Downstream Processing Performance Research Articles

A perspective on downstream processing performance for recovery of bioalcohols

A perspective on downstream processing performance for recovery of bioalcohols

Optimisation of Vacuum Distillation Units in Oil Refineries Using Surrogate Models

To ensure the optimum performance of downstream processes in a petrochemical refinery, the operation of a vacuum distillation unit (VDU) is critical. It needs to satisfy the yield and quality requirements of the downstream process. Otherwise, it will result in a loss of profitability in the refinery. Hence, it is important to optimise the operation of the VDU to ensure optimum performance. Traditionally, VDU is operated within the design envelope, and its operation condition is fine-tuned based on the operator’s experience. However, such action does not guarantee the optimum performance of the entire refinery as it only considers the operation of VDU without understanding the effects towards downstream processes. Therefore, this work presents a framework to optimise VDU operations with consideration of the downstream processes. The framework consists of process simulation, surrogate modelling, and multi-objective optimisation. The developed framework aims to determine trade-offs between high vacuum gas oil (HVGO) yield and total annualised cost (TAC) of a refinery that considers the needs of downstream operations. In this work, crude oil blending ratio, furnace outlet temperature, flash zone temperature, column top pressure, column bottom pressure, stripping steam flowrate, HVGO pump-around flowrate, and light vacuum gas oil (LVGO) pump-around flowrate of the VDU are to be optimised. Based on the optimised result, the heavy-light crude blend achieves higher HVGO yield and lower TAC, and the optimised results were validated with the simulation results via Aspen HYSYS. The proposed methodology was proven to have accurate estimations of the VDU operation in the process simulation environment. Moreover, the optimised results can provide insight into the optimal process conditions of VDU for the refiners. With this insight, effective operating strategies can be developed to overcome the limitations present in real VDU operations.

An integrated framework for sustainable process design by hybrid and intensified equipment

With the increasing concern of the competitive market and carbon emissions, a sustainable, efficient process design becomes more and more important. The task of sustainable process design is to find efficient configurations and operating parameters to produce products or utilize materials. Currently, the scientific community's major focus is on separation synthesis, which aims to identify the best downstream separation configurations through different methods such as optimization, heuristic, and hybrid methods. Besides, innovative separation techniques with lower capital/operating costs and carbon emissions were proposed and identified to further improve the downstream process performance. However, most of the separations synthesis methods were based on conventional unit operations and usually applied for generating sustainable processes with a given reaction pathway without considering the possibilities of different raw materials. Generally, to produce a given target product, multiple reaction pathways are available, and each reaction pathway leads to different downstream processes. Also, applying intensification in the early stages of process design, e.g., separation synthesis, can generate sustainable process flowsheets with higher energy efficiency and lower environmental impact. This work aims to develop an integrated process synthesis framework, which includes reaction synthesis for the reaction pathways selection and separation synthesis involving intensified/hybrid units. So, for the new process design, given the product one needs to produce, this framework could identify the optimal reaction pathway with its best separation route. The developed framework was used to solve three case studies, including the new process design of dimethyl carbonate (DMC) production and retrofitting design of cumene and styrene production. For all the case studies, the framework was able to generate multiple innovative solutions that are sustainable and energy-efficient.

Optimising of vacuum distillation units using surrogate models

Crude oil blending is an important step for the operation of crude distillation systems in the refinery to improve the yield and profitability of the products. The product’s yield and quality are strongly dependent on the properties of the crude oil. However, the products of crude distillation units, especially the vacuum distillation unit (VDU) need to satisfy the yield and quality requirements of the downstream process units in the refinery. Otherwise, the performance of downstream processes will be affected, and loss of profitability in the refinery. Hence, it is important to optimise the performance of the VDU to ensure the optimum operation of VDU. This work covers the process simulation of VDU, surrogate modelling and mathematical optimisation model. The objective of the developed optimisation model is to determine an optimal for maximum high vacuum gas oil (HVGO) yield and minimum total annualised cost (TAC) respectively. To do this, crude oil blending ratio, column temperature, column pressure, stripping steam flowrate, pump-around flowrate in the VDU are optimised. Based on the optimised result, the heavy-light crude blend achieves higher HVGO yield and lower TAC as compared to the heavy-medium crude blend and heavy-medium-light crude blend. The optimised results can provide insight into the optimal process conditions of VDU for the refiners. With this insight, effective operating strategies can be developed to overcome the limitations present in real VDU operations.

