Wattle Extract and Charcoal Process
Wattle Extract Operations
The Wattle Mimosa extract processing plant is located on the central estate of Silverstream which is 150 kilometers south of Mutare along the Chipinge – Chimanimani road.
The factory manufactures three products namely:
- Solid Mimosa Tannin
- Green Special Powder
- Ordinary Powder
The Factory has a capacity of 6500 tonnes of solid extract per year on a sustainable basis.
The factory has been able to produce high quality products and this has been achieved by adhering to high quality control standards. It also helps a lot that the Company controls the entire process from planting the trees to the final product manufacture.
Wattle extract is produced by a process of diffusion. Chopped bark is fed into one of the autoclaves through which heated water is pumped .The resulting solution or (“thin liquor”) has a concentration of approximately 15% extractives and is pumped into holding tanks. The thin liquor is concentrated in one of four multi effect evaporators, where low-pressure steam is used to evaporate water and produce thick liquor of approximately 50% extractives. Finally, in one of four finishers, again using vacuum pumps and steam heating, moisture content is reduced to approximately 18%. The “finished liquor” is bagged in hessian bags and cooled on drying racks, where it solidifies.
The key production criteria are tan content, colour, moisture content and bark to extract recovery percentage.
The heat energy for the process is provided by steam from two Babcock and Wilcox water tube boilers at a rate of up to 10 tonnes per hour. The boilers are fired by wattle wood and spent bark.