Whole-flow economic optimization method for mechanical dehydration, drying and carbonization process of municipal sludge

Abstract

The invention discloses a whole-flow economic optimization method for a municipal sludge mechanical dehydration, drying and carbonization process, which is used for improving the efficiency and the economical efficiency of a municipal sludge dehydration, drying and carbonization system. The whole-process optimization strategy in the invention is mainly represented in two aspects: 1, a hot tail gas recycling strategy in a sludge heat drying stage and a pyrolysis oil recycling strategy in a sludge carbonization stage, so that efficient utilization and alternative use of energy are realized; and secondly, aiming at the condition that the water content of the sludge is a key factor influencing drying and carbonization, the operation parameters of the optimal economic benefit are determined by accurately adapting the water content conditions of all stages of mechanical dehydration, heat drying and carbonization. According to the invention, recycling of waste heat and pyrolysis oil gas is realized, the most economic working condition points of sludge dehydration, drying and carbonization are explored, the energy consumption of the system is greatly reduced, the sludge drying and carbonization efficiency is greatly improved, and the operation cost of the system is obviously reduced.

Description

Technical Field

[0001] The invention relates to the technical field of sludge drying and carbonization, and in particular to a method for economically optimizing the entire process of municipal sludge mechanical dehydration, drying and carbonization. Background Art

[0002] The rapid development of economy and society has led to a rapid increase in the level of industrialization, an increase in the number of sewage treatment plants, and a continuous expansion in scale. It is required that by 2025, the country needs to add a daily processing capacity of no less than 20,000 tons of wet sludge (water content 80%) harmless disposal facilities. The centralized stacking of sludge not only occupies a large amount of land, but also easily causes secondary environmental pollution and wastes resources. The sludge has a high water content, complex composition, and contains a variety of organic matter, inorganic matter, heavy metals, salts, and a small amount of pathogenic microorganisms and parasites, etc., and the cost of treatment and disposal is relatively high. Sludge pyrolysis carbonization includes two stages: sludge drying and carbonization. Sludge drying is heated by a heat source to evaporate the internal water of the sludge, thereby greatly reducing the volume of the sludge. It is the main technical means for urban sludge disposal and an extremely critical link in the disposal process. However, sludge drying is often accompanied by high energy consumption, which makes the operating cost high, which is contrary to the strategies proposed in recent years, restricting its development and promotion, making the research on energy saving and consumption reduction in the sludge drying process of practical significance. During the sludge pyrolysis and carbonization process, tail gas is generated at the outlet of the drying furnace along with the dried sludge. The tail gas contains a large amount of heat energy, which can be recycled and used as a heat source in the sludge drying stage. Part of the pyrolysis oil and gas generated by sludge pyrolysis is recycled for sludge pyrolysis, and the other part is allocated to the drying stage on the premise of meeting the sludge pyrolysis requirements, providing additional energy for sludge drying. Precise control of waste heat recycling is to accurately allocate the drying tail gas generated in the drying stage and the pyrolysis oil and gas generated in the pyrolysis stage, and use the excess heat energy in the sludge drying stage to reduce energy consumption. It is one of the important measures to reduce the energy consumption of sludge pyrolysis and carbonization.

[0003] In the prior art, the waste heat recovery system was studied for the hydrothermal carbonization process of sludge, and the effectiveness of the full heat exchange technology in improving the calorific value of sludge and the efficiency of the system was confirmed through design and thermodynamic analysis. At the same time, the thermal characteristics of the sludge drying-incineration system were analyzed, pointing out that the sludge self-heating was not enough to support the operation of the system, resulting in an increase in the demand for auxiliary fuel as the sludge water content decreased. Regarding the pyrolysis characteristics of urban sludge, it was found through energy balance analysis that the pyrolysis oil and gas cycle heating is not only self-sufficient, but also saves energy in the drying stage. The prior art also studied the optimal operating conditions of the sludge drying and incineration combined system, and determined the optimal operating conditions for energy saving and consumption reduction. However, the precise control of the recovery of waste heat from sludge pyrolysis and carbonization is an important part of energy saving and consumption reduction, but it is rarely reported. Summary of the invention

[0004] The purpose of the present invention is to improve the problems of large heat loss and insufficient waste heat utilization in the operation of the current process system, and to construct an energy balance equation for the sludge pyrolysis and carbonization system based on actual operating parameters, calculate the heat consumption of each process flow, and evaluate and analyze the energy consumption and energy saving potential of each part, so as to determine a reasonable waste heat recovery ratio, fuel supply rate and air matching amount, accurately match the energy requirements of sludge drying and carbonization, and improve the overall energy utilization efficiency of the system, so as to solve the problems raised in the above background technology.

