Pilot Plant Trials Research Articles

Experimental examination of slag/refractory interface

Ladle glazes are a thin coating of slag formed when the top slag comes in contact with the refractory during draining of the ladle. It is believed that ladle glazes are a major source of inclusions in the next cast of steel held in that ladle. Pilot plant trials, simulation tests, and thermophysical property measurements have been carried out on the glazes to: (i) obtain more information about ladle glazes and the factors affecting their formation and subsequent removal from the refractory; (ii) provide direct evidence that glazes are a major source of inclusions; (iii) study the factors affecting the formation, adhesion, and thickness of the glaze; (iv) study the formation of the slag penetrated layer and the factors affecting penetration. Doping trials have shown that ladle glazes are a major source of inclusions. The calculated thickness of the adhered slag layer was appreciably lower than measured experimental values. Calculated horizontal slag infiltration depths were in reasonable agreement with values measured on plant, but measured vertical infiltration depths were much lower than calculated values. It has been shown that slag penetration can be significantly reduced by the application of an electrical potential.

Pilot plant trial of the reflux classifier

The Ludowici LMPE Reflux Classifier is a new device designed for classifying and separating particles on the basis of size or density. This work presents a series of experimental results obtained from the first pilot scale study of the reflux classifier (RC). The main focus of the investigation was to assess the particle gravity separation and throughput performance of the device. In this study, the classifier was used to separate coal and mineral matter less than 2 mm in size. The experimental results were then compared with the performance data on a teetered bed separator (TBS). It was concluded that the classifier could offer an excellent gravity separation at a remarkably high solids throughput of 47 t/ m 2 h more than 3 times higher than for a TBS. The separation performance of the RC was also better, with significantly less variation in the D 50 with particle size. A simple theoretical model providing an explanation of the separation performance is also presented.

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.

Calcium-Based Liquid Phase Formation in Pressurized Gasifier Environments

Limestone and dolomite are used for retaining sulfur in air-blown gasification systems that are being developed for cleaner coal power generation systems. An intractable deposit was observed to form, apparently from limestone, when a revised base design was being tested in a pilot scale gasifier. The deposit was found to be enriched in Ca and had formed via a melt. The present study has attempted to simulate the formation of melts by sorbent components under laboratory conditions. The detection of melting was accomplished by using impedance spectrometry. This technique measures the change in resistivity when a nonconducting solid forms an ionic melt. The validity of the technique was demonstrated by reproducing melt formation that had previously been observed in the CaO/CO2/steam system under the conditions of the CO2−Acceptor Process. SEM/EDX and XRD were used to characterize the residues from the present tests. CaCO3/CaSO4 was the only system tested that formed a melt under the experimental conditions corresponding to the pilot-plant trials. Melt formation was observed at 1010 °C at pressures in excess of 13 bara. The melting temperature was not affected by the presence of other Ca compounds (viz. CaS) that would be present in the gasifier. It is thought that CaSO4 formation occurred when CaS in the recirculating sorbent was exposed to the oxidizing conditions of the spout of the gasifier. The melt would have formed by the interaction of CaSO4 with the uncalcined CaCO3 of the sorbent particles. Oxidizing sulfided limestone and dolomite and raising the temperature to above 1010 °C, which caused a melt to form, demonstrated the sequence of reactions. The properties of the melts produced from limestone and dolomite were different; these results help to explain why dolomite did not give rise to deposits during pilot plant trials.

METHODS FOR PROCESSING EXPERIMENTAL DRYING KINETICS DATA

This paper provides a review of methods for processing the data obtained from drying kinetics rigs and pilot-plant trials. Different methods for fitting and smoothing drying curves are compared, aiming to generate curves that are usable in industrial design without losing vital information by oversmoothing. Generally, plots of drying rate need more smoothing than moisture content data. Special care is needed at low drying rates and moisture contents. It is shown that some popular methods of processing data, including use of smoothing programs or fitting to equations, may generate drying curves which are seriously in error. Recommendations are made for reliable methods of processing data; cubic splines have been found to be effective for moisture–time curves. It is important to retain the original raw experimental data as a cross-check, as smoothing can conceal valuable information.

Ethanol production in a membrane bioreactor: pilot-scale trials in a corn wet mill.

