Influence Of Bed Temperature Research Articles

Influence of bed temperature on mechanical resistance, surface and dimensional quality of 3D printed parts by robotized fused pellet modeling

Influence of bed temperature on mechanical resistance, surface and dimensional quality of 3D printed parts by robotized fused pellet modeling

Effects of Fused Deposition Model parameters on PLA-Bz composite filament

Complicated and in strict shapes can be easily mold through 3D printing technology. To take the advantage of 3D printing Technology, a new PLA filament reinforced with 14% Bronze is used to build basic shapes for mechanical testing. The composite is cut to the ASTM standard for the flexural and compression properties. The influence of bed temperature, layer thickness and nozzle temperature over the mechanical properties of samples is investigated. The samples are tested to find the flexural, compression properties with varied operating conditions. From the observation it is found noted that the nozzle temperature has significant effect on the considered mechanical properties.

Influence of bed temperature on performance of silica gel/methanol adsorption refrigeration system at adsorption equilibrium

This paper presents a thermodynamic model for predicting the cooling performance of a single-bed single-stage silica gel/methanol adsorption refrigeration system. Solar heat was collected through flat plate collectors and then stored in a hot water tank. Desorber bed was heated by the hot water from the hot water tank. The temperature of the desorber bed was varied from 65 °C to 85 °C, and its effect on system performance was observed. A numerical model was developed on the basis of mass and energy balance equations, adsorption equilibrium, and kinetic equations (Dubinin–Astakhov equation) for predicting the performance of the adsorption refrigeration system under the said conditions for four major parts (adsorber, desorber, condenser, and evaporator). A programing code was written in FORTRAN for solving these equations under pre-defined material properties, and the simulation result was observed. A refrigeration effect of 577 kJ with a coefficient of performance (COP) of 0.38 could be produced for a maximum bed temperature of 90 °C, which was restricted up to 90 °C because after this temperature, the input increases more than the refrigeration effect, and COP values reduce due to a reduction in desorption mass.

Fragmentation of biomass particles in fixed and fluidized bed combustion and gasification

It is shown that when burning (gasifying) biomass in the fixed (fluidized) bed, it is important to take into account the change in particle size due to their fragmentation. The analysis of the current state of research of fragmentation processes is carried out. It is shown that considerable contribution to the grinding of fuel particles is made by primary fragmentation, and the main factors affecting primary fragmentation are particle size, heating rate, bed temperature, and fuel characteristics. The first results of studies of primary fragmentation of wood biomass particles in an inert medium at different temperatures are presented. The influence of bed temperature, particle size and shape on the quantitative characteristics and criteria of particle fragmentation, causes and nature of wood particle cracking are considered and analyzed.

Post-combustion CO2 capture with activated carbons using fixed bed adsorption

In the current work, the capturing of carbon dioxide from flue gases of post combustion emission using fixed bed adsorption has been carried out. Two grades of commercial activated carbon (sorbent-1 and sorbent-2) were used as adsorbent. Feed consisting of CO2 and N2 mixture was used for carrying out the adsorption. The influence of bed temperature, feed rate, equilibrium partial pressure and initial % CO2 in feed were considered for analyzing adsorption-desorption process. It was found that the total adsorption-desorption cycle time decreases with increased column temperature and feed rates. The time required to achieve the condition of bed saturation decreases with increased bed temperature and feed rates. The amount of CO2 adsorbed/Kg of the adsorbent declines with increased bed temperature with in studied range for sorbent-1 and sorbent-2. It was suggested that the adsorption capacity of the both the sorbents increases with increased partial pressure of the gas.

Experimental study of SO2 and NOx emissions in fluidized bed oxy-fuel combustion

This paper studies the SO2 and NOx emissions from coal oxy-firing in bubbling fluidized bed combustors. The influence of bed temperature and excess oxygen is measured and discussed. The results are also compared with conventional air combustion, in order to determine whether oxy-firing contributes to increase emission levels. Two completely different coals, Central Europe bituminous and domestic Spanish high-sulfur lignite, have been tested in the CIRCE 90kW fluidized bed combustor. Although literature data are scarce, a comparison with the findings of the research is fair. Good SO2 capture efficiencies have been reached, even for the lignite tests, pointing towards the direct sulphation of added sorbent-limestone as the dominant mechanism. As for the NOx emissions, significant coupled influences of oxygen and carbon monoxide concentrations are reported. Notwithstanding this, no relevant differences are observed between air- and oxy-firing if NOx emissions are normalized by energy unit. The paper provides clear insights into the effect of operating conditions of oxy-fuel fluidized beds upon SO2 and NOx emissions.

