Cb = total chloride concentration in the boiler water

Boiler blowdown requirements are dictated by the limits on total allowable dissolved solids concentration in boiler water; by the economics of heat transfer for the boiler system; and by the methods of disposal or treatment for recovery of blowdown stream (Hamer, Jackson, and Thurston 1961). Blowdown may be intermittent or continuous. For intermittent blowdown, volumes are small, dissolved solids are controlled by frequency and duration of blowdown, and settled sludge is properly removed. Continuous blowdown is preferable because it provides steady control of dissolved and suspended solids concentration in boiler water. It can be used if the continuous blowdown rate is above the minimum of 200 l/hr (1 gpm). Heat recovery is also easier with continuous blowdown. Intermittent blowdown, however, is still required at longer intervals to remove sludge accumulation. Antifoam agents permit higher dissolved solids concentrations in the boiler, decreasing the rate of blowdown.

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