US3677204A - High temperature heat generator - Google Patents

Abstract

The present invention relates to a method and apparatus for generating high temperature heat in the range of 1,000* to 5,000* F. or within the range as limited by the materials of construction of the containment vessels. In the process of the present invention, single or multiple beds of cobalt oxide operating in series and/or parallel between two basic cycles of oxidizing and reducing of the metal oxide with air and fuel, respectively, discharges stack gas and heat alternately, thereby liberating very high temperature gases for various heating applications. The present invention uses many different types of fuel including gases, liquids, and/or solid fuel. In its metal oxidizing step, the lower oxide is oxidized with air to the higher oxide form liberating both heat and inert nitrogen. In the reducing step the chemical combined oxygen is used to burn the fuel thereby liberating high temperature heat for outside heating applications. The heat carrying gases are primarily carbon dioxide and/or steam depending on the type of fuel.

Description

O Umted States Patent [151 I 3,677,204 Leas et al. 1 July 18, 1972 [54] HIGH TEMPERATURE HEAT 57 ABSTRACT GENERATOR The present invention relates to a method and apparatus for 72 Inventors: Lawrence E. Leas, Simi, Calif.; Robert L. generating high temperature heat in the range of to Leas; Cecil Johnson, both f Columbia 5,000 F. or within the range as limited by the materials of city, 1 d, construction of the containment vessels. In the process of the present invention, single or multiple beds of cobalt oxide {73] Asslgnee 3 g? :kdvehpmem Corporation operating in series and/or parallel between two basic cycles of o um m l n oxidizing and reducing of the metal oxide with air and fuel, [22] Filed: Jan. 12, 1970 respectively, discharges stack gas and heat alternately, thereby liberating very high temperature gases for various [21] 245l heating applications. The present invention uses many different types of fuel including gases, liquids, and/or solid fuel. [52] US. Cl ..ll0/l In its meta] oxidizing step, the lower oxide is oxidized with air F231) to the higher oxide form liberating both heat and inert [58] Field of Search ..1 10/ 1; 23/288, 204; 48/197 nitrogen. In the reducing step the chemical combined oxygen is used to burn the fuel thereby liberating high temperature References cued heat for outside heating applications. The heat carrying gases are primarily carbon dioxide and/or steam depending on the UNITED STATES PATENTS type offuel' 1,506,322 8/1924 ONeill ..1l0/l 1,532,930 4/1925 O'Neill ..1 ml] Primary Examiner-Edward G. Favors Attorney-John J. Byrne 5 Claim, 2 Drawing Figures /3 O DEPLETED AIR STREAM VENT VENT 2 DEPLETED 5/ 55 53 AIR STREAM C02- H20 3/ HEAT EXCHANGER Am V FILL FILL C00 C00 s50 BED vsm' 67 v /7 39 V v 29 W EL 7 6.9

DUMP DUMP Patented July 18, 1972 2 Sheets-Sheet l INVENTORS LAWRENCE E. was

N M0 E5 W L0 J EM RC km m \V V V NV cum 0mm O 0 000 ii in V w O00 000 W kn hm Q P R 0 8 v 255w 12 5.531% o .5515 mi 55 5% o w Mm Wm M Patgnted July 18, 1972 2 Sheets-Sheet 2 5 AIR FEED T AIR l f p-l/s 53 I09 HOT AIR 407 Co V JF COKE COKE V V 49 /45 Q V C00 ASH C ASH COBALT COBALT I49 I33: {L 37 47 V COKE COKE (i e '2 33 /37 /53 8/ 39 93 co M C00 C (:0 TANK A H F ASH C00 TANK COBALT COBALT 95 r4] Ii 2? I I 83 4 38 25 26 97 87 HIGH TEMPERATURE HEAT GENERATOR In the prior art, electrically heated furnaces and various other heat transfer processes are expensive to construct and operate. High temperature nuclear process heat has not been fully developed and it is economically limited to only very large installations. In many of the processing industries, direct fired heaters are very difficult to stage in series flow to obtain the accumulated additive effect to obtain the ultimate high temperature ranges with thermally stable heating fluids. When using air as the oxidizing media for fuel combustion at all of the burning stages, nitrogen inert gases dilute the heat transfer fluids and therefore reduce the level of high temperature heat transfer at the use point. Expensive oxygen is used as the oxidizing agent in high temperature combustion processes and gasification processes thereby limiting the practical utilization of these high temperature applications.

