AGRIS - 

2017

Platace, R., Latvia Univ. of Agriculture, Jelgava

Birch is a sturdy tree and often the first to be found in untouched, uncultivated lands. Dry birch wood gives off 25 % more heat than aspen and 15 % more heat than pine wood. Pellet fuel is an improved alternative fuel made of compressed hardwood (birch) and perennial grass biomass. The aim of the study: to evaluate the ash melting temperature of birch and grass mixture pellets for production of fuel. The pellets produced of birch and tall fescue, festulolium and timothy biomass in various mixture proportions were used in the present research. The lowest ash melting temperature at all four ash melting phases was identified in the pellets made of birch in proportion 1/3 with tall fescue, festulolium and timothy biomass, but the pellets made of birch in proportion 3/1 with tall fescue, festulolium and timothy biomass had the highest ash melting temperature. Therefore, the most appropriate recommended proportion for pellets is 3/1 (3 birch + 1 perennial grass biomass). Ash melting temperature of birch biomass at all four melting phases ranged from 1460 to 1500 ºC, while grass biomass reached 1020-1200 ºC.

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Fundamental Library of Latvia University of Life Sciences and Technologies - Latvia

2017

Sánchez Ojeda, Federico | Armenteras Pascual, Dolors

Abstract Soils are one of the largest terrestrial pools of carbon, yet there is still little understanding of spatial variability for ecosystems in the tropics. Fire plays an important role in Neotropical savannas ecosystems and significantly contribute to global greenhouse gas (GHG) fluxes. Nevertheless, the impacts of burning on soil carbon is still uncertain in Latin America. We compared soil organic carbon (SOC) in the first 20 cm depth in savannas in pre and post fire conditions along a forests-savanna edge typically present in these landscapes of the northern South America. We established 8 transects of 20 m longitude along the border with 1m2 plots sampled every 4 m. SOC pre-disturbance was on average 1.794 (±SE 0.043) and the minimum value found (1.08%) was registered 6 months after the burning. Our results show that both the influence of the distance to the edge and the time of burning affect negatively the SOC and also there is a significant interaction between both variables. Our results provide improved estimates of the effect of fire on soil carbon stocks and its highly dynamic nature. We believe these finding will be a step to help better estimate GHG in this type of heterogeneous landscapes. Further it provides a tool for understanding C dynamics under a climate change context with predicted increased fire frequency, extent and severity. | Resumen Los suelos son una de los mayores reservorios terrestres de carbono, sin embargo, todavía hay poca comprensión de su variabilidad espacial en los ecosistemas tropicales. El fuego juega un papel importante en los ecosistemas de sabanas neotropicales y contribuye significativamente a los flujos de gases de efecto invernadero (GEI). A pesar de ello, los impactos derivados de las quemas de carbono en el suelo son todavía muy inciertos en América Latina. En este estudio se comparó el carbono orgánico del suelo (COS) en los primeros 20 cm del suelo en las sabanas de la Orinoquía en Colombia en condiciones previas y posteriores a la ocurrencia de una quema a lo largo de un borde en la interfase bosques-sabana presente en estos paisajes del norte de Sudamérica. Se establecieron 8 transectos de 20 m de longitud a lo largo del borde entre el bosque y la savana y se crearon parcelas de 1m2 muestreadas cada 4 m. El COS en transectos pre-perturbación fue en promedio de 1,794 (± SE 0.043) y el valor mínimo encontrado (1,08%) se registró 6 meses después de la quema. Nuestros resultados muestran que el SOC es superior en el interior del bosque y que existe tanto una influencia de la distancia desde su borde y del tiempo desde la quema que afecta al COS. También hay una interacción significativa entre ambas variables. Nuestros resultados proporcionan valiosa información para mejorar las estimaciones de los efectos del fuego sobre las existencias de carbono en el suelo y ayudarán a una mejor estimación de GEI en este tipo de paisajes heterogéneos. Además se proporciona una herramienta para la comprensión de la dinámica del carbono en un contexto de cambio climático con el posible aumento de la frecuencia de incendios, extensión e intensidad de estos.

