Karlstads Energi AB är ett medborgarägt företag som levererar värme och el till Karlstad med omnejd. Sedan uppförandet av det nya kraftvärmeverket Heden 3 har kraftvärmeverket Heden 2 fått förändrade driftförhållanden och körs numera ofta på låga laster under pannans drifttid vilket har resulterat i ökade NOx-utsläpp. Som energiproducent omfattas Karlstads Energi av kväveoxidavgiften och det finns en önskan om att öka marginalen för att nå miljökraven. Då NOx-utsläppen främst beror på för stort O2-överskott i pannan finns det möjlighet att ersätta en del av förbränningsluften med recirkulerade rökgaser för att minska tillgänglig O2. För att fortsätta vara relevanta på energimarknaden har Karlstads Energi ett behov av att utveckla nya tjänster och produkter. Samproduktion av syntesgas kan vara aktuellt som värdeskapande process när samhället rör sig mot en bioekonomi och det finns anledning att utvärdera hur det skulle komma att påverka förbränningsprocessen. Förbränningsprocessen inklusive rådande NOx-reducerande åtgärder i Heden 2 har modellerats i CHEMCAD. Baserat på modellen har rökgasrecirkulation samt effekterna av att samproducera syntesgas implementerats. I fallet med syntesgas ersätts en del av bränslet med förgasningskoks och värme tas ut från den externa bäddcirkulationen för att driva syntesgasreaktorn. Modellen inkluderar reaktionskinetik för NOx-bildning och -reduktion samt intern och extern bäddcirkulation. Rökgasrecirkulation fungerar som NOx-reducerande åtgärd vid drift med låg last. Beroende på bränslesammansättning kan NO-bildning minska med upp till 10% och NO-utsläpp med upp till 67%. Optimal andel recirkulerade rökgaser är 20% när flis förbränns respektive 15% vid samförbränning av förgasningskoks. Temperaturen i pannan sjunker något med ökande flöde av recirkulerade rökgaser och överstiger aldrig 800°C vilket riskerar att skapa en ineffektiv NOx-reduktion med selektiv ickekatalytisk reduktion (SNCR). Samförbränning av förgasningskoks ökar den totala effektutvecklingen med ca 1,5 MW jämfört med då endast flis förbränns och värmeuttaget från cyklonen som driver den nya syntesgasreaktorn har försumbar inverkan på bäddmaterialets temperatur. Slutsatser som dras är att rökgasrecirkulation fungerar som NOx-reducerande åtgärd vid låg last. Samproduktion av syntesgas har en NOx-hämmande effekt och kan ge ett minskat bränslebehov för att möta energibehovet.

SCA Ortvikens energiavdelning har fem stycken fastbränslepannor som försörjer interna förbrukare med processånga. Bränslet är i huvudsak bark, biologiskt slam och pelletspulver. SCA är ålagda att registrera utsläpp till luft och redovisa detta enligt de i verksamhetstillståndet villkorsbelagda utsläppen samt för kväveoxid-deklaration och för handel om utsläppsrätter för CO2. Förutom verksamhetstillståndet innefattas SCA Ortviken dessutom av förordningen 2013:252 Stora förbränningsanläggningar. För att redovisa detta används miljöredovisningssystemet ”MRS” från Entric AB. Drift-och underhåll saknar i nulägen en övergripande bild över MRS vilket skulle underlätta deras arbete för att säkerställa funktion på ingående signaler och därmed minska risken för mätbortfall vilket kan förebygga höga utsläpp under produktionen i framtiden. I detta arbete har, genom flödesscheman för de mest relevanta signaler och mätvärden vad gäller utsläpp som är kopplade till MRS, kunna underlätta för processoperatörer och underhållsorganisationen att säkerställa mätfunktionen. Arbetet har dessutom, genom analys av historiska data över driften, lett till förslag på åtgärder för att minska bildandet av olika utsläpp. Arbetet har visat att det finns många enkla åtgärder som kan göras för att minska utsläppen på redan befintligt installerad teknik på pannorna, men även gett förslag på annat teknik, och hur denna kan appliceras. Arbetet har också visat på brister i den nuvarande dokumentation-och signalhanteringen i avseende att göra mätvärden synliga i processystem andra än MRS.

