ABSTRACT Asbestos has been extensively used to insulate boilers and associated heated pipe work throughout the world. Managing human health risks posed by asbestos during the removal of lagging poses many challenges. For this reason, acquiring a better understanding of factors that lead work tasks to produce high airborne fibre concentrations is important for the development of improved control methods. Aim: The aim of this study was to link observed work tasks and work practices with measured airborne concentrations of fibres in order to identify those factors contributing to high airborne concentrations generated during boiler de-lagging. The investigation was based on a study of two employees working on a boiler de-lagging contract lasting twenty-one days and resulting in a total of 79 measurements of airborne asbestos fibres. The primary form of asbestos dust control for the duration of the contract was the application of non-amended water. Objectives: To definitively identify the presence and type of asbestos lagging as well as quantify airborne fibre concentrations for two work tasks i.e. Stripping (removing lagging) and Bagging (placing removed lagging into bags as well as cleaning spills), in order to demonstrate how they may influence airborne fibre concentrations. Methodology: The type of asbestos was confirmed by Scanning Electron Microscopy. Phase Contrast Microscopy (PCM) was selected as the primary measure of airborne asbestos fibres. A Work Practice Checklist was developed to link observed daily Work Tasks and Work Practices with the concurrent airborne fibre concentrations. The geometric mean was a useful measure of central tendency for the data since it was highly skewed to the right (positively skewed). However, for public health purposes the arithmetic mean was also considered because it provides some idea of health risk where the human respiratory system is assumed to accumulate fibres linearly with concentration. Results: Bulk sample analysis confirmed the presence of both chrysotile and amosite asbestos lagging. Work Practices such as Wetting, Stripping and Bagging asbestos, were undertaken in a relatively uncontrolled manner during the first three days of the project resulting in mean airborne fibre concentrations of 1.171 f/ml for the Stripper, ranging from 0.612 to 1.236 f/ml and 0.315 f/ml for the Bagger, ranging from 0.107 to 0.631f/ml. These means were 4.5 times and 2.3 times respectively, greater than the means calculated for the entire project. The overall mean fibre concentration was approximately five times greater for personal samples, 0.198 f/ml (± 1.647) than for the concurrent static samples, 0.039 f/ml (± 0.129). The analysis of log transformed data revealed several strong tendencies for airborne fibre concentrations when related to Work Tasks and Work Practices. The difference between stripping asbestos in small manageable as opposed to larger unmanageable pieces was highly significant (p < 0.001). Smaller manageable pieces resulted in much lowerconcentrations. The manner with which asbestos was bagged was also highly significant (p < 0.001). Bagging in an uncontrolled manner resulted in much higher airborne concentrations. Surprisingly, the degree of wetting was not as important as expected: working dry did not generate significantly more fibres than working with saturated insulation but did generate significantly more fibres (p < 0.005) than working with partially wet insulation (which lead to the highest concentrations). A limitation to interpreting the Wetting work practice was the low number of samples taken within the dry category (n = 5). The difference in mean sample concentrations between personal and static samples for this study demonstrates the importance of spatial and temporal proximity as a determinant for airborne fibre concentrations. It also showed clear associations between what can be described as rushed, reckless Work Practices, and the resulting high levels of airborne fibre concentrations (exceeding the OEL). Within the context of this project, these findings demonstrate the utmost importance of providing the appropriate training and supervision of employees, not only for protecting themselves against airborne asbestos fibres, but for removing asbestos in manner that results in the generation of the least amount of airborne fibres possible

