Flue Gas Flow Rate Research Articles

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.

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%.

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.

Flexible CO2 capture for open-cycle gas turbines via vacuum-pressure swing adsorption: A model-based assessment

As energy systems require flexible and responsive power generators to combat network imbalances, CO2 post-combustion capture (PCC) technologies need to be capable of transient operation. However, currently only amine absorption has been investigated for its efficacy in Flexible-PCC.Within this study we develop and validate a vacuum-pressure swing adsorption (VPSA) process model, capable of processing 33.8 kg/s of exhaust flow from a small-scale open-cycle gas turbine (OCGT). The Flexible response scenario is based on realistic load changes of OCGTs during a 5-h period. To handle the size of flow the system is split into two identical two bed four step VPSA processes, both using Zeolite 13X as the adsorbent material. Included in the Flexible-VPSA operation is the start-up, ramping, and shutdown procedures. Flexible-VPSA showed minute deviations in CO2 purity and recovery rate, and despite the specific energy demand increasing, results show no technical limitations to transient operation. The Flexible VPSA simulations are compared against the benchmark MEA solvent, with both technologies performing similarly when processing highly transient flue gas flowrate. Thus, VPSA is potentially an attractive alternative technology for Flexible-PCC.

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%.

Robust Economic MPC of the Absorption Column in Post-Combustion Carbon Capture through Zone Tracking

Several studies have reported the importance of optimally operating the absorption column in a post-combustion CO2 capture (PCC) plant. It has been demonstrated in our previous work how economic model predictive control (EMPC) has a great potential to improve the operation of the PCC plant. However, the use of a general economic objective such as maximizing the absorption efficiency of the column can cause EMPC to drive the state of the system close to the constraints. This may lead to solvent overcirculation and flooding, which are undesirable. In this work, we present an EMPC with zone tracking algorithm as an effective means to address this problem. The proposed control algorithm incorporates a zone tracking objective and an economic objective to form a multi-objective optimal control problem. To ensure that the zone tracking objective is achieved in the presence of model uncertainties and time-varying flue gas flow rate, we propose a method to modify the original target zone with a control invariant set. The zone modification method combines both ellipsoidal control invariant set techniques and a back-off strategy. The use of ellipsoidal control invariant sets ensure that the method is applicable to large scale systems such as the absorption column. We present several simulation case studies that demonstrate the effectiveness and applicability of the proposed control algorithm to the absorption column in a post-combustion CO2 capture plant.

Mercury removal from coal combustion flue gas by pyrite-modified fly ash adsorbent.

Pyrite and fly ash have certain advantages in adsorption and mercury oxidation. The pyrite-modified fly ash (PY + AC-FA) mercury adsorbent was prepared by mixing pyrite (PY) with acid-modified fly ash (AC-FA), which has better mercury removal effect than AC-FA. The experimental results of mercury adsorption show the following: when the reaction temperature is 50°C, the best doping proportion of modified fly ash is 20 wt%, the mass proportion of pyrite to acid-modified fly ash is 4:1, and the flue gas flow rate is 1.0 L/min; the adsorbent has the best performance, and the adsorption rate of mercury reaches 91.92%.It was also found that the quasi-second-order kinetic model could describe the entireprocess of adsorption, and its adsorption process was mainly influenced by chemisorption. XRF, BET, SEM, XRD, and TG-DSG were used to characterize these adsorbents, and the mechanism of mercury removal of pyrite-modified fly ash adsorbent is inferred: Hg0 is first adsorbed on the surface of the adsorbent, and then oxidized to HgS by the active component FeS2 in pyrite-modified fly ash.

