February 2008Pub Date : 2008-03-01DOI: 10.32964/tj7.2.26
A. A. Morais, A. Mounteer, D. Silveira
{"title":"Improvement of eucalyptus bleached kraft pulp effluent treatment through combined ozone-biological treatment","authors":"A. A. Morais, A. Mounteer, D. Silveira","doi":"10.32964/tj7.2.26","DOIUrl":"https://doi.org/10.32964/tj7.2.26","url":null,"abstract":"The aim of this work is to evaluate the combination of ozonation and biological treatment for reducing recalcitrant organic matter and enhancing the biological treatment efficiency of kraft pulp elemental chlorine-free (ECF) bleaching and similar effluents. Alkaline bleach filtrate was treated with ozone at doses of 100 and 250 mg/L, temperature of 70ºC, and pH 10 (mill conditions). The ozone-treated and untreated effluents were mixed with acid bleaching filtrate to prepare the combined effluents, which were then treated in a bench-scale activated sludge system. The constant biological treatment conditions used were: temperature = 35±2ºC, hydraulic retention time = 12 hours, and sludge retention time = 10 days. Effluents were also fractionated by molecular mass using a membrane with a 500-Da molecular-weight cutoff to characterize the high- and low-molecular-mass organic matter. Ozonation combined with biological treatment resulted in statistically significant increases in removal of COD, BOD5, TOC, lignin, and AOX compared to the effluent without ozone treatment. The high-molecular-mass fractions represented the majority of all components analyzed, and their contribution to total effluent load increased after biological treatment because of the greater removal efficiency of low-molecular-mass organic matter.","PeriodicalId":124385,"journal":{"name":"February 2008","volume":"120 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116400416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
February 2008Pub Date : 2008-03-01DOI: 10.32964/tj7.2.4
A. Sand, M. Toivakka, T. Hjelt
{"title":"Investigation of filtercake stability using numerical simulation technique","authors":"A. Sand, M. Toivakka, T. Hjelt","doi":"10.32964/tj7.2.4","DOIUrl":"https://doi.org/10.32964/tj7.2.4","url":null,"abstract":"The stability of a paper coating filtercake and the influence of Brownian motion relative to absorption flow can be described using a particle dynamics model. For such a study, we assumed that the stability of a filtercake depends on the interrelation between particle diffusion and the hydrodynamic drag force caused by the absorption flow of liquid. We simulated particle diffusion using a Brownian motion model. Our investigation included monodisperse and polydisperse particle systems of electrostatically stabilized rigid spheres. We also varied system temperatures in some of the simulations. Results characterize the stability, microstructure, density profiles, and thicknesses of the filtercake. We concluded that particle diffusion disrupted the filtercake if the size of the particles was small or the temperature high. For dewatering rates typical of paper coating processes, the simulations show that only particles less than 0.2 µm are able to diffuse sufficiently to result in a solids density gradient over the thick-ness of the filtercake. In the polydisperse system, small particles can migrate within the filtercake at low dewatering rates. The solids concentration gradient observed in some cases appeared to be the result of filtercake surface roughness, partly caused by a size segregation effect rather than of the proposed thickening mechanism.","PeriodicalId":124385,"journal":{"name":"February 2008","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130164486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
February 2008Pub Date : 2008-03-01DOI: 10.32964/tj7.2.11
H. Tran, C. A. Brown, A. Jones
{"title":"Effects of SO2 on superheater fouling in kraft recovery boilers","authors":"H. Tran, C. A. Brown, A. Jones","doi":"10.32964/tj7.2.11","DOIUrl":"https://doi.org/10.32964/tj7.2.11","url":null,"abstract":"Researchers used an entrained flow reactor (EFR) to examine the effect of SO2 concentration in combustion gas on the deposition rate, composition, and adhesion strength of carryover deposits produced from burning dried black liquor. The results indicate that SO2 is not the main cause of fouling in the superheater region of recovery boilers. High SO2 may even be beneficial, as it helps produce deposits more easily removed by soot blowers. In recovery boilers where high SO2 and excessive carryover fouling are observed at the same time, it is likely that they are a result of other boiler operating factors.","PeriodicalId":124385,"journal":{"name":"February 2008","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121602098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
