Coal gasification and fuel cell coupled combined heat and power generation system and method for papermaking

Abstract

The invention provides a coal gasification and fuel cell coupled combined heat and power generation system and method for papermaking. The system is composed of a pulping unit, a bleaching unit, a drying unit, an acidification unit, a carbonization unit, an alkalization unit, an activation unit, a primary gasification unit, a secondary gasification unit, a water-gas shift unit, a fuel cell and the like. Black liquor generated by the pulping and bleaching unit is converted into coarse carbon through the acidification and carbonization unit, part of the coarse carbon is converted into activated carbon through the alkalization and activation unit and serves as an adsorbent of the carbonization unit, part of the coarse carbon and coal are converted into CO through two-stage gasification and converted into hydrogen after water-gas conversion, and the hydrogen serves as a fuel cell raw material to generate electric energy; the system further comprises a plurality of heat exchange units and heat transfer units, high-grade energy of H2, CO, H2O and the like is utilized to the maximum extent, efficient heat production and electricity production are achieved through refined energy management and gradient utilization strategies, and stable and efficient energy supply is provided for the whole system.

Description

Technical Field

[0001] The invention belongs to the technical field of pulping and papermaking, and in particular relates to a heat and power cogeneration system and method for coupling coal gasification and fuel cells for papermaking. Background Art

[0002] The papermaking industry is an energy-intensive industry that requires a large amount of heat and electricity to drive various equipment and processes. The production capacity of China's papermaking industry has continued to expand and has leapt to the top of the world. Whether in production or life, people's demand for paper products is still increasing. Under this trend, in order to fully meet market demand, pulp and paper companies continue to expand production scale and increase production capacity.

[0003] With the expansion of production scale and the increase of production capacity, the heat and electricity required by enterprises in the papermaking process are gradually increasing. In order to meet this demand, large enterprises generally adopt self-generation to supply energy. These enterprises often have their own power plants and ensure the effectiveness of production through coal-fired power generation. Although this method is low-cost, the limited coal resources and low energy utilization efficiency have become bottlenecks restricting its sustainable development. In addition, a large amount of pollutants such as CO2, SO2, and NOx will be generated during coal-fired power generation, which will have a serious negative impact on the environment.

[0004] Most of the self-owned power plants of enterprises now use cogeneration technology. Through energy classification and heat and electricity separation, the chemical energy of coal is converted into steam energy, which then drives the steam turbine to work. The steam turbine discharges exhaust steam for paper production. Most of them use coal-fired boilers that can produce high-temperature and high-pressure steam and three-waste heating boilers to provide heat energy for the paper production line, ensure the normal operation of the steam turbine generator set, and meet the power demand of the plant. Since the standby boiler adopts the hot standby operation mode, the overall operating load is low, the capacity of some equipment cannot be fully utilized, and the operating efficiency is not high. Once a boiler fails, it is difficult for the remaining boilers to quickly increase the operating load to meet the steam demand in a short period of time, thus affecting the stable, reliable and safe operation of the entire production line.

[0005] In the process of making pulp, a large amount of black liquor wastewater containing high concentrations of pollutants is also produced. These black liquors have complex components and will cause serious pollution if discharged directly into the water body. They also contain a large number of recyclable substances, which will cause waste of resources if not treated. At present, the most widely used process for treating black liquor is the combustion alkali recovery process, which converts black liquor into solid products with sodium ferrite as the main component through evaporation, concentration, combustion and causticization. These solid products can generate sodium hydroxide alkali liquor and iron oxide after hydrolysis. Sodium hydroxide can be used in industrial alkali production or the cooking stage in papermaking, and iron oxide can be recycled. This process can achieve an alkali recovery rate of more than 90%, and can recover heat energy during the calcination process. It is a relatively mature method for treating black liquor. However, this method can only recover alkali, and a large amount of lignin can only be left in the black liquor to burn and generate heat. Moreover, this method requires large-scale equipment such as multi-stage evaporators and combustion furnaces, and the initial investment is large, so it is only suitable for large-scale papermaking enterprises.

[0006] The original coal-fired power generation has low efficiency, high energy consumption, and environmental pollution; the combined heat and power generation has insufficient heating capacity, limited heating range, and poor economic efficiency; the black liquor treatment efficiency in the alkali recovery process is limited, and the investment cost is high. The present invention proposes a combined heat and power generation system with black liquor treatment function. Summary of the invention

[0007] In view of this, the present invention proposes a cogeneration system and method for papermaking by coupling coal gasification and fuel cells. The system can prepare activated carbon by hydrothermal carbonization of black liquor produced in the papermaking process, and the crude carbon produced during carbonization is converted into CO through graded coal gasification, and then H2 is produced through water vapor conversion for use in high-temperature fuel cells to provide electrical energy for mechanical pulping and fan heat exchange. Multiple heat exchange units and heat transfer units are interspersed in the system to achieve gradient utilization of energy and efficiently produce heat and electricity.

[0008] The technical solution adopted by the present invention to solve the technical problem is:

[0009] A heat and power cogeneration system for papermaking coupled with coal gasification and fuel cells, characterized in that it comprises a pulping unit, a bleaching unit, a drying unit, an acidification unit, a carbonization unit, an alkalization unit, an activation unit, a flow control unit, a primary gasification unit, a secondary gasification unit, a combustion unit, a fan heat exchange unit, a heat exchange unit, a heat transfer unit, a water-gas conversion unit, a separation unit, and a fuel cell, wherein:

[0010] The pulping unit is used to prepare paper pulp by effectively separating the fibers of wood or other raw materials using mechanical pulping, chemical pulping or biological pulping techniques;

[0011] The bleaching unit is used to bleach the pulp so that the pulp has a corresponding whiteness. Both the pulping unit and the bleaching unit will produce black liquor containing fibers, organic matter, inorganic salts, and pigments.

[0012] The drying unit is used to remove moisture from the paper web during the process of making paper web from pulp, and the heat source for drying and dehydration is the high-temperature air generated by the fan heat exchange unit;

[0013] The acidification unit is used to acidify the lignin in the black liquor to precipitate it. The acidification process uses CO2 as an acidifier, and the reaction temperature is between 150 and 200°C. In a closed environment, the introduced CO2 reacts with the lignin in the black liquor to convert the lignin into acidified lignin precipitation, and at the same time, the sodium salt in the black liquor is converted into NaHCO3, the sodium element is enriched and separated, and the inorganic silicon salt is also converted into SiO2 precipitation, which enters the carbonization unit together with the acidified lignin. Since the temperature of the black liquor produced by the pulping unit and the bleaching unit is between 80 and 120°C, the heat transfer unit II is required for heating during the acidification and carbonization processes;

[0014] The carbonization unit is used to crack the acidified lignin precipitated from the acidification unit into small molecular organic matter and then crack it into crude carbon under a hydrothermal environment. The crude carbon is respectively introduced into the alkalization unit and the secondary gasification unit through the flow control unit I to prepare activated carbon and graded gasification of coal. Since SiO2 in the crude carbon does not affect the secondary gasification process, the crude carbon participating in the graded gasification of coal does not need to pass through the alkalization unit, but can be directly introduced into the secondary gasification unit through the flow control unit I.

