Abstract: A method for sorbing a gas using an ionic liquid to sorb a vapor having an electric multi-pole moment. The ionic liquid comprises an anion and a cation. The electric multi-pole moment may be an electric dipole moment and/or an electric quadru-pole moment. The sorption may be an adsorption or an absorption. The ionic liquid may be a liquid that substantially contains only anions and cations, while not containing other components, such as water. Alternatively, a solution containing the ionic liquid and a solvent or further compound, such as water, may be used.

Abstract: Apparatus and processes for saturating and purifying syngas are provided. In one or more embodiments, the apparatus can include two packed beds through which water and syngas flow countercurrently. In the first bed, the syngas can be at least partially saturated with water, and in the second bed hydrocarbons, byproducts, or both can be removed from the syngas. Processes for saturating and purifying syngas using the apparatus discussed and described herein are also provided.

Abstract: Systems and methods are described for removing chlorides from a SOx-containing flue gas upstream of a flue gas desulfurization system. A wet sprayer can be configured to contact at least a portion of the SOx-containing flue gas with a first solution to produce (1) a SOx-containing treated flue gas that is substantially depleted of chlorides, and (2) a chloride solution product. The treated flue gas can then be fed into a flue gas desulfurization system, which allows the downstream components to comprise less-expensive materials because of the depletion of chlorides in the treated flue gas.

Abstract: The present invention provides a method and apparatus for the treatment of process gas from an anaerobic digestion system or a landfill gas system. In one embodiment, the system comprises a caustic scrubber including a vertical column having a top and a bottom and including a counter current flow system, wherein a process gas stream flows up vertically through the column in counter current flow to a caustic liquid solution that flows downward through the column. The caustic liquid solution removes at least one acid from the process gas stream, wherein treated gas that is substantially free of acids bubbles out through an opening at the top of the vertical column.

Abstract: It is intended to provide methods of producing a chlorine gas having a small bromine content, an aqueous sodium hypochlorite solution having a small bromic acid content, and liquid chlorine having a small bromine content. More specifically, a chlorine gas is produced by a method comprising the steps of: (A) washing a chlorine gas that contains bromine, in a gas washing unit composed of a packed column or a tray tower, wherein the chlorine gas introduced via a lower part of the gas washing unit is brought into counterflow gas/liquid contact with a liquid chlorine introduced via an upper part of the gas washing unit; and (B) taking out a purified chlorine gas thus washed, via the upper part of the gas washing unit, wherein a weight ratio of the chlorine gas and the liquid chlorine introduced in the step (A) is 1/1.0 to 1/0.3.

Abstract: The invention relates to a gas liquid contactor and effluent cleaning system and method and more particularly to individually fed nozzle banks including an array of nozzles configured to produce uniformly spaced flat liquid jets shaped to minimize disruption from a gas. An embodiment of the invention is directed towards a gas liquid contactor having a plurality of modules including a liquid inlet and outlet and a gas inlet and outlet. An array of nozzles is in communication with the liquid inlet and the gas inlet. The array of nozzles is configured to produce uniformly spaced flat liquid jets shaped to minimize disruption from a gas flow and maximize gas flow and liquid flow interactions while rapidly replenishing the liquid.

Abstract: An ionic liquid solvent and gas purification method using the same are provided. The ionic liquid solvent consists of a main absorbent, a regulator for the main absorbent, an auxiliary absorbent, an activator, an antioxidant and water. The ionic liquid involves a low synthetic cost, low viscosity and high absorption capacity, and can be easily regenerated and recycled. The method, compared with traditional processes, has advantages such as a greater absorption capability and lower operation cost.

Abstract: This invention provides novel compositions comprising substituted polyamines as acid gas scrubbing solutions and methods of using the compositions in an industrial system. The invention relates to the use of such polyamine compounds in industrial processes to remove acidic contaminants from natural and industrial fluid streams, such as natural gas, combustion gas, natural gas, synthesis gas, biogas, and other industrial fluid streams. The compositions and methods of the invention are useful for removal, absorption, or sequestration of acidic contaminants and sulfide contaminants including CO2, H2S, RSH, CS2, COS, and SO2.

