Flue Gas Characteristics Research Articles

Process design and optimization of membrane-based CO2 capture process with experimental performance data for a steam methane reforming hydrogen plant and a coal-fired power plant

Membrane-based separation is one of the promising next-generation carbon capture technologies. High degrees of freedom in process design for multi-stage membrane networks, make it difficult to fully understand the impact of network configuration on the economics of capture and separation performance. Furthermore, the optimality in process design is heavily influenced by the levels of membrane performance and the characteristics of feed gas. Membrane model utilized for the study is validated and tuned with 183 experimental data measured at various operating conditions, having 2.45 % of overall prediction error. The superstructure-based framework for the optimization of multi-stage membrane networks is used, with which design interactions between network configurations, flue gas characteristics and membrane performance are systematically investigated. Techno-economic analysis is embedded in the optimization framework, which performs rigorous trade-off between capital and operating costs, as well as allows simultaneous determination of optimal process network configuration and operating variables. Flue gas streams emitted from a coal-fired power plant and a steam methane reforming hydrogen production plant are selected as CO2 capture sources for the analysis of flue gas characteristics. Case study shows capture cost ranged from 30.2 $/tCO2 to 79.9 $/tCO2, depending on the network configuration and design specifications, and clearly improves our techno-economic understanding on the network configuration of membrane capture process. In addition, cryogenic-hybridized membrane capture process is examined and the optimal level of enriched CO2 stream concentration between membrane capture and cryogenic distillation processes is determined. Study suggests how network configuration of membrane capture process can impact capture cost.

Effect of Tourmaline Addition on the Anti-Poisoning Performance of MnCeOx@TiO2 Catalyst for Low-Temperature Selective Catalytic Reduction of NOx.

In view of the flue gas characteristics of cement kilns in China, the development of low-temperature denitrification catalysts with excellent anti-poisoning performance has important theoretical and practical significance. In this work, a series of MnCeOx@TiO2 and tourmaline-containing MnCeOx@TiO2-T catalysts was prepared using a chemical pre-deposition method. It was found that the MnCeOx@TiO2-T2 catalyst (containing 2% tourmaline) exhibited the best low-temperature NH3-selective catalytic reduction (NH3-SCR) performance, yielding 100% NOx conversion at 110 °C and above. When 100-300 ppm SO2 and 10 vol.% H2O were introduced to the reaction, the NOx conversion of the MnCeOx@TiO2-T2 catalyst was still higher than 90% at 170 °C, indicating good anti-poisoning performance. The addition of appropriate amounts of tourmaline can not only preferably expose the active {001} facets of TiO2 but also introduce the acidic SiO2 and Al2O3 components and increase the content of Mn4+ and Oα on the surface of the catalyst, all of which contribute to the enhancement of reaction activity of NH3-SCR and anti-poisoning performance. However, excess amounts of tourmaline led to the formation of dense surface of catalysts that suppressed the exposure of catalytic active sites, giving rise to the decrease in catalytic activity and anti-poisoning capability. Through an in situ DRIFTS study, it was found that the addition of appropriate amounts of tourmaline increased the number of Brønsted acid sites on the catalyst surface, which suppressed the adsorption of SO2 and thus inhibited the deposition of NH4HSO4 and (NH4)2HSO4 on the surface of the catalyst, thereby improving the NH3-SCR performance and anti-poisoning ability of the catalyst.

Performance analysis of a novel biomass gasification system coupled to a coal-fired power plant based on heat and water recovery

Biomass gasification co-firing is a technology that can be implemented instantly in almost all coal-fired power plants in a relatively short period to reduce the consumption of fossil fuel. Most studies have focused on improving the system according to variations in the gasification conditions, biomass types, co-firing ratio, and boiler loads. However, the whole system process analysis and structural improvement based on the matter and energy of the co-firing system require further investigation. In this study, a novel biomass air–steam circulating fluidized bed gasification co-firing system based on waste heat and flue gas water recovery with different co-firing ratios (approximately 10 %–40 %) was simulated and compared with the original air gasification co-firing system using Aspen Plus software. The impacts of recovered water participate in gasification process and the optimal steam to biomass ratio (S/B) when it varied from 0.5 to 2, on the syngas quality, thermal characteristics of flue gas, recovered water, coal consumption, exergy loss, and efficiency of the system were analyzed. Compared with the air gasification co-firing system, the results showed that the N2 content in syngas reduced from 41.14 % to 28.92 %, and the heat yield of syngas increased by 7.73 %, along with a 110 t/h recovered water surplus at a 40 % co-firing ratio when steam to biomass ratio was equal to 1. The maximum coal saving amount was 2.26–9.11 t/h and the volume of atmospheric pollutants emissions, such as carbon dioxide (CO2), sulfur oxides (SOx) and nitrogen oxides (NOx), reduced by 0.95 %–6.02 %, 0.91 %–0.95 %, and 11.38 %–36.47 % at a co-firing ratio of approximately 10 %–40 %. Furthermore, the exergy loss can be reduced by 4.35 %–10 % with a 1.72 %–3.96 % increase in exergy efficiency, indicating that the new system mode improves the comprehensive performance of the co-firing system.

