Pellet Growth Research Articles

Three Years Experience of Operating and Selling Recovered Struvite from Full-Scale Plant

The adoption of phosphorus removal at sewage treatment works (STW) creates two main problems. Firstly large amounts of sludge are produced and secondly the quantity of the effluent deteriorates due to the increase in the phosphorus load of the sidestream. Furthermore, these processes do not remove phosphorus in a form that would enable it to be recycled. Therefore in order to control these process difficulties and produce a recyclable phosphorus product a sidestream struvite crystallisation reactor was developed. The struvite was produced in a fluidised bed reactor using dewatered filtrate from anaerobic sludge digestion. Magnesium hydroxide was added in a magnesium to phosphate ratio of 1 : 1 and the pH was adjusted to between 8.2 – 8.8 with the addition of sodium hydroxide. A retention time of 10 days allowed the growth of pellets between 0.5 – 1.0mm in size. The recovered struvite contained only minute traces of toxic substances and was sold to fertiliser companies for 27,000 yen tonne−1. It is used to enhance existing fertilisers, which are widely used on paddy rice, vegetables and flowers.

Factors governing microstructure development of Cr 2O 3-doped UO 2 during sintering

Sintering and grain growth of compacted uranium dioxide powder pellets doped with Cr 2O 3 were investigated at constant heating rates ranging from 75 to 500 K h −1 . The influence of parameters such as the oxygen potential of the sintering atmosphere and pellet green density on the final microstructure was studied. Dilatometric analysis and monitoring of microstructural development revealed a phenomenon of abnormal grain growth promoting densification. The existence of a eutectic between Cr and Cr 2O 3 is also discussed. Grain growth does not appear to be widely affected by small differences in residual porosity, which is a function of green density, so that it is possible to propose a solubility limit for Cr 2O 3 in stoichiometric UO 2 at 1700°C. Examination of microstructural changes during annealing, with or without pore formers, showed the existence of limiting grain sizes for doped samples above the solubility limit. Lastly, experimental sintering conditions need to be checked in order to obtain reproducible results.

Top seeding melt texture growth of NdBaCuO pellets in air

Most of NdBaCuO synthesis were realized under oxygen controlled melt growth (OCMG) which allows to avoid the solid solution formation. However, for industrial applications air synthesis is preferable due to its simplicity and its cost. In this work, different seeds and thermal cycles have been investigated in order to optimize the nucleation conditions for the obtention of a single domain. Several criteria have been defined for the choice of the seed. The solid solution Nd1+xBa2−xCu3Oy formed in these air synthesised samples appears in the range of x = 0.10 to 0.15, corresponding to between 60 K and 80 K. The nominal composition and the synthesis conditions (substrate, thermal treatments.) have to be accurately defined in order to avoid neodymium-rich solid solution formation.

Influence of some environmental factors on Rhizopus nigricans submerged growth in the form of pellets

Morphological changes of a steroid transforming filamentous fungus Rhizopus nigricans were studied by altering submerged growth conditions at inoculum sizes previously determined to favor pelleted growth. Beside the main classification between pelleted and clumpy growth forms, the size, concentration and structure of pellets were characterized at different cultivating temperature, initial pH value, medium composition, additives, and aeration conditions. Initial pH below 4 and above 7, the presence of Ca2+ and Tween-80 gave rise to the clumpy growth, otherwise pelleted growth prevailed. Among tested factors the pellet size was mainly influenced by the inoculum size and the presence of baffles and Ca2+ in cultivation medium. The formation of smooth pellets, prerequisite for further application in the process of steroid biotransformation, resulted in cultivations at lower temperature, high agitation rates in shaken cultures without baffles and at high nitrogen concentration.