Abstract: The present invention provides a method and apparatus for the treat en of process gas from an anaerobic digestion system or a landfill gas system. In one embodiment, the system comprises a caustic scrubber including a vertical column having a top and a bottom and including a counter current flow system, wherein a process gas stream flows up vertically through the column in counter current flow to a caustic liquid solution that flows downward through the column. The caustic liquid solution removes at least one acid from the process gas stream, wherein treated gas that is substantially free of acids bubbles out through an opening at the top of the vertical column.

Abstract: In a method of treating a gas stream, an aqueous scrubbing liquor is circulated through an essentially closed loop (20) comprising an electrochemical unit (48) for reducing the acidity of the liquor. A portion of the circulating liquor is diverted away from the closed loop (20) to a gas scrubbing unit (10). The gas stream enters the scrubbing unit (10), wherein an acid, for example HF and solid particulates, for example SiO2 particulates, within the gas stream dissolve in the diverted liquor. The diverted liquor is subsequently returned to the closed loop (20), and is replenished in the scrubbing unit (10) by fresh liquor diverted from the closed loop (20). A device (46) is provided for monitoring the acidity of the liquor at a location within the closed loop (20). The reduction in the acidity of the liquor by the electrochemical cell (48) is controlled depending on the monitored concentration.

Abstract: A method is described for treating a gas stream containing a flammable gas, such as hydrogen or a hydrocarbon gas. The gas stream is conveyed to a liquid ring pump (18), to which a gaseous oxidant and water are supplied. The water and the gas stream are discharged from the pump (18), with the discharged gas stream being subsequently separated from the liquid, and conveyed to a pyrolysis device (42) for pyrolysing the flammable gas and the oxidant. Any particulates and acidic species within the gas stream are retained by the water within the liquid ring pump to inhibit corrosion or blockage of the pyrolysis device (42). A filter or other device (40) may be provided to remove water from the gas stream before it enters the pyrolysis device (42).

Abstract: A method and apparatus for recovering a gaseous component from an incoming gas stream is described. The incoming gas stream is contacted with a lean aqueous absorbing medium to absorb at least a portion of the gaseous component from the incoming gas stream to form a lean treated gas stream and a rich aqueous absorbing medium. At least a portion of the gaseous component is desorbed from the rich aqueous absorbing medium at a temperature to form an overhead gas stream and a regenerated aqueous absorbing medium. At least a portion of the overhead gas stream is treated to recover a condensate stream. At least a portion of the condensate stream is used to form a heated stream. At least a portion of the heated stream is recycled back to the desorbing step. Novel absorbing medium compositions to recover carbon dioxide and/or hydrogen sulfide are also described.

Abstract: A two phase reactor includes a source of liquid reactant and a source of gas reactant. A chamber has an inlet coupled to the source of gas reactant and a flat jet nozzle coupled to the source of the liquid reactant.

Abstract: Gas mixtures containing HF, HCl or HBr and other constituents, in particular gas mixtures containing carboxylic acid fluorides, C(O)F2 or phosphorus pentafluoride and HCl and possibly HF, can be fractionated by means of ionic liquids.

Abstract: Chlorine is absorbed in water from gas streams of nitrogen, oxygen, argon, helium and mixtures thereof, in which process the formation of hypochlorous acid is suppressed through the regulated addition of hydrogen peroxide, and hydrochloric acid is formed.

Abstract: The invention relates to a gas liquid contactor and effluent cleaning system and method and more particularly to an array of nozzles configured to produce uniformly spaced flat liquid jets with reduced linear stability. An embodiment of the invention is directed towards a stability unit used with nozzles of a gas liquid contactor and/or an enhancer for stable jet formation, and more particularly to reducing the stability of liquid jets formed from nozzles of the gas liquid contactor. Another aspect of the invention relates to operating the apparatus at a condition that reduces the stability of liquid jets, e.g., a droplet generator apparatus. Yet another aspect of the invention relates to operation of the apparatus with an aqueous slurry. Still another aspect of the invention is directed towards to an apparatus for substantially separating at least two fluids.

