The main scope of thesis is to describe the pollutant removal techniques with a focus on heavy metals. With that relate chapters describing the formation of pollutants and their effect on human health. The thesis focuses on a detailed description of flue gas cleaning technology and its evaluation. Evaluation is shown in tables comparing emission measurement on waste incineration plant SAKO Brno, a.s. with emission limits. The thesis also briefly describes other options for municipal waste management.

Aim of this thesis is to design a technology of a flue gas desulphurization of fluidized bed boiler. Currently, the state of technology is not able to provide flue gas desulphurisation to required level. For this reason it is necessary to build additional device for the desulphurisation. Theoretical part of the thesis deals with the emission limits of sulphur dioxide, available methods of desulphurization and sorbents suitable for the desulfurization. In practical part conditioned dry sorption method is chosen for the specified source, technological and structural design for suggested desulphurization technology including design of all device is proposed. The thesis also includes a technology design and a 3D model.

At the Idbäcken combined heat and power (CHP) plant waste wood is combusted. The flue gas from the combustion is condensed and heavy metals and other toxic species ends up in the condensate water. Since the condensate water in this way contains many toxic substances it needs to be treated before it is sent to the recipient Kilaån (the Baltic Sea). Arsenic (As) is one substance that needs to be removed, and this thesis aims to find the optimal conditions for As removal by using precipitation with iron(III) chloride (FeCl3). When FeCl3 comes in contact with water it forms ferrihydrite, an efficient sorbent due to its high specific area. The adsorption of As to ferrihydrite is dependent on different variables; pH, Fe(III) dosage, competitive ions et cetera. Lab-scale experiments have shown that a pH value between 3 and 8 is required for efficient As removal. Concerning the Fe(III) dosage further experiments are needed in order to tell what dosage that is the optimal in this case. Further, the removal of metals has also been studied. A comparison between two chemicals (TMT 15 and MP 7) used for metal removal has been made, which showed that TMT 15 is to prefer for metal removal. Also, it was found that efficient removal of metals require pH > 5, preferably in the slightly alkaline pH range.

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Coal ash deposits were collected in a 160 kWth, down-fired oxy-coal reactor under staged and unstaged conditions for four different coals (PRB, Gatling, Illinois #6, and Mahoning). Concentration measurements of carbon, oxygen, sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, potassium, calcium, titanium, chromium, manganese, iron, nickel, strontium, and barium were gathered from each deposit sample using scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). Backscattered electron micrographs for each deposit sample were analyzed to gather morphological data. Particle size and shape were studied for each deposit collected. The average particle sizes of the particles in upstream deposits were much larger than the average particle sizes of the downstream deposits. The downstream deposits consisted primarily of spherical particles while the upstream deposits consisted of round, irregular polygonal, and porous particles. Deposit particles are believed to have deposited at all stages of burnout; those depositing early during pyrolysis may have continued to react after deposition. Element maps for the aforementioned elements were collected with SEM-EDS and analyzed to quantify both average composition and composition of individual particles. These values were compared to ASTM ash analyses performed for each coal and ash collected from the flue gas stream with a cyclonic particle separator. It was found that sulfur concentrations of deposits do not correlate with corresponding sulfur concentrations of the coal. Comparison of similar experiments performed with air-combustion show that oxy-combustion deposits contain about twice as much sulfur as air-combustion deposits when burning the same coal. Deposition propensity of each coal was also examined, and the PRB and Gatling coals were found to have a moderately high deposition propensity whereas the deposition propensity of the Mahoning and Illinois #6 coals was fairly low.

To mitigate the global greenhouse gases (GHGs) emissions, carbon dioxide (CO2) capture and storage (CCS) has the potential to play a significant role for reaching mitigation target. Oxy-fuel combustion is a promising technology for CO2 capture in power plants. Advantages compared to CCS with the conventional combustion technology are: high combustion efficiency, flue gas volume reduction, low fuel consumption, near zero CO2 emission, and less nitrogen oxides (NOx) formation can be reached simultaneously by using the oxy-fuel combustion technology. However, knowledge gaps relating to large scale coal based and natural gas based power plants with CO2 capture still exist, such as combustors and boilers operating at higher temperatures and design of CO2 turbines and compressors. To apply the oxy-fuel combustion technology on power plants, much work is focused on the fundamental and feasibility study regarding combustion characterization, process and system analysis, and economic evaluation etc. Further studies from system perspective point of view are highlighted, such as the impact of operating conditions on system performance and on advanced cycle integrated with oxy-fuel combustion for CO2 capture. In this thesis, the characterization for flue gas recycle (FGR) was theoretically derived based on mass balance of combustion reactions, and system modeling was conducted by using a process simulator, Aspen Plus. Important parameters such as FGR rate and ratio, flue gas composition, and electrical efficiency etc. were analyzed and discussed based on different operational conditions. An advanced evaporative gas turbine (EvGT) cycle with oxy-fuel combustion for CO2 capture was also studied. Based on economic indicators such as specific investment cost (SIC), cost of electricity (COE), and cost of CO2avoidance (COA), economic performance was evaluated and compared among various system configurations. The system configurations include an EvGT cycle power plant without CO2 capture, an EvGT cycle power plant with chemical absorption for CO2 capture, and a combined cycle power plant. The study shows that FGR ratio is of importance, which has impact not only on heat transfer but also on mass transfer in the oxy-coal combustion process. Significant reduction in the amount of flue gas can be achieved due to the flue gas recycling, particularly for the system with more prior upstream recycle options. Although the recycle options have almost no effect on FGR ratio, flue gas flow rate, and system electrical efficiency, FGR options have significant effects on flue gas compositions, especially the concentrations of CO2 and H2O, and heat exchanger duties. In addition, oxygen purity and water/gas ratio, respectively, have an optimum value for an EvGT cycle power plant with oxy-fuel combustion. Oxygen purity of 97 mol% and water/gas ratio of 0.133 can be considered as the optimum values for the studied system. For optional operating conditions of flue gas recycling, the exhaust gas recycled after condensing (dry recycle) results in about 5 percentage points higher electrical efficiency and about 45 % more cooling water consumption comparing with the exhaust gas recycled before condensing (wet recycle). The direct costs of EvGT cycle with oxy-fuel combustion are a little higher than the direct costs of EvGT cycle with chemical absorption. However, as plant size is larger than 60 MW, even though the EvGT cycle with oxy-fuel combustion has a higher COE than the EvGT cycle with chemical absorption, the EvGT cycle with oxy-fuel combustion has a lower COA. Further, compared with others studies of natural gas combined cycle (NGCC), the EvGT system has a lower COE and COA than the NGCC system no matter which CO2 capture technology is integrated. / QC 20111123

