A 15% sodium hydroxide solution at 80 F is to be concentrated in a single-effect evaporator per hour to produce a 45 % thick liquor. The capacity of the evaporator is 0.75 lb/s. The vapor space of the evaporator is to be at 4 psia and the saturated steam to be used is at 120 psia. The overall heat transfer coefficient is estimated to be 175 BTU/h-ft^2-F. Calculate the steam used (kg/h), steam economy, and heating surface area.

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