[0015] The alkalization unit uses a dilute alkali solution to wash and remove SiO2 contained in the crude carbon produced by the carbonization unit and produce coke, and the quality of the produced activated carbon is improved by purifying the crude carbon to achieve better adsorption in the acidification process;

[0016] The activation unit is used to prepare activated carbon. The process uses a method of physically activating coke with water vapor to prepare activated carbon, which can be used in the acidification unit to adsorb organic matter.

[0017] The flow control unit includes flow control unit I, flow control unit II, flow control unit III and flow control unit IV, which are used to adjust the ratio of different streams according to the actual situation in production. Among them, flow control unit I is used to adjust the ratio of the crude carbon mixture produced by the carbonization unit to the alkalization unit and the secondary gasification unit, respectively, and the ratio range is 0-100%. 0% means that the crude carbon mixture produced by the carbonization unit is all passed into the secondary gasification unit to participate in the graded gasification of coal, and 100% means that the crude carbon mixture produced by the carbonization unit is all passed into the alkalization unit to participate in the preparation of activated carbon. Since the acidification unit only needs a small amount of activated carbon to achieve a good adsorption effect, the excess coke can be passed into the secondary gasification unit. The flow control unit II is used to adjust the ratio of the CO2 separated by the separation unit to the acidification unit and the secondary gasification unit, respectively, and the ratio range is 0-100%. 0% means that the proportion of CO2 to the acidification unit accounts for 0% of the CO2 separated by the separation unit, and 100% means that the proportion of CO2 to the acidification unit accounts for 100% of the CO2 separated by the separation unit, so as to flexibly adjust according to the amount of black liquor to be processed. The flow control unit III is used to adjust the fuel cell The ratio of the generated H2O to the fan heat exchange unit and the heat transfer unit II is in the range of 0-100%, 0% represents that the ratio of the H2O to the fan heat exchange unit accounts for 0% of the H2O generated by the fuel cell, and 100% represents that the ratio of the H2O to the fan heat exchange unit accounts for 100% of the H2O generated by the fuel cell. If the original temperature of the H2O is low or the amount of black liquor to be treated is large, the H2O is directly introduced into the heat transfer unit II without passing through the fan heat exchange unit. The flow control unit IV is used to adjust the ratio of the CO generated by the secondary gasification unit to the fan heat exchange unit and the heat exchange unit. The ratio range is 0-100%, 0% represents that the ratio of the CO to the fan heat exchange unit accounts for 0% of the CO generated by the secondary gasification unit, and 100% represents that the ratio of the CO to the fan heat exchange unit accounts for 100% of the CO generated by the secondary gasification unit. If the temperature of the H2O generated by the fuel cell is high enough or the heat required by the drying unit is relatively small, the CO is directly introduced into the heat exchange unit without passing through the fan heat exchange unit.

[0018] The primary gasification unit and the secondary gasification unit are used to convert coal into coke and then into CO. The reaction temperature of the two-stage gasification unit is between 800 and 1200°C, wherein the primary gasification unit decomposes coal at high temperature under the condition of air isolation to produce coke and coke oven gas, and the coke oven gas converts chemical energy into thermal energy through the combustion unit, and the generated high-temperature flue gas can provide heat for the two-stage gasification unit through the heat transfer unit I, and the secondary gasification unit uses CO2 as a gasifying agent to gasify the coke and produce CO;

[0019] The combustion unit is used to burn coke oven gas to generate high-temperature flue gas and convert the chemical energy of the coke oven gas into thermal energy;

[0020] The fan heat exchange unit is used to utilize the high-quality energy of H2O and CO. The water temperature generated by the fuel cell is between 500 and 1000°C, and the CO temperature generated by the secondary gasification unit is between 800 and 1200°C. The unit uses a fan to blow the high-temperature H2O and CO arranged in a heat exchange pipe with a large contact area, and the generated hot air is supplied to the drying unit, and the consumed electricity is provided by the fuel cell;

[0021] The heat exchange unit is used to exchange heat between the CO stream after fan heat exchange and the H2 stream separated from the water-gas conversion unit, and heat O2 at the same time. Since the temperature of CO generated by the secondary gasification unit is between 800 and 1200°C, and the temperature of H2 generated by the water-gas conversion unit is between 200 and 300°C, part of the energy of CO is first utilized by fan heat exchange, and then CO is passed into the heat exchange unit to make H2 and O2 reach the required temperature of 500 to 1000°C for the fuel cell;

[0022] The heat transfer unit includes heat transfer unit I and heat transfer unit II, which are used to recycle the high-quality energy of the high-temperature gas stream generated by the device and provide heat for the device that needs to consume heat. The heat transfer unit I is a heat transfer interlayer, which uses the heat of the high-temperature flue gas generated by the combustion of coke oven gas to provide heat for the primary gasification unit and the secondary gasification unit. The heat transfer unit II is a heat and mass transfer unit, which divides the H2O after the fan heat exchange and the CO after the convection heat exchange with H2 into a heat transfer stream and a mass transfer stream. The heat transfer stream transports the heat of H2O and CO to the acidification unit and the carbonization unit with a reaction temperature between 150 and 200 ° C, respectively, and the mass transfer stream transports H2O and CO to the water gas shift unit for water gas shift reaction.

[0023] The water-gas shift unit is used to generate a water-gas shift reaction. The reaction temperature is between 200 and 300°C. CO and H2O react to provide sufficient CO2 for the acidification unit and the secondary gasification unit. The generated H2 can be used to power hydrogen fuel cells.

[0024] The separation unit is used to separate the H2 and CO2 produced by the water-gas shift unit and discharge the unreacted CO and H2O. The CO2 is divided into two streams through the flow control unit II, one of which is passed into the acidification unit as an acidifier to acidify lignin, and the other is passed into the secondary gasification unit to react with coke to generate CO. The H2 is passed into the high-temperature fuel cell to generate electricity after reaching the required temperature through the heat exchange unit.

