CDQ is a method of cooling red coke with an inert gas. In the process of dry quenching, the red coke is loaded from the top of the dry quenching furnace, the low-temperature inert gas is blown into the red coke layer of the cooling chamber of the dry quenching furnace by the circulating fan to absorb the heat of the red coke, the cooled coke is discharged from the bottom of the dry quenching furnace, and the high-temperature inert gas from the annular flue of the dry quenching furnace is exchanged through the dry quenching boiler, the boiler produces steam, and the cooled inert gas is re-blown into the dry quenching furnace by the circulating fan for recycling.
The CDQ process is mainly composed of red coke loading system, cold coke discharge system, dry quenching furnace and gas supply device, gas circulation system, boiler system, water treatment system, etc., and the main facilities include dry quenching furnace, loading device, coke removal car, hoist, electric locomotive and coke tank trolley, coke tank, primary dust collector, secondary dust collector, dry quenching boiler unit, circulating fan, dust removal ground station, water treatment unit, etc. Depending on the actual engineering design, the main equipment contained in the CDQ system is also different.
Fig. 2, CDQ process flow chart
Red coke is loaded into the system vol01 After the electric locomotive pulls the coke tank trolley and the coke blocking car, the rotating coke tank begins to rotate, and after the rotation is stable, it sends a coke pushing command to the coke pushing car, after the coke is completed, the rotating coke tank stops at the initial stopping position by the deceleration position, and after it is completely stopped, the electric locomotive pulls the coke tank trolley to the bottom of the dry quenching furnace lifting derrick, and after the APS positioning clamping, the empty tank is connected. Immediately the full tank alignment and lifting, the coke tank filled with red coke is lifted to the upper limit of the lifting derrick, after reaching the upper limit, the hoist begins to walk, when it reaches the top of the dry quenching furnace, the loading device is also opened in place, the hoist begins to roll down, after the coke tank is in place, the hoist continues to roll down, and the bottom door of the coke tank continues to descend with the boom under the action of gravity, and automatically completes the action of opening the door and coking. After the red coke falls into the hopper of the loading device, it is evenly loaded into the dry quenching furnace through the distribution plate and the material clock.
The CDQ red coke loading system is composed of electric locomotive, coke tank trolley, rotary coke tank, APS positioning device, hoist, loading device and various limit sensors and other equipment, which plays the role of coke, coke delivery and coke loading.
Electric locomotive
It runs on the coke quenching track on the coke side, which is used to traction and brake the coke tank trolley, and control the rotation action and coking of the circular rotating coke tank.
Rotate the coke jar
It is used to transport the red coke from the carbonization chamber and cooperate with other equipment to load the red coke into the dry quenching furnace. The coke pot rotates around the centerline during the coke process to evenly distribute the material.
Coke tank trolley
It is pulled by an electric locomotive along the coke quenching track and transports the coke tank between the coke oven and the lifting derrick.
APS alignment device
To ensure the accurate alignment and safe operation of the coke tanker under the lifting derrick, it is mainly composed of a hydraulic station and a hydraulic cylinder.
Hoist
Running on the lifting derrick and CDQ top track, the coke tank filled with red coke is lifted and moved horizontally to the top of the CDQ furnace, and the red coke is loaded into the CDQ furnace in conjunction with the loading device. After the coke is loaded, the empty tank is lifted, walked and lowered and sat on the coke tank trolley.
Loading the device
Located on the top of the dry quenching furnace, it cooperates with the elevator to load the red coke in the coke tank into the dry quenching furnace. It has two main functions, opening and closing the furnace lid according to the instructions and loading the red coke into the hopper into the dry quenching furnace.
Cold coke discharge system vol02 The cooled coke is quantitatively discharged by the electromagnetic vibrating feeder and sent to the rotary sealing valve, through the rotation of the rotary sealing valve, the coke is continuously discharged under the condition that the circulating gas in the dry quenching furnace is sealed and does not leak to the outside of the furnace, and the coke continuously discharged is sent to the belt conveyor through the coke discharge chute for output.
CDQ cold coke discharge equipment consists of two parts: coke removal device and coke transportation belt. The decoking device includes a flat gate for maintenance, an electromagnetic vibration feeder, a rotary sealing valve, a purge fan, an automatic lubrication device, a coke chute and other equipment.
