Desalination of sub-soil brine using Exhaust gas heat of Diesel Engine

Abstract

At little Rann of Kutch, underground water is brackish water and the whole landis salty. In Gujarat Maximum amount of salt is produced at Kutch, 50% of salt isproduced in the sea coastal from Gulf of Kutch to Khambhat, 20% of salt is comingfrom the Little Rann of Kutch. Approximately 50,000 workers are working in saltfarms at Little Rann of Kutch. At the salt farms `Agarias', these salt makers live forve months in the hot, dry and salty atland.Generally, the salt farms are located in the remote desert (Gulf area) without basicfacilities such as electricity, transportation, etc. In these areas, the available groundwater is salty (brine) which is a gift of nature for salt manufacturers. However,this invites the other diculty with challenges for survival due to scarcity of drinkingwater. The salt producers sometimes have to travel long distances in search of potablewater. Occasionally, drinking water is provided through tankers from sources far awayfrom the salt farms. The supply, unfortunately, is not always regular. There is thusa need for an alternative and more dependable solution.Techniques of desalination such as reverse osmosis and electrodialysis are good so-lutions when the water has salinity below that of seawater but become impracticalsolutions when the salinity of water is high as is the case with most sub-soil brines.Moreover, being in distant locations, salt farms often do not have electricity connec-tion whereas power is required to drive the above units.Solar stills have been used occasionally in salt farms to convert the saline water intodrinking water. In such stills the average production rate is around 0.8 liters persquare meter per sun hour. These could not become much popular in salt farms dueto their low productivity.Diesel engines are used to run pumps in salt works mainly to pump the sub-soilbrine from high depths. Invariably all salt workers in places such as the Little Rannviof Kutch possess such diesel engines to conduct their work of producing salt. Theexhaust gas of a typical diesel engine is emitted at temperatures in excess of 150Cand no use is made presently of this energy in such salt works. The present workdiscloses the design of a device which enables this energy to be utilized gainfully forthe production of potable water from highly saline brines at a rate far in excess ofthat achievable through a solar still of similar size. The experimental data shows theunit designed able to produce 1.3 lit distilled (potable) water per hour. The samplesof water collected show TDS 200 ppm with 8.1 pH value.