Morten Christian Melaaen

Pressure drop, flow pattern and local water volume fraction measurements of oil–water flow in pipes

Oil–water flow in horizontal and slightly inclined pipes was investigated. The experimental activities were performed using the multiphase flow loop at Telemark University College, Porsgrunn, Norway. The experiments were conducted in a 15 m long, 56 mm diameter, inclinable steel pipe using Exxsol D60 oil (density of 790 kg m−3 and viscosity of 1.64 mPa s) and water (density of 996 kg m−3 and viscosity of 1.00 mPa s) as test fluids. The test pipe inclination was changed in the range from 5° upward to 5° downward. Mixture velocity and inlet water cut vary up to 1.50 m s−1 and 0.975, respectively. The time-averaged cross-sectional distributions of oil and water were measured with a single-beam gamma densitometer. The pressure drop along the test section of the pipe was also measured. The characterization of flow patterns and identification of their boundaries are achieved via visual observations and by analysis of local water volume fraction measurements. The observed flow patterns were presented in terms of flow pattern maps for different pipe inclinations. In inclined flows, dispersions appear at lower mixture velocities compared to the horizontal flows. Smoothly stratified flows observed in the horizontal pipe disappeared in upwardly inclined pipes and new flow patterns, plug flow and stratified wavy flow were observed. The water-in-oil dispersed flow regime slightly shrinks as the pipe inclination increases. In inclined flows, the dispersed oil-in-water flow regime extended to lower mixture velocities and lower inlet water cuts. The present experimental data were compared with the results of a flow-pattern-dependent prediction model, which uses the area-averaged steady-state two-fluid model for stratified flow and the homogeneous model for dispersed flow. The two-fluid model was able to predict the pressure drop and water hold-up for stratified flow. The homogeneous model was not able to predict the pressure profile of dispersed oil–water flow at higher water cuts. The two-fluid model and the homogeneous model over-predict the pressure drop for dual-continuous flow.

Dynamic modelling of the absorber of a post-combustion CO2 capture plant: Modelling and simulations

Abstract Modelling work related to carbon dioxide (CO 2 ) capture technologies is of great importance with respect to the design, control, and optimization of the capture process. Development of dynamic models as such is important since there is much information embedded with the dynamics of a plant which cannot be studied with steady state models. A model for the absorption column of a post-combustion CO 2 capture plant is developed following the rate based approach to represent heat and mass transfer. The Kent–Eisenberg model is used to compute the transfer and generation rates of the species. Sensitivity of the model for different physiochemical property correlations is analyzed. The predictions of the dynamic model for the capture plant start-up scenario and operation of the absorption column under varying operating conditions in the up-stream power plant and the down-stream stripping column are presented. Predictions of the transient behaviour of the developed absorber model appear realistic and comply with standard steady state models.

A Unified Scaling-Up Technique for Pneumatic Conveying Systems

A major challenge facing the designers of pneumatic transportation systems is how to scale up reliably based on the results from pilot-scale test facilities. Further, even if dense phase flow condition prevails at the start of the conveying system, it may be a dilute phase flow condition at the end of the pipeline. Hence, any scaling-up technique should be able to address the dynamic change of flow condition along the pipeline. The scaling-up technique presented here using the pressure drop prediction models based on modified Darcy-Weisbach equation successfully addresses these dynamic changes. It has been shown that the pressure drop coefficient ‘K,’ as defined by the models, is independent of the pipe diameter. Further, in the case of vertical conveying, ‘K’ has been shown to be independent of particle size distribution for a given material. The predicted pressure values were found to be in reasonably good agreement with the experimental results varying from 3.5% to 19.9%.

