Patent Publication Number: US-2023152073-A1

Title: Transport of explosives

Description:
FIELD OF THE INVENTION 
     THIS INVENTION relates to transport of explosives. More specifically, the invention relates to vertical transport of explosives, particularly of emulsion explosives. The invention provides a method of vertically transporting emulsion explosive. The invention also provides an installation for vertically transporting emulsion explosive. 
     BACKGROUND TO THE INVENTION 
     VERTICAL TRANSPORT OF EMULSION EXPLOSIVES, for example down mine shafts for underground blasting operations, remains wrought with challenges. 
     The applicant has sought to address these challenges with the inventions of ZA 2011/01044 and ZA 2012/07171, which have been successfully exploited in practice. 
     Nevertheless, a need for alternative approaches remains, both to address the operational, safety and logistical challenges that are discussed in the specifications of the abovementioned patents, and to protect the emulsion product during its transport. 
     More specifically, an emulsion that is transported vertically may, if dropped freely within a conduit over a sufficient distance, break up as a result of shearing and turbulent flow. A challenge in vertical transport of emulsion explosives is therefore to maintain laminar flow of emulsion explosive under gravity force/hydrostatic pressure. 
     The present invention finds application in the above respects. 
     SUMMARY OF THE INVENTION 
     IN ACCORDANCE WITH ONE ASPECT OF THE INVENTION IS PROVIDED a method of vertically transporting emulsion explosive, the method including, using a pump, pumping a predetermined volume of emulsion explosive, from an emulsion explosive reservoir, into a vertically extending pipe, wherein pumping is effected airtightly at least between the pump and a downstream end of a volume of emulsion explosive that has been pumped into the vertically extending pipe for at least a part of the travel of emulsion explosive of the predetermined volume of emulsion explosive down the vertical pipe. 
     Airtight pumping may, more preferably, be effected between the emulsion explosive reservoir and the downstream end of a volume of emulsion explosive that has been pumped into the vertically extending pipe for at least a part of the travel of emulsion explosive of the predetermined volume of emulsion explosive down the vertical pipe. 
     It is noted that there may be ancillary piping between the vertically extending pipe and the pump, and between the pump and the reservoir. 
     An emulsion explosive is a dispersion of two relatively immiscible liquids/phases: an aqueous oxidizer phase and a hydrocarbon fuel phase. Industrial grade fuels were blended with emulsifiers and formed an emulsion fuel phase or continuous phase. Emulsion grade ammonium nitrate was used in order to produce the emulsion oxidizer phase (dispersed phase), which was a water solution of metal nitrate(s). The above materials formed a part of highly concentrated emulsion explosives where the continuous phase did not exceed 10% of the emulsion by mass. A more detailed description of the emulsions and emulsion preparation can be found elsewhere (Masalova et al. 2007, 2006). The emulsion explosive term covers all explosives used in form of emulsion (dispersion of one phase in the other) in particular, may be so-called “sticky emulsion explosive the emulsion that was designed for “up-hole” applications or any other non-sticky emulsion formulation design for the other application such as development, tunnelling, stoping, etc. 
     The vertically extending pipe may be open to the atmosphere at a downstream end thereof, and may optionally feed into a secondary reservoir. It is noted that there may be ancillary piping connected to the downstream end of the vertically extending pipe, that may connect the downstream end of the vertically extending pipe to the secondary reservoir, if provided. In such a case, reference to the “downstream end” of the vertically extending pipe above and hereinafter, is to a downstream end of such ancillary piping. 
     In an alternative embodiment of the invention, the vertically extending pipe may be closed to the atmosphere at its downstream end, being configured for positive pressure to be applied to the downstream end of the predetermined volume of emulsion explosive, or part thereof, from the downstream end of the vertically extending pipe, as the predetermined volume of emulsion explosive, or part thereof, is travelling along the vertically extending pipe. 
     The vertically extending pipe may extend vertically for a vertical distance beyond 500 m, or beyond the emulsion column length associated with emulsion minimum burning pressure. 
