Flue Gas Flow Research Articles

Improved ANN-Based Approach Using Relative Impact for the Prediction of Thermal Coal Elemental Composition Using Proximate Analysis.

The basic properties of coal influence various procedures of power generation, such as the design of power generation plants, estimation of the current condition of boilers, and total efficiency of power plants. The elemental composition is a needed factor in evaluating the process of chemical conversion and predicting the flow of flue gas and the quality of air in coal combustion. In the past, several relationships have been established using ultimate and proximate analyses. This study aims to predict the elemental compositions of 104 thermal coals used for coal-fired power plants in South Korea using an artificial neural network (ANN) that uses proximate analysis values as input parameters. The ANN-based model was optimized with six activation functions and four hidden layers after evaluating various performance indices, including R2, mean square error (MSE), and epoch, then additional calculations were derived to compare performances from previous research using the mean absolute error (MAE), average absolute error, and average bias error. It was found that the best topology was established using the Levenberg–Marquardt activation function and 10 hidden layers, resulting in the highest R2 value and smallest MSE of all topologies tested. As a result, the relative impact on calculation accuracy was derived from ANN hidden layers to analyze prediction accuracies of carbon, hydrogen, and oxygen compositions. Accuracy was improved over previous results by 4.71–0.91% via coal rank division topology optimization. Based on the MAE, the current results are even close in performance to those of adaptive neuro-fuzzy inference systems. They also outperformed previous research models by 5.40 and 7.39% in terms of MAE accuracy. Applicability of the ANN was also analyzed with limitations of the chemical composition of ANNs and present reinforcement measures in the future studies through qualitative analysis comparisons based on Fourier transform infrared spectroscopy. Consequently, the relative effect was derived from the ANN hidden layer weight for specific calculation of the relationship between elemental composition and proximate analysis properties. As a result, it was possible to qualitatively analyze how the proximate analysis value affects the composition of elements and calculate the ratio accordingly. The findings of this study provide an improved and efficient approach to predicting the elemental composition of thermal coal, based on data from South Korean power plants. Also, further research can follow schematics from this study with the applicability and accessibility of the ANN.

A high-efficiency and eco-friendly design for coal-fired power plants: Combined waste heat recovery and electron beam irradiation

To ensure the sustainable development of the economy and society, energy-saving and emission reduction is an inevitable choice to solve resource scarcity and control environmental pollution, while coal-fired power plants are an important industry to implement this strategy. A novel design combining organic Rankine cycle with electron beam flue gas treatment is proposed to reduce pollutant emissions and recover flue gas waste heat of 600 MW power plant. The flue gas flows through the organic Rankine cycle to recover waste heat, then enters the electron beam irradiation device for desulfurization-denitrification, and eventually generates by-products of ammonium sulfate and ammonium nitrate that could be applied in agriculture. The particle swarm optimization algorithm is employed to improve the thermodynamic, economic and environmental performance, then the most suitable scheme is selected by combining TOPSIS and the entropy weight method. The optimization results indicate that the integrated system could produce equivalent electric quantity of 22.58 MW, and the payback period is 4.91 years. Meanwhile, ammonium sulfate and nitrate with production of 3544 kg/h and 6165 kg/h are obtained. Compared with the referenced power plant, the thermal efficiency of the improved scheme increases by 1.26% and the standard coal consumption rate decreases by 2.72%.

Aerodynamic influences on the outer ash deposition rates during oxy-coal combustion

