Method and device for the desulphurisation of an exhaust gas return flow

A method and device are proposed for desulfurizing an exhaust gas recirculation stream of an internal combustion engine (1), which is supplied to the internal combustion engine (1) on its fresh air side (8), wherein ammonia is used for desulfurization in the exhaust gas recirculation stream (7"), and wherein at least one exhaust gas partial stream (7, 17) is branched off from the exhaust gas stream (2) of the internal combustion engine (1). According to the invention, it is proposed that at least one ammonia-releasing reactant (12) is supplied to an exhaust gas partial stream (7) branched off from the exhaust gas stream (2) of the internal combustion engine (1), and the exhaust gas partial stream (7') loaded in this manner is supplied partly as exhaust gas recirculation stream (7") to the fresh air side (8) and partly as aftertreatment partial stream (9) to an exhaust gas aftertreatment system. The exhaust gas recirculation quantity supplied to the fresh air side (8) and the quantity of the aftertreatment partial stream (9) supplied to the exhaust gas aftertreatment system are specified and/or varied as a function of at least one operating parameter defining the respective operating situation of the internal combustion engine (1) by means of a control and/or regulating device.