Flue Gas Waste Heat Research Articles

Structural optimization of S-CO2 Brayton cycle compressor impeller based on evolutionary algorithm

As the critical components for marine low-speed diesel engine flue gas waste heat recovery (WHR) supercritical carbon dioxide (S-CO2) Brayton cycle system, the structure of the compressor impeller is optimized by the evolutionary algorithm (EA) based on the co-simulation of the CAESES, ANSYS CFX and Opti Slang. The law of impeller pressure ratio, efficiency and power consumption in S-CO2 Brayton cycle (SCBC) as a function of rotational speed, inlet temperature, pressure and impeller structural parameters are revealed, and the method of improving SCBC efficiency for marine low-speed diesel engine flue gas waste heat recovery is studied. The optimized impeller structure is greatly enhanced in aerodynamic performance and safety, and the isentropic efficiency is increased by 2.54%, the pressure ratio is increased by 35.64%, and the temperature rise is increased by only 4.6%. A 100kW S-CO2 compression cycle test bench was set up to verify the simulation-optimized impeller results. The final results show that the optimized impeller structure, aerodynamic performance and safety are greatly improved. It provides theoretical support for selecting and optimising compressor impellers for marine low-speed diesel engine flue gas waste heat recovery S-CO2 Brayton cycle.

Hundred-Watt Implantable TEG Module for Large-Scale Exhaust Gas Waste Heat Recovery

In this study, we have designed and developed an implantable thermoelectric generator (TEG) module tailored for large-scale flue gas waste heat recovery. We also have established a test stand to simulate diverse operational conditions, and systematically examined the influence of different operating conditions, including flue gas temperature, flue gas velocity, and cooling water temperature, on the electrical performance of the TEG module. When the flue gas temperature is 139 °C, the flue gas flow rate is 3.4 m/s, and the cooling water temperature is 20 °C, the TEG module operates at its peak performance. It achieves an open-circuit voltage of 856.3 V and an output power of 150.58 W. Furthermore, the TEG module demonstrates a notable power generation capacity of 3.86 kW/m3 and a waste heat recovery capacity of 135.85 kW/m3. The results prove the TEG module as an effective solution for large-scale flue gas waste heat recovery in industrial settings, contributing to sustainable energy practices. This study supports the application of thermoelectric power generation in the industrial sector, offering significant potential for advancements in energy efficiency.

Poly-generation system with waste heat of low-temperature flue gas in power plants based on organic Rankine cycle

Besides fossil energy and water resources, waste heat resources have attracted more and more attention because of their wide distribution and large quantity. This paper studies a system using low-grade waste heat emitted in a coal-fired power plants as the heat source, which coupled with low-temperature organic Rankine cycle (ORC), humidification and dehumidification and desalting system (HDH) and desiccanting cooling system (DCS) with different heat recovery system strategies, aiming at using low-temperature waste heat for power generation, desalting saline wastewater/sea water and providing space cooling for residential systems. The influences of control parameters on system productivity and system performance index were studied. In addition, the effects of different ORC working media on optimal system performance were also studied and discussed. Condenser exergy loss decreased by about 33% compared to an independent ORC system. In the range of control parameters studied, the total gain output of the poly-generation system was increased by about 47% compared to that of the independent system. The system is more productive when using n-Octane and Toluene, and has the highest system performance indicators when using R245fa and R113.

Design on a novel waste heat recovery system integrated with the bypass flue and outside primary air preheater for bitumite-fired power plants

Bitumite is widely used in coal-fired power plants. However, due to its high volatile content, the temperature of primary air to coal mills is limited to a lower value because of its high risk of spontaneous combustion. The method to reduce primary air temperature by mixing with cold air leads to irreversible loss and reduces the power generation efficiency of the power plant. To address the issue, a novel flue gas waste heat recovery system integrated with the bypass flue and outside primary air preheater for bitumite-fired power plants was suggested. The thermo- and techno-economic analysis models of the waste heat recovery system were developed, and the design parameters were optimized to maximize profit. The thermo-economic analysis shows that the exergy efficiency of the waste heat recovery system can reach 49.8 %, and the coal consumption rate can be reduced by 4.75 g (kW h)−1 by integrating the optimal waste heat recovery system. The techno-economic analysis shows that the net present value of the power plant during ten years can reach 10.6 M$, and the discounted payback period is 0.6 years. The novel waste heat recovery system can effectively improve the thermo- and techno-economic performance of bitumite-fired power plants.