[0005] To achieve the above objectives, according to Fig.11 As shown, the present invention provides a method for economic optimization of the entire process of mechanical dehydration, drying and carbonization of municipal sludge, including a mechanical dehydration stage, a thermal drying stage and a carbonization stage of the sludge;

[0006] In the thermal drying stage, an internal heat rotary drying furnace is used, and a heat exchanger is added at the outlet of the drying furnace to recover the waste heat in the drying tail gas;

[0007] The pyrolysis oil and gas produced in the carbonization stage is partially recycled to the drying stage to achieve energy recycling;

[0008] Construct the energy balance equation of the sludge pyrolysis carbonization system, evaluate the heat consumption of each process flow, and determine the reasonable waste heat recovery ratio, fuel supply rate and air matching amount to accurately match the energy requirements of sludge drying and carbonization.

[0009] As a further improvement of the technical solution, the heat exchanger includes a precooler, a condenser and a heat exchanger, which are used to gradually reduce the temperature of the dried tail gas and recover the heat therein;

[0010] Part of the exhaust gas treated by the precooler is discharged, and the other part passes through the condenser to remove moisture and then is heated to the drying stage through the heat exchanger.

[0011] As a further improvement of the present technical solution, the drying tail gas is mixed with the high-temperature flue gas to form the inlet flue gas of the drying furnace, thereby realizing the waste heat recovery of the tail gas and pyrolysis oil gas. The high-temperature flue gas comes from the complete combustion of the pyrolysis oil gas generated by the pyrolysis of dry sludge in the carbonization combustion chamber.

[0012] As a further improvement of the technical solution, at different temperatures in the drying stage, as the drying temperature increases from 105°C to 150°C, the evaporation efficiency of sludge at various moisture contents is improved.

[0013] As a further improvement of the technical solution, the energy balance relationship in the drying stage includes the input energy (heat Q provided by fuel combustion) f , heat recovery of waste heat from drying tail gas Q re And the heat Q allocated to the drying part by pyrolysis oil and gas combustion gas) and output energy (energy consumed by sludge heating Q s 、The remaining water in the sludge heats up and absorbs heat Q w 、Energy required for water evaporation Q e , the exhaust gas from the drying outlet takes away energy Q out And heat loss energy Q c1 ).

[0014] As a further improvement of this technical solution, the energy distribution and reuse of drying tail gas and pyrolysis oil gas under different moisture contents were analyzed. It was found that when the sludge moisture content decreased, the energy required for water evaporation decreased accordingly, and the distribution ratio of the pyrolysis oil gas reuse in the drying and carbonization stages was 19:6, which improved the overall energy utilization efficiency.

[0015] As a further improvement of the technical solution, when the moisture content after the mechanical dehydration stage is 62%, a drying temperature of 150° C. is used in the drying stage to dry the moisture content to 20%, and then a carbonization stage is performed.