[0025] A method for cogeneration of heat and power by coupling coal gasification and fuel cells for papermaking, the method comprising:

[0026] The acidification unit is used to treat the black liquor produced by the pulping unit and the bleaching unit. In a closed system, the acidifier CO2 reacts with lignin to convert the lignin into acidified lignin, which is precipitated and enters the carbonization unit, and at the same time, the enrichment and separation of the sodium element is achieved; under a hydrothermal environment, the carbonization unit cracks the acidified lignin precipitated by the acidification unit into small molecular organic matter and then into carbon powder, which participates in the graded gasification of coal and the preparation of activated carbon; the flow control unit I can adjust the ratio of the crude carbon mixture produced by the carbonization unit to the alkalization unit and the secondary gasification unit, in which the acidification unit only needs a small amount of activated carbon to achieve good adsorption, and most of the coke is passed into the secondary gasification unit; the alkalization unit uses dilute Alkaline washing removes SiO2 impurities contained in the coke produced by the carbonization unit, and the coke after impurity removal is passed into the activation unit; the activation unit uses a method of physically activating coke with water vapor to prepare activated carbon, which is used to adsorb organic matter in the acidification unit; under the condition of air isolation, the primary gasification unit decomposes the coal at high temperature to produce coke and coke oven gas, wherein the coke continues to be passed into the secondary gasification unit, and the gasifying agent CO2 gasifies the coke and produces CO; the coke oven gas enters the combustion unit, and the high-temperature flue gas produced by the combustion passes through the heat transfer insulation of the heat transfer unit I to provide heat for the two-stage gasification unit; the CO produced by the secondary gasification unit and the H2O produced by the fuel cell contain high-grade energy, and the fan heat exchange unit uses a fan to blow high The hot H2O and CO are arranged in a heat exchange pipe with a large contact area. The hot air generated is supplied to the drying unit, and the consumed electricity is provided by the fuel cell. The CO generated by the secondary gasification unit will be determined whether to pass through the fan heat exchange first according to the actual production situation. If the temperature of the H2O generated by the fuel cell is high enough or the heat required by the drying unit is relatively small, it will be directly passed to the heat exchange unit without passing through the fan heat exchange unit. The flow control unit IV is used to adjust the ratio of CO to the fan heat exchange unit and the heat exchange unit. The H2O generated by the fuel cell should also be determined whether to pass through the fan heat exchange according to the actual situation. If the original temperature of the H2O is low or the amount of black liquor to be treated is large, it will be directly passed to the heat transfer unit II without passing through the fan heat exchange unit. The fan heat exchange unit uses the flow control unit III to adjust the ratio of H2O to the fan heat exchange unit and the heat transfer unit II; in the heat exchange unit, the CO stream after the fan heat exchange exchanges heat with the H2 stream separated from the water gas shift unit, and heats O2 at the same time; the heat transfer unit II separates the H2O after the fan heat exchange and the CO after the convection heat exchange with H2 into a heat transfer stream and a mass transfer stream, the heat transfer stream transfers their heat to the acidification unit and the carbonization unit to provide heat for the acidification and carbonization processes, and the mass transfer stream transfers H2O and CO to the water gas shift unit for water gas shift reaction; CO and H2O react to produce H2 and CO2, and the separation unit separates them and discharges the unreacted CO and H2O;CO2 is divided into two streams through the flow control unit II, which are used as the acidifier of the acidification unit and the gasifier of the secondary gasification unit respectively. The flow control unit II can flexibly adjust the proportion of CO2 flowing to the acidification unit and the secondary gasification unit according to the amount of black liquor to be processed. H2 is used for high-temperature fuel cell power generation after reaching the appropriate temperature through the heat exchange unit. ;

[0027] The beneficial effects produced by the present invention are:

[0028] (1) Through the use of efficient technologies such as acidification unit and carbonization unit, recyclable NaHCO3, lignin and other substances are accurately extracted and converted from black liquor, and the crude carbon produced by black liquor conversion is used as raw material to participate in coal graded gasification, significantly improving the comprehensive utilization efficiency of materials and resource value.

[0029] (2) A graded conversion strategy is adopted to convert coal into coke oven gas, carbon monoxide and other products. The combustion of coke oven gas generates heat, thereby providing a stable energy supply for the gasification process. Carbon monoxide is converted into hydrogen as a fuel cell raw material through water gas shift. This not only improves the overall energy utilization efficiency, but also effectively reduces the environmental burden by reducing the production of carbon dioxide and other pollutants.

[0030] (3) Multiple heat exchange units and heat transfer units are designed to maximize the utilization of high-quality energy such as H2, CO, and H2O. Through refined energy management and gradient utilization strategies, efficient heat and electricity generation are achieved, providing a stable and efficient energy supply for the entire system.

[0031] (4) The reaction temperature of high-temperature fuel cells and coal staged gasification is close, and the hydrogen produced by the conversion of carbon monoxide, a product of coal gasification, contains a small amount of carbon monoxide impurities. High-temperature fuel cells are less sensitive to carbon monoxide. Therefore, coupling coal staged gasification with high-temperature hydrogen fuel cells can not only reduce Loss can also be reduced, and the negative impact of carbon monoxide impurities in hydrogen on high-temperature fuel cells can be ignored, thereby achieving an efficient operation mode of cogeneration in the papermaking process, further improving the energy utilization efficiency and environmental protection performance of the entire process. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of a heat and power cogeneration system for papermaking coupled with coal gasification and fuel cells provided by the present invention;

[0033] Figure 2 A flow chart of a heat and power cogeneration method for papermaking coupled with coal gasification and fuel cells provided by the present invention;

[0034] Among them, 1-pulping unit, 2-bleaching unit, 3-drying unit, 4-acidification unit, 5-carbonization unit, 6-flow control unit I, 7-alkalization unit, 8-activation unit, 9-primary gasification unit, 10-secondary gasification unit, 11-combustion unit, 12-heat transfer unit I, 13-fan heat exchange unit, 14-flow control unit IV, 15-flow control unit III, 16-heat exchange unit, 17-heat transfer unit II, 18-water-gas conversion unit, 19-separation unit, 20-flow control unit II, 21-fuel cell. DETAILED DESCRIPTION

[0035] The purpose and technical solution of the present invention are described in detail below with reference to the accompanying drawings and in combination with embodiments;

