Veracel Celulose, S. A. Eunápolis, Bahia, Brazil

Veracel Celulose is located in the extreme southern portion of the Brazilian state of Bahia. The area, rich in eucalyptus, is one of the largest and productive plantations in the world.

The company is a partnership of Aracruz Celulose, the largest producer of bleached eucalyptus pulp and Stora Enso, an integrated producer of paper, packaging and forest products.

The new mill was designed for an output of 900,000 tons in which they would export product to customers in the United States, Europe and Asia.

Efficiency in operation to reach this goal was critical to the design of the facility. Concerns for the environment as well as consideration for resource consumption and safety were also key factors for this project.

In order to achieve this, maximum efficiency in the recovery boiler would require the highest solids possible while maintaining capacity. The evaporation system would need to produce 80% solids of highly viscous eucalyptus black liquor consistently while reusing as much water as possible in mill operations.

Evaporation of the black liquor was rated at 2.2 million lbs./hr (1000 T/h), making Veracel one of the largest single train evepoartion systems in the world.

To meet the rated capacity and customer operational targets, HPD designed a highly integrated, six-effect falling film evaporator train that optimizes the use of power and water intake to the mill. The evaporation system incorporated several features into the process and equipment that were critical to meeting the objectives set forth by Veracel Celulose:

• A four-body, switching falling-film concentrator was designed to minimize fouling with the precipitation of salts at high product solids. On-line washing capabilities allows no disruption of production while achieving designed rates.
  
  
• The second effect evaporator is also susceptible to scale as a result of the low critical solids point of eucalyptus liquor and the resulting solids profile of the six effect evaporator train. A split-body second effect was added to prevent this and allow for on-line washing and switching while the other is in production.
  
  

• Valuable water is recovered by effective condensate segregation. Process condensate is separated into three distinct fractions to return one high quality condensate for use in pulp washing while returning another portion to other mill operations. The third fraction, being foul condensate, is processed in the stripper and rectification columns and returned to the mill. Liquid methanol is then incinerated in the boiler.
  
  

  A condensate stripper and methanol rectification system was integrated into the process which converts the foul condensate fraction to liquid methanol. This feature makes transport of gases easier for incineration with the added feature of further generation of high-quality condensate.

• The system is also designed with the flexibility to add future enhancements such as a future CRP™ System to reduce accumulation of non-process elements that impact efficiency of boiler operations.

The pulp mill at Veracel Celulose was commissioned in mid-2005.

The evaporation system and process solution, designed by HPD, was considered successful at start up and expected to achieve designed rates when capacity is reached later in the first full year of production.