Electrical capacitance tomography (ECT) and gamma radiation meter for comparison with and validation and tuning of computational fluid dynamics (CFD) modeling of multiphase flow

The electrical capacitance tomographic (ECT) approach is increasingly seen as attractive for measurement and control applications in the process industries. Recently, there is increased interest in using the tomographic details from ECT for comparing with and validating and tuning CFD models of multiphase flow. Collaboration with researchers working in the field of computational fluid dynamics (CFD) modeling of multiphase flows gives valuable information for both groups of researchers in the field of ECT and CFD. By studying the ECT tomograms of multiphase flows under carefully monitored inflow conditions of the different media and by obtaining the capacitance values, C(i, j, t) with i = 1...N, j = 1, 2,...N and i ≠ j obtained from ECT modules with N electrodes, it is shown how the interface heights in a pipe with stratified flow of oil and air can be fruitfully compared to the values of those obtained from ECT and gamma radiation meter (GRM) for improving CFD modeling. Monitored inflow conditions in this study are flow rates of air, water and oil into a pipe which can be positioned at varying inclinations to the horizontal, thus emulating the pipelines laid in subsea installations. It is found that ECT-based tomograms show most of the features seen in the GRM-based visualizations with nearly one-to-one correspondence to interface heights obtained from these two methods, albeit some anomalies at the pipe wall. However, there are some interesting features the ECT manages to capture: features which the GRM or the CFD modeling apparently do not show, possibly due to parameters not defined in the inputs to the CFD model or much slower response of the GRM. Results presented in this paper indicate that a combination of ECT and GRM and preferably with other modalities with enhanced data fusion and analysis combined with CFD modeling can help to improve the modeling, measurement and control of multiphase flow in the oil and gas industries and in the process industries in general.

Prediction of Pressure Drop at the Entry Section from Top Discharge Blow Tank in a Pneumatic Conveying System

Although some literature can be found on the behavior of blow tanks, very few studies could be found on the pressure loss at the entry section to a pipeline (henceforth called entry pressure loss) from a top discharge blow tank in a pneumatic conveying system, even though its magnitude can be significant as compared to the total system pressure drop. This article presents the results of an experimental study carried out to assess this entry pressure loss. The results indicate that it is possible to scale up the entry pressure loss based on laboratory-scale tests with a reasonable degree of accuracy.

Kiln process impact of alternative solid fuel combustion in the cement kiln main burner - Mathematical modelling and full-scale experiment

Increased use of alternative fuels in cement kilns is a trend in the world. However, replacing fossil fuels like coal with different alternative fuels will give various impacts on the overall kiln process due to the fuel characteristics. Hence, it is important to know to what extent the fossil fuels can be replaced by different alternative fuels without severely changing process conditions, product quality or emissions. In the present study, a mass and energy balance for the combustion of different alternative fuels in a cement rotary kiln was developed. First, the impact of different fuel characteristics on kiln gas temperature, kiln gas flow rate and air requirement were observed by using coal (reference case), meat and bone meal (MBM), two different wood types, refuse derived fuel and a mixture of saw dust and solid hazardous waste as the primary fuel. It was found that the key process parameters depend largely on the chemical characteristics of the fuel. It appears that MBM shows quite different results from other alternative fuels investigated. Next, simulation of combustion of a mixture of coal and MBM in the main burner was carried out in three steps. The first step was combustion of replacing part of coal energy with MBM, and a reduction in kiln exhaust gas temperature compared to the coal reference case was found. In the second step, the fuel feed rate was increased in order to raise the kiln gas temperature to that of the reference case. In the third step, the fuel feed rate and the clinker production rate were changed in order to have not only the same kiln gas temperature but also to obtain the same volumetric flow rate of total exhaust gas from the precalciner as in the reference case. Around 7% of reduction in clinker production rate could be observed when replacing 48% of the coal energy input. Results from a full-scale test using the same mixture of coal and MBM verified the simulation results.

