CN110467943B - Method for preparing natural gas, olefin and coal tar from coal - Google Patents

Abstract

A method for preparing natural gas, olefin and coal tar from coal, directly separate hydrogen element in raw material coal into gaseous hydrocarbon under proper temperature and gas phase medium conditions; directly reacting carbon element in the coal into gaseous hydrocarbon by using hydrogen element; oxygen-rich steam is adopted to carry out water gas reaction on carbon elements in residual coke left after gaseous hydrocarbon production at high temperature to convert the carbon elements into CO and H₂So as to greatly improve the energy conversion efficiency, greatly reduce the water resource consumption and greatly reduce CO₂Discharge and environmental pollution, greatly reduces the investment of the device and reduces the production cost.

Description

Method for preparing natural gas, olefin and coal tar from coal

Technical Field

The invention belongs to the field of coal chemical industry, and particularly relates to a technique and equipment for energy regeneration of natural gas, olefin and fuel oil from coal.

Background

The existing two-step method for synthesizing oil and gas after coal gasification or one-step method for producing oil and gas by direct coal hydrogenation has the disadvantages of complicated process route and low energy conversion efficiency in the process, namely only 40% of coal oil, 3.6 tons of standard coal/ton of oil, only 50% of coal natural gas and 2.5 tons of standard coal/km³(ii) a High equipment investment, 1600 million yuan per 1000 ten thousand tons of coal-made oil, 280 million yuan per 40 million m of coal-made natural gas³(ii) a High water resource consumption, 7 ton/ton oil consumption water from coal and 7 ton/km natural gas from coal³(ii) a Heavy environmental pollution, high cost of sewage treatment, CO₂The discharge is large.

The main technical reason is that coal is gasified and then synthesized into C_nH_2n+2(n-1 is CH)₄N-8 is gasoline and n-16 is diesel) is called a two-step process, the chemical reaction nCO +2nH₂+H₂＝C_nH_2n+2+nH₂Oxygen in O and CO must be H₂To be taken out and prepare H traditionally₂The energy consumption and the cost of the two-step method are high, so the lurgi gasification furnace which is usually adopted in the coal gasification process of the two-step method is essentially a pressurized gasification furnace instead of an atmospheric gas furnace, and the hydrocarbon product can not be directly generated by hydrogenation, so the defects exist.

A Ruhr 100 type gasification furnace is a 10MPa working pressure change of a traditional normal-pressure two-stage gas furnace, except that methane in gas is increased by about 70%, gas waste water, steam decomposition rate and the like are not improved, more carbon hydrocarbon is reduced by 25% compared with a 3MPa Lurgi furnace, and the Ruiqi 100 type gasification furnace has no too many advantages, is not suitable for coal-to-oil due to excessive consumption of hydrogen by producing more methane, is greatly increased in equipment investment due to too high process pressure, is not economical when used for coal-to-natural gas, has been developed for more than 50 years so far, has no subsequent further development of the Lurgi company, and has no commercial operation achievement.

The existing one-step method for directly hydrogenating coal has low oil preparation efficiency, and firstly, the process pressure is up to 20MPa, and the equipment investment is large; secondly, the carbon element conversion rate is low, the carbon content of the residue is up to 40 percent, and CO can be generated again only by reheating in a special gasification furnace; thirdly, the entrained flow bed is adopted for coal gasification to produce hydrogen, because the hydrogen element in the coal is in the form of hydrocarbon in the process of entrained flow bed gasification, the hydrogen element is firstly pyrolyzed to gaseous hydrocarbon below 700 ℃, and then the gaseous hydrocarbon and O in the air flow are mixed immediately₂Gas reaction to CO₂And H₂O gives off heat to enable the furnace temperature to reach 1300-1700 ℃, so a great part of the high furnace temperature of the entrained flow bed is contributed by the combustion of hydrogen elements, thereby resulting in low molar fraction of hydrogen in the coal gas, particularly high CO content, and CO can be converted into hydrogen only by conversion, namely, the hydrogen production process is substantially to burn H in the coal firstly₂Then using C element in coal to prepare CO, converting CO into H₂So that the existing one-step method for directly hydrogenating coal C_nH_2n+2There are also a number of disadvantages as described above.

The existing coal-to-olefin is prepared by pressurizing and gasifying oxygen-rich water vapor of raw material coal, washing the oxygen-rich water vapor, separating coal tar, and performing CO conversion (CO/H) on the oxygen-rich water vapor₂The method comprises the following technical processes of proportion adjustment, oxygen-enriched gas acid gas removal, methanol synthesis, methanol separation, methane separation and methanol dehydration for preparing olefin, and has the advantages of long technical process, energy consumption, water consumption, environmental protection and great improvement space for investment.

