Method and arrangement for producing electrical energy at a pulp mill

摘要

The invention relates to a method and an arrangement in the production of electric energy in a boiler plant of a pulp mill. Black liquor having a dry solids content of more than 80% and combustion air are fed into a furnace of a recovery boiler for combusting black liquor and recovering chemicals contained therein. The flue gases generated in the combustion are led into an economizer of the recovery boiler, in which economizer the feed water for the boiler is heated, and after the economizer to gas cleaning. The feed water is led from the economizer onto the steam-generating bank at a temperature below the saturation temperature and further into a superheater to produce steam having a pressure of more than 80 bar. The steam is led from the recovery boiler to a steam turbine to produce electricity. The temperature of the feed water being led into the economizer is regulated by means of bleed steam of the turbine so that the flue gases exit the economizer at a temperature of more than 250° C. and that after the economizer the flue gases are cleaned in at least a hot electrostatic precipitator and the cleaned flue gases are cooled by the combustion air or the feed water.