Plant Scale Experiments Research Articles

A transient mechanistic two-fluid model for Direct Contact Condensation

Intensified heat treatment, using Direct Contact Condensation (DCC), is applied in the production of dairy products to ensure a high level of food safety. The key challenge with DCC is the protein reactions and fouling that limit operational efficiency and sustainability. The use of validated, transient models to predict temperature, phase fraction and velocity gradients is essential and can improve the operation of DCC. Pilot plant scale experiments were performed for a wide range of steam mass fluxes, inlet water temperatures, water Reynolds number and channel pressures to validate a transient 1D two-fluid model. The model was tested against steady-state experimental data and showed good agreement. In addition the model was tested against transient data in which either the water flow rate was step wise decreased or the pressure was adjusted throughout the experiment. In general the model followed the experimental trend well provided that the flow inside the channel is homogeneous.

Development of a one-dimensional system code for the analysis of downward air-water two-phase flow in large vertical pipes

In nuclear thermal-hydraulic system codes, most correlations used for vertical pipes, under downward two-phase flow, have been developed considering small pipes or pool systems. This suggests that there could be uncertainties in applying the correlations to accident scenarios involving large vertical pipes owing to the difference in the characteristics of two-phase flows, or flow conditions, between large and small pipes. In this study, we modified the Multi-dimensional Analysis of Reactor Safety KINS Standard (MARS-KS) code using correlations, such as the drift-flux model and two-phase multiplier, developed in a plant-scale air-inflow experiment conducted for a pipe of diameter 600 mm under downward two-phase flow. The results were then analyzed and compared with those based on previous correlations developed for small pipes and pool conditions. The modified code indicated a good estimation performance in two plant-scale experiments with large pipes. For the siphon-breaking experiment, the maximum errors in water flow for modified and original codes were 2.2% and 30.3%, respectively. For the air-inflow accident experiment, the original code could not predict the trend of frictional pressure gradient in two-phase flow as ⟨jg⟩/⟨j⟩ increased, while the modified MARS-KS code showed a good estimation performance of the gradient with maximum error of 3.5%.

Co-gasification of rural solid waste and biomass in rural areas: Simulation and plant-scale process

Co-gasification technology is considered to be one of the most potential technologies for solid waste treatment, and the co-gasification treatment of rural solid waste (RSW) and biomass can effectively promote waste reduction and resource utilization. In the present study, the co-gasification of RSW and biomass in an updraft fixed bed gasifier was simulated using the Aspen Plus software, where the simulation results were validated via plant-scale experiments. In this scenario, the impacts of biomass source (i.e., rice husk, rice straw, tree bark and corn straw), co-gasification ratio (CGR) (0–40%) and air equivalence ratio (AER) (0.30–0.55) on the performance of the fixed-bed were investigated. Results showed that Aspen Plus could describe the plant-scale co-gasification process well. Besides, the tree bark-RSW system had the highest heat conversion efficiency of 6.00 MJ/kg the simulation temperature of the gasification layer increased greatly from 485 to 913 °C when the AER increased from 0.40 to 0.55. In addition, the co-gasification of RSW and tree bark could achieve the highest efficiency at the AER of 0.45 and CGR of 20% w, in which the gasification temperature reached 799 °C with the gasification efficiency of 57.17%. This study explored the use of co-gasification of RSW and biomass in rural areas by simulation and plant-scale processes, which promotes the commercial application of co-gasification technology and contributes to sustainable waste management in rural areas.