Second generation oxy-combustion and load following operations are accompanied by a significant (60–70%) reduction in combustor flue gas flow rates when compared to baseload operation. Understanding the aerodynamic influences on the fly-ash particle deposition characteristics during these novel operational scenarios are critical towards anticipating operational challenges. To fill this void, a novel Computational Fluid Dynamic (CFD) methodology in conjunction with an ash deposition module was used to model the outer ash deposition process coal during combustion of coal in AIR and O2/CO2 (70/30 vol%, OXY70) oxidizer compositions and the predictions were compared with measurements. The measured fly-ash particle size distributions (PSD) were employed as inputs to represent the particle Stokes numbers near the deposition surface accurately and the capture criterion was based on a recently proposed particle viscosity and kinetic energy (PKE) based formulation. Prediction sensitivities to the particle viscosity model and fly-ash PSD were also assessed. Deposition rate predictions in AIR were in excellent agreement with the measurements. The deposition rate enhancement (OXY70/AIR) across all scenarios were in the range 2.8–3.3 which was in reasonable agreement with the measured values of 2.1–2.4. Predicted capture efficiencies were nearly 100% across all scenarios. The calculations were repeated by employing the corresponding fly-ash composition information rather than the bulk-ash compositions and did not alter the predictions significantly. The study therefore supports the hypothesis that ash deposition rates in these novel operational scenarios are likely to be dominated by PKE.

The modeling of transient phase changes of water droplets in flue gas flow in the range of temperatures characteristic of condensing economizer technologies

Heat transfer and phase change processes of water droplets in humid air flow were investigated by performing experiments and numerical simulations of heat recovery from biofuel exhaust gas at 40–250 °C, which is characteristic for condensing heat exchangers. Compared to the experiments, the numerical investigation was performed within a wider range of boundary conditions considering droplet dispersity and flue gas parameters. The reliability of the simulation was justified through the coincidence between the calculated temperature of the equilibrium evaporation of droplets (convection heat transfer) in humid air and the wet-bulb thermometer temperature. In case of droplet combined heating (radiation and convection), the methodology was justified by coincidence between the calculated equilibrium evaporation velocity and experimental results obtained by other authors. When the temperature of radiation source is lower than 150 °C, the vapor flows calculated at the surface of the droplets in equilibrium evaporation in the cases of combined heating and convective heat transfer differs about 0.1%, therefore, the radiation influence can be neglected. Based on the results obtained in the investigation of the droplet's phase changes, the work includes practical recommendations for technological water injection to ensure optimal heat recovery from wet exhaust gas in condensing economizers.

Fog Droplet Collection by Corona Discharge in a Needle–Cylinder Electrostatic Precipitator with a Water Cooling System

In this study, a needle–cylinder electrostatic precipitator with a water cooling system was designed to enhance the harvest of atmospheric water in wet flue gas. The effects of flow rate, temperature and particles on the collection of fog droplets were investigated. Meanwhile, the energy efficiency of water collection was analyzed at different voltages. The results show that the current decreases with the increase of air relative humidity under the same voltage, and the breakdown voltage increases obviously. Concurrently, by appropriately reducing the wet flue gas flow velocity, the residence time of fog droplets in the electric field can be increased, fully charging the droplets and improving the water collection efficiency. Moreover, experiments revealed that through decreasing the flue gas temperature, both the water collection rate and energy efficiency can be improved. In addition, the presence of particles in wet gas can improve the water collection rate by 5~8% at different discharge voltages. Finally, based on energy efficiency analysis, with the increase of voltage, although the water collection rate increased, the energy efficiency decreased.

Effects of rings on flow and temperature in lime kilns

A steady state, two-dimensional (2D) axisymmetric model has been developed to help understand how rings form and grow in a typical lime kiln. Rings of varying length, thickness, and geometry at the front and back faces were modeled to study the effects on flue gas flow and temperature. The results show that ring growth causes the gas velocity to increase and insulates the adjacent refractory, resulting in a lower kiln shell temperature. The results also reveal the formation of recirculation zones immediately downstream of the rings, as well as temperature deviations upstream and downstream of the rings that might promote recarbonation and further ring growth. The model was applied to a kiln from a kraft mill with front-end and mid-kiln rings and good agreement was obtained between the measured and predicted kiln shell temperatures, providing confidence in the modeling.

