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CN-122012146-A - Multi-nozzle opposite coal gasification and isothermal shift coupling method

CN122012146ACN 122012146 ACN122012146 ACN 122012146ACN-122012146-A

Abstract

The invention relates to the technical field of energy chemical industry and coal conversion, and discloses a multi-nozzle opposite coal gasification and isothermal transformation coupling method, which comprises the following steps: firstly, a multi-nozzle opposite coal gasification process is carried out, and pulverized coal with granularity less than or equal to 0.1mm and water are mixed according to the mass ratio of 1:1.8-2.2 to prepare the coal water slurry. According to the invention, through the coupling design of 'collision impact flow gasification+U-shaped pipe isothermal transformation', the carbon conversion rate and CO conversion stability are greatly improved, and the service life of core equipment is prolonged. In the gasification stage, 4-6 opposite burners spray coal water slurry and oxygen into a gasification furnace to form a hedging impinging stream reaction zone, the mixing uniformity is improved to be more than 95%, the carbon conversion rate is broken through 98% and the residual carbon loss is reduced by 60% by matching with the high temperature of 1400-1600 ℃ and the high pressure of 6.0-7.5MPa, meanwhile, the cooling water quantity is adjusted through the content feedback of CO at an outlet, the CO conversion rate is stabilized to be more than 98.5%, the service life of the catalyst is prolonged to 3-4 years, and the replacement frequency is reduced by 60%.

Inventors

  • JIANG ZICHENG
  • YAN LIQIANG
  • ZHANG JIAN

Assignees

  • 连云港碱业有限公司

Dates

Publication Date
20260512
Application Date
20251231

Claims (8)