Abstract: A separation, purification and recovery method of SF6, HFCs or PFCs is disclosed, which comprises a step for forming a gas hydrate including components in addition to SF6, HFCs or PFCs. It is possible to separate and recover fluoro-gas at a much lower cost as compared to a conventional method for thereby obtaining an economical effect and preventing an emission of SF6, HFCs or PFCs which corresponds to Non-CO2 having a higher earth warming index, which leads to preventing an earth warming phenomenon. So, the present invention might be widely applied.

Abstract: A method of use of an ionic liquid for sorption of a gas having an electric multipole moment is provided, wherein the ionic liquid comprises an anion and a non-aromatic cation. In particular, the electric multipole moment may be an electric dipole moment and/or an electric quadrupole moment. The sorption may be an adsorption or an absorption. The ionic liquid may be a pure ionic liquid, i.e. a liquid substantially only containing anions and cations, while not containing other components, e.g. water. Alternatively a solution containing the ionic liquid and a solvent or further compound, e.g. water, may be used.

Abstract: Methods and systems for the destruction of one or more PFCs in a gas stream are provided. The gas stream can come from semiconductor processing, for example. The PFCs in the gas stream are reacted with steam in the presence of a catalyst to fragment the PFCs into other compounds that are readily removed from the gas stream. The catalyst comprises gallium, and can additionally comprise zirconium oxide. The gas stream can also be pre-treated prior to reacting the PFCs with steam to remove substances that could be deleterious to the catalyst.

Abstract: It is intended to provide methods of producing a chlorine gas having a small bromine content, an aqueous sodium hypochlorite solution having a small bromic acid content, and liquid chlorine having a small bromine content. More specifically, a chlorine gas is produced by a method comprising the steps of: (A) washing a chlorine gas that contains bromine, in a gas washing unit composed of a packed column or a tray tower, wherein the chlorine gas introduced via a lower part of the gas washing unit is brought into counterflow gas/liquid contact with a liquid chlorine introduced via an upper part of the gas washing unit; and (B) taking out a purified chlorine gas thus washed, via the upper part of the gas washing unit, wherein a weight ratio of the chlorine gas and the liquid chlorine introduced in the step (A) is 1/1.0 to 1/0.3.

Abstract: A method for removing chloride from samples containing volatile organic carbon, wherein a chloride containing sample is mixed with a difficultly volatile acid, wherein hydrochloric acid gas arises, which is present in dissolved form in a sample-acid mixture and then the hydrochloric acid gas is purged by a carrier gas from the sample-acid mixture, wherein the hydrochloric acid gas is removed from the carrier gas following the purging and the carrier gas is fed back to the sample-acid mixture. In order during the hydrochloric acid purging largely to suppress the driving out of easily volatile organic compounds, the sample-acid mixture has a temperature of approximately 3° C. to 30° C., wherein, following the purging from the sample-acid mixture, the hydrochloric acid gas is removed from the carrier gas by absorption with water.

Abstract: Chlorine is absorbed in water from gas streams of nitrogen, oxygen, argon, helium and mixtures thereof, in which process the formation of hypochlorous acid is suppressed through the regulated addition of hydrogen peroxide, and hydrochloric acid is formed.

Abstract: A method for scrubbing a halogen-containing gas, comprises contacting the halogen-containing gas with water at a temperature of at least 30° C., the gas optionally subsequently being subjected to a further treatment step comprising contacting it with water at a temperature of less than 30° C. and/or a gas dilution step. An apparatus for carrying out the method comprises a hot wash chamber (6) and optionally a cold wash chamber (7) and/or a gas dilution device (13).

Abstract: The invention relates to an improvement in apparatus and process for the formation of a complex of Lewis acidic or Lewis basic gases in a reactive liquid of opposite character and for the breaking (fragmentation) of said complex associated with the recovery of the Lewis gas therefrom. The improvement resides in forming finely divided droplets of reactive liquid and controlling the temperature, pressure and concentration of said Lewis gas of opposite character to provide for (a) the formation of said complex between said gas and reactive liquid or (b) the breaking of said complex and the recovery of the atomized droplets of reactive liquid.