Flat gates
Installed at the bottom outlet of the dry quenching furnace. During normal production, the flat gate is fully opened, and when the annual repair or coke removal device needs to be overhauled, the flat gate is closed to prevent the coke at the bottom of the dry quenching furnace from falling.
Magnetic vibrating feeder
It is a coke quantitative discharge device, which changes the amplitude of the electromagnetic vibration feeder by changing the excitation current, thereby changing the discharge amount of coke. The electromagnetic vibration feeder is equipped with amplitude and temperature detectors.
Rotary seal valves
The coke discharged by the vibrating feeder is continuously discharged in a closed state. It is equipped with forward and reverse rotation, forward rotation during normal production, and reverse rotation during accidents.
Decoking chute
The coke chute is a device that sends the coke discharged from the rotary seal valve to the belt conveyor to ensure the continuous and normal operation of the CDQ device. The coke chute is located at the lower part of the rotary seal valve, and the coke continuously discharged by the rotary seal valve is discharged to the designated belt conveyor through the switching of the baffle in the coke chute.
Purge the blower
The purge fan blows air into the electromagnetic vibration feeder and the rotary seal valve uninterruptedly to ensure the positive pressure inside the equipment housing, prevent dust from entering, prolong the service life of the equipment, and reduce the temperature of the electromagnetic vibration feeder coil, and the temperature of the electromagnetic vibration feeder coil is not higher than the set value. When the purge fan fails, the three-way solenoid switching valve automatically switches to the pipeline to supply air to the compressed air or nitrogen to the electromagnetic vibrating feeder and rotary seal valve.
Automatic grease pump
The automatic lubrication pump regularly and quantitatively supplies grease to the bearings and sealing rings of the rotary seal valve. The time interval of automatic lubrication is set manually, and the device is equipped with oil level low detection and reversing detection. The automatic grease pump has three operation modes: on-site independent operation, independent operation in the control room and PLC linkage operation in the central control room.
Coke belt
The coke cooled by the cooling section of the dry quenching furnace is discharged to the coke conveyor belt through the flat gate, electromagnetic vibrating feeder, rotary sealing valve and coke discharge chute, and the coke conveyor belt transports the cold coke away. The coke conveyor is equipped with an electronic belt scale, a high-temperature radiometer and an over-temperature sprinkler device. The electronic belt scale weighs the coke continuously, and the deviation between the weighing value and the set value is fed back to the electromagnetic vibration feeder to control the coke discharge amount within a stable set value range. When the high-temperature radiometer detects that the temperature of the discharged coke exceeds the upper limit of the set coke discharge temperature, the water spray device is activated, and the water spray is used to cool down the belt conveyor to prevent burning out the belt conveyor. The head and tail blanking point of the belt conveyor are set with dust points, and the belt correction device and rope pull switch are also provided for safe and normal operation.
CDQ furnace and gas supply unit vol03 CDQ is the main equipment of CDQ, and the CDQ operation unit with different processing capacity selects CDQ furnaces of different specifications.
The circular dry quenching furnace consists of a pre-storage section, a ramp area and a cooling section. The structure of the dry quenching furnace is shown in Figure 3. The CDQ furnace is a prototype cross-section vertical tank, the shell is made of steel plate and section steel, lined with heat-insulating and wear-resistant materials, and the top of the CDQ furnace is provided with an annular water seal tank. The upper part of the dry quenching furnace is the pre-storage section, the middle part is the ramp area, and the lower part is the cooling section.
On the periphery of the pre-storage section is an annular airway that gathers 36 ramp airflows, which converge in two halves in a circumferential direction to lead to a dust collector. The pre-storage section is equipped with a level gauge pressure measuring device, a temperature measuring device and a dispersion device.
The annular airway is equipped with an air introduction device, a circulating gas bypass device, and an airflow adjustment device. The cooling section is equipped with a temperature measurement hole, a drain steam hole during drying, a manhole and an oven hole. The cooling section is equipped with a temperature measurement hole, a drain steam hole during drying, a manhole and an oven hole. There are two air intakes on the lower shell of the cooling section, and an air supply device is installed at the bottom of the cooling section.
The pre-stored section is used to accept intermittently loaded red coke, with a buffering function to compensate for fluctuations in production;In the cooling section, the red coke is heat exchanged with the low-temperature circulating gas, and then discharged after coolingThe ramp area is located between the pre-storage section and the cooling section, and the low-temperature circulating gas entering from the gas supply device at the bottom of the CDQ absorbs the sensible heat of the red coke and is discharged through the ramp and annular gas duct, and flows through the CDQ boiler for heat exchange.