Integrated process development: The key to improve Fab production in E. coli.

Bioprocess development and optimization is a challenging, costly, and time-consuming effort. In this multidisciplinary task, upstream processing (USP) and downstream processing (DSP) are conventionally considered distinct disciplines. This consideration fosters "one-way" optimization disregarding interdependencies between unit operations; thus, the full potential of the process chain cannot be achieved. Therefore, it is necessary to fully integrate USP and DSP process development to provide balanced biotechnological production processes. The aim of the present study was to investigate how different host/secretory signal/antigen binding fragment (Fab) combinations in E. coli expression systems influence USP, primary recovery performance and the final product quality. We ran identical fed-batch cultivations with 16 different expression clones to study growth and product formation kinetics, as well as centrifugation efficiency, viscosity, extracellular DNA, and endotoxin content, important parameters in DSP. We observed a severe influence on cell growth, product titer, extracellular product, and cell lysis, accompanied by a significant impact on the analyzed parameters of DSP performance. Our results provide the basis for future research on integrated process development considering interdependencies between USP and DSP; however, individual products need to be considered specifically. These interdependencies need to be understood for rational decision-making and efficient process development in research and industry.

An innovative standard for LC-MS-based HCP profiling and accurate quantity assessment: Application to batch consistency in viral vaccine samples.

Biotherapeutics, molecules produced from biological systems, require rigorous purification steps to remove impurities including host cell proteins (HCPs). Regulatory guidelines require manufacturers to monitor process-related impurities along the purification workflow. Mass spectrometry (MS) has recently been considered as a complementary method to the well-established ELISA for HCPs quantification, since it has the advantage of unambiguously identifying individual HCP. In this study, we developed an innovative standard dedicated to MS-based HCP profiling analysis in order to monitor the consistency of viral vaccine intermediate purification samples. This standard, termed the HCP-PROFILER standard, is composed of a water-soluble bead (READYBEADS technology) which, after being added into the sample, releases unlabeled peptides in controlled amounts. The standard meets three desired criteria: (1) it is composed of multiple peptides, at different concentration levels, allowing construction of a calibration curve covering the dynamic range of HCPs present in the target sample, ensuring quantification accuracy; (2) it demonstrates high batch-to-batch reproducibility, ensuring quantification robustness and consistency over time; and (3) it is easy to use and avoids user-induced analytical biases. In this study, we present the use of the HCP-PROFILER standard for vaccine batches comparison and downstream process performance studies.

Geometallurgical characterisation of Mn ores

ABSTRACT This article details two geometallurgical case studies using classification schemes developed for Mn fine and lump ores. For the first, the relative abundance of 15 material types was compared to chemistry by size fraction. Positive correlations were evident between the proportion of aluminosilicate-bearing ore groups and Al2O3 content, the ratio of Mn oxide/Fe oxide ore groups and the Mn/Fe content, the proportion of cryptomelane-bearing groups and the K2O and BaO contents, and the ratio of hard to moderately hard + friable particles and the K2O + Ba + Na content. For the second, agreement was observed between the types of predominant material types in the two different ores and their mass distributions, major and trace element chemistries. Different material types had clear variances in their envelope and apparent particle densities. These two case studies support the expanded use of particle-based ore classification schemes for the characterisation of Mn ores to better predict their downstream processing performance.

