Exit Gas Temperature Research Articles

Thermofluid process simulation of wet biomass and ammonia co-firing in an industrial watertube boiler

Co-firing of ammonia with low-carbon biomass fuels can promote cleaner energy by employing a carbon-free alternative in tandem with traditional fuels. However, doing this in a boiler specifically designed for solid fuel with high moisture content could pose challenges. In the present work, an integrated thermofluid network model of a whole boiler firing sugarcane bagasse is developed and applied to investigate the effect of co-firing ammonia on the thermal performance. The results show that the primary impacts are an increase in the adiabatic flame temperature and a reduction in total flue gas flow rates. This is due to the higher HHV of ammonia compared to biomass, along with lower excess air ratios. At a blending ratio of 0.5 kg NH3/kg biomass, there is a 58% reduction in CO2 mass flow rate in the flue gas. The impact on furnace exit gas temperature, spray water flow rates and intermediate header temperatures are small, and the economizer does not run the risk of acid corrosion. It also shows that ammonia co-firing could potentially be used to stabilize boiler efficiency and reduce the sensitivity of the temperature control system when a batch of high moisture fuel is introduced. Therefore, for this boiler the co-firing of ammonia with wet biomass has a beneficial effect on both boiler operation and environmental impact.

Optimizing building energy efficiency with a combined cooling, heating, and power (CCHP) system driven by boiler waste heat recovery

In light of increasing challenges related to fossil fuel consumption, global warming, and rising energy costs, optimizing energy systems has become essential. This study introduces a multi-purpose system designed to capture and utilize waste heat from boiler flue gases at the Tous power plant for simultaneous power generation, cooling, and heating. The system integrates an Organic Rankine Cycle (ORC) for power generation and an Absorption Refrigeration Cycle (ARC) for cooling, with the added function of recovering waste heat to preheat natural gas for the boiler and power plant. The system's performance was rigorously analyzed through energy, exergy, and exergoeconomic assessments. To determine the optimal operating conditions, a multi-objective optimization was conducted using the TOPSIS technique, focusing on critical parameters such as flue gas exit temperature, natural gas inlet temperature, and turbine inlet pressures. The results identified optimal conditions with a flue gas exit temperature of 532.5 K, a natural gas inlet temperature of 285 K, and turbine inlet pressures of 2.54 MPa and 14.62 MPa for the first and second turbines, respectively. Under these conditions, the system achieved an exergy efficiency of 41.1 %, cooling capacity of 133.1 kW, power generation of 210.4 kW, heat transfer to natural gas of 979.6 kW, and operational costs of 8.53 $/h. This study highlights the potential of the proposed system to significantly enhance energy efficiency and reduce operational costs in practical applications, offering a sustainable solution for energy management.

Analysis of Combustion Characteristics of Can-Type and Annular-Type Combustion Chamber

Abstract High performance is always desired for the propulsion system and the assortment of a better combustion type is also a vital part of the propulsion system. The analysis of different designs of combustion chambers and comparison of their combustion characteristics. In this paper, the assessment of Can-type and Annular-type combustion chambers and the design developed with SOLIDWORKS software and analysis done with ANSYS FLUENT. The systematic and translucent method approaches reduce the design complexity and time. The combustion with turbulence interface was examined to analyze with precision results, and the analysis specified that the nowadays experiment depends on the behavior of gas exit pressure, temperature, and velocity. Parametric analysis is used to acquire the sizing of the combustion chamber.

Physics-inspired AI-based model for cold crushing strength of an iron ore pellet plant

ABSTRACT The cold crushing strength (CCS) of iron ore pellets produced in a straight grate indurating machine is critical to their quality and performance. This study explored two modelling approaches to accurately predict CCS: an artificial neural network (ANN) model and a physics-informed hybrid model. The ANN model was designed to predict CCS directly from parameters such as pellet chemistry, Blaine number, and measured induration conditions. In contrast, the hybrid model combined a first-principles simulation of the induration process with the ANN model, using the simulated pellet temperatures and the exit gas temperatures as inputs to the ANN component, while keeping the other input parameters the same as the standalone ANN model. The models were validated using 1730 datasets from a 6 MTPA iron ore pelletizing plant of Tata Steel India Ltd. The hybrid model demonstrated superior performance, achieving a mean absolute percentage error (MAPE) of 3.7% compared to 4.1% for the ANN-only model. The hybrid model offers two key advantages: (1) it can provide early insights into CCS, enabling pre-emptive adjustments to the induration process, and (2) it can be used as a powerful optimization tool to enhance the overall quality and consistency of the iron ore pellets.

