US2975594A - Generation of power from ash-forming hydrocarbons - Google Patents

Description

March 2l, 1961 Du Bols EAsTMAN 2,975,594

GENERATION oE PowER FROM ASH-Femme HYDRocAREoNs Filed Feb. 1o, 1955 United States Patent l@ GENERA'IGN OF POWER FROM ASH-FORMING HYDROCARBONS Du Bois Eastman, Whittier, Calif., assigner to Texaco Inc., a corporation of Delaware Filed Feb. 10, 1955, Ser. No. '487,286

6 Claims. (Cl. 60--39.02)

This invention relates to the generation of power from liquid hydrocarbon fuels containing mineral ash-forming constituents.

Petroleum commonly contains small quantities of heavy metals. The most commont heavy metals contained in petroleum are vanadium, nickel, iron, chromium and molybdenum. These heavy metals presumably occur in petroleum as compounds. The exact chemical composition of the heavy metal compounds is subject to some question. llt is generally agreed that the metals are present, at least in part, in the form of oil-soluble metallo-organic compounds. Crude oil containing heavy metal constituents, and some heavy distillates from `such crudes, have been found unsatisfactory for many purposes because of the corrosive nature of the ash from these fuels.

In particular, the compounds of vanadium and molybdenum, upon oxidation, apparently yield very corrosive or erosive products. The extend to which compounds of these metals are present in petroleum may vary from about 1 to about 1,000 parts per million by Weight based upon the Weight of the metal contained in the compound. In general, petroleum fuels containing even minor amounts of vanadium and nickel 4are troublesome when used as fuel. The ash from these fuels is corrosive or erosive to both refractories and to alloy metals. f the heavy metal contaminants in petroleum fuels, vanadium and nickel appear to be the most detrimental to high temperature refractories, particularly aluminum oxide refractories.

The use of ash-forming hydrocarbons as fuels for the operation of gas turbines has not been generally successful. Ash from the fuel deposits on and attacks the `turbine blades resulting in excessive corrosion and short blade life. `Corrosion or erosion of the turbine blades apparently is due primarily to the ash resultingfrom the heavy metal constituents contained in the fuels. As a consequence, only the more expensive, ash-free `hydrocarbon fuels, eg., normally" gaseous hydrocarbons or relatively low boiling distillate fractions, are permissible fuels for gas turbines. The low cost and high Btu content of heavy fuel oils makes them particularly attractive as fuels `for gas turbines providing the corrosion problems can be overcome. Higher grade fuels arenot generally economical as gas turbine fuels because of the relatively low eliiciency of the -gas turbine as compared with other engines capable of utilizingthe higher grades of hydrocarbon fuels.

A number of attempts have been Vmade `to treat the ash-containing liquid hydrocarbon fuels for removal or reduction of ash-forming constituents. These attempts have not been generally successful. The heavy metal constituents of crude oils may be concentrated, to some extent, by means of distillation, the heavy metal constituents largelyA remaining in the distillation residues. Nevertheless, the metals or their compounds are also present in many distillate products, particularly in heavy fractions, such as products of vacuum distillation. The presence of the metals in the distillates may be due either ice to actual vaporization of the "metal `compounds or `to physical carryover `or entrainment. These metals have also been found in such stocks as propane-deasphalted oil and solvent-refined distillates.

This invention provides a method whereby a petroleum stock containing heavy metal constituents may be used as fuel for a combustion gas turbine. In accordance with this invention, a hydrocarbon fuel containing mineral ashforming constituents is introduced into a reaction Zone together with sufficient oxidizing agent, preferably an oxygen-containing gas, to react exothermically with the fuel at a temperature above about 2,000 F. and to convert not less than and not more than 99.5 percent of the carbon contained in the fuel to carbon oxides. The extent of conversion of the carbon may be varied Within this range depending upon the amounts of heavy metals contained in the fuel. The amount of unconverted carbon should be at least 50 times and preferably 100 times the combined Weight of the nickel and vanadium contained in the fuel, based on the Weight of the free metals. The unconverted carbon from the hydrocarbon is released in the form of free carbon or soot. Under these conditions of limited carbon conversion, the ashforming constituents, particularly the heavy metals contained in the oil, are associated With the liberated carbon. The ash-containing soot or carbon is substantially harmless to refractories and alloy metals employed in gas turbines. The gaseous eluent from the reaction zone may be passed directly to a gas turbine. The gaseous eflluent from the reaction zone usually contains a considerable amount of carbon monoxide and hydrogen.

