U.S. patent number 3,858,397 [Application Number 05/021,082] was granted by the patent office on 1975-01-07 for carrying out heat-promotable chemical reactions in sodium chloride formation cavern.
This patent grant is currently assigned to International Salt Company. Invention is credited to Charles H. Jacoby.
United States Patent |
3,858,397 |
Jacoby |
January 7, 1975 |
CARRYING OUT HEAT-PROMOTABLE CHEMICAL REACTIONS IN SODIUM CHLORIDE
FORMATION CAVERN
Abstract
Chemical reactions, requiring heat are effected without air
pollution contributions at reaction sites in underground cavities
which are uniquely located to take advantage of little known and
rarely occurring subterranean heat supply and heat conducting
characteristics of certain geological structures extending in
thermal continuity with heat sources far below reach of modern bore
hole drilling techniques. Reactants are fed to the cavity and
products are removed therefrom by means of passageways through bore
holes extending from the earth's surface into the cavities. The
activities are located at such depths, in highly heat conductive
mineral spires or domes or the like which occur in thermal
continuity with othewise inaccessible geological formations
comprising unlimited sources of earth core heat, as to draw upon
such unlimited supplies of heat at such rates and temperatures as
will promote the desired chemical reaction.
Inventors: |
Jacoby; Charles H. (Dalton,
PA) |
Assignee: |
International Salt Company
(Clarks Summit, PA)
|
Family
ID: |
21802244 |
Appl.
No.: |
05/021,082 |
Filed: |
March 19, 1970 |
Current U.S.
Class: |
405/53; 60/641.2;
166/256; 299/5; 23/299; 165/45; 299/4; 423/DIG.6 |
Current CPC
Class: |
B01J
12/005 (20130101); E21B 43/281 (20130101); F24T
10/20 (20180501); E21B 43/00 (20130101); E21B
43/24 (20130101); Y02E 10/10 (20130101); Y10S
423/06 (20130101) |
Current International
Class: |
B01J
12/00 (20060101); F24J 3/00 (20060101); F24J
3/08 (20060101); E21B 43/24 (20060101); E21B
43/28 (20060101); E21B 43/16 (20060101); E21B
43/00 (20060101); E21b 043/00 (); B65g 005/00 ();
B01j 001/00 () |
Field of
Search: |
;23/312AH,302,309,293,299 ;159/1G ;299/4,5 ;60/26,641
;165/45,106,132 ;166/302,256,259 ;61/.5 ;210/63 ;423/659 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bascomb, Jr.; Wilbur L.
Assistant Examiner: Emery; S. J.
Attorney, Agent or Firm: Bean & Bean
Claims
I claim:
1. A method of performing a chemical reaction which comprises:
determining the location of an underground sodium chloride salt
formation having heat conductivity characteristics much higher than
the surrounding geologic structures, said formation extending
downwardly into thermal connection with a deep seated heat source,
said heat source being at a depth which is inaccessible by
commercially practicable bore hole drilling techniques, said
formation extending upwardly to a level which is accessible by
commercially practicable bore hole drilling techniques,
dissolving a cavity to form a reaction cavern of selected size
within said formation at a depth of at least 10,000 feet below sea
level sufficient to insure a selected temperature of at least
100.degree.C in said cavern and terminating the dissolution of said
cavity at a selected size which provides a heat transfer area such
that heat energy will flow from said source to said cavern at a
selected rate so as substantially continuously to replenish heat
abstracted therefrom at said selected rate and maintain said
selected temperature within said cavern,
feeding material which is inert with respect to the salt and is a
reactant of a heat-promotable chemical reaction which will occur at
said selected temperature through a passageway to said cavern at
such rate as to elevate the temperature thereof to the reaction
temperature and thereby initiate and maintain the chemical reaction
while holding the reactant in said cavern for a sufficient period
of time to produce a reaction product,
and removing the reaction product from the cavern at a rate
insufficient to abstract heat energy therefrom at said selected
rate.
2. A method according to claim 1 wherein a plurality of reactants
is fed to the cavern, at least one of which is fed from
aboveground, and a reaction product is partially cooled by passage
through the ground from the cavern to aboveground by heat transfer
to the intervening rock.
3. A method according to claim 1 wherein the plurality of reactants
is fed to the cavern from aboveground through separate passageways,
and remain separate until they enter the cavern, where they are
mixed together and the temperature thereof is raised to a
temperature which is high enough to promote the heat-promotable
chemical reaction, and a product of the reaction is sent
aboveground by passage through a separate passageway from those
through which the reactants are fed from aboveground to the
cavern.
4. A method according to claim 1 wherein a plurality of reactants
is fed to the cavern through a single passageway, in which they are
mixed before reaching the cavern.
5. A method according to claim 1 wherein the flows of reactant(s)
and product(s) are so controlled that the dwell time of the
reaction mixture in the cavern is sufficient to promote substantial
completion of the chemical reaction.
6. A method according to claim 1 including the step of analizing
the chemical composition of the product and controlling the flows
of reactants and products so as to regulate the reaction
temperature and/or dwell of the reactant (s) in the reaction cavern
to obtain a satisfactory yield of product (s).
7. A method according to claim 6 wherein the proportions of
reactants are maintained substantially constant and the flow
thereof and of the reaction product are regulated in response to a
monitoring of the composition of a reaction product being
discharged from the passageway from the cavern to aboveground.
Description
In a preferred embodiment of the invention, the reaction site
cavity will be formed in a "hot" sodium chloride rock salt spire or
dome which is of highly heat conductive capabilities and in thermal
communication with a lower geologic formation which transmits its
heat through the dome or spire to the reaction cavity. In a similar
manner, reaction cavities may be utilized in other highly heat
conductive geologic formations of the spire, vein, or dome
type.
