Flue Gas Temperature Research Articles

Particulate removal characteristics of commercial-scale DeNOx catalyst cartridge coupled filter bags

The commercial-scale DeNOx catalyst cartridge coupled with filter bag have been developed for the removal of fine particulate matter and nitrogen oxides (NOx) in flue gases. The DeNOx catalyst cartridge coupled filter bag is made up of a microporous PTFE (polytetrafluoroethylene) membrane/impregnated polyimide fiber needle-punched pleated filter bag designed for the removal of ultrafine particulates, along with a pellet selective catalytic reduction catalyst-filled cartridge for the removal of NOx. V2O5-MoO3/TiO2 catalyst was used as the DeNOx catalyst. The distribution of cleaning air velocity inside the DeNOx catalyst cartridge-coupled filter bag, which is injected with compressed air from the high-volume low-pressure (HVLP) pulse injector to remove the deposited dust cake from the surface of the filter bags during pulse-jet cleaning, was confirmed using computational fluid dynamics (CFD). The particulate removal and dust cake dislodgement characteristics of the DeNOx catalyst cartridge coupled filter bag were tested in a commercial-scale filter bag test unit under conditions simulating fossil fuel combustion flue gas. The commercial-scale DeNOx catalyst cartridge coupled filter bag was 165 mm in diameter, 2000 mm in total length, and contained approximately 12 kg of DeNOx catalyst- filled cartridges. Nine commercial-scale DeNOx catalyst cartridge coupled filter bags were installed in the commercial-scale filter test unit. The experimental conditions were as follows: flue gas temperature 200 °C, flue gas flow rate 3000Nm3/h, NO, SO2, and particulate concentration in inflow flue gas 200 ppm, 7 ppm, and 5000 mg/Nm3 respectively, resulting in different values of filtration velocities. The efficiency of bag cleaning and intervals, overall collection efficiency, fractional efficiency, and filter quality were investigated. The average bag cleaning efficiency and overall collection efficiency were 95.5%, 91.5%, and 83.3% at filtration velocities of 0.8, 1.0 and 1.2 m/min, respectively. The corresponding values for overall collection efficiency were 99.9%, 99.5%, and 98.2%. So, both bag cleaning efficiency and overall collection efficiency decreased with increased filtration velocity. The present study confirmed that DeNOx catalyst cartridge coupled filter bags have relatively higher bag cleaning efficiency, collection efficiency, and filter quality for challenging fossil fuel combustion flue gas. Particularly, the fractional efficiency for micron-sized particles was considerably higher at lower filtration velocities.

Performance Analysis of a New Cogeneration System with Efficient Utilization of Waste Heat Resources and Energy Conversion Capabilities

This paper proposes a new type of cogeneration system coupled by Organic Rankine Cycle (ORC), Absorption Heat Pump (AHP), and Compression Heat Pump (CHP). The new system can meet the needs of different scenarios. Simulations were conducted to analyze the effect of different factors on the parameters and performance indexes of the new system and compared with the system of ORC, AHP, CHP. The results showed that the factors of flue gas temperature at evaporator1 outlet and CHP have the greatest effect on the parameters and performance indexes of the Organic Absorption-Compression Coupling Heat Power (OACCHP) system, and the effect of AHP on the parameters and performance indexes of the OACCHP system can be ignored. In the given range of flue gas temperature at evaporator1 outlet, the heat production of total and net work is reduced by 1.17% and 33.33%, respectively. In a given range of CHP evaporation temperature, the heat production of the total is reduced by 5.74%. In the given range of the outlet temperature of the gas cooler, the heat production of the total is increased by 10.58%. In a given working condition, compared with the single ORC system, the single CHP system, and the single AHP system, the thermal efficiency, COP, and energy earning rate of the OACCHP system are increased by up to 755.49%, 59.8%, 5.8%, respectively. Finally, the optimal operating conditions for different scenarios were determined.

