Block Sawing Research Articles

Technical, Environmental, and Cost Assessment of Granite Sludge Valorisation

The granite sludge (GS) produced during block sawing can be exploited as alternative raw material in ceramic and concrete industries. Based on the case study of a Portuguese granite processing plant, this work analysed, by experimental tests and Environmental and Cost Life Cycle analyses, the feasibility of GS valorisation as a substitute (i) for feldspar in a ceramic paste and (ii) fine–medium inert filler in structural concrete. The results demonstrated that both the valorisation pathways are more advantageous than GS landfilling. Due to granulometric, mineralogical composition and shrinkage, GS can substitute feldspar in sandstone tiles or tableware products, although its tinting effect can limit noble whitish ceramic applications. In structural concrete mixes, 5% w/w GS instead of fine inert filler reduces the compressive strength and increases the water:cement ratio. The GS generates lower environmental impacts as a substitute for inert filler than as a substitute for feldspar in most of the impact categories analysed, even though the latter valorisation pathway provides higher benefits in Climate Change and the Depletion of Fossil resources, Water, and Ozone. If no monetary value is recognised for GS valorisation by the market, the sustainability of GS life cycle cost decreases when compared to its landfilling.

A study on energy-saving optimization strategy for the stone processing industry—an improved method for modeling cutting power and energy consumption: A case study of block sawing process

Energy consumption has become one of the main costs of the stone processing industry and results in substantial stress on the environment. Consequently, the energy-saving issue has drawn increasing attention in the stone processing industry. Cutting power modeling is the crucial technology of energy prediction of stone machining process, being the foundation of energy-saving optimization in this sector. The cutting power changes dynamically during the variable material removal rate process (V-MRR process). Therefore, the power characteristic of the V-MRR process is more complicated than that of the constant material removal rate process (C-MRR process). In the stone processing industry, various machining processes belong to the V-MRR process, such as block sawing, slab chamfering, curved surface milling and grinding. In this paper, a modeling methodology of cutting energy consumption for variable-MRR process is proposed. The dynamic power characteristic can be reflected in this methodology, and the influences of cutting parameters on stone-cutting energy consumption are also fully considered. Based on the specially designed test system, experimental studies were conducted to obtain the fitting coefficients of the proposed energy consumption model. Then, energy calculations of four stone blocks sawing processes were performed. The results show that the predictive accuracy of all tested stone block sawing cases is above 90%. Finally, a case application is elaborated to demonstrate that the proposed method can help stone manufacturers determine the energy-optimal process plan. The detailed results of energy-saving & benefits-improving with using the proposed method are also proved in the case study.

LAMA DE BENEFICIAMENTO DE ROCHAS ORNAMENTAIS PROCESSADAS NO ESPÍRITO SANTO: COMPOSIÇÃO E APROVEITAMENTO

A produção de rochas ornamentais para revestimento gera um resíduo de granulação muito fina, a partir do descarte da Lama de Beneficiamento de Rochas Ornamentais (LBRO), cuja composição indica potencial de utilização em diversos setores produtivos. Neste trabalho, apresenta-se um estudo da variabilidade composicional da LBRO e de diferentes tipos de rocha, com o objetivo de identificar os fatores controladores da composição dos resíduos gerados pela serragem de blocos. Foram coletadas 35 amostras de rocha e da LBRO produzida durante a serragem dessas rochas. As amostras foram coletadas diretamente da descarga do tear em empresas de Cachoeiro de Itapemirim (ES), um dos principais polos produtores do Estado do Espírito Santo. O mapeamento do processo produtivo das empresas permitiu dimensionar a quantidade de resíduos que é gerada por bloco serrado e mostrou a importância do controle de perdas. A comparação entre rochas e LBRO evidenciou íntima semelhança entre a composição química dessas matrizes, com exceção de alguns elementos como ferro e cálcio, que são acrescentados a partir dos insumos de beneficiamento em teares convencionais. As amostras foram agrupadas em cinco conjuntos com potencial de uso em cosméticos, aplicação no solo, fabricação de cerâmica, uso na construção civil ou simplesmente como filler.

Influence of Lime Sludge and Sodium Salts on the Strength and Structural Behavior of Clayey Soils–Granite Stone Slurry Dust Composite with Curing

This study aims to show the changes in the properties of clayey soils in the presence of granite stone slurry dust and lime sludge collected from granite block sawing mill and sugar industry, respectively. Clayey soils in this study refer to black cotton soil and red earth. The changes in unconfined compressive strength of clayey soils–optimum granite stone slurry dust composite with curing stabilized with lime sludge and in the presence of sodium salts have been emphasized in this study. The unconfined compressive strength of clayey soils–optimum granite stone slurry dust composite increases marginally in the presence of lime sludge and sodium salts for samples tested immediately. However, the increase in strength was significant with curing. The maximum improvement in the strength has been observed in the presence of NaOH. Scanning electron microscope studies reveal the improvement in the structural behavior of the clayey soil–optimum granite stone slurry dust composite in the presence of lime sludge and sodium salts.