Study on Flow Characteristics of Flue Gas and Steam Co-Injection for Heavy Oil Recovery

Flue gas is composed of N2 and CO2, and is often used as an auxiliary agent for oil displacement, with good results and very promising development prospects for co-injection with steam to develop heavy oil. Although research on the oil displacement mechanism of flue gas has been carried out for many years, the flow characteristics of steam under the action of flue gas have rarely been discussed. In this paper, the flow resistance and heat transfer effect of flue gas/flue gas + steam were evaluated by using a one-dimensional sandpack, a flue gas-assisted steam flooding experiment was carried out using a specially customized microscopic visualization model, and the microscopic flow characteristics in the process of the co-injection of flue gas and steam were observed and analyzed. The results showed that flue gas could improve the heat transfer effect of steam whilst accelerating the flow of steam in porous media and reducing the flow resistance of steam. Compared with pure steam, when the volume ratio of flue gas and steam was 1:2, the mobility decreased by 2.8 and the outlet temperature of the sandpack increased by 35 °C. This trend intensified with an increase in the proportion of flue gas. In the microscopic oil displacement experiments, the oil recovery and sweep efficiency of the flue gas and steam co-injection stage increased by 4.7% and 32.9%, respectively, compared with the pure steam injection stage due to the effective utilization of blocky remaining oil and corner remaining oil caused by the expansion of fluid channels, the flow of flue gas foam, and the dissolution and release of flue gas in heavy oil.

Ash deposition characteristics of flue gas across a tube using the Eulerian multiphase model with dynamic mesh technique

The ash deposition problem majorly affects the stability, safety, and economy of industrial production processes. To investigate the transient ash deposition characteristics of the flue gas flowing across a tube, the Eulerian multiphase model combined with a dynamic mesh technique is first used in this work. The deposition and the removal processes are both taken into account. Four deposition mechanisms are considered in the deposition process, including Brownian and eddy diffusion, gravity, thermophoretic, and turbophoretic forces. Based on the experimental verification results, it is found that the Eulerian multiphase model combined with a dynamic mesh technique can more accurately predict the ash deposition behavior. The overall fouling characteristics are analyzed by the changes in net deposition mass and deposition morphology under seven different working conditions. The results showed that the ash deposits are mainly formed in two regions: β = 165° ∼ 195° and β = 305° ∼ 55°. In addition, one peak is observed in the deposition region on the windward side, and three peaks exist in the deposition region on the leeward side. The periodic shedding regularity of vortices, the separation process of the boundary layer, and the flow patterns of each feature point on the tube surface are studied to investigate the influence of the flow field characteristics on the deposition characteristics. In addition, the causes of the ash deposition in various locations are discussed in detail from the perspective of the deposition mechanism. The findings of this study are beneficial for understanding the ash deposition process and provide an improved approach for ash deposition simulation.

An Efficient Method for Heat Recovery Process and燭emperature燨ptimization

Flue gas heat loss accounts for a significant component of the overall heat loss for coal-fired boilers in power plants. The flue gas absorbs more heat as the exhaust gas temperature rises, which reduces boiler efficiency and raises coal consumption. Additionally, if the exhaust gas temperature is too high, a lot of water must be used to cool the flue gas for the wet flue gas desulfurization system to function well, which has an impact on the power plant’s ability to operate profitably. It is consequently vital to take steps to lower exhaust gas temperatures in order to increase boiler efficiency and decrease the amount of coal and water used. Desulfurization performance may be enhanced and water use can be decreased by reasonable flue gas characteristics at the entry. This study analyzed the unit’s energy consumption, investment, and coal savings while proposing four coupling strategies for regulating flue gas temperature and waste heat recovery. A graded flue gas conditioning and waste heat recovery plan was presented under the condition of ensuring high desulfurization efficiency, along with the notion of minimizing energy loss owing to energy inflow temperature difference. Numerical results show that the proposed methods improved the system performance and reduced the water consumption and regulated the boiler temperature.

