US3283814A

US3283814A - Process for deriving values from coal deposits

Info

Publication number: US3283814A
Application number: US216271A
Authority: US
Inventors: Schlicht Erika Marie; Lange Hans
Original assignee: Deutsche Erdoel AG
Current assignee: Wintershall Dea Deutschland AG
Priority date: 1961-08-08
Filing date: 1962-08-07
Publication date: 1966-11-08
Anticipated expiration: 1983-11-08
Also published as: DE1571201B2; GB1018011A; DE1571201A1

Description

Nov. 8, 1966 G. scHLlcHT ErAL 3,283,814

PROCESS FOR DERIVING VALUES FROM COAL DEPOSITS Filed Aug. 7. 1962 M LO') BRL E L@ l 'b l I SCRUBBER GUNTHER SCHLICHT,.DECEASED "5 By ERIKA MARIE SCHLICHT, ADMINISTRATOR HANS LANGE B Y 797W BLUME S ATTOR EYS INVENTORS` United States 'Patent 3,283,814 PROCESS FORDERIVING VALUES FROM COAL DEPOSITS Gnther Schlicht, deceased, late of Hamburg-Othmarschen, Germany, by Erika Marie Schlicht, administrator, Hamburg-Uthmarschen, Germany, and Hans Lange, Wietze, Kreis Celle, Germany, assignors to Deutsche Erdol-Aktiengesellschaft, Hamburg, Germany, a corporation of Germany Filed Ang. 7, 1962, Ser. No. 216,271

Claims priority, application Germany, Aug. 8, 1961,

Sch 30,106

12 Claims. (Cl. 166-11) This invention relates to the recovery of energy values from coal deposits. More particularly, the invention relates to the in situ partial combustion of the coal to provide a gas having substantial heating value.

It has been proposed heretofore to treat coal in situ in its natural environment to produce a combustible gas, and to move the gas to the surface for use. The known processes, however, have the disadvantage of producing a gas of low calorific value. Thus, these gases have a relatively high CO2 value. The ratio of CG/COZ is almost always `smaller than l. From this, it follows from the Bourdonard reaction (Kirk-Othmer: Encyclopedia of Chemical Technology, New York, vol. 3, page 181, 1949) that the mean gasification temperature within the seam must be below about 700 C. Higher seam temperatures would mean a more favorable CO/COZ ratio. Temperatures of 750-900 C. would be desirable.

Accordingly, a problem confronting the art is the maintaining of higher temperatures in the coal seam where the degasilication and gasification take place, the degasification being the evolving of contained gases by the coal, and the gasification being the production of gases by reactions involving the coal.

A principal object of the invention to provide a procedure wherein higher temperatures in the seam can be maintained.

According to the invention, a portion of the coal deposit, hereinafter called the worked portion, is provided in communication with the surface by a bore for supplying material to the deposit, and by a bore space from the supply bore and for removal of material from the deposit. In practice of the process, a heating medium is passed through the supply bore, the heating medium is heated, and it introduced, in heated condition, into the deposit from the supply bore. The heating medium is maintained under sufficient pressure so that it permeates the worked portion of the deposit and causes degasitication, fissuring, and heating of the coal in the worked portion. After a time, the flow of heating medium is interrupted and the worked portion is then ready for treatment so as to bring it to a gas-generating condition. The worked portion has been rendered permeable to gas generated in situ therefrom, and has been heated to such an extent that it is in condition for reaction at a suitable temperature so that a favorable CO/ CO2 ratio is obtained. The permeability of the worked portion provides a course for movement of material from the supply bore to the removal bores, so that gaseous material introduced through the supply bore or generated in situ can be removed by way of the removal bores.

To produce gas in situ in the seam, a material for supporting combustion of the coal is passed into the seam by way of the supply bore. Upon permeating the coal in the worked portion, which has been pre-heated, partial combustion occurs so that gasification is effected. Further, degasification occurs. The evolved gases are removed by way of the removal bores.