The Effects of Preheating the Shielding Gas Used in Gas Tungsten Arc Welding

The shielding gas used in welding processes has properties that can affect the operating characteristics of electric welding arcs. Characteristics such as welding voltage, heat input, and thermal profile, which in turn affect weld geometry, are strongly influenced by the properties of the gas used. Thus, this work aimed to evaluate how preheating the shielding gas influences the gas tungsten arc welding (GTAW) process. For this, a heating system was developed that allowed the variation and control of the gas exit temperature during the tests. A methodology for studying the electric arc was proposed, evaluating the voltagecurrent, profile, and luminosity values. Autogenous welds were performed on carbon steel plates with different gas temperatures, and penetration and width were observed. The results showed that the use of gas preheating influenced the characteristics of the arc and, consequently, weld geometry.

Calculation of the furnace exit gas temperature of stoker fired boilers

Calculation of the furnace exit gas temperature of stoker fired boilers

Multiscale CFD modelling of syngas-based chemical looping combustion in a packed bed reactor with dynamic gas switching technology

Chemical looping combustion (CLC) is a highly efficient energy conversion technology designed for burning fossil fuel with inherent carbon capture potential. The main advantage of running the CLC process in a packed bed configuration over the conventional circulating fluidized bed setup is the ability to operate at high pressure. In this work, a dynamic multiscale model was developed to simulate packed bed syngas CLC with ilmenite oxygen carrier (OC) particles, subsequently validating simulation results in terms of fuel and OC conversion, and temperature distribution using literature data for both oxidation and reduction steps. The model was used for investigation of multiple cycle operation, intraparticle fuel and OC concentration distributions, as well as effects of particle sizes and flow rates during OC reduction. Results revealed pressure drop reductions by 45% for 50% larger particle sizes and 66% for 50% lower flow rates, as well as better bed utilization for lower particle sizes and flow rates based on fuel breakthrough curves. In addition, a CFD multilayer particle model was developed to strengthen multiscale model results on pressure drops and mass transfer efficiency, and study temperature distribution with respect to particle dimensions during OC oxidation. Results indicated a positive effect on energy efficiency for smaller particles due to higher packing density and particle surface area, reaching intraparticle temperatures of 1110 ℃ and exit gas temperatures of 980 ℃ (i.e., 13% higher than base case size) during OC oxidation.

A CFD-Based Methodology for Impact Assessment of Industrial Emissions and Evaluation of Mitigation Measures for Regulatory Purposes

In a context where air quality has become a global concern, modelling techniques are becoming very popular for analysing pollutant dispersion conditions. While models based on empirical formulations are most widely used for industrial scenarios, singular cases involving complex terrain or large obstacles in the vicinity of emission sources require a more robust approach to evaluate the dispersion conditions. In this research, a computational fluid dynamics (CFD) model is developed to analyse the dispersion of pollutants from an industrial facility whose location and characteristics suggest the occurrence of complex flow features that affect the dispersion patterns. In addition, the variation of the gas exit temperatures of waste heat recovery systems is proposed as a measure to mitigate the impact of the plume. The simulation results show unexpected deviations in the plume path affecting vulnerable areas in a nearby mountainside, but increasing the gas exit temperature is useful to prevent this event. Therefore, the proposed methodology can be considered a decision support tool to find a compromise between the environmental impact and the fuel consumption of the plant.

