What are the problems in wet flue gas desulfurization and dust removal technology?

What are the problems in wet flue gas desulfurization and dust removal technology? The following Zhong Da Consulting will answer your questions.

Air purification technology: since the implementation of sulfur dioxide emission control in China, a large number of dust removal technologies have emerged, among which wet methods are the most, and many technical schemes are self-excited. There are still some unsolved or unsolved problems in defogging and exhaust temperature of this kind of technology and some new products. This problem is put forward in order to attract the attention of technology development and evaluation and avoid wasting material and financial resources.

First, demisting.

Demisting or dewatering at the outlet is a necessary function for wet dust removal.

Among inertial, gravity, wire mesh and cyclone demisters, the first two are unreliable. Even in the latter two cases, if the air volume of the induced draft fan is too large, or if a high-power fan is configured because the wet dust removal resistance is too large, water will also appear. Demister has been installed in all wet processes in China, and more attention should be paid to demisting wet additives.

The water mist after traditional wet dust removal contains more acid and less salt, and the only problem is the corrosion of flue and fan, which is slow, generally calculated in years. The water mist after wet desulfurization with desulfurizer contains many kinds of salts (desulfurization products) and has high concentration. After self-excited desulfurization with desulfurizer, the fog beads contain high concentration of desulfurization product Q, which contains weakly soluble sulfate. When lime is added for desulfurization, it is calcium sulfate, and gypsum or other salts will be precipitated after water evaporates in the flue. They form a hard shell on the flue wall, especially on the blades of the induced draft fan impeller, which destroys the dynamic balance of the impeller, easily burns out the motor and even scrapped the induced draft fan. It's faster, sometimes in months.

A complete set of wet desulfurization technology should not only demist, but also separate desulfurization products.

Second, the exhaust temperature problem

Emission requirements should be higher than dew point temperature (about 60℃) 10 ~ 20℃ to reduce flue corrosion; At the same time, the smoke exhaust speed at the chimney outlet is required to be 25 ~ 3m/s to avoid cold air backflow. When the temperature is high, the specific gravity of flue gas is much smaller, and the fan is easy to exhaust from the chimney.

According to the requirements of national standard, the height of boiler chimney in new projects generally increases, and the load of fans increases. If the flue gas temperature after wet desulfurization and dust removal is much lower than 60℃, it will increase the fan load, reduce the life of flue and fan in many ways, and affect its operation economy. Because of this, some mature wet desulfurization technologies are equipped with flue gas reheaters.

Third, the mass transfer reaction ability of desulfurization technology and the separation method of desulfurization products

In the development of desulfurization technology in the world, there has never been a very economical desulfurization scheme, and the truly complete desulfurization technology is still complex, huge and very expensive. It has not been widely used in small and medium-sized coal-fired boilers for more than 20 years. The fundamental reason is that it is difficult to realize fast (small volume of desulfurization absorption tower) and efficient (high desulfurization efficiency and saving desulfurizer) mass transfer reaction, which requires many technological processes to separate desulfurization products and the cost is too high.

The water mist produced by self-excited wet desulfurization is too large in particle size and too small in gas-liquid contact area. It is a desulfurization scheme with the lowest mass transfer reaction rate and efficiency and the largest waste of desulfurizer, and its operation economy is poor. If there is no new breakthrough in the mass transfer reaction process, the new desulfurization technology is problematic. At present, some desulfurization technologies are based on indigenous methods, and they don't know much about chemical reaction engineering, ignoring the complexity of desulfurization chemical reaction process, so they can't be commercialized, but there are gaps in policies, so they can engage in short-term behavior. Therefore, all localities should consider technical feasibility when formulating environmental protection policies.

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