Steam Boiler Surface Blowdown (Cycles of Concentration)

The steam leaves TDS-free, so the feedwater solids must exit in the blowdown at the max boiler-water concentration. Cycles of concentration CoC = boiler-water TDS limit / feedwater TDS; blowdown rate = steam rate x feedwater TDS / (limit - feedwater TDS); as a share of feedwater it is 1/CoC. A 10,000 lb/hr boiler on 100 ppm feedwater held to 3,500 ppm runs at 35 cycles and blows down about 294 lb/hr (2.9% of feedwater); cleaner makeup raises the cycles and cuts the blowdown and its heat loss. Every pound blown down is hot treated water lost -- a flash vessel and heat exchanger recover some. Steady-state surface blowdown only; bottom (mud) blowdown, the treatment program, the ASME/manufacturer limits, and a licensed operator govern. Distinct from cooling-tower makeup water.

cycles_of_concentration = max_boiler_tds / feedwater_tds; blowdown_rate_lb_hr = steam_rate x feedwater_tds / (max_boiler_tds - feedwater_tds); blowdown_pct_of_feedwater = 100 x feedwater_tds / max_boiler_tds = 100 / CoC.

Steam-boiler surface-blowdown TDS mass balance (cycles of concentration), by name; the ASME / manufacturer boiler-water limits and the treatment program govern the actual schedule.

The TDS mass balance is public first-principles (steam leaves solids behind, blowdown removes them); the feedwater TDS, the boiler-water TDS limit, and the steam rate come from the water analysis and the boiler rating.

Estimate. AHJ and licensed professional govern.

Field names used by the API: steam_rate_lb_hr, feedwater_tds_ppm, max_boiler_tds_ppm, cycles_of_concentration, blowdown_rate_lb_hr, blowdown_pct_of_feedwater

• TDS mass balance steam leaves TDS-free; CoC = BW_limit/FW_TDS; blowdown = steam x FW/(BW-FW); % of feedwater = 1/CoCboiler water-treatment practice
• Surface blowdown only steady-state continuous (surface) blowdown; bottom/mud blowdown, alkalinity/silica limits, and a licensed operator govern the scheduleASME / manufacturer boiler-water limits