This hot air furnace is designed to tightly close the furnace door. The arrangement of door openings facilitates access to various components of the equipment for maintenance and repair. An operation and maintenance platform is installed at the inspection door of the heating furnace, the operating valve, and the pulverized coal silo. There is a escalator between the upper and lower platforms. The clearance design between platforms is reasonable. Convenient for observation, operation, and maintenance. Protective railings with a height of 1.2 meters are installed at the edges of the platform and escalator. The platform adopts a grid plate structure and is equipped with a 100mm high baseboard. The allowable load for maintenance platforms and grids is 400kgf/m2.
The inner wall of the furnace wall structure is made of 350mm thick three-level high alumina refractory bricks, with a fire resistance of 1600 ºC and an AL2O3 content greater than 55%. The outer wallis a steel structure cylinder, and the furnace top is compacted and poured with materials on site. The renovation and masonry of the hot air furnace shall be carried out in accordance with the national industrial furnace masonry standards. After the completion of the hot air furnace masonry, the design basis of the industrial furnace design manual shall be strictly followed, and the relevant drying curve shall be formulated for strict drying. The furnace drying can be continuously proceeded using a combination of wood and gas. The arch of the hot air
furnace is a flat arch type, made of250mm thick arch pouring material.
Ignition plan and Instructions
( 1) The ignition system includes one atomization fan, pipelines, valve
group ,instrument, burner, high-energy ignition device, and PLC cabinet. Ignition process:
Start the induced draft fan first, based on the negative pressure of the furnace, ensuring that the furnace pressure before ignition is -50~-100Pa) → Start the secondary air fan, with the fan frequency set below 20Hz → Start the primary air fan, with the fan frequency set at 15-20Hz → Start the gas ignition device, press the ignition button, this part is automatically completed without human operation) → Open the gas flow valve according to the temperature rise of the furnace.
(3) Pulverized coal conveying and gas co firing must first be operated in a chain state for pulverized coal conveying. Start the secondary air fan first, set the fan frequency to below 20Hz → the primary air fan, the fan frequency can be set to 15- 20Hz → start the double-tube screw conveyor → (at this time, the furnace pressure is -50-150Pa) Then start the variable frequency cutter to adjust the coal feeding frequency to around 7Hz for gas coal mixed combustion, and the temperature rises sharply. (Note: The higher the furnace temperature, the easier it is to ignite the pulverized coal. When the furnace temperature rises to 600 degrees or above, bituminous coal can be sent as pulverized coal. If the furnace temperature does not meet the requirements, it is recommended to add wood and diesel fuel at the bottom of the furnace for ignition to increase the furnace temperature.)
(4) When the temperature reaches 1000 degrees, turn off the gas ignition system
(5) The coal feeding amount of the variable frequency screw conveyor, the frequency of the primary air fan, and the frequency of the secondary air fan should also be increased or decreased accordingly.
Shutdown sequence
( 1) Pulverized coal conveying system, stop the screw conveyor first. When the furnace temperature drops below 450-500 ºC, stop the primary air fan.
(2) When the furnace temperature drops below 200 ºC, stop the secondary air fan.
(3) Reduce and stop the frequency of the induced draft fan. When the temperature drops below 100 ºC, the induced draft fan can be stopped.
Local control mode
Local control, emergency chimney exhaust valve, secondary air fan, and coal conveyor are under on-site control. The primary air fan and segmented feeder can be
operated in the central control due to the use of the original control.
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