Data on 7-meter coke ovens (Ansteel)

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1.1 Overview A coking project with an annual production capacity of 5.1 million tons of coke is being constructed. The project is built in two phases, with both the first and second phases having an annual coke production capacity of 2.55 million tons each. Phase 1 of the project utilizes JNX-7-2 type 4×52-hole regenerative coke ovens, featuring a single gas collection pipe and a single gas intake pipe. The investment in the coking system is 680 million yuan. 1.2 Basic Process Parameters for Coking
Furnace type: JNX-7-2
Number of carbonization chambers: 4×52
Effective volume per carbonization chamber: 48 m³
Density of coal used for charging (dry): 0.75 t/m³
Amount of coal loaded per carbonization chamber (dry): 36 t
Coking furnace turnaround time: 19 hours
Number of working days per year for the coking furnace: 365 days
Operating coefficient due to constraints associated with the coking furnace: 1.07
Moisture content of coal used for charging: 10%
Gas yield: 320 m³/t of dry coal
Coking efficiency: 76.25% (including coke dust); 75% (excluding coke dust)
Coal output per carbonization chamber: 27 t
Estimated annual coal output from the coking furnace: 2.5893 million tons
Low calorific value of the mixed gas used for heating the coking furnace: 4182 kJ/m³
Among this, the low calorific value of blast furnace gas is 3150 kJ/m³, while that of coking furnace gas is 17432 kJ/m³
When the moisture content of coal used for charging is 10%, the energy required to heat the dry coal during coking is as follows: 2424 kJ/kg when using coking furnace gas, and 2751 kJ/kg when using mixed gas. When the moisture content is 7%, the corresponding values are 2250 kJ/kg for coking furnace gas and 2550 kJ/kg for mixed gas.
1.3 Coking Process Flow
The blended coal supplied from the coal preparation workshop is loaded into the coal tower. The coal loading vehicle retrieves coal from the coal tower according to the operation plan, and after measurement, loads it into the carbonization chamber. In the carbonization chamber, coal undergoes high-temperature dry distillation over a coking cycle to be converted into coke, while raw gas is produced. The flue gas generated during coal loading is transported to the surface station through dust collection main pipes, and after being purified of dust, it is released into the atmosphere. Once the coke in the carbonization chamber has matured, it is pushed out using a coke pusher, guided into coke drums by a coke stopper, and then pulled by a motor car to a dry quenching station for dry quenching. After quenching, the coke is sent to the screening and storage section, where it is sorted by grade and stored for shipment. When the dry quenching system needs to be maintained or in case of an accident, and backup wet quenching must be used, the mature coke inside the carbonization chamber is fed into the quenching car via a coke stopper, and then pulled by a motor car to the quenching tower for **quenching. After coking is completed, the coke is unloaded onto a cooling platform; after being left there for a certain period of time, it is sent to the screening and storage section, where it is sorted by grade and stored for shipment. The dust generated by coking is captured by the dust collection hood on the coking stopper machine, conducted to the ground station through dust collection main pipes, and discharged into the atmosphere after being purified. The raw gas generated during the carbonization process of coal in the carbonization chamber gathers in the space at the top of the chamber, and then enters the gas collection pipe via the rising pipe and bridge pipe. The raw gas, at around 800°C, is cooled to about 85°C in the bridge tube by spraying ammonia water, and substances such as tar in the raw gas are simultaneously condensed. Gas, along with the condensed tar, is sent to the gas purification workshop via coal gas pipelines together with ammonia water. The coke oven gas used for heating the coke ovens is introduced via external pipelines from above, and after preheating, it is sent to the basement of the coke ovens. The gas is fed into the bottom of the vertical flue in the combustion chamber through the lower nozzle, where it mixes with the air entering via the exhaust gas exchange valve to undergo combustion. The exhaust gases after combustion enter the downward-flowing flue through the holes at the top of the vertical flue, then pass through the regenerator, where part of the sensible heat in the exhaust gases is recovered by the lattice bricks. After that, they pass through small flues, exhaust gas exchange valves, branch flues, main flues, and finally the chimney, before being released into the atmosphere. The blast furnace gas used for heating the coke oven is introduced into the coke oven basement via external pipelines. After being mixed with a certain amount of coke oven gas, it is sent through the exhaust gas exchange valve, small flue, and regenerator to the combustion chamber’s vertical flue, where it burns together with the air introduced at the same time. The exhaust gases produced after combustion are released into the atmosphere through the same pathway as when coke oven gas is burned. The gas and air in the upward airflow, as well as the exhaust gases in the downward airflow, are periodically reversed through an exchange mechanism. 