Process for the slow pyrolysis of pulverized coal in a multi-effect hydrogenation in stages

Abstract

The application discloses a kind of segmented multi-effect hydrogenation pulverized coal medium-speed pyrolysis process, belong to coal clean and efficient conversion field, to solve the existing pulverized coal pyrolysis energy utilization efficiency low energy consumption high, product yield low quality problem and safety environmental protection hidden danger.It includes: the raw material fine coal is dried using mixed flue gas in drying section;In pyrolysis section, first, dry pulverized coal is preheated by high-temperature circulating nitrogen, then, in hydrogen atmosphere, heating is carried out by interwall temperature control and time control for pyrolysis;In cooling section, high-temperature pulverized coke is pre-cooled by low-temperature circulating nitrogen in turn, and the pulverized coke is passivated by circulating cooling flue gas for final cooling. Among them, the purified coal gas produced by pyrolysis is used as fuel for combustion chamber, the high-temperature flue gas generated is mixed with the circulating cooling flue gas from the final cooling section after interwall heat exchange to serve as drying heat source, and part of the flue gas after drying is returned to the final cooling section after cooling to form a cycle. The process is mainly used for clean and efficient conversion of weakly cohesive pulverized coal, and can produce high-quality tar, high-calorific-value coal gas and high-activity pulverized coke.

Description

Technical Field

[0001] This invention relates to the field of clean and efficient coal conversion technology. More specifically, this invention relates to a segmented, multi-effect hydrogenated pulverized coal medium-speed pyrolysis process. Background Technology

[0002] In the technological system for clean and efficient coal utilization, pulverized coal pyrolysis technology occupies a crucial strategic position. Its core value lies in the controllable thermal conversion under medium- and low-temperature conditions, transforming pulverized coal into higher-value products such as tar, coal gas, and solid coke. This represents a key pathway for transforming coal from a single fuel to a dual-use material and fuel, significantly contributing to optimizing my country's energy structure and enhancing the added value of coal utilization. Currently, the industry has developed various mainstream pyrolysis technologies, including fixed-bed, fluidized-bed, and moving-bed pyrolysis, which have played a positive role in specific historical periods. However, with the continuous improvement of energy efficiency requirements, the inherent defects exposed by these traditional processes in long-term industrial practice have become increasingly prominent, becoming a bottleneck restricting the large-scale commercialization of this technology. Especially when processing weakly viscous pulverized coal, which is abundant in my country but has specific requirements for reactivity and caking properties, existing technologies often struggle to achieve a satisfactory balance between economic and environmental benefits, severely challenging their overall technological competitiveness. Therefore, in-depth analysis and systematic solutions to these inherent defects are urgent priorities for promoting the upgrading and iteration of pulverized coal pyrolysis technology.

[0003] First, existing pulverized coal pyrolysis technologies generally face the severe challenge of low energy utilization efficiency, which directly leads to high operating costs and weakens their market competitiveness. Most traditional processes have inherent design deficiencies, typically employing a single-stage heating mode or only performing simple waste heat recovery, failing to adopt a systems engineering perspective to construct a multi-stage, multi-grade energy utilization network. Specifically, the high-grade thermal energy generated during pyrolysis is not fully utilized in stages. For example, the high-temperature flue gas generated in the pyrolysis furnace combustion chamber, after completing its primary function, is often directly discharged or only undergoes preliminary heat exchange, wasting a large amount of medium- and low-temperature heat it carries. Simultaneously, the sensible heat contained in the high-temperature pulverized coke produced by the reaction usually needs to be dissipated through an additional cooling system. This process not only fails to recover energy but also consumes water or electricity. This extensive energy management approach results in a high dependence on external fresh fuel, significantly compressing the project's profit margin. How to break down the energy barriers between process units and achieve closed-loop and tiered energy utilization throughout the entire process, thereby significantly reducing overall energy consumption, is the primary technical challenge facing all technical personnel.

[0004] Secondly, existing technologies also perform poorly in terms of the quality and yield of the final products, failing to meet market demands for high-quality chemical raw materials and clean energy. During pyrolysis, the initially generated liquid-phase tar products are prone to excessive cracking and condensation reactions at high temperatures, leading to a significant reduction in the yield of the target product, tar, typically reaching only below 80% of the theoretical yield. More seriously, these secondary reactions increase the content of heavy components (such as asphaltenes) in the tar, while reducing the proportion of light, high-value fractions. This not only lowers the product quality of the tar but also creates significant difficulties for its subsequent deep processing and utilization. Regarding gaseous products, the total content of effective components (hydrogen, carbon monoxide, and methane) in the produced gas is mostly below 80%, and its calorific value typically hovers in the lower range of 7.5 to 13.5 megajoules (approximately 1800 to 3200 kcal), limiting its utilization value and limiting its use primarily as a low-grade fuel. Furthermore, the reactivity of the solid product, pulverized coke, cannot be fully optimized due to unsuitable process conditions. The poor selectivity of this product has seriously affected the economic benefits of the entire pyrolysis process. How to effectively suppress side reactions and improve the yield and quality of high-value products constitutes the second technical challenge that urgently needs to be overcome.

[0005] Secondly, from a safety and environmental perspective, traditional pyrolysis processes pose significant hidden dangers and struggle to meet the stringent requirements of modern industry for safe production and green development. On the safety front, the core risk stems from the high-temperature coke, reaching 600-700°C. Direct air cooling would cause the coke to undergo a violent exothermic oxidation reaction with oxygen, easily leading to spontaneous combustion and posing a serious threat to the stability of continuous production and factory safety. To avoid this, large quantities of inert gases (such as nitrogen) are typically required for protection, further increasing operating costs. On the environmental front, if the flue gas generated during the process is emitted directly without thorough treatment, it carries large amounts of dust and harmful gases such as sulfur oxides and nitrogen oxides, causing pollution to the surrounding atmosphere. While end-of-pipe treatment technologies can partially address this issue, they often come with a significant increase in investment and operating costs. Therefore, fundamentally mitigating the risk of spontaneous combustion of high-temperature coke within the process and achieving near-zero emissions of pollutants is the third crucial technical challenge that must be addressed.

[0006] Finally, existing technologies have significant shortcomings in process integration, leading to problems such as system redundancy, large footprint, and high initial investment. Traditional pyrolysis plant designs typically layout core processes such as drying, pyrolysis, and cooling as independent unit operations, connected by complex material conveying systems. This not only makes the entire process lengthy but also results in substantial heat loss and material spillage. Simultaneously, the independent equipment layout occupies excessive plant space; the dispersed equipment foundations, numerous conveying machines, and independent control systems collectively drive up land costs, civil engineering expenses, and equipment procurement costs. This "cost-cumulative effect" of low integration foreshadows poor economic performance from the project's inception. The fourth key technical challenge is how to improve the overall economic efficiency of the project through innovative integration of processes and equipment, simplifying the process, achieving a compact layout, and reducing investment and operating costs.

[0007] In summary, existing pulverized coal pyrolysis technologies face severe challenges across four core dimensions: energy efficiency, product value, safety and environmental protection, and system integration. The extensive energy utilization model drives up operating costs; insufficient product selectivity limits economic benefits; safety and environmental hazards increase compliance risks and potential liabilities; and low-integration system design raises investment barriers and worsens operational economics from the outset. Therefore, the industry urgently needs a new technological solution that can systematically and comprehensively address all of these key bottlenecks. Summary of the Invention

[0008] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0009] Another objective of this invention is to provide a segmented, multi-effect hydrogenated pulverized coal medium-speed pyrolysis process, which significantly reduces the energy consumption per ton of coal pyrolysis through energy cascade utilization and material closed-loop circulation, increases tar yield to over 90% of the Grakin index and significantly increases the proportion of light components, and completely avoids the risk of spontaneous combustion of pulverized coke through low-oxygen flue gas final cooling, achieving a flue gas recycling rate of 70-90%, while equipment integration reduces investment and operating costs.