Experimental and simulation study on coal-fired power generation coupling with fluidized bed biomass gasification

Positive-pressure fluidized bed technology utilizes the pressure generated by biomass gasification to facilitate further combustion within the furnace. This technique addresses the safety risks associated with external pressure in fluidizing medium and high-temperature situations and reduces equipment investment and operating expenses. However, research on the effects of the positive-pressure process in fluidized beds on gasification coupled with coal-fired power generation systems is scarce. To fill this research gap, extensive experimentation and Aspen Plus simulation were conducted to investigate the impact of equivalence ratio (ER), gasification pressure, and gasification temperature on the gasification performance. A 660 MW coal-fired boiler model was established to reveal the coupling effect on flue gas temperature and thermal efficiency by gasification from a positive-pressure fluidized bed on the boiler, and its accuracy was proved by comparing the actual boiler design parameters. The power generation cost of the positive-pressure gasification coupled coal-fired power generation system is calculated with the established model. The results indicate that an increase in gasification pressure from 4000Pa to 8000Pa resulted in no significant change in the operating indicators of the boiler, with the tail gas temperature near 132 °C and a boiler thermal efficiency of 92.68 %. Gas yield, carbon conversion rate, and gasification efficiency were positively correlated with gasification temperature and ER. However, the heat value of combustible gas increased with the gasification temperature and decreased with an increase in ER. With the rise of the biomass gas blending ratio, the power generation cost of the unit gradually decreases. Respectively, the positive -pressure would lower the power generation costs of a 660 MW coal-fired boiler by 5.76 × 105$/year. This study demonstrates that positive-pressure fluidized bed gasification may retain high gas yields and efficiency, significantly lowering equipment investment and operating expenses, as a very efficient energy-saving and carbon-reduction technique.

Characteristics and mechanism of low-temperature NO adsorption by activated carbon

Activated carbon is widely used to purify flue gas in industries like steel and metallurgy, but its ability to adsorb NOx at medium to low flue gas temperatures is limited. This study conducted adsorption experiments in different atmospheres within −20 to 30 °C. As the temperature decreased from 30 °C to −20 °C, the NOx adsorption amount was increased by 4.61 times. Lowering temperature greatly promoted NOx adsorption. Temperature-programmed desorption experiments determined the amount of NOx adsorbed through physical adsorption and chemical adsorption. As the temperature decreased from 30 °C to −20 °C, the proportion of physically adsorbed NOx to total adsorption amount increased from 2.9 % to 45.5 %, and the proportion of physically adsorbed NO2 to total physical adsorption amount increased from 0 to71.6 %. Lowering the temperature benefited NO oxidation and NO2′s adsorption on activated carbon. Desorption curves of chemically adsorbed NOx indicated that a decrease in temperature does not affect the chemical adsorption pathways of NOx. Physical adsorption of NOx was studied by density functional theory calculations. NO2 has much stronger physical adsorption than NO and can physically adsorb near saturated carbon atoms, carbonyl groups, ether groups, hydroxyl groups, and lactone groups. At low temperatures, NO is first oxidized to NO2 on activated carbon and then NO2 is adsorbed through both physical and chemical pathways. Modifying the surface of activated carbon to increase hydroxyl, ether, and lactone groups can help enhance its performance of low-temperature NOx adsorption.

Cryogenic carbon capture design through [formula omitted] anti-sublimation for a gas turbine exhaust: Environmental, economic, energy, and exergy analysis

To achieve a net zero-emission society, current industries must transition to become less carbon-intensive while fulfilling the rising power demand. In this study, we present a novel multigeneration system that produces power, cooling, and solid carbon dioxide by applying cryogenic carbon capture to a gas turbine flue gas. The energy recovery concept is efficiently employed to avoid energy and exergy losses in the system. The system is simulated in Aspen Plus with the mathematical models of the exergy streams and solid-vapor equilibrium written in Matlab. The performance of the plant is assessed based on energy, exergy, economic, and environmental evaluations. Thermodynamic analysis indicates that 1.2 MJ of electricity is required to capture 1 kg of CO2 from the gas turbine exhaust gas (which is lower compared to conventional systems) with 100 % CO2 purity. The net generated power, energy efficiency, exergy efficiency, m˙CO2,captured, and m˙CO2,emitted for the proposed system are 179.4 MW, 41.2 %, 59.3 %, 500,000 tons annually, and 255,000 tons a year, respectively. Sensitivity analysis shows that reducing the flue gas temperature positively impacts the CO2 content in the flue gas while having a negative effect on energy and exergy efficiency. The economic investigation shows that the system is economically profitable.

