Patent GB-1466218-A (GB)
Title: Method and apparatus for neutralizing waste gases
IPC: B01D53/60
Filed: 1975-06-06
Abstract: 1466218 Treating waste gases; activating alkali metal carbonates CESKOSLOVENSKA AKADEMIE VED 6 June 1975 [12 June 1974 2 Aug 1974] 24372/75 Heading C1A Acidic components of a waste gas are removed by contact of the humid gas at 100-200‹ C. with an active carbonate prepared by heating at 30-200‹ C. in a stream of air, waste gas from a previous treatment or a mixture of waste gas with air a material selected from MHCO 3 ; MHCO 3 .MgCO 3 . y H 2 O; and  x MHCO 3 .M 2 CO 3  where M is an alkali metal, x is an integer 1-3, y is an integer between 0 and 4 or a mixture of two or more of these compounds until the carbonate is free of hydrates. The starting material may be activated in a fluidized or fixed bed with a gas having a maximum water vapour partial pressure defined by the equation wherein p is the partial pressure of water vapour gas (Torr units) and t is the gas temperature in ‹ C. After activation, the carbonate is preferably left prior to contact for a time up to 30 minutes at up to 112‹ C. in a medium having a water vapour partial pressure equal to or above that satisfying the above equation or in a medium at 112-350‹ C. In the preferred process the humid waste gas is passed in the direction of gravity through a layer of the activated carbonate of particle size of 100- 5000 microns upon a gas permeable wall in a layer of thickness -200 mm. and after treatment a transport gas is passed in the opposite direction through the layer to suspend and remove the particles and further active material in an amount corresponding to the required thickness is brought in the direction of gravity by a stream of carrier gas to the partition wall for treatment with further gas. A suitable apparatus comprises at least one couple of vertical cylindrical multifloor reactor vessels 1, 1<SP>1</SP> with a shaft in its axis connected by a transmission gear to a motor 19, each of the reactors containing at least two gas tight chambers 2, 2<SP>1</SP> arranged one above the other, a horizontal gas permeable partition wall 3 in each chamber on which the layer of active material is deposited, the gas distributor 4 above the partition wall provided with a supply tube 6 common to all chambers of each reactor, a valve 7, 7<SP>1</SP> in the tube 6 for each reactor, at least one arm 9 for the supply of the active material into each chamber connected to a common tubing 11 for the pneumatic supply thereof with individual valves 10, 10<SP>1</SP> for each arm. The supply tube 11 is connected to a mixing device 12 supplied with a carrier gas 15 and the dosing device 13 for supply of the active material. At least one rake 16 is fixed in each chamber to the rotatable shaft 17, the gap between the lower edge of the rake and the partition wall being adjustable. An outlet 21, 21<SP>1</SP> is provided in each chamber for removal of the treated gas and is connected to a tube 22 having a central valve 23, 23<SP>1</SP> for each reactor. A tube for transport gas 24 having valves 25, 25<SP>1</SP> for each reactor is connected to this tube 22. A separating device 28 is connected by tube 26 through valves 27, 27<SP>1</SP> to each reactor via the central gas supply tube 6. In operation the reactors are used alternately for gas treatment and then removal of spent material and replacement with active material.