Disclosure of Invention

The purpose of the invention is toDirectly separating H element in the raw material coal into a gaseous hydrocarbon from the coal under the conditions of the temperature and the gas-phase medium; secondly, directly reacting carbon element in the coal into gaseous hydrocarbon by using H element, and thirdly, converting the carbon element in residual coke left after the production of the gaseous hydrocarbon into CO and H by adopting oxygen-rich steam at high temperature₂So as to greatly improve the energy conversion efficiency, greatly reduce the water resource consumption and greatly reduce CO₂Discharge and environmental pollution, greatly reduces the investment of the device and reduces the production cost.

The specific invention content is as follows:

1. a process for preparing natural gas, olefin and coal tar from coal includes such steps as pressurizing and gasifying the oxygen-enriched water vapour, washing the oxygen-enriched water vapour, separating coal tar, and CO/H conversion₂The method comprises the following technical processes of proportion adjustment, oxygen-enriched gas acid gas removal, methanol synthesis, methanol separation, methanol tail gas methane separation and methanol dehydration to olefin, and is characterized in that:

the raw material coal is sequentially arranged in the same continuous downward moving pressurized gasification bed layer: heating and drying by hydrocarbon-rich hydrogen gas to remove water; the coal gas is pyrolyzed and retorted by the methane-rich hydrogen gas to prepare the coal tar-rich hydrocarbon-rich hydrogen gas; gasifying by hydrogen to obtain methane-rich hydrogen gas rich in methane; quilt H₂O+CO₂Gasifying to prepare water gas; o in vaporized oxygen gasifying agent₂Oxidizing and burning residual carbon elements.

2. The method for preparing natural gas, olefin and coal tar from coal is characterized in that hydrogen for preparing hydrogen-rich gas is sent to a hydrogen distributor arranged in the upper part of a gasification bed layer by a hydrogen circulator through a start-up heating device, then descends along a tube bundle, is heated by a heat exchange tube bundle, and then enters a coke hydrogenation gasification layer from an outlet at the lower end of the tube bundle; the hydrogen entering the coke hydrogenation gasification agent layer is deflected upwards and reacts with the carbon element in the coke directly to form C +2H₂＝CH₄Generating methane-hydrogen gas containing methane, heating the hydrogen in the tube by the released heat through the heat exchange tube bundle, and directly heating the carbon layer and generating high-temperature methane-hydrogen gas; high-temperature methane hydrogen gas enters semicoke hydrogenation gas in an ascending wayIn the formation layer, hydrogen and rich active carbon elements in the semicoke are subjected to rapid gasification reaction of C +2H₂＝CH₄The methane content in the methane-hydrogen gas is greatly increased to form methane-rich hydrogen gas, and heat is released to raise the temperature of the bed layer; the high-temperature methane-rich hydrogen gas ascends into the pyrolysis and dry distillation layer to provide heat for the pyrolysis and dry distillation of the coal, and the partial pressure content of methane in the methane-rich hydrogen gas is high, so that the generation and the separation of methane in the coal are effectively inhibited, and hydrogen elements in the coal are forced to be more combined in the coal tar with a lower hydrogen-carbon element ratio, so that the yield of the coal tar and the gasification rate of the carbon elements are effectively increased, the coal tar content of the methane-rich hydrogen gas is increased while the pyrolysis and dry distillation gasification rate of the coal is improved, and the methane-rich hydrogen gas is converted into hydrocarbon-rich hydrogen gas; the hydrogen-rich coal gas continuously goes upwards to enter a raw material coal drying layer, the moisture in the coal is dried while the raw material coal is heated, so that the adsorbed water and the chemical water in the raw material coal are converted into water vapor to enter the hydrogen-rich coal gas, and the hydrogen-rich coal gas is discharged from an outlet at the upper part of the furnace wall of the hydrogen-rich coal gas.

