US3261333A - Steam generator - Google Patents

Description

J. JONAKIN STEAM GENERATOR July 19, 1966 5 Sheets-Sheet 1 Filed Sept. 28, 1964 J. JONAKIN STEAM GENERATOR July 19, 1966 3 Sheets-Sheet 2 Filed Sept.. 28, 1964 July 19, 1966 Filed Sept. 28, 1964 J. JONAKIN STEAM GENERATOR D g h Q 5 Sheets-Sheet 3 United States Patent O 3,261,333 STEAM GENERATOR .lames .Ionakim Simsbury, Conn., assigner to Combustion Engineering, Inc., Windsor, Conn., a corporation of Delaware Filed Sept. 2S, 1964, Ser. No. 399,575 8 Claims. (Cl. 122-479) My invention relates to vapor generators and in particular to units lburning coal with slag tap operation.

Steam generating units have been used with slag tap operation wherein the ash in the coal is maintained in molten form within the furnace. This ash is then drained from the bottom of the furnace into water where it is broken up and sluiced away. Such an operation, of course, is more conveniently carried out in the lower part of the furnace. In order to maintain the slag in the molten state a high temperature level must be maintained in the lower furnace, thus limiting the flexibility of furnace operation. When tilting burners are used for steam temperature control in a furnace of this type, there is a conict between a need for raising the burners to increase steam temperature and a need for lowering the burners to keep the slag in a molten state.

This problem is avoided in my invention wherein the coal is burned in a combustor which operates as a slagging furnace. This combustor operates with a deficiency of air so that the iron products in the ash will not be likely to oxidize, and the ash or slag may be more easily kept in the molten state. The coal is gasified in this process with the gaseous effluent from the combustor containing combustible products which are directed through tilting burners into a furnace where combustion is completed and steam temperature control may be effected, without affecting the slagging operation.

It is an object of my invention to generate steam in a unit burning coal with slag tap operation having also the ability to control steam temperature by means of Varying the zone of combustion within the furnace.

It is a further object to provide an improved slagging furnace wherein the slag may be maintained in the molten state at a lower temperature.

It is a further object to provide an improved method of burning crushed coal wherein the coal is first gasied and the combustible gaseous products so formed are turbulent- 1y burned in an independent combustion zone.

Other and further objects of the invention will become apparent to those skilled in the art as the description proceeds.

With the aforementioned objects in view, the invention comprises an arrangement, construction and combination of the elements of the inventive organization in such a manner as to attain the results desired, as hereinafter more particularly set forth in the following detailed description of an illustrative embodiment, said embodiment being shown by the accompanying drawings wherein:

FIGURE l shows a sectional side elevation illustrating the arrangement of the combustor and furnace portions of the vapor generator along with pertinent associated equipment;

FIGURE 2 is a sectional plan view lof FIGURE l; and

FIGURE 3 is a detailed illustration of the horizontal combustor used in FIGURES l and 2.

Feedwater for the steam generator is supplied to the steam drum 2 wherein it is conveyed through downcomers (not shown) to the lower furnace header 4. The walls of furnace 6 are lined with steam generating tubes 8 which convey the water from the lower header 10 while a portion of this water is transformed to steam. This steam and water mixture is then conveyed through riser 12 to the steam drum 2 with the water being again recirculated and the steam conveyed through the saturated steam line ice 14 to the superheater surface 16. The steam after being superheated in this surface passes through superheater outlet header 18 and is then directed to a point of use.

The feedwater supply to steam drum 2 is also conveyed therefrom to an inlet header 20 which is a portion of the combustor 22. This combustor has tubular heating surface 24 lining its walls. The water is passed from the inlet header 20 through the tubes 24 egressing to the outlet header 26 from which it is conveyed through riser tubes (not shown) to steam drum 2.

Coal bunker 25 contains a supply of crushed coal Z7 which may be supplied to the vapor generator as desired through coal feeder 28. This coal is fed through coal pipe 30 to the inlet section of the combustor 22 in accordance with the fuel demand of the vapor generator.

