaporator through an expansion valve, a water vapor outlet of the evaporator is connected with a water vapor inlet of the absorber, and a lithium bromide dilute solution outlet of the absorber is connected with a lithium bromide dilute solution inlet of the solution heat exchanger through a solvent pump; the lithium bromide dilute solution outlet of the absorber is also connected with the spray header of the absorber through a pressure reducing valve; a lithium bromide dilute solution outlet of the solution heat exchanger is connected with a lithium bromide dilute solution inlet of the generator; the concentrated lithium bromide solution outlet of the generator is connected with the concentrated lithium bromide solution inlet of the solution heat exchanger, and the concentrated lithium bromide solution outlet of the solution heat exchanger is connected with the spray header of the absorber through a pressure reducing valve.

2. The integrated waste heat refrigerated coal-derived natural gas and methanol poly-generation system of claim 1, wherein the methanation unit comprises a first methanation reactor, a second methanation reactor, a third methanation reactor, a fourth methanation reactor, a first waste heat boiler, a second waste heat boiler, a third methanation reactor outlet heat exchanger and a dehydration separation tank;

the system comprises a first methanation reactor, a second methanation reactor, a third methanation reactor, a fourth methanation reactor, a lithium bromide waste heat refrigeration unit generator and a dehydration separation tank, wherein a gas outlet of the first methanation reactor is connected with a hot end inlet of the first waste heat boiler, a hot end outlet of the first methanation reactor is connected with a gas inlet of the second methanation reactor, a gas outlet of the second methanation reactor is connected with a hot end inlet of the second waste heat boiler, a hot end outlet of the second waste heat boiler is connected with a gas inlet of the third methanation reactor, a gas outlet of the third methanation reactor is connected with a hot end inlet of the fourth methanation reactor, a gas outlet of the third methanation reactor is connected with a gas outlet of the dehydration separation tank, and a gas outlet of the fourth methanation reactor is connected with a gas outlet of the third methanation reactor.

3. The integrated waste heat refrigerated coal-based natural gas and methanol polygeneration system of claim 1, wherein the absorber is a horizontal tube falling film absorber.

4. The integrated waste heat refrigerated coal-based natural gas and methanol polygeneration system of claim 1, wherein the generator is a submerged generator.

5. The coal-based natural gas and methanol poly-generation system integrating waste heat refrigeration as claimed in claim 1, wherein the mass concentration of the lithium bromide dilute solution is 40% -60%.

6. The coal-based natural gas and methanol poly-generation system integrating waste heat refrigeration as claimed in claim 1, wherein the mass concentration of the lithium bromide concentrated solution is 50% -65%.

7. The coal-based natural gas and methanol poly-generation method based on the integrated waste heat refrigeration of the coal-based natural gas and methanol poly-generation system based on any one of claims 1 to 6 is characterized by comprising the following steps of:

the lump coal and oxygen enter a Lurgi gasification unit to form a crude synthesis gas, and the crude synthesis gas passes through the acid gas unit to remove CO in the crude synthesis gas₂And H₂Separating S gas to form clean synthesis gas; the clean synthesis gas is divided into two parts from a synthesis gas outlet of the acid gas unit, and one part of the clean synthesis gas enters the methanation unit to synthesize a natural gas product; the other part of the clean synthesis gas enters a cryogenic separation unit, and methane is separated out as a natural gas product after the temperature of the synthesis gas is reduced by a cooler; the residual synthesis gas except methane enters methanol synthesis and methanol concentrateA distillation unit for preparing refined methanol;

the methanated air-cooled high-temperature material flow enters a generator of a lithium bromide waste heat refrigerating unit, heat is provided to enable refrigerant water to be evaporated, evaporated superheated steam is condensed in a condenser, generated condensed water is cooled and depressurized through an expansion valve to refrigerate water in the evaporator, and therefore cold energy carrier material flow is prepared, the cold energy carrier material flow enters an acid gas removing unit and a deep cooling separation unit after passing through a cold water outlet of the evaporator, and cold energy contained in the cold energy carrier material flow is supplied to the acid gas removing unit and the deep cooling separation unit.