The master thesis deals with possibilities of utilization of conventional power plant fly ash after introduction of SNCR (Selective non-catalytic reduction) as a method of flue gas denitrification. Behaviour of fly ash containing products of denitrification, ash with water and stabilizate prepared from contaminated ash was studied. Experiments were focused on the study of various factors affecting the release of ammonia from prepared mixtures. Samples were exposed to the weather conditions to simulate deposition in addition to the laboratory experiment. Influence of the fly ash containing denitrification to mechanical properties and volume stability of pastes and mortars were also studied. The interaction of denitrification products with superplasticizers was studied on pastes. Achieved results were verified on concretes.

The objective of the presented diploma thesis is reduction of nitrogen oxides from the flue gas stream on catalyst under non-standart conditions. Emphasis is places on the description of selected pollutants in flue gas (especially nitrogen oxides), legislative requirements for air protection and technologies for removal of nitrogen oxides, expecially methods of selective catalytic and non-catalytic reduction. The practical part is devoted to the reduction of nitrogen oxides by selective catalytic reduction on a pilot plant INTEQ II in the laboratory NETME Center. The subject of interest is the determination of the NOx reduction efficiency depend on the temperature for selected catalyst. The end of the practical part pursues with comparison of measurement results and their evaluation.

This diploma thesis deals with selected abatement techniques of nitrogen oxides (NOx) developed for large combustion plants. The first part describes selected NOx, their properties and explains the formation during combustion. Furthermore, there is an analysis of current legal legislation regulating the issue of emission limits. The third part presents selected primary and secondary measures that are widely used. The emphasis is placed on the description of selective catalytic (SCR) and non-catalytic reduction (SNCR). Finally, the basic design of these technologies for model combustion equipment is performed. The consumption of reducing medium and the volume of the catalyst for the mentioned techniques are calculated here. The estimate of selected operating and investment costs is a part of the basic scheme.

The subject of this study is the effect of in-cylinder selective non-catalytic reduction (SNCR) of NOx emissions in diesel exhaust gas by means of direct injection of aqueous urea ((NH2)2CO) into the combustion chamber. A single cylinder diesel test engine was modified to accept an electronically controlled secondary common rail injection system to deliver the aqueous urea directly into the cylinder during engine operation. Direct in-cylinder injection was chosen in order to ensure precise delivery of the reducing agent without the risk of any premature reactions taking place. Unlike direct in-cylinder injection of neat water, aqueous urea also works as a reducing agent by breaking down into ammonia (NH3) and Cyanuric Acid ((HOCN)3). These compounds serve as the primary reducing agents in the NOx reduction mechanism explored here. The main reducing agent, aqueous urea, was admixed with glycerol (C3H8O3) in an 80-20 ratio, by weight, to function as a lubricant for the secondary injector. The aqueous urea injection timing and duration is critical to the reduction of NOx emissions due to the dependence of SNCR NOx reduction on critical factors such as temperature, pressure, reducing agent to NOx ratio, Oxygen and radical content, residence time and NH3 slip. From scoping engine tests at loads of 40 percent and 80 percent at 1500 rpm, an aqueous urea injection strategy was developed. The final injection strategy chosen was four molar ratios, 4.0, 2.0, 1.0 and 0.5 with five varying injection timings of 60, 20, 10, 0, and -30 degrees after top dead center (ATDC). In addition to the base line and aqueous urea tests, water injection and an 80-20 water-glycerol solution reduction agent tests were also conducted to compare the effects of said additives as well. The comparison of baseline and SNCR operation was expected to show that the urea acted as a reducing agent, lowering NOx emissions up to 100% (based on exhaust stream studies) in the diesel exhaust gas without the aid of a catalyst. The data collected from the engine tests showed that the aqueous urea-glycerol solution secondary had no effect on the reduction of NOx and even resulted in an increase of up to 5% in some tests. This was due to the low average in-cylinder temperature as well as a short residence time, prohibiting the reduction reaction from taking place. The neat water and water-glycerol solution secondary injection was found to have a reduction effect of up to 59% on NOx production in the emissions due to the evaporative cooling effect and increased heat capacity of the water.

