Methanol, production recirculation rate

By separating the recycle compressor from the makeup compressor, the amount of recycle can be varied independently of the makeup compression required. Makeup gas compression is most dependent upon production rate. Recycle is most dependent upon methanol synthesis catalyst activity. As the catalyst deactivates, more and more recirculation is required. With a separate recycle compressor the recycle compression step operates efficiently over the full range of flow. When the recycle compressor is connected to the makeup compressor, the combined unit must operate inefficiently part of the time. It is somewhat more costfy to have two separate compressors, but for efficiency reasons a separate recirculation compressor is normally chosen. Having a separate reeyele eompressor can also be beneficial for synthesis catalyst reduction purposes. 

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