Traditionally, optimization of drill and blast practices have taken place with sole respect to minimizing mine unit cost (as opposed to the operation as a whole), whilst maintaining fragmentation at a level that is considered “acceptable” to mine operations. Judgments as to “acceptable” are largely based on qualitative measures and the consequences of varying blast practices on subsequent downstream processes are secondary. The objective of this work was to evaluate both the technical and economic consequences of blast practices on comminution processes at the Kemess South Project. Computer modeling indicates that without changes to crusher operating parameters, there does not appear to be much room for improving the performance of the comminution circuit. This indicates that current blasting at the mine is at or near optimal for the mill’s current configuration. Experiments to attempt to detect the effect of blasting on the crushability and grindability of rock were carried out on several different samples, including a copper-gold porphyry ore from Kemess Mine, taconite from Minnesota, granodiorite from the Kingston area, and limestone from the Kingston area. The main focus of this study was the Kemess ore. Examining rock samples from blasted and un-blasted ore, the samples that were blasted showed a significant increase in the density of very small cracks within individual fragments, which would indicate that they should break more easily during crushing and grinding. Drop-weight impact tests investigating the grindability of these samples suggested that there was improved performance with blasting effort, although the difference between some samples was not statistically significant. Preliminary testing of the taconite and the limestone indicated that crushability and grindability may be improved by blasting. Using mineral processing simulation software, the second part of the study investigated the effects of changing the ore size distribution that is fed to the Kemess Primary crusher. It was concluded that the Kemess Semi-Autogenous Grinding (SAG) mill throughput could be increased by increasing fragmentation and making adjustments to the primary crusher closed side set to take advantage of the increased fragmentation. These changes were calculated to be economically advantageous. / Thesis (Master, Mining Engineering) -- Queen's University, 2008-04-22 21:18:04.939 / Kemess Mines Ltd., MinnovEX Technologies Inc.

In the comminution industry, cone crushers are widely used for secondary and subsequent stages of size reduction. For a given crusher, the achieved size reduction is governed by the closed-side setting. Hadfield Steel is commonly used to line the crushing members to minimize wear. Yet, liner wear caused by some rock types can still be excessive. Enlargement of discharge opening induced by wear of liners produces a drift in product size which, if unchecked, can lead to high volumes of re-circulating load. Alteration of closed-side setting is now commonly achieved via hydraulic means. However, compensation of liner wear still involves plant shut down and loss of production.

Esta dissertação está baseada no trabalho desenvolvido para adequar a usina de Conceição 1 (da Vale S.A.) para o processamento de itabiritos compactos e semi compactos, situada em Itabira-MG. Até 2014, a usina de Conceição 1 foi alimentada com hematitas e itabiritos friáveis e produzia cerca de 22 Mt/ano. Com o consumo progressivo das reservas de minérios friáveis, tornou-se necessário que a usina processasse minérios mais competentes e com menor teor de Fe: itabiritos compactos e semi compactos (40%Fe). Até então, este material era considerado estéril, uma vez que os circuitos de beneficiamento não possuíam capacidade para transformá-lo em concentrados, tendo em vista às exigências de mercado. Portanto, o principal objetivo deste trabalho foi analisar o processo de ramp-up para aumentar a capacidade de alimentação da planta para 34 Mt/ano. O dimensionamento dos equipamentos, desenho dos circuitos, bem como as premissas adotadas durante o projeto de adequação serão apresentados neste estudo. Comparando a curvas de ramp-up prevista à praticada, notou-se que houve perdas mássicas consideráveis. Dentre os principais fatores responsáveis, está a grande quantidade de materiais compactos alimentados à usina com granulometria e, talvez, dureza maior do que poderia ser previsto. Os teores de ferro na alimentação da flotação e a qualidade dos concentrados (sínter feed e pellet feed) mostraram-se um pouco abaixo, também, do previsto, porém satisfatórios A estratégia de divisão por fases teve forte impacto positivo, evitando perdas maiores, pois reduziu o número de dias de parada consideravelmente. O desenvolvimento do projeto, denominado FRAGCOM (fragmentação e cominuição), pode ter ajudado a revelar as soluções para os problemas encontrados: este visou a obter melhorias no processo de desmonte e, consequentemente, na cominuição. Os resultados analisados de alguns testes deste projeto mostraram que, na britagem, a usina atingiu maiores taxas de produtividade nesta ocasião. Dado que a britagem é o primeiro circuito de processamento (um gargalo), isto é um fator relevante. Para estes testes foi utilizada uma razão de carga maior no desmonte. Com esta e outras melhorias, uma maior quantidade de material compacto pôde ser processado. Por fim, os resultados mostraram que a falta de aderência da curva de produção