US2533457A - Furnace with jet cooling - Google Patents

Description

Dm, 312, E925@ R. L. HASQHE FURNACE WITH JET COOLING Filed Dec. 8, 1945 Patented Decu 12, 1950 FURNACE WITH JET COOLING Rudolph Leonard Hasche, Johnson City, Tenn., assigner to Tennessee Eastman Corporation, Kingsport, Tenn., a corporation of Virginia.

Application December 8, 1945, SerialNo. 633,845

(ci. .2a- 277) i?. Claims. 1 My invention relates to regenerative furnaces. that is, to furnaces containing a regenerative mass which is operated through a recurrent cycle in which the regenerative mass is first heated by passing hot combustion products therethrough, and which is then used to heat gases that are passed therethrough,l the heat stored in the mass being given up .to the gases so heated. The furnace. isv particularly designed to process gases which must be very quickly heated to a yhigh ternperature and very quickly cooled after reaching the desired maximum temperature; for example, itis designed for use in processes in which acetylene is made from methane. A furnace for this purpose must be not only a furnace in which the methane is heated as near the highest temperature to which the furnace lining, euch, for example, as Carborundum, may be heated, for example, to ,3Go F., butthe furnace must provide that the methane be heated in as short a time as is practicable. for example, il@ second or preferably less, and be as quickly cooled as is praeticable t0 a temperature at which the acetylene is stablefor example, to 900 F.

.It an object of my invention to provide a furnace capable of producing acetylene in the manner above described. Such a furnace has other uses, the manufacture of acetylene from methane being given to illustrate only one use of my invention.

' In any furnace of this typel in which a mass of Carborundum or other heat refractory Substance is held at temperatures in excess of 2800@ F.,'sometmes for a period of several months, the

problem yof supporting the incandescent mass of Garborundum is a troublesome one, and it isla further object of the invention to provide means for raising the temperature of certain portions of the regenerative mass to a temperature higher than the maximum temperature to which it is desired to heat the gases to be processed, for ex ample, to a maximum temperature of 300Q F.. and to 4provide a construction which will permit the cooler portion of the regenerative mass to be supported on steel supports in such a manner that these supports will not be weakened by high temperatures.

It is a further object of the invention to provide means by which the regenerative mass is so heated that, although the gases are heated to this high temperature of 2800 F., no portion of the regenerative mass will be subjected to an excessive temperature, for example, in excess of 3000 F, ,which temperature is close to the maxieconomically used.

In producing acetylene from methane, .and when other gases are produced from othersub stances, it is often desirable to very quickly cool; the mixture containing the acetylene after it is formed to prevent the acetylene from itself". changing into undesired products, and it is a further object of my invention to provide a iure nace having means for cooling or quenching the gases as quickly as possible after they leave the regenerative mass.

It is a further object of my invention to provide a furnace structure which will allow effective and rapid means for purging, thereby Pre'- venting contamination of the gases to be heated/' with the combustion products and also loss of heated vgas in the combustionproducts.

Another object of my invention is to provide a relatively cold section directly above the top of the incandescent regenerative mass, having the dual purpose of protecting the quenching means and absorbing radiation, thereby preventing overheating of the regenerative mass.

, It is a further object o f my invention to pro. duce a furnace which will operate over long pee riods without need of repairs, vand in which-thc productive capacity is high as compared with the bulk and cost of the furnace.

Further objects and advantages will be made evident hereinafter. v

Referring tothe drawing, in which I illustrate a preferred form of furnace embodying my in;` vention:

Fig. 1 is a vertical cross section through the furnace, shown somewhat schematically, various valves,` pumps, etc., ordinarily used with the .iure nace but readily supplied by one skilled in the art, being omitted;

Fig. 2 is a section through the furnace shown in Fig. 1, this section being viewed in the direc# tion of the arrows adjoining the line 2-.2 of Fig. l., this line identifying the horizontal plane `of the section shown in Fig. 2;

Fig. 3 isa section of the furnace shownrin Fig. l, thisY section being viewed in the direction of the arrows adjoining the line 3-.3 of Fig..1thi s line identifying the horizontal vplane of saidsec tion shown in Fig. 3; and

Fig. 4 is a section through the furnace shown in Fig. l, this section being viewed in thedir-ection of the arrows adjoining the line 4-11 of 1, this line identifying the horizontal plane of the section shown in Fig, 2,