[0010] To achieve these objectives and other advantages according to the present invention, a segmented multi-effect hydrogenated pulverized coal medium-speed pyrolysis process is provided, comprising: S1. Drying section: The raw material pulverized coal is fed into the fluidized bed dryer, and the mixed flue gas is used as a heat source to dry the raw material pulverized coal to obtain dried pulverized coal and dried flue gas. S2, pyrolysis section: This includes: In the preheating stage, the dry pulverized coal obtained in step S1 is directly exchanged with high-temperature circulating nitrogen to obtain preheated pulverized coal. In the hydropyrolysis step, the preheated pulverized coal is pyrolyzed in a hydrogen atmosphere in a partitioned pyrolysis furnace by partitioned heating to generate pyrolysis gas, tar and high-temperature pulverized coke. S3, Cooling Section: This includes: In the pre-cooling stage, the high-temperature coke obtained in step S2 is exchanged with low-temperature circulating nitrogen to obtain pre-cooled coke. At the same time, the low-temperature circulating nitrogen absorbs heat and rises to form the high-temperature circulating nitrogen, which is then sent to the preheating stage. In the final cooling and passivation stage, the pre-cooled coke powder is exchanged with the circulating cooling flue gas to obtain the final cooled coke powder. In step S2, the remaining portion of the pyrolysis gas generated by the pyrolysis reaction after purification is supplied as fuel to the combustion chamber of the partition wall pyrolysis furnace to generate high-temperature flue gas to provide a heat source for the partition wall heating, and the high-temperature flue gas is converted into hot flue gas. The mixed flue gas in step S1 comes from the hot flue gas and the circulating cooling flue gas in the final cooling and passivation stage of step S3; the first part of the dried flue gas is cooled by a water cooler and then returned to the final cooling and passivation stage of step S3 as circulating cooling flue gas.

[0011] Preferably, in step S1, the particle size of the raw material pulverized coal is ≤13mm, and the temperature of the mixed flue gas is 350~400℃; the moisture content of the obtained dried pulverized coal is ≤1%, and the temperature is 100~120℃; the obtained dried pulverized coal is sent to a high-level silo for temporary storage through a pneumatic conveying system, and the high-level silo is equipped with a pressure balancing valve and inert gas protection; the second part of the dried flue gas is used as the carrier gas for pneumatic conveying, and after being pressurized, it is used to convey the dried pulverized coal, and the fluidized bed dryer is kept at a negative pressure of 1~3kpa.

[0012] Preferably, in the preheating stage of step S2, the dried pulverized coal is fed into the pyrolysis preheating silo via the first airlock feeder valve, and undergoes countercurrent direct mixing heat exchange with the high-temperature circulating nitrogen from the precooling stage. The temperature of the high-temperature circulating nitrogen is 420±30℃, and the temperature of the preheated pulverized coal is 280±5℃. The first airlock feeder valve is located between the high-level silo and the pyrolysis preheating silo, and its air leakage rate is ≤0.5%.

[0013] Preferably, in the hydropyrolysis step S2, the preheated pulverized coal is fed into the indirect-wall pyrolysis furnace from the pyrolysis preheating silo via the second airlock feed valve. The indirect-wall pyrolysis furnace is equipped with a hydrogen distributor at its lower part, through which hydrogen gas with a purity ≥95% is injected to form a hydrogenation reducing atmosphere. The volume ratio of the hydrogen flow rate to the preheated pulverized coal feed rate is 3~30:1. The second airlock feed valve is located between the pyrolysis preheating silo and the indirect-wall pyrolysis furnace. The remaining purified coal gas after extracting hydrogen and some methane from the coal gas generated by the pyrolysis reaction is used as fuel gas. The high-temperature circulating nitrogen discharged from the preheating silo is converted into low-temperature circulating nitrogen by preheating air through a gas-to-gas heat exchanger. The fuel gas mixes with the preheated air and enters the combustion chamber. The high-temperature flue gas generated after combustion has a temperature of 900±50℃. The high-temperature flue gas undergoes indirect-wall heat exchange through indirect-wall heat exchange elements, and the heat transfer coefficient of the indirect-wall heat exchange elements is ≥80W / (m²). 2 The temperature inside the partition wall pyrolysis furnace is 600~700℃, the residence time of preheated pulverized coal in the partition wall pyrolysis furnace is 15~25min, and the temperature at which high-temperature pulverized coke is generated is 550~650℃.

[0014] Preferably, in the preheating stage of step S2, nitrogen is used as the carrier gas in the pyrolysis preheating silo, and the mass flow rate of high-temperature circulating nitrogen is 1.5 to 3.5 times that of dry pulverized coal. In the precooling stage of step S3, high-temperature pulverized coke first falls into the lower silo of the pyrolysis furnace, and is then fed into the precooling silo through the third airlock feed valve to exchange heat with low-temperature circulating nitrogen to obtain precooled pulverized coke. The temperature of the precooled pulverized coke is 260°C. Nitrogen is used as the carrier gas in the precooling silo, and the mass flow rate of low-temperature circulating nitrogen is 1.5 to 3.5 times that of high-temperature pulverized coke. The third airlock feed valve is located between the partition pyrolysis furnace and the precooling silo.

[0015] Preferably, the first portion of the dried flue gas, after dust removal and water cooling, is used as circulating cooling flue gas, and the dust content of the circulating cooling flue gas is ≤10mg / m³. 3 The temperature is 60±20℃ and the oxygen content is ≤8%; the temperature of the final cooled coke is ≤80℃, and the final cooled coke is sprayed and humidified by a scraper conveyor until the moisture content is 8~12% before being output.

[0016] Preferably, part of the circulating cooling flue gas is returned to the drying section and mixed with the hot flue gas to form the mixed flue gas, which is then sent to the fluidized bed dryer as a heat source. The remaining circulating cooling flue gas is discharged after desulfurization and denitrification treatment to meet emission standards.

[0017] Preferably, the recycling rate of the high-temperature flue gas reaches 70-90%.

[0018] Preferably, the low-temperature circulating nitrogen, after exchanging heat with the high-temperature pulverized coke in the precooling stage, flows sequentially through the preheating stage and the gas-to-gas heat exchanger, forming a three-stage series heat recovery nitrogen loop that runs through the cooling section, pyrolysis section, and combustion air preheating system. Due to mass and heat losses, nitrogen sources need to be replenished, and the injection flow rate of the nitrogen source is controlled by the following model: The instantaneous mass injection flow rate L1 of the nitrogen source under the pressure balance control model: ; Compensation flow rate L2 under the heat distribution compensation model: ; Final nitrogen source injection flow rate L: L = max(L1 + L2, 0); Wherein, K1 is the first proportional control coefficient, with a value ranging from 5 to 20 kg·h. -1 kPa -1 ; P set The pressure setpoint for the circulating nitrogen outlet of the pyrolysis preheating silo; kPa; P actual The measured pressure at the circulating nitrogen outlet of the pyrolysis preheating silo is given in kPa. V is the total volume of the precooling silo, preheating silo, and connecting pipelines, in m³. 3 ; R is the gas constant of nitrogen, with a value of 296.8 J·kg⁻¹. -1 K -1 ; T avg The value in K represents the average inlet and outlet temperatures of the preheating stage. A is the heat compensation coefficient, dimensionless, with a value ranging from 0.1 to 0.3; M is the mass flow rate of high-temperature pulverized coke, kg / h; C coke The specific heat capacity of coke is kJ·kg. -1 K -1 The value ranges from 1.1 to 1.3. T coke,in and T coke,out These are the inlet and outlet temperatures of the coke powder in the pre-cooling stage, respectively, in K; H is the latent heat of vaporization of liquid nitrogen, with a value of 199.2 kJ / kg; The isobaric specific heat capacity of nitrogen is taken as 1.04 kJ·kg⁻¹. -1 K -1 ; The outlet temperature of the circulating nitrogen after the precooling stage, in K; The initial temperature of the liquid nitrogen is 77K. L3 is an empirical value for the nitrogen mass flow rate required to maintain the basic cycle of the system, in kg / h.

[0019] Preferably, the mass flow rate L4 of the residual purified coal gas used as fuel gas in step S2 is determined based on the mass flow rate of dried pulverized coal and the temperature of the high-temperature coke powder at the outlet of the indirect-wall pyrolysis furnace. ; ; Wherein, K2 is the second proportional control coefficient, with a value ranging from 8 to 25 kg·h. -1 K -1 ; T set The setpoint K for the high-temperature pulverized coke at the outlet of the partition wall pyrolysis furnace is 823.15~923.15K. T actual K represents the measured temperature of high-temperature coke powder at the outlet of the indirect pyrolysis furnace, which is obtained in real time by thermocouples installed on the lower silo or outlet pipe of the indirect pyrolysis furnace. B is the integration time constant, h, which takes a value of 0.1 to 0.5; L base The base fuel gas flow rate is based on the mass flow rate of dry pulverized coal, in kg / h; F coal The mass flow rate of dried pulverized coal in the pyrolysis preheating silo is kg / h; C coal The specific heat capacity of dry pulverized coal, kJ·kg⁻¹ -1 K -1 The value ranges from 1.3 to 1.6; T pyro The target pyrolysis temperature, K, is taken as the median value of the temperature range inside the partition wall pyrolysis furnace; T preheat The temperature, K, of the preheated pulverized coal entering the partition pyrolysis furnace; Q loss The total heat loss rate of the indirect pyrolysis furnace system is denoted as kJ / h, and is taken as 5~15% of the rated design heat load of the indirect pyrolysis furnace; NH is the net calorific value of the purified residual gas, kJ / kg, and is taken as 3600~3800.

