EXPLOSIVES & BLASTING
Hexagon ’ s MinePlan Block Model Manager provides a server-based block model management solution that enables highly efficient data management with version control and change notifications , the company says
MinePlan Block Model Manager to enable stitching together multiple Muckpile Block Models , and the option to re-block to the required selective mining unit ready for the load and haul process ,” Dampney says . “ The block model is no longer destroyed during blasting , and Block Model Manager becomes a data science platform for solving complex problems that go beyond drill and blast and ore control .”
BME PASSes on blast performance findings
A decline in blast performance at an iron ore mine in South Africa has led Omnia company BME to investigate a new mechanism for bulk emulsion breakdown , and to find innovative solutions for the customer .
In a recent article in the International Society for Explosives Engineers ’ Journal of Explosives Engineering , experts from BME revealed an encounter with potential acidic sulphate soil ( PASS ). The article ’ s authors – BME Global Manager Blasting Science , D Scott Scovira , BME General Manager Production & Logistics , Dirk Voogt , and BME Senior Chemist , Quentin Steyl – noted that iron ore mines are not normally associated with reactive or acidic ground . Indeed , the operation conducted ground sample reactivity testing , which confirmed that neither reactive ground nor acidic water was to blame .
The question which then needed to be answered was : what caused the emulsion to break down ? The same emulsion continued to be used by other customers around the country to normal effect . The teams conducted many tests , including the testing of a mixture of the straight gassed bulk emulsion plus mine blasthole water and blast cuttings – representing the total hold loading condition at the mine . These tests showed that the mixture created an environment in the blasthole , leading to autocatalytic acid generation , with subsequent over-gassing and breaking down of the emulsion .
“ A deeper investigation into the ground mineralisation revealed the presence of PASS , which is a new mechanism for bulk emulsion breakdown ,” the authors said . The condition was remarkably uncommon and it was the first occasion that it had been observed in over 50 years of emulsion usage . Despite an extensive search of publicly available knowledge in this field , no-one had described PASS in the context of bulk emulsions . Research did reveal , however , that PASS can become an acid sulphate soil in the presence of a strong oxidiser .
“ This conversion reaction results from the presence of reduced inorganic sulphur ( RIS ) in the soil ,” the authors said . “ Actual acid sulphate soils ( AASS ) – soil materials that contain RIS – have undergone oxidation to produce acid ; any pH drop indicates the soil ’ s potential to form sulphuric acid when it is disturbed and exposed to oxygen .”
In the absence of water , soil samples from the
mine showed no reactivity with the straight gassed bulk emulsion . Some samples showed the potential to become reactive and to start breaking up when a strong oxidiser was present . When a sodium nitrite-based gassing solution was used to sensitise the emulsion in contact with soil , a reaction began that impacted negatively on the emulsion matrix , they explained .
“ To manage this challenge , we therefore investigated the difference between the effect of standard sodium nitrite and water solution , and an emulsified gassing agent ( EGA ),” the authors said . “ EGA is an emulsion which is incorporated more readily into the base emulsion – thus preventing contact between the gassing agent ( a strong oxidiser ) and the PASS .”
It was this homogenising of EGA into straight bulk emulsion which significantly inhibited PASS ground reactions with the emulsion , creating a product of very high viscosity which held its form , BME says . The resulting emulsion was found to reduce contact between the gassing agent and the PASS .
“ These modifications to the bulk explosives system have provided a window of protection for the straight bulk emulsion against these site ground conditions ,” the authors said . “ They have also enhanced resistance to product degradation by the action of dynamic water present at the mine site .”
Important performance improvements were achieved , with the increased dispersion of the gassing agent in the emulsion , as well as reduced bubble size in the gassing agent . Field measurements demonstrated that detonation velocity was increased when compared with nonhomogenised gassed bulk emulsion .
The authors concluded : “ As PASS has been only recently discovered as an emulsion decomposition mechanism , we expect there will be considerable learnings achieved in the future .
Decomposed emulsion and water from the iron ore site experiencing potential acidic sulphate soil issues
70 International Mining | AUGUST 2024