カビペレットを活用した生デンプン含有食品工場排水の処理特性

Treatabilities of food-processing industrial wastewater containing raw starch were experimentally investigated in batch and continuous cultures with Aspergillus niger pellets.In batch culture using wastewater of 10, 000 mg-TOC/l containing in raw starch of 25 g/l, the removal efficiencies of starch and TOC reached 90% and 44% for 10 days, respectively. An important information from practical point of view was that starch granules were rapidly incorporated into the pellet inside with growth of pellets. It can be assumed that high removal efficiency of starch is closely related to this incorporation.In continuous culture using wastewater of 1, 000 mg-TOC/l containing raw starch of 1.25 g/l and soluble starch of 1.25 g/l, the removal efficiency of starch was held at over 77% during experimental period of 28 days by replacing the grown pellets with new ones.By use of multi-stage reactor with fungal and activated sludge processes, the removal efficiencies of total sugar and TOC in the food-processing industrial wastewater containing raw starch were held at 100%and over 86%, respectively. This result clearly shows that the actual industrial wastewater can be effectively treated in multi-stage process with Aspergillus niger pellets and activated sludge.

Melt pelletisation of a hygroscopic drug in a high shear mixer: Part 1. Influence of process variables

The applicability of a high shear mixer for melt pelletisation of binary mixtures of sodium valproate and glycerol monostearate was investigated. The effects of binder concentration, impeller speed, jacket temperature and massing time on mean pellet size and size distribution were examined in a 2 4-factorial design. Binder concentration and impeller speed were found to be the most important variables influencing the mean granule size and size distribution. An increase in each of those accelerated the granule growth. Due to the solubility of the drug in the molten binder very low amounts of binder were necessary for the formation of pellets. The modified high shear mixer was found to be suitable for batch sizes of 1–4 kg; granule growth was delayed with increasing load. A common pellet growth pattern, which can be divided into three phases, was derived and confirmed from all trials. The process was monitored by means of a torque measuring system. The torque–time curve can be used to detect the beginning of the destruction phase.

Effects of Conditioners (Standard, Long-Term and Expander) on Pellet Quality and Growth Performance in Nursery and Finishing Pigs

Effects of Conditioners (Standard, Long-Term and Expander) on Pellet Quality and Growth Performance in Nursery and Finishing Pigs

A New Method for the Control of Size of Pellets in the Melt Pelletization Process with a High Shear Mixer.

The control of the melt pelletization process in an 8-1 high shear mixer using specific energy consumption of the impeller motor was studied. Lactose was used as the bulk material with polyethylene glycol 3000 as a meltable binder. The effects of binder concentration, mean particle size of bulk material and post-melt impeller speed on the relationship of specific energy consumption and pellet growth were examined. Specific energy consumption was found to be a suitable tool for monitoring the melt pelletization process, and specific energy consumption correlated well with pellet growth. The mean size of the pellets formed becomes correspondingly larger with increasing specific energy consumption. Concerning the impeller speed, specific energy consumption is more useful as a tool for end-point control of the process than post-melt mixing time. Similar size pellets can be obtained with comparable specific energy consumption, independent of the impeller speed. The control of pellet size requires a correlation between pellet growth and specific energy consumption that is established for the formulaiton and process conditions used. For this purpose, mathematical modelling of the pellet growth process is presented. The predictions of pellet growth by the mathematical model are in agreement with the experimental findings.

The effect of pre-weaning environment on piglets' post weaning behaviour

A number of welfare and production problems are associated with weaning piglets including belly-nosing, ear and tail-biting, depressed immune responses, low intake of pelleted feed and impaired growth rate. These problems are, however, less pronounced in piglets reared on outdoor systems, which initially consume more pelleted food and show less belly-nosing and ear and tail biting than comparable indoor reared piglets. The objective of this study was to investigate how these differences in post weaning behaviour relate to the piglets' pre-weaning behaviour in the two rearing environments.The study was carried out on a 200 sow breeding herd (Camborough line 12) with sows equally divided between extensive and intensive systems. In the intensive system, sows were singly housed prior to farrowing in crates and their piglets received a pelleted “creep” feed prior to weaning. On the outdoor system, sows were allowed to build straw nests in arks for farrowing and both sow and piglets had access to pasture. Each ark had observation holes in the front and back to allow sampling of the piglet's behaviour without disturbing the sow. Indoor and outdoor piglets were weaned at three weeks of age and mixed together in groups of 90-120 in straw-yard housing with access to a pelleted feed.