Integrating sludge drying in biomass fueled CHP plants

Handling sludge through thermal conversion is environmentally friendly, which, however, requires sludge drying. This work proposed to use the waste heat of flue gas (FG) to dry sludge. The integration of sludge drying in biomass fueled combined heat and power (CHP) plants can clearly affect the performance of downstream processes in FG cleaning, such as flue gas quench (FGQ) and flue gas condenser, and further affect the energy efficiency of CHP. In order to understand the influence, a mathematical model and an Aspen PLUS model were developed to simulate the drying process and the CHP, respectively. Based on simulations, it is found that the increase of feeding rate of sludge and the moisture content of sludge after drying can decrease the water evaporation in FGQ. An increase in the feeding rate of sludge in combination with a drop of moisture content of sludge after drying can decrease the heat recovery from FG. When using dried sludge to replace biomass, the amount of saving could be influenced by the moisture content after drying and the flow rate of sludge. Simulation results show that drying sludge to a moisture content of 40% leads to the maximum biomass saving.

Lisocabtagene Maraleucel (liso-cel) Manufacturing Process Control and Robustness across CD19+ Hematological Malignancies

Background Lisocabtagene maraleucel (liso-cel) is an investigational, CD19-directed, genetically modified, autologous cellular immunotherapy administered as a defined composition of CD8+ and CD4+ components to deliver target doses of viable chimeric antigen receptor (CAR) T cells from both components. The CAR comprises a CD19-specific scFv and 4-1BB-CD3ζ endodomain. Liso-cel is being developed for the treatment of multiple B cell malignancies, including relapsed/refractory large B cell non-Hodgkin lymphoma (NHL) and chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL). The liso-cel manufacturing process design includes controls that enable robustness across heterogeneous patient populations and disease indications, minimizing between-lot variability. This is highlighted by consistency in process duration, reduction of terminally differentiated T cells present in the T cell starting material, and consistency in T cell purity across B cell NHL and CLL/SLL indications. Methods The liso-cel manufacturing process involves selection of CD8+ and CD4+ T cells from leukapheresis, followed by independent CD8+ and CD4+ activation, transduction, expansion, formulation, and cryopreservation. Liso-cel was manufactured in support of the TRANSCEND NHL 001 (NCT02631044) and TRANSCEND CLL 004 (NCT03331198) clinical trials. Phenotypic analysis of T cell and B cell composition from leukapheresis, T cell starting material, and CAR T cell product was performed by flow cytometry. Molecular characterization of T cell receptor (TCR) clonality was estimated from the T cell starting material and CAR T cell product through transcriptional profiling. Results Liso-cel manufacturing process optimizations have been implemented in advance of commercialization. These optimizations have significantly improved process duration consistency (Figure 1; F test P=4.1×10−36). Both phenotypic and molecular TCR clonality analyses demonstrated a significant reduction in terminally differentiated CD8+ T cells across the manufacturing process. Frequencies of CD45RA+ CCR7− populations were measured by flow cytometry in CD8+ T cell starting material (median=35.1%) and CAR T cell product (median=11.7%; Wilcoxon rank sum P=3.1×10−25). Characterization of TCR clonality showed a significant decrease in clonality in the CAR T cell product compared with T cell starting material (Wilcoxon rank sum P=5.6×10−6), suggesting selective expansion of clonally diverse, less differentiated T cell populations. These findings are supported by the predominant memory T cell composition observed in liso-cel. Manufacturing process robustness enabled by in-process T cell selection is further demonstrated by the capability to produce highly pure T cell products across heterogeneous patient populations and different disease indications. T cell and B cell composition were characterized in the leukapheresis, selected T cell material, and CAR T cell product, demonstrating consistent clearance of non-T cells, including CD19+ B cells in both B- cell NHL and CLL/SLL patient cohorts. Although the CD19+ B cell composition is significantly higher in leukapheresis from patients with CLL/SLL (median=10.0% of leukocytes) compared with B cell NHL patients (median=0.0% of leukocytes, Wilcoxon rank sum P=1.6×10−9), CAR T cell products manufactured from both CLL/SLL and B cell NHL patient populations consistently demonstrated clearance of non-T cells, including CD19+ cells, to below levels of quantitation. Conclusion Despite variation between B cell NHL and CLL/SLL patient leukapheresis, T cell enrichment before activation and transduction enables consistent downstream process performance and T cell purity, and a substantially reduced risk of transducing residual tumor cells. In addition, the reduction of terminally differentiated effector T cells and capacity to retain T cell diversity further improved consistency in product quality. Taken together, process modifications have enabled consistent manufacturing duration and quality of liso-cel product, which support operational efficiency and scalability for commercial production. Disclosures Teoh: Juno Therapeutics, a Celgene Company: Employment, Equity Ownership. Johnstone:Juno Therapeutics, a Celgene Company: Employment, Patents & Royalties: Author on a number of patent applications and invention disclosures relating to cell therapy and immunosequencing. Christin:Juno Therapeutics, a Celgene Company: Employment, Equity Ownership. Yost:Juno Therapeutics, a Celgene Company: Employment, Equity Ownership. Haig:Juno Therapeutics, a Celgene Company: Employment, Equity Ownership. Mallaney:Juno Therapeutics, a Celgene Company: Employment. Radhakrishnan:Juno Therapeutics, a Celgene Company: Employment, Equity Ownership. Gillenwater:Juno Therapeutics, a Celgene Company: Employment, Equity Ownership. Albertson:Juno Therapeutics, a Celgene Company: Employment, Equity Ownership. Guptill:Juno Therapeutics, a Celgene Company: Employment. Brown:Juno Therapeutics, a Celgene Company: Employment. Ramsborg:Juno Therapeutics, a Celgene Company: Employment, Equity Ownership, Patents & Royalties: Numerous patents. Hause:Juno Therapeutics, a Celgene Company: Employment, Equity Ownership. Larson:Juno Therapeutics, a Celgene Company: Employment, Equity Ownership.

