What desulfurization method is used to produce methanol from coke oven gas?

The coking pretreatment adopts a modified ADA desulfurizer wet oxidation desulfurization process. The syngas desulfurization adopts the secondary desulfurization process, and the primary desulfurization adopts the MNHD solvent absorption desulfurization process. The sulfur content of the tower gas is ≤2mg/Nm3. ； The secondary desulfurization adopts ZnO dry fine desulfurization process, and the sulfur content of the syngas is ≤0.1PPM.

The desulfurization liquid we use is made of soda ash + tannin extract. You can add some 888 appropriately.

The refined desulfurization methods used to produce methanol from coke oven gas should be NHD method and low-temperature methanol washing method.

Dry iron-manganese zinc oxide is what our company uses

Coke oven gas rough desulfurization uses tannin + PDS, hydrogen sulfide is less than 20mg/m3. For the fine desulfurization part of the coal gas, the first stage of activated carbon desulfurization is used, and then the two-stage hydrogenation conversion and the two-stage dry desulfurization (iron-manganese, zinc oxide) are used. After conversion, the first stage of fine desulfurization is performed.

What is the difference between these two methods and which one is better? Can you be more specific?

The methanol synthesis catalyst used in methanol production is easily poisoned by sulfides and loses activity. The sulfides in the coke oven gas must be removed. The sulfur in the methanol feed gas can exist in various forms of sulfur-containing compounds, such as hydrogen sulfide (H2S), carbon oxysulfide (COS), carbon disulfide (CS2), mercaptan (RSH), thioether (RSR'), cyclic sulfide (such as thiophene C4H4S), etc. Wet desulfurization technology is mainly used for the removal of hydrogen sulfide, and can only be used for primary desulfurization. The hydrogen sulfide content in the desulfurized gas can generally only reach 20 to 50 mg/Nm3. To achieve the accuracy of methanol synthesis, a solid fine desulfurization system must be connected. 1) Wet crude desulfurization: Wet desulfurization can be divided into three categories: physical absorption method, chemical absorption method and direct oxidation method. Among them, the most important one is wet oxidation desulfurization technology. At present, the desulfurization methods that are widely used and have good performance include PDS method, modified ADA method, copy glue method, tea ash method, MSQ method, modified hydroquinone method, and RCA method. (1) PDS method: The PDS desulfurization technology developed by Northeast Normal University passed the technical appraisal of Jilin Provincial Science and Technology Commission in 1986. Currently, there are hundreds of production units across the country using this technology, which is used for the desulfurization of semi-water gas, shift gas, natural gas, methanol synthesis gas, and coke oven gas. This method requires extremely low catalyst concentration, low consumption, economical operation, non-toxic catalyst, simple use method, can be used alone, no need to add other "cocatalysts", and good desulfurization effect (according to the data, the efficiency of H2S removal by the PDS method is ≥90%, and the removal of organic sulfur is 40-50%). (2) Improved ADA law: The improved ADA method is a technology developed abroad in the 1960s and has been widely used in the chemical fertilizer, city gas, and metallurgical industries. The improved ADA method has mature technology, perfect process, high degree of standardization, and good technical and economic indicators. However, the main problem of this method is that sulfur blocks the desulfurization tower packing. (3) Copy glue method: In 1976, the Guangxi Chemical Industry Research Institute successfully developed the glue-coating desulfurization technology. It has almost all the advantages of the improved ADA method, and there is no sulfur blocking phenomenon. Because the glue is rich in resources and cheap and easy to obtain, its operating cost is lower than that of the improved ADA method. It is often used in coke oven gas-moisture desulfurization. The disadvantage is that the desulfurization liquid requires a complicated preparation process before it can be added to the system. In 1986, the Guangxi Chemical Industry Research Institute successfully developed the KCA desulfurizer. Its desulfurization performance is very similar to that of the glue agent. KCA can be added directly to the system during use. Since cheap price-changing metal salts are added to the KCA desulfurizer, the desulfurization cost can be reduced. (4) Other methods: The MSQ method, which uses manganese sulfate, salicylic acid, and hydroquinone to form a desulfurization liquid, and the tea ash method, which uses benzene polyphenols and NaNO3 to form a desulfurization liquid, have also achieved good desulfurization effects in small synthetic ammonia plants. 2) Dry refined desulfurization: There are mainly physical adsorption methods and chemical adsorption methods. (1) Adsorption method: a. Iron oxide method: Belongs to chemical adsorption method. The iron oxide method has wide sources of raw materials and is cheap. It mainly removes H2S in the raw gas but cannot remove organic sulfur. The operating temperature is low (generally operated at room temperature), and the working sulfur capacity of the desulfurizer is large (generally up to 25-30%). However, the desulfurization accuracy is limited (generally it can be desulfurized to about 1ppm). b. Zinc oxide method: It is a classic, widely used, technically mature and reliable method. It is also a chemical adsorption method. It mainly removes H2S in gas, and it is difficult to remove organic sulfur. The operating temperature is generally 250 to 400°C. The desulfurizer has a large working sulfur capacity (generally up to 30%) and high desulfurization accuracy (can be less than 0.1ppm). With the advancement of technology, room temperature zinc oxide desulfurizers have been developed in recent years, but the working sulfur capacity decreases