US2706210A

US2706210A - Process suitable for converting primary hydrocarbons to secondary hydrocarbons

Info

Publication number: US2706210A
Application number: US199231A
Authority: US
Inventors: Ford W Harris
Original assignee: Wulff Process Co
Current assignee: Wulff Process Co
Priority date: 1950-12-05
Filing date: 1950-12-05
Publication date: 1955-04-12
Anticipated expiration: 1972-04-12

Description

F. w. HARRIS PROCESS SUITABLE FOR CONVERTING PRIMARY HYDROCARBONS TO SECONDARY HYDROCARBONS April 12, 1955 2 Sheets-Sheet 1 Filed Dec. 5, 1950 I Apnl 12, 1955 E. w. HARRIS 2,706,210

PROCESS SUITABLE FOR CQNVERTING PRIMARY HYDROCARBONS To SECONDARY HYDROCARBONS 2 Sheets-Sheet 2 Filed Dec. 5. 1950 by weight of the mixture.

United btates Patent PROCESS SUITABLE FOR CONVERTING PRIMARY ggDQOCARBONS T0 SECONDARY HYDROCAR- Ford W. Harris, Los Angeles, Calif., assignor to Wulff Process Company, Huntington Park, Caiif., a corporation of California Application December 5, 1950, Serial No. 199,231

4 Claims. (11]. 260--679) My invention relates to the pyrolysis of hydrocabons and more particularly to processes in which an in-gas containing a primary hydrocarbon is heated to a temperature, and under proper conditions, to produce an off-gas containing a secondary hydrocarbon.

The term primary hydrocarbon as used herein is limited to hydrocarbons defined by the formula CnH2n or CnHa-t in which n=3 or less. The term secondary hydrocarbon is limited to hydrocarbons-produced from the primary hydrocarbons by pyrolysis which have a smaller total hydrogen content than the primary hydrocarbon that is so pyrolyzed. 1

The process works satisfactorily where the in-gas contains several primary hydrocarbons and in practical operation, even when only one primary hydrocarbon is carried in the in-gas, several secondary hydrocarbons may be carried in the off-gas.

The term in-gas is limited to gases containing a substantial proportion of primary hydrocarbon or hydrocarbons and the term oil-gas is limited to gases containing a substantial proportion of secondary hydrocarbon or hydrocarbons. The term in-gas is further limited to gases which do not contain a substantial proportion of free oxygen. The term substantial proportion, as applied to any gas forming a portion of any gas mixture, means that the gas must provide at least 2% The expression under proper conditions as used herein is limited to conditions under which primary hydrocarbons having the general formula Cal-I211+ are converted by pryrolysis to secondary hydrocarbons having either the formula CnH2n or cnHznor under which primary hydrocarbons havingthe formula CnHZn are converted to hydrocarbons having the formula Cal-1211*? In either case the effect is to increase the value of the ratio CzH, the process releasing hydrogen as a by-product or, stated ditferently, the process is one of dehydrogenation.

The above definitions are stated to limit thefield in which I claim protection and to save repetition and verbosity in the specification and claims.

it is an object of my invention to provide a process by which an in-gas, as above limited, may be pyrolyzed to produce an off-gas, as above limited.

The principal present-value of the process resides .in' converting an in-gas containing methane (CH4), for ex-' ample, natural gas, or off-gas from absorption plants or petroleum refineries to an off-gas containing acetylene (Cal-I2) or ethylene (Cal-I4), or both acetylene and ethylene. Since such an operation is typical of my process, it will be described as illustrative of my invention but without limiting my invention to this particular use of my process.

