Multi-nozzle opposed coal gasification and isothermal transformation coupling method

Abstract

The invention relates to the technical field of energy chemical industry and coal conversion, and discloses a multi-nozzle opposed coal gasification and isothermal transformation coupling method which comprises the following steps: step 1, firstly, executing a multi-nozzle opposed coal gasification process, and mixing pulverized coal with the particle size of less than or equal to 0.1 mm with water according to a mass ratio of 1: (1.8-2.2) to prepare coal water slurry; through the coupling design of hedging impinging stream gasification and U-shaped pipe isothermal transformation, the carbon conversion rate and the CO conversion stability are greatly improved, and the service life of core equipment is prolonged. In the gasification stage, 4-6 opposed burners inject coal water slurry and oxygen into the gasification furnace to form a hedging impinging stream reaction zone, the mixing uniformity is improved to 95% or above, the high temperature of 1400-1600 DEG C and the high pressure of 6.0-7.5 MPa are matched, the carbon conversion rate breaks through 98%, and the residual carbon loss is reduced by 60%; meanwhile, the cooling water amount is adjusted through CO content feedback at an outlet, the CO conversion rate is stabilized at 98.5% or above, the service life of the catalyst is prolonged to 3-4 years, and the replacement frequency is reduced by 60%.

Description

Technical Field

[0001] This invention relates to the fields of energy chemical engineering and coal conversion technology, specifically a method for coupling multi-nozzle opposed coal gasification with isothermal conversion. Background Technology

[0002] In modern coal chemical industry, ammonia synthesis, IGCC, and other energy chemical fields, coal gasification is the core technology for converting coal into syngas (CO + H2), while the CO conversion process converts the high proportion of CO in the syngas into H2, providing qualified feedstock gas for subsequent chemical synthesis. Traditional coal gasification and CO conversion systems suffer from three major pain points that severely restrict production efficiency and economic viability:

[0003] Incomplete gasification reaction and low carbon conversion rate: Traditional single-nozzle gasifiers have reaction dead zones, uneven mixing of pulverized coal and oxygen, and the carbon conversion rate is often below 95%. Unreacted residual carbon is discharged with ash and slag, resulting in coal waste. Moreover, the burner is prone to coking and clogging, requiring frequent shutdowns for cleaning, and the annual operating time is less than 8,000 hours.

[0004] Thermal runaway in the conversion reaction and short catalyst life: CO conversion is a strongly exothermic reaction. Traditional adiabatic conversion furnaces lack efficient temperature control methods, and the bed temperature can easily soar to above 350℃, leading to sintering and deactivation of the Co-Mo catalyst, with a service life of only 1-1.5 years. At the same time, temperature fluctuations cause unstable CO conversion rates (fluctuation range ±5%), requiring additional adjustments and affecting product quality.

[0005] The system has low energy efficiency and high environmental pressure: the gasification and conversion processes operate independently, the sensible heat of the crude gas is not fully recovered, and the waste heat utilization rate is less than 80%; the gasification ash has a high moisture content (>30%), the process wastewater COD exceeds the standard (>500mg / L), the environmental treatment cost is high, and the direct emission of acidic gases can easily cause air pollution, which does not meet the requirements of the "dual carbon" policy.

[0006] Furthermore, traditional systems have independent pressure control, resulting in large pressure fluctuations (±0.2MPa) between the gasifier and the shift converter, which can easily cause airflow to impact the equipment and increase maintenance costs. Therefore, there is an urgent need for an integrated coupling method of "high-efficiency gasification-isothermal shift conversion-energy efficiency optimization" to solve the above-mentioned technical problems. Summary of the Invention

[0007] The purpose of this invention is to provide a method for coupling multi-nozzle opposed coal gasification and isothermal transformation to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a multi-nozzle opposed coal gasification and isothermal transformation coupling method, comprising the following steps:

[0009] Step 1: First, a multi-nozzle opposed coal gasification process is performed. Pulverized coal with a particle size ≤0.1mm is mixed with water at a mass ratio of 1:1.8-2.2 to prepare a coal-water slurry. The slurry is pressurized to 6.5-8.0 MPa by a high-pressure diaphragm pump and then injected into the gasifier along with oxygen (purity ≥99.5%) through 4-6 opposed burners. The burner axis is at an angle of 15-20° to the central axis of the gasifier, forming an opposing impingement flow reaction zone. The gasifier uses a water-cooled wall structure, with the reaction temperature controlled at 1400-1600℃ and the reaction pressure maintained at 6.0-7.5 MPa. The pulverized coal undergoes partial oxidation within the furnace to generate crude coal gas. The reaction equation is as follows:

[0010]

[0011]

[0012]

[0013] After being quenched to 900-1000℃ by a water-cooled wall, the crude coal gas enters a scrubbing tower to remove more than 99% of the ash and slag, yielding crude coal gas containing 38-45% CO, 28-35% H2, and 18-22% CO2, with a carbon conversion rate ≥98%.

