US2654350A - Combustion chamber - Google Patents

Description

Oct. 6, 1953 s. L. FITZPATRICK COMBUSTION CHAMBER 5 Sheets-Sheet l Filed Jan. 14, 1948 C. 6, 1953 s. 1 FlTzPATRlcK 2,654,350

COMBUSTION CHAMBER Filed Jan. 14, 1948 3 Sheets-Sheet 2 El E INVENTOR.

Oct. 6, 195,3 s. L. FITZPATRICK 2,654,350

COMBUSTION CHAMBER Filed Jan. 14, 1948 5 Sheets-Sheet 5 1N VEN TOR.

Patented Oct. 6, 1953 UNITED STATE.

TENT OFFICE COMBUSTION CHAMBER Stephen L. Fitzpatrick, Detroit, Mich., assignor to Blokolgas System, Inc., Detroit, Mich., a

corporation of Michigan 3 Claims.

This invention relates broadly to new and useful improvements in furnaces for solid pulverulent fuel such as powdered coal and the like and more particularly to a furnace of this character having an improved form of combustion chamber which is relatively small and compact and at the same time permits complete combustion of the fuel particles to occur.

An important object of the present invention is to provide a furnace having a combustion chamber which is primarily adapted and preeminently suited for small scale domestic installations.

Another object of the invention is to provide a furnace in which the combustion chamber is uniquely shaped to provide a relatively long travel for the products of combustion before the same pass into the stack.

Still another object of the invention is to provide a furnace of the above-mentioned character which is suitable for either high or low pressure operation.

Yet another object of the invention is to provide a furnace of the above-mentioned character having provision for introducing air at lstrategic points to assure complete combustion of the fuel before the same leaves the combustion chamber.

A further object of the invention is to provide a furnace of the above-menticned character having provision for circulating a iiuid in heat eX- change relation with the combustion chamber.

Other objects and advantages of the invention vill be apparent during the course of the followI ing description.

In the drawing forming a part of this speciflcation and wherein. like numerals are employed to designate like parts throughout the same,

Figure 1 is a vertical, longitudinal, sectional View through a furnace embodying the invention;

Fig. 2 is a vertical, transverse sectional view taken on the line 2 2 of Fig. l;

Fig. 3 is a vertical, transverse sectional View taken on the line 3 3 of Fig. 1;

Fig. 4 is a vertical, longitudinal, sectional view showing a modified furnace construction embodying the invention;

Fig. 5 is a vertical, transverse sectional view taken on the line 5-5 of Fig. 4;

Fig, 6 is a vertical, transverse sectional view taken on the line 6 6 of Fig. 4;

Fig. 7 is a vertical, longitudinal, sectional view through another modified furnace construction embodying the invention; and

Fig. 8 is a vertical, longitudinal, sectional View through still another modied furnace construction embodying the invention.

Referring now to the drawings, attention is first directed to Figs. 1-3 which illustrate a small domestic-type furnace adapted primarily for low pressure operation. In general, the furnace may be made of any suitable refractory material IQ, and the latter is fashioned to define a combustion chamber I2. The present invention resides primarily in the shape of the combustion chamber I 2 and the manner in which it functions to assure substantially complete combustion of the fuel. The furnace here shown by way of illustration is adapted for horizontal operation, i. e., the fuel is injected horizontally into the combustion chamber I2; however, it will be readily apparent that the furnace can be adapt-` ed for vertical or other operation if desired.

More specifically, the furnace here shown has a vertical wall I6. at one end of the combustion chamber I 2 and a horizontal bottom I 6 which defines the iioor of the combustion chamber. Fuel inlets I8 are provided in the lower portion of vertical wall I@ and fuel injection nozzles 2d in the inlets deliver fuel and air at a controlled rate to the combustion chamber I2. While two inlets I 8 are here shown, it will be understood that a greater or lesser number of inlets may be provided depending on the size of the furnace and the exigencies of the particular situation. Any suitable or conventional apparatus may be used to deliver the fuel to the combustion chamber, but I prefer to use equipment of the type shown in my copending applications, Serial No. 787,765, which was filed on the 24th day of November, 1947, and Serial No, 791,037, which was led on the 11th day of December, 1947, now abandoned. The fragmentary nozzle assemblies here shown correspond to the nozzle assembly shown in the last-mentioned application and include auxiliary air inlets 22 above the fuel openings i. A window 24 is provided in the wall -I between the auxiliary inlets 22 and the fuel injection nozzles 2li.