Emission characteristics of flue gas during the chemical-looping combustion process for multi-component solid waste

Abstract Solid waste has interactions with its flue-gas products during combustion, which offers the possibility of regulating its pollutant emissions. Especially, these interaction pathways would be clearer under anaerobic conditions when the chemical-looping combustion (CLC) process is used. The CLC experiments of multi-component solid waste were conducted on a homemade twin-bed reactor and the characteristics of flue gas were investigated for the effect of the mixing ratio of sewage sludge and polyvinyl chloride (PVC). The results indicated that the combustion efficiency was >99.9% for these CLC processes; the highest carbon-conversion rate was obtained at 96.3% for PVC with 60% sludge. The highest NO and SO2 emissions were 26% and 19%, respectively, when the sludge was mixed with 20% PVC. As the proportion of PVC blended into the sludge increased, the time when the concentration of NO in the flue-gas peaks moved backwards, while peak SO2 concentration moved forward. The general trend was to increase first and then decrease. In addition, there were multiple peaks in carbon emissions, corresponding to ~10%, 30% and ~70% of the carbon-conversion rate; nitrogen emissions reached 90% of total emissions before the carbon-conversion rate was 40%; sulphur emissions had a longer cycle and were mainly emitted between 10% and 60% of the carbon-conversion rate. The results are expected to provide a reference for solid-waste source suppressing to inhibit the generation of pollutants.

Design of ORC-RO system for utilizing waste heat from flue gases of coal-fired thermal power plant

Waste heat recovery is an efficient tool to reuse waste energy to provide useful energy products. This method addresses the practical solution for sustainable products, which reduces CO2 emissions. The organic Rankine cycle is the most desirable option for waste heat recovery systems as it operates with low heat source temperature, which is auspicious in designing flexible and compact systems. This paper aims to design an organic Rankine cycle coupled with reverse osmosis to drive RO system by utilizing waste heat from flue gases of the thermal power plant. The boiler feed (make-up) water has been treated using the RO system, and the concentrate from the RO system can be used to suppress coal fly ash. The recycling reverse osmosis system is designed according to the boiler feedwater input for achieving more than 80 % recovery. The RO feed water is pre-heated by condensing vapor from the ORC expander, which reduces the specific energy consumption of the RO system. Also, the flue gas characteristics are discussed, which can be utilized at above dew-point temperature to avoid corrosion. This concept design is developed for the 2 MW coal-fired thermal power plant.

Ash Deposition Characteristics of Flue Gas Across a Tube Using the Eulerian Multiphase Model with Dynamic Mesh Technique

Ash Deposition Characteristics of Flue Gas Across a Tube Using the Eulerian Multiphase Model with Dynamic Mesh Technique

Development and testing of a new post-combustion CO2 capture solvent in pilot and demonstration plant

Post-combustion CO2 capture for coal-fired power plants is an important technical option to mitigate greenhouse gas emission from coal-based power generation. CO2 capture based on chemical absorption is currently the dominant technology for large-scale capture unit. The main obstacle of commercial application is the high cost and high energy consumption, innovation of new absorption solvent is one of the keys to the performance improvement. Based on the characteristics of flue gas, combined with the analysis and comparison of potential amine components, the formula of blended amines are developed, which is further screened by true-heat flux calorimetric test combined with vapor-liquid equilibrium test, HNC-5 is selected through the lab test, because of its lower heat of absorption and higher capture performance. The test on a 1000 t/a CO2 capture pilot plant under real flue gas conditions shows that the performance index of HNC-5 is consistent with the lab test results. The CO2 capture ratio is higher than 90%, and the heat consumption during regeneration is reduced by about 20% compared with MEA. The continuous operation results of the 120,000-ton/year CO2 capture unit show that heat duty of regeneration of HNC-5 is about 2.8GJ/tCO2, the cost per ton of CO2 captured is reduced by about 63 CNY, the usage life is longer, helping improve the system availability and reliability.

Condensation heat transfer characteristics of flue gas on anti-corrosive coated finned tubes

It is still high on the agenda for the highly-effective utilization of exhaust flue gas in the condensing-type heat exchangers employing with anti-corrosive surface modification. In this paper, we carried out the wettability and condensation heat transfer characteristics of vapor-containing flue gas outside three kinds of anti-corrosive coated finned tubes. The influence of Re (160 ~ 200) and Ja (0.8 ~ 2.9) of flue gas, and coating layers (Ni-P composite plating, organic coating, Ni-P composite plating + organic coating) on condensation heat transfer were also investigated. The results showed that the contact angle hysteresis is affected by the surface roughness and surface tension. The coating layers all exhibited four condensation periods of water vapor. The combining coating layer (Ni-P composite plating + organic coating) has the most excellent heat-transfer performance. Additionally, a dimensionless formula was established among Nu, Re and Ja for different coating layers. The dimensionless criterion can be helpful for the heat and mass transfer characteristics of vapor-containing flue gas and design the similar surface-modified condensation heat exchangers.

