Academic literature on the topic 'Automatic boiler for biomass pellets'

The development and implementation of strategies to assist safe and effective transport and storage of pellets in containers and indoor facilities without heating systems are challenging. This study primarily aimed to reshape the organic fraction of municipal solid waste into a liquid-state binder in order to develop freezing–defrosting-proof non-wood pellets. The introduction of the standard solution of food waste into the process of pelleting consisted of stirring it together with the residual biomass from distillation of cellulosic bioethanol or alternatively spraying very fine droplets on the layer of the starting material before it entered the pilot-scale automatic machine at 200 MPa and 125 °C. The addition by spraying of carbohydrate-rich supplement boiled for five minutes caused the pellets to show increases in apparent density (1250.8500 kg·m−3), durability (99.7665%), and hydrophobicity (93.9785%), and consistently prevented them from suffering severe mechanical fracture by thermal shock. The fractal dimension of breakpoints, cracks, and delamination on the finished surface for these products was the smallest at 1.7500–1.7505. Sprayed pellets would fall into the strictest grid of products for residential heat-and-power units, even after freezing and defrosting. The conclusion is therefore that spraying can spectacularly ensure the reliability of liquid-state food waste as an anti-thermal shock binder for non-wood pellets.

Biomass pellets are a source of renewable energy; although, the air pollution and exposure risks posed by the emissions from burning pellets in biomass boilers (BBs) are uncertain. The present study examines the organic species in fine particle matter (PM) emissions from an BB firing switchgrass (SwG) and hardwood (HW) biomass pellets using different test cycles. The organic and elemental carbon (OC and EC) content and select semivolatile organic compounds (SVOCs) in filter-collected PM were identified and quantified using thermal-optical analysis and gas chromatography–mass spectrometry (GC–MS), respectively. Fine PM emissions from the BB ranged from 0.4 g/kg to 2.91 g/kg of pellets burned of which 40% ± 17% w/w was carbon. The sum of GC–MS quantified SVOCs in the PM emissions varied from 0.13 to 0.41 g/g OC. Relatively high levels of oxygenated compounds were observed in the PM emissions, and the most predominant individual SVOC constituent was levoglucosan (12.5–320 mg/g OC). The effect of boiler test cycle on emissions was generally greater than the effect due to pellet fuel type. Organic matter emissions increased at lower loads, owing to less than optimal combustion performance. Compared with other types of residential wood combustion studies, pellet burning in the current BB lowered PM emissions by nearly an order of magnitude. PM emitted from burning pellets in boilers tested across multiple studies also contains comparatively less carbon; however, the toxic polycyclic aromatic hydrocarbons (PAH) in the PM tested across these pellet-burning studies varied substantially, and produced 2–10 times more benzo[k]fluoranthene, dibenz[a,h]anthracene and indeno[1,2,3-c,d]pyrene on average. These results suggest that further toxicological evaluation of biomass pellet burning emissions is required to properly understand the risks posed.

This paper deals with determining the specific emissions from the combustion of two kinds of biomass fuels in a small-scale boiler. The tested fuels were pellets made of wood and pellets made of rape plant straw. In order to evaluate the specific emissions, several combustion experiments were carried out using a commercial 25 kW pellet-fired boiler. The specific emissions of CO, SO₂ and NO_x were evaluated in relation to a unit of burned fuel, a unit of calorific value and a unit of produced heat. The specific emissions were compared with some data acquired from the reference literature, with relatively different results. The differences depend mainly on the procedure used for determining the values, and references provide no information about this. Although some of our experimental results may fit with one of the reference sources, they do not fit with the other. The reliability of the references is therefore disputable.

The results of experimental research thermal and environmental performance of the boiler "Firematic 60" burning pellets, bark, pressed wood sanding dust, granulated peat and sod peat and black pellets of hydrolytic lignin are presented. The research identified the heat balance components of the boiler and gaseous emissions during burning solid fuels. The emissions of solid particles and the content of soot particles are studied. Energy survey found boiler provides high thermal and environmental performance during burning biofuels and granulated peat that should be used for buildings heating; especially in the conditions of North-Arctic region. The organization of production of black pellets of hydrolytic lignin allowed to obtain high-quality fuel from biomass wasted 40–60 years ago.

