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Less fines production in aggregate and industrial minerals industry (LESS FINES)

Deliverables

The cylinder expansion test is a testing procedure to determine the work capacity of civil explosives, measured in terms of J/kg. In this test the explosive performs work in a geometry that closely matches real rock blasting conditions. The measured work capacity EG represents a fraction ç of the chemically bound energy and this fraction depends on explosive type and different additives like aluminium grains. This makes it possible to classify explosives with respect to real work capacity instead of computed numbers based on arbitrary pressure cut-offs.
In order to assess the ability of a rock, by extension a rock-mass, to produce specified results (amount of fines, fragmentation in general) when blasted, this method will consist in the following steps: - Perform laboratory rock-mechanic tests on usual rock samples (dm3) in order to determine the constitutive law of the material; - Perform small-scaled laboratory blasts on rock samples (m3) while measuring resulting fragmentation; - Derive the specific fragmentation law for this rock when submitted to high stress and strain rate (as it is the case in blasting); - Perform numerical simulations, using a 3D dynamic numerical model, in order to predict the dynamic (time evolution) distribution of stress and displacement and thus get an idea of the fragmentation for given loading (i.e. blasting) conditions. This method should enable to estimate the result of varying blasting parameters (energy of explosives, timing of initiation) within a rock-mass of this rock-type in a relative way (variation but not absolute).
This product is a methodology consisting of general outlines based on the NBC concept, to help quarries and mines to blast so that they get the desired fragmentation not only less fines. It contains: - A general blasting methodology based historical experience; - The new Swebrec function, which gives an accurate description of the blast fragmentation, incorporated into the KUZ-Ram blast fragmentation model; - Experiences from blasting tests in the Less Fines project.
A new way of making measurements (both systems, analysis software and procedure) has been developed. This is useful in order to have a quantitative and comparable basis of blasting knowledge. It forms the basis for a correct design & layout of a blasting procedure. It is a methodology rather than a new technology itself.
The determination of the natural breakage characteristic of the rock mass is a procedure which consists of a series of laboratory experiments and respective analysis. The output from that procedure are material parameters for the rock. They describe its breakage behaviour and enable the prediction of the characteristics of the fragment size distribution for a blasted rock.
The concept of “Energy controlled blasting” is the precise adaptation of the explosives energy input during blasting into the rock mass with respect to the volume/mass to be blasted hole per hole over the total bench height. The concept consists of a systematic procedure based on geometrical measurements of the blast geometry, the back calculation of the amount of explosives necessary on a hole per hole basis and finally in a procedure of a charging technology (either explosives dilution or hole section blocking) to realise the precise amount of explosives charging in the hole over the whole bench height. While the concept is ready there is still some development need in the future to implement the concept into software, which allows one to automatically carry out the necessary calculations.
This product is a procedure about how to determine, based on field measurements, the energy balance of a blasting operation. It consists of the specifications on how to make the measurements and how to do the calculation based on the measured values.
The product is a technology for the manufacturing of explosives with properties, which contribute to a reduction of fines in rock blasting. The process and resulting explosives product also have a positive effect on the general fragmentation. The test campaign at Nordkalk has shown a reduction in explosives consumption of 5% without any noticeable effect on fragmentation, loading, hauling and crushing. The spillage of explosive on ground during the loading operation has been close to nil.
The Swebrec function is a new three-parameter fragment size distribution, which ties together rock fragmentation by blasting and crushing. It gives excellent fits to hundreds of sets of sieved fragmentation data with correlation coefficients of usually r{2} = 0,995 or better over a range of fragment sizes of 2-3 orders of magnitude. A five-parameter version reproduces sieved fragmentation curves all the way into the 100-micron range and also handles ball mill grinding data. Further, the Swebrec function: - Plugs right into the Kuz-Ram model and removes two of its drawbacks, the poor predictive capacity in the fines range and the upper limit cut-off to block sizes, - Reduces the JKMRC’s one-family description of crusher breakage functions based on the t10 concept to a minimum; - Establishes a new family of natural breakage characteristic (NBC) functions with a realistic shape that connects blast fragmentation and mechanical comminution and offers new insight into the working of the Steiner’s OCS sub-circuits of mechanical comminution. It is suggested that the extended Kuz-Ram model, with the Swebrec function replacing the Rosin-Rammler function, be called the KCO model.

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