US3396207A

US3396207A - Production of acetylene by thermal cracking of hydrocarbons

Info

Publication number: US3396207A
Application number: US95678A
Authority: US
Inventors: Bartholome Ernst; Lehrer Erwin; Schierwater Friedrich Wilhelm
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1957-08-03
Filing date: 1961-03-14
Publication date: 1968-08-06
Anticipated expiration: 1985-08-06
Also published as: CH391689A; DE1051845B

Description

PRODUCTION OF ACETYLENE BY THERMAL CRACKING OF HYDROCARBONS Filed March 14, 1961 FIG! INVENTOR2 ERNST BARTHOLOME ERWIN LEHRER FRIEg RICH W. SCHIERWATER ATT'YS United States Patent 2 Claims. Ci. 260-679) This application is a continuation-in-part of our application Ser. N0. 748,809, filed July 16, 1958 (now abandoned).

This invention relates to improvements in the production of acetylene by the thermal cracking of hydrocarbons.

It is known to produce acetylene by partial oxidation of gaseous or vaporizable hydrocarbons with oxygen by preheating the reactants either jointly or, preferably, separately, supplying the mixture to the reaction chamber, reacting it in a fiame and then rapidly cooling the reaction gases, cooling being advantageously accomplished by spraying water into the reaction gases.

In order to obtain the highest possible yield of acetylene, it is necessary to quench the reaction after a period which is defined as exactly as possible and which is determined by the preheating temperature of the gases, the mixing ratio between hydrocarbon and oxygen and the shape and dimensions of the reaction apparatus.

In apparatus of commercial scale the amount of heat to be withdrawn is quite considerable. The water serving for the quenching has therefore to be dispersed as finely as possible in order to provide sufiicient surface for the transfer of heat from the gas to be quenched to the water.

A great disadvantage of this measure is that it is impossible to impart to drops of Water sprayed from an atomizer the high speed necessary to penetrate into a swiftly moving stream of gas. The effect is not improved by raising the water pressure, since in this case the volume of the individual droplets is reduced by reason of the finer dispersion. This problem naturally becomes especially acute when the dimensions of the apparatus are increased and when high gas speeds are used.

One object of our invention is to provide a process for producing cracking gas with a high content of acetylene.

A further object of our invention is to achieve uniform quenching of the cracking gas.

These and other objects are achieved by introducing part of the water needed to quench the hot gas in a finely divided form through a plurality of outlet openings (atomizer nozzles) into the gas stream, thus cooling the border region of the gas stream and surrounding the gas stream with droplets of water. The rest of the water is introduced in the form of undivided jets through a plurality of outlet openings into the gas stream in order to uniformly cool the gas stream. These jets have varying depths of penetration and when the desired depth of penetration is reached the jet is split up into fine droplets. We prefer to use apparatus in which the pressure of the water prior to the outlet openings of the water nozzles p the dynamic pressure of the gas in the cracking chamber p the depth of penetration of the undivided water jets a and the diameter of the undivided jets d are dependent upon one another in a clearly defined manner, namely in such a Way that lies between 1 and 15.

Patented Aug. 6, 1968 "ice By working with jets having varying depth of penetration it is possible to cool the cracking gas uniformly and to ensure that there is no section of the gas stream which is not reached by the cooling water. We prefer to arrange the nozzles on a level with one another so that the gas stream is cooled as uniformly as possible.

The desired greater depth of penetration a may be achieved by increasing the diameter d of the water jet, which in general depends on the size of the outlet opening for the water jet, and/ or by increasing the water pressure p prior to the outlet opening. The dispersion of the water jets takes place by the kinetic energy of the gas stream to be quenched itself, which can be measured by the dynamic pressure 1 The dynamic pressure p is known to be half the product of the density of the gas and the square of its linear speed.

The nature of the subject invention may readily be understood by reference to the accompanying drawing in which FIG. 1 diagrammatically represents a longitudinal cross-section of the apparatus of the present invention, and FIG. 2 is a lateral cross-section of the subject apparatus.