  1. 1. The multi-nozzle opposite coal gasification and isothermal shift coupling method is characterized by comprising the following steps of: Firstly, performing a multi-nozzle opposite coal gasification process, mixing pulverized coal with granularity less than or equal to 0.1mm with water according to a mass ratio of 1:1.8-2.2 to prepare coal water slurry, pressurizing the coal water slurry to 6.5-8.0MPa by a high-pressure diaphragm pump, then spraying the coal water slurry and oxygen with purity more than or equal to 99.5% into a gasification furnace through 4-6 burners which are oppositely arranged, wherein an included angle between the axis of each burner and the central axis of the gasification furnace is 15-20 degrees, so as to form a opposite impact flow reaction zone, the gasification furnace adopts a water-cooled wall structure, the reaction temperature in the furnace is controlled at 1400-1600 ℃, the reaction pressure is maintained at 6.0-7.5MPa, and the pulverized coal undergoes partial oxidation reaction in the furnace to generate crude gas, wherein the reaction equation is that The crude gas is chilled to 900-1000 ℃ by a water cooling wall and then enters a washing tower, more than 99% of ash slag is removed, and crude gas containing 38-45% of CO and 18-22% of H 2 28-35%、CO 2 is obtained, and the carbon conversion rate is more than or equal to 98%; Step two, performing gas-solid separation and heat recovery procedures, removing fly ash with the particle size of more than or equal to 5 mu m from the washed raw gas through a cyclone separator, then entering a waste heat boiler, exchanging heat with boiler feed water, recovering heat to generate medium-pressure steam with the temperature of 3.82MPa and 450 ℃, reducing the temperature of the raw gas to 300-350 ℃, and ensuring that the thermal efficiency of the waste heat boiler is more than or equal to 90%; Step three, then an isothermal conversion coupling procedure is carried out, the cooled crude gas and the process condensate are mixed according to the water-gas ratio of 1.2-1.5, the temperature is regulated to 220-250 ℃, the mixture is fed into an isothermal conversion furnace, a Co-Mo sulfur-resistant catalyst is filled in the conversion furnace, a U-shaped heat exchange tube is arranged in a catalyst bed layer, boiler water is fed into the tube as a cooling medium, the temperature of the bed layer is kept stable at 230-280 ℃ by controlling the cooling water quantity, and the CO undergoes a conversion reaction: the reaction conversion rate is regulated through the feedback of the content of CO at the outlet, when the content of CO at the outlet is more than 0.5%, the cooling water is increased to reduce the temperature of the bed layer, and when the content of CO at the outlet is less than 0.2%, the cooling water is reduced to raise the temperature of the bed layer, so that the CO conversion rate is more than or equal to 98.5%; And finally, performing a gas-liquid separation procedure, enabling the transformed mixed gas to enter a separator, enabling part of separated process condensate to flow back to an inlet of a transformation furnace to adjust the water-gas ratio, enabling part of the separated process condensate to be sent to a coal water slurry preparation procedure for reuse, and enabling the purified gas to be sent to a subsequent desulfurization and decarbonization unit.
  2. 2. The multi-nozzle opposite coal gasification and isothermal shift coupling method according to claim 1, wherein the burner of the multi-nozzle opposite coal gasification process adopts an inner, middle and outer three-layer channel structure, the flow rate of the inner layer channel is controlled to be 2.5-3.0m/s, the middle layer channel is used for conveying oxygen, the flow rate is 80-100m/s, the outer layer channel is used for conveying sealing nitrogen, the flow rate is 15-20m/s, the pressure difference of the three-layer channel is maintained to be 0.3-0.5MPa, the burner head is made of heat-resistant alloy, and the surface of the burner is sprayed with a zirconia coating, and the thickness of the burner head is 0.8-1.2mm; the gasification furnace water-cooled wall adopts a hanging vertical pipe structure, a water circulation system with natural circulation and forced circulation coupled is arranged in the pipe, and the circulation rate is increased The calculation formula is that Wherein the method comprises the steps of For the amount of water to be circulated, In order to evaporate the amount of water, The temperature is controlled to be 5-8, the natural circulation is automatically switched under an emergency state, the water circulation safety coefficient is more than or equal to 1.5, the thickness of water-cooling wall-mounted slag is maintained to be 50-80mm, the furnace temperature is controlled in real time by adjusting the oxygen flow, and the response time of the furnace temperature adjustment is less than or equal to 10s.
  3. 3. The multi-nozzle opposed coal gasification and isothermal shift coupling method according to claim 1, wherein the coal water slurry preparation process adopts a two-stage grinding process, raw coal is crushed to a particle size less than or equal to 3mm by one-stage grinding, the coal particles are ground to a target particle size by a ball mill by the two-stage grinding, the ball mill rotating speed is controlled to be 18-22r/min, grinding media are steel balls with a diameter of 20-50mm, the steel ball grading is matched according to a mass ratio of 3:4:3, the grinding time is 20-30min, the coal water slurry concentration is monitored in real time by an online densimeter, the density is controlled to be 1200-1300kg/m < 3 >, when the density deviates from a set value, the water adding amount is regulated by a PID controller, and the regulation formula is that Wherein the method comprises the steps of In order to add water after the adjustment, For the initial water addition amount, For the purpose of the target density, For measuring the density, the stability of the coal water slurry is ensured, and the coal water slurry is kept stand for 48 hours without layering.
