Relationship between coal volatile matter content and Texaco gasifiers
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1. The Texaco gasifier has high requirements regarding the volatiles content of coal. I wonder what advantage high-volatility coal brings to the gasification process in a Texaco gasifier? Is it the high volatile content that allows for instantaneous combustion in the furnace, thereby providing some heat for the gasification of the coal? 2. Additionally, what is the relationship between the volatiles in coal and its reactivity? 3. Why is the oxygen consumption high in water-coal slurry gasification?
The people from the design institute say that the volatiles in coal produce not much heat, and thus play a limited role in maintaining the thermal balance inside the furnace. I don’t think this view is entirely correct; let’s discuss it.
The first two questions are actually the same: the higher the volatility of coal, the greater its activity, which facilitates gasification reactions. Therefore, for Texaco’s water-coal slurry gasification process, the higher the volatility of the coal, the better the gasification results. There is no direct relationship between high volatile matter content and the calorific value of coal; coal with low volatile matter content does not necessarily have a low calorific value. For example, anthracite has low volatile matter content but a high calorific value. The third issue is that due to the presence of water in coal water slurry, a considerable amount of energy is required during the gasification process to supply water for participation in this reaction; thus, energy consumption is high. However, coal water slurry gasification is an appropriate method for coal chemical processing.
I’ll give a brief answer: 1. The Texaco gasifier has high requirements regarding the volatiles content in coal. Coal with high volatiles has good reactivity, making it suitable for the Texaco gasifier’s residence time of 3–10 seconds, which allows for relatively thorough gasification. Moreover, the volatiles are organic hydrocarbons, which have a high calorific value. 2. There is a linear relationship between the volatiles content of coal and its reactivity; the higher the volatiles content, the better the reactivity. However, coal with high volatiles content should not be stored for long periods as it is prone to spontaneous combustion. 3. In coal water slurry gasification, the feed slurry contains nearly 40% water, and vaporizing this water requires some heat. As a result, a portion of the coal does not participate in the gasification reaction but instead takes part in the combustion reaction that produces CO2, thereby generating heat to supply the amount of heat needed for the coal gasification reaction; hence, the oxygen consumption is higher.
How much heat can the volatiles of coal provide to the furnace? Volatile matter can account for 30% or more of carbon and hydrogen; the heat it can provide must be significant, right?