[0016] As a further improvement of the present technical solution, the pyrolysis oil and gas generated in the carbonization stage is transported to the carbonization combustion chamber through a separator, where it is fully burned to produce high-temperature flue gas; a portion of the high-temperature flue gas is recycled to the carbonization furnace to meet the operation of the pyrolysis system, and the remaining high-temperature flue gas is mixed with the recycled tail gas from the drying furnace and the high-temperature flue gas provided by the combustion raw materials in the drying combustion chamber to form the inlet flue gas of the drying furnace, thereby realizing the recovery and utilization of the waste heat of the drying tail gas and the pyrolysis oil and gas.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] In the economic optimization method of the whole process of mechanical dehydration, drying and carbonization of municipal sludge, the whole process optimization strategy is mainly manifested in two aspects: first, the reuse of hot tail gas in the thermal drying stage of sludge and the reuse strategy of pyrolysis oil in the carbonization stage of sludge, which realizes the efficient utilization and alternative use of energy; second, the moisture content of sludge is the key factor affecting drying and carbonization, and the moisture content conditions of each stage of mechanical dehydration, thermal drying and carbonization are accurately adapted to determine the operating parameters with the best economic benefits. Taking the municipal sludge produced by the A2O process sewage treatment plant as an example, when the moisture content of the sludge is 62% after mechanical dehydration, the drying temperature is 150℃ to the moisture content after drying is 20%, the operating cost of the whole system is the lowest, and the cost of treating each ton of sludge is 257.47 yuan. While realizing the recycling of waste heat and pyrolysis oil and gas, the present invention explores the most economical operating point of sludge dehydration, drying and carbonization, greatly reduces the energy consumption of the system, and greatly improves the efficiency of sludge drying and carbonization, and significantly reduces the operating cost of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1The energy consumption potential analysis diagram of the drying stage (A) and carbonization stage (B) at different initial moisture contents;

[0020] Figure 2 This is the energy balance diagram of sludge drying;

[0021] Figure 3 This is the energy balance diagram of sludge carbonization;

[0022] Figure 4 The energy balance diagram for the waste heat recovery of drying tail gas (A) and pyrolysis oil gas (B);

[0023] Figure 5 This is the analysis diagram of drying efficiency and tail gas recycling rate at different drying temperatures;

[0024] Figure 6 It is the analysis diagram of high temperature drying flue gas flow at different drying temperatures;

[0025] Figure 7 Schematic diagram of the energy output (A) and energy input (B) distribution during the drying stage at different drying temperatures;

[0026] Figure 8 A schematic diagram showing the comparison of fuel quantity at different sludge moisture contents before and after improvement;

[0027] Fig. 9 This is a schematic diagram of waste heat recovery under different sludge moisture content;

[0028] Fig.10 This is a schematic diagram of the disposal cost of sludge dehydration and drying during the whole life cycle under different moisture contents of mechanical dehydration;

[0029] Fig.11 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the accompanying drawings in the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0031] (1) With a certain A 2Taking the sludge treatment of the sewage treatment plant as an example, the sewage treatment plant is designed to treat 150t / d of sludge, and adopts pyrolysis carbonization process to realize the resource utilization and reduction of sludge. The main process includes mechanical dehydration stage, drying stage, carbonization stage and flue gas treatment stage. The sludge discharged from the sewage treatment plant is transported to the mud cake bin after dehydration. The wet sludge in the bin is crushed and then transferred to the internal heat rotary drying furnace. It is in contact with the high-temperature flue gas provided by the drying heating system for heat exchange and temperature rise. The water in the wet sludge evaporates and the moisture content drops to about 20%. The outlet flue gas generated by the drying furnace contains water vapor, volatiles and other substances. After separation by the flue gas treatment system, the water vapor is condensed into sewage and returned to the sewage treatment plant for secondary treatment. The remaining flue gas is discharged after being treated to meet the standards. The dry sludge is transported to the external heat carbonization furnace to absorb the heat conducted from the high-temperature flue gas to the inner wall of the carbonization furnace, and the temperature rises to about 500℃ for pyrolysis. The pyrolysis products enter the carbon storage bin for collection and disposal. The pyrolysis oil and gas produced by the pyrolysis of dry sludge contains a small amount of gaseous tar, which flows back to the carbonization heating system and reacts with air to completely burn to produce high-temperature flue gas, which provides a heat source for the carbonization furnace and maintains the operation of the pyrolysis system.

[0032] (2) The sludge drying stage in this case uses an internal heating rotary drying furnace. Figure 1 The energy saving potential analysis of the sludge pyrolysis carbonization stage under different sludge moisture content conditions is given. The results show that when the initial sludge moisture content exceeds 60%, the energy consumption demand increases significantly due to the need to evaporate a large amount of water. If the tail gas is directly discharged without being utilized, it will become the main link of energy loss in the system. On the contrary, when the initial sludge moisture content is lower than 60%, the dry weight increases, the proportion of organic components increases, and the pyrolysis oil and gas output is higher, becoming a very valuable energy source. Therefore, in the process of process improvement, the focus is on improving the distribution of dried tail gas and pyrolysis oil and gas and the recovery of waste heat.