[0036] like Figure 1 As shown, Figure 1 Schematic diagram of a heat and power cogeneration system for papermaking coupled with coal gasification and fuel cells provided by the present invention, the system comprising a pulping unit 1, a bleaching unit 2, a drying unit 3, an acidification unit 4, a carbonization unit 5, a flow control unit I6, an alkalization unit 7, an activation unit 8, a primary gasification unit 9, a secondary gasification unit 10, a combustion unit 11, a heat transfer unit I12, a fan heat exchange unit 13, a flow control unit IV14, a flow control unit III15, a heat exchange unit 16, a heat transfer unit II17, a water-gas conversion unit 18, a separation unit 19, a flow control unit II20, and a fuel cell 21, wherein:

[0037] The pulping unit 1 is used to prepare paper pulp by effectively separating the fibers of wood or other raw materials using mechanical pulping, chemical pulping or biological pulping techniques;

[0038] The bleaching unit 2 is used to bleach the pulp so that the pulp has a corresponding whiteness. Both the pulping unit 1 and the bleaching unit 2 will produce black liquor containing fibers, organic matter, inorganic salts, and pigments;

[0039] The drying unit 3 is used to remove moisture from the paper web during the process of making paper web from pulp, and the heat source for drying and dehydration is the high-temperature air generated by the fan heat exchange unit 13;

[0040] The acidification unit 4 is used to acidify the lignin in the black liquor to precipitate it. In the closed system, the acidifier CO2 introduced reacts with the lignin in the black liquor to convert the lignin into acidified lignin precipitation, and at the same time, the sodium salt in the black liquor is converted into NaHCO3, the sodium element is enriched and separated, and the inorganic silicon salt is also converted into SiO2 precipitation, which enters the carbonization unit 5 together with the acidified lignin. The acidification unit 4 and the carbonization unit 5 are both heated by the heat and mass transfer unit 17;

[0041] The carbonization unit 5 decomposes the acidified lignin produced by the acidification unit 5 into small molecular organic matter under a hydrothermal environment and then decomposes it into crude carbon containing SiO2 impurities;

[0042] The flow control unit I6 is used to pass the crude carbon produced by the carbonization unit 5 into the alkalization unit 7 and the secondary gasification unit 10 respectively. A part of the crude carbon enters the alkalization unit 7 through the flow control unit I6 to be converted into carbon powder. The carbon powder enters the activation unit 8 as a raw material for preparing activated carbon, and a part enters the secondary gasification unit 10 as a gasification raw material to react with carbon dioxide to produce carbon monoxide.

[0043] The alkalization unit 7 uses a dilute alkali solution to wash and remove SiO2 in the crude carbon produced by the carbonization unit 5 to produce carbon powder, which is passed into the activation unit 8 as a raw material for preparing activated carbon;

[0044] The activation unit 8 is used to prepare activated carbon. The carbon powder is physically activated by water vapor to prepare activated carbon. The activated carbon is passed into the acidification unit 4 to adsorb organic matter in the black liquor.

[0045] The primary gasification unit 9 is used to decompose coal at high temperature under the condition of air isolation to produce coke and coke oven gas. The coke is introduced into the secondary gasification unit 10 to participate in the reaction. The coke oven gas converts chemical energy into thermal energy through the combustion unit 11. The generated high-temperature flue gas is passed through the heat transfer unit I 12 to provide heat for the primary gasification unit 9 and the two-stage gasification unit 10.

[0046] The secondary gasification unit 10 uses CO2 as a gasifying agent to react with the coke produced by the primary gasification unit 9 and the crude carbon produced by the carbonization unit 5 to produce CO, and the CO is recycled for heat and then introduced into the water-gas shift unit 18 to participate in the reaction;

[0047] The fan heat exchange unit 13 is used to recover heat from the H2O generated by the fuel cell 21 and the CO generated by the secondary gasification unit 10, and includes a fan a and a heat exchange tube coil b. The heat exchange tube coil b has at least two inlets and two outlets, one inlet is connected to an H2O outlet of the flow control unit III 15, and one inlet is connected to a CO outlet of the flow control unit IV 14. The H2O outlet is connected to the H2O inlet of the heat and mass transfer unit 17, and the CO outlet is connected to the CO inlet of the heat and mass transfer unit 17. The high-temperature H2O generated by the fuel cell 21 enters the heat exchange tube coil b of the fan heat exchange unit 13 through the flow control unit III 15, and the CO generated by the secondary gasification unit 10 enters the heat exchange tube coil b of the fan heat exchange unit 13 through the flow control unit IV 14. The fan a purges the heat exchange pipe b containing the high-temperature H2O and CO, recovers the heat of the H2O and CO and generates high-temperature air. The generated high-temperature air is supplied to the drying unit 3 as a heat source, and the electric energy consumed by the fan a is provided by the fuel cell 21;

[0048] The flow control unit IV 14 is used to pass the CO generated by the secondary gasification unit 10 into the fan heat exchange unit 13 and the heat exchange unit 16 respectively. The CO stream flowing into the fan heat exchange unit 13 is cooled by the fan purge and generates high-temperature air. The high-temperature air serves as the heat source of the drying unit 3. The CO stream flowing into the heat exchange unit 16 is heat-exchanged with the H2 separated by the separation unit 19 and the newly added O2 to recover heat.

[0049] The flow control unit III 15 is used to pass the H2O generated by the fuel cell 21 into the fan heat exchange unit 13 and the heat and mass transfer unit 17 respectively. The H2O stream flowing into the fan heat exchange unit 13 is cooled by the fan and generates high-temperature air. The high-temperature air serves as the heat source of the drying unit 3. After passing through the fan heat exchange unit 13, it flows into the heat and mass transfer unit 17. A part of the H2O stream first passes through the fan heat exchange unit 13 for heat recovery and then passes through the heat and mass transfer unit 17 for secondary heat recovery, and a part of the H2O stream directly passes through the heat and mass transfer unit 17 for heat recovery;

[0050] The heat exchange unit 16 is used to exchange heat between the CO produced by the secondary gasification unit 10 and the H2 separated from the separation unit 19, and to preheat the O2;

[0051] The heat and mass transfer unit 17 is used to perform secondary heat recovery on the H2O stream and CO stream that have undergone heat recovery. The H2O and CO streams flowing out of the outlet of the fan heat exchange unit 13 and the CO separated from the separation unit 19 are divided into a heat transfer stream and a mass transfer stream by the heat and mass transfer unit 17. The heat transfer stream transports the heat of H2O and CO to the acidification unit 4 and the carbonization unit 5 respectively, and the mass transfer stream transports H2O and CO to the water gas shift unit 18 for water-gas shift reaction.

