Spiral Heat Exchangers Preheat High Solids Black Liquor Without Plugging
Superior heat transfer and condensing abilities find increased application in black liquor, turpentine, and tall oil recovery systems
PULP & PAPER
By BRIAN ALLEN and RICH ZOLDAK
The manufacture of nearly all pulp and paper products relies on several heat transfer applications, ranging from the most simple to the most complex from heating, cooling, and condensing duties to heat recovery and energy conservation. An essential component of any heat transfer system is a reliable, easy-to-maintain heat exchanger.
The spiral heat exchanger (SHE) is particularly well suited to the heat transfer needs of a modern pulp and paper mill. The unit has typically been used in blow heat recovery systems and for heating and cooling of a number of caustic and acidic wash water, mill water, and whitewater. However, the spiral unit also has specific application in black liquor recovery boilers and the turpentine and tall oil recovery systems.
The highly fouling and scaling fluids found in pulp and paper mills often cause severe plugging and fouling in other types of heat transfer equipment. Such problems can lead to interruptions in a mill's operation, resulting in less efficiency and considerable cost. Spiral units can easily handle these fiber-laden solutions and high-viscosity liquors found in pulping and papermaking operations.
The spiral unit can sometimes be the best solution to heat transfer. However, because the initial unit cost of a spiral heat exchanger tends to be slightly higher than the shell-and-tube exchanger, many mills shy away from it. Mill experience has proven that cost reductions are possible using the spiral unit in pulp and paper production.