[0014] Step 2: Next, the gas-solid separation and heat recovery process is carried out. The washed crude gas first passes through a cyclone separator to remove fly ash with a particle size ≥5μm, and then enters the waste heat boiler to exchange heat with the boiler feedwater. The recovered heat generates medium-pressure steam at 3.82MPa and 450℃, and the temperature of the crude gas drops to 300-350℃. The thermal efficiency of the waste heat boiler is ≥90%.

[0015] Step 3: Subsequently, the isothermal conversion coupling process is executed. The cooled crude gas and process condensate are mixed at a water-to-gas ratio of 1.2-1.5, and the temperature is adjusted to 220-250℃ before being fed into the isothermal conversion furnace. The furnace is filled with a Co-Mo sulfur-resistant catalyst, and the catalyst bed has built-in U-shaped heat exchange tubes. Boiler feedwater is circulated through the tubes as a cooling medium. The bed temperature is maintained stable at 230-280℃ by controlling the cooling water flow rate, and CO undergoes a conversion reaction.

[0016]

[0017] The reaction conversion rate is adjusted by feedback from the outlet CO content. When the outlet CO > 0.5%, the cooling water flow is increased to reduce the bed temperature; when the outlet CO < 0.2%, the cooling water flow is reduced to increase the bed temperature, ensuring a CO conversion rate ≥ 98.5%.

[0018] Finally, the gas-liquid separation process is performed. The converted mixed gas enters the separator. Part of the separated process condensate is returned to the inlet of the converter to adjust the water-gas ratio, and part is sent to the coal-water slurry preparation process for reuse. The purified gas is sent to the subsequent desulfurization and decarbonization unit.

[0019] Preferably, the burner in the multi-nozzle opposed coal gasification process adopts a three-layer channel structure: inner, middle, and outer. The inner channel transports coal-water slurry at a flow rate controlled at 2.5-3.0 m / s, the middle channel transports oxygen at a flow rate of 80-100 m / s, and the outer channel transports sealing nitrogen at a flow rate of 15-20 m / s. The pressure difference between the three channels is maintained at 0.3-0.5 MPa. The burner head is made of heat-resistant alloy material and coated with a zirconium oxide coating with a thickness of 0.8-1.2 mm.

[0020] The gasifier's water-cooled wall adopts a suspended vertical tube structure, with a water circulation system inside the tubes that couples natural and forced circulation, and a circulation ratio of [missing information]. The calculation formula is

[0021]

[0022] in For circulating water volume, This refers to the amount of water evaporated. The temperature is controlled between 5 and 8. In an emergency, it automatically switches to natural circulation. The water circulation safety factor is ≥1.5. The slag thickness on the water-cooled wall is maintained at 50-80mm. The furnace temperature is controlled in real time by adjusting the oxygen flow rate. The furnace temperature adjustment response time is ≤10s.

[0023] Preferably, the coal-water slurry preparation process employs a two-stage grinding process. The first stage grinding crushes the raw coal to a particle size ≤3mm. The second stage grinding uses a ball mill to grind the coal particles to the target particle size. The ball mill speed is controlled at 18-22 r / min, and the grinding media are steel balls with a diameter of 20-50mm, graded in a mass ratio of 3:4:3. The grinding time is 20-30 minutes. The coal-water slurry concentration is monitored in real-time using an online density meter, and the density is controlled at 1200-1300 kg / m³. When the density deviates from the set value, the water addition is adjusted using a PID controller, with the adjustment formula being:

[0024]

[0025] in To adjust the amount of water added, This is the initial water volume. For the target density, To ensure the actual density and stability of the coal-water slurry, it was left to stand for 48 hours without stratification.

[0026] Preferably, the isothermal conversion furnace adopts a tube-and-shell structure, with the catalyst bed divided into upper, middle, and lower sections. The upper section is filled with Co-Mo catalyst with a particle size of Φ3×5mm, the middle section with Co-Mo catalyst with a particle size of Φ4×6mm, and the lower section with Co-Mo catalyst with a particle size of Φ5×8mm. The catalyst bulk density is 1.2-1.4 g / cm³, and the bed height to diameter ratio is 2.5-3.0. The U-shaped heat exchange tubes are made of 316L stainless steel, and the tube spacing is 2-3 times the catalyst particle size. The heat exchange area is calculated using the following formula:

[0027]

[0028] in The reaction is exothermic. The overall heat transfer coefficient (valued at 80-100 W / (m²・℃)). To ensure a logarithmic mean temperature difference and an axial temperature difference of ≤15℃, a static mixer is installed at the inlet of the converter to fully mix the crude gas and process condensate, achieving a mixing uniformity of ≥95%, thus preventing local overheating that could lead to catalyst deactivation.