Further objects and advantages will be specifically de-- scribed hereinafter or willbe obvious to a person skilled in the art to which the invention claimed herein appertains or with which it is most nearly connected.

cation Serial No. 40,208, and how the different parts thereof are' connected together;

Fig. 2 is a central section through the furnace shown:

in Fig. 1;

Fig. 3 is a view of the upper end of the furnace as,

shown in Fig. 2;

- In the drawings, which are for illustrative purposes Patented Apr. 12, 1955 Fig. 4 is a section of the furnace on a plane represented by the line 4--4 of Fig. 2;

Fig. 5 is a section of the furnace on a plane represented by the line 55 of Fig. 2;

Fig. 6 is a section of the furnace on a plane represented by the line 66 of Fig. 2,

Fig. 7 is a section of the furnace on a plane represented by the line 7-7 of Fig. 2;

Fig. 8 is a section of the furnace on a plane represented by the line 8-8 of Fig. 2;

Fig.9 is a section of the furnace on a plane represented by the line 9-9 of Fig. 2;

Fig. 10 is a view of the lower end of the furnace as shown in Fig. 2;

Fig. 11 is a view on the plane represented by the line 6-6 of Fig. 2 of a part of the furnace, Fig. 11 being on a larger scale than Fig. 6; and

Fig. 12 is a side view of one the bricks of the furnace shown in Fig. 1.

'All of the elements of my apparatus except the furnace 20 shown in Figs. 2 to 12, inclusive, are old in the art and can be readily supplied by a person skilled in the art who has read this specification and therefore understands the function to be performed by each of said elements. The furnace 20 may be described as follows: It consists of an outer steel shell 21 and an inner steel shell 22 which are cylindrical about the axis 23--23 of the furnace. ter space 24 and inside the inner shell 2 is a fire box space 25. The outer shell 21 may be covered or surrounded by heat insulating material 26, and both shells form gas-tight enclosures capable of withstanding considerable internal pressure. The process hereinafter claimed is, however, what is generally called a high temperature, low pressure process, the reacttion of primary hydrocarbons to secondary hydrocarbons preferably oc curring near or below atmospheric pressure.

The wall of the inner shell 22 which surrounds the fire box space 25 is lined with heat-resistant material 27 such as fire brick or other heat refractory material.

. A burner nozzle 30 projects through an opening 31 in the upper end wall of the fire box space 25, this nozzle being supplied with oxygen through an oxygen supply pipe 32 which has an oxygen valve 33. Hydrogen is supplied to the space in the opening 31 around the nozzle 30 through a hydrogen supply pipe 34 having a first hydrogen valve 35. Oxygen may be supplied to the oxygen supply pipe 32 and hydrogen may be supplied to the hydrogen supply pipe 34 from any convenient source. Combustion is established beyond the inner end of the burner nozzle 30 and the products of combustion flow through the fire box space 25. If oxygen and hydrogen are so supplied, the product of combustion is superheated steam.

The temperature of an oxygen-hydrogen combustionis high and the steam formed by this combustion may have an initial temperature as high as 4500 F. duce temperature in the fire box space, I prefer to introduce saturated steam into the space 25 at a temperature a little above 212 F. This steam is introduced through a plurality of steam nozzles 40 which project through the walls of the furnace and which are supplied with steam from a steam pipe 42 having a first steam valve 43;

Steam is supplied to the pipe 42 from any convenient source. The steam so supplied acts as a diluting agent for the in-gas and reduces the partial vapor pressure on any primary hydrocarbon carried in the in-gas during the reaction period, as will be hereinafter explained,

and it also acts as a heat carrier, absorbing heat in the" fire box space and delivering this heat at the point where the primary gas is converted to secondary gas, the supershown in Figs. 11 and 12. The mass 50 has the very definite function of insuring that the gases passing there,

Between the two shells is a wa-- To rethrough are evenly heated. Perfect mixing of hot gases of combustion and primary hydrocarbon cannot be expected in the fraction of a second available for such mixing and the mixed gas passes into the slots in the first mass 50 in small gas masses, some of which are hotter than the average temperature of the first mass 59, and some of which are cooler than this temperature. The mass 50 absorbs heat from the hot gas masses thus preventing over-cracking and delivers heat to the cold gas masses thus preventing under-cracking. The first refractory mass 50 also acts as a partition in the fire box space 25 to separate this space from the upper end wall of the water space 24. The channels 51 conduct the diluting agent or diluent gas containing superheated steam through the mass 50 to a first intermediate space 56. A second refractory mass 57 has channels 58 through which gas is delivered from the first intermediate space 56 to a second intermediate space 59. The second refractory mass 57 surrounds and is heat insulated from an extension of the water space which extends upwardly,

as seen in Fig. 2, and forms the lower wall of the space 56.