In a preferred embodiment of the present invention, partial combustion of the ash-forming petroleum fuel is carried out in a primary reaction zone. Free carbon and associated ash are separated from the gaseous etlluent from the primary reaction zone, preferably without substantial cooling of the gas stream, and the resulting ashfree gases then subjected to exothermic reaction with an additional amount of oxygen-containing gas, e.g., air, to effect substantially complete oxidation of carbon monoxide and hydrogen contained therein to fully oxidized products of reaction. Separation of the carbon from the effluent gas stream from the primary reaction zone elfects simultaneous removal of heavy metal constituents originally present in the fuel.

ln a preferred method of operation in accordance with the present invention, a liquid hydrocarbon fuel containing heavy metal constituents is subjected to reaction in an unpacked compact prim-ary reaction zone under superatmospheric pressure at an autogencusly maintained temperature Within the range of 2,000 to 3,200" F. with oxygen-containing gas. The quantity of oxygen-containing gas is limited so that an -amount of carbon by Weight at least 50 times the combined Weight of nickel and vanadium in the fuel remains unconverted and is liberated as free carbon. The unconverted carbon and associated ash from the fuel "are separated from the gaseous efuent from the primary reaction zone and the resulting gases, substantially free from heavy metals, subjected to additional reaction with oxidizing gas in a secondary reaction Zone maintained at a temperature above about 2,000 F. effecting substantially complete oxidation of the combustible constituents contained therein. The gases from the secondary reaction zone are passed to a gas turbine as working iluid for the turbine.

Fig. l is a diagrammatic view illustrating in simplified form one method of operation of a gas turbine in accordance With the present invention.

Fig. 2 is a diagrammatic view of a two-stage combustor suitable for use in the present invention and forming a part of the present invention.

Fig. 3 is a diagrammatievew in simplified Iform of 3 another method of operation of gas turbines in accordance with the present invention.

With reference to Fig. 1, oil from line 3 is atomized with steam from line 4 into a primary combustion zone 6 or precombustor where it is mixed with air from line 7. The precombustor, or primary reaction zone, is a compact reaction zone free from packing and catalyst. A temperature above about 2,000 F. and preferably above 2,200 F. and below 3,20v0 F., suitably 2,500 to 2,900 F., is maintained in the primary reaction zone. Suflcient air is supplied to the precombustor to convert from 90 to 99.5, preferably 95 to 99, percent of the carbon in the oil to carbon oxides. The remainder of the carbon is released as free carbon. The amount of unconverted carbon is at least 50 times (by weight) the combined weight of the nickel `and vanadium contained in the fuel.

Free carbon released in the primary reaction zone is entrained in the gaseous products of reaction. Ash from the fuel is substantially completely retained in the carbon. The carbon, containing ash from the fuel, is separated from the gas stream by means -of a separator 8, for example, a cyclone separator. The free carbon and ash are discarded. The solid-free, hot gases are passed to a secondary combustion zone or main combustor 9. The separation -of the carbon and ash from the hot gases is carried out at an elevated temperature, preferably 'at a temperature substantially equal to the temperature `of the primary reaction zone. In some instances it is desirable to add a coolant to the gases from combustion zone 6 prior to separation of the carbon. For example, steam -may be added through line 11, the steam serving to reduce the temperature yof the gases.

In the main combustor 9, or secondary reaction zone, the combustible gases from the primary reaction zone are mixed with suicient air from line 12. for complete combustion. Generally an excess of air is used, part of the air serving to control the temperature as will be evident from a description of Fig. 2 hereinafter.

The gases from combustion zone 9, comprising fully oxidized products of combustion, yare passed into a gas turbine 13 driving the turbine and associated air compressor 14 and delivering excess power which may be used for any suitable purpose. Steam from line 1S may be mixed with the gases from combustor 9, and additional air may be added, ifdesired, by way of line 16.

Air compressor 14 delivers air under pressure through line 17 from which it is delivered to lines 7 and 12 and, if desired, also to line 16. Hot gases from turbine 13 are passed in indirect heat exchange with air from the compressor 14 preheating the air supplied to combustors 6 and 9 and the air which by-passes the combustor through line 16. Separate heat exchangers 18, 19 and 20 are shown for separately heating the streams of air to lines 7, 12 and 16. It is to be understood that, in place of separate heat exchangers, a single heat exchanger may be used. Separate heat exchangers permit different preheating temperatures for each of the various air streams.