[0029] Preferably, the waste heat boiler in the heat recovery process adopts a natural circulation structure, specifically:

[0030] The boiler feedwater is preheated to 190-210℃ by the economizer and then enters the steam drum. It is then sent to the lower header of the water-cooled wall through the downcomer. After absorbing heat, it generates a steam-water mixture, which returns to the steam drum through the riser for steam-liquid separation. The separated saturated steam is heated to 450℃ by the heat exchanger.

[0031] The heat transfer coefficient of the waste heat boiler is adjusted by the flue gas velocity, which is controlled at 8-12 m / s. When the heat transfer coefficient is lower than 70 W / (m²・℃), the sonic soot blower is started to remove ash from the heated surface. The soot blowing cycle is 2-4 hours, and each soot blowing time is 3-5 minutes, ensuring that the continuous operating efficiency of the waste heat boiler is not less than 88%.

[0032] The formula for calculating the separation efficiency of a cyclone separator is as follows:

[0033]

[0034] in To segment particle size, Where n is the separator diameter and n is the separation index, ensuring a separation efficiency of ≥99%.

[0035] Preferably, the pressure coordination control of gasification and transformation adopts a series regulation method, specifically:

[0036] The pressure of the gasifier is controlled by an oxygen flow regulating valve, and the pressure is set. =6.5MPa, when the pressure inside the furnace deviates At that time, adjust the oxygen flow rate using the following formula:

[0037]

[0038] in To adjust the oxygen flow rate, This is the initial oxygen flow rate. This is the actual measured pressure;

[0039] The inlet pressure of the isothermal converter is controlled by the crude gas flow regulating valve to maintain the inlet pressure 0.1-0.2 MPa lower than the gasifier outlet pressure, with a pressure fluctuation range of ≤±0.05 MPa.

[0040] Meanwhile, a buffer tank is installed between the gasifier and the shift converter, with a volume designed to handle 10-15 seconds of crude gas, to further stabilize the gas flow pressure and flow rate.

[0041] Preferably, the catalyst activation and regeneration process includes the following steps:

[0042] After the catalyst is loaded, nitrogen is first introduced to conduct an airtightness test. The pressure is increased to 4.0 MPa and maintained for 24 hours. The leakage rate is ≤0.5% / h.

[0043] Then, the temperature is raised to 120℃ and dried for 4 hours, then raised to 200℃ and nitrogen gas containing 5% H2 is introduced for reduction and activation. The reduction time is 24-30 hours. The criterion for the reduction endpoint is that the H2 content at the outlet is ≥4.5% and no moisture is produced.

[0044] When the catalyst activity drops to 70% of its initial activity, regeneration is performed. First, nitrogen gas is introduced to cool the catalyst to 180°C, and then nitrogen gas containing 2% O2 is introduced for oxidation regeneration. The regeneration temperature is controlled at 200-250°C, and the regeneration time is 18-24 hours. After regeneration, the catalyst activity is restored to more than 90% of its initial activity, extending the catalyst service life to 3-4 years.

[0045] Preferably, the system also includes energy efficiency optimization and environmental protection processes. Energy efficiency optimization is achieved through energy cascade utilization, where part of the medium-pressure steam generated by the waste heat boiler is used to drive the syngas compressor unit, and part is used for process heating, with a steam utilization rate of ≥95%. The ash produced by gasification is dehydrated to a moisture content of less than 20% and sent to a building materials plant to prepare cement clinker, with an ash utilization rate of ≥98%.

[0046] In the environmental protection process, the process wastewater is degassed by flash evaporation and then enters the biochemical treatment system. The A / O process is used to degrade COD and ammonia nitrogen. After treatment, the wastewater COD is ≤50mg / L and ammonia nitrogen is ≤5mg / L. After meeting the circulating water makeup water standard, it is reused. The acidic gas generated during the gasification and conversion process is collected and sent to the sulfur recovery unit. The Claus process is used to produce sulfur with a sulfur recovery rate of ≥99.5%.

