Oil, gas, coke and electricity coupling co-production process of low-rank coal

Abstract

The invention provides an oil, gas, coke and electricity coupling co-production process of low-rank coal, and relates to the technical field of comprehensive utilization of coal, the oil, gas, coke and electricity coupling co-production process comprises the following steps: raw material pretreatment: taking power coal or low-rank coal as a raw material, drying and crushing, and inputting into a dry distillation device; destructive distillation and pyrolysis: pyrolyzing the raw materials by a destructive distillation device to produce raw gas and high-temperature red coke; gas purification and tar separation: purifying and separating the raw gas to obtain chemical products such as coal tar and purified gas; the purified coal gas is divided into two paths, one path flows back to the dry distillation device to serve as a combustion heating heat source, and the other path serves as a product to be sold or used for producing chemical products such as methanol and LNG; directly combusting the red coke: directly inputting the high-temperature red coke into a boiler device for combustion without a coke quenching process; the high-temperature red coke can be separated into coke particles and coke foam by the screening device before entering the boiler device, the coke particles are sold as products, and the coke foam is input into the boiler device for combustion; the low-rank coal is effectively and fully utilized through the co-production process for steam and electric power production.

Description

Technical Field

[0001] The present invention belongs to the technical field of comprehensive utilization of coal, and more specifically, relates to a coupled co-production process of oil, gas, coke and electricity from low-rank coal. Background Art

[0002] my country's energy structure is characterized by being "rich in coal, short of oil, and low in gas." Low-rank coal (such as lignite and long-flame coal) reserves account for over 20% of the country's total coal resources, but their high volatile matter (32%-43%) and low sulfur content are not fully utilized. Waste of economic value: Traditional thermal power plants directly burn low-rank coal to generate electricity, burning the high-value components of the coal (coal tar and coal gas). The economic value of coal tar (valued at approximately 2,500 yuan per ton) and coal gas (valued at approximately 0.7 yuan per cubic meter) remains unrealized. Low energy efficiency: Boilers that directly burn low-rank coal are inefficient, and the sensible heat of high-temperature red coke (above 600°C) (about 5% of the total energy of the coal) is wasted in the wet quenching process (the quenching water removes the heat); Prominent environmental problems: The wet quenching process produces a large amount of wastewater containing phenol and cyanide (COD ≥ 5000 mg / L) and dust, which pollutes the atmosphere and water bodies (0.4-0.5 tons of water is consumed per ton of red coke). Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a low-rank coal oil, gas, coke, and electricity coupled production process to solve the above problems.

[0004] A process for the coupled production of oil, gas, coke and electricity from low-rank coal comprises the following steps: (1) Raw material pretreatment: Steam coal or low-rank coal (volatile matter Vdaf ≥ 32%) is used as raw material, crushed and dried, and then directly input into the dry distillation device; (2) Dry distillation and pyrolysis: The dry distillation device pyrolyzes the raw materials (pyrolysis temperature is 650-950°C, and produces raw gas and high-temperature red coke; (3) Gas purification and tar separation: The raw gas enters the gas purification device (which undergoes initial cooling and tar removal, ammonia and light impurities removal, desulfurization and decyanation, and benzene recovery in sequence) to separate and obtain chemical products such as coal tar (tar yield ≥ 10.3%, density ≥ 1.045 g / cm³) and purified gas; the purified gas is divided into two paths, one of which is refluxed to the dry distillation device as a heating source, and the other is sold as a product or used to produce chemical products such as methanol and LNG; (4) Direct combustion of red coke: The high-temperature red coke is directly fed into the boiler for combustion without undergoing a quenching process. The high-temperature red coke can also be separated into coke particles (≥1mm) and coke foam (<1mm) by a screening device before entering the boiler. The coke particles are sold as products (the particle size can be screened according to market demand), and the coke foam is fed into the boiler for combustion. (5) Steam and electricity production: The boiler device burns red coke to generate steam, which is divided into two paths: one path is supplied as a product (for industrial steam or heating), and the other path is input into the power generation device (steam turbine generator set) to generate electricity; (6) Power output: The power generated by the power generation device is sold through the power grid except for the power used by the thermal power plant.

