Fuel Feed Rate Research Articles

Comprehensive numerical investigations on direct ammonia-fed planar solid oxide fuel cell

This study aims at presenting comprehensive insights into the ammonia-utilization in SOFCs using a numerical model developed in 3D for a laboratory-size SOFC and also enlarged to a commercial-size to provide more realistic insights. The verification of the model using the experimental data, and the description of the Ammonia Decomposition Reaction (ACR) kinetics using a rate equation derived from a real SOFC anode make the model, computations, and analyses more accurate. Temperature appears as the most effective on the ACR rate, whereas the impacts of the cell potential and fuel feed rate are insignificant. The ACR rate and endothermic cooling peak around the fuel inlet. However, the distributions of the ACR rate, concentration of species, temperature, and current depend strongly on the active area. In the commercial-size SOFC, except the fuel inlet region, the remaining area exhibits the characteristics which are usually observed when a SOFC is fed by hydrogen.

Aspen Simulation Study of Dual-Fluidized Bed Biomass Gasification

This article establishes a thermodynamic model of a dual-fluidized bed biomass gasification process based on the Aspen Plus software platform and studies the operational control characteristics of the dual-fluidized bed. Firstly, the reliability of the model is verified by comparing it with the existing experimental data, and then the influence of different process parameters on the operation and gasification characteristics of the dual-fluidized bed system is investigated. The main parameters studied in the operational process include the fuel feed rate, steam/biomass ratio (S/B), air equivalent ratio (ER), and circulating bed material amount, etc. Their influence on the gasification product composition, reactor temperature, gas heat value (QV), gas production rate (GV), carbon conversion rate (ηc), and gasification efficiency (η) is investigated. The study finds that fuel feed rate and circulating bed material amount are positively correlated with QV, ηc, and η; ER is positively correlated with GV and ηc but negatively correlated with QV and η; S/B is positively correlated with GV, ηc, and η but negatively correlated with QV. The addition of CaO is beneficial for increasing QV. In actual operation, a lower reaction temperature in the gasification bed can be achieved by reducing the circulating bed material amount, and a larger temperature difference between the combustion furnace and the gasification furnace helps to further improve the quality of the gas. At the same time, GV, ηc, and η need to be considered to find the most optimized operating conditions for maximizing the benefits. The model simulation results agree well with the experimental data, providing a reference for the operation and design of dual-fluidized beds and chemical looping technology based on dual-fluidized beds.

An experimental investigation into the fate of fuel-bound N-species during fluidised bed combustion of a dried coal slime in O2/Ar mixtures

The formation of NO, NO2, N2O and N2 from fuel-bound nitrogen species during the combustion of a coal slime (CS) and its char (CS char) were investigated in a laboratory bench-scale fluidised bed reactor by tracking the N-containing gas species using a gas chromatograph and an electrochemical gas analyser. Quartz sand with a particle size fraction of 0.3–0.38 mm was used as the bed material. A stream of an Ar/O2 mixture of varying O2 concentration was used as the oxidant and fluidisation gas. The effect of operating temperature (900–1300 K), initial O2 concentration (3–8%), fuel feed rate (0.0041 g min−1 for CS, 0.0036 g min−1 for CS char) and C/O2 mole ratio (0.14–0.78) on carbon burnout, NOx, N2O and N2 formation were systematically studied. It was found that the oxidation process of CS in the fluidised bed is controlled by mass diffusion under the tested conditions. N2, N2O and NO concentrations in the flue gas during CS combustion were higher than during CS char combustion under the same experimental conditions due to the presence of the greater N content in CS (1.56%) than in CS char (1.34%). At low combustion temperatures of 900 K and 1000 K, the fuel-N was mainly converted to NO and N2O. However, as the operating temperature increased, NO and N2 became the dominating species in both the CS and CS char combustion experiments. The NO concentration increased with increasing initial O2 concentration due to enhanced oxidation of char-N. Comparing the N2 formation data during CS and CS char combustion, it is inferred that in the presence of volatile, fuel-N was preferentially converted to N2.