In the step wherein the worked portion is pre-heated, a nuclear reactor can be used. The reactor can be placed "ice within the seam and in the supply bore. It can be operated as a control reactor, and a fluid can be passed through the supply bore to pick up heat from the reactor and convey this heat to the worked portion. Thus, water, hydrocarbons, or other suitable liquids, could be passed, as liquids, through the supply bore to the nuclear reactor, wherein the liquid would be vaporized. The resulting vapor would pass into the permeable worked portion to effect the desired pre-heating, lissuring, and degasication.

In a preferred embodiment of the invention, following the pre-heating of the worked portion and before passing material for supporting combustion through the supply bore, the charge in the supply bore can be exploded to further fissure the worked portion before the combustion is started. In a preferred embodiment of the invention, a nuclear reactor is employed as aforesaid to heat material such as water, hydrocarbon or other suitable material introduced into the supply bore for passage through the worked portion to impart permeability thereto, and during such use of the nuclear reactor, it is employed as a control reactor; and then, to provide an explosion as will further fissure the worked portion, the nuclear reactor can be released so as to permit the reaction to proceed uncontrolled and therefore to provide the desired explosion.

To further improve the permeability of the Worked portion, before the introduction of material for supporting combustion, a charge or charges can be exploded in the removal bore holes. Desirably, a charge can be exploded in each of the removal bore holes and in the supply bore hole, and, preferably, the charges in the two types of bore holes are exploded simultaneously.

The material introduced in the supply bore holes to support combustion, i.e. partial combustion, of the coal can be air or oxygen enriched air, e.g. an air-oxygen mixture containing up to about oxygen. Pure oxygen or higher oxygen concentrations can be used.

The gas removed from the worked portion via the removal bores, during the partial combustion of the coal, will contain a substantial portion of CO2, H28, some lower organic compounds, and some higher organic compounds such as C3 and higher. It may be desired to remove such constituents from the gas before distribution of the gas from the vicinity of the coal deposit. Known means can be employed for cleaning up the gas as is desired. -It is to be noted, however, that the process of the invention can be operated in the manner that the gas issuing from the withdrawal bores is at an elevated pressure, whereby the cleaning up of the gas as is desired would be facilitated. Thus, the material to support combustion supplied through the supply bore, can be supplied at a suitable pressure, and means can be provided for maintaining at the exit of the removal bores a suitable back pressure in the system, whereby the gas issuing from the withdrawal bores is at a pressure such that cleaning up of the gas as is appropriate is facilitated.

The invention is further described in reference to the accompanying drawings, of which:

FIG. 1 is a plan of the bore holes for recovering values from a coal seam, according to the invention;

FIG. 2 is an alternative scheme for recovering values from acoal deposit; and

FIG. 3 is a schematic representation, in elevation, of an installation according to the invention.

In the various views of the drawings, like reference characters are used to indicate corresponding parts.

It is known in the recovering of values from coal deposits by in situ partial combustion of the coal, to place a pipe in a pipe through a bore from tthe surface to the coal deposit, whereby there is provided within the single bore .a course for supply of material from the surface to the coal deposit, and a course from the coal deposit to the surface. material for supporting partial combustion of the coal can be passed through one of the courses, and the products of partial combustion can be withdrawn from the other The invention does not, however, contemplate the use of such a lay-out. Rather, the invention contemplates the use of a lay-out characterized in that a bore for delivery of material to the deposite is associated in operative relation with one or more, usually more than one, bores for removal of material, and the supply bore and removal bores are in spaced relation with respect to each other.

Usually, in the practice of the invention, several removal bores will be associated with one supply bore, `and the spacing of these bores Will depend on various considerations. In the case of a deposit which is dicult to break up, the spacing will be less; in the case of a brittle deposit, the spacing may be greater. In the case of greater seam thickness, a greater spacing can be use-d, since, in such cases, larger explosive charges can be used. Where the seam is associated with a thin and/ or brittle cap rock, a smaller interval should be used. In practice, the intervals can be selected following evaluation of test drilling to obtain samples of the seam and of the cap rock as well as the pertinent dimensions. Consideration of these various factors will not only permit determination of the intervals to be employed, but, in addition, will permit planning to select the time for the exploding of charges, following preheating of the portion of the seam worked and before the introduction of material for supporting combustion into the supply bore.