  4. 4. The multi-nozzle opposed coal gasification and isothermal conversion coupling method according to claim 1, wherein the isothermal conversion furnace adopts a tubular structure, a catalyst bed is divided into an upper section, a middle section and a lower section, the upper section is filled with Co-Mo catalyst with granularity phi 3 multiplied by 5mm, the middle section is filled with Co-Mo catalyst with granularity phi 4 multiplied by 6mm, the lower section is filled with Co-Mo catalyst with granularity phi 5 multiplied by 8mm, the catalyst stacking density is 1.2-1.4g/cm < 3 >, the height-diameter ratio of the bed is 2.5-3.0, U-shaped heat exchange tubes are made of 316L stainless steel, the tube spacing is 2-3 times of the catalyst particle size, and the heat exchange area calculation formula is Wherein the method comprises the steps of In order to react with the amount of heat released, For the total heat transfer coefficient (value 80-100W/(m2.+ -. C.)), For logarithmic average temperature difference, the axial temperature difference of the bed layer is ensured to be less than or equal to 15 ℃, a static mixer is arranged at the inlet of the conversion furnace, the raw gas and the process condensate are fully mixed, the mixing uniformity is more than or equal to 95%, and the catalyst deactivation caused by local overheating is avoided.
  5. 5. The multi-nozzle opposed coal gasification and isothermal shift coupling method according to claim 1, wherein the waste heat boiler of the heat recovery process adopts a natural circulation structure, specifically: The boiler water supply is preheated to 190-210 ℃ by an economizer and then enters a steam drum, then is sent to a water-cooled wall lower header through a downcomer, a steam-water mixture is generated after heat is absorbed, the steam drum is returned by an ascending pipe for steam-liquid separation, and the separated saturated steam is heated to 450 ℃ by a heater; The heat transfer coefficient of the waste heat boiler is regulated through the flue gas flow rate, the flue gas flow rate is controlled at 8-12m/s, when the heat transfer coefficient is lower than 70W/(m < 2 > and the temperature is lower than the temperature), the sound wave soot blower is started to remove the ash of the heated area, the soot blowing period is 2-4h, the soot blowing time is 3-5min each time, and the continuous operation efficiency of the waste heat boiler is ensured to be not lower than 88%; The separation efficiency of the cyclone separator is calculated as follows Wherein the method comprises the steps of In order to divide the particle size into particles, For the diameter of the separator, n is the separation index, and the separation efficiency is ensured to be more than or equal to 99 percent.
  6. 6. The multi-nozzle opposed coal gasification and isothermal shift coupling method according to claim 1, wherein the coordinated control of gasification and shift pressure adopts a series adjustment mode, specifically: the pressure of the gasification furnace is controlled by an oxygen flow regulating valve, and the pressure is set When the pressure in the furnace deviates from 6.5MPa When the oxygen flow is regulated, the regulation formula is that Wherein the method comprises the steps of In order to adjust the flow rate of the oxygen after the adjustment, For the initial oxygen flow rate, Is the measured pressure; the inlet pressure of the isothermal shift converter is controlled by a raw gas flow regulating valve, the inlet pressure is maintained to be lower than the outlet pressure of the gasifier by 0.1-0.2MPa, and the pressure fluctuation range is less than or equal to +/-0.05 MPa; meanwhile, a buffer tank is arranged between the gasification furnace and the shift converter, and the volume is designed according to the treatment capacity of the raw gas of 10-15s, so that the pressure and the flow of the air flow are further stabilized.
  7. 7. The multi-nozzle opposed coal gasification and isothermal shift coupling method according to claim 1, wherein the catalyst activation and regeneration process comprises the steps of: After the catalyst is filled, nitrogen is firstly introduced to carry out an airtight test, the pressure is increased to 4.0MPa, the pressure is maintained for 24 hours, and the leakage rate is less than or equal to 0.5%/h; then heating to 120 ℃ and drying for 4 hours, heating to 200 ℃, introducing nitrogen containing 5%H 2 for reduction and activation, and reducing for 24-30 hours, wherein the judgment standard of the reduction end point is that the content of the outlet H 2 is more than or equal to 4.5% and no moisture is generated; When the activity of the catalyst is reduced to 70% of the initial activity, the regeneration treatment is carried out, nitrogen is firstly introduced to cool to 180 ℃, then nitrogen containing 2%O 2 is introduced to carry out oxidation regeneration, the regeneration temperature is controlled to be 200-250 ℃, the regeneration time is 18-24h, the activity of the regenerated catalyst is recovered to more than 90% of the initial activity, and the service life of the catalyst is prolonged to 3-4 years.
  8. 8. The multi-nozzle opposed coal gasification and isothermal shift coupling method according to any one of claims 1 to 7, further comprising a system energy efficiency optimization and environmental protection treatment process, wherein the energy efficiency optimization is realized through energy cascade utilization, one part of medium-pressure steam generated by a waste heat boiler is used for driving a synthesis gas compressor unit, the other part of the medium-pressure steam is used for process heating, the steam utilization rate is more than or equal to 95%, the water content of ash generated by gasification is reduced to below 20% after dehydration, and the ash is sent to a building material factory to prepare cement clinker, and the ash utilization rate is more than or equal to 98%; In the environment-friendly treatment procedure, the process wastewater enters a biochemical treatment system after flash evaporation and degassing, COD and ammonia nitrogen are degraded by adopting an A/O process, COD of the wastewater after treatment is less than or equal to 50mg/L, ammonia nitrogen is less than or equal to 5mg/L, the wastewater meets the water supplementing standard of circulating water and is reused, acid gas generated in the gasification and transformation process is collected and then sent to a sulfur recovery device, sulfur is produced by adopting a Claus process, and the sulfur recovery rate is more than or equal to 99.5%.