<p>In order to reduce the discharge of the greenhouse gas CO2, the use of biomass is nowadays promoted as fuel in boilers. Compared to boilers fired with coal and oil the biomass-fired boilers have more complications related to both fouling and corrosion on the heat transfer surfaces. After the combustion, unburned inorganic matter in state of vapour, melts and solid particles are transported in the flue gas and may form deposits on heat transfer surfaces.</p><p>Deposits on the heat transfer surfaces may result in both increasing corrosion and decreasing boiler efficiency as the heat transfer rate to the superheaters and reheaters decrease by deposits.</p><p>In order to understand the process of deposit build-up, the whole combustion and transport process had to be analysed including aspects such as, boiler design, fuel properties and combustion environment, followed by particle transport phenomena and the probability for particles to get stuck on the heat transfer tubes.</p><p>In this thesis numerical simulation of particle trajectories has been conducted as well as measurements of deposits on a special designed deposit probe followed by investigation of on-site measurements of deposit depth on the super-heater tubes in a circulating fluidised bed in Västerås, Sweden.</p><p>Numerical simulations of particle trajectories in the vicinity of two super-heater tubes were conducted in an Eulerian-Lagrangian mode considering the flue gas and ash particles phase. Particle impingements on the tubes were investigated for different particle sizes. The results from the particle trajectory simulations show that particle larger than 10 µm will mainly impinge on the windward side of the first tube but, however also on the sides of the second tube in the flue gas flow direction. In theory as well as from observations and measurements two tubes can merge together by the deposit build-up. Smaller particles are usually more dispersed due to turbulence and thermophorectic forces, resulting in a more even impingement distribution on the whole surface of the tubes.</p><p>Probe measurements reveal that the deposit layer growth rate have a significant temperature and time dependence. After the initial deposit build-up a sintering process occurs and sintering is also proven to be dependent on temperature and exposure time.</p><p>Soot-blowing is the most common method to reduce the effect of deposits on the heat transfer tubes. In the present thesis the soot boiling efficiency is therefore also investigated. The soot-blowing show a strong positive effect on the heat transfer rate in a short time (hours) perspective after a soot-blowing cycle is completed. This positive effect is much weaker when considering a time period of three years. This is an effect of fact that soot-blowing mostly remove the loose part of the deposit material leaving the hard sintered part unaffected.</p><p>The subject of deposit build up on superheater tubes in large scale boilers involves multi-discipline knowledge and historically, the related research is mostly conducted as measurements and experiments on operating plants. Possibly in the future, theoretical simulations will have a bigger part of research on deposit build-up where the calculations are to be calibrated through measurements on real sites plants.</p>

Co-generation is an efficient energy system that generates steam and electricity simultaneously. In ordinary operation, fuel cost accounts for more than 60% of the operational cost. As a result, the boiler efficiency and optimization level of co-generation are both high. To achieve further energy conservation, objectives of this thesis are to find the Profit-maximizing dispatch and efficiency enhancing strategy of the co-generation systems under deregulation. In a coexistent environment of both Bilateral and Poolco-based power market, there are bid-based spot dispatch, and purchases and sales agreement-based contract dispatch. For profit-maximizing dispatch, the steam of boilers, fuels and generation output will be obtained by using the SQP(Sequential Quadratic Programming ) method. In order to improve the boiler efficiency, this thesis utilizes artificial neural networks(ANN) and evolutionary programming(EP) methods to search for the optimal operating conditions of boilers. A co-generation system (back-pressure type and extraction type) is used to illustrate the effectiveness of the proposed method.

Emissions from residential combustion appliances vary significantly depending on the firing behaviours and combustion conditions, in addition to combustion technologies and fuel quality. Although wood pellet combustion in residential heating boilers is efficient, the combustion conditions during start-up and stop phases are not optimal and produce significantly high emissions such as carbon monoxide and hydrocarbon from incomplete combustion. The emissions from the start-up and stop phases of the pellet boilers are not fully taken into account in test methods for ecolabels which primarily focus on emissions during operation on full load and part load.  The objective of the thesis is to investigate the emission characteristics during realistic operation of residential wood pellet boilers in order to identify when the major part of the annual emissions occur. Emissions from four residential wood pellet boilers were measured and characterized for three operating phases (start-up, steady and stop). Emissions from realistic operation of combined solar and wood pellet heating systems was continuously measured to investigate the influence of start-up and stop phases on total annual emissions. Measured emission data from the pellet devices were used to build an emission model to predict the annual emission factors from the dynamic operation of the heating system using the simulation software TRNSYS.  Start-up emissions are found to vary with ignition type, supply of air and fuel, and time to complete the phase. Stop emissions are influenced by fan operation characteristics and the cleaning routine. Start-up and stop phases under realistic operation conditions contribute 80 – 95% of annual carbon monoxide (CO) emission, 60 – 90% total hydrocarbon (TOC), 10 – 20% of nitrogen oxides (NO), and 30 – 40% particles emissions. Annual emission factors from realistic operation of tested residential heating system with a top fed wood pelt boiler can be between 190 and 400 mg/MJ for the CO emissions, between 60 and 95 mg/MJ for the NO, between 6 and 25 mg/MJ for the TOC, between 30 and 116 mg/MJ for the particulate matter and between 2x1013 and 4x1013 /MJ for the number of particles. If the boiler has the cleaning sequence with compressed air such as in boiler B2, annual CO emission factor can be up to 550 mg/MJ. Average CO, TOC and particles emissions under realistic annual condition were greater than the limits values of two eco labels. These results highlight the importance of start-up and stop phases in annual emission factors (especially CO and TOC). Since a large or dominating part of the annual emissions in real operation arise from the start-up and stop sequences, test methods required by the ecolabels should take these emissions into account. In this way it will encourage the boiler manufacturers to minimize annual emissions.  The annual emissions of residential pellet heating system can be reduced by optimizing the number of start-ups of the pellet boiler. It is possible to reduce up to 85% of the number of start-ups by optimizing the system design and its controller such as switching of the boiler pump after it stops, using two temperature sensors for boiler ON/OFF control, optimizing of the positions of the connections to the storage tank, increasing the mixing valve temperature in the boiler circuit and decreasing the pump flow rate. For 85 % reduction of start-ups, 75 % of CO and TOC emission factors were reduced while 13% increase in NO and 15 % increase in particle emissions was observed.