Pilot plant trials were conducted in a corn wet mill with a 7000-L membrane recycle bioreactor (MRB) that integrated ceramic microfiltration membranes in a semi-closed loop configuration with a stirred-tank reactor. Residence times of 7.5-10 h with ethanol outputs of 10-11.5% (v/v) were obtained when the cell concentration was 60-100 g/L dry wt of yeast, equivalent to about 10(9)-10(10) cells/mL. The performance of the membrane was dependent on the startup mode and pressure management techniques. A steady flux of 70 L/(m2 x h) could be maintained for several days before cleaning was necessary. The benefits of the MRB include better productivity; a clear product stream containing no particulates or yeast cells, which should improve subsequent stripping and distillation operations; and substantially reduced stillage handling. The capital cost of the MRB is $21-$34/(m3 x yr) ($0.08-$0.13/[gal x yr]) of ethanol capacity. Operating cost, including depreciation, energy, membrane replacement, maintenance, labor, and cleaning, is $4.5-9/m3 ($0.017-$0.034/gal) of ethanol.

Simulation and Pilot Plant Trials Aid Commissioning of Neuro Self-Tuning PI Controller

The paper presents the results of a simulation study and some pilot plant trials used in assessing the performance of a neuro self-tuning PI controller to be used (eventually) at a water treatment plant. The development and training of the adaptive loop is discussed and the benefits of neuro control over fixed gain PI control are demonstrated.

UKWIR initiatives for implementing expert group recommendations to minimise Cryptosporidium risk in water treatment—a summary review

The UK Expert Group on Cryptosporidium in Water Supplies provided recommendations to the Water Industry on optimising water treatment for the removal of oocysts. UK Water Industry Research Ltd (UKWIR), on behalf of the UK Water Utilities, commissioned research to facilitate the implementation of these recommendations. This involved extensive pilot plant trials, the results of which were disseminated through research reports and workshops. The findings of the research were also included in a water treatment manual which provided more detailed operational guidance to supplement the Expert Group recommendations. A brief overview of this research is provided, with examples of the findings to illustrate thenature of the operational guidance in the manual.

Foaming during reduction of iron oxide in molten slag

Coal based direct liquid ironmaking processes, also known as smelting reduction (SR) processes, are now receiving serious consideration in the industry. However, although several processes have reached pilot plant trials, only one, namely Corex, has been commercialised. In all SR processes, most of the iron oxide is reduced in the molten slag phase and foaming is an important phenomenon. Better understanding of the foaming behaviour will result in design of a more efficient and economic reactor. Accordingly, some basic studies on the foaming behaviour of some typical SR process slags have been undertaken in this work. Experimental data on foaming in a 50 kW capacity plasma reactor are discussed in this paper. The data generated are analysed in terms of foaming index, which is equal to the residence time or travelling time of the gas in the foam layer. The influence of FeO percentage in the slag, slag basicity, crucible surface area, initial slag height, and CaF2addition in the slag on foaming has been studied.

Enhancement of Capacity and Efficiency of a Biological Waste Water Treatment Plant

The capacity and efficiency of the existing activated sludge waste water treatment plant at SCA Graphic Laakirchen AG needs to be enhanced due to an expected future increase in waste water flow and COD-load. For the case of an existing upper limit of COD discharges into the river, the COD reduction rate of the waste water treatment has to be increased to a degree which is unobtainable by biodegradation only. Laboratory and pilot plant trials using a moving bed biofilm technique and an activated sludge treatment combined with ozone treatment and subsequent biofiltration have been performed with the aim to increase the COD reduction capacity and efficiency of the plant. The results show that the COD reduction capacity of the existing activated sludge plant can be increased by more than 100% by integrating a moving bed biofilm pre-treatment stage into the plant. In addition, improved sludge separation in the secondary clarifier was established. A special benefit of the ozonation plus biofilter treatment is a controllable COD reduction between 20 - 90% related to the outflow of the activated sludge plant. It is concluded that by integrating the investigated treatment techniques in the existing activated sludge plant the future increases in waste water flow and COD-Load can be handled satisfactorily without increasing bioreactor volume.