The powdered coal is blown into the combustion chamber I2 in a forced draft of air and the fuel is ignited as soon as it enters the chamber. When the fuel is injected horizontally in the manner here shown, it travels above the floor of the combustion chamber to the remote or distal end thereof. According to the present invention, the bottom IB of the furnace is formed with a plurality of laterally spaced parallel elongated openings 26 immediately in front of the injection nozzles 20 and each opening 26 is closed by a 3 pivoted, rotatable plate 28, as shown in Fig. 2. As the flame travels above the floor of the combustion chamber I2 a small amount of fly ash settles out and accumulates on the plates 28 which normally are positioned horizontally as shown in the drawings to close the openings 26. The closure plates or traps 28 may be rotated continuously or intermittently in. any suitable manner to dump the fly ash into a suitable chamber or receptacle (not shown) disposed below the openings 26.

The combustion chamber I2 is generally rectangular in transverse section as shown in Fig. 2 and is horizontally elongatedin longitudinal section as shown in Fig. 1. Also, it will'be observed that the exhaust stack or opening 30 is located at the inlet end of the combustion chamber 'adjacent the vertical wall I4 and directly above4 the fuel inlets I8. At the end thereof remote from fuel inlets I8 the floor I6 curves upwardly, as at 32, and the upper portion of the-distal end wall 34 is reversely curved at 3b. The reversely curved top portion 36 merges smoothly with a downward protuberance or re-entrant portion 33 adjacent the exhaust opening or stack'30. The protuberance 38 extends downwardly into the combustion chamber I2 and defines a restricted opening or passage d between the distal end 34 of the furnace and the inlet and exhaust openings I8 and 36.

In operation, flame sweeps above the floor of the combustion chamber and is deflected upwardly by the portion 32. The upwardly deflected flame is again deflected by the upper curved portion 36 so that it'doubles back and completes a 180 turn. At this point, the flame is deflected downwardly by the protuberance 38 before passing back through the restricted passage i0 into the exhaust opening 30. The opening 3B may lead directly to a stack or'it may lead to a heat exchange-unit'where further heat is extracted from theflue gases. In most instances thelatter condition will prevail. However, all of the flaming products of combustion do not pass directly into the exhaust'opening 30. The downward deflection of the flame by protuberance 38 causes. some of the combustion products to sweep downwardly, as indicated by the arrows in Fig. 1, so that' theyl merge with the flame sweeping along the floor. of the combustion chamber; Thus, aA constant eddying or circulation of the flame occurs in the relatively largev distal end of the; combustion. chamberA to assure substantially complete4 combustion vof the fuel.

Also, itis significant to notethatithe. auxiliary air inlet 22 is located to supply airto the combustion chamber just before'the products of combustion enter the exhaust opening 30 sothat any unburned fuel which may be carried over to this point is completely burned. before it` leaves the combustion chamber.

The particular shape of the combustion .chamber provides a relatively long travel for the fuel and. this factoris exceedingly important in .maintaining complete combustionvvithin the` chamber. Also, the constant circulationand turbulence of the flame in the. rearward or distal end of the combustion chamber maintains the fuel particles in constant agitation and prevents particles of fuel from clinging together or' accumulating on the oor of the combustion chamber. This condition is largely due to the fact that the flame is deflected through an angle greater than 180 but less than.270 since this pallu' .4 lar configuration provides the necessary long travel and causes the products of combustion to circulate in a turbulent condition in the rearward portion of the furnace.

To obtain complete burning of a, fuel, it is necessary that the fuel be intimately mixed with air and that every bit of the fuel come in contact .withoxygen in the air. Also, for best efflciency and control, it is necessary that the correct proportion of coal and air be uniformly present throughout the combustion chamber at alltimes; These conditions can be maintained in the furnace construction here shown, if the fuel .is properlypulverized and delivered together witha proper. amount of air in the manner disclosed in my previous applications hereinabove referred to.