Also included within the invention are various apparatuses for
effecting the desired reaction and passage of materials to and from
the reaction cavity. Specific geologic formations and the chemical
reactions which best lend themselves to the practice of the
invention are also disclosed.
BACKGROUND OF THE INVENTION
Chemical reactions, in which molecular configurations of atoms are
changed, often require the addition of energy in the form of heat
which is normally obtained by combustion of fuels with air. The
combustion of fuels invariably gives rise to pollutant products
which ultimately are released to the atmosphere. To a certain
extent undesirable emissions can be controlled by utilizing nuclear
energy as a source of heat, but even in such cases there are often
thermal pollution problems associated with the operation of the
nuclear plant.
It is to be especially noted that because of the continuing
increase in technological processes and production, whereby
manufacturing and chemical operations are expected to increase
substantially in future years, pollution of the atmosphere and
waterways would be expected to correspondingly continue to
increase. Accordingly, it is important to develop improved reaction
processes in which releases of pollutants are eliminated or at
least minimized. When such processes can be employed economically
or, as in the present case, exceptionally economically, their
physio-social and economic values from many standpoints are
manifoldly increased.
It is known that the interior of the earth comprises a tremendous
source of heat, some of which is conveyed through the crust
structure and to the surface of the earth, although the effects of
this heat are hardly apparent at the earth's surface or in modern
well drilled bore holes, or in so-called "deep" mines. The
temperatures in such holes, even at the greatest economically
marginal depths thereof, are not high enough, nor are the heat
supply recuperative powers thereof sufficient that the heat energy
to be abstracted therefrom may be usefully employed. For example,
it has been found that at depths of 5,000 feet or more, the
underground temperatures in normally encountered strata will
sometimes be as high as 110.degree.-115.degree.F or thereabouts.
Although efforts have been made to recover such heat energy from
the earth, as from hot springs, and volcanoes, etc., past efforts
have been economically unsuccessful.
Typically, present-day methods for recovery of geothermal energy
require that geothermal heat is transported to its point of use in
a mobile carrier such as a gas or liquid, thereby involving certain
inadequacies and/or disadvantages. For example, if gas is employed,
there must be sufficient pressure to allow sustained production
from the well, and the gas must contain sufficient energy to drive
a prime mover engine. Or, if the heat is contained for example in
an aqueous hot brine, the temperature must be sufficiently high to
permit flashing of the water content of the brine into steam for
driving a steam engine or the like. The separated steam must not
contain an undue amount of corrosive salts or gas such as ammonia
or hydrogen sulfide, and the waste water/brines must be disposable
without polluting surface or other potable waters. In contrast, the
present invention avoids liberation at the earth's surface of any
geothermal vapors or liquids; being a completely "closed system"
whereby the heat removed from the earth's core is utilized as
desired without polluting the earth's surface atmosphere.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to the utilization of geothermal
energy of the "clean heat" type for chemical reaction purposes, and
provides a system avoiding the liberation of any reaction and/or
geothermal vapors or fluids, such as would otherwise contaminate
the earth'surface surfacse atmosphere.
As a result of this invention, a chemical reaction which requires
heat can be undertaken within a reaction vessel developed in an
environment furnishing a free and continuous and virtually
inexhastible source of heat. Such reaction is controllable, and
various reagents can be employed at different times for reaction in
the same reaction vessel. It is adaptable to both batch and
continuous processes. Furthermore, the geological formations most
favorable to use in the present reaction often occur adjacent to
sources of raw materials for the reaction, e.g., liquid or gaseous
hydrocarbons.
In accordance with the present invention, a method of promoting a
chemical reaction comprises feeding one or more reactants of a
heat-promotable chemical reaction to an underground site of
geothermal energy; which site is at a temperature high enough to
promote the heat-promotable chemical reaction while holding the
reactant in communication with such site of geothermal energy for a
period of time sufficient to raise the temperature of the reaction;
then removing a reaction product from such communication with the
site of geothermal energy after said reaction; and finally cooling
the reaction product.
Although the invention contemplates, broadly, that whereas chemical
reactions have not heretofore been performed in a reaction site as
set forth herein, it also includes many more specific subinventions
involving factors such as the types of sites employed; direct
contact of the chemical reactants with the natural walls of such
site; the method by which the reactants are transported to the
site, and by which the product is removed; the uses of reactants;
and the production of products in certain physical states to
facilitate transport to and from the reaction site. Also, the
apparatus employed to effect the transport of reactants and to
control the chemical reaction; and the uses of particular chemicals
in the reactions which are compatible with the chemical composition
of the rock wall structure at the reaction site.
It has been found that a cavern for the chemical reaction may be
located at a depth of from about 5,000 to about 20,000 feet below
sea level; which depths can be reached by economical and feasible
drilling techniques. Thus for example, in a salt spire or dome, or
in other geologic formations in which the heat conductive mineral
extends farther down than from a 20,000 foot level into heat
conductive continuity with more intensely heated lower geologic
sections such as at 40,000 or 50,000 feet below sea level, heat is
conducted from such lower levels to such upper levels through the
intermediate highly heat conductive dome or spire of salt or the
like. Such a salt formation, being somewhat plastic under pressure,
forms an excellent vitreous-like vessel for the intended chemical
reaction, especially when the reactions involve organic materials
such as will not dissolve or react with salt. Unlike typical
"sedimentary strata" for example, rock salt and certain other
igneous and metamorphic formations are so-called "competent" and
provide leakproof wall surfaces preventing escape of reactants or
loss of pressure through the walls of a reaction cavern fabricated
therein in accordance with the present invention. Furthermore, the
water soluble rock salt deposite referred to lend themselves
readily to mining techniques which do not require the presence of
men or heavy equipment underground. Thus, a reaction cavern can be
formed in such formations by solution mining techniques, such as
wherein water is injected through a bore hole to dissolve out salt,
which is then removed as brine and thereby creating a cavern. As an
additional benefit of this method, the salt removed is a useful
product of commercial value. Or, the cavern may be formed by a
chemical/nuclear explosive device.
