Highly Integrated Design-Build Black Liquor Recovery System
Smurfit-Stone Container Corporation is one of the world's largest manufacturers of packaging products ranging from consumer goods, printed displays and container board.
The Hopewell, Virginia facility is dedicated to providing linerboard for corrugated container end products.
HPD was chosen to replace the existing three evaporator trains that were currently in place at this facility with one very highly-integrated system.
Due to the age of the current evaporation trains, MACT I compliance was necessary in any new design with system efficiency and reducing overall operation costs as key considerations in the development of process equipment and system design.
This project, provided on a design-build basis, showcased the total project management approach and engineering capabilities of HPD with responsibility for the entire recovery island. The engineering disciplines utilized for this installation were in the areas of chemical, mechanical, electrical, civil/foundation, and structural.
The entire scope of the project included construction of a new island that would be home to a six-effect, falling film evaporator train that would produce 74% product solids at an evaporation rate of 897k lbs/hr (407 T/h). The system would also process precipitator slurry, tall-oil brine, and other recovered boilout liquor streams.
Two major components of the process equipment were instrumental in achieving the objectives for the mill. These included:
Enhanced forced circulation technology which enables turbulence of the black liquor at high viscosities with lower recirculation rates, thus requiring less horsepower than conventional forced circulation.
This allows mixing of the bulk product solids that results in increased heat transfer efficiency to minimize the laminar layer on the tube wall surface to greatly reduce fouling in the heater to achieve higher solids concentration.
Analysis of the precipitator slurry revealed high levels of chloride. If left untreated, unfavorable conditions could develop such as plugging of the super heater, corrosion in the recovery boiler and increased steam demand.
The CRP (Chloride Removal Process) system removes non-process elements such as chloride and potassium from the chemical makeup that accumulate in the recovery cycle. Removal of these elements via the CRP, rather than purging the raw precipitator ash, reduces the amount of purge to achieve the same results.
Other equipment supplied to the evaporator island included a salt cake crystallizer, a soap skimming tank, cooling towers and chemical building, a foul condensate tank, a new MCC facility and control system. Outside of the island, a new indirect black liquor heater system was installed.
Designed production rates and operational targets were reached by use of innovative process solutions and advances in technology by HPD. MACT I compliance was attained through optimum condensate segregation that also provided fresh water resources for re-use in the mill.
The evaporator system and peripheral equipment installed proved to be a success.
