M.S.A. Bradley

Climate Change and Sustainable Development: Realizing the Opportunity

Abstract Manifold linkages exist between climate change and sustainable development. Although these are starting to receive attention in the climate exchange literature, the focus has typically been on examining sustainable development through a climate change lens, rather than vice versa. And there has been little systematic examination of how these linkages may be fostered in practice. This paper examines climate change through a sustainable development lens. To illustrate how this might change the approach to climate change issues, it reports on the findings of a panel of business, local government, and academic representatives in British Columbia, Canada, who were appointed to advise the provincial government on climate change policy. The panel found that sustainable development may offer a significantly more fruitful way to pursue climate policy goals than climate policy itself. The paper discusses subsequent climate change developments in the province and makes suggestions as how best to pursue such a sustainability approach in British Columbia and other jurisdictions.

A model to predict the solid particle erosion rate of metals and its assessment using heat-treated steels

Abstract A new predictive model for the wear rate of metals during solid particle impact erosion is presented. The model proposes that erosion rate is related to the product of toughness ( U T ) and uniform strain ( e U ). Predictions for the variation of erosion rate with impact angle are also made. The validity of the model was assessed using an extensive set of new experimental data generated for heat-treated steels. Two steels were heat treated to form a total of 12 different microstructures, each having distinctly different mechanical behaviour. Erosion tests were carried out at a combination of three impact velocities and three angles of particle impingement in a rotating disc accelerator erosion tester. Fine olivine sand was used as the abrasive at one feed rate. Tensile tests were carried out on all the heat-treated steels over a range of temperatures from room temperature to 400°C. The model predictions were not satisfied by mechanical property measurements made at room temperature. However, for each given erosion test condition, a good linear relationship was found between room temperature erosion rate and 1/ U T e U when mechanical properties were measured at elevated temperatures. The elevated temperature chosen to give the best-fit was between 200 and 300°C depending on the impact velocity. It is believed that the significance of the elevated temperature property measurements is that they account for localised heating occurring at the impacting particle during the high strain/strain-rate deformation typical of erosion. Certain heat-treatments gave a poorer fit to the relationship and explanations for this are proffered. The model was also able to account for changes in erosion rate with impact angle. Suggestions are made for improving the model and to refine its predictive capability.

The influence of particle rotation on the solid particle erosion rate of metals

Abstract It has long been recognised that particle spin may have a significant effect on the impact erosion rate, particularly of ductile metals. However, no work has previously been carried out to quantify this effect, partly due to the practical difficulty of measuring the magnitude of the rotational speed. Particle spin is a feature of the centrifugal accelerator erosion tester. In this tester it has proved possible to examine the effect on erosion of particle spin direction by varying the target orientation. The results indicated a strong effect of the spin direction on erosion rate at low impact angles when the targets were impacted by angular particles. A quantitative model was developed to explain the effect of particle spin direction on the observed differences. The model is a modification of the Finnie–Bitter model [Wear 3 (1960) 87; Wear 6 (1963) 5; Wear 6 (1963) 160], and is the first to explicitly incorporate the effect of rotating particles on the subsequent erosion rate when the particles impact a metal target. The model supposes that the effective impact velocity, the contact velocity between the particle and the target, is altered due to spin of the particles. The predictions of the model were validated through actual measurement of particle rotational speed by high-speed photographic techniques; the first such measurements. Experimental erosion results conformed to the predictions of the model. An effect of particle spin on the peak erosion rate is also predicted by the model and confirmed by the experimental results.

Aggregation and caking processes of granular materials: continuum model and numerical simulation with application to sugar

Aggregation and caking of particles are common severe problems in many operations and processing of granular materials, where granulated sugar is an important example. Prevention of aggregation and caking of granular materials requires a good understanding of moisture migration and caking mechanisms. In this paper, the modeling of solid bridge formation between particles is introduced, based on moisture migration of atmospheric moisture into containers packed with granular materials through vapor evaporation and condensation. A model for the caking process is then developed, based on the growth of liquid bridges (during condensation), and their hardening and subsequent creation of solid bridges (during evaporation). The predicted caking strengths agree well with some available experimental data on granulated sugar under storage conditions.

Constructing an engineering model for moisture migration in bulk solids as a prelude to predicting moisture migration caking

The aim of this study was to examine one of the mechanisms behind moisture migration caking, where liquid solution bridges form between particles in a bulk solid system because of an increase in local relative humidity, and then solidify as the local relative humidity drops - the effect being increased as more cycles occur. The goal was to develop a one-dimensional model for the heat and mass transfer processes involved, based on established physics and the characteristic moisture sorption curve of the solid (in this case sugar). The model was verified using scaled-down equipment (a caking box) to simulate the caking in a big bag. The results of this study will assist in the prediction of caking produced in this way.