[0052] In the water-gas shift unit 18, CO and H2O undergo a water-gas shift reaction, providing sufficient CO2 for the acidification unit 4 and the secondary gasification unit 10, while the generated H2 serves as a raw material for the fuel cell 21;

[0053] The separation unit 19 is used to separate the H2 and CO2 produced by the water-gas shift unit 18, and discharge the unreacted CO and H2O. The CO2 is divided into two streams through the flow control unit II 20, one of which is introduced into the acidification unit 4 as an acidifying agent to acidify lignin, and the other is introduced into the secondary gasification unit 10 to react with coke to generate CO. The H2 is heated by the heat exchange unit 16 and then introduced into the fuel cell 21 to generate electricity.

[0054] The flow control unit II 20 is used to pass the CO2 separated by the separation unit 19 into the acidification unit 4 and the secondary gasification unit 10 respectively, a part of the CO2 enters the acidification unit 4 as an acidifier to react with the lignin in the black liquor to produce acidified lignin precipitation, and a part of the CO2 enters the secondary gasification unit 10 as a gasifier;

[0055] The fuel cell 21 is used to convert the chemical energy in H2 into electrical energy, and includes a hydrogen inlet, an oxygen inlet and a water outlet. Hydrogen and oxygen generate electrical energy through the fuel cell 21 accompanied by a high-temperature H2O flow. The generated electrical energy is used to power the fan a of the fan heat exchange unit 13.

[0056] The CO generated by the secondary gasification unit 10 flows into the fan heat exchange unit 13 and the heat exchange unit 16 through the flow control unit IV 14. The CO stream flowing into the fan heat exchange unit 13 is cooled by the fan and generates high-temperature air. The high-temperature air serves as the heat source of the drying unit 3. The CO stream flowing into the heat exchange unit 16 is heat-exchanged with the H2 separated by the separation unit 19 and the newly added O2 to recover heat. The CO is respectively heat-recovered by the fan heat exchange unit 13 and the heat exchange unit 16 and then passed into the heat and mass transfer unit 17 for secondary heat recovery. The recovered heat is used to heat the acidification unit 4 and the carbonization unit 5. The CO enters the water-gas shift unit 18 to participate in the reaction after passing through the heat and mass transfer unit 17. The flow control unit IV14 is used to adjust the ratio of CO flowing into the fan heat exchange unit 13 and the heat exchange unit 16 respectively. The ratio adjustment range is 0-100%. 0% means that the CO generated by the secondary gasification unit 10 flows into the heat exchange unit 16 through the flow control unit IV14, and 100% means that the CO generated by the secondary gasification unit 10 flows into the fan heat exchange unit 13 through the flow control unit IV14.

[0057] The H2O generated by the fuel cell 21 flows into the fan heat exchange unit 13 and the heat and mass transfer unit 17 respectively through the flow control unit III15. The H2O stream flowing into the fan heat exchange unit 13 is cooled by the fan purge and generates high-temperature air. The high-temperature air serves as the heat source of the drying unit 3. After passing through the fan heat exchange unit 13, it flows into the heat and mass transfer unit 17. A part of the H2O is firstly heat-recovered through the fan heat exchange unit 13 and then through the heat and mass transfer unit 17 for secondary heat recovery. A part of the H2O is directly heat-recovered through the heat and mass transfer unit 17. The flow control unit III15 adjusts the ratio of the two H2O flows according to the heat required by the drying unit 3, the acidification unit 4 and the carbonization unit 5. The ratio adjustment range is 0-100%. 0% represents that all the H2O generated by the fuel cell 21 enters the heat and mass transfer unit 17 through the flow control unit III15, and 100% represents that all the H2O generated by the fuel cell 21 enters the fan heat exchange unit 13 through the flow control unit III15.

[0058] The flow control unit I6 is used to adjust the ratio of the crude carbon produced by the carbonization unit 5 to the alkalization unit 7 and the secondary gasification unit 10 respectively, and the adjustment range is 0-100%, 0% means that the crude carbon produced by the carbonization unit 5 is all passed into the secondary gasification unit 10 through the flow control unit I6, and 100% means that the crude carbon produced by the carbonization unit 5 is all passed into the alkalization unit 7 through the flow control unit I6.

[0059] The flow control unit II 20 is used to adjust the ratio of the CO2 separated by the separation unit 19 entering the acidification unit 4 and the secondary gasification unit 10 respectively, and the adjustment range is 0-100%, 0% means that the CO2 separated by the separation unit 19 flows into the secondary gasification unit 10 through the flow control unit II 20, and 100% means that the CO2 separated by the separation unit 19 flows into the acidification unit 4 through the flow control unit II 20.

[0060] The heat exchange tube coil b of the fan heat exchange unit 13 adopts finned tubes, and has two forms: single coil and multi-coil.

[0061] Embodiment, applied to the above-mentioned papermaking coal gasification and fuel cell coupled heat and power cogeneration method, the method comprises:

[0062] The pulping unit 1 and the bleaching unit 2 produce black liquor containing fiber, organic matter, inorganic salts and pigments. The black liquor enters the acidification unit 4 to react with the acidifier CO2, and is converted into acidified lignin precipitation through activated carbon adsorption, and SiO2 precipitation is produced at the same time; the acidified lignin precipitation and the SiO2 precipitation enter the carbonization unit 5 and are converted into crude carbon under a hydrothermal environment; the crude carbon is respectively led to the alkalization unit 7 and the secondary gasification unit 10 through the flow control unit Ⅰ6, and the flow control unit Ⅰ6 can adjust the ratio of the two flows of the crude carbon; the crude carbon reacts with the dilute alkali solution in the alkalization unit 7 to remove SiO2 Impurities are removed to produce carbon powder, which is then passed into the activation unit 8 for physical activation by water vapor to prepare activated carbon. The activated carbon is passed into the acidification unit 4 to adsorb organic matter in the black liquor, and the crude carbon reacts with CO2 in the secondary gasification unit 10 to produce CO; the coal is passed into the primary gasification unit 9 for high-temperature decomposition in a closed environment to produce coke and coke oven gas, wherein the coke is further passed into the secondary gasification unit 10 to react with CO2 to produce CO; the coke oven gas enters the combustion unit 11, and the high-temperature flue gas produced by the combustion is passed through the heat transfer unit I 12 to provide heat for the primary gasification unit 9 and the two-stage gasification unit 10;

