US3481648A

US3481648A - Multiple flame jet channeling method

Info

Publication number: US3481648A
Application number: US699452A
Authority: US
Inventors: Rudolph H Kohler
Original assignee: Union Carbide Corp
Current assignee: L-Tec Co
Priority date: 1968-01-22
Filing date: 1968-01-22
Publication date: 1969-12-02
Anticipated expiration: 1986-12-02
Also published as: AT287621B; FR2000561A1; GB1202135A; DE1901923A1

Description

Dec. 2, 1969 R. H. KOHLER 3,481,648

MULTIPLE FLAME JET CHANNELING METHOD Filed Jan. 22, 1968 2 heets-She.et l

L INVENTOR RUDOLPH H. KOHLER %Mum ATTORNEY Dec. 2, 1969 R. H. KOHLER MULTIPLE FLAME JET CHANNELING METHOD 2 Sheets-Sheet 2 Filed Jan. 22, 1968 INVENTOR RUDOLPH H. KOHLER ATTORNEY United States Patent US. Cl. 299-14 7 Claims ABSTRACT OF THE DISCLOSURE A channel is created by removing material from a spallable mineral body by directing at least two separate and distinct high temperature, high velocity gas jets against the mineral surface, to heat such surface to a temperature sufficiently high to cause the surface to spall, moving such gas jets in successive passes along the surface of such body, thereby forming a channel therein, and simultaneously advancing such gas jets in the direction of the channel to be formed while maintaining the gas jets in contact with the end wall of the channel so formed. Each gas jet is maintained at a suflicient distance from the adjacent gas jets so that the intense spalling portion of any gas jet does not interact with an adjacent gas jet. Also, each gas jet is directed at the mineral surface at an angle whereby the intense spalling portion of the gas jets impinge upon a maximum area of such mineral surface.

BACKGROUND OF THE INVENTION The present invention relates to a method and apparatus for working of minerals, and more particularly to a jet channeling proc ss wherein flames are applied to a rock surface for the purpose of cutting a slot or channel in the rock.

It is to be understood that as used herein, the term flames is intended to mean a jet of high velocity, high temperature gas which may or may not be burning. It is also to be understood that as used herein, the term dual jet burner is intended to mean a burner having one or two internal combustion chambers and two jet orifices in communication with the combustion chamber(s). It is to be further understood that as used herein, the term internal combustion chamber is intended to include the combustion zone of a throat combustion burner.

Jet channeling is a process for cutting a slot or channel, normally about 3 inches wide, in quarry stone by the use of supersonic flame directed against the stone causing rock deterioration by a process known as thermal spalling. The conventional jet channeling process is disclosed by Vasselin in US. Patent No. 3,019,004. In Vasselin, a channel is created by the action of a single flame offset at an angle from the axis of a high intensity combustion burner which is moved in a substantially vertical direction in a manner whichmaintains the flame in a generally downward direction, but inclined from the vertical against the generally vertical face of the rock to be treated, while simultaneously being advanced horizontally in the direction of said flame along a sel cted channel path. While present jet channeling processes are conventionally carried out with the burner working a generally vertical face, the same process may be used on rock bases having any slope, from truly perpendicular to horizontal.

OBJECTS It is an object of this invention to provide more efficient mineral working apparatus, i.e. apparatus capable of cutting more square feet of channel per unit of reactants consumed than can be cut by any apparatus heretofore commercially available. It is another object to provide both method and apparatus capable of cutting more square feet of channel per unit of labor input than heretofore available.

SUMMARY OF INVENTION These and other objects, which will become apparent from the detailed disclosure and claims to follow, are achieved by the present invention which provides in a method of jet channeling by removing material from a spallable mineral body by (a) directing high temperature, high velocity jet of gas against a surface of said body, to heat said surface to an elevated temperature sufliciently high to cause said surface to spall, (b) moving said jet of gas in successive passes along the surface of said body thereby forming a continuous channel therein, (c) simultaneously advancing said jet of gas in the direction of the channel to be formed while maintaining said jet of gas in contact with the end wall of the channel so formed, and (d) continuing said channeling method until the desired channel is cut in said mineral body, the improvement comprising:

(1) directing at least two separate and distinct gas jets at said mineral service,

(2) maintaining each of said gas jets in a plane substantially parallel to the surface being treated,

(3) maintaining each of said gas jets at a sufiicient distance from the adjacent gas jets so that the intense spalling portion of any gas jet does not interact with an adjacent gas jet, and

(4) directing each of said gas jets at the surface to be treated at an angle formed between said surface and the axis of said gas jets such that the intense spalling portion of the gas jets impinge upon a maximum area of said mineral body surface.

