Performance of a Horizontally Mounted Venturi in Low-pressure Wet Gas Flow

The performance of a Venturi tube used in wet gas flow have been explored mainly under higher-pressure condition, but very often, low-pressure test exists in some oil and gas fields in Tianjin Dagang Oil and Gas Field in China. In this study, the performance of horizontally mounted Venturi meters in low-pressure wet gas flow is discussed. Three 50 mm Venturi meters were tested systematically, with fl values of 0.4048, 0.55 and 0.70, the opera- tion pressure of 0.15 MPa, 0.20 MPa, 0.25 MPa, the gas densiometric Froude number from 0.6 to 2.0, the modified Lockhart-Maretinelli parameter from 0.0022 to 0.06, and the ratio of the gas liquid mass flow rate from 0.5 to 0.99. The effects of modified Lockhart-Maretinelli parameter, pressure, gas densiometric Froude number, diameter ratio, and gas-liquid mass flow rate ratio to the Venturi tube are analyzed with new independent data. Furthermore, low-pressure performance was compared with that under high pressure.

Ternary System of Fe-based Ionic Liquid,Ethanol and Water for Wet Flue Gas Desulfurization

Fe-based ionic liquid （Fe-IL） was synthesized by mixing FeCl3·6H2O and 1-butyl-3-methylimidazolium chloride [Bmim]C1 in this paper. The phase diagram of a ternary Fe-IL, ethanol and water system was investigated to construct a ternary desulfurization solution for wet flue gas desulfurization. The effects of flow rate and concentration of SO2, reaction temperature, pH and Fe-IL fraction in aqueous desulfurization solution on the desulfiariza- tion efficiency were investigated. The results shows that the best composition of ternary desulfurization solution of Fe-IL, ethanol and water is 1 ： 1.5 ： 3 by volume ratio, and pH should be controlled at 2.0. Under such conditions, a desulfurization rate greater than 90% could be obtained. The product of sulfuric acid had inhibition effect on the wet desulfurization process. With applying this new ternary desulfurization solution, not only the catalyst Fe-IL can be recycled and reused, but also the product sulfuric acid can be separated directly from the ternary desulfurization system.

Wet Gas Meter Development Based on Slotted Orifice Couple and Neural Network Techniques

A slotted orifice has many superiorities over a standard orifice. For single-phase flow measurement, its flow coefficient is insensitive to the upstream velocity profile. For two phase flow measurement, various characteristics of its differential pressure （DP） are stable and closely correlated with the mass flow rate of gas and liquid. The complex relationships between the signal features and the two-phase flow rate are established through the use of a back propagation （BP） neural network. Experiments were carried out in the horizontal tubes with 50ram inner diameter, ooerated with water flow rate in the range of 0.2m^3·h^-1 to 4m3·h^-1, gas flow rate in the range of 100m^3·h^-1 to 1000m^3·h^-1, and pressure at 400kPa and 850kPa respectively, where the temperature is ambient temperature. This article includes the principle of wet gas meter development, the experimental matrix, the signal processing techniques and the achieved results. On the basis of the results it is suggested that the slotted orifice couple with a trained neural network may provide a simple but efficient solution to the wet gas meter development.

Natural Gas Storage in Wet Active Carbons-A Report on Research Progress

Storing natural gas in wet active carbon is a recently proposed method. The research progress shows that this method considerably decreases the storage pressure while maintaining the storage capacity equal to or even higher than compressed natural gas （CNG）. There is no requirement of pre-sifting any component out of natural gas for the storage, and the thermal effect on fast charging/discharging has almost no effect on the storage capacity. The charging and discharging processes are reversible and show good dynamic behavior. Although the storage temperature is a little lower than the ambient, the new method seems technically and costly more competitive than the available methods.

Experimental study on performance of flow & desulfurisation of a gas-liquid screen scrubber for wet flue gas desulfurization

In the paper, the gas-liquid two-phase flow performance and desulfurisation performance of the gas-liquid screen scrubber were experimentally studied when limestone was used as absorbent. Experiments were carried out at varying the flue gas velocity and slurry flux in concurrent and countercurrent tower respectively. The experimental results showed that the flow resistance of absorber increased rapidly with an increase of the flue gas velocity whether in concurrent or in countereurrent tower, and the up trend of the flow resistance in the cotmtercurrent tower was higher than those in the concurrent one. The influence of the flue gas velocity on the flow resistance of absorber was more than those of the slurry flux density. Whether in the concurrent tower or in the cotmtercurrent one, increasing the flue gas velocity or the slurry flux density would enhance the desulphurization efficiency. The influence of the slurry flux density on the desulfurisation efficiency was greater than those of the flue gas velocity.