Various means for transporting reactants and products from the
underground reaction site may be employed, as may be different
means for controlling the reactions. For example, the reactants may
be kept apart until they reach the reaction site, or they may be
blended in an inlet feed pipe. The product (s) may be removed
through a separate casing in the inlet bore hole, or it may be
taken out through a different exit line in a separate bore hole.
The exit pipes may be so located in the cavern as to remove either
gases or liquids, selectively. Controls may be employed to regulate
the flows of reactants and the withdrawals of products so as to
best maintain the reaction time for most efficient and/or complete
reaction. The dwell or detention time of the reactants in the
cavern is of course a function of the volume of the cavern and the
flow rates, and this can be controlled so that the heat extracted
in the reaction is continually replaced by a replenishment heat
flow through the conductive mineral to the cavern from the greater
depth.
It is a particular feature of the invention that when the reaction
chamber of the system is fabricated within the "hot" portion of a
heat conducting spire as explained hereinabove, the reaction
chamber may be fabricated either by a solution mining process or by
a mechanical "under-reaming" process; and that in either case the
size and shape and wall surface area of the cavity can be
constructed exactly in accordance with previously calculated data
so as to insure that the reaction cavity will continuously furnish
the desired heat supply.
Although the use of liquid reagents and the removal of liquid
product are contemplated as within the invention, for most
efficient continuous processes it may be preferred to employ
gaseous reagents and to obtain a gaseous product. By doing so, if
the product volume is less or if the average temperature thereof is
higher than that of the reagents, flow will be facilitated in the
outlet and inlet passageways, respectively. Normally, it will be
preferred to avoid reactions which generate solid products because
these will tend to fill in the cavern, and will not be recoverable
unless they are suspended in liquid products or are periodically
flushed out. In some enbodiments of the invention, as where gaseous
products are made, to facilitate heat transfer from the walls of
the cavern to the reactants the cavern may preliminarily be at
least partially filled with a heat conductive fluid, e.g.,
diphenyl; and the reagents may be bubbled through this in contact
with each other, to better absorb heat therefrom and to promote the
desired reaction.
The general nature of the present invention and some exemplary
embodiments thereof have been described, but a more detailed
description of the invention, together with specific preferred
embodiments and examples will now be given. Some of the more
specific aspects of the invention will be exemplified, setting
forth by way of examples reactions in a cavern in a salt spire or
dome. It will be understood that these are also applicable to less
preferred reaction sites in other materials, which will be of
sufficiently high heat conductivity as to continuously replenish
the heat extracted. The invention will be readily understood from
the following descriptions, in conjunction with the drawing in
which:
THE DRAWING
FIG. 1 is a geological sectional view of a salt spire containing a
reaction site or cavern in accordance with the present invention,
and a dual bore hole system for adding reactants and removing
products to an aboveground facility;
FIG. 2 is a schematic diagram, illustrating means for addition of
reactants and removal of product from the reaction cavern site,
together with controls to regulate the process and the reaction
temperature;
FIG. 3 is a vertical section of apparatus of this invention,
showing the use of plural bore holes with separate addition of
reactants through plural passageways in one bore hole and removal
of product or product mixtures through the other bore hole;
FIG. 4 illustrates the use of plural bore holes communicating with
different remote portions of a reaction cavity, showing two
reagents entering through separate passageways in one bore hole and
two products, one in gaseous form and the other in liquid form,
being removed through separate passageways in the other bore hole;
and
FIG. 5 is a vertical section of another well-cavern apparatus of
the invention, wherein the single bore hole contains three
passageways, in which reagents enter the cavity through the central
casing and the middle passageway and the product leaves through the
external annular passageway.
As is shown by way of example in FIG. 1, a salt spire 11,
culminating in a dome 13, rises out of a mother bed 15 through
comparatively non-conductive heat-insulating rock formations 19 to
a topmost point beneath a cap rock 20 (FIG. 1,) such as typically
exists above the dome. At the earth's surface above the salt spire
is illustrated schematically the reagent input and reaction control
and product output facility, as indicated generally at 21
comprising a housing accommodating the various facilities and
controls for operation of the process and apparatus of the
invention. Bore holes 23 and 25 descend from the surface of the
earth 27 through the cap rock 20 and into a cavity or cavern 29 in
the salt spire. Such cavity as illustrated herein may be
established by solution mining out a portion of the salt from the
spire 11 by pumping water through bore hole 23 whereupon it
dissolves the salt at the bottom of the hole producing a brine
which is then removed through bore hole 25. As stated hereinabove,
however, it is to be understood that in lieu of use of a solution
mining technique, the cavity 29 may be established by other means;
such as by under-reaming an uncased lower end portion of one or
both of the bore holes. A pipe string or casing (not illustrated)
will preferably be installed to maintain the integrity of the size
and shape of the passageways to and from the reaction cavity.