An objective classification of condensation regimes in direct contact condensation

AbstractIntensified heat treatment, using direct contact condensation (DCC), is applied in the production of dairy products to ensure a high level of food safety. The key challenge with DCC is the fouling due to the protein reactions that limits operational efficiency and sustainability. Using a condensation regime map can improve operational decision‐making. Pilot plant scale experiments were conducted for a wide range of steam mass fluxes and inlet temperatures at high and low channel pressures. High‐speed images were recorded and analyzed to obtain penetration lengths and plume area. The experimental data and image analysis supplemented with temperature and pressure measurement, were processed using machine learning (ML) to develop a data driven model to predict the regime maps. The linear discriminant analysis (LDA) was found to be the most suitable model. From the ML models it was also found that the best parameters to make a condensation regime map are the steam pressure, channel pressure, subcooling temperature, water Prandtl number, and the relative velocity ratio between gas and liquid. The condensation outcomes were presented with various two‐dimensional regime maps. New regime maps are proposed using the Prandtl number and velocity ratio as dimensionless parameters.

Plant-scale experiments of an air inflow accident under sub-atmospheric pressure by pipe break in an open-pool type research reactor

In an open-pool type research reactor with a downward forced flow in the core, pipes can be under sub-atmospheric pressure because of the large pressure drop at the reactor core in the atmospheric pool. Sub-atmospheric pressure can result in air inflow into the pipe from the pressure difference between the atmosphere and the inside of the pipe, which in a postulated pipe break scenario can lead to the breakdown of the cooling pump. In this study, a plant-scale experiment was conducted to study air inflow in large piping systems by considering the actual operational conditions of an advanced research reactor. The air inflow rate was measured, and the entrained air was visualized to investigate the behavior of air inflow and flow regime depending on the pipe break size. In addition, the developed drift-flux model for a large vertical pipe with a diameter of 600 mm was compared with other correlations. The flow regime transition in a large vertical pipe under downward flow was also studied using the newly developed drift-flux model. Consequently, the characteristics of two-phase flow in a large vertical pipe were found to differ from those in small vertical pipes where liquid recirculation was not dominant.

A Static Model for Energy‐Optimizing Furnace

In an integrated steel‐making plant, crude steel is produced mainly through a basic oxygen furnace (BOF) and an electric arc furnace (EAF). Apart from these two, energy‐optimizing furnace (EOF) is also evolving as a competent technology in the primary steel‐making process. Currently, a few plants are using the EOFs for crude steel production. The process control tools available in the EOFs are also limited, which may be the reason for limited reported attempts to improve this process. Mass and heat balance are essential methodologies to understand the mass flow of a process much better. Many mass and heat balance‐based studies have been carried out for the BOFs and EAFs, which can aid the operation of these furnaces toward process optimization. The present work focuses on developing a static model for the EOF process that can give a better understanding of the process and can aid the operation. A Microsoft Excel‐based model has been developed considering heat and mass balance coupled with thermodynamic data and operating conditions of the furnace from the plant scale experiments. The present model can predict the entire mass flow in the process and its accuracy is also assessed. The possible reasons for the present accuracy level were also elaborated.

Retrospective quality by design r(QbD) for lactose production using historical process data and design of experiments

Quality by Design (QbD) is a popular formal approach for designing, upscaling and optimizing industrial production facilities towards guaranteed quality. To avoid the many costly experiments required for QbD, historical production data may be exploited for optimization instead in what is known as a retrospective QbD (rQbD) study. Current rQbD literature does limitedly discuss data-driven identification of Critical Process Parameters (CPPs) to optimize limited process knowledge availability, and does not cover situations where technical operation limits have not yet been fully explored and/or where parallel equipment (lines) are used. This work presents a new rQbD strategy that addresses these challenges by balancing knowledge that can be obtained from statistical analysis of historical data, together with process experts with a carefully designed set of plant-scale experiments within current operational limits. This novel strategy is demonstrated on a long-running industrial lactose production facility. By digitally and experimentally exploring historical operation variability, we found new operational regimes for this production that may lead to up to 7% product quality improvement, reduced energy consumption and increased process understanding. Although optimizing a specific process by necessity requires a process-specific approach, the way in which we systematically optimize the current process with Hybrid AI (combining available knowledge with new insights from historical data) shows that approaches that are currently used in prospective process upscaling may be modified to be invaluable for optimization of full-scale processes with a long operational history.

