US 1990499 A
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Patented Feb. 12, 1935 UNITED STATES LIQUID FUEL PACKAGE William W. Odell, Chicago, Ill.
' No Drawing. Application October 2, 1930,
Serial No. 486,044
5 ing and delivering combustible fuels, such as propane and the like, but which is adapted for use with volatilizable fuels having relatively low vapor pressures under the atmospheric conditions prevailing during the winter season, the vapor pressure of the fuel being supplemented by the use of a confined non-oxidizing expelling gas which is substantially insoluble in the liquid fuel, and which is preferably substantially free from moisture so as to avoid the freezing of such moisture at abnormally low! temperatures.
One of the objects of my invention is the preparation for use and for storage under superatmospheric pressure of liquid fuels, particularly those that are readily volatilized by the application of heat. Another object is to make available for discharge under pressure, even at low temperatures, liquid fuels that do not have vapor pressures equal to or as great as 15.0 pounds absolute pressure per square inch at the temperatures at which they may be used.
Recent developments in the natural gas industry have brought forth for the first time in commercially large quantities such products as propane, butane, mixtures of the two, mixtures with other products, and similar combustibles. Some of these are now being marketed under the general name of bottled gas and are used to supply gas for domestic heating and kindred purposes, as well as for other heating operations. It is customary to market such materials in the liquid state under their own vapor pressure.
Two methods of using the bottled gas are known to me; in one, it is customary to stand the metal container, known as a bottle, on end and connect the outlet at the top with a pipe line having gages, a reducing valve, and a shutofi valve, to a gas-burning appliance. When the valve is opened the gas passes from above the liquid in the bottle through the connections and when mixed with air in the usual atmospheric type of burner is ignited and burned in said appliance. As the gas is thus withdrawn the liquid fuel in the bottle boils, supplying the necessary vapor or gas. Simultaneous with this boiling, the liquid becomes-cooled because of the heat absorbed by vaporization. Now, when using normal butane for example, if the gas is withdrawn rapidly the cooling effect becomes-an important factor because at 40 Fahrenheit the vapor pressure of butane'is only 3.0 pounds gage and at 25 Fahrenheit the pressure is less than atmospheric; at the latter temperature gas would not pass out through the system because of insufficient pressure.
The other method of delivering gas from "botof their low vapor tles differs from the foregoing in that the offtake pipe extends substantially to the bottom of the bottle in such a manner that the pressure of the vapor in the upper portion of the bottle (the vapor pressure of the butane for example) forces liquid up from the bottom through the outlet at the top in the liquid phase. Although this eliminates the serious cooling effect referred to above, the cooling effect of the weather when the bottled gas is exposed to the atmosphere during severe winter weather is not thus eliminated.
My invention relates to a method of bottling liquid combustible materials whereby the above named difliculties are not encountered. I find that in practice the tendency has been to employ propane in preference to butane, or mixtures of the two or other liquid fuel because it has a much lower boiling point and therefore-a higher vapor pressure at a given-temperature.
Briefly my method comprises, charging the container with the liquid fuel leaving a little space for vapor and charging said space in part at least with a gas other than the vapor of the said fuel at a superatmospheric pressure. The gas used is preferably one that it not highly soluble in the fuel and one that is not readily condensed to a liquid. The use of air is attended with some danger on account of the fact that it may form an explosive mixture with the fuel, and accordingly I prefer to use nitrogen, hydrogen, stack gas, water gas, engine exhaust gas, carbon dioxide or the like.
Using butane or other volatile liquid fuels having similar or higher boiling points it is common practice to incorporate therewith a rather large percentage of propane in order'that butane with accumulated pentane or other high-boiling liquids (originally present in small amounts'as impurities in the commercial products) should not remain in the container unavailable to the consumen after some of the fuel has been with-- drawn. Removal of fuel from the container through a tube reaching to about the bottom thereof is helpful in overcoming this difiiculty; the removal of the last portion of fuel in this instance depends upon the fuel having a vapor pressure greater than atmospheric at the prevailing temperature. Under climatic conditions characteristic of the winter season in our northern States butane, pentane, and liquid fuels having similar physical properties may have a vapor pressure less than '1 atmosphere absolute.
The use of a gas having a high vapor pressure at low temperatures, which is not so readily soluble in liquid fuels as propane, as a medium for expelling the fuel is an advantage over the systems with which I am familiar andmakes possible the use of fuels not now in extensive use because pressure under ordinary conditions.
I find that when certain grades of natural gasoline that commonly sell for 5 to 8 cents a gallon are fractionated with the removal of butane and some pentane that a high grade motor fuel is obtained that is salable at a higher price. Undoubtedly this would be common practice if there was a market for the butane and pentane which I make available for use as bottle gas in my process. Furthermore, I find that there is a lower percentage fluctuation in the pressure in the charged container due to change-of temperature, when an inert gas or a gas such as is referred to above is used than when straight liquid fuel is charged.