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Processindustrin är den största källan för utsläpp av svaveldioxid (SO2) i Sverige, vilket även inkluderar icke­järnmetallindustrin. Kopparsmältverket Boliden Rönnskär har ett miljötillstånd som tillåter SO2­-utsläpp på maximalt 3500 ton/år, en gräns som Rönnskär har legat nära under de senaste åren. För att minska svaveldioxidutsläppen på Rönnskär så har våtskrubbning (tillsammans med ett bagfilter för stoftrening) föreslagits som en metod för att rena de SO2-­bärande och intermittenta tappgaserna från flashugnen. För att göra ett optimalt val av våtskrubberteknik för ändamålet, undersöktes, utvärderas och jämfördes våtskrubbningstekniker baserade på de följande kemikalierna i denna rapport: lut, soda, peroxid, kalk and zinkoxid. Mätningar gjordes också på sekundärhuvsgaserna från konvertrarna, som också kan användas i skrubbern då flashugnens tappgaser har ett fluktuerande flöde. Vidare gjordes tester på olika processvatten på Rönnskär, som skulle kunna återanvändas i skrubbern. Skrubbrarna utvärderades sedan baserat på indata och olika systemkrav med hjälp av simulerings­ och designprogram samt teoretiska beräkningar. Resultaten visade att det är rimligt att rena sekundärhuvsgaser i skrubbern, då de innehöll ca 280 ton SO2/år. Detta kan jämföras med flashugnens tappgaser som innehöll ca 445 ton SO2/år. Bland skrubbrarna, så utvecklade peroxidskrubbern sig till att vara den mest attraktiva tekniken på grund av dess relativt låga livscykelkostnader och dess lämplighet med både lakverket och flashkyltornsprocessvattnet. De andra teknikerna med packade torn, lut­ och sodaskrubbern, hade högst livscykelkostnader, huvudsakligen på grund av deras höga kemikaliekostnader. Sodaskrubbern, som var den billigare av de två natriumbaserade skrubbarna, skulle kunna vara lämplig ändå på grund av teknikens enkelhet. De öppna tornen hade lägre livscykelkostnader jämfört med de packade tornen. Dock så hade kalkskrubbern flera nackdelar som gör att den inte är ett lämpligt alternativ. Zinkoxidskrubbning har i sin tur inte studerats tillräckligt och är en relativt oprövad teknik, men den bör studeras vidare då den skulle kunna integreras med zinksmältningsprocessen på Rönnskär. Användningen av processvatten i skrubbern skulle leda till en nettominskning av processvatten till reningsverket. Det skulle även leda till minskade reagentkostnader ifall en stripper installeras för att ta bort SO2 från processvattnen innan de går in i skrubbern. / The processing industry is the largest source of sulfur dioxide (SO2) emissions in Sweden, which includes the non­ferrous metals industry. The copper smelter Boliden Rönnskär has an environmental permit to emit a maximum of 3500 tonnes of SO2/year, a limit that the smelter has been close to in recent years. To reduce the SO2 emissions at Rönnskär, wet scrubbing (together with a bag filter for dust cleaning) has been proposed as a method for cleaning the SO2­-bearing, intermittent tapping gases from the flash furnace. To find the optimal wet scrubbing technique for the purpose, wet scrubbing techniques based on the following reagents were investigated, evaluated and compared in this report: caustic soda, soda ash, peroxide, lime and zinc oxide. Measurements were also done on the secondary hood gases from the converters, which could make use of the remaining capacity in the scrubber. Further, tests were conducted on various process waters from other processes at Rönnskär, waters that could be reused in the scrubber. The scrubber techniques were then evaluated based on the input data and system requirements using simulation and design software as well as theoretical calculations. The results suggested that it is reasonable to clean secondary hood gases in the scrubber, as they contained approximately 280 tonnes of SO2/year. This could be compared to the flash tapping gases that contained approximately 445 tonnes of SO2/year. Among the scrubbers, the peroxide scrubber evolved as the most attractive technique due to its relatively low life cycle cost and due to its suitability with the leaching plant and the flash cooling tower process water. The other packed tower techniques, caustic soda and soda ash had the highest life cycle costs, mainly due to their high reagent costs. The soda ash scrubber, which was the cheaper of the two sodium­-based scrubbers, could still be a suitable alternative due to its simplicity. The open spray towers had lower life cycle costs than the packed towers. However, the lime scrubber had several disadvantages that makes it an unsuitable alternative. In turn, the zinc oxide scrubber is a relatively under­researched and unproven technique, but should still be studied further as it could be integrated with the zinc smelting process at Rönnskär. The use of process waters in the scrubber would lead to a net reduction of process water to the process water treatment plant and would lead to reduced reagent costs if a stripper is installed to remove the SO2 from the process waters before entering the scrubber.