8. The coal-based natural gas and methanol poly-generation method integrating waste heat refrigeration as claimed in claim 7, wherein the evaporation temperature of the evaporator is 0-6 ℃.

9. The coal-based natural gas and methanol poly-generation method integrating waste heat refrigeration as claimed in claim 7, wherein the condensation temperature of the condenser is 30-45 ℃.

10. The coal-based natural gas and methanol poly-generation method with integrated waste heat refrigeration according to claim 7, characterized in that the temperature interval of the air-cooled high-temperature material flow is 100-200 ℃; the temperature of the cold energy carrier stream is between 2 and 8 ℃.

Technical Field

The invention relates to a coal-based natural gas and methanol poly-generation technology, in particular to a coal-based natural gas and methanol poly-generation system and method integrating waste heat refrigeration.

Background

Natural gas is a clean, safe and convenient high-quality energy, plays an important role in the world energy field all the time, and is widely applied to the fields of chemical industry, power generation and other industries, commerce, civilian use and the like. Methanol is an important organic chemical raw material with large demand, and the methanol plays an important role in the field of carbon chemical industry. Methanol is a cleaner fuel and can be directly blended into gasoline and diesel oil as fuels. China is limited by the resource structure of rich coal, poor oil and little gas, so that the production of chemicals and fuels by coal is an important route. The core of coal-to-chemical and fuel technology is coal gasification, which produces syngas through coal gasification, and the syngas is treated as a production raw material. The lurgi gasifier is a gasifier widely used, but the raw synthesis gas produced by the lurgi gasifier contains a large amount of methane, so that a cryogenic separation unit is required to separate the methane in the synthesis gas as an SNG product in a coal-based natural gas and methanol poly-generation system. The coal-based natural gas co-production methanol poly-generation system specifically comprises the following units: lurgi coal gasification, acid gas removal, methanation, cryogenic separation, methanol synthesis, methanol rectification and the like.

The large-scale poly-generation technology of coal-based natural gas and methanol is always influenced by high energy consumption and incapability of fully utilizing waste heat. Especially the cryogenic units in coal based poly-generation are very energy intensive, such as acid gas removal units and cryogenic separation units. Meanwhile, a plurality of reaction units have much waste heat and need to be cooled by circulating water, such as a methanation unit. The flow diagram of the coal-based natural gas and methanol poly-generation system is shown in figure 1, lump coal passes through a Lurgi gasification unit to generate crude synthesis gas, and the crude synthesis gas passes through an acid gas removal unit to remove CO₂And H₂S forms clean synthetic gas, one part of the clean synthetic gas enters a methanation unit to synthesize natural gas, the other part of the clean synthetic gas enters a cryogenic separation unit, and the cryogenic separation unit is used for separating CH₄The separated natural gas is used as a natural gas product, and the residual synthesis gas enters a methanol synthesis and methanol rectification unit to generate refined methanol.

One of the reasons for the high energy consumption of the acid gas unit is that the raw synthesis gas needs to be cooled step by step before separation, and therefore a certain amount of low-temperature cooling energy of 0-10 ℃ is required for the primary precooling process of the raw synthesis gas. Similarly, the synthesis gas needs to be cooled step by step in the cryogenic separation unit, and a certain amount of low-temperature cold energy of 0-10 ℃ is also needed for primary precooling. In a general poly-generation process of coal-based natural gas and methanol as shown in fig. 1, a refrigeration unit needs a large amount of electric energy to prepare cold energy to meet the cold energy requirements of an acid gas removal unit and a cryogenic separation unit, so that the power consumption is high.

Disclosure of Invention

In order to overcome the defects and shortcomings in the prior art, the invention aims to provide a coal-based natural gas and methanol poly-generation system integrating waste heat refrigeration, so that the load of a refrigeration system is reduced, and the energy consumption is reduced.

The invention also aims to provide a coal-based natural gas and methanol poly-generation method integrating waste heat refrigeration.

