Energikartläggning av blekeristeget för produktion av pappersmassa
(2018) KETM05 20181Chemical Engineering (M.Sc.Eng.)
- Abstract
- Stora Enso Nymölla is a pulp and paper mill mainly producing office paper. Their most well-known product is the MultiCopy paper. Every fourth year all large companies are by law required to present an energy audit. This can be done as one large report or by presenting smaller reports during the four-year period. Nymölla Mill has decided to publish short overviewing reports every year and combining these with reports that give a more in-depth look at different parts of the process. This way Nymölla Mill can present a better picture of the energy at the site. This report focuses on the bleaching process in the pulp mill during the winter of 2017-2018. The process is divided into two production lines, one for softwood-based pulp and one for... (More)
- Stora Enso Nymölla is a pulp and paper mill mainly producing office paper. Their most well-known product is the MultiCopy paper. Every fourth year all large companies are by law required to present an energy audit. This can be done as one large report or by presenting smaller reports during the four-year period. Nymölla Mill has decided to publish short overviewing reports every year and combining these with reports that give a more in-depth look at different parts of the process. This way Nymölla Mill can present a better picture of the energy at the site. This report focuses on the bleaching process in the pulp mill during the winter of 2017-2018. The process is divided into two production lines, one for softwood-based pulp and one for hardwood-based pulp. When the pulp is bleached, the pulp passes through several filters where it is washed in hot water. Hydrogen peroxide is then added to bleach the pulp. Then the pulp is washed again in two more filters. The energy used during the bleaching process exists in three forms, electricity, steam and warm water (60°C - 90°). The water stands for more than 90% of the energy and is therefore by far the largest energy source. The main electricity consumers are the pumps, the stirrers and the filters. The pumps consume the most electricity followed by the stirrers. The conifer-line used more electricity during the studied period. This is mainly due to the line having a higher production rate during the period and not because the line has more electricity consuming units. Steam is the smallest energy source used in the bleaching. During the focus period, the steam consumption is even and correlates well with the amount of steam that has been used previous years. In January, the steam consumption is slightly higher than the rest of the months within the period. Some of the energy in the warm water that is used is recycled back to the warm water system via seven heat exchangers. Parts of the warm water system were also examined in order to understand how it cooperates with the bleaching. Around 6% of the energy in the hot water that is used in the bleaching process is recycled back. This seemingly low number partly depends on the fact that only a very limited part of the pulping process is studied. Some of the warm water that is used has received its energy from recycling in other parts of the process. In addition, the pulp is not completely cool after it has been bleached meaning that a lot of the energy added is still inside the pulp when it leaves the bleaching. The amount and temperature of the warm water used is also the most uncertain number within the report due to a lack of flow and temperature indicators. This means that the recycle ratio is a number that rests on many assumptions making it very uncertain. It is therefore suggested that more flow and temperature indicators are installed. It is also suggested that the process drawings and the computer system are looked over and any errors revised since some of the drawings of the process are incomplete. (Less)
- Popular Abstract
- The industrialization of our society has led to many technological advances and has increased the standard of living for many people. The drawback of this is the negative effect it has had on the environment. Since the negative effects that production industries have on our planet has become better known, efforts to try to make production of goods more environmentally friendly have started. One step that has been taken towards a more environmentally friendly production in Sweden is the new law that was passed in 2014 as an effect of the EU:s energy efficiency directive from 2012[1][2]. This law is called ”Lag (2014:266) om energikartläggning i stora företag”. It states that all large companies in Sweden must present an energy audit every... (More)
- The industrialization of our society has led to many technological advances and has increased the standard of living for many people. The drawback of this is the negative effect it has had on the environment. Since the negative effects that production industries have on our planet has become better known, efforts to try to make production of goods more environmentally friendly have started. One step that has been taken towards a more environmentally friendly production in Sweden is the new law that was passed in 2014 as an effect of the EU:s energy efficiency directive from 2012[1][2]. This law is called ”Lag (2014:266) om energikartläggning i stora företag”. It states that all large companies in Sweden must present an energy audit every fourth year starting in 2015.[2] The energy audit report should contain how much energy that is used in MWh and in what form the energy requirements are and where it is used. The report should also contain suggestions on how to improve the energy usage in the company. Lastly, the report should contain energy statistics from previous years and background information about the company. This is to create a context for the energy usage presented in the report. The overall purpose of the energy audit is to get a better picture of how much energy the company uses and where it is utilized. This information is then used to find suggestions for improvements. A more effective energy consumption is better for the environment and is also often cheaper in the long term perspective.