Mikkeli, Finland
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Paoliello F.,Celulose Nipo Brasileira Cenibra | Pulliainen M.,Savcor Forest Oy | Niemelainen P.,Savcor Forest Inc.
NACE - International Corrosion Conference Series | Year: 2012

Digester corrosion has become a major topic for the pulp and paper industry in that it brought about the need for high expenditures with repairs, replacement of components and upgrade of materials, as well as losses in connection with unplanned outages. Risks to life and property are also significant, as catastrophic failure of pressurized equipment may result. From the eighties to present day, corrosion problems in many pulp and paper mills around the world have been intensifying, for reasons ranging from materials and design aspects of the digesters themselves, to process modifications introduced ever since. The present work has the main objective to study the corrosive behavior of continuous digesters with modified processes. Actual corrosion cases in two digesters are presented: (i) carbon steel and (ii) stainless steel clad (316L) digester. Electrochemical testing, metallurgical analyses, corrosion testing and field inspections were used to support the discussions and conclusions. In one field case, a carbon steel digester experienced rapid thinning on its top sections with wall loss of 5 mm over 30 months, after a process change. In the second case, also following a process change, a type 316L stainless-clad continuous digester, the only one in such material known in the Kraft pulping, presented an altered electrochemical profile indicating prospective stress corrosion cracking risk. This prompted the execution of studies and protective measures that are unique for stainless cooking vessels. The risks to carbon or austenitic stainless steel digesters running on modern cooking processes are demonstrated to be significant. The effectiveness of the protective technologies, as well as their compatibility, was proved. The need to consider these technologies upon cooking retrofit projects was established. ©2012 by NACE International.


Vepsalainen M.,VTT Technical Research Center of Finland | Vepsalainen M.,Lappeenranta University of Technology | Kivisaari H.,University of Jyväskylä | Pulliainen M.,Savcor Forest Oy | And 2 more authors.
Separation and Purification Technology | Year: 2011

This study investigated the effect of electrocoagulation treatment on toxic pollutant removal from pulp mill effluents. Synthetic wastewaters containing wood rosin and copper or pure resin acids were used to investigate the removal of resin acids and copper by electrocoagulation. Removal of pollutants by electrocoagulation was also tested with real debarking effluent. In this study, statistical experimental design and partial least squares modeling were used to investigate the effect of initial pH, current (current density) and treatment time. Electrocoagulation and subsequent filtration removed resin acids and copper from the synthetic wastewaters with high efficiency. Toxicity to algae (Pseudokirchneriella subcapita) was completely eliminated by the treatment, however reduction of bacterial toxicity (Vibrio fischeri) was more limited. While the initial EC50 value for bacteria in debarking effluent was around 8-14 vol%, toxicity was approximately halved by electrocoagulation. Toxicity removal from the debarking effluents was associated with color removal. © 2011 Elsevier B.V. All rights reserved.


Vepsalainen M.,University of Eastern Finland | Selin J.,UPM Kymmene Oyj | Rantala P.,UPMKymmene Oyj | Pulliainen M.,Savcor Forest Oy | And 5 more authors.
Environmental Technology | Year: 2011

The precipitation of dissolved sulphide ions by electrocoagulation was studied at laboratory scale using pulp and paper mill wastewaters. Concentrations of dissolved organic carbon and phosphorus were analysed before and after the electrocoagulation process to examine the suitability of the process for treatment of sulphide odour from pulp and paper mill wastewater. The electrochemical cell used in this study was constructed from monopolar dissolving iron electrodes. The dissolved iron concentration was directly proportional to the applied electric charge (C/L) at the tested current densities. Electrochemically produced ferrous iron (Fe2+) precipitated dissolved sulphide ions efficiently. Electricity consumption of the treatment was 4-8 C/mg S2- while iron consumption was 1.1-2.2 mg/mg S2- during the initial phase of the sulphide precipitation when the applied electric charge was 10-60 C/L. When 60 C/L was applied, 88% of dissolved sulphides and 40% of phosphorus was precipitated. The reduction in DOC was low during the sulphide precipitation. According to these results, electrocoagulation can precipitate dissolved sulphides effectively and thereby reduce sulphide odours of pulp and paper mill wastewaters. © 2011 Taylor & Francis.


