Soda ash filter

This post was last edited by cl6119 on 2011-7-27 at 10:27. The vacuum drum can recover the mother liquor quite completely through the cleaning section, and the moisture content of the processed material should also be lower. Band filters can be configured in many different models due to the various arrangements and combinations of the pressing rollers. It features a simple structure, high dehydration efficiency, large processing capacity, low energy consumption, low noise level, high degree of automation, the ability to operate continuously, and easy maintenance. Its cost and operating expenses are more than 30% lower than those of plate and frame filter presses, making it the preferred equipment for urban sewage treatment. The vacuum drum consists of a horizontal drum with openings in its wall; a support plate and filter cloth are placed on the surface of the drum to form the filtering surface. The space below the filtering surface is divided into several separate fan-shaped filter chambers. Each filter chamber is connected to a distribution valve via a conduit. With each rotation of the drum, the various filter chambers take turns being connected to either the vacuum system or the compressed air system via distribution valves, thereby sequentially carrying out operations such as filtration, slag washing, drying, slag removal, and regeneration of the filtering medium (filter cloth). Across the entire filtering surface of the drum, the filtering zone accounts for about 1/3 of the circumference, the slag washing and drying zone accounts for 1/2, and the slag discharge zone accounts for 1/6; there are transition zones between these different zones. During filtration, the lower part of the drum is immersed in the suspension and rotates slowly. The filter chamber submerged in the suspension is connected to a vacuum system; the filtrate is drawn out of the filter, while the solid particles get adsorbed on the filter surface to form filter residue. After the filter chamber rotates away from the suspension along with the drum, it continues to draw out the liquid contained in the filter residue. When it is necessary to remove the residual filtrate from the filter residue, washing water can be sprayed when the filter chamber rotates to the upper part of the drum. At this point, the filter chamber is connected to another vacuum system, and the washing water passes through the filter residue layer to displace the residual filtrate between the particles. The filtrate is drawn into the filter chamber and discharged separately, after which the filter residue that has been dried out is removed. At this point, the filter chamber is connected to the compressed air system, which blows air against the filter cloth to loosen the filter residue, which is then removed by a scraper. Compressed air (or steam) continues to blow back against the filter cloth, thereby clearing the pores and regenerating it.

A belt-type alkali filter was seen this year at the new plant of Tianjin Alkali Plant. It’s said to be pretty good

This post was last edited by chen-jun-1024 on 2012-8-20 11:27 using a vacuum drum filter. A vacuum drum filter features a horizontally rotating drum that moves in a continuous cycle, operating in synchronization with the filter belt. For any part of the surface, when it moves to a certain position on the machine, the corresponding operation is carried out. For example, the filtration operation is carried out when reaching the suction filtration zone ； When he moved to the drying area, he dried the filter cake ； When it moves on to the discharge and filter cloth regeneration area, corresponding actions are carried out again: the filter cloth is pulled out, the material is discharged using a scraper, and the filter belt is washed with spray. After that, it returns to the initial filtration position; one rotation of the drum represents one cycle, and this process of rotation and cycling continues. For the entire machine, filtration, drying, discharge, and regeneration take place simultaneously at different locations (a second washing and second drying area can be added according to the user’s requirements).

This post was last edited by mkp369 on 2012-8-27 at 16:56. Belt-type machines are useful in Dahuai, Tianjian, Jiangsu Jingshen, and Henan Jindadi; the washing equivalent can reach 0.5 m3/t of alkali, with the salt content in the finished product being below 0.5%. The moisture content in the heavy alkali is 15%, but it’s not clear what the actual capacity is. The 81 m2 belt-type machine at Tianjian currently has an annual production capacity of 5,000 tons of soda ash per unit area, though it has not yet been operating at full capacity. The greatest advantage of this system is that the water from the third washing stage can be reused in the second stage, and the water from the second washing stage can be reused in the first stage, resulting in a high rate of water utilization. It’s very difficult to do this with a drum type.

Using belts is an inevitable trend, with advantages as Jiang Beipiao has said. This is essentially the consensus within the soda ash industry; another advantage is the high processing capacity of individual units.

Ammonia-alkali manufacturers can consider using drum filters; for combined-alkali processes, belt filters are the better choice. Their greatest advantage is their low washing water equivalent, which helps to address the issue of mother liquor expansion. The moisture content in the heavy alkali is also low, and from an energy-saving perspective, they help to reduce the use of medium-pressure steam required for calcination. Additionally, the sodium carbonate produced has a low salt content. However, for the same production volume, using a drum filter should require less floor space compared to a belt filter, thus saving on costs related to building construction.

Why do ammonia-alkali enterprises consider only drum filters rather than belt filters?

What I mean is that for the ammonia-soda process, drum filters can be used; the main reason for this is that ammonia-soda manufacturers do not face the problem of mother liquor expansion. Of course, filter presses can also be considered for this process. However, domestically produced filter presses are not yet suitable at present, so imported ones should be considered; as a result, the cost of such equipment is likely to be higher than that of drum filters.

Understood, thank you for your reply. I feel that in the soda ash industry, the quality of some domestically produced equipment currently available is somewhat inferior to that of imported equipment.

Belt-type systems require a higher initial investment; the cost for imported ones is around 10 million, while that for domestic ones is about 5.5 million. In terms of capacity, a 60-square-meter unit can produce 1,500 tons per day. Due to the use of continuous washing processes, the water consumption is relatively low, at around 0.35–0.45. The concentration of the mother liquor is high, which allows ammonia-alkali plants to save medium-pressure steam used in calcination furnaces. The combined-alkali process can help address the issue of mother liquor expansion. Of course, there is still room for further improvements. The fourth-generation capacity of the rotary drum has also seen significant improvements; it requires less space, with an initial investment of around 3.5 million. In terms of capacity, it can produce 800 tons per day on a 20-square-meter area. As for water washing, once properly adjusted, the efficiency can reach around 0.45–0.5. The concentration of the mother liquor is relatively low, leaving little room for further improvement.