This master thesis deals with the properties of digestate in combustion, design of construction solution of digestate boiler and experimental verification of boiler parameters. The first chapter deals with the properties of digestate as a fuel. It is followed by a chapter dealing with the existing measured results on a similar boiler. This is followed by a stoichiometric calculation of the digestate boiler. The next chapter is devoted to combustion chamber models. This chapter is followed by a chapter with experimental verification of chamber models and combustion process tuning. The last chapter contains design of construction and operational measures.

Energiåtervinning av avfall genom förbränning är en av de dominerande metoderna i Sverige för att reducera mängden avfall. I Sverige förbränns cirka 6 miljoner ton avfall årligen och detta genererade år 2019 16 TWh värme och 2 TWh elektricitet. Värmevärdens värmeverk Källhagsverket i Avesta producerade 185 000 MWh fjärrvärme från avfallsförbränning via deras avfallseldade rosterpanna 2019. Källhagsverket har under de senaste säsongerna haft problem med mängden kolmonoxid (CO) som bildats från avfallsförbränningen, då de har haft överträdelser av dygnsmedelvärdet av kolmonoxid. Projektets syfte var att undersöka hur en stabil förbränning kan uppnås genom att undersöka bidragande orsaker till ofullständig förbränning och projektets mål var att reducera mängden kolmonoxid som bildas från avfallsförbränningen. Vid projektets början bedrevs en litteraturstudie för att skapa bättre förståelse för förbränning och avfallsförbränning i rosterpannor. Resultatet från denna litteraturstudie visade att de faktorer som kunde bidra till höga mängder bildad kolmonoxid var bland annat rosterpannans bränslebädd, luftfördelningen i pannan och pannans tillförda luftmängd. Metoden som applicerades för projektet utgick från arbetssättet för försöksplanering. Försöksplaneringsmetodiken kan sammanfattningsvis beskrivas som ett samlingsbegrepp för ett arbetssätt för metoder som möjliggör att ta fram slutsatser och samband hos en process olika faktorer. Källhagsverkets rosterpanna undersöktes och driftdata från tidigare driftsäsonger analyserades med hjälp av statistiska analyser i form av enkel linjär regressionsanalys och multipel linjär regressionsanalys. Resultatet från de statistiska analyserna visade att luftfaktorer såsom luftflöden och luftfördelning hade signifikans för mängden bildad kolmonoxid av pannan. Flertalet olika försök genomfördes för att identifiera faktorer som påverkade förbränningen, bildningen av kolmonoxid och pannans begränsningar. Försöken utfördes bland annat för att testa olika luftfördelningar hos pannan, ändra mängden tillförd torkluft och rosterhastighetsfördelningar. Efter dessa initiala försök bedrevs två större försök, ett 2-faktorförsök och ett försök där pannans sekundärluft fick reglera på syrehalten i stället för kolmonoxidmängden i rökgaserna. 2-faktorförsöket genomfördes där tre faktorer ändrades från en låg nivå till en hög nivå. Faktorerna var syrehalten i rökgaserna, sekundärluftsfördelningen mellan övre och nedre sekundärluftsregistret och sekundärluftsregleringen mellan främre och bakresekundärluftsregistret. Resultatet från de genomförda försöken visade att de signifikanta faktorerna för den bildade kolmonoxiden var syrehalten i rökgaserna, sekundärluftsfördelningen och primärluftsmängden hos torkzonen (roster 1) och förbränningszonen (roster 3). Resultatet visade även att kolmonoxidmängden och mängden kväveoxid kunde reduceras om sekundärluftsregleringen reglerade på syrehalten i rökgaserna i stället för kolmonoxiden. När sekundärluften reglerade på syrehalten reducerades mängden kolmonoxid med cirka 30 % och mängden kväveoxid reducerades med cirka 15 %. Det som gav mest effekt under projektet var att låta sekundärluften reglera på syrehalten (O2) i stället för kolmonoxiden (CO). Detta gav en kolmonoxid-minskning med cirka 30 % och reducerade även kväveoxid-utsläppen (NOx) med 15 %. Följande rekommendationer gavs för att reducera mängden bildad kolmonoxid: sekundärluftsreglering bör ske via syrehalten för att reducera mängden kolmonoxid och kväveoxid. minska luftöverskottet till nivåer med syrehalt på cirka 5,5 % – 6,0 %. Nyckelord: avfallsförbränning, rosterpanna, försöksplanering. / Energy recovery of waste via waste incineration is one of the dominant methods in Sweden for reducing the amount of waste. In Sweden, approximately 6 million tonnes of waste are incinerated annually and in 2019 this generated 16 TWh of heat and 2 TWh of electricity. Värmevärden’s heating plant Källhagsverket in Avesta produced 185 000 MWh of district heating by waste incineration from their waste-fired grate boiler in 2019. In recent seasons, Källhagsverket has had problems with the amount of carbon monoxide (CO) formed from waste incineration, as they have violated the daily average value of carbon monoxide. The aim of the project was to investigate how a stable combustion can be achieved by investigating contributing causes of incomplete combustion and the project’s goal was to reduce the amount of carbon monoxide formed from the waste incineration. At the beginning of the project, a literature study was conducted to create a better understanding of combustion and waste combustion in grate boilers. The results from this literature study showed that the factors that can contribute to high amounts of carbon monoxide were, among other things, the fuel bed of the boiler, the air distribution in the boiler and the amount of air supplied to the boiler. The method applied to the project was based on the experimental design approach. The experimental planning methodology can in summary be described as a collective concept for a way of working regarding methods that makes it possible to draw conclusions and relationships between different factors in a process. Källhagsverket’s grate boiler was examined and operating data from previous operating seasons were analysed using statistical analyses in the form of simple linear regression analysis and multiple linear regression analysis. The results of the statistical analyses showed that air factors such as air flows and air distribution was significant for the amount of carbon monoxide formed in the boiler. Several different experiments were performed to identify factors that affected the combustion, the formation of carbon monoxide and the limitations of the boiler. Attempts included testing different air distributions at the boiler, changing the amount of drying air supplied and grate speed distributions. After these initial experiments, two larger experiments were conducted, a 2-factor experiment and an experiment where the boiler’s oxygen content operated as a the setpoint for the secondary air instead of the amount of carbon monoxide in the flue gases. The 2-factor experiment was carried out where three factors were changed from a low level to a high level and these factors were the oxygen content in the flue gases, the secondary air distribution between the upper and lower secondary air register and the secondary air distribution between the front and rear secondary air register. The results from the experiments showed that the significant factors for the carbon monoxide formed were the oxygen content in the flue gases, the secondary air distribution and the primary air flow of grate 1 and grate 3. The results also showed that the carbon monoxide content and the amount of nitric oxide could be reduced. When oxygen content operated as the setpoint for the secondary air the amount of carbon monoxide was reduced by about 30 % and the amount of nitric oxide was reduced by about 15 %. What resulted in the best results during the project was to let the oxygen content (O2) operate as the setpoint for the secondary air instead of carbon monoxide (CO). This resulted in a carbon monoxide reduction of about 30 % and also reduced nitric oxide (NOx) emissions by 15 %. The following recommendations that were given to reduce the amount of carbon monoxide formed: secondary air control should be done via the oxygen content to reduce the amount of carbon monoxide and nitric oxide. reduce the excess air to levels with an oxygen content of about 5.5 %. Keywords: waste combustion, grate boiler, design of experiments.