An object of the present invention is to overcome the problems and inadequacies of the prior art pointed out above. Another object of the present invention is to use cobalt oxide as the oxygen recovery and dispensor reagent.

A further object of the present invention is to use metal oxides of similar reactive and disassociation characteristics as cobalt oxide with relation to oxygen recovery from air and discharge to fuels for combustion and heating processes. Yet another object of the present invention is to stage the series flow heat generating units wherein the temperature is sequentially increased in each of the completed stages to produce the accumulative additive temperature increase at the point of heat consumption.

Another object of the present invention is to yield a high temperature heating fluid that is either a reducing gas, an oxidizing gas, or an inert gas at the point of heat transfer.

A still further objective of the present invention is to have a very effective heat exchange train to maximize heat recovery within the process and beyond the consuming high temperature heat exchanger. An object of the present invention is to facilitate the installation of valves and other moving parts away from the higher temperature zones to reduce the maintenance costs and to facilitate increasing the temperature ranges and capabilities of the process. An object ofthe present invention is to use coke as the fuel in which the coke can be readily transported and/or stored at or near the point of consumption.

Another object of the present invention is to have parallel trains so that the output high temperature heat transfer is continuous. Also another object of the present invention is to have a single unit that operates in a cyclic time period that is compatible with the cyclic period of the heat consuming element. Another object of the present invention is to produce an inerting gas that is essentially free of sulfur. For example, during the metal reduction cycle the sulfur oxides are absorbed as metal sulfides thereby removing sulfur from the stack gas or inert gases (carbon dioxide and nitrogen). On the next or oxidation cycle the sulfur is removed through another duct wherein it can be processed at a lower temperature more adequately. Another object of the present invention is to use the clean nitrogen and carbon dioxide for chemical or urea fertilizer production.

These and other objects of the invention will become more apparent to those skilled in the art by reference to the following detailed description when viewed in light of the accompanying drawings wherein FIGS. 1 and 2 illustrate the schematics of operation.

Referring now to FIG. I where like elements are referred to by like numerals, two C beds are shown as l and 3. Cobalt oxide is used in the drawing but it is to be understood that other lower metal oxides or metals can be used provided their reaction rates, oxidation and dissociations are within the range of temperature and pressure of interest to this present invention. Initially, beds 1 and 3 are packed with the lower form of metal oxide and the sequence is as follows: continuous operation is maintained by the use of two beds on alternate oxidation and reduction cycles.

At start-up, the beds and incoming air are heated by another source but once operation is in progress, the heat liberated provides the heat for the air and fuel. For purposes of this description, assume bed 1 is being oxidized and bed 3 is reduced and start-up has been accomplished. Air enters the system from line 5, is compressed in compressor 7 and exits the compressor via line 9. The air flows through heat exchanger 11 where it is heated by the exit oxygen depleted stream from line 13. The heated air flows into bed 1 via line 15 and valve 17. The metal oxide is oxidized to its higher oxide form and the hot oxygen depleted air stream exits through line 13, heat exchanger 11, line 19, heat exchanger 21 to provide heating of the fuel for bed 3 and is vented through line 23 and valve 25. Line 27 and valve 29 are used to provide air to bed 3 on the next cycle. Line 31 is used for the exit oxygen depleted air on the next cycle where it would flow through heat exchanger 11, line 33, heat exchanger 21, line 35 and be vented via valve 37. While oxidation is in progress in bed 1, reduction of the higher metal oxide (which has been oxidized on a previous cycle by air) to the lower metal oxide takes place in bed 3, by fuel such as natural gas, carbon monoxide or other highly volatile type hydrocarbon. The natural gas enters via line 39 and is heated to a degree in exchanger 21 and enters bed 3 via line 41 and valve 43. Line 45 and valve 47 are used to permit fuel flow into bed 1 on the next cycle. If natural gas is used (methane illustrated) the following overall reaction takes place:

4C0 0, CH [2 C00 CO 2 H O heat. Substantial heat is given off and superheats the gaseous products of combustion which exit through line 49. heat exchanger 51, and are vented through line 53 and valve 55.

