Please discuss the advantages and disadvantages of tannin desulfurization and organic amine desulfurization in ammonia synthesis

Advantages of tannin desulfurization: 1. Tannins are abundant resources; they come from wild plants, are non-toxic, and are inexpensive and easily available； 2 The tannin method for desulfurization does not have the problem of sulfur clogging in the tower ； 3 Tannin acts as both an oxidizing agent and a complexing agent for vanadium ； Disadvantage: 1. Tannin needs to be pre-treated before it can be added to the system; otherwise, it will cause severe foaming of the solution ； The tannin desulfurization solution has low corrosivity, but as by-products of side reactions and other impurities increase in the solution, its corrosivity rises. Among them, a high content of sodium sulfate is the main factor causing corrosion. The organic amine method can remove gases such as sulfur dioxide; it is not clear whether it can also remove hydrogen sulfide. Those who know the answer are encouraged to conduct further analysis! I’ll just talk about the characteristics of using organic amines to remove sulfur dioxide: organic amines are very expensive, and it seems that they cannot be produced domestically in China! Its advantage is that it can be reused!

Let me add here the characteristics of organic amine desulfurization: organic amines. It is a general term for a class of extractants whose extraction functional group is a nitrogen atom, including four types: primary amines RNH2, secondary amines R2NH, tertiary amines R3N, and quaternary ammonium salts R4N+X-. The relative molecular mass of alkyl amines used as extractants is usually between 250 and 600. Their extraction of metal ions follows an anion exchange or ion association mechanism. Primary, secondary, and tertiary amines are moderately strong basic extractants; in acidic media, they must first react with hydrogen ions (H+) before they can extract metal complex anions such as FeCl4_, CoCl42-, ZrO(SO4)22-, and UO2(SO4)22-. Quaternary ammonium salts are strongly basic extractants; they contain the ammonium cation R4N+, which allows them to be used for extraction from both acidic or neutral solutions as well as from alkaline solutions, such as for extracting the UO2(CO3)34- complex anion from carbonate solutions. Their properties: Monoethanolamine (MEA): Molecular formula: H2NCH2CH2OH ； Molecular weight: 61.08 ； Freezing point: 10.5℃ ； Boiling point: 171.0℃ ； Specific gravity: 1.0147 (20°C) ； Viscosity: 24.14 mPa·s (20°C) ； Diethanolamine (DEA): Molecular formula: HN(CH2CH2OH)2 ； Molecular weight: 105.14 ； Freezing point: 28.0℃ ； Boiling point: 269.1℃ ； Specific gravity: 1.0828 (40°C) ； Viscosity: 196.4 mPa·s (40°C) ； Triethanolamine (TEA): Molecular formula: N(CH2CH2OH)3 ； Molecular weight: 149.19 ； Freezing point: 21.2℃ ； Boiling point: 360.0℃ ； Specific gravity: 1.1196 (25°C) ； Viscosity: 613.3 mPa·s (25°C) ； N-Methyldiethanolamine (MDEA): Molecular formula: CH3-N(CH2CH2OH)2 ； Molecular weight: 119.16 ； Freezing point: -21.0℃ ； Boiling point: 246-269℃ ； Specific gravity: 1.0425 (20°C) ； Viscosity: 101 cP (12°C) ； 1. Monoethanolamine method (MEA): Monoethanolamine is the most basic among these alkyl alcohol amines; as a result, it reacts most rapidly with acidic gases such as hydrogen sulfide. It also has the lowest molecular weight of all these amines. When it comes to removing acidic gases using alcohol amine desulfurizers per unit mass, monoethanolamine possesses the highest absorption capacity. In addition, it is stable, undergoes minimal thermal degradation, and can be easily recovered from contaminated solutions. The disadvantages include the formation of degradation products between the MEA and COS and CS2, a higher vapor pressure compared to other amines, resulting in significant losses, and a lack of selectivity in the absorption of hydrogen sulfide. 2. Methyl diethanolamine method (MDEA method): It exhibits high selectivity for hydrogen sulfide absorption, is not prone to degradation, and has low corrosiveness. Since its solution circulation volume is lower than that of other amines, both capital and operating costs are reduced.

Thank you to the two people above. The tannin-based desulfurization method is quite popular in the ammonia synthesis industry, but for organic amine desulfurization, there are dedicated thermodynamic packages available in Aspen and PROII; it can be said that foreigners have conducted very thorough and in-depth research on this topic, so I’m really interested in knowing the advantages and disadvantages of each method!

The use of the organic amine method for desulfurization is not common in China, I guess.

I would like to ask why the organic amine method is not used? If it’s used abroad and the technology is so advanced, why don’t we use it?

50,000 to 80,000 per ton; it can be produced domestically, with Sichuan Huaxi Chemical Industry being capable of doing so. The advantage is that saying \"reusable\" isn’t quite accurate; rather, its feature is reusability. As for how much loss there is, only experts know!