Microscopic and macroscopic atomization characteristics of a pressure-swirl atomizer,injecting a viscous fuel oil

Combustion of heavy fuels is one of the main sources of greenhouse gases, particulate emissions, ashes, NOxand SOx. Gasification is an advanced and environmentally friendly process that generates combustible and clean gas products such as hydrogen. Some entrained flow gasifiers operate with Heavy Fuel Oil(HFO) feedstock. In this application, HFO atomization is very important in determining the performance and efficiency of the gasifiers.The atomization characteristics of HFO(Mazut) discharging from a pressure-swirl atomizer(PSA) are studied for different pressures difference(Δp) and temperatures in the atmospheric ambient. The investigated parameters include atomizer mass flow rate( _m), discharge coefficient(CD), spray cone angle(θ), breakup length(Lb), the unstable wavelength of undulations on the liquid sheet(λs), global and local SMD(sauter mean diameter) and size distribution of droplets. The characteristics of Mazut sheet breakup are deduced from the shadowgraph technique. The experiments on Mazut film breakup were compared with the predictions obtained from the liquid film breakup model. Validity of the theory for predicting maximum unstable wavelength was investigated for HFO(as a highly viscous liquid). A modification on the formulation of maximum unstable wavelength was presented for HFO. SMD decreases by getting far from the atomizer. The measurement for SMD and θ were compared with the available correlations. The comparisons of the available correlations with the measurements of SMD andθ show a good agreement for Ballester and Varde correlations, respectively. The results show that the experimental sizing data could be presented by Rosin-Rammler distributions very well at different pressure difference and temperatures.     

Numerical simulation of heavy fuel oil atomization using a pulsed pressure-swirl injector

It is known that increasing the injection pressure reduces the breakup length and the droplet size. Adding pulses, on the other hand, helps to atomize the liquid into finer droplets, similar to air-assisted injectors but without altering the air-to-fuel concentration.To further reduce the droplet size and breakup length, a novel injector type, called ‘‘Pulsed Pressure-Swirl"(PPS), is introduced in this work, which is a combination of pressure-swirl and ultrasonic pulsed injectors. A pressure-swirl atomizer was designed and fabricated specifically for Mazut HFO(Heavy Fuel Oil). The droplet formation process and droplet size distribution have been studied experimentally(by shadowgraphy high speed imaging) and numerically(with the open-source Volume-of-Fluid code Gerris).Changing liquid injection pressure effect on the spray angle and film thickness has been quantified.These simulations have been used to study the primary breakup process and quantify the droplet size distributions, using different injection pulse frequencies and pressures.The numerical results have revealed that the new injector concept successfully produces finer droplets and results in a decrease in the breakup length, especially when applying high pulse frequencies, with no significant changes in the spray angle.     

Analytical study of the effluents from a high-temperature entrained flow gasifier

Effluents from a high temperature, high pressure, entrained flow gasifier were analysed for possible inorganic and organic pollutants. The effluents and product gases from this type of reactor are very clean compared to those produced in established commercial gasification processes. The only major potential pollutants are the particulate matter and NH₄⁺ in the scrubber water, the bottom ash, and the H₂S and HCN in the product and flash gases. All of the non-volatile organic compounds produced are quantitatively adsorbed by the particulate matter in the scrubber water. Increasing the pressure and decreasing the $\text{O}{}_2\text{coal}$ ratio tended to reduce pollutants in the effluents and increase coal conversion efficiency.     

Numerical study on the coal gasification characteristics in an entrained flow coal gasifier

The coal gasification process of a slurry feed type, entrained-flow coal gasifier was numerically predicted in this paper. By dividing the complicated coal gasification process into several simplified stages such as slurry evaporation, coal devolatilization and two-phase reactions coupled with turbulent flow and two-phase heat transfer, a comprehensive numerical model was constructed to simulate the coal gasification process. The k– turbulence model was used for the gas phase flow while the Random-Trajectory model was applied to describe the behavior of the coal slurry particles. The unreacted-core shrinking model and modified Eddy break-up (EBU) model, were used to simulate the heterogeneous and homogeneous reactions, respectively. The simulation results obtained the detailed information about the flow field, temperature and species concentration distributions inside the gasifier. Meanwhile, the simulation results were compared with the experimental data as a function of O₂/coal ratio. It illustrated that the calculated carbon conversions agreed with the measured ones and that the measured quality of the syngas was better than the calculated one when the O₂/coal ratio increases. This result was related with the total heat loss through the gasifier and uncertain kinetics for the heterogeneous reactions.     

