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Development of Optical Sensor for Spectroscopic Determination of Glass Content in Refuse-derived Fuels for Heat and Power Production

Publicerad 2017-10-09

Om uppdragsgivaren
Mälarenergi AB is a city-owned company that supplies electricity, district heating, water, district cooling and fast communication solutions. The company sells electricity to private and corporate customers throughout Sweden. The group is owned by Västerås city and has a turnover of approximately SEK 3 billion. The company operates in Mälardalen and has its headquarters in Västerås.

Beskrivning av examensarbetet
Composition and properties of the waste-based fuel intended for incineration has substantial effect on combustion process performance and formation of environmentally harmful emissions. Fuel composition vary significantly depending on the material source, sorting procedures and other pretreatment methods. In general, it typically contains wood, paper, plastics, textile, other organic materials and further undesired substances including e.g. glass and metals.
Prior to incineration, waste is processed in the sorting plant to separate incombustible substances, separation is however not fully efficient. Produced refuse-derived fuel RFD therefore still contain glass residues. The presence of glass in the RDF, which is intended for incineration in fluidized bed boilers, causes increased risk of operational problems. This is due to the poor heat resistance of glass. The most soda-lime glass containing mostly SiO2. Glass material combined with elements such as K, Na, Cl, S, Si, and P from the fuel form low-melting compounds. These compounds deposit on the bed particles silica sand; i.e. SiO2 in the form of quartz, forming agglomerates and cause bed defluidization which result in a malfunction or failure of the combustion equipment followed by the necessity of replacing the bed material. Furthermore, when glass is heated to temperatures close to its melting point, a high viscous silicate phase can form, which causes clogging problems during sand/ash extraction and the boiler may need an unscheduled shut down. This leads to increased operating cost for the facility and environmental issues due to the increased production of used bed material and enlarged emissions during operation, start-up and shutdown of the boiler.
These problems can be minimized by improving process monitoring and control followed by appropriate operational measures. Therefore, the challenge is to find a method for rapid and reliable on-line characterization of the fuel fed into the boiler. Glass detection methods would be beneficial for improving boiler operating conditions, such as optimising the maintenance schedule for the bed sands and the use of additives for reducing agglomeration rates.
Non-destructive solid material characterization may be achieved by employing a near infrared NIR spectroscopy. This method is based on vibrational spectroscopy, which measures the interactions of electromagnetic NIR radiation with the covalent chemical bonds of the sample constituents at different wavelengths. The NIR spectroscopy technique is used widely and for many years in the field of food science as well as the pharmaceutical industry for quality monitoring. It is also extensively used in forestry as well as the pulp and paper industry for identification of wood and characterization of its properties and for measurements of pulp properties. Moreover, it’s also used in waste management for many applications such as monitoring of the landfilled material, separation of recyclables, recovery of biodegradable materials etc.

Thesis tasks
The thesis work flow consist of following specific tasks:
-Evaluation the potential and limitations of using NIR spectroscopy measurements for the characterization of fuel/feedstock material properties literature review.
-Correct material sampling and sample preparation.
-Spectral data acquisition on top-notch spectroscopy instruments in the lab and at Mälarenergi.
-Build reliable and robust models from NIR spectra by employing linear or non-linear regression/machine learning techniques.
-Define potentials and limitations for on-line measurements and suggest implementation of the sensor for process control

Expected results
-Thesis writing
-Participation in the writing of scientific conference or journal paper
-The feasibility of on-line measurement of glass at Mälarenergi combined heat and power plant.
Practical information
Group size: 1-4 students
Credits: 15hp or 30hp
Duration: 10 or 20 weeks

Jan Skvaril
Box 883; 721 23 Västerås; Sweden


Mälardalens University, Future Energy Center and Mälarenergi AB


Sista ansökningdag

2017, 2018

Spectroscopic Determ

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