references
Reading time:Zong Tian He Chuan (Inner Mongolia, China)
the problem:
Zong Tian He Chuan is a large carbochemical site producing methanol and olefin bases. A zero liquid discharge solution was selected so as to minimise the environmental impact of the industrial site’s environmental impact and to limit the use of the region’s water resources which are already under stress. The condensates produced should have a concentration level in dissolved salts of less than 100mg/l and a dry content of salts higher than 80%.
solution selected:
Two-stage crystallization under forced circulation with a capacity of 26m3/day with thermal stream compression. Condensate is cooled down to 35°C by indirect cooling and transferred to a polishing stage. The salts are rehydrated centrifugally. This is a zero liquid discharge type installation.
Four West Mine (Pennsylvania, USA)
problem:
Four West Mine is an existing coal mine where the salinity of mine water can be as high as 10g/l. This saline water cannot be disposed of in the natural environment without prior treatment. A solution therefore had to be implemented in order to partially remove these salts.
solution selected:
Mine effluent (110m3/h) is pretreated using a physico-chemical treatment process, then filtered and then concentrated through membrane osmosis. The brine resulting from osmosis is transferred to a single-effect, 11m3/h crystallizing unit whose energy is supplied by a mechanical steam compression system. Condensates are cooled down by the feed brine through indirect heat exchangers then mixed with osmosis permeates before being discharged into the river. The salts are centrifugally dehydrated.
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