Fig. 3, dry quenching furnace structure diagram
Gas Circulation Equipment Vol04 CDQ gas circulation equipment is composed of circulating fan, feed water preheater, dry quenching furnace, primary dust collector, boiler and secondary dust collector.
Circulating fan
It provides power for the gas cycle and adjusts the speed to adjust the circulating air volume according to the operating conditions.
Primary dust collector
The principle of gravity dust removal is used to separate the large particles of coke powder in the circulating gas, so as to reduce the erosion and wear of the circulating gas on the boiler furnace tube (mainly the secondary superheater pipe), and achieve the purpose of protecting the boiler tube.
Fig. 4, the structure of the primary dust collector
Emergency release valves
In case of boiler bursting, the steam is released urgently. There is an ash hopper at the bottom of the primary dust collector to collect coke powder. The ash hopper is connected to 4 water-cooled casings, which are connected to the ash storage hopper. The upper part of the water-cooled casing is provided with a level gauge, and the ash discharge format valve at the lower part of the water-cooled casing discharges the coke powder to the ash storage hopper after reaching the material level, and the upper part of the ash storage hopper is equipped with a level gauge, and the ash discharge format valve at the lower part of the ash hopper discharges the coke powder to the scraper after reaching the material level.
Secondary dust collector
Vertical multi-pipe cyclone separation and dust removal is used to separate the small particles of coke powder in the circulating gas system to achieve the purpose of protecting the gas circulating fan. The ash hopper is equipped with two level gauges up and down, the material level reaches the upper limit, the ash discharge format valve at the outlet of the ash hopper discharges the coke powder to the scraper below the ash storage hopper, and the coke powder is stopped when the material level reaches the lower limit (to prevent negative pressure from entering the air).
Fig. 5, the structure of the secondary dust collector
Coke powder collection device
The coke powder discharged from the ash hopper of the secondary dust collector is collected by the scraper, and then sent to the dust collector through the bucket elevator and enters the coke powder bin. The coke powder enters the humidification mixer through the ash discharge format valve and the ash discharge gate, and the coke powder processed by humidification and stirring is transported by car.
CDQ boiler vol051How it works
It is a kind of pressurized and heated equipment that uses the high-temperature circulating gas that absorbs the heat of red coke and the pure water of desalination and oxygen removal to exchange heat, generate steam with rated parameters (temperature and pressure) and quality, and convey it to the heat user. CDQ boilers are waste heat boilers.
Process flow
CDQ boilers are an important part of CDQ systems. After the inert circulating gas cools the red coke in the dry quenching furnace, the high-temperature circulating gas that absorbs the heat of the red coke enters the boiler after removing the coarse-grained coke powder through the primary dust collector, and the boiler absorbs heat to produce steam, and the cooled inert circulating gas removes the fine-grained coke powder through the secondary dust collector, and then blows into the dry quenching furnace by the circulating fan to continue circulating and cooling the red coke.
The process of CDQ boiler is briefly described as follows according to the process of the main flue gas system, the process of the main steam and water system and the boiler system
1) The flue gas system process of the boiler bodyThe circulating flue gas that absorbs the heat of red coke comes out of the CDQ cooling chamber, enters from the boiler inlet after the coarse coke powder is removed by the primary dust collector, and passes vertically down through the secondary superheater, the primary superheater, the fluorescent tube evaporator, the fin tube evaporator, the economizer, and finally leads out from the bottom of the dry quenching furnace.
Fig. 6, CDQ boiler flue gas flow chart
2) The process of the boiler body steam and water systemThe boiler feed water is pressurized by the multistage centrifugal pump and then supplied water to the boiler, and the pure water for desalination and deoxygenation enters the boiler steam drum after being preheated by the economizer. Boiler drum furnace water can be divided into forced circulation part and natural circulation part.
Natural circulation section
The steam drum furnace water enters the membrane water cooling wall through the steam drum descending pipe, and the furnace water absorbs heat and vaporizes into a steam-water mixture and returns to the steam drum through the membrane cold wall riser.