Experimental investigations of water droplet transient phase changes in flue gas flow in the range of temperatures characteristic of condensing economizer technologies

The heating and phase changes of water droplets in 140 °C air flow humidified up to water vapor volumetric fraction of 0.3 were investigated experimentally in the context of heat recovery from flue gases with condensing economizers. The experiments were performed in experimental set-up, where atmospheric air of certain temperature and humidity passed over a water droplet suspended on thermocouple ball. It was demonstrated that initial temperature of droplet and humidity of gas flow are defining factors in transitional phase changes. However, initial droplet temperature had no effect on the equilibrium evaporation regime. The experiments performed confirmed that humidification of atmospheric air flow causes changes in magnitude of heating and phase change process of water droplets suspended in the air flow. These changes translate into increased temperature of equilibrium evaporation of the droplet, formation of favorable conditions for the condensation regime, and a change in dynamics of the droplet's geometrical parameters in initial stage of phase changes. In additionally humidified air flow, the droplet volume increased by three percent, and evaporation temperature of the droplet increased by 17 °C. Practical recommendations for water injection were produced to ensure optimal heat recovery from wet exhaust gases in a condensing economizer.

Novel Tube Design for Superheater Heat Exchanger Enabled Via Additive Manufacturing

Abstract Superheater tubes are critical boiler components that operate at relatively higher temperatures and pressure. Amongst the primary concerns for these tubes is the deposition of ash particles on the tube surface, leading to the reduced thickness of the tube due to material corrosion, consequently causing early creep failure of the component. In this research, a novel tube design has been proposed which resembles a teardrop or ogive shape to reduce the drag and concurrently improve the creep life of the superheater tubes. To administer the practicality of novel tubes, metal additive manufacturing (AM), for instance, laser-powder bed fusion (L-PBF), has been proposed. These unconventional designs were assessed and compared with the baseline circular tube design for mechanical design requirements (hoop stress and creep life) and the particle and flue gas flow characteristics around the differently shaped tubes. A thermomechanical finite element (FE) analysis was performed for hoop stress calculations. This study also emphasizes on effect of circumferential thermal variation on hoop stress distribution in tubes. Therefore, a detailed two-dimensional (2D) thermal simulation has been performed to report the circumferential thermal variation on the tube. A computational fluid dynamics (CFD) analysis coupled with particle tracing was performed for gas flow visualization and particle tracing around the proposed shapes and baseline circular-shaped tube design. The Schlieren optic setup was built and leveraged for qualitative validation of the proposed design. The complete design methodology established in the paper shows teardrop-shaped tubes better in terms of drag and creep life in contrast to the circular-shaped tube.

Thermal and aerodynamic parameters radiation chambers of the hydrocarbon pyrolysis furnace

THE PURPOSE. To carry out mathematical modeling of interrelated physicochemical processes in radiation chambers of tubular furnaces of pyrolysis of hydrocarbons. Perform numerical calculations of heat and mass transfer in the furnace furnace chamber with a multi-tiered arrangement of wall burners on the side lined walls.METHODS. Using our own package of applied programs based on the numerical solution of a system of differential equations of energy conservation and equations of radiation gas dynamics, the fields of velocities and temperatures of natural gas combustion products in the radiation chamber of a hydrocarbon pyrolysis tubular furnace are calculated. Interrelated processes of natural gas combustion, radiant-convective heat transfer, and turbulent flow of flue gases take place in the radiation chamber. These processes are modeled by two-dimensional equations of the combustion model, energy transfer by radiation, and equations of motion. In the side walls of the radiation chamber on both sides in eight horizontal tiers there are wall burners in the amount of 128 pieces. Combustion products emerging from the nozzles of these burners create complex velocity and temperature fields in the chamber volume. Due to the radiation of flue gases, the smallest soot particles and hot lined walls of the radiation chamber, heat flows are formed to the tubular screen, where hydrocarbons are pyrolyzed to produce ethylene.RESULTS. As a result of calculations, the velocity fields, the temperature in the volume of the radiation chamber and the concentration of the main components of the combustion products were obtained. Local values of surface densities of radiant heat fluxes to reaction pipes for methane and propane pyrolysis furnaces are calculated. Comparisons of some of the results obtained with the readings of the devices of existing technological installations are carried out.CONCLUSION. Calculations show that the developed software package makes it possible to obtain realistic values of local velocities and temperatures in the radiation chambers of tube furnaces, surface densities of convective and radiant heat fluxes to boundary surfaces, and other thermal and gas-dynamic parameters in the furnace volume. With a multi-row arrangement of a large number of wall burners of low thermal power, a complex field of temperature and velocities of combustion products in the furnace volume is formed on the side walls of the radiation chamber of the furnace. At the same time, this arrangement of the burners ensures a fairly uniform distribution of heat flows over the surface of the tubular screen of the hydrocarbon pyrolysis furnace.

