Dual purpose power/water plants utilizing both distillation and reverse osmosis

The energy consumption of several alternate dual purpose plants are compared for application in the range of 10–50MW with 1 to 20 MGD water production. This shows that the combined gas turbine-steam turbine system is considerably more energy efficient than a steam only system. Single stage R.O., used in conjunction with this combined cycle offers the minimum overall energy consumption but has the disadvantage of producing product water with high TDS. By utilizing both R.O. and distillation, energy consumption lower than with distillation alone is achieved and product water purity is acceptable. p]A specific design of a combined dual purpose plant is presented. This plant would have a net electrical output of 29,050 kw and 3.25 MGD of 440 ppm TDS, requiring 297.1 BTU/hr. The total capital costs of this combined plant is estimated at $41,150,000 and annual operating costs at $15,087,000. The unit production costs with fuel at $2.50/MM BTU would be 4.08¢/kw-hr and $2.44 per 1000 gal. This represents an annual savings of $1,961,000 over single purpose production or 44.5% reduction in water production costs with the same electrical production costs. p]It is concluded that the combined dual purpose plant presented is the most efficient, economical and flexible method of producing power and water in the range of 10 to 50 MW and 1 to 20 MGD.