Application of Jets in the Oxidation Treatment of Desulfurization Slurry

In the wet limestone-gypsum flue gas desulfurization system, the desulfurization slurry is highly corrosive and abrasive. Moreover, in order to obtain qualified by-products, the oxidation rate of desulfurization products (such as calcium sulfite and ammonium sulfite) must reach over 99%. Therefore, special requirements are placed on the structure and material selection of the aeration device.

The jet aeration oxidation device is powered by a slurry circulation pump. Through the negative pressure generated by the jet, air (or oxygen) is drawn into the mixing chamber. In the mixing chamber, the gas and liquid are in close contact, and the oxidation efficiency is much higher than that of conventional oxidation devices. No oxidation blower is required, there are no rotating parts, and no other mechanical stirring device is needed (with a built-in secondary enhancement device).

It has the following features:

1) Finer bubbles are one of the main features of jet aeration. The smallest bubbles of micro-pore or medium-pore bubble diffusers can only reach the millimeter level, while the bubble diameter of a jet aerator can reach about 100 microns, providing the largest gas-liquid contact specific surface area.

2) Liquid-gas jet aeration provides much greater mixing intensity than air injection and does not require a separate stirring device.

3) Longer retention and contact time. From the moment air is drawn into the jet aerator mixing chamber, bubble breakup and gas-liquid mixing are achieved under the strong jet action. Oxygen and slurry begin the contact reaction inside the jet aerator, then enter the secondary enhancement device through the piping, which entrains and mixes more slurry, achieving repeated mixing and contact reaction between the gas-liquid mixture and the liquid in a limited space. Finally, the mixture is released into the oxidation tank from the bottom, greatly extending the contact time between oxygen and slurry, thus ensuring a mass transfer efficiency far higher than that of air injection devices.

4) Jet aeration has the best reliability. Because the jet aeration device has no rotating parts, it largely overcomes the clogging and damage defects of air injection devices in complex slurries with strong corrosion and strong abrasion (high solid content), and is more stable and reliable than mechanical stirring devices. Compared with other aeration devices, the jet aeration device can achieve the longest period of stable performance with the fewest failures and the least maintenance.

5) Jet aeration does not require an oxidation blower, nor the corresponding humidification and cooling measures.

6) In general, the circulation pump required for jet aeration does not need a very high head. Basically, the same head as the slurry circulation pump for flue gas spray washing can be used. At the same time, the relatively high liquid-gas ratio required for spray washing means that the circulating slurry for aeration may not need a separate circulation pump.

7) When conditions permit, pure oxygen or oxygen-enriched air can also be used for jet aeration, which not only has higher efficiency, but also lower investment, a wide load adaptation range, stable performance and high reliability.

From domestic and international experience, in various wastewater treatment processes requiring aerobic aeration, jet aeration — due to its efficient mass transfer, simple and reliable operation, no clogging, no failures, and stable non-degrading performance — has gradually replaced various air-blown aeration methods. More and more users prefer this simple installation method that does not require draining or emptying the tank during upgrades and retrofits. It is foreseeable that the application of jet aeration in the oxidation treatment of desulfurization slurry will also usher in a period of rapid development.

The design and equipment layout of the jet aeration system are closely related to the air suction capacity, retention time, mixing intensity and energy consumption. Therefore, to ensure the aeration effect, our company will provide the design and construction drawings of the aeration system, including the installation positions of the liquid circulation pump, jet aerator and secondary enhancement device, the determination of the performance parameters of all system equipment, and the design of the system piping. The jet aerator and secondary enhancement device are developed, designed and manufactured by our company.