Must the trends of CO2 and CH4 in the syngas produced by a water-coal slurry gasifier be opposite to each other?
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The online analysis instrument is a mass spectrometer of the imported Prima Pro brand. However, when the process indicates a rising trend in CO2 levels, it suggests that the furnace temperature is increasing; accordingly, CH4 levels should show a downward trend. Yet sometimes the analyzer shows simultaneous increases or decreases in both of these levels, which is puzzling. The instrument maintenance personnel also carried out calibration repeatedly using standard gases, and concluded that the analyzer was accurate. I would like to ask my colleagues what causes this phenomenon.
Generally, this is the trend for gasized fluidized bed processes (slurry and dry coal powder). The CO2 content increases as the furnace temperature rises, while methane increases as the furnace temperature drops. So generally, CO2 and methane levels are used as indicators to guide furnace temperature regulation. However, it is relatively rare for both CO2 and methane levels to rise or fall simultaneously; the issue is most likely due to the monitoring instruments, but process-related factors cannot be ruled out either. I wonder what the pressure differences at the burner of the original poster are (the pressure difference between the slurry and the gasifier, and the pressure difference between oxygen and the gasifier), as well as what the oxygen-to-coal ratio is? Is it normal? Is this the case for a single furnace or for all of them? If it’s a single furnace, comparing its operational parameters with those of a normal furnace can help identify the cause.
The pressure difference between the coal slurry and the gasifier is 0.27–0.3, while the pressure difference between oxygen and the gasifier is 0.92–1.05. The oxygen-to-coal ratio is 444–476. If one unit has a problem, the other one still functions properly. There is one mass spectrometer, which is used by switching the flow paths.
The slurry pressure difference seems a bit low, while the oxygen pressure difference seems a bit high; the oxygen-to-coal ratio is normal. How long has this burner been in use?
This situation occurs when the device is far from a stable equilibrium, I guess.
This phenomenon occurs when the slag outlet gets blocked.
What type of burners do you have? What is the central oxygen flow rate?