Preheated air is supplied through combustion hot air duct 34 with the aid of booster fan 36 to the combustor 22. The primary air is here introduced tangentially so that a rotating ow is established within the combustor. As these products pass through the combustor, the ash at high temperature is thrown to the periphery of the combustor and a layer of molten slag is maintained on the surfaces. Coal is burnt partially in suspension and partially after being impinged on the molten slag layer while being scrubbed with the rotating air flow.

The molten slag 38 is drained through the slag tap 40 into the water in the sluice box 42. Water introduced through pipe 44 passes through the sluice box carrying the ash gathered therein out through the sluice line 46.

The air supply to the combustor is regulated by means of damper 48 so that complete combination of the coal is not effected in the combustor. A setting of this damper is preselected in relation to the speed of the feeder 28 so that the air supplied to the combustor is just slightly greater than that required to gasify the carbon in the coal to carbon monoxide. The deficiency of air in the combustor deters the oxidation of iron in the ash. Since the fusion temperature of ash is greatly decreased when the lower oxide of iron is formed, the fluidity of the slag is greatly increased for any given slag temperature, and conversely, a lower required temperature for a given fluidity.

The gaseous effluent from the combustor passes through the combustor pipe Si) and contains along with the nitrogen from the air predominantly carbon monoxide. This combustor pipe 50 is divided supplying two tilting burner nozzles 52 and introduced into the furnace 6. Additional preheated air supplied through duct 32 passes through the secondary air duct 54 entering the furnace through openings 56 thereby supplying the required air for the completion of combustion. The carbon monoxide is then burned in the furnace 5 with the secondary air flow being controlled by damper 58.

As shown in FIGURE 2, one of these combustors is supplied in each corner of the furnace and the carbon monoxide products are introduced into the furnace 6 tangent to an imaginary cylinder 60. Inasmuch as it is difficult to maintain the combustion of carb-on monoxide, a great improvement in effectiveness is obtained with this type of furnace arrangement since the impingement of the flames on one another help to sustain ignition and the extreme turbulence produced improves the combustion.

The gaseous products of combustion pass through duct 62 thereby passing over heating surface 16 effecting the heat transfer from the gases to the steam. Temperature indicator 64 senses the temperature of the final steam and in response thereto sends a signal through control l-ine 64 to the burner tilt drive mechanism 66 which operates to vary the tilt olf nozzles 52 and therefore the direction in which the car-bon monoxide is introduced into the fu'rnace. Such an adjustment varies the zone of combustion within the furnace in relation to the flue location thus aaeias 3 varying the amount of heat that is absorbed in furnace wall 8 and .affecting the amount of heat picked up in the steam heating surface 16. This regulation is operative to maintain the steam temperature leaving the superheater outlet header 18 at a preselected value.

As previously described, the feeder 28 and the primary air yflow damper 48 are regulated on a preselected basis so that the combustor operates with a deficiency of air therein. A combustible analyzer may be introduced taking .a sample from the combustor line 50 to measure the amount of combustible in the efiiuent from the cornbustor. A reading obtained from this analyzer may be used to correct the relationship between the feeder and damper with a slow correction while the strongest control si-gnal is 'based on the preselected ratio. This permits proper variation of the air-coal ratio for diffe-rent coal qualities which may be encountered.

While I have illustrated and described a preferred embodiment of my invention it is to be understood that such is merely illustrative and not restrictive and that variations and modifications may be made therein without departing from the spirit and scope of the invention. I therefore do not wish to be limited to .the precise details set forth but desire to avail myself of such changes as fall within the purview of my invention. For instance, although the invention is directed to coal it .would be equally applicable on any slag forming fuel capable of gasification and while the description is directed to a subicritical drum type unit, it would be equally applicable to a oncethrough of either supercritica-l or subcritical type although in suc-h a case the tilting burners may be operated to control reheat temperature or furnace wall outlet temperature.