FEATURES OF FIRE PROTECTION TREATMENT OF LOAD-BEARING BUILDING STRUCTURES

The article emphasizes that wood is a flammable material, flames spread quickly, which poses a threat to building structures. Therefore, it must be protected by effective means of fire protection. Regulatory and technical documentation is presented, which establishes requirements for the quality of fire protection of wooden structures. Using the example of state reserve enterprises, it is shown that there are many methods of fire-resistant treatment of wooden structures with flame retardants. Among them are the impregnation of wood with inorganic salts and the application of coatings on an organic basis. These include impregnation of wood with inorganic salts and application of coatings on an organic basis. It is shown that the specified methods of processing have disadvantages during application and operation, which include the moistening of wood under the influence of external natural factors, which leads to the dissolution and leaching of salts, increased smoke formation, and the formation of toxic combustion products. The constituent parts of the intumescent coating are proposed and their effectiveness in relation to fire protection of wood is determined. Depending on the content of PVA-dispersion, a change in the coefficient of swelling was determined, which is in the range from 14.3 to 25.1. Thus, it was determined that when mineral fillers are added to the composition of the organo-mineral composition in the amount of 10%, it helps to increase the coefficient of swelling from 30 to 36.7, which is 1.5...1.84 times greater than the value of the coefficient of swelling of the optimal composition of the organo-mineral composition without fillers. The article presents research on the creation of fire-resistant intumescent coatings capable of providing a wide range of fire-resistant and operational properties. After testing samples treated with an intumescent coating, under the action of a burner flame, a sample weight loss of no more than 6% was obtained, and the temperature of flue gases did not exceed 184ºС, which refers the treated wood to the group of non-combustible materials. Thus, the intumescent coating provides the first group of fire protection efficiency. Keywords: building structures, fire-resistant treatment, state reserve enterprises, intumescent coatings, fire-resistant properties, efficiency.

Online monitoring of the size distribution of lime nodules in a full-scale operated lime kiln using an in-situ laser triangulation camera

To maximize efficiency of the recausticizing process in a pulp mill, producing a reburned lime with high and consistent reactivity is process critical. Prior investigations have demonstrated a correlation between the reactivity of lime and its nodule size, as well as the dusting behavior of the kiln. Therefore, monitoring the nodule size produced in the lime kiln could be a promising indirect method to measure the performance of the lime kiln. The objective of this investigation was to evaluate the utility of a laser triangulation camera for online monitoring of nodule size distribution for the lime kiln. A series of full-scale trials were performed in a lime kiln of a kraft pulp mill in which a camera was installed at the exit conveyor to analyze the lime discharging from the kiln. The nodule size distribution was analyzed for correlation with the lime temperature, flue gas temperature, and rotational speed of the kiln. The monitoring demonstrated temporal stability, and the results showed that the lime temperature had the most significant effect on the nodule size. The rotational speed of the lime kiln and the flue gas temperature showed limited effect on nodule size, but they had significant impact on the specific energy demand. The overall conclusion of the study is that the camera methodology effectively correlates lime temperature with nodule size distribution, and it advocates for the methods of implementation in automating lime temperature control, facilitating the production of consistently reactive lime at a lower specific energy consumption.

Thermal-economic performance evaluation and bi-objective optimization of organic Rankine cycles using pure and mixed working fluids for waste heat recovery

To further enhance the recovery rate of low temperature waste heat, the low temperature flue gas in the sinter annular cooler is chosen as the heat source of organic Rankine cycle (ORC) system in the current study, and the system thermal-economic performance evaluation are conducted. The thermal-economic performance models of ORC system are established firstly, and the butane and isopentane are selected to constitute the mixed working fluid. Then the changes of system performance with the mass fraction of isopentane (MR601a) and ORC crucial parameters are evaluated comprehensively, and the bi-objective optimization is applied to ascertain the optimal ORC crucial parameters under various MR601a. The results indicate that the MR601a of 0.6 can obtain the maximum glide temperature. The higher the evaporating temperature is, and the lower the condensing temperature is, the larger the exergy efficiency is, while the smaller the levelized energy cost is. There is an optimal superheat degree to make the ORC system achieve the better overall performance under various MR601a. The exergy efficiency of butane is the maximum with a respectable waste heat recovery rate of 64.18 %, while the levelized energy cost of isopentane in the whole conditions is the minimum with the better economic performance.