Performance analysis of ocean thermal energy conversion system integrated with waste heat recovery from offshore oil and gas platform

To improve ocean thermal energy conversion (OTEC) system efficiency, four systems utilizing the waste heat recovery from offshore oil and gas platform are proposed, including flue gas boosting OTEC (system I), production water boosting surface seawater OTEC (system II), production water boosting working medium OTEC (system III), and production water boosting vapor OTEC (system IV). The system thermodynamic performance are investigated. The results show that system IV has larger power generation (Wnet), thermal efficiency (ηth) and exergy efficiency (ηex) than others. Compared with single OTEC system, for system IV, Wnet, ηth and ηex are increased by 1569.13 %, 70.35 % and 138.26 %, respectively. For system IV, with the increase of flue gas waste heat quantity from 2000 to 4000 kW, Wnet, ηth and ηex are increased by 562 %, 390 % and 181 % respectively; with the increase of production water waste heat quantity from 0 to 100 kW, Wnet, ηth and ηex are 12.59 %, 5.73 % and 2.86 % respectively. Wnet rises first and then decreases with the increase of evaporation pressure (Peva) or base fluid concentration (xb), presenting an optimal Peva of 1.5 MPa and xb of 0.82 corresponding to the maximum Wnet; Wnet decreases with the increase of condensation temperature.

Thermodynamic and emission characteristics of a hydrogen-enriched natural gas-fired boiler integrated with external flue gas recirculation and waste heat recovery

Hydrogen-enriched natural gas (HENG) is a low-carbon fuel and its utilization in combustion devices has been under extensive discussion recently as it is a promising way to reduce the CO2 emission during combustion. The applicability of HENG in the existing natural gas-fired combustion equipment in terms of its efficiency and emissions attracts increasing attention, especially for industrial and domestic small-scale boilers. In this study, the thermal efficiency and pollutant emissions of a 4.2 MWth HENG-fired boiler integrated with external flue gas recirculation (FGR) were respectively evaluated based on the thermodynamic and heat transfer models and the Chemical Reaction Network model. Results suggested that NOx emission rose by ∼19% as the hydrogen volumetric fraction in the fuel increased from 0 to 0.4 at a constant excess air ratio and FGR rate. To suppress the NOx rise, the FGR rate was tuned higher while the system thermal efficiency decreased subsequently. To further improve the overall system thermal efficiency, a cascade flue gas waste heat recovery strategy including sensible heat recovery using an external economizer and latent heat recovery using dual-spray heat exchangers was proposed. The thermodynamic analysis demonstrated that the external economizer improved the overall system thermal efficiency by 0.4% - 0.7% and the dual-spray heat exchangers promoted the overall system thermal efficiency by over 5%. Thus, a comprehensive performance optimization strategy was developed for HENG-fired boilers in terms of their overall system thermal efficiency promotion, NOx emission control, and CO2 emission reduction.

Waste Heat Recovery: An Energy-Efficient and Sustainability Approach in Industry

Waste heat recovery (WHR) is a method that improves energy efficiency and sustainability in industries like distillation, gas systems, and power generation. It captures and reuses waste heat from condensers and reboilers, reducing the need for external heating or cooling. Flue gas waste heat recovery (FGWHR) also holds potential for energy conservation. Technologies like Organic Rankine Cycle (ORC) and Kalina Cycle (KC) convert low-grade waste into electricity, enhancing overall efficiency. Combined Heat & Power Systems (CHP) achieve efficiency above 80%. However, feasibility studies are crucial before applying WHR technologies in practical applications.

