US1769790A - Manufacture of useful products from mineral oils - Google Patents

Description

july n, ma. W. G. LEMON www@ MANUFACTURE OF USEFUL PRODUCTS FROM MINERAL OILS Filed May 1, 192e 2 sheets-sheet 1 July l, 1930. w. G. LEAMON 1,769,790

MANUFACTURE OF USEFUL PRODUCTS FROM MINERAL OILS Filed May l, 1926 A2 Sheets-Sheet 2 Patented July 1, 1,930

PATENT OFFICE WILLIAM G. LnAMoN, or NEWARK, onIo MANUFACTURE 0F USEFUL PRODUCTS FROM MINERAL OILS Application led May 1, 1926. 4Serial No. 106,072.

This invention relates to manufacture of useful products from mineral oils; and more particularly it relates to methods of and apparatus for producing motor fuel by thermal decomposition of mineral oil materials, wherein the temperature of decomposition or cracking is controlled in accordance with variations in rate of output of a product of the process .other than the main product sought, ywith resultant increase in accuracy of control and general smoothness of operation.

' It has become well established renery practice to decompose oils composedbf large molecules for the purpose of producing therefrom oils composed of smaller molecules, the object usually being to produce as large a percentage as possible of such smaller-molecule products as are adapted for use as fuel for internal combustion engines. The fracturing or decomposing energy in all these processes is obtained b y raising the temperature, and the processes of thus producing motor fuel have been termed cracking processes. Determination of the optimum temperature to which the oil should be raised in order to produce the greatest percentage of motor fuel has been a serious practical operating problem, because the optimum tem erature for cracking one oil or mixture o oils may vary considerably from that of another. It has therefore been very desirable to devise some means of automatically 'arriving at a practical operating temperature for any given oil and automatically maintaining same.

This invention has to do with a process or method of, and apparatus for, automatically determining and maintaining the correct temperature for the oil being treated in the cracking system at any given time, and automatically varying said temperature to meet the requirements of the varying characteristics4 of tlie oils undergoing cracking.v In all cracking systems/a zone exists, usually the zone o fmaximum temperature, in which the large-molecule oils are undergoing rapid decomposition. This zone unay be properly designated as the reaction zone of the system. In the process of disrupting or breaking down the large molecules it is impossible to confine the size of all the fragments within specified limits. The resultant product always consists of a mixture of fragments of all sizes ranging down to and including the smallest to which the elements of the original oil are capable of being reduced., In fact, in any. given system at any given temperature an ap-I proximate equilibrium is reached wherein the quantity of fragments of one size bears a somewhat definite ratio or proportion to the quantity of fragments of another size. This makes possible in any given cracking system the indirect measurement of the quantity of one product of the process by interpretation from the direct measurement of the quantity of another product. Thus,l it has been found by this applicant that for a given cracking system, measurement of the amount of fixed gases produced from a given quantity of originalv oil during cracking is a good index of-the amount of motor fuel distillate produced, and 'in the practice of the present invention advantage is taken of this fact to achieve accurate and most desirably automatic control of temperatures in cracking operations, in a relatively simple manner.