Estimating growth kinetics of Penicillium chrysogenum by nonlinear regression

A simple unstructured microbial growth model was used to describe the dynamics of fungal growth in batch cultures. Biokinetic parameters were evaluated using the integral form of the Contois equation by nonlinear regression. Monte Carlo simulations and sensitivity analyses were performed to evaluate the effectiveness of the nonlinear parameter estimation technique for obtaining unique and accurate estimates of the Contois equation parameters. This technique was subsequently used to estimate growth kinetic parameters of Penicillium chrysogenum grown on glucose. Microbial growth and substrate depletion were accurately described by the Contois equation and the kinetic parameters were estimated as μ max=0.103 h −1, K c=0.145 and Y= 0.445. The applicability of the Contois equation to describe both pellet and filamentous fungal growth was verified using previously published data. The use of the integrated Contois equation is advantageous as biokinetic parameters can be estimated from a single substrate depletion curve.

Production of l-lactic acid byRhizopus oryzae in a bubble column fermenter

Two distinctive forms of growth (mycelial filamentous and mycelial pellets) of Rhizopus oryzae were obtained by manipulating the initial pH of the medium with the controlled addition of CaCO3 in a bubble fermenter. In the presence of CaCO3, diffused filamentous growth was obtained when the initial pH of the substrate was 5.5. In the absence of CaCO3, mycelial pellet growth was obtained when the initial pH was 2.0. The fermentation study indicated that the mycelial growth has a shorter lag period before the onset of acid formation. Both physical forms of growth of Rhizopus exhibited a high yield of L-lactic acid in the bubble fermenter when the initial glucose concentration exceeded 70 g/L. A final lactic acid concentration of 62 g/L was produced by the filamentous form of Rhizopus from 78 g/L glucose after 27 h. This showed a weight yield of 80% of glucose consumed, with an average specific productivity of 1.46 g/h/g. Similarly, the pellet form of Rhizopus produced a final lactic acid concentration of 66 g/L from 76 g/L glucose after 43 h, with a weight yield of 86% and an average specific productivity of 1.53 g/h/g.

Improvement of tylosin production from Streptomyces fradiae culture by decreasing the apparent viscosity in an air-lift bioreactor

Tylosin production in the culture of Streptomyces fradiae T1558 was improved by decreasing the apparent viscosity by means of a newly designed medium. When a medium containing 15 g/ l Pharmamedia (a proprietary nutrient derived from cotton seed) and 25 g/ l gluten meal was used in a 3- l air-lift bioreactor, the tylosin concentration and apparent viscosity of the broth were 2.1 g/ l and 190 cP, on day 10 with preferential filamentous growth, while the DO level could hardly be controlled at an appropriate level during fermentation because of the high apparent viscosity. However, when a newly designed medium containing 10 g/ l Pharmamedia and 10 g/ l gluten meal was used, the tylosin production and apparent viscosity of the broth were 7.4 g/ l and 50 cP, on day 10 with preferential pellet growth and appropriate control of DO level. The decrease in the apparent viscosity which was dependent on morphological change, was effective in increasing the tylosin productivity in an air-lift bioreactor through the improvement of mass transfer.

Optimization of the Processing of Matrix Pellets Based on the Combination of Waxes and Starch Using Experimental Design

An experimental design was used in order to optimize the one-step production process of matrix pellets based on the combination of waxes and starch. The parameters tested were the impeller speed (x1) and the mixing time (x2). Ibuprofen and theophylline were used as model drugs at a concentration of 60 and 70% (w/w), respectively. The 0.8–1.25 mm yield fraction of the matrix pellets was evaluated as the response factor Y. A quadratic equation was fitted to the experimental data and used to predict the response factor Y of the theophylline and the ibuprofen. The contour plots of both formulations revealed a flat and therefore rugged region from the upper left to the lower right of the domain investigated. The energy input into the system during the production process controlled the pellet growth, the impeller speed having a greater impact on the energy input compared to the mixing time.