The purpose of the invention is realized by the following technical scheme:

a coal-based natural gas and methanol poly-generation system integrating waste heat refrigeration comprises a Lurgi gasification unit, an acid gas removal unit, a cryogenic separation unit, a methanation unit, a methanol synthesis unit, a methanol rectification unit and a lithium bromide waste heat refrigeration unit which are sequentially connected;

the air-cooled high-temperature material flow of the methanation unit is connected with a waste heat inlet of a lithium bromide waste heat refrigerating unit, and a cold water outlet of the lithium bromide waste heat refrigerating unit is connected with a cooling water inlet of an acid gas removal unit; or a cold water outlet of the lithium bromide waste heat refrigerating unit is simultaneously connected with a cooling water inlet of the cryogenic separation unit and a cooling water inlet of the acid gas removal unit;

the lithium bromide waste heat refrigerating unit comprises a generator, a condenser, an evaporator, an absorber, a solution heat exchanger and a solvent pump;

a water vapor outlet of the generator is connected with a water vapor inlet of the condenser, a condensed water outlet of the condenser is connected with a condensed water inlet of the evaporator through an expansion valve, a water vapor outlet of the evaporator is connected with a water vapor inlet of the absorber, and a lithium bromide dilute solution outlet of the absorber is connected with a lithium bromide dilute solution inlet of the solution heat exchanger through a solvent pump; the lithium bromide dilute solution outlet of the absorber is also connected with the spray header of the absorber through a pressure reducing valve; a lithium bromide dilute solution outlet of the solution heat exchanger is connected with a lithium bromide dilute solution inlet of the generator; the concentrated lithium bromide solution outlet of the generator is connected with the concentrated lithium bromide solution inlet of the solution heat exchanger, and the concentrated lithium bromide solution outlet of the solution heat exchanger is connected with the spray header of the absorber through a pressure reducing valve.

Preferably, the methanation unit comprises a first methanation reactor, a second methanation reactor, a third methanation reactor, a fourth methanation reactor, a first waste heat boiler, a second waste heat boiler, a third methanation reactor outlet heat exchanger and a dehydration separation tank;

the system comprises a first methanation reactor, a second methanation reactor, a third methanation reactor, a fourth methanation reactor, a lithium bromide waste heat refrigeration unit generator and a dehydration separation tank, wherein a gas outlet of the first methanation reactor is connected with a hot end inlet of the first waste heat boiler, a hot end outlet of the first methanation reactor is connected with a gas inlet of the second methanation reactor, a gas outlet of the second methanation reactor is connected with a hot end inlet of the second waste heat boiler, a hot end outlet of the second waste heat boiler is connected with a gas inlet of the third methanation reactor, a gas outlet of the third methanation reactor is connected with a hot end inlet of the fourth methanation reactor, a gas outlet of the third methanation reactor is connected with a gas outlet of the dehydration separation tank, and a gas outlet of the fourth methanation reactor is connected with a gas outlet of the third methanation reactor.

Preferably, the absorber is a horizontal tube falling film absorber.

Preferably, the generator is an immersion type generator.

Preferably, the mass concentration of the lithium bromide dilute solution is 40-60%.

Preferably, the mass concentration of the lithium bromide concentrated solution is 50-65%.

A coal-based natural gas and methanol poly-generation method based on integrated waste heat refrigeration of a coal-based natural gas and methanol poly-generation system based on integrated waste heat refrigeration comprises the following steps:

the lump coal and oxygen enter a Lurgi gasification unit to form a crude synthesis gas, and the crude synthesis gas passes through the acid gas unit to remove CO in the crude synthesis gas₂And H₂Separating S gas to form clean synthesis gas; the clean synthesis gas is divided into two parts from a synthesis gas outlet of the acid gas unit, and one part of the clean synthesis gas enters the methanation unit to synthesize a natural gas product; the other part of the clean synthesis gas enters a cryogenic separation unit, and methane is separated out as a natural gas product after the temperature of the synthesis gas is reduced by a cooler; the residual separated synthesis gas except methane enters a methanol synthesis and methanol rectification unit to prepare refined methanol;

the methanated air-cooled high-temperature material flow enters a generator of a lithium bromide waste heat refrigerating unit, heat is provided to enable refrigerant water to be evaporated, evaporated superheated steam is condensed in a condenser, generated condensed water is cooled and depressurized through an expansion valve to refrigerate water in the evaporator, and therefore cold energy carrier material flow is prepared, the cold energy carrier material flow enters an acid gas removing unit and a deep cooling separation unit after passing through a cold water outlet of the evaporator, and cold energy contained in the cold energy carrier material flow is supplied to the acid gas removing unit and the deep cooling separation unit.

