Principle of Desulfurization using Wet PDS Tannin.docx
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Wet desulfurization involves chemical absorption using alkaline solutions (sodium carbonate solution or ammonia water), and includes methods such as the modified anthraquinone disulfonate sodium method (modified ADA method), tannin method, PDS method, HPH method, etc. The AS method for gas desulfurization is a wet absorption process that uses ammonia present in coke oven gas as the alkaline source; generally, after passing through the ammonia scrubber, the H2S content in the gas is ≤500 mg/m3. For coke oven gas with H2S levels ≤ 500 mg/m3 after AS method gas desulfurization, a wet PDS + tannin desulfurization process is employed for secondary desulfurization to reduce the H2S content in the coke oven gas to ≤ 20 mg/m3.
In 1981, our country established 8 standards for tannin products such as Maoyangmei, Yugan, and Xiangwan, namely GB2616–2623-81. In 1993, black wattle tannin was added, mixed tannin was discontinued, and these standards were transformed into forestry industry standards LY/T1084–1091-1993. In 2010, the standards for acacia tannin were updated, and at the same time the standards for Myrica rubra tannin, Phyllanthus emblica tannin, Quercus dentata tannin, and larch tannin were revised. The tannin products in our country that have been discontinued one after another due to a lack of raw material resources include red-root tannin, oak tannin, wood*** tannin, black wattle tannin, and larch tannin. The tannin products that are still being produced domestically at present are Chinese bayberry tannin, guigang tannin, oak bowl tannin, and acacia tannin. Recently, the standard \"Tannin Gum\" (LY/T 1087—2021), prepared under the leadership of Associate Researcher Zhang Liangliang from the Institute of Forest Chemical Industry of the Chinese Academy of Forestry, was approved for issuance by the **Ministry of Forestry and Grassland Affairs, and it came into effect on January 1, 2022. The \"Tannin\" standard, based on the actual needs of tannin production in China, standardizes the technical requirements, testing methods, inspection rules, packaging, labeling, storage, and transportation for seven types of tannin products: Quercus acutissima tannin, Emblica officinalis tannin, Acacia mangium tannin, Quercus dentata tannin, Larix gmelinii tannin, Wood*** tannin, and Acacia melanoxylon tannin. It possesses strong practicality and operability. The quality grades for standard Chinese poplar tannin, guava tannin, acacia tannin, oak bowl cold-soluble tannin, larch tannin, wood*** tannin, and black wattle tannin are uniformly classified into three grades: top grade, first grade, and qualified grade ； The quality grade levels of oak bowl thermosoluble tannin product are divided into two grades: first-class and qualified. Technical parameters include appearance, moisture, insoluble matter, tannins, precipitates, pH value, total color, as well as red, yellow, and blue indicators. This standard is a consolidation of the existing standards LY/T 1084‑2010 \"Castanopsis carlesii gum\", LY/T 1086‑2010 \"Castanopsis eyrei gum\", LY/T 1091‑2010 \"Castanopsis sclerophylla gum\", LY/T 1932‑2010 \"Acacia mangium gum\", LY/T 1085‑2010 \"Larix gmelinii gum\", LY/T 1087‑1993 \"Castanopsis *** gum\", and LY/T 1090‑1993 \"Acacia melanoxylon gum\". The main changes in the new standard are as follows: the technical specifications for the current standard’s Maoyangmei tannin, Yugan tannin, Acacia mangium tannin, Quercus glauca tannin, Larix tannin, and Mu** tannin remain unchanged. The light-colored tannin from the premium grade of Acacia tannin was integrated, the grade for light-colored tannin under the super-grade in the technical specifications for Acacia tannin was removed, and the ordinary tannin in the super-grade was designated as the premium grade.