Gasification of biomass wastes in an entrained flow gasifier: Effect of the particle size and the residence time

Experimental tests in an entrained flow gasifier have been carried out in order to evaluate the effect of the biomass particle size and the space residence time on the gasifier performance and the producer gas quality. Three types of biomass fuels (grapevine pruning and sawdust wastes, and marc of grape) and a fossil fuel (a coal-coke blend) have been tested. The results obtained show that a reduction in the fuel particle size leads to a significant improvement in the gasification parameters. The thermochemical characterisation of the resulting char-ash residue shows a sharp increase in the fuel conversion for particles below 1 mm diameter, which could be adequate to be used in conventional entrained flow gasifiers. Significant differences in the thermochemical behaviour of the biomass fuels and the coal-coke blend have been found, especially in the evolution of the H₂/CO ratio with the space time, mainly due to the catalytic effect of the coal-coke ash. The reaction temperature and the space time have a significant effect on the H₂/CO ratio (the relative importance of each of these parameters depending on the temperature), this value being independent of the fuel particle size.     

On the scaling-up of a two-stage air blown entrained flow coal gasifier

A two-stage air blown entrained flow gasifier is being developed in Japan for the IGCC process. However, its scale-up up faces significant difficulties because of ash/slag deposition problems. The ash/slag deposition in the gasifier depends on both the ash properties and entrainment produced by the swirling gas flow. Therefore, the flow hydrodynamics are critical issues for the control of the ash behavior. In this paper, a comprehensive simulation model is used to examine the effects of the gasifier geometry and jet configuration on the flow hydrodynamics in order to control the ash deposition on the gasifier walls. A swirl number for the multi-stage injection swirling gas flow is defined and proved to be the most important hydrodynamic scaling law for the entrained flow gasifier.     

Experimental and numerical study on improvement performance by wave parallel flow field in a proton exchange membrane fuel cell

The performance and operation stability of proton exchange membrane fuel cells (PEMFCs) are closely related to the transportation of reactants and water management in the membrane electrode assembly (MEA) and flow field. In this paper, a new three-dimensional wave parallel flow field (WPFF) in cathode was designed and analyzed throughout simulation studies and an experimental method. The experimental results show that the performance of PEMFC with WPFF outperforms that of PEMFC with straight parallel flow field (SPFF). Specifically, the peak power density increased by 13.45% for the PEMFC with WPFF as opposed to PEMFC with SPFF. In addition, the flow field with area of 11.56 cm² was formed by the assembly of transparent end plate used for cathode and the traditional graphite plate used for anode. To understand the mechanism of the novel flow field improving the performance of PEMFC, a model of PEMFC was proposed based on the geometry, operating conditions and MEA parameters. The thickness of gas diffusion layers (GDL), catalytic layers (CL) and proton exchange membrane were measured by scanning electron microscope. The simulation result shows that compared with SPFF, the WPFF based PEMFC promote the oxygen transfer from flow channel to the surface of CL through GDL, and it was beneficial to remove the liquid water in the flow channel and the MEA.     

Synthesis and mechanism analysis of a new oil soluble viscosity reducer for flow improvement of Chenping heavy oil

Oil soluble viscosity reducers have gradually attracted the attention of petrochemical research due to their cleanliness and high efficiency. Considering the high viscosity and non-Newtonian fluid properties of Chenping heavy oil found in China, a series of new oil soluble viscosity reducers with different proportions and molecular weights were prepared by free radical polymerization using octadecyl acrylate, 2-allylphenol and N-methylolacrylamide as monomers. The viscosity reducer was applied t...     

Influence of Atomizing Parameters on Droplet Properties in a Pulse Combustion Spray Dryer

A pulse combustor employed in a spray-drying system offers a new approach for liquid atomization that yields high-quality powders at low cost. Using a pulse combustion atomizer, there is no need for any form of nozzle dispersion and its atomization mechanism differs from those of conventional atomizers, such as rotary atomizers and pressure and pneumatic nozzles. In this work, based on the analysis of atomization mechanism, experiments of unsteady pulsating atomization were carried out in an experimental system of a Helmholtz-type pulse combustor. An optical analyzer was used for measuring the mean diameter of atomized droplet and droplet distribution. The effects of liquid feed rate, air flow oscillatory frequency, and liquid viscosity on atomized droplet size and size distribution were investigated and analyzed. The results indicate that the uniform droplet size distribution can be obtained under the conditions of a low feed rate, high-frequency pulsating flow, and moderate viscosity. The range of the droplets' Sauter mean diameter (SMD) is between 50 and 80 µm. The pulsating air flow from the pulse combustor can be used to atomize liquid or slurry without a nozzle and the atomizing quality can meet the requirements of spray drying.     