The invention contemplates the systematic working of portions of a carbon deposit seam rather than the Working of a seam indiscriminately or over a large area at a single time. Thus, in a preferred embodiment of the invention, a relatively small portion of the seam is worked `at a given time. It has been found that by practicing the procedure in this manner, better control of temperature in the area of partial combustion can be realized. Thus, a higher temperature can be maintained with good consistency if a relatively small portion of the seam is worked at one time. As has been indicated hereinbefore, this has advantages in respect to the composition of the gas produced in that a higher CO/COZ ratio is thereby obtained.

Referring to FIG. l, there is represented here a lay-out for boring an underground bituminous seam. Removal bores BRrJ and supply bores BB are spotted in a pattern throughout the seam or an extended portion of the seam. The spotted portion can be then divided into generator units each of which includes an area such as the area indicated by the horizontal dimension Gu. The generator Gu is composed of a first stage generator GR, a transition generator GZ, and a second stage generator GRU. The rst stage generator GR includes a supply bore BB and four withdrawal bores disposed about the supply bore. The transition generator GZ includes the supply bore BB and two withdrawal bores BRL. The second stage generator is constituted as is the -rst stage generator.

Other generator units such as the unit Gu are associated with the generator unit Gu, and the other units are aligned with and parallel to the generator unit Gu. Thus, a generator unit Gu, is disposed parallel to and alongside the unit Gu. Between these two generator units, provision is made for isolation for these units, so the one will operate independently of the other and gas production and withdrawal from the seam can be controlled in an efficient manner. To provide the desired isolation, the areas RB are provided. These are areas or, more properly, volumes of the seam which are of such dimension that they are not substantially penetrated by fissures, and, hence, these parts of the seam prevent passage of gas from one generator unit to the other, and likewise substantially limit production of gas to a particular generator unit, or fa- In the utilization of such an arrangement,

ycilitate the limiting of production to a particular generator unit.

In the working of a seam spotted as is indicated in FIG. 1, a nuclear reactor N (see FIG. 3) can be deposited in a supply bore BB of first stage generator GR of generator unit Gu, within the seam S. This nuclear reactor N can then be operated for controlled reaction to generate heat, and a fluid such as water, hydrocarbon liquids or other suitable liuid can be introduced into the supply bore BB through line L. The uid so introduced passes through the supply bore, and, if liquid, is vaporized by the heat of the nuclear reactor N, and the vapor then passes into the seam S to effect degasication and ssuring of the coal of the seam. The medium supplied through line L is a heating medium and serves to pre-heat the portion of the seam being worked as well as to ssure and degasify. The heating medium must be supplied under sufficient pressure so that penetration to the extent desired is realized.

Following operation of the nuclear reactor N in cooperation with the heating medium to the extent that the portion of the seam being Worked is sufliciently preheated and tissured, the supply of heating medium is interrupted. The time at which it is appropriate to interrupt the supply of heating medium can be set from experience with a particular coal seam, as by observing pressure variations in the system. Also, the time for such interruption can be selected on the basis of the appearance of gas from the seam in the withdrawal bores BRL. Thus, the ssuring occasioned by the introduction of heating medium would occur to the extent that the vaporized heating medium and gas resulting from degasiiication would nd its way into the withdrawal bores BRL. The appearance of the gas in the withdrawal bores will be taken as an indication of the time to cease supply of heating medium to the supply bore BB.

Following interruption of the supply of heating medium, further fissuring of the portion of the seam being worked can be effected by exploding charges in various of the boreholes. Charges can be supplied to the withdrawal -b'ores 'BRL along with oxygen material for supporting combustion of the charges, and/or charges may be supplied to the supply bore BB. If desired, the nuclear reactor can 'be allowed to go uncontrolled following introduction of heating medium, so lthat an explosion is effected and tissu-ring results.