[0020] The present invention has at least the following beneficial effects: Firstly, this invention achieves efficient cascaded energy utilization by constructing a multi-stage energy circulation system of hot flue gas-drying and sensible heat from pulverized coke-nitrogen preheating-pulverized coal preheating. The high-temperature flue gas generated in the combustion chamber of the pyrolysis section is used for drying, while the sensible heat released from the cooling of pulverized coke is used to heat the circulating nitrogen, thereby preheating the pulverized coal to be pyrolyzed. This significantly reduces the consumption of external heat sources and the energy consumption per ton of coal pyrolysis, saving more than 30% energy compared to traditional processes. It fundamentally solves the technical problems of low energy utilization efficiency and high operating costs in the pulverized coal pyrolysis process. Secondly, this invention introduces a hydrogenation process and a partition wall heating method into the pyrolysis section. By injecting high-purity hydrogen to form a reducing atmosphere, and using high-efficiency partition wall heat exchange elements for precise temperature and time control, the secondary cracking reaction of tar products is effectively suppressed, increasing the tar yield to over 90% of the Gram-King index and the proportion of light components to over 80%. At the same time, the calorific value of the gas is increased to 3900-4200 kcal, successfully solving the core technical problems of poor product quality and low yield in traditional pyrolysis technology. Thirdly, this invention uses low-oxygen circulating flue gas in the cooling section for final cooling and passivation of pulverized coke, and achieves a high proportion of flue gas recycling. By using the treated low-oxygen flue gas as a cooling medium, the risk of spontaneous combustion of high-temperature pulverized coke during the cooling process is completely avoided. At the same time, the system performs efficient dust removal and recycling of flue gas, with a recycling rate of 70-90%. The final pollutant concentration is far below the national standard, perfectly solving the major safety and environmental hazards of the pyrolysis process. Fourth, this invention establishes a pressure-heat coupling control model based on nitrogen sources, which enables precise dynamic regulation of the nitrogen loop throughout the cooling, pyrolysis, and combustion preheating systems. This model can calculate and adjust the nitrogen source replenishment in real time according to the system pressure deviation and the change in coke heat load, thereby synergistically maintaining the stability of the loop pressure and the balance of heat. It effectively solves the complex control problem of system pressure instability and uneven heat distribution caused by operating condition fluctuations, ensuring the continuous, stable, and efficient operation of the entire process.

[0021] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the segmented multi-effect hydrogenated pulverized coal medium-speed pyrolysis process according to one technical solution of the present invention. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0024] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0025] like Figure 1 As shown, this invention provides a segmented multi-effect hydrogenated pulverized coal medium-speed pyrolysis process, comprising: S1. Drying section: The raw material pulverized coal is fed into the fluidized bed dryer, and the mixed flue gas is used as a heat source to dry the raw material pulverized coal to obtain dried pulverized coal and dried flue gas. S2, pyrolysis section: This includes: In the preheating stage, the dry pulverized coal obtained in step S1 is directly exchanged with high-temperature circulating nitrogen to obtain preheated pulverized coal. In the hydropyrolysis step, the preheated pulverized coal is pyrolyzed in a hydrogen atmosphere in a partitioned pyrolysis furnace by partitioned heating to generate pyrolysis gas, tar and high-temperature pulverized coke. S3, Cooling Section: This includes: In the pre-cooling stage, the high-temperature coke obtained in step S2 is exchanged with low-temperature circulating nitrogen to obtain pre-cooled coke. At the same time, the low-temperature circulating nitrogen absorbs heat and rises to form the high-temperature circulating nitrogen, which is then sent to the preheating stage. In the final cooling and passivation stage, the pre-cooled coke powder is exchanged with the circulating cooling flue gas to obtain the final cooled coke powder. In step S2, the remaining portion of the pyrolysis gas generated by the pyrolysis reaction after purification is supplied as fuel to the combustion chamber of the partition wall pyrolysis furnace to generate high-temperature flue gas to provide a heat source for the partition wall heating, and the high-temperature flue gas is converted into hot flue gas. The mixed flue gas in step S1 comes from the hot flue gas and the circulating cooling flue gas in the final cooling and passivation stage of step S3; the first part of the dried flue gas is cooled by a water cooler and then returned to the final cooling and passivation stage of step S3 as circulating cooling flue gas.

[0026] The aforementioned technical solution constructs an energy and material circulation network spanning the three stages of drying, pyrolysis, and cooling. In the drying stage, it innovatively mixes the hot flue gas generated in the pyrolysis stage with the circulating cooling flue gas returning from the cooling stage, forming a mixed flue gas at a suitable temperature. This is directly used for drying the raw coal powder, cleverly recovering the heat from the flue gas exhaust after pyrolysis and the waste heat from the cooling stage. This directly addresses and solves the technical challenges of high external heat source consumption and low energy utilization efficiency in traditional processes, reintegrating potentially wasted energy into the process chain. In the pyrolysis stage, the synergistic effect of preheating and hydropyrolysis aims to improve product quality and yield. The preheating stage utilizes high-temperature circulating nitrogen from the cooling stage, already heated by the sensible heat of the coke powder, to initially raise the temperature of the dried coal powder. The subsequent hydropyrolysis stage takes place in a closed, indirect-wall pyrolysis furnace. Deep pyrolysis is achieved through indirect heating in a hydrogen atmosphere, with controlled temperature and time heating under a reducing atmosphere. This directly addresses the technical challenge of low tar yield and high heavy component content due to secondary cracking of liquid-phase products during pyrolysis, creating crucial conditions for obtaining high-yield, high-quality tar and high-calorific-value gas. In the cooling section, the high-temperature coke first enters the pre-cooling stage, where its large amount of high-grade sensible heat is recovered by low-temperature circulating nitrogen. This not only cools the coke but also heats the low-temperature circulating nitrogen into the high-temperature circulating nitrogen required for pyrolysis preheating, achieving in-situ energy conversion and efficient utilization. The final cooling and passivation stage introduces circulating cooling flue gas to finally cool the coke. This circulating cooling flue gas originates from the dried and treated flue gas, forming an internal circulating stream. This invention utilizes the process's own circulating gas for cooling, particularly using flue gas with controllable components, effectively addressing the safety challenge of high-temperature coke's susceptibility to spontaneous combustion upon contact with air, while simultaneously reducing waste gas emissions.

[0027] According to the above technical solution, a specific workflow of the segmented multi-effect hydrogenated pulverized coal medium-speed pyrolysis process provided by the present invention is as follows: Raw material pulverized coal is fed into a fluidized bed dryer. Inside the dryer, the raw material pulverized coal comes into direct contact with mixed flue gas from the system. The mixed flue gas is composed of hot flue gas from the pyrolysis section and circulating cooling flue gas returning from the cooling section. Here, the raw material pulverized coal is dehydrated and heated, transforming into dried pulverized coal, which is temporarily stored in a low-level silo, while simultaneously generating post-drying flue gas. The dried pulverized coal is transported to the pyrolysis section, while most of the post-drying flue gas is guided to the subsequent system for circulation. After entering the pyrolysis section, the dried pulverized coal first encounters high-temperature circulating nitrogen from the pre-cooling section in the preheating stage, undergoing efficient heat exchange, significantly increasing the pulverized coal temperature, thus becoming preheated pulverized coal. Next, the preheated pulverized coal is fed into a partition wall pyrolysis furnace, where, in a reducing atmosphere filled with hydrogen, it receives heat transferred from the combustion chamber through the partition wall, undergoing a medium-speed pyrolysis reaction to generate pyrolysis gas, tar, and high-temperature pulverized coke. The pyrolysis gas, after purification (extracting hydrogen and some methane, the remaining gas has a calorific value sufficient for the combustion chamber), is returned to the system as fuel. The high-temperature flue gas generated during combustion heats the pyrolysis furnace, transforming it into lower-temperature hot flue gas for the next cycle of utilization. High-temperature pulverized coke leaves the pyrolysis section and enters the cooling section. In the pre-cooling stage, it exchanges heat with low-temperature circulating nitrogen from the system, initially lowering the coke temperature. Simultaneously, the low-temperature nitrogen is heated into high-temperature circulating nitrogen, returning to the preheating stage of the pyrolysis section. The pre-cooled coke then enters the final cooling and passivation stage, where it exchanges heat with the circulating cooling flue gas, further cooling to near ambient temperature, becoming the final cooled coke before being output to the system. The circulating cooling flue gas used for final cooling and passivation originates from a portion of the dried flue gas generated in the drying section. This portion of flue gas, after cooling treatment, is introduced into the cooling section. After fulfilling its purpose, part of it continues to participate in the cycle, while the other part is extracted from the system for further processing, thus forming a complete, internally circulating flow of materials and energy.

