Waste heat power generation system for producing activated carbon by rotary kiln

Abstract

The waste heat power generation system comprises a secondary combustion chamber, a waste heat boiler, a steam turbine generator unit and a waste gas treatment system which are sequentially communicated, the secondary combustion chamber is of a single-channel multiple-fold-back structure, waste carbon powder and combustion-supporting air are sprayed into the secondary combustion chamber to achieve complete combustion of combustible substances in flue gas, and the flue gas temperature is increased; the waste heat boiler achieves gradient heat exchange with the high-temperature and high-pressure parameters of 9.81 MPa-540 DEG C, and waste heat is recycled to the maximum degree. The steam turbine generator unit adapts to the parameter of 8.83 MPa-535 DEG C, and steam heat energy is converted into electric energy through steam-water circulation; the waste gas treatment system is integrated with an SNCR ammonia spraying device and desulfurization, denitrification and dust removal integrated equipment, and SO2, NOx and dust are synchronously removed by a ceramic fiber filter tube loaded with a bifunctional substance; according to the system, the generating capacity is improved by 15-30%, pollutant emission meets the ultra-low standard, and unification of economic benefits and environmental protection benefits is achieved.

Description

Technical Field

[0001] This invention relates to the field of waste heat utilization technology, and more specifically, to a waste heat power generation system for rotary kiln activated carbon production. In the process of rotary kiln activated carbon production, an integrated system is realized to achieve efficient waste heat recovery for power generation and synergistic purification of flue gas, which is particularly suitable for activated carbon production scenarios using coal as raw material. Background Technology

[0002] Activated carbon, a special carbon material with a porous structure and high specific surface area, is widely used in various fields such as water purification, air purification, medical purification, and food processing decolorization due to its excellent adsorption properties. In the industrial production of activated carbon, rotary kilns have become the mainstream production equipment due to their core advantages of large processing capacity, stable operation, and strong adaptability to raw materials.

[0003] The core process of activated carbon production includes four main stages: raw material pretreatment, carbonization, activation, and post-treatment. The carbonization stage requires heating under air-isolated or inert gas protection conditions to decompose organic components such as cellulose and lignin in the raw material, removing volatiles such as methane and tar, and forming carbonized material with a carbon content of 60%–80%. The activation stage requires introducing activating agents such as steam into a rotary kiln at a temperature of 800–1100℃, reacting with the carbonized material for 8–12 hours. This process expands the pore structure by etching the carbon skeleton, resulting in a product specific surface area of ​​500–2000 m². 2 / g, ultimately forming activated carbon with adsorption properties. Using a rotary kiln to produce activated carbon allows for the simultaneous completion of the two key processes: carbonization and physical activation within the kiln.

[0004] However, the existing rotary kiln activated carbon production process and supporting systems have significant technical defects, as follows: High energy consumption and waste of waste heat are prominent issues: According to GB29995-2024 "Energy Consumption Limits per Unit Product of Coal-based Activated Carbon and Semi-coke" implemented on May 1, 2025, the energy consumption per unit product for producing activated carbon from crushed raw coal is as high as 3750~4250 kg. 标准煤 / t 活性炭 If we calculate based on the calorific value of raw coal at 5000 kcal / kg, producing 1 ton of activated carbon requires 5.25 to 5.95 tons of raw coal. A large amount of heat energy is directly emitted with the flue gas, resulting in serious energy waste. As the scale of activated carbon production continues to expand, the economic losses and environmental pressure caused by this kind of energy waste are becoming increasingly significant.

[0005] Heavy burden of flue gas treatment and loss of calorific value: The flue gas discharged from the rotary kiln contains combustible substances such as CO, volatile organic compounds (VOCs), and residual carbon powder particles. These substances are not only rich in unrecovered calorific value, but also increase the difficulty and cost of subsequent flue gas treatment, resulting in the dual problems of energy waste and environmental treatment pressure.

[0006] Low efficiency of waste heat utilization: Existing waste heat power generation systems in the industry generally suffer from problems such as low steam parameters and poor equipment coordination. The steam pressure and temperature of waste heat boilers are low, and the turbine parameters are low, making it difficult to improve the waste heat recovery and utilization rate and power generation efficiency, and failing to fully convert the wasted heat energy into economic benefits.