Vilhunen S.,Mikkeli University of Applied Sciences | Vilve M.,Mikkeli University of Applied Sciences | Vepsalainen M.,Savcor Forest Oy | Sillanpaa M.,Mikkeli University of Applied Sciences
Journal of Hazardous Materials | Year: 2010

A re-circulated flow-through photoreactor was used to evaluate the ultraviolet (UV) photolysis and UV/H2O2 oxidation process in the purification of three different water matrices. Chemically coagulated and electrocoagulated surface water, groundwater contaminated with creosote wood preservative and 1,2-dichloroethane (DCE) containing washing water from the plant manufacturing tailor-made ion-exchange resins were used as sample waters. The organic constituents of creosote consist mainly of harmful polycyclic aromatic hydrocarbons (PAH) whereas 1,2-DCE is a toxic volatile organic compound (VOC). Besides analyzing the specific target compounds, total organic carbon (TOC) analysis and measurement of change in UV absorbance at 254nm (UV254) were performed. Initial TOC, UV254 and pH varied significantly among treated waters. Initial H2O2 concentrations 0-200mg/l were used. The UV/H2O2 treatment was efficient in removing the hazardous target pollutants (PAHs and 1,2-DCE) and natural organic matter (NOM). In addition, high removal efficiency for TOC was achieved for coagulated waters and groundwater. Also, the efficiency of direct photolysis in UV254 removal was significant except in the treatment of 1,2-DCE containing washing water. Overall, UV254 and TOC removal rates were high, except in case of washing water, and the target pollutants were efficiently decomposed with the UV/H2O2 method. © 2010 Elsevier B.V.


Niemelainen P.,Savcor Forest Oy | Pulliainen M.,Savcor Oy | Kahala J.,Savcor Oy | Luukkainen S.,Savcor Oy
Tappi Journal | Year: 2016

Black liquor high solids (about 80%) concentrators have often been found to suffer from aggressive corrosion. In particular, the first and second effect bodies are susceptible to corrosion attacks resulting in tube leaks and wall thinning, which limit the availability and lifetime of evaporator lines. Corrosion dynamics and construction materials have been studied extensively within the pulp and paper industry to understand the corrosion process. However, it has been challenging to identify root causes for corrosion, which has limited proactive measures to minimize corrosion damage. Corrosion of the first phase concentrator was studied by defining the potential regions for passive area, stress corrosion cracking, pitting corrosion, and general corrosion. This was achieved by using a technique called polarization scan that reveals ranges for the passive area in which the equipment is naturally protected against corrosion. The open circuit potential, also known as corrosion potential, and linear polarization resistance of the metal were monitored online, which allowed for definition of corrosion risks for stainless steel 304L and duplex stainless steels 2205 and SAF 2906. An online temperature measurement added insight to the analysis. A process diagnostics tool was used to identify root causes of the corrosion attacks. Many of the root causes were related to process conditions triggering corrosion. Once the metal surface was activated, it was difficult to repassivate the metal naturally unless a sufficient potential range was reached. © 2016, TAPPI Press. All rights reserved.