[0028] The most direct benefit of the above-mentioned technical solution lies in the leap in energy utilization efficiency. The process no longer relies heavily on external energy supply; instead, it maximizes energy recovery and cascade utilization by using the waste heat of pyrolysis flue gas for drying, the sensible heat of pulverized coke for preheating reaction raw materials, and internally recycling process tail gas. This significantly reduces the overall energy consumption per ton of coal processed, demonstrating excellent energy-saving characteristics. Another particularly prominent advantage of this technical solution is the significant improvement in product quality and yield. Introducing hydrogen and employing indirect heating during the pyrolysis stage creates a mild reducing environment that inhibits excessive cracking of large molecules. This not only ensures that tar can be collected at a higher yield but, more importantly, significantly increases the proportion of light, high-value tar components. Simultaneously, the coal gas produced under these optimized conditions has a more concentrated effective component, resulting in a higher calorific value and greatly enhancing the product's market competitiveness and economic benefits. In terms of safety and environmental protection, the above-mentioned technical solution utilizes treated, controllable-component circulating cooling flue gas for final cooling of high-temperature pulverized coke, fundamentally eliminating the possibility of spontaneous combustion of pulverized coke due to contact with air, and greatly improving the intrinsic safety level of the production unit. In addition, throughout the entire process, multiple airflow streams, such as hot flue gas and circulating cooling flue gas, are recycled at a high rate within the system, minimizing the direct discharge of waste gas, reducing the environmental burden from the source, and embodying the principle of clean production.

[0029] In one technical solution, in step S1, the particle size of the raw material pulverized coal is ≤13mm, and the temperature of the mixed flue gas is 350~400℃; the moisture content of the obtained dried pulverized coal is ≤1%, and the temperature is 100~120℃; the obtained dried pulverized coal is sent to a high-level silo for temporary storage through a pneumatic conveying system, and the high-level silo is equipped with a pressure balancing valve and inert gas protection; the second part of the dried flue gas is used as the carrier gas for pneumatic conveying to transport the dried pulverized coal and to keep the fluidized bed dryer operating at a negative pressure of 1~3kpa.

[0030] This invention further designs a pneumatic conveying system including a high-level silo, a pressure balancing valve, and inert gas protection. The dried pulverized coal is conveyed to the high-level silo for temporary storage via this system. A portion of the dried flue gas is pressurized by a screw blower and used as the transport carrier gas to convey the dried pulverized coal from the low-level silo to the high-level silo, achieving closed-loop material transport. The pressure balancing valve and inert gas protection in the high-level silo effectively isolate the pulverized coal from air, preventing oxidation or even spontaneous combustion due to oxygen contact during storage. Simultaneously, by maintaining the fluidized bed dryer under a negative pressure of 1-3 kPa, dust escape and equipment air leakage are effectively suppressed, improving the safety of the operating environment and systematically addressing safety and environmental hazards in the pulverized coal processing process. Regarding heat source utilization, the above-mentioned technical solution uses mixed flue gas at 350~400℃ to dry the raw coal powder. On the one hand, it ensures that enough heat can be provided to effectively evaporate the moisture in the coal, reducing the moisture content of the dried coal powder to below 1% and raising the temperature to 100~120℃. On the other hand, the medium-temperature heating method avoids overheating of the coal powder, preventing changes in the properties of the coal powder or waste of energy grade that may be caused by excessively high temperatures. This is a concrete implementation of the principle of energy cascade utilization and directly addresses the problem of high heat source consumption in traditional drying processes.

[0031] The aforementioned technical solution, by constructing a closed system including an inert-protected high-level silo and a negative-pressure operating dryer, significantly improves the inherent safety level of pulverized coal drying and subsequent transportation and storage. The pressure balancing valve and inert gas protection fundamentally eliminate the risk of pulverized coal explosion and spontaneous combustion, while the negative-pressure operation of the fluidized bed dryer effectively controls dust pollution, significantly improves the working environment, and solves the major safety and environmental hazards of traditional open or semi-open drying systems. Simultaneously, the solution cleverly utilizes the dried flue gas as the carrier gas for pneumatic conveying, achieving sealed material transportation and internal recycling of waste gas resources. This not only saves the cost and risk of introducing additional conveying media (such as air or fresh nitrogen) but also reduces the consumption of fresh inert gas and lowers the total amount of waste gas requiring external treatment, demonstrating the economic and environmental benefits brought by process integration and resource recycling from multiple dimensions.

[0032] In one of the technical solutions, in the preheating stage of step S2, the dried pulverized coal is fed into the pyrolysis preheating silo via the first airlock feeder valve, and undergoes countercurrent direct mixing heat exchange with the high-temperature circulating nitrogen from the precooling stage. The temperature of the high-temperature circulating nitrogen is 420±30℃, and the temperature of the preheated pulverized coal is 280±5℃. The first airlock feeder valve is located between the high-level silo and the pyrolysis preheating silo, and its air leakage rate is ≤0.5%.

[0033] This invention further optimizes the specific process of the preheating stage in the thermal phase. By precisely installing a first airlock feed valve on the material channel between the high-level silo and the pyrolysis preheating silo, a gas phase isolation barrier is constructed, effectively preventing the high-pressure, high-temperature circulating nitrogen in the preheating silo from leaking back to the lower-pressure high-level silo in the drying section. This ensures the independence and stability of the atmosphere in each process section and solves the problem of media interference caused by pressure fluctuations in the integrated system. In terms of heat transfer, the dried pulverized coal and the high-temperature circulating nitrogen from the precooling stage undergo countercurrent direct mixing heat exchange in the pyrolysis preheating silo. This direct contact heat exchange mode between the gas and solid phases, compared with indirect heat exchange, can achieve more complete and faster heat exchange, controlling the temperature of the circulating nitrogen within the range of 420±30℃. This ensures that the dried pulverized coal can be efficiently preheated to the target temperature of 280±5℃, providing a suitable and uniform feed for the subsequent hydropyrolysis stage, directly improving the initial thermal efficiency of the entire pyrolysis stage.

[0034] The aforementioned technical solution combines specific equipment (the first airlock feed valve), a defined material flow (high-temperature circulating nitrogen), and clear process parameters (temperature control range, air leakage rate index) to form a highly efficient and sealed preheating subsystem. It not only completes the task of heating the material but also, through its inherent sealing design, maintains the necessary pressure balance and atmosphere isolation between the drying and pyrolysis sections. This allows the sometimes contradictory requirements of energy recovery and process isolation to be achieved synergistically, creating ideal preliminary conditions for the smooth progress of subsequent reactions.

[0035] In one technical solution, in the hydropyrolysis step S2, the preheated pulverized coal is fed into the indirect-wall pyrolysis furnace through the pyrolysis preheating silo via the second airlock feed valve. The indirect-wall pyrolysis furnace is equipped with a hydrogen distributor at its lower part, through which hydrogen gas with a purity ≥95% is injected to form a hydrogenation reducing atmosphere. The volume ratio of the hydrogen flow rate to the preheated pulverized coal feed rate is 3~30:1. The second airlock feed valve is located between the pyrolysis preheating silo and the indirect-wall pyrolysis furnace. The remaining purified coal gas after extracting hydrogen and some methane from the coal gas generated by the pyrolysis reaction is used as fuel gas. The hot circulating nitrogen discharged from the preheating silo is converted into low-temperature circulating nitrogen by preheating air through a gas-to-gas heat exchanger. The fuel gas mixes with the preheated air and enters the combustion chamber. The high-temperature flue gas generated after combustion has a temperature of 900±50℃. The high-temperature flue gas undergoes indirect-wall heat exchange through indirect-wall heat exchange elements, the heat transfer coefficient of which is ≥80W / (m²). 2 The temperature inside the partition wall pyrolysis furnace is 600~700℃, the residence time of preheated pulverized coal in the partition wall pyrolysis furnace is 15~25min, and the temperature at which high-temperature pulverized coke is generated is 550~650℃.