Prospects for percussion sawing machines in production of high-strength dimension stone

One of the most labor-intensive operations in production of dimension stone is separation of a stone monolith from rock mass, cutting of the monolith into blocks and sawing of the blocks into slabs. This article reviews in brief the methods of cutting and sawing of high-strength rocks. The new method of percussion sawing is described. Based on the method, the structural layouts of machines for cutting and sawing of stone blocks are proposed. The percussi on sawing method is efficient in brittle hard and super-hard rocks such as granite and sometimes marble, with Protodyakonov-scale hardness from 6 to 20. The method provides high quality finishing of surfaces at average productivity and low cost of sawing. The authors describe various structural layouts and operation modes for different percussion sawing machines suitable for operation in stone quarries, stone working plants and workshops. The basic elements of percussion sawing machines are frame, percussion assembly, tooth saw, vertical and horizontal feed drives, and the cut blowing or washing facilities. The article describes the machine capacity calculation procedure confirmed by the experimental research data. The major machine parameters to affect its capacity are: blow energy of the percussion assembly, number of percussion assemblies, saw area at the contact with stone, seesaw velocity, and ultimate compression strength of stone. A new estimated figure is put forward as specific blow energy per kerf bottom surface. The change in the capacity of a quarry percussion sawing machine as a function of time of one saw pass is determined. The obtained relation is compared with performance of other two types of sawing machines.The comparative analysis of mechanical methods of hard rock sawing is performed. The efficiency of the proposed method for percussion sawing of hard and super hard rocks is proved.

Characterization of Ornamental Stones Wastes for Use in Ceramic Materials

Ornamental stones processing produces large amounts of wastes, which without treatment, are disposed in deposits, constituting the major environmental problem in this sector in Brazil. There is a great variety of rocks and different technologies in the ornamental stones processing. Rock block sawing can be performed using multi-blade gangsaw, the conventional technology, or multiwire gangsaw, latest technology which uses only diamond wire and water to cut blocks. In recent years there has been a great change in the use of ornamental stones sawing technologies, where currently almost 50% of the sawed materials are processed by the multi wire technology. The ornamental stones wastes have compounds that can collaborate in the processing of the ceramic. Due to the great variety of Brazilian ornamental stones and technologies in addition to the growth of de sector in recent years, there is a need for new studies regard to the characterization and environmental classification of waste, for a better management and application. Therefore, the objective of this work was the characterization and environmental classification of ornamental stones wastes aiming their use in red ceramics. The wastes were characterized with the determination of its chemical composition and mineralogical analysis, particle size, morphological analysis and environmental, the latter by means of the leaching and solubilization tests, for subsequent classification. The wastes are composed mainly of SiO2, Al2O3, alkaline oxides, earth alkaline oxides and iron, and those which were submitted to the leaching and solubilization tests are classified as non-inert.

Selection of a sustainable technology for cutting granite block into slabs

Over the last decades, stringent regulations forced the stone industry to take concrete steps towards cleaner production. Despite promotion in environmental friendliness through implementation of clean technologies, this sector still needs other efforts to minimize environmental impacts of production processes. It is generally known that the environmental and economic performances of the granite processing organization are greatly influenced by its block sawing technology. However, the selection of the sawing technology is commonly based on the experience and preference of the manager. It is complicated to select the most appropriate technology from a set of alternatives in a scientific way and therefore, this study focused on the granite block sawing process and used sustainability-based Multiple-Attribute Decision-Making (MADM) method to evaluate the performance and cross-media effects of alternatives applicable for this process. The method was illustrated by a granite processing firm in Shandong Province, China. The gangsaw technology was chosen as the reference technology due to its wide range of applications. Five sawing technologies were identified as the alternatives by considering several constraints proposed by experts. The performances of alternatives were expressed and compared using relevant environmental, economic and technical indicators. The decision-making algorithm was developed by integrating the Analytic Hierarchy Process (AHP) model and the Technique For Order Preference by Similarity to Ideal Solution (TOPSIS) model. The priorities of the five alternatives were achieved by the designed algorithm. The results showed that the Diamond Multi-Circular Saw with 30 blades (DMCS 30) technology had the largest closeness coefficient to the ideal solution. So it was recommended to be the most sustainable technology for the case firm. The case study illustrated that the method can reduce the environmental impacts, whilst providing the economic benefits to the granite processing firms. This research showed that the proposed method is helpful and practical in providing guidelines for the decision-makers to select the sustainable technology for cutting granite block into slabs. It also demonstrated the method can complement the technological approach in fostering the cleaner production mode in the granite processing sector.