As represented in the drawing herewith, the cavern 29 is at a depth
of say 15,000 feet below sea level, which is in the desired range
of over 5,000 feet below sea level and preferably between 10,000
and 20,000 feet. For best results the cavern will perhaps be at a
depth greater than 12,000 feet below sea level, depending upon how
"hot" the dome is. The mother salt bed is shown as being at a depth
of several miles below the earth surface. To make the invention
operative in a most useful form, wherein heat is communicated as
contemplated herein to the cavern 29 from hotter portions of the
spire below the cavern, the spire should probably extend at least
40,000 feet below the earth surface, and preferably even deeper
than that.
The requisite pumps, blowers, fans, etc. for feeding reactant
liquids or gases to the reaction cavern 29 through passageway 23
and for removing products of reaction through passageway 25 are
conveniently located in the housing 21; as well as tanks or other
containers for the reactants and for storage of the product, as may
be required. The facility will also include analytical means for
monitoring the contents of the product as it emerges from
passageway 25 to the aboveground facility. Equipment is also
provided to control the flow of the reaction products, as by
appropriately operating the pumps, blowers or fans; either to speed
up or slow down the flow of materials through the cavern in
response to variations in analysis of the product. Thus, for
example if at any time it is indicated that the reaction is not
proceeding as completely as is desired, the analytical equipment
will operate a control to slow down the passage of reactants and
product through the cavern; thereby increasing the dwell time
therein to obtain a more complete reaction.
Similarly, when the reaction process is proceeding to completion,
the speed of the materials through the cavern will be automatically
controlled so that the most efficient overall operation for the
prevailing conditions will be maintained. Also, thermostatic
controls may be used to raise or lower the temperatures of the
reactants in the cavern for best effect, by varying the speed of
passage of the reactants through the cavern. Or, if preferred, a
diluent gas or liquid might be fed into the cavern with the
reactants to absorb heat, in order to lower the cavern temperature
to maintain the most efficient temperature for the desired
reaction. Exemplary contents of the building and the relationship
thereof to the bore holes and to the reaction cavity site are
illustrated schematically in FIG. 2.
Thus, for example as illustrated in FIG. 2, vessels 41 and 43 are
shown to contain gaseous reactants that are sent by blowers 45 and
47, respectively, through concentric passageways 49 and 51 in a
single bore hole 52 leading into a cavern 53 which is located in a
salt spire 55 as explained hereinabove. Thus, heat conducted to the
cavern 53 from the lower reaches of the spire operates to promote
the desired reaction; and the reaction products or products are
withdrawn through passageway 57 in bore hole 58 by means of fan or
blower 59. Pumps will be normally used when the materials being
reacted are liquids and the products are liquids; whereas when they
are gases, blowers or fans will be preferred. In lieu of such means
for moving the materials through the reaction cavern 53, a natural
chimney effect may be employed, such as may be created by reason of
the lower density of the product than of the feed; and in any event
the rate of circulation through the cavern may be controlled by
baffles or valves or pumps or blowers or fans, or the like, so as
to properly maintain the requisite circulation and temperature and
pressure on the reaction.
As shown at FIG. 2, as the reaction product is raised through
passageway 57 it is automatically sampled at 61 and analyzed by
analyzer 63 to determine the extent of completion of the reaction
and the degree of obtaining of desired product. Analyzer 63 signals
blower 59 to slow down when the desired product is not being
obtained in a sufficient proportion, due to the reaction time being
too short. Also, when more than the optimum quantity of product is
obtained or when near the maximum proportion of desired prodict is
in the reaction product mixture being removed, the analyzer 63 will
signal the blower 59 to speed up so as to operate more efficiently
and produce more of the desired product, assuming of course that
the reaction time can be shortened without interfering with
completion of the desired reaction. Switch 65 is normally closed
when the analyzer is controlling the operation of the blower, pump
or other means, for regulating flow of the reactants and
products.
Instead of controlling the flow rate in response to analysis of the
product, it may be controlled by the temperature of the reaction
cavern, or by the temperature of the reactants or of the products
at other points in the system. For example, as illustrated, a
thermocouple probe 67 may be provided to extend to cavern 53 to
measure the temperature at the top thereof. The thermocouple
operates a relay controller 69 which speeds or slows the rate of
flow of materials through the cavern so as to increase or reduce
the heating process. Switch 71 allows isolation of the thermocouple
control from the blower, as switch 65 allows isolation of the
analyzer control from the blower. In addition to the control means
shown, other mechanisms may be employed to regulate the reaction by
varying the proportionings of the reactants; by adding diluents or
by externally cooling or heating the reactants; etc. Such controls
may be operated automatically or manually or
semi-automatically.
In FIG. 3, 81 represents a salt cavern to which bore hole 83
connects from an aboveground installation 85. The bore hole is
fitted with concentric casings as indicated at 87 and 89, to
separately convey reactants to the reaction site cavern. The
reactants may be either gaseous or liquid, and as illustrated in
this figure the product is gaseous and is withdrawn through bore
hole 91 which is cased by a single string of pipe 93 operating to
intercommunicate the top of the cavern to which the lighter gases
rise and the aboveground installation 95. Appropriate auxiliary
equipment are not illustrated in these views since the primary
purpose of the drawing is to show only some preferred arrangements
for carrying reactants and products to and from the reaction
site.
FIG. 4 illustrates a reaction cavity 101 which may have been formed
either naturally; by solution mining; blasting; or by any other
suitable technique in a suitable heat conductive mineral formation
as explained hereinabove. Reactants, either liquids or gases, are
fed to the cavern through passageways 103 and 105; and bore hole
107 intercommunicating the cavern and the aboveground installation
109. Products of the reaction are removed through passageways 111
and 113 in the bore hole 115, and delivered to the surface
installation 117. As illustrated, the bottom of the cavern is
filled with a liquid 119, which may be either a reactant or
product, or some other medium utilized to assist heat transfer from
the walls of the cavern. If the product of reaction is a gas, it is
removed through annular passageway 113. If the product is a liquid,
it may be removed through tube 111 by sealing off annular
passageway 113 and applying pressure through passageways 103 and
105.