Design and Performance Analysis of a Small-Scale Prototype Water Condensing System for Biomass Combustion Flue Gas Abatement

This article outlines the design and performance of a flue gas condensation system integrated with a biomass combustion plant. The system comprises a biomass plant fuelled by wood chips, generating flue gases. These gases are condensed via a double heat exchanger set-up, extracting water and heat to reduce concentrations of CO, CO2, and NOx while releasing gases at a temperature close to ambient temperature. The 100 kW biomass plant operates steadily, consuming 50 kg of wood chips per hour with fuel energy of 18.98 MJ/kg. Post combustion, the gases exit at 430 °C and undergo two-stage cooling. In the first stage, gases are cooled in a high-temperature tube heat exchanger, transferring heat to air. They then enter the second stage, a flue gas/water heat exchanger, recovering sensible and latent thermal energy, which leads to water condensation. Flue gas is discharged at approximately 33 °C. Throughout, parameters like the flue gas temperatures, mass flow, fuel consumption, heat carrier temperatures, and water condensation rates were monitored. The test results show that the system can condense water from flue gas at 75 g/min at 22 °C while reducing pollutant emissions by approximately 20% for CO2, 19% for CO, 30% for NO, and 26% for NOx.

Numerical and experimental analysis of the formation of nitrogen oxides in a non-premixed industrial gas burner

Nitrogen oxides (NOx) formation in a non-premixed industrial gas burner is analyzed with Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics, using the Flamelet Generated Manifold (FGM) approach for chemistry and the Reynolds stress model for turbulence closure. Analysis and validation of the numerical methodology use both the RANS and the Large Eddy Simulation methods to study the Sandia flame D experiment. Four regimes of the gas burner, differing by thermal power, are studied experimentally and numerically, comparing measured and computed flue gas temperature and emissions. The flow features leading to NOx formation are analyzed. At low power, most NOx formation occurs in the flame core, where temperatures are highest. At high power, a significant amount of NOx forms where a secondary stream of oxidizer meets the high-temperature burnt gas stream. The NOx formation rate is modeled either by summing the contributions of the main paths relevant to the studied problem or via two variants of the FGM scalar transport approach. One of these variants features a correction to the transported scalar approach that enables accounting for the effects of non-adiabatic phenomena, e.g. heat radiation, on NOx formation without increasing the look-up table dimensionality and the required memory usage. The correction is shown to improve emission predictions over the baseline model, although quantitative differences between predicted and measured emission levels remain significant. The approach computing the NOx formation rate as by summing contributions yields the best agreement with measurements when the thermal path predominates, and the formation of nitrogen dioxide is negligible.

Influence of blowing ratio on double-wall cooling characteristics under the condition of high-temperature flue gas

Double-wall cooling has been extensively investigated due to its exceptional cooling performance. However, most previous studies on the cooling characteristics of double-wall geometry have been conducted under non-reacting conditions, neglecting the influence of high-temperature flue gas radiation. In this paper, an experiment investigation was carried out to evaluate the impact of blowing ratio <italic>M</italic> and coolant-to-gas temperature ratio on the cooling characteristics of effusion/impingement cooling at reacting flow conditions. The experiments were performed at atmospheric pressure with flame temperatures of 1,800 and 1,900 K respectively. Flue gas temperature was measured by S-type thermocouples, while an infrared camera and N-type thermocouples were employed for the gas-side wall surface temperature distribution measurements. The results demonstrate that the laterally averaged cooling effectiveness of the effusion/impingement cooling system increases with the increase of <italic>M</italic>. However, beyond a blowing ratio of 5.1, further increments in <italic>M</italic> do not significantly affect the cooling effectiveness. Moreover, it is observed that the laterally averaged cooling effectiveness gradually improves along the flow direction but at a reduced rate. Additionally, no significant changes in cooling effectiveness are observed after <italic>X</italic>/<italic>D</italic> > 50. Furthermore, when considering a blowing ratio of 4, higher coolant temperatures result in higher cooling effectiveness compared to lower coolant temperatures.