1.4 Layout of coking process: The 4×52-chamber JNX-7-2 type coke ovens are arranged on the same central line, forming two oven groups. A large platform is located in between them, and each oven group has a chimney about 135 meters high, situated outside the boundary of the building on the side of the coal tower crane. Each 2×52-chamber coke oven constitutes an independent furnace unit, with a three-span coal tower located in between; a platform is set up between the coal tower and the coke ovens. The ends of Cokers 1# and 4# are equipped with end platforms, while machine and coke side operation platforms are located on both sides. A set of new standby wet quenching system is installed outside the furnace end platform of Coke Oven No. 1. To facilitate the maintenance of coke quenching vehicles and their rapid replacement, a vehicle transfer platform is provided at each end of the furnace unit. Among them, the car transfer platform outside the furnace end platform of Coke Oven No. 1 requires longer transfer platform carts due to the large length of the backup wet quenching coke cars parked there, whereas the car transfer platform outside the furnace end platform of Coke Oven No. 4 only houses dry quenching coke vehicles, so its length is shorter. The lower floors of the coal tower are equipped with an electronic scale control room, a power distribution room, and a switchgear room, respectively. The furnace bay is mainly equipped with a single-bin coal hoist and gas heating inlet pipes. The top layer of the furnace end platform houses a worker’s rest room; the middle layer contains a furnace door repair station as well as stations for replacing push rods and coal leveling rods; the bottom layer includes warehouses, tool rooms, and a slurry mixer room. 10-ton electric hoists are installed on the outside of each of the two furnace end platforms. Coke side head and tail coke is collected by the coke catcher in the tail coke hopper, and then discharged into coke tanks or quench cars. The machine-side head and tail coke is collected by the coke pusher into the tail coke hopper, then unloaded into the machine-side tail coke box; thereafter, a specialized forklift is used to transport the tail coke box to the return coke chute. After the coke is unloaded, the tail coke box is sent back to its original location. For the centralized control and management of the coke quenching station and to optimize the overall process layout, the 2×160 t/h coke quenching unit associated with the 4×52-chamber coke ovens in this project is located in the coke-side area of the central large platform of the oven bank. Taking into account factors such as the layout of the dry quenching system and the placement of the backup quenching machines, the length of the Omaida platform is 130m. Given that quench boxes are more prone to failure than other coke oven machinery, 4 quench boxes are installed in this project. Due to the increased height of the quenching machine and the dust collection hood, and to enhance their stability, this project includes a third rail outside the track of the quenching car for the quenching machine. To facilitate the parking and maintenance of the quenchers, the quenchers on both sides of the main hall do not pass through the dry quenching area. Based on the fact that the control panel at the end of Furnace No. 2 and the lifting frame of Furnace No. 1 for dry quenching do not interfere with each other, it was determined that the distance between the center line of the carbonization chamber at the end of Furnace No. 2 and the center line of Furnace No. 1 is 46.5 meters. This distance also ensures that the spare wet quenching vehicles parked in the carbonization chamber at the end of Furnace No. 2 do not interfere with the dry quenching vehicles used in Furnace No. 1. The length of the coke side control panel at the end of Furnace No. 2 is 39 m, which allows another spare quenching machine to be parked outside when one quenching machine is used to remove coke from the furnace. It should be noted that the quench boxes installed on Cokes Ovens No. 1 and No. 2 are both of the left type, as this takes into account the possibility of wet quenching for these ovens. If wet quenching is not considered and only dry quenching is taken into account, it is more reasonable to use a right-type quench stopper, and the length of the coke side control panel can also be reduced by about 4 meters. Similarly, the distance between the center line of the carbonization chamber at the end of furnace No. 3 and the center line of furnace No. 2 for dry quenching is set at 42 m. The distance between the center line of #1 dry quenching furnace and the center line of #2 