Wet flue gas desulfurization performance of 330 MW coal-fired power unit based on computational fluid dynamics region identification of flow pattern and transfer process

Wet Flue Gas Desulfurization(WFGD)unit based upon spray scrubber has beenwidely employed to control SO_(2) emissions from flue gas in coal-fired power plant.To clarify the dependence of desulfurization performance on inter-phase transfer behaviors with non-ideal contacting patterns of flue gas and slurry droplets,three regions in spray scrubber are distinguished in terms of gas-slurry flow structures using CFD method in the Eulerian-Lagrangian framework.A comprehensive model is established by involving the transfer process between two phases and chemical reactions in aqueous phase,which is validatedwith the measured data froma WFGD scrubber of 330 MW coal-fired power unit.Numerical results show that the overall uniformity degree of flue gas in whole scrubber is largely determined by the force-balanced droplets in the middle part of scrubber,which is dominated by counter-current mode.Both momentum transfer behavior and SO_(2) chemical absorption process present the synchronicity with the evolution of gas-slurry flow pattern,whilst the heat transfer together with H_(2)O evaporation has little effect on overall absorption process.Three regions are firstly defined as Gas Inlet Region(GIR),Dominant Absorption Region(DAR)and Slurry Dispersed Region(SDR)from the bottom to top of scrubber.SO_(2) is mainly scrubbed in DAR,which provides much more intensive interaction between two phases compared to GIR or SDR.A better understanding of the desulfurization process is obtained from the fundamental relationship between transport phenomena and chemical reactions based upon the complicated hydrodynamics of gas-slurry two-phase flow,which should be useful for designing and optimizing the scrubber in coal-fired power unit.

Experimental study on prediction model of wet gas pressure drop across single-orifice plate in horizontal pipes in the low gas phase Froude number region

The pressure drop prediction of wet gas across single-orifice plate in horizontal pipes had been solved satisfactorily under an annular-mist flow in the upstream of orifice plates.However,this pressure drop prediction is still not clearly determined when the upstream is in an intermittent flow or stratified flow,which is corresponding to a region of low FrG(gas phase Froude number)in the flow pattern map of wet gases.In this study,the wet gas pressure drop across a single-orifice plate was experimentally investigated in the low FrG region.By the experiment,the flow pattern transition in the downstream of single-orifice plates,as well as the effects of FrG and FrL(liquid phase Froude number)on UG(gas phase multiplier),were determined and compared when the upstream is in the flow pattern transition and the stratified flow region,respectively.Prediction performances were examined on the available pressure drop models.It was found that no model could be capable of jointly predicting the wet gas pressure drop in the low FrG region with an acceptable accuracy.With a new method of correlating FrG and FrL simultaneously,new correlations were proposed for the low FrG region.Among which the modified Chisholm model shows the best prediction accuracies,with the prediction deviations of UG being within 7%and 3%when the upstream is in flow pattern transition and stratified flow region,respectively.

Noninvasive Flow Regime Identification for Wet Gas Flow Based on Flow-induced Vibration

A novel noninvasive approach, based on flow-induced vibration, to the online flow regime identification for wet gas flow in a horizontal pipeline is proposed. Research into the flow-induced vibration response for the wet gas flow was conducted under the conditions of pipe diameter 50 mm, pressure from 0.25 MPa to 0.35 MPa, Lockhart-Martinelli parameter from 0.02 to 0.6, and gas Froude Number from 0.5 to 2.7. The flow-induced vibration signals were measured by a transducer installed on outside wall of pipe, and then the normalized energy features from different frequency bands in the vibration signals were extracted through 4-scale wavelet package transform. A "binary tree" multi-class support vector machine(MCSVM) classifier, with the normalized feature vector as inputs, and Gaussian radial basis function as kernel function, was developed to identify the three typical flow regimes including stratified wavy flow, annular mist flow, and slug flow for wet gas flow. The results show that the method can identify effectively flow regimes and its identification accuracy is about 93.3%. Comparing with the other classifiers, the MCSVM classifier has higher accuracy, especially under the case of small samples. The noninvasive measurement approach has great application prospect in online flow regime identification.