Study on the performance of oil fume heat recovery heat exchanger based on micro heat pipe array

In China, the utilization of high-temperature flue gas waste heat recovery has been widely studied and developed, while the large number of low-temperature flue gas waste heat recovery has not been fully developed. Therefore, research has been conducted on the heat transfer characteristics of plate heat exchangers for low-temperature oil fume. The heat exchanger were 28–44 ℃ at the hot end and − 10 to 5 ℃ at the cold end. The outlet temperature, wind speed, etcetera were measured and recorded by changing indoor and outdoor temperature, variable flow rate and variable fin size. The impact of different working conditions on heat transfer and heat transfer efficiency of the heat exchanger was analyzed. The result showed that within the range of effective experimental test temperature, the variation trend of Nu and h was the same for heat exchangers with different finned fins and heat pipes with a different liquid-filled working medium The Nu value increased linearly with the increase of the Reynolds coefficient (Re), and the heat transfer coefficient presented a quadratic curve and increased with the increase of Re. Smaller fins had a higher efficiency and higher heat transfer. The heat exchange efficiency was stable between 0.75 and 0.97, which was higher than the value required by the national standard. At the same time, the heat exchanger also met the demand for high-efficiency heat recovery at low outdoor temperature, which has a wide application prospect.

Removal of multiple pollutants in air pollution control devices of a coal-fired boiler installed with a flue gas condensation scrubber

This work was conducted through field tests on a coal-fired circulating fluidized bed boiler with a condensation scrubber (CS) for flue gas waste heat recovery installed behind the wet flue gas desulfurization (WFGD) scrubber. Levels of multiple pollutants were investigated along various flue gas devices of the boiler, with the CS being the main focus. The CS demonstrated an excellent effect in removing filterable particulate matter (FPM), reducing it from 10.63–14.00 mg/Nm3 to less than 1 mg/Nm3, providing an alternative solution for ultra-low emission. The CS had the ability to remove SO2, reducing it from 211.8–272.0 mg/Nm3 to 11.1–13.0 mg/Nm3, which could be an aid to the WFGD scrubber. The CS showed an effect on SO3 removal, reducing it from 17.49–17.53 mg/Nm3 to 1.07–1.13 mg/Nm3, which might address the discharge of sulphate aerosols. The CS exhibited an effect in removing condensable particulate matter (CPM), reducing it from 29.68–38.48 mg/Nm3 to 12.18–22.80 mg/Nm3, providing a potential solution for CPM emission control. In addition, the escape of fine desulfurization slurry droplets from the WFGD scrubber could also be mitigated by the CS with the reduction efficiency of 88.30–90.51%. Overall, the synergistic removal of multiple pollutants including FPM, SO2, SO3, and CPM by the CS was verified in this case study. Considering its original function of waste heat recovery, the adoption of the CS is a promising measure for energy conservation and environmental protection.

Thermodynamic and thermo-economic analysis, performance comparison and parameter optimization of basic and regenerative organic Rankine cycles for waste heat recovery

In order to recycle the sinter waste heat efficiently, the possibility of taking the low temperature flue gas emitted from sinter waste heat boiler as heat source of organic Rankine cycle for power generation is investigated in the current study. The thermodynamic and thermo-economic models of basic organic Rankine cycle (BORC) and regenerative organic Rankine cycle (RORC) were constructed, and R236ea, R245fa and R601a were selected as the working fluids of BORC and RORC. Subsequently, the parametric effects on the thermodynamic and thermo-economic performances under various working fluids for BORC and RORC were analyzed and compared, and then the suitable thermal parameters of BORC and RORC were established through the multi-objective optimization. The results show that, the thermal efficiency of RORC is apparently greater than that of BORC for the given thermal parameters, while the levelized energy cost of RORC is a little bigger than that of BORC. The net output power of R236ea is the largest in the whole optimal conditions, and the flue gas waste heat recovery rate of R236ea for BORC is also the largest at a respectable 65.07 %, while the levelized energy cost of R601a is the smallest for BORC and RORC, showing better thermo-economic performance.