Abstract: The invention relates to a gas liquid contactor and effluent cleaning system and method and more particularly to individually fed nozzle banks including an array of nozzles configured to produce uniformly spaced flat liquid jets shaped to minimize disruption from a gas. An embodiment of the invention is directed towards a gas liquid contactor having a plurality of modules including a liquid inlet and outlet and a gas inlet and outlet. An array of nozzles is in communication with the liquid inlet and the gas inlet. The array of nozzles is configured to produce uniformly spaced flat liquid jets shaped to minimize disruption from a gas flow and maximize gas flow and liquid flow interactions while rapidly replenishing the liquid.

Abstract: A method for removing fluorine gas from a selected environment comprises contacting the fluorine gas with water to generate a solution of hydrofluoric acid and contacting the solution of hydrofluoric acid with an ion exchange resin having an active state operative to exchange selected ions therein for fluoride ions in the solution. The apparatus (200) may include a dual resin setup (222, 223) such that one of the ion-exchange resin can be in the service cycle while the other of the ion-exchange resins undergoes the regeneration and rinse/refill cycles.

Abstract: Gas mixtures containing HF, HCl or HBr and other constituents, in particular gas mixtures containing carboxylic acid fluorides, C(O)F2 or phosphorus pentafluoride and HCl and possibly HF, can be fractionated by means of ionic liquids.

Abstract: A separation, purification and recovery method of SF6, HFCs or PFCs is disclosed, which comprises a step for forming a gas hydrate including components in addition to SF6, HFCs or PFCs. It is possible to separate and recover fluoro-gas at a much lower cost as compared to a conventional method for thereby obtaining an economical effect and preventing an emission of SF6, HFCs or PFCs which corresponds to Non-CO2 having a higher earth warming index, which leads to preventing an earth warming phenomenon. So, the present invention might be widely applied.

Abstract: Bromine is scrubbed from a gaseous mixture of bromine and hydrogen bromide by passing the mixture into a mixture formed from (i) diphenylethane and/or partially brominated diphenylethane with average bromine number less than about 2 and (ii) a catalytic quantity of iron and/or iron halide in which the halogen atoms are bromine atoms and/or chlorine atoms. Component (i) is brominated, and during such bromination, the mixture is kept hot enough to melt the organics to provide a liquid phase in the scrubber. Gaseous mixtures of bromine and hydrogen bromide are formed in processes of the invention in which decabromodiphenylethane products are produced using the partially brominated diphenylethane as feed to the bromination, which is conducted using an aluminum-based catalyst. Effective ways of removing iron catalyst residues from partially brominated diphenylethane or from decabromodiphenylethane product are also described.

Abstract: The present invention relates to a system and method for the recycling of sulfur hexafluoride (SF6), from a waste gas of a manufacturing process, such as a semiconductor processing method. In particular, the present invention provides a simplified system and method that utilizes additional SF6 as a purge gas for the system pump and allows relatively easy separation of the SF6 from the other waste gas components.

Abstract: A process for producing a solution of a gas in a liquid in which the gas is soluble, the solution having a predetermined concentration up to saturation. The gas and the liquid are brought together under controlled supply in a proportion corresponding to the predetermined concentration of the solution, and the gas and the liquid are caused to form a stream passing through a common conduit. The gas and the liquid in the stream are caused to intermix under the action of gravity, and the intermixing is repeated before the gas and the liquid have separated, so that the gas is substantially absorbed in the liquid, forming a gas-liquid solution of the predetermined concentration. The stream may be brought into turbulence for intensifying the intermixing of the gas and the liquid. An apparatus for performing the process comprises a conduit including a continuous tubular coil formed with a plurality of upwardly and downwardly directed sections.

Abstract: Methods for recovering and recycling helium and unreacted chlorine from a process for manufacturing optical fiber are disclosed. Helium-rich and chlorine-rich gas streams are recovered from the consolidation furnace and separated. The helium-rich stream is dried and blended with make-up helium and the chlorine-rich stream is purified and blended with make-up chlorine so that each may be reused in the optical fiber production process.

Abstract: An elimination process of fluorinated anionic sufactants from exhausted gaseous streams, wherein the gaseous stream is put into contact with aqueous solutions having in the range from 3.5 to 13.8, the aqueous solution density being lower than 1.05 g/cm3, wherein the concentration in the aqueous solution of the fluorinated anionic surfactant removed by the gaseous stream is lower than or equal to 70 ppm.

