Why does coal with a ash fusion temperature of 1100–1200 degrees not tend to form slag?
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This post was last edited by *ansheng on 2011-2-18 08:56. Coal with a ash melting point of 1100–1200 degrees why does not tend to form slag? A high ash melting point allows operation at high temperatures, while a low ash melting point permits operation at low temperatures; yet such coal still tends to form slag easily. I would appreciate some guidance from experts. I forgot to mention that our furnace has water-cooled walls.
Reply 1# *ansheng: The vaporization temperature is too high, and the slag has too good fluidity, making it impossible to form a slag layer. The solution is to mix in some coal with a high ash fusion point, thereby adjusting the ash fusion point to between 1300–1400°C.
It might be that the operating temperature is too high, resulting in good fluidity of the slag, which makes it difficult for the slag to adhere
The size of your furnace design, as well as the size of the slag outlet, also have an impact
Our gray melting point is also 1100–1200°C; slag adhesion is good, and the chromium content in the slag is only 20 ppm
It is advisable to maintain the normal operating temperature of the gasifier at 200–250°C below the ash melting point; in general, the operating temperature should be increased as much as possible, provided that it remains within the limits allowed by the ash melting point. Too low a temperature leads to poor vaporization, while too high a temperature causes slag formation.
The water wall operates on the principle of slag resistance, requiring slag to accumulate on its surface； Otherwise, it will damage the water wall. The low ash melting point and good slag fluidity make it difficult to achieve slag adhesion. I hope the experts on water wall systems can speak freely.
Reply to 7# xuqinger: This is probably related to the difference between the designed coal quality and the actual coal used, right? Of course, boiler design is definitely based on the type of coal specified in the design; so, what extent of adaptability does a circulating fluidized bed boiler have if there are differences in the coal quality? Or should we adapt by adjusting the process parameters? I hope everyone can give some guidance on this issue. Thank you!
What was said on the second floor is correct: a high temperature in the gasification zone results in excessive fluidity for coals with a low ash melting point, making it difficult for slag to form. It is possible to adjust the ash fusion point of the coal fed into the furnace by using coal types with a higher ash fusion point or by adding additives.
Reply to 6# 3968668: You are referring to dry slag discharge, which is carried out at temperatures below the ash melting point. They are talking about water-cooled wall slag furnaces.
When operating a gasification furnace, it is necessary to consider not only the ash fusion point of the coal but also the melting properties of its ash.