On .the other hand, the above conditions cannot'be obtained in a Stoker or hand-red coal furnace. In the latter type furnaces, lumps of coal are mixed with slack and ashes and it is not possible for every particle of coal to come in contact with the air. Air flows erratically andV unevenly through the large bed of coal so that part of the fuel burns slowly and part burns rapidly. Moreover, inadequate distributionV of air causes clinker formation; and the clinkers usually include substantial amounts of unburned coal. Further, combustible gases released in areas where air flow is restricted may escape unburned. Also, if there is a local excess of air, the lowered temperature may prevent complete combustion of the carbon and volatile matter in the coal.

It is generally recognized inthe art that one pound of coal burning to carbon dioxide liberates 14,545 B. t. u. On the other hand, one pound of coal burning to carbonmonoxide liberates only 4,375 B. t. u. These statistics clearly point out theimportanceof providing an ade- 4quate supply of air inthe combustion chamber and of maintaining uniform distributionof the coal particlesl in.. the. air. It is impossible to obtain aneven mixture of air. with the coalin hand or'stoker fired furnaces. As a result, much of'thecarbon in the coal is converted to carbon monoxideinstead of carbon dioxide. Each pound of carbon converted to carbon monoxide represents a loss of 10,170 B.r t. u. The system. of which the combustion chamber embodying the present inventionis a part, assures suicient oxygen inthe. combustion chamber to. convert. all of thecOalpartiCles to carbon dioxideandthus obtain maximum heatfrom thev fuel. The particular shape and construction of the combustion chamber assures an adequate supply and proper distribution of air in the chamber, and -the manner in which the fuel is circulated and recirculated in the rear portion of the combustion chamber assures ample time for complete combustion before the products of combustion are exhausted from the chamber. Y

When coal is properly pulverized, 180,000,000 particles are produced from each cubic inch of solidK fuel. The millions of tiny particles have 550 times as much burning surface area as a corresponding amount of the original solid fuel. When the finely divided coal particles are uniformly distributed in an air stream, the combustible mixture thus produced will flow in the same manner as a liquid fuel. It is contemplated that finely divided fuel of this type properly mixed with air be injected into the combustion chamber I2. If the flow of the combustion mixture to the chamber is properlyv controlled, every particle of coal is completely burned within the chamber; and a maximum amount of heat is extracted from the fuel. There is no waste of heat and black sooty smoke is not exhausted from the combustion chamber to plague the adjacent community.

Preferably, the combustion chamber l2 is surrounded by a network of passages or pipes through which water circulates. The purpose of these pipes is to maintain the walls of the combustion chamber at a temperature well below the fusion point of the refractory material or of fly ash which might come in contact with it. This prevents warping of the combustion chamber wall and prevents clinkering of the iiy ash. The water may be circulated through the pipes or passages in any suitable or conventional manner and the heat absorbed by the water may be salvaged when the water is cooled.

In a hot air furnace, water drawn from the furnace is circulated through cooling coils before being returned to the chamber walls. Air blown across the cooling coils becomes heated and may be used as the intake air of a hot air system. At the same time, the water in the coils is cooled before being returned to the furnace. Thus, the air receives initial heat from the coils before passing to the main heating element.

Alternatively, if the combustion chamber is used in a steam heating system, the preheated water drawn from the furnace is directed to a boiler where it is turned into steam in the conventional manner. |The condensate from the radiators is returned to the pipes or passages in the furnace to complete the cycle.

.A third suggested procedure for salvaging heat absorbed into the water which flows through the walls of the combustion chamber would be to use such water for domestic hot water.

Any suitable means may be employed for circulating the water in heat exchange relation with the wall of the combustion chamber l2. A typical means for accomplishing this result is shown in the drawings. According to the present invention, the top, distal end, and bottom of the furnace are made up of individual vertical sections !12 placed side by side as shown in Fig. 2. Each section 42 is provided with a longitudinal passage Ml which communicates at opposite ends thereof with upper and lower headers li and t8 (Fig. l). Forwardly of the bottom header d8 are parallel sections 5t which are laterally spaced apart to denne the elongated openings 2e. Each section 5B is provided with a longitudinal passage 52 which communicates with the header 48.

The two sides of the furnace and the front wall lli are similarly formed of independent vertical sections placed side by side. Each of the side sections 5d is formed with a longitudinal passage 56 which communicate with the longitudinal passage it in the adjacent section d2.

