Is two-stage condensation necessary?
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I have a question for the seniors. In production, a reaction kettle is used to evaporate the solvent, and now two-stage condensation (two spiral cooling systems in series) is used. The first one uses cooling water, and the second one uses frozen brine. I would like to ask, is it necessary, or can one-stage condensation (larger area) replace two-stage condensation?
1. The temperature outlet of the cooled solvent needs to be accurate. 2. The temperature of the cooling water or frozen brine needs to be increased due to the next step. 3. The environmental conditions at the reactor outlet are required.
The original poster should explain the relevant temperature, as mentioned above.
Of course, because the first uses cooling water and the second uses chilled brine. These are two media with different cold capacities, which are reasonable utilization of cold capacity. If only cooling water is used, the purpose will not be achieved, and the cost of using only frozen brine will be too high.
If it is just to completely cool the gas phase, then the two condensers should be connected in parallel (the cold brine cools the first-stage condenser without cooling the gas phase). After being connected in series, the energy consumption of the cold brine will increase (if the process requires cryogenic cooling of the solvent, it can be connected in series) In fact, whether to connect in series or parallel depends on factors such as the boiling point of your solvent. If the boiling point is high and normal cooling water cannot condense it, then cold brine must be used for series cooling. If the cooling water can completely condense the solvent, you can consider a heat exchanger with a large heat exchange area or two-stage condensation. It is mainly based on your actual process conditions: handshake
The main reason for using secondary cooling is to rationally utilize the coolant and try to use economical coolant. In general, if the previous design used secondary cooling with different coolants, it is not feasible or economical to combine the two into one by increasing the heat exchange area. However, for process control, the use of secondary cooling is often disadvantageous. Either the condensed materials must be processed separately or mixed, but the purity of the mixed materials is often out of control, especially for intermittent processes. If you have the conditions, don’t engage in secondary cooling just to save some money. I personally think that secondary cooling is not cost-effective.
Mainly a question of cooling effect and cost! ! ! ! Single-stage cooling requires higher ice machine capacity than multi-stage cooling, which involves the cost of purchasing a high-power single ice machine and multi-stage cooling at different temperatures.
Technically, it is possible, but costs must be considered, which requires detailed analysis.
Thank you all for your answers. In fact, the problem I am talking about is mainly about solvent recovery by steaming the reactor in the workshop. I have not calculated the specifics. They are all based on previous experience. I can't say anything else.