Techno-economic assessment of post-combustion CO2 capture using aqueous piperazine at different flue gas compositions and flowrates via a general optimization methodology

An overall techno-economic assessment of a post-combustion CO2 capture process using aqueous piperazine is presented. A two-step techno-economic optimization approach is developed and implemented. First, two-objective technical optimization problems are solved at different combinations of CO2 capture efficiencies and CO2 concentrations in the flue gas, which aim at minimizing the specific equivalent work while maximizing the volume-based productivity of the capture process. Increasing minimum specific reboiler duties between 2.4 and 2.9 MJthkgCO2captured−1 are obtained for decreasing flue gas CO2 concentrations between 33 and 4 vol%, on a dry basis, with absorber packing heights below 10 m. Then, costs are computed at the technical optimal conditions as a function of the CO2 capture efficiency, flue gas flowrate and CO2 concentration. As a result, maps of minimum cost of CO2 captured, of minimum cost of CO2 avoided, and of minimum cost of CO2 generated by the CO2 point source are obtained, as well as of the associated optimal operating conditions and performance indicators of the capture process, which allow to assess the economic feasibility and performance of the capture process under different cost scenarios and assumptions when applied to different flue gas compositions and flowrates typical of industrial CO2 intensive point sources.

Updraft Gasifier-Stirling Engine Biomass Incineration System Power Generation

Biomass, the world's largest renewable energy source, will continue to grow in the following energy markets. As a result, small biomass conversion systems are more competitive than large stand-alone converters because most of the biomass sources have low energy density and are widely distributed in space. The current study offers a small solid biomass power generation system to examine the possibility of direct connection of updates fixed bed gasifiers and a Stirling engine. The fixed bed updraft gasifier uses a combustion burner built into the gasifier to completely burn the synthetic gas produced by the gasifier. The exhaust gases generated by the synthesis gas combustion in the combustion tube are directed to the Stirling engine heater head. The engine then converts the heat contained in the exhaust gases. Output depends on the heat input. And the heat input is proportional to the flue gas flow rate and temperature Preliminary studies on the proposed straight couplings of the energy derived from the gasifier to mechanical energy of 300 mW and electrical energy of 50 mW. The outcomes of the Stirling engine with Updraft gasifier test shows that Pradauk biomass is more effective than charcoal biomass. Current research shows that no supplemental fuel is needed to keep the current system running smoothly. The technology and units presented can be considered as a viable solid biomass power generation system and enlarge to produce more electricity in rural areas of Thailand in the next step.
 HIGHLIGHTS
 
 The outcomes of the Stirling engine with Updraft gasifier test shows that Pradauk biomass is more effective than charcoal biomass
 The technology and units presented can be considered as a viable solid biomass power generation system and enlarge to produce more electricity in rural areas of Thailand in the next step
 Current studies show that the proposed system is technically feasible because it can generate electricity without interference so as to maintain an almost stable process
 
 GRAPHICAL ABSTRACT

온실가스 저감을 위한 암모니아 혼소가 초임계 화력 발전시스템 보일러에 미치는 열성능 영향성 평가

Co-firing ammonia with coal is emerging as a transitional technology in the power industry for the major reduction of greenhouse gas emissions. Although ammonia has the disadvantages of low combustion reactivity and the generation of nitrogen oxides, it can effectively reduce greenhouse gas due to the generation of only moisture and nitrogen after the combustion. Therefore, for the efficient co-firing of the coal and ammonia in the power plant system, it is essential to evaluate the effect of co-firing ammonia on the boiler system. We selected the 870 MWe supercritical coal-fired boiler system and developed the process simulation model of the target boiler system. In this study, process simulation of the target boiler system was performed according to the ammonia co-firing ratio of 0, 5, 10, 20, and 30%. In addition, the effect of ammonia co-firing on the boiler thermal performance was evaluated according to the load condition and the quality of coal. As the ammonia co-firing ratio increases, the flue gas flow rate and the radiation and convective heat transfer rate decrease. Accordingly, the main and reheat steam temperatures decrease. Although the reduction of carbon dioxide is quantitatively confirmed according to the co-firing ammonia, the boiler thermal efficiency decreases due to the increase in the amount of moisture in the flue gas.

