GE coal-water slurry gasification uses steam to heat the coal slurry and oxygen
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Is it practical to use steam in GE coal slurry gasification to heat the coal slurry and oxygen, thereby increasing their latent heat and improving the efficiency of gasification?
If the steam is not waste steam, using it to preheat the coal slurry and oxygen does not constitute preheating for practical purposes; from an energy balance perspective, it does not improve the gasification efficiency. However, reducing the residual carbon in the slag after preheating may improve the gasification efficiency.
Specifically in terms of the design data, it is quite meaningful. For the Shenhua Baotou Olefins project, there was someone in charge of accelerating the progress, and this person had some research on this area; currently, a patent application is likely still pending – it’s not clear whether it has been approved yet. I was fortunate enough to have a chance to read the content of that patent.
Heat exchange always involves heat loss; the best way to recover heat is through direct contact. Using steam to heat coal slurry is certainly not as economical as heating it by burning coal directly.
It should make sense, but it depends on the source of steam and the scale of the project.
Although slurry heating reduces oxygen and coal consumption, the cost of steam also needs to be taken into account; the actual situation will have to be verified through practice.
It can be implemented using oxygen first, which can consume the excess low-pressure steam in the factory.
I personally think it’s better to try using slurry first, especially in the north where temperatures are low in winter, which affects the fluidity of the slurry. Starting the slurry circulation earlier during feeding may lead to freezing and blockages in dead zones, resulting in feeding failures.
I remember that in the early days of water-coal slurry gasification, the slurry was heated, but in later industrial applications heating was no longer used. Heating water-coal slurry involves only sensible heat, so not much heat is required; even less heat is needed for heating with oxygen.