     The emulsion explosive is typically not sensitised emulsion explosive, and the method may include sensitising the emulsion explosive at a downstream end of emulsion application, e.g. during charging blast holes with emulsion explosives. 
     Pumping may be effected at a velocity equal to the velocity due to gravity flow rate of the predetermined volume of emulsion explosive in the vertically extending pipe, i.e. the velocity of the predetermined volume of emulsion explosive when moving in the vertically extending pipe solely under gravity. More typically, pumping may be effected at a velocity higher than the gravity flow rate, or at a velocity lower than the gravity flow rate. 
     Preferably, pumping is effected at a velocity lower than the gravity flow rate. 
     Pumping may continue until the predetermined volume of emulsion explosive has passed through the pump. Pumping may then be discontinued. This may include airtightly isolating the pump from an upstream end of the predetermined volume of emulsion explosive, e.g. by means of a valve, typically downstream of the pump, that is closed. 
     After pumping is discontinued, or even before, travel of the predetermined volume of emulsion explosive, or part thereof, along the vertically extending pipe, and ancillary piping upstream of the vertically extending pipe, if provided, would at least in part be under gravity. 
     When pumping has been discontinued, further travel of the predetermined volume of emulsion explosive, or part thereof, along the vertically extending pipe would be solely under gravity. 
     Continued travel of the predetermined volume of emulsion explosive, of part thereof, along the vertically extending pipe after pumping has been discontinued would result in a suction being formed between the pump, of a valve that separates the pump from the vertically extending pipe, and an upstream end of the predetermined volume of emulsion explosive. 
     It would be appreciated that the predetermined volume of emulsion explosive would therefore need to be sufficient to move under the force of gravity, against a suction pressure at its upstream end. 
     The predetermined volume of emulsion explosive may have a weight in the order of a number of tons, The maximum volume/weight restriction is applicable in connection with emulsion minimum burning pressure and the stationary emulsion column should not generate a hydrostatic pressure that exceeds emulsion minimum burning pressure. 
     In some embodiments of the invention, depending on the length of the vertically extending pipe, and ancillary piping, and the volume of the predetermined volume of emulsion explosive, pumping may continue after some of the predetermined volume of emulsion explosive, or part thereof, has started exiting the downstream end of the vertically extending pipe, with pumping only being discontinued thereafter. It would be appreciated that, in such embodiments, the vertically extending pipe would never contain the entire predetermined volume of emulsion explosive at any point in time. 
     In other embodiments of the invention, pumping may be discontinued before the downstream end of the predetermined volume of emulsion explosive has reached the downstream end of the vertically extending pipe. It would be appreciated that, in such embodiments, the vertically extending pipe would typically contain the entire predetermined volume of emulsion explosive at some point in time. 
     IN ACCORDANCE WITH ANOTHER ASPECT OF THE INVENTION IS PROVIDED an installation for transporting emulsion explosive vertically, in accordance with the method of the invention, the installation including
         an emulsion explosive reservoir, for containing emulsion explosive, and having an outlet;   optionally, a pump arranged to withdraw emulsion explosive from the emulsion explosive reservoir through its outlet, by applying suction to emulsion explosive contained in the emulsion explosive reservoir;   a vertically extending pipe having an upstream end; and
           a continuous conduit extending from the pump to the upstream end of the vertically extending pipe, and into the vertically extending pipe.   
               

     The characteristics of features of the installation carrying the same name as features of the method of the invention may be as hereinbefore described in respect of the method of the invention. 
     The vertically extending pipe may extend vertically for a vertical distance beyond 100 m, even beyond 500 m, e.g. 680 m, and even beyond 980 m. 
     Having a continuous conduit extend from the outlet of the emulsion explosive reservoir, through the pump, to the upstream end of the vertically extending pipe, and into the vertically extending pipe, allows airtight pumping of emulsion explosive from the pump into the vertically extending pipe, such that no air is allowed into the installation between the pump and a downstream end of a volume of emulsion explosive that has been pumped into the vertically extending pipe for at least a part of the travel of emulsion explosive of the predetermined volume of emulsion explosive down the vertical pipe. 