Influence of Atomizing Parameters on Droplet Properties in a Pulse Combustion Spray Dryer

A pulse combustor employed in a spray-drying system offers a new approach for liquid atomization that yields high-quality powders at low cost. Using a pulse combustion atomizer, there is no need for any form of nozzle dispersion and its atomization mechanism differs from those of conventional atomizers, such as rotary atomizers and pressure and pneumatic nozzles. In this work, based on the analysis of atomization mechanism, experiments of unsteady pulsating atomization were carried out in an experimental system of a Helmholtz-type pulse combustor. An optical analyzer was used for measuring the mean diameter of atomized droplet and droplet distribution. The effects of liquid feed rate, air flow oscillatory frequency, and liquid viscosity on atomized droplet size and size distribution were investigated and analyzed. The results indicate that the uniform droplet size distribution can be obtained under the conditions of a low feed rate, high-frequency pulsating flow, and moderate viscosity. The range of the droplets' Sauter mean diameter (SMD) is between 50 and 80 µm. The pulsating air flow from the pulse combustor can be used to atomize liquid or slurry without a nozzle and the atomizing quality can meet the requirements of spray drying.     

水冷壁气化炉熔渣流动的实验研究

水冷壁气流床气化炉的核心思想是"以渣抗渣",因此对熔渣沉积形态与流动规律的研究尤为重要。文中在实验室小型水冷壁气化炉热模装置上,以神府煤气化灰渣、柴油和纯氧气为原料模拟气流床水冷壁气化实验,采用高温内窥镜并结合数字图像处理技术研究了熔渣的沉积、流动过程。实验结果表明:气化炉操作温度高于熔渣临界黏度温度时,渣层表面灰渣处于熔融状态;运动到壁面处的灰渣颗粒主要被熔融渣层吸收;熔渣的流动速度和渣层表面温度有关系,渣层表面温度越高,熔渣流动速度越大。在实验条件下,熔渣层表面速度约为0.002 6—0.003 m/s。     

稠油化学降黏实验研究

以塔河某稠油为样,在优化条件下进行降黏实验研究。试油40g,降黏剂WWS质量分数0.4%,碳酸钠质量分数0.2%,加水量20mL(矿化度5 000mg/L),实验温度65℃,搅拌下反应80min,稠油的黏度从65℃时的5 620mPa.s降至180mPa.s,降黏率达到96%以上,改善了稠油的流动性。     

Combustion of sprayed liquid fuel in a swirling flow

A physicomathematical model and results of numerical studies of aerodynamics and combustion of liquid fuel in a coaxial swirling flow of a gaseous oxidizer are presented. The characteristics of liquid-fuel spraying by a centrifugal injector were determined on the basis of experimental data obtained under isothermal conditions. The influence of flow swirling on the burner characteristics is analyzed.__________Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 2, pp. 26–37, March–April, 2005.     

Behaviour of heavy metals in the partial oxidation of heavy fuel oil

The behaviour of heavy metals in the partial oxidation of heavy fuel oils under a pressure of up to 100 bar (10 MPa) has been investigated. The tests were carried out in a 5 MW HP POX (High Pressure Partial Oxidation) test plant, that is operated by the IEC (Department of Energy Process Engineering and Chemical Engineering, TU Bergakademie Freiberg) in cooperation with Lurgi GmbH. In several test campaigns preheated oil with a viscosity of up to 300 cSt (= 300 mm²/s) at the burner inlet has been gasified. The heavy metals nickel Ni, iron Fe and vanadium V occur in heavy residual oils in considerable concentration and may seriously impact the gasification itself and the synthesis gas conditioning and usage. While iron is largely recovered in the gasification residue, the recovery rates of nickel and vanadium depend on the process conditions. Volatile nickel compounds were detected in the raw synthesis gas. It was found that an incomplete carbon conversion enables the capture of nickel Ni and vanadium V in the solid residue phase and can thus mitigate the problem of volatile metal compounds in the raw synthesis gas.     

Adsorptive removal of nitrogen compounds from fuel oil by a poly ionic liquid PVIm-PXDC

ABSTRACT

A poly ionic liquid, poly(1-vinyl imidazole)-p-xylylene dichloride (PVIm-PXDC), was synthesized and used for fuel oil denitrogenation. The structure of PVIm-PXDC was characterized and the denitrogenation performance was investigated. Results indicate that the pseudo-second-order kinetic model and Langmuir model are appropriate to describe the adsorption kinetics and thermodynamics, respectively. The adsorption ability of PVIm-PXDC for different nitrogen compounds follows the order of indole > pyrrole > quinoline > pyridine. The equilibrium adsorption amount decreased about 10% for all the nitrogen compounds after six regeneration cycles and the denitrogenation and regeneration processes have no influence on the structure of PVIm-PXDC.     