The object of the thesis is to design a grate boiler for bagasse and brown coal combustion with a heat output of 160 MW. Calculations of a flue gas stoichiometry are based on known element analyses of each fuel. The crucial part of the thesis includes designs of heat-exchanging surfaces, where the bagasse is considered as the main fuel while the brown coal is the spare one. Overall thermal balance and an actual boiler efficiencies are provided in last chapters. The boiler-outlet flue gas temperature is compared with the dew point temperature at the very end of the thesis. As a part of the thesis there is a design of the boiler attached.

This thesis deals with the design grate boilers with natural circulation for the combustion of contaminated biomass. The boiler output is output 45 t/h. Produced superheated steam with the output parameters of 440 °C 4,2 at MPa feed water temperature 115 °C. The stoichiometric calculations and the thermal calculation are based on the specified fuel composition. Thanks to this, the basic dimensional design of the boiler and its efficiency are determined. Calculation of this work focuses mainly on thermal calculations and dimensional design of individual heat transfer surfaces. Basic drawing of the boiler is available in the attachment of the thesis.

The master’s thesis deals with the design of a boiler for RDF combustion, based on the required power output and superheated steam parameters. The first part of the thesis focuses on combustion calculations. Boiler efficiency is also calculated in this chapter, using the heat balance efficiency method. The main part of the thesis consists of dimensional design and heat transfer calculations. The precision of the calculations is checked at the end of the thesis along with the chlorine corrosion, which is considered because of the higher amount of chlorine in the fuel. The thesis comes with a basic schematic of the designed boiler.

The aim of the thesis is a design of a grate steam boiler with capacity of 35 t/h and output steam parameters with temperature 430 °C and pressure 4,1 MPa. The first part of the thesis deals with stoichiometric calculations and boiler efficiency. The theses mainly focuses on the heat transfer calculation and the geometric design of individual heat transfer surfaces. The specifics of fuel are taken into consideration. The drawing of the basic boiler scheme is a part of the thesis.

This master thesis deals with design of grate biomass boiler with 50 t/h power. A fuel of the boiler is a mixture of contaminated biomass and woodchips. The boiler produces steam with parameters of 4,2 MPa and 420 °C. Stochiometric and thermal calculations are based on given fuel composition and output steam parameters. Heat exchangers are designated in accordance with the calculations. General drawing of the boiler is attached to this document. Anti-corrosion measures are considered, due to chlorine content in biomass. Hydraulic and aerodynamic losses and dew point of the flue gas is calculated in the end.

The master´s thesis deals with steam boiler design that burns contaminated wood with output 55 tons of steam per hour, steam pressure 4,2 MPa and temperature 423 °C. First two chapters focuses on stoichiometry and calculation of heat losses and boiler efficiency. Great part of thesis constitutes of thermal and dimensional calculations of every heat transfer surface. Some specific boiler parts are described considering special fuel properties. Final chapters contain pressure losses calculation of flue gas and heated medium for pumps and fans design. Drawing is also part of the work which is included as an attachment.

The diploma thesis deals with the design of a grate boiler for the combustion of a mixture of RDF and wood chips with the specified output and parameters of superheated steam. The introduction consists of stoichiometric calculations and determination of the thermal efficiency of the boiler. The thesis is devoted to determining the dimensions of the boiler, heat transfer calculations, determining pressure losses, checking the heat balance and chlorine corrosion.

The thesis is dedicated to the design of the steam boiler which burns wood chips, with a natural circulation of the water. It is a grate boiler, which produces 20 t/h of the steam. The output parameters of the steam are 420 °C and 5 MPa. The feedwater temperature is 125 ° C .The thesis gradually deals with stoichiometric calculations and determines the efficiency of the boiler. Then it describes the design of the fireplace and thermal calculations of each heat transfer surfaces. The appendix includes drawings of the boiler.