dry quenching furnace is 41.5 m. This arrangement is made primarily because the furnace units on both sides of the large platform are two relatively independent units; during dry quenching, the quenching vehicles coming from each furnace unit can enter their respective dry quenching stations without interfering with one another. Due to the large length of the interstage area, in order to make full use of it, this project involves splitting the middle part of that area. That is, aside from 30-meter-long interstages at each end of furnaces No. 2 and No. 3 for the operation and maintenance of coal loading vehicles, the remaining part of the interstage area is separated; however, the tracks for coal loading vehicles on the furnace roof, as well as the maintenance passages on both sides, the tracks for coke pushers, and the tracks for coke quenching vehicles remain connected. The machine-focus side control panel is also disconnected accordingly. In this way, the coal loading cars, coke pushers, and coke quenching cars can still pass through the Omaida area smoothly, while the space under the tracks for the coal loading cars in Omaida is used to house the comprehensive control rooms for systems such as coke ovens, dry coke quenching, and dust removal. 1.5 Coke Oven Body 1.5.1 The main dimensions and technical specifications of the coke oven body are shown in Table 2-1. Main Dimensions and Technical Specifications of the Coke Oven Body Table 2-1 Sequence Number Name Unit Quantity 1 Total length of the carbonization chamber mm 16960 2 Effective length of the carbonization chamber mm 16100 3 Total height of the carbonization chamber mm 6980 4 Effective height of the carbonization chamber mm 6630 5 Average width of the carbonization chamber mm 450 6 Taper of the carbonization chamber mm 50 7 Center distance between carbonization chambers mm 1400 8 Effective volume of the carbonization chamber m³ 48 9 Center distance between the heating channels mm 480 10 Heating level mm 1050 1.5.2 Structure and characteristics of the coke oven body The JNX-7-2 type coke oven body is a large-scale coke oven that has been newly developed based on a summary of the design and production experience of the JN60 type coke ovens, JNX series coke ovens, 8-meter experimental ovens, as well as various large-volume coke ovens from abroad. The JNX-7-2 type coke oven is a regenerative downward-type coke oven with dual flues, exhaust gas recycling, bottom injection of coke oven gas, and side injection of blast furnace gas. It features a rigorous and rational structure, uniform heating, high thermal efficiency, low investment costs, and a long service life, making it a new generation of large-scale coke ovens suitable for China’s national conditions. 2.5.2.1 To ensure uniform heating in both the vertical and horizontal directions for the JNX-7-2 type coke ovens, the following measures were taken: a) The JNX-7-2 model utilizes a dual-flue and waste gas circulation heating system that has proven to be effective and reliable over many years of use. Based on the design principles and operational experience gained from the JN60 type coke ovens, 8-meter experimental furnaces, as well as large-volume coke ovens with a capacity of 41.6 cubic meters abroad, measures such as increasing the amount of waste gas circulation and installing higher gas nozzles were adopted. It ensures the uniformity of high-direction heating. b) Based on a summary of the sizes and arrangements of the chutes at large-capacity coke ovens abroad, as well as domestic experience in operating coke ovens with reduced heights, the opening sizes and arrangement dimensions of the chutes for the JNX-7-2 type coke oven were determined, which can effectively ensure uniform heating along the length direction of this type of coke oven. c) The regenerator is equipped with a segmented and grate brick adjustable structure, which enables a proper distribution of airflow within the regenerator. This reduces airflow segregation, increases the scouring coefficient of the grate bricks, lowers the temperature of the exhaust gases, and improves the thermal efficiency of the coke oven. d) To ensure that the heating in the side flues meets the requirements, special designs have been adopted for the side regenerator, the regenerator partition walls, the outlet of the furnace head chute, and the vertical flues of the furnace head, thereby ensuring uniform maturation of the coke cake. e) Replaceable adjustment bricks are installed at both the grate bricks in the heat storage chamber and the outlet of the inclined chute, enabling simple, easy, accurate, and reliable adjustment of the coke oven, thus ensuring uniform heating in the JNX-7-2 type coke oven. 2.5.2.2 To improve the service life and environmental performance of the JNX-7-2 type coke ovens, the following structural improvements were made to these ovens: a) The structure of the main walls, individual walls, partition walls of the regenerator chambers, as well as the sealing walls of these chambers was improved, thereby ensuring the