Assessing the benefits of automatic grinding control using PST technology for true on-line Particle Size Measurement

Despite the recognized significance of ground product fineness on both line capacity and downstream process performance (typically flotation), less than 10% of mineral ore concentrators today use real-time particle size measurements in automatic control applications for the final product particle size. Although “near-line” particle size measurement instrumentation has been in place for several decades and is commonly installed in most modern concentrators, its availability and low measurement frequency have typically been inadequate for reliable use in automatic control. Their low availability is often associated with problems with slurry sample collection and handling systems required to present the samples to the size measurement instrument. Recently, an innovative technology for real-time, on-line particle size measurement has been developed by CiDRA Minerals Processing, under its commercial name Particle Size Tracking (PST), already proven in several commercial installations, demonstrating near 100% availability with minimal maintenance, thus overcoming the limitations of previous technologies. Investment decision makers require convincing, reliable estimates of the expected economic value that automatic grind control projects will deliver. This paper presents a methodology for estimating such value from the installation of the new PST particle size measurement technology, capable of tracking particle size on each individual hydrocyclone overflow stream, thus adding significant new options for improved process stability and performance. Based on actual plant operating records, accumulated over long periods of time, the evaluation approach herein described assesses and highlights the significant potential contribution to be expected from this unique PST technology.

Flow through autohydrolysis of spruce wood chips and lignin carbohydrate complex formation

Autohydrolysis technology is widely used for extracting lignocellulose from wood chips. In this study, the flow through autohydrolysis of spruce wood chips was studied fundamentally. In addition to rising temperature to 185 °C and prolonging time of hydrolysis to 75 min, a flow rate of 2 L/min led to significant lignocellulose removal from wood chips. However, the lower temperature of 170 °C, 15 min and flow rate of 6 L/min led to lignocellulose with larger molecular weight in the hydrolysis liquor. Gel permeation chromatography analysis confirmed the existence of lignin–carbohydrate complexes (LCC) in the hydrolysis liquors. The compositions of lignin, hemicelluloses and LCC in hydrolysis liquors were related to autohydrolysis conditions. Nineteen percent of lignin moieties were in LCC form in the hydrolysis liquor produced under the conditions of liquid/solid (L/S) ratio of 10 (wt/wt), 180 °C and 15 min. Furthermore, the hydrolysis liquor produced under the conditions of L/S ratio of 5/1, 190 °C and 15 min contained 89% of lignin in LCC forms. Moreover, the efficiencies of membrane dialysis, acidification and ethanol extraction in extracting lignocellulose were different for different hydrolysis liquors implying that the properties of hydrolysis liquors (and thus the hydrolysis conditions) would significantly affect the performance of downstream processes for isolating lignocellulose from hydrolysis liquors.