3. The method for preparing natural gas, olefin and coal tar from coal is characterized in that the hydrogen-rich coal gas after being discharged is subjected to tar dust removal by a tar dust separator, the temperature is reduced by a heat exchanger, the hydrogen-rich coal gas is cooled to normal temperature by a cooler and is separated to remove oil and water, the hydrogen-rich coal gas enters an acid gas separation process to separate H₂S、COS、CO₂And the CO acid gas and the hydrogen gas are converted into the coal-based synthetic natural gas which meets the GB/T33445-2016 standard, wherein one part of the gas enters a methane oxygen-free olefin/aromatic hydrocarbon preparation device, a large amount of generated hydrogen gas directly enters a hydrogen main pipe while the olefin/aromatic hydrocarbon is prepared, the hydrogen gas separated from the acid gas-hydrogen separation process and the hydrogen gas from the water gas-acid gas removal process are subjected to pressure increase by a hydrogen circulator and then enter a furnace again to produce the hydrogen gas rich in hydrocarbon.

4. The method for preparing natural gas, olefin and coal tar from coal is characterized in that a gasifying agent formed by mixing oxygen and water vapor enters a furnace from the bottom of the furnace, passes through a grate to the lower part and the upper part to pass through an ash layer, absorbs heat carried by the gasifying agent, the temperature is raised to about 600 ℃, the gasifying agent enters an oxygen gasification combustion layer,the oxygen in the gasifying agent makes the residual carbon element in the residual coke burn and gasify quickly to produce CO₂And a large amount of heat is released, so that the temperature of water vapor and a bed layer in the gasifying agent reaches over 1000 ℃ and is below an ash melting point; containing CO₂The high-temperature water vapor from bottom to top transfers heat to the hydro-gasification residual coke from the hydrogen gas section, and simultaneously performs heat absorption water vapor gasification reaction C + H with carbon element in the residual coke₂O＝CO+H₂Most of carbon elements in the residual coke react with 30-40% of water molecules in the water vapor and are converted into CO and H in the raw gas₂The crude gas is made into wet and hot crude gas with the temperature of about 700 ℃, the crude gas ascends to enter a gas collector at the upper part of a crude gas reaction layer, and then is discharged from a furnace through a crude gas outlet on the furnace wall.

5. The method for preparing natural gas, olefin and coal tar from coal is characterized in that raw coal gas discharged from a furnace is subjected to dust removal and steam superheater heating, enters furnace steam, enters a waste heat steam boiler to produce steam required by partial coal gasification, enters a water gas washing waste heat recovery device, utilizes the process patent of No. 2011100943882 coal gas waste heat recovery and utilization, converts 30-75% of water vapor in the coal gas into gasification water vapor, enters a CO conversion process, and performs CO + H on more than 95% of CO through a catalyst₂O＝CO+H₂Carrying out a shift reaction; the converted gas is called converted gas, and the main component of the converted gas is H₂And CO₂(ii) a Converting CO in gas₂Acid gas and small amount of H₂S acid gas is removed by adopting a pressure swing adsorption PSA separation process, and the heat value of combustible components is 400kJ/Nm³Part of CO above₂And (3) desorbing the gas, and sending the desorbed gas into a gas turbine tail gas boiler or a low-calorific-value gas boiler to convert combustible components in the desorbed gas into steam energy for recycling.

6. According to the invention, the method for preparing natural gas, olefin and coal tar from coal is characterized in that during normal production, steam in a steam oxygen gasifying agent fed into a furnace is provided by a water jacket steam drum connected with a water jacket, a coal gas waste heat boiler, CO conversion reaction heat and a water gas washing waste heat recovery device; wherein the water gas washing waste heat recovery device is used for recovering the water gas washing waste heatThe produced steam is already above the condensation temperature, and the recovered steam contains a small amount of O₂And corrosive impurities and dissolved salt, in order to prolong the service life of the steam superheater, the recovered steam produced by the water gas washing waste heat recovery device does not enter the steam superheater but is mixed with superheated steam at the outlet of the steam superheater, and then proper amount of O is added₂After the steam-oxygen ratio of the gasifying agent reaches the technological requirement, the gas enters the furnace through the steam-oxygen gasifying agent inlet.

7. According to the method for preparing the natural gas, the olefin and the coal tar from the coal, which is disclosed by the invention, during normal production, 30-80% of total oxygen is added into a gasifying agent as a stripping medium in a water gas washing waste heat recovery device according to the water vapor content in water gas and the amount of water vapor required to be stripped, and 20-70% of total oxygen is added into the gasifying agent as a supplement amount meeting the requirements of a steam-gas ratio.