[0036] This invention further constructs a highly integrated, self-sufficient, and precisely controllable pyrolysis reaction system. A second airlock feed valve achieves reliable gas-phase isolation between the pyrolysis preheating silo and the indirect-wall pyrolysis furnace. Together with the first airlock feed valve, this forms a sealed system throughout the material flow path, effectively preventing leakage of hydrogen atmosphere and pyrolysis product gases from the pyrolysis furnace to the preheating system. It also avoids interference from preheating gases on the pyrolysis reaction, solving the core problems of cross-contamination and media loss in complex processes. A hydrogen distributor is installed at the bottom of the indirect-wall pyrolysis furnace, injecting hydrogen with a concentration of not less than 95%, creating a strongly reducing reaction atmosphere. The volume ratio of hydrogen to preheated pulverized coal feed is 3~30:1, providing a crucial operating window for flexibly adjusting the hydrogen-to-oil ratio for different coal characteristics and deeply suppressing secondary tar cracking reactions. Meanwhile, the heat required for the pyrolysis reaction is provided by an independent combustion chamber, whose fuel comes from the residual purified coal gas after the extraction of hydrogen and some methane from the system's self-produced pyrolysis coal gas. This greatly reduces the process's dependence on external fuel, realizes self-production and self-use of energy, and directly addresses and solves the technical problem of high external energy consumption in traditional processes.

[0037] The heat transfer in the indirect-wall pyrolysis furnace utilizes highly efficient indirect-wall heat exchange, with a heat transfer coefficient of not less than 80 W / (m²). 2 The heat exchange elements of the K-type furnace indirectly and evenly transfer the heat from the high-temperature flue gas (up to 900±50℃) generated in the combustion chamber to the materials inside the furnace, avoiding direct contact between the combustion flue gas and the reactants and ensuring the purity of the pyrolysis product gas. Through precise control of the temperature inside the pyrolysis furnace between 600~700℃ and the material residence time between 15~25min, a mild and thorough medium-speed pyrolysis process is ensured, ultimately producing high-temperature pulverized coke at a temperature between 550~650℃. Furthermore, the residual heat of the preheated nitrogen gas discharged from the preheating silo is used in the gas-to-gas heat exchanger to preheat the air entering the combustion chamber, further tapping the energy recovery potential within the system and forming another closed-loop energy cycle.

[0038] The aforementioned technical solution, by creating a reducing atmosphere with high hydrogen concentration and employing a gentle and precise indirect heating method, significantly inhibits the excessive cracking and condensation of tar macromolecules. This not only directly results in higher tar yield but also substantially increases the proportion of light, high-value tar components. Simultaneously, the pyrolysis gas produced under these optimized conditions has a more concentrated effective component and an improved overall calorific value, fundamentally improving the product output structure and economics of the entire pyrolysis process. The pyrolysis reaction system uses self-produced purified coal gas as fuel and deeply recovers the energy from the waste heat of circulating nitrogen to preheat the air, achieving a high degree of energy self-sufficiency and cascaded utilization. The combustion chamber uses byproducts generated by the process itself as the main fuel, significantly reducing the consumption of external fossil fuels. Furthermore, the waste heat from the circulating nitrogen discharged after the preheating stage is used to heat the combustion air, further tapping the system's internal thermal energy potential, resulting in a significant reduction in the overall energy consumption of the entire pyrolysis unit and demonstrating excellent energy-saving characteristics.

[0039] In one technical solution, in the preheating stage of step S2, nitrogen is used as the carrier gas in the pyrolysis preheating silo, and the mass flow rate of high-temperature circulating nitrogen is 1.5 to 3.5 times that of dry pulverized coal. In the precooling stage of step S3, high-temperature pulverized coke first falls into the lower silo of the pyrolysis furnace, and is then fed into the precooling silo via the third airlock feed valve to exchange heat with low-temperature circulating nitrogen to obtain precooled pulverized coke. The temperature of the precooled pulverized coke is 260°C. Nitrogen is used as the carrier gas in the precooling silo, and the mass flow rate of low-temperature circulating nitrogen is 1.5 to 3.5 times that of high-temperature pulverized coke. The third airlock feed valve is located between the partition wall pyrolysis furnace and the precooling silo. By precisely controlling the mass flow rate ratio of circulating nitrogen to material, sufficient and suitable heat carriers are ensured in the preheating and precooling stages, thereby significantly improving heat exchange efficiency and system stability, while avoiding excessive nitrogen consumption, achieving a balance between efficient energy recovery and economical operation.

[0040] In one technical solution, the first portion of the dried flue gas, after dust removal and water cooling, is used as circulating cooling flue gas, wherein the dust content of the circulating cooling flue gas is ≤10mg / m³. 3The temperature is 60±20℃, and the oxygen content is ≤8%. The temperature of the final cooled coke is ≤80℃. The final cooled coke is humidified by spraying on a scraper conveyor until the moisture content is 8~12% before being output. The pre-cooled coke temperature is 260℃. At the same time, strict upper limits are set for dust content, temperature, and oxygen content in the circulating cooling flue gas, forming a highly efficient and safe coke cooling and passivation system. This fundamentally eliminates the risk of spontaneous combustion of high-temperature coke due to oxygen exposure, significantly improving the inherent safety of the process. Simultaneously, it greatly reduces the total amount of pollutants discharged, ensuring that emission indicators meet national ultra-low emission standards and effectively reducing negative environmental impacts. Finally, by cooling the final cooled coke to below 80℃ and subjecting it to spray humidification, the properties of the coke are further stabilized, facilitating storage and transportation, and creating favorable conditions for its subsequent resource utilization. Overall, this enhances the environmental benefits and operational reliability of the process.

[0041] In one technical solution, a portion of the circulating cooling flue gas is returned to the drying section and mixed with hot flue gas to form a mixed flue gas, which is then fed into a fluidized bed dryer as a heat source. The remaining circulating cooling flue gas undergoes desulfurization and denitrification treatment before being discharged in compliance with standards. Returning a portion of the circulating cooling flue gas to the drying section for reuse significantly improves the flue gas recycling rate within the system, reduces the total amount of waste gas requiring end-of-pipe treatment, and ensures clean and compliant final emissions through desulfurization and denitrification treatment of the remaining flue gas, achieving the dual benefits of energy conservation and environmental protection.

[0042] In one of the technical solutions, the recycling rate of the high-temperature flue gas reaches 70-90%, which significantly reduces external energy consumption and total exhaust emissions, and achieves synergistic optimization of system energy consumption and environmental performance.

[0043] In one technical solution, the low-temperature circulating nitrogen, after exchanging heat with the high-temperature pulverized coke in the precooling stage, flows sequentially through the preheating stage and the gas-to-gas heat exchanger, forming a three-stage series heat recovery nitrogen loop that runs through the cooling section, pyrolysis section, and combustion air preheating system. Due to mass and heat losses, nitrogen sources need to be replenished, and the injection flow rate of the nitrogen source is controlled by the following model: The instantaneous mass injection flow rate L1 of the nitrogen source under the pressure balance control model: ; Compensation flow rate L2 under the heat distribution compensation model: ; Final nitrogen source injection flow rate L: L = max(L1 + L2, 0); Wherein, K1 is the first proportional control coefficient, with a value ranging from 5 to 20 kg·h. -1 kPa -1 ; P setThe pressure setpoint for the circulating nitrogen outlet of the pyrolysis preheating silo; kPa; P actual The measured pressure at the circulating nitrogen outlet of the pyrolysis preheating silo is given in kPa. V is the total volume of the precooling silo, preheating silo, and connecting pipelines, in m³. 3 ; R is the gas constant of nitrogen, with a value of 296.8 J·kg⁻¹. -1 K -1 ; T avg The value in K represents the average inlet and outlet temperatures of the preheating stage. A is the heat compensation coefficient, dimensionless, with a value ranging from 0.1 to 0.3; M is the mass flow rate of high-temperature pulverized coke, kg / h; C coke The specific heat capacity of coke is kJ·kg. -1 K -1 The value ranges from 1.1 to 1.3. T coke,in and T coke,out These are the inlet and outlet temperatures of the coke powder in the pre-cooling stage, respectively, in K; H is the latent heat of vaporization of liquid nitrogen, with a value of 199.2 kJ / kg; The isobaric specific heat capacity of nitrogen is taken as 1.04 kJ·kg⁻¹. -1 K -1 ; The outlet temperature of the circulating nitrogen after the precooling stage, in K; The initial temperature of the liquid nitrogen is 77K. L3 is an empirical value for the nitrogen mass flow rate required to maintain the basic cycle of the system, in kg / h.

