Some discussions on the purposes of hot and cold blowing in sulfur-based acid production

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3 1 Some considerations regarding hot and cold blowing in sulfur-based acid production: 1. The purpose of hot blowing is primarily to keep the vanadium catalyst above its ignition temperature (400°C for domestic catalysts, 380°C for foreign catalysts). This allows any remaining SO2 in each catalyst layer to be converted into SO3, which can then be blown together with the remaining SO3 in the catalyst layer into the dry absorption section for absorption. This prevents the catalyst layer temperature from dropping too low, which could lead to SO3 accumulating within the catalyst or in downstream equipment, resulting in the formation of condensed acid and causing catalyst caking as well as corrosion of downstream equipment. 2. The purpose of cold blowing is that, after hot blowing is completed, there is a small amount of SO2 remaining in the converter catalyst; cold blowing is used to remove any unreacted SO2 along with SO3 from the converter, thereby facilitating easier inspection, replacement, and screening of the catalyst. 3. In our system, hot and cold blowing are carried out by burning diesel, expelling exhaust gases, and using blowers to dry the air before it enters the preheater for indirect heat exchange, followed by entry into stages 1, 3, and 4 for hot and cold blowing. At the same time, cold exchange is utilized to reduce heat loss, allowing the air to return directly to stage 4. II. Key points: 1. The hot blowing temperature must be carefully controlled; this is primarily determined by the size of the oil nozzles in the preheating furnace and the control of air flow. 2. The air that has been dried and heated in the preheating furnace enters the converter, and the air pressure must be high enough so that it can penetrate the converter and thus ensure an effective purging effect. 3. The air that has been dried and heated in the preheating furnace enters the converter; it is important that the flow rate of this air be sufficient to maintain a constant temperature, otherwise the process will take too long and this will affect the effectiveness of the purging. 4. It is best to first ensure that stages 1 and 2 are thoroughly purged before proceeding to purge stages 3 and 4. 5. The acceptable standard for successful purging through hot and cold blowing is that the SO2 and SO3 levels at the outlet of each stage should be less than 0.05%, indicating that the purging has been successful. 6. For the transition from hot blowing to cold blowing, the oil pressure should be reduced gradually until an increased air flow is used for purging. Keep the purging rate around 30–40°C; cold purging can be stopped once the temperatures at various sections at the converter outlet drop to 80°C. I hope that all the experts here can offer their valuable suggestions and opinions. If there are better methods for hot and cold blowing, please send them to 489559071@qq.com so that we can share knowledge. Thank you very much! Sulfuric Acid Xiaobai urgently needs the help and support of experts.