8. The method is characterized in that the same continuously downward moving pressurized gasification bed layer is arranged into a two-section pressurized moving bed gas furnace with different functional structures at the upper section and the lower section, the lower part of the two-section pressurized moving bed gas furnace is designed to adopt a mixed gasification agent of oxygen and water vapor, residual coke from a hydrocarbon-rich hydrogen gas section is used as a raw material to produce a water gas section of hydrogen and carbon monoxide, and the height-diameter ratio of the residual coke gasification bed layer is 0.5-1.5; the upper part of the reactor is designed to adopt methane less than or equal to 15 percent, hydrogen 80-95 percent, CO + CO₂+H₂O+N₂≤5％，H₂S≤0.5％，O₂The hydrogen gasification agent takes hydrogen as a main component, and the raw material coal is directly used for producing a multi-carbon hydrogen gas section which takes natural gas, olefin and coal tar as main products, wherein the height-diameter ratio of a gasification raw material coal bed layer is 2-6.8.

9. According to the method for preparing the natural gas, the olefin and the coal tar from the coal, the highest temperature of the water gas section is a dry slag gasification mode below an ash melting point temperature or a slag gasification mode above the ash melting point temperature.

10. The method for preparing the natural gas, the olefin and the coal tar from the coal is characterized in that the process pressure of a pressurized coal gasification bed layer is 1-3 MPa, or 3-6 MPa, or 6-10 MPa, and the process pressure of preparing the olefin from the methane in an oxygen-free mode is 0.95-0.6 time, or 0.6-0.3 time, or 0.3-0.1 time, or 0.1-0.05 time of the outlet pressure of the hydrogen-rich coal gas.

The invention has the following positive effects:

during normal production, the gasified steam realizes self-supply, namely a boiler is not needed to provide process steam for gasification, so that the investment and the energy are saved, the environmental pollution is reduced, the water resource consumption and the CO are reduced₂And (5) discharging.

Compared with the method for preparing olefin by gasifying the entrained flow bed, synthesizing methanol and dehydrating methanol, the method greatly simplifies the process of preparing olefin from coal, and has the advantages of investment, process energy consumption, oxygen consumption, water resource consumption and CO₂The emission and the environmental pollution are both greatly reduced; oxygen-free preparation of olefin from methane and decomposition of large amount of H₂The hydrogen gas is directly used as the raw material for preparing the hydrogen-rich gas by coal hydrogenation, so that the demand of coal hydrogen production is greatly reduced;

and thirdly, the methane-rich hydrogen gas is adopted for coal pyrolysis and dry distillation, so that the yield of the coal tar is greatly increased, and the coal tar has the advantages of mild temperature, good quality of the coal tar and high additional value, is used for preparing oil by hydrogenation, and can reduce the production cost.

And fourthly, the consumption of coal, water resources and oxygen for preparing the natural gas raw material from the coal is greatly reduced, the catalytic synthesis process of methane and the dehydration process of methane are saved compared with the Fischer-Tropsch synthesis process, and the investment is saved.

Coal hydrogenation direct C +2H₂＝CH₄The reaction heat for generating methane is used for pyrolysis and dry distillation of raw material coal, drying and dehydration and heating raw coal, and is also used for heating jacket circulating water to produce water vapor required by water gas reaction, the heat of the water vapor is fully coupled and utilized, and the heat efficiency of the coal-based natural gas is effectively improved.

Drawings

FIG. 1 is a schematic diagram of a process flow of a method for producing natural gas, olefins and coal tar from coal.

In the drawings

1. A steam oxygen gasifying agent inlet;

2. a cooling water inlet of the jacket shell of the gas furnace;

3. a raw gas outlet;

4. a hydrogen gasification agent inlet;

5. a hydrocarbon-rich hydrogen gas outlet;

6. a cooling water outlet of the jacket shell of the gas furnace;

7. charging raw material coal;

8. locking the coal;

9. a coal distributor;

10. drying the layer;

11. a dry distillation layer;

12. a stirrer;

13. a sieve plate;

14. a hydrogen gas distributor;

15. a semicoke hydrogenation gasification layer;

16. a heat exchange tube bundle;

17. a coke hydrogenation gasification layer;

18. a manhole;

19. a gas collector;

20. a water gas reaction layer;

21. an oxidizing combustion layer;

22. a layer of ash;

23. a pressure-bearing jacket shell of a gas furnace;

23A, a gas furnace jacket circulating cooling water gas-liquid separator, namely a jacket steam drum;

jacket steam and piping;

24. locking with ash;

25. slag;

26. driving steam and pipelines;

27. oxygen for gasification and a pipeline;

oxygen for stripping water vapor (required for the water vapor process in the recovered water gas);

27B, adjusting the steam-oxygen ratio by using oxygen;

