Spray issues in bag-type pulse jet dust collectors

Not only should alkaline solution be used for spraying, but an activated carbon absorption unit is also necessary (given the complex composition of flue gas, it is required to remove not only acidic substances but also toxic elements such as heavy metals and dioxins); a concentration of 20-30% for the alkaline solution is appropriate. I hope this helps you.

Reply 1# wo_call_you: Waste incineration flue gas treatment system. The pollutants present in the flue gas generated by the incineration of municipal waste can be classified into four categories: particulates (dust), acidic gases (HCl, HF, SOx, NOx, etc.), heavy metals (Hg, Pb, Cr, etc.), and highly toxic organic pollutants (dioxins, furans, etc.). To prevent secondary environmental pollution during waste incineration, strict measures must be taken to control the emission of waste incineration smoke using smoke purification systems. Research and practices in economically developed countries show that \"low-temperature control\" and \"efficient particulate capture\" are key factors for the successful operation of flue gas purification systems. Therefore, in the purification process of waste incineration flue gas, the temperature must be kept as low as possible (above the dew point), and efficient dust collectors should be used. There are various flue gas purification processes, which can be classified into wet, semi-dry, and dry types depending on whether wastewater is generated in the system. Each process has multiple combinations, each with its own advantages and disadvantages. The wet purification process has the highest efficiency in removing pollutants and can meet stringent emission standards; therefore, it is widely used in economically developed countries abroad, with a variety of process combinations available. The disadvantages of wet purification are its complex process, numerous supporting equipment, high initial investment and operating costs, as well as subsequent wastewater treatment issues. Wet scrubbing purification combines dust removal with the elimination of other pollutants; under permissible conditions, no dedicated high-efficiency dust removal equipment (electrostatic precipitators or bag filters) is required. The absorbent used for wet purification can be Ca(OH)2 or NaOH. Since CaSO3 is insoluble in water, NaOH is preferred to avoid scaling inside the equipment. The temperature of the flue gas after wet purification **decreases**, and it often needs to be heated before being released into the atmosphere through the chimney. The semi-dry purification process not only achieves a high efficiency in removing pollutants, but also boasts advantages such as low investment and operating costs, a simple process flow, and no generation of wastewater. It is a highly promising technology that is increasingly being used in the flue gas purification systems of municipal solid waste incineration plants. This process has been designated by the U.S. **Environmental Protection Agency as the best process for purifying flue gases from municipal solid waste incineration. Its drawback is the high requirements for operating parameters (such as the residence time of the flue gas in the spray drying absorption tower, and the particle size and concentration of the absorbent in the absorption slurry) as well as for the nozzles. The pollutant removal efficiency of the dry purification process is relatively low compared to wet and semi-dry processes; however, it features a simple process, significantly lower investment and operating costs than wet processes, requires less operational expertise, and involves no subsequent wastewater treatment issues. In recent years, economically developed countries have continuously improved dry purification equipment, enhancing the efficiency of pollutant removal; as a result, this technology remains practical and is particularly suitable for use in regions with relatively underdeveloped economies and less stringent emission standards. The above three processes exhibit high purification efficiency for particulate matter and acidic gases that are easy to remove; they also have a high removal efficiency for heavy metals, dioxins, furans, etc., but their effectiveness in removing NOx is minimal. Therefore, in economically developed **regions where emissions of NOx from waste incineration flue gas are restricted, separate NOx purification systems are often installed in the waste incineration flue gas purification systems. Furthermore, with economic development, the emission standards for flue gases from waste incineration in developed countries have become increasingly strict; strict emission limits have been set for heavy metals as well as PCDDs and PCDFs. Therefore, the method of injecting activated carbon for adsorption is often used to further purify these three types of pollutants. It should be noted that the purification of NOx or adsorption through activated carbon injection cannot on their own constitute a complete flue gas purification system; these two purification methods serve to complement and enhance the main flue gas purification processes (wet, semi-dry, or dry). 　　Different countries and regions have various smoke emission standards, and accordingly, waste incineration plants also have different smoke treatment systems. Flue gas treatment systems generally consist of the following combinations of equipment: The first two combinations are the types of flue gas treatment systems commonly used in waste incineration plants around the world, while the last combination can be considered for use in areas with lower flue gas emission standards when constructing small-scale waste incineration plants. In recent years, dioxin pollution has attracted widespread concern among people around the world. Waste incineration plants are one of the main sources of dioxins. Since there is currently no consensus on the mechanism by which dioxins are formed, it is difficult to determine the effectiveness of suppressing their generation by merely controlling the incineration parameters. The methods currently used to remove dioxins are mainly activated carbon injection systems and bag filters.

Spraying sodium hydroxide to remove acidic gases is an uneconomical approach; as the flue gas load fluctuates, it is difficult to control the amount of sodium hydroxide used in spraying. The crystals formed after the sodium hydroxide crystallizes tend to stick to the bag filters, which requires high standards for the material of these filters. To date, there is no evidence of semi-dry desulfurization processes that make use of sodium hydroxide spraying on a widespread basis.