Following exploding of charges as is resorted to, the generator unit is ready for service to supply energy containing gas. Material as will support combustion can then be supplied to the supply bore BB via line L. This material can .be air Ior oxygen enriched air `such as a nitrogen-oxygen mixture containing oxygen. Usually, it will not be in order to use water vapor or substantial water vapor for supporting combustion, since the reaction involving the water vapor and Ithe coal tends 4to lower the temperature of the gas produced by the reaction, whereas it is, in general, desired to maintain this temperature at a high level. In the procedure of the invention, this temperature can be as high as 900 C., or even higher.

The gas resulting from the degasication and gasification fof the c-oal leaves the seam through the withdrawal bores BRL, and passes to scrubber Sb via lines Lo. In the scrubber, CO2 is removed from the gas.

Following exhaustion or substantial exhaustion of values from the generator GR dependence for supply can be placed on `another generator unit in the field. Following operation of the generator GR of the generator unit Gu, the second stage generator of this generator unit, namely, 'generator GRU can be placed in service, and subsequent to this, or before this transfer, the intermediate generator stage GZ can be placed in service. The generator unitt Gu' can be brought into service when this is desired and appropriate.

In the generator unit Gu between, and overlapping the Aintermediate stage generator GZ and the first stage generator GR, is an area RLF containing withdrawal bores BRL. These areas RLF can be made suitably 'permeable at an appropriate time, and are worked in coordination with lthe operation of the supply bores BB.

It will be appreciated that in the working of a seam, various lay outs for bore holes and various procedures or plans for progressing over the seam can be utilized. An alternuative procedure to that depicted in FIG. 1 is shown in FIG. 2, wherein like reference characters indicate corresponding elements, and a like legend is used. The embodiment of FIG. 2 would be suitable to a more friable seam than the seam for which the plan of FIG. l is provided. Thus, in FIG. 2 fewer bore holes are utilized.

Where the coal deposit being worked comprises overlying seams, suitable provisions must -be made for protecting the bore tub-ing. Guide-shoes may be used, and the tubing can be reinforced a-t appropriate intervals to ensure against change or at least reduce change in shape. Further, the bore hole tubing can be provided with liners which are easily penetratable by drilling, so that if obstructions result in the bore holes, lthey can be removed by drilling. The precautions mentioned here for ioverlying coal seams, can be utilized as well with respect to deposits contained in a single seam.

While the invention contemplates the working of any underground carbon deposits, the invention is particularly concerned with deposits of bituminous coal.

To further assist in the comprehension 'of the present invention, a specific operating example of the process described herein wherein additional heat is continuously introduced into the gasification zone will next be described in detail.

The underground gasification according to the present process was conducted in a 'bituminous deposit ylocated at the depth of 900 meters and consisting `of pit coal classified as a long-fiame -gas coal. The average dimensions of a seam of the deposit was 2 meters thick, 3000 meters long and 1200 meters wide. The rock formation overlying the deposit consisted of impermeable shale.

The portion of the seam in which the generator units were to be laid tout had -a length of 1000 meters and a Width of 250 meters. The generator units are square and the sides are 250 meters long. A supply bore BB is drilled in the center of a generating unit and four remover bores BRL are drilled .at the corners of the firststage generator GR land are in a distance `of 150 m. from the central supply 1bore BB. The supply -bores of the first-stage generator, the intermediate-stage generator, and the second-stage generator are spaced from each `other a distance of 450 m. The supply bores have a diameter of 311 mm. and the remover bores have a diameter of 152 mm. The upper 300 m. of each of the bores are lined with a casing and the individual sections lof the casing are provided with pressure pads.

These pressure pads, arranged around the bore-tubes at the height of suitable rock formations are fixedly connected with the wall of the bore by concrete bridges. The concrete bridges, each of which may have a height of 25-30 m. in the dry state of the concrete, are spaced at distances of about 300 m. The sections of the bore positioned outside of the casing are filled with a highly viscous bore flushing liquid. `On the sections of the concrete bridges, below the pressure pads but on the bore casings, a plastic layer is positioned which dloes not set with the concrete. Thereby the casings are protected when the rocks are settling during the gasification of the seam and thus their exterior sealing is maintained.

