Method and device for exhaust gas cleaning

摘要

In the method a substance is fed into the exhaust gas flow flowing in the exhaust gas passage (10), which substance reacts with harmful compounds in the exhaust gas, whereby compounds are generated, which are less harmful for the environment. The reactive substance can be urea. The exhaust gas flow is with the aid of a flow guide (50) divided into two parts: a centre flow (20) flowing in the centre of the cross-section of the exhaust gas passage and an edge flow (22) circulating and advancing around the centre flow. The reactive substance is fed into the centre flow. The flow guide has a first passage part and a second passage part. The first passage part is fitted to form a centre flow from the exhaust gas passing through it in the centre of the exhaust gas passage and the second passage part is fitted to form an edge flow surrounding the centre flow from the exhaust gas passing through it. The first passage part is an inner duct (52) and the second passage part has at least one blade (54) for steering the exhaust gas into a motion circulating the inner duct. The flow guide can comprise several blades, which are placed symmetrically around the inner duct. The flow guide comprises a casing, inside which the inner duct and the blades are placed.