It has been found possible, in accordance with the invention, to control the conditions of operation of a cracking system quite as effectively by observing and controlling the rate of gas production as by observing and controlling the quantity of motor fuel distillate production. Furthermore, inasmuch as it is desirable to operate the cracking system under lconditions such that the yield of motor fuel distillate bears the largest possible ratio to the amount of fixed gas produced, it has been found highly desirable to control the cracking temperature directly by utilizing the rate of fixed gas production to effect suchA control. It has also been found that the ratio of the amountof motor fuel to the amount of fixed gas produced under any given temperature conditions varies considerably with the cracking system employed but only slightly with the character of the oil being cracked. Therefore, if a given cracking system be operated at such a temperature that, for a definite rate of feed of oil to be cracked, fixed gas is produced at a definite rate, a definite rate of production of oil of proper volatility for use as motor fuel will also result; and if the rate of production of fixed gas is adjusted to yield the maximum ratio of quantity of motor fuel distillate to the quantit of fixed gas for some particular type of oi, said ratio will be maintained approximately maximum over a very wide range of varying composition of original oil, assuming the rate of production of fixed gas to be kept the same, although the temperature required to maintain said ratio will vary widely. The ratio of fixed gas production to cracking stock may vary considerably, but, by way of example, it may be stated that good results have been obtained where the weight of fixed gases ran about 13% of the weight of cracking stock used, with a correspondin cracking temperature of 540o to 565o C. he great advantage of controlling the temperature of a cracking system in this way can readily be seen from the following consideration. If the temperature of the cracking system is lower than that required to produce the maximum ratio of motor fuel distillate to fixed gas then the yield of motor fuel per cycle is reduced, the number of cycles required to attain any given result is increased, the amount of fuel and other operating expense is thereby increased, and the production from any given unit is decreased. If the temperature of the cracking system is maintained above the temperature which gives a maximum ratio of quantity of motor fuel distillate to the quantity of fixed gas, then a portion of the oil that might properly be made into motor fuel is further decomposed to fixed as which has a lower value to the refiner. oreover an increased decomposition of the smaller molecules to fixed gas also results in an increased quantity of fixed carbon which is highly disadvantageous.

In the practice of the invention, therefore, the rate at which fixed gas is produced in the cracking operation is made use of, through appropriate means, to effect regulation of the cracking operation itself by controlling the principal variable factor involved in cracking. an oil,` namely, the temperature. The utilization of the rate of fixed gas roduction to accomplish this end may be e ected 1n various different ways, and in its broader aspects the invention is not restricted to any particular way.

For the sake of a concrete illustrative example by means of which the principles of the invention can be further explained, a typical apparatus installation which embodies .1n practical form the principles of the invention and by which the method of the invention can be practiced to ood advantage will now'be described. In t e accompanying drawings, Fig. 1 is a more or less schematic showing of such typical installation in side elevation; Fig. 2 is a similar showing but with more details of the specific control mechanism employed; and Fig. 3 illustrates details of mechanism whereby the desired temperature control 1s effected in a somewhat different manner. In both Figs. 2 and 3, the showing 0f parts of the cracking system has been simplified in some respects.

'In the typical example here illustrated, regulation of the cracking temperature is attained by causing the flow of the fixed gas, or a proportional part of it, leaving the condenser system, to produce a differential pressure on mechanical actuating means which, in turn, upon suitable variation in the pressure corresponding to change in rate of fixed gas production, acts either to increase or diminish the rate of supply of fuel to the furnace by which the cracking zone is heated (Figs. 1 and 2), or, if the fuel supply be maintained constant, to increase or diminish the rate at which theoil to be cracked is fed to the cracking zone (Fig. 3) In either case the temperature in the cracking zone is thereb adjusted `as may be necessary to restore tlie rate of fixed gas production to the predeterminednormal'selected beforehand as desirable.

The crackin system illustrated here by way of examp e only, and not because the invention is in any sense limited thereto, is adapted for vapor phase cracking andcomprises a pipe still heater 10, in coil 11 of which mineral oil cracking stock is heated to a temperature suiiciently high to vaporize a substantial part thereof and is then delivered into a separator 12 where heavy tarry constituents drop out, the oil vapors passing thence to a second coil 13 of the heater through which they pass at highlvelocity and attain just before leaving said coil a temperature vslightly above the cracking temperature which it is desired shall prevail in the succeeding cracking operation proper. The hot va ors then pass into cracking chamber 14, which in this particular instance is maintained at the desired cracking temperature by the heat contained in the entering vapors. This chamber may desirably be filled with adsorptive contact material effective to promote the cracking reaction. Said vapors travel slowly through the chamber and undergo extensive cracking therein. The cracked vapors are then led through heat exchanger 15 and fractionating column 16 where high-boiling constituents are liquefied and led thence to tank 17. The persisting vapors are led from the top of column 16 to a condensing and separating system 18, 19, (indicated generally at C in Figs. 2 and 3), where a liquid motor fuel distillate is recovered, part ofwhich is returned by pump 2O to the top of column 16 to serve as the reflux therefor, and the remainder gging to storage.