Preferably, the evaporation temperature of the evaporator is 0-6 ℃.

Preferably, the condensation temperature of the condenser is 30-45 ℃.

Preferably, the temperature range of the air-cooled high-temperature material flow is 100-200 ℃; the temperature of the cold energy carrier stream is between 2 and 8 ℃.

Compared with the prior art, the invention has the following advantages and beneficial effects:

1. the method effectively recovers the low-grade waste heat of the air-cooled stream of the methanation unit, reduces the discharge of the waste heat and the extra required cooling energy consumption, and achieves the purpose of energy conservation.

2. The invention adopts the lithium bromide waste heat refrigeration unit to replace the traditional compression refrigeration station, thereby reducing the power consumption of the compression refrigeration station.

Drawings

FIG. 1 is a process flow diagram of a conventional coal-to-natural gas methanol co-production system; wherein: 1 is a lurgi gasification unit, 2 is an acid gas removal unit, 3 is a cryogenic separation unit, 4 is a methanation unit, 5 is a methanol synthesis unit, 6 is a methanol rectification unit, 7 is a conventional electric refrigeration unit, 8 is lump coal, 9 is oxygen, 10 is crude synthesis gas, 11 is clean synthesis gas, 12 is clean synthesis gas, 13 is separation synthesis gas, 14 is crude methanol, 15 is refined methanol, 16 is CO₂And H₂S, 17 is electric energy required by refrigeration, 18 is natural gas, and 19 is CH₄20 is natural gas and 21 is a cold energy carrier stream.

FIG. 2 is a process flow diagram of a coal-based natural gas co-production methanol system with integrated waste heat refrigeration in embodiment 1 of the present invention; wherein: 1 is a lurgi gasification unit, 2 is an acid gas removal unit, 3 is a cryogenic separation unit, 4 is a methanation unit, 5 is a methanol synthesis unit, and 6 is methanol rectificationThe unit, 7' is lithium bromide waste heat refrigeration unit, 8 is lump coal, 9 is oxygen, 10 is crude synthesis gas, 11 is clean synthesis gas, 12 is clean synthesis gas, 13 is separation synthesis gas, 14 is crude methanol, 15 is refined methanol, 16 is CO₂And H₂S, 18 is natural gas and 19 is CH₄20 is natural gas, 21 is a cold energy carrier stream, 22 is an air-cooled high temperature stream, and 23 is an air-cooled low temperature stream.

FIG. 3 is a schematic diagram of the configuration of the methanation unit, acid gas removal unit and cryogenic separation unit of the present invention; wherein: 2 is an acid gas removal unit; 3 is a cryogenic separation unit; 7' is a lithium bromide waste heat refrigerating unit; 22 is an air-cooled high-temperature material flow, 23 is an air-cooled low-temperature material flow, 24 is a first methanation reactor, 25 is a second methanation reactor, 26 is a third methanation reactor, 27 is a fourth methanation reactor, 28 is a first waste heat boiler, 29 is a second waste heat boiler, 30 is an outlet heat exchanger of the third methanation reactor, 31 is a dehydration separation tank, 32 is clean synthesis gas, 33, 34, 35, 36, 37 and 38 are reaction gases, 39 is process condensate water, and 40 is a natural gas product.

