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Nitrogen blasting in open-pits

#KR-1185


Technology and Automated System for Hardrock Destruction by Blasting of Condensed Nitrogen

Tech Area / Field

  • MAN-ROB/Robotics/Manufacturing Technology
  • MAT-EXP/Explosives/Materials
  • OBS-NAT/Natural Resources and Earth Sciences/Other Basic Sciences

Status
3 Approved without Funding

Registration date
26.10.2004

Leading Institute
Kyrgyz-Russian Slavonic University, Kyrgyzstan, Bishkek

Collaborators

  • NASA / Kennedy Space Center / Sierra Lobo Inc., USA, FL, Brevard County

Project summary

In Project suggested there will be extended research and developments, performed on ISTC # KR-341 Project.
The purpose of the Project is to develop a new technology and device for mass line hard rock blasting with charges of condensed nitrogen.
Up-to-date drilling and blasting operations at open-pits - mass blasting of ammonium nitrate explosives in deep big-diameter holes have three unremovable drawbacks: oversize in rock broken excludes more effective and continuous mining of deposits; emission of noxious gaseous blast products to atmosphere causes damage to environment and human health inside and outside of the open-pits; seismic vibrations of rock block reduce stability of slopes, break open-pit walls, buildings and constructions at the surface.
Search of approaches to eliminate mentioned drawbacks presumes a reconstruction of all conventional complex of overburden and mining operations at open-pits. In this connection the first task is to suggest new methods and techniques for hard rock destruction, for example, with the use of quick blasting of charges of non-explosive and environmentally appropriate substances – condensed nitrogen or water.
In Project #KR-341 there are new technology and drill and blast planer suggested for mass line mining in hardrock. These allow to make controlled destruction of rock in shallow layer of high bench slopes with no oversize by quick blasting of condensed or gaseous hydrogen (methane) and oxygen charges, to move a rock flow to the bottom work area and to transfer rock blasted to the face belt conveyor by telescopic re-loader.
Comparative assessment of conventional and new technologies and devices has shown high efficiency of suggested solutions.
Stochiometric mixture of hydrogen and oxygen, used as explosive components has some drawbacks - high cost, fire- and explosion hazard. One of the principal tasks of this Project is to obviate above drawbacks with maximum economic efficiency.
Liquid nitrogen as an explosive gains an advantage due to unlimited resources of raw material, simplicity of obtaining, available low price equipment for storage and transportation, relatively easy conversion to gaseous state.
Thermodynamic parameters of nitrogen as a cryogenic liquid and relative safety of its use are well known. But, information on application of liquid nitrogen as an explosive for continuous rock destruction is nearly absent: some patents describe solutions for deep holes of big diameter. Patent copies are in Supplement 3.
However, use of the liquid nitrogen properties in critical point, when there occurs virtually instantaneous transition from condensed to gaseous state at the heating to temperature –149C and more, provides a good reason to contend that liquid nitrogen might be successfully used as an actuating fluid for quick physical explosions, energy of which would be enough to perform effective destruction of hard rock.. Stored energyof gaseous nitrogen can be increased by preheating if necessary.
Today due to lack of appropriate technology of drilling and blasting operations at open pits, liquid nitrogen is not used for hardrock blasting. However, low cost of nitrogen (condensed nitrogen is several times cheaper than ammonium nitrate explosives widely used at open-pit mining) and absolute ecological compatibility inevitably bring to wide and persistent expansion of liquid nitrogen as a convenient and safe actuating fluid for making physical explosions.
The feature of suggested technology is in combination of continuous drilling of holes near free surface of bench and in supply of few charges of liquid nitrogen a minute at a rate of 0.8 – 1.0 l nitrogen for 1.0 cub.m rock. The implementation of principle of continuous mining will allow to develop an automatic drill and blast device with no need to initiate charge blasts, that will lead to distinctly simplified design of breaking devices, to notable increase in planer safety and performance. Preliminary tests confirm this conclusion.
New technology and device will enable to profit from safe surface and underground mining of diamond, gold, uranium and other mineral deposits meeting high environmental challenges at the operating and new unmanned open-pits in adverse mining and climatic conditions.
Reaching the purpose posed requires solving of following principal tasks:
1) to investigate thermodynamic parameters of nitrogen in area near critical point, that is prior to explosion, during explosion and after explosion;
2) to develop an automated system - generator for conversion of liquid nitrogen to gaseous state in closed space;
3) to produce and test pilot device for hardrock destruction by blasting nitrogen charges in holes;
4) to incorporate generator and control system for nitrogen charge preparation and blasting processes into drill and blast planer developed earlier on ISTC #KR-341 Project and meant for continuous hardrock blasting in oblique plane of high bench slopes with charges of oxygen and hydrogen;
5) to combine modernized drill and blast planer with suggested in #KR-341 Project technology of continuous mining of mineral deposits in hardrock.
Use of liquid nitrogen as an acting fluid for making physical blasts in automated drill and blast systems will enable to reach following positive results:
– to create auspicious conditions for people staying in worked out area of open-pits, especially when mining deep part of deposits of diamond, gold, uranium ore and other minerals;
– to reduce power- and metal-consumption of mining equipment, noticeably cut down capital and operational outlays for mining operations;
– to simplify planers design, to increase reliability of all face complex of machinery;
– to increase safety of works on hardrock destruction by quick blasting, as relatively dangerous mixture of hydrogen and oxygen, suggested earlier in Project #KR-341, is changed for safe nitrogen and also at the expense of elimination of high-voltage devices for charge blast initiation by spark discharges;
-– to reduce loss and minerals impoverishment resulted from mining of deposits by oblique layers with separate detachment of beds and host rocks from massif; considerable economic effect will be especially noticeable when mining of diamonds, gold, uranium ore, other minerals;
– to cut down current coefficient of overburden at the expense of keeping natural structure of rock outside open-pit outlines and as a result to increase an angle of pit walls slope, that will extend a term of works service and increase profit;
– to enlarge scope of open-pit mining, to involve less reach deposits in mining thereby increasing source of raw materials of operating and new open-pits.
Project implementation will provide scientists and specialists who took part in development and test of weapon and explosives, an opportunity to redirect their knowledge and skills to peaceful activity and will promote solving of national and international technical problems in area of new and environmentally appropriate automated technologies of open-pit mining in adverse geological and climatic conditions, creation of safe explosives, meeting purposes and lines of ISTC activity.
On results of work the applications for an invention are supposed to be submitted to claim a right for design features of devices and technological methods of mass line mining in hardrock.
Leader of participating institution – Kyrgyz Russian Slavic University and Project Manager are agree that role of foreign collaborator Dr. Stan D. Augustynowicz, cryogenics expert from Kennedy Space Center, Florida will be highly helpful for Project implementation.
Joint work of Dr. Stan D. Augustynowicz with Project Participants will include more accurate development and coordination of Work Plan, participation in research on some specific tasks, report examination and estimation of work results, organization of workshops, meetings, in consulting on issues of intellectual property right.


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