In order to reduce the discharge of the greenhouse gas CO2, the use of biomass is nowadays promoted as fuel in boilers. Compared to boilers fired with coal and oil the biomass-fired boilers have more complications related to both fouling and corrosion on the heat transfer surfaces. After the combustion, unburned inorganic matter in state of vapour, melts and solid particles are transported in the flue gas and may form deposits on heat transfer surfaces. Deposits on the heat transfer surfaces may result in both increasing corrosion and decreasing boiler efficiency as the heat transfer rate to the superheaters and reheaters decrease by deposits. In order to understand the process of deposit build-up, the whole combustion and transport process had to be analysed including aspects such as, boiler design, fuel properties and combustion environment, followed by particle transport phenomena and the probability for particles to get stuck on the heat transfer tubes. In this thesis numerical simulation of particle trajectories has been conducted as well as measurements of deposits on a special designed deposit probe followed by investigation of on-site measurements of deposit depth on the super-heater tubes in a circulating fluidised bed in Västerås, Sweden. Numerical simulations of particle trajectories in the vicinity of two super-heater tubes were conducted in an Eulerian-Lagrangian mode considering the flue gas and ash particles phase. Particle impingements on the tubes were investigated for different particle sizes. The results from the particle trajectory simulations show that particle larger than 10 µm will mainly impinge on the windward side of the first tube but, however also on the sides of the second tube in the flue gas flow direction. In theory as well as from observations and measurements two tubes can merge together by the deposit build-up. Smaller particles are usually more dispersed due to turbulence and thermophorectic forces, resulting in a more even impingement distribution on the whole surface of the tubes. Probe measurements reveal that the deposit layer growth rate have a significant temperature and time dependence. After the initial deposit build-up a sintering process occurs and sintering is also proven to be dependent on temperature and exposure time. Soot-blowing is the most common method to reduce the effect of deposits on the heat transfer tubes. In the present thesis the soot boiling efficiency is therefore also investigated. The soot-blowing show a strong positive effect on the heat transfer rate in a short time (hours) perspective after a soot-blowing cycle is completed. This positive effect is much weaker when considering a time period of three years. This is an effect of fact that soot-blowing mostly remove the loose part of the deposit material leaving the hard sintered part unaffected. The subject of deposit build up on superheater tubes in large scale boilers involves multi-discipline knowledge and historically, the related research is mostly conducted as measurements and experiments on operating plants. Possibly in the future, theoretical simulations will have a bigger part of research on deposit build-up where the calculations are to be calibrated through measurements on real sites plants.

Nova Scotia has over 100 commercial greenhouses covering an area of 186,245 square meters. Heating costs have become the largest energy expenditure in greenhouses mainly due to increasing fuel prices and the use of imported fuel oils. Increasing fuel prices combined with a growing desire to stabilize energy supply has led to a renewed interest in alternative fuel options for greenhouse heating. Agricultural or herbaceous biomass has the potential to become a sustainable and cost effective heating option for the greenhouse industry. Although high inorganic content create challenges during the combustion of herbaceous biomass, these crops create an opportunity if sufficient land mass is available for greenhouse growers to meet their own fuel needs. This research will review energy use and operational practices in the greenhouse industry to identify energy saving opportunities. This study will further investigate biomass feedstocks, processing and combustion technologies suitable for heating greenhouse industry in Nova Scotia.