[0005] Preferably, in step (1), the total moisture content Mt of the thermal coal or low-rank coal is ≤20%, the ash content Ad is ≤7%, and the sulfur content St is ≤0.40% (selected from low-rank coal from Inner Mongolia, Shaanxi or Xinjiang); in step (2), the dry distillation device is a low-rank coal pyrolysis separation device; in step (3), the chemical products such as coal tar include coal tar and crude benzene; in step (4), the sensible heat utilization rate of the high-temperature red coke is ≥90%, and the sensible heat power generation per ton of red coke is 100-120 kWh; in step (4), the screening device is a high-temperature vibrating screen (the mesh size is 0.5 mm, 1 mm, 3 mm); in step (5), the boiler device is a circulating fluidized bed boiler or a pulverized coal boiler; in step (5), the power generation device generates electricity by using steam generated by burning the red coke produced by the dry distillation device in the boiler device, and the steam is derived from the combustion heat energy and sensible heat of the red coke.

[0006] Preferably, the material balance rate of the process is ≥97% (dry basis), wherein the coke powder yield is ≤55.5%, the tar yield is ≥10.3%, the coal gas yield is ≥446m³ / ton of dry coal, and the ammonia yield is ≤25.4% (in compliance with GB / T 18916.12-2012 "Water Quota Part 12: Coking" standard). The environmental benefits of the process include: saving 0.4-0.5 tons of quenching water per ton of red coke (compared to traditional wet quenching, the water saving rate is ≥80%); avoiding SO during wet quenching. x 、NO x and dust emissions.

[0007] Compared with the prior art, the present invention has the following beneficial effects: Improved economic value: By extracting high-value chemical products such as coal tar and coal gas before burning thermal coal and low-grade coal, we can avoid their direct combustion for power generation in the traditional power industry, thus avoiding waste. Compared with the single model of using coal as fuel, this significantly taps into the diversified economic value of low-grade coal and greatly improves the profitability of thermal power plants.

[0008] Improved energy efficiency: The high-temperature red coke produced by the distillation unit does not need to go through the traditional coke quenching process and is directly burned in the boiler, making full use of the sensible heat of the red coke. Compared with the problem of large amounts of sensible heat being wasted in the wet quenching process, this effectively improves energy utilization efficiency.

[0009] Environmentally friendly: Eliminating the wet quenching process not only saves quenching water, but also avoids the phenolic wastewater, dust and sulfide (SO x ), nitrogen oxides (NO x ) and other pollutant emissions, reducing pollution to the atmosphere and water bodies, and meeting the requirements of clean production and sustainable development.