Exergy, energy, economy analysis and multi-objective optimization of a comprehensive energy utilization system for LNG-powered ships based on zero-carbon emissions

To realize efficient utilization of energy in LNG-powered ships and zero-carbon emissions, a comprehensive energy utilization system based on zero-carbon emissions for LNG-powered ships is proposed in this study coupling the full utilization of LNG cold energy and flue gas waste heat with the carbon capture technology of oxygen-enriched combustion with the LNG dual-fuel-powered bulk carrier as the object as well. By system modeling, the system is analyzed using the thermoeconomic method and the operating parameters are studied. The results demonstrate the selection of the working fluid combinations and the settings of the operating parameters of equipment affect the system's thermodynamic and economic performance. Based on the parameters analysis, a multi-objective genetic algorithm is adopted for optimization. The optimization results indicate that 51.71 % exergy efficiency and 511 kW net output power are achieved under the zero-carbon emissions condition, while the initial investment cost and cost of power generation are 6.33·106$ and 0.0869$/kWh, which indicate the system is of excellent environmental and economic benefits.

Research on Thermodynamic Characteristics of the Saturated Flue Gas Waste Heat Recovery to Reduce Turbine Extraction Steam

Research on Thermodynamic Characteristics of the Saturated Flue Gas Waste Heat Recovery to Reduce Turbine Extraction Steam

Hydrogen-rich carbon recycling complex system establishment and comprehensive evaluation

Hydrogen-rich carbon recycling complex system coupling CO2 reduction with waste heat conversion efficiently is becoming a vigorous horizon stepping forward carbon peak and carbon neutrality with great strides in metallurgical industrial sectors. This article originally proposes an in-situ waste plastics gasification complex system utilizing blast furnace flue gas waste heat for hydrogen-rich preparation and CO2 reduction simultaneously, and the effect of parameters such as temperature, pressure, etc. on syngas yield, CO2 conversion rate, etc. are systemically discussed in detail, furthermore, the techno-economic analysis and priorities of this complex system are obtained through originally comparing intensifying factor and substitution coke ratio. The results show that waste plastics conversion rate, hydrogen and syngas yield have a positive relationship with temperature, but opposite with pressure. Hydrogen preparation is intensifying when water vapor is feeding into, and CO yield is augmented when flue gas is injected. The maximum H2 plus CO preparation efficiency is 61.3–77.4% and H2 yield is 95.9–135.5%,when pressure, temperature, H2O/P ratio and CO2/P ratio should be controlled in 1 bar, 800–1000 °C, 1.5–3.0 and 0.1–0.5, respectively, meanwhile, CO2 conversion rate is 28.4%.Otherwise, this complex system has a maximum CO2 reduction efficiency 73.6–99.0%, when 1 bar, 800–1000 °C, 0.1–0.2, 0.1–3.0 are adopted. Under the optimum conditions above, CO2 reduction efficiency is 171.1 kg/t for an ironmaking sector with capacity 54,000 tons, hydrogen preparation efficiency is 15.6 kg/t at 800 °C, corresponding coke ratio substitution amount is 460.0 kg/t. Besides, the maximum H2 preparation intensifying factor is 8.3% at 1000 °C and the maximum CO2 emission reduction intensity factor is 91.0%, which increases by 49.6–71.3% comparing to predecessors. Through this researches above, hydrogen-rich carbon recycling complex system has unique advantages for CO2 deep reduction and coke ratio decrease, and has a significant contribution suppling with a new horizon and methodology for low-carbon metallurgical process development in the future.

