Discussion on using higher ash melting point coal in GE gasifier
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Generally speaking, coal-water slurry technology has requirements for the ash melting point in the selection of coal types because liquid slagging is required, which is generally below 1300C. If the ash melting point is too high and the viscosity is too high, it will cause strong erosion on the furnace wall, reduce the life of the refractory bricks, and may also block the slag discharge port below. Please add other harmful effects to members and friends. Nowadays, the general methods to deal with coal with high ash melting point are:: 1. Increase the gasification temperature, but the increase in gasification temperature will inevitably affect the life of the refractory bricks. In addition, the oxygen consumption will also increase and the effective gas will decrease. 2. Add co-solvent to lower the ash melting point. Limestone is usually added here, but not too much. Now, 50% of the coal in China is high ash melting point coal. Please express your opinion on this issue.
For coal with high ash melting point, coal-water slurry furnace is not suitable, and dry pulverized coal furnace is a good choice.
Coal with high ash melting point can choose fixed-bed crushed coal pressurized gasification technology, such as traditional Lurgi furnace gasification technology. However, the limitation of this gasification technology is that the sewage treatment process is long and the cost is high.； The gasification raw coal requirement is 5~50mm. Nowadays, coal mines adopt fully mechanized mining. The content of lump coal is low and the content of fine coal is high. The supply of raw coal may be subject to certain restrictions.
For coal types with high ash melting points, dry pulverized coal entrained bed gasification technology is also a good choice, such as HT-L furnaces and Shell furnaces. They all represent advanced gasification technologies. But they are liquid slagging. If the coal ash has a high melting point, it requires a high gasification temperature. The gasification temperature is high and the oxygen consumption is high. ； It is generally recommended to add some flux or blend coal to lower the gasification temperature, thereby reducing oxygen consumption and improving efficiency.
Pulverized coal gasification has advantages in almost all indicators. Unfortunately, the operation is not smooth. Solid-phase transportation is the main problem.； The effective gas component of lurgi is low. The key is that the phenol content in sewage is high, which is a big problem in sewage treatment. ； Coal water slurry gasification is relatively mature and stable. As for the ash melting point, because it involves multi-phase fusion, a lot of research is being done. We can only do experiments to find the optimal dosage.
I remember that at the Fifth Annual Meeting of Chemical Engineering and Biochemical Industry last year, Liangsaku Hegen of the Northwest Research Institute of Chemical Industry reported that they had a patented technology that could achieve dry ash removal from coal-water slurry gasification, but the conversion rate was slightly reduced. But he did not disclose more information at that time and did not know what the actual situation was. If the host is interested, you can contact them. I think coal with a high ash melting point should be suitable for this technology.
I remember that Luhua had a paper about solid-state slag removal from GE furnaces, which can increase the effective gas production rate. When the melting point of ash is low, solid slagging is also used.
If the ash melting point is high, use dry coal pulverized gasification technology, and then make further choices based on the requirements for the gas in the subsequent process, such as whether it is used as industrial gas or as a chemical product.
Some personal opinions on using high ash melting point coal in refractory brick gasification furnace: (1) Life span of refractory bricks* * shortened, because the erosion of refractory materials by high temperature is far greater than the erosion of refractory materials by molten slag ； (2) If flux is added to lower the ash melting point, consumption will be increased, and the water system will also be prone to scaling and blockage. ； (3) Dry ash discharge is still immature and is limited by coal types. This is mainly due to the large difference in the melting characteristics of different coal types near DT. ； (4) Water-cooled wall lining can be used for coal with a temperature greater than 1400 degrees Celsius, but the operating temperature of the water-cooled wall is generally around 1500 degrees Celsius. The purpose of controlling this temperature is to reduce consumption, and to protect the water-cooled wall and extend its service life.
personal opinion: For inferior coal, including three-high coal, the best utilization method should be coal blending, which can improve activity, change melting point, ash content and composition, etc. The economic benefits may not be good in the short term because it requires medium and long-distance transportation and the construction of a coal blending system. But in the long run, it should be a good way to improve the effective utilization of resources.