Commercialization of bioleaching for base-metal extraction

This paper is a progress report on the commercialization of using bioleaching for base-metal concentrates. The paper focuses on bioleach processes for recovering copper from chalcopyrite and nickel/cobalt from pentlandite/pyrrhotite. Data is discussed from pilot-plant trials in which an overall recovery >95% was obtained for the bioleaching of copper from chalcopyrite. The pilot plant was operated in closed circuit with solvent extraction and electrowinning circuits for final metal recovery. For the bioleaching of nickel and cobalt from pentlandite/pyrrhotite, an overall recovery of 97% was achieved. Precipitation routines were used to produce a final nickel/cobalt product. The pilot plants were capable of treating a few kilograms of concentrate per day. Prominent features in the design of a 1-t/day (1.1-stpd) copper-bioleach demonstration plant for the treatment of chalcopyrite concentrate are discussed. The plant, which is now under design, will be constructed and operated based on the results obtained from the laboratory pilot-plant campaigns. Issues of scale-up for the demonstration plant, together with integration into upstream and downstream processing, are also addressed. Independently derived capital and operating costs are presented for a possible commercial plant. These cost studies indicate the principle economic issues in considering the application of bioleaching to the extraction of base metals. The benefits of bioleaching complex concentrates that are not amenable to physical beneficiation and economic treatment by conventional smelting are highlighted. Issues, such as the environmental aspects, that illustrate the benefits of bioleach technology are given.

Strategies for optimal operation of the tellurium electrowinning process

Empirical models predicting the purity of electrowon tellurium have been developed using data from 36 pilot-plant trials. Based on these models, a numerical optimization of the process was performed to identify conditions which minimize the total contamination in Pb and Se while reducing electrical consumption per kilogram of electrowon tellurium. Results indicate that product quality can be maintained and even improved while operating at the much higher electroplating production rates obtained at high current densities. Using these same process settings, the electrical consumption of the process can be reduced by up to 10 pct by operating at midrange temperatures of close to 50 °C. This is particularly attractive when waste heat is available at the plant to help preheat the electrolyte feed. When both Pb and Se are present as contaminants, the most energy-efficient strategy involves the use of a high current density, at a moderate temperature with high flow, for low concentrations of TeO2. If Pb is removed prior to the electrowinning process, the use of a low current density and low electrolyte feed concentration, while operating at a low temperature and moderate flow rates, provides the most significant reduction in Se codeposition.

Enhancement of capacity and efficiency of a biological waste water treatment plant

The capacity and efficiency of the existing activated sludge waste water treatment plant at SCA Graphic Laakirchen AG needs to be enhanced due to an expected future increase in waste water flow and COD-load. For the case of an existing upper limit of COD discharges into the river, the COD reduction rate of the waste water treatment has to be increased to a degree which is unobtainable by biodegradation only. Laboratory and pilot plant trials using a moving bed biofilm technique and an activated sludge treatment combined with ozone treatment and subsequent biofiltration have been performed with the aim to increase the COD reduction capacity and efficiency of the plant. The results show that the COD reduction capacity of the existing activated sludge plant can be increased by more than 100% by integrating a moving bed biofilm pre-treatment stage into the plant. In addition, improved sludge separation in the secondary clarifier was established. A special benefit of the ozonation plus biofilter treatment is a controllable COD reduction between 20 - 90% related to the outflow of the activated sludge plant. It is concluded that by integrating the investigated treatment techniques in the existing activated sludge plant the future increases in waste water flow and COD-Load can be handled satisfactorily without increasing bioreactor volume.

