16 ANDRITZ


Pulp Paper & Logistics


Turning trash into treasure


Rather than send paper mill waste to landfill, which is costly and environmentally sensitive, a new alternative – called waste-to-value – collects, treats, and converts waste into energy or saleable by-products, thereby improving a mill‘s profitability. Michael Waupotitsch and Regina Puschnig* explain how


and to dispose of it. And waste can have serious environmental implications, if it contains potentially harmful chemicals. In recycled paper mills, waste


W


can be particularly bothersome. Waste comes in with the raw materials: plastics, textiles, wood, scrap, wires, glass, and other contaminants are an unavoidable part of the waste paper collection process. Depending on the grade of the recovered paper, rejects can account for more than 10 per cent of the raw material; they can have various sizes (from the size of a grain of sand to large and heavy particles) and characteristics (wet or dry; of different densities; loose,


aste is expensive. Waste costs money to transport, handle


compacted, or twisted). There are several ‘protection’


systems in mills to detect and screen out these impurities before they make their way into the paper stock. On the other hand, rejects can also contain recyclable materials like metals or burnable material with a considerable calorific value, such as plastics and textiles. When recycled fibres are


processed and deinked, sludge is generated, as is when raw water and waste water are treated. These mill sludges can sometimes be difficult to handle and dewater. Since transportation costs, gate fees, and landfill costs are often assigned on a per-ton basis, the extra weight of water in the waste increases the cost. Much of this cost can be avoided, however, with a good dewatering system.


Typical mill waste ● Pulper rags, pulping rejects, and coarse screening rejects


● Sludge from deinking systems, paper machine loops, make-up water treatment, and sedimentation


● Sludge from biological waste water treatment ● Raw sludge and sludge from fresh water treatment ● Bark and waste wood ● Forest waste and residuals


● Other biomass, such as sawmill residuals, furniture industry scrap, demolition wood, etc.


Figure 1: Typical mill ‘waste’, which can be utilised as fuel sources or converted into valuable by-products


Creating an opportunity Where there is a problem, there is potentially an opportunity. When discussing waste, the opportunity is that it becomes economically attractive to


recycle the mill waste (as shown in Figure 1) being the source of renewable energy (such as gas and oil) and valuable by-products, such as metals (like aluminium) and bio-char.


Figure 2: Schematic overview of a waste-to-value process turning mill waste into renewable fuels and valuable goods May/June 2016


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