Gas turbine power generation plant including: - a solid fuel gasifier for the production of a fuel gas stream, - a fuel gas treatment arrangement including at least one fuel gas treatment device, - a combustor for receiving the fuel gas stream and for the production of a flue gas stream, - a gas turbine unit having an inlet for said flue gas stream and being mechanically coupled to an electric generator for the extraction of useful work, and - a compressor unit for the supply of oxygen to the combustor, wherein - a steam generator is arranged for heat recovery in the flue gas stream downstream of the turbine unit, - a condenser is positioned for water recovery in the flue gas stream, said condenser having a connection for water supply to the steam generator, - the steam generator is fluidly connected to the fuel gas treatment arrangement for the supply of steam for the treatment of the fuel gas stream, wherein it is arranged that steam supplied to the fuel gas treatment arrangement and used for treatment of the fuel gas stream is subsequently transmitted, and thereby indirectly supplied, to the combustor for contributing as process gas, - the fuel gas treatment arrangement includes a heat exchanger arranged for cooling fuel gases with steam produced in the steam generator, the steam being passed on to the heat exchanger over a conduit, and steam heated by the fuel gas is passed on to the combustor through a conduit, and - the fuel gas treatment arrangement includes a mixing device for mixing hot water supplied over a conduit connected to the steam generator into the hot fuel gases for cooling purposes, the mixing device being arranged directly downstream of the gasifier and upstream of the heat exchanger. - a solid fuel gasifier for the production of a fuel gas stream, - a fuel gas treatment arrangement including at least one fuel gas treatment device, - a combustor for receiving the fuel gas stream and for the production of a flue gas stream, - a gas turbine unit having an inlet for said flue gas stream and being mechanically coupled to an electric generator for the extraction of useful work, and - a compressor unit for the supply of oxygen to the combustor, wherein - a steam generator is arranged for heat recovery in the flue gas stream downstream of the turbine unit, - a condenser is positioned for water recovery in the flue gas stream, said condenser having a connection for water supply to the steam generator, - the steam generator is fluidly connected to the fuel gas treatment arrangement for the supply of steam for the treatment of the fuel gas stream, wherein it is arranged that steam supplied to the fuel gas treatment arrangement and used for treatment of the fuel gas stream is subsequently transmitted, and thereby indirectly supplied, to the combustor for contributing as process gas, - the fuel gas treatment arrangement includes a heat exchanger arranged for cooling fuel gases with steam produced in the steam generator, the steam being passed on to the heat exchanger over a conduit, and steam heated by the fuel gas is passed on to the combustor through a conduit, and - the fuel gas treatment arrangement includes a mixing device for mixing hot water supplied over a conduit connected to the steam generator into the hot fuel gases for cooling purposes, the mixing device being arranged directly downstream of the gasifier and upstream of the heat exchanger.