US1698825A - Apparatus for generating steam - Google Patents

Description

2 Sheets-Sheet 2 s E l f w um@ -i @TN R E C. SCHWARTZ APPARATUS FOR GENERATING STEAM Filed May 16. 1923 l VE TOR ATTORNEYS Jan. l5, 1929.

induced and it, therefore, travels at lower velocity than the descending fuel, and the fuel, therefore, travels past or is projected through slower moving bodies of air admitted substantially transversely of the direction of movement of the fuel, the result of which is' that a slight eddying is set up securing proper admixture of the fuel and proceeds, is ensured of being surrounded with air not impoverished of its oxygen. This manner of supplying the air needed for combustion directly meets two very important practical considerations; namely, first, that the fuel is progressing through the combustion-space, and second, that combustion itself is a progressive operation. Thus combustion is rendered more perfect and the size of the furnace kept within practical limits. At the l,same time zones of localized intense heat in the flame are avoided.

ltwill be observed that the velocities are such that objectionable, violent eddying, as well as forcible impingement on any furnace or boiler part, is avoided.

A portion of the air admitted through the inlets 22 travels in a downward direction between the descending fuel and flame stream .and the'front wall, because of the force e'ect of the descending fuel stream and because of the difference in temperautre between the entering air and the interior of the combustion chamber. This portion of the air protects the front wall against erosion. A portion also of the air, particularly that admitted in the lower rows of the inlets, borders the fuel and flame stream onuits lower side providing a body of air into which the heavier unconsmed or partially consumed particles of fuel will gravitate and there find oxygen nee-ded for combustion.

As combustion proceeds and gasification becomes more and more complete, the fuel and flame stream bends and reverses its direction of motion, this being brought aboutl by the tendency of the hot gases to rise because of their lower specific gravity and also by reason of the draft. The combustion is completed within a space defined by the top wall 16, the bottom 23, the front wall 15 and the inner tubes of three groups B, C and D.. For pulverzed coal this space would be such that there would be approximately 1/2 cu. ft. per lb. of coal burned. For oil burning, the

size of this space could be cut down.

u Air is supplied to the space between the descending and ascending portions of the fuel and dame stream through ne upper mesme rows of inlets 22, a portion of the air induced therethrough passing inwardly between the streams of entering fuel before they unite into a single stream.

The descending portion of the stream of fuel and llame is subjected to the heatof the rising portion.

The gaseous products of combustion leave the combustion space passing to the sides and to the rear over the tops of the three bullies 18, then downwardly in the passes between the baliles 18 and 19, and then upwardly in the passes formed by the balles 19 and the side and rear walls of the chamber A, leaving such passes through the outlets 20. The drawing of the gases to the sides and rear necessarily results in the spreading of the flames toward the sides and the rear, thus 'not only securing afmore uniform applica- "requirements with respect to air admission 1n relation to fuel travel and the progress of combustion peculiar to the burning of pulverized coal. lt will further be noted that,

broadly Speaking? the gaseous products of combustion are drawn laterally through the banks of tubes to the outlets.

With such an arrangement it is not only possible to burn the coal most efliciently but also far greater boiler capacity is obtained.

The refuse matter which gravitates out of the gases of combustion at the inner passes of the boiler units may be readily removed through doors 2e which may be suitably located for this purpose.

With regard to the deposit of refuse mattei` which collects in the ash pit E, slugging may be prevented by admitting what would be material excess of air through the clean-out doors 25 or elsewhere, such cooling air being admitted beneath the fuel and flame stream and providing a zone of relatively cooler temperature through which the refuse matter will gravitate and be cooled below the fusion point and which will absorb radiant heat from the deposit on the floor, maintaining its temperature below the fusion point.

l prefer, however, to prevent this slagging by means of a water screen G, located some distance above the floor 23 and comprising a plurality of tubes 26 connected at one end into the drum 9 and at the other end into a header 27, and the tubes 28 connected at one end with the header 27 and at the other end with the upper drum This water screen is thus Elli a boiler unit, connected into the circulation of the boiler and its function is to absorb radiant heat from the deposit on the floor Q3, preventing fusion thereof. In this connection the tubes 26 and 28 should be suiiiciently for apart to permit the refuse matter to free: y pass to the bottom, but they should be in sufficient number to adequately cool the bottom of the combustion space to prevent the slagging above referred to. It will be obvious that these tubes will be immediately below the zone of high temperatures and will materially assist in generating steam.

By using this water screen, I am enabled to use only the amount of air practically reuired to effect combustion. Practically a s ight excess of air over the theoretical necessary for combustion is required. Air cooling ,to prevent slagging requires still further quantities of air, i. e., a. material excess of air. Where a material excess of air is employed for cooling purposes, the temperature within the combustion space is uselessly lowered and limitations are imposed upon the efficiency and the percentage ofCO2 obtainable; whereas with the water screen and only the amount of air required for combustion, maximum efliciency and CO2 are obtainable.