This paper presents the design and test results of an external thermoelectric generator that utilizes the waste heat from a small-scale domestic biomass boiler with nominal rated heat output of 25 kW. The low-temperature Bi2Te3 generator based on thermoelectric modules has the potential to recover waste heat from gas combustion products as effective energy. The small-scale generator is constructed from independent segments. Measurements have shown that up to 11 W of electricity can be generated by one segment. Higher output power can be achieved by linking thermoelectric segments. The maximum output power is given by the dew point of the flue gas. The electrical energy that is generated can be used, e.g., for power supply or for charging batteries. In the near future, thermoelectric generators could completely eliminate the dependence an automated domestic boiler system on the power supply from the electricity grid, and could ensure comfortable operation in the event of an unexpected power grid failure.

The arch is an important component of a biomass boiler. Initial arch design of most boilers is generally gained through manual computation, thus resulting in uncertain reasonability of flue gas flow. Moreover, biomass fuels in the market have instable characteristics, which influence the utilization of biomass energies considerably. To address the problems concerning reasonable flue gas flow caused by the collaborative design of arch and air staging and the combustion adaptability of fuels, a cold modeling experiment of a 1 t/h biomass boiler under different staged air distribution ratios when the rear arch coverage varies was conducted using Fluent software in this study after thermal performance computation and initial structural design of grate and furnace. Furthermore, a boiler performance test based on main fuels and a combustion adaptation test of auxiliary fuels were also performed. The experiments show that the best flue gas flow in the furnace is achieved when the rear arch coverage is 60% and the primary–secondary air distribution ratio is 4:6. The mean boiler efficiency and the mean boiler heat output are 81.26% and 715.76 kW/h by using Pinus koraiensis pellets, wood–straw mixed pellets, and cotton straw briquettes as main fuels; and the tested pollutant emissions are in compliance with the limits of the national standard. The results of the combustion adaptation test reveal that the excessive particle size, the high ash content and the relatively low calorific value of biomass molded fuels are all against the combustion of biomass boilers. Fuel upgrading based on washing process and other methods is suggested. This study can provide references to the performance optimization of traditional small-scale biomass chain heating boilers.

Vineyards waste has a great importance as biomass, a renewable source of energy. In this paper eight vine shoot varieties were used for the production of pellets by densification of feedstock materials with four ranges of moisture contents (6–8%, 8–10%, 10–12% and 12–15%). A moisture content of 10% gave durability higher than 97.5% and a calorific value greater than 17 MJ kg−1 and the small durability was obtained for 6–8% moisture. The study shows the significant influence of water during densification. The physicochemical and energetic properties of pellets were evaluated in accordance with ISO 17225-6 (2014). The obtained pellets were also structurally characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). SEM analysis showed the formation of carbon microsphere after pelletization, due to the increase of bulk density and durability of pellets. Also, XRD analysis revealed the crystallinity of cellulose, while TGA analysis showed a total decomposition of pellets. The obtained pellets were burned in a domestic boiler and the flue gases were measured. The preliminary results showed that the vineyard residues had higher emissions, but below the admitted limits, with the exception of carbon monoxide content. The obtained results suggested that the biomass wastes can be used for the production of pellets, aiming to enhance the research for the manufacturing of these sustainable biofuels with some remarks regarding risk of corrosion and slag formation during prolonged use.

