US3399245A

US3399245A - Process and apparatus for partial combustion of hydrocarbons

Info

Publication number: US3399245A
Application number: US526680A
Authority: US
Inventors: Spencer L Knapp
Original assignee: Monsanto Co
Current assignee: Monsanto Co
Priority date: 1966-01-28
Filing date: 1966-01-28
Publication date: 1968-08-27
Anticipated expiration: 1985-08-27
Also published as: FR1509569A; GB1135967A

Description

2 Sheets-Sheet 1 FIG. 3

' 'mwzmok. Spencer L. Knapp ATTORNEY x x x x s. 1.. KNAPP FIG. I

Aug. 27, 1968 PROCESS AND APPARATUS FOR PARTIAL COMBUSTION OF HYDROCARBONS Filed Jan. 28, 1966 PIC-3.2

21 1968 s. L. KNAPP 3,399,245

PROCESS AND APPARATUS FOR PARTIAL COMBUSTION OF HYDROCARBONS Filed Jan. 28, 1966 2 Sheets-Sheet 2 FIG. 4 FIG. 7

FIG.5 F|G.6 F|G.8 FIG.9

FIG. FIG.I2 F|G.l3

INVENTOR.

Spencer L. Knapp ATTORNEY United States Patent 3,399,245 PROCESS AND APPARATUS FOR PARTIAL COMBUSTION 0F HYDROCARBONS Spencer L. Knapp, Texas City, Tex., assignor to Monsanto Company, St. Louis, Mo., a corporation of Delaware Filed Jan. 28, 1966, Ser. No. 526,680 9 Claims. (Cl. 260679) ABSTRACT OF THE DISCLOSURE A process and apparatus for the partial combustion of hydrocarbons to such products as acetylene wherein a mixture of hydrocarbon and oxygen is passed through a gas distributor having means located in the gas distributor tubes for imparting a swirling motion to the gases passing therethrough. Deposition of carbon on the face of the gas distributor is thus reduced.

This invention relates to a process for partial combustion of hydrocarbons and oxygen and to an apparatus therefor.

It is known to prepare acetylene and other products such as ethylene, hydrogen and carbon monoxide by the partial combustion of gaseous or vaporized hydrocarbons and oxygen. In these known processes, a preheated gaseous hydrocarbon and a preheated oxygen-containing gas are reacted in a flame reaction and then cooled as by quenching with water. The apparatus for such a reaction generally includes a mixing chamber wherein the hydrocarbon and oxygen-containing gas are mixed and a reaction chamber. The mixing chamber is connected to the reaction chamber by a plurality of channels which conduct the mixed gases from the mixing chamber to the reaction chamber wherein the combustion reaction occurs as the mixed gases exit from-the channels.

A particular disadvantage of this process is the deposition of carbon on the walls of the reaction chamber, particularly on the wall containing thechannel openings, referred to hereafter as the face of the burner block. These deposits have to be periodically removed in order to continue regular operation of the process.

It is, therefore, an object of the present invention to provide an apparatus and a process for the incomplete combustion of hydrocarbons and oxygen which can be operated continuously without the disadvantage of having to frequently remove carbon deposits.

Another object of the present invention is to provide an apparatus and process for the partial or incomplete combustion of hydrocarbons and oxygen whereby substantially less carbon is deposited on the walls of the reaction chamber than in prior art apparatus and processes. Additional objects will become apparent from the following description of the invention herein disclosed.

These and other objects are accomplished by the present invention which, in one of its embodiments, is an apparatus for the partial or incomplete combustion'of a hydrocarbon and an oxygen-containing gas which comprises a mixing chamber and a reaction chamber, said reaction chamber in open communication with said mixing chamber by means of a plurality of channels, at least one of said channels containing means for imparting a swirling motion to the gases passing from said mixing chamber into said reaction chamber, said means being located more than half the distance from said mixing chamber to said reaction chamber.