28. steam and piping recovered from the water gas;

29. a gas dust removal and steam superheating combined device, namely a dust removal superheater;

30. a gas exhaust-heat boiler;

31. a water gas washing and gas waste heat recovery device;

32. a gas CO conversion process;

33.CO₂、H₂s, acid gas removal process;

33A. a sulfur recovery step;

34. the heat value discharged in the acid gas removal process has a recovery value, and the main component is CO₂Removing tail gas to burn the boiler;

35. a hydrogen header pipe;

35a. hydrogen circulator;

36. a hydrogen heating device is put into the furnace when the vehicle is started;

37. a tar dust separator;

coal tar, dust and water separated by the tar dust separator;

38. a hydrocarbon-rich hydrogen gas waste heat recovery process device;

39. hydrocarbon-rich hydrogen gas cooling and oil-water separation process device

39a. separated oil and water;

H2S, COS acid gas and hydrogen separation process units;

40A. a sulfur recovery step;

41. a process unit for preparing olefin/aromatic hydrocarbon by methane without oxygen;

olefin/aromatic products;

42. coal tar, oil, coal gas sewage separation process units;

42a coal tar, oil products;

H₂-hydrogen and molecular formula;

CH₄-methane and molecular formula;

CO₂-carbon dioxide and molecular formula;

a-hydrogen gas section;

b-water gas section.

Detailed Description

With regard to the gasification furnace:

firstly, designing and manufacturing a pressurized gas furnace containing a water gas section and a hydrogen gas section and equipment of each process unit, and then transporting the pressurized gas furnace to an installation site for installation in place, process piping, electrical instrument installation, corrosion prevention and heat preservation, system leakage test, pressure test and debugging qualification, so that the pressurized gas furnace has the structure and the function required by design.

Then, sequentially paving 300mm thick gas furnace ash residues on a grate of the water gas section, wherein the required granularity of a water vapor gasification layer is 20-80 mm, and the coke thickness is 2000 mm; adding coke with the granularity of 20-80 mm and the thickness of 3000mm into a coke hydrogenation gasification layer of an oil gas section, adding semicoke with the thickness of 3000mm into a semicoke hydrogenation gasification layer, adding weakly caking coal with the granularity of 20-80 mm and the thickness of 2000mm into a carbonization layer, and adding weakly caking coal with the granularity of 20-80 mm and the thickness of 1000mm into a drying layer.

Firstly, air is used at a rate of 5000-10000 Nm/hour³The flow rate of the gas is sent into the furnace at the temperature rise rate of 50 ℃/h, and the gas is discharged from a hydrocarbon-rich hydrogen gas outlet; about 6 hours, because the ignition point of coke is about 350 ℃, the phenomenon that the temperature of an oxygen combustion layer in the water gas section exceeds the temperature of air entering a furnace begins to occur, and when the temperature of the oxygen combustion layer rapidly rises to about 700 ℃, the air is discharged after a water gas outlet pipe in the water gas section; can add a proper amount of nitrogen into the air entering the furnace to reduce the O content₂And (3) controlling the temperature rise rate of the oxygen combustion layer to be about 100 ℃/h, gradually changing the temperature rise of air into an oxygen-water vapor mixed gasifying agent after the temperature of the oxygen combustion layer reaches 900-1000 ℃, and controlling the temperature not to rise any more so as to prevent the water gas section from being over-temperature scabbed.

② hot nitrogen which has the same temperature with the flue gas at the water gas outlet is heated at the rate of 5000-10000 Nm³The flow rate of the hydrogen gas is increased to the hydrogen gas section through a hydrogen inlet of the hydrogen gas section, and the hydrogen gas is discharged from a hydrogen outlet, so that a proper amount of air can be supplemented into hot nitrogen (actually, oxygen is supplemented, the highest temperature of a coke hydrogenation gasification layer and a semicoke hydrogenation gasification layer is not higher than 700 ℃) for further heating coke, semicoke and raw material coal of the hydrogen gas section, and the temperature rise rate is accelerated by utilizing the combustion heat of the oxygen and the coke;

when the temperature of the dry distillation layer of the hydrogen gas section is higher than 400 ℃, the stirrer can be started to run at a low speed in real time, and the coal feeding device starts the automatic control loop so as to automatically feed raw material coal in due time.

