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Working principle of catalytic combustion equipment

Published Time:

2020-08-10

The system's operation is mainly divided into three states: parameter setting, combustion operation, and combustion stop.

1. Parameter Setting State

This state prepares the data before combustion operation. The ignition temperature and the initial frequency of the inverter can be set as needed to control the air volume of the fan. The ignition temperature ensures the reliability of the ignition process. The starting frequency ensures a flaming combustion of the catalytic burner at the initial stage; the combustion ratio should not be too low, and the air volume should not be too large.

2. Combustion Operation State

(1) Combustion Starting Process

When the control system is in standby and receives a start command, it enters the combustion operation state. First, the control system performs a self-check, followed by a pre-purge. The inverter output signal controls the rotation of the fan, and the air volume gradually changes from low speed to high speed and then back to low speed. Fresh air blows through the combustion furnace to ensure that no residual fuel gas remains, guaranteeing the safety and reliability of the ignition process. Specifically, the inverter starts first, and the PLC analog output signal causes the inverter frequency to rise from the set starting frequency. After reaching a certain frequency, it is maintained for a period of time before decreasing, completing the pre-purge. Then, an ignition signal is issued, the high-voltage igniter operates, and the ignition pipeline valve is opened for small-fire ignition. After the ultraviolet sensor detects the small-fire ignition, the main gas valve is opened. At this time, the catalytic combustion furnace plate undergoes flaming combustion until the detected temperature signal reaches the set ignition shutdown temperature. The ignition valve closes, completing the ignition process and entering the combustion regulation stage.

(2) Air-Fuel Ratio Adjustment

Literature shows that the "gas/air ratio" during catalytic combustion generally ranges from 4% to 11%; under certain combustion conditions, with a gas/air ratio of 6%, natural gas can achieve better catalytic combustion effects, the combustion system can achieve maximum thermal efficiency, and better emission effects can be obtained.

The gas-to-air ratio of this system is adjusted through a zero-pressure valve. When the air volume of the fan is changed, the gas/air ratio can also be changed accordingly to meet the requirements of the catalytic burner combustion operation. During startup, adjusting the output frequency of the inverter can achieve the change in gas/air ratio required for ignition, from flaming combustion to catalytic combustion.

(3) Combustion Temperature Regulation

The combustion temperature can be adjusted by keyboard input on the text display to change the output frequency of the inverter and adjust the appropriate air volume. When the air volume increases and the combustion temperature exceeds the set value, the PLC controls the inverter to reduce the output frequency and reduce the air volume to stabilize the temperature of the burner. If the inverter output frequency is lower than the set value (fan air volume frequency, set to 5 Hz), but the air volume is still higher than the set value, the PLC starts timing. If it decreases to the set value within a certain time, the PLC stops timing and continues variable frequency speed regulation. If the temperature is still higher than the set value within a certain time, the PLC will continue to adjust until the set value is reached. The PLC controls the frequency output of the inverter through PID calculation; if the temperature is insufficient, the frequency increases and is maintained for a certain time. Vice versa.

3. Combustion Stop State

The burner stops after receiving a stop command from the text display. First, the main gas valve is shut off, then the system performs a post-purge to disperse residual fuel gas and forcibly air-cools the combustion plate. After a period of time, the fan is turned off, and the inverter stops working, completing the burner shutdown process.

Keywords:

Catalytic combustion equipment, working principle, combustion operation

Central dust removal equipment working principle

The process of catalytic combustion

Central dust removal equipment working principle

The process of catalytic combustion

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