1、 The reason for the filter cloth itself
1. The quality of filter cloth is determined by various factors such as its material, weaving process, and interface process.
2. Polyester material: This material is an ideal choice under acidic conditions, with high temperature resistance (less than 150 degrees Celsius for pH values 1-9), strong tensile strength, longitudinal and transverse stability, and wear resistance second only to nylon.
3. Polypropylene: It has good acid and alkali resistance, with a pH value of 1-13 and a usage temperature of less than 90 degrees, but its tensile strength is not high. Most foreign filter cloth manufacturers do not use this material. Due to the pH value of the slurry from the absorption tower being generally between 4-7 and the temperature of gypsum being between 70-80 degrees, the filter cloth is woven with 100% polyester thread that is resistant to high temperatures and alkalis for flue gas desulfurization.
4. Weaving process: Internationally, the single filament and double filament blended satin weaving process is generally used. The advantage of this weaving method is that the surface is smooth, the back is rough, and the size of the front and rear openings is different. The surface holes are large and the back holes are small, which makes it easy to intercept solids and drain them. The smooth surface makes it more efficient to remove solids from the surface. Many filter cloth manufacturers' polyester threads contain polypropylene, which is not 100% polyester material. The filter cloth is affected by the temperature and pH value of the gypsum slurry in the absorption tower, and is prone to deformation and tearing
2、 Due to the nature of the filter itself:
1. Host flushing system: Because the filter cloth flushing water uses process water, it generally does not clog. The filter cake flushing water generally uses process water+filter cloth flushing water return+vacuum pump circulating water return (using a water ring vacuum pump), mainly vacuum pump circulating water+filter cloth flushing water return, and process water is only occasionally replenished. The gypsum content in the filter cloth flushing water return is relatively high, so it is easy to cause clogging of the filter cake flushing water nozzle. The pressure of the nozzle in the host flushing system is generally greater than 3 kilograms. When it is less than this value, the flushing effect on the filter cloth cannot be achieved. If it is not cleaned thoroughly for a long time, gypsum will accumulate on the surface of the filter cloth and blockage may occur.
2. The distance between the scraper and the surface of the filter cloth is too large, causing a large amount of gypsum to accumulate on the surface of the filter cloth, making it difficult to clean. Over time, it is also easy to scale on the surface of the filter cloth, resulting in a high rate of surface blockage.
3. Sealing of the host: If the moisture content of the secondary dehydrated gypsum is greater than 10%, the sealing of the host should also be considered. Poor sealing can lead to low vacuum degree in the entire system, and the moisture content of the dehydrated gypsum filter cake is significantly higher, affecting the filtration effect. The main reasons for this problem are:
A、 The joint of the vacuum chamber may come loose. The vacuum chamber is usually made of high molecular weight polymer, which has strong elasticity and deformation. If it is not fixed in time or not fixed properly, it may cause the vacuum chamber to come loose. In this case, the only solution is to stop the vehicle, put down the vacuum chamber, re glue it, and fix each section of the vacuum chamber.
B、 There is a leak at the flange connection below the vacuum chamber. This is usually accompanied by a whistling sound. To solve this problem, the vacuum chamber needs to be lowered after parking, and the gasket condition should be checked. If there is a problem with the gasket, it should be replaced; If it's not a gasket issue, then simply tighten the flange bolts at the leak location
C、 If the filtrate main pipe leaks, simply tighten the bolts at the leakage point. If there is a problem with the gasket, it needs to be replaced after parking. To prevent vacuum leakage, it is necessary to conduct a vacuum degree test after the system is installed and before the filter cloth is installed. This can control the problem before driving and avoid trouble after driving.
How to clean clogged filter cloth:
When cleaning the filter cloth used for alkaline filter media, it is necessary to soak it in weak acid solution;
2. When cleaning the filter cloth used for acidic filter media, it is necessary to soak it in a weak alkaline solution.
The soaking time is 1 to 2 days. Then clean it.
Or:
1. High pressure water gun cleaning;
2. Use a cloth washing machine to clean and add cleaning agents;
3. Use hydrochloric acid or citric acid for cleaning;
4. Cleaning with caustic soda or hydrogen peroxide;
5. The washing cycle should be determined based on the actual situation, generally not exceeding 2 months.