Referring to FIG. 1, a mixture of hydrocarbon and oxygen passes from chamber 1 through openings 2 of distributor block 3 into a reaction chamber 4 which is defined by wall 5. The cooling water is sprayed from a plurality of nozzles 6 arranged annularly around the outlet of the reaction chamber and contacts the stream of reaction gas in the form of fine droplets. In the subject apparatus undivided water jets 9 are introduced laterally into the stream of reaction gas through

nozzles

7 and 8. The water is split up into droplets by the dynamic pressure of the gas.

We prefer to arrange a plurality of outlet openings annularly around the stream of gas to be quenched, at right angles thereto and on a level with one another as is shown in FIG. 2.

The jets of Water are preferably introduced at an angle to the flow of gas and preferably perpendicular thereto. By using jets having different depths of penetration those sectors of the gas stream which are not covered by one group of jets of the same depth of penetration are covered by jets of another group with a different depth of penetration, and the total amount of Water supplied is thus uniformly distributed over the entire cross-section.

Since it is difficult to "achieve dissipation of an undivided jet at the border of a gas stream, we quench the border region of the gas stream by the additional spraying of water in the form of fine droplets. With a suflicient amount of this finely divided water and with a uniform arrangement of outlet openings for this water around the gas stream, it is possible for the gas to be completely surrounded by an envelope of finely divided water. All these effects increase the yield of acetylene because no fraction of the gas stream can escape the action of the water.

The process according to the present invention is not only applicable to the production of acetylene by partial oxidation of hydrocarbons, but also to methods in which the energy for the cracking of the hydrocarbons to acetylene is sup lied from other thermal sources.

The following examples will further illustrate this invention, but the invention is not restricted to these examples.

Example 1 1,600 cubic meters (S.T.P.) per hour of methane are heated to a temperature of 640 C. in a preheater and 890 cubic meters (S.T.P) per hour of oxygen are also heated to a temperature of 640 C. in a second preheater. The hot gases are supplied to a mixing apparatus. After thorough mixing has been completed, the mixture enters through parallel channels into a reaction chamber in 3 which the methane reacts with the oxygen with the formation of a flame.

The diameter of the stream of reaction gas at the outlet from the reaction chamber is 265 millimeters and its dynamic pressure 17 7.3 X atmospheres. The reaction gas is cooled with a total of 16 cubic meters per hour of water introduced through 40 atomizer nozzles. A gas mixture is obtained containing 8.05% by volume of acetylene and 2.36 grams per cubic meter of carbon black.

Example 2 The same conditions are used as in Example 1, but undivided water jets are additionally introduced under a pressure p of 1.5 atmospheres gage into the gas stream from 12 nozzles, each having a diameter of 2.8 millimeters. These jets penetrate the gas stream to a depth a of 130 millimeters and the value of (P :P )-(d:a) equals 4.4.

Undivided water jets under a pressure P of 1.2 atmospheres gage are also introduced into the gas stream from 12 further nozzles, each having a diameter of 2 millimeters. The jets from these nozzles penetrate into the spaces between the first 12 additional nozzles described above to a depth a of 70 millimeters. The value of (P :P (dza) amounts to 4.7. A gas mixture is obtained which contains 8.52% by volume of acetylene and 1.77 grams per cubic meter of carbon black.

Example 3 The same conditions as described in Example 1 are used, but undivided water jets are additionally introduced under a pressure P of 3.0 atmospheres gage into the gas stream from 8 nozzles with a diameter d of 4.7 millimeters. These jets penetrate the gas stream to a depth a of 130 and the value of (P :P -.(d:a) is equal to 14.8. Undivided water jets under a pressure P of 1.2 atmospheres gage are also introduced into the gas stream from 12 further nozzles each having a diameter of 2 millimeters. The jets from these nozzles penetrate into the spaces between the first 8 additional nozzles described above to a depth of 70 millimeters. The value of (P :P )-(d:a) is 4.7. A gas mixture is obtained which contains 8.28% by volume of acetylene and 2.0 grams per cubic meter of carbon black.