integrity and strength of these walls. It reduces CO emissions and improves the thermal efficiency of the coke oven. b) The newly designed JNX-7-2 type chamber brick for coke ovens builds on the advantages of the JN series of coke ovens, enhancing the shear strength of these bricks and reducing the likelihood of damage to them ； It improves the tightness of the wall tiles in the carbonization chamber, reducing leakage between the carbonization chamber and the combustion chamber ； At the same time, the number of tile types used for the walls of the carbonization chamber was reduced as much as possible to facilitate maintenance. c) The structure of the partition wall in the vertical flue of the combustion chamber was improved, ensuring the integrity of the combustion chamber as well as a tight seal between the vertical flues. d) By increasing the amount of exhaust gas circulation and installing high nozzles for coke oven gas, both the uniformity of heating in the carbonization chamber is ensured and the generation of NOX is reduced. e) The redesigned roof structure can reduce heat loss from the roof and improve the operating conditions there ； A proper arrangement of coal charging holes and their structure can not only reduce the emission of intermittent pollutants during coal charging but also ensure uniform coal loading, thereby reducing the number of times coal leveling is required and minimizing pollutant emissions. f) The heat storage chamber adopts a structure with two burners per cell. The height of the inclined channel was increased to 900 mm, which prevented direct exposure of the regenerator’s top grid bricks to the flames in the vertical flue, thereby reducing the temperature of those grid bricks. 2.5.2.3 To improve the bonding properties of coal, a narrow carbonization chamber with a width of 450 mm is used, and the thickness of the furnace walls is reduced to 95 mm as well. These two measures can increase the coking rate in the carbonization chamber, reduce the proportion of highly cohesive coals such as coking coal and fat coal, thereby lowering coking costs and improving economic efficiency. 2.5.2.4 The combustion chamber walls of the JNX-7-2 type coke oven have sufficient stability and strength. After detailed calculations and comparison with various types of coke ovens, the maximum lateral load on the furnace walls of this coke oven is greater than 9000 Pa, which represents a significant improvement over domestic 6-meter coke ovens. 2.5.2.5 The selection of materials used in the JNX-7-2 type coke oven, as well as the design of the brick patterns, have been carefully planned to ensure ease of procurement, high yields in brick production, and simplicity in construction; it is thus a modern coke oven with advanced technology that is suitable for China’s national conditions. In summary, compared with 6m coke ovens, the furnace body of the JNX-7-2 type coke oven has seen significant improvements in heating uniformity, structural strength, and environmental performance. 1.5.3 Quantity of bricks used in coke ovens: See Table 2-2, Table of Bricks Used in Coke Ovens. Table 2-2: Sequence Number, Name, Unit, Quantity. 1. Silica bricks, t: 11,743; 2. Clay bricks, t: 2,473; 3. Grid bricks, t: 2,433; 4. High-alumina bricks, t: 43; 5. Cylinder bricks, t: 208; 6. Diabase bricks, t: 185; 7. Clay bricks for flue lining, t: 1,318; 8. High-strength insulating bricks, t: 295; 9. Perlite bricks, t: 55; 10. Pumice bricks, t: 302. Note: The quantities listed represent those required for one JNX-7-2 type coke oven with 1×52 chambers. 1.6 Coke oven machinery: 1.6.1 Configuration of coke oven machinery: See Table 2-3. Coke oven machinery configuration table Table 2-3 Sequence Number Name Quantity (units) Operating Spare 1 Coal charging car 2 1 2 Coke pusher 2 1 3 Coke stopper 2 2 4 Coke quenching car 1 1 5 Motor car 2 1 6 Hydraulic switch 4 0 1.6.2 Main performance and characteristics of coke oven machinery The coke oven machinery for the JNX-7-2 type coke ovens was designed and manufactured based on accumulated experience in operating domestic coke oven machinery, while also incorporating advanced technologies from foreign models. It is designed with the goals of improving mechanical efficiency, reducing labor intensity, and enhancing the working environment, adhering to the principles of advancement, safety, and practicality. The complete set of coke oven machinery operates according to a 5-2 push sequence, is controlled by unit programs, and is equipped with manual control devices. An emergency interlock device is installed between the coke pusher and the motor car. The main performance and features of each machine are as follows: 1) Coal loading vehicle – The coal loading vehicle is a dust-removing type. One-time positioning is used, with mechanical lifting to open and close the coal charging hole covers, and mechanical closing for the riser covers. It is equipped with a mechanically operated water seal valve and a high/low pressure ammonia switch mechanism, as well as mechanical cleaning for the rising