US2500771A

US2500771A - Tubular air preheater for steam generator units and the like

Info

Publication number: US2500771A
Application number: US694792A
Authority: US
Inventors: John V Pyle
Original assignee: Kennedy Van Saun Manufacturing and Engineering Corp
Current assignee: Kennedy-Van Saun Manufacturing & Eng Corp; Kennedy Van Saun Manufacturing and Engineering Corp
Priority date: 1946-09-04
Filing date: 1946-09-04
Publication date: 1950-03-14
Anticipated expiration: 1967-03-14

Description

March 14, 1950 J. v'. PYLE 2,500,771

TUBULAR AIR PREHEATER FOR STEAM GENERATOR UNITS AND THE LIKE 2 Sheets-Sheet 1 Filed Sept. 4, 1946 INVENTOR JO/l/V u m: BY 7 v ZMM'@71I-Z-w will? ATTO R N EYS March 14, 1950 J. v. PYLE 2,500,771

" TUBULAR AIR PREHEATER FOR STEAM GENERATOR unrrs AND THE LIKE Filed Sept; 4, i946 2 sheets-she??? lN ENTOR Jail/V PYLE 'ATTORNEYS Patented Mar. 14, 1950 UNITED This invention relates to improvements in tubular air preheaters such as the preheaters used in connection with large steam generator units.

In large steam generator is usually built as a part positioned that the hot combustion gases from the upper part of the unit pass over into the tubes of the air preheater and pass downwardly through the tubes of the air preheater in heat exchange with air passing around the tubes, which is prereplacement of lower tubes is necessary in the heated for use in the generator. It has been found expedient in the case of large steam generators to build the airpreheater in two sections one above the other. In such practice each secfeet or more in length,

or otherwise secured in tube sheets. The two sections are commonl constructed alike and one section set above the other in spaced relation so between the two adjacent sections.

One of the difiiculties in such constructions is that in order to make repairs in the lower section of the air preheater it The primary object of improved air preheaterfor section. In the preferred I provide an air preheater as for example for a large steam generator unit with upper and lower tube sections. The lower the same number of tubes tion, but they are of a diameter. such that tubes of the lower section may be passed through the tubes of the upper section. In this connection I arrange the sections so lower section are directly below the tubes of the STATES PATENT OFFICE TUBULAR AIR PREHEATER FOR STEAM GENERATOR UNITS AND THE-LIKE John V. Pyle, Briarclifi Manor, N. Y., assignor to Kennedy-Van Saun Mfg. & Eng. Corp., New York, N. Y., a corporation of Delaware Application September 4, 1946, Serial N 0. 694,792

10 Claims. (Cl. 257-224) units the air preheater placements are made.

of the setting and so 5 with their ends rolled is necessary to remove In the drawings: the present invention invention. use in connection with on an enlarged scale.

form of my invention tube section includes that the tubes of the as those in the upper tube section.

My improved tubular air preheater includes other features, objects, and advantages which will be readily understood from the following detailed For one thing the tubes of the lower section redescription thereof taken in connection with the quire much more frequent cleaning, to remove soot, than the upper'tubes, as well as much more frequent repair and replacement.

upper section so that the smaller lower tube may be moved upwardly through the corresponding tubes of the upper section, When repairs or re- An air preheater constructed in accordance with the features of my invention has been found to have a number of advantages over preheaters made in accordance with known practices. example, I have found that much less repair or new construction and that a greater efficienc is achieved in the transfer of heat from furnace gases to the air being preheated. cleaning of the lower tube section has also been tion is constructed with vertically arranged tubes 16 found necessary. This increase in eficiency is quite unexpected since the use of smaller diameter tubes in the lower section of the air preheater reduces considerably the heat exchange surface between the combustion gases and the that it is possible for man to get in and work 20 air being preheated. However, it appears that the smaller tubes in the lower section have the function of keeping up a relatively high combustion gas velocity which results in the maintenance of cleaner tubes and a higher rate of heat transthe tubes in the upper section, that is in order 25 fer than in the case of tubes of the same diameter to remove tubes in the lower section. It has also been found that most of the tube difiiculties arise in connection with the lower section. Some of the reasons for this are not clearly understood.

accompanying diagrammatic drawings forming a part of this application.

Fig. 1 is a broken vertical sectional view showtherefore is to provide an improved tubular air ing a portion of alarge steam generator unit proprcheater which will be free of the difficulties and disadvantages referred to above.

