Method and device for the post-combustion of sewage sludge ash produced in a sewage sludge mono-incineration plant

Abstract

In the case of mono sewage sludge incineration, a solution may be created that enables sewage sludge ash, which may still have a low proportion of unburned carbon, to be discharged from a mono sewage sludge incineration plant. This is achieved by a method for the post-combustion of sewage sludge ash obtained in a mono sewage sludge incineration in a rotary kiln by means of a hot and a low oxygen content, such as an oxygen content of 5-10 vol. % oxygen. The gas stream from the rotary kiln may escape the sewage sludge ash and is fed to the gas flow. This sufficiently hot gas flow may cause oxidation or afterburning of unburned carbon contained in the sewage sludge ash.

1 . A method for the post-combustion of sewage sludge ash produced during sewage sludge mono-incineration in a rotary kiln using a hot gas or flue gas stream having a low oxygen content, wherein the method comprises:
 obtaining sewage sludge ash from a fired incineration chamber of an incineration plant associated with the rotary kiln or from a power plant associated with the rotary kiln;   feeding the sewage sludge ash exiting the rotary kiln into the gas or flue gas stream;   optionally adjusting the sewage sludge ash to the low oxygen content required for post-combustion, and   oxidizing or post-combusting unburned carbon contained in the sewage sludge ash by the hot gas or flue gas stream.   
     
     
         2 . The method according to  claim 1 , further comprising supplying the mixture of hot gas or flue gas stream and supplied sewage sludge ash into a reaction space. 
     
     
         3 . The method according to  claim 1 , further comprising adjusting the temperature of the hot gas or flue gas stream in such a way that, on the one hand, it is sufficiently high to cause the oxidation or post-combustion of the unburned carbon contained in the sewage sludge ash and, on the other hand, it is sufficiently low so that the temperature increase of the sewage sludge ash and gas stream mixture or sewage sludge ash and flue gas stream mixture resulting from the oxidation or post-combustion of the unburned carbon contained in the sewage sludge ash does not cause slagging of the reaction chamber or the reaction space or of the gas or flue gas line carrying the sewage sludge ash and gas stream mixture or sewage sludge ash and flue gas stream mixture. 
     
     
         4 . The method according to  claim 2 , further comprising supplying cold flue gas into the reaction space or the reaction chamber; wherein the cold flue gas comprises a temperature ranging from 100° C. to 250° C. 
     
     
         5 . The method according to  claim 1 , further comprising ginding the sewage sludge ash in a mill. 
     
     
         6 . The method according to  claim 1 , further comprising feeding the sewage sludge ash, after exiting the rotary kiln, into a first cooling conveyor configured as a cooling screw. 
     
     
         7 . The method according to  claim 1 , wherein the sewage sludge ash/gas stream mixture or sewage sludge ash/flue gas stream mixture is fed downstream of the reaction space or the reaction chamber to a centrifugal separator, and further comprising separating, in the centrifugal separator the sewage sludge ash and the gas or flue gas stream from one another. 
     
     
         8 . The method according to  claim 7 , further comprising feeding the gas or flue gas stream into the rotary kiln downstream of the centrifugal separator. 
     
     
         9 . The method according to  claim 1 , wherein the feeding of the sewage sludge ash into the gas or flue gas stream and the oxidation or post-combustion of the unburned carbon content contained in the sewage sludge ash are carried out continuously and without intermediate storage. 
     
     
         10 . The method according to  claim 1 , wherein the feeding of the gas or flue gas stream separated from the sewage sludge ash in the centrifugal separator to the rotary kiln is carried out continuously and without intermediate storage. 
     
     
         11 . A device for carrying out the method according to  claim 1 , wherein the device comprises:
 a sewage sludge mono-incineration plant comprising a rotary kiln for sewage sludge incineration with connected sewage sludge feed and a first sewage sludge ash discharge with connected sewage sludge ash line opening into a gas or flue gas line in which a gas or flue gas stream branched off from a fired incineration chamber of an incineration plant associated with the rotary kiln or a power plant associated with the rotary kiln is fed.   
     
     
         12 . The device according to  claim 11 , wherein at least one oxygen supply device or oxygen introduction device is arranged in the gas or flue gas line upstream of the inlet of the sewage sludge ash line, by means of which oxygen can be supplied to the flue gas stream carried in the gas or flue gas line. 
     
     
         13 . The device according to  claim 11 , characterized wherein a reaction space or a reaction chamber is formed in the gas or flue gas line downstream of the inlet of the sewage sludge ash line, in which, during operation of the sewage sludge mono-incineration plant and the fired incineration chamber, the oxidation or post-combustion of the unburned carbon contained in the sewage sludge ash takes place. 
     
     
         14 . The device according to  claim 11 , wherein a first cooling conveyor is configured as a cooling screw, wherein a rotary valve and a mill are arranged in the sewage sludge ash line before the latter opens into the gas or flue gas line in the direction of flow of the sewage sludge ash, which are integrated into the sewage sludge ash line and through which the sewage sludge ash can flow. 
     
     
         15 . The device according to  claim 11 , wherein a centrifugal separator for separating the sewage sludge ash and gas or flue gas stream is arranged in the gas or flue gas line in the direction of flow of the sewage sludge ash/gas stream or flue gas stream mixture downstream of the confluence of the sewage sludge ash line and the reaction chamber or reaction space. 
     
     
         16 . The device according to  claim 15 , wherein the centrifugal separator comprises an exhaust gas line opening into the rotary kiln and a sewage sludge ash discharge line opening into a further cooling conveyor configured as a cooling screw. 
     
     
         17 . The device according to  claim 11 , wherein the gas or flue gas line comprises, in the direction of flow of the gas or flue gas stream upstream of the confluence with the sewage sludge ash line, at least one oxygen supply device or oxygen introduction device. 
     
     
         18 . The device according to  claim 11 , wherein the associated incineration plant is a waste incineration plant or the associated power plant is a waste-fired power station. 
     
     
         19 . The device according to  claim 13 , wherein at least one flue gas introduction device for supplying cold flue gas opens into the reaction space or the reaction chamber.