[0007] Low integration of flue gas purification equipment: Traditional flue gas treatment requires separate desulfurization, denitrification and dust removal equipment, which has problems such as large footprint, high investment cost and complex treatment process. Moreover, it is difficult to achieve simultaneous and efficient removal of pollutants and cannot meet the current strict ultra-low emission environmental protection requirements.

[0008] Therefore, developing a system that can efficiently recover waste heat from activated carbon production, simultaneously purify flue gas, and improve energy utilization efficiency is key to solving current industry pain points and is of great significance for promoting energy conservation, emission reduction, green development, and building an environmentally friendly society in the activated carbon industry. Summary of the Invention

[0009] To address the technical shortcomings of existing rotary kiln activated carbon production processes, such as severe waste of waste heat, heavy burden on flue gas treatment, low waste heat utilization efficiency, and insufficient integration of flue gas purification equipment, this invention provides a waste heat power generation system for rotary kiln activated carbon production, aiming to achieve the following objectives: Complete combustion of combustible materials in flue gas reduces the load on subsequent flue gas treatment systems and lowers environmental treatment costs; Improving the recovery and utilization efficiency of flue gas waste heat, and increasing power generation by optimizing system parameters, can create significant economic benefits for enterprises. Simultaneous removal of SO2 and NO from flue gas x Highly efficient removal of pollutants such as particulate matter ensures that emissions meet ultra-low environmental standards; Optimize system structure design, improve equipment integration, reduce floor space and investment costs, and simplify operation and maintenance processes.

[0010] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a waste heat power generation system for producing activated carbon in a rotary kiln, comprising a secondary combustion chamber, a waste heat boiler, a steam turbine generator set, and a waste gas treatment system. Each component works collaboratively to complete the functions of waste heat recovery power generation and flue gas purification. The specific technical solution is as follows: The secondary combustion chamber is sealed and connected to the outlet of the activated carbon rotary kiln, and is used for secondary combustion treatment of the kiln tail flue gas. The secondary combustion chamber includes a secondary combustion chamber shell and a burner. The secondary combustion chamber shell adopts a single-channel multi-folding structure, and the folding method can be selected as horizontal folding or vertical folding, which ensures complete combustion by extending the residence time of flue gas in the shell. The upper part of the secondary combustion chamber is equipped with no less than three burners. The burners are injected with waste carbon powder (industrial production waste) and combustion air through pipes. The oxygen brought in by the combustion air works synergistically with the residual oxygen in the original flue gas to completely burn the combustible substances such as CO, volatile organic compounds (VOCs), and residual carbon powder particles in the flue gas. The flue gas velocity in the secondary combustion chamber is controlled to be no more than 4 m / s to ensure that the combustible material has sufficient time to burn. At the same time, the heat released by combustion further heats the flue gas, improving the efficiency of subsequent waste heat recovery.

[0011] The waste heat boiler is sealed and connected to the air outlet of the secondary combustion chamber, and is used to convert the heat energy of high-temperature flue gas into high-temperature and high-pressure steam. The waste heat boiler includes a waste heat boiler shell, an economizer, an evaporator, a superheater, a boiler drum, and a superheater header. After the high-temperature flue gas discharged from the secondary combustion chamber enters the waste heat boiler, it exchanges heat with the medium water (steam) in the superheater, evaporator and economizer in sequence in the shell, and fully absorbs the heat energy of the flue gas through gradient heat exchange. The steam parameters of the waste heat boiler are set at 9.81MPa-540℃, which is the highest steam parameter level for waste heat boilers in the activated carbon industry, and can significantly improve the steam's work capacity. The exhaust gas temperature of the waste heat boiler is designed to be 30°C higher than the flue gas dew point temperature (the flue gas dew point temperature is calculated based on the sulfur content of the flue gas in actual production) to avoid condensation and corrosion of the equipment, while ensuring full recovery of heat energy.

