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Home > BLOG > How to prolong the service life of PPS filter bag in the process of filtering sulfur containing flue gas from coal fired boiler?

How to prolong the service life of PPS filter bag in the process of filtering sulfur containing flue gas from coal fired boiler?

April 20,2022

The possible chemical reaction of PPS filter bag in the process of filtering the chemical flue gas containing “sulfur” in the coal fired boiler of power station and the possible serious consequences of the application of bag filter to the dust removal of coal-fired boiler of power station.


Coal and other fuels contain hydrogen, which reacts with oxygen in the air during combustion to form water, which increases the humidity of flue gas, and there are problems of condensation and dew point temperature.


Coal, heavy oil and other fuels contain a certain amount of “sulfur”. Generally speaking, if coal contains 1% sulfur, 600ppm “sulfur dioxide” will be formed in the flue gas after combustion


If the flue gas contains excess “oxygen”, part of “sulfur dioxide” will be oxidized to “sulfur trioxide” SO3 + H2O = H2SO4.


During the combustion of coal in the boiler, a large amount of air needs to be supplemented, and the air contains 21% oxygen and 79% nitrogen (volume ratio). When the temperature is not high, nitrogen is very stable, but high temperature will break the nitrogen molecular chain and react with oxygen to form “NO” and “NO2”. “NO” cannot be considered more, but “NO2” is a strong oxidant and can oxidize most of the fibers used for filtration.


The chemical composition of the material fiber of PPS filter bag is “Polyphenylene sulfide”. Sometimes when using chain boiler, excessive air will be blown in, and a large amount of oxygen can attack and combine with the “s” bond in PPS molecule. The result of the reaction is that the fiber of PPS filter bag material becomes dark and brittle, and the strength decreases. Sometimes you will find that the surface color of PPS fiber or filter bag exposed to the sun will turn brown. We must choose the leadingpps filter bag supplier.


In the technical parameter list of PPS filter bag material, we list the continuous working temperature of PPS filter bag as 180 ℃ and the instantaneous temperature resistance as 200 ℃, which only represents the service temperature without strong oxidant and acid-base gas components. During the treatment of tail gas from power plants, coal-fired boilers and waste incineration, try to set a lower flue gas temperature (under the condition that the flue gas temperature is more than 20 ℃ higher than the “acid dew point”), and it is appropriate to use it within the range of 140 ℃ – 160 ℃. However, sometimes many on-site working conditions are limited by various factors, the operating temperature cannot be controlled within the appropriate temperature range, and the composition and oxygen content of flue gas cannot be controlled at a low level, so relevant chemical reactions will occur. For example, for every 10 ℃ increase in the operating temperature, the chemical reaction speed will double, which will significantly shorten the service life of the filter bag. This is the main reason why many of our filter bags and filter materials cannot reach the service life of three to four years.


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