[0010] Energy structure optimization: The extracted coal tar can be used as a chemical raw material to replace part of crude oil, and coal gas can be used as clean fuel gas to replace part of natural gas. This will help alleviate the contradiction in my country's energy structure of "rich in coal, lacking oil, and little gas" and promote the transformation of energy consumption towards diversification and low carbonization. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0012] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0013] See also Figure 1 The present invention provides a process for the coupled production of oil, gas, coke and electricity from low-rank coal, comprising the following steps: (1) Raw material pretreatment: Steam coal or low-rank coal (volatile matter Vdaf ≥ 32%) is used as raw material, dried and crushed, and then directly input into the dry distillation device; (2) Dry distillation and pyrolysis: The dry distillation device pyrolyzes the raw materials (pyrolysis temperature is 650-950℃, and produces raw gas and high-temperature red coke (temperature ≥600℃); (3) Gas purification and tar separation: The raw gas enters the gas purification device (which undergoes initial cooling and tar removal, ammonia and light impurities removal, desulfurization and decyanation, and benzene recovery in sequence), and is separated to obtain chemical products such as coal tar (tar yield ≥10.3%, density ≥1.045g / cm³) and purified coal gas (gas yield ≥446m³ / ton of dry coal); the purified coal gas is divided into two paths, one of which is refluxed to the dry distillation device as a combustion heating heat source, and the other is sold as a product or used to produce chemical products such as methanol and LNG; (4) Direct combustion of red coke: High-temperature red coke does not need to go through the quenching process and is directly fed into the boiler for combustion. The high-temperature red coke can also be separated into coke particles (≥1mm) and coke foam (<1mm) by a screening device before entering the boiler. The coke particles are sold as products (the particle size can be screened according to market demand), and the coke foam is fed into the boiler for combustion. (5) Steam and electricity production: The boiler burns red coke to produce steam, which is divided into two paths: one path is used as a product for external supply (for industrial steam or heating), and the other path is input into the power generation device (steam turbine generator set) for power generation; (6) Power output: The power generated by the power generation device is sold through the power grid except for the power used by the thermal power plant itself.

[0014] In step (1), the total moisture content Mt of the thermal coal or low-rank coal is ≤20%, the ash content Ad is ≤7%, and the sulfur content St is ≤0.80% (selected from low-rank coal from Inner Mongolia, Shaanxi or Xinjiang). In step (2), the dry distillation device is a low-rank coal pyrolysis separation device. In step (3), the chemical products such as coal tar include coal tar and crude benzene. In step (4), the sensible heat utilization rate of high-temperature red coke is ≥90%, and the sensible heat power generation per ton of red coke is 100-120 kWh. In step (4), the screening device is a vibrating screen. (sieve hole size is 0.5mm, 1mm, 3mm), coke particle yield ≥78.65% (≥0.5mm particle size), coke foam yield ≤21.35% (<0.5mm particle size), coke particle size can be screened according to market demand, in step (5), the boiler device is a circulating fluidized bed boiler or a pulverized coal boiler, in step (5), the power generation device uses the steam generated by the boiler device burning the red coke produced by the dry distillation device to generate electricity, and the steam comes from the combustion heat energy and sensible heat of the red coke.

[0015] During the pyrolysis process, the material balance rate of the process is ≥97% (dry basis), with a semi-coke yield of ≤55.5%, a tar yield of ≥10.3%, a gas yield of ≥446m³ / ton of dry coal, and an ammonia yield of ≤25.4% (in compliance with GB / T 18916.12-2012 "Water Quota Part 12: Coking"). The environmental benefits of the process include: saving 0.4-0.5 tons of quenching water per ton of red coke (compared to traditional wet quenching, the water saving rate is ≥80%); avoiding SO during wet quenching. x 、NO x and dust emissions.

[0016] The core logic of this process is "differential utilization + energy cascade recovery". The specific steps are as follows: (1) Raw material input: low-rank coal is crushed and dried and then directly input into the dry distillation device; (2) Drying and pyrolysis: The dry distillation unit pyrolyzes coal at 650-950℃, producing raw coal gas (containing tar and coal gas) and high-temperature red coke (above 600℃); (3) Gas purification: It undergoes preliminary cooling and tar removal, removal of ammonia and light impurities, desulfurization and decyanation, and benzene recovery. Part of the purified gas is refluxed to the dry distillation unit (as a heating source to save external fuel), and the other part is sold or used to produce chemical products such as methanol and LNG. (4) Red coke processing: High-temperature red coke does not need to be quenched and can be directly fed into the boiler for combustion. It can be fed into a screening device (to separate coke particles and coke foam) according to market demand, and coke particles (≥1mm) can be sold (for sintering in steel plants). (5) Steam and power generation: The boiler burns red coke to generate steam, part of which is supplied to other places (for industrial heating) and the other part drives the steam turbine to generate electricity; (6) Power output: The power generated by the power generation device, except for the power used by the thermal power plant itself (such as the distillation device and pump group), the rest is sold through the power grid; Experimental steps: 1. Test materials: Select Xinjiang Naomaohu low-rank coal (coal sample analysis results are shown in Table 1, coal sample particle size composition is shown in Table 2, and ash component element analysis is shown in Table 3):

[0017] Total moisture Mt=17.8%, internal moisture Mat=15.09%, ash Ad=6.98%; Volatile matter Vdaf=49.36%, sulfur content St=0.40%, fixed carbon FC=39.99%.