prevista com respeito à praticada, deveu-se entre outros fatores, à maior dificuldade de alimentação do circuito de moagem, impactado pelo baixo rendimento operacional da britagem. / This dissertation is based on the work developed to adapt the plant of Conceição 1 (Vale S.A.) to the processing of compact and semicompact itabirites, located in Itabira-MG, southeastern Brazil. Conceição 1 plant was fed with friable hematite and itabirite and produced 22 Mt/year) until 2014. With the progressive consumption of friable ore reserves, it became necessary to process more competent and lower grade ores: compact and semicompact itabirites. Until then, this material was considered waste, since the beneficiation circuits did not have the capacity to transform it into concentrates, especially regarding market requirements. Therefore, the main objective of this work was to analyze the ramp up process in order to fed 34Mt/year. The adopted strategies and their impacts on ramp up process to achieve the production rate were analyzed. Equipment scaling, circuit design, as well as, premises and tests, which were performed during the adaptation project, are presented in this study. Comparing the planned ramp-up curve to the implemented curve, it was noted considerable mass losses. The amount of compacts that fed the plant with particle size and perhaps hardness greater than could be predicted is among main responsible factors The content of Fe in the feed of the flotation and the quality of the concentrates (sinter feed and pellet feed) was a little lower than was expected, but satisfactory. The phasing strategy had a strong positive impact, avoiding greater losses, as it considerably reduced the number of shutdown days. The development of the FRAGCOM (fragmentation and comminution) project may have helped to reveal solutions to the encountered problems: this project aimed to improve the blasting process and, consequently, the comminution. The results of some tests of this project showed that the crushing achieved higher productivity rates at that time. Since crushing is the first processing circuit (a bottleneck), this is a relevant factor. For these tests, a higher blasting load ratio was used. With this and other improvements, a greater amount of compact material could be processed. Finally, the results suggested that the mass losses occurred greater difficulty in feeding the grinding circuit, impacted by the low operational efficiency of the crushing.

Esta dissertação está baseada no trabalho desenvolvido para adequar a usina de Conceição 1 (da Vale S.A.) para o processamento de itabiritos compactos e semi compactos, situada em Itabira-MG. Até 2014, a usina de Conceição 1 foi alimentada com hematitas e itabiritos friáveis e produzia cerca de 22 Mt/ano. Com o consumo progressivo das reservas de minérios friáveis, tornou-se necessário que a usina processasse minérios mais competentes e com menor teor de Fe: itabiritos compactos e semi compactos (40%Fe). Até então, este material era considerado estéril, uma vez que os circuitos de beneficiamento não possuíam capacidade para transformá-lo em concentrados, tendo em vista às exigências de mercado. Portanto, o principal objetivo deste trabalho foi analisar o processo de ramp-up para aumentar a capacidade de alimentação da planta para 34 Mt/ano. O dimensionamento dos equipamentos, desenho dos circuitos, bem como as premissas adotadas durante o projeto de adequação serão apresentados neste estudo. Comparando a curvas de ramp-up prevista à praticada, notou-se que houve perdas mássicas consideráveis. Dentre os principais fatores responsáveis, está a grande quantidade de materiais compactos alimentados à usina com granulometria e, talvez, dureza maior do que poderia ser previsto. Os teores de ferro na alimentação da flotação e a qualidade dos concentrados (sínter feed e pellet feed) mostraram-se um pouco abaixo, também, do previsto, porém satisfatórios A estratégia de divisão por fases teve forte impacto positivo, evitando perdas maiores, pois reduziu o número de dias de parada consideravelmente. O desenvolvimento do projeto, denominado FRAGCOM (fragmentação e cominuição), pode ter ajudado a revelar as soluções para os problemas encontrados: este visou a obter melhorias no processo de desmonte e, consequentemente, na cominuição. Os resultados analisados de alguns testes deste projeto mostraram que, na britagem, a usina atingiu maiores taxas de produtividade nesta ocasião. Dado que a britagem é o primeiro circuito de processamento (um gargalo), isto é um fator relevante. Para estes testes foi utilizada uma razão de carga maior no desmonte. Com esta e outras melhorias, uma maior quantidade de material compacto pôde ser processado. Por fim, os resultados mostraram que a falta de aderência da curva de produção prevista com respeito à praticada, deveu-se entre outros fatores, à maior dificuldade de alimentação do circuito de moagem, impactado pelo baixo rendimento operacional da britagem. / This dissertation is based on the work developed to adapt the plant of Conceição 1 (Vale S.A.) to the processing of compact and semicompact itabirites, located in Itabira-MG, southeastern Brazil. Conceição 1 plant was fed with friable hematite and itabirite and produced 22 Mt/year) until 2014. With the progressive consumption of friable ore reserves, it became necessary to process more competent and lower grade ores: compact and semicompact itabirites. Until then, this