When several seams are superposed, a normal bore casing having a casing pressure pad which is additionally reinforced by iron rings is mounted up to a height of 3-0 m. above the highest positioned seam. An aluminum tube that can subsequently be easily perforated leads from the upper edge of the reinforced bore casing down into the deposit, the section of which that is positioned in the deposit is perforated and serves `as a liner. Thereby, beneath the reinforced pressure pad a predetermined breaking point having a circular cross-section is formed from where, after the destruction of the aluminum tube and after the drilling out of the destructed lower bore section, a new aluminum tube can be inserted again.

Special reactors which do not constitute the subject matter of the present invention and having an exterior diameter of 30() mm. as well as a casing with a diameter of 5.5" are lowered down onto the base of the borehole through the supply bore BB. Within said string of casing an ascending tube having a diameter of 23/8 is connected to the head of the reactor Ifor supplying the heating medium and is provided at its upper end with a pressureresistant ange for 350 atmospheres absolute, which fiange is screwed into the flange of the casing having a diameter of 51/2. In order to avoid a backfiow in the ascending tube, there are provided therein non-return aps spaced rn. from each other. In the annular space between the tubes of 51/2" and 5% diameter a normal packing is mounted.

The heat energy of the power reactor is about 1,000,000 kcal./h. This heat is transmitted on the secondary side of its heat exchanger to the heating medium passing by, which medium consists of a mixture of light `fuel during the first operation, and later on of extracted liquid hydrocarbons and water in a relation by volume yof 1:1. The power reactor in the bore has a high negative temperature coefficient and by means of its automatic control devices it continuously transfers -only as much heat as is needed, since it is continuously -heated up to its highest temperature. This is true also when only small quantitles of the heating medium are passing through its heat exchanger.

In the beginning of the operation, 3 tons of mlxture per hour of liquid mixture are fiowed through the heat exchanger of the reactor int-o the deposit. The pressures are such that fissures are formed in the deposit. These pressures are from 2-3 times the hydrostatic depth pressure with to 27-0 atmospheres absolute. The heating medium penetrating into the deposit heats 6 tons of the deposit to 250 C. per h-our. By means of such a heating to 250 C., 50 m.3 per ton of deposit are freed from degasication gas. This gas and the liquid mixture reach under the crushing pressure of the ldeposit in 100 hours a volume of 450 m.3 with a great stored pressure energy from the gas. After 2-3 days a break-through of the heating medium takes place from the supply bore to a fissure removal bore. The removal bore is then closed and one or two days later the eruption occurs at the other fissure removal bores. At that time, 25 kg. of explosives are positioned in each of the fissure removal bores and are exploded. Under this added stress, the fissures around the fissure removal bores are enlarged. If the explosive 1n the removal bore is not exploded simultaneously, the introduction of the heating medium is continued for another 24 hours. If until that moment the pressing pressure is not reduced, an uncontrolled -decompo-sition in the reactor is then caused, which frees a great quantity of heat from its explosive force. However, this decomposition can as well be caused to occur simultaneously with the explosions in the fissure removal bores. This will always occur in case the thickness of the seams is from 3 to 4 m. When good permeability has been obtained, the bores with the destroyed casings, are drilled out again and new casings -are hung into the bore casing shoe. At this moment, oxy-gen is introduced for the degasification and the gasification. The nitrogen is so enriched with oxygen that it can be seen from the ycomposition of the producer gas under what temperature the reduction zone is operating. Temperatures exceeding 850 C. are desired. An enrichment in oxygen -by more than 80% of oxygen can become necessary.

12,000 m/h. of oxygen are introduced at a pressure of l2 atmospheres absolute into the supply bores of an underground generator. However, different quantities are introduced into each bore according to how far the gasification process has proceeded in the respective bore. The degasification front leads the gasification front in the underground reactor. Since no temperature measuring instruments can be mounted into the deposit, the temperature at the reduction front can only be calculated according to the Bourdonard rule. In the underground generator, 32,00() m.3/h. of generator gas are extracted through the fissure removal bores at a pressure of 9 atmospheres absolute. The volume of said generator gas has a heating value of 2800 kcal. According to the provided employment of the generator gas a line washing is carried through.