FIG. 5 illustrates the use of a single bore hole 121 containing a
main string of pipe 123, a hanging string of pipe 125 and central
tubing 127. These define passageways, through the central two of
which reactants are fed, and through the external annulus of which
product is removed. As shown, the product 129 is a gas and the
reagents are fed into a liquid zone 131. Reactants are fed to and
product is removed from installation 133 aboveground, which is in
communication with cavern 135 through the passageways defined by
the pipes and tubing as shown.
From the foregoing general description and from the illustrative
examples of preferred embodiments of the processes and the
apparatuses of this invention, it is seen that an economical method
is provided whereby chemical reactions can be effected in certain
geologic formations as explained hereinabove, utilizing the
materials of certain mineral formations as reaction vessels while
at the same time utilizing otherwise unavailable heat to promote
the reactions. A primary advantage of locating such a reaction site
or cavern in the mineral formations referred to is to take
advantage of heat source which is available for replenishment of
the heat extracted from the cavern, so that the heat constantly
available from the reaction cavity will not diminish below that
required for the programmed reaction.
Such reactions may be effected without pollution of the earth land
surfaces or atmosphere or waterways, such as accompanies emission
of products of combustion such as result from the generation of
heat by the burning of fossil fuels or the like. Also, the
invention operates without thermal pollution of waterways such as
often attends the employment of nuclear reactants to generate heat.
Also, it will be appreciated that in accordance with the present
invention a virtually explosion-proof reaction vessel is provided,
while requiring no specifically complicated and/or expensive
fabrication. Many variations of the invention may be successfully
employed according to various cavern material and reactant and
product conditions. Some of these will be outlined below in detail,
and specific working examples will be furnished to illustrate
certain preferred methods as contemplated by the invention.
The reaction site or cavern will in accordance with the present
invention be located in a geologic formation which is characterized
by being highly heat conductive and such formation should perhaps
extend below the cavern to a distance of say 40,000 or 50,000 feet,
whereby the more intense heat available from such depths furnishes
a constantly available supply of heat such as will maintain the
temperature of the cavern high enough to promote the desired
chemical reactions involving large quantities of reactants. For
example, it has been found that formations having conductivities of
at least 12 .times. 10.sup..sup.-3 calories per centimeter per
second per .degree.C. are sufficiently conductive to readily
replenish heat to a reaction cavern for the purposes of the
invention. Exemplary of materials having such high conductivity
rates in addition to the preferred rock salt domes or spires, are
hematite, magnetite, grossularite, anhydrite, chlorite, quartzite,
rutile, dolomite, calcareous mica phyllite. Thus, it is
contemplated that the conducting of heat through thermally
integrated deposits of such materials to the reaction cavern is
within the invention.
However, the creation of a reaction cavern in a salt spire for the
purposes of the present invention is considered to be the most
preferred embodiment thereof. Such spires often extend from the
near the surface of the earth for distances of miles therebelow.
For example in the Gulf Coast region of the United States, the
formations of salt extend under the Gulf of Mexico, and the spires
thereof rise vertically for miles from the "mother beds" thereof to
the earth's surface, such as in Louisiana and neighboring
states.
The employment of salt spires as sites for reaction caverns is
advantageous in many ways. The drilling or boring of a well into a
deep salt deposit is fairly easily done, since salt is not as
resistant to drilling as many other mineral formations. Because of
its plastic nature at great depth, rock salt closes in on the
casing of a bore hole and holds it firmly in place, thereby
improving the heat conduction therebetween. Whenever a cavity wall
in rock salt becomes cracked, it instantly tends to re-seal.
Further, because of the solubility of salt in water, a cavern at
the bottom of a bore hole can be readily created by forcing water
into the hole and removing the resultant brine solution.
A single bore hole may be employed to create the reaction cavern.
In this case a central casing is inserted within the outer casing
and water may then be forced down the center casing and removed
through the annulus, or vice versa. By employing directing nozzles
or other such means at the base of the well, the water may be so
aimed at the walls of rock salt as to create a cavern of the
desired shape. Such a cavern ultimately may for example be from 10
to 500 feet in diameter, and from 100 to 10,000 feet long. It is
presently preferred to employ caverns which are about 50 to 200
feet in diameter and from 500 to 5,000 feet long. Generally, the
shape of the cavern will approximate a vertically cylindrical
shape, but horizontally extended caverns also may be used.
The cavern may if desired be lined with a suitable material, such
as a polymeric synthetic organic plastic, rubber, metal, or other
lining material such as can be plated or otherwise deposited or
chemically formed upon the walls thereof after creation of the
cavern. The bore hole or bore holes leading to the cavern may
contain separate conduits or ducts or passageways for conveyance of
different reactants or diluents to the cavern, and the materials of
construction that will be employed may be of any of various types,
such as stainless steel, synthetic organic plastics, e.g.,
polyester resins containing chopped glass fibers, or the like. The
materials will be selected to withstand chemical reaction with the
materials to be brought into contact therewith, and to be of
sufficient strength to withstand the physical rigors of the
operation.