Abstract: The present invention relates to a process for preparing largely HBr-free HCl gas and largely HBr-free aqueous HCl solution, which comprises the following steps: a) providing HBr-containing HCl gas; b) passing the HBr-containing HCl gas through aqueous HCl solution saturated with HCl; c) separating off HBr-containing aqueous HCl solution saturated with HCl; d) if desired, passing the largely HBr-free HCl gas obtained in step b) into water to obtain largely HBr-free aqueous HCl solution; with largely HBr-free aqueous HCl solution produced in step d) being able, if desired, to be recirculated to step b) of the process. The process of the present invention allows high-purity aqueous HCl solution for use in the semiconductor industry to be prepared inexpensively and on an industrial scale. However, the purified HCl gas obtained by means of steps a) to c) can also be used for any other purposes. The invention likewise provides an apparatus for carrying out the process of the present invention.

Abstract: An exemplary method and apparatus for abating reaction products from a vacuum processing chamber includes a reaction chamber in fluid communication with the vacuum processing chamber, a coil disposed about the reaction chamber, and a power source for supplying RF energy to the coil. The coil creates a plasma in the reaction chamber which effectively breaks down stable reaction products from the vacuum processing chamber such as perfluorocarbons (PFCs) and hydrofluorocarbons (HFCs) which significantly contribute to global warming. According to alternative embodiments, the plasma may be generated with grids or coils disposed in the reaction chamber perpendicular to the flow of reaction products from the vacuum processing chamber.

Abstract: In accordance with the invention, there is provided a method of binding a gas or volatile compound in a cucurbituril, by contacting the gas or volatile compound with the cucurbituril to form a cucurbituril-gas/volatile complex. There is also provided a method of separating a gas or volatile compound from a mixture of compounds wherein the mixture is contacted with a cucurbituril and whereby at least some of the gas or volatile compound is bound to the cucurbituril to form a cucurbituril complex, followed by the release of at least some of the bound gas or volatile compound from that complex. The present invention is thus advantageous in that it allows use of cucurbiturils in binding gases and volatile compounds for storage, safety, delivery or other uses, such as the trapping of an unpleasant or toxic gas or volatile compound.

Abstract: This invention relates to a novel method, which can be carried out according to industrial standards, for producing high-purity hydrochloric acid with a very low particle content, for use in the production of semiconductors.

Abstract: A process for removing chlorine gas from the tail gas stream of a chlor/alkali plant or other chemical processes comprising the steps of: (a) contacting a chlorine-, hydrogen-, and carbon dioxide-containing tail gas stream with a zeolite molecular sieve having a molecular pore diameter greater than the molecular diameter of the carbon dioxide and hydrogen and smaller than the molecular diameter of chlorine so that at least a portion of the carbon dioxide is absorbed onto the molecular sieve, and thereby producing a purified tail gas stream that contains substantially all of the chlorine and hydrogen values and a reduced amount or no amount of carbon dioxide values; and (b) contacting the purified tail gas stream with an aqueous sodium hydroxide scrubbing solution in order to remove substantially all of the chlorine values from the purified tail gas stream, whereby producing a purified sodium hypochlorite solution that is substantially free of sodium carbonate.

Abstract: An elimination process of fluorinated anionic sufactants from exhausted gaseous streams, wherein the gaseous stream is put into contact with aqueous solutions having in the range from 3.5 to 13.8, the aqueous solution density being lower than 1.05 g/cm3, wherein the concentration in the aqueous solution of the fluorinated anionic surfactant removed by the gaseous stream is lower than or equal to 70 ppm.

Abstract: Hydrogen chloride gas contaminated with foreign hydrogen halides may be purified by a process comprising selectively absorbing the foreign hydrogen halide in an absorption medium, preferably water or an aqueous hydrogen chloride solution. To minimize the mass flow of the foreign hydrogen halide loaded absorption medium which is discharged from the process, the absorption medium is preferably conveyed countercurrent to the gas in at least two coupled circuits in the absorber.

