METHOD FOR PRODUCING BY-PRODUCT SALT

• Main Authors: HIRATA SHUICHI, KOBAYASHI TAKASHI, MIYOSHI FUMIHIRO
• Format: Patent
• Language: English; Japanese
• Published: 01.03.2018
• Subjects: CHEMISTRY; COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM,RUBIDIUM, CAESIUM, OR FRANCIUM; INORGANIC CHEMISTRY; METALLURGY; PERFORMING OPERATIONS; PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL; SEPARATION; TRANSPORTING; TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

PROBLEM TO BE SOLVED: To provide a method for producing by-product salts where sodium chloride and potassium chloride in a mixed treatment water treating exhaust gas are recovered as by-product salts.SOLUTION: A method for producing by-product salts comprises: a first fluorine removal step 23 where sodium hydroxide is added to mixed treatment water to precipitate calcium fluoride, and further, a carbonate source is added to the mixed treatment water, and the calcium fluoride and the calcium carbonate are co-precipitated so as to be separated away; a concentration step 24 where a concentrated mixed treatment water is generated from the mixed treatment water; a second fluorine removal step 25 where sodium hydroxide and a carbonate source are added to the concentrated mixed treatment water to further co-precipitate the calcium fluoride and the calcium carbonate so as to be separated away; an evaporation crystallization step 26 where the concentrated mixed treatment water is heated to crystallize out the sodium chloride; a sodium chloride separation step 27 where the crystallized-out sodium chloride-containing salt slurry is subjected to solid-liquid separation; a cooling crystallization step 28 where the separated liquid is cooled to crystallize out potassium chloride; and a potassium chloride separation step 29 where the crystallized-out potassium chloride-containing salt slurry is subjected to solid-liquid separation.SELECTED DRAWING: Figure 1 【課題】排ガスを処理する混合処理水中の塩化ナトリウムと塩化カリウムを副生塩として回収する副生塩の製造方法を提供する。【解決手段】混合処理水に水酸化ナトリウムを添加してフッ化カルシウムを析出するとともに、混合処理水に炭酸源を添加してフッ化カルシウムと炭酸カルシウムとを共沈させ分離除去する第一フッ素除去工程２３と、混合処理水から濃縮混合処理水を生成する濃縮工程２４と、濃縮混合処理水に水酸化ナトリウムと炭酸源を添加してさらにフッ化カルシウムと炭酸カルシウムとを共沈させ分離除去する第二フッ素除去工程２５と、濃縮混合処理水を加熱し塩化ナトリウムを晶析する蒸発晶析工程２６と、晶析した塩化ナトリウムを含む塩スラリを固液分離する塩化ナトリウム分離工程２７と、分離した分離液を冷却し塩化カリウムを晶析する冷却晶析工程２８と、晶析した塩化カリウムを含む塩スラリを固液分離する塩化カリウム分離工程２９とを有する。【選択図】図１