pipe; the design features a spiral feeder and a furnace top cleaning device. The opening and closing of the coal tower discharge nozzle, as well as the operation for shaking the coal in the tower, are all controlled from the driver’s cabin, ensuring convenience and reliability. The driver’s cab and electrical compartment are hermetically insulated and equipped with air conditioning, improving the operating conditions. To achieve smoke-free coal loading, the coal loader is equipped with a sleeve that connects to the dust collection main pipe on the coke side, as well as a sealing guide sleeve for discharging coal. The main technical specifications of the dust removal coal loading vehicle are as follows: Number of coal hoppers – 4; Coal loading method – screw feeding; Travel speed – approximately 90 m/min; Track gauge – 8270 mm; Total motor power – approximately 420 kw. 2) Coke pusher: The coke pusher uses a 5-2 sequence for simultaneous alignment, with the coke pushing current being displayed and recorded automatically. It is equipped with coke pushing, coal leveling, and furnace door closing devices, as well as mechanical cleaning mechanisms for the furnace door, furnace frame, and small furnace doors, plus devices for handling end coals, cleaning the graphite at the base of the rising tubes. The dust escaping from the furnace door on the slave side is collected and discharged after dry dust removal. The driver’s cab and electrical room are equipped with air conditioning. The operation of each unit program is controlled by a PC. The main technical specifications of the coke pusher are as follows: The main structural framework is of the gantry type; the traveling speed is approximately 60 m/min; the track gauge is 14,000 mm; the total motor power is about 690 kW. 3) Coke stopper: The coke stopper uses a one-time positioning mechanism and is equipped with mechanisms for opening and closing the furnace door as well as for guiding the coke; it also has mechanical systems for cleaning the furnace door and its frame, devices for recovering the coke at the front and back ends, mechanisms for collecting and removing dust, and a system for cleaning the furnace bed. The main technical specifications of the coke stopper are as follows: traveling speed of about 60 m/min, track gauge of 2700 mm, total motor power of about 350 kw. 4) Electric locomotives and coke quenching vehicles – The electric locomotive serves as the traction engine. This motorized cutting tool can meet the requirements of both dry quenching of coke and wet quenching of coke. The motor car is equipped with an air compressor and an air circuit system to control the coking discharge door of the coking car, ensuring stability and reliability. Detailed specifications for the electric locomotive can be found in the section on dry quenching of coke. The coking quenching vehicle uses a fixed-point coke receiving method; its compartment doors open and close pneumatically. The compartment features a fixed inclined bottom, resulting in a simple structure and rapid water drainage, which reduces the amount of water contained in the coke after quenching. To prevent the elevation of the bottom of the carbonization chamber from being too high and affecting the layout of the lower layers of the coke oven, there are restrictions on the elevation of the top surface of the coke quenching vehicle. Therefore, this vehicle is designed with a saddle-shaped structure that is concave in the middle in order to increase its effective volume. The main technical specifications of the locomotive and coking car are as follows: track center distance of 2300 mm; inclination angle of the coking car’s bottom plate at 28°; effective length of the coking car’s carriage at ~7000 mm; load capacity of the coking car (dry coke) at 27.5 T. 5) Hydraulic switch: Each hydraulic switch is equipped with a hydraulic station, an electrical control panel, an operation console, and a travel indication device. The hydraulic station features a dual-pump, dual-valve system that serves as a backup for each other, along with a manual control device. When the gas pressure is low, safety measures such as automatic alarms and the shutdown of the gas supply are employed, and all operations of the switch are controlled by a PC. The main technical specifications of the hydraulic exchanger are as follows: switching cycle – 20–30 minutes; time for automatic switching – 46 seconds; time for manual switching – approximately 10 minutes; operating pressure – 6–8 MPa. 1.7 Process equipment: 1.7.1 Gas collection system – The gas collection system includes rising pipes, bridge pipes, valve bodies, water seal covers, gas collection pipes, high and low pressure ammonia spray systems, as well as the corresponding control panels. A single gas collection pipe is used. A U-shaped gas collection pipe is installed on the machine side of the coke oven, and an automatic venting and ignition device is provided in the collection pipe to meet environmental protection requirements. The rising tube is lined with clay