The present invention also provides in an apparatus for jet channeling by removing material from a spallable mineral body comprising: (a) at least one internal combustion burner capable of discharging a high temperature, high velocity jet of gas from (b) orifice means communicating with the combustion chamber thereof, (c) means for supplying an oxidant gas and a fuel to each burner for combustion in said combustion chamber, (d) means for moving said burner in successive passes along the surface of said mineral body to be treated so that the jet of gas continuously impinges upon said body, thereby forming a continuous channel therein, (e) means for simultaneously advancing said burner in the direction of the channel to be formed, the improvement comprising: providing at least two jet orifices positioned with their axes lying substantially in the same plane, wherein each jet orifice is located at a sufficient distance from the adjacent orifices so that the intense spalling portion of any gas jet does not interact with an adjacent gas jet, and wherein each orifice is directed at an angle from the burner such that the axis of each gas jet and the surface to be treated will form therebetween an angle whereby the intense spalling portion of said gas jets impinge upon a maximum area of said mineral body surface.

FIGURE 1 is a side view of a dual jet burner, illustrative of the invention;

FIGURE 2 is a diagrammatic view illustrating in fragmentary cross-section a mineral body with the dual jet burner of FIGURE 1 shown in operating position while forming a channel in said body;

FIGURE 3 is a plan view of a portion of the mineral body shown in FIGURE 2, illustrating the channel formation;

FIGURE 4 is a diagrammatic view illustrating an embodiment of the dual jet burner adapted for jet channeling a sloping wall;

FIGURE 5 is a longitudinal cross-sectional view of apparatus according to an embodiment of the invention showing a single combustion chamber, multi-orifice burner;

FIGURE '6 is a fragmentary view, paitly in section, of apparatus according to an embodiment of the invention showing a manifolded multi-burner blowpipe.

Referring to FIGURE 1, a dual jet burner illustrative of the present invention comprises a lower blowpipe assembly and an upper blowpipe assembly 12. The lower and

upper assemblies

10 and 12, respectively, consist of conventional

internal combustion burners

14 and 16, respectively, attached at their inlet ends to respective blowpipe stems 18 and 20. Burners 1 4 and 16 are provided at their discharge ends with respective

flame jet orifices

22 and 24.

Metal tubes

26, 28 and 30 are provided for supplying oxidant gas, fuel and coolant to assembly 10. Also, a metal tube 32 is provided for upper burner 16 to divert the flow of heated coolant, such as water, from the immediate working area where it might otherwise interfere with the channeling operation.

A rigid support for interconnecting the

assemblies

10 and 12 at a fixed position relative to one another comprises two steel collars 34-and 36 firmly secured to their

respective assemblies

10 and 12 and also to each other. Collars 34 and 36 are designed so that they maintain, in rigid fashion, the lower burner 14 at an angle relative to the upper burner 16 and at a distance h directly below the latter so that the two flames are in the same vertical plane.

Referring to FIGURE 2, the dual jet burner of FIG- URE 1 is shown supported in its operative position by a suspension assembly 38 located at the upper face of a section of rock '40. In operation, the

burners

10 and 12 are raised and lowered in succession at a desirable speed while being maintained very close to, or in contact with the end wall 42 of the channel. Such positioning insures maximum contact of the flames with the rock and, consequently, higher channeling rates. As the intense flame heats the end wall 42 of the channel to high temperatures, progressive spalling takes place thereby cutting a channel to the mineral rock 40. Simultaneous with the vertical up and down movement, the

dual jet burner

10, 12 is advanced horizontally along a selected channel path (in FIG. 2 this direction is from left to right) as the heated rock spalls away from the end wall 42, leaving a fresh surface of rock.

Referring to FIG. 3, there is a plan view of a portion of the mineral rock 40 shown in FIG. 2 illustrating the full channel formed by two

side Walls

46 and 48, the end wall 42 and the channel bottom 44 of the rock 40.

In the practice of jet channeling, it often happens that the generally vertical rock face (against which the high temperature high velocity gas jet is directed) is initially almost perpendicular as shown in FIG. 2 but, as the channeling operation continues, the rock face gradually acquires a slope so that the generally vertical rock face becomes inclined from the perpendicular as shown in FIG. 4. Thus, the term generally vertical is intended to include both types of configurations as shown in FIGURES 2 and 4.

Referring to FIG. 4, there is shown a dual jet burner being employed for jet channeling a sloping wall with a multijet burner of this invention. Here, the burner blowpipes 50 and '52 with their

respective jet orifices

54 and 56 are moved in the direction of the end wall 58 of the channel at a desirable speed while being maintained very close to, or in contact with the end wall 58. The

glowpipes

50 and 52 will be supported in suitable spaced apart positions with their orifice axes fixed at an angle with respect to the surface of end wall 58 'which provides maximum contact of the flames wi h e ock.

