US1914604A - Air preheater - Google Patents

Description

June 20, 1933.

W. F. KEENAN, JR, ET AL AIR PREHEATER Original Filed Jan. 24, 1930 Vv V - perature of .air to be Patented June 20, 1933 wn'raa 1-. menu, :12... or ranmm warnmrn, or rmwoon, roaurron, or new xoax, 1:.

H1303, NEW NEW JERSEY,

Y, A CORPORATION OF NEW YORK YORK, nu) JOSEPH swarm! asslonoas 'ro ros'rna wnanmm coam l mina-ma Original application filed January 24,

1980, Serial No. 483,051. Divided and this application filed [arch in, 1981. Serial Ro.,524,832.

This application is a division of our copending application Serial No. 423,051, filed January 24th, 1930.

Our invention relates to air preheaters and more particularly to air preheaters for heating air for combustion in a boiler plant by means of the products of combustion or flue gases leaving theboiler plant.

Amongst the objects of the invention are: to provide means for regulating the flow of air through an air preheater so as to maintain proper temperature conditions; to prevent formation of moisture within an air 'preheater; to selectively feed air to dif- I ferent .sectionsof an air preheater to obtain predetermined temperatures of fluids; to coordinate the flow of air to the flow of products of combustion through an air preheater so as to obtain desired temperatures of heated air and'to obtain desired temperatures of products of combustion; to regulate air. flow through an air preheater so as to obtain desired and preferably constant temsupplied to fuel pulverizing apparatus and like devices; to automatically regulate ,the flow of air through an air preheater; to automatically regulate the flow of air through an air pre-v heater to obtain desired conditions of temperature and to prevent formation of moisture within an air preheater; to provide an air prehcater in combination with a plurality of paths or conduits for flow of air to a furnace and to regulate the relative quantities of air flowing in the various paths to obtain the best operating conditions; and other objects as will appear.

The nature and advantages of the invention and the various phases thereof will become apparent from consideration of the following specification taken in conjunction with the accompanying drawing which 7 forms a part of this specification, and on which:

' Fig. 1 is a side or elevational view of an air. 'preheater embodying the invention; and

Fig. 2 is a cross-sectional, horizontal view taken on the line 2-2 of Fig. 1.

The air preheater is indicated, in general, by reference character 10. It comprises bustion pass through four sections, tion comprises side walls 15 and 16. Within each section are partitions 17 consisting of vertically arranged parallel plates. The plates are arranged to form alternate spaces separated fromeach other. For this purpose the lates are joined at the sides as shown in ig. 2 in pairs, and each plate of a pair is joined at the top to the adjacent plate of the next pair, as shown for examglae, in U. S. Patent No. 1,727 ,124, granted gtember 3rd, 1929, to William Lonsdale. etween the sections are intermediate conduits or sections 19 which connect corresponding spaces of the difierent sections to permit flow of fluid, specifically gas, serially through the sections, vertically, in one set of alternately disposed spaces. The sides of the sections are connected by intermediate conduits or return bends 20, connecting the other set of spaces for serial flow of fluid horizontally through the sections. .It will be seen that the gases (air) flowin horizontally are separated from the gases products of combustion) flowing vertically downward; Products of combustion are supplied to the air preheater at the top throu h connection 21 and flow straight downwar ly through all the sections of the air preheater, passing through the connections 19 into and through the soot hopper 34 and thence into the flue 35. 7

Referring to Fig. 2, the products of comthe spaces 24. Air is admitted to the preheater by means of the lower conduit 23, passes transversely through section 14, thence through the intermediate conduit 20 connecting section 14- with section 13, thence transversely through section 13, thence through the right-hand conduit 20, thence transversely through'section 12, thence through the upper left-hand intermediate conduit 20, thence transversely through the upper section 11 and thence to the boiler in which'the heated air is to be used. Referring further to Fig. 2, it will be seen that the air asses through the spaces 22. It will also seen that the air and the products of combustion do not come into direct contact.

11, 12, 13 and 14. Each sectages in that the heat I at certain .l

Eeroducts of combustion would be lowered to 27 presence of moisture,

With the arrangement thus fardescribed, wherein roducts of combustion pass through al of the sections of the air preheater Fug air rob b h tionsote air eater itispossilet at (wi the temperature of the low what is known'as the dew-point, at which point of temperature, steam, carried in the products of combustion, condenses and recipitates. It is desirable to avoid the owerlng of the temperature of the products of combustion to the dew-point in order to prevent preci itation of moisture, particularly with certain fuels of high sulphur content, since water and the sulphur dioxide resultin from the combustion of such fuels combine to form sulphuric acid, which is highly corrosive. Corrosion causes uneven surfaces of metal. With moisture present, ash in the dproducts of combustion tends to deposit an form a sticky mass on the uneven surface produced by corrosion. Such sticky deposit may form a distinct coating on the metal and may causefurther deposits. The passa es of air preheaters are small in order. to 0 tain eiiiciency of heat transfer and in order to economize on space. The formation of such depositsidue to the corrosion and ash content of the products of combustion may materially diminish the cross-sectional'area of flow in the passages between the plates of the preheater, that is, between partitions 17.

rrosion itself is undesirable because it decreases the life of ap aratus, but, in this case, there is the added disadvantage of the dliacreasel1 of Th d f t e re eater is ecrease o flow in ea carrie s with it several disadvantransfer capacity of the plates is reduced; the draft loss is increased, as a result of which more power is of plants already equipped with the preheater at a sutlicient rate.