FIG. 4 is a schematic structural diagram of a lithium bromide waste heat refrigeration unit of the present invention; wherein: 21 is a cold energy carrier material flow, 22 is an air cooling high temperature material flow, 23 is an air cooling low temperature material flow, 41 is a generator, 42 is a condenser, 43 is an expansion valve, 44 is an evaporator, 45 is an absorber, 46 is a solvent pump, 47 is a solution heat exchanger, 48 is a pressure reducing valve, 49 is superheated water vapor, 50 is condensed water, 51 is water vapor, 52 and 56 are both cooling water, 53 and 57 are both lithium bromide dilute solution, 54 is spray solution, and 55 and 58 are both lithium bromide concentrated solution.

Fig. 5 is a process flow diagram of a system for co-producing methanol from coal-based natural gas by integrating waste heat refrigeration in embodiment 2 of the invention.

Fig. 6 is a schematic structural diagram of an acid gas removal unit and an acid gas removal unit of a coal-based natural gas co-production methanol system integrated with waste heat refrigeration in embodiment 2 of the present invention.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited to these examples.

Example 1

The cold energy carrier stream 21 in this example is cold water.

As shown in fig. 2 to 4, the coal-based natural gas co-production methanol system integrated with waste heat refrigeration of the embodiment includes a lurgi gasification unit 1, an acid gas removal unit 2, a cryogenic separation unit 3, a methanation unit 4, a methanol synthesis unit 5, a methanol rectification unit 6, and a lithium bromide waste heat refrigeration unit 7' which are connected in sequence; and the air-cooled high-temperature material flow 22 of the methanation unit 4 is connected with a waste heat inlet of a lithium bromide waste heat refrigerating unit 7', and a cold water outlet of the lithium bromide waste heat refrigerating unit 7' is simultaneously connected with a cooling water inlet of the acid gas removal unit 2 and a cooling water inlet of the deep cooling separation unit 4.

The methanation unit comprises a first methanation reactor 24, a second methanation reactor 25, a third methanation reactor 26, a fourth methanation reactor 27, a first waste heat boiler 28, a second waste heat boiler 29, a third methanation reactor outlet heat exchanger 30 and a dehydration separation tank 31; the gas outlet of the first methanation reactor 24 is connected with the hot end inlet of a first waste heat boiler 28, the hot end outlet of the first waste heat boiler 28 is connected to the inlet of the second methanation reactor 25, the outlet of the second methanation reactor 25 is connected with the hot end inlet of a second waste heat boiler 29, the hot end outlet of the second waste heat boiler 29 is connected to the inlet of the third methanation reactor 26, the outlet of the third methanation reactor 26 is connected with the hot end inlet of the third methanation reactor outlet heat exchanger 30, the hot end outlet of the third methanation reactor outlet heat exchanger 30 is connected with the waste heat inlet of the generator 41 of the lithium bromide waste heat refrigeration unit 7', the residual heat outlet of the lithium bromide residual heat refrigeration unit generator 41 is connected with the inlet of the dehydration separation tank 31, and the gas phase outlet of the dehydration separation tank 31 is connected with the gas inlet of the fourth alkylation reactor 27.

The lithium bromide waste heat refrigerating unit comprises a generator 41, a condenser 42, an expansion valve 43, an evaporator 44, an absorber 45, a solvent pump 46, a solution heat exchanger 47 and a pressure reducing valve 48; the waste heat inlet of the generator 41 is connected with the air-cooled high-temperature material flow 21, and the cold water outlet of the evaporator 44 is simultaneously connected with the cooling water inlet of the acid gas removal unit 2 and the cooling water inlet of the cryogenic separation unit 4.

A water vapor outlet of the generator 41 is connected with a water vapor inlet of a condenser 42, a condensed water outlet of the condenser 42 is connected with a condensed water inlet of an evaporator 44 through an expansion valve 43, a water vapor outlet of the evaporator 44 is connected with a water vapor inlet of an absorber 45, a part of a lithium bromide dilute solution outlet of the absorber 45 is connected with a lithium bromide dilute solution inlet of a solution heat exchanger 47 through a solvent pump 46, the other part of the lithium bromide dilute solution outlet is connected with a spray header of the absorber through a pressure reducing valve 48, and a lithium bromide dilute solution outlet of the solution heat exchanger 47 is connected with a lithium bromide dilute solution inlet of the generator 41; the concentrated lithium bromide solution outlet of the generator 41 is connected with the concentrated lithium bromide solution inlet of the solution heat exchanger 47, and the concentrated lithium bromide solution outlet of the solution heat exchanger 47 is connected with the spray header of the absorber 45 through a pressure reducing valve 48.