One advantage of the dual jet burner over a conventional single burner is a reduction in labor cost per square unit of channel cut. In some cases this reduction is as much as 50 percent. A reduction in reactant cost per unit of channel cut, as well as labor, may be realized if two or more burners are designed in accordance with this invention by appropriate selection of burner size reactant flow rates, angle of the jet flame orifices in relation to the surface of the rock, and the spacing between the burners.

Testing was conducted to determine the effect that oxygen flow rates have on oxygen efliciency, in terms of ft? of channel formed per ft. of oxygen consumed. It should be obvious that to test only one conventional internal combustion burner, while operating at flow rates both within and outside of its design range, for the purpose of evaluating efficiency versus flow rate is neither a fair nor conclusive test, since variables, such as gas exit velocity and combustion efficiency, will have a substantial effect upon burner efficiency 'when outside the design range. To provide a meaningful test, a series of internal combustion burners designed to operate at different flow rates, ranging from 1000 to 3000 c.f.h. oxygen, were each operated only within their particular design flow range at the standard oxygen-fuel ratio of 1000 cubic feet of oxygen to 43 pounds of kerosene.

Table I below tabulates the test results:

The results generally indicate that the oxygen efficiency decreases as the single jet burner size, in terms of their rated oxygen flow rate, increased. For example, a single jet burner designed for 1500 c.f.h. oxygen channeled at a rate of 12.5 ft. /hr. or efficiency of 0.0083 ft. channel/ft. oxygen while a single jet burner rated for 3000 c.f.h. oxygen channeled at a rate of 21.0 ft. /hr. or efficiency of 0.0070 ft. channel/H 0 The lowest flow burner tested, designed for 1000 c.f.h. O channeled at a rate of 11.5 ft. /hr. with an oxygen efficiency of 0.0115 ft. channel/K 0 Of the burners tested, the smallest burner operated at the highest efficiency.

In addition to the tabulation in Table I of single jet burner test results, testing was also conducted to compare the efliciency of a single jet burner with multi-jet burners having the same total flow rate. The results are shown in Table II.

Table II shows that a higher efliciency is achieved utilizing a multiplicity of jet eflluents rather than a single jet effiuent having the same total flow rate. In the example, the dual jet burner having two jet effluents, each operating from oxygen flow rates of 1500 c.f.h., was capable of channeling 25.4 ftP/hr. with oxygen efficiency of 0.0085 ft. channel/R 0 while the single jet burner operation at its rated 3000 c.f.h. oxygen channeled at a rate of only 21 ftF/hr. with oxygen efficiency of 0.0070 ft. channel/'ft. O Thus, a dual jet burner operating at oxygen flow rates of 1500 c.f.h. per each jet provides 21% greater channeling efficiency than a single jet burner utilizing an oxygen flow of the same total flow,

i.e., 3000 c.f.h. Furthermore, in the same manner, a burner producing three jet etfluents of 1000 c.f.h. oxygen each, channeled at a rate of 34.5 ftF/hr. with oxygen efficiency of 0.0115 ft. channel/K 0 Thus, the three jet burner operated with higher efliciency than the dual jet burner comprising two 1500 c.f.h. gas jets.

It is believed that the intense supersonic portion of a flame does the bulk of the spalling. As the angle of the flame against the rock surface decreases, the area of rock, which may be called the footprint, over which this intense portion impinges, increases, and consequently the channeling rate increases. Of course, a point is reached near 0 where the flame becomes almost parallel to the rock and cannot touch it. i

' Inthe embodimentshown in FIGURES 1 and 2, the upper blowpipe assembly 12 is supported in a vertical position with the burner orifice 24 offset at an angle a, for example, of 12 relative to the burner axis which is substantially parallel to vertical rock surface 42. C01-

lars

34 and 36 are welded together to fix lower assembly at an angle b, for example, of 6, relative to the upper assembly 12 as well as to surface 42. Lower burner orifice 22 is offset at an angle 0, for example, of 6 relative to the burner axis. The sum of angles b and c is represented in FIGURE 1 as angle d, which angle is substantially equal to the angle a so that the flames of both burners impinge on the rock surface 42 at the angle which results in the highest channeling rate. Both burners are positioned in the same vertical plane.

TABLE III Angle of flame to rock Channeling rate Table III illustrates the effect of the flame angle upon channeling rate, using a conventional burner at constant flow rates of 1500 c.f.h. oxygen and 65 lbs./hr. kerosene with all other variables such as velocity and reactant composition remaining constant and with the jet orifice of the burner located close to the surface to be tretaed. Use of a 6 flame angle resulted in a 20 percent increase in channeling rate over the rate obtained with a 12 flame angle. While the optimum flame angle is, from a theoretical standpoint, between 06, the use of angles smaller than 6 is not practical. It is to be noted that the optimum flame angle may vary when using less intense air burners or when channeling other types of minerals than those used to obtain the data presented in Table III. It is also to be noted that a different section of rock was channeled to obtain the data in Table III than the section of rock used in obtaining the results shown in Tables I and II.