Removal of SO_2 from flue gas using Bayer red mud:Influence factors and mechanism

The absorbent composing of Bayer red mud and water was prepared and applied to removing SO2 from flue gas.Effects of the ratio of liquid to solid(L/S),the absorption temperature,the inlet SO2 concentration,the O2 concentration,SO4^2-and other different components of Bayer red mud on desulfurization were conducted.The mechanism of flue gas desulfurization was also established.The results indicated that L/S was the prominent factor,followed by the inlet SO2 concentration and the temperature was the least among them.The optimum condition was as follows:L/S,the temperature and the SO2 concentration were 20:1,25℃and 1000 mg/m^3,respectively,under the gas flow of 1.5 L/min.The desulfurization efficiency was not significantly influenced when O2 concentration was above 7%.The accumulation of SO4^2-inhibited the desulfurization efficiency.The alkali absorption and metal ions liquid catalytic oxidation were involved in the process,which accounted for 98.61%.

Dynamic optimization oriented modeling and nonlinear model predictive control of the wet limestone FGD system

Nonlinear model predictive control(NMPC)scheme is an effective method of multi-objective optimization control in complex industrial systems.In this paper,a NMPC scheme for the wet limestone flue gas desulphurization(WFGD)system is proposed which provides a more flexible framework of optimal control and decision-making compared with PID scheme.At first,a mathematical model of the FGD process is deduced which is suitable for NMPC structure.To equipoise the model’s accuracy and conciseness,the wet limestone FGD system is separated into several modules.Based on the conservation laws,a model with reasonable simplification is developed to describe dynamics of different modules for the purpose of controller design.Then,by addressing economic objectives directly into the NMPC scheme,the NMPC controller can minimize economic cost and track the set-point simultaneously.The accuracy of model is validated by the field data of a 1000 MW thermal power plant in Henan Province,China.The simulation results show that the NMPC strategy improves the economic performance and ensures the emission requirement at the same time.In the meantime,the control scheme satisfies the multiobjective control requirements under complex operation conditions(e.g.,boiler load fluctuation and set point variation).The mathematical model and NMPC structure provides the basic work for the future development of advanced optimized control algorithms in the wet limestone FGD systems.

Gas cyclone-liquid jet absorption separator used for treatment of tail gas containing HCl in titanium dioxide industry

In the titanium dioxide industry,there is a lack of a low-cost and high-efficiency treatment method for chloride containing tail gas.In this paper,the removal of HCl from the titanium dioxide industry by gas cyclone-liquid jet separator was studied,while Ca(OH)_(2),Na_(2)CO_(3),NaOH solution,and water were used as absorbents.This paper investigated the influence of gas cyclone-liquid jet separator’s various process parameters on the removal rate of hydrogen chloride gas.The mechanism of mass transfer in the process of removing hydrogen chloride was discussed,and the effect and feasibility of HCl gas removal in the gas cyclone-liquid jet absorption separator were studied.The results showd that the removal efficiency of hydrogen chloride maintained above 95%,up to 99.9%,and the total mass transfer coefficient reached0.28 mol·m^(-3)·s^(-1)·k Pa^(-1).Under the same conditions,the absorption effect and total mass transfer coefficient of weak basic absorption liquid can be greatly improved by increasing the flow rate of absorption liquid,but the absorption effect and total mass transfer coefficient of strong alkaline absorption liquid can’t be improved obviously.The larger the inlet gas volume,the higher the gas concentration,the lower the absorption efficiency and the lower the total volumetric mass transfer coefficient.

Wet air oxidation treatment of H-acid wastewater

This paper presents the effect of reaction factors on wet air oxidation(WAO) of H acid wastewater. Higher COD Cr removal were observed at low initial pH, high reaction temperature and no addition of Na 2SO 4. Initial oxygen pressure P O 2 should be consistent with the initial H acid concentration. The changes of some indexes were also studied. A significant initial (about 10 min) rapid reduction in COD Cr was observed at 200℃ and 250℃. The decline of pH and the increase of SO 2- 4 concentration were found in all the experiments. Some formic acid and large amount of acetic acid were detected in the treated solution in this study. The analysis of off gas indicated undetectable amount of SO 2 and nitrogen oxides. The biodegradability of H acid solution was greatly improved after WAO treatment. The ratio of BOD 5/COD Cr increased from initial 3 4% to 33 3% after one hour reaction at 160℃ and 3 MPa initial oxygen pressure(initial H acid concentration:10 g/L, mixing speed:300 r/min). The result of WAO of H acid production wastewater was similar to that of WAO of H acid pure compound in distilled water.