[0063] The CO generated by the secondary gasification unit 10 and the H2O generated by the fuel cell 21 contain high-grade energy. The CO generated by the secondary gasification unit 10 flows into the fan heat exchange unit 13 and the heat exchange unit 16 through the flow control unit IV 14. The CO stream flowing into the fan heat exchange unit 13 is cooled by the fan purge and generates high-temperature air. The high-temperature air serves as the heat source of the drying unit 3. The CO stream flowing into the heat exchange unit 16 is heat-exchanged with the H2 separated by the separation unit 19 and the newly added O2 to recover heat. The CO is respectively heat-recovered by the fan heat exchange unit 13 and the heat exchange unit 16 and then passed into the heat transfer unit II 17 for secondary heat recovery. The recovered heat is used to heat the acidification unit 4 and the carbonization unit 4. 5. CO passes through the heat transfer unit II 17 and enters the water gas shift unit 18 to participate in the reaction. The H2O generated by the fuel cell 21 flows into the fan heat exchange unit 13 and the heat transfer unit II 17 through the flow control unit III 15. The H2O stream flowing into the fan heat exchange unit 13 is cooled by the fan and generates high-temperature air. The high-temperature air serves as the heat source of the drying unit 3. After passing through the fan heat exchange unit 13, it flows into the heat transfer unit II 17. A part of the H2O is firstly recovered by the fan heat exchange unit 13 and then by the heat transfer unit II 17 for secondary heat recovery. A part of the H2O is directly recovered by the heat transfer unit II 17. The ratio of the two H2O flows is regulated according to the heat required by the drying unit 3, the acidification unit 4 and the carbonization unit 5.

[0064] The H2O and CO after the primary heat recovery are divided into a heat transfer stream and a mass transfer stream through the heat transfer unit II 17. The heat transfer stream transfers the heat of H2O and CO to the acidification unit 4 and the carbonization unit 5 respectively, and the mass transfer stream transfers H2O and CO to the water gas shift unit 18 for water-gas shift reaction; CO and H2O react in the water gas shift unit 18 to produce H2 and CO2, and the separation unit 19 separates H2 and CO2 and discharges the unreacted CO and H2O; CO2 is divided into two streams through the flow control unit II 20, which are used as the acidifying agent of the acidification unit 4 and the gasifying agent of the secondary gasification unit 10 respectively. The flow control unit II 20 adjusts the ratio of CO2 to the acidification unit 4 and the secondary gasification unit 10 according to the amount of black liquor to be processed, and H2 reaches the reaction temperature after passing through the heat exchange unit 16 and enters the fuel cell 21 to convert chemical energy into electrical energy.

[0065] In one embodiment, the presence of the flow control unit III 15 can adjust the ratio of H2O generated by the fuel cell 21 to the fan heat exchange unit 13 and the heat transfer unit II 17. The H2O first passes through the fan heat exchange unit 13 to generate hot air, and then passes into the heat transfer unit II 17 to provide heat; however, when the original temperature of the H2O is relatively low or the amount of black liquor to be processed is large, the H2O can be directly passed into the heat transfer unit II 17 without passing through the fan heat exchange unit 13.

[0066] In another embodiment, the presence of the flow control unit IV14 can adjust the ratio of the CO generated by the secondary gasification unit 10 to the fan heat exchange unit 13 and the heat exchange unit 16. CO first passes through the fan heat exchange unit 13 to generate hot air, and then passes through the heat exchange unit 16 for convection heat exchange with H2; however, when the temperature of the H2O generated by the fuel cell 21 is high enough or the heat required by the drying unit 3 is relatively small, CO can be directly passed to the heat exchange unit 16 without passing through the fan heat exchange unit 13.

[0067] In another embodiment, part of the coal enters the primary gasification unit 9 to participate in staged gasification, and part enters the combustion unit 11 to be burned to generate high-temperature flue gas for heat supply.

[0068] Therefore, those skilled in the art should understand that the description of the specific embodiments of the present invention is not intended to limit the concept and scope of the present invention. Without departing from the technical solution of the present invention, any modification and improvement of the technical solution will still fall within the protection scope of the present invention.