Antrojoje darbo dalyje aprašyta gaminio paskirtis ir panaudojimo galimybės bei alternatyvos, išnagrinėti pakūrą sudarantys elementai: mazgai, mechanizmai. Atlikta katilo pakūros mazgų konstrukcijos variantų apžvalga – įvairiausių detalių, standartinių gaminių, konstrukcinių sprendimų palyginimas. Atlikti gaminio techniniai skaičiavimai (šiluminės izoliacijos ir nuostolių skaičiavimas, hidrostotelės elementų skaičiavimas, ardelių judinimo hidraulinių cilindrų skaičiavimas, pelenų šalinimo mazgo techniniai skaičiavimai). Trečiojoje darbo dalyje išanalizuota vienos detalės, iš kiekvieno pakūros mazgo, technologiniai maršrutai, nustatyti apdirbimo operacijoms reikalingi įrengimai, apskaičiuotas jų kiekis. Atliktas užlaidų, pjovimo režimų nustatymas bei techninis normavimas. Ketvirtojoje darbo dalyje pateikiama žmonių ir aplinkos saugos reikalavimai eksploatuojant įrenginį, jo ergonomiškumas ir įtaka aplinkai. Penktojoje darbo dalyje atlikti ekonominiai skaičiavimai, kurių pagalba nustatyta ir pagrįsta 1,5 megavato katilo pakūros savikaina. / The aim of the study is to design Boiler-stove furnace of 1,5 megawatt. The first part of bachelor thesis analyses the main technical parameter of boiler-stove furnace of 1,5 megawatt, its operating efficiency, the production volume is provided. The second part describes the function of the product, its usability and possible options, the assemblies and mechanisms - elements constituting the furnace are examined. The review of boiler furnace assembly options design is carried out – various details, standard products, constructive solutions are compared. Technical calculations of the product are performed (calculation of thermal insulation and loss, calculation of hydro-station elements, fire bars moving hydraulic cylinders calculation, technical calculation of ash removal unit). In the third part technological routes of one detail from every furnace component are analyzed, the equipment necessary for processing operations is assigned, calculated its amount. The allowance, determination of cutting regimes and technical rationing is accomplished. The fourth part presents human and environmental safety requirements while operating a device, its ergonomics and environmental impact. Economic calculations are fulfilled in the fifth part. With the help of them the cost of 1,5 megawatt boiler stone Furnace is determined and justified.

Alternative fuels like biomass have become really popular in the last decades as a substitute to fossil fuels. One of the most used technologies in Sweden for the obtention of the energy from the biomass is its direct combustion in a boiler. Bomhus Energi is a company with the purpose of creating steam and district heating for Billerudkorsnäs pulp and paper mill in Gävle and district heating for the city by operating a biomass BFB boiler. Despite being a quite new boiler, there are many sources of errors, losses and unnecessary costs. Between huge number of different losses that can happen in this kind of industrial boilers, the concern about internal leakages is not usually popular among plant designers and operators. This often leads to forget about them or not giving the importance that they could have.This study consists on, firstly, an analysis of different boiler equipment that have potential possibilities of internal leakages by mass and energy balances and by the tracking of possible mass losses. The second point of this thesis is to evaluate the cost of internal leakages that could have happen before, in order to be aware of how important they are. Additionally, measures are proposed in order to avoid or reduce the duration of the internal leakages, where the most common problem is the ignorance of their existence. This study focuses partially on the valve condition and maintenance. It is highly important to carry out valve maintenance procedures at least once per year during the general stop of the plant. Checking and verifying valve perfect conditions, can avoid a waste of a huge quantity of money just by replacing some internal elements that are possibly damaged due to the extreme working conditions. This small damages in valve can lead to a non-proper water tightening, which will be increasing its leakage over time. In the present paper, possible internal leakages through the valves belonging to the feedwater, steam drum, preheater and pressure vessel in general have been the principal aim. The key of this study was to take into account that biggest part of the draining system and valves that are supposed to be closed end in the Bottom blowdown tank. By then a deep study was done regarding this tank. The results show that there is a clear relationship between mass that is getting loss from feedwater tank and pressure vessel and the necessary cooling flow in the bottom blowdown tank. This means that if the cooling flow increases at the same rate as a possible leakage in mass and energy balance, there is an internal leakage somewhere in the system. The author proposes add an alarm to the DCS system in order to alert the plant operations of possible internal leakages. On the other hand, this paper also recommends to carry out a general valve maintenance per year and check which of them could be leaking, a general stop is the perfect time for carrying it out.In conclusion, the study finds that internal leakages can be even automatically detected if the system is provided with the necessary tools for it. The study concludes that internal leakages are not impossible to detect and their cost is non-negligible: the latest two internal leakages in the boiler, happened in the last two years, were from the feedwater draining system and from the steam drum heating loop with a total cost of 200,000 SEK (4240 SEK/day during 47 days) and 263,000 SEK (2120 SEK/day during 124 days) respectively. Additionally, days after the study, the plant general stop was carried out, finding that 12 valves were leaking due to internal damage. The cost of repairing the broken or damaged elements were almost negligible compared with the expected savings estimated in 2 Million SEK per year.

