Dense Phase Conditions Research Articles

Ultra-long-distance transport of supercritical natural gas (SNG) at very-high mass flow rates via pipelines through land, underground, water bodies, and ocean

A detailed study of SNG transport using a computational model that accounts for compressibility and Joule-Thomson effects is presented, for the first time. It shows that the transport distance and mass flow rate of supercritical natural gas (SNG) - above the cricondenbar and cricondentherm, and beyond the anomalous state - can exceed far beyond that achieved or proposed under high pressure, dense phase conditions, thus far. As an example, SNG (average composition of USA/Canada gas), at 800 kg/s can travel, without recompression, to 4801 km. It is revealed that the pressure-drop and pumping power per unit length decrease asymptotically as the inlet pressure increases beyond 20 MPa; orders-of-magnitude lower than that at low pressures. The increase in inlet pressure, pipe diameter, and/or heat conductance of the pipe wall increases the distance travelled by SNG whereas the increase in mass flow rate and surrounding temperature has a negative effect, including the strengthening of Joule-Thomson cooling near the exit. SNG pipelines at ocean bottom offer many advantages, including shorter distances, isothermal flows (∼4 °C), and balance between the outer and inner pressures. Also, SNG delivery at 6 MPa can allow regional distribution without immediate recompression. SNG pipelines therefore offer enormous possibilities of energy-efficient transport of natural gas to far-distant intra- and inter-continental destinations, not feasible thus far, which is urgently needed for uninterrupted supply of natural gas and worldwide energy security.

Gas transport at dense phase conditions for the development of deepwater fields in the Colombian Caribbean sea

The purpose of this article is to set out the benefits of using the dense phase gas transport in future projects in the Caribbean Sea and to verify that when operating pipelines at high pressures, more mass per unit of volume is transported, and liquid formation risks are mitigated in hostile environments and low temperatures.This study contains key data about gas production fields in deep and ultra-deep waters around the world, which serve as a basis for research and provide characteristics for each development to be contrasted with the subsea architecture proposed in this paper. Additionally, analogies are established between the target field (Gorgón-1, Kronos-1 and Purple Angel-1) and other offshore gas fields that have similar reservoir properties. Using geographic information systems, the layout of a gas pipeline and a subsea field architecture that starts in the new gas province is proposed.Finally, using a hydraulic simulation tool, the gas transport performance in dense phase is analyzed and compared with the conventional way of transporting gas by underwater pipelines, achieving up to 20 % in cost savings when dense phase is applied.

CFD-DEM simulation of pneumatic conveying in a horizontal pipe

In this paper, the combined approach of computational fluid dynamics (CFD) and discrete element method (DEM) is used to study pneumatic conveying in a horizontal pipe. A new three-dimensional modified wall roughness (WR) model and the discrete random walk (DRW) model are introduced into the CFD-DEM approach to simulate the effect of wall roughness and the random effect of turbulence on particle dispersion respectively. The interaction between particles and fluid of the pneumatic conveying in a horizontal pipe is calculated by both the one-way coupling method and the two-way coupling method. The flow characteristics of the pneumatic conveying in a horizontal pipe, including the particle velocity, the particle mass flux, and the particle trajectory are obtained by the simulations. The particle mass flux predicted by the CFD-DEM with WR-DRW is quite different with that predicted by the traditional CFD-DEM approach although the particle horizontal velocities obtained by two different approaches are similar, and the distribution of particles across the pipe cross section predicted by the CFD-DEM with WR-DRW is more uniform than that predicted by the traditional CFD-DEM approach. The accuracy of the CFD-DEM with WR-DRW is validated by the corresponding experiments from literatures. Comparing to the computational fluid dynamics - discrete phase model (CFD-DPM) without considering collision between particles, the CFD-DEM with WR-DRW developed in this work can be applied to study the pneumatic conveying in a horizontal pipe under both dilute and dense phase conditions.

CFD–DEM simulation of pneumatic conveying in a horizontal channel

In this paper, the pneumatic conveying in a horizontal channel is simulated by the combined approach of computational fluid dynamics (CFD) and discrete element method (DEM). A modified wall roughness model and the Discrete Random Walk (DRW) model are introduced into the CFD–DEM approach to investigate the effect of the wall roughness and the random effect of the turbulence on particle dispersion respectively, and this combined approach is named as the improved CFD–DEM approach. The interaction between the particles and the fluid is calculated by both the one-way coupling method and the two-way coupling method. The accuracy of the improved CFD–DEM approach is validated by corresponding experiments from the literatures. By using the improved CFD–DEM approach, several dense channel gas–solid flows are simulated. The simulation results indicate that with the increase of mass loading rate, the particle agglomeration is more significant, and the trend of increasing the particle concentration near the upper and lower walls is more obvious. This research shows that the improved CFD–DEM approach developed in this work is an effective tool for studying the particle phase properties under both dilute and dense phase conditions.

