scholarly journals Thermodynamic modelling of the lead sintering roasting process

2019 ◽  
Vol 55 (1) ◽  
pp. 21-29
Author(s):  
Sánchez Rojas ◽  
Romero Serrano ◽  
Hernández Ramírez ◽  
Rodríguez López ◽  
Guzmán Almaguer ◽  
...  
Keyword(s):  
Gas Flow ◽  
Chemical Species ◽  
Packed Bed ◽  
Operating Conditions ◽  
Sintering Process ◽  
Gaseous Species ◽  
Proposed Model ◽  
Roasting Process ◽  
Simulation Strategy ◽  
Experimental Trials

This work proposes a simulation strategy of the lead sintering process assuming that it takes place in a horizontally moving packed bed with transverse air flow. Some local chemical reactions occur at rates that depend on the temperature, and chemical species formed in one volume stage will flow for further reaction in other stages. To simulate this process, the model reactor is divided into a number of sequential stages. Condensed species flow horizontally, and gaseous species leave each stage vertically. The compositions and temperatures of the species are calculated considering that the local thermodynamic equilibrium is reached in each stage without external heat transfer, apart from the gas flow, before moving on to the next stage. The model calculates the temperature profile along the sintering machine, the compositions of the sinter and the exhaust gas. The results of the proposed model were compared with sinter pot experimental trials and a reasonably good agreement was obtained. This model can be used to optimize the operating conditions of the lead sintering process.

scholarly journals CFD Steady Model Applied to a Biomass Boiler Operating in Air Enrichment Conditions

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2513
Author(s):  
Miguel Gómez ◽  
Rubén Martín ◽  
Joaquín Collazo ◽  
Jacobo Porteiro
Keyword(s):  
Gas Flow ◽  
Chemical Species ◽  
Experimental Tests ◽  
Packed Bed ◽  
Accurate Method ◽  
Combustion Products ◽  
Energy Performance ◽  
Thermal Conversion ◽  
Computational Effort ◽  
Operating Conditions

A numerical model is proposed to perform CFD simulations of biomass boilers working in different operating conditions and analyse the results with low computational effort. The model is based on steady fluxes that represent the biomass thermal conversion stages through the conservation of mass, energy, and chemical species in the packed bed region. The conversion reactions are combined with heat and mass transfer submodels that release the combustion products to the gas flow. The gas flow is calculated through classical finite volume techniques to model the transport and reaction phenomena. The overall process is calculated in a steady state with a fast, efficient, and reasonably accurate method, which allows the results to converge without long computation times. The modelling is applied to the simulation of a 30 kW domestic boiler, and the results are compared with experimental tests with reasonably good results for such a simple model. The model is also applied to study the effect of air enrichment in boiler performance and gas emissions. The boiler operation is simulated using different oxygen concentrations that range from 21% to 90% in the feeding air, and parameters such as the heat transferred, fume temperatures, and emissions of CO, CO2, and NOx are analysed. The results show that with a moderated air enrichment of 40% oxygen, the energy performance can be increased by 8%, CO emissions are noticeably reduced, and NOx remains practically stable.

Decomposition of Toluene, o-Xylene, Trichloroethylene, and Their Mixture Using a BaTiO3 Packed-Bed Plasma Reactor

1996 ◽  
Vol 1 (1) ◽  
Author(s):  
Toshiaki Yamamoto ◽  
Jen-Shih Chang ◽  
Alex A Berezin ◽  
Hitoshi Kohno ◽  
Shigeo Honda ◽  
...  
Keyword(s):  
Gas Flow ◽  
Plasma Reactor ◽  
Nonthermal Plasma ◽  
Packed Bed ◽  
Operating Conditions ◽  
Destruction Efficiency ◽  
Volatile Organic ◽  
Reactor Operating ◽  
Reactant Conversion ◽  
Plasma Technologies

AbstractNonthermal plasma technologies offer an innovative approach to the problem of decomposing various volatile organic compounds (VOCs). We focused on an AC-energized ferroelectric packed-bed plasma reactor to study the decomposition/destruction efficiency and byproduct analysis for toluene, o-xylene, trichloroethylene, and their mixture from 50 to 230 ppm in dry air. The effects of gas flow rate, concentration, moisture content, and reactor operating conditions on the decomposition and analysis of reactant conversion for each VOC were investigated for suitable applications of the emerging technology. Laboratory-scale packed-bed plasma technology was successfully demonstrated for the application of VOC control in semiconductor clean room environments.