Low grade lignite upgrading using a novel dewatering-binderless briquetting combined process

ABSTRACT The low-grade lignite reserve is large and it is an important basic material for coal gasification and liquefaction. However, it has high moisture content, high ash content, and low calorific value, and its use value is low without upgrading. The calorific value of lignite can be effectively improved by drying and dehydration. Meanwhile, due to the fine particle size of lignite powder, it is not convenient for storage and transportation, but it has certain utilization value. The efficient recovery and rational utilization of this part of the pulverized coal resources through coal powder briquetting increases its utilization value. In this paper, a study on the high-efficiency upgrading of low-grade lignite was carried out by using the combined process of multi-layer cross-flow drying and binderless pulverized coal briquetting. The migration and distribution law of lignite moisture in each drying bed was emphatically analyzed, and the influence of drying temperature and hot flue gas flow rate on drying effect under different treatment capacity was systematically studied. At the same time, the influence of coal powder with different particle size fraction on the briquetting load during the briquetting process and the influence of the −0.125 mm coal powder content on the quality of the briquetting product were analyzed. The drying and coal powder binderless briquetting test were carried out under the optimal parameters. The results show that the material moisture content decreases gradually from top to bottom along the bed height direction, and decreases gradually from the feed end to the discharge end for every layer. The dehydration rate is directly related to the feeding quantity. For the same drying temperature, the less the feeding quantity is, the lower critical point the optimal drying temperature reaches. During the binderless pulverized coal briquetting, as the briquetting load increases, the compressive strength of briquette products for different particle size fraction showed an increasing trend, while the falling strength increase firstly and then decreases. As the −0.125 mm fine coal content increases, the compressive strength increases, while the falling strength increases firstly and then decreases. The average drying temperature of hot flue gas is 200°C; the flow quantity of hot flue gas is 445–455 m3/h; the drying time is 12 minutes; the briquetting load is 120KN; the moisture content added is 12%. Under condition mentioned above, the moisture content of the dry lignite product is 9.75%; the ash content is 26.12%, and the calorific value is 23.47 KJ/g. For the briquetted lump coal, the total moisture content is 10.16%; the ash content is 25.78%; the calorific value is 23.21 KJ/g; the compressive strength is 2.56MPa and the falling strength is 93%.

Novel method for flue gas flow of gas turbines in offshore oil production facilities

The flue gas flow in gas turbines is an important parameter for determining the accurate capacity of waste heat boilers for recovering the waste heat released by the flue gas of gas turbines in offshore oil production facilities. The theory of flue gas composition ratio pertaining to boiler combustion is applied to calculate the flue gas flow in gas turbines. The given gas fuel composition, fuel characteristic coefficient and tested dry combustion products of gas fuel are used to calculate the excess air factor α using the theory of flue gas composition ratio; thus, the flue gas flow of gas turbines can be obtained. The results show that the value of α of a gas turbine ranges from 7 to 3 with different loads and is significantly greater than the α value of boilers, which is obtained during the burning of gas fuel; moreover, the calculation mode of O d 2 while considering β coincides more with the actual operation data of gas turbines. This mode is useful for the engineering application of recovering the waste heat released by the flue gas of gas turbines and provides an important guidance to improve the waste heat recovery process in gas turbines.