Effect of Chemical Impurities on Centrifugal Machine Performance: Implications for Compressor Sizing In A CO2 Transport Pipeline

Several research studies have been published on CO2 pipeline transportation. Most of them focus on developing hydraulic models of entire CO2 pipeline networks. From these studies, a lot of original knowledge has been produced to understand the behaviour of CO2 pipeline networks under dense phase or supercritical conditions. The globalized modelling approach used in these studies are generally sufficient for carrying out an overall design and operation of an entire CO2 pipeline network. However, such models are too insufficiently detailed for use in optimizing the performance of a compressor in a CO2 transport pipeline. This is because in hydraulic models, compression is simulated with adiabatic or polytropic equations which do not account for the geometry and internal fluid flow processes within the compressor. Moreover, in energy requirement calculations involving these equations, compressor efficiency is assumed to be fixed, where as in reality, it varies with change in the purity of the CO2 stream being compressed. Given that compressors consume most of the energy needed to operate an entire CO2 pipeline network, it is vital that a detailed analysis of the effect of impurities on machine performance is done as a prerequisite for developing an optimal procedure for compressor sizing and selection. To this end, a quasi-dimensional model based on the laws of conservation was developed and validated for a detailed investigation of the effect of various impurities on the performance of a centrifugal machine handling supercritical carbon dioxide. Results of the study confirm that the power requirement of a compressor is affected by the impurities and provides an insight into the relationship between compressor size, work input and the pressure required to maintain the CO2 stream flowing in a transport pipeline network in supercritical state.

Solid-Mass Flow-Rate Prediction in Dense-Phase Pneumatic Conveying of Pulverized Coal by a Venturi Device

This paper aims at predicting the solid-mass flow rate of pulverized coal in dense-phase pneumatic conveying systems. A one-dimensional model was developed based on the proper modification of a dilute-flow model by inserting a two-phase flow multiplier. The relationships between the model parameters (discharge coefficient and pressure ratio parameter) and the hydrodynamic nondimensional numbers (Reynolds and Stokes numbers) were determined, and the fitting coefficients were obtained from calibration tests by using regression analysis. Two methods attached to the model were proposed to predict the solid-mass flow rate, and both can provide satisfactory predictions with acceptable errors. These results indicated the possibility of applying a venturi device to measure the solid-mass flow rate at high-pressure and dense-phase conditions.

Understanding and application of CO2 adsorption capacity estimation models for coal types

Geosequestration is an attractive mechanism to store CO2 for geologically significant time periods in order to minimise climate changing impacts on the environment. Reservoirs such as coal seams are used as storage reservoirs. However, it is very important to estimate the quantity of CO2 that can be stored in a coal reservoir. In this study, existing storage models such as correlation models and Equations of State (EOSs) in the context of different coal types are compared, together with the experimentally-observed isotherms. Under highly dense phase non-ideal conditions, CO2 storage potential will be maximised. Therefore, the use of fugacity in place of pressure is suggested to estimate CO2 storage capacity under highly dense phase conditions. Further, four new modified correlation type models are suggested and found to be of good agreement with existing correlation-type adsorption models such as the DR and Toth models. By using various adsorbed phase density values, it was found that use of value as 1.028g/cm3 gave the most consistent results across all the proposed isotherm equations. Fugacity did not improve the results for the correlation models, nor did it worsen them. The correlation models were clearly less accurate than the EOS adsorption models, especially under highly dense phase conditions. For less dense phase conditions, all the isotherm models gave comparable results to the experimental adsorption isotherms, while for highly dense phase conditions there were varying results.

Understanding the consequences of CO2 leakage downstream of the capture plant

This paper describes results of computer-based analyses of the dispersion of CO2 from pipelines or other containment vessels under a variety of conditions relevant to power plants fitted with Carbon Capture & Storage (CCS). A single methodology is proposed which will enable the prediction of a source term for a CO2 release from pipeline or storage vessel under gaseous, liquid and dense phase conditions. This methodology provides the source term input to a number of case studies of CO2 dispersion from a pipeline using both CFD and Gaussian-type dispersion models. The effects of solid CO2 formed within the dispersing jet on the subsequent dispersion and plume characteristics is investigated.