Leino T.J.,VTT Technical Research Center of Finland | Aho M.J.,VTT Technical Research Center of Finland | Gynther S.J.,Savcor Forest Oy | Ruuskanen T.A.,Savcor Forest Oy | Hakkinen M.H.,Savcor Forest Oy
Energy and Fuels | Year: 2013

The operation of a pilot-scale online corrosion sensor system was studied at VTT's 100 kW grate pilot plant. The feedstock composition in tests was varied from 100% wood chips to a blend that also contained 40 en-% d.b. corn stover. The mass flow of alkali chlorides was varied with sulfur-containing additives. The measurements included electrical resistance (ER) of deposit and linear polarization resistance (LPR) for both St45.8 and AISI347H alloys. The number of fine particles (online data), alkali chloride mass flow, chloride content of the deposit, and flue gas composition (online data) were simultaneously measured to study how the furnace conditions correlate with the ER and LPR signals. Information on the risky furnace conditions can be obtained with these methods. The decrease in sensor signals after starting to feed in fuel blended with corn stover indicated increasing corrosion. The ER and LPR values started to increase again after changing the fuel back to 100% wood chips. The deposit composition, alkali chloride flow, and corrosion sensor signals predicted a low corrosion rate on the alloys with the corn stover-containing blend, when the mass flow of additive was sufficient to destroy the corrosive alkali chlorides before meeting the probe. © 2013 American Chemical Society.


Vilve M.,University of Eastern Finland | Vilhunen S.,University of Eastern Finland | Vepsalainen M.,Savcor Forest Oy | Kurniawan T.A.,University of Eastern Finland | And 3 more authors.
Environmental Science and Pollution Research | Year: 2010

Background, aim, and scope: Chlorinated volatile organic compounds (CVOCs), widely used in industry as solvents and chemical intermediates in the production of synthetic resins, plastics, and pharmaceuticals, are highly toxic to the environment and public health. Various studies reported that Fenton's oxidation could degrade a variety of chlorinated VOCs in aqueous solutions. In acidic conditions, ferrous ion catalyzes the decomposition of H2O2 to form a powerful •OH radical. In this study, wastewater from wash of ion-exchange resin containing typical CVOC, 1,2-dichloroethane, was treated using Fenton's oxidation. To reduce environmental load and processing costs of wastewater, Fenton process as a simple and efficient treatment method was applied to degrade 1,2-dichloroethane of wash water. Materials and methods: The water samples were collected from three different washing stages of ion-exchange resin. The degradation of 1,2-dichloroethane and total organic carbon (TOC) of wash water of ion-exchange resin by Fenton process was studied with response surface method (RSM). Design of the experiments was conducted by central composite face, and factors included in three models were Fe2+ and H2O2 doses and treatment time. Relevant quadratic and interaction terms of factors were investigated. Results: According to ANOVA, the model predicts well 1,2-dichloroethane reduction of all water samples and TOC reduction of samples 2 and 3. The Fe2+ and H2O2 doses used in the present study were most suitable when 1,2-dichloroethane concentration of the wash water is about 120 mg L-1. In that case, Fenton's oxidation reduced 1,2-dichloroethane and TOC up to 100% and 87%, respectively, according to the RSM model. With 90-min reaction time and H2O2 dose of 1,200 mg L-1, the required Fe2+ doses for 1,2-dichloroethane and TOC were 300 and 900 mg L-1, respectively. The optimal H2O2/Fe2+ stoichiometric molar ratio was between 4-6. Then, concentration of Fe2+ was low enough and the amount of residual sludge can thus be reduced. It seems that most of TOC and part of 1,2-dichloroethane were removed by coagulation. Discussion: Up to a certain extent, increase of Fe2+ and H2O2 doses improved the removal of 1,2-dichloroethane and TOC. High Fe2+ doses increased the formation of ferric-based sludge, and excessive H2O2 doses in sample 2 decreased the degradation of 1,2-dichloroethane. Excess amount of hydrogen peroxide may scavenge hydroxyl radicals, thus leading to loss of oxidative power. Also, the residual hydrogen peroxide of different samples increased with increasing H2O2 dose and H2O2/Fe2+ molar ratio and decreasing treatment time probably also due to scavenging reactions. Due to the saturated nature of 1,2-dichloroethane, the oxidation mechanism involves hydrogen abstraction before addition of hydroxyl radical, thus leading to lower rate constants than for direct hydroxyl radical attack, which for one increases the treatment time. Conclusions: Complete removal of 1,2-dichloroethane was attained with initial concentration >120 mg L-1. Also, TOC degraded effectively. Wash water with higher concentration of 1,2-dichloroethane requires longer treatment times and higher concentrations of Fe2+ and H2O2 for sufficient 1,2-dichloroethane removal. Recommendations and perspectives: Due to the results achieved in this study, Fenton's oxidation could be recommended to be used for organic destruction of wash water of ion-exchange resin. Residual sludge, the main disadvantage in Fenton process, can be reduced by optimizing the ferrous dose or by using heterogeneous treatment where most of the reusable iron remains in the solid phase. © 2010 Springer-Verlag.