[0047] This invention provides a method for coupling multi-nozzle opposed coal gasification with isothermal shift reaction. It has the following beneficial effects:

[0048] 1. This invention significantly improves carbon conversion rate and CO conversion stability, and extends the life of core equipment through a coupled design of "opposing impact flow gasification + U-tube isothermal transformation". In the gasification stage, 4-6 opposed burners inject water-coal slurry and oxygen into the gasifier, forming an opposing impact flow reaction zone, increasing the mixing uniformity to over 95%. Combined with a high temperature of 1400-1600℃ and a high pressure of 6.0-7.5MPa, the carbon conversion rate exceeds 98%, and residual carbon loss is reduced by 60%. The burners adopt a three-layer channel structure with a pressure difference of 0.3-0.5MPa, effectively preventing coking and blockage, and extending the annual operating time to over 8500 hours. During the conversion stage, the isothermal converter has built-in U-shaped heat exchange tubes, which remove the heat of reaction in real time through boiler feedwater, stabilizing the bed temperature at 230-280℃ and the axial temperature difference at ≤15℃, thus avoiding catalyst sintering. At the same time, the cooling water volume is adjusted by feedback of the CO content at the outlet, and the CO conversion rate is stabilized at over 98.5%, extending the catalyst life to 3-4 years and reducing the replacement frequency by 60%.

[0049] 2. This invention innovatively optimizes the entire process of "sensible heat recovery - media reuse - waste resource utilization," significantly improving energy efficiency and environmental protection. In terms of energy recovery, the gasified crude gas is heat-exchanged in a waste heat boiler to generate medium-pressure steam at 3.82 MPa and 450℃, with a thermal efficiency ≥90%. Part of the steam drives the syngas compressor unit, and the other part is used for process heating, with a utilization rate ≥95%. Simultaneously, the water circulation system adopts a natural + forced circulation coupling mode, automatically switching to natural circulation in emergency situations, with a safety factor ≥1.5, further reducing energy consumption. In terms of environmental treatment, the gasification ash is dehydrated to a moisture content ≤20% and sent to a building materials plant to prepare cement clinker, with a utilization rate ≥98%. Process wastewater is treated using an A / O process, reducing COD to below 50 mg / L and ammonia nitrogen to ≤5 mg / L, and is reused after meeting the circulating water makeup water standard. Acidic gases are processed through the Claus process to produce sulfur, with a recovery rate ≥99.5%. The system's overall energy efficiency is improved to over 45%, reducing energy consumption by 15% compared to traditional systems, and achieving near-zero emissions of solid waste, wastewater, and exhaust gas. Attached Figure Description

[0050] Figure 1 This is a flowchart of the overall process of multi-nozzle opposed coal gasification and isothermal conversion coupling of the present invention;

[0051] Figure 2 This is a flow chart of the coal-water slurry preparation and gasification process of the present invention;

[0052] Figure 3 This is a flowchart of the gas-solid separation and heat recovery process of the present invention;

[0053] Figure 4 This is a flowchart of the isothermal transformation coupling and gas-liquid separation process of the present invention;

[0054] Figure 5 This is a flowchart illustrating the catalyst activation and regeneration process of the present invention.

[0055] Figure 6 This is a flowchart of the system pressure control and environmental protection process of the present invention. Detailed Implementation

[0056] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0058] Example 1

[0059] A preferred embodiment of the multi-nozzle opposed coal gasification and isothermal transformation coupling method provided by the present invention is as follows: Figure 1-6 As shown: A multi-nozzle opposed coal gasification and isothermal transformation coupling method includes the following steps:

[0060] Step 1: First, a multi-nozzle opposed coal gasification process is performed. Pulverized coal with a particle size ≤0.1mm is mixed with water at a mass ratio of 1:1.8-2.2 to prepare a coal-water slurry. The slurry is pressurized to 6.5-8.0 MPa by a high-pressure diaphragm pump and then injected into the gasifier along with oxygen (purity ≥99.5%) through 4-6 opposed burners. The burner axis is at an angle of 15-20° to the central axis of the gasifier, forming an opposing impingement flow reaction zone. The gasifier uses a water-cooled wall structure, with the reaction temperature controlled at 1400-1600℃ and the reaction pressure maintained at 6.0-7.5 MPa. The pulverized coal undergoes partial oxidation within the furnace to generate crude coal gas. The reaction equation is as follows:

[0061]

[0062]

[0063]

[0064] After being quenched to 900-1000℃ by a water-cooled wall, the crude coal gas enters a scrubbing tower to remove more than 99% of the ash and slag, yielding crude coal gas containing 38-45% CO, 28-35% H2, and 18-22% CO2, with a carbon conversion rate ≥98%.

[0065] Step 2: Next, the gas-solid separation and heat recovery process is carried out. The washed crude gas first passes through a cyclone separator to remove fly ash with a particle size ≥5μm, and then enters the waste heat boiler to exchange heat with the boiler feedwater. The recovered heat generates medium-pressure steam at 3.82MPa and 450℃, and the temperature of the crude gas drops to 300-350℃. The thermal efficiency of the waste heat boiler is ≥90%.

