What is the reason for the continuous decrease in the pH value of low-pressure graywater?
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Using the water-coal slurry pressurized gasification technology, after the change in coal quality, the pH value of the low-pressure ash water has continued to decrease, while the dosage of flocculants and dispersants remains unchanged. Currently, the pH value of the low-pressure ash water is 5.9; please analyze the reasons for this.
When the coal quality changes, the control parameters for gasification also change; could this lead to an increase in the amount of formic acid produced?
Is it true that as the nitrogen content in coal decreases, less alkaline substance is produced?
We are also currently analyzing the issues related to formic acid, but its production mechanism is very complex. There is no specific solution.
Well, there has been no analysis of nitrogen recently, so that might be the main reason.
It is possible to conduct a thorough analysis of the operating conditions from front to back as well as across different coal qualities, to determine which location is responsible for the low pH value
It’s happened to me as well; I think apart from the coal factor, there must be other reasons. By the way, have you changed to coal with a higher volatility content than before?
Yes, it might be the same issue; the volatile matter on an air-dry basis of the coal we use can reach as high as 40%. Please explore this in depth, thank you.
It is very likely, so the reaction mechanism for formic acid, or formates, needs to be studied.
Please also check whether the flash vaporization unit is operating properly; the black water must not contain air. Has the sulfur content in coal increased?
This indicates that there is an excess of humic acid in your raw coal, but the level of this substance in such coal may fluctuate only for a few days; once past that coal layer, the level will return to normal.