     More preferably, the continuous conduit may extend from the outlet of the reservoir, through the pump, to the upstream end of the vertically extending pipe, and into the vertically extending pipe, allowing for airtight pumping along such an, extended, conduit. 
     The installation would typically be at an underground mining operation, with the vertically extending pipe extending vertically to an underground location at which the emulsion explosive is required. 
     As provided for in respect of the method of the invention, the installation may include a secondary emulsion explosive reservoir located at a downstream end of the vertically extending pipe, for emulsion explosive to be discharged into the secondary reservoir. 
    
    
     DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT 
     THE INVENTION WILL NOW BE DESCRIBED IN MORE DETAIL in terms of an exemplary embodiment, with reference to the accompanying diagrammatic drawings in which  FIG.  1    shows an installation according to the invention, installed at an underground mining operation, and  FIGS.  2  to  7    show various stages of operation of two embodiments of the installation. 
     Referring to the drawings an more specifically fir  FIG.  1   , reference numeral  10  generally indicates an underground mining operation that includes a mine shaft  15  that has been sunken into a body of earth through a surface  13  of the body of earth. 
     The mining operation  10  includes an installation  11  according to the invention. 
     The installation  11  includes a primary emulsion explosive reservoir  12  that contains non-sensitised, bulk emulsion explosive. 
     The primary reservoir  12  has an outlet  14 , from which emulsion explosive can be withdrawn from the reservoir  12 . 
     The installation  11  further includes a pump  16 , located downstream of the reservoir  12 . 
     An inlet of the pump  16  is connected to the outlet  14  of the reservoir by a first ancillary pipe section  18 . Thus, by applying suction with the pump  16  along the pipe section  18 , to emulsion explosive contained in the reservoir  12 , the pump  16  can withdraw emulsion explosive from the reservoir  12  along the pipe section  18 . 
     The installation  11  also includes a vertically extending pipe  20  that extends vertically down the mine shaft  13  to an underground location  22 , to which underground location emulsion explosive would be delivered by the installation  11 . 
     The underground location  22  is located at a depth of 500 m or more beneath the surface  13  of the body of earth of the mining operation, e.g. 680 m. Thus, the vertically extending pipe  20  has a length of over 500 m, approximating the depth of the underground location  22 . 
     The installation  11  further includes, upstream of the vertically extending pipe  20  a second ancillary pipe section  24  that connects an outlet of the pump  16  to an inlet  26  to the vertically extending pipe  20 . 
     The pipe section  24  has a so-called goose-neck configuration  28  immediately upstream of the inlet  26  to the vertically extending pipe  20 . 
     A first valve  30  is located in the pipe section  24  between the pump  16  and the goose-neck configuration  28 . 
     A second valve  32  is located in the goose-neck configuration  28 . 
     The first valve  30  is configured to close-off the pump  16  from the goose-neck  28 . 
     The valve  32  is configured selectively to allow and disallow atmospheric air into the goose-neck  28  from outside of the pipe section  24 . 
     Connection of the outlet  14  of the reservoir  12  to the inlet  26  to the vertical pipe section is such that emulsion explosive can be withdrawn from the reservoir  12  and pumped, continuously and airtightly, into the vertically extending pipe  20 , wherein airtight refers to the region between the outlet  14  of the reservoir  12  and a downstream end of a continuous volume of emulsion explosive extending from the outlet  14  into the vertically extending pipe  20 . 
     The installation  11  also includes a secondary emulsion explosive reservoir  34  at the underground location. 
     The installation  11  further includes a third ancillary pipe section  36  that extends between a downstream end of the vertically extending pipe  20  and the secondary reservoir  34 , such that emulsion explosive travelling along the vertically extending pipe  20  can be fed into the reservoir  34  along the pipe section  36 . 
     Use of the installation  11  in performing the method of the invention will now be described with reference to  FIGS.  2  to  7   . 
