Abstract: A debris filter trap to prevent potentially damaging debris carried by the feedwater entering the pressure vessel of a once through steam generator from entering into the section of tubes which are positioned within the confines of an integrally contained economizer of the once through steam generator. The trap will remove foreign material, from the feedwater flow, that is larger than the space between the tubes, and thus prevent debris particles that are large enough to get lodged in the tube spacing from entering the economizer.

Abstract: The present invention relates to an arrangement for introducing black liquor into a furnace of a recovery boiler, said arrangement comprising an elongated tube having an interior surface and an exterior surface, through which tube the black liquor being fed into the furnace is supplied, whereby the black liquor is taken into contact with said interior surface prior to being sprayed into the furnace. The interior surface of said elongated tube is provided with heat transfer elements and surfaces, such as fins or grooves. The heat transfer element or surface increases the heat conductivity between the tube and the black liquor above the conductivity achieved with a normal tube passage.