The preferred form of furnace shown in the drawing is generally symmetrical about avertical-axis 4--4 and includes a regenerative mass Il above whicha /quencher -I2 is .supported,.;if

necessary, by a structure external to the surface and not shown. The regenerative mass II may be formed of loose Carborundum bricks so placed as to provide vertical, substantially straight, and open primary passages I3 which extend through the mass II and connect a primary space I4 below the mass with a secondary space I5 above the mass. The quencher I2 consists of a shell I6 preferably formed of steel and having a chamber I1 therein which is kept full of Water. An explosion door I8 is pivoted at I9 and suitably weighted or closed by hydraulic means to form a tight seal with the walls of an opening in the top of the quencher I2. This door I8 also has a chamber I9a therein which is kept full of water by flexible pipe connections (not shown) which connect the chamber IBa with the chamber I7. Nozzles fed from a manifold 20a project a cooling or quenching agent, such as water or steam, into a tertiary space 2I inside the shell I6.

Cooling water is circulated in the chambers I1 and ISa by means of standard boiler feed and exhaust devices (not shown). If desired, the chainbers I1 and I9a may be kept full of water, which flows to a steam drum 23, in which the steam separates from the Water.. Steam is taken from the drinn 23 through a pipe 24, and, due to thermo-siphon and gravity action, Water flows from the drum 23 through a pipe 25 back into the shell I6 near its lower end.

The nozzles 2U are evenly spaced around the periphery of the tertiary space 2I, and the water, steam, or other cooling agent is projected therefrom under sufficient pressure to project the cooling agent to a point near the axis of the furnace, thus intimately mixing this cooling agent with the hot gases as they emerge from the primary passages I3 and Very quickly cooling the gases. It is of the utmost importance that the jets of cooling agent be as close to the top of the regenerative mass II as possible without coming into actual contact with the mass II. The nozzles may be so disposed with relation to each other that impingement occurs, or they may project a flow of cooling medium tangentially into the tertiary space 2 I For convenience in illustration, the passages I3 are somewhat simplified in the drawing, being much more numerous and of greater area in proportion to the diameters of the mass II and the f quencher I2 in the actual furnace than they are shown in the drawing.

The regenerative mass I I is so constructed that it can be supported wholly on a steel structure 25a in the primary space I4. This space I4, as will be understood from the description appearing later herein, never contains gas at a temperature which will substantially impair the strength of steel, and the lower end of the regenerative mass II neverreaches such a destructive temperature.

While in the furnace which I have constructed carborundum is the preferred lining for the combustion chamber and to form the regenerative mass I I, a combustion chamber may be lined with any other highly refractive material, such as high alumina tile, since it is not called upon to be a heat transfer medium. However. it is essential that the regenerative mass II be composed of Carborundum or an equivalent highly conductive and refractory material for reasons herein set forth.

Surrounding the upper end of the regenerative mass II is the annular combustion chamber 30, which is in communication with the secondary ffl Cil

space I5 through an uninterrupted annular throat 3l. The combustion space 30 is preferably lined with Carborundum brick or any other highly refractory material. Combustion in this space is provided by five equally spaced burners 32 each fed with gas through pipes 33a from a fuel gas manifold 33. The combustion products in the space I5 may have a temperature of 3200 to 3400 F. The burners 32 discharge through openings 34 in the lower wall of the combustion space 30, these openings connecting the coinbustlon space 30 with pipes 35 forming part of each burner. A shell 36 surrounds the combustion space 30 and the mass II, forming a gas-tight joint with the shell I6. Surrounding the mass II inside the shell 36 is an annular layer of heat-insulating material 31. The quencher I2 and various pipes may also be heat-insulated externally by heatinsulating material (not shown). Air is supplied to the pipes 35 from an air manifold 40, and steam may be supplied to the pipes 33a from a steam manifold 4I.

The primary space I4 is provided with an inlet pipe 42 through which the gas to be processed may be supplied to the space I4, and steam or other inert diluent gas may be supplied to the primary space I4 through a pipe 43. ' ihe pipes 42 and 43 are provided with valves, as are the pipes that supply I'uel gas to the pipes 3o, and as is the pipe supplying steam to the burners 32, these Valves also not being shown. 'The primary space I4 also has an outlet pipe c5 through which combustion gases are conducted to a stack t3 through a valve 41. Processed gases are taken from the tertiary space 2i through a valve 43 to a pipe 49, these gases being the product desired.

r'he water-cooled inner surface of the dome I6 and door i8, which looks downward in a vertical projection plane onto the top of the hot regenerative mass I I, serves a most important function of absorbing radiation and protects the latter from overheating.

The operation of the furnace may be manually controlled by operating the various valves, but in practice these valves are automatically controlled by mechanism forming no part oi' the furnace and hence not described or shown.

