Impact Crusher Research Articles

Distribution and Shape of the Pores in Water Permeable Concrete

Porous concretes with continuous voids have been gaining more interest as an ecological material because of their useful functions such as water permeability and adsorption ability. So pore size distribution and the shape of especially open pores are the key point to permeability. In this study, the size and shape of pores of water permeable concrete were primary controlled by the size and shape of aggregates and secondly by the expanding agents to the cement pastes. 2 types of raw coase aggregate, type I and type C which mean fabricated by impact crusher and concrusher, were taken into uses and 3 sizes of aggregate were used, namely 3 to 5mm, 5 to 13 mm, and 13 to 20 mm. The compressive strength was found to be higher when using impact crushed aggregate. And the smaller size of aggregate was used, the higher compressive strength was achieved.

Comparison of natural and manufactured fine aggregates in cement mortars

The performance of cement mortars using manufactured fine aggregates produced by cone crushing or impact crushing has been compared to that of mortars prepared from a natural sand control-sample. Samples from both crusher products have been additionally subjected to classification for partial removal of fines, being also used in preparing mortars. Particle shape analyses indicated that material produced by impact crushing presented intermediate sphericity and aspect ratio, between those found in natural fine aggregate and cone-crushed material, and that the aspect ratio of the cone-crushed material increased for finer particle sizes. The unclassified impact crusher product presented the highest packing density, and mortars produced from it had comparatively low porosity and low absorptivity and the highest unconfined compressive strength. The classified product from cone crushing presented low packing density and mortars were characterized by the highest porosities, absorptivities and lowest unconfined compressive strength, probably mostly due to its poor particle shapes. Modeling of the stress–strain response with scalar damage mechanics showed that manufactured aggregate produced from classification of the cone crusher yielded a mortar with highly inelastic deformation response, whereas mortars produced from unclassified product of impact crushing showed more elastic deformation response. Results were also analyzed in light of de Larrard's Compressible Packing Model.

Measuring characteristics of aggregate material from vertical shaft impact crushers

Natural gravel has traditionally been the main choice of material for Swedish concrete manufacturers. However, due to the fact that natural gravel also acts as a fresh water filter, the deposits are limited. The obvious question is how to compare machine made and natural gravel in terms of particle shape, rheology and other material characteristics. This paper will present some methods and results that demonstrate performance of different machine made rock materials. Particle shape characteristics were assessed from flow measurements in a standard cone. The vertical shaft impact crusher (VSI) produces gravel that is a good alternative to natural gravel. The quality of the material and the particle shape seem to meet concrete producers’ demands.

Recovery of copper from waste printed circuit boards

A highly effective process based on a hammer mill, a pneumatic column separator and an electrostatic separator was developed for recovering copper from waste printed circuit hoards. The factors influencing the degree of copper liberation are discussed. Two physical separation methods were compared and discussed. Experimental results show that a well-controlled impact crusher can produce satisfactory copper liberation at a relatively coarse particle size. Around 90% copper recovery from waste printed circuit boards can be achieved using a combination of electrostatic separation and pneumatic separation.

Applying discrete element modelling to vertical and horizontal shaft impact crushers

The PFC3D (particle flow code) that models the movement and interaction of particles by the DEM techniques was employed to simulate the particle movement and to calculate the velocity and energy distribution of collision in two types of impact crusher: the Canica vertical shaft crusher and the BJD horizontal shaft swing hammer mill. The distribution of collision energies was then converted into a product size distribution for a particular ore type using JKMRC impact breakage test data. Experimental data of the Canica VSI crusher treating quarry and the BJD hammer mill treating coal were used to verify the DEM simulation results. Upon the DEM procedures being validated, a detailed simulation study was conducted to investigate the effects of the machine design and operational conditions on velocity and energy distributions of collision inside the milling chamber and on the particle breakage behaviour.

Stress distribution in unbound aggregate of road structure: influence of surface roughness and particle shape

Aggregate used for road structures has to meet requirements regarding abrasion, strength and shape. These properties are largely influenced by the crushing operation. To improve these properties the aggregate can be cubicised in a vertical-shaft impact crusher. During this process, sharp edges will be rounded and the surface will be polished, which can have negative effects on road stability. This paper presents laboratory work on the load distribution by aggregate used in the unbound layers of the road structures. The aggregate used had different surface roughness and particle shape. The equipment used was a ring chamber consisting of 15 steel rings. The chamber's diameter was 320 mm and the height was 360 mm. Using this equipment, the stability of aggregates was studied with reference to particle shape and surface roughness for six types of aggregates by measuring the horizontal and the vertical stress that appear under a vertical loading. The grain size of the aggregates used was 8–11.2 mm. The aggregate was divided into three grades of surface roughness, depending on the level of cubicisation. Each level of surface roughness was divided into two groups, one flaky and one more cubic, in order to study the influence of aggregate shape. The laboratory tests showed that aggregate shape had an influence on the aggregate stability. Surface roughness also influenced the stability, but this was not as important as the aggregate shape.

95/03310 Dust suppression at an impact crusher with high-pressure water

95/03310 Dust suppression at an impact crusher with high-pressure water

Repeated impact-abrasion testing of alloy white cast irons

A small Hazemag rotary impact crusher has been adapted for the assessment of the repeated impact-abrasion properties of alloy white cast irons. The test specimens were cast as blow bars for use in the crusher, and each test involved the comminution of 2000 kg of quarry stone. A series of six alloy white cast irons has been tested in the crusher in order to assess the influences of chemical composition, hardness, eutectic carbide volume fraction and retained austenite content on combined repeated impact-abrasion performance. The results showed that hardening by heat treatment, and hence variations in retained austenite content, had no influence on weight loss, but that weight loss increased significantly with increasing eutectic carbide volume fraction. Post-wear examination of worn blow bars revealed significant gouging and impact damage on the surface, and on a finer scale, extensive fracture of eutectic carbides, decohesion at carbide/matrix interfaces, matrix fracture, and microscopic spall formation.

インパクトクラッシャにおける摩耗の解析

The process of wear on the hammers of the impact crushers was analyzed by assuming that the wear rate is proportional to the energy lost through friction between the hammers and the rock particles colliding against them. The calculated result explained the concentration of the wear at the tip of the hammers observed in field operation. Wear rates of various materials were measured by using a laboratory impact crusher and were presented as a func-tion of hardness. Hard metals were found to be the best material for the tip of the hammers.

インパクトクラッシャの破砕特性と新しい用途

New applications for impact crushers were examined by using a laboratory impact crusher. The results on the characteristics of the impact crushing were summarized as follows: 1) less excess fine results in the product and with the same efficiency as compared to crushing by static compression, 2) the particle size distribution in the product agrees with JIS standard for sand used as fine aggregate for construction material, 3) the crushing efficiency in pre-crushing of cement clinker is the same as that of the roller press.

CRYOGENIC SEPARATION of CITRUS FRUIT INTO INDIVIDUAL JUICE SACS

ABSTRACTCitrus fruits were crushed by a falling ball type impact crusher at low temperature and their juice sacs were separated into individual sacs. the effect of freezing temperature on the degree of separation was examined, using four kinds of citrus fruits, Unshu orange, sweet orange, grapefruit, and lemon. the results indicated that the degree of separation depended solely on temperature regardless of sample size, applied force, and fruit kind. No shattering occurred above ‐ 30°C. the degree of separation increased until below − 120°C, there was little further separation. the cause of no shattering at or above − 30°C was attributable to the mechanical property of juice.