An integrated real-time optimization, control, and estimation scheme for post-combustion CO2 capture

This study presents a novel operational scheme for post-combustion CO2 capture (PCC) plants downstream from fuel-fired power plants. The approach is comprised of real-time optimization (RTO), nonlinear model predictive control (NMPC), and moving horizon estimation (MHE) layers. These layers are integrated to operate the system economically via a new economic function that accounts for the most significant economic aspects of PCC, including the carbon economy, energy, chemical, and utility costs. The proposed approach was employed on the case study of an MEA-based PCC absorber section, which uses a mechanistic process model to provide an accurate representation of the system. The NMPC layer is novel in its ability to enable flexible control of the plant by manipulating fresh material streams to impact CO2 capture and the MHE layer is the first to provide accurate system estimates to the controller with realistically accessible measurements. The proposed scheme was subjected to a cofiring scenario, whereby the switching between two fuels (i.e., biomass and coal) is reflected in the flue gas composition. In this scenario, a ∼19% steady-state cost improvement is observed with respect to the pre-disturbance cost. Moreover, the MHE was shown to cause an acceptable ∼0.5% of performance loss in the process economics through its effect on the NMPC. The scheme was also subjected to a ±20% diurnal variation in power plant load through steps in the flue gas flowrate and was found to provide consistent steady-state economic improvements (from ∼12% cost improvement to ∼17% loss abatement) for each of the disturbances observed. Furthermore, a price variation scenario highlighted the operational dependence of the system upon changes in economic incentives via the prices. When compared to a ‘no RTO’ case, the scheme was found to yield economic improvement ranging from ∼3% to ∼14% depending on the pricing. All scenarios in the case study displayed steady-state cost savings that exceeded the energy penalty imposed on the power plant by the PCC plant. This suggests the proposed scheme is an effective framework for the economic operation of a general class of PCC plants (i.e., with different solvents, process designs and control schemes, etc.) and can help enable the viability of PCC for the continued use of fuel-firing.

Discussion on calculation method of natural frequency of flue design in thermal power plant based on temperature field simulation

The vibration of the boiler tail flue not only leads to tearing and steam leakage at the welding point between the superheater and manhole, but also makes the acoustic soot blower in the tail flue basically unable to be put into operation, which seriously affects the safe operation of the unit. In order to reduce the size of external reinforcing ribs, the minimum number of internal struts should be used in large section flue. By means of temperature field simulation, the author adds a flow guide device at the junction of the down flue and the horizontal flue to forcibly guide the flue gas to the convection heat exchange area. The simulation results show that the vertical velocity field distribution of the horizontal flue tends to be uniform after adding the diversion device. Measures should be taken to prevent the vibration of the inner strut, such as selecting the inner strut with appropriate specifications; Install fins on the inner strut; Change the natural frequency of the inner strut; Select appropriate flue gas flow rate, etc.

Maximizing the power output and net present value of organic Rankine cycle: Application to aluminium industry

This study presents an integrated design and optimization of an Organic Rankine Cycle (ORC) for the recovery of waste heat from aluminium production. Non-Linear Programming (NLP) models were developed, with the objectives of maximizing electricity production and the Net Present Value (NPV) of the system. The models account for optimizing the operating conditions and changes in thermodynamic features of the system. The developed models are applied to a case study of Slovenian aluminium company where the performance of three different working fluids (R245fa, R1234yf and R1234ze) are compared. The optimization is performed considering different temperatures and prices of produced hot water and electricity, minimum approach temperature (ΔTmin), concentration of CO2 in flue gas and temperature and flowrate of flue gas. Results show that the selected working fluids for the proposed waste heat-based ORC system have the potential to substitute up to about 830 kW of electricity in a sustainable and economic manner. Out of the three working fluids considered, R245fa showed up to 7.9% efficiency of the ORC cycle and was identified as the best performing working fluid considering both economic viability and the amount of electricity produced by the system, however the refrigerant inherently has higher GHG footprint.

Simulation study of using macroporous ceramic membrane to recover waste heat and water from flue gas