The operation in producing acetylene from methane will be described, as such operation is typical of many uses for which the furnace may be utilized. The furnace is operated in a periodically recurring cycle consisting of a heating, a purging, and a treating period. At the beginning of the heating period, the valve 43 is closed and the valve 1 is open, and during this heating period no gas or diluent is supplied to the primary space I through the pipe 42. The tertiary space 2l during the treating period is preferably kept full of steam suppLed by the nozzles 20 at a slow rate so as to furnish a relatively inert blanket of steam in the tertiary space 2I.

Fuel gas is supplied to the burners 32 from the manifold 33, and air for combustion is supplied to the pipes 35 from the manifold 40. It is important to so regulate the flow of air and gas that each of the burners will produce combustion products of about the saine volume and at about the same temperature. In the drawing, I show live burners 32, but in large furnaces more than ve burners are desirable. It is understood that the burners may also be inserted through the side walls of the combustion chamber. Their location depends upon convenience of construction and upon the size of the furnace. operated, the combustion chamber 36 is filled with If the burners are properly' an annular ring of combustion gases at a fairly uniform temperature of 3200 F. to 3400vo F. I have found that in a properly designed furnace a heat liberation o 750,000 to 1,000,000 B. t. u. per hour for each cubic foot oi combustion space is possible. It is very important that the rate of burning or heat liberation be maintained close to the maximum. By so doing, it will prevent cornbustion occurring in the checkers, which makes for non-uniformity of heating and insures that l the lower end oi the checkers never gets too hot. It also provides a minimum amount of combustion volume requiring purging. I have found that the total volume of the combustion space as related to the total volume of the regenerative passa-ges I3 should be maintained within the limits of ratios 1.0 to 3.0. This ring of combustion pro:in uc-ts surrounds the upper end oi the regenerative mass I I and tends to heat it.

The combustion products flow evenly through the throat 3 I, which is constricted to an area perpendicular to the gas flow of about one-third of the area on a horizontal plane of the combustion space 30. This constriction tends to promote an even and uniform flow of combustion products from the combustion chamber 3J through the throat Si into the secondary space I5. Carborundum stands up well at temperatures materially below 3000o ll., but deteriorates rapidly at temperatures materially above 3000 F. I prefer to operate the furnace so that the upper and hottest portion of the regenerative mass is at a temperature of about .3000o F., or as close as practicable to this temperature, so as to improve the degree of conversion oi the methane to acetylene. A uniform heating of the mass I i can only be accomplished by uniform.ty of temperature of the combustion products in the combustion chamber and a uniform ow of gases through the throat 3 I.

The primary passages I3 should be of such size and the volume of the combustion products should be such that the combusion products passing downwardly through the primary passages attain a high velocity, preferably in excess of 10,000 feet a minute. These products lose heat rapidly by convection; in l'act, I have found that in a properly designed and operated furnace the combustion products lose about 80% of their sensible heat in their passage from the throat 3i to the primary space I4. The products of combustion are drawn from the primary space lli through the pipe and valve Il into the stack 46, which provides a draft, thereby aiding in the withdrawl of the products of combustion from the furnace. The regenerative mass II should be of suicient length to insure a temperature at the bottom of the mass of about 900 F. when the top of the mass is' at 3000 F., and when the mass reaches these temperatures the ring period terminates, and the now of gas to the burners 32 from the manifold 33 and the ow of air to the pipes 35 are shut off. This firing period, when the furnace is operating on the cycle, may be from one 'to two minutes. During the firing period I allow steam to flow slowly from the steam manifold il through the pipes 33a and the burners 32 to protect the burners and adjacent structure from the eects of the hot combustion gases.

The purging period, which may require three seconds, then occurs. Steam is admitted to the combustion space 30 from the pipe si through the pipes 33a and burners 32, and flows down- Wardly through the primary passages I3, the

space I4, andthe outlet pipe Vt5 to the chimneyl 40 through the valve 'l. This ow purges the primary passages I3 of combustion products.

During the treating period, the valve 48 is. opened and the valve l is closed, and a mixture of methane and diluent is delivered to the p'1l.i mary space lli from the pipe 42, which diluent flows upwardly through the primary passages I3, being heated by contact with the hot regenerative mass. In making acetylene, I prefer not to heat the methane-diluent mixture before it enters the primary space I4, as preheating occurs inthe. lower portion of the regenerative mass. In its' passage upwardly through the primary passages: the mixture is heated to a temperature of about 2,800o F, Somewhat below this temperature, the methane is converted into acetylene, hydrogen being released. rIhis reaction absorbs large quanV A titles of heat which is obtained from the regem erative mass il. At this high temperature, the reaction is very rapid, taking not more than 2/1oq of a second, and it is important that the flowr of gas should be such that the gas passes through the upper ten per cent of the regenerative mass in 2/100 of a second or less.