[0044] This invention further optimizes nitrogen energy management. In a three-stage series heat recovery nitrogen loop that runs through the cooling section, pyrolysis section, and combustion air preheating system, the low-temperature circulating nitrogen, as the working medium, first exchanges heat with high-temperature pulverized coke in the precooling stage. After absorbing a large amount of sensible heat, its temperature rises significantly, transforming into high-temperature circulating nitrogen. The heated high-temperature circulating nitrogen is then transported to the preheating stage of the pyrolysis section, where it directly exchanges heat with dry pulverized coal as a heat source. This indirectly uses the sensible heat of the pulverized coke to preheat the pulverized coal, achieving an effective transfer of energy from solid waste to raw materials. This directly addresses and solves the problems of difficult recovery of sensible heat from pulverized coke and insufficient energy utilization in traditional processes. To maintain the stability of this nitrogen loop during long-term operation, the above scheme introduces a nitrogen source (provided by a nitrogen generator) as a necessary medium supplement and control measure. Due to inevitable heat loss and minor leakage in the system, the volume and pressure of nitrogen will change. This invention provides a control model to achieve precise injection of the nitrogen source, which combines pressure balance control with heat distribution compensation. The pressure balance control section calculates the nitrogen source flow compensation required to maintain the system's base pressure by monitoring the deviation and trend of the pressure setpoint and actual values ​​at key points in the loop. This solves the technical problem of pressure instability caused by operating condition fluctuations in the closed loop. Specifically, the pressure balance control section is based on the PD controller principle in automatic control theory and is specifically designed for the dynamic characteristics of the nitrogen loop pressure balance in this invention. It is based on the ideal gas law and constructs the dynamic relationship between the nitrogen source injection flow and the pressure deviation by combining its differential form with the control system response. The proportional term... Provides an immediate response to current pressure deviations, ensuring that system pressure quickly approaches the setpoint. (Differential term) By predicting pressure change trends, it can proactively regulate pressure fluctuations in the pressure system, effectively suppressing pressure vibrations caused by sudden changes in coke processing volume.

[0045] The heat distribution compensation section goes a step further, considering the heat load brought into the pre-cooling stage by high-temperature coke in real time. Through complex calculations, it determines the additional nitrogen compensation required to balance this heat and maintain the system's preset temperature distribution, thus resolving the problem of heat recovery and distribution imbalance that may arise from changes in production load. Specifically, the heat distribution compensation section is based on the application of the law of conservation of energy in the nitrogen loop's heat distribution. It establishes a quantitative compensation relationship between the coke heat load and the nitrogen source replenishment amount. The sensible heat released by the coke should be equal to the sum of nitrogen source vaporization absorption and low-temperature nitrogen heating absorption. By introducing a heat compensation coefficient to correct the difference between the theoretical calculation value and the basic flow rate, a compensation model adapted to the actual system's heat loss is established. The final output is a combination of these two calculation results, ensuring that the injected flow rate is non-negative. Through a dynamic and coupled control strategy, the replenishment of the nitrogen source is no longer a simple pressure maintenance, but becomes an operational variable that actively adjusts the energy distribution and pressure state of the system. This allows the entire nitrogen loop to adaptively respond to changes in the amount of coke processed at the front end, ensuring a stable and suitable heat source for the preheating stage and guaranteeing the pressure safety of the loop itself. This achieves coordinated optimization control of interrelated pressure and heat parameters in an integrated system, effectively addressing the technical challenges of multivariate coupled control in complex systems.

[0046] The aforementioned technical solution constructs a three-stage series-connected heat recovery nitrogen loop, sequentially using the sensible heat of pulverized coke for preheating pulverized coal and combustion air. This achieves deep exploitation and tiered utilization of low-temperature thermal energy, minimizing the system's dependence on external energy sources. Simultaneously, it can rapidly respond to pressure and heat fluctuations within the system, ensuring the entire nitrogen loop and its closely connected preheating and combustion subsystems operate stably under optimal parameters, effectively avoiding production fluctuations caused by operational disturbances. Because this technical solution simultaneously responds to pressure signals and heat load changes, the system can adapt to varying operating conditions due to different coal qualities and throughput, enhancing the process's adaptability to different feed conditions and production demands, and strengthening the robustness of the entire production line.

[0047] In one of the technical solutions, the mass flow rate L4 of the remaining purified coal gas used as fuel gas in step S2 is determined based on the mass flow rate of dried pulverized coal and the temperature of high-temperature coke at the outlet of the indirect-wall pyrolysis furnace. ; ; Wherein, K2 is the second proportional control coefficient, with a value ranging from 8 to 25 kg·h. -1 K -1 ; T set The setpoint K for the high-temperature pulverized coke at the outlet of the partition wall pyrolysis furnace is 823.15~923.15K. T actual K represents the measured temperature of high-temperature coke powder at the outlet of the indirect pyrolysis furnace, which is obtained in real time by thermocouples installed on the lower silo or outlet pipe of the indirect pyrolysis furnace. B is the integration time constant, h, which takes a value of 0.1 to 0.5; L base The base fuel gas flow rate is based on the mass flow rate of dry pulverized coal, in kg / h; F coal The mass flow rate of dried pulverized coal in the pyrolysis preheating silo is kg / h; C coal The specific heat capacity of dry pulverized coal, kJ·kg⁻¹ -1 K -1 The value ranges from 1.3 to 1.6; T pyro The target pyrolysis temperature, K, is taken as the median value of the temperature range inside the partition wall pyrolysis furnace; T preheat The temperature, K, of the preheated pulverized coal entering the partition pyrolysis furnace; Q loss The total heat loss rate of the indirect pyrolysis furnace system is denoted as kJ / h, and is taken as 5~15% of the rated design heat load of the indirect pyrolysis furnace; NH is the net calorific value of the purified residual gas, kJ / kg, and is taken as 3600~3800.

[0048] This invention further defines a precise control method for fuel gas mass flow rate to address the problem of unstable outlet temperature control in the coal pyrolysis process caused by coal quality fluctuations, feed rate changes, and external disturbances. This invention establishes a control model with the mass flow rate of dried pulverized coal as the main feedforward variable and the high-temperature coke temperature at the pyrolysis furnace outlet as the feedback variable. The fuel gas flow rate in this control model is calculated by combining the real-time collected mass flow rate of dried pulverized coal with its specific heat capacity, the sensible heat change required to rise from the preheating temperature to the target pyrolysis temperature, and taking into account a specific proportion of heat loss from the system's rated heat load, then dividing by the net calorific value of the fuel gas. The feedforward component rapidly responds to changes in the feed load, providing the system with a basic energy input matching the current processing capacity, pre-compensating for major energy demands, and thus mitigating the lag of simple feedback control. To achieve higher precision temperature stability, this invention superimposes a feedback correction term with proportional and integral actions on top of the basic flow rate. This term can quickly respond to instantaneous deviations between the actual outlet temperature and the set value of the pyrolysis furnace, adjusting the fuel gas flow rate in a timely manner to suppress temperature fluctuations. Integral control targets persistent, small temperature deviations, gradually eliminating steady-state errors by accumulating historical deviation values ​​to prevent long-term temperature deviations from the setpoint. The combination of proportional-integral feedback control and feedforward control enables the system to respond quickly to external disturbances while maintaining precise long-term temperature stability, effectively addressing the control difficulties caused by the large inertia and delay characteristics of the pyrolysis reactor. The model output is the target fuel gas flow rate calculated through feedforward and feedback, which is sent to the actuator (control valve) on the fuel gas pipeline. Adjusting the valve opening precisely controls the amount of fuel gas supplied to the combustion chamber. Changes in the combustion chamber's heat load alter the amount of high-temperature flue gas produced, which in turn affects the heat transferred to the material in the pyrolysis furnace through the heat exchange elements, ultimately achieving closed-loop control of the coke temperature at the pyrolysis furnace outlet. The entire control process relies on real-time, accurate measurement of multiple key process parameters, such as the dry pulverized coal flow rate, preheated pulverized coal temperature, and pyrolysis furnace outlet temperature, forming a multi-variable, collaborative intelligent control loop that ensures the core pyrolysis reaction proceeds under optimal and stable temperature conditions.

[0049] The aforementioned technical solution, by introducing a composite strategy combining feedforward control based on feed load and proportional-integral feedback control for temperature deviation, proactively anticipates and responds to major changes in energy demand while rapidly correcting unforeseen disturbances. This suppresses temperature fluctuations at the outlet of the indirect-wall pyrolysis furnace to an extremely small range, creating an exceptionally stable and uniform temperature environment for the pyrolysis reaction. This is fundamental to obtaining highly selective, high-quality products. Furthermore, achieving precise and stable temperature control directly optimizes product quality and process economy. This is because a stable pyrolysis temperature effectively suppresses excessive tar cracking or incomplete reaction caused by temperature fluctuations, ensuring high tar yield and quality, while also facilitating the generation of stable, high-calorific-value gas. Temperature stability also means a smoother reaction process, reducing thermal stress on equipment caused by drastic operating condition fluctuations, extending equipment lifespan, reducing maintenance costs, and providing a core guarantee for the long-term, safe, and stable operation of the entire system.

