Abstract: In a process for the removal of nitrogen oxides (NO.sub.x) from pretreated flue gases having a nitrogen oxide content which is low by means of a multi-stage washing process employing a nitric acid (HNO.sub.3) solution to which is added hydrogen peroxide (H.sub.2 O.sub.2), the process including a first stage in which the pretreated flue gases are received and contacted with nitric acid (HNO.sub.3) vapor to at least partially oxidize nitrogen monoxide (NO) present in the pretreated flue gases to nitrogen dioxide (NO.sub.2) and result in a first stage flue gas, and a second stage in which the first stage flue gas in received and washed with an aqueous nitric acid (HNO.sub.3) solution to which is added H.sub.2 O.sub.2 to remove nitrogen dioxide (NO.sub.2) and any remaining nitrogen monoxide (NO) from the first stage flue gas and result in a second stage flue gas, wherein the pretreated flue gases have been treated to free the flue gases of contaminants including at least one of sulfur dioxide (SO.sub.

Abstract: The invention relates to the treatment of aqueous materials such as clarified sludge. Disposal of such materials in large quantities is difficult and expensive. The present invention is directed to a treatment method that is economical and results in products which are at least as useful as the starting material. According to the invention, a treatment method comprises mechanical dewatering followed by drying in a fluidized bed drier and burning in a fluidized bed boiler. The heat generated in the boiler is at least sufficient to fulfill the requirements of the drier. The heat generated in the boiler is normally used directly in the drier.

Abstract: The invention relates to the thermal treatment of flowable material using heated contact surfaces in a fluidized bed. Known processes use a gas, often air, to fluidize the bed. This imposes limits on the temperatures that can be allowed to be reached as higher temperatures can cause the material to be treated to burn. It also often produces sterilization of the material. Further there is the problem of disposal of the gases generated in the treatment process. In an attempt to alleviate these problems, the present invention proposes a process generally of the above kind but in which the fluidizing gas comprises gases generated in the bed itself. This is economical as it reduces the heat losses, environmentally desirable as it reduces the amount of gas discharge and more efficient as these gases are generally inert, thus enabling higher temperatures to be generated in the bed without risk of the material burning, thus also facilitating sterilization of the material.