The gases leaving the condensing and sep- -arating system, or a known proportion thereof, consisting principally of fixed gas but carrying a small percentage of very low boiling constituents recoverable as hereinafter explained but uncondensable under the conditions prevailing in the condensing and separating system aforesaid, are now caused to pass through a metering appliance @,a Venturi meter in the case illustrated, which transmits to a sensitive control device 21 through appropriate connections 22, differential pressures in the gas line G pro ortional to the rate of gas flow therethroug Control device 21, which functions in a manner to be presently described, has electrical actuating connections 23 to a solenoid valve R in the fuel oil line'24 feeding the burners which lire the heater 10.` An auxiliary controlling device 25, electrically connected to said valve Rand to pyrometer v26 at the eX- isting point of the vapors from heater coil 13, provides supplemental control means for use in starting up and controlling conditions the heater furnace.

may enter the system through line 29 and- -go to tank 17 from which it may be drawn,

luntil the Whole system is working normally.l

4After passing through the metering appliance o, the gases may o to a gasoline recovery plant 27 Where a further small quantity of low-boiling hydrocarbons utilizable as motor fuel may be liquefied, by compression for example, and the stripped or fixed gas may be led through line 28 to be burned in The oil to bev cracked together with heavy condensate from 15 and 16, and forced by pump 30 via line 31 through heatexchanger 15 to coil 11 o-f the heater.A A by-pass connection 32, governed by a sole` noid-operated valve 33, affords means for cutting out'the heat exchanger when temperatureconditions in separator 12, as indicated by pyrometer 34, render this desirable.

A To this end control device 35 is electrically connected to said pyrometer and to valve 33,l

as shown'. A solenoid valve 36 may be provided in resi'duum line '37 going from separator 12, and another, 38, in cracker stock supply line 29. y These as 'Well as numerous4 other details hereinabove referred to are not essential to apparatus embodying the principles of the present invention and are referred to here merely for the sake of completeness in describing the particular form of apparatus here illustrated.

Returning now to the subject matter with which the invention is more especially concerned, and referring more particularly to Fig. 2, the differential pressure produced by -the flow of gas through the metering, appliance 'v is communicated to opposite sides' of a diaphragm D .Which operates a lever L -Which in' turn trips an electric switch S.

This switch closesor opens an electric circuit for operation of the solenoid-valve R on the fuel line to the furnace ofthe cracking systhe diaphragm moves to a position such that the switch S is closed and the valve R is opened, thereby admitting more fuel to the furnace and bringing about an increase in temperature. The differential pressure at which this operation is effected is adjustable by means of the counterweight W. When the rate of How of gas reaches an amount which produces a differential pressure through the Venturi tube in excess of the predetermined amount, the diaphragm moves in the opposite direction causing the circuit to be broken by the sWitcl1`S and the valve R in the fuel line is closed, thereby effecting a reduction in temperature.

Another practical application, illustrated in Fig. 3, is to install the solenoid valve R in the cracker feed line 31 to the heater coils so that, as already stated, thereduction in temperature may be effected by passing more cracker feed oil through the heater coils and the increase in temperature is eected by passing less.- Connecting the valve R in the by-pass 39 permits of cutting out the automatic control and adjusting the feed man-- ually when starting up and until the system is operating normally.

It is to be understood, of course, that the scope of the invention is not limited to employment of the specic types of apparatus escribed, Wide variation being possible in the form and operation of apparatus used to effectthe desired control in accordance with the principles of the invention. Any suitable type of flow meter may be used. For instance, a Pitot tube or orifice platermight be used instead of a Venturi tube. Many modiications of differential gauge could be provided and the said differential gauge might be made to operatethe valves or regulators directly instead of through an electric circuit. The regulation of temperature might,

scribed, some other property or. characteristie of the gases, capable of producing an effect variable4 With the rate of gas produc' tion, vcan be made use of in anl analogous manj ner. Thus the resistance and radiation thermometer principle, for example, could be employed for control of the devices governing the fuel supply or oil feed supply.' The differential pressure control has given excellent satisfaction in practice, however, and is deemed an important feature of the invenlao tion in its more specific aspects.