With reference to Fig. 2, a two-stage combustor suitable for use in the present process is shown in some detail. As shown in the gure, air is introduced through passageway 21 into one end of a primary reaction zone or precombustor 22. Vanes 23 impart a swirling motion to the air stream. Oil is charged through line 24 to a spray nozzle 26 where it is sprayed into the swirling air stream. Steam may be admitted with the oil through line 24 to increase the atomization of the oil. The combustion chamber 22 is a compact reaction zone free from packing and catalyst provided with a refractory Wall 27 surrounded by a pressure-resistant steel shell 28.

In the primary reaction zone 22 the oil is incompletely reacted with air so that from 90 to 98 percent of the carbon in the oil is converted to carbon oxides, mainly carbon monoxide. The remaining carbon, liberated as free carbon associated with the ash from the oil, is

thrown outwardly against the periphery of the combustion chamber by the centrifugal action of the swirling gas stream.

The gases from precombustion zone 22, substantially free from solid particles, pass through port 3-1 into the interior of a second combustion chamber provided with a perforated wall 32, suitably of metal with a ceramic refractory coating. Port 31 is of smaller diameter than the interior of precombustion chamber 22. Port 31 extends through a refractory piece 33 which separates the precombustion chamber 22 from the secondary combustion chamber 32. l

A slit 34 between the end of refractory wall 27 and the refractory piece 33 provides a circumferential opening at the outlet end of the precombustion chamber through which the solid particles are discharged by centrifugation from the gas stream. The solid particles are collected in a collector ring 36 and discharged through an outlet 37. Steam or water may be introduced into the collector ring 36 through line 38 t-o cool the solids and gases in the collector ring. Gas which nds its way out through the slit into collector ring 36 may be drawn olf through line 39 into pipe 41 and returned to the second or main combustor 32. Air for combustion is introduced through pipe 41 into vessel 42 and then through openings 43 in the wall `of the combustion chamber 32. Sucient secondary air is introduced through pipe 41 for complete combustion of the fuel contained in the gas introduced into combustion chamber 32 through port 31. Products of combustion from combustion chamber 32 are discharged into a gas turbine. The combustion chambers are operated under pressure to provide gases at the desired elevated pressure for the gas turbine.

With reference to Fig. 3, which shows an alternative arrangement for carrying out the method of this invention, oil is supplied through line 51, mixed with steam from line 52, and injected into prim-ary combustion zone 53. Preheated air in an amount sulicient for conversion of to 99.5 percent of the carbon in the oil to carbon oxides is introduced through line 54 into admixture with the oil and steam.

Gaseous partial combustion products are discharged from the primary combustion chamber 53 into a separator S6 in which the carbon and associated ash are separated from the gas stream. A tempering agent, for example, steam, may be introduced into the gas stream through line 57.

The resulting hot gases, substantially free from solid carbon and ash, are passed to turbine 58 where a part of the energy is recovered from the gas stream. The exhaust from turbine 58 is sent tov secondary combustion zone 59 where lit is mixed with additional air from line 61 in an amount sufcient for complete combustion. Hot gases from combustor 59 are passed to turbine 62. A tempering agent, for.example, steam from line 63, may be mixed with the gases from the combustor. The exhaust from turbine 62 passes through heat exchangers 64 and 66. Air compressors 67 and 68 supply air under pressure to heat exchangers 64 and 66, respectively, for heat exchange with exhaust gas from turbine 62, and to lines 61 and 54, respectively.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed Yas are indicated in the appended claims.

I claim:

1. In the generation of power in a heat engine wherein working fluid for said engine is generated from an ashforming hydrocarbon liquid comprising naturally-occurring heavy metal compounds containing vanadium and nickel wherein said hydrocarbon liquid is subjected to re action with gaseous oxidizing agent at elevated pressure and gaseous oxidation products of said reaction are utilized in a heat engine as working uid therefor, the im provement which comprises reacting a hydrocarbon liquid containing a substantial amount of said heavy metal compounds with oxidizing gas in relative proportions such that at least 0.5 percent and not more than percent of the carbon contained in said hydrocarbon is unreacted and is liberated as solid carbon in an amount at least 50 times the combined weight of nickel and vanadium contained in said hydrocarbon liquid wherein said unreacted carbon combines with said nickel and vanadium to form a carbonash solid composite, separating said carbon-ash solid composite containing said vanadium and nickel from gaseous products of said reaction, and utilizing resulting ash-free gas as a source of working iluid for said engine.