bricks and insulating material, and an insulating cover is installed on the outside to reduce the temperature of its outer surface, thereby improving the operating conditions at the furnace top. The lower part of the rising tube is connected to the furnace body via a cast-iron base, while the upper part is sealed with a water seal. The connection between the bridge pipe and the water seal valve employs a water seal mechanism; ammonia can form a water seal inside, preventing the leakage of raw coal gas. The bridge pipe is equipped with low- and high-pressure ammonia nozzles; these can be switched using three-way ball valves to spray low-pressure ammonia in order to reduce the temperature of the raw gas, or to inject high-pressure ammonia to facilitate coal loading in sequence. This allows most of the raw gas to be directed into the gas collection pipe, while the remaining smoke generated during coal loading is drawn away by the dust removal coal loader and sent to the dust collection main pipe, from where it is transported to the on-ground dust removal station, thereby enabling smoke-free coal loading. The gas collection duct is equipped with a high-pressure ammonia water cleaning device for regular sectional cleaning, which reduces the workload on workers, prevents the leakage of unused gas, and improves the operating conditions at the top of the furnace. The gas collection pipe for each furnace is divided into two sections; selecting an appropriate cross-sectional area helps to achieve pressure balance within the gas collection pipe, ensuring the smooth discharge of raw gas. This approach guarantees uniform pressure in all carbonization chambers of the furnace, as well as maintaining a pressure of ≥5 Pa at the bottom of each carbonization chamber throughout the coking process. 1.7.2 Furnace protective iron parts The furnace protective iron parts include furnace columns, longitudinal and transverse struts, springs, protective plates, furnace doors, and furnace door frames, etc. The furnace door is equipped with a spring-loaded edge, a spring door latch, and a suspended air-cooled door; it maintains good precision in its alignment. The elastic edge exerts constant pressure on the furnace door frame, preventing smoke and fire from escaping from the door. The small furnace door is of a detachable, upward-opening type that allows for the replacement of the equipment while maintaining effective sealing. The protective plate is a large I-shaped plate that enhances its strength, providing effective protection for the burner head against damage. The furnace column is made of single H-shaped steel with dimensions of 550×320. Nine small springs are arranged along the height of the coke oven, which helps to ensure a more even distribution of forces across the column’s height. Spring assemblies are installed at the ends of the longitudinal and transverse struts, enabling even application of a certain pressure to the furnace body, thus ensuring the integrity and tightness of the coke oven’s overall structure. 1.7.3 Heating and exchange system: The coke oven is equipped with two systems for heating, namely coke oven gas heating and mixed gas heating. The main gas heating pipeline is equipped with devices for measuring and regulating temperature, pressure, and flow rate. The measurement, display, recording, adjustment of various operating parameters, as well as the low-pressure alarm, are all carried out by automatic control instruments. The heating of coke oven gas is of the downward injection type; the main pipes are located in the basement. Exchange valves, control valves, and orifice plate boxes are used to facilitate gas exchange between various rows of pipes as well as to regulate the gas flow rate. The flow rate in the smaller branches of the coke oven gas is controlled by nozzles. The heating with mixed gas is of the side-in type, and regulating valves as well as orifice plate boxes are used to control the gas flow rate between various branch pipes. In the exhaust gas system, automatic control flaps are installed in the smoke ducts of each coke oven, while manual control flaps are provided in the main smoke duct, so as to appropriately adjust the suction force of the heating system and thereby ensure stable heating of the coke ovens as well as reduce energy consumption in coke production. The flow of gas, air, and exhaust gases after combustion used for coke oven heating within the heating system is controlled by a hydraulic switch-driven switching mechanism, with the direction being changed every 20 to 30 minutes. The switching system is an automatic control system, but it can also be controlled manually. Furthermore, this system is equipped with an N2 supplementation system for low-pressure gas pipeline accidents, to ensure the stability and safety of the heating system. 