Measurement of the propylene content in dual-US AA absolute methanol and energy consumption issues in the 3-tank process in actual production
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A few days ago, I went to the Second Design Institute of the Ministry of Chemical Industry and met a project manager; I discussed two issues with him. 1. The AA standard in the United States requires that the propylene content in pure methanol be less than 10PPM. He said that it is basically difficult to determine the propylene content in pure methanol in China, which means that it may not be possible to meet the AA standard. 2. The energy consumption in the energy-saving design scheme for the three-tower process is often lower than that achieved after the system is operating stably in practice; for example, the designed energy consumption is 1 ton of steam per ton of purified methanol, but the actual energy consumption after stable operation is higher than 1 ton. I’d like netizens or experts working on the production front to discuss this.
Our two production lines do not meet the double-A standard, and such a high requirement was probably not taken into account during the design phase. For units that produce using steam, it doesn’t really matter much whether the amount of steam used is more or less, as the measurement of steam consumption in many such units is not very accurate; in some cases, the calculations of both production and consumption are highly inaccurate.
Regarding the second question, I would like to say a few things: Making comparisons is difficult, as different factories have different designs, operating conditions, compositions of crude alcohol, steam quality, and heat utilization conditions; it’s hard to determine which one has lower energy consumption or is more suitable for a given company. For some companies, two towers or even just one tower is more appropriate for them. In terms of energy savings, I believe the dual-effect three-tower system is more energy-efficient; however, it requires a higher pressure for steam, its condensate temperature is also high, and it does not make full use of the heat from the steam. Now the David Five-Tower process has emerged again; each process has its own characteristics, advantages, and disadvantages. When making a choice, it is essential to determine which one is more suitable for one’s own needs. Only the method that suits one’s situation can help save energy and improve efficiency; otherwise, energy-saving devices cannot function effectively, and energy savings will not be achieved.