How are lumps and filaments formed in ash?
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The ash from the Texaco water-coal slurry gasifier comes in lump-shaped, fibrous, granular, and rock wool-like forms. How was it formed? If any experts know, please give some guidance. Thank you. There’s a big prize!
The shape of the ash can directly reflect the operating condition of the gasification furnace. To accurately assess the operation of the gasification furnace, it is necessary to examine the oxygen-to-coal ratio; a comprehensive judgment must be made based on years of practical experience as well as various relevant parameters displayed on the DCS. The blocky indication suggests that the furnace temperature is low; it can be adjusted according to actual conditions. The filamentous appearance is likely due to the low viscosity of the slag; the blockage of the slag outlet indicates that, prior to this, the high viscosity and poor fluidity of the slag caused it to accumulate inside the furnace. As the furnace temperature rose rapidly, the flow rate increased beyond the capacity of the slag outlet to handle it. Of course, the above applies to the current coal quality; even with the same oxygen-to-coal ratio or gasification temperature, such a situation can occur due to the sharp changes in the viscosity-temperature characteristics of the coal ash. If fine sand-like particles appear, treatment must be carried out after comprehensive evaluation based on coal quality analysis and central oxygen content.
Experienced technicians on site can determine the furnace temperature based on aspects such as the shape, size, and color of the slag. Generally, fine-grained slag with a light green color indicates a high furnace temperature; in such cases, the amount of O2 should be reduced to lower the furnace temperature； An increase in particle size and a darkening of color are caused by a low furnace temperature; the amount of O2 should be increased to raise the furnace temperature. The above is due to the high furnace temperature, which results in a high conversion rate of C. The stringing phenomenon in the slag is caused by the narrowing of the slag outlet and an increase in flow velocity; in such cases, it is necessary to raise the furnace temperature appropriately to soften the slag and restore the condition of the slag outlet. The formation of large, highly hard slag masses is due to excessively high furnace temperatures, which result in slag adhering to the furnace walls or the slag outlet and falling off; at such times, it is important to monitor the temperature of the furnace walls and assess the potential damage caused by high temperatures to the gasification furnace, so that appropriate actions can be taken
The shape and size of the slag need to be determined based on its viscosity-temperature characteristic curve, that is, the relationship between viscosity and temperature. It is also necessary to consider the flow rate and temperature of the quench water.
The shape, size, and color of the slag can be used to determine the temperature of the furnace. Generally, the size of normal coarse slag ranges from 5 to 8 mm, and it is normal for such slag to account for 7% to 8%. Fine slag indicates a high furnace temperature, while large pieces indicate a low furnace temperature. Threads in the slag suggest that slag is accumulating at the slag outlet, and this issue needs to be addressed immediately.