     At start-up, as illustrated in  FIG.  2   , the reservoir  12  would contain a predetermined stored volume of emulsion explosive, a predetermined volume of which needs to be transported to the underground location  22 . 
     With valve  30  open and valve  32  closed, the pump  16  is activated to apply suction to the emulsion explosive contained in the reservoir  12 , thereby withdrawing emulsion explosive from the reservoir  12  and pumping withdrawn emulsion explosive into the vertically extending pipe  20  along the pipe sections  18  and  24 . 
     Thus, a continuous volume of emulsion explosive, extending from the reservoir  12 , through the outlet  14 , the pipe section  18  and, the pipe section  24 , and into the vertically extending pipe  20 , is formed, air-tightly between the reservoir and a downstream end of the continuous volume of emulsion explosive. 
     As pumping continues (see  FIG.  3   ), the volume of emulsion explosive pumped into the vertically extending pipe  20  extends progressively further along the vertically extending pipe  20 . Initially, movement of the emulsion explosive in the vertically extending pipe  20  is driven by the pump, but once a sufficient volume of emulsion explosive has been pumped into the vertically extending pipe  20 , movement is assisted by gravity. 
     In accordance with the invention, discontinuation of pumping is required. In this regard, two scenarios may exist. These are discussed with reference to  FIGS.  4  to  7   . 
     In one scenario, referring to  FIGS.  4  and  5   , pumping is discontinued only after discharge of emulsion explosive into the reservoir  34  has commenced. 
     As will be seen from  FIG.  4   , a continuous volume of emulsion explosive extends from the reservoir  12  into the reservoir  34 , signifying that pumping continued beyond the commencement of discharge of emulsion explosive into the reservoir  34 . 
     Once a predetermined volume of emulsion explosive has been withdrawn from the reservoir  12 , and has passed beyond the valve  30 , pumping is discontinued and the valve  30  is closed. 
     Discharge of emulsion explosive downstream of the valve  30  then continues under force of gravity, with a vacuum being created downstream of the valve  30 , and upstream of an upstream end of the volume of emulsion explosive contained in the vertically extending pipe  20 , as shown in  FIG.  5   . 
     To ensure complete discharge of emulsion explosive from the vertically extending pipe into the reservoir  34 , it may be necessary to allow air into the vertically extending pipe  20 , which would be achieved by opening the valve  32 . 
     In another embodiment, as discussed with reference to  FIGS.  6  and  7   , pumping is discontinued before discharge of emulsion explosive into the reservoir  34  has commenced. 
     As shown in  FIG.  6   , a downstream end of a volume of emulsion explosive pumped into the vertically extending conduit is still spaced from the reservoir  34 , at a time when a predetermined volume of emulsion explosive has been pumped passed the valve  30 . At that time, pumping is discontinued, and the valve  30  is closed. Thus, a discreet “slug” of emulsion explosive is created downstream of the valve  30 , again with a vacuum being formed as described above. 
     Continued movement of the slug down the vertically extending pipe  20  would be under force of gravity, ultimately resulting in the slug discharging into the reservoir  34 , as shown in  FIG.  7   . 
     Again, as in the first-mentioned embodiment, it may be necessary to allow air into the vertically extending pipe by opening valve  32  for complete draining of emulsion explosive from the vertically extending pipe. 
     DISCUSSION 
     THE CONVENTIONAL APPROACH to vertical transport of emulsion explosive is to drop emulsion explosive freely, under gravity, along a pipe that is open to the atmosphere. 
     Beyond a certain depth, this approach is no longer feasible, however, due to the flow of emulsion explosive becoming turbulent as a result of shearing between the emulsion explosive and a pipe along which it is dropped. 
     In the present invention, the applicant has surprisingly found that by positively pumping explosive down a vertically extending pipe in an air-tight manner, and thereafter discontinuing pumping, after a predetermined volume has been pumped into the vertically extending pipe, such damage is significantly reduced and even avoided. 
     In this regard the applicant has found that pumping at a rate lower than the gravity flow rate for a particular predetermined volume of emulsion explosive is particularly advantageous, in that damage to the emulsion is virtually obviated.