Determination of the optimal total oxygen concentration and oxygen partitioning ratio based on the heat transfer characteristics of oxy-coal combustion in a swirl burner

Oxy-coal combustion is an attractive option for CO2 capture from coal-fired power plants due to high carbon capture efficiency and favorable economic performance. It is critical for the operation of the power plants to maintain similar heat transfer characteristics by rationalizing the partitioning strategy of the oxidant streams when retrofitting coal-fired power plants with oxy-fuel combustion technology. In the present work, the oxy-coal combustion characteristics under various total oxygen concentrations XO2,total of 21 %–32 % and oxygen partitioning ratio conditions in a 100 kW vertical swirl burner were numerically investigated by using computational fluid dynamics (CFD) models. And the effects of the XO2,total and oxygen partitioning ratio on the heat transfer characteristics of oxy-coal combustion were numerically simulated to quantitatively obtain the optimal oxygen supply partitioning strategy for the retrofitting of coal-fired power plants. Then the flame structure, heat transfer flux, and char burnout rate at different oxygen partitioning ratios between the primary and secondary streams were systematically analyzed to further determine the optimal oxygen partitioning ratio. The results showed that the maximum flue gas temperature Tmax increased by 220 K and the total heat transfer flux on the furnace wall increased by 42 % when the XO2,total was increased from 21 % to 32 %, respectively. Under oxy-coal combustion conditions, the Tmax at the XO2,total of 32.4 % was consistent with that under air combustion condition, while the total heat transfer flux at the XO2,total of 29.4 % matched with that under air combustion condition. Moreover, the total heat transfer flux and the flame length were increased by 17.3 % and 46.3 %, respectively, as the oxygen concentration of the primary stream XO2,Pri was increased from 6.5 % to 45 % at the XO2,total of 29 %. More importantly, the total heat transfer flux at the XO2,Pri of 31.9 % under oxy-coal combustion condition matched with that under air combustion condition. The optimal total oxygen concentration and oxygen partitioning ratio of oxy-coal combustion based on the heat transfer characteristics were quantitatively determined, which gave an important reference for the oxy-coal combustion retrofitting of traditional coal-fired power plants.

MODELING AND SIMULATION OF POST-COMBUSTION CO 2 CAPTURE PROCESS FOR 6.4 MWE BAGASSE FUELED POWER PLANT

The emission of carbon dioxide, a greenhouse gas, contributes to the phenomenon of climate change; the largest source of carbon dioxide emissions are fossil fuel power plants. Post-combustion carbon capture (PCC) technology, which is based on solvents, is currently the most advanced technology for reducing carbon dioxide emissions from power plants. The Post-combustion Process, which uses conventional solvents, has a number of disadvantages, including high energy consumption for regeneration, solvent losses, corrosion of equipment, thermal instability, and environmental impact. Ionic liquids (ILs) and IL-based solvents have produced a novel method of CO 2 capture that is highly efficient, economical, and environmentally friendly. A rate-based steady-state model of the PCC process using the ionic liquid 1-hexyl-3-methylimidazolium glycine ([Hmim] [Gly]) was investigated using Aspen Plus ®. In Aspen Plus ® Electrolyte NRTL method and RK equation of state are used to compute liquid and vapor properties. From the process analysis carried out, it was found that the height and diameter of the absorber packing, the liquid-to-gas ratio and the solvent and flue gas temperatures have a positive effect on the CO 2 capture efficiency. The result showed a maximum CO 2 capture efficiency of 92% at a packed height of 12m and diameter of 0.9m. The best capture efficiency of 98.82% was achieved at an L/G ratio of 4.0.the process simulation study examined five key parameters for ([Hmim] [Gly]) solvent which may reduce the energy and cost required for CO 2 capture. The results show that aqueous ([Hmim] [Gly]) is a promising absorbent for CO 2 capture. Offering a pathway towards more sustainable and efficient carbon capture technologies. This study contributes to the advancement of carbon capture technologies and underscores their significance in mitigating climate change impacts.

