US2217250A - Production of oil gas - Google Patents

Description

Patented Oct. 8, 1940 UNITED STATES PATENT OFFICE PRODUCTION OF OIL GAS No Drawing. Application November 4, 1938, Serial No. 238,929

4 Claims.

This invention relat s to the production of oil gas; and it comprises an improvement in methods of making oil gas in intermittently heated hot checkerwork chambers, the improvement consisting in feeding petroleum oil into the chamber at a diminishing rate generally corresponding with the drop in temperature during the run, the rate of oil introduction being so controlled as to maintain an efiluent gas of constant character, constancy being usually ascertained by observation of the density of the eiiluent gas; the gas being then freed of non-gaseous components and re-treated in a checker under like condition, that is, with a diminishing feed as the temperature of the checker drops; all as more fully hereinafter set forth and as claimed.

In the commercial production of gas for heating and lighting from low grade petroleum oils, such as gas oil, fuel oil, etc., it is customary to perform the gasification in intermittently heated hot checker chambers. Heating is effected by burning oil or gas in the checker until it reaches a high temperature, say 1600 to 2000 F. Oil is then fed into the heated checker chamber as long as there is enough heat to effect a substantial amount of gasification. The character of gas produced during the run is not constant, but varies. Storage and averaging are required.

Not all the oil can be converted into gas, there being an incidental production of by-products. These by-products help defray the cost of operation and it is an object to recover them in salable form. In certain prior Patents Nos. 1,409,709 and 1,466,648, whereon the present invention is in some aspects an improvement, I have discussed the formation and recovery of by-products in making oil gas.

In a general way it may be said that oil heated to any very high temperature tends to give a great volume of gas of low heating value, while at low gasification temperatures the converse is true. At very high temperatures there is a tendency toward the production of hydrogen, aroo matic oils, tar and pitch, while at low temperatures the side products are more of the nature of gasoline and kerosene and fuel oil. In making oil gas in a hot checker work, both types of action occur; the gas and by-products are of both types.

All these things are well recognized in the art. It is also recognized that it is diflicult to obtain a standard city gas of, say, 500 to 600 B. t. u. in

4 a single operation. Sometimes the difliculty is 55 met by making a high temperature lean gas and a low temperature rich gas as separate operations and mixing the two.

I have discovered that in gasifying oil in a checker a much more constant product can be obtained throughout a run by feeding oil at a 5 diminishing rate corresponding roughly to the drop in temperature in the checker and correlating the feed with the character of the gas produced. The effort is to so correlate the feed as -to obtain an eiliuent gas of constant density. 10

Operating in this way it is easy to make a gas of constant composition during a run and to obtain the same character of gas in different runs. The operation may be so conducted, for example, as to give a gas of, say, 0.74 per cent apparent 15 density as compared withatmospheric air at 60 F. As the gas leaves the checker it carries condensable matter with it and comparative observation of density must be made after cooling to the ordinary temperature.

Gas made in the checker in the described way is unduly high in fuel value and it is often worth while to polymerize the ethylene, propylene and butylenes in part and remove a condensate of light oils. Or the olefins may be utilized for 25 chemical purposes; in the manufacture of chlorhydrins, chlorides, glycols, etc. 7

It is of course feasible to dilute down the rich gas with lean gas, with or without polymerizing treatments.

But I find the best results are obtained by making a rich gas as described, removing condensable oils, with or without some polymerization to add to their amount, and then re-forming and standardizing the gas by passage through an- 35 other checker fired at intervals. As before, the feed through the checker in a run is gradually lessened as the heat drops and is controlled by the observed density of the issuing gas, the density being kept constant. Volatiles accompanying the re-formed gas are condensed and collected.

With a double operation of this type a high yield of commercial gas of standard type can be secured, with an abundant production of high grade by-products, in tolerably direct operation; that .is, without the necessity of storage and blending of great volumes of gas.

A good yield of condensable oil'is obtained at each stage and there is a good utilization-of the 5 low grade oil treated in the yield of gas and of by-products taken together.