With sustainable energy being the key to reaching climate neutrality, the utilization of non-wooden biomass is a necessity. This article compares the emissions and efficiency of combusting a number of types of agrobiomass and wood pellets. A comparison was made on a moving grate pellet burner mounted in a boiler, where flue gas had a vertical flow via two pass heat exchangers with turbulization elements. Tests were conducted on wood pellets (ENPlus), miscanthus straw pellets, sunflower husk pellets, and corn stover pellets. During combustion, both wood and miscanthus pellets met the PN-EN 303-5:2012 emission and efficiency requirements. Corn stover pellets met the requirement on the nominal capacity. Sunflower husk pellets are characterized by excessive CO and particulate matter emissions. Sunflower husk pellets were the most problematic fuel from the point of view of the results of this research. During combustion of the miscanthus straw pellets there was a need to decrease the nominal heating capacity due to ash sintering.

Pollutant emission from a heat station supplied with agriculture biomass and wood pellet mixtureTests for combustion of hay and sunflower husk pellets mixed with wood pellets were performed in a horizontal-feed as well as under-feed (retort) wood pellet furnace installed in boilers with a nominal heat output of 15 and 20 kW, located in a heat station. During the combustion a slagging phenomenon was observed in the furnaces. In order to lower the temperature in the furnace, fuel feeding rate was reduced with unaltered air stream rate. The higher the proportion of wood pellets in the mixture the lower carbon monoxide concentration. The following results of carbon monoxide concentration (in mg/m3presented for 10% O2content in flue gas) for different furnaces and fuel mixtures (proportion in wt%) were obtained: horizontal-feed furnace supplied with hay/wood: 0/100 - 326; 30/70 - 157; 50/50 - 301; 100/0 - 3300; horizontal-feed furnace supplied with sunflower husk/wood: 50/50 - 1062; 67/33 - 1721; 100/0 - 3775; under-feed (retort) furnace supplied with hay/wood: 0/100 - 90; 15/85 - 157; 30/70 - 135; 50/50 - 5179; under-feed furnace supplied with sunflower husk/wood: 67/33 - 2498; 100/0 - 3128. Boiler heat output and heat efficiency was low: 7 to 13 kW and about 55%, respectively, for the boiler with horizontal-feed furnace and 9 to 14 kW and 64%, respectively, for the boiler with under-feed furnace.

The aim of this diploma thesis is the research of automatic boilers for biomass pellets and their burners, design of automatic boiler for biomass pellets which include calculation part and drawing part and technical-economics assessment for building in the end. Thesis is divided into four main parts. The first part deals with general information about pellets, automatic boilers for pellets, burners and the standard for boiler. In the second part the pellet boiler is calculated. In the third part the automatic pellet boiler is designed. The fourth section compares three possible variants. Comparison is done for economics and the user.

The diploma thesis deals with the design of the industrial boiler for biomass, Which deals with the issue of the energy future of combustion of fuels using current power generation - microcogeneration, designed for larger houses or smaller com- panies. The shape of the device is the interconnection of individual functional and technological parts of the boiler, a view of a new product that re ects its function. It uses modern and timeless materials, color and control technology to achieve overall comfort and time savings and service.

Thesis deals with stoves, considering them as the main source of heating. The theoretical part is focused on practical and theoretical stove designing and burnnig proces. The designing addresses three of the countless variations on the koncept of modern stove heating. Each variant is unique in its technical and design way of solution. Experiment affects the properties hypokaust stove.

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.