It is an essential characteristic of the underground generator unit that the oxygen carrier is always heated to a high degree when it arrives at the gasification front. In the first-stage generator, the intermediate generator and the second-stage generator the oxygen carrier is provided with the necessary heat by the reactor. After these generators are degasified and gasified, the oxygen carrier is then introduced through the fissure removal bores arranged at great distances so that they recover the heat loss from the above-mentioned generators from the stored heat in the roof of the seam, the floor of the seam and the ashes upon passing through. The degasification and the gasification are carried out at this high preheating. In this process, the direction of the oxygen carrier is not changed, since the temperature of the reduction front is impaired if such a change occurs frequently, although it will be successful for a short time. By supplying 2000 kg. of steam per hour together with the oxygen carrier, the quantity of oxygen together with the oxygen carrier can be decreased and the heating value of the generator gas can be improved to 2900 thermal units. The introduction of the steam is limited by its endothermic transformation process.

Only such elements which do not have long half-lives are introduced into the removal bores. As a safety measure against the formation of isotopes in the deposit from the very temporary isotopes of the elements H2, N2, OZ-i-C, each removal bore is provided at a depth of 50 rn. with a Geiger counter, which as a pulse sender automatically closes an endangered extraction bore. Through such a bore smaller quantities are extracted later on, so that the retention time of a formed isotope is prolonged whereby it decays to a greater extent. An average charge of the underground generator to 10 atmospheres absolute will reduce the arising gases to 1/10 of their volume and thereby the retention times become longer. The underground generator can also be operated at 2O atmospheres absolute. However, in case a maximum accident in the deposit would cause a blow-by in the deposit, the Geiger counters will then close all of the bores. A second switching pulse can be taken from the vibration waves in the vicinity of the supply bores which will switch in a second seal on the bores.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and condi/tions, and, accordingly, it is desired to comprehend such modifications within this invention as may fall Within the scope of the appended claims.

What is claimed is:

1. A process for recovery of values from coal deposits wherein a portion of the deposit is communicated with the surface by a bore for supplying material to the deposit and by at least one bore spaced from the supply bore and for removal of material from the deposit, said process comprising:

(a) passing a heating medium through the supply bore, heating the heating medium by passing the heating medium in indirect heat exchange relation with a nuclear reactor positioned in the supply bore, introducing the heated heating medium into the deposit from the supply bore, maintaining the heating medium under sufficient pressure so that it permeates the said portion of the deposit, whereby degasication, fissuring, and heating of the said portion is effected,

(b) following working of the said portion as aforesaid, exploding a charge in the supply bore to effect further fssuring of the coal within the worked portion, and thereafter,

(c) passing a material for supporting combustion of the coal through the supply bore for introduction into the deposit and reaction with coal of the worked portion in the path between the supply bore and said one removal bore to gasify and degasify the coal and provide a fuel gas,

(d) and withdrawing said gas from the deposit through said removal bore.

2. A process according to claim 1, the heat for heating as called for in step (a) being provided by a controlled reaction of said nuclear reactor, and the exploding of step (b) being provided by uncontrolled reaction of said nuclear reactor.

3. A process according to claim 2, wherein following said step (a) and before said step (c) a charge is exploded in said removal bore to further fissure the worked portion.

4. A process according to claim 3, the explosions in the supply bore and in the removal bore being effected substantially simultaneously.

5. A process according to claim 1, wherein following said step (a) and before said step (c), charges are exploded in said removal bore to further fissure the worked portion.

6. A process according to claim 5, wherein the charges exploded in the removal bore and the charge exploded in the supply bore are set off substantially simultaneously.

7. A process according to claim 1, wherein the material for supporting combustion called for in step (c) is selected from the group consisting of air and oxygen enriched air.

S. A process according to claim 1, wherein said portion is communicated with the surface by a plurality of removal bores disposed about the supply bore, and each of the removal bores is utilized as aforesaid.

9. A process according to claim 1, wherein said degasification, fissuring, and heating in step (a) effects communication of the supply bore and the removal bore while coal remains in the path between the supply bore and the removal bore.