Experimental Investigation of the Heat Transfer between Finned Tubes and a Bubbling Fluidized Bed with Horizontal Sand Mass Flow

The sandTES technology utilizes a fluidized bed counter current heat exchanger for thermal energy storage applications. Its main feature is an imposed horizontal flow of sand (SiO2) particles fluidized by a vertical air flow across a heat exchanger consisting of several horizontal rows of tubes. Past international research on heat transfer in dense fluidized beds has focused on stationary (stirred tank) systems, and there is little to no information available on the impact of longitudinal or helical fins. Previous pilot plant scale experiments at TU Wien led to the conclusion that the currently available correlations for predicting the heat transfer coefficient between the tube surface and the surrounding fluidized bed are insufficient for the horizontal sand flow imposed by the sandTES technology. Therefore, several smaller test rigs were designed in this study to investigate the influence of different tube arrangements and flow conditions on the external convective heat transfer coefficient and possible improvements by using finned tubes. It could be shown that helically finned tubes in a transversal arrangement, where the horizontal sand flow is perpendicular to the tube axes, allows an increase in the heat transfer coefficient per tube length (i.e., the virtual heat transfer coefficient) by a factor of 3.5 to about 1250 W/m2K at ambient temperature. Based on the literature, this heat transfer coefficient is expected to increase at higher temperatures. The new design criteria allow the design of compact, low-cost heat exchangers for thermal energy storage applications, in particular electro-thermal energy storage.

Modelling of heat transfer in a straight grate pellet induration reactor complemented with plant scale experiments

ABSTRACT Straight grate furnaces are widely used for induration of hematite pellets where typically 1%–2% carbon is added to the green mix to help in generating heat by combustion. The quality of the pellets in such reactor varies from top to bottom of the bed as different layers of pellets are exposed to varying thermal and gaseous environments. The thermal evolution (as a function of time) at a specific location in a moving pallet car was studied through plant scale experiments. Subsequently, these experimental temperature measurements were supplemented with a 1-D heat transfer model of the pellet bed. It was observed, from simulation results, that peak temperature faced by the pellets in top layer and bottom layer of the pellet bed differed by 105°C. The effect of bed height and grate velocity on the pellet bed thermal profile was studied using the model. With increase in production rate through increase in grate velocity and bed height, this difference further intensified. These findings can provide insight to plant operator to optimise production rate.

Simulation of Choghart AG mill circuit using JKSimMet software and investigating the possibility of converting to SAG mill

Summary The variation of feed characteristics of the Choghart Iron Processing Plant has resulted in the reduction of AG mill efficiency. In this research, the possibility of converting the Choghart AG mill to SAG mill to stabilize the mill power draw and improve the grinding process was investigated. The JKSimMet software was used to simulate the circuit and predict the effect of charging steel balls to the AG mill. The results of grinding tests on the ore samples were used to simulate the circuit. The product size distribution predicted by the software was very close to the actual product size of the AG mill. The simulation of the circuit, using different tonnage of 100 mm steel balls showed that the mill throughput could increase by around 6 percent with a slight increase in the mill product size. The actual results of adding the steel ball to the plant were in agreement with the simulation results. Introduction The throughput of Choghart AG mill circuit was lower than the expected level for grinding the oxidized (or high Fe/FeO ratio) ores. Converting the AG mill to SAG mill to increase the grinding of this type of ore was the investigated option. The circuit was simulated by JKSimMet software and then adding of steel ball to the system was evaluated. The results were validated using the plant-scale studies. Methodology and Approaches Samples from the feed and product streams were collected, the relevant grinding tests were conducted and the selection and breakage functions of the ore were determined. The ore breakage test results and the specification of the feed material and AG mill and vibrating screen were used as input data to the JKSimMet software. Then charging different tonnage of the steel balls to the AG mill was evaluated. Plant-scale experiments were also conducted. Results and Conclusions Based on the impact and abrasion tests of the feed samples this ore was considered as a medium hard type ore. The simulation result for the mill product size distribution was very close to the actual data of the plant. Therefore, this software could be used to predict other changes in the circuit. The simulation results showed that by adding 5 and 10 percent (volume) of 100 mm steel balls to the Choghart AG mill its throughput could be increased by around 3 and 7 percent, respectively. The plant scale experiments with the same type of steel ball were in agreement with the simulation results. As it was expected the mill product size increased slightly