Pellet Combustion in Stove: Perfomance and Emissions Statistical Approach

Small scale stoves, producing heat and hot water, are suited for domestic purposes. A pilot 24 kWt fixed bed pellet stove has been developed for the study of pellet combustion in laboratory. Its design and construction was done in order to permit its maximum flexibility for the simulation of different stove configurations and operational circumstances. Temperatures, pressures, flows and gas compositions are measured and analysed. An extensive study of different load conditions is presented through the application of an experiment design technique and a subsequent statistical analysis of the results. It is shown that the main features of the plant are controlled mainly by fuel feed rate and by air-fuel equivalence ratio, being very low influenced by the temperature of the water. Very good correlation between the studied parameters have been found together with a great agreement between the predicted and the measured values.

EFFECT OF REFUSE-DERIVED FUEL FEEDING RATIO ON PERFORMANCE AND STABILITY OF COMBUSTION TEMPERATURE CONTROL

In this study, the effect of Refuse-Derived Fuel type 3 (RDF-3) feeding ratio on a performance and a stability of combustion temperature control was exmined. A new direct-combustion furnace was designed and constructed for co-combustion of RDF-3 and woodchip (WC) feedstock. In this work, four main ratios on wet basis of WC and RDF-3; 100 : 0, 90 : 10, 80 : 20, and 70 : 30 wt.% were tested at the combustion temperature of 970°C. The results showed that the complete combustion was achieved from all of feeding ratios. From an actual fuel feed rate, an increase in RDF mixing ratio could reduce the using of pure woodchip by 5.3 wt.%, 14.3 wt.% and 34.0 wt.% when mixing the RDF at 10 wt.%, 20 wt.% and 30 wt.%, respectively. At increasing of RDF mixing ratio, non-smoothy burning was also found to increase, however, a more rapid ignition behavior of was achieved

Development and evaluation of a vision driven sensor for estimating fuel feeding rates in combustion and gasification processes

A machine vision driven sensor for estimating the instantaneous feeding rate of pelletized fuels was developed and tested experimentally in combustion and gasification processes. The feeding rate was determined from images of the pellets sliding on a transfer chute into the reactor. From the images the apparent area and velocity of the pellets were extracted. Area was determined by a segmentation model created using a machine learning framework and velocities by image registration of two subsequent images. The measured weight of the pelletized fuel passed through the feeding system was in good agreement with the weight estimated by the sensor. The observed variations in the fuel feeding correlated with the variations in the gaseous species concentrations measured in the reactor core and in the exhaust. Since the developed sensor measures the ingoing fuel feeding rate prior to the reactor, its signal could therefore help improve process control.

Self-Excited Thermoacoustic Instability Behavior of a Hedge Premixed Combustion System with an Asymmetric Air/Fuel Supply or Combustion Condition

Self-excited thermoacoustic instability (SETAI) is an undesirable and dangerous phenomenon in combustion systems. However, its control is difficult, thus greatly limiting the development of combustion technology. Our previous works clarified how the premixed chamber length (LP) and equivalence ratio (φ) influence SETAI behavior in a symmetrical hedge premixed combustion system. On real-world sites, however, the supply structure or combustion condition in a multi-flame system could be asymmetric due to space limitations or combustion adjustment needs. This paper aims to clarify the SETAI behavior of a combustion system with an asymmetric supply structure or an asymmetric combustion condition. The results indicate that the sound pressure amplitude under strong oscillation can reach 160 dB, which is about 5% of the total pressure. The SETAI state under the asymmetric condition is determined by the coupling between the heat release oscillation and sound pressure oscillation on each side and their cooperation. The asymmetric supply structure leads to asynchronous heat release oscillations between the two sides; it may be that one promotes oscillation and that the other suppresses it, or that both have a promotion effect but with asynchronous action, thus partly canceling each other out to lower the system’s oscillation intensity. This brings an advantage for controlling SETAI, which can be achieved by only changing one side of the structure. The oscillation amplitude can be reduced by 80–90% by appropriately changing one LP only by ~20%. Under an asymmetric combustion condition with φ differing between the two sides, the heat release oscillation on each side is dependent on the local φ but not the global φ. Consequently, SETAI can also be controlled by changing the distribution but maintaining a constant fuel feeding rate and φ. The concepts identified in this paper demonstrate that SETAI can be effectively controlled by adopting an asymmetric φ distribution or an asymmetric structure of the supply system. This provides a convenient SETAI control approach without affecting the equipment’s thermal performance.

