Some thoughts on the dust accumulation issue in SCGP coolers
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During the operation of SCGP technology, dust accumulation is likely to occur on the surface of the cooler coils, which affects the heat exchange efficiency and can lead to issues such as an excessively high temperature at the syngas outlet. In my opinion, since the temperature of the syngas drops to around 900 degrees after quenching, it is possible to take advantage of the various properties of fly ash at temperatures below 1000 degrees; this approach is independent of the ash melting point of the coal used. Numerous studies have examined the sintering properties of fly ash at temperatures around 700–800 degrees, and this information can be useful in addressing the problem of dust accumulation in the pipelines.
The question now is how to conduct experiments on fly ash at seven or eight hundred degrees to determine its physical properties
The characteristics of fly ash still require looking for the issues in the raw coal itself. Moreover, the temperature of 900 degrees is also determined based on the ash fusion point of 1500 degrees for the coal suitable for SHELL; therefore, the ash fusion point needs to be taken into account as well. In addition, it is the composition of the fly ash that affects the value of the ash fusion point. Well, these also have an impact on fly ash scaling. According to SHELL, the particle size of fly ash has a significant impact on its tendency to form scale; therefore, I believe that factors affecting the particle size of fly ash, including the flow field, temperature field, and the particle size of the raw coal, should all be included in the scope of research.
When discussing the ash accumulation issue in SGC, please pay attention to one detail: is it on the upper part or the lower part of SGC? If it occurs in the upper part, it is reasonable to infer that the HT/ST/FT of the ash is likely low, but what if it happens in the lower part? How to explain it? Is the melting temperature of this ash really only 300–400°C? It doesn’t seem explainable? Another point is that sometimes we find that the 15-unit filters are clogged, and the mechanism behind this requires further discussion and research.
The design temperature of the upper airflow is also below 900 degrees; it is basically unrelated to the melting point of ash. Feature temperatures such as ST will not drop below 1000 degrees either
During the SGC inspection at our plant, it was found that the accumulation of ash increased from top to bottom. It is inferred that the flow velocity of the syngas decreases in the lower sections; as a result, larger particles have been ground into smaller ones due to erosion. The heat exchange efficiency of the superheater is insufficient, which also leads to higher temperatures in the lower areas. The impactors are not functioning properly. These are just my preliminary observations; I welcome any discussions on this topic