Experimental Studies of Dilute Vertical Pneumatic Transport

Dilute vertical pneumatic transport has been studied by using the experimental techniques LDA and PIV. LDA and PIV are two different techniques, but they are both common methods used to gain a better understanding of gas/particle multiphase flows. A comparison between the two methods has been performed. The main focus of this study was an experimental LDA investigation of ZrO2 particles and glass beads. The particles have approximately the same particle size distribution but different densities. The superficial gas velocity and the particle loading have also been varied in the experiments. The effects of superficial gas velocity, particle loading, and particle density on the particle mean velocities, particle u-rms, particle v-rms, and particle cross-moment were investigated. From the experimental investigation it was found that the axial particle velocities showed a dependence on the particle volume fraction for the ZrO2 particles. It was also observed that the axial fluctuations decreased for both glass and ZrO2 particles when the particle volume fraction increased. The axial fluctuations measured for the glass beads were higher than the fluctuations measured for the ZrO2 particles. The mean axial particle velocity measured by LDA and PIV showed good agreement.

CFD Modeling of Meat and Bone Meal Combustion in a Rotary Cement Kiln

 Abstract—This paper presents a three-dimensional computational fluid dynamics (CFD) modeling study carried out for a rotary cement kiln withal multi-channel burner with swirl and high momentum air components. The simulations are performed using the commercial CFD software ANSYS FLUENT, version 13.0, and are carried out for coal as well as for meat and bone meal (MBM) combustion using the eddy-dissipation model for combustion. Steady-state solutions are obtained using the Lagrangian approach for the particle phase and the Eurasian approach for the continuous phase. The turbulence is modeled by the RNG k-e model, and gas-phase radiation is modeled by the P1 radiation model. The effect of MBM fuel properties on combustion characteristics such as temperature, fuel devolatilization, volatiles and char burning, in comparison with coal, are presented and discussed. It was found that MBM combustion products temperatureis300K lower than that of coal, and the char burnout of MBM is 83%. This poor burnout is mainly due to bigger MBM particles.

Investigating the influence of fines in fluidized bed reactors using 3D ECT images

Electrical Capacitance Tomography (ECT) has become a useful measurement tool in process technology applications, especially in fluidized bed research. The ECT system is neither intrusive nor invasive which make the system practically viable for monitoring the internal flow behaviour in a fluidized bed. The sensor is placed on the outside of the non-conductive experimental reactor thus making implementation very convenient. ECT also presents user friendly equipment that is safe and easy to use compared to some of the other tomographic modalities currently available. There hasbeen postulatedthatthe insertionoffines into a powderwill give more uniform flow behaviour in a fluidized bed. Smaller and more evenly distributed bubbles are observed. These conditions lead to better mixing of gas and solids in a fluidized bed and thus improving the reactions in the reactor. These phenomena have been investigated in the present study using ECT and a reconstruction program developed in the present study. This reconstruction program created three dimensional images of the fluidized bed reactor under consideration. The reconstructions allow the user to get a three dimensional visual image of the flow behaviour inside the experimental reactor without disturbing the flow. Bubbleand bed characteristics of several powders with different percentages of fines were investigated. The volume, location and shape of individual bubbles were studied and thus the average bubble size, volume and frequency of a particular experimental set up was calculated. These quantities are of great importance for numerous industrial applications. Applications of these results are in almost all fields involving fluidization. The research is part of ongoing global research in optimizing and understanding fluidized beds better.

Waste Heat Utilization for CO2 Capture in the Cement Industry

The focus of this work is utilization of waste heat in a cement kiln flue gas in an amine-based CO2 absorption process. The high temperature flue gas from the cement kiln is used to generate steam in a waste heat boiler. The steam is then used to replace some of the steam required in the stripping section of the CO2 capture plant. The required surface area for heat exchange, the cost of installing this area and the payback time of the installation is calculated. The flue gas capture model was developed using the Aspen Plus simulation software. The available excess heat in the cement manufacturing process is calculated to 18 MW for the base case considered. The heat transfer area is calculated as 3115m. The total cost of the heat exchanger was