In another embodiment, the present invention is a process for the partial combustion of hydrocarbons and oxygen which comprises mixing a hydrocarbon and an oxygen-containing gas in a mixing zone, passing the resulting mixture at elevated temperatures and in the gaseous 3,399,245 Patented Aug. 27, 1968 ICC form to a reaction zone through a plurality of channels wherein the gaseous mixture encounters in at least one of said channels a means for imparting a swirling motion to the gases, said means being located more than half the distance from said mixing zone to said reaction zone, and partially burning said mixture in said reaction zone.

The term swirling motion as used herein refers to a rotational or spiral motion in which the path of the motion does not lie in a single plane and in which the path followed by the motion describes a cone. The term swirlers as used herein refers to the means within the channels for imparting swirling motion.

To further define the present invention, reference is made to the accompanying diagrammatic drawings of different views and embodiments of the present invention. The same reference characters are used in each of the drawings to denote like features of the apparatus of the present invention.

FIGURE 1 is a sectional view of an apparatus used for mixing and reacting hydrocarbons in accordance with the present invention.

FIGURE 2 is a sectional view of a channel connecting the mixing and reacting chambers without any means for imparting swirling motion to the gases passing therethrough.

FIGURE 3 is a sectional view of a channel containing means for imparting a swirling motion to the gases passing therethrough.

FIGURES 4 through 13 are drawings of various embodiments of the means used to impart a swirling motion to the gases exiting from the channels of the apparatus of the present invention.

Referring specifically to FIGURE 1, preheated oxygen or oxygen-containing gas enters mixing chamber 1 through line 2 where it meets and is mixed with a stream of preheated gaseous hydrocarbon introduced through line 3. From mixing chamber 1, the mixed gases pass through -a burner block 4 by means of channels 5. In channels 5, the gases encounter a swirler 6 which imparts a swirling motion to the gases as they exit into the reaction chamber 7 where the mixed gases react in a flame reaction. The reaction chamber 7 is bounded by walls 8 and the face of burner block 4. After leaving the reaction chamber 7, the gases are cooled by quench water 9.

While the apparatus has been pictured in FIGURE 1 as having only three channels in the burner block, it is to be understood that in actual operation the apparatus can have varying numbers of channels. These channels may be of various configurations such as round, square, or rectangular. The channels may also be Venturi-shaped. The channels 5 shown in FIGURE 1 'are usually substantially parallel with one another though some deviation from such parallel alignment may be permitted. Also, the ap paratus does not have to be operated in the position pictured so that any reference herein to such terms as up or down are only relative to the apparatus as shown.

It has been found that means inserted within the burner block channels to provide a swirling motion in accordance with the present invention substantially prevents carbon deposits from forming on either the Walls of the reaction chamber or around the channel exits on the face of the burner block. Further, the motion imparted by the swirlers causes the gases to have a greater angle of expansion than those gases exiting from an unobstructed channel as is illustrated in FIGURES 2 and 3 described below.

FIGURE 2 is a sectional view of a channel 5 within the burner block 4 and shows the angle of expansion 01 of the gases exiting from an unobstructed channel. FIGURE 3 is a sectional view of channel 5 in which a means 6 for imparting swirling motion is located and is intended to show the angle of expansion b of the exiting gases is greater than the angle of expansion a obtained by the corresponding channel without a swirler.

The swirlers encompassed by this invention may have various shapes andconfigurations as long as they impart swirling motion to the gases exiting from the channels. In a particularly useful embodiment of the present invention, the swirler comprises two surfaces of substantially the same size and configuration within a channel, both surfaces being inclined at substantially equal angles of less than 90 with respect to the vertical or longitudinal axis of said channel but being inclined in substantially different directions with respect to one another such that the segments of the two surfaces lying within a transverse .or horizontal plane of said channel are substantially perpendicular to and on opposite sides from one another of a straight line lying within said plane passing through the axis of said channel. The inclined surfaces are preferably flat though they may also be curved either longitudinally or transversely. For optimum results, the edge of the inclined surfaces nearest the walls of the channel, usually referred to as the outer edge, should be substantially contiguous with the wall of the channel. Also, the two inclined surfaces are usually located approximately equidistant from the exit end of the channels.

The above-defined particularly useful embodiment of the swirlers of the present invention is further described and illustrated by FIGURES 4 through 13 which show various shapes that swirlers may take within this embodiment.

