Using hot flue gas as heat source, help in designing ammonia evaporator
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This post was last edited by yggswl on 2019-12-20 16:14: Using hot flue gas as the heat source, the design of ammonia evaporator requires a flue cross-section size of 2 meters. * 4 meters, flue gas temperature 220℃, flue gas volume 200,000 standard cubic meters/hour. Ammonia concentration for denitration is 20% ； The flow rate is 300-500kg/h, and all ammonia and water evaporate ； We are going to make and install a tubular heat exchanger (316L) in the flue section. The ammonia water goes through the pipe side, low in and high out, and the flue gas goes through the shell side (i.e. the flue). Ammonia enters the heat exchanger in liquid form at the bottom. After being heated and vaporized by the hot flue gas, a mixed gas of ammonia and water vapor is generated. The gas outlet temperature is ≥120°C. There are several questions:: 1. Is this process feasible? 2. Because ammonia evaporates, will the pressure of the mixed gas be too high, causing a safety accident? 3. Approximately how much will the smoke temperature drop? 4. What are the main issues to pay attention to when designing this equipment? 5. Prepare to use a metering pump to automatically adjust the amount of ammonia water. 6. What are the design options for the inlet and outlet pipe diameters of the heat exchanger and the pipe diameter of the heat exchanger? The ammonia water inlet is selected as DN25 according to the metering pump. 7. Seek cooperation from equipment manufacturers, thank you.
It involves 200,000 cubic meters of flue gas per hour. It is best to find a qualified designer. I have no design capabilities. A brief introduction for reference. The flue gas flow rate is close to 7m/S. The area occupied by this heat exchanger on the flue gas section cannot be too large so as not to affect the flue gas. It is estimated that it will be difficult to heat the ammonia water to 120°C. A single cross-section should not be enough. It is possible to set up a long pipe parallel to the flue gas. If the outlet pressure relief capacity is sufficient, the problem of ammonia water vaporization and pressure increase should not be big.
It is recommended to make a snake-type fin heat exchanger, with n groups connected in parallel. The tube diameter and number of groups are subject to the gas flow rate within the appropriate range after all the ammonia is vaporized. You can find the equipment manufacturer to design and manufacture it. Control the ammonia water inlet flow during use
The pressure at the ammonia outlet pressure relief point is relatively low (<10000Pa) and the pipe diameter is relatively large (>400mm), so the ammonia pressure relief capacity is sufficient
This process is not feasible. Generally, ammonia evaporators can be purchased directly. The heat source is hot air or steam. Hot air or steam can directly dilute the evaporated ammonia to prevent the ammonia concentration from reaching the explosion limit.
The explosion limit of the evaporated ammonia mixture must be considered and corresponding measures must be taken. Moreover, there are many kinds of ammonia evaporators on the market, and you can choose accordingly according to your subsequent process.
20% ammonia water is to enrich and recover ammonia, not to evaporate and dilute it to discharge
If possible, I would also like to ask this question.
The process is not good and the evaporator type is wrong.； The second question does not appear ； The required flue gas volume of 300kg/h is about 3000Nm3, and the temperature reaches 150℃, otherwise it will not evaporate dry. If necessary, you can send a private message