The front sections Sii also are formed with longitudinal passages 58 and these passages are connected by transverse passages 6d which are located as required to by-pass the window 25 and fuel inlets I8 (Fig. 3). It will be observed that the vertical and transverse passages 58 and et form a network of passages which communicate at the lower end thereof with certain of the passages 52 in the bottom of the furnace and at the upper end thereof with a suitable header EiZ.

Connections (not shown) are adapted to be coupled to headers i6 and 62 to charge relatively cool water to the heat exchange system of the furnace and to withdraw heated water therefrom.

Preferably, the relatively cool water is charged to header 46 and as the water is circulated through the walls of the furnace, heated water is removed from the header B2. However, it will be readily apparent that, if desired, the water may be circulated in a reverse direction through the furnace.

Reference is now had to Figs. 4-6 which show a modified furnace construction having a high pressure combustion chamber 6&5 which is capable of giving greater heat for a given size. This type of furnace is particularly adapted for larger installation than the furnace rst described or for use in installations where quick heat pick-up is desired. The greater heat is obtained by charging the fuel and air mixture to the combustion chamber under higher pressure.

In general, the furnace here shown has substantially the same shape as the furnace hereinabove described, but it is constructed somewhat differently to provide a different arrangement of the heat transfer passages. In the latter form of the invention, the sides 5S of the furnace preferably are made from single units and the top, distal end and bottom preferably are made up of a plurality of individual units 68 laid side by side, as shown in Fig. 4. Also, it will be observed that the sides 66 and the units t8 are formed with passages which intercommunicate to provide a Water circulatory system through the walls of the furnace.

Also, in -this form of the invention, the for- Ward bottom sections 5@ are omitted, and the opening 'l0 produced by their omissions is cov ered by a plurality of vertically spaced, stepped, overlapping plates 12. The series of plates 'I2 preferably extends rearwardly for a short distance across the floor of the combustion chamber substantially to the point where the latter begins to slope upwardly. Pipes 'lli arranged transversely across the opening 'lll and preferably inoorporated in the water circulation system of the furnace, supports those plates 'i2 which cover the opening. The plate or plates disposed above the floor of the combustion chamber may be supported in any suitable manner.

A forced draft of air is blown upwardly through the opening 1l), past the pipes lil, and between the pla-tes 'l2 into the combustion chamber, as shown by the arrows in Fig. 4. This air may be obtained from any suitable source and preferably is prehea-ted to assure satisfactory combustion. In this connection, it will be readily apparent that air entering the combustion chamber 5t through the opening lil supplies available oxygen to the fuel injec-ted through nozzle assemblies 2l) and thus promotes combustion of the fuel immediately upon entering `the chamber. The particular arrangement of the plates I2 directs the air rearwardly in the combustion chamber til, and the current of air thus created sweeps along any ily ash that might tend to settle. Since the combustion chamber begins to slope upwardly immediately adjacent the endmost plate 12, the rising current of air carries any fly ash that may be present upwardly vand does not permit it to settle on the floor of the chamber.

Advantages also are obtained by supporting the plates l2 on the pip-es lll, since the water traversing the pipes cools the plates and keeps them from warping. I have found that, by arranging the pipes and passages horizontally in the manner here shown, the furnace is easier to assemble and maintain and al morecomplete cooling capacity is obtained. Also, the individual sections which make up the furnace are less expensive to make'than sections-which fol.- low the contour of the furnace asin the form of the invention rst described.

Water circulated thro-ugh the walls of the furnace and through the pipes 'M is heated, and the heat conveniently can be salvaged in the manner hereinabove described by `transfer to hot air, by using the water for a boiler, or by using it for domestic hot water.