Effects of backwash conditions on out-to-in membrane microfiltration

North West Water Ltd (NWW) has applied hollow-fibre membrane microfiltration (MF) for treatment of potable water at full scale (15–80 MLD). NWW has currently five MF plants either in operation, commissioning or under construction (total capacity 240 Ml/d). The adoption of this technology has been driven by a number of factors, one of which is to provide a barrier to Cryptosporidium. As part of the development of large systems, NWW's Technology Development Team have performed an extensive series of pilot trialling. The efficacy of the backwash is one of the key criteria in ensuring the efficient and effective operation of the MF system. This is particularly important with out-to-in hollow-fibre membrane systems, since the bundle of fibres can act as a depth filter and accumulate deposits from the feed water. Moreover, the internal membrane hydraulics of an out-to-in system, during backwash, is complex. This makes optimisation of the efficient removal of solids from the membrane surface, by the backwash, an important task. Poor flow distribution, within the membrane module, can lead to the development of areas of low flow rates or “dead areas”. There is a risk of solids accumulation, within these dead areas, which will lead to increased transmembrane pressure during production. Pilot plant trials have been performed to optimise the backwash conditions at all the sites at which NWW have applied MF. The work has explored a variety of parameters associated with the backwash operation, such as backwash pressure, interval, duration, volume, chemical assistance, fibre integrity and the use of water pulsing. Results show that all the variables must be addressed to develop an optimised backwash strategy. By optimising backwash pressure, interval, duration, volume and use of chemicals (oxidants) run times can be extended and hence operating costs controlled. The most promising results, in terms of removal of deposited foulant from the membrane surface, are obtained with the pulsed backwash, where the backwash water is delivered in a series of discrete pulses. These studies have clearly demonstrated that the majority of deposited material is detached from the membrane surface during the initial phase of the backwash. This suggests that the detachment mechanism is more likely to be mechanical, caused by the sudden expansion of the bundle, and not hydraulic shear. Optimisation of pulse duration, the interval between pulses and the number of pulses applied in any one backwash cycle, has been performed. It has been possible to show that after time a steady state is achieved and backwash efficiency approaches 100%. Interestingly, backwash efficiency was found to increase as a run progressed. At the outset of a run backwash efficiency was typically low (∼14%) and increased with time to nearly 100%. This indicates that some form of steady state system is in operation whereby the solids being removed from the system are a function of the incoming solids and the previously retained solids. The effect of fibre breakage on backwash efficiency, with an out-to-in membrane system was found to result in serious degradation of backwash efficiency. The likely explanation is that a broken fibre will take a significant proportion of the backwash flow. This effect was observed during pilot plant trials when backwash efficiency and permeate water quality deteriorated simultaneously. Subsequent bubble point tests revealed fibre breakage. Once this damage was repaired. backwash efficiency was restored.

Processing of leather waste: pilot scale studies on chrome shavings. Isolation of potentially valuable protein products and chromium

Hides come to the tanner as a by-product of the meat industry. The tanning process, in turn, generates much greater quantities of by-products and wastes than leather. One ton of wet salted hides yields only 200 kg of leather but over 600 kg of solid waste, or by-product if a market can be found. In the United States, nearly 60,000 metric tons of chromium-containing solid waste, i.e. chrome shavings, are generated by the leather industry each year, and approximately ten times this amount is generated worldwide. Land application for the disposal of chromium-containing tannery and other leather wastes has been widely practiced during most of the twentieth century, but fewer landfill sites can be found every day and the cost of transportation and disposal increases. Historically, these materials were used in the production of fertilizer or composite boards, but while once the company producing and marketing fertilizer or boards would pay for the waste and its transportation, nowadays, the tanner has to pay for such things. Over several years, we have demonstrated that it is possible to isolate protein products (gelatin and collagen hydrolysate) from chrome shavings by using an alkaline protease under mild conditions. The objective of the present work was to perform pilot plant trials to isolate protein products from chrome shavings, treat and purify the remaining chrome cake and tan hides with the recovered chromium. Because of the high nitrogen content, the isolated collagen hydrolysate has potential use as a fertilizer and in animal feed additives. The gelatin has potential use in cosmetics, adhesives, printing, photography, microencapsulation, films or even as an additive in finishing products for the leather industry.

Robust optimal fermentation operating policies

The bioprocess industry is starting to face new commercial pressures leading to a greater emphasis on improving manufacturing, and delivering relatively low-volume, high value-added products at costs acceptable to health-care providers. A major challenge in this industry is the rapid development of new integrated processes for optimal large scale production. Accurate predictive models of biochemical unit and process operations are required if optimal design is to be achieved without extensive pilot plant trials (Richardson and Peacock, 1994). In the literature there exist many models of unit operations used in bioprocesses. In principle, these should be particularly useful in determining the optimal operation of the process, but a wide range of uncertainty associated with each model presents a number of problems. The main obstacle is that using an operating policy which has been optimised for the nominal model parameter values in an uncertain system can lead to dramatic changes in the performance of the process. It is preferable to use a policy in which these changes are kept to a minimum, while maintaining a good performance in the nominal case. Therefore a comprehensive design of the process must account explicitly for these uncertainties. This paper concentrates on the optimisation of fermenter operating policies. Here, we consider an appropriate definition of “robustness” for biochemical processes, and go on to describe one means of ensuring such robustness during the optimisation of the dynamic operation of a formenter. We use an illustrative example to contrast, using stochastic simulation, the proposed robust approach with a deterministic design based on nominal parameter values.

