Sewage sludge digestion tank heating system - controlled by adjusting hot water circuit through heat exchanger

摘要

Heating system for digestion tanks transfers heat from a hot water circuit with a heating boiler to the circulating sewage sludge in a heat exchanger. When the sludge absorbs more heat, the drop in the returning hot water temperature to a lower critical value is compensated by reducing its flow rate through the heat exchanger by a bypass. When the return temperature rises above an upper critical temperature, the hot water flow rate is adjusted to maintain the desired temperature of the circulating sludge. This is a reliable way of preventing the hot water temperatures from dropping below the critical figure of 65 deg.C and of eliminating any thermal shocks in the digestion tank when fresh sludge is charged.