US1941976A

US1941976A - Regenerator construction

Info

Publication number: US1941976A
Application number: US577556A
Authority: US
Inventors: Etherington Harold
Original assignee: AO Smith Corp
Current assignee: AO Smith Corp
Priority date: 1931-11-27
Filing date: 1931-11-27
Publication date: 1934-01-02
Anticipated expiration: 1951-01-02

Description

1934. H. ETHERINGTON REGENERATOH CONSTRUCTION Filed NOV. 27, 1931 BY wzalf :32 INVENTOR. N I

Harold Ether" ATTORNEY.

Patented Jan. 2, 1934 UNITED STATES REGENERATOR CONSTRUCTION Harold Etherington, Milwaukee, Wis., assignor to A. 0. Smith Corporation, Milwaukee, Wis.,

a corporation of New York Application November 27, 1931 Serial No. 577,556

9 Claims.

This invention relates to heating apparatus and more particularly to structure. for preheating incoming air in a furnace. It has for its object an improved flue construction and operation whereby incoming air will be more efiectively heated.

The rate of heat transfer from the walls of a flue to a gas passing therethrough can be materially increased by increasing the velocity of the gas and also by decreasing the diameter of the flue. In applying this knowledge to regenerator systems, as built heretofore, it has not been found practical to increase the velocity of the gases above a certain limit which is governed by pressure considerations. Waste gases have to be sucked down against the hydrostatic head of the hot gas and any greatly increased resistance due to friction becomes serious, especially where nat ural draft is employed. Decreased diameter of the hot gas flues greatly increases the resistance even for any given velocity and where the velocity is increased by using narrow passages, the result is an immediate choking up of the narrow passages in the regenerator checker-work by. flue dust. The passage of air through the heated regenerator on the other hand is helped by the chimney effect of the regenerators, is cooler and therefore less bulky, and lastly, by the use of fans, the necessary pressure to overcome any increased resistance is readily obtainable. The difference between pressure conditions during the air and gas periodsis well illustrated by figures obtained in the operation of an open hearth furnace. During the air period, the pressure at the bottom of the regenerator chambers was from 0 to inch of water, while during the gas period it is about 2 inches. Thus it is obvious that as the regenerators are constructed at-present, it is the waste gas conditions which determine the maximum velocity and minimum flue diameter.

According to the present invention, it is con-' templated to maintainthe present or customary velocity and flue diameter duringthe hot gas period and increase the velocity and decrease the flue diameter during the air period. In order to efiectuate this change, it is proposed. to'provide special small channels or fiues through which the air is caused to pass at high velocities and larger channels or fiues through which the gas is caused to pass at normal, or present velocities. Specifically, it is proposed to pass the air through aplurality of small flues, or channels, at high velocity and pass the hot gases in part through these same small channels and in part through separate, larger flues at a relatively lower velocity.

A specific embodiment of the invention is illustrated inthe following description taken in conjunction with the accompanying drawing. It is understood that modifications may be made in the illustrated embodiment without departin from the invention.

In the drawing:

Figure 1 is a sectional view in elevation of a regenerator unit in accordance with the specific embodiment of the invention. The section is taken along line 11 of Fig. 4;

Fig. 2 is a horizontal cross-sectional view taken along line 22 of Fig. 1;

Fig. is a similar view taken along a line 3-'-3 of Fig. 1;

Fig. 4 is another sectional view taken. along line 44 of Fig. l.

Referring to the drawing, the numeral 1 refers to a regenerative unit for preheating incoming air to an open hearth furnace. Hot gases, coming from the combustion'chamber of a furnace (not shown), enter the regenerator chamber 2 in the directionindicated by arrow 3, pass downflues l and 5 into

channels

6 and 7 which lead to opposite sides'and discharge the gases into the side chambers 8' and 9, respectively,which are'formed by the enlarged walls 8 and 9 as shown in Fig. 2. From the chambers 8 and 9' the gases are discharged into the stack through openings 23 and 24. When the regenerator unit is sufficiently heated, the direction of flow of gases therethrough is reversed and air is passed through the unit to the combustion chamber of the furnace.

The air is introduced through inlet 25 at the bottom of the unit from one side only, passes into channels 6 and upwardly through flues 4. There is no reverse flow of gases through channels '7 and flues 5.' Thus thegeneral mode of 'operation is that the hot gases descend through all flues of the unit and the incoming air ascends only through some of these fiues. Y Having given the general construction and op eration of the regenerator unit, a detailed explanation of the structure will now be given.

