Gasification technologies for anthracite
Thread Content
There are still many ammonia and methanol production facilities in China that use anthracite as raw material; the gasification technology used is mostly fixed-bed atmospheric gas generation. Some of these facilities have been modified to use oxygen-enriched gas generation, but fundamentally they still rely on fixed-bed atmospheric batch gas generation. This technology has been classified as a restricted technology by the National Development and Reform Commission. Due to the special properties of our country’s anthracite, it is not widely used as a raw material in industries other than the chemical sector. I’m posting this thread to discuss the future development directions of anthracite gasification technology; I hope those who are interested will actively participate so that we can all improve together. Hehe
I believe it is advantageous to use anthracite for the production of syngas, as its gas composition can contain over 90% carbon monoxide and hydrogen. Mature gasification technologies such as coal water slurry, GSP, and space furnace can be employed for this purpose.
Bituminous coal generally has a too high ash fusion point, and can only be used in combination with other fuels in the furnace types mentioned above. Currently, fixed-bed furnaces and Rudolf furnaces are used for burning bituminous coal solely, but Rudolf furnaces face significant environmental pressures.
1. Fluidized bed gasification generally involves liquid slag discharge, and the gasification operating temperature is closely related to the ash melting point. The melting points of major domestic anthracite ashes are generally above 1500 degrees, making them unsuitable for existing fluidized-bed gasification technologies. 2. Fluidized bed gasification generally uses solid slag discharge, and it has low requirements regarding coal quality. However, the low operating temperature in fluidized bed gasification affects the gasification efficiency. 3. To adopt fluidized bed gasification, one approach is to add fluxes to refractory coals; however, the components of these fluxes are generally based on Fe, which can have an impact on subsequent gasification processes. Therefore, the gasification of high ash fusion temperature anthracite remains quite challenging.
We are using Texaco’s technology with anthracite, but it hasn’t been put into operation yet; we hope experts can offer us some guidance
There are several issues with using bituminous coal as a raw material to produce syngas through existing gasification technologies: (1) Bituminous coal has low gasification activity, and its reaction capacity is inferior to that of lignite and brown coal. In the design of gasification furnaces, it is necessary to consider both gasification stability and the residence time of the material within the furnace in order to compensate for this low gasification activity. Of course, adding catalysts and reducing the particle size of the raw material can also help improve the gasification activity. (2) Bituminous coal is not suitable for water-coal slurry gasification. Research shows that coal types suitable for slurry coal gasification also exhibit higher gasification efficiency and greater output per unit of equipment in dry powder gasification. The problem is that in slurry coal gasification, water must be evaporated before combustion gasification can take place, which necessitates a longer reaction time and thus results in a lower output from the equipment. Bituminous coal has low reactivity and poor slurry-forming properties; it can only be used as a blending component together with bituminous coal that is suitable for slurry production, and the amount used is limited. For these reasons, bituminous coal is not suitable for water-coal slurry gasification. As for its other disadvantages such as a high ash melting point and poor grindability, they will not be discussed here. (3) The highly metamorphosed characteristics of anthracite enable it to demonstrate its economic value in other applications. Anthracite with varying degrees of metamorphism accounts for about 20% of China’s coal resources. Its economic value can be realized in the field of new materials; currently, lightweight materials used in aviation, refractory materials, and activated carbon all require anthracite. So why must it be used for burning?
The Ruhr process uses anthracite, and there are examples of its application in China. However, its poor reactivity and high ash melting point make it difficult to operate the Ruhr process stably. Additionally, since this process relies on solid slag discharge, the gasification temperature is limited; therefore, weakly bonded bituminous coal is the most suitable for Ruhr gasification. As for the issue of high methane content in the syngas and the complexity of the treatment processes, those will be discussed later.
Bituminous coal has a high ash fusion point; a cosolvent can be added, and this cosolvent is mainly limestone, which has little impact on subsequent processing stages. Using fluidized bed gasification to produce raw material gas for ammonia synthesis offers the greatest advantages.
Pressurized fluidized bed gasification processes that use dry pulverized coal as feedstock, such as SHELL, GSP, HTL, Corin……
Well, it seems that bituminous coal is indeed not suitable for gasification