In English

Energy Efficiency Opportunities within the Heat Treatment Industry

Malin Källen
Göteborg : Chalmers tekniska högskola, 2012. 52 s.
[Examensarbete på avancerad nivå]

Energy efficiency measures have become a top priority for large energy consuming companies because of the increasing energy prices and implemented energy policies. Many companies also receive demands from their customers to reduce their climate impact. Heat treatment processes are performed at high temperature, sometimes up to 1000°C, and the holding time can be up to several hours. A large amount of energy is needed for these processes and this reflects in a large energy cost for these companies. The purpose of this project was to identify advantageous, both economically and environmentally, energy efficiency improvements in a specific steel heat treatment plant. The first part of the project was to perform an energy audit and map the energy consumption in the plant. When the distribution of the energy consumption had been determined, the largest energy consumers could be identified. The search for energy efficiency opportunities was then focused on the largest energy consumers in the plant. The profitability of the identified energy saving possibilities was evaluated as well as the environmental benefits of the suggestions. The energy audit showed that the major part of the energy was consumed in the process itself and that the largest energy consumer among the support processes is the ventilation system. The hardening and nitrokarburizing furnaces, or the main furnaces, are the largest energy consumers of the process equipment. It was found that 753 MWh/year (7.7%) of electricity can be saved by housekeeping measures. The suggested measures were to remove unnecessary lighting, turn off the manual equipment during weekends, plan the production more energy efficiently, search the compressed air system for leaks and close a damper in a preheating furnace. The proposed energy saving investment measures will all together save 418 MWh/year (4.3%) of electricity and remove the district heating demand. The suggested investments were to switch the lighting to low energy lamps, insulate the door hoods of the main furnaces, move the intake to the compressor outdoors, heat exchange exhaust furnace gases with washing water and heat exchange the waste heat from the compressor with the heating of the offices. All suggested investment were shown to be profitable, i.e. having a positive net present value. However, the payback periods for the heat exchanging between the compressor and the offices and the low energy lighting may be regarded to be too long as they were more than five years. If all housekeeping measures and all investment measures were implemented, the energy cost for the plant would decrease with almost 1 MSEK/year.

Nyckelord: heat treatment, energy audit, energy efficiency

Publikationen registrerades 2012-06-27. Den ändrades senast 2013-04-04

CPL ID: 159604

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