[0012] The steam turbine generator set is connected to the steam outlet of the waste heat boiler through the main steam pipeline and is used to convert steam heat energy into electrical energy. The steam turbine generator set includes key equipment such as steam turbine, generator, condenser, condensate pump, deaerator and feed water pump. In specific engineering projects, depending on the power generation capacity, it may also include equipment such as shaft seal heater, several stages of low-pressure heater, and several stages of high-pressure heater. The steam turbine is a high-temperature and high-pressure type steam turbine, which is adapted to steam parameters of 8.83MPa-535℃, which is the highest parameter level in the industry at present, ensuring maximum steam power efficiency; The high-temperature and high-pressure steam of 9.81MPa-540℃ generated by the waste heat boiler is fed into the steam turbine, which drives the turbine impeller to rotate at a speed of 3000 rpm, thereby driving the generator to operate synchronously and generate electricity. After the steam turbine performs its work, the steam pressure and temperature drop to the appropriate parameters, forming low-pressure wet steam with a certain humidity. This steam is discharged through the exhaust port into the condenser and condensed into condensate. The condensate is then pumped to the deaerator for deep deoxygenation (to remove dissolved oxygen from the water to prevent equipment corrosion). After deoxygenation, the water is pressurized by the feed water pump and then pumped to the waste heat boiler, completing the steam-water cycle.

[0013] The waste gas treatment system includes an integrated desulfurization, denitrification, and dust removal device, an induced draft fan, a chimney, and an SNCR ammonia injection device. The flue gas outlet of the waste heat boiler is sealed and connected to the flue gas inlet of the integrated desulfurization, denitrification, and dust removal device for purifying the heat-exchanged flue gas. The SNCR ammonia injection device is arranged on the flue gas inlet duct of the waste heat boiler. It injects ammonia water into the high-temperature flue gas duct, and the ammonia water vaporizes and reacts with NO in the flue gas. x A non-selective catalytic reduction reaction occurs, reducing NO... x It is converted into nitrogen and water; The integrated desulfurization, denitrification, and dust removal equipment has its flue gas inlet connected to the flue gas outlet of the waste heat boiler, its flue gas outlet connected to the inlet of the induced draft fan, and the outlet of the induced draft fan connected to the inlet of the chimney. The integrated desulfurization, denitrification, and dust removal equipment uses a 10-20mm thick porous ceramic fiber filter tube as its core carrier. The filter tube is made of rigid material and has a filtration function. The ceramic fiber filter tube surface is uniformly loaded with two types of functional materials: one type is a vanadium-titanium catalyst (V2O5-WO3 / TiO2), used to react with excess ammonia injected into the SNCR ammonia injection unit to reduce NO. x One type of substance is used for catalytic reduction reactions; another type of substance is alkaline metal oxides such as CaO, MgO, and Al2O3, which are used to adsorb and remove SO2. Within a temperature window of 180~250℃, the ceramic fiber filter tube captures particulate matter through inertial collision and interception (dust removal efficiency reaches 99%). Simultaneously, through the aforementioned catalyst, catalysis and adsorption work synergistically to simultaneously remove NO. x Catalytic reduction to N2 (denitrification efficiency >95%) and SO2 adsorption removal (desulfurization efficiency >98%). After purification, the flue gas is pressurized by an induced draft fan and then discharged into the atmosphere through a chimney, with the outlet dust concentration controlled at <10mg / Nm³. 3 .

[0014] Beneficial effects Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Improve waste heat recovery and power generation efficiency: The heat released by the combustion of combustibles and the supplementary combustion of waste carbon powder in the secondary combustion chamber further increases the flue gas temperature and increases the recoverable waste heat of the waste heat boiler.

[0015] 2. The waste heat boiler and steam turbine are designed with the highest-level high-temperature and high-pressure parameters in the industry (9.81MPa-540℃ and 8.83MPa-535℃ respectively), which greatly improves the steam work efficiency and power generation efficiency. Compared with the traditional system, the power generation is increased by 15-30%, bringing significant economic benefits to enterprises.

[0016] 3. Excellent and compliant flue gas purification effect: Utilizing integrated desulfurization, denitrification, and dust removal equipment, with ceramic fiber filter tubes loaded with functional materials as the core, it effectively removes SO2 and NO... x Simultaneous and efficient removal of particulate matter, with denitrification efficiency >95%, desulfurization efficiency >98%, dust removal efficiency up to 99%, and outlet dust concentration <10mg / Nm³. 3 It meets ultra-low emission standards and solves the problems of complex and ineffective traditional multi-equipment treatment processes.

