Where does the water used in methanol production go?
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Most of the data available so far indicate that more than 10 tons of water are consumed per ton of methanol produced. So where does all this water go? From a material balance perspective, the amount of water used in the gasification reaction and shift processes should be relatively small. Even if it is assumed that all the hydrogen in methanol comes from water, then 1.125 tons of water are required per ton of methanol. Therefore, the remaining water is likely to be used for heat exchange with the gasifier, as well as for other cooling purposes and in boiler operations. This water can be reused and is not completely consumed. Even taking into account losses due to circulating cooling water, steam leaks, and wastewater discharge, the amount of water used still does not reach 8 or 9 tons! Where does the water used in methanol production go? I’m a beginner who is struggling; I earnestly ask for guidance from all the experts out there
The water consumed includes wastewater that needs to be discharged, water lost through evaporation, water lost as steam, as well as the water that is added to the system to participate in reactions, as you mentioned
The main sources of water consumption are evaporation from cooling towers, as a large amount of water vapor is released during vaporization; there’s also wastewater from boilers, and the cooling water used for pumps usually ends up in drainage systems without being recycled. Our water consumption per ton is roughly 8.
The water consumption you mentioned is probably water vapor – it’s the vapor used in methanol distillation!
Reply to 4# kya15: This steam turns into condensate and returns to the system. What exactly does this refer to regarding where the water that cannot be recovered goes?
The water consumption in methanol synthesis is mainly the consumption of cooling water. Whether in a cyclic or non-cyclic mode, an appropriate amount of water is required for cooling. The water consumption in methanol production is a quantitative metric; it does not mean that such an amount of water disappears. Rather, it means that if the required amount of cooling water is not available, the cooling requirements cannot be met. As for whether the water is fresh water or treated recycled water, this is not part of the consideration regarding water consumption in methanol production.
The water consumption is less than 10 tons; it’s around 3 tons, with the main components being reaction water, evaporated water, and wastewater. As environmental regulations and wastewater treatment technologies advance, the amount of wastewater generated is very small, while reaction water and evaporated water remain the main components.
It seems that there is wastewater discharge from both the bottom of the synthesis tower and the drum!