FIGURES 4 through 6 are pictorial drawings of a swirler designed in accordance with the above-defined particularly useful embodiment of the present invention. FIGURE 4 is a top view of FIGURE 5 while FIGURE 6 is a view of FIGURE 5 as rotated 45 to the left. The swirler includes two inclined surfaces and 11 each of which, when placed in a channel, will divert the gases downward along the inclined surfaces thereby imparting a swirling motion to the gas exiting from the channel. The angle c represents the angle; the surfaces are inclined with respect to the axis of the channel.

The swirler of FIGURES 4 through 6 may be readily fabricated from sheet metal or other suitable material and inserted into existent burner block channels. For instance, a strip of sheet metal, the end of which has been rounded to fit the inside ofa channel, can be split lengthwise for a small distance than that portion of the strip on each side of the split bent in opposite directions at the desired angle as shown in FIGURES 4 through 6. If desired, the portion of the strip of sheet metal which is not split and bent will form a shaft which may be used to suspend the swirler within the channels. FIGURES 5 and 6 show this shaft cut off immediately above the swirling surfaces 10 and 11.

FIGURES 7 through 9 are pictorial drawings of another swirler designed according to the above-defined particularly useful embodiment of the present invention. FIG- URE 7 is a top view of FIGURE 8 while FIGURE 9 is a view of FIGURE 8 as rotated 45 to the left. This swirler, like that of FIGURES 4 through 6, has two

surfaces

12 and 13 which direct the gas downward and in a swirling motion. This swirler differs from that of FIG- URES 4 through 6 in that the

surfaces

12 and 13 are bent.

The angle at which the inclined surfaces of the swirlers are inclined with respect to the longitudinal axis of the channel, shown in FIGURE 5 as angle 0, for the type of swirlers shown in FIGURES 4 through 6 and 7 through 9 generally is between 15 and 40, and preferably is to 35. The optimum angle will depend on such variables as the gas velocity, the position of the swirler within the channel, and the channel diameter and length. Too great an angle of inclination will result in too large a pressure drop through the channel and is preferably avoided.

The swirlers .of FIGURES 4 through 6 and 7 through 9 are of the type which may be suspended within the channels of existent burner blocks. However, a burner block may be fabricated which has the swirler built into the channels. For example, a burner block may be fabricated by casting a refractory material around ceramic tubes which have swirlers molded within the tubes. The insides of these tubes form the channels for the passage of gases from the mixing chamber to the reaction chamber. A channel with a built-in swirler is shown in FIGURES 10 through 13. FIGURE 10 is a top view of FIGURE 11 while FIGURE 12 is a view of FIGURE 11 rotated 45 to to'the left and FIGURE'13 is a side view of FIGURE 11. As may be seen from the illustration, the swirler is formed by two semi-elliptical shaped

surfaces

14 and 15 inclined at opposite angles with respect to one another within the tube. These surfaces are formed by (l) a first substantially flat surface extending at an inclined angle across or substantially across onehalf the cross-sectional area of the channel, this first surface being inclined at an angle of less than with respect to the axis of the channel as indicated by angle d in FIGURE 13 and (2) a second substantially flat surface having no common line of intersection with said first surface extending at an inclined angle across that part of the channel cross-sectional area not containing said first surface, the second surface being inclined with respect to the axis of the channel in a direc tion different from the first surface, and the angle of inclination of the second surface with respect to the axis of the channel being the same as that of the first surface. If both surfaces are the same distance from the channel exit which is preferred, then both would include a straight line passing perpendicularly through the axis of the channel. In this type swirler, as in the other types illustrated, the optimum angle of inclination of the surfaces depends on factors such as channel diameter and length. This type of swirler, however, is generally inclined less with respect to the channel axis than those of the type shown in FIG-

URES

5 and 8, the angle of inclination generally being from 10 to 25", preferably 12 to 18.

The exact location of a swirler within the channels of the burner block will vary with the type swirler used, the channel diameter, the channel length, and the like. Positioning the swirler too close to the exit of the channel may result in flame instability due to the extreme turbulence of the exiting gases, while a swirler located too far from the channel exit will not affect the exiting gases sufiiciently to prevent carbon deposits from forming. However, it has been found that the swirler must be located in the lower half of the channel, i.e., more than half the distance from the channel entrance to the channel exit or more than half the distance from the mixing chamber to the reaction chamber.

