A. Ahlstrom Corporation

Ahlstrom Machinery Oy

Markku Tanttu

Raimo Paju

Samuli Nikkanen

Jukka Savolainen

Kari Palmu

The intensity of explosions as a result of hot (750-820 degrees C.) smelt from a pulp mill recovery boiler impacting cool (70-100 degrees C.) liquid in a dissolving tank is minimized by more effectively disrupting the flow of smelt from a spout free end tip into the tank. First and second nozzles which issue jets of disrupting fluid (such as steam or green liquor) are positioned on opposite sides of the center line of the spout, and are positioned and spaced from the spout tip and each other so that the jet emanating from at least one of the nozzles always intersects the flow of smelt from the spout even though the smelt flow path varies during normal operation of the recovery boiler. The first and second nozzles are preferably each spaced from the spout free end tip a distance of between about 300-700 mm, but different by at least 50 mm from the other nozzle, and are positioned downwardly and obliquely at an angle to the vertical so that the jets move downwardly and obliquely making an angle of between about 20-40 degrees with respect to the vertical. Other nozzles--e. g. in front of the smelt flow--can also be provided within a hood covering the spout area.

Disrupting the flow from the smelt spout of a recovery boiler

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.

Method and apparatus for feeding air into a furnace

A simplified method and apparatus for handling black liquor (or other spent liquor from the pulp industry) includes utilization of a mixing tank directly with a black liquor storage tank. The mixing tank has a side wall defined by a part of the side wall of the black liquor storage tank, and the mixing tank may either be disposed within the volume of the storage tank, or immediately exterior of it. Fly ash from a recovery boiler and make-up chemical are introduced into the mixing tank along with black liquor from evaporators, and the mixed liquid from mixing tank overflows into the interior volume of the black liquor storage tank. From the storage tank the black liquor is sent to a recovery boiler where it is burned. Also, some black liquor from the recovery boiler is recirculated to the storage tank, and introduced into the storage tank remote from the mixing tank.

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Varkaus, Finland

Markku Tanttu