CFD simulation and experimental validation of multiphase flow in industrial cyclone preheaters

A hybrid multiphase model (Dense Discrete Phase Model, DDPM) coupled with a k-ω sst turbulence model, which includes gas–solid heat exchange was developed for the simulation of industrial-scale cyclone preheaters operating under high solid loadings. The model results are validated by experimental measurements from an industrial cyclone preheater with a diameter of 1.6 m, with respect to the pressure drop, gas and particle exit temperature, local gas velocity profiles, measured using the LDA, and gas temperature profiles, measured using thermocouple and FTIR. Reasonable agreement between the data from experiments and simulations was obtained. In addition, the major trends, such as changes in the pressure drop, overall heat transfer rate, and flow pattern, caused by the changes in the operating parameters can be captured accurately by the model.

Heat Rate Deviation Analysis of a Coal-Fired Power Plant (CFPP) with the Influence of Applicable Coal Prices (ACP)

The assessment of a Coal-Fired Power Plant (CFPP) performance is an intricate process that involves the determination of Heat Rate (HR) deviations of current operational parameters from baseline or target values. This study focuses on HR deviations of a CFPP based on the Applicable Coal Price (ACP), and the influence of the ACP price on daily losses or gains are thoroughly analyzed for key performance parameters for three fixed ACP of RM12, 18, and 24 per GJ. This paper mainly investigates key parameters and related equipment that significantly affect the HR of the CFPP and ranks the parameters affecting HR from most significant to least significant. The baseline or target values are obtained from the plant commissioning manuals and the Performance Guarantee Test (PGT). Actual real-life operational data from a 700MWn CFPP is utilized to improve the accuracy and confidence levels of the results obtained. It was found that at the nominal operating baseload, the most significant negative HR deviation is for the Rotary Air Heater (RAH) gas exit temperature with a negative HR deviation of -137.9 kJ/kWh leading to an annual loss of RM17.6 million at ACP of RM24/GJ while the superheater and reheater spray flows are contributing least to the HR deviation. This analysis highlighting the impact of key parameters affecting the performance enables plant operations and maintenance teams to focus on such parameters to mitigate losses.

Techno-Economic Analysis of Co-firing for Pulverized Coal Boilers Power Plant in Indonesia

The utilization of co-firing (coal-biomass) in existing coal-fired power plants (CFPPs) is the fastest and most effective way to increase the renewable energy mix, which has been dominated by pulverized coal (PC) boilers, particularly in the Indonesian context. This study aims to investigate the technical and economic aspects of co-firing by conducting a pilot project of three PC boiler plants and capturing several preliminary figures before being implemented for the entire plants in Indonesia. Various measured variables, such as plant efficiency, furnace exit gas temperature (FEGT), fuel characteristic, generating cost (GC), and flue gas emissions, were identified and compared between coal-firing and 5%-biomass co-firing. The result from three different capacities of CFPP shows that co-firing impacts the efficiency of the plant corresponding to biomass heating value linearly and has an insignificant impact on FEGT. Regarding environmental impact, co-firing has a high potential to reduce SO2 and NOx emissions depending on the sulfur and nitrogen content of biomass. SO2 emission decreases by a maximum of 34% and a minimum of 1.88%. While according to economic evaluation, the average electricity GC increases by about 0.25 USD cent/kWh due to biomass price per unit of energy is higher than coal by 0.64×10-3 USD cent/kcal. The accumulation in the one-year operation of 5%-biomass co-firing with a 70% capacity factor produced 285,676 MWh of green energy, equal to 323,749 tCO2e and 143,474 USD of carbon credit. The biomass prices sensitivity analysis found that the fuel price per unit of energy between biomass and coal was the significant parameter to the GC changes.

Oil Palm Wastes Co-firing in an Opposed Firing 500 MW Utility Boiler: A Numerical Analysis