material was considered waste, since the beneficiation circuits did not have the capacity to transform it into concentrates, especially regarding market requirements. Therefore, the main objective of this work was to analyze the ramp up process in order to fed 34Mt/year. The adopted strategies and their impacts on ramp up process to achieve the production rate were analyzed. Equipment scaling, circuit design, as well as, premises and tests, which were performed during the adaptation project, are presented in this study. Comparing the planned ramp-up curve to the implemented curve, it was noted considerable mass losses. The amount of compacts that fed the plant with particle size and perhaps hardness greater than could be predicted is among main responsible factors The content of Fe in the feed of the flotation and the quality of the concentrates (sinter feed and pellet feed) was a little lower than was expected, but satisfactory. The phasing strategy had a strong positive impact, avoiding greater losses, as it considerably reduced the number of shutdown days. The development of the FRAGCOM (fragmentation and comminution) project may have helped to reveal solutions to the encountered problems: this project aimed to improve the blasting process and, consequently, the comminution. The results of some tests of this project showed that the crushing achieved higher productivity rates at that time. Since crushing is the first processing circuit (a bottleneck), this is a relevant factor. For these tests, a higher blasting load ratio was used. With this and other improvements, a greater amount of compact material could be processed. Finally, the results suggested that the mass losses occurred greater difficulty in feeding the grinding circuit, impacted by the low operational efficiency of the crushing.

Esta dissertação está baseada no trabalho desenvolvido para adequar a usina de Conceição 1 (da Vale S.A.) para o processamento de itabiritos compactos e semi compactos, situada em Itabira-MG. Até 2014, a usina de Conceição 1 foi alimentada com hematitas e itabiritos friáveis e produzia cerca de 22 Mt/ano. Com o consumo progressivo das reservas de minérios friáveis, tornou-se necessário que a usina processasse minérios mais competentes e com menor teor de Fe: itabiritos compactos e semi compactos (40%Fe). Até então, este material era considerado estéril, uma vez que os circuitos de beneficiamento não possuíam capacidade para transformá-lo em concentrados, tendo em vista às exigências de mercado. Portanto, o principal objetivo deste trabalho foi analisar o processo de ramp-up para aumentar a capacidade de alimentação da planta para 34 Mt/ano. O dimensionamento dos equipamentos, desenho dos circuitos, bem como as premissas adotadas durante o projeto de adequação serão apresentados neste estudo. Comparando a curvas de ramp-up prevista à praticada, notou-se que houve perdas mássicas consideráveis. Dentre os principais fatores responsáveis, está a grande quantidade de materiais compactos alimentados à usina com granulometria e, talvez, dureza maior do que poderia ser previsto. Os teores de ferro na alimentação da flotação e a qualidade dos concentrados (sínter feed e pellet feed) mostraram-se um pouco abaixo, também, do previsto, porém satisfatórios A estratégia de divisão por fases teve forte impacto positivo, evitando perdas maiores, pois reduziu o número de dias de parada consideravelmente. O desenvolvimento do projeto, denominado FRAGCOM (fragmentação e cominuição), pode ter ajudado a revelar as soluções para os problemas encontrados: este visou a obter melhorias no processo de desmonte e, consequentemente, na cominuição. Os resultados analisados de alguns testes deste projeto mostraram que, na britagem, a usina atingiu maiores taxas de produtividade nesta ocasião. Dado que a britagem é o primeiro circuito de processamento (um gargalo), isto é um fator relevante. Para estes testes foi utilizada uma razão de carga maior no desmonte. Com esta e outras melhorias, uma maior quantidade de material compacto pôde ser processado. Por fim, os resultados mostraram que a falta de aderência da curva de produção prevista com respeito à praticada, deveu-se entre outros fatores, à maior dificuldade de alimentação do circuito de moagem, impactado pelo baixo rendimento operacional da britagem. / This dissertation is based on the work developed to adapt the plant of Conceição 1 (Vale S.A.) to the processing of compact and semicompact itabirites, located in Itabira-MG, southeastern Brazil. Conceição 1 plant was fed with friable hematite and itabirite and produced 22 Mt/year) until 2014. With the progressive consumption of friable ore reserves, it became necessary to process more competent and lower grade ores: compact and semicompact itabirites. Until then, this material was considered waste, since the beneficiation circuits did not have the capacity to transform it into concentrates, especially regarding market requirements. Therefore, the main objective of this work was to analyze the ramp up process in order to fed 34Mt/year. The adopted strategies and their impacts on ramp up process to achieve the production rate were analyzed. Equipment scaling, circuit design, as well as, premises and tests, which were performed during the adaptation project, are presented in this study. Comparing the planned ramp-up curve to the implemented curve, it was noted considerable mass losses. The amount of compacts that fed the