Nonlinear state estimation of a power plant superheater by using the extended Kalman filter for differential algebraic equation systems

A nonlinear estimator was developed for process monitoring of a power plant superheater system to estimate the transient temperature profiles of the critical measured and unmeasured variables under load-following operations. The model used in the estimator was a detailed, distributed, first-principles, differential–algebraic equation model. The superheater geometry is characterized based on an operating natural gas combined cycle power plant. The model included mass and energy balances for the operating fluids, i.e., steam and flue gas, with due consideration of tube wall temperature dynamics. The dynamic model was used for state and parameter estimation by using a modified extended Kalman filter. When results are compared with the data from a natural gas power plant, the estimator yielded root mean squared error of 0.2 °C for the main steam temperature compared to 1 °C obtained from the first-principles model. While the first-principles model yielded as high as 2.5 °C absolute instantaneous error for the tube temperatures, the estimator reduced the absolute instantaneous error below 0.3 °C for most variables. Performance of the estimator for estimating critical variables like the main steam temperature and flue gas temperature was evaluated in the presence of high model mismatch and noisy measurement data by simulating load-following operation of the plant. The estimator yielded maximum absolute instantaneous error of 3.4 °C for the flue gas and 1 °C for the main steam temperature.

Investigation of flue gas temperature effects in natural gas fueled Systems: Experimental thermal performance and structural optimization

This paper presents an innovative approach by employing experimental and analytical methods to examine the impact of temperature changes in flue gases following combustion on design.Thermal performance experiments conducted on chimney samples have shown that a 2 mm axial expansion, resulting from thermal expansion, affects support designs. To analyze the impact of this often-neglected elongation in support designs and the axial movements caused by temperature, tensile tests were applied to five double-riveted samples with a diameter of 4.8. Subsequently, finite element analyses were conducted on the same model. The ratio between the stress results of the tensile tests and the finite element analysis was found to be 1.04, consistent with the literature. Following the validation of the tensile test, an analytical approach was developed by incorporating forces neglected due to expansion. This approach was complemented by an optimization study to improve the placement of rivets on the plate, for which a code was written. When run on a sample model, the code determined that the coordinates of the six rivets should be (119,50), (97,88), (53,88), (31,50), (53,12), and (97,12), respectively, within the constraints. Additionally, the code was executed with different optimization techniques to compare the results for composite force, number of rivets, circular radius, and coordinates.Furthermore, to observe the effect of temperature on chimney draft, calculations were made for different diameters like Ø 200, Ø 225, and Ø 250. It was observed that as the temperature increased towards 450 °C, there was an increase in pressure difference up to the saturation point.The findings may contribute to the existing literature for researchers and practitioners in this field. Additionally, the presented code offers the capability to quickly calculate the distribution of any fasteners on the plate according to the given data, without the need for a tensile test, finite element analysis, or any other numerical calculation method.

Experimental combustion characteristics and NOx emissions for a 600‐MWe utility boiler after the retrofitted: Effects of load variation

AbstractTo enhance the rapid switching ability of the boiler load and reduce NOx emissions, a new combustion system was implemented in a 600‐MWe wall‐fired boiler with swirl burners. This system included two levels of overfire air (OFA) and low NOx combustion technology. Industrial tests were conducted at 300‐, 450‐, and 600‐MWe loads before and after the retrofitted. These tests included measuring flue gas and furnace temperatures with thermocouples and analyzing local gas concentrations using a gas analyzer. The research results indicate that under conditions where the OFA ratio exceeds 30%, the burner exhibits good ignition performance at different loads. At the 600‐MWe load, the nitrogen oxides (NOx) emissions were reduced by 55% compared to before the retrofit. After the retrofit, the flame center inside the furnace of different loads was located at the height of 33.36 m, the first and second‐stage cooling water quantities were slightly higher, the reheat cooling water quantity was greatly reduced after the retrofit, and contributes to the boiler's safe operation. Under different load conditions after the retrofit, the gas temperature near the sidewall was below 850°C, and the O2 concentration near the sidewall was above 5%, effectively suppressing sidewall high‐temperature corrosion and slagging.

Improving the performance of a condensing heat exchanger for biomass combustion at household scale

A computational CFD model representing the behavior of a condensing heat exchanger used in domestic heating and hot water applications has been presented and validated, obtaining a flow output gas temperature error of 7%. An analysis of the heat exchanger internal aerodynamic performance revealed the need for geometry enhancements which involved increasing the number of combustion gas passages, reducing the cannon diameter, and incorporating turbulence generators.The geometric modifications produced a significant increase in variables of interest for the performance of the equipment when compared to the baseline case. The improvement is quantified as the 68% increase in turbulent intensity, 57% increase in velocity, doubling of flue gas residence time and 96% increase in total heat transfer rate.The design that contains turbulence generators presents the best performance, obtaining the highest heat transfer rate equal to 3.5 kW, which produces a decrease in the flue gas temperature equal to 62% and an increase in the water outlet temperature equal to 53% compared to the base case. In contrast, the prototype without turbulence generators showed a relatively lower performance in terms of heat transfer, but with a 9 times lower pressure drop.