Theoretical Analysis of Acid Dew Point Temperature and Vapour Condensation Characteristics of the Flue Gas

Based on the gas-liquid phase equilibrium and multi-component diffusion theory, an analytical model for predicting acid dew point temperature and vapour condensation characteristics of flue gas was developed. The effects of components content, ash particle radius, wall temperature, coal-burned type and excess air ratio have been investigated. The results indicated that the acid dew point temperature and vapour condensation rate will increase with both water and sulfuric acid vapour contents increase. Vapours are not prone to condense on the ash particles when the particle radius is less than the corresponding critical condensing radius. The vapour condensation characteristics can be divided into two different stages with the wall temperature varies. The particle radius has a significant influence on the vapour condensation characteristics in the higher temperature stage. The acid dew point temperatures present significant differences for different coal-burned types, and the water vapour condensation rate is more sensitive to excess air ratio compared with the acid condensation rate.

The Effects of Coke Parameters and Circulating Flue Gas Characteristics on NOx Emission during Flue Gas Recirculation Sintering Process

The new process of flue gas recirculation, which reduces coke consumption and reducing NOx emissions, is now extensively used. Compared with traditional sintering, the characteristics of circulating flue gas and coke parameters significantly affect the combustion atmosphere and coke combustion efficiency. Based on the actual complex process of sintering machine, this study proposes a relatively comprehensive one-dimensional, unsteady mathematical model for flue gas recirculation research. The model encompasses NOx pollutant generation and reduction, as well as SO2 generation and adsorption. We focus on the effects of cyclic flue gas characteristics on the sintering-bed temperature and NOx emissions, which are rarely studied, and provide a theoretical basis for NOx emission reduction. Simulation results show that during sintering, the fuel NOx is reduced by 50% and 10% when passing through the surface of coke particles and CO, respectively. During flue gas recirculation sintering, the increase in circulating gas O2 content, temperature, and supply-gas volume cause increased combustion efficiency of coke, reducing atmosphere, and NOx content in the circulating area; the temperature of the material layer also increases significantly and the sintering endpoint advances. During cyclic sintering, the small coke size and increased coke content increase the char-N release rate while promoting sufficient contact of NOx with the coke surface. Consequently, the NOx reduction rate increases. Compared with the conventional sintering, the designed flue gas recirculation condition saves 3.75% of coke consumption, i.e., for 1.2 kg of solid fuel per ton of sinter, the amount of flue gas treatment is reduced by 21.64% and NOx emissions is reduced by 23.59%. Moreover, without changing the existing sintering equipment, sintering capacity increases by about 5.56%.

Study of the flue gas characteristics and gasification reaction of pulverized coal combustion in O2/CO2/H2O atmosphere

ABSTRACTThe impacts of O2 and H2O on the combustion characteristics of pulverized coal in O2/CO2/H2O atmosphere were studied. The gasification reaction ratio was calculated from the components of flue gas. The competition exists between C-CO2 and C-H2O reactions under rich CO2 atmosphere. At various H2O concentrations, the differences were found in generation amounts of CO and H2 in flue gas. At O2 concentrations <10%, C-CO2 reaction decreased while C-H2O reaction increased with increasing H2O concentration; while at O2 concentration >30%, H2O showed no obvious specific patterns of effects. The gasification ratio was reduced as coal ranks increase.

Emission characteristics of harmful air pollutants from cremators in Beijing, China.

The process of corpse cremation generates numerous harmful air pollutants, including particulate matter (PM), sulfur dioxide (SO2), nitrogen oxides (NOx), volatile organic compounds (VOCs), and heavy metals. These pollutants could have severe effects on the surrounding environment and human health. Currently, the awareness of the emission levels of harmful air pollutants from cremators and their emission characteristics is insufficient. In this study, we obtained the emission characteristics of flue gas from cremators in Beijing and determined the localized emission factors and emission levels of harmful air pollutants based on actual monitoring data from nine typical cremators. The results show that the emissions of air pollutants from the cremators that directly discharge flue gas exceed the emission standards of China and Beijing. The installation of a flue gas post-treatment system could effectively reduce gaseous pollutants and the emission levels of PM. After being equipped with a flue gas post-treatment system, the emission concentrations of PM10, PM2.5, CO, SO2 and VOCs from the cremators are reduced by 97.6, 99.2, 19.6, 85.2 and 70.7%, respectively. Moreover, the emission factors of TSP, PM10, PM2.5, CO, SO2 and VOCs are also reduced to 12.5, 9.3, 3.0, 164.1, 8.8 and 19.8 g/body. Although the emission concentration of VOCs from the cremators is not high, they are one of major sources of “odor” in the crematories and demand more attention. Benzene, a chemical that can seriously harm human health, constitutes the largest proportion (~50%) of the chemical components of VOCs in the flue gas from the cremators.