Effects of [formula omitted]-pentanol blending on soot formation in swirl-stabilized turbulent spray flames of Jet A-1 in a laboratory gas turbine combustor

Although the influence of alcohol supplement on soot in hydrocarbons fuel combustion in laminar flames and transportation engines is widely investigated, the information from well-controlled spray flames with clean boundary conditions are scarce, especially with kerosene type fuels doped with n-pentanol. Favorable physical properties of n-pentanol makes it an attractive oxygenated fuel extender for transportation fuels. We investigated the effects of adding 10% and 20% n-pentanol, by energy content, to a JetA-1 fuel on sooting characteristics of spray combustion in a swirl-stabilized model combustor. At an identical fuel feed rate, two different air flow rates were considered yielding global equivalence ratios of 0.64 and 0.69. Flow field generated by the combustion of swirling air and the injected fuel was measured using stereoscopic particle image velocimetry, and a diffraction based instrument was utilized to quantify the spray droplet size distribution. Laser-induced incandescence was used to measure the soot concentration distribution within the combustor and to estimate the primary soot particle sizes. Very small but measurable changes were observed in the spray droplet characteristics caused by the addition of n-pentanol to JetA-1. 10% replacement of JetA-1 by n-pentanol reduced the soot volume fractions and the total soot loading in the combustor significantly when the global equivalence ratio was 0.69, whereas with global equivalence ratio of 0.64, soot loading was almost zero. When the n-pentanol replacement increased to 20%, no soot was detected for both air flow rates, probably due to soot volume fractions well below the lower limits of laser-induced incandescence. The primary soot particle diameters covered a range from 25 to 50 nm mostly unaffected by the presence of n-pentanol in JetA-1.

A Swiss-Roll-Type Methanol Mini-Steam Reformer for Hydrogen Generation with High Efficiency and Long-Term Durability.

This paper proposes a Swiss-roll-type mini-reformer employing a copper-zinc catalyst for high-efficient SRM process. Although the commercially available copper-zinc catalysts commonly used in cylindrical-type reformers provide decent conversion rates in the short term, their long-term durability still requires improvement, mainly due to temperature variations in the reformer, catalyst loading, and thermal sintering issues. This Swiss-roll-shaped mini-reformer is designed to improve thermal energy preservation/temperature uniformity by using dual spiral channels to improve the long-term durability while maintaining methanol-reforming efficiency. It was fabricated on a copper plate that was 80 mm wide, 80 mm long, and 4 mm high with spiral channels that were 2 mm deep, 4 mm wide, and 350 mm long. To optimize the design and reformer operation, the catalyst porosity, gas hourly speed velocity (GHSV), operation temperature, and fuel feeding rate are investigated. Swiss-roll-type reformers may require higher driving pressures but can provide better thermal energy preservation and temperature uniformity, posing a higher conversion rate for the same amount of catalyst when compared with other geometries. By carefully adjusting the catalyst bed porosity, locations, and catalyst loading amount as well as other conditions, an optimized gas hourly space velocity (GHSV) can be obtained (14,580 mL/g·h) and lead to not only a high conversion rate (96%) and low carbon monoxide generation rate (0.98%) but also a better long-term durability (decay from 96% to 88.12% after 60 h operation time) for SRM processes. The decay rate, 0.13%/h, after 60 h of operation, is five-folds lower than that (0.67%/h, 0.134%/h) of a commercial cylindrical-type fixed-bed reactor with a commercial catalyst.

Experiment and Numerical Studies of the Effect of Equivalent Ratio on Combustion Characteristics in Fluidized Bed Gasifier

The effect of equivalent ratio on fluidized bed gasifier on using kernel mixed palm cake as feedstock was studied experimentally and numerically. A 3-D numerical model of the reactor, similar to the experimental setup, was created using the commercial computational fluid dynamics (CFD) software ANSYS 2019 (Fluent). The fuel feed rate was fixed at 3 kg/hour and the mass flow rate of the air was varied, setting it to equivalent ratios (ER) of 0.1, 0.3, 0.5, and 0.7. The axial temperature profile in the reactor was compared between experimental measurements and numerical simulations and a good agreement was found. Carbon monoxide and volatiles increased when the equivalent ratio decreased, according to the simulations. It was found that ER = 0.1 and ER = 0.3 are suitable equivalent ratios, although the former would not give continuous combustion due to too low reactor temperature.