In addition to utilizing a single cavern with one or tow bore holes
as illustrated in the drawing, caverns with many more bore holes,
judiciously located, may also be employed. Products may be
selectively withdrawn therefrom depending on the height to which
they rise in the cavern, which again will depend on their physical
states and densities. In addition to utilizing plural bore holes,
serially connected plural cavities may be employed, which may be
interconnected by relatively small passageways. Such caverns may be
at different heights and may be located in different geologic
formations so as to be operative at different temperatures for
plural stage reactions. The sizes of the caverns will be such as to
result in the desired dwell time of reactants in each one,
serially. Also, a plurality of caverns may be employed in parallel,
when so desired.
The preferred rate of flow of heat to a reaction cavern as
contemplated by the present invention will occur when the path from
the lower heat source is minimally of a cross sectional area at
least equal to the surface area of the cavern boundaries. Also, the
reaction cavern should usually be of a volume greater than the sum
of the bore hole volumes, to better function as a combination
reaction vessel and heat source.
The reactions to be completed in the underground caverns of this
invention will most probably involve fluids. Thus, for example,
gaseous reactants may be employed and gaseous products obtained in
a preferred embodiment of the invention. In such an embodiment it
is highly desirable for the densities of the different gases to be
sufficiently different so that they will gravitate to different
portions of the cavern, from which they may be selectively removed.
Of course, the points of addition will be located in a
corresponding manner, so that between inlet and outlet there will
be sufficient room for reaction. Also, of special interest are
reactions in which the reactants are liquids and the products are
gases. The reverse type reactions, wherein gaseous reactants yield
liquid products aare also feasible, although more power will be
required to force the liquid out of the cavern unless the reaction
generates gas pressures such as will aid in expulsion of the
product. Liquid reactants yielding liquid products are also
contemplated by the invention, but again, density differences are
desired so as to enable selective removal of product. In such cases
multiple caverns interconnected through restricted openings would
provde useful means for preventing the discharge of reactants
rather than the product, from the cavern.
Desirably, the production of solids will be avoided, but if and
whenever they are produced in conjunction with liquids, they will
be suspended therein and removed with the liquids. In other cases,
inert liquids may be beneficially added to the cavern to help wash
out any solid products of reaction. Such a liquid may preferably be
a brine solution, such as will not further dissolve the walls of
the cavern. Such solutions may also be used as reaction media, or
as inert diluents and/or may aid in heat transfer to the reactants.
Although continuous processes are considered preferable, batch
processes may also be performed; and between batches the presence
of a brine solution or other inert liquid materials such as a
petroleum oil, diphenyl, diphenyl either or the like will aid in
extracting heat from the walls of the cavern, and will make the
heat more readily available to the reactants when subsequently
added. Although the preceding discussion has been with respect to a
plurality of reactants and products, it will be understood that the
invention also applies to those reactions wherein a single reactant
and/or product is involved.
Among control facilities contemplated in connection with operation
of the invention are thermocouples, analyzers, relays integrators,
computers, cooling devices, clocks, enthalpy measuring devices, and
flow meters. Also storage vessels, tanks, pressurizing means,
mixers, heaters, coolers, filters and purifying equipment may be
used, but will not be described herein in detail inasmuch as use
thereof will be evident from this specification to one of skill in
the art. Such controls may be utilized to regulate the rates of
flow, reaction times, reaction temperatures, etc., so as to best
use the heat furnished by the reaction cavern. Temperatures can be
controlled by either speeding or slowing the flow of reactants
through the cavern; by preheating or cooling the reactants; by
heating or cooling the product; or by changing the direction of
flow or the distance travelled by the reactants when together in
the cavern before removal therefrom.
The type of chemical reactions that may be effected in the
underground heat caverns are manifestly diverse. They include all
the actions in which heat is a useful promoter, whether the
reaction is ultimately exothermic or endothermic. Such reactions
include for example halogenations of hydrocarbons, esterifications,
etherifications, hydrogenations, polymerizations, condensations and
nitrations; all of which may be performed in caverns of the present
invention. Such are only a few of the various types of reactions
which may be performed.
Preferably, the temperature in the reaction cavern will be
maintained at over 100.degree. and usually over 120.degree.C.
Constant temperatures of 150.degree.C. or more are quite possible,
and in some cases even higher temperatures, e.g., 200.degree. to
250.degree.C. are preferred. In reactions that require the addition
of water, this may be added as a salt brine; but in such cases
temperatures will have to be relatively low or a suitable pressure
maintained to prevent boiling off of the water. Such brines, being
saturated with salt, will not dissolve salt from the cavern walls,
and thus the cavern will remain constant in size and shape.
In some cases catalytic reactions may be performed, whereupon
suitable catalyst may be placed in any preferred manner in the
cavern, such as by lowering a deposit thereof as illustrated by way
of example at 96 (FIG. 3). Catalysts for such reactions may be
activated carbon, platinum on carbon, alumina, highly porous
silica, rhodium on alumina, ruthenium on silica, platinum on
asbestos, ar any other catalysts such as may be required according
to the reaction to be performed.
In addition to the features hereinafter referred to, including the
advantage of lack of pollution problems, the present invention
provides an overall improved safety factor. For example, reactions
involving the creation of explosive compounds or flammable
materials may be effected in the caverns of the invention without
fear that if there is an explosion, it will have a devastating
effect on personnel working on the project or on nearby property.
In fact, if an explosion does occur within a cavern in a salt
spire, the plastic salt will immediately reseal the cavern,
allowing it to be used again as if nothing had happened. Also, a
cavern of this type is not subject to leakages in or out, whereby
the reaction products are not lost and remain free of
contaminations from exteriorly of the reaction chamber. If the
reaction is exothermic the product may be passed through the
exterior annular passageway of the concentrically cased exit bore
hole, and will be thereby cooled as it travels through the cooler
portions of the earth structure approaching the earth's surface.