plant with particle size and perhaps hardness greater than could be predicted is among main responsible factors The content of Fe in the feed of the flotation and the quality of the concentrates (sinter feed and pellet feed) was a little lower than was expected, but satisfactory. The phasing strategy had a strong positive impact, avoiding greater losses, as it considerably reduced the number of shutdown days. The development of the FRAGCOM (fragmentation and comminution) project may have helped to reveal solutions to the encountered problems: this project aimed to improve the blasting process and, consequently, the comminution. The results of some tests of this project showed that the crushing achieved higher productivity rates at that time. Since crushing is the first processing circuit (a bottleneck), this is a relevant factor. For these tests, a higher blasting load ratio was used. With this and other improvements, a greater amount of compact material could be processed. Finally, the results suggested that the mass losses occurred greater difficulty in feeding the grinding circuit, impacted by the low operational efficiency of the crushing.

Student number : 0318567G School of Chemical and Metallurgical Engineering Faculty of Engineering / Comminution is an important process in mineral processing, power plants, cement production and pharmaceutical industries. It is costly and an inefficient process in terms of energy requirements and steel consumption related to grinding media and liners. Spherical grinding media are predominantly used in final stages of ore grinding. The spherical balls change shape through breakage and wear. Though this is universal in milling, its contribution and effect on milling kinetics, load behaviour and mill power is not fully established. One area that is usually ignored is the relationship between media shape and mill power. The objective of this dissertation was to investigate how media shape affects grinding. Ball size distribution inside an industrial mill was analysed in terms of shapes and sizes. Load behaviour, mill power and breakage as affected by media shapes were studied in a pilot laboratory mill. An inductive proximity probe, light emitting diode, phototransistor and video photographs were used to determine the load orientation in terms of toe and shoulder positions. A load beam was used to measure the torque exerted by the charge. The variation in load orientation and mill power with speed among different media shapes was observed. Higher shoulder positions were noted with cylpebs than with worn and spherical balls. The power increased to a maximum with increasing mill speed for all media shapes reaching its peak at different mill speeds for the three shapes studied. Variations of breakage rates with media shapes were found; higher breakage rates were noted with spherical media but the differences narrows with decreasing feed size and increasing material fractional filling U. Considering that worn balls in an industrial mill charge constitute about 15 to 40 percent and that the highest difference in breakage rate observed being nine percent for purely one shape charge; it is very doubtful whether it is worthwhile in attempting to develop techniques for removing worn balls from the mill.

Na área de moagem secundária, ou remoagem, a preocupação com a eficiência energética se mostra de extrema importância. Em geral, os consumos específicos desta etapa são superiores aos da etapa primária. Além disso, tem se observado uma tendência de afinamento das granulometrias de moagem nos novos projetos de minerais metálicos, o que leva cada vez mais a uma maior necessidade de gastos nesta etapa, tanto em termos de custos de implantação como de operação. Nos novos projetos que incluem remoagem no Brasil granulometrias de remoagem da ordem de 40 a 20 m têm se mostrado necessárias. Neste contexto, os moinhos tubulares de bolas, adequados para moagem primária, apresentam eficiências decrescentes em termos de aproveitamento de energia, quando são necessários produtos abaixo de 50 m. A fim de avaliar as melhores alternativas tecnológicas disponíveis para estas aplicações de remoagem, este trabalho estudou moinhos de carga agitada, com foco em moinhos verticais. O presente trabalho apresenta e discute os resultados de amostragens em escala industrial com o moinho vertical em quatro usinas em operação no Brasil. Foi desenvolvido também um novo ensaio em escala laboratorial para simular o consumo de energia e a distribuição granulométrica dos moinhos verticais, que se mostrou válido para a aplicação estudada. / Energy efficiency is extremely important in secondary grinding (regrinding) as specific consumption are greater than obtained in primary grinding. Moreover, finer grinding sizes are a trend in new grinding circuits therefore increasing the energy consumption, as well as respective capital and operating costs. In Brazil regrinding sizes between 40 a 20 m are common in greenfield projects. As horizontal ball mills show decreasing efficiency as grinding sizes are finer than 50 m, this work shows regrinding equipment alternatives to ball mills focusing on vertical mills. A number of survey campaigns were carried out on four industrial operations in which vertical mills were installed in the respective regrind circuit. A new batch test was developed and validated to predict the energy consumption and product size distribution associated to vertical mills.

