A SELECTIVE CATALYTIC REDUCTION SYSTEM AND A METHOD FOR NOx REDUCTION

Abstract

A selective catalytic reduction system applying diesel oil as reductant for converting nitrogen oxides by a catalyst into diatomic nitrogen and water in a diesel engine is provided. The selective catalytic reduction system includes an oil injection system, a reactor and a number of selective catalytic reduction catalysts provided in a first section. The selective catalytic reduction system includes at least one additional section including a number of selective catalytic reduction catalysts. The at least one additional section is provided in a non-zero distance from the first section.

1 - 24 . (canceled) 
     
     
         25 . A selective catalytic reduction system applying diesel oil as reductant for converting nitrogen oxides in diesel engine exhaust, through a NO reduction process by a catalyst, into diatomic nitrogen and water in a diesel engine, wherein the selective catalytic reduction system is configured to be installed and used in a two-stroke diesel engine or a four-stroke diesel engine for marine purposes, wherein the selective catalytic reduction system comprises:
 an oil injection system;   a reactor;   a number of selective catalytic reduction catalysts provided in a section comprising a plurality of layers provided in a non-zero distance from each other, wherein the selective catalytic reduction system comprises a number of selective catalytic reduction catalysts provided in separated layers in a first section, wherein the selective catalytic reduction system comprises at least one additional section comprising a number of selective catalytic reduction catalysts in separated layers, wherein the at least one additional section is provided in a non-zero distance from the first section, wherein the reactor is configured to house the sections in order to facilitate the NO reduction process, wherein the distance between the layers is selected to ensure that a minimum average residence time for the exhaust is provided between each layer, wherein the minimum average residence time for moving a gas molecule from one layer to the next layer is no smaller than 0.025 seconds.   
     
     
         26 . A selective catalytic reduction system according to  claim 25 , wherein the minimum average residence time for moving a gas molecule from one layer to the next layer is no smaller than 0.04 seconds. 
     
     
         27 . A selective catalytic reduction system according to  claim 25 , wherein the minimum average residence time for moving a gas molecule from one layer to the next layer is no smaller than 0.135 seconds. 
     
     
         28 . A selective catalytic reduction system according to  claim 25 , wherein a plate member is provided between at least some of the adjacent sections. 
     
     
         29 . A selective catalytic reduction system according to  claim 25 , wherein the selective catalytic reduction catalysts are arranged in the layers each having a thickness within the range 40-120 mm, or in the range 50-100 mm, or in the range 60-90 mm. 
     
     
         30 . A selective catalytic reduction system according to  claim 25 , wherein the selective catalytic reduction catalysts are selected among the following: Ce/Cu-ZSM-5, Ce—Zr/Cu-ZSM-5, Ce/Fe-ZSM-5 or Ce—Zr/Fe-ZSM-5, Ce/Mg-ZSM-5 or Ce—Zr/Mg-ZSM-5. 
     
     
         31 . A selective catalytic reduction system according to  claim 25 , wherein the selective catalytic reduction system comprises a tubular structure extending centrally along the longitudinal axis of the reactor. 
     
     
         32 . A selective catalytic reduction system according to  claim 25 , wherein the selective catalytic reduction system comprises a diffuser. 
     
     
         33 . A selective catalytic reduction system according to  claim 25 , wherein the selective catalytic reduction system comprises a heat recovering unit. 
     
     
         34 . A method for nitrogen oxides reduction in diesel engine exhaust, said method comprising the step of using a selective catalytic reduction system configured to be applied for selective catalytic reduction of NOx in an exhaust stream either after a four-stroke diesel engine or between the exhaust receiver and the exhaust turbine(s) on a two-stroke diesel engine and applying diesel oil as reductant for converting nitrogen oxides through a NO reduction process by a catalyst into diatomic nitrogen and water in a diesel engine, wherein the method comprises the step of providing evaporated diesel oil in a reactor, wherein a NOx conversion is carried out including a NO reduction followed by a heterogeneous catalyzing process followed by a homogeneous catalyzing process by applying a number of selective catalytic reduction catalysts provided in a section having a plurality of layers, and further that the selective catalytic reduction system comprises a number of selective catalytic reduction catalysts provided in separated layers in a first section, wherein the selective catalytic reduction system comprises at least one additional section comprising a number of selective catalytic reduction catalysts in separated layers, wherein the at least one additional section is provided in a non-zero distance from the first section, wherein the reactor is configured to house the sections in order to facilitate the NO reduction process, wherein the distance between the layers is selected to ensure that a minimum average residence time for the exhaust is provided between each layer, wherein the minimum average residence time for moving a gas molecule from one layer to a next layer is no smaller than 0.025 seconds. 
     
     
         35 . A method according to  claim 34 , wherein the minimum average residence time for moving a gas molecule from one layer to a next layer is no smaller than 0.04 seconds. 
     
     
         36 . A method according to  claim 34 , wherein the minimum average residence time for moving a gas molecule from one layer to a next layer is no smaller than 0.135 seconds. 
     
     
         37 . A method according to  claim 34 , wherein the method comprises the step of cracking at least a portion of the evaporated diesel oil, carrying out a heterogeneous NOx conversion that causes formation of the radical NH4 + , wherein the radical NH4 +  is used for carrying out homogeneous NO x  conversion. 
     
     
         38 . A method according to  claim 34 , wherein the method is applied for selective catalytic reduction of NOx in an exhaust stream either after a four-stroke diesel engine or between the exhaust receiver and the exhaust turbine(s) on a two-stroke diesel engine. 
     
     
         39 . A selective catalytic reduction system according to  claim 25  wherein an oxidation catalyst arranged to oxidise one or more compositions in the exhaust gas. 
     
     
         40 . A selective catalytic reduction system according to  claim 39 , wherein the selective catalytic reduction system comprises a flow-through type diesel oxidation catalyst and a soot particle filter. 
     
     
         41 . A selective catalytic reduction system according to  claim 39 , wherein the oxidation catalyst is a wall flow type particle filter comprising walls coated with a catalyst configured to oxide at least CO or HC. 
     
     
         42 . A selective catalytic reduction system according to  claim 39 , wherein the oxidation catalyst is provided downstream the selective catalytic reduction catalysts and a particulate filter. 
     
     
         43 . A selective catalytic reduction system according to  claim 39 , wherein the selective catalytic reduction system comprises or is connected to a generator. 
     
     
         44 . A method according to  claim 34  wherein the method comprises the step of applying an oxidation catalyst arranged to oxidise one or more compositions in the exhaust gas. 
     
     
         45 . A method according to  claim 44 , wherein the method comprises the step of applying a wall flow type particle filter comprising walls coated with a catalyst configured to oxide at least CO or HC. 
     
     
         46 . A method according to  claim 44 , wherein the method comprises the step of applying a flow through type diesel oxidation catalyst and a particle filter. 
     
     
         47 . A method according to  claim 44 , wherein the method comprises the step of applying an oxidation catalyst provided between the selective catalytic reduction catalysts and a particulate filter. 
     
     
         48 . A method according to  claim 44 , wherein the method comprises the step of applying a generator connected to a turbine to produce electrical energy. 
     
     
         49 . A method according to  claim 44 , wherein the method comprises the step of applying a distillation apparatus to produce distilled water, wherein the distillation apparatus is connected to the selective catalytic reduction system.