Abstract: A gas treatment apparatus for treating a gas by bringing the gas into contact with a treatment liquid. The gas treatment apparatus includes a gas-liquid contact chamber for a gas-liquid contact of the gas with the treatment liquid, a storage chamber, located over the gas-liquid contact chamber, for storing the treatment liquid, and a treatment liquid supplying unit for supplying the treatment liquid stored in the storage chamber to an inside of the gas-liquid contact chamber with a gravity-drop.

Abstract: A polyisocyanate production method that can allow effective use of hydrogen chloride produced secondarily in a polyisocyanate production process, while allowing reduction of environmental burdens, and a polyisocyanate production system for performing the polyisocyanate production method. After chlorine is allowed to react with carbon monoxide to produce carbonyl chloride in a carbonyl chloride producing reactor, the carbonyl chloride produced in the carbonyl chloride producing reactor is allowed to react with polyamine in an isocyanate producing reactor to produce polyisocyanate. Then, after hydrochloric gas produced secondarily in the isocyanate producing reactor is purified in a hydrogen chloride purifying column, the purified hydrochloric gas is oxidized in a hydrogen chloride oxidizing reactor to produce chlorine.

Abstract: A polyisocyanate production method that can allow effective use of hydrogen chloride produced secondarily in a polyisocyanate production process, while allowing reduction of environmental burdens, and a polyisocyanate production system for performing the polyisocyanate production method. After chlorine is allowed to react with carbon monoxide to produce carbonyl chloride in a carbonyl chloride producing reactor, the carbonyl chloride produced in the carbonyl chloride producing reactor is allowed to react with polyamine in an isocyanate producing reactor to produce polyisocyanate. Then, after hydrochloric gas produced secondarily in the isocyanate producing reactor is purified in a hydrogen chloride purifying column, the purified hydrochloric gas is oxidized in a hydrogen chloride oxidizing reactor to produce chlorine.

Abstract: A polyisocyanate production system is provided that can stably produce chlorine from hydrogen chloride produced secondarily while reacting stably between carbonyl chloride and polyamine and can perform an effective treatment of the hydrochloric gas produced secondarily. A hydrochloric gas control unit 32 controls a flow-rate control valve 23 to keep constant an amount of hydrogen chloride supplied from a hydrogen chloride purifying tank 4 to a hydrogen chloride oxidation reactor 6 via a second hydrochloric-gas connection line 11 to be constant, and also controls a pressure control valve 22 based on an inner pressure of the hydrogen chloride purifying tank 4 input from a pressure sensor 25 to discharge the hydrochloric gas from the hydrogen chloride purifying tank 4 to the hydrogen chloride absorbing column 5 via a first hydrochloric-gas connection line 10, so as to keep an inner pressure of the hydrogen chloride purifying tank 4 to be constant.

Abstract: A gas treatment apparatus for treating a gas by bringing the gas into contact with a treatment liquid. The gas treatment apparatus includes a gas-liquid contact chamber for a gas-liquid contact of the gas with the treatment liquid, a storage chamber, located over the gas-liquid contact chamber, for storing the treatment liquid, and a treatment liquid supplying unit for supplying the treatment liquid stored in the storage chamber to an inside of the gas-liquid contact chamber with a gravity-drop.

Abstract: A polyisocyanate production method that can allow effective use of hydrogen chloride produced secondarily in a polyisocyanate production process, while allowing reduction of environmental burdens, and a polyisocyanate production system for performing the polyisocyanate production method. After chlorine is allowed to react with carbon monoxide to produce carbonyl chloride in a carbonyl chloride producing reactor, the carbonyl chloride produced in the carbonyl chloride producing reactor is allowed to react with polyamine in an isocyanate producing reactor to produce polyisocyanate. Then, after hydrochloric gas produced secondarily in the isocyanate producing reactor is purified in a hydrogen chloride purifying column, the purified hydrochloric gas is oxidized in a hydrogen chloride oxidizing reactor to produce chlorine.

Abstract: A polyisocyanate production system is provided that can stably produce chlorine from hydrogen chloride produced secondarily while reacting stably between carbonyl chloride and polyamine and can perform an effective treatment of the hydrochloric gas produced secondarily. A hydrochloric gas control unit 32 controls a flow-rate control valve 23 to keep constant an amount of hydrogen chloride supplied from a hydrogen chloride purifying tank 4 to a hydrogen chloride oxidation reactor 6 via a second hydrochloric-gas connection line 11 to be constant, and also controls a pressure control valve 22 based on an inner pressure of the hydrogen chloride purifying tank 4 input from a pressure sensor 25 to discharge the hydrochloric gas from the hydrogen chloride purifying tank 4 to the hydrogen chloride absorbing column 5 via a first hydrochloric-gas connection line 10, so as to keep an inner pressure of the hydrogen chloride purifying tank 4 to be constant.

Abstract: A cleavage method of bisphenols capable of yielding a product containing high-purity isopropenylphenol and phenol is disclosed, including (1) a cleavage step of supplying the mixture containing bisphenols together with chroman derivatives and flavan derivatives formed as by-products in the production process of bisphenols to a cleaving vessel and carrying out a cleavage reaction in the presence of a basic or acidic catalyst at a temperature of from 150 to 260° C. under a reduced pressure condition of not higher than 300 mmHg, (2) a distillation step of supplying the cleavage step product formed in the cleavage step in a vapor state to a distillation column and distilling at a temperature of from 130 to 200° C. under a reduced pressure condition of not higher than 300 mmHg, and (3) a reflux step of condensing the distillate from the distillation step, refluxing a part thereof to the distillation step at a reflux ratio of from 0.01 to 3, and discharging out the residue from the system.