Malaysia is rich in palm oil plantations, where oil palm wastes (OPWs) are one of the readily accessible biomass resources. OPWs has the potential to be used as a fuel for electricity generation. Hence, the evaluation of OPWs co-firing for one of Malaysia's 500 MW utility boilers was executed numerically. Three types of OPWs were tested including empty fruit bunches (EFB), palm kernel shell (PKS), and palm mesocarp fibres (PMF). The predicted furnace exit gas temperature (FEGT) from the numerical model was validated against the actual FEGT from the power plant where the current boiler is situated, revealing a difference of less than 10%. The nose area temperature was predicted to exceed the cap of 1200°C in OPWs co-firing cases due to higher volatile matter (VM) in OPWs than the baseline of pure coal case, leading to higher levels of volatile release. When co-firing with OPWs, the predicted unburned carbon (UBC) at the boiler's outlet is lower because OPWs-coal blends contain less fixed carbon (FC) than the pure coal blend. UBC levels were anticipated to be lower than the loss of ignition (LOI) limit in all cases, highlighting its positive impact on carbon reduction. Slightly lowered mill performance was observed as a result of the calculated OPWs fuel flow surpassing the normal operation in the power plant to make up for the low gross calorific value (GCV) of OPWs while meeting the required load from the boiler. OPWs co-firing was predicted to emit lower carbon monoxide (CO) and carbon dioxide (CO2) than baseline coal due to lower FC. Nonetheless, higher thermal nitrogen oxides (NOx) were predicted due to the higher flame temperature created by OPWs co-firing. Even so, it is recommended that the ash mineral composition be included in future numerical studies since the ash minerals may have an effect on the emitted NOx.

Characteristics of Co-firing Solid Recovered Fuel with sub-bituminous Coal on Pulverized Coal Boiler Power Plant 300 MWe

The biomass co-firing test was conducted at a pulverized coal power plant with a capacity of 300 MWe to determine the effect of cofiring on the operating parameters, such as Mill Outlet Temperature (MOT), Furnace Exit Gas Temperature (FEGT), Specific Fuel Consumption (SFC) and environment. Biomass Solid Recovered Fuel (SRF) and coal was mixed in a stockpile with a composition of 5 % SRF and 95 % coal. Fuel mix was fed into the four operating bunker mills. The load stabilization process duration is 1 h after the biomass is fed to the boiler by keeping the loading constant at the maximum capacity rate. The data was recorded for 2 h with a retrieval interval of every 15 min. The results showed that the FEGT value during co-firing was 0.7 % lower than during coal firing. The mill outlet temperature ranges from 58 °C to 60 °C in both test conditions. NOx emissions increase by 10.1 %, and SO2 emissions increase by 5.5 % during co-firing than coal-firing conditions. There is no significant change in SFC where the value equals 0.54 kg kWh-1 on both tests.

SO3 Migration and Emission Characteristics of CFB Boilers

In order to study the migration and transformation of SO3 from circulating fluidized bed boiler (CFB) in the air preheater and flue gas treatment facilities, 10 circulating fluidized bed boilers with installed capacities between 150 MW and 330 MW were measured by controlled condensation method. Ten circulating fluidized bed boilers with installed capacities ranging from 150 MW to 330 MW were measured using the controlled condensation method. It is showed that the SO3 removal rate of the air preheater was affected by the air preheater flue gas exit temperature, which ranged from 6.7 % to 36.5 %, and the SO3 removal rate of the rotary air preheater was higher than that of the tubular air preheater. The SO3 removal rate of cloth bag filter and electric bag filter is above 40 %; the SO3 removal rate of electrostatic precipitator is between 6.1 % and 10.8 %. The SO3 removal rate of wet desulfurization method ranges from 41.7 % to 73.4 %, with the highest SO3 removal rate of double tower double cycle. The SO3 removal rate of off-furnace CFB semi-dry desulfurization reached 89.7 %~97.9 %, and the dry process inside the furnace + off-furnace CFB semi-dry process could reduce the SO3 at the desulfurization outlet to below 0.3 mg/m3 under the tested conditions. The conclusions of the test analysis in this paper can provide reference for SO3 control in circulating fluidized bed boilers and related policy formulation.

Integrated use of CFD and field data for accurate thermal analyses of oil/gas boilers