The preferred amount of gas charged with the liquid fuel is not necessarily the same for all fuels or for all sets of conditions. The solubility of the gas in the liquid fuel is a factor. The more soluble it is in the fuel the greater the amount required to charge or pack the fuel for marketing.
'Ethane, for example, has a high vapor pressure at low temperature, the absolute pressures at -50 and Fahrenheit being respectively 94 and 64 pounds per square inch, but it is appreciably soluble in propane and other fuels. Under certain conditions it obviously can be used in packing liquid fuels under pressure. Carbon dioxide at -0, and at 50 Fahrenheit has absolute vapor pressures of 300 and about 118 pounds per square inch and although it is quite soluble in water under pressure it 'is not very soluble in liquid hydrocarbons. Carbon monoxide has an absolute vapor pressure of pounds per square inch at -2'74 Fahrenheit and, of course, a much higher vapor pressure at warmer temperatures. Methane has an absolute vapor pressure of 80 pounds at about -220 Fahrenheit. This gas alsois appreciably soluble in liquid hydrocarbons at low temperatures. It is usable however and is generally superior to ethane. Propane, at 50, 20, 0 and 40 Fahrenheit has absolute vapor pressures of about 90, 54, 39 and 16 pounds per square inch respectively. Desirable properties of packing the liquid fuels are: (a) Low solubility in the fuel and (b) Low critical temperature. Sometimes it is desirable that the gas be nonoxidizing, that is, oxygen alone or in a mixed gas is undesirable; in other cases a non-combustible gas is desiredand in still other cases combustible gases are preferred.
The volume of the gas used should preferably be as great as or greater than the volume of the empty container; this is particularly true when liquid fuels are used having relatively low volatility.
Assume that a cylinder of 10 cubic feet capacity is filled, for example, with '7 cubic feet of liquid normal butane and 10 cubic feet of a gas X insoluble in the butane (having zero solution pressure), at 10 Fahrenheit. The absolute vapor pressure of the butane at 10 Fahrenheit is 9 pounds and the absolute pressure of the. gas X is (10.0+3.0) (14.7) =50.0 pounds per square inch, therefore the total pressure on the system at 10 Fahrenheit would be approximately 50.0+9.0 or 59.0 pounds and the percentage of butane vapor in the gas above the liquid butane would be about 13.25 per cent, the remainder being the gas X. Upon withdrawing the liquid butane, at 10 Fahrenheit the partial pressure relations change, that is the gas expands until finally its partial pressure is one atmosphere and that of the butane remains at 9 pounds absolute, the total pressure being 14.'7+9 or 23.7 pounds per square a gas for tive pressure of said gas approaches zero as the liquid contents of the container is expelled. If the gas is partly soluble in the liquid fuel the effective pressure as the liquid is expelled approaches a limit less than one atmosphere. Because most gases have a definite solubility in the liquid fuels under pressure and because it is frequently necessary to maintain a gas pressure above atmospheric within the container confining the liquid fuel, I frequently prefer to introduce into the container, with the liquid fuel, a volume of gas greater than the total capacity of said container. When the gas used is a combustible gas such as hydrogen the solubility effect is of little consequence as long as enough of it is used so that there will be a total pressure in the container greater. than atmospheric as the liquid is being expelled. I usually prefer to use combustible or inert gases that are substantially free from free oxygen in charging the fuel containers. I introduce enough of said gas initially so that there is sufficient pressure to expel substantially all of the liquid fuel from the container upon opening the outlet for removing said liquid.
Obviously, as the liquid fuel is substantially all expelled the gas-vapor mixture remaining will have a composition varying according to the kind of liquidfuel used but depending also upon the vapor pressure of said fuel. Knowledge of the vapor pressure or the dew point data for the various liquid fuels is an aid in determining the amount of gas that must remain as the fuel container is emptied of its content of liquid fuel. For this reason the dew points of certain liquid fuels are given to show this relation as follows Dew points at atmospheric pressure Temperature Fahrenheit Propane CaHa "a 44 0 Butane C4H1o (normal) +309 Butane C4H1o (iso-) +10.0 Pentane C5H12 (normal) ,+97.0 Hexane CGHM +156. 1 Propylene C3H6 -52. 6 Butylene C4H8 +23. 0 Pentylene CsHio +l04.0 Ethanol CzHsOH +144. 0 Propanol C3H7OH +207.0 Butanol C4H9OH +244.0 Ethyl ether (C2H5)2O +9 6.0 Propyl ether (CaHnzO +l 92.0 But-yl ether (C4H9)2O +2814 Benzene CsHs +l'75.0
More gas is required in charging containers stantially dry. This is less essential using the alcohols than when using the parafiins.
It will be observed that upon recharging containers that have once been filled and emptied as described above, less gas need be introduced than initially because of the gas left in the container.
Here again the amount required depends upon the solubility factor, because the more soluble the gas in the fuel the more of it is discharged with the discharge of said fuel. If the gas has zero solubility in the fuel the amount of make-up gas required should be or approach zero.