As the flame 4circulates up and around the back of the combustion chamber 64 a great deal of heat is developed due to the high pressure system of operation. As a result, a hotspot tends to develop near the top of the combustion chamber @Il atl the point where the hot gases have completely doubled back and" are moving toward the exhaust opening or stack 3E. The general location of this spot is designatedby the numeral 'I in Fig. li. In order to prevent the concentrated heat from burning out the furnace, I provide an air opening 'I8 immediately Ibehind the point at which the hot spottends to develop. Air is sucked into the combustion chamber 64 through the opening 'I8 and the inrushing air accomplishes several important results. It cools the hot spot 1S, it helps draw down hot gases which otherwise might be trapped at the top of the back of the combustion chamber 54, it adds fresh air to assure complete combustion before the flaming gases pass into the exhaust opening or stack 30, and it tends to force the gases to make a complete circle before owing away from the rear of the combustion chamber. Since the fuel flows into the combustion chamber under relatively high pressure it moves along rapidly, and, consequently, an occasion-al particle of fuel might pass entirely through the combustion chamber without complete burning if some provision were not made to. extend'the travel in the chamber. In the instant arrangement, the downdraft created by air entering through opening 'I3 deflects the hot gases o-f combustion downwardly; and, as shown by the arrow Bil in Fig. 4, tends to induce circulation of the fuel in therear portion of the combustion chamber Eli.

In this form of the invention the combustion chamber 64 preferably is lined witha suitable refractory material 82 in order to assure ample protection against the terrific heat which is developed therein. The `portions of the liner at opposite sides of opening I8 preferably overl-ap, as shown in Fig. 4, to provide a baille 84 which deflects the air entering through the opening forwardly and across the hot area 16. Also, the depending baffle 84 assists the downdraft of air traversing opening 'IE5 to induce circulation of the combustion gases in the rearward portion of the furnace.

Attention is now directed to Fig. 7 whereinis shown still another modified furnace construction which is preeminately suited for highpressurev operation and is primarily intended to be used in relatively large installations. The furnace here shown is generally similar to the one shown in Figs. 4-6 but it is horizontally elongated to move the front wall I4 farther away from the rearward portion of the furnace and to provide room for a vertical generally tubular stack B6 in front of the exhaust opening 30. A

fuel injection nozzle assembly 20 is mounted in the forwardY wall Ilto project a combustible mixture of fuel andv air-horizontally -across the floor of the combustion chamber 64, and a second nozzle injection assembly 20a is mounted in the top of stack 8B to project a combustible mixture of fuel and air downwardly into the combustion chamber through the sta-ck. It is contemplated that the nozzle assemblies 20 and 20a be operated either independently or simultaneously depending on the exigencies of the particular situation.

In this form of the invention, the furnace is surrounded by an air jacket Sii having an air inlet duct 90. Air under pressure is forced into the duct Sii in any suitable manner and a portion of this air is conducted downwardly outside the forward wall Iii where it enters the combustion chamber B through slots Q2 and eli. A vertical partition 96 directs air to slot 92 and a vertical partition S8 directs air to the slot SLi. In addition, the air travels downwardly behind partir tion 93 and enters the portion of jacliet S8 disposed under the furnace. A portion of this air is directed upwardly between the stepped plate l2 in the manner hereinabove described by vertically spaced ho izontal baffles ISEE, while a portion of the air passes under the lowermost baite |06 and continues upwardly around the rearward wall of the furnace. A portion of the latter air enters the opening 'I8 for the purpose hereinabove set forth, and the air which passes over the opening i8 is divided by a baffle |62 and directed to openings IIM and |86 in the wall of exhaust stack 36.

In addition to the above, a portion of the air entering the jacket through duct eil passes downwardly through a by-pass |83 between the two stacks 3e and 8B. spaced vertical bales I Iii, I I2, and H4 divide the air and direct it to slots H6, |I8, |29, |22 and |25 provided in the stacks 30 and 86.

The flue gases escape from the furnace through an opening |26, thence pass through fly ash precipitators |28 which trap any fly ash which is carried-along to this point by the nue gases, and then exit through an exhaust passage i3d.

The air blown into the jacket 88 becomes heated as it flows along the walls of the furnace. As a result of heat exchange between the walls of the furnace and the air in jacket 83, the walls are cooled and the air is heated. This has the double advantage of preventing overheating of the furnace walls and of increasing the combustion efficiency in the furnace by injecting heated air therein. The various slots or openings through which air is introduced into the combustion chamber are strategically located to assure complete combustion of the fuel before the latter reaches the exhaust passage |35.