Characteristics and Modification of Non-metallic Inclusions in Titanium-Stabilized AISI 409 Ferritic Stainless Steel

This study describes an investigation into the improvement of castability, final surface quality and formability of titanium-stabilized AISI 409 ferritic stainless steel on an industrial scale. Non-metallic inclusions found in this industrially produced stainless steel were first characterized using SEM-EDS analyses through the INCA-Steel software platform. Inclusions were found to consist of a MgO·Al2O3 spinel core, which acted as heterogeneous nucleation site for titanium solubility products. Plant-scale experiments were conducted to either prevent the formation of spinel, or to modify it by calcium treatment. Modification to spherical dual-phase spinel-liquid matrix inclusions was achieved with calcium addition, which eliminated submerged entry nozzle clogging for this grade. Complete modification to homogeneous liquid calcium aluminates was achieved at high levels of dissolved aluminum. A mechanism was suggested to explain the extent of modification achieved.

Laboratory and pilot plant scale study on water dechlorination by medium pressure ultraviolet (UV) radiation

Ultra violet (UV) dechlorination was performed to eliminate residual chlorine as the byproducts of chlorination process. UV dechlorination utilizes photon energy generated by medium pressure (MP) UV lamp to produce powerful hydroxyls which in return break down chemical bond of the residual chlorine. This study was undertaken to investigate the removal of residual chlorine under a medium pressure UV radiation and evaluate the influence of UV fluence on chlorine removal efficiency based on both laboratory and plant scale experiments. In laboratory experiments, water samples were exposed to a UV collimated beam apparatus equipped with a medium pressure (MP) UV lamp over a specified exposure time. Chlorine concentrations were measured before and after UV exposure to calculate its chlorine removal efficiency. Results showed that chlorine residual decreased over time and the removal efficiency increased as the UV fluence increased. The maximum UV fluence applied in the laboratory experiments (513 mJ/cm2) resulted in less than 25% of total chlorine reduction. The field experiments were conducted at a waterworks in Singapore with total capacity of 22 l/s using an existing UV system. The plant scale studies supported laboratory findings with about 9% of chlorine removal efficiency. The chlorine decay rates (fluence-based first order constant) were also calculated.

Development of Suitable Plant-Scale Drying Conditions That Prevent API Agglomeration and Dehydration

Alisertib sodium, an investigational oral oncology drug, posed some challenges toward developing a robust and scalable drying process employing an agitated filter dryer that manifested themselves during the technical transfer to a new manufacturing site. The API studied was a monohydrate that was found to readily dehydrate and agglomerate, impacting both drug product (DP) manufacture and in vitro dissolution. A scale down agitated filter dryer was designed that was used to study the drying unit operation and identify key process parameters. Through a combination of lab- and pilot plant-scale experiments, suitable drying conditions were developed that minimized agglomeration, eliminated dehydration, and produced API that behaved acceptably in downstream DP manufacture.