By utilization of what may be termed a "tapered feed, overheating and underheating are obviated and a constant efliuent of accurately predetermined character is obtained in each operation- While the invention is based upon the fact that the continually changing temperature conditions within an intermitttently heated chamber should be compensated by regulation of the input 'of petroleum hydrocarbons, it is found that a simple pyrometric determination of the temperature at any point within the chamber is not an adequate means of control. The conditions within a preheated checkerwork are complex and the surface temperature of the brickwork at any instant is onlyroughly related to the rate and character of the decomposition of the oil which takes place. Other factors such as the ratio of refractory surface to the volume of the passing hydrocarbon, the conductivity of the refractory, the total amount of heat stored in the refractory and the like, affect the heat transfer to the gas and thus affect the composition of the resultant products. On the other hand, by correlating the input of the hydrocarbon with a property of the efiluent gas such as the density, all the complicated factors are compensated for at once and an eflluent of substantially constant composition may be readily obtained. This is done in the present invention.

In carrying out the method of my invention, the checkerwork or other form of refractory contact surface is best preheated to a temperature above that at which a gas and by-products of the desired composition are produced by the ordinary method. If, for example, products of the 1 character ordinarily obtained in the intermedi- ;85

ate temperature range of 1200 to 1600 F., as described above, are desired, the initial temperature of the refractory contact surface should be substantially higher than 1600" F. The upper limit of temperatures for the production of gas and by-products of any desired composition is not critical except as limited by practical operating considerations and apparatus size. With higher temperatures longer production cycles are obtainable and the character of the products obtained can be regulated by regulating the rate of oil feed. For example, when products of the character produced in the intermediate temperature range are desired, a convenient initial op.- erating temperature is about 1650 F. However, higher initial temperatures such as 1800 to 2000" F. may be used and the same type of products produced by using an increased rate of oil feed. V

In practical operation, after the checker has been heated by internal firing, oil is fed in and the feed continued through the run at a diminishing rate as described. After firing the checker is left full of hot products of combustion and these mix with and dilute the first portions of gas made. .This must be allowed for in taking the density in the first stage.

The character of the gas made and of the byproducts obtained by controlling the density of the eflluent at difierent values varies. ample, the specific gravity is controlled at values on the order of 0.4 (air=1 at 60 F., atmos: pheric pressure), large volumes of gas of relativelylow heating value are produced with but little yield of condensable by-products, say about one-half gallon of 400 F. end-point liquids per 1000 cubic feet of gas. n the other hand at a relatively high specific gravity such as 0.83 a yield as high as four gallons of 400 E. P. liquid per 1000 cubic feet of gas may be obtained together with a smaller volume of gas of higher If, for exheating value. Good yields of gas of high heating value and of valuable by-products are obtainable, for example, when the specific gravity .is controlled at 0.74 to 0.75 or 0.78 to 0.79. In

accordance with common usage in this art, the terms density and specific gravity are used interchangeably herein; and in both cases, numerical values are based on air (at standard conditions) =1.

In a typical operation according to the method of my present invention, a checkerwork of refractory brick was heated to a temperature of about 1650 F. by internal firing. Oil was then sprayed into the chamber at a rate sufiicient to produce an eiiluent gas having a density about 0.74 of that of air at the ordinary temperature and pressure. The rate of oil feed was progressively decreased to maintain the density of the efliuent substantially constant. At the end of the run the rate of oil feed had been reduced to about one-third that at the beginning and the temperature of the refractory checkerwork had dropped about 320 F. to a final temperature of about 1330 F.

In commercial operation the method of my invention may be utilized repeatedly in a sin gle manufacturing process, in conjunction with various supplemental operations in order to effect best results. For example, in a typical complete gas making system producing a city gas of 570 B. t. u. per cubic foot together with byproducts as gasoline, benzol, higher olefines, tar and lampblack, the manufacturing process may involve the following steps:

(I) Petroleum oil is introduced into a preheated refractory checkerwork with a properly adjusted density of the eiiiuent and a properly tapered oil input to produce in each run a substantially uniform quality of effluent gas of high heat value (1000 to 1500 B. t. u. per cubic foot as desired) which contains from 5 to 20 per cent of olefines including propylenes and butylenes together with substantial quantities of gasoline and benzol, the residuum being a tar containing more or less of the original oil. The efliuent is passed through suitable condensing apparatus for removal of tar, gasoline and benzol. The gas, now substantially free of readily condensable hydrocarbons may then be treated by any suitable polymerization process such as catalytic or thermal processes to convert the propylene and butylenes into polymer gasoline. The residual gas which is still rather rich (900-1400 B. t. u. per cubic foot) is then passed on to the next step.

