Method for baking and adjusting a water-coal slurry gasifier

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The four key factors in furnace operation are: 1. Steam pressure and negative pressure; 2. Natural gas pressure and flow rate; 3. Make-up air volume (valve opening); 4. Liquid level in the gasification furnace. Among these, the liquid level in the gasification furnace and steam pressure are the easiest to control. As long as the boiler is stable and the pumps are operating properly, it is simple to maintain these two parameters. Usually, what we adjust the most are the natural gas pressure and the air supply volume; negative pressure is adjusted only during ignition, as well as for controlling the length and color of the flame. 1. Regarding negative pressure, it should be low during ignition; a negative pressure of 7 millimeters of water column is generally sufficient for ignition with four nozzles, while Texaco can tolerate up to 10 millimeters. During temperature increase or when maintaining a constant temperature, changes in negative pressure can cause the flame to go out, and adjusting this value is an art – the flame should be adjusted to have a mix of yellow and blue colors. Although a purely blue flame burns most efficiently, it is also the most fragile and cannot withstand many fluctuations; therefore, some margin for variation in the pressure should be allowed, as it is much safer and more economical to keep the flame burning rather than having to ignite it again. 2. Regarding natural gas pressure and flow rate, it is generally necessary to have at least a valve in front of and one behind the control valve. The pressure at the control valve can be maintained through PCV, but it is most difficult to control the flow rate; often, even a slight movement of the manual valve or a valve position adjustment of 0.1% can cause the flame to go out. The most reliable method is to keep the manual valve behind the control valve fully open, while opening the manual valve in front by 4 to 5 notches – this depends on the actual conditions on site and whether there is any internal leakage in the control valve. Under normal circumstances, when the furnace is at a temperature of 300 degrees or less, the opening degree of the control valve does not exceed 1%. When operating the manual valve, it must be done slowly. In cases of internal leakage in the control valve, the flame can easily go out at an opening degree of 3 to 4 notches. If the control valve functions properly, then it is sufficient to adjust it directly, but again, the adjustment must be done slowly, perhaps even with adjustments of 0.01 in terms of valve position. It is important to observe the situation on site, and when adjusting the valve position, care must be taken to ensure consistency in the inputs. 3. Regarding the amount of make-up air and the opening degree of the dampers, adjusting the damper opening degree is the most effective method for controlling the furnace temperature in low-temperature areas, especially in constant-temperature zones. Often, a slight adjustment is sufficient to maintain the furnace temperature within a certain range. The principle for making such adjustments lies in the color of the flame; in my opinion, it’s best if two-thirds of the flame is blue. However, it’s also necessary to monitor the readings from the thermocouples in the control room. It’s important to ensure that the temperature difference between different areas does not exceed 100 degrees, and that the negative pressure is at an appropriate level. Generally, during the constant-temperature phase, the negative pressure is already set appropriately, so in most cases, simply adjusting the damper opening degrees and making minor tweaks to the control valves is sufficient to maintain a constant temperature. This is because the constant-temperature phase is the most difficult to control, as the temperature tends to fluctuate frequently. 4. For the liquid level in the gasification furnace, as long as the opening degree of the control valve is properly adjusted, the amount of water added should not be too large; it’s sufficient to meet the required amount. However, the water supply must not be interrupted when it exceeds 150, to prevent damage to the quenching ring.