[0066] Step 3: Subsequently, the isothermal conversion coupling process is executed. The cooled crude gas and process condensate are mixed at a water-to-gas ratio of 1.2-1.5, and the temperature is adjusted to 220-250℃ before being fed into the isothermal conversion furnace. The furnace is filled with a Co-Mo sulfur-resistant catalyst, and the catalyst bed has built-in U-shaped heat exchange tubes. Boiler feedwater is circulated through the tubes as a cooling medium. The bed temperature is maintained stable at 230-280℃ by controlling the cooling water flow rate, and CO undergoes a conversion reaction.

[0067]

[0068] The reaction conversion rate is adjusted by feedback from the outlet CO content. When the outlet CO > 0.5%, the cooling water flow is increased to reduce the bed temperature; when the outlet CO < 0.2%, the cooling water flow is reduced to increase the bed temperature, ensuring a CO conversion rate ≥ 98.5%.

[0069] Finally, the gas-liquid separation process is performed. The converted mixed gas enters the separator. Part of the separated process condensate is returned to the inlet of the converter to adjust the water-gas ratio, and part is sent to the coal-water slurry preparation process for reuse. The purified gas is sent to the subsequent desulfurization and decarbonization unit, realizing the efficient coupling of coal gasification and isothermal conversion.

[0070] The burner in the multi-nozzle opposed coal gasification process adopts a three-layer channel structure: inner, middle, and outer. The inner channel transports coal-water slurry at a velocity controlled at 2.5-3.0 m / s, the middle channel transports oxygen at a velocity of 80-100 m / s, and the outer channel transports sealing nitrogen at a velocity of 15-20 m / s. The pressure difference between the three channels is maintained at 0.3-0.5 MPa to prevent coal slurry backflow. The burner head is made of heat-resistant alloy material with a zirconium oxide coating of 0.8-1.2 mm thickness, ensuring continuous operation for more than 100 days in high-temperature environments.

[0071] The gasifier's water-cooled wall adopts a suspended vertical tube structure, with a water circulation system inside the tubes that couples natural and forced circulation, and a circulation ratio of [missing information]. The calculation formula is

[0072]

[0073] in For circulating water volume, This refers to the amount of water evaporated. The temperature is controlled between 5 and 8. In an emergency, it automatically switches to natural circulation. The water circulation safety factor is ≥1.5. The slag thickness on the water-cooled wall is maintained at 50-80mm. The furnace temperature is controlled in real time by adjusting the oxygen flow rate. The furnace temperature adjustment response time is ≤10s.

[0074] The coal-water slurry preparation process employs a two-stage grinding process. The first stage crushes the raw coal to a particle size ≤3mm. The second stage uses a ball mill to grind the coal particles to the target particle size. The ball mill speed is controlled at 18-22 r / min, and the grinding media are steel balls with a diameter of 20-50mm, blended in a mass ratio of 3:4:3. The grinding time is 20-30 minutes. The coal-water slurry concentration is monitored in real-time using an online density meter, and the density is controlled at 1200-1300 kg / m³. When the density deviates from the set value, the water addition is adjusted using a PID controller. The adjustment formula is as follows:

[0075]

[0076] in To adjust the amount of water added, This is the initial water volume. For the target density, To ensure the actual density and stability of the coal-water slurry, it was left to stand for 48 hours without stratification.

[0077] The isothermal converter adopts a tube-and-shell structure. The catalyst bed is divided into upper, middle, and lower sections. The upper section is filled with Co-Mo catalyst with a particle size of Φ3×5mm, the middle section with Co-Mo catalyst with a particle size of Φ4×6mm, and the lower section with Co-Mo catalyst with a particle size of Φ5×8mm. The catalyst bulk density is 1.2-1.4 g / cm³, and the bed height to diameter ratio is 2.5-3.0. The U-shaped heat exchange tubes are made of 316L stainless steel, and the tube spacing is 2-3 times the catalyst particle size. The heat exchange area is calculated using the following formula:

[0078]

[0079] in The reaction is exothermic. The overall heat transfer coefficient (valued at 80-100 W / (m²・℃)). To ensure a logarithmic mean temperature difference and an axial temperature difference of ≤15℃, a static mixer is installed at the inlet of the converter to fully mix the crude gas and process condensate, achieving a mixing uniformity of ≥95%, thus preventing local overheating that could lead to catalyst deactivation.

[0080] The waste heat boiler in the heat recovery process adopts a natural circulation structure, specifically:

[0081] The boiler feedwater is preheated to 190-210℃ by the economizer and then enters the steam drum. It is then sent to the lower header of the water-cooled wall through the downcomer. After absorbing heat, it generates a steam-water mixture, which returns to the steam drum through the riser for steam-liquid separation. The separated saturated steam is heated to 450℃ by the heat exchanger.