To protect the top wall, this is cooled as by making it hollow and passing a current of cooling air therethrough. This may be done by provi-ding the burner castings with openings communicating with the space in the wall and during operation, air will be drawn through the space and through the burner castings into the combustion chamber. This is shown in Figs. 5 and 6. It will be seen that by this arrangement the air which passes through the burner castings to intermingle with the incoming fuel is preheated and ignition of the fuel is thus materially assisted.

In the arrangement ,of Fig.vl 4 the fuel is admitted at two ends of the combustion space and the two fuel and flame streams are bent inwardly toward each other and unite, passing upwardly and then over bales as before. In this instance, however, but two boiler units, B and D, and the water screen would be employed.

In both arrangements the overall length of the combined furnace Aand boiler is greatly reduced and the cross sectional area is not greatly increased, so that losses by external radiation of heat from the walls are not objectionable.

With respect to the burnin yof oil, substantially the same process is llowed with the exception that a greater percentage of air is delivered from the burner mechanism with the oil and less is admitted through the auxiliary air inlets, some of the lower rows of which may be entirely closed.

In a furnace and boiler as described, the maintenance of the brick work is negligible and the walls should remain in service without substantial repair practically indefinitely. There is no impingement on any refractories nor any slag deposit thereon which, in runing down, would wash away the surface of the bricks. Should there be' deposit on the boiler tubes, this will be chilled below the fusion point and would build out in individual hairs or horns in a direction substantially opposite the direction of movement of the fuel and flame stream until they break off of their own weight. For all practical purposes, therefore, the boiler tubes remain clean.

Generally speaking, to warrant burning pulverized coal under a stationary boiler, the installation should be capableof meeting peak loads, of substantially continuous operation without shut downs for the removal of slag, and of developing an efficiency sutticiently greater than possible in stoker practice to more than pay for the cost, of preparing and handling the coal, in addition to which the cost of brick maintenance must not be prohibitive. The arrangement described is one well adapted to fulfill all these conditions and at the same time develop capacities far in excess ofvpresent arrangements.

Blistering of the tubes so characteristic of installations in which the flame or hot burn'- ing gases are forced into the tubes resulting in localized application of great heat, is avoided by my invention; the heat' is more uniformly applied;- and the losses are morel than made up by the more effective application of radiant heat, in the passes.

Vhat I claim is:

l. An arrangement for burning lfuel in suspension including a chamber, means for admitting the fuel in a downward direction adjacent the front wall of the chamber, means for admitting auxiliary air -into the chamber at the front thereof, and a boiler in the chamber adjacent the Zone of high temperature and assisting in defining the combustion space, the gaseous products of combustion leaving from the upper part of the combustion space whereby the fuel and flame stream changes its movement from a downward to an upward direction in its travel through such space, such boiler including ay plurality of tubes substantially vertically disposed and arranged on three sides of the chamber and the chamber having outlets in the upper part at the said three sides.

2. An arrangement for burning fuel in suspension including a chamber, a boiler in the chamber defining three sides and the bottom of the combustion space, the front and top Walls of the chamber defining the other side and the top of the combustion space, means for admitting the fuel through the top wall in a downward direction, means for admitting air for combustion, and outlets for the. gaseous products of combustion at the said three sides of the chamber at the top.

3. An arrangement for burning fuel in suspension including a chamber having boiler units arranged along three sides thereof, division walls between adjacent boiler units,

burner means for admitting the fuel substantially verticallyv downward adjacent the fourth side and in aI plane at the top of the boiler units, and an outlet from the chamber for the gaseous products of combustion adjacent the top of each boiler unit.

r 4r. An arrangement for burning fuel in suspension including a chamber having boiler units arranged along three sides thereof, each boiler unit having an upper and lower drum and banks of upright tubes connecting corresponding upper and lower drums for admitting the fuel substantially vertically downward, burner means adjacent the upper drums, and outlets from said chamber for retenes the gaseous products of combustion adjacent the upper drums.

5. ln combination, a pulverized'fuel burning boiler furnace, means for admitting fuel to be burned in space therein, a water screen in the lower portion of said furnace including a row of tubes inclined somewhat from thehorizontal, a boiler havin upper and lower drums, a bank of substantially upright tubes connecting the drums and vexposed to radiant heat, upcom'er connections for the tubes of the water screen, comprising a row of tubes connecting into the upper drum, which tubes are substituted for and form the front row of tubes of said bank and means for supplying the said water screen with water.

- In testimony whereof, l have hereunto signed my name.

CARL SCAR'ECZ.

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