Growth analysis of the particle layer in a small-scale ESP with biomass combustion

This study presents experimental results of the particle layer growth with the operation of a small-scale ESP as a flue gas cleaning method from domestic biomass combustion. The retention efficiency of the ESP is maintained above 90% for 40 h of operation, which is in agreement with its natural regeneration by partial collapses of the dust layer. The measurements of profile and thickness of the dust layer endorse the aforementioned collapses as discontinuous re-entrainment events that are also identified as abrupt peaks on the particle concentration at the outlet of the ESP and drops on the current values.Agencia Estatal de Investigación | Ref. PID2021-126569OB-I0

Study of the effects of thermally thin and thermally thick particle approaches on the Eulerian modeling of a biomass combustor operating with wood chips

Two particle treatments, thermally thin and thick, are applied to Eulerian combustion modeling for biomass packed beds and tested through the simulation of an experimental plant. The paper shows the efficiency of the Eulerian approach for large packed beds and tests the behavior of both particle treatments, tested with in-bed and flame temperatures and released volatiles measurements at different locations, which is not common in the literature for a full size boiler. Both approaches are implemented in a model with a comprehensive framework that includes several submodels for the thermal conversion kinetics, bed motion, heat and mass transfer with the gas phase, and gas flow and reaction. Two experiments are performed with wood chips fuels with different moisture contents. The simulations of the two cases result in reasonably good predictions for both particle treatments. The results are similar for higher moisture content and, for the low-moisture test, the bed temperature distribution and reaction fronts are slightly different due to the different predictions of the drying and devolatilization fronts. The volatile measurements show that the T. Thin model results in slightly more accurate predictions than the T. Thick, possibly because the wood chips have a more thermally thin behaviorMinisterio de Ciencia, Innovación y Universidades | Ref. PID2021-126569OB-I00Universidade de Vigo/CISU

CFD modeling and simulation of fouling and particulate-matter deposition mechanisms on biomass combustion

El empleo de biomasa, bien de origen natural o como residuo de la actividad humana, como combustible es habitual en la sociedad actual. Su uso en países con grandes recursos de biomasa supone un elevado porcentaje en el consumo energético y con una clara tendencia al alza, pues se engloban dentro de la categoría de energías renovables. No obstante, su empleo como combustible entraña grandes complejidades, derivadas de su alta heterogeneidad en composición, estado físico y geometría. Las emisiones de los sistemas de combustión de biomasa hasta hace poco no estaban sujetas a vigilancia pues se englobaban dentro del ciclo cerrado de carbono. Numerosos estudios médicos han arrojado que la emisión de ciertos componentes y tamaños de partículas en suspensión son la causa de problemas de salud en el entorno alrededor del sistema. Resulta, por tanto, necesario un mayor esfuerzo en el estudio de la combustión de biomasa para paliar estos problemas y para derribar las barreras que impiden un mayor crecimiento de esta energía renovable. En este trabajo conducente a tesis doctoral, se buscará contribuir a la modelización mediante técnicas CFD de la combustión de lecho fijo de biomasa. Se dotará al modelado existente de una mayor complejidad que aporte la posibilidad de ahondar en la problemática presente tanto en el lecho como en la fase gaseosa.O uso da biomasa, ben de orixe natural ou como un residuo da actividade humana, como combustible é común na sociedade de hoxe. O seu uso en países con grandes recursos de biomasa supón unha porcentaxe elevada do consumo de enerxía e cunha clara tendencia ascendente, pois englóbanse na categoría das enerxías renovables. Con todo, o seu uso como combustible supón grandes complexidades derivadas da súa elevada heteroxeneidade na composición, condición física e xeometría. As emisións procedentes de sistemas de combustión de biomasa ata hai pouco non estaban suxeitos a vixilancia, xa que se englobaban dentro do ciclo pechado do carbono. Numerosos estudos médicos arroxaron que a emisión de certos compoñentes e tamaños de partículas en suspensión son a causa de problemas de saúde no ámbito arredor do sistema. Resulta, por tanto, necesario un maior esforzo no estudo da combustión de biomasa para paliar estes problemas e para romper as barreiras que impiden un maior crecemento desta enerxía renovable. Neste traballo conducente a esta tese doutoral, procurarase contribuír á modelaxe mediante técnicas CFD da combustión en leito fixo de biomasa. Dotarase á modelaxe existente de una maior complexidade que aporte a posibilidade de afondar na problemática presente tanto no leito como na fase gaseosa.The use of biomass, either natural or as a residue of human activity, as fuel is common in today's society. Its use in countries with large biomass resources represents a high percentage in energy consumption and it has a clear upward trend, because it is included within the category of renewable energy. However, its use as fuel entails great complexities arising from its high heterogeneity in composition, physical condition and geometry. Emissions from biomass combustion systems until recently were not subject to surveillance, as they were included within the closed carbon cycle. Numerous medical studies have reported that the emission of certain components and sizes of suspended particulate-matter are the cause of health problems in the environment around the system. It is therefore necessary a greater effort in the study of the combustion of biomass to alleviate these problems and to break down barriers that prevent further growth of this renewable energy. This work that leads to Ph.D., will seek to contribute to the modeling using CFD techniques of the biomass fixed bed combustion. It will add to the existing model a bigger complexity to provide the opportunity to delve into the problems present in both the bed and in the gas phase

CFD simulation of an internally cooled biomass fixed-bed combustion plant

The reduction of bed temperature in fixed-bed biomass combustion is an effective measure to lower pollutant emissions. Air staging and bed cooling solutions are active strategies to decrease the fuel bed temperature. This work presents a CFD study of a biomass fixed-bed combustion plant that is equipped with an internal cooling bed system. Eight different cases are calculated to analyze the effect of the total airflow, air staging ratios and bed cooling system on biomass combustion. The findings are validated against experimental data from the literature. The results show good accordance between the numerical results and the experimental data. The primary airflow rate has the biggest influence on the bed’s maximum temperatures. The internal bed cooling system is able to achieve an average bed temperature reduction of 21%, slowing the biomass thermal conversion processes. Bed cooling techniques can be combined with air staging and primary airflow reduction to reduce bed temperatures in order to reduce pollutant emissions and other undesirable phenomena, such as fouling or slagging.Agencia Estatal de Investigación | Ref. RTI2018-100765-B-I00Agencia Estatal de Investigación | Ref. PRE2019-09011