[0082] The heat transfer coefficient of the waste heat boiler is adjusted by the flue gas velocity, which is controlled at 8-12 m / s. When the heat transfer coefficient is lower than 70 W / (m²・℃), the sonic soot blower is started to remove ash from the heated surface. The soot blowing cycle is 2-4 hours, and each soot blowing time is 3-5 minutes, ensuring that the continuous operating efficiency of the waste heat boiler is not less than 88%.

[0083] The formula for calculating the separation efficiency of a cyclone separator is as follows:

[0084]

[0085] in To segment the particle size (values ​​range from 3 to 4 μm). Where n is the separator diameter and n is the separation index (ranging from 1.2 to 1.5), ensuring a separation efficiency of ≥99%.

[0086] The pressure coordination control of gasification and transformation adopts a series regulation method, specifically as follows:

[0087] The pressure of the gasifier is controlled by an oxygen flow regulating valve, and the pressure is set. =6.5MPa, when the pressure inside the furnace deviates At that time, adjust the oxygen flow rate using the following formula:

[0088]

[0089] in To adjust the oxygen flow rate, This is the initial oxygen flow rate. This is the actual measured pressure;

[0090] The inlet pressure of the isothermal converter is controlled by the crude gas flow regulating valve to maintain the inlet pressure 0.1-0.2 MPa lower than the gasifier outlet pressure, with a pressure fluctuation range of ≤±0.05 MPa, to ensure stable gas flow and avoid equipment damage caused by sudden pressure changes.

[0091] Meanwhile, a buffer tank is installed between the gasifier and the shift converter, with a volume designed to handle 10-15 seconds of crude gas, to further stabilize the gas flow pressure and flow rate.

[0092] The catalyst activation and regeneration process includes the following steps:

[0093] After the catalyst is loaded, nitrogen is first introduced to conduct an airtightness test. The pressure is increased to 4.0 MPa and maintained for 24 hours. The leakage rate is ≤0.5% / h.

[0094] Then, the temperature is raised to 120℃ and dried for 4 hours, then raised to 200℃ and nitrogen gas containing 5% H2 is introduced for reduction and activation. The reduction time is 24-30 hours. The criterion for the reduction endpoint is that the H2 content at the outlet is ≥4.5% and no moisture is produced.

[0095] When the catalyst activity drops to 70% of its initial activity, regeneration is performed. First, nitrogen gas is introduced to cool the catalyst to 180°C, and then nitrogen gas containing 2% O2 is introduced for oxidation regeneration. The regeneration temperature is controlled at 200-250°C, and the regeneration time is 18-24 hours. After regeneration, the catalyst activity is restored to more than 90% of its initial activity, extending the catalyst service life to 3-4 years.

[0096] Example 2

[0097] Please see Figures 1-6 Furthermore, based on Example 1, the system also includes system energy efficiency optimization and environmental protection processes. Energy efficiency optimization is achieved through energy cascade utilization, where part of the medium-pressure steam generated by the waste heat boiler is used to drive the syngas compressor unit, and part is used for process heating, with a steam utilization rate of ≥95%. The ash residue generated by gasification is dehydrated to a moisture content of less than 20% and then sent to a building materials plant to prepare cement clinker, with an ash residue utilization rate of ≥98%.

[0098] In the environmental protection process, the process wastewater is degassed by flash evaporation and then enters the biochemical treatment system. The A / O process is used to degrade COD and ammonia nitrogen. After treatment, the wastewater COD is ≤50mg / L and ammonia nitrogen is ≤5mg / L, and it is reused after meeting the circulating water makeup water standard. The acidic gases generated during the gasification and conversion process are collected and sent to the sulfur recovery unit to produce sulfur using the Claus process. The sulfur recovery rate is ≥99.5%, realizing clean production of the system.