Since no reaction occurs in the channels 51, these channels act merely to mix and heat the diluent gas flowing therethrough.

Tubes 60 are secured at their upper ends as shown in Fig. 2 in gas-tight union with the inner shell 22 and at their lower ends in the outer shell 21 and conduct gas from the intermediate space 59 through the water in the water space 24 to an off-gas chamber 61. ln-gas is delivered through an in-gas pipe 64 having an in-gas valve 65 to a pipe 66 which passes through the chamber 61, the water space 24, and its extension, and delivers the in-gas to the center of the first intermediate space 56 where it is mixed with diluent gas from the fire box space 25, the mixture of in-gas and diluent flowing downwardly as seen in Fig. 2 through the channels 58 to the second intermediate space 59 and from there through the tubes 60 to the space 61, being converted during this flow to off-gas. This off-gas is taken off through an off-gas pipe 62 having an off-gas valve 63 therein. Steam may be taken off from the boiler through a pipe '70 and water supplied thereto through a water pipe 71 having a valve 72 therein. The channels 58 contain the reaction zone in which the conversion of primary to secondary hydrocarbons occurs or at least a part of this zone, which in some cases may extend down into the tubes 66.

The furnace is illustrated for convenience of delineation in Fig. 2 as if it were installed with the axis 23-23 vertical. It may be so installed but I prefer to install it with the axis 2323 in a horizontal position. The furnace is provided with thermometers or thermocouples,

not shown, so that temperatures in various parts are at times indicated and preferably recorded, and suitable flow meters, not shown, are provided to indicate and preferably record the rates of flow of gases and steam.

In addition to the furnace 20, other parts are needed, as shown in Fig. 1, to make the apparatus complete.

Since the desired product is a secondary gas or gases, as previously defined, and the off-gas delivered by the pipe 62 is a mixture containing other gases, additional. apparatus must be supplied to segregate the desired prodnet or products. Also, it is desirable to furnish additional apparatus to facilitate the operation and increase the efficiency of the furnace 20. This additional apparatus shown in Fig. 1 will now be described.

The principal apparatus other than the furnace which has been previously described is a conventional fractionator or gas separator which is needed to separate from the off-gas any desired component or components thereof.

The fractionator 80 is shown in Fig. 1 as a rectangle but in practice it consists of compressors, bubble towers, coolers, and condensers. Such fractionating devices are quite old in the art and can readily be supplied by a person skilled therein. The fractionator operates as fl-- lows: Off-gas is drawn through the pipe 62 from the space 61 in the furnace by an exhauster 90 which delivers the off-gas to the fractionator 80 preferably above atmospheric pressure.

Conventionally, in operating the fractionator 80, the

off-gas would be first cooled, thus condensing the steam to water which is removed from the fractionator 80 through one of several pipes 81. The gas freed from steam is then subjected to several absorption steps each of which removes one or more constituents of the gas, each of. these constituents being taken off through one of the pipes 81. Hydrogen or a fuel gas rich in hydrogen is delivered from the fractionator through the pipe 84.

Excess hydrogen or fuel gas, if any is produced by the process, may be taken off through, or hydrogen or fuel gas may be delivered to, the apparatus through a valve 85. Hydrogen may be taken from or forced into the pipe 84 by an exhauster 100. Steam may be taken from or delivered to the apparatus through a steam pipe 86 having a steam valve 87. An exhauster 90 pulls off-gas through the pipe 62 from the chamber 61, preferably maintaining a pressure in the chamber 61 below atmospheric pressure and preferably delivering gas to the fractionator 80 at superatrnospheric pressure. A portion, or in some cases all, of the steam needed for diluting purposes may be taken from the pipe 70 by the pipe 42.