The total (absolute) pressure in the charged container, as initially prepared for use, should normally be in excess of 2 to 3 atmospheres. I
prefer to use an amount of gas appreciably in excess of that required to give an initial absolute pressure of 3 atmospheres. By initial pressure is meant not necessarily the pressure exerted within the container at the moment of charging but is inclusive of the pressure obtaining within the container after equilibrium has been reached with relation toprevailing atmospheric temperature conditions. This is true because it is conceivably possible to so cool the gas and liquid fuel prior to charging that the pressure immediately after charging may be very or abnormally low.
Using a non-oxidizing gas such as a gas containing or comprising hydrogen I obtain satisfactory results using it in amounts whereby an initial pressure as high as 90 pounds gage is obtained. Lower or higher pressures may be employed but not appreciably below 45 pounds gage unless the vapor pressure of the liquid fuel charged therewith is appreciable under the prevailing atmospheric temperature conditions, or the conditions under which the fuel is discharged.
The term non-oxidizing gas is used to .distinguish the combustible and most non-combustible gases from oxygen and from gases containing appreciably large amounts of oxygen, such as air. Carbon dioxide is not considered to be an oxidizing gas in this specification or in the claims.
Compressible-gases only are satisfactory for use in my process because I largely depend upon their partial pressures as medium fordischarging the liquid fuel from the containers. Accordingly,
acetylene is not suitable because it can not, with safety, be separately compressed to the extent necessary for charging the containers. Similarly, to accomplish my purpose in the use of gases in the exercise of my process I employ non-soluble gases or those that are not extensively soluble in the liquid fuel.
Reference has been made to the use of a gas but it is understood that the term is inclusive of mixed gases as well as elemental gases and specific gaseous compounds.
Before defining my claims I call attention to the fact that I have found that it is possible to control, within certain limits, the calorific value of the mixture of volatilized liquid fuel and gas by the choice of the gas and the pressure under which the fuel-is confined by said gas. The greater the pressure the greater the solubility of the gas in the liquid fuel and the more of the gas is discharged in solution in said fuel. In this manner the buming. properties of a vaporized liquid fuel can be varied. For example, when using propane or butane, increasing the pressure and using hydrogen or hydrogen and ethylene, the effect is to produce a' gas, after vaporization of the discharged liquid fuel, that, in mixtures with air has a greater rate of flame propagation than a similar mixture made when the liquid fuel is confined under carbon dioxide, nitrogen, carbon monoxide, or mixtures of them.
I also find that ethylene, propane, propylene, butane, butylene and mixtures of them are very soluble in alcohols, ethers, mixed ethers and mixtures of one or more alcohol with an'ether. The importance of this discovery is that I am enabled to use the former materials along with the latter and employ only a minimum amount of other gaseous material, in fact under ordinary conditions when the temperature is not low, no additional gas is necessary for causing the liquid contents ofthe confining container to be discharged.
One of the fields of application of my process I believe is in the supplying of combustible gas by city gas companies tocustomers in outlying district's, namely those beyond reach of the gas mains. By using city gas or water gas as the pressure-confining fluid, the advantages derived are:
-(a) The burning characteristics of the vaporized fuel are improved.
(b') The gas used with the liquid fuel is actu ally sold since the price is based upon the available heat energy.
(c) Liquids not usually considered to be satisfactory for the purpose may be successfully used.
factorily used, a gaseous fuel can be produced that has a lower air requirement than some of the liquid hydro-carbons now commonly used; this permits more satisfaction in burning the gaseous fuel in various appliances.
Having described my invention so that one skilled in the art can practice it, I claim:
1. A fluid-fuel package, comprising a manually portable fuel-dispensing reservoir having means communicating with substantially the bottom of said reservoir for drawing olf liquid fuel therefrom, said reservoir confining a readily volatilizable, liquid fuel having a vapor pressure less than 1 atmosphere at 10 F., and a definite amount of a compressed non-oxidizing expelling gas, which is.substantially insoluble in the said liquid fuel, confined above said fuel but in contact with it, said definite amount of gas having a volume, when expanded to atmospheric pressure greater than the volume of said reservoir being sufiicient only to provide an initial pressure in the charged reservoir of about 45 to 90 pounds gage at 10 F.
2. A fluid-fuel package, comprising a manually portable fuel-dispensing reservoir having means communicating with substantially the bottom of said reservoir for drawing off liquid fuel therefrom, said reservoir confining a readily volatilizable, liquid, hydrocarbon fuel having a vapor pressure less than that of propane, and a definite amount of a compressed mixed expelling gas, which is substantially insoluble in the said liquid fuel, confined above but in contact with said liquid fuel, said gas including hydrogen but being substantially free from oxygen, said definite amount of gas having a volume greater than that of said reservoir when said gas is expanded to atmospheric pressure, being suflicient only to pro- ,wherein the expelling gas is substantially free from moisture.
WILLIAM w. ODELI...