A. Ahlstrom Corporation

Ahlstrom Machinery Oy

Samuli Nikkanen

Marjo Kuusio

Markku Tanttu

A method of recovering energy from waste liquors from cellulose pulp processes produces high quality superheated steam, a savings in material costs is achieved, and the utilization factor of the pulp mill is improved (that is the number of shutdowns for service is reduced). A main stream of waste liquor from cellulose pulp processing is divided into first and second streams. The first stream is combusted in the recovery boiler to produce steam and the steam is fed to a superheating boiler. The second stream of waste liquor is gasified outside the recovery boiler to produce a combustible gas and an inorganic fraction. The inorganic fraction is not fed to the recovery boiler, but is separately recovered. The combustible gas is burned in the superheating boiler to superheat steam produced from combusting the first stream of waste liquor, the combustible gas providing substantially the only source of fuel for superheating the steam in the superheating boiler.

Method of recovering energy from waste liquors from pulp processes

Combustion gas is fed to a furnace, preferably a recovery boiler for combusting black liquor from cellulose pulp processing, through a gas nozzle disposed in association with a wall of the furnace. The nozzle has a longitudinal axis of elongation, an exterior, and a hollow interior. Cooling gas is directed into contact with the nozzle exterior, and typically also the furnace wall where the nozzle engages the furnace wall. The cooling gas typically moves in a direction substantially perpendicular to the longitudinal axis of the nozzle (e.g. at a velocity of between 10-30 m/sec), and cools the nozzle. Combustion gas passes through the nozzle hollow interior and enters the furnace facilitating combustion of black liquor within the furnace. Desirably the cooling gas is redirected and enters the nozzle interior as the combustion gas. The nozzle may be further cooled by cooling fins or studs on a portion of the nozzle exterior impacted by cooling gas. The rate of gas flow may be regulated to control the amount of gas redirected into the nozzle for use as combustion gas. The invention results in effective cooling of the nozzle to extend its life, recovery of heat from the nozzle by utilizing it to preheat the combustion air, and the prevention of clogging of the cooling air flow paths because they are maintained distinct from areas where furnace impurities exist.

Growing community of inventors

Varkaus, Finland

Samuli Nikkanen