The walls surrounding the water space 24 in effect form a steam boiler which is provided with such auxiliary equipment, not shown or described, as a man skilled in the operation of such boilers would consider necessary for the safe operation of such a boiler.

How the apparatus shown in Fig. 2 is used to produce an off-gas containing acetylene from an in-gas containing methane will now be described as illustrative of how the object of my invention may be attained.

To start the furnace, combustion is started in the fire box space by opening the oxygen valve 33 to admit oxygen and the hydrogen valve to admit hydrogen and igniting the mixture. The combustion, of course, produces water in the form of steam superheated to a high temperature. Saturated steam is admitted to the fire box space by opening the steam valve 43, this saturated steam becoming superheated and preventing too high a temperature in the fire box space. In general, it may be said that the weight in pounds of saturated steam which is needed per minute may be several times the weight in pounds of the oxygen consumed, if the diluent gas containing the steam flowing through the channels 51 is to be held below 3000 F. This diluent gas may contain a considerable volume of excess hydrogen as it is desirable to produce a complete combustion of the oxygen. The diluent gas flows through the tubes during the starting period and to the fractionator, from which it may be discharged in vapor form if the amount of hydrogen present therein during starting is not large enough to pay for fracationating.

When the furnace reaches a heat equilibrium, that is, when the

masses

50 and 57 are at a temperature close to, but below, 3000 F., in-gas is admitted by opening the valve 65. The in-gas flows through the pipe 66 where it is heated above atmospheric temperature and into the first or upper intermediate space 56. This space has the hot first, or upper, refractory mass 50 forming its upper wall and the upper wall of the extension to the water space 24 forming its lower wall. The in-gas flows radially outward in the space 56, is further heated in this space, and mixes with the diluent gas as it enters the channels 58. While the capacity and efliciency of the apparatus will be low, the reaction of methane to acetylene which occurs in the channels 58 will occur if the diluent gas and the

refractory masses

50 and 57 are at as low a temperature as 2000 R, but it is desirable to start at the higher, more efficient, and productive temperature of 3000 F. when converting methane to acetylene. .Lower temperatures, perhaps as low as. 1500 F., may be used when converting any primary gas. other than methane to acetylene or when converting any primary gas to secondary gases other than acetylene. The reaction of primary gases to secondary gases is endothermic, heat being extracted from the diluent gas to supply the negative heat of reaction.

When operating with methane as the primary gas at initial temperatures below 3000 F., good results will be obtained when the temperature of the off-gas, produced by this reaction, at the point where the off-gas leaves the channels 58 is about 1500 F. These conditions are obtained during the starting period by gradually increasing combustion, by further opening the

valves

33 and 35, by further opening the valve 43 to increase the steam dilution, and by further opening the valve to increase the rate of in-gas feed.

A skilled operator can increase or decrease the amount of acetylene in the off-gas by regulating the rate of flow of the various gases but, within the limits herein given, by using an in-gas containing methane, substantial amounts of acetylene will be produced since acetylene maybe produced from methane over awide range of conditions. For example, the channels 51 and 58'1nay have a cross-sectional area of about eight square feet and the mass 57 may have a length of three feet. No reaction takes place in the mass 50 and its length is not critical as long as it forms a rigid fire wall between the space 56 and the remainder of the fire box space 25. Combustion having been established long enough to obtain stable temperatures, the feeds may be gradually built up to the following values per minute:

240 lbs. of oxygen 50 lbs. of hydrogen 300 lbs. of methane To maintain a temperature in the first refractory mass 50 and in the diluent gas passing therethrough of 3000 F. or less, about 1800 lbs. per minute of steam must be injected through the nozzles 40. in the channels 58 the heat of reaction for the methane to acetylene reaction, or 3300 B. t. u. per pound of acetylene, is extracted from the diluent gas and the temperature of the mixture as it flows through the channels 58 may fall to 1500 F, at which temperature it enters the tubes 60.