From landfill to water, land and life: The creation of the Centre for stone materials aimed at secondary processing

This paper focuses on the creation of a Centre for the recycling of stone materials. The Centre will be able to offer a range of activities amongst which is the improvement of the production chain of the Orosei Marble district in Sardinia, Italy. Several companies operate within the marble producing area, specializing in both quarrying and stone processing. They have formed a Consortium in order to rehabilitate an area of more than 17ha. The restoration will be carried out through an environmentally sustainable procedure. The area was previously used as a landfill for waste deriving from marble quarrying and processing. At that time unshaped blocks of various sizes (which are unsuitable to block-cutter sawing), waste deriving from both block sawing and slab/strip cutting (such as broken slabs, strips, tiles) and microfine dust from filter presses of water treatment plants were representing an environmental problem. The local administration was struggling to find new areas which could be used for landfills, resulting in an additional cost for the landfill, ultimately affecting the variable production costs. The project involves the building of a venue to be used for temporary storage, treatment of wastes produced by both quarrying and primary processing, in order to make them suitable as secondary raw materials. The project also deals with the catch basin hydrology of the area involved in the project, the building of a multifunctional centre, the landscaping and other environmental features such as vehicle traffic and slopes greening.

Viabilidade técnica da fabricação de cimento com mistura de escória de aciaria LD e resíduo de granito

Esse trabalho estuda a viabilidade técnica da fabricação de cimento com uma mistura de resíduo proveniente da serragem de blocos de granito e escória de aciaria LD. Para isso, foi preparada uma mistura desses materiais de modo que a relação %CaO / %SiO2 fosse 1,2. Essa mistura foi fundida e resfriada rapidamente em água. A amostra foi caracterizada e o difratograma de raios X mostrou um material amorfo e a presença das fases mineralógicas Akermanita e Gehlenita, as quais são consideradas como as fases mineralógicas ideais para a atividade hidráulica. Essa mistura foi adicionada ao clínquer para a fabricação de cimento. Com o cimento fabricado, foram feitos ensaios cujos resultados são apresentados e comparados com os valores obtidos para o cimento de alto-forno. Esses resultados indicam a viabilidade técnica da utilização da mistura na fabricação de cimento.

Sawing of blocks of siliceous dimension stone: influence of texture and mineralogy

The sawing of granite blocks using multi-blade gangsaws and an abrasive mixture is one of the most complex operations in the rock transformation industry. The surface quality of the finished slabs is the major determinant of the volume of material to be removed in subsequent polishing operations, thus influencing the final cost of the product. To determine this quality, a portable piece of equipment which records direct measurements of the roughness of the slab surface was developed. The measurements were carried out on two types of granite slabs of high commercial value. These granites showed mineralogical similarities, but great differences in cutting speed and the cost of the industrial process. The paper discusses the results in relation to Knoop hardness, Amsler wear, deep abrasion and petrography and concludes that the texture of the rock has the most important influence on the cost of production of polished slabs.

Estratégias competitivas para empresas de rochas ornamentais na região metropolitana do Rio de Janeiro

The strategy to accelerate the development of mining-beneficiationtechnology-competitivity management of dimension stone companies involves various analysis and alternative methodologies. In this project the Life-Cycle Matrix methodology was used with its main external (industry maturity) and internal (overall measure of the competitive position of a business) factors to analyze in detail the block cutting (sawing) sector of the metropolitan region of Rio de Janeiro and the competitive position of the main companies that are active in the sector. Special attention was given to the dimension stone plates production process, describing the main methods used to beneficiate blocks and to undertake secondary beneficiation. A Case Study was used as the data base for the adoption and selection of strategies for the block cutting companies located in the metropolitan region of Rio de Janeiro. The following block sawing companies were described with special attention to their infra-structure, organization, installed production capacity, granite plates production lines, critical success factors, technology, inputs, vertical integration, sales, market share, and products quality: Thor, Brasilstone, Rio Segran, Gutimpex, Cavaliere, Belmonte, Real Brasil and Marcovaldi. The objective of identifying future possible main strategic thrusts-action programs-functional strategies and action plans to accelerate the development of the dimension stone companies in the metropolitan region of Rio de Janeiro was achieved. A Strategy Diagnostic Study also was undertaken and will be of great value for the companies and entrepreneurs that are already active in the sector and for the new national and foreign companies and new investors that may have interest to invest in this sector in short and medium time periods.