Programa Doutoral em Engenharia Mecânica.
Biomass is a renewable source of energy, used in combustion on both domestic and industrial applications. Biomass combustion has a high impact in the environment due to the released products, which must be measured and analyzed. The main goal of this work was to study the viability of alternative biomass fuels, both for the economic valorization of these alternative materials and to ease the pressure on the demand of pine sawdust. This viability will depend on the characteristics of the combustion release products and the effects on the combustion equipments of using such materials. For achieving this goal, combustion test were performed with alternative biomass fuels in a domestic boiler and in a large-scale furnace. The raw materials examined were pine sawdust, furniture residues, cork residues and branches of vine, olive, kiwi and platanus. The combustion characteristics of these biomass fuels were studied by thermogravimetry, fouling and slagging indexes, chemical analysis of bottom and fly ashes, gaseous and particulate matter emissions and a scanning electron microscope for analysis of the particulate matter. The characteristics of the traditional biomass fuel (pine sawdust) and alternative biomass fuels used were significantly different. The alternative biomass fuels presented higher heating value and lower nitrogen content. However, they contained more ashes, and the undesirable chemical composition of those ashes can constitute a problem. The thermogravimetric results showed that the alternative residues studied are good alternatives to the pine sawdust in terms of combustion parameters such as level of heat released and activation energy. The ashes indexes disclosed some problems related to slagging and fouling, due to the high levels of silica in pine sawdust and potassium in agriculture residues. The combustion in the pellet-fired domestic boiler revealed some operational problems with the alternative biomass fuels. Accumulation of ashes in the grate by sintering mechanisms was observed and higher concentrations of CO were also measured, which was accompanied by the emission of soot particles, as detected by x-ray spectroscopy. The particulate matter emissions were also significantly higher (especially for vine and olive pellets) than those from the pine sawdust pellets, mainly for particles with very low diameter (0.32 and 0.76 μm). High levels of potassium were also found in the particulate matter from the alternative biomass pellets, which are an important source of particles with low sintering characteristics. However, the high presence of silicon in pine sawdust proved to be the biggest problem in terms of slag formation. The combustion of pulverized biomass in the large scale furnace was performed for furniture and cork residues, and kiwi and platanus branches. The results showed that the cork residues are the most problematical regarding the particulate matter emissions, followed by the agricultural biomass fuels (kiwi and platanus). Particles with a diameter around 0.26 μm were those released in greater amounts for all biomass fuels tested, reaching a maximum of 137 mg/Nm3@6%O2 for cork residues. The scanning electron microscope analysis revealed high quantities of carbon in all samples of the particulate matter, especially for the lower diameters. Regarding the chemical composition of the particulate matter, the more representative element was potassium, followed by smaller quantities of chlorine and sulphur. The pine sawdust and furniture residues, which are commercialized products, proved to be the best raw materials for combustion and originated less problematic products. The other biomass fuels studied can represent good alternatives when using equipment that does not require such high quality fuels, such as in industrial applications. However, the emissions of particulate matter with sizes below 2.5 μm, that are very harmful to human health by causing respiratory problems, need to be captured to prevent its release into the atmosphere.
A biomassa é uma fonte de energia renovável, usada em combustão para aplicações, quer domésticas quer industriais. A combustão de biomassa tem um elevado impacto no ambiente devido aos produtos libertados, que é necessário medir e analisar. O principal objetivo deste trabalho foi estudar a viabilidade de combustíveis de biomassa alternativos, quer para a valorização económica desses materiais, quer para aliviar a procura de serrim de pinho. Esta viabilidade dependerá das características dos produtos de combustão libertados e dos efeitos do uso desses materiais nos próprios equipamentos. Para alcançar este objetivo foram efetuados testes de combustão de biomassas alternativas numa caldeira doméstica e numa fornalha laboratorial de grandes dimensões. As matérias-primas analisadas foram o serrim de pinho, resíduos de mobiliário, resíduos de cortiça e ramos de videira, oliveira, kiwi e plátano. As características da combustão dessas biomassas foram examinadas recorrendo à termogravimetria, índices de fouling and slagging, análise química das cinzas residuais e volantes, emissões gasosas e de partículas e microscopia eletrónica do material particulado. As características da biomassa tradicional (serrim de pinho) e das biomassas alternativas apresentaram diferenças significativas. As biomassas alternativas apresentaram um maior poder energético e baixos teores em azoto. No entanto, a presença de maiores teores de cinzas e uma composição química indesejável das mesmas podem constituir um problema nestas biomassas alternativas. Os resultados termogravimétricos mostraram que os resíduos estudados são boas alternativas ao serrim de pinho em termos de parâmetros de combustão, tais como o nível de calor libertado e a maior taxa de energia. No entanto, os índices das cinzas antecipam alguns problemas relacionados com slagging e fouling, devido a elevados níveis de silício no serrim de pinho e potássio nos resíduos agrícolas. A combustão de pellets na caldeira doméstica revelou alguns problemas operacionais no caso das biomassas alternativas. Observou-se a acumulação de cinzas na grelha por mecanismos de sinterização e maiores concentrações de CO, acompanhadas por maior quantidade de partículas de fuligem emitidas, tal como observado nas análises de espectroscopia de raio-x. A concentração de partículas em suspensão também foi significativamente maior do que no caso do serrim de pinho (especialmente para os pellets de videira e oliveira), principalmente para partículas com pequenos diâmetros (0,32 e 0,76 μm). Foram encontrados elevados níveis de potássio resultantes da queima dos pellets alternativos, que originam partículas com fraca sinterização. No entanto, a elevada presença de silício no serrim de pinho provou ser o aspeto mais problemático em termos de formação de escórias. Foram realizados testes de combustão de biomassa pulverizada na fornalha laboratorial de grandes dimensões, com resíduos de mobiliário e cortiça, e ramos de kiwi e plátano. Os resultados mostraram que os resíduos de cortiça, seguido pelas biomassas agrícolas (kiwi e plátano) são os mais problemáticos relativamente a emissões de partículas. As partículas com um diâmetro em torno de 0,26 μm foram as libertadas em maior quantidade para todas as biomassas testadas, atingindo um máximo de 137 mg/Nm3@6% de O2 para os resíduos de cortiça. A análise das partículas com o microscópio eletrónico revelou grandes quantidades de carbono em todas as amostras, especialmente nas de menor diâmetro. Em relação à composição química, o elemento mais representativo foi o potássio, seguido de menores quantidades de cloro e enxofre. O serrim de pinho e os resíduos de mobiliário, produtos atualmente já comerciados, provaram ser a melhor matéria-prima para combustão, com produtos menos problemáticos. As outras biomassas estudadas podem representar boas alternativas para utilizar em equipamentos que não exijam combustíveis tão nobres, nomeadamente em aplicações industriais. No entanto, é necessário capturar as emissões de partículas com diâmetros inferiores a 2,5 μm para que não sejam libertadas para a atmosfera, pois são muito prejudiciais para a saúde humana causando problemas respiratórios.