Attrition of lignite char under fluidized bed gasification conditions: The effect of carbon conversion

The effect of carbon conversion on the attrition of lignite char particles during fluidized bed gasification by CO2 was studied in a lab-scale apparatus. The influence of bed temperature and inlet CO2 concentration on carbon conversion and, consequently, on attrition was studied. The mechanical resistance of the char particles was also characterized at different stages of char conversion by specific attrition experiments. A predictive kinetic model for CO2 gasification of the lignite char was developed from the experimental results, that was able to correctly predict the evolution of carbon conversion versus time. On this basis a semi-empirical model was developed in order to simulate the evolution of carbon elutriation rate with carbon conversion degree, i.e. the gasification-assisted attrition enhancement effect.

Attrition of lignite char during fluidized bed gasification

Fragmentation and attrition phenomena occurring to lignite char particles during fluidized bed gasification by CO2 have been studied in a lab-scale apparatus. The influence of bed temperature, fluidizing velocity and inlet CO2 concentration on attrition and carbon conversion was investigated. Secondary fragmentation and attrition by abrasion of char particles during gasification were significant, suggesting a gasification-assisted attrition enhancement effect. This mechanism, associated to the low reactivity of the generated fines, made the loss of carbon by fines elutriation during char gasification more significant than that typically found under combustion conditions. Up to 10% of the carbon initially fed was lost in the elutriated fines. The carbon loss by elutriation increased with the fluidization velocity, and when the bed temperature and CO2 concentration decreased. The effect of these last two variables was connected to their influence on the char gasification rate.

CFD simulation of bubbling fluidized beds using kinetic theory of rough sphere

Flow behavior of particles is simulated using an Eulerian–Eulerian two-fluid model based on the kinetic theory of rough spheres. The interactions of the short and fast collisions of particles are incorporated to consider the redistribution of momentum and kinetic energy between the collision and friction interactions. The fluctuating kinetic energy by collisions of particles has taken the transfer of particle kinetic energy between the rotational and translational degrees of freedom and also the energy losses into account. Two coefficients, normal restitution coefficient and tangential restitution coefficient, are used to characterize the collisions of particles. The friction coefficient is used to predict the frictional stresses caused by the enduring contacts of particles. The collisional and frictional constitutive relations are used to predict the stresses of rough spheres. The solid pressure and viscosity are obtained in terms of the normal and tangential restitution coefficients and empirical friction constants. Distributions of concentrations and velocities of particles are predicted in the 2-D bubbling fluidized bed. The influence of bed temperature and particle diameter on fluctuation kinetic energy is analyzed in the bubbling fluidized beds. Simulated results are compared with measured axial velocity of particles and bubble diameter published in literature.

Primary fragmentation of limestone under oxy-firing conditions in a bubbling fluidized bed

Primary fragmentation of two limestones was studied in a lab-scale bubbling fluidized bed under simulated oxy-firing conditions and, for comparison, under traditional air-firing conditions. The influence of bed temperature, particle size and simultaneous occurrence of sulphation reaction was tested. Additional experiments in a heated strip apparatus were performed to determine if primary fragmentation occurred under high heating rate conditions, but in the absence of particle collisions. Results of the experiments show that only limited fragmentation occurred to both limestones tested under all operating conditions. Under oxy-firing conditions primary fragmentation was significantly reduced with respect to air-fired operation, most likely because of the absence of limestone calcination under high CO 2 atmospheres. Thermal shock upon limestone injection in the hot bed appears not to be able to induce significant particle fragmentation by its own. Particle size, bed temperature and simultaneous occurrence of sulphation reaction were found not to influence significantly the limestone primary fragmentation extent under both oxy-firing and air-firing conditions. On the contrary, the limestone type was found to be a more important variable with respect to the fragmentation tendency.

An experimental study on gasification of Colombian coal in fluidised bed

The main results of an experimental work on gasification of Colombian coal in a fluidised bed are reported in this paper. Experiments were carried out at different steam/coal ( F s/ F c) and air/coal ( F a/ F c) ratios and temperatures of gasifying agent. In addition, the influence of bed temperature on coal conversion was analysed. Results show a maximum value in the curve of high heating value versus F a/ F c. From the environmental standpoint, low concentrations of sulphur compounds were obtained but more work should be done in order to decrease particulate matter.

Influence of fuel on the emission of nitrogen oxides (NO and N 2O) from an 8-MW fluidized bed boiler

Emissions of nitric oxide (NO) and nitrous oxide (N 2O) from an 8-MW circulating fluidized bed boiler have been measured. The influence of the volatile content of the fuel was investigated by using three different fuels and operating the boiler at different bed temperatures, primary air stoichiometries, and excess air ratios. The measurements show that the emissions of NO are extremely low and dependent upon the char loading of the boiler as well as on the existence of unburned combustible matter such as CO and H 2 in the gas phase. The char content and CO levels are influenced by the fuel, the bed temperature, and the air-to-fuel ratio in the combustion chamber. The levels of N 2O emission are high and caused by the low temperatures used in fluidized beds. The N 2O emission is influenced by bed temperature and oxygen concentration as well, but the influence of bed temperature is opposite compared to the dependence of bed temperature on the NO emission.