Another type of swirler within the above-described particularly useful embodiment of the present invention may be obtained by rotating one end of a fiat strip of flexible material while maintaining the other end substantially stationary and fixing such strip in the form so obtained. The amount of rotation would, of course, depend on the amount of swirling motion which is desired as well as such factors as the length, width, and thickness of the flexible strip, the location of the strip in the channel, the gas velocity, etc.

It is again emphasized that the means to impart a swirling motion to the gases is not limited to the foregoing embodiment, i.e., two inclined surfaces. It will be apparent to one skilled in the art that other various means may be devised to impart a swirling motion to the gases exiting the channels. For example, a screw-shaped object as is formed by a continuous helical surface projecting from a central shaft or spindle or from the walls of a channel will provide a single continuous surface to direct gases downward and in a swirling motion if such object is placed within a tube or channel. Also, rotating spinners supported within the channels will impart a swirling motion to the gases. It is, of course, within the scope of the present invention that different types of swirlers may be used in different channels of the same apparatus.

The number of channels in which swirlers are placed will, of course, vary with the number of channels within the burner block being used, the reduction of carbon deposits desired and other considerations. Generally, swirlers will be placed in all of the channels in order to insure optimum results. However, the deposition of carbon may be reduced where onlypart of the channels in the burner block containswirlers.

The following example is given in order to illustrate but not to limit the invention.

EXAMPLE 1 An apparatus as pictured in FIGURE 1 containing 127 tubes or channels which were 6% inches in length was used in this experiment. Approximately 4,050 pounds per hour of natural gas preheated to 600 C. was introduced into the mixing chamber of the apparatus where it was mixed with approximately 4,750 pounds per hour of oxygen also preheated to 600 C. The mixture of gases, which contained 37 mole percent oxygen, was then passed through the channels, each of which was fitted with metallic swirlers of the type shown in FIGURE 5. The inclined surfaces of the swirlers were inclined at an angle of 29 with respect to the axis of the channel and had a height as measured longitudinally of the channel of inch. The bottom of the swirlers inclined surfaces were 1 /2 inches from the exit of the channel. After passing through the channels, the gaseous mixture was reacted in a flame reaction and then quenched with water. The afiiuent gas contained 8.2 mole percent acetylene, 52.0 mole percent hydrogen, 29.0 mole percent carbon monoxide, 0.5 mole percent ethylene and 3.7 mole percent carbon dioxide with the remainder being unreacted feed components. The apparatus was operated one week with no deposition of carbon on either the walls of the reaction chamber or on the face of the burner block. With the particular swirlers used in this experiment, the gases exiting from the channels had an angle of expansion of 38 degrees on entering the reaction chamber.

Operation of an apparatus as described above except with no swirlers in the channels and under the conditions described above resulted in substantial deposition of carbon on the walls of the reaction chamber and on the face of the burner block within a one week period. With no swirlers in the channels, the gas exiting from the'channels had an angle ofexpansion of about 26 degrees.

The preferred hydrocarbon used in the process of this invention is methane; however, various other hydrocarbons are suitable. such as ethane, propanes, butanes, and pentanes, etc., including parafiinic hydrocarbons of carbon atoms and higher. Ordinarily, the hydrocarbon will be a paraflinic hydrocarbon with less than 7 carbon atoms. Natural gas, comprising essentially methane, is a preferred hydrocarbon feed stream for use in this invention.

The oxygen-containing stream which is mixed with the hydrocarbon stream is preferably oxygen; however, any oxygen-containing stream such as air or oxygen-enriched air can be used.

Pressure is not critical in the partial combustion of hydrocarbons for producing products such as acetylene. The converter operates at essentially atmospheric pressure under normal conditions but also operates satisfactorily as high as 40 p.s.i.a. and higher and as low as 5 p.s.i.a. and lower, the preferred range being from 10 p.s.i.a. to 24 p.s.i.a.