Growth mechanisms of high-shear pelletisation

Two high-shear mixers, Gral 10 and Gral 25, were used to prepare pellets of microcrystalline cellulose and lactose, using water as binder liquid. Growth of pellets was investigated by measuring the pellet size distribution during the process. On the basis of the experiments the destructive nucleation growth mechanism was defined. Pelletisation was started with the formation of large primary nuclei. Small secondary nuclei were formed due to break-up of the primary nuclei. This nucleation process could be described by the comparison of the theoretical tensile strength of the nuclei and the dynamic impact pressure. Due to densification, the secondary nuclei became stronger and growth proceeded exponentially by coalescence. During the kneading stage, net growth was diminished until a steady state was observed. The mean pellet size did not change during the final stage of the kneading phase which resulted in a well-defined product.

A multi‐thermal model of cumulus glaciation via the hallett‐Mossop process

AbstractAnalysis of field observations has yielded the conclusion that the Hallett‐Mossop process (H‐M) of secondary ice production plays a major role in the glaciation of summertime cumulus clouds over New Mexico. Other studies have revealed that these clouds possess a characteristic multi‐thermal structure.In an effort to quantify more fully the role of H‐M in such clouds, and to establish which of the salient dynamical and microphysical parameters play important roles in the glaciation process, a model of ice‐particle growth and splinter production in a simple multi‐thermal framework is developed. the characteristics of the model are prescribed with values that are based on the above‐mentioned field studies. the model cloud possesses four distinct regions: the main updraught, a quiescent (debris) region, the cloud top, and a downdraught region.The trajectories of all primary ice particles introduced into the cloud at t = O, together with those created as a consequence of the operation of H‐M, are followed as they grow and are transported around the cloud. the sensitivities of these trajectories and a multiplication factor f to variations in parameters such as updraught speed, liquid‐water content, L, thermal depth, inter‐thermal interval, and downdraught characteristics are examined.These tests reveal that f is particularly sensitive to the values of L in the distinct regions of the cloud. Basically, combinations of parameter values which produce rapid growth of graupel pellets, large number of thermals, and efficient transport between cloud top and the Hallett‐Mossop temperature band yield the most rapid ice‐particle multiplication.

A multi-thermal model of cumulus glaciation via the Hallett-Mossop process

Analysis of field observations has yielded the conclusion that the Hallett-Mossop process (H-M) of secondary ice production plays a major role in the glaciation of summertime cumulus clouds over New Mexico. Other studies have revealed that these clouds possess a characteristic multi-thermal structure. In an effort to quantify more fully the role of H-M in such clouds, and to establish which of the salient dynamical and microphysical parameters play important roles in the glaciation process, a model of ice-particle growth and splinter production in a simple multi-thermal framework is developed. the characteristics of the model are prescribed with values that are based on the above-mentioned field studies. the model cloud possesses four distinct regions: the main updraught, a quiescent (debris) region, the cloud top, and a downdraught region. The trajectories of all primary ice particles introduced into the cloud at t = O, together with those created as a consequence of the operation of H-M, are followed as they grow and are transported around the cloud. the sensitivities of these trajectories and a multiplication factor f to variations in parameters such as updraught speed, liquid-water content, L, thermal depth, inter-thermal interval, and downdraught characteristics are examined. These tests reveal that f is particularly sensitive to the values of L in the distinct regions of the cloud. Basically, combinations of parameter values which produce rapid growth of graupel pellets, large number of thermals, and efficient transport between cloud top and the Hallett-Mossop temperature band yield the most rapid ice-particle multiplication.

Sintering behaviour of niobia-doped large grain UO2 pellet

The densification and grain growth of niobia-doped UO2 pellets have been studied with the purpose of obtaining a large grain size. The solid solution limit of niobium oxides in UO2 was about 0.5 wt% Nb2O5 as measured by the variation of the lattice parameter. The addition of 0.3 wt% Nb2O5 or NbO2 increased the grain size more when the oxygen partial pressure in the sintering atmosphere was above the equilibrium value for Mb5+ than when it was above that of Nb4+. This effect of the oxygen partial pressure made it possible to manufacture a large grain UO2 pellet doped with a small amount of niobia below the solid solution limit and sintered at a low temperature in a sintering atmosphere in which the oxygen partial pressure was controlled.