[0018] 2. Test equipment: Dry distillation unit: KXJL-CYL-20 environmentally friendly test coke oven (top inlet and outlet, electric heating, effective volume Φ400×280mm); Gas purification equipment: cooler, oil-water separation tank; 3. Test process: (1) Coal loading: 21.76 kg of wet basis coal sample (17.91 kg of dry basis) was loaded into the coke oven with a bulk density of 0.75 t / m³; (2) Dry distillation: Start electric heating, raise the temperature of the coke cake center to 830℃, maintain for 30 minutes, and then stop heating; (3) Gas treatment: The raw gas was cooled and filtered to obtain 1.84 kg of tar (yield 10.3%) and 7988 L of gas (yield 446 m³ / ton of dry coal); (4) Red coke processing: After cooling, the high-temperature red coke directly enters the screening device, separating 7.82 kg of coke particles (≥0.5 mm, yield 78.65%) and 2.12 kg of coke foam (<0.5 mm, yield 21.35%); 4. Test results Material balance: dry basis material balance rate 97.0% (coke powder 55.5%, tar 10.3%, coal gas 26.8%, ammonia water 25.4%); Economic benefits: By extracting high-value chemical products such as coal tar and coal gas before burning low-rank coal, it avoids its waste in traditional direct combustion power generation. Compared with the single model of using coal as fuel, it significantly taps the diverse economic value of low-rank coal and greatly improves the profitability of thermal power plants.

[0019] Environmental benefits: Each ton of red coke saves 0.4-0.5 tons of water and avoids SO x Emissions. (Compared to traditional wet quenching).

[0020] This process has been validated in a 40kg environmentally friendly test coke oven, achieving a material balance rate of ≥97%. Compared to the traditional power industry, this process offers significantly improved economic returns and significant environmental benefits. It is suitable for thermal power plants in low-rank coal-rich regions such as Inner Mongolia, Shaanxi, and Xinjiang, and can be directly scaled up.

[0021] Example: Application of low-grade coal, oil, gas and electricity cogeneration coupling process in a 100MW thermal power plant: Located in Naomaohu, Xinjiang (a low-rank coal-rich area), the thermal power plant has an installed capacity of 100MW and operates 8,760 hours annually (365 days x 24 hours). To enhance the economic value of low-rank coal and reduce power generation costs, the plant utilizes the patented "Coupling Process for the Cogeneration of Oil, Gas, Coke, and Electricity from Low-Rank Coal" to process the local low-rank coal with a yield of 5,000 kcal / kg (as received), achieving full component utilization through "oil and gas extraction plus semi-coke power generation."

[0022] Raw material parameters: Local low-rank coal is selected, and the industrial analysis is as follows (meeting the patented "high volatile matter, low ash" raw material requirements): Received calorific value: 5000kcal / kg; Total moisture (Mt): 17.8% (auxiliary test data); Volatile matter (Vdaf): 49.36% (auxiliary test data, with high oil and gas extraction potential); Ash content (Ad): 6.98% (auxiliary test data, low ash content is conducive to semi-coke combustion).