[0033] (3) The drying tail gas directly discharged in the original process is utilized for energy. A heat exchanger is added at the outlet of the drying furnace, which includes three parts: a precooler, a condenser, and a heat exchanger. The drying tail gas heats the circulating water through the precooler, and the tail gas is cooled. After cooling, part of the tail gas is discharged to take away the ash produced by sludge drying. The other part is removed from the water carried by the heat exchange process through the condenser, and is heated by contact with the hot circulating water through the heat exchanger and reused in the sludge drying stage. The pyrolysis oil and gas produced by the sludge pyrolysis are transported to the carbonization combustion chamber through the separator, where they are fully burned to produce high-temperature flue gas. Part of the high-temperature flue gas is reused in the carbonization furnace to meet the operation of the pyrolysis system, and the remaining part of the high-temperature flue gas is mixed with the recycled tail gas of the drying furnace and the high-temperature flue gas provided by the combustion of raw materials in the drying combustion chamber to form the inlet flue gas of the drying furnace, thereby realizing the reuse of waste heat of tail gas and pyrolysis oil and gas.

[0034] (4) During the sludge drying stage, the wet sludge exchanges heat with the inlet flue gas, where the heat Q provided by the fuel combustion is the input energy in the system energy balance. f(563000kJ / T), the heat Q of the waste heat recovered from the drying tail gas re (557000kJ / T) and the heat Q allocated to the drying part by pyrolysis oil and gas combustion gas (1842000kJ / T) three parts. The output energy is mainly the energy consumed by sludge heating Q s (23940kJ / T), the remaining water in the sludge heats up and absorbs heat Q w (29800kJ / T), the energy required for water evaporation Q e (1349000kJ / T), the exhaust gas from the drying outlet takes away energy Q out (1559000kJ / T) and heat loss energy Q c1 (98000kJ / T) five parts. Energy balance relationship is as follows Figure 2 shown.

[0035] (5) In the energy balance of the sludge carbonization stage, the input is only the drying sludge energy Q d (2842400kJ / T), output is the pyrolysis product energy Q p (422980kJ / T), the energy Q allocated to the drying stage to maintain the operation of the system after the pyrolysis oil and gas is burned gas (1842000kJ / T) and heat loss energy consumption Q c2 (588300kJ / T). The energy balance relationship is as follows Figure 3 shown.

[0036] (6) The exhaust heat recovery system at the drying outlet only uses the exhaust gas energy Q out (1559000kJ / T) is the input, and the output is the energy Q taken away by flue gas cooling c (582800kJ / T), external exhaust smoke exhaust heat dissipation energy loss Q out2 (409000kJ / T) and the recycled flue gas energy Q re (557000kJ / T). In terms of the pyrolysis oil and gas waste heat recovery system, its energy input depends on the complete combustion of the pyrolysis oil and gas. g (2417000kJ / T), the output energy is divided into energy Q g1 (575000 kJ / T) and the energy Q allocated to the drying stage for recycling gas (1842000kJ / T). The energy balance relationship in the waste heat recovery stage is as follows: Figure 4 shown.

[0037] (7) Figure 5The drying efficiency of sludge and the recovery rate of tail gas heat at different drying temperatures were analyzed. As can be seen from the figure, as the drying temperature increases from 105°C to 150°C, the evaporation efficiency of sludge at various moisture contents is improved. Especially when the sludge moisture content is 55%, its combustion efficiency is improved most significantly, and the fuel consumption is reduced from 105.89kg / T to 26.42kg / T, a reduction of 75.05%. However, this improvement trend gradually flattens as the temperature rises. The proportion of heat recovered from the drying tail gas decreased by 2.5% during this process.

[0038] (8) Figure 6 As shown in the figure, with the increase of drying temperature, the decline rate of flue gas flow rate gradually slows down. This shows that although increasing the temperature helps to improve the drying efficiency, the reduction of flow rate offsets this effect to a certain extent, making the growth eventually stabilize.