February 2008Pub Date : 2008-03-01DOI: 10.32964/tj7.2.19
E. Axelsson, T. Berntsson
{"title":"Heat integration opportunities in an average Scandinavian fine paper mill: model study and comparison with a market pulp mill","authors":"E. Axelsson, T. Berntsson","doi":"10.32964/tj7.2.19","DOIUrl":"https://doi.org/10.32964/tj7.2.19","url":null,"abstract":"The pulp and paper industry has a potential for significant energy savings, as shown by many studies on both market pulp mills and integrated pulp and paper mills. In this study, we compare the opportunities for energy savings through heat integration in the two mill types. To do this systematically, we used model mills with an identical pulp mill connected to either a pulp dryer or to two paper machines. An energy analysis of the integrated mill showed that there are steam-saving opportunities of about 16%, which enable increased electricity production or fuel savings in the form of reduced bark burning. For electricity production, the break-even electricity price was 25–50 €/MWh depending on economic conditions. For fuel savings, the break-even bark price was 5–11 €/MWh depending on economic conditions and electricity price (the electricity production decreased when fuel was saved). When comparing the integrated pulp mill with the market pulp mill, the authors identified inherent differences that influenced the steam-saving opportunities in favor of the market pulp mill, implying a payback period about 0.4 years longer in the case of electricity production in the integrated mill. In the case of fuel savings, however, the integrated mill would have significantly better profitability, because fuel savings in the market pulp mill had to be in the form of lignin extraction from the black liquor, which would entail additional investment and operating costs.","PeriodicalId":124385,"journal":{"name":"February 2008","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128281002","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
February 2008Pub Date : 2008-03-01DOI: 10.32964/tj7.2.18
J. Colodette, C. Gomes, Marcos Souza Rabelo, Kátia Maria MORAIS EIRAS, Adriana de Fatima Gomes, K. D. Oliveira
{"title":"Eucalyptus kraft pulp bleaching: state-of-the-art and new developments","authors":"J. Colodette, C. Gomes, Marcos Souza Rabelo, Kátia Maria MORAIS EIRAS, Adriana de Fatima Gomes, K. D. Oliveira","doi":"10.32964/tj7.2.18","DOIUrl":"https://doi.org/10.32964/tj7.2.18","url":null,"abstract":"Chemical demand, yield, water consumption, effluent load and treatability, pulp organic chlorine compounds (OX), brightness stability, refinability, and strength are drivers for choosing bleaching technology. This work critically reviews the state-of-the-art processes for oxygen delignification, first stage, second stage, and final bleaching of eucalyptus kraft pulp in light of those drivers. Emerging technologies, such as the PMo stage and formaldehyde assisted bleaching, are discussed. Implementation of single- or double-stage oxygen delignification is determined by the pulp “true” lignin content. High pulp HexAs content and poor selectivity limits dropping kappa number under 9-10 in single or double O-stage. Mo-catalyzed acid peroxide delignification after O-stage allows further reduction of kappa number to 3-4. Efficient post-oxygen washing is the key for low cost bleaching, with a kilogram of COD/o.d. ton consuming the equivalent to 0.085% active chlorine. A/D-(EP)-D type three-stage sequence suffices for bleaching eucalyptus kraft pulps. The inclusion of a fourth stage is desirable for high brightness/low reversion pulps. Chemical consumption is strongly influenced by brown pulp origin, with variations of 3.2% to 7.7% active Cl2 demand, depending upon the pulp type. The type of elemental chlorine free (ECF) bleaching technology, based on chlorine dioxide, affects chemical consumption only slightly. Hot acid/hot chlorine dioxide bleaching technology saves small amounts of active chlorine for high bleachability pulps, but none for low bleachability ones. Atmospheric extraction (EP) suffices for eucalyptus kraft pulp bleaching. Formaldehyde saves more chlorine dioxide when used in D1 than in D0/DHT stages. A final peroxide stage improves pulp brightness stability. The production of organically bound chlorine decreases by 30% with hot chlorine dioxide bleaching, but this gain disappears after effluent biological treatment.","PeriodicalId":124385,"journal":{"name":"February 2008","volume":"56 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113960867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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