Experimental study on waste heat recovery characteristics of inorganic ceramic membrane flue gas

The wet saturated flue gas discharged by coal-fired utility boilers leads to a large amount of low-temperature wasteheat loss. Inorganic ceramic membrane is acid-base resistant and has strong chemical stability. It is an ideal material forrecovering low-temperature waste heat from flue gas. The experiment of waste heat recovery of flue gas was carried outwith inorganic ceramic membrane as the core, and the characteristic parameters of low-temperature flue gas at the tailof the boiler were analyzed; taking 316 L stainless steel as the comparative object, the strengthening effect of inorganicceramic film on improving heat recovery power and composite heat transfer coefficient was discussed. The results showthat the waste heat recovery of flue gas is mainly the evaporation latent heat recovery of water, accounting for about90%; circulating water is used as cooling medium, and the waste heat recovery capacity of flue gas is stronger;compared with circulating water, when air is used as the cooling medium, the effect of inorganic ceramic membraneflue gas waste heat recovery is more significant, and the enhancement coefficient is as high as 9; increasing the flue gasflow is helpful to improve the heat recovery power and composite heat transfer coefficient; at the same time, inorganicceramic membrane can also recover condensate with high water quality. The results of this paper can provide areference for the application of inorganic ceramic membrane in flue gas waste heat recovery.

Intrinsic insight of energy-efficiency optimization for CO2 capture by amine-based solvent: effect of mass transfer and solvent regeneration

Here the energy-efficiency performance of CO2 capture is investigated based on the combination of bench-scale experiments and simulated calculation. A comprehensive evaluation is performed by L25(56) orthogonal tests to analyze the effect of crucial operating conditions on CO2 capture. Experiments reveal desorption temperature and flue gas flow play a major role for CO2 capture efficiency. Rising flue gas flow could promote interfacial area, but decreases contact time, overally, net CO2 flow approximately determines the linear relationship of capture efficiency and absorption rate. With combination of Eulerian-Eulerian method with the population balance model, we predict the dynamics evolution process of dispersed bubble, in order to provide the detailed information of interphase contact area and multiphase flow for modelling complete mass transfer parameters. Meanwhile, rigorous process simulation is developed to analyze the energy consumption of carbon capture. Higher desorption temperature provides much leaner solvent, which is beneficial to CO2 absorption, but consumes greater energy penalty.

DMC-PID cascade control for MEA-based post-combustion CO2 capture process

The capture and recovery of carbon dioxide (CO2), the main source of greenhouse gases, are the principal means to reduce CO2 emissions. The optimization and control of the CO2 capture process plays a vital role in reducing energy costs, with the post-combustion CO2 capture (PCC) device using amine-based solvents considered to be the most feasible strategy to reduce CO2 emissions from coal-fired thermal power plants. In this paper, a DMC-PID cascade strategy is proposed to manipulate the PCC process order to obtain better performance. PID algorithm is used to adjust the flue gas flow to stabilize the flue gas entering absorber, and DMC algorithm is adopted to manipulate and constrain the lean solvent flow optimally order to increase CO2 capture rate. First, the corresponding steady-state model is established in Aspen Plus to get the best operating point parameters. Next, a dynamic model is built in Aspen Plus Dynamics to analyze the dynamic changes between the main variables of the system through dynamic testing, and the transfer function of the system is obtained through experimental data. Finally, three control strategies of DMC-PID, PID-PID and DMC are used to compare the control effect of CO2 capture rate. The results show that the proposed DMC-PID cascade control strategy has better performance, which improves the stability and flexibility of the PCC system, and provides a more feasible and effective operation for the CO2 capture.

