In English

Modellering och energiintegrering av en pappersmaskin

Jörgen Persson
Göteborg : Chalmers tekniska högskola, 2002.
[Examensarbete på avancerad nivå]

In this diploma work a model of an integrated pulp and paper mill has been evaluated and analysed. The pulp mill is a reference model mill, defined in the research program “The Ecocyclic Pulp Mill”, and it consists of the best technology built and run in the Nordic pulp and paper industry. The paper mill however, is modelled in this study. The heat demand of the mill has been analysed using Pinch Technology. The paper mill in the reference model mill is a conventional paper mill, and consists of wire and press section with a white water system, and a cylinder dryer followed by a soft calender. Since the dryer is the most energy demanding section of the paper mill, mainly different ways to improve the drying section have been studied. Three different ways to change the dryer section have been studied, higher dry solids content before the cylinder dryer and a combination of the cylinder dryer with either an impulse dryer or a superheated steam dryer. Apart from the mill’s energy demand, changes in fuel costs and emissions of carbon dioxide with the different dryer models have been studied. When part of the cylinder dryer is replaced with an impulse dryer or a superheated steam dryer the live steam demand decreases, while the electricity or natural gas demand increases. A reduction in steam consumption, i.e. reduction in steam production, also leads to a decrease of the electricity production in the mill. To compensate this the mill has to buy externally produced electricity. The bark, which has been made available through the reduced production of steam, can be used to decrease the deficit of bark in the mill. In the base case the reference model mill has a heat demand of 9,46 GJ/t paper, while the cylinder dryer has a heat demand of 3,77 GJ/t paper. If the dry solids content increases with five percentage units, the heat demand in the cylinder dryer decreases with 15 %. When part of the cylinder dryer is replaced with an impulse dryer drying the paper to a dryness of 65 % the steam demand decreases in the cylinder dryer section with 42 %. At the same time the electricity or natural gas demand increases with 290 or 326 kWh/t paper respectively. When using a combination of a superheated steam dryer and cylinder dryer, where 50 % of the drying is carried out in each of the dryer, the live steam demand decreases with roughly 50 %, while the natural gas demand increases with 622 kWh/t paper. The reduced steam demand and the raised electricity and natural gas demand leads to decreased emissions of carbon dioxide in the mill, if it can be assumed that the bark that is made available is used to replace oil elsewhere. The emissions decreases with 111 and 148 kg/t paper for the combination of a cylinder dryer and an impulse dryer heated with electricity or natural gas respectively, and with 197 kg/t paper when using the combination of a superheated steam dryer and a cylinder dryer. The fuel cost increases when using a combination of a cylinder dryer and an impulse dryer or a superheated steam dryer, compared to only using a cylinder dryer. The cost increases with 48 SEK/t paper for the impulse dryer when heated by electricity, and 26 SEK/t paper when heated by natural gas. For the superheated steam dryer the fuel cost increases with 51 SEK/t paper. The cylinder dryer is therefore a better alternative regarding fuel cost.



Publikationen registrerades 2007-12-21. Den ändrades senast 2013-04-04

CPL ID: 63803

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