What I claim is:

1. A method of burning coal and generating steam in an apparatus having a first zone, a second zone, and nozzles for varying the location of said second zone, wherein the temperature of the steam may be controlled comprising: 'burning coal in a first zone; separating slag formed during such combustion .from the gaseous efiiuent; draining .the slag from said first zone; conveying the effluent from said first zone to a second zone and directing the effluent into said second zone through nozzles which are directionally adjustable; passing water in heat exchange relationship with said first and second zones thereby generating steam; subsequently passing the steam thus generated in heat exchange relationship with the efiiuent from said second zone at a preselected location downstream of said second zone; sensing this temperature of the steam thus heated; and regulating the direction of introduction of the effluent from said first zone int-o said second zone in response to said sensed temperature whereby the steam temperature may be regulated at 'a predetermined value.

`2. A method of burning coal and generating steam wherein the steam temperature may be controlled comprising burning coa-l in a first zone with a deficiency of air; controlling the air supply to said first zone so that the efiiuent from said zone includes a large amount of carbon monoxide; conveying the efiiuent from said first zo-ne to a second zone; supplying air to said second zone and completing the combustion of the efliuent from said first zone, thereby forming combustion products; passing water in heat exchange relationship with said first zone and passing water in heat exchange relationship with said second zone thereby generating steam; passing the steam .thus generated in heat exchange relation with the combustion products formed in said second combustion zone at a preselected location; sensing the temperature of the steam thus heated; and regulating the location of said second co-mbustion zone in relation to said preselected location in response to said sensed temperature, to regulate the steam temperature at a predetermined value.

I3. A method of burning coal and generating steam at a controlled temperature comprising: introducing coal and air into a first zone and gasifying the coal by burning it with a deficiency of air; centrifugally separating slag formed by the combustion of the coal and centrifugally separating the slag from the gaseous products; maintaining said slag in a molten state and draining it from said first zone; conveying the effluent from said rst zone to a second zone and introducing it therein; supplying air to said second zone and burning the effluent from said first zone thereby forming combustion products; passing water in heat exchange relation with said first yand second zones thereby generating ste-am; passing t-he steam thus generated in heat exchange relation with the combustion products formed in said second combustion zone at a preselected location; sensing the temperature of the steam thus heated; and regulating the location of said second combustion zone in relation to said preselected location predominantly in response to said sensed temperature, whereby the steam may be regulated to a predetermined value.

4. In an apparatus `having a first zone, a second zone 4and a plurality of nozzles for introducing effluent from said first zone tangentially into ysaid second zone, the method as in claim 6 including directing the efiiuent from said first zone into said second zone through said plurality of nozzles tangent to an imaginary cylinder located near the center of said second zone, whereby improved combustion may be obtained by the turbulence estab-lished and stalbility of ignition may be improved by the interaction of the gaseous streams.

5. A method as in claim 4 wherein the variation in the location of the zone of combustion is obtained by; adjusting the nozzles introducing the effiuent into said second zone regulatingly toward or away from said preselected location.

6. A vapor generator for slag tap operation wherein steam temperature may be controlled comprising: a generally cylindrical first combustion chamber; means for supplying fuel to said first combustion chamber; means for introducing air tangentially into said first combustion chamber; tubular surface covering the walls of said first combustion chamber having water therein; and operative lto generate steam; means for removing molten sla-g from said first com-bustion chamber; a second chamber; hea-ting surface lining at least a portion of the walls of said second chamber containing water and operative .to generate steam; means for collecting the steam generated in said first and second chamber-s; means for conveying the efiiuent from said first chamber to said second chamber; a flue for conveying the efliuent from said second chamber; tubular heating surface located in said flue and means for conveying the steam collected through said heating ysurface located in said Hue; and means for regulatingly introducing the effluent from said first chamber to said second chamber so that it may be introduced toward or away from -said flue; means for detecting the temperature of the steam leaving said heating surface, and means regulating the direction of introduction of the efiiuent in response to the sensed temperature to Amaintain said temperature at a preselected value.