Effect of hydrogen-enriched natural gas on flue gas waste heat recovery potential and condensing heat exchanger performance

Hydrogen-enriched natural gas (HENG) is one of the significant ways to store, transport, and utilize hydrogen energy. This paper presents the characteristics of HENG and flue gas, energy saving, carbon reduction, and condensate recovery potential of flue gas waste heat. Based on the theoretical and experimental study of the existing flue gas condensing heat exchanger (FGCHE) added at the rail of gas-fired boiler, the performance of the FGCHE under different hydrogen blending ratios is studied. The results show that augmenting the hydrogen blending ratio decreases the volume heating value of HENG, and CO2 content of flue gas. Meanwhile, the mass heating value of the HENG, the water vapor content, and dew point temperature of flue gas increase as the hydrogen blending ratio increases. The flue gas waste heat recovery utilization ratio and energy-saving efficiency of the FGCHE can be promoted. Moreover, the heat transfer capacity of the FGCHE using HENG is enhanced, while the flue gas flow pressure drop is reduced. Compared with the FGCHE used in pure natural gas systems, the all-hydrogen system increases the flue gas waste heat recovery amount by 62.4–120.4 %, reduces the flue gas flow pressure drop by 33.9 %, and reduces the carbon emission by 100 %.

Study on hydro-thermal coupling heat transfer performance of flue gas-water heat exchanger

The finned tube heat exchanger is the core component of the flue gas waste heat utilization system. In order to optimize and control the heat transfer efficiency of the heat exchanger in real time under smart heating conditions, we use the entransy dissipation thermal resistance as a kernel index to assess its heat exchange performance, and Trnsys simulation software is employed to figure out the influence of heat exchanger operating parameters (flue gas inlet velocity) and fin structure parameters (fin height, fin pitch) on heat exchanger heat transfer characteristics. The results show that in a reasonable range, increasing the flue gas inlet velocity can decrease the irreversible loss of heat transfer, obviously improving the heat transfer effect. The pitch and height of the fin also have a large impact on the performance of heat transfer. To significantly promote the performance of the heat exchanger, it is useful to reduce the pitch of the fin and increase the fin height within a reasonable range.

The Combination of Simulation and Heat Pump Technology for the Treatment and Reconstruction of “Wet Plume” in fossil-fuel power station

The saturated wet flue gas discharged from the power plant chimney after wet desulfurization often forms a thick “white plume” at the chimney’s mouth. This “wet plume” phenomenon has a very bad impact on the lives of local people, and it will also cause corrosion damage to surrounding equipment while polluting the environment. This paper simulates the “wet plume” phenomenon caused by flue gas emissions under different flue gas parameters and environmental parameters by using the CFD simulation method and the new technology of “smoke tower integration” of power plant emissions. Through the simulation data, the “wet plume” pollution change is studied, which provides a reliable theoretical basis for the design of new power plants and the reconstruction of old power plants. At the same time, through the simulation data, the combination of flue gas indirect condensation technology and heat pump technology is selected to realize the recovery and reuse of flue gas waste heat and realize the dual embodiment of social value and practical value.

Design and Characterization of Flue Gas Waste Heat Power Generation Plant

This paper proposes a waste heat recovery system based on temperature difference power generation, which aims to utilize the residual heat in the exhaust flue of chimneys or kilns. The system consists of three parts such as heat collection module, semiconductor power generator, and heat dissipation module, and the residual heat is directly converted into electrical energy and output by temperature difference power generation. The voltage and resistance are measured and analyzed on this basis. This design realizes the waste heat recovery of boiler flue gas, prevents a large amount of waste heat from being discharged into the environment, reduces the greenhouse effect and makes secondary use of the waste heat.

Characteristics of the S-CO2 Brayton cycle for full-scale multi-condition diesel engines