In the present study we develop a complete Computational Fluid Dynamics (CFD) modeling procedure suitable for accurate simulations of industrial boilers fed alternatively with gaseous and liquid fuels. The model is developed and validated by means of data from on-site testing.Two different boilers are considered: a 6-burner steam generator of a refinery for the model definition, and a 32-burner thermal power plant boiler for validation, fed by flare-gas/natural-gas or Heavy-Fuel-Oil (HFO). Selected reliable experimental data coming from performance testing are used for both the set-up of the CFD simulations as well as to compute the Flue Exit Gas Temperatures (FEGTs) employed as validation criteria. The flare-gas testing on the 6-burner boiler allows us to accurately determine that a membrane wall emissivity around 0.60 is appropriate as a boundary condition for radiation. By a sensitivity analysis, the relevance of wall emissivity with respect to fouling thermal resistance on the overall heat transfer inside the furnace is established. For boilers alternatively operating with gaseous fuel and HFO a value of 2.8 kW/(m2·K) has been found appropriate. HFO testing on the 6-burner boiler provides data to develop the additional soot modeling, crucial to properly catch oil flame emissivity, based on the model of Khan and Greeves. This allows the matching of a mean soot mass fraction of 1%–3% in the flame zone, a range found by in-flame measurements in the literature and confirmed in the present study by overall heat exchange data in the whole furnace coming from HFO boiler testing. Finally, the 32-burner boiler is considered for validation: using the same procedure and parameters, excellent agreement is found between experimental and CFD results, both on a 100% load natural gas and on a 107% load HFO performance testing.The study demonstrates how field data can be used to validate CFD simulations and confirms that the use of physically meaningful parameters and models exempts from repeated tuning: no change is needed for emissivity and fouling thermal resistance between gaseous and liquid fuel operation, and even a simple soot modeling can be used, just ensuring physically consistent particulate concentration in the oil flame.

Numerical investigations on overfire air design for improved boiler operation and lower NOx emission in commercial wall-firing coal power plants

Air staging using overfire air (OFA) is a common practice in a pulverized coal combustion for reduction of NOx emission without deteriorating the combustion efficiency. In opposed wall-firing boilers, a simple single-level arrangement of OFA nozzles aligned with swirl burners is typically employed. In this study, an ideal OFA design was developed using computational fluid dynamics for efficient combustion, heat transfer, and emission reduction in a 595-MWe industrial-scale boiler. Using the modeling methodology validated using boiler design data, various OFA designs were evaluated for detailed impact on the boiler performance including char burnout, NOx emission, furnace exit gas temperature (FEGT), and heat absorption including convective heat exchangers. Comparing with single-level arrangements at various heights or two-level arrangements with an increased number of nozzles, the most favorable results were achieved for a two-level staggered arrangement with wide spacings between nozzles and a doubled flow ratio in the upper level. Stronger upper-level jets penetrated deeper into the central region, whereas weaker lower-level jets covered the near-wall region. This enhanced mixing with hot gas from the burner zone resulted in a uniform flow and temperature distributions in the upper furnace. In addition to the reduction of NOx emission, a detailed analysis of the results revealed various benefits of an ideal OFA design that have not been identified in existing studies, including i) reduced ash deposition potential in the tube bundles because of the lower FEGT, ii) reduced attemperating water spray requirement for steam because of the increased heat absorption in the evaporator, and iii) alleviated tube metal overheating because of a lower peak heat flux in the platen superheater. The proposed OFA design can be applied to other large-scale wall-firing boilers.

Numerical analysis of coal size influencing the performance and slag flow characteristics of gasifier based on a comprehensive model

A comprehensive char gasification model based on random pore model with correction factor η is established to depict the char conversion process for entrained-flow gasification. The new comprehensive model uses advanced correlations for char gasification process parameters, including the correlations of a simplified multicomponent molecular diffusion, the evolution of particle size and density, char specific surface area and char thermal deactivation. A one-dimensional slag flow model coupled with the particle capture model is used to describe the deposition, flow and heat transfer process of the molten slag on the wall of HNCERI (Huaneng Clean Energy Research Institute) gasifier. The species mole fractions, carbon conversion efficiency, outlet temperature and the wall heat loss of the gasifier under the baseline are compared with the operating data. The simulation results indicate that the comprehensive model has sufficient accuracy to model the multiphase reactions and slag flow characteristics of HNCERI gasifier. The effect of coal size on exit gas temperature, detailed char heterogeneous reactions, gasification performance and slag flow characteristics of the gasifier are studied. Results show that, as coal size increases from 10 μm to 320 μm, the volume average rate of C + CO2 drops from 0.0095 to 0.0035 kmol/m3·s and C + H2O increases from 0.0064 to 0.012 kmol/m3·s at the first stage, and the carbon conversion efficiency at the first stage decreases from 99.72 % to 93.42 % while that at the second stage increases from 65 % to 93 %. The increase of coal size with values<80 μm has none significant influence on the formation of slag in the gasifier. With coal size further increasing, the formation of slag is highly promoted and thereby results in a rapid increasing thickness of the solid and liquid slag at the slag tap hole. An optimum coal size might be<80 μm for the first stage while an appropriate increase of coal size at the second stage is beneficial to improve carbon conversion efficiency.

