Method of spray drying and washing and method of controlling air pollution

A method of spray drying and washing using a spray drying apparatus,

• when spray-drying is performed, comprising:
• spraying dehydrated filtrate supplied from a dehydrator via a dehydrated filtrate feed line, from a spray nozzle hung down from a top side of the spray drying apparatus into a spray drying apparatus body;
• introducing a part of flue gas into an introduction port of the spray drying apparatus to dry the dehydrated filtrate sprayed from the spray nozzle and thereafter discharging the part of flue gas from a discharge port of the spray drying apparatus;
• introducing a compressed air via a first air feed line into the spray nozzle to facilitate the spraying and into a wash nozzle provided on an inside wall of the spray draying apparatus via a second air feed line to perform air purging during the spray drying;
• and
• detecting spray failure or dry failure by a detection unit, and
• when washing the spray nozzle is performed in a case that the spray failure or the dry failure is determined as a result of the detecting, comprising:
• suggesting and instructing by a controller to stop feeding of the dehydrated filtrate to the spray nozzle, stop inflow of the flue gas into the spray drying apparatus, stop the introduction of the compressed air to the wash nozzle and thereafter feeding washing liquid to the wash nozzle via a washing liquid feed line branched from the filtrate feed line, and jet the washing liquid from the wash nozzle to wash the spray nozzle and an inside of the spray drying apparatus body.