SCA Obbola AB is a kraft pulp mill that produces and sells packaging paper. The steam demand is covered by a recovery boiler and a solid fuel boiler (consists of two parallel solid fuel furnaces and a boiler). Adjustments in steam production are foremost made by the solid fuel boiler. Previously made energy-reducing measures at the mill has lowered the steam demand which forces the solid fuel boiler to low steam production. The solid fuel boiler produces over 25 GWH/year and is therefor bound by the Swedish nitrous oxide charge, but is also restricted to a monthly mean value of 70 mg/MJ. This mean value was exceeded in July 2016, which is thought to be a result of forced limitation in steam production. NOx emissions are reduced secondarily by an urea-based SNCR-system where its efficiency depends on several parameters, foremost sufficiently high flue gas temperatures. This work has identified parameters that effects foremost hydrogen-based combustion emission from the solid fuel boiler. This was achieved by evaluating historical data and by conducting tests during operation of the solid fuel boiler, which was planned and evaluated using a software called MODDE. Emission reducing measures and recommended ways to operate the boiler was then presented from the collected data. Practical measures including down-winding supply machinery of secondary air and replacement of urea injection showed no tendencies in reducing NOx emissions. However, complete shut down of one the furnaces produced at least 100 °C higher flue gas temperatures produced from the active furnace. Low NOx emissions was noted when secondary air was supplied from machinery with original speed. therefor, during stretched periods with low steam production, it's recommended that: Only one furnace should be active as steam producer, urea should be injected at its original placement in the flue gas chamber close the furnace and that secondary air should be supplied by machinery with original speed. Comparison test made in this work showed that this way of operating the solid fuel boiler could reduce NOx emissions with 45 % compared to mean NOx emissions at low steam production in July 2016.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:umu-139441 |
| Date | January 2017 |
| Creators | Larsson, Albin |
| Publisher | Umeå universitet, Institutionen för tillämpad fysik och elektronik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | Swedish |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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