Discussion on slag disposal solutions for gasification
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Some coal chemical enterprises have set up open-air slag storage areas within their plant premises; the waste slag generated by the gasification units is transported there using conveyors for storage. This practice has a significant impact on the environment, especially in autumn when dust pollution is severe, with sand and dust filling the air. It does not conform to environmental protection policies nor to the principles of clean and civilized production. I believe this processing method is unreasonable – it is an outdated approach that has been phased out domestically – yet it is still used in imported facilities in China, which puzzles me. Please share your thoughts on the reasons behind storing waste residues on-site in the factory Mainly discuss whether the process plan for setting up an open-air slag storage area within the plant site is reasonable This post was last edited by ralph31 on 2008-5-20 16:04]
I’m not quite sure what that means. Why does it have to be taken to the factory? Coal slag is very useful these days and can be sold.
Yes, slag can be sold to cement plants for use as building material, which is both environmentally friendly and economically beneficial!
It can also be sold to brick factories for use in making gray bricks; it’s very easy to handle
The C content in gray material is less than XXX percent, allowing it to be reused; the slag can be purchased easily as it is in high demand in many places. (The XXX value) cannot be disclosed due to confidentiality reasons
Cinder can be sold to cement plants or brick factories; in particular, carbon black is of higher value and can be used for various purposes. Cinder can be transported by vehicle directly, with it taking up almost no significant space
The method of use is determined based on the carbon content: high levels are used for magnetic separation, while low levels are used for making bricks
Perhaps I didn’t explain myself clearly; what I mean is the buffer storage area for waste residues within the plant. I believe it is inappropriate to have an open buffer storage area for waste residues inside the plant, but currently many gasification units in China do have such open buffer storage areas for waste residues within their plants
For slag with a high content of fixed carbon, it can be mixed with the coal supplied to boilers to make full use of resources, especially given the ongoing rise in coal prices. The final residue can be used by brick factories or for roofing and road construction. . . . . . . . . .
Ugh, most of the answers are about comprehensive utilization plans for waste
If buffer storage is effective, it has little practical value other than being returned to be mixed in as a flux. If anyone understands, please feel free to share your insights!
Using gasification fly ash as a building material； Waste catalysts and waste molecular sieves are sent to manufacturers for recycling ； The slag discharged from the gasification system has been vitrified; the fly ash has a low carbon content, and no heavy metals leach out during storage. It has potential for utilization and can be used as building materials such as road surfacing and cement. Boiler ash, due to the lower furnace temperature, has good activity when discharged, making it promising for use as a good raw material for road construction and cement production.
Generally, the remaining ash is very fine and can be used as a cement material!
Wind shields can be installed around the slag storage area; they can be made of color steel or fiberglass. Many coal storage areas in coastal ports use such shields (I think Dalian Port has them), and the results are quite good. You might want to go and take a look
Just build a slag pool – soak the slag in wastewater and retrieve it when needed. This should basically solve the problem of excessive dust, but the odor remains an issue. =.
Installing wind shields around the slag storage area does not solve the problem of dust generation; it only provides some improvement, and it requires a large amount of space； A slag pond can be built to soak the slag in wastewater, but this approach presents problems such as water pollution and complicating the treatment system. In fact, the process we use involves removing the slag using a slag skimmer and storing it directly in a closed storage facility; thereafter, it is transported by vehicle for further utilization or landfilling. This method has a simple process flow, requires less space, and results in lower investment costs. This post was last edited by ralph31 on 2008-5-22 09:03]
Agree with what LZ said. Setting up an open-air intermediate slag yard within the plant area as a buffer does indeed have a significant impact on the environment; it is more of a decision made to save on investment costs. It can also be said that it is inevitable to allocate limited funds to key gasification technologies as well. A better approach is to build a larger buffer silo; although the initial investment is higher, the operating costs are low, and equipment such as loaders can be eliminated. However, the pressure to sell increases due to the limited capacity of the silo.
In fact, in the developed cities of our country, the utilization rate of ash and slag is very high, with demand often exceeding supply. In smaller cities, the utilization rate is lower. From an environmental protection perspective, the approach adopted in China is to build ash and slag storage sites outside the factories; previously, the capacity of these storage areas was designed to cover a storage period of over 9 hours, but now there is a tendency to use smaller storage facilities. In some projects, buffer storage areas are even omitted, and trucks are used instead as temporary storage solutions, which also works well. These approaches are less costly than using conveyor belts to transport the ash and slag to outdoor storage areas within the factory premises – a method that has been in use in China since the 20th century. This post was last edited by ralph31 on 2008-5-23 09:43]
Yes, another process should be added: a waste residue processing plant to process building materials.
In the long term, it is recommended that plants with high amounts of slag establish their own brick-making factories based on their specific circumstances, in order to extend the industrial chain and make use of this resource over the long term. In the short term, it is possible to construct a slag storage tank as mentioned above and use industrial wastewater for spraying to keep dust at bay.