7. A vapor generator wherein the steam temperature may be controlled comprising: a generally cylindrical combustor; means for supplying coal to said combustor and means for tangentially introducing air to said combustor; means for burning the coal within the combustor with a deficiency of air including means for regulating said air supply to the combustor so that the efiiuent Acontains a large proportion of carbon monoxide; tubular -sunface lining the wa-lls of said combustor, containing Walter and operative to generate steam; a furnace and tubes lining at least a portion of the walls of `said furnace containing water and operative to generate steam; means for conveying the efiiuent from said combustor including 'burners introducing said efiiuent into said furnace; means for supplying air to said furnace and effecting the combustion of said carbon monoxide in a zone within the fur-i nace; a ilue conveying gases from said furnace at a location remote from said burners; means for collecting said generated steam and passing said .steam through heating surface located Within said flue; temperature sensing means sensing the temperature of the steam leaving said heating surface; means rfor adjusting the zone oif Combustion of carbon monoxide Within the furnace in relation to said flue; and means responsive predominantly to said temperature .of the steam regulating the adjustment o-f said zone of combustion.

8. A vapor generator for sla-g tap operation comprising: a generally cylindrical combustor; means for supplying coal to said .combustor and means .for tangentially introducing air to said combustor; means for burning coal Within said combustor with a deiiciency of air including means for regulating said air so that the eflluent contains a large proportion of gaseous combustible; tubular surface lining the walls of said combustor, contain-ing water and operative to generate steam; means for separating molten slag formed during the combustion of the coal from the gaseous products formed; means .for draining molten slag formed during combustion of the coal from said com- Ibustor; a furnace and tubes covering at least a portion of the Walls of said furnace containing waiter and opera- -tive to generate steam; means for conveying the eluent from said combustor including burners introducing said effluent into sai-d furnace; means `for sup-plying air to said furnace and effecting the combustion of the combustible gaseous products and a flue conveying gases from said furnace at a location remote from said burners; and means for adjusting said burners introducing said eilluent into said furnace to project the effluent regulatingly .toward and away from said ue.

References Cited by the Examiner UNITED STATES PATENTS 2,808,012 10/1957 Schindler 110-28 2,865,344 12/1958 lFiDl 122-478 2,899,942 8/ 1959 Braun 122-479 2,941,518 6/1960 Firl 122-235 FOREGN PATENTS 702,488 1/ 1954 Great Britain.

CHARLES J. MY-HRE, Primary Examiner.

Claims (1)

1. A METHOD OF BURNING COAL AND GENERATING STEAM IN AN APPARATUS HAVING A FIRST ZONE, A SECOND ZONE, AND NOZZLES FOR VARYING THE LOCATION OF SAID SECOND ZONE, WHEREIN THE TEMPERATURING OF THE STEAM MAY BE CONTROLLED COMPRISING: BURNING COAL IN A FIRST ZONE; SEPARATING SLAG FORMED DURING SUCH COMBUSTION FROM THE GASEOUS EFFLUENT; DRAINING THE SLAG FROM SAID FIRST ZONE; CONVEYING THE EFFLUENT FROM SAID FIRST ZONE TO A SECOND ZONE AND DIRECTING THE EFFLUENT INTO SAID SECOND ZONE THROUGH NOZZLES WHICH ARE DIRECTIONALLY ADJUSTABLE; PASSING WATER IN HEAT EXCHANGE RELATIONSHIP WITH SAID FIRST AND SECOND ZONES THEREBY GENERATING STEAM; SUBSEQUENTLY PASSING THE STEAM THUS GENERATED IN HEAT EXCHANGE RELATIONSHIP WITHT HE EFFLUENT FROM SAID SECOND ZONE AT A PRESELECTED LOCATION DOWNSTREAM OF SAID SECOND ZONE; SENSING THIS TEMPERATURE OF THE STEAM THUS HEATED; AND REGULATING THE DIRECTION OF INTRODUCTION OF THE EFFLUENT FROM SAID FIRST ZONE INTO SAID SECOND ZONE IN RESPONSE TO SAID SENSED TEMPERATURE WHEREBY THE STEAM TEMPERATURE MAY BE REGULATED AT A PREDETERMINED VALUE.

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