Evaluation of the Gas Turbine Inlet Temperature with Relation to the Excess Air

This paper shows the effect of excess air on combustion gas temperature at turbine inlet, and how it determines power and thermal efficiency of a gas turbine at different pressure ratios and excess air. In such a way an analytic Equation that allows calculating the turbine inlet temperature as a function of excess air, pressure ratio and relative humidity is given. Humidity Impact on excess air calculation is also analyzed and presented. Likewise it is demonstrated that dry air calculations determine a higher level for calculations that can be performed on wet air.

Experimental research on influencing factors of wet removal of NO from coal-fired flue gas by UV/H_2O_2 advanced oxidation process

Wet removal of NO from coal-fired flue gas by UV/H2O2 Advanced Oxidation Process (AOP) were investigated in a self-designed UV-bubble reactor. Several main influencing factors (UV intensity, H2O2 initial concentration, initial pH value, solution temperature, NO initial concentration, liquid-gas ratio and O2 percentage content) on the NO removal efficiency were studied. The results showed that UV intensity, H2O2 initial concentration, NO initial concentration and liquid-gas ratio are the main influencing factors. In the best conditions, the highest NO removal efficiency by UV/H2O2 advanced oxidation process could reach 82.9%. Based on the experimental study, the influencing mechanism of the relevant influencing factors were discussed in depth.

Effect of wet flue gas desulfurization(WFGD) on fine particle(PM_(2.5)) emission from coal-fired boilers

In this study, the characteristics of fine particles before and after wet flue gas desulfurization(WFGD) in three coal-fired heating boilers in northern China were investigated by using a dilution-based emission sampling experimental system. The influences of the WFGD process on the mass and number concentrations as well as the chemical composition of fine particles were analyzed. The removal efficiency of desulfurization processes on particulate matter mass was 30.06%–56.25% for the three study units. The WFGD had a great influence on the size distributions of particle mass concentration and number concentration. A significant increase in the number and mass concentration of particles in the size range of 0.094–0.946 μm was observed. The watersoluble ion content accounted for a very large proportion of PM_(2.5) mass, and its proportion in PM_(2.5) increased from 28.39%–41.08% to 48.96%–61.21% after the WFGD process for the three units. The desulfurizing process also drastically increased the proportion of cation component(Ca^(2+) for unit A, Mg^(2+) for unit B, and Na+for unit C) and the proportion of SO_4^(2-) in PM_(2.5), and it increased the CE/AE values of PM_(2.5) from 0.82–0.98 to 0.93–1.27 for the three study units.

Influence of Chromium on Corrosion Behavior of Low-alloy Steel in Cargo Oil Tank O_2-CO_2-SO_2-H_2S Wet Gas Environment

As international maritime organization （IMO） draft 289 was adopted to develop a low-alloy anti-corrosion steel for the deck of cargo oil tank and to understand corrosion mechanism, corrosion behavior of a low-alloy steel with chromium contents was studied in O2-CO2-SO2-H2 S wet gas environment. Corrosion rate was measured, and the microstructure and morphology of corrosion product film were characterized by scanning electron microscopy （SEM）. The phase and chemical composition of the corrosion product film were investigated by X-ray diffraction （XRD） and energy dispersive spectroscopy （EDS）, respectively. The effect of misorientation distribution on corro- sion resistance of steel was evaluated by electron backscattered diffraction （EBSD）. The results showed that corro- sion rate decreased with increasing chromium content in the low-alloy steel, and the corrosion type was general corrosion. The phenomenon of chromium enrichment was found in corrosion product film consisting of a-FeOOH, γ- FeOOH, sulphur, FeS2 and Fel-xS. The increase of chromium content decreases the amount of high-angle grain boundaries, thus resulting in the improvement of corrosion resistance.

Transformation and removal of ammonium sulfate aerosols and ammonia slip from selective catalytic reduction in wet flue gas desulfurization system

Selective catalytic reduction(SCR) denitration may increase the emission of NH4+and NH3.The removal and transformation characteristics of ammonium sulfate aerosols and ammonia slip during the wet flue gas desulfurization(WFGD) process, as well as the effect of desulfurization parameters, were investigated in an experimental system equipped with a simulated SCR flue gas generation system and a limestone-based WFGD system.The results indicate that the ammonium sulfate aerosols and ammonia slip in the flue gas from SCR can be partly removed by slurry scrubbing, while the entrainment and evaporation of desulfurization slurry with accumulated NH4+will generate new ammoniumcontaining particles and gaseous ammonia.The ammonium-containing particles formed by desulfurization are not only derived from the entrainment of slurry droplets, but also from the re-condensation of gaseous ammonia generated by slurry evaporation.Therefore,even if the concentration of NH4+in the desulfurization slurry is quite low, a high level of NH4+was still contained in the fine particles at the outlet of the scrubber.When the accumulated NH4+in the desulfurization slurry was high enough, the WFGD system promoted the conversion of NH3 to NH4+and increased the additional emission of primary NH4+aerosols.With the decline of the liquid/gas ratio and flue gas temperature, the removal efficiency of ammonia sulfate aerosols increased, and the NH4+emitted from entrainment and evaporation of the desulfurization slurry decreased.In addition, the volatile ammonia concentration after the WFGD system was reduced with the decrease of the NH4+concentration and p H values of the slurry.