The effect of process variables during drying on the physical and chemical characteristics of corn dried distillers grains with solubles (DDGS) – Plant scale experiments

Corn dried distillers grains with solubles (DDGS) are highly valued as an animal feed for its nutrient content. The amount of wet distillers grains (WDG) and condensed distillers solubles (CDS) blended together during drying affects nutritive value and physical characteristics of DDGS. Effect of changing the ratio of WDG and CDS, and recycled DDGS during drying on particle size, particle size distribution, particle and bulk densities, color, chemical composition, and amino acid content was studied. Moisture content and particle size of DDGS decreased with decreasing amount of CDS added. About 80% of the particles were within a narrow size range (<1500 μm). Bulk density and tapped density of samples produced with different CDS content ranged from 420.5 to 458.1 and 498.8 to 544.3 kg/m 3, respectively. True density decreased with reduction in CDS added. As the CDS content reduced, DDGS became lighter in color. Insoluble fiber contents (protein and insoluble fiber) and amino acids increased while fat, total soluble sugars and glycerol decreased as the CDS content added to WDG reduced. The correlation coefficient of individual chemical components with CDS was above 0.90. Results from this study will be helpful in predicting the physical and nutritive property changes due to variable ratios of blending CDS to WDG during the drying process.

Results of Field Tests on Radio-Wave Heating for Soil Remediation

After developing the radio-wave technique for various conditions in laboratory-scale and technical plant-scale experiments, field tests in combination with biodegradation and soil vapor extraction were carried out at three sites: (i) a bioremediation facility for ex situ cleaning of soil, (ii) in situ remediation of contamination at a former storage facility for organic solvents, and (iii) a polluted soil under a former petrol station. Various electrode arrangements such as parallel plates, rod arrays, and coaxial antenna were applied in order to meet the site-specific requirements optimally. Soil temperatures between 35 and 100 degrees C were established. The successful tests gave much insight into the engineering, physical, biological, and chemical aspects of radio-wave application. General conclusions on the appropriateness and competitiveness of the radio-wave method as well as on preferred application fields are drawn.

Shortstopping and jet mixers in preventing runaway reactions

Runaway reactions are continuing to be a major problem in the chemical industry (26% of major accidents). One of the main reasons for runaways is power failure. Runaway reactions could be inhibited in two ways: by the addition of cold diluents and by the addition of an inhibitor (chemical reaction stopper). This technology is called shortstopping. After a power failure, the process of adding an inhibiting agent and mixing it with the reactor contents becomes a major problem in the shortstopping process. Jets or impellers, driven by a small generator, however, can be used for mixing the inhibitor with the reactor contents. Dakshinamoorthy et al. [2006. CFD simulations of shortstopping runaway reactions in vessels agitated with impellers and jets. Journal of Loss Prevention in the Process Industries 19, 570–581] compared the efficiency of using jet mixers versus impeller stirred vessels in shortstopping runaway reactions. On the basis of equal power consumption, this comparative study showed that jet mixers are ineffective when used for shortstopping. One needs to identify additional factors, to effectively shortstop when using jet mixers. Due to the hazardous nature of runaway reactions, these factors cannot be determined with lab scale or pilot plant scale experiments. Recent developments with CFD make it possible to carry out virtual experiments. The computational model is solved using FLUENT. Shortstopping studies via the addition of a reaction inhibitor and cold diluent are discussed in detail. The results reported in this study identify the major and minor factors, which contribute to effective shortstopping; i.e., power requirements, locations for adding the inhibitor, the quantity of inhibitor added, rate of the inhibition, the use of cold diluent and the use of multiple nozzles. These results especially demonstrate the value of using CFD simulations in situations that are experimentally prohibitive.

Synthesis of high ion exchange zeolites from coal fly ash

This study focuses on the synthesis at a pilot plant scale of zeolitic material obtained from the coal fly ashes of the Teruel and Narcea power plants in Spain. After the optimisation of the synthesis parameters at laboratory scale, the Teruel and Narcea fly ashes were selected as low and high glass fly ashes. The pilot plant scale experiments were carried out in a 10 m3 reactor of Clariant SA (Barcelona, Spain). The results allowed obtaining 1.1 and 2.2 tonnes of zeolitic material with 40 and 55% of NaP1 content, in two single batch experiments of 24 and 8 hours, for Teruel and Narcea fly ashes, respectively. The cation exchange capacities (CEC) of the final product reached 2.0 and 2.7 meq g-1 for Teruel and Narcea zeolitic material, respectively, which are very close to the usual values reached by the high quality natural zeolitic products. Finally, with the aim of testing possible applications of the commercial NaP1-IQE and pilot plant NaP1-Narcea zeolitic products in water decontamination, efficiency for metal uptake from waste waters from electroplating baths was investigated