Example 4 The same conditions as described in Example 1 are used, but undivided water jets are additionally introduced under a pressure P of 1.0 atmosphere gage into the gas stream from nozzles with a diameter d of 1.2 milli- 4 meters. These jets penetrate the gas stream to a depth a of 130 mm. and the value of (P :P )-(d:a) is equal to 1.26. Undivided water jets under a pressure P of 1.2 atmospheres gage are also introduced into the stream from 12 further nozzles each having a. diameter of 2 millimeters.

The jets from these nozzles penetrate into the spaces between the first 20 additional nozzles described above a depth of millimeters. The value of (P :P )-(d:a) is 4.7. A gas mixture is obtained which contains 8.25% by volume of acetylene and 2.05 grams per cubic meter of carbon black.

We claim: 7

1. An improvement in a process for the production of acetylene by the thermal cracking of hydrocarbons wherein said acetylene is rapidly cooled in a quench zone which comprises: passing a current of said acetylene from a cracking zone into said quench zone, and thereafter cooling said acetylene by injecting a plurality of compact jets of liquid into said current, said jets of liquid being supplied laterally to said current of acetylene under varying pressure heads to insure that substantially an entire crosssection of the current is contacted by said liquid, whereby said jets of liquid are split up into fine droplets by the current and the acetylene is thereby rapidly cooled the dynamic pressure p of the gas stream, the depth of penetration a of the water into the gas stream, the diameter d of the jets, and the water pressure p prior to the outlet openings being selected so that the numerical values of (p zp -=(a':a) lie between 1 and 15.

2. An improved process as in claim 1 wherein atomized water is also passed into the quench zone so that the current of acetylene is surrounded by droplets of water.

References Cited UNITED STATES PATENTS 2,998,464 8/ 1961 Burleson et a1 260679 2,998,465 8/ 1961 Drummond et al 260679 2,978,521 4/1961 Braconier et al 260679 2,533,457 12/1950 Hasche 23277 2,765,358 10/ 1956 Pichler et a1 260679 2,719,184 9/ 1955 Kosbahn et al 260679 FOREIGN PATENTS 207,827 2/ 1960 Austria. 831,105 3/1960 Great Britain.

DELBERT E. GANTZ, Primary Examiner.

J. D. MYERS, Assistant Examiner.

Claims

1. AN IMPROVEMENT IN A PROCESS FOR THE PRODUCTION OF ACETYLENE BY THE THERMAL CRACKING OF HYDROCARBONS WHEREIN SAID ACETYLENE IS RAPIDLY COOLED IN A QUENCH ZONE WHICH COMPRISES: PASSING A CURRENT OF SAID ACETYLENE FROM A CRACKING ZONE INTO SAID QUENCH ZONE, AND THEREAFTER COOLING SAID ACETYLENE BY INJECTING A PLURALITY OF COMPACT JETS OF LIQUID INTO SAID CURRENT, SAID JETS OF LIQUID BEING SUPPLIED LATERALLY TO SAID CURRENT OF ACETYLENE UNDER VARYING PRESSURE HEADS TO INSURE THAT SUBSTANTIALLY AN ENTIRE CROSSSECTION OF THE CURRENT IS CONTACTED BY SAID LIQUID, WHEREBY SAID JETS OF LIQUID ARE SPLIT UP INTO FINE DROPLETS BY THE CURRENT AND THE ACETYLENE IS THEREBY RAPIDLY COOLED THE DYNAMIC PRESSURE PD OF THE GAS STREA, THE DEPTH OF PENETRATION A OF THE WATER INTO THE GAS STREAM, THE DIAMETER D OF THE JETS, AND THE WATER PRESSURE PW PRIOR TO THE OUTLET OPENINGS BEING SELECTED SO THAT THE NUMERICAL VALUES OF (PW:PD).(D:A) LIE BETWEEN 1 AND 15.