Attention is now directed to Fig. S which shows still another modified type of furnace construction embodying the invention. The furnace here shown is generally similar to the larger form shown in Fig. 7, but is adapted primarily for use in somewhat smaller installations. In general, the rearward portion of the combustion chamber is shortened considerably to provide a shorter passage for the combustion gases. The shorter distance is ample in this case since the horizontal fuel injection nozzle assembly 2G is omitted and only the single vertical fuel injection nozzle assembly 23a is used. Also, a somewhat simplied baiiie arrangement is employed in this case. For example, one of the baffles IQ@ can be omitted due to the fact that the bottom of the furnace is considerably shorter, andthe baie H32 is entirely 9 omitted for obvious reasons. Otherwise, the operation and advantages inherent in this form of the invention are identical to those described in connection with the form shown in Fig. 7.

It is to be understood that the forms of the invention herewith shown and described are to be taken as preferred examples of the same and that various changes in the size, shape, and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the appended claims.

What is claimed is:

1. A furnace comprising refractory material forming a combustion chamber having rightangularly related inlet and exhaust openings, the major portion of the combustion chamber disposed in front of the inlet and laterally of the exhaust opening, the wall of said chamber adjacent to the exhaust opening formed with a reentrant portion and the latter dening a relatively restricted passage between the major portion of the chamber and said inlet and exhaust openings, whereby products of combustion charged to the combustion chamber through said inlet and said restricted passage are circulated in the combustion chamber before being returned through said restricted passage to the exhaust opening, the side of said re-entrant portion remote from said exhaust opening having an air inlet, a baffle arranged to deflect air entering the combustion chamber through said air inlet against the surface of said re-entrant portion and into said exhaust opening, the wall of the combustion chamber immediately in front of said fuel inlet having an opening opening exteriorly of the furnace, a plurality of plates covering said opening, said plates arranged in stepped relation and spaced from each other so that air from outside the furnace enters the combustion chamber through said opening and the spaces between the individual plates.

2. A furnace having a combustion chamber provided with a fuel inlet and an exhaust opening for discharging combustion gases from the chamber, a wall of the combustion chamber along which combustion gases pass to the exhaust opening being formed with a re-entrant portion and the side of said re-entrant portion remote from the exhaust opening having an air inlet through which atmospheric air enters the combustion chamber, a baffle in the chamber disposed in spaced generally parallel relation with respect to the mentioned side of said re-entrant portion for delecting incoming air across said side of the re-entrant portion and into said exhaust opening, i.

a wall of the combustion chamber immediately in front of said fuel inlet having an opening communicating exteriorly of the furnace, a plu`- rality of plates covering said opening, said plates arranged in stepped relation and spaced from each other so that air enters the combustion chamber through the spaces between the individual plates, and means for circulating coolant liquid across said opening including pipes supporting said plates.

3. A furnace having a combustion chamber provided with a fuel inlet and an exhaust opening for discharging combustion gases from the chamber, a wall of the combustion chamber along which combustion gases pass to the exhaust opening being formed with a re-entrant portion and the side of said re-entrant portion remote from the exhaust opening having an air inlet, a baffle in the chamber disposed in spaced generally parallel relation with respect to the mentioned side of said re-entrant portion for deflecting air entering the combustion chamber through said air inlet across said side of the reentrant portion and into said exhaust opening, a wall of the combustion chamber immediately in front of said fuel inlet having an opening, and a plurality of plates covering said opening, said plates arranged in stepped relation and spaced from each other so that air enters the combustion chamber through said opening and the spaces between the individual plates.

STEPHEN L. FITZPATRICK.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 405,966 Mason June 25, 1889 406,659 Mason July 9, 1889 406,753 Mason July 9, 1889 1,369,200 Stephens Feb. 22, 1921 1,376,010 Fesler Apr. 26, 1921 1,701,836 Cannon et al Feb. 12, 1929 1,754,277 Lundgren Apr. 15, 1930 1,773,173 Dearborn Aug. 19, 1930 1,947,496 Schmidt Feb. 20, 1934 2,001,721 Hall Dec. 21, 1935 2,063,261 Mees Dec. 8, 1936 2,099,827 Schrenk Nov. 23, 1937 2,395,103 Clausen et al. Feb. 19, 1946 2,479,376 Lemaire Aug. 16, 1949 2,500,323 Puckett Mar. 14, 1950 FOREIGN PATENTS Number Country Date 57,765 Sweden Nov. 4, 1924 202,312 Great Britain Oct. 23, 1924 285,402 Great Britain July 26, 1928 427,974 Germany Apr. 19, 1926

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