Modeling the Transient VOC (toluene) Oxidation in a Packed-Bed Catalytic Reactor

2016 ◽  
Vol 14 (6) ◽  
pp. 1177-1185 ◽  
Author(s):  
Tristán Esparza-Isunza ◽  
Felipe López-Isunza
Keyword(s):  
Heat Transport ◽  
Gas Flow ◽  
Packed Bed ◽  
Operating Conditions ◽  
Packed Bed Reactor ◽  
Phase System ◽  
Transport Parameter ◽  
Catalytic Reactor ◽  
Toluene Oxidation ◽  
Reaction Fronts

Abstract A model is developed to study the transient behavior of a non-isothermal, non-adiabatic packed-bed reactor during VOC (toluene) oxidation with air on a mixed-oxide catalyst via Mars-van Krevelen kinetic scheme. The aim is to find a safe reactor design and operating conditions for VOC elimination, which has been collected in a battery of adsorption units from dilute VOC streams. Once each adsorption column is saturated, a non-isothermal desorption takes place, and the gas stream exiting the sequence of VOC desorption columns feeds continuously the catalytic reactor for VOC elimination. The reactor model describes a 2D two-phase system interacting through the gas-solid interphase, including convection and axial and radial dispersions of mass and heat. The simulations show that the gas flow velocity, and reactor and particle diameters, are key parameters to achieve a safe design, and that traveling reaction fronts in the packed-bed exist when a series of reversible stepwise changes are performed in the concentration and temperature at the feed, as a result of the transient balance between heat generation and heat elimination along the packed-bed. When comparing the perturbation in VOC concentration at the feed versus those in temperature, a large parametric sensitivity is observed for the latter case without the presence of multiple steady states. Due to the uncertainty in the values of the effective heat transport parameters, transient responses of different magnitude are observed for the same operating conditions when using heat transport parameter of different magnitude.

Nonempirical Apparent Permeability of Shale

2014 ◽  
Vol 17 (03) ◽  
pp. 414-424 ◽  
Author(s):  
H.. Singh ◽  
F.. Javadpour ◽  
A.. Ettehadtavakkol ◽  
H.. Darabi
Keyword(s):  
Fluid Flow ◽  
Pore Size ◽  
Flow Rate ◽  
Gas Flow ◽  
Operating Conditions ◽  
Pore Geometry ◽  
Apparent Permeability ◽  
Knudsen Flow ◽  
Proposed Model ◽  
Shale Reservoirs

Summary Physics of fluid flow in shale reservoirs cannot be predicted from standard flow or mass-transfer models because of the presence of nanopores, ranging in size from one to hundreds of nanometers, in shales. Conventional continuum-flow equations, such as Darcy's law, greatly underestimate the fluid-flow rate when applied to nanopore-bearing shale reservoirs. As a result of the existence of nanopores in shales, the molecular mean free path becomes comparable with the characteristic geometric scale, and we hypothesize that under this condition, Knudsen diffusion, in addition to correction for the slip boundary condition, becomes the dominant mechanism. Recently, a few models have been developed that use various empirical parameters to account for these modifications (Javadpour 2009; Civan 2010; Darabi et al. 2012). This paper aims to provide a different approach to modeling apparent permeability in shale reservoirs. The proposed model is analytical, free of any empirical coefficients, and has been derived without invoking the assumption of slip flow at the pore wall. Our model of apparent permeability represented by a single analytical equation, depends only on pore size, pore geometry, temperature, gas properties, and average reservoir pressure. The proposed model is valid for Knudsen numbers less than unity and it stands up under the complete operating conditions of a shale reservoir. Our model reasonably predicts results as reported by other models. Finally, the model shows that pore-surface roughness and mineralogy have a negligible influence on gas-flow rate, whereas pore geometry and pore size play a significant role in the proportion of diffusion in total flow rate. Our study shows that a combination of Darcy flow and Knudsen flow—ignoring the Klinkenberg effect—can describe gas flow for a range of Knudsen flow applicable to a shale-gas system.