Pyrolysis of torrefied crop residue: Optimization using response surface methodology and benefits of bio-char in co-combustion with coal

The present study includes optimizing process parameters using response surface methodology (RSM) for the pyrolysis of torrefied pigeon pea stalk to maximize its bio-oil yield. Substantial improvements have been observed in terms of calorific value (29–34% increase), water content (29–33% decrease), and oxygen content (9–12% decrease) for the bio-oil obtained from the pyrolysis of torrefied biomass compared to raw biomass. The results obtained in the present study indicate that the torrefaction of raw biomass could increase the effectiveness of hydrodeoxygenation (HDO) significantly. Hence, it could help achieve desired properties even in a single stage HDO compared to two stages HDO, leading to substantial cost reduction. Furthermore, bio-char from torrefied biomass has a better fuel ratio (FR), less particulate emission, and higher fuel value index (FVI) compared to bio-char from raw biomass and shows better compatibility with bituminous coal in co-combustion. Also, as much as 13.4% and 41.7% reduction in required fuel feed rate and ash production rate have been observed for 60% blending of bio-char with bituminous coal. The yield of pyrolytic gas decreased; however, on the qualitative front, the concentration of CH4 and H2 increased with CO2 being decreased significantly.

Numerical simulation on influencing factors of co-firing of municipal solid waste and leather

Incineration is an important method of recycling municipal solid waste (MSW). As an industrial waste, leather has a higher calorific value and more combustible components than MSW. The blending of leather can make up for the high moisture content and insufficient calorific value of MSW, providing a good solution to reduce the capacity of MSW and industrial waste. This study predicts the effect of blending combustion by means of numerical simulation; the effects of leather blending ratio, the ratio of primary air and secondary air, total air volume, and fuel feed rate were analyzed. The results showed that the appropriate increase of blending ratio improves the furnace chamber temperature, and the best blending amount of leather is approximately 10%. The best primary and second air ratio is 0.72:0.28. Insufficient airflow caused inadequate combustion, and excessive airflow reduced the furnace temperature. The feed volume in the range of 500 to 550 t/d had a good burning effect.

Exergetic optimisation of a solar-biomass hybrid greenhouse dryer in drying banana slices

In this study, an elitist non-dominated sorting genetic algorithm was applied in exergetic optimisation of a solar-biomass hybrid greenhouse dryer in drying banana slices. To develop comprehensive relationships for objective functions under each drying mode (solar, biomass, and solar-biomass), the system was linearised around drying and exit air temperatures. The objective functions involved maximising exergy efficiency and drying air temperature of the system. The trade-offs showed that solar and solar-biomass modes required the same airflow rate (0.05 kg/s) indicating that at these combinations the dryer received almost equal energy input. Biomass mode trade-offs indicated that a lower flow rate (0.01 kg/s) was required for drying. Further, both solar-biomass and biomass modes must maintain a fuel feed rate of 0.001 kg/s for maximum exergy efficiency (solar-biomass: 80.21% ± 14.26%; biomass: 79.28% ± 10.38%) and drying air temperature of 333 K. Performance evaluation of the optimised system demonstrated its superiority compared to the unoptimised system.

Experimental Study of Preheated Secondary Air on the Performance of an Updraft Coal Heating Stove.

Although the Chinese government encourages using clean fuels for heating, many households in remote areas still rely on coal as their energy, especially in the Qinghai Tibet Plateau. An updraft coal heating stove was modified to preheat secondary air. The performance of the modified stove was studied compared with a baseline stove. The temperatures in the combustion chamber and near the chimney exit are measured, and the undiluted exhaust concentrations of CO, NO x , and SO2 are obtained. The results indicated that the temperatures and exhaust gas concentrations varied periodically with the coal addition. The oxygen concentration in the flue gas for the modified stove is higher than that for the baseline stove, and the O2 concentration was decreased with the increase in fuel feed rate. The CO concentration peaked 5-15 min after fuel addition and descended quickly toward a baseline with the higher fuel feed rates. It remained almost unchanged at the beginning and then slightly increased when the combustion began to fade with a lower fuel feed rate for the modified stove. The NO x emission for the modified stove is generally lower than that for the baseline stove. The NO x formation during coal combustion mainly comes from prompt NO and fuel NO, while the SO2 emission is mainly related to the sulfur element in the raw coal in the present work. The modified stove is effective in reducing NO x and SO2 emissions. However, the CO emission of the modified stove is higher than that of the baseline stove, especially at the end of the batch.