2. The method according to claim 1 wherein said gaseous oxidizing agent is air.

3. The method according to claim 1 wherein said heat engine is a gas turbine.

4. A process as defined in claim 1 wherein said reaction of ash-forming liquid hydrocarbon with oxygen-containing gas is conducted under conditions such that re snlting reaction products are given a spiral motion eiiecting concentration of said solid carbon-ash composite containing said vanadium and nickel along the periphery of a spirally moving stream of reaction products, said solid composite is removed peripherally from said reaction zone, and gaseous products of reaction substantially free from ash are discharged frornsaid reaction zone.

5. In the generation of power in a heat engine wherein working uid for said engine is generated by reaction of a hydrocarbon with a gaseous oxidizing agent at elevated temperature and pressure in a plurality of reaction zones in one of which the hydrocarbon is partially oxidized and in another of which gaseous products of partial oxidation from the rst reaction zone are substantially completely oxidized and wherein said substantially cornpletely oxidized gaseous reaction products are utilized in an engine as working fluid therefor, the improvement which comprises reacting a hydrocarbon liquid containing a substantial amount of naturally-occurring heavy metal compounds including vanadium and nickel in a rst reaction zone under superatmospheric pressure with relative proportions of oxidizing agent and hydrocarbon such that at least 0.5 percent and not more than l0 percent of the carbon contained in said hydrocarbon is liberated as solid carbon in an amount at least times the combined weights of nickel and vanadium contained in said hydrocarbon wherein said unreacted carbon combines with said nickel and vanadium to form a carbon-ash solid composite, separating said solid composite containing said vanadium and nickel from gaseous reaction products of said first reaction zone, passing substantially ash-free gaseous eilluent from said rst reaction zone to a second reaction zone effecting substantially complete oxidation of said partially oxidized reaction products and passing gaseous effluent from said second reaction zone into an engine as working uid therefor.

6. The method according to claim 5 wherein gaseous effluent from said first reaction zone after separation of said solid composite therefrom is passed to a heat engine as working fluid therefor prior to introduction of said partially oxidized reaction products to said second reaction zone.

References Cited in the file of this patent UNITED STATES PATENTS 2,458,992 Hague Jian. 11, 1949 2,511,385 Udale June 13, 1950 2,660,521 Teichmann Nov. 24, 1953 2,692,477 Toogood Oct. 26, 1954 2,706,150 Lloyd Apr. 12 ,1955 2,711,075 Perrett June 21, 1955 FOREIGN PATENTS 675,583 Great Britain July 16, 1952 697,101 Great Britain Sept. 16, 1953

Claims (1)

1. IN THE GENERATION OF POWER IN A HEAT ENGINE WHEREIN WORKING FLUID FOR SAID ENGINE IS GENERATED FROM AN ASHFORMING HYDROCARBON LIQUID COMPRISING NATURALLY-OCCURRING HEAVY METAL COMPOUNDS CONTAINING VANADIUM AND NICKEL WHEREIN SAID HYDROCARBON LIQUID IS SUBJECTED TO RECACTION WHICH GASEOUS OXIDIZING AGENT AT ELEVATED PRESSURE AND GASEOUS OXIDATION PRODUCTS OF SAID REACTION ARE UTILIZED IN A HEAT ENGINE AS WORKING FLUID THEREFOR, THE IMPROVEMENT WHICH COMPRISES REACTING A HYDROCARBON LIQUID CONTAINING A SUBSTANTIAL AMOUNT OF SAID HEAVY METAL COMPOUNDS WITH OXIDIZING GAS IN RELATIVE PROPORTIONS SUCH THAT AT LEAST 0.5 PERCENT AND NOT MORE THAN 10 PERCENT OF THE CARBON CONTAINED IN SAID HYDROCARBON IS UNREACTED AND IS LIBERATED AS SOLID CARBON IN AN AMOUNT AT LEAT 50 TIMES THE COMBINED WEIGHT OF NICKEL AND VANADIUM CONTAINED IN SAID HYDROCARBON LIQUID WHEREIN SAID UNREACTED CARBON

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