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Preparation and Adhibition of Chlorine Dioxide Bleaching Solution and Its Effects on Bleaching Wastewater

Author: FangHaiFeng
Tutor: XieHuiFang
School: Nanjing Forestry University
Course: Environmental Engineering
Keywords: Chlorine dioxide (ClO2) bleaching solutions ECF Straw pulp bleaching Bleaching effluent AOX
CLC: X793
Type: Master's thesis
Year: 2011
Downloads: 39
Quote: 0
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Abstract


Pulp and paper industry is one of pillar industries of national economy, but recent years environmental protection issues became the bottleneck hindered its development. The traditional bleaching processes with the element chlorine could not satisfy the new environmental standards, need to seek new environmental friendly bleaching technology. And under domestic economic and technical level, bleaching processes with chlorine dioxide instead of element chlorine became more actual and economic method. But, research through domestic pulp and paper enterprise and equipment manufacturing enterprise suggested that chlorine dioxide preparation system localization faced many problems, such as production process, the response relationship between wastewater pollutant load and chlorine dioxide bleaching solution composition, equipment selection and so on. This paper researched chlorine dioxide preparation process, bleaching result and wastewater pollutant load with composite chlorine dioxide bleaching solution had realistic significance.First, chlorine dioxide preparation process with sodium chlorate and Hydrochloric acid was studied in this paper, and then selected appropriate bleaching solution used to follow-up researches. Through orthogonal experiment optimization analysis and significant factor analysis, we preliminary got the effects of process conditions on chlorine dioxide bleaching solution:the mole rate of sodium chlorate and hydrochloric acid mostly affected the purity of chlorine dioxide and temperature took second place. By orthogonal experiment table analysis, the best preparation process was:the mole rate of sodium chlorate and Hydrochloric acid was 2:4, temperature was 70℃and reaction time was 0.5h.In validation test of the mole rate of raw materials and reaction time, we got the same result with orthogonal experiment.But validation test of reaction temperature showed that in chlorine dioxide solution prepared under different mole rate of raw materials, concentrations of chlorine dioxide increased with the rise of temperature,but the best reaction temperature got the largest purity of chlorine dioxide was different under different mole rate of raw materials,which reduced with the rise of hydrochloric acid scale.Therefore, in different hydrochloric acid concentration conditions, choosing their appropriate reaction temperature also became particularly important.In this paper,the best reaction temperature was respectively 80℃,70℃and 60-70℃under mole rate of raw materials 2:2、2:3 and 2:4.Through contrastive analysis of the bleaching result with different purity of chlorine dioxide solution we found, bleaching result with chlorine dioxide was much better than those with hypochlorite bleaching solution. And Through contrastive analysis with different active chlorine dosage, active chlorine dosage directly affect the bleaching result, whiteness rose obviously from 0.5% to 1.5%, and could reach similar and best result 75% ISO when 1.5%. And active chlorine dosage of hypochlorite bleaching solution needed to reach 3.5% then could reach the similar bleaching result under 1.5% of chlorine dioxide solution. The test results of pulp yIyellowindex and strength performance showed that the pulp after chlorine dioxide bleaching was much better than those after hypochlorite bleaching.Wastewater pollution load experiment results indicated bleaching with chlorine dioxide bleaching solution could effectively reduce AOX, COD, SS production in wastewater. When purity of chlorine dioxide reached 3.25, each pollutant index could achieve better level, provided effective help to follow-up wastewater treatment.

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CLC: > Environmental science, safety science > Processing and comprehensive utilization of waste > Light industrial waste disposal and comprehensive utilization > Paper Industry
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