[0039] (9) When the amount of water evaporated during the drying process remains constant, the required drying energy, the ash removed, and the total amount of volatile gases remain constant. When the drying flue gas changes from low temperature and high flow to high temperature and low flow, the proportion of energy required for tail gas purification increases, resulting in a decrease in the heat recovery rate. Figure 7 The figure shows the energy distribution of the drying stage at different drying temperatures. When the water content of the sewage is 65%, the drying is carried out. Although the temperature rise reduces the proportion of exhaust gas recycling energy, the reduced flow rate reduces the heat loss carried away by the outlet exhaust gas, thereby reducing fuel demand. In the temperature range of 105℃ to 150℃, the higher the drying temperature, the more the efficiency of the drying stage is improved.

[0040] (10) The moisture content of sludge is closely related to the energy consumption of evaporating water, the hot flue gas flow rate in the drying stage, and the dry basis components of sludge in the carbonization stage. Figure 8 It shows that when the drying temperature is 150℃, when the sludge moisture content drops from 85% to 55%, the original process biomass fuel consumption is reduced by 106kg / t, while the improved process is reduced by 173kg / t. When the moisture content is 85%, the fuel consumption saving rate is 19.31%, while when the moisture content is 55%, the saving rate is as high as 83.34%. Therefore, after the process improvement, waste heat recycling can achieve fuel savings in treating sludge with different moisture contents.

[0041] (11) Fig. 9The energy distribution and reuse of drying tail gas and pyrolysis oil gas at different moisture contents of sludge were analyzed through energy balance. As the moisture content of sludge decreases, the energy required for water evaporation decreases accordingly. When the moisture content of sludge is 55%, about 19% of the total heat of drying tail gas can be reused, creating conditions for the reuse of drying tail gas. Since the sludge carbonization stage is a thermal exothermic reaction, pyrolysis oil and gas are produced at the same time. Generally, as the moisture content decreases, the proportion of dry mass in the sludge increases, thereby increasing the pyrolysis oil and gas production in the carbonization stage, creating conditions for its reuse. The distribution ratio of the reused pyrolysis oil and gas in the drying and carbonization stages is 19:6. In addition, by Fig. 9 It can be seen that as the water content decreases, the total reused calorific value of the drying tail gas and pyrolysis oil and gas increases. This is due to two reasons: first, the recyclable heat in the drying tail gas decreases at a rate of 14970 kJ per 1% decrease in water content. Second, the reused energy in the pyrolysis oil and gas used in the drying stage increases at a rate of 48475 kJ per 1% decrease in water content.

[0042] (12) In the economic benefit analysis of the whole life cycle of sludge dehydration and drying, the sludge dehydration process level is considered at the same time. The moisture content of the sludge is a key factor affecting economic benefits and energy utilization. In the sludge mechanical dehydration stage, assuming that the wet sludge is dehydrated to the moisture content, the hourly sludge deep dehydration power consumption can be calculated by the formula. When the sludge is dehydrated to a certain moisture content, it enters the sludge drying stage. In this process, energy consumption is mainly concentrated in the water evaporation and the mixing fan air supply link. During the drying process, the biomass fuel is mixed with the recycled flue gas to form high-temperature flue gas, which is heat-exchanged with the dehydrated sludge to achieve water evaporation. In this step, the cost mainly comes from the consumption of biomass fuel. At the same time, the mixing fan transports the combined flue gas into the drying furnace. The hourly fan power is obtained according to the fan model of the research project. The price of biomass fuel is calculated at 1.2 yuan / kg, and the average price of industrial electricity is 0.59 yuan / kWh. The total cost of the system can be obtained by calculation. After mechanical dehydration, the sludge enters the drying stage. The drying temperature is 150°C. The sludge moisture content in the mechanical dehydration stage is examined at 55%-85%. As the moisture content of the sludge decreases, its cost gradually increases. For example, at 85%, it is 73.49 yuan / ton, and at 55%, it is 270.22 yuan / ton. On the contrary, the lower the sludge moisture content, the less cost is required to enter the carbonization stage. For example, at 85%, it is 213.66 yuan / ton, and at 55%, it is 2.90 yuan / ton. Because the cost of sludge in the carbonization stage is offset by the reuse of pyrolysis oil and gas, the cost is calculated as 0 yuan. Fig.10 It can be seen that when the sludge moisture content after mechanical dehydration is 62%, the operating cost of the entire system is the lowest. At this time, the cost of mechanical dehydration is 205.39 yuan / ton, and the drying cost is 50.08 yuan / ton.