[0050] The following is a specific implementation process of applying the segmented multi-effect hydrogenated pulverized coal medium-speed pyrolysis process of the present invention to Yulin weakly caking fine coal: Raw material preparation and process start-up: Weakly viscous fine coal from the Yulin area was used as raw material, with industrial analysis results showing 12% moisture, 8% ash, and 38% volatile matter. The raw coal was fine coal from the sorting of lump coal, with a particle size ≤13mm, to be used in the pyrolysis process. During initial system start-up, nitrogen was first introduced into the nitrogen circuit through a nitrogen source to a slightly positive pressure, and the combustion chamber was started to gradually raise the system temperature to the operating temperature.

[0051] Drying Section Operation: The prepared raw coal powder is continuously fed into the fluidized bed dryer at a rate of 40 t / h. The drying heat source is a mixed flue gas, which consists of hot flue gas from the combustion chamber of the subsequent pyrolysis section (approximately 600°C) and circulating cooling flue gas from the final cooling and passivation stage (approximately 160°C), mixed in a specific ratio to form a mixed flue gas at 380°C. Inside the dryer, the raw coal and the mixed flue gas directly contact each other for heat exchange, rapidly evaporating the moisture content from 12% to 0.8%, and raising the coal temperature to 110°C. The dried coal powder is then conveyed via a pneumatic conveying system, using a portion of the dried flue gas as a pressurized carrier gas, to a high-level silo for temporary storage. A slightly positive pressure nitrogen protective atmosphere is maintained in the high-level silo, while the entire fluidized bed dryer operates under a negative pressure of approximately 2 kPa under the action of the induced draft fan.

[0052] Pyrolysis section operation: Dry pulverized coal is fed from the high-level silo into the pyrolysis preheating silo (effective volume 60 m³) via the first airlock feed valve (air leakage rate ≤0.5%). 3In the preheating silo, pulverized coal undergoes countercurrent direct mixing and heat exchange with high-temperature circulating nitrogen gas from the precooling stage at 420°C. The mass flow rate of the high-temperature circulating nitrogen gas is controlled at 2.0 times the mass flow rate of the dry pulverized coal. After approximately 12 minutes of heat exchange residence, the pulverized coal is uniformly heated to 280°C, becoming preheated pulverized coal. The preheated pulverized coal is then fed into a rectangular-structured partitioned pyrolysis furnace (structural dimensions: 4.5m × 6m × 12m, total heat exchange element area 450 m²) via a second airlock feed valve. 2 The lower part of the pyrolysis furnace is supplied with hydrogen gas of ≥95% purity via a hydrogen distributor with an opening ratio of 0.8%. The volume ratio of hydrogen to preheated pulverized coal feed is controlled at 4:1 to create a stable hydrogen-reducing atmosphere. The heat required for pyrolysis is provided by an independent combustion chamber, which uses the remaining purified coal gas after hydrogen and partial methane extraction from the self-produced pyrolysis gas as fuel. The combustion air is provided by high-temperature circulating nitrogen preheated from the preheating silo and flowing through a gas-to-gas heat exchanger. The combustion chamber generates high-temperature flue gas at 900℃, which is then transferred through a heat transfer coefficient ≥80 W / (m³). 2 The heat exchange elements of the K) indirectly heat the pulverized coal in the furnace, stabilizing the temperature inside the pyrolysis furnace at 620℃. The pulverized coal slowly falls into the furnace and remains for about 15 minutes to complete the pyrolysis reaction, generating pyrolysis gas, tar, and high-temperature pulverized coke at approximately 620℃.

[0053] Cooling section operation: High-temperature coke powder first falls into the lower hopper of the pyrolysis furnace, and is then fed into the pre-cooling hopper (effective volume 60 m³) via the third airlock feed valve. 3 Inside the pre-cooling silo, pulverized coke undergoes convective heat exchange with low-temperature circulating nitrogen at 60°C. The mass flow rate of the low-temperature circulating nitrogen is 2.0 times that of the high-temperature pulverized coke. The temperature of the pulverized coke drops from 620°C to 250°C, while the low-temperature circulating nitrogen absorbs heat and rises to 420°C, transforming into high-temperature circulating nitrogen, which is then returned to the pyrolysis preheating stage for reuse.

[0054] The pre-cooled coke powder (250℃) was then sent to the final cooling and passivation silo (effective volume 90 m³). 3 Here, the coke powder exchanges heat with the circulating cooling flue gas. This circulating cooling flue gas is discharged from the drying section and passes through a dust removal system (dust content ≤10mg / m³). 3 The first part consists of dried flue gas cooled to approximately 60°C by water cooling, with its oxygen content controlled at 7%. The coke powder is further cooled to 75°C. Finally, the final cooled coke powder is output via a scraper conveyor, and its moisture content is adjusted to 12% by spray humidification before being used as the product output boundary.

[0055] Energy Integration and Environmental Protection: Hot flue gas at approximately 600°C, discharged from the pyrolysis furnace in the pyrolysis section, mixes with a portion of the circulating cooling flue gas from the final cooling and passivation stage to form a mixed flue gas at 380°C, which serves as a heat source for the drying section. Approximately 92% of the circulating cooling flue gas after final cooling and passivation is returned to the system to participate in the above cycle, while the remaining approximately 8% is directed to the desulfurization and denitrification system for treatment, ensuring that the dust emission concentration is ≤25mg / Nm³. 3 , SO2 and NO x The sum of emission concentrations ≤20mg / Nm 3 The system achieves emission standards after completion. The recycling rate of high-temperature flue gas within the system reaches 92%.

[0056] After the system stabilized, the individual products were analyzed. The properties of the tar products are shown in Table 1, and the gas phase products are shown in Table 2.

[0057] Table 1 Properties of Tar Products Table 2. Content of gas phase products As shown in Tables 1 and 2, the tar product has a tar yield of 10.26% (reaching over 91% of the Grakin index), with light tar (distillation point ≤320℃) accounting for 82%; the coal gas has a calorific value of 4154 kcal, and an H2+CO+CH4 content of 85.52%; the specific surface area of ​​the pulverized coke is 350 m². 2 / g; Energy consumption per ton of coal: 1660 MJ (56.73 kgec); Flue gas recycling rate: 92%; Dust emission: 25 mg / Nm³ 3 SO2 + NO x Emissions 20 mg / Nm 3 The pollutant emissions are far below the national ultra-low emission standards. Therefore, the segmented multi-effect hydrogenated pulverized coal medium-speed pyrolysis process provided by this invention can achieve the industrial operation goals of low energy consumption, high-quality product output, safety, reliability, and clean and environmentally friendly operation when processing weakly viscous pulverized coal.

[0058] The number of devices and processing scale described herein are for simplification of the invention. Applications, modifications, and variations of the segmented multi-effect hydrogenation pulverized coal medium-speed pyrolysis process of this invention will be readily apparent to those skilled in the art.

[0059] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A segmented, multi-effect hydrogenated pulverized coal medium-speed pyrolysis process, characterized in that, include: S1. Drying section: The raw material pulverized coal is fed into the fluidized bed dryer, and the mixed flue gas is used as a heat source to dry the raw material pulverized coal to obtain dried pulverized coal and dried flue gas. S2, pyrolysis section: This includes: In the preheating stage, the dry pulverized coal obtained in step S1 is fed into the pyrolysis preheating silo through the first airlock feeder valve, and undergoes countercurrent direct mixing and heat exchange with the high-temperature circulating nitrogen from the precooling stage to obtain preheated pulverized coal. The first airlock feeder valve is located between the high-level silo and the pyrolysis preheating silo. In the hydropyrolysis stage, the preheated pulverized coal is fed into the indirect pyrolysis furnace from the pyrolysis preheating silo via the second airlock feed valve. The indirect pyrolysis furnace is equipped with a hydrogen distributor at the bottom, and hydrogen with a purity of ≥95% is injected through the hydrogen distributor to form a hydrogenation reducing atmosphere, so that the preheated pulverized coal is in the hydrogen atmosphere. The volume ratio of the hydrogen flow rate to the preheated pulverized coal feed rate is 3~30:

1. The second airlock feed valve is located between the pyrolysis preheating silo and the indirect pyrolysis furnace. The preheated pulverized coal undergoes a pyrolysis reaction in the indirect pyrolysis furnace through indirect heating, generating pyrolysis gas, tar, and high-temperature coke. The remaining purified gas after extracting hydrogen and some methane from the gas generated by the pyrolysis reaction is used as fuel gas. The high-temperature circulating nitrogen discharged from the preheating silo is converted into low-temperature circulating nitrogen by preheating air through a gas-to-gas heat exchanger. The fuel gas is mixed with the preheated air and enters the combustion chamber. The high-temperature flue gas generated after combustion undergoes indirect heat exchange through indirect heat exchange elements. S3, Cooling Section: This includes: In the pre-cooling stage, the high-temperature coke obtained in step S2 is exchanged with low-temperature circulating nitrogen to obtain pre-cooled coke. At the same time, the low-temperature circulating nitrogen absorbs heat and rises to form the high-temperature circulating nitrogen, which is then sent to the preheating stage. In the final cooling and passivation stage, the pre-cooled coke powder is exchanged with the circulating cooling flue gas to obtain the final cooled coke powder. In step S2, the remaining portion of the pyrolysis gas generated by the pyrolysis reaction after purification is supplied as fuel to the combustion chamber of the partition wall pyrolysis furnace to generate high-temperature flue gas to provide a heat source for the partition wall heating, and the high-temperature flue gas is converted into hot flue gas. The mixed flue gas in step S1 comes from the hot flue gas and the circulating cooling flue gas in the final cooling and passivation stage of step S3; the first part of the dried flue gas is cooled by a water cooler and then returned to the final cooling and passivation stage of step S3 as circulating cooling flue gas.