Mineral characterization as a tool in the implementation of geometallurgy into industrial mineral mining

Industrial minerals play an important role in the Norwegian mining industry. The presented research focuses on defining marble deposit variability in order to evaluate parameters that can potentially be related to downstream process performance. Two types of marble raw material (K2 and K5) from the Verdalskalk open pit, used for precipitated calcium carbonate production (PCC) were tested for possible differences within texture, grain boundaries shape, grain size, accessory mineral assemblage. Additionally, surface hardness was measured using the Proceq Equotip 3 D device. K5 type was found to be finer-grained compared to K2. The presence of quartz was more pronounced in K2 type material, which possessed higher surface hardness values and presented higher variation of those.

Evaluation of Small-Scale Powder Flow Characterization Tests in the Prediction of Large-Scale Process Failures

In pharmaceutical development, powder flow characteristics are notoriously difficult to predict. Although tests exist that aim to determine the flowability of powders, many have not been definitively correlated with a powder’s performance in downstream processes. Part of the challenge is that powder flow must occur over a broad range of consolidating stresses, including low-stress flow regimes such as the filling of a die cavity in a tablet press and high-stress flow regimes such as the deformation associated with tablet compression. The objective of this work was to characterize several placebo formulations utilizing a variety of standardized and non-standardized experiments and contrasting those results with downstream tablet compression performance. Angle of repose, bulk and tap density, Hausner ratio, Carr’s compressibility index, a visual powder flow assessment, a mass flow rate test, Flodex, and powder shear testing were evaluated on several different blends of placebo powders to determine a predictive test for downstream process performance. The placebo powders consisted of a standard base unit formula, mixed with various levels of four different “pseudo-active pharmaceutical ingredients (APIs)” (i.e., excipients that mimic poorly flowing active pharmaceutical ingredients). All formulations were evaluated by the individual flow tests and then compressed on a rotary tablet press. Formulations were deemed failures if the relative standard deviation of tablet weight was >2 %, material stuck to punches (low lubrication), or exhibited ejection forces high enough to trigger automatic shutdown of tablet press. The 2 % RSD limit is based on internally developed best practices for transferring tablet compression processes from development into manufacturing. The results of the tablet compression process were then compared to the results of the flowability tests to detect any correlations. The Hausner ratio and powder shear test results discriminated marginally between successful and failed batches and were highly correlated with each other.

Iron ore textural information is the key for prediction of downstream process performance

Textural information or information about the presence of porosity, different material or mineral types and their structural arrangement in iron ore is crucial for understanding, predicting and optimising downstream processing performance. Ores with the same chemical and mineral composition may behave very differently during downstream processing due to differences in textural components.To produce a textural description of iron ore, it is preferable to use an automated system to avoid subjectivity and to collect additional information about mineral abundance, liberation and association. CSIRO created a unique dedicated optical image analysis software package for automated textural classification and characterisation of different minerals, sinters and coke. This software, called Mineral4/Recognition4, has been used extensively to collect data for this article.Four case studies of CSIRO research are presented to demonstrate the importance of textural information.•The first example shows that iron ore samples with different texture but similar mineralogy undergo different degrees of assimilation in compact sintering.•The second example shows that empirical modelling of sinter properties was improved considerably after introducing textural information.•The third example demonstrates the application of classification by ore texture to model and optimise hydrocyclone performance.•The last example is an experimental study of ultrasonic treatment of hematitic–goethitic iron ore fines. It demonstrates how the resulting breakdown or deagglomeration of different particles, and the mineral deportment, can be better understood when textural information is also considered.In all cases, the availability of textural information was critical, providing a better prediction of process performance or a deeper understanding of the unit process.