[0099] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0100] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for coupling multi-nozzle opposed coal gasification with isothermal transformation, characterized in that, Includes the following steps: Step 1: First, a multi-nozzle opposed coal gasification process is performed. Pulverized coal with a particle size ≤0.1mm is mixed with water at a mass ratio of 1:1.8-2.2 to prepare a coal-water slurry. The slurry is pressurized to 6.5-8.0 MPa by a high-pressure diaphragm pump and then injected into the gasifier along with oxygen (purity ≥99.5%) through 4-6 opposed burners. The burner axis is at an angle of 15-20° to the central axis of the gasifier, forming an opposing impingement flow reaction zone. The gasifier uses a water-cooled wall structure, with the reaction temperature controlled at 1400-1600℃ and the reaction pressure maintained at 6.0-7.5 MPa. The pulverized coal undergoes partial oxidation within the furnace to generate crude coal gas. The reaction equation is as follows: After being quenched to 900-1000℃ by a water-cooled wall, the crude coal gas enters a scrubbing tower to remove more than 99% of the ash and slag, yielding crude coal gas containing 38-45% CO, 28-35% H2, and 18-22% CO2, with a carbon conversion rate ≥98%. Step 2: Next, the gas-solid separation and heat recovery process is carried out. The washed crude gas first passes through a cyclone separator to remove fly ash with a particle size ≥5μm, and then enters the waste heat boiler to exchange heat with the boiler feedwater. The recovered heat generates medium-pressure steam at 3.82MPa and 450℃, and the temperature of the crude gas drops to 300-350℃. The thermal efficiency of the waste heat boiler is ≥90%. Step 3: Subsequently, the isothermal conversion coupling process is executed. The cooled crude gas and process condensate are mixed at a water-to-gas ratio of 1.2-1.5, and the temperature is adjusted to 220-250℃ before being fed into the isothermal conversion furnace. The furnace is filled with a Co-Mo sulfur-resistant catalyst, and the catalyst bed has built-in U-shaped heat exchange tubes. Boiler feedwater is circulated through the tubes as a cooling medium. The bed temperature is maintained stable at 230-280℃ by controlling the cooling water flow rate, and CO undergoes a conversion reaction. The reaction conversion rate is adjusted by feedback from the outlet CO content. When the outlet CO > 0.5%, the cooling water flow is increased to reduce the bed temperature; when the outlet CO < 0.2%, the cooling water flow is reduced to increase the bed temperature, ensuring a CO conversion rate ≥ 98.5%. Finally, the gas-liquid separation process is performed. The converted mixed gas enters the separator. Part of the separated process condensate is returned to the inlet of the converter to adjust the water-gas ratio, and part is sent to the coal-water slurry preparation process for reuse. The purified gas is sent to the subsequent desulfurization and decarbonization unit.

2. The multi-nozzle opposed coal gasification and isothermal transformation coupling method according to claim 1, characterized in that, The burner in the multi-nozzle opposed coal gasification process adopts a three-layer channel structure: inner, middle, and outer. The inner channel transports coal-water slurry at a flow rate controlled at 2.5-3.0 m / s, the middle channel transports oxygen at a flow rate of 80-100 m / s, and the outer channel transports sealing nitrogen at a flow rate of 15-20 m / s. The pressure difference between the three channels is maintained at 0.3-0.5 MPa. The burner head is made of heat-resistant alloy material and coated with a zirconium oxide coating with a thickness of 0.8-1.2 mm. The gasifier's water-cooled wall adopts a suspended vertical tube structure, with a water circulation system inside the tubes that couples natural and forced circulation, and a circulation ratio of [missing information]. The calculation formula is in For circulating water volume, This refers to the amount of water evaporated. The temperature is controlled between 5 and 8. In an emergency, it automatically switches to natural circulation. The water circulation safety factor is ≥1.

5. The slag thickness on the water-cooled wall is maintained at 50-80mm. The furnace temperature is controlled in real time by adjusting the oxygen flow rate. The furnace temperature adjustment response time is ≤10s.

3. The multi-nozzle opposed coal gasification and isothermal transformation coupling method according to claim 1, characterized in that, The coal-water slurry preparation process employs a two-stage grinding process. The first stage crushes the raw coal to a particle size ≤3mm. The second stage uses a ball mill to grind the coal particles to the target particle size. The ball mill speed is controlled at 18-22 r / min, and the grinding media are steel balls with a diameter of 20-50mm, blended in a mass ratio of 3:4:

3. The grinding time is 20-30 minutes. The coal-water slurry concentration is monitored in real-time using an online density meter, and the density is controlled at 1200-1300 kg / m³. When the density deviates from the set value, the water addition is adjusted using a PID controller. The adjustment formula is as follows: in To adjust the amount of water added, This is the initial water volume. For the target density, To ensure the actual density and stability of the coal-water slurry, it was left to stand for 48 hours without stratification.

4. The multi-nozzle opposed coal gasification and isothermal transformation coupling method according to claim 1, characterized in that, The isothermal conversion furnace adopts a tube-and-shell structure. The catalyst bed is divided into upper, middle, and lower sections. The upper section is filled with Co-Mo catalyst with a particle size of Φ3×5mm, the middle section with Co-Mo catalyst with a particle size of Φ4×6mm, and the lower section with Co-Mo catalyst with a particle size of Φ5×8mm. The catalyst bulk density is 1.2-1.4 g / cm³, and the bed height to diameter ratio is 2.5-3.