Claims

1. A cogeneration system for papermaking by coupling coal gasification and fuel cells, characterized in that: The invention comprises a pulping unit (1), a bleaching unit (2), a drying unit (3), an acidification unit (4), a carbonization unit (5), a flow control unit I (6), an alkalization unit (7), an activation unit (8), a primary gasification unit (9), a secondary gasification unit (10), a combustion unit (11), a heat transfer unit I (12), a fan heat exchange unit (13), a flow control unit IV (14), a flow control unit III (15), a heat exchange unit (16), a heat and mass transfer unit (17), a water-gas conversion unit (18), a separation unit (19), a flow control unit II (20), and a fuel cell (21), wherein: The pulping unit (1) is used to prepare paper pulp by effectively separating the fibers of wood or other raw materials using mechanical pulping, chemical pulping or biological pulping techniques; The bleaching unit (2) is used to bleach the pulp so that the pulp has a corresponding whiteness. Both the pulping unit (1) and the bleaching unit (2) will produce black liquor containing fibers, organic matter, inorganic salts, and pigments. The drying unit (3) is used to remove moisture from the paper web during the process of making paper web from pulp, and the heat source for drying and dehydrating is the high-temperature air generated by the fan heat exchange unit (13); The acidification unit (4) is used to acidify the lignin in the black liquor to precipitate it. In the closed system, the acidifying agent CO2 is introduced to react with the lignin in the black liquor to convert the lignin into acidified lignin precipitate. At the same time, the sodium salt in the black liquor is converted into NaHCO3, and the sodium element is enriched and separated. The inorganic silicon salt is also converted into SiO2 precipitate and enters the carbonization unit (5) together with the acidified lignin. The acidification unit (4) and the carbonization unit (5) are both heated by the heat and mass transfer unit (17); The carbonization unit (5) decomposes the acidified lignin produced by the acidification unit (5) into small molecular organic matter under a hydrothermal environment and then decomposes it into crude carbon containing SiO2 impurities; The flow control unit I (6) is used to pass the crude carbon produced by the carbonization unit (5) into the alkalization unit (7) and the secondary gasification unit (10) respectively. A portion of the crude carbon enters the alkalization unit (7) through the flow control unit I (6) to be converted into carbon powder. The carbon powder enters the activation unit (8) as a raw material for preparing activated carbon, and a portion of the crude carbon enters the secondary gasification unit (10) as a gasification raw material to react with carbon dioxide to produce carbon monoxide. The alkalization unit (7) uses a dilute alkali solution to wash and remove SiO2 in the crude carbon produced by the carbonization unit (5) to produce carbon powder, and the carbon powder is introduced into the activation unit (8) as a raw material for preparing activated carbon; The activation unit (8) is used to prepare activated carbon. The carbon powder is physically activated by water vapor to prepare activated carbon. The activated carbon is introduced into the acidification unit (4) to adsorb organic matter in the black liquor. The primary gasification unit (9) is used to decompose coal at high temperature under air-isolated conditions to produce coke and coke oven gas. The coke is introduced into the secondary gasification unit (10) to participate in the reaction. The coke oven gas converts chemical energy into thermal energy through the combustion unit (11). The generated high-temperature flue gas is used to provide heat for the primary gasification unit (9) and the two-stage gasification unit (10) through the heat transfer unit I (12). The secondary gasification unit (10) uses CO2 as a gasifying agent to react with the coke produced by the primary gasification unit (9) and the crude carbon produced by the carbonization unit (5) to produce CO, and the CO is recycled for heat and then introduced into the water-gas shift unit (18) to participate in the reaction; The fan heat exchange unit (13) is used to recover heat from H2O generated by the fuel cell (21) and CO generated by the secondary gasification unit (10), and comprises a fan (a) and a heat exchange tube coil (b). The heat exchange tube coil (b) has at least two inlets and two outlets, one inlet is connected to an H2O outlet of the flow control unit III (15), one inlet is connected to a CO outlet of the flow control unit IV (14), the H2O outlet is connected to an H2O inlet of the heat and mass transfer unit (17), and the CO outlet is connected to a CO inlet of the heat and mass transfer unit (17). The high-temperature H2O generated by the fuel cell (21) enters the heat exchange tube coil (b) of the fan heat exchange unit (13) through the flow control unit III (15), and the CO generated by the secondary gasification unit (10) enters the heat exchange tube coil (b) of the fan heat exchange unit (13) through the flow control unit IV (14). The fan (a) purges the heat exchange pipe (b) containing the high-temperature H2O and CO, recovers the heat of the H2O and CO and generates high-temperature air. The generated high-temperature air is supplied to the drying unit (3) as a heat source. The electric energy consumed by the fan (a) is provided by the fuel cell (21); The flow control unit IV (14) is used to pass the CO generated by the secondary gasification unit (10) into the fan heat exchange unit (13) and the heat exchange unit (16) respectively. The CO stream flowing into the fan heat exchange unit (13) is cooled by fan blowing and generates high-temperature air. The high-temperature air serves as a heat source for the drying unit (3). The CO stream flowing into the heat exchange unit (16) is heat-exchanged with the H2 separated by the separation unit (19) and the newly added O2 to recover heat. The flow control unit III (15) is used to pass the H2O generated by the fuel cell (21) into the fan heat exchange unit (13) and the heat and mass transfer unit (17) respectively. The H2O stream flowing into the fan heat exchange unit (13) is cooled by the fan and generates high-temperature air. The high-temperature air serves as a heat source for the drying unit (3). After passing through the fan heat exchange unit (13), the air flows into the heat and mass transfer unit (17). A portion of the H2O stream first passes through the fan heat exchange unit (13) for heat recovery and then passes through the heat and mass transfer unit (17) for secondary heat recovery. A portion of the H2O stream directly passes through the heat and mass transfer unit (17) for heat recovery. The heat exchange unit (16) is used to perform heat exchange between the CO generated by the secondary gasification unit (10) and the H2 separated from the separation unit (19), and to preheat the O2 at the same time; The heat and mass transfer unit (17) is used to perform secondary heat recovery on the H2O stream and the CO stream that have undergone heat recovery. The H2O and CO streams flowing out of the outlet of the fan heat exchange unit (13) and the CO separated from the separation unit (19) are separated into a heat transfer stream and a mass transfer stream by the heat and mass transfer unit (17). The heat transfer stream transports the heat of the H2O and CO to the acidification unit (4) and the carbonization unit (5), respectively, and the mass transfer stream transports the H2O and CO to the water gas shift unit (18) for water gas shift reaction. In the water-gas shift unit (18), CO and H2O undergo a water-gas shift reaction to provide sufficient CO2 for the acidification unit (4) and the secondary gasification unit (10), and the generated H2 is used as a raw material for the fuel cell (21); The separation unit (19) is used to separate the H2 and CO2 generated by the water-gas conversion unit (18) and discharge the unreacted CO and H2O. The CO2 is divided into two streams through the flow control unit II (20). One of the streams is introduced into the acidification unit (4) as an acidifying agent to acidify lignin, and the other is introduced into the secondary gasification unit (10) to react with coke to generate CO. The H2 is heated by the heat exchange unit (16) and then introduced into the fuel cell (21) to generate electricity. The flow control unit II (20) is used to pass the CO2 separated by the separation unit (19) into the acidification unit (4) and the secondary gasification unit (10) respectively, a part of the CO2 enters the acidification unit (4) as an acidifier to react with the lignin in the black liquor to produce acidified lignin precipitation, and a part of the CO2 enters the secondary gasification unit (10) as a gasifier; The fuel cell (21) is used to convert the chemical energy in H2 into electrical energy, and comprises a hydrogen inlet, an oxygen inlet and a water outlet. Hydrogen and oxygen generate electrical energy through the fuel cell (21) accompanied by a high-temperature H2O stream. The generated electrical energy is used to power the fan (a) of the fan heat exchange unit (13).

2. A cogeneration system for papermaking by coupling coal gasification and fuel cells, characterized in that: The CO generated by the secondary gasification unit (10) is heat-utilized in a stepwise manner. The CO generated by the secondary gasification unit (10) flows into the fan heat exchange unit (13) and the heat exchange unit (16) through the flow control unit IV (14). The CO stream flowing into the fan heat exchange unit (13) is cooled by fan blowing and generates high-temperature air. The high-temperature air serves as a heat source for the drying unit (3). The CO stream flowing into the heat exchange unit (16) is heat-exchanged with the H2 separated by the separation unit (19) and the newly added O2, thereby recovering heat. The CO is respectively heat-recovered once by passing through the fan heat exchange unit (13) and the heat exchange unit (16), and then passed into the heat and mass transfer unit ( 17) for secondary heat recovery, the recovered heat is used to heat the acidification unit (4) and the carbonization unit (5), the CO passes through the heat and mass transfer unit (17) and enters the water gas shift unit (18) to participate in the reaction, the flow control unit IV (14) is used to adjust the ratio of CO flowing into the fan heat exchange unit (13) and the heat exchange unit (16), respectively, the ratio adjustment range is 0-100%, 0% means that the CO generated by the secondary gasification unit (10) flows into the heat exchange unit (16) through the flow control unit IV (14), and 100% means that the CO generated by the secondary gasification unit (10) flows into the fan heat exchange unit (13) through the flow control unit IV (14).