Comparative study of different hydro-dynamic flow in microbial fuel cell stacks

This work has investigated the scale-up potential of microbial fuel cells (MFCs) under stacking mode. Stacking was done in batch mode and continuous mode. Batch feeding mode stacks were operated in electrical series (S) and parallel (P) mode. Continuous feeding mode stacks were kept in electrically par-allel mode with different hydro-dynamic patterns. The two continuous stacks were connected hydro-dynamically in series (i.e. Parallel Dependent;PD) and parallel (i.e. Parallel Independent;PID) configura-tions. The performance of the continuous stacks was evaluated on the basis of COD consumption rate, power generation and coulombic efficiency. PID obtained highest power (0.47 mW) which was approx-imately 3.6 times that of PD configuration (0.13 mW). The rate of COD consumption was also highest in PID stack (3091.75 mg·L-1·d-1). Coulombic efficiency of the PID stack was 14.26％ which was approxi-mately 292.8％ of the PD stack. The results confirmed that the parallel electrical connection hybridized with the independent hydro-dynamic flow gives the best possible results when working with stacking of MFCs.     

Investigation of fuel spray atomization in a DI heavy-duty diesel engine and comparison of various spray breakup models

In the last decade 3D-CFD has been successfully established for the simulation of IC-engine fuel spray formation and propagation processes. The accuracy of the calculation results, however, strongly depends on the models adopted for simulation of the primary and secondary atomization processes. Hence, careful validations of the individual models serve as major prerequisites for the successful analysis and optimization of high-pressure sprays in diesel engines. In the present work, a CFD code has been used to study the detailed modeling of spray and mixture formation in a caterpillar heavy-duty diesel engine. With respect to the liquid-phase, spray calculations are based on a statistical method referred to as the Discrete Droplet Method (DDM). This paper presents a comparison of four Lagrangian fuel spray breakup models that are in use with commercial softwares in diesel engine simulation. In this paper, we tried to highlight this models prediction difference for sample case, compare their result and explain some possible reasons for differences. The predicted results are validated by comparing with existing experimental data. A good agreement between the predicted and experimental values ensures the accuracy of the numerical predictions collected with the present work.     

Experimental study of a reverse flow catalytic converter for a dual fuel engine

Theperformance of a reverse flow catalytic converter for a methane/diesel dual fuel engine, a monolith honeycomb converter with palladium catalyst washcoat, was evaluated under steady and transient engine conditions. The reverse flow converter provided superior performance (that is, higher conversion of pollutants) for several steady engine operations, compared with unidirectional flow operation. For transient operation following a step change in engine operating conditions, reverse flow is better than unidirectional flow when the change in engine operation results in a reduction in exhaust gas temperature. For an increasing exhaust gas temperature, reverse flow decreased the rate of increase of reactor temperature. The reverse flow converter was tested using the transient Japanese 6‐Mode tests. Reverse flow operation gave higher conversions than unidirectional flow for this test, with a switch time of 5 s giving the best results.     

Experimental investigation and modelling of CO2-foam flow in heavy oil systems

In this work, the C_14-16 alpha olefin sulphonate (AOS) surfactant, octylphenol ethoxylate (TX-100), and methyl bis[Ethyl(Tallowate)]-2-hydroxyethyl ammonium methyl sulphate (VT-90) surfactant were selected as representatives of anionic, nonionic, and cationic surfactant to stabilize foam. The effects of surfactant concentration and gas/liquid injection rates on foam performance were examined by performing a series of oil-free foam flow tests by injecting CO₂ and a foaming surfactant simultaneously into sandpacks. Foam flooding was conducted as a tertiary enhanced oil recovery (EOR) method after conventional water flooding and surfactant flooding. Furthermore, a new method was proposed to determine the residual oil saturation. The foam stability in the presence and absence of heavy oil was studied by a comparative evaluation of the mobility reduction factor (F_MR) in both cases. The foam fractional flow modelling by Dholkawala and Sarma^[36] was modified based on experimental results obtained in this study. The range of the ratio of two important model parameters (C_g/C_c) at various foam qualities was determined and could be used for large-scale predictions. The results showed that during the oil-free foam displacement experiments higher foam apparent viscosities () were attained at lower gas flow rates and the maximum was attained at a total gas and liquid injection rate of 0.25 cm³/min with a gas fractional flow ratio of 0.8 for the foam in the absence of oil. The presence of oil reduced the foam mobility reduction factors (F_MR) to different degrees with F_MR-_{without oil} / F_MR-_{with oil} ranging from 4.25–13.69, indicating that the oil had a detrimental effect on the foam texture. The foam flooding successfully produced an additional 8.1–21.52 % of OOIP, which can be attributed to the combined effect of increasing the pressure gradient and oil transporting mechanisms.