necessary to operate the fan to draw the gases through the preheater; and, in the case fans of given capacity, the accumulation of deposits may reduce the capacity of the steam generating unit due to the inability of the fans to draw the products of combustion through To overcome this diiiiculty we have provlded a by-pass conduit 25, a damper or valve 26 in by-pass' con :lult 25, and a damper or valve 27 inthe intermediate conduit 20 between sections 13 and 14. By-pass conduit 25 connects the air supply conduit 23 with the intermediate conduit 20 between sections 12 and 13. By closing damper 22- and opening damper 26, all the air to be heated passes directly to section 12. -Damper may be used to prevent recirculation of air around sections 18- and 14 when the damper 26 is open. By partially opening damper 26 and having damper 2'? open, or

passes through all of the or in para and cross-sectional area of flow of 0 products of combustion partially open, some of the air will pass thro b all the sections and some will pass only ugh two sections. The proportion of air passing through all sections and bypassing some sections can be regulated by proper manipulation of the dampers 26 and If the air is cold or if other conditions prevail such that there is a lowering of the temperature of the products of combustion to or below' the dew-point, the air can be passed through by-passconduit 25 in whole thus a temperature can be maintain in the outlet for of combustion which is above the dewint.- By regulating the dampers it is possi le to obtain a constant temperature in the products of .combustion leav' the air pre heater, or in any degree, 31m limitations, of variation of temperature desired, independentl or in spite of variations of load.

It wil be readily seen that one or more of the sections may be b -passed in this way. The conduit 25 may be connected between conduit 23 and the air inlet for section v13, or even with the air inlet for section' 11.

The damper 26 may be interconnected with the damper 27 and they may be automatically controlled in accordance with the temperature of products of combustion leaving the reheater.

t wil be understood that variations may be made within the spirit and scope of the invention; g

What we claim is: e 1 Apparatus for heating air by products f com ustion comprising a plura i nected to form two sets of separated spaces means to connect .the sections for flow o serially. through the sections in one set of separated spaces, lateral return bends connecting the sections for passage of air serially through the sections in the other set of separated spaces, an air supply conduit, an air discharge conduit means tos'uppl combustion, a yconnection between the air su ply con uit and one of the return bends, and a damper in said by-pass connection.

2. A paratus for heating air by products I of com ustion comprising a plura i of sections, each having closely sp plates connected to form two sets of se arated spaces, means'to connect the sections or flow of products of combustion serially through the sections in one set of se arated spaces, lateral return bends connecting the sections for passa of air serially through the sections in 0 other set 0 separated spaces,

an air supply conduit, an air discharge conduit, means to supply and discharge products of combustion, a by-pass connection bethe products ty of sectime, each having closely spaced pla'tesconand discharge products of tween the air supply conduit and a return bend connected to the next to the last section in the line of flow of roducts of combustion, and a damper in said iy-pass connection.

3. Apparatus for heating air b products of combustion comprising a plura ity of sections, each having closely spaced plates connected to form two sets of separated spaces, means to connect the sections for flow of m products of combustion serially throu sections in one set of'separated spaces, ateral return bends connecting the sections for passage of air serially through the sections in the other set of separated spaces, an air supply conduit, an air discharge conduit, means to supply and discharge products of combustion, a y-pass connection between the air supply conduit and the return bend connecting the second and third sections in the line of air flow, a damper in said by-pass connection, and means to cut ofi flow through the return bend connecting the first and second sections in the line of air flow. a

4. Apparatus for heating air by products of combustion comprising a plurality of sections, each having closely spaced plates connected to form two sets of separated spaces, means to connect the sections for flow of products of combustion serially through the 39 sections in one set of separated spaces, lateral return bends connecting the sections for passage of air serially through the sections in the other set oil separated spaces, and means to supply air to cheer the other or both of the first and third sections in the line of flow of air. 7

5. In a due gas preheater of the plate type including a plurality of sections, the method of controlling thetemperature of flue gases leaving the preheater which comprises sup plying air to the one or the other or both of the first and third sections in the line of air flow to maintain the temperature of the flue gases above the dew point. p 6. Apparatus for heating air by products of combustion comprising a plurality of sections, each section having a passage for the flow of products of combustion therethrough and a passage for the flow of air therethrough out of contact with said products of combustion, means for connecting the sections so that the products of combustion flow serially through the several sections, conduits connectin the sections and the air passages so that t e air flows serially through the several sections, an air supply conduit, an air discharge conduit, means to sup ly and discharge products of combustion, a bypass connection between the air supply conduit and one of the conduits connecting said air passages, a damper in said by-pass connection, and a damper for controlling the flow of air through the conduit connecting the air passages in the sections which are 6e by-passed.

h the' 7. Apparatus for heating air b products of com ustioncomprising a plura ity of sections, each section having a passage for the flow of products of combustion therethrough and a passage for the flow of air therethrough out of contact with said products of combustion, means for connecting the sections so that the products of combustion flow serially through the several sections, conduits connecting the sections and the air passages so that the air fiows serially through the several sections, an air supply conduit, an air discharge conduit, means to supply and discharge products of combustion, and means to supply air to one or the other or both of two sections separated by one or more other sections.

8. In a flue gas prcheater having a plurality of sections, each provided with a passage for the flow of products of combustion therethrough and a passage for the flow of air therethrough out of contact with the products of combustion, the products of combustion and air passages respectively of the several sections being connected in series, method of controlling the temperature of flue gases leaving the preheater which comprises supplying air to two sections separated by one or more other sections to maintain the temperature of the due gases above the dew point.

In testimony whereof, we have hereunto afiixed our signatures.

WALTER F. KEENAN, da.

JOSEPH STANLEY W ETHERALD.

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