Abstract: A heating vessel for concentration is formed in an elongated one, and a baffle plate is arranged to increase sulfuric acid liquid concentration at an outlet to a high level. The heating vessel for concentration and a heating vessel for distillation are installed so that the respective heating vessels have substantially the same waste sulfuric acid liquid level therein, forming continuous flow of the sulfuric acid liquid without presence of a valve or an intermediate tank in a connecting pipe. The heating vessel for distillation is formed in an elongated one with a baffle plate arranged therein to increase the impurity concentration included in concentrated sulfuric acid liquid at an outlet to a high level.

Abstract: Fluorine-containing water is treated by contacting the fluorine-containing water with calcium carbonate to react the fluorine in the fluorine-containing water with the calcium carbonate and fix it as calcium fluoride. After the fluorine-containing water is contacted with the calcium salt in the reaction tank to react the fluorine in the fluorine-containing water with the calcium salt and fix it as calcium fluoride, it is subjected to solid/liquid separation, and the treated water is removed while a portion of the sludge concentrated by the solid/liquid separation is returned to the reaction tank.

Abstract: A system for discharging gas emitted from an apparatus or facility having a vacuum pump which sucks the gas emitted from the apparatus or facility while being supplied with a gas other than the sucked gas, the system comprising a unit for recovering at least part of the gas discharged from the vacuum pump, and recirculating the recovered gas to the vacuum pump as the gas other than the sucked gas. Part of the recovered gas may be recirculated to the apparatus or facility emitting the gas. The system reduces or eliminates emission to the atmosphere of global warming gases such as perfluorocompounds discharged from the vacuum pump, and also reduces the energy required for operating the vacuum pump. A method for discharging gas emitted from an apparatus or facility using a vacuum pump, wherein emission of global warming gases to the atmosphere is reduced or eliminated, is also disclosed.

Abstract: A heating vessel for concentration is formed in an elongated one, and a baffle plate is arranged to increase sulfuric acid liquid concentration at an outlet to a high level. The heating vessel for concentration and a heating vessel for distillation are installed so that the respective heating vessels have substantially the same waste sulfuric acid liquid level therein, forming continuous flow of the sulfuric acid liquid without presence of a valve or an intermediate tank in a connecting pipe. The heating vessel for distillation is formed in an elongated one with a baffle plate arranged therein to increase the impurity concentration included in concentrated sulfuric acid liquid at an outlet to a high level.