Lines 57 and 59 and valve 61 provide an exit for these gaseous products from bed 1 on the next cycle. By controlling the valves on all exit lines, the gaseous flow from each reactor can be moved through the heat exchanger as described above. Beds 1 and 3 are filled with metal oxide via lines 63 and 65, respectively, and can be discharged through lines 67 and 69, respectively. Heat exchanger 51 is designated as a process heat exchanger. This exchanger is used as a heat source for process streams, etc., to provide heat as required. The stream entering the heat exchanger via either line 49 or 57 has a very high temperature and in this exchanger, large quantities of heat can be exchanged. Also, the amounts depend upon the size of unit designed. In addition, various types of fuel or reducing agents can be used but natural gas or highly volatile hydrocarbons would be preferred over heavier hydrocarbons. More heat would be required to vaporize them in exchanger 21.

A method of using this operation to provide a high temperature heat generator from coke is shown in drawing 2. In this design, two columns containing two cobalt oxide beds and two coke beds each are shown stacked so that the top section is a coke bed, the second section from the top is a cobalt oxide bed, then followed by another coke section with a cobalt oxide bed on the bottom. Once again the operation is made continuous by the use of two columns on alternate oxidizing and reducing cycles. All of the stacked columns are denoted as l and 3, respectively, with various sections. The beds are arranged so that no solids flow downward between the sections but gaseous components are permitted to flow upward through the various sections.

For description purposes column 1 is being oxidized while column 3 is providing the high temperature heat stream. Assume that startup has been accomplished. Cold excess air from line 5 is fed through line 7, compressed by compressor 9 and is heated in exchanger 11, exchanger 13 and coils 15 contained in bed 17 and part of it is injected into the bottom lower oxide bed 19 via lines 21 and 23 and valve 25. Line 24 and valve 26 are used on the alternate cycle. The air flows upward through the bed and oxidizes the lower oxide to its higher oxide form. The air burns part of the coke in bed 27 to carbon dioxide and carbon monoxide and continues its upward flow to bed 17 to oxidize this cobalt oxide bed to its higher oxide.

Also, part of the CO formed can be converted to CO,1 in this bed. The gaseous stream flows upward to the coke bed 29 where the air burns the coke to CO and, some CO. The gaseous products leave the column via line 31. Valves 37 and 38 remain closed during this stage. The exit gases are burned with hot air to insure complete removal of CO in the vented gases from lines 49 and 51 and valve 53 in combustor 55. The exit gases of combustion flow through line 57, high temperature heat exchanger 59, line 61, heat exchanger 1 1, turbine 63, and vented through valve 65 and line 67. By controlling pressure control valve 65, the gaseous flow and pressure can be maintained on this cycle. While this cycle is on and the operation has been described for column 1, the generation of more high temperature process heat takes place in column 3. In order to prevent the burn-out of the air preheating coils in the cobalt v oxide beds, a smaller stream of air from source 5 is sent through line 69, compressor 71, heat exchanger 73, line 75, heat exchanger 77, coils 79 and into either line 21 or 49 where it combines with air from line 7. Also, the pressurized carbon monoxide rich stream from tank 8 (used for starting this cycle) is sent through either line 83 or 85 and either valves 87 and 89 (valve 91 is closed on this cycle) and compressor 93 is used later on in the cycle for compressing the CO rich stream) through line 95 and valve 97 to the higher metal oxide bed 99. In this bed, the exothermic reaction of C 0,, CO 3CoO CO heat occurs and the heated gaseous products flow upward to coke bed 101 where the coke is gasified to more carbon monoxide via C CO 2C0. This stream rich in CO is then further superheated by the exothermic reaction C0 0 CO 3CoO CO heat in the higher metal oxide bed 103. The carbon dioxide portion of the gaseous stream gasifies the coke in bed 105- to additional carbon monoxide and the products exit via line 107 and a portion is burned with hot air from lines 49, 109 and valve 111 in combustor 113. The major portion of the hot air in this section is sent to combustor 113 while a lessor amount is sent to combustor 55 on this cycle but is reversed on the alternate cycle. The superheated products of combustion exit via line 115, high temperature heat exchanger 117, line 119, exchanger 73, turbine 121, pressure control valve 123 and vented via line 125.