[0017] 4. High equipment integration and small footprint: The waste gas treatment system integrates desulfurization, denitrification and dust removal functions into the same equipment, eliminating the need for multiple separate devices, reducing the number of devices and floor space, lowering system investment costs and operation and maintenance difficulty, and is especially suitable for technical transformation scenarios of existing factories.

[0018] 5. Dual benefits of energy saving and environmental protection: This system not only recovers the waste heat resources that would otherwise be wasted, reducing fossil energy consumption and carbon emissions, but also reduces pollutant emissions through efficient flue gas purification, achieving a unity of economic, environmental and social benefits, which is in line with the industry's green development trend. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a waste heat power generation system for producing activated carbon using a rotary kiln, according to the present invention.

[0020] Explanation of reference numerals in the attached figures: 1. Activated carbon rotary kiln; 2. Secondary combustion chamber; 21. Secondary combustion chamber shell; 22. Burner; 3. Waste heat boiler; 4. Steam turbine generator set; 41. Steam turbine; 42. Generator; 43. Condenser; 44. Condensate pump; 45. Deaerator; 46. Feedwater pump; 5. Waste gas treatment system; 51. Integrated desulfurization, denitrification and dust removal equipment; 52. Exhaust fan; 53. Chimney; 54. SNCR ammonia injection device. Detailed Implementation

[0021] The following is in conjunction with the appendix Figure 1 The specific embodiments of the present invention will be further described in detail below: The waste heat power generation system for activated carbon production using a rotary kiln provided in this embodiment has the following workflow and parameters: like Figure 1 As shown, the present invention provides a waste heat power generation system for producing activated carbon in a rotary kiln, comprising a secondary combustion chamber 2, a waste heat boiler 3, a steam turbine generator set 4, and a waste gas treatment system 5.

[0022] Secondary combustion treatment of flue gas: The flue gas discharged from the activated carbon rotary kiln 1 (temperature 700~900℃, containing combustible substances such as CO, VOCs, and residual carbon powder) enters the secondary combustion chamber 2 through the air inlet of the secondary combustion chamber 2; the shell 21 of the secondary combustion chamber adopts a horizontally folded single-channel multiple-folded structure, and three burners 22 are arranged in the upper part of the secondary combustion chamber 2. The burners 22 continuously inject waste carbon powder (particle size ≤100μm) and combustion air (excess air coefficient ≥1.15) to form a stable flame in the secondary combustion chamber 2; the flue gas flows in the secondary combustion chamber 2 at a flow rate of 3~4m / s and the residence time is more than 4 seconds to ensure that combustible substances such as CO, VOCs, and residual carbon powder are completely burned. After combustion, the flue gas temperature rises to 1100℃ and is discharged through the air outlet of the secondary combustion chamber 2. Depending on the enterprise's production scale, it may include several activated carbon rotary kilns 1. In the embodiment of the present invention, each rotary kiln is equipped with a secondary combustion chamber 2, and the flue gas discharged from the secondary combustion chamber 2 is collected into the flue gas header at the outlet of the secondary combustion chamber 2.

[0023] Waste heat boiler 3 heat exchange and steam generation: The 1100℃ high-temperature flue gas from the flue gas header at the outlet of the secondary combustion chamber 2 enters the waste heat boiler 3 through the flue gas inlet. Inside the shell of the waste heat boiler 3, the flue gas undergoes gradient heat exchange with the medium water (steam) in the superheater, evaporator, and economizer in sequence. During the heat exchange process, the medium water is preheated, evaporated, and superheated to form high-temperature and high-pressure steam of 9.81MPa-540℃, which is transported to the steam turbine generator set 4 through the main steam pipeline. After heat exchange, the flue gas temperature drops to below 200℃ (the flue gas dew point temperature is calculated, and the exhaust gas temperature is designed to be 30℃ higher than the dew point temperature. Currently, the acid dew point temperature of the flue gas produced by activated carbon production is less than 170℃), and it is transported to the integrated desulfurization, denitrification, and dust removal equipment 51 through the flue gas pipeline.