[0023] 3. Process steps and core parameters This process follows the coupled logic of "drying distillation and pyrolysis → oil and gas extraction → semi-coke combustion → steam power generation". The core steps are as follows: (1) Dry distillation and pyrolysis: Extraction of high-value oil and gas components Low-rank coal (490,560 tons / year, equivalent to 5,000 kcal / kg) enters the dry distillation unit and is pyrolyzed at 650-950°C to produce three types of products: Semi-coke: 199,706 tons / year (yield 40.71%); Tar: 32,180 tons / year (yield 6.56%); Coal gas: 129,998 tons / year (yield 26.5%).

[0024] (2) Gas purification and utilization: output of high-value products Tar: sold as a chemical raw material, the price is 2,500 yuan / ton, the output value is 80,451,840 yuan / year; Crude benzene: yield 1%, i.e. 4,905.6 tons / year, price 4,000 yuan / ton, output value 19,622,400 yuan / year; Purified coal gas: density 0.45kg / m³, volume approximately 289 million m³ / year (129,998 tons ÷ 0.45kg / m³), of which 52% is recycled to the furnace as a heat source for the dry distillation unit, reducing external fuel consumption; the remaining 48% is sold as clean fuel gas at a price of 0.3 yuan / m³, with an output value of 86,665,600 yuan / year (net output value after deducting recycling consumption is 41,599,488 yuan / year).

[0025] (3) Semi-coke utilization: dual recovery of sensible heat and calorific value The high-temperature semi-coke (temperature ≥ 600°C) produced by dry distillation does not need to be quenched and is directly burned in a circulating fluidized bed boiler. Its calorific value of 6500kcal / kg (dry basis) is used to generate steam to drive a 100MW steam turbine to generate electricity.

[0026] Semi-coke power generation: 199,706 tons / year × 2,500 kWh / ton of standard coal × (6,500 / 7,000) = 463,603,214 kWh / year, with an output value of 83,448,986 yuan / year (electricity price 0.18 yuan / kWh); Semi-coke sensible heat power generation: Each ton of semi-coke generates 100kWh of sensible heat power, with an annual sensible heat power generation of 19,970,600kWh / year and an output value of 3,594,708 yuan / year.

[0027] (4) Power generation and output The steam generated by the coke combustion in the boiler drives the steam turbine for power generation. Some of the steam can be supplied externally (e.g., for industrial heating), but in this embodiment, it is primarily used for power generation. The total annual power generation is 483,573,814 kWh, of which 19,970,600 kWh comes from the sensible heat energy of the coke.

[0028] 4. Output and output value analysis According to the data in the table, the annual output and output value of this process are as follows (unit: yuan):

[0029] 5. Benefit Summary (1) Improvement of economic value The combined process's total output value increased by 45.05% compared to the traditional power-only process, generating approximately 71.037 million RMB (RMB 229 million to 158 million) in annual revenue. The extraction of high-value components (tar, crude benzene, and coal gas) is the core driver of economic growth (accounting for 62% of the total output value), fundamentally transforming the single-value model of low-rank coal, which was previously used solely as a fuel.

[0030] (2) Improved energy efficiency The sensible heat of semi-coke is fully recovered, generating an additional 100 kWh of electricity per ton of semi-coke. The annual additional sensible heat power generation is approximately 20 million kWh, equivalent to saving approximately 8,000 tons of standard coal (20 million kWh ÷ 2,500 kWh / ton of standard coal). The combustion efficiency of semi-coke is higher than that of direct combustion of traditional low-rank coal.

[0031] (3) Environmentally friendly Emission reduction: Avoiding phenol-containing wastewater, dust and SO during wet quenching x 、NO x emissions, in line with the “dual carbon” target requirements.

[0032] (4) Optimization of energy structure The produced coal tar can be used to produce diesel, aviation kerosene and other fuels through subsequent tar hydrogenation process; 139 million m³ of coal gas is supplied annually, equivalent to replacing approximately 69.5 million m³ of natural gas; It has alleviated the local energy structure contradiction of "rich in coal, lacking in oil and little gas" and promoted the implementation of the "coal-to-gas linkage" strategy.