10. A process for recovery of values from coal deposits wherein a portion of the deposit is communicated with the surface by a bore for supplying material to the deposit and by at least one bore spaced from the supply bore and for removal of material from the deposit, said process comprising:

(a) passing a heating medium through the supply bore, heating the heating medium by passing the heating medium in indirect heat exchange relation with a nuclear reactor positioned in the supply bore, introducing the heated heating medium into the deposit `from the supply bore, maintaining the heating medium under sufficient pressure so that it permeates the said portion of the deposit, whereby degasication, fissuring, and heating of the said portion is effected,

(b) following working of said portion as aforesaid, exploding a charge in one of said bores to effect further fissuring of the coal within the worked portion, and thereafter,

(c) passing a material for supporting combustion of the coal through the supply bore for introduction into the deposit and reaction with coal of the worked portion in the path between the supply bore and said References Cited by the Examiner UNITED STATES PATENTS 2,593,477 4/1952 Newman 262-1.2 3,070,165 12/1962 Stratton 166-42.1 3,079,995 3/1963 Natland 166-11 3,080,918 3/1963 Natland 166-11 3,085,957 4/1963 Natland 166-11 3,113,620 12/1963 Hemminger 166-11 10 FOREIGN PATENTS 9/ 1958 Australia. 10/ 1954 Great Britain. 11/ 195 6 Great Britain. l/ 1961 Great Britain.

OTHER REFERENCES UCRL-5678 Plowshare Series, Part 1V, Lawrence Radiation Laboratory, Livermore, and AEC, San Francisco Operations Oflice. Proceedings of Second Plowshare Symposium, May 13-15, 1959, pp. 80-101.

Les Applications de lEXplosion Thermonucleaire, by Camille Rougeron, Paris editions, Berger-Levrault, 1956, pp. 192-202.

The Gas World, Nov. 25, 1944, pp. S45-550.

REUBEN EPSTEIN, Primary Examiner.

20 CARL D. QUARFORTH, Examiner.

Claims

1. A PROCESS FOR RECOVERY OF VALUES FROM COAL DEPOSITS WHEREIN A PORTION OF THE DEPOSIT IS COMMUNICATED WITH THE SURFACE BY A BORE FOR SUPPLYING MATERIAL TO THE DEPOSIT AND BY AT LEAST ONE BORE SPACED FROM THE SUPPLY BORE AND FOR REMOVAL OF MATERIAL FROM THE DEPOSIT, SAID PROCESS COMPRISING: (A) PASSING A HEATING MEDIUM THROUGH THE SUPPLY BORE. HEATING THE HEATING MEDIUM BY PASSING THE HEATING MEDIUM IN INDIRECT HEAT EXCHANGE RELATION WITH A NUCLEAR REACTOR POSITIONED IN THE SUPPLY BORE, INTRODUCING THE HEATED HEATING MEDIUM INTO THE DEPOSIT FROM THE SUPPLY BORE, MAINTAINING THE HEATING MEDIUM UNDER SUFFICIENT PRESSURE SO THAT IT PERMEATES THE SAID PORTION OF THE DEPOSIT, WHEREBY DEGASIFICATION, FISSURING, AND HEATING OF THE SAID PORTION IS EFFECTED, (B) FOLLOWING WORKING OF THE SAID PORTION AS AFORESAID, EXPLODING A CHARGE IN THE SUPPLY BORE TO EFFECT FURTHER FISSURING OF THE COAL WITHIN THE WORKED PORTION, AND THEREAFTER, (C) PASSING A MATERIAL FOR SUPPORTING COMBUSTION OF THE COAL THROUGH THE SUPPLY BORE FOR INTRODUCTION INTO THE DEPOSIT AND REACTION WITH COAL OF THE WORKED PORTION IN THE PATH BETWEEN THE SUPPLY BORE AND SAID ONE REMOVAL BORE TO GASIFY AND DEGASIFY THE COAL AND PROVIDE A FUEL GAS, (D) AND WITHDRAWING SAID GAS FROM THE DEPOSIT THROUGH SAID REMOVAL BORE.