Fourthly, when the highest temperature of a coke hydrogenation gasification layer and a semicoke hydrogenation gasification layer reaches 600 degrees centigrade, starting system pressure boosting at the rate of 1MPa per hour, and paying attention to the pressure boosting process as much as possible: the pressure difference between the water gas outlet and the hydrogen inlet is reduced to be close to zero, so that the gas in the hydrogen gas section is prevented from descending into the water gas collector and flowing out of the water gas outlet.

Fifthly, when the pressure is increased to 2MPa, the oxygen added into the hot nitrogen is turned off for 30 minutes, or the oxygen is turned off, after the temperature of the hot spot is reduced by 100 ℃, the hot nitrogen is put into a furnace and is changed into hot hydrogen with the speed of 5000-10000 Nm³The flow of the hydrogen gas is fed into the furnace, the hydrogen gas section is switched into the process for preparing the hydrogen gas rich in hydrocarbon, the hydrogen gas section is gradually increased at the speed of 1MPa per hour, and the pressure is finally stabilized at the specified pressure of the process.

Controlling the furnace temperature: controlling the temperature of an oxygen combustion layer of the water gas section to be 30-80 ℃ below an ash melting point through the steam-oxygen ratio in the furnace; the highest temperature of the semicoke hydrogenation section is controlled to be less than or equal to 1000 ℃ by controlling the temperature of the hydrogen and the content of methane in the hydrogen gas section;

controlling the components of the hydrocarbon-rich hydrogen gas: the content of methane in the hydrocarbon-rich hydrogen gas is finally controlled to be 50-60 percent and other gaseous hydrocarbons are 100-200 g/Nm according to the activity and the volatile component of the coal by controlling the flow rate, the temperature and the content of methane in the hydrogen gas entering the furnace³Oil gas.

With respect to hydrocarbon-rich hydrogen gas heat recovery, purification, separation and oxygen-free olefin production:

as the water vapor contained in the hydrogen-rich coal gas comes from the raw material coal, namely the moisture content of the coal as fired is a key determining factor of the discharging temperature of the hydrogen-rich coal gas and is also a key factor of the amount of the coal gas wastewater, the moisture in the raw material coal can be reduced, and the coal gas wastewater can be effectively reduced.

As the water vapor in the hydrocarbon-rich hydrogen gas is greatly reduced, the residual heat is also greatly reduced, and the equipment cost is also reduced.

Due to the CO and CO in the hydrocarbon-rich hydrogen gas₂The content is low, after cooling and oil-water separation, different separation processes are designed according to the use of methane: if the methane is mainly used as Liquefied Natural Gas (LNG), cryogenic separation is adoptedAnd (3) hydrogen extraction, wherein if methane is mainly used for the process for preparing olefin by using methane without oxygen, and the pressure of the process for preparing olefin by using methane without oxygen is low, the Pressure Swing Adsorption (PSA) process is adopted for hydrogen extraction so as to greatly reduce the process energy consumption.

The method comprises the following steps of water gas waste heat recovery, purification and separation and hydrogen production:

because the raw material coal of the water gas is all the residual coke of hydro-gasification, the coal gas has no tar, less methane content and about 700 ℃ of temperature, the water gas discharged from the furnace can be used for removing more than 98 percent of dust by adopting a common dry cyclone dust collector to obtain dust, then the temperature of the water gas is reduced by about 100 ℃ through a steam superheater, the water gas enters a waste heat steam boiler, the heat is converted into process steam heat energy, the temperature of the water gas is reduced to about 250 ℃, the water gas enters a No. 2011100943882 patent water gas washing and waste heat recovery device, the excessive temperature inactivation of a CO conversion catalyst is caused due to the overhigh water vapor content in the coal gas, the excessive water vapor in the coal gas is converted into recovered steam which can be fed into the furnace again, the CO conversion catalyst is protected, the gasified water vapor is obtained, and the discharge capacity of the coal gas sewage is reduced.

Since the final objective of water gas production is hydrogen production, the CO shift uses a deep shift with a rate of change of more than 95% to obtain as much hydrogen as possible, the shifted gas is called shift gas, and its composition is mainly H₂And CO, because the PSA system is decarbonized by a dry method through pressure swing adsorption, water is not consumed, the process is simple, and the automation degree is high. The yield of hydrogen can reach 98%, and the separated CO₂Wherein the composition contains small amount of CO and CH₄The combustible substance is CO with the heat quantity of more than 400kJ/Nm3₂The separated hydrogen is used as raw material hydrogen of hydrogen-rich coal gas and sent to a hydrogen main pipe.