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Scientific Electronic Library Online Colombia - Colombia

2017

Golubkovich, A.V. | Dadyko, A.N., Federal Research Agro-engineering Center VIM, Moscow

A theoretical substantiation of heat and mass transfer by heating solid fuel particles, in particular, by burning plant waste. Drying of large particles proceeds in the period of the drooping process rate, accompanied by deepening the front of evaporation inside the material, separating and firing volatile components (VC) and coke residue (CR). In the conditions of convective and radiant heat exchange with the combustion gases which are in case of high temperature, the particle practically at once gets warm to a water boiling point. The front of intensive evaporation of moisture moves deep into material with time. "Dry" and "wet" zones are formed in a particle. Warming up, separation of VC and their inflaming in "the dry" zone begin in the course of deepening the evaporation zone. 3 periods of drying are provided for burning a large particle of the wet fuel with a radius of more than 1 mm: before inflaming VC; visible burning VC before inflaming coke on a surface; drying proceeding in parallel with coke burning-off. A certain location of an evaporation zone corresponds to each of these periods according to which particle dryness and drying duration can be calculated. The total duration of drying represents duration of particle ignition. Processes of particles drying and ignition with different initial humidity and under various conditions of heat emission were calculated. Processes of drying, separation and inflaming of VC, as well as burning of CR take place at the same time in a large wet particle of plant refuse in case of arrival into the furnace chamber. Duration of ignition is defined by end time of burning CR and can be calculated according to complete drying of a particle. In the furnace unit TBR-2.0 drying and ignition of wet soft plant refuse particles with a radius of less than 0.25 mm takes for less than for 2 s, drying with the subsequent ignition of particles with a radius of 1-3 mm lasts 30 s. | Проведено теоретическое обоснование процессов тепломассопереноса при нагреве частицы твердого топлива, в частности при сжигании растительных отходов. Сушка крупных частиц протекает в периоде падающей скорости процесса, сопровождается углублением фронта испарения внутрь материала, выделением, зажиганием летучих компонентов (ЛК) и коксового остатка (КО). В условиях конвективного и лучистого теплообмена с дымовыми газами, находящимися при высокой температуре, частица практически сразу прогревается до температуры кипения воды. Фронт интенсивного испарения влаги с течением времени перемещается вглубь материала. Внутри частицы образуются "сухая" и "мокрая" зоны. В процессе углубления зоны испарения начинается прогрев, выделение ЛК и их воспламенение в "сухой" зоне. Для случая горения в топке крупной частицы влажного топлива радиусом более 1 мм в предлагаемой модели предусмотрены 3 периода сушки: до воспламенения ЛК; видимого горения ЛК до воспламенения кокса на поверхности; сушки, протекающей параллельно с выгоранием кокса. Каждому из этих периодов соответствует определенное положение зоны испарения, по которому можно рассчитать остаточное влагосодержание частицы и длительность сушки. Определили, что суммарная продолжительность сушки представляет собой длительность зажигания частицы. Рассчитали процессы сушки и зажигания частиц с разной начальной влажностью и при различных условиях теплоотдачи. Установили, что в крупной влажной частице растительных отходов при поступлении в топочную камеру одновременно происходят процессы сушки, выделения и воспламенения ЛК, а также горения КО. Длительность зажигания определяется временем окончания горения КО и может быть рассчитана по выражению полного высушивания частицы. В топочном блоке ТБР-2,0 сушка и зажигание влажных мягких частиц растительных остатков радиусом менее 0,25 мм происходит менее чем за 2 с, сушка с последующим зажиганием частиц радиусом 1-3 мм занимает до 30 с.

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Central Scientific Agricultural Library - Russian Federation

2016

gerhard keller-grein | josé m. toledo

Gerhard Keller-Grein, José M. Toledo, 'Nueva tecnologia de pasturas para la Amazonia', Centro Internacional de Agricultura Tropical (CIAT), Programa de Pastos Tropicales, 2016

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GARDIAN - United States of America

2016

ge navas | h hayashi | james m. spain | carlos e. lascano | lh franco

James M. Spain et al., 'A strategy for the gradual replacement of native savanna on an Oxisol in Eastern Colombia', Centro Internacional de Agricultura Tropical (CIAT), 2016

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GARDIAN - United States of America

2016

Kuznetsov, Yu.A. | Goncharenko, V.V. | Semeshin, А.L., Orel State Argarian Univ.