An investigation on simultaneous freshwater production and CO2 capture using flue gas of a power plant

AbstractThis paper presents an investigation on simultaneous freshwater production and CO2 capture using the flue gases of a 500 MWe coal‐fired power plant. Generally, a fan/cooler is used to reduce the temperature of flue gas before flowing into the absorber column of a CO2 capture unit. It has been replaced with a heat exchanger in this study. Seawater and flue gas were passed through the heat exchanger to raise the temperature of seawater and reduce the temperature of flue gas. The high‐temperature seawater was subsequently fed into a membrane distillation (MD) unit for freshwater production. The cold flue gas was directed to the CO2 capture unit. The heat exchanger and CO2 capture unit were modeled with Aspen Plus software. Whereas MATLAB software was used to develop and solve the MD mathematical model software for freshwater production. The seawater flow rate was varied from 4000 L/min to 7000 L/min in the heat exchanger. As a result, the flue gas (flow rate 781.6 t/h) and the outlet seawater temperatures were reduced from 27.498 to 22.360°C and 73.384 to 52.670°C, respectively. However, higher inlet seawater temperature in the MD unit produced more freshwater. An increase in inlet seawater feed temperature in the MD unit from 52.670 to 73.384°C increased the freshwater production from 211,956.5 to 299,244 L/day. Furthermore, the CO2 capture process has been analyzed by varying the methyldiethanolamine (MDEA) and piperazine (PZ) concentrations in weight% (45 and 5, 40 and 10, 35 and 15, and 30 and 20, respectively). It was observed that the energy requirement reduced from 3.55 to 3.26 MJ/kg CO2 by increasing the PZ content from 5 to 20 wt.%. At 15 and 20 wt.% of PZ content in the blended solution of MDEA/PZ, the energy required to regenerate the solvent was 3.31 and 3.26 MJ/kg CO2, respectively. PZ emissions from the absorber were also increased with the raising of PZ content in the blended solution. The energy requirement was not much higher at 15 wt.% than 20 wt.%. Therefore, MDEA/PZ solution (15/35 wt.%) was considered an optimal concentration. The reboiler duty was reduced up to 3.25 MJ/kg CO2 at 15/35 wt.% concentration with stripper pressure of 2.3 bar. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.

High-temperature technology survey and comparison among incineration, pyrolysis, and gasification systems for water resource recovery facilities.

Solids from wastewater treatment undergo processing to reduce mass, minimize pathogens, and condition the products for specific end uses. However, costs and contaminant concerns (e.g., per‐ and polyfluoroalkyl substances [PFAS]) challenge traditional landfill and land application practices. Incineration can overcome these issues but has become complicated due to evolving emissions regulations, and it suffers from poor public perception. These circumstances are driving the re‐emergence of pyrolysis and gasification technologies. A survey of suppliers was conducted to document differences with technologies. Both offer advantages over incineration with tailored production of a carbon‐rich solid, currently less stringent air emission requirements, and lower flue gas flows requiring treatment. However, incineration more simply combines drying and thermal processing into one reactor. Equipment costs provided favor pyrolysis and gasification at lower capacities but converge with incineration at higher capacities. Long‐term operational experience will confirm technology competitiveness and elucidate whether pyrolysis and gasification warrant widespread adoption.Practitioner Points Pyrolysis and gasification systems are gaining traction in the wastewater industry with several full‐scale installations operating, in construction, or designSeveral advantages, but some disadvantages, are considered in comparison with incinerationOrganic contaminants, including PFAS, will undergo transformation and potentially complete mineralization through each process

Demonstration of non-linear model predictive control for optimal flexible operation of a CO2 capture plant

Due to the penetration of renewable intermittent energy, there is a need for coal and natural gas power plants to operate flexibly with variable load. This has resulted in an increasing interest in flexible and operational issues in the capture plant as well. In the present paper a nonlinear model predictive control (NMPC) system was tested at the Tiller pilot plant in Norway. The most important part of the NMPC software is the dynamic model representing the absorber/desorber plant. A previous first principle (mechanistic) dynamic model of the plant using MEA was modified for a solvent of AMP and piperazine, and then successfully verified by step response tests. The NMPC, which was set up to minimize the deviation from the capture rate setpoint and minimize the specific reboiler duty was then tested in a closed loop with large changes in flue gas flow and CO2 composition. Even for gas rate variations of more than 300% (110–340 m3/h) and CO2 concentration changes of 30%, the dynamic response was satisfactory. A test with frequently occurring constraints on the reboiler duty revealed a need for an extension to include direct control of the lean loading. Test of setpoint changes in total CO2 recovery showed that the control system managed to rapidly change from one capture rate to another with a time constant of typically 10 min. This might be used in a second layer of optimization, a dynamic real-time optimizer, that minimizes the capture costs during a longer horizon considering varying energy prices.