Acetylene vis quite unstable, and it is important that the converted products of the primary passages be cooled quickly, which is accomplished in the tertiary space 2I. Suflicient cooling agent. should be supplied through the nozzles 20 so that the gases are cooled in the tertiary space to about 900 F. and so that the time required for such cooling will be le of a second or less. It is not' advisable to cool the gas much below 900 F.,

. as at lower temperatures any tars carried in the.

gases tend to condense and collectcarbon, thus blocking the conduits through which. the gas. passes from the pipe d. This tar and carbon can be removed in a scrubber after theV gas. leaves the pipe 49. The treating period continues until the regenerative mass EI cools to such a degree that it is not highly efficient in its conversion of methane to acetylene, when the treating period ends by shutting off the flow of mixed methane and diluent into the primary space I4, by partially shutting off the how of steam into the pipes 33a, and by opening the valve 41 and closing the valve t8. The cycle is then complete, and the firing period of the next cycle starts. The treating period may have been about one minute.

While I have described the use of my furnace vin producing acetylene from methane, it may be also used to produce butadiene, and the olens, such as ethylene, propylene, and butylene, or the aromatics, such as benzene, toluene, and xylene, or hydrocyanic acid from the reaction of hydrocarbons and ammonia. All of these products are endothermic in nature, and the formation is very rapid at high temperatures. These products are also unstable at high temperatures and must be quickly cooled if they are to be preserved against disintegration. To successfully produce and pre` serve each of these other products, they must be held at formation temperatures no longer than a fraction of a second.

While I have described my furnace `as using methane as `a gas to be processed, in practice it will be more often used to process natural gas, which is largely methane, waste hydrocarbon gases from oil refineries, or other sources which may or may not contain methane but contain other hydrocarbons such as ethane, butane, propane, or the like, or natural gasoline or other petroleum derivatives which are liquid at normal temperatures and which must be gasied by heating prior to being delivered to the primary space I4.

rI'he general dimensions of the regenerative mass in regard to the dimensions of the primary passages therethrough and the thickness of the walls therebetween may be those set forth in the Hasche et al. patents, No. 2,318,688, issued May 11, 1943, and No. 2,319,679, issued May 18, 1943. Other structural modications of apparatus of the type illustrated and described herein are also shown and described in applicants copendng applications Serial No. 633,839, now Patent No. 2,432,885, and Serial No. 633,834, now abandoned, both led December 8, 1945.

I claim as my invention:

1. A regenerative furnace comprising an outer shell enclosing an enlongated upright regenerative mass having passageways extending lengthwise therethrough, a chamber surrounding one end of said regenerative mass forming a substantially annular combustion space about the end portion of said regenerative mass, a plurality of burners opening into said annular combustion space, an annular throat constituting a communication between said annular combustion space and a space adjacent said end of said mass into which said passageways open, a heat exchanger in proximity to said last mentioned space, said heat exchanger including spaced nozzles positioned to project a uid heat exchange medium directly into said last mentioned space, a second chamber providing a primary space in direct communication with said passageways at the opposite end of said regenerative mass, an inlet communicating with said second chamber for admitting gas to be treated during a, treating cycle and an outlet communicating with said second chamber for the escape of products of combustion during a heating cycle.

2. A regenerative furnace comprising an outer shell enclosing a regenerative mass having pase;A

sageways extending lengthwise therethrough,A a chamber surrounding one end of said regenerative mass forming a combustion space about the end portion of said regenerative mass, a plurality of burners opening into said combustion space, a throat constituting a communication between said combustion space and a space adjacent said end of said mass into which said passageways open, a heat exchanger in proximity to said last mentioned space, said heat exchanger including spaced nozzles positioned to project a fluid heat exchange medium directly into said last mentioned space, a second chamber providing a, primary space in direct communication with said passageways at the opposite end of said regenerative mass, an inlet communicating with said second chamber for admitting gas to be treated during a treating cycle and an outlet communicating with said second chamber for the escape of products of combustion during a heating cycle.

RUDOLPH LEONARD HASCHE.

REFERENCE S CIT ED The following references are of record in the ile of this patent:

UNITED STATES PATENTS .TF In" Name Date 2,164,762 Baumann et al July 4, 1939 2,432,885 Hasche Dec. 16, 1947 FCFREIGN PATENTS Number Country Date l 593,153 France Feb. 10, 1925

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