Transport membrane condenser based on macroporous ceramic membranes can better meet the requirements of power plants for the recovery of waste heat and water from flue gas. This paper proposes a condensation and permeation model for describing the process of waste heat and water recovery from flue gas by macroporous transport membrane condenser. The results obtained from model are compared with the experimental results. According to results of condensation and permeation rate, errors between the calculated and experimental data are less than 10%. According to results of outlet water and flue gas temperatures, errors between the calculated and experimental results are within 0.06%. Therefore, accuracy of the model is verified. Based on the model, effects of the parameters including flue gas temperature and flow velocity, cooling water temperature and flow velocity, flue gas relative humidity, membrane porosity, and local atmospheric pressure are studied in terms of water and heat recovery performances. The research results show that increasing the flow rate of flue gas and cooling water, increasing the relative humidity of flue gas, increasing the local atmospheric pressure, reducing the temperature of flue gas and cooling water can increase the condensation rate of water vapor, thereby enhancing the recovery performance of the ceramic membrane. The increase of the porosity of the ceramic membrane can increase the penetration rate of the condensate, and more condensate can be recycled into the ceramic membrane, so that the overall recovery effect is better.

How much can novel solid sorbents reduce the cost of post-combustion [formula omitted] capture? A techno-economic investigation on the cost limits of pressure–vacuum swing adsorption

This paper focuses on identifying the cost limits of two single-stage pressure–vacuum swing adsorption (PVSA) cycles for post-combustion CO2 capture if the “ideal” zero-cost adsorbent can be discovered. Through an integrated techno-economic optimisation, we simultaneously optimise the adsorbent properties (adsorption isotherms and particle morphology) and process design variables to determine the lowest possible cost of CO2 avoided (excluding the CO2 conditioning, transport and storage) for different industrial flue gas CO2 compositions and flow rates. The CO2 avoided cost for PVSA ranges from 87.1 to 10.4 € per tonne of CO2 avoided, corresponding to CO2 feed compositions of 3.5 mol% to 30 mol %, respectively. The corresponding costs for a monoethanolamine based absorption process, using heat from a natural gas plant, are 76.8 to 54.8 € per tonne of CO2 avoided, respectively showing that PVSA can be attractive for flue gas streams with high CO2 compositions. The “ideal” adsorbents needed to attain the lowest possible CO2 avoided costs have a range of CO2 affinities with close to zero N2 adsorption, demonstrating promise for adsorbent discovery and development. The need for simultaneously optimising the particle morphology and the process conditions are emphasised.

Modular monolith adsorbent systems for CO2 capture and its parameterized optimization

A key challenge for power plant carbon capture systems is operating economically under varying load conditions. Daily variations may be handled through control systems with reduced economic performance, but longer term seasonal cycles will require different solutions to enable robust and economic operation. We propose to use modular monolith adsorbent (MMA) designs whose capacity and configuration can be altered to respond to variations in flue gas flow. The configuration of the blocks is defined by the pattern of their serial and parallel connection. The ability to present a shorter, but wider, bed at different flue gas flowrates can then be exploited to improve performance and continuing to meet constraints on product purity and recovery. This additional degree of freedom afforded by the modular nature of the design allows an active response to the flowrate conditions and increases the flexibility of the system over the space of flowrate and concentration. In order to compare the proposed MMA systems and the conventional passive design method, case studies with varying flue gas amounts in a power plant are carried out. Simulation results show that the proposed MMA systems have improved optimal solutions because of their design flexibility, compared to the conventional passive design approach. Lastly, the optimized solutions are presented as a parametric map with different CO2 capture fractions and flowrate of flue gas. These parametric off-line solutions can be a guideline for the process implementation and reduce the operating complexity even if the MMA systems are used.

Exergy analysis of municipal solid waste incineration processes: The use of O2-enriched air and the oxy-combustion process

This work provides a complete exergy analysis of municipal solid waste incineration process. The work was based on a previous study, and was enriched considering the possibility to increase the O2 %mol in the combustion air, up to oxy-combustion conditions. Two configurations have been considered, with and without flue gas recirculation, and the environmental aspects of oxy-combustion were taken into account, as well as its exergetic cost. The flue gas was used in a boiler for high pressure steam production, expanded in three turbines for power generation. The exergy analysis allowed to identify the process units characterized by major irreversibility and exergy loss as waste. The results showed that the flue gas recirculation led to an exergy efficiency increase of the whole process of about 3% (from 31.1% up to 34% at adiabatic flame temperature equal to 1200 °C). The O2 %mol increase in the combustion air allowed to reduce the flue gas flowrate, leading to environmental benefits. Oxygen-enriched air adoption led to limited exergetic improvements, due to the exergy cost of the air separation unit. The specific energy generation of the plant increased at fixed combustion chamber temperature adopting flue gas recirculation.