(H) In this step the gas maybe re-formed by being introduced into a second refractory checker-work heated to a temperature higher than that used in the first step, the purpose being to increase the volume of the gas and reduce the heat value to about 570 B. t. u. per cubic foot. During this step the method of my invention is again applied. The rate of introduction of the hydrocarbons is correlated'with the density of the effluent gas to obtain products of the desired quality throughout the run. The by-products formed during this step may include small amounts of benzol, lampblack and tar. The by-products and gas are condensed and recovered in known ways. .The eiiluent gas is suitable for domestic and industrial supplies.

(III) The residual tar recovered in the first step may be sold as such or processed to produce road oils or the like or it may be used as the raw material for the production of further amounts of gas. In this case the tar may be heated at a rather high temperature to produce a gas having a heat content of say 450 to 500 B. t. u. per cubic foot and this lean gas may be blended with richer gas to produce a city gas. so that the output of the entire gas works will have a heat value of about '70 B. t. u. per cubic foot. In the production of this lean gas the input of tar and the density of the eiliuent gases may again be correlated according to the method of my invention to produce a gas of uniform quality throughout the run.

As illustrative, I cite an operation in which the oil gasified was a typical cracked oil residue of 12 A. P. I. This was run through a hot checker in the way described with the eiliuent density maintained at 0.83. A large yield of liquid hydrocarbon boiling in the gasoline range was obtained. The condensed oils were 70 per cent aromatic. The amount was 3.5 gallons per 1000 cubic feet of 0.83 gas. The gas from this operation was then further cracked in a second generator to produce a resultant gas of 5'70 B. t. u of density approximately 0.4, with an additional yield of liquid hydrocarbons boiling in the gasoline range of 0.75 gallon per thousand cubic feet of 0.83 gas, making a total recovery for both operations of 4.25 gallons of highly aromatic liquid hydrocarbons boiling in the gasoline range. This quantity amounts to 3.05 gallons per thousand cubic feet of 0.4 density final gas.

When the tar resulting from the first operation was gasified to produce additional quantities of domestic or 0.4 density gas, an additional quantity of liquid hydrocarbons boiling in the gasoline range amounting to 0.5 gallon per thousand cubic feet of 0.4 density gas was produced, making a total yield of liquid hydrocarbons boiling in the gasoline range of 2.28 gallons per thousand cubic feet of 0.4 density gas from the reforming and tar cracking operations.

What I claim is:

1. In the production of gas and by-products from petroleum oils by pyrolysis in intermittently heated checkerwork, with removal and collection of the gas formed and recovery of by-products, the improvement which comprises introducing the oil into preheated checkerwork at an initial rate which is regulated to yield a gaseous effluent having a substantial by-product content and having a definite density after removal of condensable by-products therefrom, gradually reducing the oil flow as the checkerwork cools, this reduction in the oil flow being at a rate so con-. trolled as to maintain the density of the gaseous eflluent substantially constant throughout the run after removal of condensable by-products therefrom, removing condensable constituents from the said gaseous efl'luent, introducing the resulting gas into a second preheated checkerwork at an initial rate regulated to yield a gaseous effluent of a different density, and diminishing the rate of gas introduction as the said second checkerwork cools to maintain the density of the gaseous efliuent therefrom substantially constant.

2. The method of claim 1, wherein the said oil flow is so regulated that the density of the gas produced therefrom is maintained between 0.74 and 0.79.

3. The method of claim 1, wherein the checkerwork into which the said oil is introduced is preheated to a temperature above 1600 F., and the run is stopped when the temperature falls to about 1330" F.

4. The method of claim 1, wherein the said condensable constituents removed from the gas