3.7 A process requires pure water which can be produced satisfactorily either by

Question

3.7 A process requires pure water which can be produced satisfactorily either by distillation or by ion exchange using activated resins.The cost of installation for a distillation unit is $8000 with operating costs of $1.00 per 1000 gal of water produced. The ion-exchange installation costs $2.00 per galon per hour feed rate, and suitable resins cost $1.00 per pound. After operating the ion-exchange system to produce pure water for 1 hour it is necessary to regenerate the resins for 20 minutes before pure water can be obtained again. resin needs may be considered as 1 pound per 10,000 gallons of treated water, and operating costs are $0.40 per 1000 gallons. Based on present worth, determine which installation is more economical for a water duty of 1,000gal/h. Assume 8400 h/year operation and 10 year life for both interet at 12 percent.

Explanation / Answer

Annual requirement= 8400*1000=8400000 gallons/year Distillation Ion Exchange Installation 8000 $2/1000*8400000 16800 Annual costs: Operating cost 1/1000*8400000 8400 0.4/1000*8400000 3360 Annual depn. 800/10 800 16800/10 1680 Resins 1/10000*8400000*$1 840 Total Annual cost 9200 5880 Present worth of options Distillation Ion-Exchange Installation costs 8000 16800 PV of annual costs Ie. @ PV F 12%,10 yrs.5.650 9200*5.650 51980 5880*5.650 33222 Total Present Worth 59980 50022 ION EXCHANGE is more ECONOMICAL as Present worth of the costs are lesser compared to the distillation option.

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