Another object of my invention is to provide an vided with an air preheater constructed and arranged in accordance with the features of my Fig. 2 is a broken vertical sectional view showlarge steam generators which is easy to repair ing a portion of the apparatus illustrated in Fig. 1 and maintain.

I have discovered that most if not all of the difiiculties referred to may be eliminated if the lower tube section is constructed of tubes of smaller diameter than those of the upper tube trating the method of removing and replacing tubes of the lower tube section of the heater.

Fig. 5 is abroken elevational view of the tubular preheater shown in'Fig. 1, looking from the left. Fig. 1 of the drawings shows a portion of a as the upper tube seclarge steam generator unit mounted in a building structure having a side wall It and a roof l2. The portion of the generator as shown includesv a water and steam drum M, in the upper part of the setting, and a lower drum it, which are connected by long steam generating tubes l8.

Fig. 3 is a broken horizontal sectional view taken on the broken line 3-3 of Fig. 2.

Fig. 4 is a view similar to that of Fig. 2 illus- For Much less eter. upper and lower tube sheets 45 carrying regularly spaced heat exchange tubes 48.

The steam generator includes a firing chamber and other conventional elements from which the combustion gases pass upwardily through a chamber to heat the tubes i8 mounted in the furnace. These gases pass around the upper ends of the tubes l 8 into a tubular air preheater which may extend substantially across the generator and which, as shown, comprises an upper tube section or bank 22 and a lower tube section or bank 24. As an example, these sections may be 20 feet or more in height.

The

tube sections

22 and 24 are mounted in the steam generator setting in the usual manner and carried by the usual steel framework structure as, for example, by steel beams 26. The tubular air preheater is enclosed by the refractory walls as indicated and the two sections are mounted one above the other with anintervening space or chamber 28 suitable for a man to enter for inspection, replacement, or for installation work. The side of the chamber 28 is provided with a row of refractory lined doors 30 which are removably by a block and tackle.

The combustion gases from the chamber 1 which pass over into the tube bank 22 pass downwardly through both sections of the tubular air preheater and out through ducts 3t and to a stack or exhaust fan not shown. Any dust 1 settled out of the gases leaving the section M is The air to be removed through a dust trap 31. preheated is introduced around the tubes of the section 24 at the bottom of the setting and passed upwardly around bailies 38, through a by-pass duct shown in Fig. 5 and then upwardly around the tubes of section 22. Baffles 42 causes the air to pass in a zigzag path across the tubes of the preheating section 22 until it reaches the top of the section 22 where the hot or preheated air is discharged through a duct M, and con.-

ducted to the combustion chamber of the generator unit by means not shown.

An important feature of my invention as pointed out above is the construction of the preheater section v22 with one size of tubes and the preheater section 24 with tubes of a smaller diam- It will be noted that the section 22 includes The lower preheater section 24 comprises upper and lower tube sheets 50 in which are mounted tubes 52 having an outside diameter slightly less than the inside diameter of the tubes 48, for example, the tubes 52 may be one size smaller than the tubes 66.

This relationship is illustrated in enlarged scale in Figs. 2 and 3. The

tubes

48 and 52 may be rolled in their respective tube sets or welded therein. It will be noted that in accordance with the showing in Fig. 3 the tubes 52 are mounted directly below and axially in line with the tubes 48.

In most generator installations the conditions are such that the tubes in the lower preheater section require more frequent replacing than thetubes in the upper section. In the present in stance, this replacement of the tubes in the lower preheater section is made rather simple since each lower tube may be removed directly through one of the tubes 48, that is, the tube directly above. Fig. 4 of the drawings illustrates the manner in All.

which this may be readily accomplished. If an inspection of the tubes 52 shows that some of them must be removed, they are cut away or otherwise removed from the tube sheets 50 after which a rope 54 is lowered through the tube d8 directly above and also through the tube 52 to be removed. A knot or other suitable attachment 56 is applied to the end of the rope below the tube 52 and then the latter is raised through the tube 48 by the rope 54 which may be passed through a sheave 58 as indicated. A new tube may be inserted in its proper place in the tubular section 24 by following the foregoing procedure in reverse. If the rope 54 is a metal rope or cable, it may be used for holding the new tube while it is spot welded in place. In making repairs the closures 3H and 32 are removed and a man enters the space below the section 26, through trap 31 or an end door 68 as shown in Fig. 1.