2. The segmented multi-effect hydrogenated pulverized coal medium-speed pyrolysis process as described in claim 1, characterized in that, In step S1, the particle size of the raw material pulverized coal is ≤13mm, and the temperature of the mixed flue gas is 350~400℃; the moisture content of the obtained dried pulverized coal is ≤1%, and the temperature is 100~120℃; the obtained dried pulverized coal is sent to a high-level silo for temporary storage through a pneumatic conveying system, and the high-level silo is equipped with a pressure balancing valve and inert gas protection; the second part of the dried flue gas is used as the carrier gas for pneumatic conveying, and after being pressurized, it is used to convey the dried pulverized coal, and the fluidized bed dryer is kept at a negative pressure of 1~3kpa.

3. The segmented multi-effect hydrogenated pulverized coal medium-speed pyrolysis process as described in claim 1, characterized in that, In the preheating stage of step S2, the temperature of the high-temperature circulating nitrogen is 420±30℃, the temperature of the preheated pulverized coal is 280±5℃, and the air leakage rate of the first airlock feed valve is ≤0.5%.

4. The segmented multi-effect hydrogenated pulverized coal medium-speed pyrolysis process as described in claim 3, characterized in that, In step S2, during the hydropyrolysis process, the temperature of the high-temperature flue gas generated after combustion is 900±50℃, and the heat transfer coefficient of the partition wall heat exchange element is ≥80W / (m²). 2 ·K), the temperature inside the partition wall pyrolysis furnace is 600~700℃, the residence time of preheated pulverized coal in the partition wall pyrolysis furnace is 15~25min, and the temperature at which high-temperature pulverized coke is generated is 550~650℃.

5. The segmented multi-effect hydrogenated pulverized coal medium-speed pyrolysis process as described in claim 1, characterized in that, In step S2, during the preheating stage, nitrogen is used as the carrier gas in the pyrolysis preheating silo, and the mass flow rate of the high-temperature circulating nitrogen is 1.5 to 3.5 times that of the dry pulverized coal. In step S3, during the precooling stage, the high-temperature pulverized coke first falls into the lower silo of the pyrolysis furnace, and is then fed into the precooling silo via the third airlock feed valve to exchange heat with the low-temperature circulating nitrogen to obtain precooled pulverized coke. The temperature of the precooled pulverized coke is 260°C. Nitrogen is used as the carrier gas in the precooling silo, and the mass flow rate of the low-temperature circulating nitrogen is 1.5 to 3.5 times that of the high-temperature pulverized coke. The third airlock feed valve is located between the partition pyrolysis furnace and the precooling silo.

6. The segmented multi-effect hydrogenated pulverized coal medium-speed pyrolysis process as described in claim 1, characterized in that, The first portion of the dried flue gas, after dust removal and water cooling, serves as circulating cooling flue gas, wherein the dust content of the circulating cooling flue gas is ≤10mg / m³. 3 The temperature is 60±20℃ and the oxygen content is ≤8%; the temperature of the final cooled coke is ≤80℃, and the final cooled coke is sprayed and humidified by a scraper conveyor until the moisture content is 8~12% before being output.

7. The segmented multi-effect hydrogenated pulverized coal medium-speed pyrolysis process as described in claim 1, characterized in that, The circulating cooling flue gas is partially returned to the drying section and mixed with the hot flue gas to form the mixed flue gas, which is then sent to the fluidized bed dryer as a heat source. The remaining circulating cooling flue gas is discharged after desulfurization and denitrification treatment to meet emission standards.

8. The segmented multi-effect hydrogenated pulverized coal medium-speed pyrolysis process as described in claim 1, characterized in that, The recycling rate of the high-temperature flue gas is 70-90%.

9. The segmented multi-effect hydrogenated pulverized coal medium-speed pyrolysis process as described in claim 4, characterized in that, The low-temperature circulating nitrogen, after exchanging heat with the high-temperature pulverized coke in the precooling stage, flows sequentially through the preheating stage and the gas-to-gas heat exchanger, forming a three-stage series heat recovery nitrogen loop that runs through the cooling section, pyrolysis section, and combustion air preheating system. The system mass and heat loss are compensated by a nitrogen source, and the injection flow rate of the nitrogen source is controlled by the following model: The instantaneous mass injection flow rate L1 of the nitrogen source under the pressure balance control model: ； Compensation flow rate L2 under the heat distribution compensation model: ； Final nitrogen source injection flow rate L: L = max(L1 + L2, 0); Wherein, K1 is the first proportional control coefficient, with a value ranging from 5 to 20 kg·h. -1 kPa -1 ; P set The pressure setpoint for the circulating nitrogen outlet of the pyrolysis preheating silo; kPa; P actual The measured pressure at the circulating nitrogen outlet of the pyrolysis preheating silo is given in kPa. V is the total volume of the precooling silo, preheating silo, and connecting pipelines, in m³. 3 ; R is the gas constant of nitrogen, with a value of 296.8 J·kg⁻¹. -1 K -1 ; T avg The value in K represents the average inlet and outlet temperatures of the preheating stage. A is the heat compensation coefficient, dimensionless, with a value ranging from 0.1 to 0.3; M is the mass flow rate of high-temperature pulverized coke, kg / h; C coke The specific heat capacity of coke is kJ·kg. -1 K -1 The value ranges from 1.1 to 1.

3. T coke,in and T coke,out These are the inlet and outlet temperatures of the coke powder in the pre-cooling stage, respectively, in K; H is the latent heat of vaporization of liquid nitrogen, with a value of 199.2 kJ / kg; The isobaric specific heat capacity of nitrogen is taken as 1.04 kJ·kg⁻¹. -1 K -1 ; The outlet temperature of the circulating nitrogen after the precooling stage, in K; The initial temperature of the liquid nitrogen is 77K. L3 is an empirical value for the nitrogen mass flow rate required to maintain the basic cycle of the system, in kg / h.

10. The segmented multi-effect hydrogenated pulverized coal medium-speed pyrolysis process as described in claim 9, characterized in that, In step S2, the mass flow rate L4 of the remaining purified coal gas used as fuel gas is determined based on the mass flow rate of dried pulverized coal and the temperature of the high-temperature coke powder at the outlet of the indirect pyrolysis furnace. ； ； Wherein, K2 is the second proportional control coefficient, with a value ranging from 8 to 25 kg·h. -1 K -1 ; T set The setpoint K for the high-temperature pulverized coke at the outlet of the partition wall pyrolysis furnace is 823.15~923.15K. T actual K represents the measured temperature of high-temperature coke powder at the outlet of the indirect pyrolysis furnace, which is obtained in real time by thermocouples installed in the lower silo or outlet pipe of the indirect pyrolysis furnace. B is the integration time constant, h, which takes a value of 0.1 to 0.5; L base The base fuel gas flow rate is based on the mass flow rate of dry pulverized coal, in kg / h; F coal The mass flow rate of dried pulverized coal in the pyrolysis preheating silo is kg / h; C coal The specific heat capacity of dry pulverized coal, kJ·kg⁻¹ -1 K -1 The value ranges from 1.3 to 1.6; T pyro The target pyrolysis temperature, K, is taken as the median value of the temperature range inside the partition wall pyrolysis furnace; T preheat The temperature, K, of the preheated pulverized coal entering the partition pyrolysis furnace; Q loss The total heat loss rate of the indirect pyrolysis furnace system is denoted as kJ / h, and is taken as 5~15% of the rated design heat load of the indirect pyrolysis furnace; NH is the net calorific value of the purified residual gas, kJ / kg, and is taken as 3600~3800.

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