0. The U-shaped heat exchange tubes are made of 316L stainless steel, and the tube spacing is 2-3 times the catalyst particle size. The heat exchange area is calculated using the following formula: in The reaction is exothermic. The overall heat transfer coefficient (valued at 80-100 W / (m²・℃)). To ensure a logarithmic mean temperature difference and an axial temperature difference of ≤15℃, a static mixer is installed at the inlet of the converter to fully mix the crude gas and process condensate, achieving a mixing uniformity of ≥95%, thus preventing local overheating that could lead to catalyst deactivation.

5. The multi-nozzle opposed coal gasification and isothermal transformation coupling method according to claim 1, characterized in that, The waste heat boiler in the heat recovery process adopts a natural circulation structure, specifically: The boiler feedwater is preheated to 190-210℃ by the economizer and then enters the steam drum. It is then sent to the lower header of the water-cooled wall through the downcomer. After absorbing heat, it generates a steam-water mixture, which returns to the steam drum through the riser for steam-liquid separation. The separated saturated steam is heated to 450℃ by the heat exchanger. The heat transfer coefficient of the waste heat boiler is adjusted by the flue gas velocity, which is controlled at 8-12 m / s. When the heat transfer coefficient is lower than 70 W / (m²・℃), the sonic soot blower is started to remove ash from the heated surface. The soot blowing cycle is 2-4 hours, and each soot blowing time is 3-5 minutes, ensuring that the continuous operating efficiency of the waste heat boiler is not less than 88%. The formula for calculating the separation efficiency of a cyclone separator is as follows: in To segment particle size, Where n is the separator diameter and n is the separation index, ensuring a separation efficiency of ≥99%.

6. The multi-nozzle opposed coal gasification and isothermal transformation coupling method according to claim 1, characterized in that, The pressure coordination control of gasification and transformation adopts a series regulation method, specifically: The pressure of the gasifier is controlled by an oxygen flow regulating valve, and the pressure is set. =6.5MPa, when the pressure inside the furnace deviates At that time, adjust the oxygen flow rate using the following formula: in To adjust the oxygen flow rate, This is the initial oxygen flow rate. This is the actual measured pressure; The inlet pressure of the isothermal converter is controlled by the crude gas flow regulating valve to maintain the inlet pressure 0.1-0.2 MPa lower than the gasifier outlet pressure, with a pressure fluctuation range of ≤ ±0.05 MPa. Meanwhile, a buffer tank is installed between the gasifier and the shift converter, with a volume designed to handle 10-15 seconds of crude gas, to further stabilize the gas flow pressure and flow rate.

7. The multi-nozzle opposed coal gasification and isothermal transformation coupling method according to claim 1, characterized in that, The catalyst activation and regeneration process includes the following steps: After the catalyst is loaded, nitrogen gas is introduced to conduct an airtightness test. The pressure is increased to 4.0 MPa and maintained for 24 hours. The leakage rate is ≤0.5% / h. Then, the temperature is raised to 120℃ and dried for 4 hours, then raised to 200℃ and nitrogen gas containing 5% H2 is introduced for reduction and activation. The reduction time is 24-30 hours. The criterion for the reduction endpoint is that the H2 content at the outlet is ≥4.5% and no moisture is produced. When the catalyst activity drops to 70% of its initial activity, regeneration is performed. First, nitrogen gas is introduced to cool the catalyst to 180°C, and then nitrogen gas containing 2% O2 is introduced for oxidation regeneration. The regeneration temperature is controlled at 200-250°C, and the regeneration time is 18-24 hours. After regeneration, the catalyst activity is restored to more than 90% of its initial activity, extending the catalyst service life to 3-4 years.

8. The multi-nozzle opposed coal gasification and isothermal transformation coupling method according to any one of claims 1-7, characterized in that, It also includes system energy efficiency optimization and environmental protection processes. Energy efficiency optimization is achieved through energy cascade utilization, where part of the medium-pressure steam generated by the waste heat boiler is used to drive the syngas compressor unit and part is used for process heating, with a steam utilization rate of ≥95%. The ash produced by gasification is dewatered and its moisture content is reduced to below 20%, and then sent to the building materials plant to prepare cement clinker, with an ash utilization rate of ≥98%. In the environmental protection process, the process wastewater is degassed by flash evaporation and then enters the biological treatment system. The A / O process is used to degrade COD and ammonia nitrogen. After treatment, the wastewater has COD ≤ 50 mg / L and ammonia nitrogen ≤ 5 mg / L, and can be reused after meeting the circulating water makeup water standard. The acidic gases generated during the gasification and conversion process are collected and sent to the sulfur recovery unit to produce sulfur using the Claus process, with a sulfur recovery rate of ≥99.5%.

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