Specifically, the air-cooled high-temperature material flow with the temperature of 180 ℃ enters a generator 41 in a lithium bromide waste heat refrigerating unit 7', the air-cooled high-temperature material flow exchanges heat with a 57% lithium bromide dilute solution, superheated water vapor with the temperature of 81-91 ℃ is generated and enters a condenser 42 from a water vapor outlet at the top end of the generator 41, then the superheated water vapor is condensed into condensed water with the temperature of 35-45 ℃, and a lithium bromide concentrated solution with the mass concentration of 62% flows out of the bottom of the generator 41 to a solution heat exchanger 47 and then reaches a spray header of an absorber 45 through a pressure reducing valve 48. The condensed water is cooled to 0-6 deg.C by expansion valve 43, and the water in evaporator 44 is evaporated and refrigerated under the condition of 0.616-0.935KPa, so as to obtain cold water. This cold water is then passed from the cold water outlet of the evaporator 44 to the cryogenic separation unit 3 and the acid gas removal unit 2 for cooling. The water vapor formed in the evaporator 44 enters the absorber 45 and is absorbed by the lithium bromide concentrated solution with the mass concentration of 62% to form a lithium bromide dilute solution, a part of the lithium bromide dilute solution is pressurized by the solvent pump 46, enters the solution heat exchanger 47 to exchange heat with the lithium bromide concentrated solution, enters the generator 41 to continue to participate in the refrigeration cycle, and the other part of the lithium bromide dilute solution is mixed with the 62% lithium bromide concentrated solution by the pressure reducing valve 48 and then reaches the spray header of the absorber 45. Therefore, the lithium bromide waste heat refrigerating unit 7' can continuously produce cold water with the temperature of 2-8 ℃ and supply cold energy for the cryogenic separation unit 3 and the acid gas removal unit 2.

Specifically, the coal-based natural gas co-production methanol system adopting the integrated waste heat refrigeration comprises the following steps of:

after entering the lurgi gasification unit 1, the lump coal 8 and the oxygen 9 generate a crude synthesis gas at the temperature of 800-.

The raw synthesis gas is separated in an acid gas removal unit 2 into three fractions, i.e. CO₂And H₂S16, clean syngas 11 to the cryogenic separation unit 3 and clean syngas 12 to the demethanization unit 4.

The clean syngas 12 forms natural gas 18 in the methanation unit 4, while the clean syngas 11 is separated into two parts in the cryogenic separation unit 3: namely natural gas 19 and separated syngas 13. The separated synthesis gas 13 enters a methanol synthesis unit 5 to form crude methanol 14, and the crude methanol 14 enters a methanol rectification unit 6 to form refined methanol 15. And natural gas 18 and CH₄19 into a final natural gas product 20.

The coal-based natural gas co-production methanol system integrating waste heat refrigeration also carries out a waste heat recycling process in the process of producing natural gas and methanol, and the process is as follows:

the clean synthesis gas 32 entering the methanation unit 4 sequentially passes through a first methanation reactor 24, a first waste heat boiler 28, a second methanation reactor 25, a second waste heat boiler 29, a third methanation reactor 26 and a third methanation reactor outlet heat exchanger 30, then the air-cooled high-temperature material flow 22 enters a generator 41 of a lithium bromide waste heat refrigeration unit 7', the air-cooled high-temperature material flow 22 heats a lithium bromide dilute solution in the generator 41 to evaporate refrigerant water to form superheated steam 49, the superheated steam 49 is condensed in a condenser 42, the generated condensed water 50 is cooled and depressurized through an expansion valve 43 to refrigerate water in an evaporator 44 to prepare a cold energy carrier material flow 21, the cold energy carrier material flow 21 passes through an evaporator cold water outlet and then enters an acid gas removal unit 2 and a cryogenic separation unit 3, and the cold energy contained in the cold water can be supplied to 0-10 parts required by the acid gas removal unit 2 and the cryogenic separation unit 3 Cold energy at C. The air-cooled low-temperature material flow 23 flowing out from the residual heat outlet of the generator 41 returns to the methanation unit 4, then enters the dehydration separation tank 31 to separate the process condensate water 39, and the reaction gas 38 enters the fourth alkylation reactor 27 to form a natural gas product.