Experimental verification of a mathematical model for pelleted growth of Streptomyces coelicolor A3(2) in submerged batch culture

A published mathematical model for growth of pellets of filamentous microorganisms has been tested by comparison of model predictions with experimental data on growth of Streptomyces coelicolor in liquid batch culture. The original model considered the classification of pellets into a range of size classes. Growth resulted in movement of pellets to classes of increasing size, while shear forces produced mycelial fragments which entered the smallest size class, from which they grew to form further pellets. This model did not correctly describe changes in pellet size distributions during growth and was therefore modified in two ways. In the first, new pellets were assumed to be formed by the break-up, by shear forces, of existing pellets into two pellets of equal size, rather than removal of small hyphal fragments from the pellet surface. The second modification assumed that the outer shell of active mycelial biomass had a density less than 1 g cm-3 and that hyphal density within this shell decreased with distance from the pellet centre. The modified model generated predictions which agreed closely with experimental data on biomass concentration, pellet size distribution, pellet number and pellet radius during batch growth, thereby supporting the assumptions on which the model was based. The model did not accurately describe final biomass concentration, through lack of consideration of autolysis of mycelia at the centre of larger pellets in which growth was limited by diffusion of nutrients. Attempts to incorporate autolysis into the model improved prediction of biomass concentration but were not based on sound biological assumptions and increased the complexity of the model. Further experimental work is required for accurate description of the effects of autolysis on pellet growth.

Experimental verification of a mathematical model for pelleted growth of Streptomyces coelicolor A3(2) in submerged batch culture.

A published mathematical model for growth of pellets of filamentous microorganisms has been tested by comparison of model predictions with experimental data on growth of Streptomyces coelicolor in liquid batch culture. The original model considered the classification of pellets into a range of size classes. Growth resulted in movement of pellets to classes of increasing size, while shear forces produced mycelial fragments which entered the smallest size class, from which they grew to form further pellets. This model did not correctly describe changes in pellet size distributions during growth and was therefore modified in two ways. In the first, new pellets were assumed to be formed by the break-up, by shear forces, of existing pellets into two pellets of equal size, rather than removal of small hyphal fragments from the pellet surface. The second modification assumed that the outer shell of active mycelial biomass had a density less than 1 g cm-3 and that hyphal density within this shell decreased with distance from the pellet centre. The modified model generated predictions which agreed closely with experimental data on biomass concentration, pellet size distribution, pellet number and pellet radius during batch growth, thereby supporting the assumptions on which the model was based. The model did not accurately describe final biomass concentration, through lack of consideration of autolysis of mycelia at the centre of larger pellets in which growth was limited by diffusion of nutrients. Attempts to incorporate autolysis into the model improved prediction of biomass concentration but were not based on sound biological assumptions and increased the complexity of the model. Further experimental work is required for accurate description of the effects of autolysis on pellet growth.

A mathematical model for the growth of mycelial pellet populations

In liquid culture, filamentous organisms often grow in the form of pellets. Growth result in an increase in radius, whereas shear forces result in release of hyphal fragments which act as centers for further pellet growth and development. A previously published model for pellet growth of filamentous microorganisms has been examined and is found to be unstable for certain parameter values. This instability has been identified as being due to inaccuracies in estimating the numbers of fragments which seed the pellet population. A revised model has been formulated, based on similar premises, but adopting a finite element approach. This considers the population of pellets to be distributed in a range of size classes. Growth results in movement to classes of increasing pellet size, while fragments enter the smallest size class, from which they grow to form further pellets. The revised model is stable and predicts changes in the distribution of pellet sizes within a population growing in liquid batch culture. It considers pellet growth and death, with fragmentation providing new centers of growth within the pellet population, and predicts the effects of shear forces on pellet growth and size distribution. Predictions of pellet size distributions are tested using previously published data on the growth of fungal pellets and further predictions are generated which are suitable for experimental testing using cultures of filamentous fungi or actinomycetes.