1.7.4 Quenching System: The design adopts dry quenching, with a new type of wet quenching system as a backup to be used during annual maintenance or failures of the dry quenching equipment (for details on the dry quenching process, see Section 3 on Dry Quenching Process). The design adopts a new type of rapid wet quenching technology for reducing pollution, and its advantages include: (1) a short quenching time, which can be controlled within 70–80 seconds ； ⑵The moisture content of coke after coking can be kept between 2-4%, with stable levels ； ⑶The quench tower is equipped with a water mist capture device as well as a new type of baffle-style capture device. The wet quenching system includes a quenching pump room, a quenching tower, quenching spray pipes, a water mist capture device, a baffle-type dust removal device, a fine coke sedimentation tank, a clean water tank, a fine coke dewatering station together with a grab crane, a point-positioning quenching vehicle, a high-level tank, and an automatic control system. In the wet quenching process, the amount of water used is applied in stages throughout the quenching process. At the initial stage of the coking quenching process, a small amount of water is used to extinguish the red coke on the top layer of the coking quenching tank and to stabilize the surface of the coke. After a certain period of time, a larger amount of water is sprayed; the steam generated when this water comes into contact with the hot coke helps to extinguish the coke in the bottom, middle, and upper-middle sections of the tank, from bottom to top. This coking quenching method replaces spraying with high-pressure water jets, improving the water distribution along the depth of the coke within the quenching car, thereby achieving the goal of reducing the coking time and lowering the moisture content of the coke. 1.7.5 Coke oven dust removal facilities: For controlling the intermittent and continuous emissions of dust during the coke oven production process, the following measures are taken in this project: 1.7.5.1 Control of intermittent dust emissions: a) For dust removal during coal loading, high-pressure ammonia water is sprayed through a single collection duct, creating a certain negative pressure inside the rising pipe; this allows some of the dust generated during coal loading to be drawn into the collection duct. The remaining dust is removed by dust removal fans at the ground station, thereby ensuring that the exhaust gases meet environmental regulations. To improve the coal dust capture efficiency, the coke pusher is also equipped with a flat coal door sealing device. b) Dust removal during coke discharge: The smoke and dust generated during coke discharge on the coke side are removed using a dust removal system at the ground station. A dust collection hood is installed on the coke catcher, and the smoke produced during coke discharge is drawn through this hood and the dust collection main pipe to the ground station, where it is purified before being discharged outside ； On the machine side, the dust emitted from the furnace door is collected and treated through the dust removal system installed on the coke pusher. c) Coking quenching and dust removal (new low-moisture wet coking quenching): A new type of baffle-style capture device is installed at the top of the coking quenching tower to capture the large amount of coke dust and steam generated during coking quenching. 1.7.5.2 Control of continuous dust emissions a) The coal loading hole cover uses a spherical seal, ensuring spherical contact between the cover and its seat, which enhances the tightness of the coal loading hole cover. b) The furnace door is equipped with a spring-loaded edge; the sealing of this edge is achieved through spring pressure, which ensures even force distribution and thus good sealing performance. c) The rising pipe cover at the furnace top, as well as the connections between the bridge pipe and the valve body, all utilize a water seal mechanism, which prevents smoking at those connection points. d) A cast iron base is used at the root of the rising pipe, preventing smoking and flaming caused by damage at that location. 1.7.6 Auxiliary facilities: A furnace door repair station is located on the middle level of the furnace end platform, as well as stations for testing and replacing pusher rods and coal pushing rods. A single-bin elevator for residual coal is installed on the furnace inter-platform, and a 10-t electric hoist is placed outside the furnace end platform. These facilities facilitate production operations and reduce the workload on workers. In addition, a furnace door fixing frame, coke pushing rod, and coal leveling rod replacement station are also installed at the Omaida area. 1.8 Main production operation indicators of coke ovens The main production operation indicators of coke ovens are shown in Table 2‑4. Table 2–4: Key operational parameters of coke ovens. Sequence Number, Parameter, Unit, Specification: Heated with coke oven gas, Heated with mixed gas. 1 Standard channel temperature on the machine side, °C: 1270; Standard channel temperature on the coke side, °C: 1320. 2 Excess air coefficient α: 1.2–1.3, 1.15–1.25. 3 Temperature difference between the upper and lower parts of the coke cake ℃