Method and system for the removal of particulate matter and heavy metals from engine exhaust gas

Abstract

Method and system for removal of soot, ash and heavy metals, and optionally additionally NOx and SOx being present in exhaust gas from an engine operated on heavy fuel oil.

1 . A method for removal particulate matter, hydrocarbons, and heavy metals being present in exhaust gas from an engine operated on heavy fuel oil, comprising the steps of
 operating the engine at a load to obtain an exhaust temperature of the exhaust gas of at least 325° C.;   passing the exhaust gas at exhaust gas temperatures of 325° C. to 550° C. through the at least one filter unit each comprising at least one particulate filter and capturing the particulate matter and heavy metals contained in the exhaust gas;   continuously burning the captured soot and adhered hydrocarbons off the at least one particulate filter by contact with a catalyst being arranged on the particulate filter;   periodically disconnecting the at least one filter unit from flow of the exhaust gas;   applying a pneumatic pulse at the outlet of the at least one particulate filter by pulse injecting air into the outlet in reverse to the previous flow of the exhaust gas and blowing off the captured particulate matter together with the heavy metals from the at least one particulate filter;   applying suction at inlet of the at least one particulate filter; and   conveying the blown off particulate matter and heavy metals from the at least one particulate filter, optionally through an external auxiliary filter unit, to a container.   
     
     
         2 . The method of  claim 1 , wherein the at least one particulate filter is in form of a wall flow filter. 
     
     
         3 . The method of  claim 2 , wherein the catalyst is coated on or inside the walls of the at least one particulate filter. 
     
     
         4 . The method of  claim 1 , wherein the catalyst comprises of titanium dioxide, oxides of vanadium and tungsten and metallic palladium. 
     
     
         5 . The method of  claim 1 , wherein body of the at least one particulate filter is prepared from silicon carbide, cordierite, mullite, aluminium titanate or sintered metal. 
     
     
         6 . The method of  claim 1 , wherein the air is pulse injected with injection pulse duration of between 10 and 600 msec, preferably 300 msec. 
     
     
         7 . The method of  claim 1 , wherein the air for pulse injection is withdrawn from an accumulator tank with compressed air at a pressure 4 to 10 bar abs, preferably 6.5 bar abs. 
     
     
         8 . The method of  claim 1 , wherein the at least one filter unit is arranged in a pressure vessel upstream an engine turbocharger. 
     
     
         9 . The method of  claim 8 , wherein the exhaust gas is passed through the at least one filter unit at a pressure of between 0 and 3 bar abs. 
     
     
         10 . The method according to  claim 1 , comprising the further step of selective catalytic reduction of nitrogen oxides in the exhaust gas prior to the gas is passed through the at least one filter unit or after the gas has passed through the at least one filter unit. 
     
     
         11 . The method according to  claim 1 , comprising the further step of reducing amounts of sulphur oxides contained in the exhaust gas by scrubbing the gas with an alkaline solution or sea water in an open or closed loop, downstream of the at least one filter unit. 
     
     
         12 . A system for removal of particulate matter comprising soot, ash and heavy metals being present in exhaust gas from an engine operated on heavy fuel oil comprising
 one or more exhaust gas inlet pipes connecting each the engine with inlet of each of one or more filtration units;   one or more exhaust gas outlet pipes connected to outlet of each of the one or more filtration units;   arranged within the one or more filtration units at least one particulate filter catalyzed with a catalyst for effectuating burning off of soot and hydrocarbons;   an air pulse jet arrangement mounted at the outlet of the at least one particulate filter for blowing off the particulate matter collected at the at least one particulate filter;   and the air pulse jet arrangement comprises   one or more air blow pipes connected to an air supply, nozzles in the air blow pipes and an eductor arranged at the outlet of the at least one particulate filter for pulse injection of air into the at least one particulate filter; and   a suction pipe installed close to the inlet of the least one particulate filter, the suction pipe being connected to a suction source.   
     
     
         13 . The system of  claim 12 , wherein the at least one particulate filter is in form of a wall flow filter. 
     
     
         14 . The system of  claim 13 , the at least one particulate filter is coated on walls or inside walls with a catalyst catalysing burning of captured soot of the filters. 
     
     
         15 . The system of  claim 12 , wherein the catalyst consists of titanium dioxide, oxides of vanadium and tungsten and metallic palladium. 
     
     
         16 . The system according to  claim 12 , wherein body of the at least one particulate filter is prepared from silicon carbide, cordierite, or mullite or aluminium titanate or sintered metal. 
     
     
         17 . The system of  claim 12 , wherein the one or more air blow pipes are connected to an accumulator tank with compressed air. 
     
     
         18 . The system of  claim 12 , wherein the one or more filtration units are arranged in a pressure vessel upstream an engine turbocharger. 
     
     
         19 . The system of  claim 12 , wherein the one or more filtration units are arranged downstream an engine turbocharger. 
     
     
         20 . The system of  claim 12 , wherein the one or more exhaust gas outlet pipes connect the one or more filtration units to a downstream selective catalytic reduction unit comprising a denitrification catalyst. 
     
     
         21 . The system of  claim 12 , wherein the one or more exhaust gas inlet pipes connect the one or more filtration units to an upstream selective catalytic reduction unit comprising a denitrification catalyst. 
     
     
         22 . The system of  claim 12 , wherein the one or more exhaust gas outlet pipes connect the one or more filtration units to a scrubber unit. 
     
     
         23 . The system of  claim 12 , wherein a selective catalytic reduction unit comprising a denitrification catalyst unit is connected upstream to the one or more filtration units and downstream to a scrubbing unit. 
     
     
         24 . The system of  claim 20 , wherein the selective catalytic reduction unit is arranged upstream or downstream an engine turbocharger 
     
     
         25 . The system of  claim 12 , further comprising a by-pass pipe by-passing the exhaust gas at least one of the one or more filtration units. 
     
     
         26 . The system of  claim 12 , further comprising one or more auxiliary filter units connected to the suction pipe. 
     
     
         27 . The system of  claim 12 , wherein the air pulse jet arrangement further comprises an isolation valve at outlet of the at least one particulate filter. 
     
     
         28 . The system of  claim 12 , wherein the suction pipe connects an exhaust gas inlet side of the filter unit/s or the particulate filter/s with an exhaust gas outlet side from the filter unit/s or the particulate filter/s.