Boiler water quality and reuse

Abstract

The objective of this work was to evaluate the quality of water coming from the boiler and to propose ways of reusing water from purging processes, discharge of safety valves and bottom discharge of boilers. It was proposed to reuse the purge discharge water and the boiler safety valves to return to the production process and to design a reservoir for the bottom discharge to irrigate the roofs of the industry. To check the water quality of a fogotubular boiler, safety valves and purge, analyzes of the following variables were performed: temperature, total alkalinity, bicarbonate alkalinity, carbonate alkalinity, hydroxide alkalinity, electrical conductivity, total dissolved solids , total hardness, chlorides, total iron, residual chlorine and pH. Three temperature analyzes were carried out with a dry bulb thermometer in triplicate in the period of the greatest insolation of the day, with the system in use and in disuse, in order to verify the irrigation efficiency on the roof after reuse. As for the proposed reuse, the process proved to be satisfactory, complementing the sustainability base, with the reuse of this water in the boiler itself with a temperature of approximately 70 to 80°C. It was observed a cost reduction due to lower water consumption, since previously water from the concessionaire was used at room temperature and less energy expenditure for heating water for vaporization, that is, less use of raw wood material (reduction of 3.5 m³ of firewood to 2 m³). The average monthly water expenditure would be 87 m³ x 3.7088 = R $ 320.684 - 30% = R $ 96.21 in savings for reusing the bottom discharge water and safety valves. The average expenditure of firewood per day was 3.5 m³ - 2.0 m³, started to save 1.5 per day after reusing the water from the bottom discharge and safety valves, 1.5 m³ x 30 days = 45 m³ x R $ 55.00 = R $ 2,475.00 of savings per month. Regarding the variables of the safety valve and traps, pH and total alkalinity are outside the limits established by the technical specifications. It was concluded that the purge discharge water and the boiler safety valves that reach approximately 70 to 80°C can be reused in the boiler itself with consequent saving of firewood and water, however, it is necessary to proceed to a treatment with the addition of lime and/or caustic soda, according to USI analysis.