Upon the bottom 10 of the regenerator unit 1 are placed a plurality of parallel, vertical walls", or partitions, 11 having alternate channels "7 formed therebetween closed at the sides by walls 12 and alternate channels 6 closed at their other sides by walls 13. Across the tops of these walls or partitions. 11, is placed a layer of brick work 14 arrangedin checker fashion. In Figure 2, the bricks 15 are shown as spanning channels '7 at regular "intervals and bricks 16 as spanning channels 6 at regular intervals. Bricks 15 and 16 are staggered so that the portions of channels 6, which are covered, intervene or are staggered with respect to those portions of channel 7 which are covered. The channels 6 thus communicate with the upper portion of the regenerator through passages 6' between bricks 15 and channels '7 through passages 7' between bricks l6.

Positioned above the layer of bricks 14 is other brick work 17 arranged to form a plurality of hollow rectangular forms 18 as shown in Fig. 3. These rectangular forms are positioned centrally above passages 7 and the side walls of the forms 18 partially overhang passages 6'. As shown, these forms are uniformly spaced apart to give narrow channels 19 therearound. The passages 7' thus communicate with the interior-passages of the hollow forms 18 and the passages 6 communicate with the space 19 exterior to and around the forms 18. The forms 18 extend upwardly to' the chamber 2 'in the top of the regenerator unit 1 thus forming fiues 5. From a substantial distance above the layer of bricks 14 to the top of forms 18, for instance, fromthe level 22 as shown inFig. l, thespace. 19 is further broken up, or divided by a plurality of regularly positioned bricks 20 as shown in Fig. 4. The spaces 19 are therefore divided into a plurality of passages 2Iwhich extend upwardly to the chamber 2' and serve as flues 4 through which all the. air ascends from. channels 6 in the bottomof the regenerator. 1 J

Thebricks employed may bemadeof the refractories commonly used for checker bricks. The thickness of the bricks should preferably be such that the walls between adjacent air and gas fines; for instance flues4 and 5; shall be; about 1 inch in thickness and the wallsbetween adjacent air flues 4 shall be double this thickness when practicable; Thus bricks in forms 18* may be about 1 inch thick .and'the bricks 20 about 2 inches thick. The flues 5 may eachbe about 6 inches square and the flues 4, of which there-are four for. each flue 5; may each be about 2 inches square. This gives a cross-sectional area of about sixteen square inches for flues 4 for each thirty six square inches of cross-sectional area for 'fiues 5; or about sixteen square inches of flue area for the incoming airfor each fifty-two square inches of fine area for the outgoing hot gases. 1 I Referring to Fig. 2, it will be observed that there are two outlets. 23 and 24, one ateach side of the regenerator, which outlets lead to thesmoke stack. Adjacent to-the outlet 23 there is another passage 25 which leads through the wall '8 of the regenerator 1 to a fan (not shown) for supplying air underpressure. A valve26 pivoted at 27- is arrangedto-close either outlet 23 or inlet 25. and another valve 28 pivoted at 29 controls the outlet 24. "The modeof operation of the invention is as follows:

Valve 26 is moved to close inlet 25 and open outlet 23 to the stack. Valve 28 ismoved to. 'open the outlet 24 to the stack. Hot 'gases leaving the furnace enter chamber 2 in the direction of arrow 3,-p ass downwardly through'flues 4 and '5, passages 6} and 7 and'thence throughchannels d and 7, respectively, to the bottom of the. regeneratorunit. The gases passing through channels Genter'the stack through outlet 23 and gases passing through channels '7' enter thestack through outlet 24. After a sufficient interval of time for the checker bricks to become thoroughly heatedby the hot gases; the valves 26 and 28'are moved to close outlets 23 and 24 to the stack and open inlet 25 of the air supply. The flow of gases is now reversed in the furnace with the air entering through inlet 25 and traversing the regenerator unit 1 in the opposite direction to that in which the hot gases flowed. This air is introduced from only one side of the regenerator unit and is restricted so as to pass only through channels 6, passages 6', flues 4 and chamber 2 to the furnace. Due to the restricted total area of the flues carrying the air as compared with the total area of the flues carrying the hot gases and to the small cross-section of the air fiues, the velocity of the air is very high and its temperature is raised considerably.

