Patent EA-000771-B1 (EA)
Title: A method and apparatus for removing gaseous elementary mercury from a gas
Inventor: ALLGULIN TORKEL
IPC: B01D53/78
Filed: 1998-05-22
Abstract: 1. A method of removing gaseous elementary mercury from a gas that can be permitted to contain sulphur dioxide, in which method the gas is treated in a washing tower with washing liquid that circulates in a closed system and that contains 0.01-300 mmol/l mercury (II) ions and at least twice this amount of chloride ions, and in which the elementary mercury present in the gas is oxidized and solid mercury (I) chloride is formed, characterized by passing a part of said formed solid mercury (I) chloride to a reaction unit for oxidation to mercury (II) chloride; causing chlorine intended for said oxidation and liquid intended for taking-up mercury (II) ions formed by said oxidation process to pass up through a reaction zone in the bottom part of the reaction unit, said zone being kept substantially full of solid mercury (I) chloride; adapting said quantity of chlorine so that said chlorine will be essentially consumed during its passage up through the reaction zone; uniting the liquid and its content of formed mercury (II) ions with the washing liquid present above said reaction zone; and thereafter passing the so united washing liquid with its increased mercury (II) content to the closed circulating system to be recycled to said washing tower as a compensation for the mercury (II) ions consumed for the oxidation of elementary mercury. 2. A method according to claim 1, characterized by delivering chlorine and liquid to the reaction zone from beneath said zone. 3. A method according to claim 1, characterized by delivering chlorine and liquid to the reaction zone from above said zone, through pipes and/or hoses that open out close to the bottom of said reaction zone. 4. A method according to claims 1-3, characterized by monitoring the calomel content of the reaction unit essentially continuously. 5. A method according to claims 1-4, characterized by controlling the amount of chlorine delivered per unit of time on the basis of the mercury (II) ion concentration in the washing liquid in the closed system. 6. A method according to claims 1-5, characterized by effecting oxidation in the reaction unit essentially continuously. 7. A method according to claims 1-6, characterized by taking from the liquid circulating system a sub-flow of washing liquid for the reduction of mercury (II) ions, preferably with zinc powder, such as to form mercury (I) chloride (calomel) which is separated from the system, wherewith a purified bleed can be taken out. 8. Apparatus for effecting the method according to preceding claims, characterized in a washing tower (11) and a reaction unit (26) having a smaller cross-section than the tower (11) connected to the bottom of the tower (11) and having conduits and means for maintaining a closed circuit system of washing liquid from a liquid outlet (41) in the lower part of the tower (11) to a liquid inlet (40) in the upper part of the tower (1 1), wherein the lower part (42) of the washing tower (11) below the level of the liquid outlet (41) has a tapering cross-section for adaptation to the reaction unit (26) and wherein the reaction unit (26) in its lower part (26B) is arranged for supplying oxidation agent and liquid. 9. Apparatus according to claim 8, characterized in that the washing tower (11) below the level of the washing liquid outlet (41) has means (45) for preventing any horizontally or rotationally liquid flowing.