Исследовали восстановление работоспособности радиаторов пайкой с использованием водородно-кислородного пламени и клеевых составов. Для пайки деталей радиаторов рекомендовано использовать сварочные водородно-кислородные установки "Энергия 1.5 УХЛ4", "МБВ-500", "Москва-20". В данных установках для получения газовой смеси используется 20% раствор щелочи КОН в дистиллированной воде, в качестве флюса – раствор следующего состава: хлористый цинк 25%, хлористый аммоний 10% и вода 65% или хлористый цинк 40%, вода 60%. При пайке нагрев изделия рекомендуется проводить 3-ей зоной пламени, на расстоянии 15-20 мм от конца ядра, причем в момент введения припоя следует отвести пламя от шва на 30-40 мм, чтобы не вызвать перегрева припоя. Использование клеевых составов позволяет устранить место течи без разборки радиатора. В качестве клеевого материала при ремонте сердцевины радиатора охлаждения рекомендуется использовать компаунд "Десан-Термо". В отличие от эпоксидных клеев, он влагостоек, хорошо "держит удар" в агрессивных средах, стоек к щелочам, органическим растворителям, маслам, бензину и антифризу, не токсичен. Клеевое соединение может работать в диапазоне температур от -185 град. С до +300 град. С. Данный способ ремонта радиатора повышает теплопроводность отремонтированного участка благодаря циркуляции воздуха через тонкостенные трубки, проходящие насквозь через радиатор, что исключает возможность нарушения теплового режима работы двигателя. Рассмотренные технологические процессы ремонта радиаторов системы охлаждения двигателей внутреннего сгорания обеспечивают ресурс восстановленных изделий не менее 80-90% от новых, а также позволяют значительно снизить эксплуатационные расходы. | Studied is restoration of operability of radiators by means of soldering using hydrogen-oxygen flame and adhesive compositions. For soldering of radiator parts, it is recommended to use the Energiya 1.5 UKHL4, MBV-500, Moska-20 hydrogen-oxygen welding plants. To obtain a gas mixture, these plants use a 20% alkali solution of KOH in distilled water and as a flux - a solution of the following composition: zinc chloride (25%), ammonium chloride (10%), water or zinc chloride (65% and 40%, respectively) and water (60%). In the process of soldering, it is recommended to heat products with the 3-d zone of the flame at a distance of 15-20 mm from the end of the core. What is more, at the time of injecting a solder the flame should be back away from the solder joint to 30-40 mm not to cause overheating of the solder. Use of adhesive compositions enables to eliminate a leaky area without disassembling a radiator. The "Dezan-Termo" compound is recommended to use as an adhesive material in the process of repairing the radiator core. Unlike epoxy adhesives, it is alkalis, organic solvents, oils, gasoline, antifreeze and water resistant, non-toxic and "takes the blow" in the corrosive medium. Adhesive joint can be operable in the temperature range from -185 deg. C to +300 deg. C. This repairing method of a radiator increases the thermal conductivity of a repaired area due to air circulation through thin-walled tubes passing through the radiator and eliminating the possibility of violation of engine thermal conditions. The above considered technological processes of repair in a cooling system of internal combustion engines provide reconditioned life of products of not less than 80-90% of the new ones and can considerably reduce operating costs.