[0033] The embodiments of the present invention are presented for purposes of illustration and description and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. The embodiments are chosen and described in order to better illustrate the principles of the invention and its practical application and to enable those skilled in the art to understand the invention and design various embodiments with various modifications as suited for specific applications.

Claims

1. A process for the coupled production of oil, gas, coke and electricity from low-rank coal, characterized by: The following steps are involved: (1) Raw material pretreatment: Steam coal or low-rank coal is used as raw material, crushed and dried, and then fed into the dry distillation device; (2) Dry distillation and pyrolysis: The dry distillation device pyrolyzes the raw materials to produce raw gas and high-temperature red coke; (3) Gas purification and tar separation: The raw gas enters the gas purification device and is separated to obtain chemical products such as coal tar and purified gas; the purified gas is divided into two paths, one of which is returned to the dry distillation device as a combustion heating heat source, and the other is sold as a product or used to produce chemical products such as methanol and LNG; (4) Direct combustion of red coke: The high-temperature red coke does not need to go through the coke quenching process and is directly fed into the boiler device for combustion. The high-temperature red coke can also be separated into coke pellets and coke foam by a screening device before entering the boiler device. The coke pellets are sold as products, and the coke foam is fed into the boiler device for combustion. (5) Steam and electricity production: The boiler device burns red coke to generate steam, which is divided into two paths, one for external supply as a product and the other for input into the power generation device for power generation; (6) Power output: The power generated by the power generation device is sold through the power grid except for the power used by the thermal power plant.

2. The process for the co-production of oil, gas, coke and electricity from low-rank coal as claimed in claim 1, characterized in that: In step (1), the total moisture content Mt of the thermal coal or low-rank coal is ≤20%, the ash content Ad is ≤8.0%, and the sulfur content St is ≤0.8%.

3. The process for the co-production of oil, gas, coke and electricity from low-rank coal as claimed in claim 1, characterized in that: In step (2), the dry distillation device is a low-rank coal pyrolysis and separation device.

4. The process for the co-production of oil, gas, coke and electricity from low-rank coal as claimed in claim 1, characterized in that: In step (3), the chemical products such as coal tar include coal tar, crude benzene, etc.

5. The process for the co-production of oil, gas, coke and electricity from low-rank coal as claimed in claim 1, characterized in that: In step (4), the sensible heat utilization rate of the high-temperature red coke is ≥90%, and the sensible heat power generation per ton of red coke is 100-120 kWh.

6. The process for the co-production of oil, gas, coke and electricity from low-rank coal as claimed in claim 1, characterized in that: In step (4), the screening device is a high-temperature vibrating screen, the coke particle yield is ≥78.65%, and the coke foam yield is ≤21.35%. The size and ratio of the screening particle size can be adjusted according to market demand.

7. The process for the co-production of oil, gas, coke and electricity from low-rank coal as claimed in claim 1, characterized in that: In step (5), the boiler device is a circulating fluidized bed boiler or a pulverized coal boiler.

8. The process for the co-production of oil, gas, coke and electricity from low-rank coal as claimed in claim 1, characterized in that: In step (5), the power generation device generates electricity by using steam generated by burning the red coke produced by the dry distillation device in the boiler device, and the steam is derived from the combustion heat energy and sensible heat of the red coke.

9. A process for the co-production of oil, gas, coke and electricity from low-rank coal according to any one of claims 1 to 8, characterized in that: The material balance rate of the process is ≥97% (dry basis), wherein the semi-coke yield is ≤55.5%, the tar yield is ≥10.3%, the coal gas yield is ≥446m³ / ton of dry coal, and the ammonia yield is ≤25.4%.

10. The process for the co-production of oil, gas, coke and electricity from low-rank coal according to any one of claims 1 to 8, characterized in that: The environmental benefits of the process include: saving 0.4-0.5 tons of quenching water per ton of red coke; avoiding SO during wet quenching; x 、NO x and dust emissions.

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