Abstract: Provided are ionic purifiers and methods that are suitable for providing an ultra-high-purity chemical to a semiconductor manufacturing process. The ionic purifiers include a vapor inlet introducing a chemical vapor to be purified into a column. A high-purity water inlet continuously introduces high-purity water into the column. The high-purity water contacts the chemical vapor to be purified, thereby forming a purified chemical vapor and contaminated water. A vapor outlet removes the purified chemical vapor from the column. A liquid outlet removes the contaminated water from the column. The invention has particular applicability in the semiconductor manufacturing industry.

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: Hydrogen fluoride production apparatus removes phosphate rock dust from a hot gas mixture exhausted from a phosphate rock defluorination kiln; cools the hot gas mixture in a heat exchanger to a low enough temperature that it can be brought into contact with acid-resistant polymeric materials without destroying them; uses a water spray scrubber for further cooling the gas and absorbing the fluoride values as HF-rich liquor; and pumps the HF liquor to a holding tank. One such plant uses a gas tube steam boiler as the heat exchange and has several series-connected scrubbers to extract the fluorine values from the kiln exhaust so that the residual gas mixture can be exhausted into the atmosphere without exceeding permissible fluorine value levels. In this arrangement water is fed into the scrubber furthest from the boiler to extract HF from the process gas, and an HF-laden process liquor is fed out of the furthest scrubber into the second furthest scrubber, where it is sprayed into the gas stream.

Abstract: A process for recovering metal from spent catalyst, containing at least a metal component, comprising providing a heated, liquid metal bath, at a temperature sufficient to melt the metal in the spent catalyst, and create off gas from any volatile non-metal catalyst components, adding spent catalyst to the bath, collecting off gas from the bath, transporting the collected off gas to a gas cooler, and maintaining the off gas during the transportation at a temperature of at least about 875.degree. F.; rapidly cooling the off gas to less than about 275.degree. F. in no more than about 0.15 seconds, to prevent the formation of dioxin; and withdrawing melted metal from the bath, for reuse as catalyst.

Abstract: Disclosed is a method of removing chlorine from a mixture of gases. The mixture of gases is contacted with dichlorotoluene, whereby chlorine in the mixture of gases is absorbed by the dichlorotoluene. The dichlorotoluene is separated from the mixture of gases and is heated to desorb the chlorine and separate it from the dichlorotoluene.

Abstract: A hydroprocessing process includes two hydroprocessing reaction stages, both of which produce a liquid and a vapor effluent, and a liquid-vapor contacting stage. The first stage vapor effluent contains impurities, such as heteroatom compounds, which are removed from the vapor by contact with processed liquid effluent derived from one or both reaction stages and, optionally, also liquid recovered from processed vapor. The first and contact stage liquid effluents are passed into the second stage to finish the hydoprocessing. The contact and second stage vapor effluents are cooled to recover additional hydroprocessed product liquid.

Abstract: A silane-containing gas is treated by contacting it with a liquid containing silanes or disilanes which are higher boiling than the silanes in the silane-containing gas, thereby easily removing or reducing the amount of silanes in the gas and enabling the recovery of these silanes.

Abstract: One or more contaminants selected from the group consisting of acidic gases, inert particulates, and mixtures thereof are removed from steam by contacting the contaminated steam with a nonaqueous sorbent such as crystalline molecular sieves, silica gels, soda ash, carbonaceous adsorbents, and amine liquid ion exchange resins.

Abstract: A recirculating fume scrubber system in which fume is evolved from an aqueous bath in a process vessel, such as an HCl pickling tank, and the evolved fume is scrubbed with water and then the scrubbed gas is divided into two portions, one of which is released to a stack vented to atmosphere and the other portion is recirculated to the scrubber.

Abstract: A process for separating chlorine of high purity from a chlorine-containing feed gas by absorption of the chlorine using an inert absorbent and downstream desorption of the chlorine from the absorbent/chlorine mixture drawn off from the absorption stage by the supply of mixture to a desorption distillation column which is coupled to a chlorine separation column in such a way that the top of the chlorine separation column and an upper section of the desorption distillation column and a lower section of the desorption distillation column and the bottom of the chlorine separation column are connected to one another on both the gas and the liquid side, the absorbent/chlorine mixture being supplied exclusively to the desorption distillation column, and high-purity chlorine being drawn off from a middle region of the chlorine separation column.