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Central Scientific Agricultural Library - Russian Federation

2016

Flores Ancira, Ernesto | Luna Luna, Miguel | Haubi Segura, Carlos | Díaz Romo, Abraham | Luna Ruiz, José de Jesús

Abstract In Calvillo, Aguascalientes, Mexico, from 2012 and 2013, the effect of fire (burned Q and without burning SQ treatments) on production and nutritional quality of natal grass in three phenological stages was evaluated: growth C, maturity M, and latency L. The fire was applied in April 2012 to 16 m2 plots. During 2012 and 2013 forage production (dry basis) was different (p≤ 0.05) with 168.7, 393.7 g m2 and 53.9, 192.7 g m2 for Q and SQ treatments respectively. Crude protein was similar between treatments (p≥ 0.05) but different (p≤ 0.05) between C, M, L stages, with a total of 13.3, 5.2, 5.6% and 12.6, 4.6, 3.2% respectively. The digestibility of dry matter (DISMS) was different (p≤ 0.05) between treatments Q and SQ and between stages of C, M, and L, with a total of 61.6, 46.0, 48.3% and 50.3, 42.5, 44% respectively. Neutral detergent fiber (FDN) was different (p≤ 0.05) between stages C, M, and L, but not between Q and SQ with values 67.1, 76.5, 78% and 66.4, 76.3, 79.6% respectively. The acid detergent fiber (FDA) showed differences (p≤ 0.05) between stages but not between treatments with a total of 35.8, 50.6, 57.4%, and 33.2, 54.6, 56.3% respectively. The fire increased both production and quality of natal grass forage and could be used as a strategy for ecological management in areas of extensive grazing invaded with natal grass. | Resumen En Calvillo, Aguascalientes, México, durante 2012 y 2013, se evaluó el efecto del fuego (tratamientos de quema Q y sin quema SQ) sobre la producción y calidad nutritiva del zacate rosado en tres etapas fenológicas: crecimiento C, madurez M, y latencia L. El fuego se aplicó en abril de 2012 a parcelas de 16 m2. Durante 2012 y 2013 la producción de forraje (base seca) fue diferente (p≤ 0.05) con 168.7, 393.7 g m2 y 53.9, 192.7 g m2 para los tratamientos Q y SQ respectivamente. La proteína cruda fue similar entre tratamientos (p≥ 0.05), pero diferente (p≤ 0.05) entre etapas C, M, L, con un total de 13.3, 5.2, 5.6% y 12.6, 4.6, 3.2% respectivamente. La digestibilidad de la materia seca (DISMS) resultó diferente (p≤ 0.05) entre tratamientos Q y SQ y entre las etapas de C, M, y L, con un total de 61.6, 46.0, 48.3% y 50.3, 42.5, 44% respectivamente. La fibra detergente neutro (FDN) resultó diferente (p≤ 0.05) entre las etapas C, M, y L, no así entre tratamientos Q y SQ con valores 67.1, 76.5, 78% y 66.4, 76.3, 79.6% respectivamente. La fibra detergente ácido (FDA) mostró diferencias (p≤ 0.05) entre etapas C, M, y L, más no entre tratamientos Q y SQ con un total de 35.8, 50.6, 57.4%, y 33.2, 54.6, 56.3% respectivamente. El fuego incrementó tanto la producción y calidad del forraje del zacate rosado y podría utilizarse como estrategia de manejo ecológica en áreas de pastoreo extensivo invadidas con zacate rosado.

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Scientific Electronic Library Online Mexico - Mexico

2016

Kalis, H., University of Latvia, Riga

Mathematical modelling and experimental study of the electric field control of combustion dynamics and development of exothermal combustion of volatiles downstream the swirling flame flow at biomass thermo chemical conversion are carried out with the aim to provide electric control of the combustion characteristics and to improve combustion conditions in the flame reaction zone. A mathematical model is developed for fuel combustion in a cylindrical pipe for an inviscid, compressible, axially symmetric swirling flow, which considers the development of the exothermic reaction of fuel combustion and approximation of the reaction rate by first order Arrhenius kinetics. The goal of the mathematical modelling is to illustrate the development of the flow velocity, temperature and composition fields and stream function provided the electric field is applied to the flame and considering its effects on development of the swirling flame reaction zone. The approximations of non-linear problems and development of fuel combustion are based on implicit finite-difference and alternating direction (ADI) methods.