Cometabolism in biofilm reactors

1995 ◽  
Vol 31 (1) ◽  
pp. 215-225 ◽  
Author(s):  
Gerald E. Speitel ◽  
Robert L. Segar
Keyword(s):  
Chlorinated Solvents ◽  
Packed Bed ◽  
Operating Conditions ◽  
Mixed Cultures ◽  
Treatment Technology ◽  
Hydraulic Residence Time ◽  
Slow Growth Rate ◽  
Biofilm Reactors ◽  
Aerobic Cometabolism ◽  
Degrading Bacteria

Aerobic cometabolism of chlorinated aliphatic solvents in biofilm reactors is a potential treatment technology for contaminated water and air streams. This research investigated cometabolism by pure and mixed cultures of methanotrophs and mixed cultures of phenol-degrading bacteria. Initial experiments with continuous-flow, packed-bed bioreactors proved unsuccessful; therefore, the major focus of the work was on sequencing biofilm reactors, which cycle between two modes of operation, degradation of chlorinated solvents and rejuvenation of the microbial population. Particular success was obtained with a mixed culture of phenol degraders in the treatment of chlorinated ethenes (e.g., trichloroethylene - TCE). Under the best operating conditions, 90% removal of TCE occurred at a 14-minute packed-bed hydraulic residence time. The bioreactors required only two, 1.5 h biomass rejuvenation periods per day to sustain this removal. Experiments with Methylosinus trichosporium OB3b were less successful because of the organism's slow growth rate, relatively poor ability to attach to surfaces, and its inability to successfully compete with other methanotrophs in the bioreactor environment. Overall, however, the research demonstrated the potential attractiveness of sequencing biofilm reactors in treating water contaminated with chlorinated solvents.

Degradation of Organophosphorus Pesticide in a Packed-Bed Plasma Reactor: Effects of Operating Parameters and Kinetics Study

2013 ◽  
Vol 781-784 ◽  
pp. 1637-1645 ◽  
Author(s):  
Ting Jun Ma ◽  
Yi Qing Xu
Keyword(s):  
Removal Efficiency ◽  
Flow Rate ◽  
Gas Flow ◽  
Plasma Reactor ◽  
Organophosphorus Pesticide ◽  
Packed Bed ◽  
Pulse Frequency ◽  
Gas Flow Rate ◽  
Peak Voltage ◽  
Initial Concentration

The degradation effectiveness and reaction kinetics of representative organophosphorus (OP) pesticide in a packed-bed plasma reactor have been studied. Important parameters, including peak voltage, pulse frequency, gas-flow rate, initial concentration, diameter of catalyst particles, and thickness of catalyst bed which influences the removal efficiency, were investigated. Experimental results indicated that rogor removal efficiency as high as 80% can be achieved at 35 kV with the gas flow rate of 800 mL/min and initial concentration of 11.2 mg/m3.The removal efficiency increased with the increase of pulsed high voltage, and pulse frequency, the decrease of the diameter of catalyst particles and the thickness of catalyst bed. Finally, a model was established to predict the degradation of the rogor, which generally can simulate the experimental measurements to some degree.