A high demand of both electricity and heat exists in Arizona Chemical (a chemical plant dedicated to the distillation of Crude Tall Oil) for production processes. Due to the rising cost of resources and electricity, more and more companies are trying to decrease the energy expenses to increase their competitiveness in a global market, thus increasing their profit. Some companies look at their energy consumption in order to diminish it or to explore the opportunity to generate their own and cheaper energy. In companies where the production of steam already takes place, cogeneration can be a good solution to palliate the cost of the energy used. This study addresses this issue through three actions such as the characterization of the boiler, a better steam flow measurement grid and the generation of electricity. The first one addresses the state of one of the key parts of steam production, the boiler, through the calculation of its efficiency with two different methods (direct and indirect calculation). These methods require some measurements which were provided afterwards by the company supervisor. This will allow the company to identify the weaknesses of the boiler to be able to improve it in the future. The second one aims to improve the knowledge about the steam system. New flow measurement points were suggested after doing an analysis of the current controlled flows to have a better overview outline of the steam use.The third one studies the generation of electricity with a Rankine cycle. The limitations in the characteristics of the steam were identified and different configurations are proposed in accordance to the restrictions identified. An efficiency of 93% is obtained for the boiler with the direct method and 82.3 % for the indirect one. The difference between them can be explained by the use of datafrom different time frames for both methods. The main contributors to the losses are the ones related to the dry flue gas and the hydrogen in the fuel. In the current status only 40% of the steam flows are identified, a number which is expected to raise with the new measurement points. It was not possible to estimate the effect of the new points due to the desire of the company to not disturb the current production. Due to the fuel price the production of steam for only electricity was not profitable and instead the generation of both electricity and heat from the same steam is proposed. This integrated system is now possible to implement due to its low payback time (2.3 years). This solution can generate 758 kW of electricity and provide the company with 6437 MWh of electricity each year. Then, the effect of the variation of different variables over the performance of the cycle were studied: different electricity prices, steam rate production, fuel cost and the state of the condensate recovery were discussed. The variation of both the condensate recovery and fuel cost did not affect the payback time due to their costs being neutralised by the revenues obtained from them. The variation of the electricity prices and steam production affects the payback but due to the high revenue that is expected it does not hamper the good nature of the investment. The generation of electricity is recommended due to the low payback time obtained. The different variations studied in the system did not change the payback time notably and showed that the investment is highly profitable in all the scenarios considered. The use of two smaller turbines instead of the one chosen (with a maximum rated power of 6 MW while only 758 kW is generated with the proposed solution) should be studied since the turbines would work closer to their maximum efficiency.

For power plants that make use of high energy boiler feed pumps, there is a risk that the boiler feed pump may experience cavitation and overheating at low load and start-up conditions. These plants make use of a leak off or recirculation system that diverts some of the flow back to the feed water tank, ensuring that a minimum flow through the pump is maintained at low load and start-up operating conditions. The recirculation valve, also known as a leak off valve, experiences a very high pressure difference and cavitation pitting is common due to the water being close to saturation. There are various ways in which the recirculation flow is controlled in the industry such as open orifice, on/off binary type control valves, automatic recirculation valves (ARC) or modern modulating leak off systems. The valves themselves can also be simple plug type or make use of pressure staging to reduce the risk of cavitation. This project involves modelling the flow system around the boiler feed pump and its control for the various architectures employed in Eskom. This is to assist in understanding the reasons for cavitation damage that is found in some recirculation valves as well as the low load capability of the system. Single stage components with extremely high pressure drops are singled out as components with the highest risk of cavitation in the systems. Although extremely high pressure drops are found across the leak off valves themselves, the majority of the valves are multistage valves which are specifically designed to accommodate cavitation development and are therefore not of major concern. Some of the findings of the study are: The rule of thumb used within Eskom to determine the amount of pressure reducing stages on leak off valves could be more conservative. The specification of new valves and components for the leak off systems requires accurate specification based on detailed process models, such as the ones developed for this study. The full range of all possible operational cases must also be considered during the design.