Decontamination of wastewater contaminated by polychlorinated biphenyls (PCBs)

Wastewater contaminated by PCBs obtained from three different sources was treated at both laboratory and pilot plant scale conditions by ultraviolet oxidation of organics at the presence of hydrogen peroxide after partial adsorption of impurities and PCBs on activated carbon and/or activated bentonite. The procedure was conducted both with and without a Fe(II) catalyst and considerable reduction of PCB concentration was achieved in both cases. In pilot plant scale experiments, activated carbon polishing step followed UV oxidation. The following three types of contaminated waste water were examined: a) aqueous extracts originated in the course of clean-up of contaminated soil by extraction with aqueous solvents. Concentrations of PCBs in extracts were between 1 microg/L to 3,000 microg/L; b) wastewater condensates originated in the process of thermal desorption of PCB from soils. Concentrations of PCBs in condensates were between 300 microg/L and 5,000 microg/L. c) underground water contaminated by PCBs extracted from the sites of old contamination. The content of PCBs was up to 50,000 ng/L. Biodegradation of PCBs with a mixture of indigenous soil bacteria (selected strains of Pseudomonas and Acitenotobacter) was also tested. It was carried out in a reactor with volume of 1.5 m3 by application of the bacteria in a slurry of bentonite with adsorbed PCBs.

Promotion of Desulphurization in Ladle through Slag Emulsification by Stirring with Stationary AC Electromagnetic Field

Strong electromagnetic stirring enables promotion of interfacial reaction between slag and metal in ladle refining processes. This study elucidates the interfacial phenomena through plant scale experiments by using stationary alternative current (AC) electromagnetic field, cold models to make clear the hydrodynamic behavior of fluids, and the numerical simulation of the magnetohydrodynamic (MHD) and chemical reaction analyses. They revealed that the enhancement of the interfacial reaction is strongly related to the state of the slag-metal interface and that there exist critical values of the intensity of electromagnetic power supply, which govern the reaction rate.

Development of adsorptive removal process for treatment of explosives contaminated wastewater using activated carbon

The adsorption characteristics of nitro-organics such as trinitro-toluene (TNT), dinitro-toluene (DNT) and nitrobenzene (NB) on granular activated carbon (GAC) were studied to understand their dynamic adsorption behaviour for dilute aqueous solutions. A model was developed to predict the dynamics of the adsorption process and the effect of various design and operating parameters on adsorption characteristics. The model predictions would provide inputs to design of bench scale and pilot plant scale experiments. Section 2 of the paper describes the assumptions, predictions, development of the model and its validation with experimental data generated during bench scale and pilot plant trials. Section 3 presents the breakthrough characteristics obtained by conducting experimental runs for GAC of different surface areas from 650 to 1500 m 2/g, hydraulic loading rates (HLR) ranging between 12 and 24 m 3/h/m 2, feed concentrations from 50 to 130 mg/l and bed heights between 300 and 1000 mm for TNT, DNT and NB solutions. The effect of these independent parameters on the breakthrough time, adsorption capacity and the minimum concentration achieved in the effluent was studied and the results obtained are presented in this paper. These indicate that the adsorption capacity goes though a maximum when studied as a function of HLR and feed concentration. The adsorption capacity per unit surface area also shows a maximum around 1000 m 2/g. The minimum bed height required for meeting environmental effluent discharge limit of 1 ppm was experimentally found to be about 800 mm. These results compare well with the predictions based on the model developed for column adsorption process. Data from these experimental runs and the model predictions have been used to optimise various parameters for the design of a pilot plant unit with 200 l per hour capacity.