Break-Up of Threads From Laminar Open Channel Flow Influenced by Cross-Wind Gas Flow

2014 ◽  
Author(s):  
Jens Kamplade ◽  
Tobias Mack ◽  
Andre Küsters ◽  
Peter Walzel
Keyword(s):  
Size Distribution ◽  
Channel Flow ◽  
Gas Flow ◽  
Drop Size ◽  
Open Channel ◽  
Open Channel Flow ◽  
Drop Size Distribution ◽  
Operating Conditions ◽  
Breakup Process ◽  
Breakup Length

The breakup process of threads from laminar operating rotary atomizer (LamRot) is in the scope of this investigation. A similarity trail is used to investigate the influence of the thread deformation within a cross-wind flow on the thread breakup process. The threads emerge from laminar open channel flow while the liquid viscosity, the flow rate, the pipe inclination towards the gravity as well as the cross-wind velocity is varied. The breakup length and drop size distribution are analyzed by a back-light photography setup. The results thus obtained are compared with results of previous examination by Schröder [1] and Mescher [2]. It is found that the breakup length decreases and that the drop size grows with rising cross-wind intensity, while the width of the drop size distribution increases. At the same operating conditions, the breakup length for laminar open channel flow is smaller compared to completely filled capillaries. In contrast to this observation, the drop size distribution remains nearly unchanged. The critical velocity for the transition from axisymmetric to wind-induced thread breakup was found to be smaller than for completely filled capillaries.

Experimental Inverstigations On the Pressure Fluctuations in the Sealing Gap of Dry Gas Seals with Embedded Pressure Sensors

2021 ◽  
Author(s):  
Jingjing Luo ◽  
Dieter Brillert
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Static Pressure ◽  
Pressure Sensors ◽  
Operating Conditions ◽  
Test Facility ◽  
Experimental Investigations ◽  
Mechanical Seals ◽  
Process Gas ◽  
Sealing Gap

Abstract Dry gas lubricated non-contacting mechanical seals (DGS), most commonly found in centrifugal compressors, prevent the process gas flow into the atmosphere. Especially when high speed is combined with high pressure, DGS is the preferred choice over other sealing alternatives. In order to investigate the flow field in the sealing gap and to facilitate the numerical prediction of the seal performance, a dedicated test facility is developed to carry out the measurement of key parameters in the gas film. Gas in the sealing film varies according to the seal inlet pressure, and the thickness of gas film depends on this fluctuated pressure. In this paper, the test facility, measurement methods and the first results of static pressure measurements in the sealing gap of the DGS obtained in the described test facility are presented. An industry DGS with three-dimensional grooves on the surface of the rotating ring, where experimental investigations take place, is used. The static pressure in the gas film is measured, up to 20 bar and 8,100 rpm, by several high frequency ultraminiature pressure transducers embedded into the stationary ring. The experimental results are discussed and compared with the numerical model programmed in MATLAB, the characteristic and magnitude of which have a good agreement with the numerical simulations. It suggests the feasibility of measuring pressure profiles of the standard industry DGS under pressurized dynamic operating conditions without altering the key components of the seal and thereby affecting the seal performance.

Researches of technological mode of operation of gas wells with a single-lift elevator at a critical speed of upper flow

2021 ◽  
pp. 97-103
Author(s):  
R.A. Gasumov ◽  
◽  
E.R. Gasumov ◽  
Keyword(s):  
Gas Flow ◽  
Operating Conditions ◽  
Physical Parameters ◽  
Gas Wells ◽  
Gas Well ◽  
Field Development ◽  
Mode Of Operation ◽  
Water Drops ◽  
Liquid Flows ◽  
Technological Mode

The article discusses the modes of movement of gas-liquid flows in relation to the operating conditions of waterlogged gas wells at a late stage of field development. Algorithms have been developed for calculating gas well operation modes based on experimental work under conditions that reproduce the actual operating conditions of flooded wells of Cenomanian gas deposits. The concept of calculating the technological mode of operation of gas wells with a single-row elevator according to the critical velocity of the upward flow is considered based on the study of the equilibrium conditions of two oppositely directed forces: the gravity of water drops directed downward and the lifting force moving water drops with a gas flow directed upward. A calculation was made according to the method of the averaged physical parameters of formation water and natural gas in the conditions of flooded Cenomanian gas wells in Western Siberia. The results of a study of the dependence of the critical flow rate of Cenomanian wells on bottomhole pressure and diameter of elevator pipes are presented.

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