Time filter

Source Type

Rauma, Finland

Isokangas A.,University of Oulu | Ala-Kaila K.,University of Oulu | Ohenoja M.,University of Oulu | Sorsa A.,University of Oulu | Leiviska K.,Metsa Fibre Oy
Nordic Pulp and Paper Research Journal

The purpose of this paper is to analyse the log loading process of wood room, which is typically the first processing unit in pulp and paper mills. The aim is to improve the log loading process to obtain production with a constant log flow of well de-iced logs to the debarking drum. This way it is possible to reduce costs and enhance product quality. The research was carried out utilising a log loading simulator. The parameters of the simulation model were selected on the basis of process observations on a mill. The results indicate that it is essential to adjust the process and equipment parameters, raw material properties and truck loader operation together in order to reach the target capacity with minimum costs. Especially the speed of the infeed conveyor affects all performance criteria and should be selected carefully. In addition, wood yard logistics and raw material properties have a remarkable effect on the wood room performance. The results can be utilised in mills to allow the upper level control perform in a planned way so that small wood loss and good product quality can be obtained. Source

Isokangas A.,University of Oulu | Ala-Kaila K.,University of Oulu | Sorsa A.,University of Oulu | Ohenoja M.,University of Oulu | Leiviska K.,Metsa Fibre Oy
Nordic Pulp and Paper Research Journal

The objective of this work was to develop a log loading simulator of the wood room in pulp and paper industry. In the first stage the log loading process is modelled. Then the criteria for evaluating the effects of log loading on the wood room performance are defined. The motivation for the research is that log loading can be identified as playing a central role if the production and cost-effectiveness of the wood room is to be increased. The lack of reliable process measurements and changes in raw material quality, which are not measured on-line, make the data-based modelling of an industrial log loading process difficult. For these reasons, the research was performed via mathematical modelling of the process. The simulated results confirm that the same production can be obtained in many ways, but there can be differences in costs. Especially too high speed of the infeed conveyor in relation to capacity leads to several drawbacks, which typically result in increased wood loss and decreased chip quality. For this reason it is important to consider all aspects of log loading for the best performance. The results give insight into the log loading process and may help to improve the log loading process. Source

Rantamaki J.M.,Metsa Fibre Oy | Rantamaki J.M.,VTT Technical Research Center of Finland
Journal of Quality in Maintenance Engineering

Purpose-This paper deals with the identification and diagnosis of operational variability in chemical processes, which is a common problem in mills but little explored in literature. The Cross-Industry Standard Process for Data Mining (CRISP-DM) is a widely used approach in problem solving. The purpose of this paper is to: first, contribute to the body of knowledge on applying CRISP-DM in a pulp mill production process and the special issues that need to be considered in this context. Exact amounts of a cost increase due to variation in pulp production have not been reported previously. Second, to quantify the cost of variation. Design/methodology/approach-In the case studied, the variation in a pulp mill batch cooking process had increased. In order to identify the causes of variation, CRISP-DM was applied. Findings-The cycle of variation was identified and found to be related to the batch cooking process cycle time. By using information from this analysis it was possible to detect otherwise unobserved defective steam nozzles. The defective equipment was repaired and improved. Further improvement was achieved when the fouling of a heat exchanger was found by analysis to be the root cause of long-term variability parameters. By applying CRISP-DM, equipment defects and fouling were identified as the root causes of the higher manufacturing costs due to increased variation were detected and estimated. The Taguchi loss function is a possible tool for estimating the cost of variation in pulp manufacturing. Originality/value-This paper provides new knowledge in the context of implementing CRISP-DM and the Taguchi loss function in the pulp and paper manufacturing process. © Emerald Group Publishing Limited 1355-2511. Source

Testova L.,Aalto University | Roselli A.,Aalto University | Costabel L.,Aalto University | Kovasin K.,Metsa Fibre Oy | And 2 more authors.
Industrial and Engineering Chemistry Research

Alkaline pre-extraction of birch wood was performed to isolate polymeric xylan and subsequently produce a paper-grade pulp. At 95 °C and 2.5 mol/L NaOH, 7% of wood was transferred to the E-lye as polymeric xylan with an anhydroxylose-lignin ratio of 6.5. Xylan with a weight-average molar mass of 20 kDa was quantitatively precipitated from the solution previously concentrated from 7.4 to 37 g/L. The anhydroxylose-lignin ratio in the carbohydrate fraction increased to 29 g/g upon precipitation. Enzymatic hydrolysis of the commercial birch xylan with Pentopan Mono PG resulted in a uniform xylooligosaccharide product with low xylose content at a yield of 61%. The pre-extracted pulp had excellent papermaking properties but its yield was 4.9% units lower than that of the reference pulp. Commercial potential of the modified process was discussed. © 2014 American Chemical Society. Source

Wedin H.,KTH Royal Institute of Technology | Fiskari J.,University of Helsinki | Kovasin K.,Metsa Fibre Oy | Ragnar M.,Svenskt Gastekniskt Center | Lindstrom M.E.,KTH Royal Institute of Technology
Nordic Pulp and Paper Research Journal

Extended-impregnation kraft cooking (EIC) is a cooking concept that combines prolonged impregnation with modern improved modified kraft cooking. In the current investigation, the EIC cooking of birch was studied in relation to conventional kraft cooking. Specifically, the reject content and carbohydrate yield retention when terminating at a high cooking kappa number were examined. It was demonstrated that EIC cooking reduced the reject content. Unexpectedly, a high cooking kappa number led to no increase in carbohydrate yield, possibly due to the chemical composition of birch wood and the EIC cook lab procedure. A large amount of liquor was withdrawn after the impregnation, resulting in a loss of dissolved xylan that otherwise could have redeposited on the fibres and contributed to the carbohydrate yield. The effects of EIC cooking on extended oxygen delignification, bleaching chemical requirement in a D(OP)DP sequence, and strength properties were also examined. Compared with conventional lab cooking, EIC cooking resulted in a lower bleaching chemical requirement and similar strength properties. Source

Discover hidden collaborations