O desgaste de corpos moedores constitui um custo importante na indústria mineral, que depende da operação de cominuição para promover a liberação das espécies minerais e produzir concentrados. Embora se conheça alguns dos mecanismos individuais que afetam o desgaste, a interação entre eles num sistema tão complexo quanto um moinho ainda precisa ser melhor entendido. Este trabalho avaliou o efeito da corrosão no desgaste de bolas de aço e de ferro fundido branco de alto cromo durante a moagem de minério de ferro, através de ensaios eletroquímicos e de desgaste em moinho de laboratório. Foi feita uma alteração no modo tradicional de realização do ensaio de polarização potenciodinâmica, utilizando polpa de minério de ferro a 70% de sólidos (em peso) como eletrólito. As curvas de polarização obtidas foram compatíveis com os resultados de desgaste, de modo que as curvas correspondentes aos metais na condição mais ativa estavam associadas às menores taxas de desgaste nos ensaios de moagem em laboratório, demonstrando que os ensaios de polarização realizados podem ser utilizados como indicativo do comportamento do metal na moagem de minério de ferro. Sobretudo, os testes demonstraram que o desgaste das bolas de aço é devido, principalmente, à abrasão, já que uma pequena diferença, de apenas 8%, foi observada nas taxas de desgaste nas condições avaliadas (polpa no pH 5 e pH 8). Por outro lado, as bolas de ferro fundido branco de alto cromo, que são mais caras, são mais propensas a resistir ao desgaste em polpa ácida, em que a taxa de desgaste foi 40% menor que a determinada em pH 8. / The wear out of grinding media represents a major cost in the mineral industry, which strongly depends on the mineral liberation to achieve the production of concentrates. Although some of the individual mechanisms that affect wear are already known, the interaction between them in such a complex system as an ore mill still needs further investigation. This work analyzed the effect of corrosion on the wear of balls made of steel and high chromium cast iron, while grinding iron ore, by means of electrochemical tests and wear tests conducted in a laboratory mill. A modification of the traditional potenciodynamic polarization test is proposed, using iron ore slurry at 70% w/w as an electrolyte. The results of the polarization curves were compatible with those from the wear tests, as the curves corresponding to the condition in which the metal showed the more active behavior were associated to the lower wear rates in the wear tests, suggesting that the modified polarization tests can be used as an indicative of the metal alloy behavior while grinding iron ore. Moreover, it demonstrated that the wear of steel balls is mainly due to abrasion, as a slight difference of 8% in their wear rates was observed in both conditions investigated (pH 5 and pH 8). On the other hand, the high chromium cast iron balls, which are more expensive, were more likely to resist wear in slurry at pH 5, achieving a wear rate 40% lower than in pH 8.