Experimental Investigation of SO2 Removal from Flue Gases by Cleaning with Solution of Lime Suspension and Formic Acid

The experimental investigation presented in this research was performed in order to examine the possibility of the removal of SO2 from flue gases by cleaning with a solution of lime suspension and formic acid (Ca(OH)2 and HCOOH). Research was conducted in a laboratory plant (rotary kiln) of 44 kW. The mass of the lime suspension (LS) was 400 g. The mass of the LS was homogenized (mixed) in a sample cup with 2 g (0.5%), 4 g (1%) and 8 g (2%) of 60% formic acid. The solution was placed in a gas washing bottle, where a partial flow of flue gas generated by the combustion of diesel fuel was injected. Simultaneously with the diesel fuel combustion, SO2 from a bottle was injected in a rotary kiln. The average mass concentration of SO2 in the flue gas at the entry point of the gas washing bottle was around 2900 ppm. The results indicated that the absorption of SO2 by the cleaning of flue gas with LS was 96.83%. Adding formic acid to the LS in mass ratios of 0.5% (2 g), 1% (4 g) and 2% (8 g) resulted in absorptions of 99.25%, 98.77% and 98%, respectively. The absorption of flue gases in the gas washing bottle with LS, with the addition of formic acid in the mentioned ratios, showed a reduction in sulfates and pH value, and a rise in sulfides and calcium, respectively.

Increase in processing flue gas flow rate while maintaining the fluidization state and filtration performance in a low-temperature continuous regeneration filter using a fluidized bed

To increase the processing gas flow rate in a fluidized bed filter, the effects of superficial velocity and fluidization state on PM filtration and combustion were examined by experiments using large bed particles (710 μm). The fluidization state at 710 μm was measured by image analysis and recurrence plot, and the superficial velocities as experimental conditions were determined to obtain almost the same fluidization state and filtration efficiency as those for small bed particles (420 μm) in previous studies. The BET-surface area of 710 μm is slightly larger than that of 420 μm, and the amount of potassium catalyst doped on large bed particles is comparable to that at 420 μm. The gas phase velocity is increased by increasing the processing gas flow rate, and the contact probability between PM and oxidizer increases. The PM combustion reaction is significantly promoted owing to the effects of the potassium catalyst and the increase in the gas phase velocity, and the minimum continuous regeneration temperature is 30 °C lower than that at 420 μm. As a result, fluidized bed filters using large bed particles can be operated in continuous regeneration mode at a bed temperature of 320 °C while maintaining a filtration efficiency of 100%.

Dynamic performance of a multi-mode operation CO2-based system combining cooling and power generation

The CO2-based combined cooling and power generation system (CCP) is considered as a promising solution for waste heat recovery due to its multiple energy outputs, environmental protection, and compactness. In this work, for waste heat recovery in refrigerated trucks, a dynamic simulation model of a multi-mode CO2-based CCP system is established in Matlab/Simulink and the experimental data verifies the dynamic simulation model well. The effect of engine heat source, condenser cooling water, and operation mode on the dynamic behavior of the CCP system is analyzed. The results show that the power output will slightly improve when switching from integrated refrigeration and power mode to full power mode. In addition, exhaust gas temperature, flue gas flow, and condenser cooling water temperature are the main disturbance factors affecting the operation of the CCP system. Moreover, in the case of sufficient condenser cooling water, the correlation between the power sub-cycle and the refrigeration sub-cycle of the CO2-based CCP system is weak, so the two sub-cycles can be controlled independently. The preliminary results presented in this paper will be helpful for the future design and the development of control strategies for the CO2-based CCP system.