| A low carbon economy concept and energy saving requirement makes waste paper pulp becoming the indispensable part of modern paper industry. Waste paper recycling is to save energy and to reduce pollution; scales in papermaking system with deinking pulp become more serious, and scales in heat dispersion influence equipment production efficiency, energy consumption and product quality. This paper will provide theoretical foundation for the control of scales in heat dispersion, and will promote the paper industry in China to develop according with a low carbon economy.With the research of scales species and pulp fluid dynamics, composition of scales in plates were analyzed by chemical and instrumental analysis methods; then, chemicals in DIP system and the key machines'structure and their running parameters in heat disperser system were analyzed; further, the solid phase of pulp flow was analyzed by solid particle model and pulp flows were simulated and analyzed with "fluent" fluid software; scales'chemical and physical formation mechanism in heat disperser were discussed; finally, the design idea of heat disperser's structure were established.The results were as follows:(1) Total removed scales in heat disperser is less than those in coarse screen and fine screen in pulping process; and it achieved 85% in the pulp.(2) Scales on plates of heat disperser with waste paper deinking are composed of disk metal(0.50% below), CaCl2 and MgCl2(mass fraction in 4.50～5.00%), SiO2 (37.20%), CaMgSi2O6(2.50%), CaSiO3(2.12%), CaCO3(11.20%), CaMgSiO4(4.50%), Ca(OH)2(1.80%), CaO(0.40%), MgO(0.80%), organic matter mainly composed of tiny fiber(15.00% or so); total content of Ca2+ in scales is 11.40%, while total content of Mg2+ is 1.44%, and Silicon sol is the main adhesive medium.(3) Scales in heat disperser is resulted from NaOH, CaCl2, NaSiO3, chelating agent, deinking agents, (NH2)(NH)CSO2H and flocculant. And these chemicals interweave with silicon sol and fiber.(4) Compared with multiple disk filters, plug screw, inwall headbox and forming wire, sediments on heat disperser have more complex species and composition and are numerous in quantity.(5) Following measures can be used to control scales in heat disperser:increasing beating degree; reducing particle degree; reducing slurry flow; reducing fluid viscosity; reducing fluid density; reducing the pulp consistency; increasing turbulence intensity; reducing effective time and area (for example, reducing density of tooth arrangement, reducing alveolar deepness and reducing quantity of teeth); decreasing dynamic disk rotation velocity; amplifying distance between fixed and active plates; increasing smoothness of equipment surface.(6) Scales on heat disperser are influenced by dynamic distribution of fluid physical parameters; kinetic energy and thermal energy of solid-liquid two-phase flow in plates is too low, so scales on heat disperser are easy to form and numerous in quantity; when slurry kinetic and thermal energy changing trends have been reduced, deposits'formation on disc heat disperser can be controlled well. |
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