Uma parcela considerável do consumo energético, e consequentemente, dos custos das operações de tratamento de minérios é atribuída a cominuição. O High Pressure Grinding Rolls (HPGR) surge com o apelo de eficiência energética, o que, potencialmente, reduziria os custos operacionais. Nesta pesquisa, esta tecnologia é analisada como uma alternativa à rota convencional de cominuição de óxido de alumínio eletrofundido de um empreendimento em particular, que compreende um complexo circuito de britadores de rolos. Duas amostras de óxido de alumínio eletrofundido, denominadas BT e TB, foram submetidas a ensaios de HPGR (circuito aberto) e de caracterização física (DWT, WI, AI, densidade). Adicionalmente, foram realizadas simulações no software JKSimMet® 6.0 com o objetivo de prever o desempenho do equipamento em circuito fechado e realizar o escalonamento da unidade industrial. As distribuições granulométricas dos produtos dos ensaios de HPGR em circuito aberto e as distribuições granulométricas dos produtos dos circuitos fechados de HPGR simulados foram comparadas às granulometrias do produto requeridas pelo circuito industrial. Avaliou-se, também, o atendimento da vazão mássica requerida. Os resultados demonstram que a rota alternativa baseada no HPGR oferece um expressivo potencial de simplificação do circuito, com uma redução considerável do número de equipamentos de cominuição de 13 para 1, o que, além de, possivelmente, impactar na redução de custos operacionais, facilita o controle da operação. / A considerable portion of energy consumption and, as a consequence, operational costs in mineral processing is associated with comminution. High Pressure Grinding Rolls (HPGR) are appealing for their energy efficiency, which would potentially reduce operating costs. This study evaluates this technology as an alternative to the conventional electrofused aluminum oxide comminution route of a specific plant comprising a complex roll crushing circuit. Two electrofused aluminum oxide samples, called BT and TB, were submitted to HPGR (open circuit) and physical characterization (DWT, WI, bulk density, specific gravity) tests. In addition, simulations were conducted using JKSimMet® 6.0 software, aiming to predict the performance of a closed-circuit equipment and scale-up of an industrial scale unit. Product size distributions of the open-circuit HPGR tests and closed circuit HPGR simulations were compared with the product size distribution required by industrial comminution circuit. The required throughput was also evaluated. Results show that the alternative HPGR route provides a remarkable potential for circuit simplification, while considerably reducing the number of comminution equipments from 13 to 1, which facilitates operational control and possibly reduces operating costs.

Optimization of comminuting and heating conditions for surimi gel preparation obtained from three fish species: Alaska pollock (AP) (Theragra chalcogramma), Pacific whiting (PW) (Merluccius productus), and threadfin bream (TB) (Nemipterus spp.) was the focus of this study. Three parameters during comminution were separately evaluated: chopping time, chopping temperature, and salting time. Results from fracture gel analysis suggested a strong relation between the fish's environmental habitat and optimal final chopping temperature. Extending chopping time to 15 min under strictly controlled temperature at 0 ��C was preferable for cold water fish AP surimi. Even though high chopping temperature (20 ��C) for a shorter time (12 min) surprisingly resulted in strong gel texture similar to that of 0 ��C for 15 min, high chopping temperature should not be employed for AP surimi. AP could set as a gel at this temperature within a shorter time in a holding tank which could subsequently cause a problem when extruded on the cooking belt. Temperate water fish Pacific whiting, demonstrated its maximum gel strength when chopped at 15-20 ��C. The optimum comminution condition for warm water fish threadfin bream surimi was to chop the surimi until the paste temperature reached between 25-30 ��C. Prolongation of chopping once the surimi hit its threshold (optimum) temperature diminished the quality of the resulting protein gel. Cooling system connected to the chopping bowl is strongly recommended as it will allow the comminution process to be extended as long as possible until the surimi paste reaches its target temperature. Raman spectroscopy disclosed the different level of protein unfolding based on secondary structure of ��-helix and ��-sheet during various comminuting conditions. Unfolding of protein was facilitated by increased chopping temperature to a greater degree than extended chopping time. Extending chopping could denature the light meromyosin structure as it could not form a semi gel-like structure at temperatures between 32-40 ��C. Protein solubility of surimi paste in salt solution always decreased with prolonged chopping time. The decrease rate accelerated with increased chopping temperature. The formation of disulfide interchange gradually took place during chopping as observed from Raman spectroscopy. Also the surface hydrophobicity increased with extended chopping time. However, gel strength behaved differently according to the various chopping conditions indicating the lack of its relationship between salt soluble protein, disulfide formation, and surface hydrophobicity to gel strength. During extending chopping time, not only more mechanical force is applied to unfold protein structure, but proteins also have longer time to be extracted more by salt. Addition of salt at a different time during chopping process was therefore conducted using threadfin bream surimi due to its higher thermostability. Extending chopping time without salt followed by salt addition at the last step resulted in lower gel texture compared to the conventional chopping protocol where salt is always added at the early stage of comminution. Mechanical chopping could unfold protein structure; however, proteins, rather than staying solubilized, would precipitate and form a randomized structure under the chopping condition without salt. The heating condition greatly affected the gelation and rheological properties of AP surimi. The highest elastic modulus was obtained with the slowest heating rate at 1 ��C/min. Increased heating rate did not only shorten the time for proteins to unfold and form a well-organized network, it also interfered with the protein network through the vibration of water molecules as phase angle increased. This suggested that AP surimi gained more viscous properties and failed to form an elastic gel. Adjusting moisture content along with applying various frequencies did not alter the pattern of G' formation when paste was heated at different heating rates. AP surimi favored the slow heating. / Graduation date: 2013