Method and system for purification of exhaust gas from diesel engines

A system for purification of an exhaust gas from a combustion engine, wherein the system comprises in series

• a heat exchanger;
• a diesel oxidation catalyst;
• a diesel particulate filter;
• and
• a selectively reducing catalyst;
• and wherein the heat exchanger has
• a first side communicating with inlet side of the diesel oxidation catalyst and being equipped with a by-pass across the first side of the heat exchanger;
• a second side communicating with outlet side of the selectively reducing catalyst and being equipped with a by-pass across the second side of the heat exchanger;
• at least one vane installed in the by-pass across the first side of the heat exchanger adapted to control the amount of exhaust gas flowing through the first side of the heat exchanger;
• and
• at least one vane installed in the by-pass across the second side of the heat exchanger adapted to control the amount of exhaust gas flowing through the second side of the heat exchanger;
• a housing;
• a number of rectangular plates installed in parallel in the housing forming spaces between adjacent plates;
• a plurality of wires disposed in the spaces between the adjacent plates, the wires being squeezed between the adjacent plates, so that two adjacent wires of said plurality of wires and the adjacent plates form channels;
• the channels in every other space forming a first set of channels, the channels of the first set of channels in parallel with each other and having an S-shape, so that the channels of the first set of channels lead a gas stream from one corner of the plates to a diametrically opposite corner;
• the channels in the remaining spaces between adjacent plates forming a second set of channels, the channels of the second set of channels having a shape that is a mirror image of the S-shape of the first channels of the first set of channels;
• and
• inlets for gas streams flowing through the channels of the first and second sets of channels are positioned on the same side of the housing, thereby obtaining counter-current gas flow through the channels of the first and second sets of channels.