What is claimed is:

1. In the conversion of mineral oil into lower-boiling products, the process -which comprises thermally decomposing mineral oil in a suitable reaction zone into condens- Vable products and fixed gas, condensing a liquid product from the mixture, 'obtaining from the remaining uncondensed products a quantitative indication of the rate of fixed gas production, and upon variation in such rate from a predetermined Vdesired normal adjusting the temperature of the reaction zone to vrestore the rate approximately to such normal.

2. In the conversion of mineral oil into lower-boiling products, the process which comprises cracking mineral oil ina suitable reaction zone to produce condensable products and fixed gas, supplying cracking stock to said reaction zone at a predetermined approximately constant rate, condensing a liquid product from the vapors and gas leaving said reaction zone, obtaining from the remaining uncondensed products a quantitative indication of the rate of fixed gas production, and, upon variation in such rate from the normal required to maintain substantially constant a predetermined desired ratio between the production of fixed gas and the amount of cracking stock supplied to said reaction zone, adjusting the temperature of the reaction zone to restore the rate of gas production substantially to such normal. 3. In the conversion of mineral oil into lower-boiling products, the process which comprises cracking mineral oil in a suitable reaction zone to produce condensable products and fixed gas, and utilizing variation in the rate of fixed gas production to control the temperature of the reaction zone.

4. In the treatment of mineral oils to ob tain lower-boiling products therefrom, the process which comprises heating mineral oil to cracking temperature to evolve therefrom a mixture of condensable vapor and fixed gas, condensing a desired product from the mixture, and utilizing a quantitative measurement of the residual gas to regulate the heating operation and thereby to maintain the rate of production of vfixed gas substantially at a predetermined value.

5. In the treatment of mineral oils to obtain lower-boiling products therefrom, the process defined in claim 4, further characterized by the fact that differential pressure variations, due to change in velocity of the gas fiow in a given gas line, are utilized to effect the desired control.

6. In the conversion of mineral oil into lower-boiling products, the process which comprises cracking oil by suitable heat treatment, vcondensing a motor fuel distillate from y the cracked products, leading away and metering the` remaining gas, and increasing or decreasing the cracking temperature according as the metering indicates a decrease or increase of fixed gas production with respect to a predetermined normal rate corresponding to a desired ratio between production of motor fuel distillate and production of fixed gas in said heat treatment.

7. Apparatus for thermal decomposition of mineral oil comprising, in combination, a suitably heated cracking chamber, means for regulating the heating of said chamber, electric circuit means arranged to actuate said regulating means, means for condensing and separating condensable products from the vapors and gases issuing from said cracking chamber, a flow meter through which fixed gas from such condensingr and separating means may flow, a differential pressure gauge arranged to be affected by differential pressure produced by fiow of gas through said meter, switch means in said electric circuit means and arranged to be actuated by said pressure gauge, upon predetermined variation in. flow of gas through said meter, to close the circuit and cause operation of said regulating means.

8. In an oil-cracking system, the combination, with a cracking chamber, means for controlling the temperature therein, condensing and separating means into which cracked products pass from said cracking chamber, and a pipe line for conducting fixed gas away from said condensing and separating means, of a metering appliance in said line, and actuating connections between said metering appliance and such temperature-controlling means whereby the latter is automatically actuated to increase or decrease the temperature in said cracking chamber according as the fiow of fixed gas through said line falls below or rises above a predetermined rate. Y 9. Apparatus for thermal decomposition of mineral oil comprising, in combination, a converting chamber providing a reaction zone, means for heating the saine, means for supplying oil to said chamber, means for sep-. arating condensate from fixed gas contained in the products leaving saidA chamber, means for measuring said fixed' gas flow, means for varying the amount of heat supplied to said reaction zone, and means for transmitting movement of said measuring means to said heat supplying means, whereby a quantitative indication is obtained of the flow `of fixed gases from such separating means and the temperature in said reacting means is controlled by the rate of production of fixed gases.

In testimony whereof I hereunto affix my signature.

WILLIAM G. LEAMON.

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