Dissertação de mestrado em Engenharia Mecânica
O mercado de equipamentos de queima de pellets residenciais está já bastante desenvolvido em alguns países da Europa como Alemanha, Áustria e Itália. Em Portugal, encontra-se ainda numa fase embrionária, tendo-se verificado um forte crescimento da procura nos últimos tempos. A produção de pellets tem também crescido, sendo essencialmente para exportação. A sua queima, devido à existência de elementos químicos como, por exemplo, Na, K e Si, pode dar origem a cinzas aglomeradas na grelha do queimador, que levantam problemas ao seu bom funcionamento. O presente trabalho teve como objectivo o estudo da influência da temperatura e dos fluxos de ar na aglomeração de cinzas no leito. Para este fim, efectuou-se a montagem de uma instalação experimental constituída genericamente por: i) Caldeira, cujo queimador permite a regulação dos caudais de ar primário e secundário; ii) Sistema de extracção de gases de caudal variável; iii) Sistema de alimentação controlável; iv) Sistema de dissipação de calor; v) Sistema de aquisição de dados e controlo; vi) Sistema de análise de gases. A investigação experimental incluiu ainda a monitorização da emissão de poluentes (nomeadamente CO e NOx), a avaliação da eficiência da combustão (pelo teor de CO nos gases de exaustão) e o cálculo do rendimento global do equipamento através do método das entradas e saídas. Os resultados apontam para um aumento da formação de cinzas aglomeradas com o aumento de temperatura. Para além disso, estes apontam também para a influência do excesso de ar e da fracção de ar primário na formação, e para a existência de um ponto óptimo para elevados excesso de ar e fracções de ar primário em torno dos 30%. Por outro lado, estes demonstram também a existência de outros factores que influenciam a aglomeração de cinzas, provavelmente relacionados com a alteração da proporção entre elementos químicos devido à vaporização dos mais voláteis.
The market for residential pellet burning equipments is well developed in some European countries like Germany, Austria and Italy. In Portugal, it’s still in an early state, although it has experienced a strong growth in demand over the last years. The pellet production has also grown, mostly for exportation. Due to the existence of chemical elements such as Na, K and Si, the pellet combustion can lead to agglomerated ashes on the grate of the burner causing problems for its proper operation. The present work aimed to study the influence of temperature and air flows in the ash agglomeration at the grate. For this purpose, it was assembled an experimental setup that in a brief description consists of: i) boiler, whose burner allows the regulation of the primary and secondary air flow, ii) variable flow exhaust gases extraction system, iii) controllable feeding system, iv) heat dissipation system, v) data acquisition and control system, vi) exhaust gases analysis system. The experimental research has also included the monitoring the emission of pollutants (CO and NOx), evaluation of the efficiency of combustion (by the CO content in the exhaust gases) and calculation of the overall efficiency of the equipment through the inputs and outputs method. The results indicate an increased formation of agglomerated ash with increasing of temperature. In addition, they also suggest the influence of excess air and primary air fraction in that formation, and the existence of an optimum working condition for high excess air and a primary air fraction of around 30%. Moreover, they also show that there are other factors that influence the ash agglomeration, probably related to the changing of the chemical elements ratio due to vaporization of the more volatile species.