[3] This report is an energy audit of the energy usage in the bleaching process at Stora Enso Fine Paper Nymölla Mill. Nymölla Mill has chosen to present their required energy audit in small parts instead of presenting one big report every fourth year. This allows them to focus on specific parts of the process, such as this in-depth view of the energy usage in the bleaching process. In the bleaching step, pulp is bleached to ensure that the finished paper is white enough for writing and printing to appear clearly. Nymölla Mill is a pulp- and paper mill creating office paper, which is why having a well bleached paper is very important. The pulp is produced by using the more uncommonly used sulphite process. Hydrogen peroxide is used as the bleaching chemical.[4] The bleaching process consists of several washing filters where hot water is added. Water washes the pulp and it is then removed in the filter. The hydrogen peroxide is added in a reaction tower where the main bleaching takes place. It is then followed by additional washing filters to remove the added chemicals. Energy is utilized in three forms during the bleaching process at Nymölla Mill: electricity, steam and hot water. Electricity is mainly used in pumps that transports the pulp and the water throughout the bleaching process, and for stirrers that are installed in several of the tanks in the bleaching process. The filters are also powered by electricity. The steam is only used to add extra heat to some of the water streams that are used. The utilization of warm water is the hardest energy source to calculate. The water is taken from the pulp-mills warm-water system. Some of the energy in the water that is used in the bleaching process is then recycled back to the warm-water system via seven heat exchangers. This means that to estimate the energy requirements in the form of warm water that is used during the bleaching of the pulp, it is necessary to understand how the warm-water system and the bleaching process interacts with each other. The energy in the water is exchanged through heat exchangers. Most of these exchangers are plate exchangers. Plate heat exchangers consists of several corrugated metal plates with a rubber gasket that lines the edges. The plates are then pressed together in a stack. The corrugated surface then acts like channels across the plate’s surface. The main advantages of using plate heat exchangers are their versatility. Plates that starts to corrode can easily be replaced by new ones. It is also possible to modify how much energy the heat exchanger can transfer by adding or removing plates.[5] The result of the energy audit was that the warm water was by far the largest energy source used in the bleaching process. No suggestions on how the process could be made more energy efficient was given because the available data from the process was not enough to investigate the process in such detail. There were however suggestions made on how to make future energy audits more exact. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/8959968
- author
- Sandgren, Märta LU
- supervisor
- organization
- course
- KETM05 20181
- year
- 2018
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- Energikartläggning, Pappersmassa, Blekeri, El, Ånga, Varmvatten, Värmeväxlare, kemiteknik, chemical engineering
- language
- Swedish
- id
- 8959968
- date added to LUP
- 2018-11-26 14:42:11
- date last changed
- 2018-11-26 14:42:11
@misc{8959968,
abstract = {{Stora Enso Nymölla is a pulp and paper mill mainly producing office paper. Their most well-known product is the MultiCopy paper. Every fourth year all large companies are by law required to present an energy audit. This can be done as one large report or by presenting smaller reports during the four-year period. Nymölla Mill has decided to publish short overviewing reports every year and combining these with reports that give a more in-depth look at different parts of the process. This way Nymölla Mill can present a better picture of the energy at the site. This report focuses on the bleaching process in the pulp mill during the winter of 2017-2018. The process is divided into two production lines, one for softwood-based pulp and one for hardwood-based pulp. When the pulp is bleached, the pulp passes through several filters where it is washed in hot water. Hydrogen peroxide is then added to bleach the pulp. Then the pulp is washed again in two more filters. The energy used during the bleaching process exists in three forms, electricity, steam and warm water (60°C - 90°). The water stands for more than 90% of the energy and is therefore by far the largest energy source. The main electricity consumers are the pumps, the stirrers and the filters. The pumps consume the most electricity followed by the stirrers. The conifer-line used more electricity during the studied period. This is mainly due to the line having a higher production rate during the period and not because the line has more electricity consuming units. Steam is the smallest energy source used in the bleaching. During the focus period, the steam consumption is even and correlates well with the amount of steam that has been used previous years. In January, the steam consumption is slightly higher than the rest of the months within the period. Some of the energy in the warm water that is used is recycled back to the warm water system via seven heat exchangers. Parts of the warm water system were also examined in order to understand how it cooperates with the bleaching. Around 6% of the energy in the hot water that is used in the bleaching process is recycled back. This seemingly low number partly depends on the fact that only a very limited part of the pulping process is studied. Some of the warm water that is used has received its energy from recycling in other parts of the process. In addition, the pulp is not completely cool after it has been bleached meaning that a lot of the energy added is still inside the pulp when it leaves the bleaching. The amount and temperature of the warm water used is also the most uncertain number within the report due to a lack of flow and temperature indicators. This means that the recycle ratio is a number that rests on many assumptions making it very uncertain. It is therefore suggested that more flow and temperature indicators are installed. It is also suggested that the process drawings and the computer system are looked over and any errors revised since some of the drawings of the process are incomplete.}},
author = {{Sandgren, Märta}},
language = {{swe}},
note = {{Student Paper}},
title = {{Energikartläggning av blekeristeget för produktion av pappersmassa}},
year = {{2018}},
}