rapidly as the operating temperature decreases. The disadvantage is that the desulfurizer is more expensive. c. Activated carbon method: It is a physical adsorption method that can remove H2S and most organic sulfides. It has the advantages of normal temperature operation, high purification, large air velocity, and regeneration. However, it has low sulfur capacity and high regeneration energy consumption. It is generally used in situations where trace amounts of organic sulfur are controlled. (2) Transformation-absorption method: a. Manganese ore method: Manganese ore can partially convert organic sulfur and has the function of absorbing hydrogen sulfide. It is cheap and has an operating temperature of 300 to 400°C. Its disadvantages are that the purification degree is not high (generally it can only remove total sulfur to ≤3~5mg/Nm3), the sulfur capacity is too low (generally it can only reach 6~8%), its life is short, it cannot be regenerated, and it is prone to side reactions. b. Composite desulfurizer: Represented by the MF series desulfurizer developed by Sichuan Science and Technology Co., Ltd., it can not only convert organic sulfur, but also absorb the hydrogen sulfide generated by the conversion. It has high desulfurization accuracy (can be less than 0.1ppm) and is not expensive. The disadvantage is that when the CO and H2 content is too high (such as water gas), there are more carbonylation reactions and the temperature is difficult to control. ； In addition, the sulfur content is not very high (generally only 12 to 16%). This method is widely used in natural gas refined desulfurization. c. Cobalt molybdenum + zinc oxide: It can convert various organic sulfides into hydrogen sulfide, and is especially suitable for treating gases containing thiophene. The hydrogen sulfide generated by conversion is removed with zinc oxide. The operating temperature is 350~430℃, the operating pressure is 0.7~7.0MPa, and the airspeed is 500~2000/h. The hydrogenation catalyst can be regenerated, but it cannot be used in situations containing CO, CO2 and other carbonylation side reactions that are prone to carbonylation side reactions (such as coke oven gas, water gas, etc.), and it is more expensive. d. Iron-molybdenum + manganese ore method: It is commonly used in small fertilizer plants that use coke oven gas as raw material, and the operating temperature is 300 to 400°C. The iron-molybdenum catalyst first converts the organic sulfur in the gas into H2S, which is then absorbed by the manganese ore. The organic sulfur removal efficiency is about 90%. The iron-molybdenum + manganese ore method for desulfurization has the advantages of being cheap and readily available raw materials, but the purification degree of manganese ore is not high, the sulfur capacity is too low, the life is short, it cannot be regenerated, and it is prone to side reactions. It can be used in small and medium-sized fertilizer and methanol plants. However, when used on large installations, the manganese ore tank is either designed to be very large, making it difficult to transport the equipment for processing. ； Either the manganese ore desulfurizer is replaced frequently, causing difficulties in production and management. Manganese ore must be restored before being put into use, making production management troublesome. In addition, because the sulfur content is too low, waste manganese ore after a large amount of use must be disposed of in a yard, which brings great difficulties to the treatment of three wastes. e. Iron molybdenum + zinc oxide: It is similar to the iron-molybdenum + manganese ore method, but the absorption of the hydrogen sulfide generated by the conversion is completed by the zinc oxide desulfurizer, which fully takes advantage of the large sulfur capacity of the zinc oxide desulfurizer, but the zinc oxide desulfurizer is more expensive. This method is suitable for use on large installations. In view that the wet desulfurization of coking has removed H2S in the coke oven gas to less than 100mg/Nm3, this project plans to adopt the following desulfurization measures: first step: In order to reduce the consumption of high-temperature solid desulfurizer, normal temperature iron oxide desulfurizer is used to remove H2S in coke oven gas to less than 1 mg/Nm3 at normal temperature and pressure. Step 2: Before the coke oven gas is pressurized into the reformer, at a temperature of 350 to 400°C, iron-molybdenum catalytic hydrogenation is used to convert organic sulfur + ZnO desulfurizer to remove the total sulfur in the coke oven gas to less than 3 mg/Nm3, reaching a content that the second-stage reforming catalyst can withstand. Step 3: After pure oxygen conversion, almost all the remaining organic sulfur in the coke oven gas is converted into H2S, which is absorbed by ZnO at room temperature to make the total sulfur in the syngas ≤0.1ppm.

AS desulfurization + atmospheric desulfurization + NHD desulfurization technology and dry desulfurization remove inorganic sulfur and most organic sulfur components in coke oven gas. Dry desulfurization uses iron-molybdenum hydrogenation conversion, and then dry desulfurization through manganese ore and zinc oxide to desulfurize the total sulfur to less than 0.1ppm.

A large state-owned factory has three-stage desulfurization, the first-stage desulfurization using ammonia water as an alkali source and ordinary wet desulfurization, the second-stage sodium carbonate as an alkali source wet desulfurization, and the third-stage zinc oxide dry desulfurization.

When treating methanol with coke oven gas, it is necessary to ensure that the sulfur content of the synthesis gas imported into the synthesis tower is ≤0.1ppm, so as to ensure the life of the synthesis catalyst. This can be done in two steps. The first step is to use wet desulfurization for rough desulfurization. Our company uses the "modified ADA method"”； The second step uses dry desulfurization. Our company uses the "iron molybdenum + zinc oxide method". The specific method used will depend on the specific circumstances of the company.