[0043] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for economic optimization of the whole process of mechanical dehydration, drying and carbonization of municipal sludge, characterized in that: It includes the mechanical dewatering stage, thermal drying stage and carbonization stage of sludge; In the thermal drying stage, an internal heat rotary drying furnace is used, and a heat exchanger is added at the outlet of the drying furnace to recover the waste heat in the drying tail gas; The pyrolysis oil and gas generated in the carbonization stage is partially recycled to the drying stage, thus realizing energy recycling.

2. The method for economic optimization of the whole process of municipal sludge mechanical dehydration, drying and carbonization process according to claim 1 is characterized in that: The heat exchanger includes a precooler, a condenser and a heat exchanger, which are used to gradually reduce the temperature of the dried tail gas and recover the heat therein; Part of the exhaust gas treated by the precooler is discharged, and the other part passes through the condenser to remove moisture and then is heated to the drying stage through the heat exchanger.

3. The method for economic optimization of the whole process of municipal sludge mechanical dehydration, drying and carbonization process according to claim 1 or 2, characterized in that: The drying tail gas is mixed with the high-temperature flue gas to form the inlet flue gas of the drying furnace, realizing the waste heat recovery of the tail gas and pyrolysis oil gas. The high-temperature flue gas comes from the complete combustion of the pyrolysis oil gas generated by the pyrolysis of dry sludge in the carbonization combustion chamber.

4. The method for economic optimization of the whole process of municipal sludge mechanical dehydration, drying and carbonization process according to claim 1, characterized in that: It also includes constructing the energy balance equation of the sludge pyrolysis and carbonization system, evaluating the heat consumption of each process flow, and determining the reasonable waste heat recovery ratio, fuel supply rate and air matching amount to accurately match the energy requirements of sludge drying and carbonization.

5. The method for economic optimization of the whole process of municipal sludge mechanical dehydration, drying and carbonization process according to claim 1, characterized in that: At different temperatures in the drying stage, as the drying temperature increased from 105°C to 150°C, the evaporation efficiency of sludge at various moisture contents increased.

6. The method for economic optimization of the whole process of municipal sludge mechanical dehydration, drying and carbonization process according to claim 1, characterized in that: The energy balance relationship in the drying stage includes the input energy (heat provided by fuel combustion Q f , heat recovery of waste heat from drying tail gas Q re And the heat Q allocated to the drying part by pyrolysis oil and gas combustion gas ) and output energy (energy consumed by sludge heating Q s 、The remaining water in the sludge heats up and absorbs heat Q w 、Energy required for water evaporation Q e , the exhaust gas from the drying outlet takes away energy Q out And heat loss energy Q c1 ).

7. The method for economic optimization of the whole process of municipal sludge mechanical dehydration, drying and carbonization process according to claim 1, characterized in that: The energy distribution and reuse of drying tail gas and pyrolysis oil gas under different moisture contents were analyzed. It was found that when the moisture content of sludge decreased, the energy required for water evaporation decreased accordingly, and the distribution ratio of pyrolysis oil gas reuse in the drying and carbonization stages was 19:6, which improved the overall energy utilization efficiency.

8. The method for economic optimization of the whole process of municipal sludge mechanical dehydration, drying and carbonization process according to claim 1, characterized in that: When the moisture content after the mechanical dehydration stage is 62%, the drying stage is carried out at a drying temperature of 150° C. to a moisture content of 20%, and then the carbonization stage is carried out.

9. The method for economic optimization of the whole process of municipal sludge mechanical dehydration, drying and carbonization process according to claim 1, characterized in that: The pyrolysis oil and gas generated in the carbonization stage are transported to the carbonization combustion chamber through a separator, where they are fully burned to generate high-temperature flue gas; a portion of the high-temperature flue gas is recycled to the carbonization furnace to meet the operation of the pyrolysis system, and the remaining high-temperature flue gas is mixed with the recycled tail gas from the drying furnace and the high-temperature flue gas provided by the combustion raw materials in the drying combustion chamber to form the inlet flue gas of the drying furnace, thereby realizing the recovery and utilization of the waste heat of the drying tail gas and the pyrolysis oil and gas.

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