With the diesel engine test data of the flue gas as the initial conditions and the boundaries, the arrangement of the S-CO2 recompression Brayton cycle (SCRBC) was established and the optimization of the S-CO2 Brayton cycle (SCBC) system for 6EX340EF, 6L16/24, and CHD622V20 diesel engine were studied. Additionally, the model accuracy was validated with the test data from Sandia National Laboratories (SNL). Meanwhile, the parameter optimization determined the optimal system operating conditions via a multi-objective genetic algorithm (MOGA). Finally, the feasibility of the SCBC applied in flue gas waste heat recovery (WHR) for marine engines was comprehensively assessed from the efficiency, net output power, fuel consumption rate, and exergy. The results showed that with the recompression Brayton cycle layout in the optimal configuration, the low-speed marine diesel engine could reach 1.68% of the maximum total efficiency improvement and 6.43 g/kWh of the fuel consumption rate reduction at 100% load, the maximum net output power increased to 178.14 kW; the medium-speed marine diesel engine could reach 2.37% of the maximum total efficiency improvement and 11.60 g/kWh of the fuel consumption rate reduction at 100% load, the maximum net output power increased to 31.69 kW; the high-speed marine diesel engine could reach 1.00% of the maximum total efficiency improvement and 5.58 g/kWh of the fuel consumption rate reduction at 25% load, the maximum net output power increased to 21.54 kW. By comparing the SCRBC of the marine diesel engine, the high-speed engine has the highest efficiency of flue gas WHR, followed by the medium-speed engine and finally, the low-speed engine. The cooler, flue gas heat exchanger, and high-temperature recuperator (HTR) modules were the weak points of the SCRBC system through the exergy analysis, and further optimization of the SCRBC system can be extended to other engines to improve efficiency and emission.

Comparative analysis of two cogeneration systems with different connection modes

This study explores the differences between two novel cogeneration systems with different connection modes. These two systems are the series and parallel systems composed of the Brayton cycle, the organic flash cycle, and the organic Rankine cycle, respectively, which both recover flue gas waste heat and LNG cold energy. First, the equipment and overall system performance of the series system and the parallel system are compared from three aspects of thermodynamics, economy, and exergoenvironment to evaluate the basic performance of the two systems under initial conditions. Next, the performance variations of both systems are assessed by varying the compressor outlet pressure, flash pressure, R14 mass flow rate, and heat source temperature. Finally, the Multi-Objective Cuckoo Search algorithm is used to optimize the systems for two and three objectives, taking the exergy efficiency, payback period and product unit exergoenvironmental impact as objective functions. The final results indicate that the three-objective optimized parallel system has the best performance, the exergy efficiency, payback period, and product unit exergoenvironmental impact of that is 62.25%, 1.389 years, and 7.799 × 10−3 mpt/kJ, respectively. By comparing the performance differences between the series system and the parallel system, this study provides application ideas for engineering requirements.

Experimental research on the effect of acid and ash deposition on heat transfer characteristics of PTFE-coated 3-D finned tube

With characteristics of strong flow disturbance and high heat transfer coefficient, 3-D finned tubes have significant advantages in recovering flue gas waste heat. However, fly ash particles and sulfuric acid vapor in power plant flue gases can foul and corrode 3-D finned tubes when deposited on their wall surfaces, resulting in a reduction in the efficiency of the heat exchanger. To protect the heat exchanger from corrosion, corrosion resistance coatings are the most economical solution. However, acid and ash deposition and their effects on heat transfer performance of the 3-D finned tube coated with corrosion resistance coating have not been clear. In this work, firstly, uncoated, ceramic-coated, Teflon lacquer-coated and PTFE-coated 3-D finned tubes were immersed in sulfuric acid solution and the PTFE coating with better corrosion resistance was screened by corrosion weight loss method and SEM characterization. Then, the heat transfer performance of PTFE-coated 3-D finned tubes under acid-ash coupling conditions was investigated using the simulated flue gas method. Impacts of fin structure parameters (fin height, fin width and axial fin spacing) and experimental working conditions (cooling water inlet temperature, fly ash concentration and sulfuric acid volume fraction) on Nu number were investigated. Results demonstrate that PTFE-coated 3-D finned tube have a lower Nu at the initial moment than uncoated tubes. That is because PTFE coating increases the thermal resistance. However, as the experiment progressed to a steady state, Nu were higher and ash deposition weight was smaller in the PTFE-coated 3-D finned tube. In addition, the effects of fin structural parameters and experimental conditions on heat transfer characteristics of PTFE-coated 3-D finned tube were investigated. In the acid-ash coupled condition, the Nu value increases with an increase of fin height or a decrease of fin width and axial fin spacing. Also, decreasing the cooling water inlet temperature, the fly ash concentration, or the sulfuric acid vapor volume fraction increases the Nu value.