Parameterization of a Rising Smoke Plume for a Large Moving Ship Based on CFD

The plume rising height of a ship will directly affect the maximum ground concentration and distance from the source caused by flue gas emission. Ship movement has an important effect on plume rising, but it is often ignored in previous studies. We simulated the weakening effect caused by ship movement by considering the influence of four main parameters (wind speed, ship speed, flue gas exit velocity, and flue gas exit temperature) on the smoke plume rising height, using the computational fluid dynamics (CFD) model (PHOENICS version 6.0 CHAM, London, UK). The main parameters affecting the difference in plume rising height between stationary and moving sources for the same parameter settings are the wind speed and the ship speed. Therefore, we established two simplified calculation methods that corrected the flue gas exit velocity (Vexit′) and the flue gas exit temperature (T′) for approximately simulating the smoke plume rising height of the moving ship using the formula of a stationary ship. Verification cases indicated that the corrected Vexit′ (the average of relative error is 5.48%) and the corrected T′(the average of relative error is 60.07%) not only saved calculation time but also improved the simulation accuracy compared with the uncorrected stationary source scheme (the average of relative error is 135.38%). Of these correction methods, the scheme with corrected Vexit′ is more effective. The intention is to provide some references for the field experimentation of moving ship plume rising in different ports in the future and to further study the mechanism of moving ship plume rising.

Influence of a double vortex chamber on temperature reduction in a counter-flow vortex tube

This article reports the effect of double vortex-chambers with multiple inlet snail entries of N = 1, 4 and 6 nozzles on the energy separation referred to cold gas exit temperature difference (ΔTc) in a counter-flow vortex tube type. The experimental work focused on ascertaining the effects of entry air pressure (Pi = 2, 3 and 4 bar), distance ratios between the two vortex-chamber to the vortex tube diameter (l/D = 0.875–1.125) and the cold gas mass ratio (μc) in a vortex tube. It was found that cold gas exit temperature difference (ΔTc) increased with increasing inlet air pressure (Pi) and number of inlet nozzles (N), and decreasing l/D. Among the studied conditions, the double vortex-chamber operated at the highest Pi of 4 bar, N = 6, the smallest l/D = 0.875 and μc = 0.38 gave the highest cold gas exit temperature difference (ΔTc) of 31.5 °C. In addition, the deep learning optimization technique was also developed to predict the temperatures for different combination of parameters used in this study. It was found that the optimal models provide maximum R2 value of 0.99317.

Neuro-genetic approach for optimization of the water flowrates distribution on a hydrogen sulphide cooling system

Efficient utilities usage and enhanced heat transfer are imperative in todays’ industrial and technological processes. However, there are several facilities in the nickel industry not upgraded yet. This research studied a hydrogen sulphide production plant with limited heat exchange capacity. Within this context, a neuro-genetic procedure was proposed for optimization of the water flowrates distribution on a hydrogen sulphide gas coolers system. It relied on Genetic Algorithms, combined with an improved ɛ-NTU model for simulation of jacketed shell-and-tube heat exchangers. Artificial Neural Networks were furtherly applied to correlate the optimum water flowrates to predictive variables. The heat transfer incremental was estimated from 3695 to 10514 W, while reduction of the gas exit temperature was projected between 2.9 and 9.8 K. Calculated heat recovery averaged 12.44 %. The optimized water distribution scheme have improved the system energy performance. Applied concept of fixed network and unvaried overall feed water flowrate avoided the additional costs related to topology modifications. A technological solution was provided, consisting on installation of automatic valves and programmable flow control-loops linked to a PLC.