Pillow jacket sheet exchanger for black wastewater from paper pulp
Laser welding heat transfer plate:
The heat transfer plate is made by automatic laser welding and forming process. Its special pillow structure makes the fluid form the best turbulent state, achieves efficient heat transfer, and has the characteristics of dust resistance, high temperature and high pressure resistance, easy cleaning and so on.
Principle of heat transfer plate:
The heat transfer plate consists of two thin plates, which are completely welded around by laser welding process, and the middle area is full of pillow pattern; after forming process, pillow shaped cavity is formed inside the heat transfer plate. Pillow design creates excellent turbulence and provides self-supporting structure. In practical application, additional welding path is often added in the heat transfer plate to adjust and control the interface position of fluid in and out of the heat transfer plate, the flow velocity and flow rate of fluid in the plate, so as to optimize the heat transfer effect.
Black liquor is the waste liquor from the kraft pulping process after pulping is completed. It contains most of the original cooking inorganic elements and the degraded, dissolved wood substance. The latter includes acetic acid, formic acid, saccharinic acids, numerous other carboxylic acids (all as the sodium salts), dissolved hemicelluloses (especially xylans), methanol, and hundreds of other components. It is an extremely complex mixture. About 7 tons of black liquor at 15% solids (about 10% organic chemicals and 5% inorganic chemicals with a total solid is produced per ton of pulp. The black liquor must be concentrated to as high a solids content as possible before being burned in the recovery boiler to maximize the heat recovery. The viscosity rises rapidly with concentration above 50%, with softwood black liquors being more viscous than hardwood black liquors. Black liquor is usually fired at 65%–70% solids content.
Black liquor evaporation
Black liquor recovered from pulping contains 14-17% dissolved solids
These solids are composed of about 1/3 inorganic chemicals that were in the white liquor added to the digester
The remaining 2/3 consist of the organic chemicals extracted from the wood
Black liquor must be concentrated to above 60% solids so that it will burn without supplemental fuel
|item||5 effect station||combined evaporation process|
|MVR pre concentration||5-effect evaporation station|
|Evaporation water (t/h)||100||64.28||35.72|
|RMB/T water evaporation capacity||45||25.93|
Highly efficient condensate segregation in the evaporator ducts and lamellas, plus the integrated stripping of foul condensate fractions, produce clean and re-usable water. Methanol in the liquor is separated from the condensate and recovered as an auxiliary fuel in a methanol liquefaction system.
Efficient chloride and potassium removal
Crystallization technology is used in the integrated system. Energy is conserved by using the secondary vapor from the evaporator for the crystallization process.
Best possible energy efficiency
The use of fully integrated foul condensate stripping, optimized liquor distribution, and the ability to use various heat sources within a single thermal effect ensure an evaporation system that meets unique customer requirements while providing the best possible availability and energy efficiency.