In the above process, the temperature of the air-cooled high-temperature stream 22 was 180 ℃ and the pressure was 2.8 MPaA. The temperature of the air-cooled low temperature stream 23 returning from generator 41 is 120 c. The mass concentration of the dilute lithium bromide solution in the generator 41 before heat exchange with the air-cooled high-temperature stream 22 is 57%.

When the coal-to-natural gas co-production methanol system integrating waste heat refrigeration is used for producing natural gas and methanol, the flow rate of raw lump coal is 580t/h, the gasification temperature is 1050 ℃, the pressure is about 4.0MPaA, and the components of the produced crude synthesis gas are shown in Table 1:

TABLE 1 composition of raw syngas 10

Composition (I)	H2	CO	CH4	CO2	O2	H2O	H2S	N2
									Mole fraction%	39.1	14.7	12.9	31.6	0.3	0.2	0.7	0.3

In the process of producing natural gas and methanol, the heat produced by the lithium bromide waste heat refrigerating unit can meet the cooling capacity of 0-10 ℃ required by the acid gas removing unit by 100% and meet the cooling capacity of 0-10 ℃ required by the cryogenic separation unit by 100%, and the power consumption is reduced by about 60%.

Example 2

As shown in fig. 5 and 6, the coal-based natural gas co-production methanol system integrating waste heat refrigeration of the embodiment includes a lurgi gasification unit 1, an acid gas removal unit 2, a cryogenic separation unit 3, a methanation unit 4, a methanol synthesis unit 5, a methanol rectification unit 6, and a lithium bromide waste heat refrigeration unit 7' which are connected in sequence; and an air-cooled high-temperature material flow 22 of the methanation unit 4 is connected with a waste heat inlet of a lithium bromide waste heat refrigerating unit 7', and a cold water outlet of the lithium bromide waste heat refrigerating unit 7' is connected with a cooling water inlet of the acid gas removal unit 2.

The lithium bromide waste heat refrigerating unit comprises a generator 41, a condenser 42, an expansion valve 43, an evaporator 44, an absorber 45, a solvent pump 46, a solution heat exchanger 47 and a pressure reducing valve 49; the waste heat inlet of the generator 41 is connected with the air-cooled high-temperature material flow 22, and the cold water outlet of the evaporator 44 is connected with the cooling water inlet of the acid gas removal unit 2.

A water vapor outlet of the generator 41 is connected with a water vapor inlet of a condenser 42, a condensed water outlet of the condenser 42 is connected with a condensed water inlet of an evaporator 44 through an expansion valve 43, a water vapor outlet of the evaporator 44 is connected with a water vapor inlet of an absorber 45, a part of a lithium bromide dilute solution outlet of the absorber 45 is connected with a lithium bromide dilute solution inlet of a solution heat exchanger 47 through a solvent pump 46, the other part of the lithium bromide dilute solution outlet is connected with a spray header of the absorber 45 through a pressure reducing valve 48, and a lithium bromide dilute solution outlet of the solution heat exchanger 47 is connected with a lithium bromide dilute solution inlet of the generator 41; the concentrated lithium bromide solution outlet of the generator 41 is connected with the concentrated lithium bromide solution inlet of the solution heat exchanger 47, and the concentrated lithium bromide solution outlet of the solution heat exchanger 47 is connected with the spray header of the absorber 45 through a pressure reducing valve 48.

The difference between this embodiment and embodiment 1 is that the cold water containing cold produced by the lithium bromide waste heat refrigeration unit is supplied only to the acid gas removal unit 2, and is not supplied to both the cryogenic separation unit 3 and the acid gas removal unit 2.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.