Various modifications of the invention may be made without departing from the spirit or" the invention. The thickness of the flue walls may be varied according to the temperature of the gases and the period of reversal for the flow of gases. The essential requirement is that the air shall move at a high velocity which implies that it shall'travel at a higher velocity than the outgoing gases and that the diameter of the air flues shall be reduced; and hence they shall be less than that of the hot gas flues.

Increased velocity and decreased flue diameter provide two distinct and independent changes which favorably affect the heat transfer from flues to gases. Used conjointly, they constitute most efiicient means for heating of the air.

I claim: I p

1. A device for preheating gas which comprises a checkerwork having a plurality of independent fiues in heat conducting relationship to each other; means for conducting hot flue gas to one end of all the fines; means having communication with the other. ends of the fiues for conduct ing away flue gas; means for closing said communication; and meansfor delivering unheated gas to said other ends of part only of said fiues.

2. A device for preheating gas'which comprises a stack; a refractory structure having a plurality of substantially parallel flues invheat conducting relationship to each other; means forming a chamber for conducting furnace gases to the adiacent endsof all the fines; means including a chamber for conducting the furnace gases from the opposite ends of said fiues to the stack; means for closing the conductor to the stack; and means for introducing a cold gas to the said opposite ends of'part only of said fiuesf 3. A preheater comprising refractory bodies having a plurality of independent passages therethrough in heat conducting relationship to each other; means forming a chamber into which one end of all said passages lead; means forming a second chamber with which the other ends of "all said passages communicate, said second chamber having communication with a stack; means for opening and closing the communication between said second chamber and the stack; and means for introducing a cold gas to said other ends of part only of said passages.

'4. A preheater for incoming gas for a combustion chamber of a furnace which comprises means forming a channel for conducting gases to or from said furnace'combustion chamber; a plurality of independent flues leading from said channel in heat conducting relationship to each l other, part of said fiues having a smaller crosssectional area than the others; means forming a second chamber for communicating with the other ends of the larger flues, said second chamher having communication with a stack; means for closing communication between said second chamber and said stack; means forming a third chamber communicating with the other ends of the smaller flues and with the stack; means for closing communication between said third chamber and said stack; a gas conduit and means for opening communication between said third chamber and gas conduit to permit another gas to enter therein.

5. A regenerator system for an open-hearth furnace which comprises means forming a chamher for conducting gases to and from said furnace; a plurality of fiues leading from said chamber; a plurality of independent smaller flues in heat conductive relationship to said first named flues likewise leading from said chamber; means for conducting gases from the other ends of all said flues; and means for conducting a relatively cool gas to said other ends of thesmaller flues only.

6. A regenerative unit for a combustion furnace which comprises means forming a plurality of independent flues some of which have a smaller cross-sectional area than the others, the smaller flues being in heat conductive relationship to the larger ones; means for'delivering hot gases from said furnace to one end of all the flues; means for conducting these gases from the other end of all these flues; and means for conducting a relatively cooler gas to said other ends of said smaller flues only.

7. A preheating unit for heating gases which comprises a structure having a plurality of independent flues; means for conducting gas into one end of all the flues; means for conducting gas from the other ends of said fines; and means for conducting a relatively cooler gas to said other ends of some only of said flues, the last named flues being in heat-conducting relationship to the remainder of the fiues.

8. A heat regenerating device for providing heated gases which comprises a furnace discharge and supply conduit, a stack, a plurality of walls disposed to form discharge fines of relatively large cross-sectional areas communicating at one end with said conduit for conducting hot gases from the furnace, alternate flues of relatively smaller cross-sectional areas in heat conductive relation with said discharge fines for conducting gases to and from said conduit, means disposed to form stack connections with'the other ends of said fiues, a conduit for supplying relatively cool gas, means to discontinue the flow of flue gas, and means forming a communication with the cool gas conduit for conducting the cool gas only to said other ends of the alternate flues when the fiow of flue gas is discontinued.

9. A heat regenerating device for providing heated combustion gases to a furnace which comprises a conduit for alternately conducting flue gas from the furnace and heated air to the furnace, a plurality of stack connections, a plurality of walls between said conduit and stack connections disposed to form discharge flues of relatively large cross-sectional areas communieating at one end with said conduit and at the other end with one of said stack connections, said walls being disposed to form alternate fiues of relatively smaller cross-sectional areas in heat conductive relation with said larger flues communicating at one end with said conduit and at the other end with another stack connection, means for supplying air to said other ends of the smaller flues, means for discontinuing the flow of flue gas through said conduit, fines and stack connections, and means for establishing communication from the air supply means to said conduit through said smaller fiues.