The production process of particleboard requires that the wood fibre (wood chips that are used in particle board) is dried before it enters the production process. The resin that is used to bind the particleboard also needs to be heat-activated after the particleboard mattress has been compressed. To supply the heat needed for these two processes, a 45 Mw step-grade thermal energy plant was specifically designed and built for PG Bison’s particleboard production facility in Ugie. The energy plant is fuelled by using recycled packaging and biowaste material (specifically bark and sanding dust generated from other processes in the facility).
The Vyncke energy plant generates 32 500 000 kcal/h of energy to heat 72 000 litres of thermal oil to 280 °C to dry 38 tons of wood fibre from 120% bd to approximately 1,5% bd per hour. Hot air (300 000 m³/h flue gas), is generated in a mixing chamber at a temperature of 750 °C, which in turn heats up the Recalor rotary wood dryer and the Thurbex oil heater. The resin activation process requires 68 000 litres of heated oil to be continuously fed through the ‘contiroll’ press and MFB press, after which it recycles back into the system to be reheated and reused.
The heat:mass balance of the thermal plant was specifically calculated and predetermined in accordance with the amount of fuel (waste material) that the thermal plant would need.
This ensures that the production facility will only be supplied with material from its own processes without PG Bison having to buy or supplement the plant with additional material for fuel. By using self-generated and 100% sustainable biowaste material, a cost saving of an estimated R13.2 million per year is achieved.
Optimising energy efficiency through technology and new infrastructure
Two initiatives at PG Bison’s new Siempelkamp Generation 8 Contirol continuous medium density fibreboard (MDF) line at its plant in Boksburg are aimed at electricity and thermal energy savings. The new MDF plant, commissioned during October 2013, has been fitted with the latest technology high-efficiency motors with variable frequency drive (VFD) speed control, which regulates motor speed (and energy consumption) electronically by changing the frequency of the electric current supplied to the motors. By installing this technology, the estimated electricity savings equate to approximately 500 kW/h or R3 million per annum.
A Dieffenbacher ClassiSizer was also installed at the new plant to resize production waste material into combustible fine dust for heating the thermal oil required for the new MDF line. This initiative will generate approximately 2 MW of thermal energy, and will reduce the need to burn fossil fuels for energy and thus reduce carbon emissions, resulting in an annual saving of approximately R7.5 million.
A 300 m³ fibre silo was also installed to capture residues from the MDF production process, either to recycle back into the process or to utilise as fuel.