The problem of two-effect distillation of methanol
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I’ve been working on a calculation for methanol distillation recently, and the vapor consumption always exceeds the required level. I haven’t considered two-effect distillation yet; I hope to obtain satisfactory results. Does anyone have examples of calculations using two-effect distillation? Or, let’s talk about how double-effect distillation is actually carried out Thanks first
You can try adding a throttle valve behind the heat exchanger
Could the expert explain in more detail? I’m a bit at a loss as to where to start
It should be to control an appropriate heat transfer temperature difference
To ensure achievement of the low energy consumption target of tons of steam per ton of methanol, the following points need to be considered: 1. Use the steam condensate from the pre-tower reboiler to preheat the crude alcohol feed； 2. The discharge from the pressurized reactor bottom is used to preheat the feed to the pressurized reactor ； 3. The gaseous fraction resulting from the flashing of the steam condensate in the pressure column reboiler is incorporated into the steam line of the pre-column reboiler ； 4. The thermal coupling of the pressurized column and the atmospheric column (recovery ratio, heat loss, etc.) is considered together.
Double-effect distillation involves using the vapor from the top of a tower operating at a higher pressure to heat the bottom of another tower operating at a lower pressure; the key is to ensure proper pressure and energy matching. Pressure matching is essentially temperature matching, and adjustments need to be made during simulation; generally, the temperature difference between the top of the high-pressure tower and the bottom of the low-pressure tower should be around 15–20 degrees ； Energy matching, which refers to the allocation of material extraction, also needs to be adjusted in the simulation; by adjusting the amount of material extracted, it is ensured that the thermal load on the condenser of the high-pressure tower is slightly greater than the thermal load on the reboiler at the bottom of the low-pressure tower (taking heat losses into account). To make full use of energy, the liquid from the high-pressure tower bottom is generally required to exchange heat with the liquid from the low-pressure tower bottom.
The condenser of the pressurized tower is used as the reboiler for the atmospheric pressure tower; a control module is employed to manage the thermal coupling. It is not necessary for the concentrations of the distillates at the tops of both towers to be identical – the two streams can be mixed together, and an optimizer is used to determine the optimal combination of methanol concentrations at the tops of the two towers