Experimental Study on Simultaneous Desulfurization and Denitrification by DBD Combined with Wet Scrubbing

A dielectric barrier discharge (DBD) reactor combined with a wet scrubbing tower was used to carry out an experimental study on desulfurization and denitrification. The effects of the packing type, packing height, spray density, mass fraction of the NaOH solution, discharge power in the DBD reactor, and simulated flue gas flow rate on the desulfurization and denitrification efficiency were analyzed, along with the influence weight of each factor, using orthogonal testing. The experimental results showed that SO2 was easily absorbed by the scrubbing solution, while the desulfurization efficiency remained at a high level (97–100%) during the experiment. The denitration efficiency was between 12 and 96% under various operating conditions. Denitration is the key problem in this system. The influence weights of the DBD power, simulated flue gas flow rate, mass fraction of the NaOH solution, spray density, packing type, and packing height on the denitration efficiency were 56.96%, 18.02%, 11.52%, 5.02%, 4.33%, and 4.16%, respectively. This paper can provide guidance to optimize the desulfurization and denitrification efficiency of this DBD reactor combined with a wet scrubbing system.

Numerical Investigation on the Evaporation Performance of Desulfurization Wastewater in a Spray Drying Tower without Deflectors

The desulfurization wastewater evaporation technology with flue gas has been widely applied to dispose of desulfurization wastewater. This paper investigates the effect of flue gas flow rate and temperature, wastewater flow rate and initial temperature, and droplet size on the evaporation performance of the desulfurization wastewater in a spray drying tower without deflectors. The results show that the flue gas flow rate and temperature affect the evaporation performance of desulfurization wastewater. The larger flow rate and higher temperature of flue gas correspond to the faster evaporation speed and the shorter complete evaporation distance of the wastewater droplet. Decreasing the flow rate and increasing the initial temperature of the desulfurization wastewater is advantageous to enhance the evaporation speed and shorten the complete evaporation distance of the wastewater droplet. Reducing the droplet size is beneficial to improve the evaporation performance of the desulfurization wastewater. The orthogonal test results show that the factors affecting droplet evaporation performance are ranked as follows: flue gas flow rate > wastewater flow rate > flue gas temperature > wastewater initial temperature > droplet size. Considering the evaporation ratio and the complete evaporation distance, the optimal setting is 14.470 kg/s for flue gas flow rate, 385 °C for flue gas temperature, 0.582 kg/s for wastewater flow rate, 25 °C for wastewater initial temperature, and 60 μm for droplet size. These studied results can provide valuable information to improve the operational performance of the desulfurization wastewater evaporation technology with flue gas.

Model predictive control for amine-based CO[formula omitted] capture process with advanced flash stripper

Advanced flash stripper (AFS) has been suggested as a process alternative for conventional absorption-based post-combustion carbon capture process, which can significantly reduce the solvent regeneration energy. However, such reduction is enabled through energy integration achieved by two additional heat exchangers, which can pose serious challenges to the control and operation of carbon capture processes. For complex energy-integrated processes, simple decentralized control scheme, where multiple proportional–integral–derivative (PID) controllers are employed, typically shows limited control performances. Thus, this study aims to propose an effective control structure for the carbon capture process with AFS, which can regulate the process under various dynamic scenarios involving significant changes in operational variables such as flue gas flowrate and carbon capture rate. Specifically, a dynamic model for the post-combustion carbon capture process is built in gPROMS, where 30 wt% Monoethanolamine (MEA) solvent is used in the absorber. Then, step responses of the controlled outputs with respect to the manipulated and disturbance inputs are analyzed to characterize the dynamic behavior of such process. A model predictive control (MPC) strategy is proposed on the basis of the understanding from the analysis. Finally, the closed-loop performances of the proposed control strategy and decentralized PID controllers are compared to demonstrate the effectiveness of the MPC strategy. The MPC strategy demonstrates that it can track the set-point change at least 20 min faster than the PID strategies, and stabilize the stripper section about 200 min faster.