Claims (6)

1. A method for preparing natural gas, olefin and coal tar from coal is characterized by comprising the following steps:

the raw material coal is sequentially arranged in the same continuous downward moving pressurized gasification bed layer: heating and drying by hydrocarbon-rich hydrogen gas to remove water; the coal gas is pyrolyzed and retorted by the methane-rich hydrogen gas to prepare the coal tar-rich hydrocarbon-rich hydrogen gas; is gasified by hydrogen to obtainMethane-rich hydrogen gas rich in methane; quilt H₂O+CO₂Gasifying to prepare water gas; o in vaporized oxygen gasifying agent₂Oxidizing and burning residual carbon elements;

the hydrogen circulator (35A) feeds hydrogen for preparing hydrogen-rich gas into a hydrogen heating device (36) during start-up, the hydrogen is sent into a hydrogen distributor (14) arranged in the upper part of the gasification bed layer, descends along the tube bundle, is heated by a heat exchange tube bundle (16), and then enters a coke hydrogenation gasification layer (17) from an outlet at the lower end of the tube bundle; the hydrogen entering the coke hydrogenation gasification layer (17) is deflected upwards and reacts with the carbon element in the coke directly to form C +2H₂＝CH₄Generating methane-hydrogen gas containing methane, heating the hydrogen in the pipe by the released heat through a heat exchange pipe bundle (16), and directly heating the carbon layer and generating high-temperature methane-hydrogen gas; the high-temperature methane hydrogen gas enters the semicoke hydrogenation gasification layer (15) in an upward way, and the hydrogen and the abundant active carbon elements in the semicoke carry out rapid gasification reaction C +2H₂＝CH₄The methane content in the methane-hydrogen gas is greatly increased to form methane-rich hydrogen gas, and heat is released to raise the temperature of the bed layer; the high-temperature methane-rich hydrogen gas ascends into the pyrolysis and dry distillation layer (11) to provide heat for the pyrolysis and dry distillation of the coal, and the methane partial pressure content in the methane-rich hydrogen gas is high, so that the generation and the separation of methane in the coal are effectively inhibited, and hydrogen elements in the coal are forced to be more combined in the coal tar with a lower hydrogen-carbon element ratio, so that the yield and the carbon element gasification rate of the coal tar are effectively increased, the coal tar content of the methane-rich hydrogen gas is increased while the pyrolysis and dry distillation gasification rate of the coal is improved, and the methane-rich hydrogen gas is converted into hydrocarbon-rich hydrogen gas; the hydrocarbon-rich hydrogen gas continuously goes upwards to enter a raw material coal drying layer (10), the moisture in the coal is dried while the raw material coal is heated, so that the adsorbed water and the chemical water in the raw material coal are converted into water vapor to enter the hydrocarbon-rich hydrogen gas, and the hydrocarbon-rich hydrogen gas is discharged from a hydrocarbon-rich hydrogen gas outlet (5) at the upper part of the furnace wall of the hydrocarbon-rich hydrogen gas;

the hydrocarbon-rich hydrogen gas after being discharged out of the furnace is removed with tar dust through a tar dust separator (37), the temperature is reduced through a hydrocarbon-rich hydrogen gas waste heat recovery process device (38), and then the hydrocarbon-rich hydrogen gas is cooled to normal temperature through a hydrocarbon-rich hydrogen gas cooling and oil-water separation process device (39) and is separated to remove oil and water,into H₂S, COS acid gas and hydrogen separation process unit (40) for separating H₂S、COS、CO₂The CO acid gas and the hydrogen gas become the coal-based synthetic natural gas which meets the GB/T33445-2016 standard, wherein one part of the gas enters a methane oxygen-free olefin/aromatic hydrocarbon preparation device (41), and a large amount of hydrogen H is generated while the olefin/aromatic hydrocarbon is prepared₂Directly into the hydrogen header (35) and with H₂S, COS separating hydrogen H from acid gas and hydrogen gas in the process unit (40)₂Water gas CO₂、H₂Hydrogen H from S acid gas removal step (33)₂The first step is pressurized by a hydrogen circulator (35A) and then enters the furnace again to produce hydrogen-rich gas;