Evaluation of the performance of the cross/updraft type gasification technology with the sliding bed over a circular grate

In this article, a novel, pilot-scale gasification technology is closely described from the technological and design points of view. The construction of the fuel bed within the reactor is circular, operating according to the sliding bed principle, equipped with a tangential oxidiser intake. The technology combines principles of cross-draft and updraft gasification reactor type in an autothermal regime. In the model process with softwood pellets (spruce wood) as source fuel, the LHV of the producer gas reached 4.3 MJ·m−3, with the overall conversion ratio reaching 80.3%. These results were obtained in a 709 ± 10 °C environment with the fuel feed rate equal to exactly 30 kg·h−1 while the flow rate of the oxidising media was 17 ± 1 m3∙h−1.The gas quality in terms of its content is a major factor to be considered. The purity of the producer gas is crucial for most final-use technologies. Thus, the question of polluting agents and undesired substances is analysed and discussed in this article. The custom-made cleaning track of hereby described scientific technology can operate with 99.9% particulate matter removal efficiency, while tar compounds within the producer gas are kept as low as 9.7 g·m−3.This article summarises a detailed description of a specific pilot-scale gasification unit where results of an experimental analysis are depicted along with real-time values and detailed schematic descriptions and illustrations, providing a base for comparison with conventional technology designs.

Performance of a dual-chamber microbial fuel cell as a biosensor for in situ monitoring Bisphenol A in wastewater

This research explores the possibilities of a dual-chamber microbial fuel cell as a biosensor to measure Bisphenol A (BPA) in wastewater. BPA is an organic compound and is considered to be an endocrine disruptor, affecting exposed organisms, the environment, and human health. The performance of the microbial fuel cells (MFCs) was first controlled with specific operational conditions (pH, temperature, fuel feeding rate, and organic loading rate) to obtain the best accuracy of the sensor signal. After that, BPA concentrations varying from 50 to 1000 μg L−1 were examined under the biosensor's cell voltage generation. The outcome illustrates that MFC generates the most power under the best possible conditions of neutral pH, 300 mg L−1 of COD, R 1000 Ω, and ambient temperature. In general, adding BPA improved the biosensor's cell voltage generation. A slight linear trend between voltage output generation and BPA concentration was observed with R2 0.96, which indicated that BPA in this particular concentration range did not real harm to the MFC's electrogenic bacteria. Scanning electron microscope (SEM) images revealed a better cover biofilm after BPA injection on the surface electrode compared to it without BPA. These results confirmed that electroactive biofilm-based MFCs can serve to detect BPA found in wastewaters.

Integrated thermal modeling, analysis, and sequential design of heat exchanger surfaces of a natural circulation RDF boiler including evaporator tubes

Although the design methodology of individual heat transfer surfaces in a natural circulation boiler such as evaporator tubes, convective and radiative superheaters are available in the literature, the multiple feasible design solutions of boiler heat exchanger surfaces coupled with drift flux based model of evaporator tube and cost-based optimal solution of the surfaces is not common. The present study proposes a sequential iterative design methodology for all heat transfer surfaces (from the evaporator to air preheater) in a single boiler to bridge the gap between industrial needs and academia. The salient temperature points in different locations are used in the design, alternate solutions are considered, and the overall cost is minimized. The evaporator tubes are designed based on a two-phase flow drift flux model and fixed volume constraint. The radiant and radiative-convective superheaters are modeled using weighted average flue gas temperature. The models of evaporator section and other heat exchangers are validated extensively with data of natural circulation loop and components integrated into real plants, respectively. The feasible and optimal design solutions of all heat transfer surfaces are proposed for a medium-scale (35 MW) Refused-Derived Fuel-fired Boiler (RDFB). The variation of mass flux through the evaporator tubes with the fuel feed rate is observed to be gravity-driven initially followed by friction-dominated. It is observed that for lowering the exit flue gas temperature of 14.93% below 150 °C, the required area of air preheater is 21.83% higher, while for a reduction of temperature of 21.42%, the area increment is 55.8%, which increases the investment cost rapidly. Results also indicate that the radiative heat exchangers require less heat transfer surface for a higher pitch to diameter ratio while the opposite characteristic is observed for the convective heat exchangers.