機械パルプと非木材パルプ Ｔｈｅｒｍｏｐｕｌｐ 省エネルギーＴＭＰプロセスの誕生

A new two-stage refiner mechanical pulping system utilizing the well-known reduction of energy to rupture in the wood structure at elevated temperature well above the softening point of lignin has been offered by Sunds Defibrator AB, with the new process name Thermopulp®, in the production of mechanical pulp for printing grades. In this paper, a summary of mill scale trials of Thermopulp® concept carried out on Scandinavian spruce at Ortviken, SCA is presented ; about 20% of refining energy consumption was reduced with equivalent pulp qualities except a small reduction in brightness and tear index compared to the referenced conventional TMP system for news quality pulp. Application of the same concept to TMP reject pulp refining has also been proven with acceptable result. Extending the raw material reference base, some pilot plant trials have also been carried out on Pines with encouraging results. Totally 4, 500 t/d of printing grade pulp plants designed on Thermopulp® process have been installed in Sweden, Canada and Chile and under operation with great success. Now a users group has been formed in North America and started realistic activities to exchange and divide all experience and requirement on research and optimization of the new process, with the common goal of 40% energy saving in the near future. An interstage bleaching in the new process is also one technology shall be chased and developed.

Rapid piloting of a selective flocculation process for product purification

The development of a bioprocess from the bench scale to industrial scale involves a highly demanding and time consuming piloting phase. This often occurs at a critical time in process development and there is considerable pressure on the responsible scientist/engineer to arrive at an acceptable specification with minimum number of pilot plant trials. Real-time decision making can be made possible by the availability of rapid information and the use of on-line predictive model design to give the development engineer new process information in an optimum graphical form. A potential operation for the downstream processing of intracellular proteins is selective flocculation. By selectively removing cell debris and nucleic acids in a single stage, considerable saving can potentially be made on the overall cost of protein purification. When developing the process from bench to pilot scale, it is important to identify the desired cut fraction for contaminant removal and product recovery. The study demonstrates that with real-time measurements of the product and contaminants, as well as the use of advanced statistical analysis tools, it is possible to identify, in real-time, appropriate piloting conditions necessary to develop process understanding.

Pilot and full scale plant trials using thiourea enhanced Zadra stripping of activated carbon

Bench scale tests have been carried out to determine ways of improving the relatively slow kinetics of elution of gold from activated carbon. These indicate that a solution of 3.0 wt% thiourea, 2.0 wt% NaOH and 0.05 wt% NaCN represents the best prospects for greatly improved throughout in industrial cells. This paper presents the results of pilot plant trials of this solution. Pilot plant results reflected the results obtained in the laboratory and encouraged the subsequent introduction of the solution as a modification to the commercial Zadra plant operation. Although the initial plant trials were disappointing slight modifications to allow for staged additions of the NaCN and increased flow rates did result in significant improvement in the elution rates. This improvement in the kinetics of elution is reflected in the overall recovery and consequently in the throughput rates for the plant.

History, overview and applications of mediated lignolytic systems, especially laccase-mediator-systems (Lignozym®-process)

After discovery of ligninases (lignin peroxidases and manganese peroxidases) in the 1980s, participation of a naturally occurring mediated system in the degradation of lignin was intensively discussed due to the fact that the size of these enzymes seemed to be too large for penetration of the cell wall or the middle lamella. Several groups have published hypotheses about a possible mechanism and some patents have been filed. Different compounds were considered to play the `key-role' together with an enzyme in delignification, but until now only indirect indications for a mediated process have been found. Euphoric expectations associated with the discovery of the ligninases—that an effective biological, cell-free delignification process could be quickly developed—were not answered. With respect to this concept a general overview about the literature with a special focus on laccase-assisted reactions will be given. Our recent discovery applying laccase and compounds with –NO, –NOH or HRNOH– groups for delignification will be discussed in more detail, especially regarding effects on pulps, kinetic data and specificity of the reaction. The general applicability of the laccase-mediator-system (Lignozym®-process) will be given by a comparison of results obtained with pulps from different sources of wood and from several pulping processes. The technical feasibility of this enzyme-mediator-based technology for delignification of pulps could be demonstrated in a pilot plant trial already.