In the tubes 60 the ofi-gasis quickly cooled to a temperature at which the secondary gas produced by the reaction is stable. All secondary gases as defined herein are stable at 900 R, which may be regarded as the highest permissible temperature ut this point.

The exhauster 90 pulls the off-gas out of the chamber 61 and maintains a small sub-atmospheric pressure therein. The off-gas is subjected to fractionation in the fractionator 80 by methods well known in the art.

The apparatus above described may be used for various purposes other than in the practice of the process above described. For example, any fuel gas may be delivered through the pipe 32 to the burner 30 and air or oxygen may be delivered through the pipe 34 in excess of the combustion requirements of the fuel gas. The diluent gas will then contain substantial amounts of free oxygen and partial combustion of the in-gas may occur in the channels 53, which combustion supplies all or part of the heat of reaction. Under these conditions, little or no steam need be supplied through the pipe 42. Similarly, by supplying a very considerable excess of hydrogen through the pipe 34, little or no steam need be supplied through the pipe 42. Or, using a hydrocarbon as a fuel gas and injecting steam through the pipe 42, a water-gas reaction may occur in the fire box space 25, the CO so produced being carried in the diluent gas. Using an in-gas containing a primary gas of the nature previously described, the off-gas will contain secondary hydrocarbons.

The time that the mixture of in-gas and diluent is held at temperatures above 900 F. is important, particularly when acetylene is produced. I prefer, if possible, to maintain gas velocities sufiiciently high to insure that the gas passes from the firstintermediate space 56 to the space 61 in less than ,4 second since lower velocities will result in some of the acetylene breaking down to release free carbon, which reduces the yield. Also, it is desirable that methane be supplied to the reaction zone in greater amounts than will be pyrolyzed in that zone as such excess methane tends to inhibit the breaking down of the acetylene to release carbon and a plentiful supply of methane tends to reduce the temperature of the offgas where it enters the tubes 60. This excess methane may be removed in the fractionator 80 and delivered to methane storage through one of the pipes 81 or it may be left in the hydrogen and form a part of the fuel gas.

I claim as my invention:

1. A process of producing an oft-gas containing a substantial proportion of acetylene from an in-gas containing a substantial proportion of a hydrocarbon whose molecules contain a larger proportion of hydrogen than acetylene, which comprises: (a) producing gases of combustion in a fire box space, said gases as produced being at a temperature above 3000 F.; (b) injecting into said fire box space a loW temperature diluent gas, such as steam, said diluent gas being introduced in sufiicient amount to reduce the temperature of the mixed gases where they leave the fire box space and produce a mixed gas having a temperature substantially below 3000 F.; (c) passing said mixed gas through open and unobstructed channels in a first regenerative mass to produce a first mixed gas having a substantially uniform temperature throughout its mass; (d) injecting, into said mixed gas, a

f primary hydrocarbon in amounts insufiicient to reduce the temperature of the resulting second mixed gas to a temperature substantially below a temperature of 2000 F.; (e) passing said second mixed gas through open and unobstructed channels in a second regenerative mass; and (f) promptly cooling said second mixed gas to a temperature below 900 F.

2. A process of producing an oif-gas containing a substantial proportion of acetylene from an in-gas containing a substantial proportion of a hydrocarbon whose molecules contain a larger proportion of hydrogen than acetylene, which comprises: (a) producing gases of combustion in a fire box space, said gases as produced being at a temperature above 3000 F.; (b) injecting into said fire box space a low temperature diluent gas, such as steam, said diluent gas being introduced in sufiicient amount to reduce the temperature of the mixed gases where they leave the fire box space and produce a mixed gas having a temperature substantially below 3000 F.; (c) passing said mixed gas through open and unobstructed channels in a first regenerative mass to produce a first mixed gas having a substantially uniform temperature throughout its mass; (d) injecting, into said mixed gas, a primary hydrocarbon in amounts insufficient to re duce the temperature of the resulting second mixed gas to a'temperature substantially below a temperature of 2000 F (e) passing said second mixed gas through open and unobstructed channels in a second regenerative mass; and (g) promptly passing said second mixed gas into intimate contact with water cooled surfaces for a suflicient period to reduce the temperature of said second mixed gas and form an off-gas at a temperature below 900 F., said off-gas containing a substantial proportion of acetylene.

