How to calculate the steam consumption during the heating-up phase of starting up low-pressure methanol synthesis
Thread Content
Question: During the commissioning of low-temperature methanol synthesis (taking an annual production capacity of 100,000 tons of methanol as an example), the energy required is generated by superheated steam. This heat is used, in my understanding, to raise the temperature of the catalyst, the reducing gases, and the water inside the synthesis tower. Those who have experience in this process could please explain in detail how the amount of steam needed is calculated? Thank you. Feel free to reply or contact me via email at zhaoyy98@163.com
During reduction, an estimated power of 50–100 kW per cubic meter of catalyst can be used, which can then be converted into the corresponding steam consumption. The pressure of the water (drum) inside the tower needs to be increased; otherwise, some heat will be used to produce steam.
:) Thank you for the reminder; I really hadn’t noticed the pressure issue of the water inside the synthesis tower. By using 1 cubic meter of catalyst and a power output of 50–100 kW, I can estimate the heat required per hour. I can find out the enthalpy value of the steam at the initial state; the heat required is equal to the initial enthalpy of the steam minus its enthalpy at the final state. Since the process of heating and reducing using steam is not clear, it is unknown what the final state will be.
I would also like to ask you about the heating process; for example, at the very beginning when the start-up steam is introduced, is the water in the synthesis tower at room temperature? Then steam is introduced using a injector; how does the temperature of the water inside the tower change at this point?
At first, normal-temperature deionized water was used, and later the temperature of the deionized water gradually increased as the pressure in the synthesis tower’s drum rose.
Since the temperature of the desalinated water rises as the pressure in the synthesis tower’s drum increases, and this temperature keeps changing, it is not possible for me to determine the state of the system after steam is added when calculating the amount of steam required. As a result, it is impossible to use enthalpy values for calculations. Moreover, it’s unlikely that only steam will be introduced into the synthesis tower and the drum without any water being removed; presumably, an equal amount of water will be removed for every amount of steam introduced.