This master thesis aims to study the possibilities of eliminating, or separation of ammonium shares from technological water of plants, where is introduced a secondary method of flue gas denitrification (SCR, SNCR). The need for elimination of ammonium shares arose after introduction of emission cap, which have been tightened since January 2015. The denitrification technologies were installed on devices that did not comply with the new limits. The theoretical part of the thesis deals with the description of combustion processes, as a fluid, and high temperature combustion of solid fuels, mechanisms of emissions and their reduction options. At the conclusion of the theoretical part is discussed the contents of the ammoniacal nitrogen in waters used in electricity and heating facilities to transport, or from which are separated by solid products of some processes such as desulphurization. There are also discussed some options for removal of ammonium salts from technological waters. Experimental part deals with finding appropriate method of determination of ammoniacal nitrogen, and the possibilities of its elimination by conversion to insoluble compound. Last but not least, the work deals with the evaluation of the sustainability of the proposed solutions. And as well as the real possibilities of their application in practice.

Questa tesi di dottorato analizza l’utilizzo del sorgo (Sorghum bicolour (L.) Moench) al fine di produrre energia elettrica, tramite combustione diretta della biomassa. Il focus della tesi è stato quello di sottolineare i benefici ed i rischi associati all’uso di tre genotipi di sorgo caratterizzati da diversa lunghezza del ciclo culturale (precoce, medio-tardivo e tardivo). La dinamica e la durata del processo di essicazione in campo sono state simulate attraverso un modello ad hoc (“sorghum haying model”), il quale integrato a CropSyst, è stato utilizzato per realizzare un’analisi del rischio produttivo stimando le perdite di biomassa (respirazione e meccanizzazione), ed i mancati affienamenti. Nell’analisi del rischio vengono stimati il numero di ettari necessari e la probabilità di eccedere la soglia di 64.000 ton ss anno-1 necessari per l’alimentazione di una centrale nell’Oltrepò pavese . Inoltre uno studio di Life Cycle Assessment è stato condotto per la valutazione dell’impatto ambientale dell’utilizzo del sorgo integrato a quello della paglia per il completamento del fabbisogno totale della centrale 94.000 ton ss anno-1. Particolare attenzione inoltre è stata data alla variazione del contenuto di C organico del suolo dovuto alla rimozione della paglia ed all’interramento dei mancati affienamenti di sorgo. Il genotipo precoce mostra le migliori performance produttive ed energetiche oltre che la più alta probabilità di eccedere la soglia di 64.000 ton ss anno-1. Lo studio di LCA non ha mostrato differenze significative tra i genotipi anche se il minor impatto ambientale, è stato evidenziato dal genotipo tardivo conseguenza dell’interramento della più alta quantità di mancati affienamenti. / This PhD thesis explores the use of sorghum (Sorghum bicolour (L.) Moench) as a dedicated bio-energy crop and highlights the benefits and risks associated with the use of early, medium-late and late sorghum genotypes to generate electricity by direct combustion in a biomass power plant. The dynamics and duration of the field drying process were simulated through the development of a specific model ("sorghum haying model"), which integrated with CropSyst, was used to perform a production risk assessment analysis estimating the biomass losses (respiration and mechanical), the haymaking failures and consequently to quantify the amount of dry baled biomass available for the power plant. In addition, the number of hectares needed to plant sorghum and the probability to exceed the threshold of 64000 Mg DM y-1, necessary to feed a biomass power plant in Oltrepò Pavese, were estimated. A complete Life Cycle Assessment (LCA) study was carried out in order to evaluate the environmental impact of the three sorghum genotypes involved in this study. The LCA study takes into consideration the use of winter wheat straw as an additional biomass source to satisfy the total biomass power plant needs (94000 Mg DM y-1). Particular attention was given to the soil organic C change (ΔSOC) due to straw removal and haymaking failures soil incorporation. Early genotype showed the best biomass production and energy performance as well as the highest probability to exceed the threshold of 64000 Mg DM y-1. The LCA results did not show significant differences between genotypes although the lower environmental impact, has been achieved by the late genotype due to the highest amount of haymaking failures incorporated in the soil.