3. A process of producing an oft-gas containing a substantial proportion of acetylene from an in-gas containing a substantial proportion of a hydrocarbon whose molecules contain a larger proportion of hydrogen than acetylene, which comprises: (a) producing gases of combustion in a fire box space, said gases as produced being at a temperature above 3000 F.; (b) injecting into said fire box space a low temperature diluent gas, such as steam, said diluent gas being introduced in sufiicient amount to reduce the temperature of the mixed gases where they leave the fire box space and produce a mixed gas having a temperature substantially below 3000 F.; (d) injecting, into said mixed gas, a primary hydrocarbon in amounts insufiicient to reduce the temperature of the resulting second mixed gas to a temperature substantially below a temperature of 2000 F.; (e) passing said second mixed gas through open and unobstructed channels in a regenerative mass; and (f) promptly cooling said second mixed gas to a temperature below 900 F.

4. A process of producing an off-gas containing a substantial proportion of acetylene from an in-gas containing a substantial proportion of a hydrocarbon whose molecules contain a larger proportion of hydrogen than acetylene, which comprises: (at) producing gases of combustion in a fire box space, said gases as produced being at a temperature above 3000" F.; (b) injecting into said fire box space a low temperature diluent gas, such as steam, said diluent gas being introduced in sufiicient amount to reduce the temperature of the mixed gases where they leave the fire box space and produce a mixed gas having a temperature substantially below 3000 F.; (d) injecting, into said mixed gas, a primary hydrocarbon in amounts insufiicient to reduce the temperature of the resulting second mixed gas to a temperature substantially below a temperature of 2000 F.; (e) passing said second mixed gas through open and unobstructed channels in a regenerative mass; and (g) promptly passing said second mixed gas into intimate contact with Water cooled surfaces for a sufiicient period to reduce the temperature of said second mixed gas and form an oflf-gas at a temperature below 900 F., said offgas containing a substantial proportion of acetylene.

References Cited in the file of this patent UNITED STATES PATENTS 2,377,847 Allen et al June 12, 1945 2,475,093 Hasche July 5, 1949 2,498,444 Orr Feb. 21, 1950 2,552,277 Hasche May 8, 1951

Claims

1. A PROCESS OF PRODUCING AN OFF-GAS CONTAINING A SUBSTANTIAL PROPORTION OF ACETYLENE FROM AN IN-GAS CONTAINING A SUBSTANTIAL PROPORTION OF A HYDROCARBON WHOSE MOLECULES CONTAIN A LARGER PROPORTION OF HYDROGEN THAN ACETYLENE, WHICH COMPRISES: (A) PRODUCING GASES OF COMBUSTION IN A FIRE BOX SPACE, SAID GASES AS PRODUCED BEING AT A TEMPERATURE ABOVE 3000* F., (B) INJECTING INTO SAID FIRE BOX SPACE A LOW TEMPERATURE DILUENT GAS, SUCH AS STEAM, SAID DILUENT GAS BEING INTRODUCED IN SUFFICIENT AMOUNT TO REDUCE THE TEMPERATURE OF THE MIXED GASES WHERE THEY LEAVE THE FIRE BOX SPACE AND PRODUCE A MIXED GAS HAVING A TEMPERATURE SUBSTANTIALLY BELOW 3000* F., (C) PASSING SAID MIXED GAS THROUGH OPEN AND UNOBSTRUCTED CHANNELS IN A FIRST REGENERATIVE MASS TO PRODUCE A FIRST