Implementation of transmission NIR as a PAT tool for monitoring drug transformation during HME processing

The aim of the work reported herein was to implement process analytical technology (PAT) tools during hot melt extrusion (HME) in order to obtain a better understanding of the relationship between HME processing parameters and the extruded formulations. For the first time two in-line NIR probes (transmission and reflectance) have been coupled with HME to monitor the extrusion of the water insoluble drug indomethacin (IND) in the presence of Soluplus (SOL) or Kollidon VA64 hydrophilic polymers. In-line extrusion monitoring of sheets, produced via a specially designed die, was conducted at various drug/polymer ratios and processing parameters. Characterisation of the extruded transparent sheets was also undertaken by using DSC, XRPD and Raman mapping. Analysis of the experimental findings revealed the production of molecular solutions where IND is homogeneously blended (ascertained by Raman mapping) in the polymer matrices, as it acts as a plasticizer for both hydrophilic polymers. PCA analysis of the recorded NIR signals showed that the screw speed used in HME affects the recorded spectra but not the homogeneity of the embedded drug in the polymer sheets. The IND/VA64 and IND/SOL extruded sheets displayed rapid dissolution rates with 80% and 30% of the IND being released, respectively within the first 20min.

A novel sensing technique for measurement of magnitude and polarity of electrostatic charge distribution across individual particles

Electrostatic charge is generated during powder handling due to particle-particle and particle-wall collisions, rubbing, sliding, and rolling. In case of bipolar charge generation, the electrostatic forces may significantly change the inner forces and increase powder adhesion and cause a serious problem in material handling process. Therefore, the knowledge of distribution of charge across the individual particles is helpful to identify the role of triboelectrification and the effects of various relevant variables especially change in the contact materials, environmental conditions during processing, etc. A novel approach based on inductive sensor has been developed to detect the either polarity of charged particle and to characterise the bipolar charge distribution in the population of particulate material. To achieve this, an amplification unit configured as a pure integrator and signal processing techniques has been used to de-noise and correct the baseline of signal and MATLAB algorithm developed for peak detection. The polarity of charged particles obtained by this method is calibrated with Faraday pail method and the results are promising. Experimental study has been carried out by using two distinct populations of oppositely charged particles (glass beads-PVC, olivine sand, and silica sand). The obtained results indicate that the method is able to detect the distribution of polarities of charged particles.

One-step continuous extrusion process for the manufacturing of solid dispersions

The purpose of this study was to evaluate the performance of synthetic magnesium aluminometasilicate (MAS) as a novel inorganic carrier in hot melt extrusion (HME) processing of indomethacin (IND) for the development of solid dispersions. A continuous extrusion process at various IND/excipient blend ratios (20%, 30% and 40%) was performed using a twin-screw extruder. Physicochemical characterization carried out by SEM, DSC, and XRPD demonstrated the presence of IND in amorphous nature within the porous network of the inorganic material for all extruded formulations. Further, AFM and FTIR studies revealed a single-phase amorphous system and intermolecular H-bonding formation. The IND/MAS extrudates showed enhanced INM dissolution rates within 100% been released within 1h. Stability studies under accelerated conditions (40°C, RH 75%) showed that MAS retained the physical stability of the amorphous solid dispersions even at high drug loadings for 12 months.

Segregation of binary mixtures of particles during the filling of a two-dimensional representation of a hopper

Abstract This paper contains a summary of results obtained from experiments carried out at The Wolfson Centre for Bulk Solids Handling Technology at the University of Greenwich on the segregation of dry binary particle mixtures of the same material when they fill a hopper. A test facility has been built which represents a two-dimensional segment of a hopper. Binary mixtures were fed into this container using amplitude feedback-controlled vibratory feeders via a static in-line mixer and one of two different feed chute designs; one curved and the other straight. ‘Thieving’ probes were used to sample the segregated heap of material from the hopper. The contents of each probe then underwent size analysis to ascertain the change in the size distribution from that of the original mixture. It is shown that a mechanism, termed embedment, caused by the vertical component of the feed velocity on impact with the forming heap, has a dramatic effect on the segregation process. A detailed discussion of the relationship between the possible mechanisms occurring in the heap formation process in the light of the segregation patterns observed is given.

Continuous twin-screw granulation for enhancing the dissolution of poorly water soluble drug

The article describes the application of a twin-screw granulation process to enhance the dissolution rate of the poorly water soluble drug, ibuprofen (IBU). A quality-by-design (QbD) approach was used to manufacture IBU loaded granules via hot-melt extrusion (HME) processing. For the purpose of the study, a design of experiment (DoE) was implemented to assess the effect of the formulation compositions and the processing parameters. This novel approach allowed the use of, polymer/inorganic excipients such as hydroxypropyl methylcellulose (HPMC) and magnesium aluminometasilicate (Neusilin(®)-MAS) with polyethylene glycol 2000 (PEG) as the binder without requiring a further drying step. IBU loaded batches were processed using a twin screw extruder to investigate the effect of MAS/polymer ratio, PEG amount (binder) and liquid to solid (L/S) ratios on the dissolution rates, mean particle size and the loss on drying (LoD) of the extruded granules. The DoE analysis showed that the defined independent variables of the twin screw granulation process have a complex effect on the measured outcomes. The solid state analysis showed the existence of partially amorphous IBU state which had a significant effect on the dissolution enhancement in acidic media. Furthermore, the analysis obtained from the surface mapping by Raman proved the homogenous distribution of the IBU in the extruded granulation formulations.