Influence of nitrogen source and pH value on undesired poly(γ-glutamic acid) formation of a protease producing Bacillus licheniformis strain.

Bacillus spp. are used for the production of industrial enzymes but are also known to be capable of producing biopolymers such as poly(γ-glutamic acid). Biopolymers increase the viscosity of the fermentation broth, thereby impairing mixing, gas/liquid mass and heat transfer in any bioreactor system. Undesired biopolymer formation has a significant impact on the fermentation and downstream processing performance. This study shows how undesirable poly(γ-glutamic acid) formation of an industrial protease producing Bacillus licheniformis strain was prevented by switching the nitrogen source from ammonium to nitrate. The viscosity was reduced from 32 to 2.5 mPa s. A constant or changing pH value did not influence the poly(γ-glutamic acid) production. Protease production was not affected: protease activities of 38 and 46 U mL(-1) were obtained for ammonium and nitrate, respectively. With the presented results, protease production with industrial Bacillus strains is now possible without the negative impact on fermentation and downstream processing by undesired poly(γ-glutamic acid) formation.

Investigation of the impact of Tat export pathway enhancement on E. coli culture, protein production and early stage recovery

The twin arginine translocation (Tat) pathway occurs naturally in E. coli and has the distinct ability to translocate folded proteins across the inner membrane of the cell. It has the potential to export commercially useful proteins that cannot be exported by the ubiquitous Sec pathway. To better understand the bioprocess potential of the Tat pathway, this article addresses the fermentation and downstream processing performances of E. coli strains with a wild-type Tat system exporting the over-expressed substrate protein FhuD. These were compared to strains cell-engineered to over-express the Tat pathway, since the native export capacity of the Tat pathway is low. This low capacity makes the pathway susceptible to saturation by over-expressed substrate proteins, and can result in compromised cell integrity. However, there is concern in the literature that over-expression of membrane proteins, like those of the Tat pathway, can impact negatively upon membrane integrity itself. Under controlled fermentation conditions E. coli cells with a wild-type Tat pathway showed poor protein accumulation, reaching a periplasmic maximum of only 0.5 mg L⁻¹ of growth medium. Cells over-expressing the Tat pathway showed a 25% improvement in growth rate, avoided pathway saturation, and showed 40-fold higher periplasmic accumulation of FhuD. Moreover, this was achieved whilst conserving the integrity of cells for downstream processing: experimentation comparing the robustness of cells to increasing levels of shear showed no detrimental effect from pathway over-expression. Further experimentation on spheroplasts generated by the lysozyme/osmotic shock method--a scaleable way to release periplasmic protein--showed similar robustness between strains. A scale-down mimic of continuous disk-stack centrifugation predicted clarifications in excess of 90% for both intact cells and spheroplasts. Cells over-expressing the Tat pathway performed comparably to cells with the wild-type system. Overall, engineering E. coli cells to over-express the Tat pathway allowed for greater periplasmic yields of FhuD at the fermentation scale without compromising downstream processing performance.

Electrocoagulation as a clarifiation and pre-purification step in plant based bioprocesses

Electrocoagulation is a technique that has been applied to water and wastewater treatment. We propose here extension of this technique to the field of plant downstream processing (DSP), where plants are used as a bioreactors for recombinant protein production. The main problem in plant-based bioreactors is the presence of chlorophyll and phenolic compounds in plant extracts, which tend to precipitate and denature proteins. Their removal from the extracts is essential, since they have a large impact on the DSP performance. In the present work we studied the application of an electrocoagulation based technique to clarify tobacco leaf extracts by removing chlorophyll and phenolic compounds. By manipulating the pH of electrocoagulation, 90% of chlorophyll, 65% of phenolic compounds, and only 23% of total protein were removed from the extract. The process preferentially removes proteins with more acidic pI (below 6.03) and the pH of the process differentially effects removal of acidic and basic proteins.