Competitive Adsorption of C20−C36 Linear Paraffins on the Amorphous Microporous Silica−Alumina ERS-8 in Vapor Phase and Liquid Phase

Adsorption of C20−C36 linear paraffins on the amorphous microporous silica−alumina ERS-8 was studied at vapor phase and liquid phase conditions. Henry adsorption constants and low coverage adsorption enthalpies were determined using the pulse chromatographic method at temperatures between 90 and 370 °C in gas phase. The low coverage adsorption enthalpy increases linearly with carbon number with 5.5 kJ/mol per additional methyl group. Competitive adsorption in liquid and dense vapor phase conditions was studied by performing column breakthrough experiments with various binary C20−C36 n-paraffin mixtures diluted in short chain length alkane solvents or undiluted as bulk mixture, at temperatures ranging from 25 to 300 °C and pressures from 3 to 110 bar. Both the adsorption capacity and the selectivity are strongly temperature and pressure dependent. At low temperature and high pressure, all n-paraffins are adsorbed equally and no separation is possible. With increasing temperature and decreasing pressure, the density of the bulk phase decreases, and a transition from a pure liquid paraffin stream to a dense vapor stream occurs. In such conditions, longer n-paraffins are adsorbed preferentially compared to the shorter n-paraffins. The selectivity increases with increasing difference in chain length between the adsorbing n-paraffins.

Modeling Solids Friction for Dense-Phase Pneumatic Conveying of Powders

This article results from an ongoing investigation aimed at developing a new validated test-design procedure for the accurate prediction of pressure drop for dense-phase pneumatic conveying of powders. Models for combined pressure drop coefficient (“K”) for solids-gas mixture were derived using the concept of “suspension density” by using the steady-state “straight pipe” pressure drop data between two different tapping locations of the same pipe and also for two different diameter pipes. It was observed that the derived models were different depending on the location of tapping points (for the same pipe) and selected pipe diameters. The derived models were then evaluated by predicting the pressure drop for pipelines with various diameters or lengths (69 mm I.D. × 168 m, 105 mm I.D. × 168 m, 69 mm I.D. × 554 m) for the conveying of power station fly ash. A comparison between the predicted pneumatic conveying characteristics (PCC) and the experimental plots showed that the models resulted in significant over-predictions. In the second part of the article, the “system” approach of scaleup was evaluated. “Total” pipeline pressure drop characteristics for test-rig pipelines were scaled up to predict the PCC for larger/longer pipes. It was found that the “system” approach generally resulted in grossly inaccurate predictions. It was concluded that further studies are needed for a better understanding of the solids-gas flow mechanism under dense-phase conditions.

A Unified Single-Event Microkinetic Model for Alkane Hydroconversion in Different Aggregation States on Pt/H−USY-Zeolites

A single-event microkinetic model for the catalytic hydroconversion of hydrocarbons on Pt/H-US-Y bifunctional zeolite catalysts developed for low-pressure vapor phase conditions was extended to cover high-pressure vapor phase and liquid phase conditions. The effect of the density of the bulk hydrocarbon phase on the physisorption as well as on the protonation steps of the reaction network was accounted for explicitly and can be interpreted in terms of "compression" of the hydrocarbon sorbate inside the zeolite pores and "solvation" of the catalyst framework by the dense bulk hydrocarbon phase. The bulk phase density effect on the physisorbed state is described via a single excess free enthalpy of physisorption. A dense bulk hydrocarbon phase destabilizes the sorbate molecules inside the catalyst pores. An expression of the excess free enthalpy of physisorption involving the fugacity coefficient and a zeolite dependent factor allows description of physisorption data. Typical excess free enthalpy values are in the range 1.5-5.1 kJ mol(-1) increasing with carbon number in the series of C5-C16 alkanes. At high-pressure vapor phase and liquid phase conditions, the excess standard protonation enthalpy is estimated at -7.8 kJ mol(-1) leading to relatively more stable carbenium ions at dense bulk phase conditions. As a result of the excess physisorption and protonation properties, the lightest hydrocarbons in mixtures are more competitive at dense phase conditions and their conversion is enhanced compared to low-density conditions.

Effect of dilute and dense phase operating conditions on bed-to-wall heat transfer mechanism in a circulating fluidized bed combustor

In the present paper investigations are conducted on bed-to-wall heat transfer to water-wall surfaces in the upper region of the riser column of a circulating fluidized bed (CFB) combustor under dilute and dense phase conditions. The bed-to-wall heat transfer depends on the contributions of particle convection, gas convection and radiation heat transfer components. The percentage contribution of each of these components depends on the operating conditions i.e., dilute and dense phase bed conditions and bed temperature. The variation in contribution with operating conditions is estimated using the cluster renewal mechanistic model. The present results contribute some fundamental information on the contributions of particle convection, gas convection and radiation contributions in bed-to-wall heat transfer under dilute and dense phase conditions with bed temperature. This leads to better understanding of heat transfer mechanism to water-wall surfaces in the upper region of the riser column under varying load conditions i.e., when the combustor is operated under dilute and dense phase situations. The results will further contribute to understanding of heat transfer mechanism and will aid in the efficient design of heat transfer surfaces in the CFB unit.