3. A cogeneration system for papermaking by coupling coal gasification and fuel cells, characterized in that: The H2O generated by the fuel cell (21) is heat-utilized in a stepwise manner. The H2O generated by the fuel cell (21) flows into the fan heat exchange unit (13) and the heat and mass transfer unit (17) respectively through the flow control unit III (15). The H2O stream flowing into the fan heat exchange unit (13) is cooled by the fan and generates high-temperature air. The high-temperature air serves as a heat source for the drying unit (3). After passing through the fan heat exchange unit (13), the air flows into the heat and mass transfer unit (17). A portion of the H2O is firstly heat-recovered by the fan heat exchange unit (13) and then flows through the heat and mass transfer unit (17). Secondary heat recovery is performed, a portion of which is directly recovered through the heat and mass transfer unit (17). The flow control unit III (15) adjusts the ratio of the two flows of H2O according to the heat required by the drying unit (3), the acidification unit (4) and the carbonization unit (5). The ratio adjustment range is 0-100%. 0% means that all the H2O generated by the fuel cell (21) enters the heat and mass transfer unit (17) through the flow control unit III (15), and 100% means that all the H2O generated by the fuel cell (21) enters the fan heat exchange unit (13) through the flow control unit III (15).

4. A cogeneration system for papermaking by coupling coal gasification and fuel cells, characterized in that: The flow control unit I (6) is used to adjust the ratio of the crude carbon produced by the carbonization unit (5) to be respectively passed into the alkalization unit (7) and the secondary gasification unit (10), and the adjustment range is 0-100%, 0% means that the crude carbon produced by the carbonization unit (5) is completely passed into the secondary gasification unit (10) through the flow control unit I (6), and 100% means that the crude carbon produced by the carbonization unit (5) is completely passed into the alkalization unit (7) through the flow control unit I (6).

5. A cogeneration system for papermaking by coupling coal gasification and fuel cells, characterized in that: The flow control unit II (20) is used to adjust the ratio of the CO2 separated by the separation unit (19) to be respectively introduced into the acidification unit (4) and the secondary gasification unit (10), and the adjustment range is 0-100%, 0% means that the CO2 separated by the separation unit (19) flows completely into the secondary gasification unit (10) through the flow control unit II (20), and 100% means that the CO2 separated by the separation unit (19) flows completely into the acidification unit (4) through the flow control unit II (20).

6. A cogeneration system for papermaking by coupling coal gasification and fuel cells, characterized in that: The heat exchange tube coil (b) of the fan heat exchange unit (13) adopts finned tubes and has two forms: single coil and multi-coil.

7. A cogeneration method for papermaking by coupling coal gasification with a fuel cell, applied to the system described in any one of claims 1 to 6, characterized in that: The method includes: The pulping unit (1) and the bleaching unit (2) produce black liquor containing fiber, organic matter, inorganic salts and pigments. The black liquor enters the acidification unit (4) to react with the acidifier CO2, and is converted into acidified lignin precipitate through activated carbon adsorption, and SiO2 precipitate is produced at the same time. The acidified lignin precipitate and the SiO2 precipitate enter the carbonization unit (5) to be converted into crude carbon under a hydrothermal environment. The crude carbon is respectively led to the alkalization unit (7) and the secondary gasification unit (10) through the flow control unit I (6). The flow control unit I (6) can adjust the ratio of the two flows of the crude carbon. The crude carbon reacts with the dilute alkali solution in the alkalization unit (7) to remove SiO2. Impurities are removed to produce carbon powder, which is then passed into an activation unit (8) to be physically activated by water vapor to prepare activated carbon, and then passed into an acidification unit (4) to adsorb organic matter in black liquor. The crude carbon reacts with CO2 in a secondary gasification unit (10) to produce CO; the coal is passed into a primary gasification unit (9) to be decomposed at high temperature in a closed environment to produce coke and coke oven gas, wherein the coke is further passed into the secondary gasification unit (10) to react with CO2 to produce CO; the coke oven gas enters a combustion unit (11), and the high-temperature flue gas produced by the combustion is used to heat the primary gasification unit (9) and the two-stage gasification unit (10) through a heat transfer unit I (12); The CO generated by the secondary gasification unit (10) and the H2O generated by the fuel cell (21) contain high-quality energy. The CO generated by the secondary gasification unit (10) flows into the fan heat exchange unit (13) and the heat exchange unit (16) through the flow control unit IV (14). The CO stream flowing into the fan heat exchange unit (13) is cooled by the fan and generates high-temperature air. The high-temperature air serves as a heat source for the drying unit (3). The CO stream flowing into the heat exchange unit (16) exchanges heat with the H2 separated by the separation unit (19) and the newly added O2, thereby recovering heat. After the CO passes through the fan heat exchange unit (13) and the heat exchange unit (16) for primary heat recovery, it is passed into the heat and mass transfer unit (17) for secondary heat recovery. The recovered heat is used to heat the acidification unit (4) and the carbonization unit (5). After passing through the heat and mass transfer unit (17), the H2O enters the water-gas conversion unit (18) to participate in the reaction. The H2O generated by the fuel cell (21) flows into the fan heat exchange unit (13) and the heat and mass transfer unit (17) respectively through the flow control unit III (15). The H2O stream flowing into the fan heat exchange unit (13) is cooled by the fan and generates high-temperature air. The high-temperature air serves as the heat source of the drying unit (3). After passing through the fan heat exchange unit (13), it flows into the heat and mass transfer unit (17). A part of the H2O is firstly heat-recovered through the fan heat exchange unit (13) and then through the heat and mass transfer unit (17) for secondary heat recovery. A part of the H2O is directly heat-recovered through the heat and mass transfer unit (17). The ratio of the two H2O flows is regulated according to the heat required by the drying unit (3), the acidification unit (4) and the carbonization unit (5). The H2O and CO after primary heat recovery are separated into a heat transfer stream and a mass transfer stream by a heat and mass transfer unit (17). The heat transfer stream transfers the heat of H2O and CO to the acidification unit (4) and the carbonization unit (5) respectively, while the mass transfer stream transfers H2O and CO to the water gas shift unit (18) for water gas shift reaction. CO and H2O react in the water gas shift unit (18) to produce H2 and CO2. The separation unit (19) separates H2 and CO2 and discharges the unreacted CO and H2O. CO2 is separated into two streams by a flow control unit II (20), which are used as an acidifying agent for the acidification unit (4) and a gasifying agent for the secondary gasification unit (10) respectively. The flow control unit II (20) adjusts the ratio of CO2 to the acidification unit (4) and the secondary gasification unit (10) according to the amount of black liquor to be processed. H2 passes through the heat exchange unit (16) and reaches the reaction temperature before entering the fuel cell (21) to convert chemical energy into electrical energy.

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