[0024] The power generation cycle of the steam turbine generator set 4 is as follows: High-temperature and high-pressure steam at 9.81MPa-540℃ is introduced into the steam turbine 41 (high-temperature and high-pressure type, suitable parameters 8.83MPa-535℃), driving the impeller of the steam turbine 41 to rotate at a speed of 3000 rpm, which in turn drives the generator 42 to generate electricity; after the steam turbine 41 performs work, the steam pressure drops to a low pressure (gauge pressure is negative), forming wet steam with a certain humidity, which is discharged into the condenser 43 (cooling water temperature 25℃) through the exhaust port, and condensed into condensate at about 40℃; the condensate is transported to the deaerator 45 (working pressure 0.49MPa, working temperature 151℃) by the condensate pump 44 (head 80~100m) for deep deaeration, and the oxygen content of the feedwater after deaeration is ≤0.05mg / L; the deaerated water is pressurized by the feedwater pump 46 (head 1250~1500m) and then transported to the waste heat boiler 3 to complete the steam-water cycle.

[0025] Flue gas purification to meet emission standards: Flue gas ≤200℃ discharged from waste heat boiler 3 enters the integrated desulfurization, denitrification and dust removal equipment 51. Within a temperature window of 180~250℃, ceramic fiber filter tubes efficiently capture particulate matter through inertial collision and interception. The vanadium-titanium catalyst loaded on the surface of the filter tubes removes NO. x Catalytic reduction to N2, and adsorption of SO2 by alkaline metal oxides; after testing, the SO2 removal rate in the treated flue gas reached 98%, and NO... x The removal rate reached 95%, and the dust concentration was reduced to 10 mg / Nm³. 3 The system meets ultra-low emission standards. The purified flue gas is pressurized by induced draft fan 52 and then discharged into the atmosphere through chimney 53, the height of which is constructed according to the environmental impact assessment report. The SNCR ammonia injection device 54 is located on the inlet flue gas duct of the waste heat boiler 3. It injects ammonia water into the high-temperature flue gas duct, and the vaporized ammonia water reacts with NO in the flue gas. x A non-selective catalytic reduction reaction occurs, reducing NO... x It is converted into nitrogen and water; The integrated desulfurization, denitrification, and dust removal equipment 51 is a high-efficiency flue gas purification device. It uses ceramic fiber filter tubes as its core carrier. These filter tubes have a porous structure with a wall thickness of 10-20mm. Through inertial collision and interception of flue gas, they efficiently capture particulate matter, achieving a dust removal efficiency of 99% and an outlet dust concentration of <10mg / Nm³. 3 Ceramic fiber filter tubes are characterized by their rigid material nature. The surface of the filter tube is uniformly loaded with a vanadium-titanium catalyst (V₂O₅-WO₃ / TiO₂) and alkaline metal oxides such as CaO, MgO, and Al₂O₃. Within a temperature window of 180–250°C, they can catalytically reduce NO. x It produces N2, which can also remove sulfur dioxide (SO2) from flue gas. Through the synergistic effect of catalysis and filtration, sulfur dioxide (SO2) and nitrogen oxides (NOx) can be removed simultaneously within the same equipment. x It achieves efficient removal of particulate matter and meets ultra-low emission standards.

[0026] In this embodiment, all aspects based on the technical solution of this invention, including the multiple-turn structure and number of turns in the secondary combustion chamber 2, the secondary combustion design of the secondary combustion chamber 2, the number of burners 22, the high-temperature and high-pressure parameter configuration of the waste heat boiler 3 and the steam turbine 41, the configuration of more equipment such as shaft seal heaters, low-pressure heaters, and high-pressure heaters between the condensate pump 44 and the boiler feedwater inlet according to the power plant scale, the number of ceramic fiber filter tubes and catalyst loading of the integrated desulfurization, denitrification, and dust removal equipment 51, and the connection method and cooperative working principle of each component, can be adaptively adjusted according to the actual production scale and flue gas characteristics. Any modifications or equivalent substitutions made based on the parameter optimization and structural improvement of this invention should be included within the protection scope of this invention.