Many of the large steam generator installations are housed in buildings so arranged that the use of Vertically spaced air preheater sections of the type of

sections

22 and 24 are highly desirable from the standpoint of repair and replacement of parts. While it is possible in making the original installation to install

sections

22 and 24 as units, the section 24 being installed first, it is not usually possible in view of all the other equipment such as flue ducts, air ducts, and various auxiliary units, to remove a section as a whole. The present invention therefore provides a novel construction and procedure by which repairs and replacements of tubes in such a tubular air preheater may be made. The improved construction not only facilitates repairs to the lower section of the air preheater, but also provides a preheater which is more efiicient than present preheaters and which, because of the use of smaller tubes in the lower section, is less expensive.

From the foregoing description it will be understood that certain minor changes in the construction and arrangement of the various parts may be made without losing any of the advantages of the apparatus. Such changes are contemplated as coming within the spirit and scope of the appended claims.

What I claim as new is:

1. In a tubular air preheater of a steam generator unit adapted to receive hot combustion gases and air to be preheated thereby, an improved air preheater comprising vertically arranged tube sections each of which includes a bank of vertically mounted tubes for the passage of hot combustion gases, said tube sections being spaced apart to provide access for repairs between sections and arranged so that the hot combustion gases from the upper tube section pass downwardly through the tubes of the lower tube section, and the tubes of the lower tube section having an outside diam eter slightly smaller than the inside diameter of the tubes of the upper section, whereby the tubes of the lower section may be removed through the tubes of the upper section for repairs and replacements.

2. An air preheater as defined by claim 1 in which the tubes of the lower tube section are mounted in axial alignment with tubes of the upper tube section.

3. An air preheater as defined by claim 1 in which the air preheater is mounted within. the steam generator setting and includes a removable closure above the upper tube section, a removable closure for the space between the tube sections;

and a removable closure for the space below the lower tube section.

4. An air preheater as defined by claim 1 in which means is provided for passing air to be preheated first around the tubes of the lower tube section and then around the tubes of the upper tube section.

5. In a tubular air preheater for preheating air by heat exchange with hot combustion gases, a pair of upright tubular heat exchange sections mounted one above the other and each including a bank of long vertically arranged tubes, the tubes of the lower section having an outside diameter slightly less than that of the inside diameter of the tubes of the upper section and being arranged with their axes substantially coincident with the axes of the tubes of the upper section, whereby tubes of the 1ower section may be passed through tubes of the upper section.

6. A tubular heat exchange unit comprising upper and lower tube banks comprising upwardly extending tubes, means for mounting one bank of tubes directly above the other and in spaced relation with respect thereto, the tubes of the lower bank being mounted below and in line with tubes of the upper bank and having an outside diameter slightly smaller than the inside diameter of the tubes of the upper bank, whereby tubes of the lower bank may be moved through tubes of the upper bank.

7. In a tubular heat exchange unit comprising tubular sections arranged one above the other and each having vertically arranged tubes, the tubes of the lower section being of an outside diameter slightly smaller than the inside diameter of the tubes of the upper section and arranged with their axes substantially coincident with the axes of the tubes of the upper section whereby tubes to be replaced in the lower section may be passed respectively through vertically aligned tubes of the upper section.

8. A tubular heat exchange apparatus including vertically arranged tubular sections in which the tubes of the upper section are mounted in axial alignment with the tubes of the lower section, and the tubes of the upper section having an inside diameter slightly greater than the outside diameter of the tubes of the lower section, means extending through a tube of the upper section adapted to be attached to a tube of the lower section, and means for elevating the tube to which said means is attached through a tube of the upper section.

9. A tubular heat exchange apparatus as defined by claim 8 in which the means extending through an upper tube comprises a rope.

10. In a tubular air preheater adapted to receive air to be preheated and hot combustion gases for effecting preheating, the improvement which comprises an upright tubular air preheater including means at its upper end for receiving hot combustion gases, means at the bottom of the preheater for discharging hot combustion gases, the tubular air preheater including vertically spaced banks of vertical tubes the ends of which are mounted in tube sheets, the tubes of the lower bank having an outside diameter slightly smaller than the inside diameter of the tubes of the upper tube bank and being mounted with their axes aligned respectively with the axes of tubes of the upper tube bank, a removable closure above the upper tube bank for access thereto, and a removable closure for the space between the tube banks for access thereto.

JOHN V. PYLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 854,980 Bonus May 28, 1907 2,245,720 Rohrer June 17, 1941 2,418,815 Baver Apr. 15, 1947 FOREIGN PATENTS Number Country Date 234,923 Great Britain June 11, 1925 636,388 Germany Oct. 7, 1936 86,349 Switzerland Oct. 16, 1920