Thus, in many instances, no special product cooling steps will be
required.
The following working examples illustrate a few specific
embodiments of the present invention. These examples are
illustrative only and are not to be considered as limiting the
invention, especially since it is evident that the invention
involves a broad concept of which many other embodiments thereof
are practicable.
EXAMPLE 1
A reaction site is prepared in a Gulf Coast salt spire which
extends from about 200 feet below the surface to about 80,000 feet
below sea level. The reaction site is developed by first boring a
ten inch diameter bore hole down to 12,000 feet below sea level in
a central portion of the salt spire; then casing the hole and then
directing fresh water to flow through the bore hole so as to
dissolve the salt at the bottom of the hole. The brine so produced
is removed by means of a 6 inch string of tubing suspended in the
center of the cased borehole. At the bottom of the water inlet pipe
a deflector may be set up to aim the inflowing water radially, and
to thereby increase the horizontal cross section of the cavern
being created. The water pipe is progressively lowered to increase
the depth of the cavern to the desired size. The system may then be
allowed to "rest" for awhile while full of water, so as to dissolve
salt from the sides thereof and provide a smoothly walled cavern.
This technique will create a reaction cavern extending along a
substantially vertical axis, from say the 12,000 foot depth to
14,000 feet below sea level, and about 100 feet in diameter. Thus,
the volume of such a cavern would be about 15 million cubic feet;
capable of holding about 20,000 lb. moles of gaseous materials. The
temperature in the lower part of such a cavern would be of the
order of about 250.degree.C.
After preparation of the cavern and removal of the brine therefrom,
the pipes, casings and tubing, as illustrated in FIG. 5, are
installed; the outer pipe being of the order of 10 inches in
diameter; the middle tubing being about 6 inches in diameter; and
the intervening pipe being about 8 inches in diameter. The central
tube extends to within about 100 feet of the bottom of the cavity,
and the middle pipe extends to about 400 feet from the bottom of
the cavity. Operational controls employed are those such as are
illustrated in FIG. 2, with the exception that no thermocouple is
shown since the control of the process is illustrated as being
regulated by the analysis of the products, only.
Stoichiometric proportions of methane and chlorine to make carbon
tetrachloride are led through central tubing 127 and the interior
annulus defined by the hanging string of pipe 125 and central tube
127, respectively. The methane, being lighter, rises through the
chlorine and reacts therewith to form a plurality of chlorinated
hydrocarbons and hydrogen chloride byproduct. The feed rates of the
gases are regulated so as to allow sufficient reaction time in the
cavern for desired reaction. Thus, to allow as much as 1/2 hour
total reaction time, the feed rates total about 15 lb. moles per
second. Since such feed rates require high gas flow rates through
the inlet passageways, in some instances it is found desirable to
raise the outlet portions of the passageways so that a smaller
proportion of the cavern is employed for a particular short-time
reaction. In other cases, an inert compound, such as a brine
solution in lower temperature reactions, or a high boiling liquid
organic material in higher temperature reactions, may be employed
to take up some of the cavern volume and thereby diminish dwell
time. However, the present apparatus is most useful in those
reactions of gaseous phase materials requiring longer reaction
times, since the large volume available, once filled with
reactants, allows good production rates with long dwells at
elevated temperatures. The products of the reaction are removed
through the external annulus defined by pipes 123 and 125. They
include methyl chloride, methylene chloride, chloroform and carbon
tetrachloride.
At the top of the installation, product is automatically sampled at
61 (FIG. 2) and analyzed by analyzer 63 to determine the content of
carbon tetrachloride, and flow rates of materials are adjusted
accordingly. The carbon tetrachloride is separated from the other
chlorinated methane derivatives and the less highly chlorinated
products are recycled to the reaction zone, with either of the
reagents, usually preferably the chlorine, to undergo further
chlorination. In the event that the temperature of the reaction
site is not high enough to yield a sufficiently high proportion of
carbon tetrachloride, the flow rate of reagents is slowed, and in
some cases additional heat may be supplied to the cavern by
lowering heating means thereinto.
By following the described procedure and utilizing recycle, almost
stoichiometric yields of the desired carbon tetrachloride and
byproduct HCl are obtained. The hydrogen chloride may be utilized
as such in other chemical operations at the surface facility, or
may be reconverted to chlorine and employed further to chlorinate
more hydrocarbon. In similar manner the reaction site may be
employed for the halogenation of other hydrocarbons, such as
homologues of methane; of unsaturated hydrocarbons, especially
lower hydrocarbons; and other chlorinatable organic materials.
Depending upon the physical states of the reagents and the
products, the arrangements of the reactant input and product outlet
passageways may be adjusted to be similar to those shown in FIGS.
3-5, or modifications thereof, as may be indicated for best
performance in any case.
The procedure described hereinabove is also applicable to various
other chemical reactions, such as the burning of hydrogen and
chlorine to form hydrogen chloride; the oxidation of ethanol to
form acetaldehyde; the oxidation of formaldehyde to formic acid;
addition reactions to acetylene; the nitration of glycerine;
tri-nitration of toluene; the dehydration of maleic acid; the
production of water gas; the production of hydrochloric acid from
sodium chloride and sulfuric acid; the manufacture of amines from
nitro compounds by reduction with hydrogen; and many other
reactions, including metathetical, rearrangement, condensation, and
replacement reactions.
The reactions described may be conducted at substantially
atmospheric pressure or slightly above, due to the gas column at
the top of the cavern; but to facilitate pressure responsive
reactions additional pressure may be applied to the reaction site.