[0027] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural modifications made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A waste heat power generation system for producing activated carbon using a rotary kiln, wherein the waste heat power generation system is based on the recovery and purification of waste heat from the flue gas discharged from the activated carbon rotary kiln (1); characterized in that, The waste heat power generation system includes a secondary combustion chamber (2), a waste heat boiler (3), a steam turbine generator set (4), and a waste gas treatment system, which are sequentially sealed and connected. Each component works together to complete the functions of waste heat recovery power generation and flue gas purification: wherein: the input end of the secondary combustion chamber (2) is connected to the activated carbon rotary kiln (1), and the output end of the secondary combustion chamber (2) is sealed and connected to the waste heat boiler (3); the output end of the waste heat boiler (3) is connected to the waste gas treatment system; and the waste heat boiler (3) and the steam turbine generator set (4) are connected in parallel to form a closed-loop steam treatment system, wherein: The secondary combustion chamber (2) includes a secondary combustion chamber shell (21) and a burner (22); the burner (22) is arranged on the upper part of the secondary combustion chamber (2), and the burner (22) injects waste carbon powder and combustion air through a pipe; The waste heat boiler (3) includes a waste heat boiler (3) shell, economizer, evaporator, superheater, boiler drum, and superheater header; The steam turbine generator set (4) includes a steam turbine (41), a generator (42), a condenser (43), a condensate pump (44), a deaerator (45), and a feedwater pump (46). The exhaust gas treatment system includes an integrated desulfurization, denitrification and dust removal device (51), an induced draft fan (52), a chimney (53), and an SNCR ammonia injection device (54).

2. The waste heat power generation system for producing activated carbon in a rotary kiln according to claim 1, characterized in that: The steam turbine generator set (4) is connected to the steam outlet of the waste heat boiler (3) through the main steam pipeline. After the steam turbine (41) does work, the steam is condensed into condensate by the condenser (43) and then flows back to the waste heat boiler (3) through the condensate pump (44), deaerator (45), and feed water pump (46) to complete the steam-water cycle. The desulfurization, denitrification and dust removal integrated equipment (51) is sealed and connected to the flue gas outlet of the waste heat boiler (3). The desulfurization, denitrification and dust removal integrated equipment (51) uses a porous ceramic fiber filter tube as the core carrier. The surface of the filter tube is uniformly loaded with vanadium-titanium catalyst and alkaline metal oxide, and desulfurization, denitrification and dust removal are realized simultaneously within the temperature window of 180~300℃.

3. The waste heat power generation system for producing activated carbon in a rotary kiln according to claim 1, characterized in that: The secondary combustion chamber shell (21) is a single-channel multi-fold structure; the fold structure of the secondary combustion chamber shell (21) is horizontal or vertical; the burner (22) injects waste carbon powder and combustion air through a pipe; the flue gas velocity in the secondary combustion chamber (2) is less than 3~4m / s; the number of burners (22) arranged on the upper part of the secondary combustion chamber (2) is at least 3.

4. The waste heat power generation system for rotary kiln activated carbon production according to claim 1, characterized in that, The SNCR ammonia injection device (54) is arranged on the flue gas inlet pipe of the waste heat boiler (3); the flue gas exchanges heat with the medium water (steam) in the superheater, evaporator and economizer in sequence in the shell. The steam parameters of the waste heat boiler (3) are set to 9.81MPa-540℃, and the exhaust gas temperature is designed to be 30℃ higher than the flue gas dew point temperature.

5. The waste heat power generation system for rotary kiln activated carbon production according to claim 2, characterized in that, The steam turbine (41) is adapted to steam parameters of 8.83MPa-535℃.

6. A waste heat power generation system for producing activated carbon in a rotary kiln according to claim 2, characterized in that: The filter tube has a wall thickness of 10~20mm and is made of rigid material.

7. The waste heat power generation system for rotary kiln activated carbon production according to claim 2, characterized in that, The vanadium-titanium catalyst is V2O5-WO3 / TiO2, and the alkaline metal oxide includes at least one of CaO, MgO, and Al2O3.

8. The waste heat power generation system for rotary kiln activated carbon production according to any one of claims 1-7, characterized in that, The steam turbine generator set (4) may also be equipped with shaft seal heaters, several low-pressure heaters and several high-pressure heaters according to the power generation capacity.

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