Specialty Heat Exchangers
Digester Liquor Heaters
Heating the cooking liquor using external, indirect heat exchangers gives improved operation and reduced K# variability of the digester operation.
Our Digester Liquor Heaters are vertical arrangement, units specially designed to tolerate repeated thermal and hydraulic shock inherent in these services.
Weak Liquor CoolersIWeak black liquor typically tends to run at 85 - 90 degrees C, thus many mills recover the heat from the WBL to make hot water, which is used in many different locations within a mill.
Our weak black liquor coolers will provide efficient energy recovery while reducing the temperature of the liquor, resulting in reduced non-condensible gas emissions.
Heavy Liquor Heater
A.H. Lundberg Systems pioneered the technology of indirect black liquor heating in 1982. The benefits of indirect black liquor heating are several fold. First is that the liquor temperature can be maintained more closely than a direct unit, giving better control of combustion and reduction of carry over. Second is that there is no dilution of the liquor with steam condensate. This results in an increase in firing solids or evaporator/concentrator capacity and allows recovery of the clean steam condensate. Finally, the absence of direct contact minimizes the risk of diluting the black liquor below the safe firing concentration.
The Lundberg Systems heating system utilizes liquor re-circulation to maintain velocity within the heater at varying boiler operating rates. Further, the location of the heater downstream of the boiler nozzle feed pumps and the use of the recirculation pump does not necessitate any change to the nozzle feed pumps.
The additional pressure drop of the heater is taken up by the recirculation pump. This pressure drop is minimized by the use of flow enhancers (REX inserts) inside the tubes that promote turbulence, allowing the total amount of recirculated flow to be reduced. The orientation and piping arrangement must facilitate the removal and drainage of wash condensate or weak liquor from the heater.
The Heavy Liquor Heater is a shell and tube unit with the liquor within the tubes. The unit may be installed in either a slightly inclined horizontal position or a vertical position.
Chlorine Dioxide Solution Heaters
To reduce energy cost both for chilling and heating the chlorine dioxide solution, A. H. Lundberg recommends the use of heaters for recovering some of the heat value from the chlorine dioxide solution leading to the bleach plant.
To save on chilling capacity, we recommend chlorine dioxide solution from the absorption tower exchange heat with the water leading to the chiller. The cold chlorine dioxide solution from storage is heated by the warm water, consequently the water now going into the chiller is cooler, thus requiring less chilling capacity and the chlorine dioxide solution is warmer requiring less steam in the process for heating.
For example, for a 10 tpd chlorine dioxide plant producing 8 gpl solution in the summer will operate at about 9o C, while the warm water to the chiller runs at 25o C. Thus exchanging the heat between the two streams can save the chilling capacity by about 50%. This means a smaller chiller and less specific energy consumption to produce the 40 C absorption water.
Additional heating of the chlorine dioxide solution will further reduce the steam demand in the bleach plant. A second heater can be used to exchange heat between the chlorine dioxide solution and the first extraction stage filtrate, which can result in a savings of about 71,000 Kg/day of steam.
In each case, A.H. Lundberg provides shell and tube units for this service, installed in a slightly inclined horizontal position, to accommodate safe removal of any gasses released from the solution.