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Fundamental Library of Latvia University of Life Sciences and Technologies - Latvia

2016

Cubars, E., Rezekne Academy of Technologies

Reed growths are important regulators of the content of heavy metals in water bodies and silt. While growing, reed captures heavy metals, therefore it can be considered that the extraction of reeds would facilitate removal of heavy metals from water bodies. However, after burning reeds, heavy metals would remain in a concentrated amount in reed ash. Reed ash could be disposed by incorporating them in the soil, but the content of heavy metals that would determine the maximum allowable dose of ash dispersion is not known. It raises the need for further studies on this issue. To determine the maximum 5-year dose of ash that can be dispersed in 1 hectare of soil, maximum values of heavy metal content in reed ash were chosen, by using limiting values of heavy metal content determined for sewage sludge. Analysis of heavy metal content was carried out in relation to chrome (Cr), copper (Cu), cadmium (Cd), nickel (Ni) and lead (Pb). The analysed reed samples were taken from 11 natural and artificial water bodies in Latvia, whose resources of reeds are considered to be significant. It was found that the main heavy metal in reed ash that limits the dose of ash dispersion in the soil is Cr, the maximum 5-year dose for reed ash dispersion in sandy, sandy clay soil constitutes 14.3 tons of ash per hectare, while in loam and clay soils it amounts to 16.6 tons, which is more than in wood ash. Therefore, it can be concluded that in case of burning crushed reed together with wood, maximum reed ash dispersion dose would be greater than the dose of wood ash, and thus it would require smaller soil areas for ash disposal.

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Fundamental Library of Latvia University of Life Sciences and Technologies - Latvia

2016

Ivanov, Yu.G. | Belopukhov, S.L. | Shafeev, A.F. | Vorob'ev, V.A., Russian State Agrarian Univ., Moscow

It is known that direct burning the litter of poultry farms leads to complications, preventing long-term and efficient operation of solid fuel boilers. The determination of the conditions of litter manure thermal decomposition on the basis of determining the activation energy, which must be taken into account in operating the combustion modes in boilers, was done. Derivatograph was used during the research. Speed of sample heating was 20 deg/min, top temperature limit – 1000 deg C. It has been found that heating of clean litter to the temperature of 400 deg C leads to a surge of heat generation, i.e. intense burning of volatile components, as opposed to burning sawdust or manure mixed with sawdust. This can cause sintering of the particles of mineral components and the formation of agglomerates, which may lead to their sticking to convective surfaces including a fire grate, which may lead to damage, failures and repair of solid fuel boilers. It has been found that the introduction of cellulose with sawdust components with low decomposition temperatures contributes to the lowering of the peak temperature, the temperature fluctuations in the furnace and, as a consequence, the more uniform combustion process. Combustion rate, composition of gas phase and components produced after combustion are possible to optimize, changing the content of oxygen in the coming air. | Известно, что прямое сжигание помета птицефабрик приводит к осложнениям, препятствующим долговременной и эффективной работе твердотопливных котлов. Выявляли условия термического разложения подстилочного помета на основе определения энергии активации, которую необходимо учитывать при управлении режимами его сжигания в котлах. В ходе исследования применяли дериватограф. Скорость нагрева образца составляла 20 град. /мин, верхний предел температуры – 1000 град. С. Установили, что при нагревании чистого помета до t 400 град. С происходит всплеск выделения тепла, т.е. интенсивного горения летучих составляющих, в отличие от сжигания опилок или помета с опилками. Это может вызвать спекание частиц минеральных составляющих и образование агломератов, приводящих к их налипанию на конвективные поверхности, в том числе колосниковой решетки, что может привести к выходу из строя, остановке и ремонту твердотопливных котлов. Установили, что добавление опилок с целлюлозосодержащими компонентами с невысокими температурами разложения способствует снижению пиковых значений температур, колебаний температуры в топке и, как следствие, более равномерному процессу горения. Проведенные термодинамические расчеты и экспериментальные измерения энергии активации компонентов сырья позволяют оптимизировать температурные режимы горения в твердотопливных котлах. Скорость горения, состав газовой фазы и компонентов, образующихся после сгорания можно оптимизировать, изменяя содержание кислорода в поступающем воздухе.

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Central Scientific Agricultural Library - Russian Federation