after entering the furnace from the furnace bottom, a gasifying agent formed by mixing oxygen and water vapor passes through the grate to the lower part and the upper part to pass through the ash layer (22) to absorb the heat carried by the gasifying agent, the temperature is raised to about 600 ℃ and then enters the oxidation combustion layer (21), and the oxygen in the gasifying agent enables the carbon element remained in the residual coke to be rapidly combusted and gasified to generate CO₂And a large amount of heat is released, so that the temperature of water vapor and a bed layer in the gasifying agent reaches over 1000 ℃ and is below an ash melting point; containing CO₂The high-temperature water vapor transfers heat to the hydro-gasification residual coke from the hydrogen gas section (A) from bottom to top, and simultaneously performs heat absorption water vapor gasification reaction C + H with carbon element in the residual coke₂O＝CO+H₂Most of carbon elements in the residual coke react with 30-40% of water molecules in the water vapor and are converted into CO and H in the raw gas₂The raw gas is wet and hot and enters a gas collector (19) at the upper part of a water gas reaction layer (20) and then is discharged from the furnace through a raw gas outlet (3) on the furnace wall;

heating raw gas discharged from a furnace by a dedusting superheater (29), feeding the raw gas into furnace steam, feeding the raw gas into a gas waste heat boiler (30) to produce steam required by partial coal gasification, feeding the steam into a water gas washing waste heat recovery device (31), converting 30-75% of the steam in the gas into steam for gasification, feeding the gas into a CO conversion process (32), and carrying out CO + H on more than 95% of CO by a catalyst₂O＝CO+H₂Carrying out a shift reaction; the converted gas is called converted gas, and the main component of the converted gas is H₂And CO₂(ii) a Converting CO in gas₂Acid gas and small amount of H₂S acid gas is removed by adopting a pressure swing adsorption PSA separation process, and the heat value of combustible components is 400kJ/Nm³Part of CO above₂And (3) desorbing the gas, and sending the desorbed gas into a gas turbine tail gas boiler or a low-calorific-value gas boiler to convert combustible components in the desorbed gas into steam energy for recycling.

2. The method of claim 1, wherein during normal production, steam in the steam-oxygen gasification agent fed into the furnace is provided by a water jacket steam drum connected with a water jacket, a coal gas waste heat boiler, CO shift reaction heat and a water gas washing waste heat recovery device; wherein the steam produced by the water gas washing waste heat recovery device is already higher than the condensation temperature, and the recovered steam contains a small amount of O₂And corrosive impurities and dissolved salt, in order to prolong the service life of the steam superheater, the recovered steam produced by the water gas washing waste heat recovery device does not enter the steam superheater but is mixed with superheated steam at the outlet of the steam superheater, and then proper amount of O is added₂After the steam-oxygen ratio of the gasifying agent reaches the technological requirement, the gas enters the furnace through the steam-oxygen gasifying agent inlet.

3. The method for preparing natural gas, olefin and coal tar from coal according to claim 1, wherein during normal production, 30-80% of total oxygen in the steam-oxygen gasifying agent fed into the furnace is added into the gasifying agent as a stripping medium in the water gas washing waste heat recovery device according to the water vapor content in the water gas and the amount of water vapor required to be stripped, and 20-70% of the total oxygen is added into the gasifying agent as a supplement amount meeting the requirements of a steam-gas ratio.

4. The method of claim 1, wherein the same continuously downward moving pressurized gasification bed is configured as a two-stage pressurized moving bed gas furnace with different functional structures in the upper and lower stages, and the lower part of the two-stage pressurized moving bed gas furnace is designed to use a mixed gasification agent of oxygen and water vapor to generate a hydrocarbon-rich gasThe residual coke of the hydrogen gas section is used as a raw material to produce hydrogen and carbon monoxide, and the height-diameter ratio of a gasification bed layer of the residual coke is 0.5-1.5; the upper part of the reactor is designed to adopt methane less than or equal to 15 percent, hydrogen 80-95 percent, CO + CO₂+H₂O+N₂≤5％，H₂S≤0.5％，O₂The hydrogen gasification agent takes hydrogen as a main component, and the raw material coal is directly used for producing a multi-carbon hydrogen gas section which takes natural gas, olefin and coal tar as main products, wherein the height-diameter ratio of a gasification raw material coal bed layer is 2-6.8.

5. The method of claim 1, wherein the highest temperature of the water gas section is a dry-slagging gasification mode below an ash melting point temperature or a slag gasification mode above the ash melting point temperature.

6. The method for preparing natural gas, olefin and coal tar from coal according to claim 1, wherein the process pressure of the pressurized coal gasification bed is 1-3 MPa, or 3-6 MPa, or 6-10 MPa, and the process pressure of the methane-oxygen-free olefin preparation is 0.95-0.6 times, or 0.6-0.3 times, or 0.3-0.1 times, or 0.1-0.05 times of the outlet pressure of the hydrocarbon-rich hydrogen gas.

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