Thermo‐economic analysis of gas‐to‐wire: A case for utilizing gas flaring in the Niger Delta region of Nigeria

AbstractThis work investigated the thermo‐economics of gas‐to‐wire as a gas flaring mitigation option in a selected gas production facility, in the Niger Delta region of Nigeria, which flares 294 thousand standard cubic feet of natural gas, daily. The thermodynamics and economics aspects of the gas‐to‐wire plant were modeled, and implemented in the Engineering Equation Solver software. The thermodynamics was carried out to ascertain the technical feasibility of the proposed plant, while the economics analysis was done to ensure its cost competitiveness. The findings suggested that 19.2 MW of electricity could be generated from the flare gases. This could be achieved at a life cycle cost of 19.24 billion naira, and a unit cost of energy of 13.47 naira per kWh. Parametric simulation of interest rate, excess combustion air, exit temperature of flue gases, and expansion ratio of gas turbine were also done. Furthermore, the proposed power plant could meet the electricity needs of not less than 60,000 households in Delta State where the gas production facility is located at 550 kWh electricity per capita. The study has shown that gas‐to‐wire is one of the viable approaches to tackle gas flaring activities in Nigeria, to meet both the energy demand of its people and to preserve the environment. Thus, it is recommended that the Federal Government of Nigeria should give gas‐to‐wire a priority in its gas flaring utilization agenda.

Numerical study of particle behaviours and heat transfer in a complex rotary kiln

Rotary kiln is widely used for thermal disposal of solid waste due to its effectiveness and high efficiency in recent years. To further improve the processing efficiency, a newly designed rotary kiln with three-section structure is proposed, and the behaviours of particle motion and heat transfer are investigated. Firstly, a lab-scale rotary kiln is manufactured, and experiments are carried out. Verified by experimental data, a CFD-DEM numerical model is developed to analyze the particle motion and heat transfer characteristics with the effects of inlet flue gas temperature, feeding rate and rotating speed. The results show that the outlet temperature increases linearly with the flue gas temperature, while it is negatively correlated with the feeding rate and rotating speed. In addition, the volumetric heat transfer coefficient in this complex rotary kiln is analyzed, the overall heat transfer coefficient is between 200 and 700 W/(m3 K).

Performance Evaluation of Low-Concentration Methane Combustion in a Four-Layer Gradually-Varied Porous Burner

ABSTRACT Porous media combustion (PMC) has made a comeback as a practical technology for the utilization of low-concentration methane (LCM) from coal mining. However, the conventional direct-fired PM burner still suffers from the rampart of flame stability and combustion efficiency not addressing industrial demands. Herein, a four-layer gradually-varied porous burner was innovatively developed for LCM combustion to investigate combustion performance under lean combustion conditions (CH4 volume fraction below 5%). The methane conversion, pollutant emissions, and flue gas temperature were also evaluated in detail. The results indicated that the burner offered a favorable combustion resistance due to the gradually-varied PM arrangement to heighten combustion stability with subtle temperature fluctuation and flame migration. The flammability limit of LCM was extended to the lowest equivalence ratio of 0.43 with stationary combustion at 240°C for 120 min. The energy efficiencies of the LCM combustion under lean combustion conditions were greatly boosted with the highest combustion and thermal efficiencies attained at 99.52% and 70.05%, respectively. The maximum 99.93% CH4 conversion was acquired at an equivalence ratio of 0.45 and a flow rate of 80 L/min. LCM combustion in the burner achieved extremely low pollutant emission levels and the overall CO and NOx emissions were 58.04 ppm and below 23 ppm respectively under the experimental conditions. In addition, the high-quality flue gas with an average temperature of more than 516°C was detected in the operating process, which allowed the available heat utilization at the coal mine scenes or in other industries.