Design, Performance and Cost Analysis of Automated Smoking Machine for Village-level Smoked Fish Production

The automated smoking machine is a pilot initiative towards the development of integrated processing machinery for the village-level production of smoked fish in Cavite, Philippines. Considering the traditional processing activities and the code of practice for the processing and handling of smoked fish, the machine was designed and fabricated with an estimated capacity of 75 kg per batch of operation. The machine can accomplish both hot and cold smoking processes by maintaining temperatures between 70-90 and 30-60 °C. Using sawdust and wood trimmings as biomass fuel, preliminary tests were conducted to examine the function of machine components and to establish the fuel feed rate and fuel ignition time. Meanwhile, at full capacity testing, smoked fish was produced for sensory analysis while monitoring the smoking temperature and relative humidity in the processing chamber. Results revealed that the minimum, maximum and average temperatures during hot smoking were 60.90, 72.58 °C and 79.93±5.01 °C, respectively, with an average relative humidity of 58.30%. When loaded at full capacity, the average smoking temperature reached 71.72±13.46 °C with no significant difference in the smoking temperature and relative humidity across the sections of the processing chamber. On average, the sensory properties that include the color, aroma, texture and taste of the smoked fish products scored 8.43 (extremely liked) among the participants of the sensory evaluation. A simple economic analysis revealed an initial investment of Php 170,000.00 that is recoverable in 1.59 years, a benefit-cost ratio of 1.29 and a return of investment of 34% – indicative of the machine’s financial viability.

High-throughput generation of aircraft-like soot

High-throughput, laboratory units for generation of aircraft-like soot are needed to quantify and understand the impact of such emissions on public health and climate change due to the high costs and limited access to aircraft engines. Enclosed spray combustion of jet fuel is used here to generate high soot concentrations, up to 255 mg/m3, three orders of magnitude higher than those typically obtained by widely used soot generators that use vapor-fed flames. This is attributed mostly to the use of real jet fuels. The large mass concentrations enable routine characterization of the soot specific surface area (SSA) and pore size distribution (PSD) by N2 adsorption. The geometric mean mobility diameter, d¯m, of soot agglomerates was systematically varied from 15 to 180 nm by varying the equivalence ratio (EQR) at constant fuel feed rates, while the organic to total carbon (OC/TC) ratio is low (<20%) at all conditions. The geometric mean primary particle (PP) diameter, d¯p, standard deviation, σg,p, and mass-mobility exponent, Dfm, were hardly altered in that EQR range. These measured Dfm and σg,p indicate that soot PPs were sinter-bonded by surface growth, in agreement with aircraft emissions literature. Most importantly, soot made at EQR ≤ 1.34 has mainly small pores (<2 nm) and similar morphology (Dfm = 2.52 ± 0.17), SSA (160 − 239 m2/g), OC/TC (< 20%), d¯m (15 − 61 nm) and d¯p (14 nm) with those from high-thrust aircraft emissions.

Experimental study on flame height and heat release rate estimation of diesel-wetted wood powder fire

This paper experimentally studied the temperature profile and flame height variation of diesel-wetted wood powder fire. Fuel component ratio (the mass ratio of diesel to wood powder) and burner diameter were considered. Results show that due to difference of flash/ignition point between diesel and wood powder, main combustion component changes gradually from diesel to wood powder. Hence, the axial temperature rises sharply first and then decreases gradually. According to axial temperature, combustion is generally divided into three stages: (1) rapid burning, (2) transition and (3) steady burning. In rapid burning stage, lateral temperature profile conforms to Yokoi profile above the flame height and to ‘Top-hat’ profile below the flame height. Heat release rate (HRR) is estimated using axial temperature profile based on McCaffrey's model. HRR of this kind of fire is much lower than that of pool fire with the same burner size. Due to decrease of fuel feed rate, flame height decreases constantly and was correlated with mass loss rate per unit area. Flame transits into ‘mass fire’ when dimensionless flame height decrease to about 0.3. The work is expected to help evaluate the thermal hazard and facilitate the detection of this kind of fire.