Thus, by filling the well passageways with reactant/product fluids,
the weights of the fluid columns may be as much as 600 atmospheres
at a 20,000 foot depth, if the liquids are of the density of
water.
Although a preferred embodiment of the invention will involve those
reactions which require additional heat, to promote some reactions
to go most efficiently, catalysts are required. For example, using
the apparatus described in this example, ortho-xylene, as a liquid,
is added to the reaction cavern together with air or oxygen, with
the proportion of air being in great excess to avoid explosions,
and the reaction mixture is passed over a catalyst bed as indicated
at 96 (FIG. 3). A preferred catalyst in such case is vanadium
pentoxide on a suitable base, such as a highly porous inert
substrate. In lieu of the arrangement shown, the catalyst may be
located in the inlet or the exit passageway instead of in the
reactor itself; but in any case in such manner that the reagents
pass through it after being heated. The product phthalic anhydride,
being above its boiling point, may be removed as a gas. Or, when a
liquid is produced, due to lower cavern temperature, it may be
pumped out of the cavern or driven out by application of pressure
as explained hereinabove. If liquid, the passageway design may be
varied to have the exit passageway communicate with the liquid at
the bottom of the cavern, as illustrated in FIG. 4.
EXAMPLE 2
A dual well reaction site is prepared in a Gulf Coast salt spire of
the type described in Example 1, to produce a reaction cavern and
associated passageways as shown in FIG. 4. The wells extend to a
depth of about 12,000 feet below sea level and lead into a cavern
having a total volume of about 4 million cubic feet. The outer
casing comprises a 12 inch diameter pipe, and the inner casing is
of about 6 inch diameter. The cavern is made by boring separate
wells 105, 115; extracting salt from below them by circulating
water through them as described in Example 1, and thus causing the
wells to communicate with each other, as shown.
For the reaction of ortho-xylene and oxygen to produce phthalic
anhydride, as described in Example 1, air and ortho-xylene are
delivered into the cavern through the inlet passageways, and by
maintaining the temperature in the cavern below the boiling point
of phthalic anhydride, the phthalic anhydride collects as a liquid
in the bottom of the cavern and is removed through passageway 111,
while the unused nitrogen is removed through passageway 113. As
mentioned in Example 1, a catalyst is employed to promote the
reaction. Also, controls are employed to optimize the reaction, as
in Example 1.
Instead of the production of phthalic anhydride, the method of this
example may be applied to the manufacture of other chemical
compounds, such as ammonia from nitrogen and hydrogen; formaldehyde
from alcohol and air; lower polymers of ethylene from ethylene;
dimethyl ether from methanol and diethyl; ether from ethanol by
catalytic dehydration of alcohols; of methanol from natural gas by
use of a pressure of 750 lbs. per square inch and a deposited
copper catalyst; plus many other commercial organic and inorganic
reactions. In those instances where no liquid products are
produced, all the gaseous product may be removed through passageway
113.
By utilizing the two-well system of this example, a clearly defined
path including a horizontal component, is required to be traversed
by the reactants before removal from the reaction site. This allows
a greater flexibility of operations of the chemical reactions;
permits the uses of caverns of different shape designs and volumes;
and in some cases allows two-stage reactions to proceed
sequentially; the first reaction being effected in a comparatively
small volume under the inlet pipes and tubes, and the second
reaction in the larger cavern portion.
EXAMPLE 3
A reaction cavity of the order of 2 million cubic foot capacity is
prepared by boring into a deposit of quartzite at a depth of about
10,000 feet below sea level and blasting a cavity therein. The
crushed rock is removed by mechanical means, when feasible, or by
chemical means, e.g., dissolving in suitable acid. Also, it may be
removed while suspended in a heavy fluid such as an aqueous gel,
pumped through the cavity. After creation of the cavity, chemical
reactions such as those described in Examples 1 and 2 are conducted
therein. As a specific embodiment of such types of reactions,
utilizing passageways such as shown in FIG. 3, wherein the tubing
is 6 inches in diameter and the pipes are 12 inches in diameter,
ethylene oxide is made from ethylene and air, using a silver
catalyst promoted with an alkaline earth metal oxide, supported on
alumina. The temperature of the reaction and of the reaction
cavern, is about 230.degree.C. and the pressure is about
atmospheric. The feeds of ethylene and oxygen are in substantially
stoichiometric proportions, at rates designed to produce short
reactions times, e.g., from 5 to 45 minutes.
Another reaction such as may be effected in this apparatus is that
wherein ethyl acetate is produced from ethanol and acetic acid.
Although this reaction does not require heat to make it go, the use
of the present reaction cavern, usually of comparatively small
volume, serves to furnish not only a ready-made reaction vessel,
but also a useful regulator of the temperature of the reaction. The
product is cooled to near room temperature by its passage to the
aboveground facility through the exit pipe which is in heat
exchange relation with the relatively cool environmental earth
structure. Also, chemical reactions wherein heat is operative to
vaporize a liquid reactant may be practiced herein, even if, once
vaporized, no further heat is needed to complete the reaction.
Similarly, reactions effected by heat and conducted in conjunction
with physical separations of materials are usefully effected by the
method of this invention. For example, solvents may be partially
removed from reactants by vaporization thereof by application of
the cavern heat, and the more concentrated solutions resulting may
be more reactive.
Among other reactions that may be effected in caverns of the
invention are neutralizations, acidifications, hydrogenations,
dehydrogenations, etherifications, esterifications, isomerizations,
nitrations, carbonylations, oxidations, reductions, catalytic
reactions, pressure reactions, high temperature and low temperature
reactions, etc.
* * * * *