Pulp and paper mills generate various quantities of energy-rich biomass as wastes, depending on technological level, pulp and paper grades and wood quality. These wastes are produced in all stages of the process: wood preparation, pulp and paper manufacture, chemical recovery, recycled paper processing, waste water treatment. Energy recovery from wastes of different origin has become a generally accepted alternative to their disposal. Pulp and paper industry expresses an interest in adapting and integrating advanced biomass energy conversion technologies into its mill operations. Industrial adoption of these new technologies has the potential for higher efficiency, lower capital cost, and safer operation than conventional operations that burn fossil fuels for energy. Incineration with energy recovery has the advantage of hygienic disposal, volume reduction, and the recovery of thermal energy by means of steam or super heated water that can be used for heating and power generation. The paper reviews the current state and tendencies in using as a fuel of solid wastes generated in pulp and paper mills. A description of biomass-derived wastes regarding their opportunity to be used for energy recovery is presented. The heating properties of wood wastes, rejects from recycled paper processing, paper sludge, and low-quality recovered paper grades are discussed. Some aspects of emission of greenhouse gases (GHG) are also presented.
The paper aims to present the environmental impact of pulp and paper manufacturing and the most important production and control practices to minimizing this impact. The environmental consequences of manufacturing pulp and paper from pulping and bleaching processes are discussed in qualitative and quantitative terms. In these processes, sulfur compounds and nitrogen oxides are emitted to the air, and chlorinated and organic compounds and nutrients are discharged to the wastewaters. Large quantities of solid wastes and sludges are also generated.
The kraft pulp mill generates various quantities of solid wastes, depending on technological level, pulp grade and wood quality. These wastes are generated in all stages of pulp manufacturing: wood processing, pulping, pulp washing and screening, chemical recovery. The minimizing of solid waste generation and the ways of their processing are important problems for the pulp producers. These problems are in strong connection with both the economical and environmental aspects. Aims of this paper are to identify the sources of solid wastes in the kraft pulp mill and to discuss the best ways of their processing. The woodroom represents the major area of wood wastes that are very different regarding their shapes, dimensions and properties. Bark is the most common wood waste and its volume ranged between 0.4-0.6 m3/t o.d. pulp. Besides bark, other wood residues appear in the woodroom: fines, pins, large chips. Their quantities are very different depending on the wood quality, debarking method, and chipper performance. The most common way for is their valorization by firing for energy using fluidized bed furnace boilers. Wood-waste burning allows to obtain 0.8-1.2 t steam (1.2 MPa) /t of o.d. pulp, depending of the wood losses at pulpwood preparation. Another source of solid waste is the pulp screening stage where results 2-8 % knots and fine-screen rejects. The third major source of solid wastes in the kraft pulp mill is the recovery plant, generating sodium salts enriched with NaCl and KCl from recovery boiler, dregs from green liquor clarifier/filter, and grit separated at slaker. Landfilling is the way of dregs and grit disposal. Waste materials for landfill consist of ash, (10-25 Kg/t of pulp), dregs and grit, (15-40 Kg/t of pulp). The volume of waste materials for landfilling represents 9.7-25 m 3 /day, depending on fiber line capacity. A good waste management in pulp manufacturing will lead to enhancing of economical performance as well as to an environmental sound process
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