Although preheating of the feed gases to between 500 C. and 600 C. is preferred for best results, the scope of this invention includes preheating feed gases from about 400 C. to as high as 800 C. and higher.

In the manufacture of acetylenes, the combustion of the gas mixture must develop temperatures in the range of about 1200" C. to about 1800 C. Although it is possible to carry out the combustion and conversion reactions at temperatures higher than 1800 C., optimum results are not obtained due to the production of large quantities of carbon or coke. At temperatures below the above range, conversions obtained from the combustion reaction are too low. The preferred range within the reaction chamber is from about 1400 C. to 1600 C.

What is claimed is:

1. An apparatus for the partial combustion of a hydrocarbon and an oxygen-containing gas which comprises a mixing chamber and a reaction chamber, said reaction chamber in open communication with said mixing chamber by means of a plurality of channels, said channels containing means for imparting a swirling motion to the gases passing from said mixing chamber and into said reaction chamber, said means being located between the midpoint of said channels and said reaction chamber.

2. The apparatus of claim 1 wherein said means for imparting a swirling motion comprises two surfaces of substantially the same size and configuration, both surfaces being inclined at substantially equal angles of less than degrees with respect to the longitudinal axis of said channel but being inclind in substantially different directions with respect to one another, both surfaces being positioned with respect to one another such that the segments of the two surfaces lying within a transverse plane of said channel are substantially perpendicular to and on opposite sides from one another of a straight line lying within said plane passing through the axis of said channel.

3. The apparatus of claim 1 wherein said means for imparting a swirling motion comprises (1) a first substantially fiat surface extending at an inclined angle substantially across one-half the cross-sectional area of the channel, said first surface being inclined at an angle of less than 90 degrees with respect to the axis of the channel and (2) a second substantially fiat surface having no common line of intersection with said first surface, said second surface extending across that part of the channel crosssectional area not containing said first surface, said second surface being inclined with respect to the axis of the channel in a direction different from said first surface, the angle of inclination of said second surface with respect to said axis of said channel being the same as that of said first surface, and both said first surface and said second surface including a straight line passing perpendicularly through the axis of the channel.

4. A process for the partial combustion of hydrocarbons and oxygen which comprises mixing a hydrocarbon and an oxygen-containing gas in a mixing zone, passing the resulting mixture at elevated temperatures and in the gaseous form to a reaction zone through a plurality of channels wherein the gaseous mixture encounters in said channels means for imparting a swirling motion to the gases, said means being located between the midpoint of said channels and said reaction zone, and partially burning said mixture in said reaction Zone.

5. The process as described in claim 4 wherein said means for imparting a swirling motion comprises two surfaces of substantially the same size and configuration, both surfaces being inclined at substantially equal angles of less than 90 degrees with respect to the longitudinal axis of said channel but being inclined in substantially different directions with respect to one another, both surfaces being positioned with respect to one another such that the segments of the two surfaces lying within a transverse plane of said channel are substantially perpendicular to and on opposite sides from each other of a straight line lying within said plane passing through the axis of said channel.

6. The process as described in claim 4 wherein said means for imparting a swirling motion comprises (1) a first substantially flat surface extending at an inclined angle substantially across one-half the cross-sectional area of the channel, said first surface being inclined at an angle of less than 90 degrees with respect to the axis of said channel and (2) a second substantially flat surface having no common line of intersection with said first surface, said second surface extending across that part of the channel cross-sectional area not containing said first surface, said second surface being inclined with respect to the axis of the channel in a direction different from said first surface, the angle of inclination of said second surface with respect to the axis of said channel being the same as that of said first surface, and both said first surface and said second surface including a straight line passing perpendicularly through the axis of the channel.

7; The process of claim 4 wherein said hydrocarbon is natural gas comprising essentially methane and wherein said process is for the production of acetylene.

8. The process of claim 4 wherein said partial combustion takes place at from 1200 C. to 1800 C.

9. The process of claim 4 wherein said partial combustion takes place at from 1400 C. to 1600 C.

References Cited DELBERT E. GANTZ, Primary Examiner.

J. D. MYERS, Assistant Examiner.