3D Experimental Investigation on Enhanced Oil Recovery by Flue Gas Coupled with Steam in Thick Oil Reservoirs

Flue gas is a kind of non-condensate gas that mainly consisted of CO2 (volume percentage about 20%) and N2 (volume percentage about 80%), and is applied in petroleum industry as a kind of displacement agents. In this paper, flue gas is introduced into the thermal recovery process of thick heavy oil reservoir. First, the dissolution characteristics of flue gas in crude oil were researched through the PVT experiments under different conditions. Then, a series of 3D physical simulations were carried out to analyze the oil displacement effect of flue gas coupled with steam flooding in thick reservoir with the consideration of the important production parameters including oil production, water cut, oil-steam ratio and oil recovery in both steam flooding process and the flue gas coupled with steam flooding process. Finally, the EOR mechanisms of flue gas coupled with steam flooding were summarized by analyzing the variation of temperature field, the properties of heavy oil and the distribution of remaining oil....

Study on the Effect of the Jet Speed of Air Curtain on Smoke Control in Tunnel

Abstract The corresponding physical model was established by using a tunnel, and the appropriate fire source power was selected. The minimum export momentum was calculated by the minimum export momentum method, and the minimum outlet jet velocity of the air curtain is given as umin = 14m/s. The change of the concentration of CO, visibility and temperature in the same fire environment under the influence of piston wind was analyzed by CFD simulation software under different jet velocity of air curtain, comparison of the concentration of CO, visibility and temperature at different jet speed of air curtain changes with time simultaneously, to study the effect of jet velocity of air curtain on the spread characteristics of flue gas of tunnel fire. The results show that when the jet velocity of air curtain is 14m/s, it can control the smoke best.

Numerical Simulations on Flow Characteristics of Flue Gas in Furnace with Four-Wall Tangential Firing

ABSTRACTFour-wall tangential firing (FWTF) is a newly developed furnace arrangement used in supercritical and ultra-supercritical 600-MW boilers. In this study, flow characteristics of the flue gas in furnace of a 660-MW boiler firing pulverized coal with FWTF arrangement were investigated through numerical simulations. The variation characteristics of the tangential circle size of the furnace and flue gas bias at the furnace exit were determined. The results show some differences in the flue gas characteristics between the FWTF and traditional four-corner tangential firing (FCTF) in the furnace. In the FWTF, the variation in the actual sizes of the tangential circle in the burner zone is insignificant; the maximum size with respect to geometric limitations is largely maintained. Hence, unlike conventional FCTF, the size of the tangential circle cannot be used as a reliable parameter to analyze the variation in flue gas characteristics in the FWTF. Moreover, the flue gases are uniform and have high filling factors in the furnace. The simulation results show that, in the FWTF, the residual rotational momentum near the furnace exit is significant, thereby leading to variations in the flow and temperature on both sides of the furnace exit. This behavior is similar to that observed in the FCTF, which requires sufficient attention.

5-5 過給式流動炉実証運転における下水汚泥の排ガス特性((2)燃焼,Session 5 燃焼・熱利用)

5-5 過給式流動炉実証運転における下水汚泥の排ガス特性((2)燃焼,Session 5 燃焼・熱利用)

Effects of Wall Fins Patterns on the Flue Gas Performance of Condensing Heat Exchanger

Heat exchanger is an important element of thermal systems. The wall fins patterns with different shape have strong effects on flue gas flow, which affects the performance of heat exchanger. A numerical model of heat exchanger was established based on computational fluid mechanics theory and the flow and heat transfer characteristics of flue gas were studied by the method of CFD and experiment. The optimal form of the wall fins patterns of flue gas channel was proposed. The results showed that the traditional circular fins reduce the effective contact time and lower the heat transfer efficiency between the flue gas and fin. When the optimal elliptical fins were used, the location of the detachment point was postponed, the effective heat transfer area was increased by 7.6% and the average heat transfer coefficient was increased by 12.1%. At the end, the fitting formula of convective heat transfer coefficient of Nu number was obtained in the optimized conditions.