Kahala J.,Savcor Forest Oy | Suojarvi M.,Savcor Forest Oy | Niemelainen P.,Savcor Forest Inc.
Paper Conference and Trade Show, PaperCon 2013 | Year: 2013

Profile measurements are typically monitored visually with 2D-profile maps. 2D-profile maps are usually designed for viewing purposes and it is difficult to extract useful detailed information from those. Process measurements cannot be studied together with profile maps and therefore it is not possible to perform root-cause analysis to find origin of profile quality disruptions. There is a need for flexible profile data handling system with an online connection to process data. With a new system profile data can be handled similarly like any other process measurement. The user can freely select any time interval for study and clear outlier data points from the data set. The analysis can be focused to certain time periods, i.e. grade runs or jumbo rolls etc. Profile variations can be characterized with calculated indices which pinpoint problems in the profile measurements. The profile variation indices can be compared with process measurements to find those process changes that cause changes in CD profiles. This methodology ensures uniform and high quality CD profile of produced paper. This presentation is a follow on to the presentation in PaperCon 2010.


Vepsalainen M.,VTT Technical Research Center of Finland | Vepsalainen M.,Lappeenranta University of Technology | Pulliainen M.,Savcor Forest Oy | Sillanpaa M.,Lappeenranta University of Technology
Separation and Purification Technology | Year: 2012

This study analyzed the effect of electrocoagulation cell construction on NOM removal from Finnish surface water. Three types of cells were used in this research: one that only had aluminum electrodes, one that had aluminum anodes and inert cathodes, and one that had inert anodes and aluminum cathodes. Main water quality parameters such as TOC, apparent color, and concentrations of residual metals were measured from the samples. A statistical model was made from the results using partial least squares (PLSs) regression. According to the results, electrocoagulation was able to produce high quality water with low NOM concentration. Lowest measured TOC concentration was 4.02 mg/l (78% removal). The potential applications of water after the treatment could be potable water or industrial fresh water. Aluminum originating from the anodes or cathodes had similar NOM removal efficiency. According to TOC and ζ-Potential results, the mechanism of NOM removal was similar to chemical coagulation in different pHs. It seems that in low pH, double layer compression was the main destabilization mechanism whereas in higher pH, adsorption and bridging dominated.© 2012 Elsevier B.V. All rights reserved.


A method for measuring and controlling a chip level and/or a chip-liquor combination level and/or liquor level height of a liquid-steam phase digester or a hydraulic digester which digester comprises a chip screw for feeding chips into a digesting volume. The method comprises mounting electrode pairs in certain heights and vertically at distances from each other in the digesting volume of the digester, the electrode pairs being formed of electrodes; connecting the electrode pairs to electric circuits; measuring in each electric circuit a current or voltage value during operation of the digester; determining, based on the measurement, type of material layer (for example, steam, chips, combination of chips and liquor, or liquor) located in a certain height, based on the electrical conductivity of the materials in the digesting volume. An arrangement for measuring and controlling a chip level and/or a chip-liquor combination level and/or a liquor level height of a liquid-steam phase digester or a hydraulic digester.

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