Integration of PEGylation and refolding for renaturation of recombinant proteins from insoluble aggregates produced in bacteria—Application to a single-chain Fv fragment

The conjugation of polyethylene glycol (PEGylation) with downsized compact antibodies is an effective method for overcoming the problem of rapid elimination of the compact antibodies from the body. We integrated site-specific PEGylation with the refolding of a single-chain Fv (scFv) of humanized monoclonal antibody 528 with affinity for the epidermal growth factor receptor, to prepare active PEGylated scFv from insoluble aggregates produced in an Escherichia coli expression system. The insertion of a cysteine residue at the C-terminus of scFv to serve as the conjugation site for PEG led to the formation of highly multimeric scFv during the refolding process; however, PEGylation after refolding drastically dispersed the multimer into monomeric active scFv fragments. Further, the PEGylation of partially refolded scFv during the refolding process improved the PEGylation efficiency and suppressed the formation of highly multimeric scFv; consequently, monomeric active scFv fragments were obtained directly from the insoluble aggregates in E. coli. We show that in vitro refolding of PEGylated scFv should be useful for improving downstream processing performance in the production of clinically useful small antibodies from insoluble fractions.

Influence of explosive energy on the strength of the rock fragments and SAG mill throughput

Extensive in-situ testings has shown that blast fragmentation influences the performance of downstream processes in a mine, and as a consequence, the profit of the whole operation can be greatly improved through optimised fragmentation. Other unit operations like excavation, crushing and grinding can all be assisted by altering the blast-induced fragmentation. Experimental studies have indicated that a change in blasting practice would not only influence fragmentation but fragment strength as well. The strength of the fragments produced in a blast is clearly important to the performance of the crushing and grinding circuit as it affects the energy required to break the feed to a target product size. In order to validate the effect of blasting on fragment strength several lumps of granite were blasted, under controlled conditions, using three very different explosive products. The resulting fragments were subjected to standard comminution ore characterisation tests. Obtained comminution parameters were then used to simulate the performance of a SAG mill. Modelling results indicate that changes in post blast residual rock fragment strength significantly influences the performance of the SAG mill, producing up to a 20% increase in throughput.

Critical Comparison of Julius Kruttschnitt Mineral Research Centre (JKMRC) Blast Fragmentation Models

Blast fragmentation can have a significant impact on the profitability of a mine. An optimum run of mine (ROM) size distribution is required to maximise the performance of downstream processes. If this fragmentation size distribution can be modelled and controlled, the operation will have made a significant advancement towards improving its performance. Blast fragmentation modelling is an important step in Mine to Mill™ optimisation. It allows the estimation of blast fragmentation distributions for a number of different rock mass, blast geometry, and explosive parameters. These distributions can then be modelled in downstream mining and milling processes to determine the optimum blast design. When a blast hole is detonated rock breakage occurs in two different stress regions - compressive and tensile. In the-first region, compressive stress waves form a ‘crushed zone’ directly adjacent to the blast hole. The second region, termed the ‘cracked zone’, occurs outside the crush one. The widely used Kuz-Ram model does not recognise these two blast regions. In the Kuz-Ram model the mean fragment size from the blast is approximated and is then used to estimate the remaining size distribution. Experience has shown that this model predicts the coarse end reasonably accurately, but it can significantly underestimate the amount of fines generated. As part of the Australian Mineral Industries Research Association (AMIRA) P483A Mine to Mill™ project, the Two-Component Model (TCM) and Crush Zone Model (CZM), developed by the Julius Kruttschnitt Mineral Research Centre (JKMRC), were compared and evaluated to measured ROM fragmentation distributions. An important criteria for this comparison was the variation of model results from measured ROM in the-fine to intermediate section (1-100 mm) of the fragmentation curve. This region of the distribution is important for Mine to Mill™ optimisation. The comparison of modelled and Split ROM fragmentation distributions has been conducted in harder ores (UCS greater than 80 MPa). Further work involves modelling softer ores. The comparisons will be continued with future site surveys to increase confidence in the comparison of the CZM and TCM to Split results. Stochastic fragmentation modelling will then be conducted to take into account variation of input parameters. A window of possible fragmentation distributions can be compared to those obtained by Split. Following this work, an improved fragmentation model will be developed in response to these findings.