PVT behaviour of fluids with potential models optimised for phase equilibria

NPT and NVT Monte Carlo simulations are applied to models for methane and water to predict the PVT behaviour of these fluids over a wide range of temperatures and pressures. The potential models examined in this paper have previously been presented in the literature with their specific parameters optimised to fit phase coexistence data. The exponential-6 potential for methane gives generally good prediction of PVT behaviour over the full range of temperature and pressures studied with the only significant deviation from experimental data seen at high temperatures and pressures. The NSPCE water model shows very poor prediction of PVT behaviour, particularly at dense conditions. To improve this, the charge separation in the NSPCE model is varied with density. Improvements for vapour and liquid phase PVT predictions are achieved with this variation. No improvement was found in the prediction of the oxygen–oxygen radial distribution by varying charge separation under dense phase conditions.

04/02025 Industrial waste combustion boiler installed at paper mill - EBARA internally circulating fluidized bed boiler (ICEB) & gasifier (ICFG): Tsukamoto, K. and Miyoshi, N. Kami Pa Gikyoshi, 2003, 57, (5), 645–653. (In Japanese)

In the present paper investigations are conducted on bed-to-wall heat transfer to water-wall surfaces in the upper region of the riser column of a circulating fluidized bed (CFB) combustor under dilute and dense phase conditions. The bed-to-wall heat transfer depends on the contributions of particle convection, gas convection and radiation heat transfer components. The percentage contribution of each of these components depends on the operating conditions i.e., dilute and dense phase bed conditions and bed temperature. The variation in contribution with operating conditions is estimated using the cluster renewal mechanistic model. The present results contribute some fundamental information on the contributions of particle convection, gas convection and radiation contributions in bed-to-wall heat transfer under dilute and dense phase conditions with bed temperature. This leads to better understanding of heat transfer mechanism to water-wall surfaces in the upper region of the riser column under varying load conditions i.e., when the combustor is operated under dilute and dense phase situations. The results will further contribute to understanding of heat transfer mechanism and will aid in the efficient design of heat transfer surfaces in the CFB unit.

Evaporative liquid jets in gas–liquid–solid flow system

Some aspects of the fundamental characteristics of evaporative liquid jets in gas–liquid–solid flows are studied and some pertinent literature is reviewed. Specifically, two conditions for the solids concentration in the flow are considered, including the dilute phase condition as in pneumatic convey and the dense phase condition as in bubbling or turbulent fluidized beds. Comparisons of the fundamental behavior are made of the gas–solid flow with dispersed non-evaporative as well as with evaporative liquids. For dilute phase conditions, experiments and analyses are conducted to examine the individual phase motion and boundaries of the evaporative region and the jet. Effects of the solids loading and heat capacity, system temperature, gas flow velocity and liquid injection angle on the jet behavior in gas and gas–solid flows are discussed. For dense phase conditions, experiments are conducted to examine the minimum fluidization velocity and solids distribution across the bed under various gases and liquid flow velocities. The electric capacitance tomography is developed for the first time for three-phase real time imaging of the dense gas–solid flow with evaporative liquid jets. The images reflect significantly varied bubbling phenomenon compared to those in gas–solid fluidized beds without evaporative liquid jets.

The viscosity of ammonia: Experimental measurements for the dense gaseous phase and a reduced state correlation for the gaseous and liquid regions

AbstractThe unsteady state flow of ammonia gas has been investigated to determine its viscosity at elevated pressures and moderate temperatures. This was accomplished in an experimental unit of the transpiration type which was calibrated with nitrogen, for which viscosity data at high pressures were available in the literature. To obtain the viscosity at the operating conditions the basic differential equation for the unsteady state flow caused by the experimental procedure was developed and solved with an IBM‐650 digital computer.Experimental runs were conducted for pressures ranging from 250 to 5,000 lb./sq. in. and temperatures from 100° to 200°C. This information has been used to establish the viscosity of ammonia at these dense phase conditions for which no viscosities had been previously reported. These values were used to develop a unique correlation between the residual viscosity and the density. This correlation then enabled the determination of ammonia's viscosity at the critical point μc = 2,395×10−5 centipoises.The Enskog viscosity equation has been used with the values resulting from this study and PVT data for ammonia to develop a relationship for the probability of nearness. This relationship enables viscosities to be calculated for densities up to 0.450 g./cc. which are in close agreement with the experimental values.