Description

Multi-nozzle opposite coal gasification and isothermal shift coupling method Technical Field The invention relates to the technical field of energy chemical industry and coal conversion, in particular to a multi-nozzle opposite coal gasification and isothermal transformation coupling method. Background In the fields of modern coal chemical industry, synthetic ammonia, IGCC and other energy chemical industry, coal gasification is a core technology for converting coal into synthetic gas (CO+H 2), and a CO conversion procedure converts high-duty CO in the synthetic gas into H 2, so that qualified raw material gas is provided for subsequent chemical synthesis. Three core pain points exist in the traditional coal gasification and CO conversion system, and the production efficiency and the economy are severely restricted: The gasification reaction is insufficient, the carbon conversion rate is low, the traditional single-nozzle gasification furnace has a reaction dead zone, the pulverized coal and oxygen are unevenly mixed, the carbon conversion rate is often lower than 95%, unreacted carbon residues are discharged along with ash residues, coal waste is caused, the burner is easy to coke and block, frequent shutdown and cleaning are needed, and the annual running time is less than 8000 hours. The transformation reaction is thermal runaway, the service life of the catalyst is short, CO is transformed into strong exothermic reaction, a traditional adiabatic transformation furnace does not have an efficient temperature control means, the temperature of a bed layer is easy to surge to be higher than 350 ℃, the sintering deactivation of a Co-Mo catalyst is caused, the service life is only 1-1.5 years, meanwhile, the CO conversion rate is unstable (the fluctuation range is +/-5 percent) due to temperature fluctuation, the subsequent additional adjustment is needed, and the product quality is influenced. The system has low energy efficiency and high environmental protection pressure, the gasification and transformation processes are independently operated, the sensible heat of the raw gas is not fully recovered, the waste heat utilization rate is lower than 80%, the water content of gasified ash is high (30%), the COD of the process wastewater exceeds standard (500 mg/L), the environmental protection treatment cost is high, and the direct discharge of acid gas is easy to cause atmospheric pollution and does not meet the requirement of the 'double-carbon' policy. In addition, the pressure control of the traditional system is independent, the pressure fluctuation of the gasification furnace and the conversion furnace is large (+ -0.2 MPa), the air flow impact equipment is easy to be triggered, and the maintenance cost is increased. Therefore, an integrated coupling method of efficient gasification-isothermal transformation-energy efficiency optimization is needed to solve the above technical problems. Disclosure of Invention The invention aims to provide a multi-nozzle opposite coal gasification and isothermal shift coupling method for solving the problems in the background art. In order to achieve the purpose, the invention provides the technical scheme that the multi-nozzle opposite coal gasification and isothermal shift coupling method comprises the following steps: Firstly, performing a multi-nozzle opposite coal gasification process, mixing pulverized coal with granularity less than or equal to 0.1mm with water according to a mass ratio of 1:1.8-2.2 to prepare coal water slurry, pressurizing the coal water slurry to 6.5-8.0MPa by a high-pressure diaphragm pump, then spraying the coal water slurry and oxygen with purity more than or equal to 99.5% into a gasification furnace through 4-6 burners which are oppositely arranged, wherein an included angle between the axis of each burner and the central axis of the gasification furnace is 15-20 degrees, so as to form a opposite impact flow reaction zone, the gasification furnace adopts a water-cooled wall structure, the reaction temperature in the furnace is controlled at 1400-1600 ℃, the reaction pressure is maintained at 6.0-7.5MPa, and the pulverized coal undergoes partial oxidation reaction in the furnace to generate crude gas, wherein the reaction equation is that The crude gas is chilled to 900-1000 ℃ by a water cooling wall and then enters a washing tower, more than 99% of ash slag is removed, and crude gas containing 38-45% of CO and 18-22% of H 228-35%、CO2 is obtained, and the carbon conversion rate is more than or equal to 98%; Step two, performing gas-solid separation and heat recovery procedures, removing fly ash with the particle size of more than or equal to 5 mu m from the washed raw gas through a cyclone separator, then entering a waste heat boiler, exchanging heat with boiler feed water, recovering heat to generate medium-pressure steam with the temperature of 3.82MPa and 450 ℃, reducing the temperature of the raw gas to 300-350 ℃, and ensuring that the the