Investigation on the relationship between the fine particle emission and crystallization characteristics of gypsum during wet flue gas desulfurization process

The relationship between the fine particles emitted after desulfurization and gypsum crystals in the desulfurization slurry was investigated,and the crystallization characteristics varying with the operation parameters and compositions of the desulfurization slurry were discussed.The results showed that the fine particles generated during the desulfurization process were closely related to the crystal characteristics in the desulfurization slurry by comparison of their morphology and elements. With the higher proportion of fine crystals in the desulfurization slurry,the number concentration of fine particles after desulfurization was increased and their particle sizes were smaller,indicating that the optimization of gypsum crystallization was beneficial for the reduction of the fine particle emission. The lower p H value and an optimal temperature of the desulfurization slurry were beneficial to restrain the generation of fine crystals in the desulfurization slurry. In addition,the higher concentrations of the Fe3＋ions and the F- ions in the desulfurization slurry both promoted the generation of fine crystals with corresponding change of the morphology and the effect of the Fe3＋ ions was more obvious.With the application of the desulfurization synergist additive,it was beneficial for the inhibition of fine crystals while the thinner crystals were generated.

Calculating densities and viscosities of natural gas with a high content of C_(2+) to predict two-phase liquid-gas flow pattern

The paper is devoted to the two-phase flow simulation.The gas-condensate mixture flow in a horizontal pipe under high pressure is considered.The influence of the equation of state(EOS)choice for mixture properties modelling on the flow regime calculation results is studied for gas with high content of methane homologues.An analytical overview of the methods to predict the flow pattern is provided.Based on this analysis,two techniques are selected.For these techniques,values of density and viscosity for each phase are required.Density calculation for the gas phase is performed with Van der Waals based EOS.The propriate EOS is selected based on studies of calculation errors for test mixtures.Calculation of liquid phase density is done by means of Patela-Teja and Guo-Du equations,two different models are considered for viscosity estimation.The flow patterns of gas-condensate mixture in a range of temperatures and pressures are calculated and verified via probability map.The results of study allow to recommend the Brusilovsky EOS for calculation of densities for similar gas mixtures and make more rigorous flow regime evaluation.The probability map shows that for the chosen composition and parameters of media the flow pattern is mostly transitional between segregated and annular independent from EOS.

Field Studies on the Removal Characteristics of Particulate Matter and SO_(x) in Ultra-Low Emission Coal-Fired Power Plant

In order to reduce the environmental smog caused by coal combustion,air pollution control devices have been widely used in coal-fired power plants,especially of wet flue gas desulfurization(WFGD)and wet electrostatic precipitator(WESP).In this work,particulate matter with aerodynamic diameter less than 10μm(PM_(10))and sulfur oxides(SO_(x))have been studied in a coal-fired power plant.The plant is equipped with selective catalytic reduction,electrostatic precipitator,WFGD,WESP.The results show that the PM_(10)removal efficiencies in WFGD and WESP are 54.34%and 50.39%,respectively,and the overall removal efficiency is 77.35%.WFGD and WESP have effects on the particle size distribution.After WFGD,the peak of particles shifts from 1.62 to 0.95μm,and the mass concentration of fine particles with aerodynamic diameter less than 0.61μm increases.After WESP,the peak of particle size shifts from 0.95 to 1.61μm.The differences are due to the agglomeration and growth of small particles.The SO_(3)mass concentration increases after SCR,but WFGD has a great influence on SO_(x)with the efficiency of 96.56%.WESP can remove SO_(x),but the efficiency is 20.91%.The final emission factors of SO_(2),SO_(3),PM_(1),PM_(2.5)and PM_(10)are 0.1597,0.0450,0.0154,0.0267 and 0.0215(kg·t^(−1)),respectively.Compared with the research results without ultra-low emission retrofit,the emission factors are reduced by 1~2 orders of magnitude,and the emission control level of air pollutants is greatly improved.