[Weekly Topic] Discussion on the Impact of Water-Coal Slurry Heating on Gasification (March 14–20, 2016)
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I invite experts to discuss this technology. For example, how to design the heat exchanger, the choice of heating temperature, the selection of the heating medium, and most importantly, the extent to which heating can improve the gasification efficiency.
GE is also planning to promote this approach; from the perspective of heat recovery, there are certainly significant benefits. As for the extent of these benefits, it will depend on the actual results of factory renovations. From the perspective of heat exchange, using a heat exchanger is not very practical due to issues such as blockages and dead zones, as well as the difficulty in ensuring thorough cleaning. I think it is better to design the coal slurry pipeline as a double-walled tube.
Another point is the issue of steam balance in the factory; if there is an excess supply of steam, this task can be considered, but if there isn’t enough steam available, it’s not necessary to carry out this work.
In fact, from the moment it is prepared, the temperature of the coal slurry is already around 40 degrees Celsius; it is advisable to maintain this temperature once it enters the large coal slurry tank. Throughout the entire transportation process via the high-pressure coal slurry pump, the slurry remains hot. My advice is not to heat it. The reasons are as follows: 1. Uneven heating can easily lead to the formation of large particles, causing valve sticking and fluctuations. 2. In the heat tracing system for coal slurry pipelines, the heat tracing tubes do not come into direct contact with the pipelines; there is an insulating layer in place. 3. Coal slurry is a non-Newtonian fluid whose properties are variable and irregular; the conditions of coal slurry vary from one facility to another, so there is not much that can be used as a reference. 4. In most cases, the viscosity of coal slurry decreases when it is heated; it also decreases under the action of stirring. 5. The situation becomes more complex under the coal blending process.
This is a good topic; I’ve also been struggling to find articles that discuss it. If the coal slurry is heated, does that essentially mean indirect savings in oxygen usage? Given that it’s in the form of water-coal slurry, it would be best to install jackets on the coal slurry feed pipelines, using excess low-grade steam or hot water from the factory to heat it. As for the appropriate temperature, it depends on factors such as the heat source and the need to avoid significant changes in the properties of the coal slurry.