Force loop section
The steam drum furnace water is sent to the fin tube evaporator and the light tube evaporator by the steam drum descending pipe through the forced circulation pump, and the furnace water absorbs heat and vaporizes into a steam-water mixture and returns to the steam drum through the evaporator rising pipe.
Fig. 7, dry quenching coke boiler steam flow chart
The steam-water mixture produced by these two parts is separated from the steam in the steam drum, and the saturated steam is exported from the upper part of the steam drum, and after being heated by a superheater, it enters the desuperheater to spray water to reduce temperature, and then enters the secondary superheater to continue to heat up, and the steam drawn from the secondary superheater is the main steam for external supply.
CDQ boiler subsystem
1) Boiler main feed water systemAfter the deaerator effluent is pressurized by the boiler feed pump, it is sent to the CDQ boiler through the external thermal pipe network, and the feed water is interlocked with the evaporation capacity of the CDQ boiler and the water level of the steam drum, and the opening of the boiler feed water regulating valve is automatically adjusted according to the feedback signal, so as to adjust the boiler feed water.
2) Main steam systemThe steam-water mixture in the drum of the CDQ boiler is separated by the steam-water separation device to produce saturated steam. Saturated steam is introduced into the primary superheater through the manifold, and the heat exchange with the high-temperature circulating gas in the primary superheater makes the steam rise to a certain temperature, and then sent to the desuperheater to spray water to reduce the temperature, and the steam enters the secondary superheater after dropping to a certain temperature, and the superheated steam drawn from the secondary superheater is the main steam after heat exchange with the high-temperature circulating gas.
3) Desuperheating water systemA part of the main feed water of the boiler is sent to the spray desuperheater of the CDQ boiler, and the desuperheater water is adjusted through the automatic regulating valve according to the temperature of the main steam at the outlet of the secondary superheater, so as to ensure that the temperature of the superheated steam supplied by the CDQ boiler meets the set requirements.
4) Sewage and emergency discharge system
When the boiler is running, only a small part of the impurities that enter the boiler through the boiler feed water will be carried away by the saturated steam, and most of them will remain in the boiler water. Over time, the salt content and slag content in the furnace water will accumulate more and more, which may cause the furnace tube to clog. Therefore, in order to keep the salt content and silicon content of the boiler water below the limit allowable value and remove the water slag in the boiler water, a part of the boiler water must be released frequently during the boiler operation, and the same amount of feed water must be added, which is called boiler blowdown. Boiler blowdown is divided into two types: continuous blowdown and regular blowdown.
Continuous sewage discharge
Also known as surface blowdown or upper blowdown, this blowdown method is to continuously release effluent from the part of the boiler steam containing the highest concentration of salt to maintain the rated furnace water content. The blowdown is generally 1% and 2% of the rated evaporation capacity of the boiler;At the same time, the emergency discharge pipeline and the continuous sewage discharge pipeline are also located on the same main pipeline to ensure that the electric valve on the emergency discharge pipeline can be opened in the event of an accident, and the furnace water in the steam drum can be quickly discharged to ensure the safe and stable operation of the boiler.
Regular sewage discharge
Also known as intermittent blowdown or bottom blowdown. This method is to supplement the deficiency of continuous blowdown, and regularly discharge the boiler water from the lowest point of the boiler water circulation system in a short period of time, so as to remove the sediment in the boiler water and improve the quality of the boiler water.
5) Hydrophobic and exhaust systemsThe exhaust system is used for draining and exhausting the dry quenching boiler for start-up and operation, so as to ensure the safe and economical operation of the CDQ boiler system and reduce the loss of steam and water.
6) Secondary steam systemIn the continuous blowdown expansion of the CDQ boiler, the continuous blowdown water of the CDQ boiler is expanded and separated. The secondary steam is separated and sent to the deaerator in the deaerator of the deaerator through the external thermal pipe network to improve the utilization rate of the coke quenching boiler.
7) Circulating cooling water systemThe circulating cooling water connected to the external pipeline cools the operating equipment of the CDQ boiler system and returns to the cooling tower through the external pipeline for recycling.
ConclusionCDQ has great advantages in environmental protection and energy utilization, but its investment and operation costs are high, which limits its promotion. Therefore, the rational selection of advanced production technology and equipment to reduce operating costs is the primary problem to be solved in the promotion of CDQ process. In addition, the advantages of CDQ in terms of energy saving and emission reduction will be valued by more and more people in the future and will be developed by leaps and bounds.