| abstract |
In a sorption bed which is formed as a fluidized bed reactor possibly with circulating fluid, or as a fixed-bed reactor, for dry waste gas or waste air, purification sorbents introduced in the dry state are contacted at a temperature range between about 30 and 130 DEG C. by the waste gas with an at least 2% oxygen content and the acidic and/or oxidizable noxious gaseous components of the waste gas are found by the sorbent. Noxious gaseous components potentially include SOx, HCl, HF, NOx, Co and also hydrocarbons. The average dwelling time of the sorbents is at least about 20 minutes, in general several hours or days, and the average grain size of sorbent is at most 125 microns. The sorbent is introduced fresh and in stoichiometric ratio, with spent sorbent being correspondingly removed. Sorbents which may be considered are primarily baking soda (sodium bicarbonate), Ca(OH)2 and Mg(OH)2. Chlorides, fluorides, sulfate/sulfite mixtures, and nitrate/nitrite mixtures or mixtures of all of these compounds, occur in spent or used up sorbents. In particular, the reaction product that is carbonized in a low-temperature sorption stage, is reactivated through decarbonization by being returned to a combustion chamber of the combustion process, so that it can be used in a preliminary stage, primarily for removal of sulfur, chlorine, or fluorine. Due to the low temperature characteristics, the method herein can also be used for waste air purification, in particular for purifying tunnel waste air with carbon monoxide and hydrocarbons being oxidized. The spent or used-up sorbent is carbonized in the process, so that in this case, it can still be used completely (100%) for high temperature purification of the combustion chamber gases in a combustion chamber. |