TABLE IV Burner spacing (in.): Channeling rate (ft. /hr.) 19.5 10 21.6 15 25.0 25.4

Referring to Table IV, the variation in channeling rates are tabulated against the spacings between two burners, such as the distance indicated by h in FIGURE 1. Both

burners

14 and 16 were operated at constant flow rates of 1500 c.f.h. oxygen each and 65 lbs/hr. kerosene With all other variables such as velocity, reactant composition and flame angle remaining constant. Above a distance h of 20 inches, the channeling rate was constant at a maximum value of 25.4 ftF/hr. As the burners were brought together, the channeling rates were reduced considerably at spacings less than 15 inches. The results indicate that the channeling rate is greatest when the distance h is sufficient to prevent the flame footprints on the surface of rock made by the intense spalling portion of each flame from overlapping. At such distance the flames act independently.

The minimum spacing required between effluent jets is dependent upon the flow rate issuing from the individual orifices. Turbulent jet theory predicts that jets decay similarly as a function of x/d where d is the jet orifice diameter and x is the linear stream-wise space coordinate. In effect this means that effective jet length is related to orifice diameter. For equivalent exit velocities, exit orifice diameter is proportional to the square root of orifice flow rate. Hence, for multiple jet channeling applications, the minimum spacing can be predicted by the expression:

where F is the nominal design oxygen flow rate per burner orifice. This relationship predicts minimum spacings of 12.2", 15", and 21" for multiple jets of oxygen flow ratings of 1000', 1500, and 3000' c.f.h., respectively.

While the FIGURES 1-4 which are provided to illustrate the invention show a dual jet burner having two separate blowpipe assemblies with their individual combustion chambers, it is to be understood that a dual jet burner having a single combustion chamber leading to two or more orifices appropriately spaced from each other will also be suitable. Similarly, a multijet burner similar to the dual jet burners shown in FIGURES l-4 but comprising more than two separate blowpipe assemblies rigidly connected together can be employed.

Referring to FIGURE 5, another embodiment of the burner of this invention is shown comprising a burner body 60 with a single combustion chamber leading into a plurality of jet orifices 64.

FIGURE 6 shows still another embodiment of the invention to illustrate a further variation of the multiplejet concept of the invention. More particularly, a manifolded, multi-jet burner comprises a plurality of individual burner bodies 68, each having a combustion chamber 70 and a jet orifice 72 associated therewith, which are connected to the manifold body 66.

While the burners were described above as utilizing oxygen gas, other oxidizers such as air or oxygen enriched air may also be employed by the burner in carrying out the invention.

What is claimed is:

1. In a method of jet channeling by thermal spalling of a mineral body by (a) directing high temperature, high velocity jet of gas against a surface of said body, to heat said surface to an elevated'temperature sufliciently high to cause said surface to spall, (b) moving said jet of gas in successive passes along the surface of said body thereby forming a continuous channel therein, (c) simultaneously advancing said jet of gas in the direction of the channel to be formed while maintaining said jet of gas in contact with the end wall of the channel so formed, and (d) continuing said channeling method until the desired channel is cut in said mineral body, the improvement comprising:

(1) directing at least two separate and distinct gas jets at said mineral surface,

(2) maintaining each of said gas jets in a plane substantially parallel the surface being treated,

(4) directing each of said gas jets at the surface to be treated at an angle formed between said surface and the axis of said gas jet such that the intense spalling portion of the gas jets impinge upon a maximum area of said mineral body surface.

2. The method of claim 1, wherein the angle at which each of said gas jets is offset from the surface of the mineral body to be treated is less than 12.

3. The method of claim 1 wherein the angle at which each of said gas jets is offset from the surface of the mineral body to be treated is less than 6.

4. Themethod of claim 1 wherein eachof said gas jets is supplied with oxidant equivalent to a rate of 500-3000 c.f.h. of gaseous oxygen.

5. The method of claim 4 wherein each of said gas jets is maintained at a minimum distance it from each adjacent gas jet which is determined by the expression:

7. The method of claim 5, wherein three individual gas jets directed at said mineral. surface are supplied with oxidant at a rate of 1000 c.f.h. of gaseous oxygen for each jet, and maintained at a minimum distance of about 12.2 inches from each adjacent gas jet.

References Cited UNITED STATES PATENTS 1,919,764 7/1933 Anderson 239--556 X 2,071,808 2/1937 Anderson 239-556 X 2,130,261 9/1938 Bucknam 239566 X 2,882,017 4/1959 Napiorski 17514 3,019,004 1/1962 Vasselin 299-14 3,245,721 4/1966 Margiloff 29914 ERNEST R. PURSER, Primary Examiner US. Cl. X.R.