On the alternate cycle, this operation is reversed and the major heat transfer is accomplished in exchanger 59. After the operation is started with CO exiting through line 107, the valves to the surge tank are closed and valve 91 is opened and part of the CO is recycled back via line 78, exchanger 77, valve 91, compressor 93, line 95 and valve 97 to bed 99 to maintain the high temperature heat generation cycle. After relatively pure CO is obtained in line 78, a small bleed-off is sent to the CO storage tank, 81, through valve 87 to initiate the next cycle for CO reaction with the higher metal oxide. The valves to the surge tank are then closed. Line 35, 41, and

43, valves 37, 47 and 45 and compressor 39 are used on the al-- ternate cycle in column 1 to fill the CO tank 33, while valve 38 provides the CO into bed 19. Since the CO tanks are small, the time of filling for the next cycle is small and only a small bleedoff is required. In other words, air is being supplied to the bottom of the column 1 in bed 19 and the products exit through and burned in combustor 55 while part of the CO is recycled to bed 99 in column 3 to maintain the continuity of the cycle.

The reverse can occur on alternate cycles of the operation. The CO tanks are used only for initiating the higher oxide reducing cycle since recycling of the CO at the top will main tain the cycle for the set interval. Exchangers 59 and 117 transfer large quantities of heat at very high temperatures for process heat or other purposes as required. Coke bed 29 is filled via line 127 and the ash residue leaves via line 129. The cobalt oxide bed 17 is filled and emptied through lines 131 and 133, respectively. Coke bed 27 is filled and ash residue leaves through lines 135 and 137, respectively. Cobalt oxide bed 19 is filled and emptied via lines 139 and 141, respectively. Bed 105 is filled and dumped via lines 143 and 145, respectively. Bed 105 is filled and emptied via lines 147 and 149,

respectively Bed 101 is filled and emptied via lines 151 and 15 respectively. Bed 99 1s filled and emptied through lines 155 and 157, respectively. The amount of process heat transferred to a process stream depends upon the size of the unit and upon the availability of material of construction and upon the number of stacked units.

Because the process of the present invention is so flexible in using several different types of fuel, number of parallel trains and stages, and procuring different levels of high temperature ranges; the process variables are relatively broad to accommodate the desired results. It should be understood that these variables can be changed over a spectrum without decreasing the scope and spirit of the present invention.

Having illustrated the present invention by the above description and drawings, 1 claim:

1. A method for generating high temperature heat which comprises alternately oxidizing and reducing a metal oxide, said oxidation resulting from the reaction of said metal oxide in a lower valence state with an oxygen-containing gas to oxidize said metal oxide to a higher valence state and said heat generated by the reaction of said higher valence metal oxide with a combustible fuel, and wherein the alternate oxidationreduction reactions are conducted in single or multi-parallel trains or single or multi-stage series.

2. A method as defined by claim 1 wherein the combustible fuel is methane gas and the metal oxide is cobalt oxide.

3. A method as defined by claim 1 wherein the combustible fuel is coke and the metal oxide is cobalt oxide.

4. A method as defined by claim 3 wherein the metal oxide is maintained vertically above the coke.

5. A method as defined by claim 3 wherein the coke is injected intermittently or continuously.

Claims (4)

1. 2. A method as defined by claim 1 wherein the combustible fuel is methane gas and the metal oxide is cobalt oxide.
2. 3. A method as defined by claim 1 wherein the combustible fuel is coke and the metal oxide is cobalt oxide.
3. 4. A method as defined by claim 3 wherein the metal oxide is maintained vertically above the coke.
4. 5. A method as defined by claim 3 wherein the coke is injected intermittently or continuously.

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