【Wet Process】Flue gas desulfurization technology
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The last edit to this post was made by Aggregated Cat_IEB8P on 2020-6-29 at 10:07. According to incomplete statistics, there are currently over 200 different flue gas desulfurization technologies in the world, among which wet flue gas desulfurization is the most widely used. In our country, the limestone-gypsum wet flue gas desulfurization technology and the ammonia-based flue gas desulfurization technology account for over 95% of the market share in wet flue gas desulfurization technologies. https://image.juhecat.com/wp-content/uploads/2020/06/part-00538-2722.jpg?x-oss-process=image%2Fformat,webp Introduction to the limestone-gypsum wet flue gas desulfurization technology: This technology originated in the 1930s with the limestone scrubbing method used by the London Electricity Company in the UK; it began to be widely adopted on a large scale in countries such as the United States, Germany, and Japan in the 1970s. The limestone-gypsum wet flue gas desulfurization technology uses a limestone (CaCO3) slurry as an absorbent to wash the flue gas in an absorption tower, removing SO2 from the flue gas while producing gypsum (CaSO4·2H2O) as a by-product; the desulfurization efficiency can reach 95%~99.7%. The chemical equation for desulfurization is: https://image.juhecat.com/wp-content/uploads/2020/06/WechatIMG703.png?x-oss-process=image%2Fformat,webp Introduction to ammonia-based flue gas desulfurization technology: The German company Krupp developed the world’s first ammonia-based flue gas desulfurization technology in the 1970s. China’s ammonia-based flue gas desulfurization technology originated from the treatment of waste gases generated in the chemical sulfuric acid industry. It has seen rapid development in recent years, with advancements in areas such as ammonia escape control, desulfurization efficiency for high-sulfur coals, and the recovery rate of ammonia; it has been successfully applied to the flue gas desulfurization of coal-fired power units. The ammonia-based flue gas desulfurization technology uses ammonia water (NH3) as an absorbent, which reacts with SO2 in the flue gas to carry out desulfurization and produce ammonium sulfate ((NH4)2SO4) as a by-product. Ammonium sulfate is a raw material for fertilizers, enabling resource recycling; the desulfurization efficiency can reach 95%~99.7%. The chemical equation for desulfurization is: https://image.juhecat.com/wp-content/uploads/2020/06/WechatIMG704.png?x-oss-process=image%2Fformat,webp. The main differences between limestone-gypsum wet flue gas desulfurization and ammonia-based flue gas desulfurization lie in the properties of the absorbents, their availability, and the by-products resulting from desulfurization. Limestone is a common non-metallic resource in large quantities; China has the largest reserves and production of limestone in the world, and it is inexpensive and readily available. Ammonia water is a hazardous chemical, which imposes certain limitations on the use and dissemination of ammonia-based flue gas desulfurization technology ； However, sulfuric acid, the by-product of the ammonia-based flue gas desulfurization technology, possesses a high economic value added, which is in line with the principles of circular economy involving resource recycling; as such, this technology has always been a focus of research in the field of engineering technology.
Both of these are obsolete technologies. 1. The preparation of limestone slurry consumes a large amount of energy and pollutes the environment ； The slurry circulation system is severely worn ； Discarded gypsum is difficult to store, posing environmental and safety risks ； Corresponding CO2 is emitted along with the removal of SO2. The removal efficiency isn’t as high as you say. 2. The ammonia method is a bit better. However, the value of sulfuric acid AN is too low, far below the costs of ammonia and production operations. Ammonia escape and SO2 removal efficiency are also issues.
Professional manufacturers of desulfurization circulation pumps – worth paying attention to
Both the ammonia method and the calcium method are mature technologies that can achieve ultra-low emissions. The calcium method is relatively simple and rough, relying on a high liquid-to-gas ratio to achieve absorption. By-products are difficult to handle (requiring landfilling or further treatment), and operating costs are high. The ammonia process requires a high level of technical expertise, stringent process design requirements, and a relatively long production sequence; meanwhile, the by-product ammonium sulfate has a low selling price, resulting in low operating costs. Ammonia-based desulfurization is the **recommended method**, but if it isn’t implemented properly, many problems arise (mainly corrosion, failure to crystallize, aerosols, etc.). Therefore, it’s better to choose a qualified and experienced provider for this process. Furthermore, the reaction mechanism for ammonia-based desulfurization involves not just the overall reaction equation mentioned by the original poster, but also 4 other reactions, with absorption and oxidation being separate processes. For oxidation to occur, forced oxidation is required; increasing the residence time and the oxygen excess coefficient are necessary to achieve the desired oxidation effect.
Gypsum can’t be sold right now, while ammonium sulfate sells a bit better
I heard that Shell has a Consolf process
Cansolv organic amine desulfurization is said to consume a large amount of amine solution, which is also very expensive. High consumption of regenerative steam. In short, the operating costs are high.