Environmental concerns and the drive to reduce the dependence on petroleum based fuels brought the use of renewable energies to the forefront. Biomass appears as a very interesting option for direct conversion into heat. In this context, densified forms of biomass such as pellets are of great relevance because of their easy of use, high efficiency and low emissions. Expected trends in the biomass market suggest that equipments should operate over a wide range of thermal loads and with fuels derived from lower quality raw materials; simultaneously, a high efficiency and low emissions are taken for granted. Currently, biomass domestic boilers prove to be very sensitive to fuel characteristics and load conditions. This work reports on the development of a 15 kW net pellet boiler. A prototype was built that enables the independent control of the air supply into various regions of the combustion chamber and an accurate supply of fuel. The test rig also includes: boiler and flue gases extraction system; feeding system; heat dissipation system; flue gas analyzer; data acquisition system and all sensors. In order to optimize the combustion conditions, pollutant emissions and their relation with feeding conditions, primary and secondary air flow rate and excess of air was analyzed. The results suggest that this burner is a promising for implementation in domestic boilers. The advantages are: CO emissions well below those observed in similar equipments and the capacity to maintain the emissions level constant under different loading conditions.

With legislation requiring utilities to produce a significant fraction of their electrical energy with renewable fuel supplies, it is anticipated that cofiring biomass in large utility boilers will become increasingly popular. Boilers that are designed to burn pulverized coal (PC) can typically burn woody biomass at up to 5% of the rated heat input. An 800 MW PC-fired unit could, therefore, produce up to 40 MW of renewable energy with biomass co-firing. The generating plant may experience a net capacity de-rating whenever biomass is co-fired. This potential reduction in net plant output may be attributed to reduced boiler efficiency and additional auxiliary power requirements. Biomass fuel handling related auxiliary power requirements are dependent upon the form in which biomass is delivered to the plant. Preparation of woody biomass for co-firing in large PC-fired boilers is typically performed onsite with hammer mills or by off-site processing. For an 800 MW unit, onsite fuel size reduction will usually result in an incremental increase in auxiliary power of 3–4 MW, whereas the use of pre-processed biomass such as wood pellets will require a minimal increase in parasitic load. However, delivered fuel costs for raw wood requiring onsite processing are at least 60% lower than that of densified biomass on a heat input basis. This paper includes an economic comparison of co-firing woody biomass that is processed onsite by direct injection vs. co-firing densified woody biomass by co-milling in a large PC-fired boiler. This comparison will consider delivered fuel costs, capital costs, CO2 emissions and impacts upon boiler efficiency and net heat rate.