US843878A - Process of calcining lime and cement forming material. - Google Patents

Description

No. 843,878. PATENTED FEB. 12, 1907.

' 0. ELLIS.

PROCESS OF OALGINING LIME AND CEMENT FORMING MATERIAL. APPLICATION FILED DEC. 6, 1905.

CARLETON ELLIS, OF WHITE PLAINS, NEW YORK.

PROCESS OF CALCFNING LHWE AND CEMENT FORWHNG MATEREALH Specification of Letters Patent.

Patented Feb. 12, 1907.

Application filed December 6,1905. Serial No. 290,580.

To (all whom it may concern: I

Be it known that I, CARLETON ELLIS, a citizen of the United States, and a resident of White Plains,- in the county of'Westchester and State of New York, have invented certain new and useful Process of Calcining Lime and Cement Forming Material, of which the following is a specification.

This invention relates to process of burning lime in upright vertical or shaft kilns by means of coal fuel, the combustion of which i is conducted in an artificially-accelerated draft containing less oxygen than that normal to air and containing in addition a catalyzing body which facilitates the decarbonation of limestone.

The object of this invention is to control the temperature and volume of flame or com- I bustion and so modify the character of the flame that it is better adapted to the calcination of limestone than the flame customarily employed? l-ieretofore the burning of lime with coal as the fuel has been most successfully conducted with a draft-current of air and a neutral gaseous diluent of suitable volume and velocity, the diluent consisting, preferably, of products of the calcination of lime and of substantially complete combustion of the fuel. This diluent when present in suitable proportion serves to 'cool the fire and to retard the chemical activity of the flaming cur-- rent of gases and air passing from the fuelbed, thereby increasing the volume of flame, so that the combustion is completed to a great extent in the body of the lime-rock.

The present process involves the use of, stack-gas or products of combustion or other diluent gas for the purpose of securing the low temperature desired and in addition involves, essentially, the use of a catalyzing agent, preferably water-vapor or steam, to effect the easy liberation of carbon dioxid from the limestone. v 7

Experiments have shown that if carbonate of lime be heated up to a temperature at which it dissociates and a current of air is passed thereover that the carbon dioxid is rapidly removed, provided the temperature is maintained. As soon, however, as the temperature is allowed to fall the carbon dioxid forthwith decreases in amount and l finally ceases altogether. At this point if water-vapor or steam be introduced with. the air-current carbon dioxid will again be given off from the limestone, although at too lto shorten the low a temperature for dissociation with the dried or moisture-free air. This important fact is made the basis of the present invention.

My invention consists in conducting combustion with an artificiallynccelerated draftless oxygen than that con said draft-current be by mixing with orcurrent containing tained in ordinary air, ing preferably produced dinary or fresh tent of approximately twenty-one per cent. of oxygen a definite or predetermined quantity of diluent gas, such as the products of substantially complete combustion departing from the upper part of a lime-kiln or the stack-gases of combustion produced in any other type of furnaces, in mixing therewith, either below or above the fire, a quantity of a catalytic agent, (water-vapor being-about the cheapest and most eflicient,) and in subjecting the lime-rock to the action of the flame carrying said diluent gas and catalytic a ent until calcination is substantially or wdiolly complete. This catalytic agent facilitating the calcination of the lime acts also to a considerable extent as a catalytic agent, tending to accelerate and intensify the chemical union of the carbon monoxid of the flaming current of gases and air passing from the fuel-bed. For this reason it has a tendency flame, thereby tending to cause higher fuel-bed and fire-box temperatures and to decrease the percentage of fuelgases burned in the calcining-chamber in contact with the lime-rock. By suitably" regulating the proportions of the draftcurrent constituents in accordance with my present invention the favorable catalytic action of the water vapor in liberating, carbon dioxid (00,) from the lime-rock may be increased to a considerable extent without too greatly increasing unfavorable effects of itscatalytic action in quickening combustion.

By reference to the accompanying drawings it will be seen in what manner my invention may be performed.

In said drawings, Figure 1 shows in a conventional way a sectional view of a limekiln of the continuous-draw type. Fig. 2 is a section of an atomizer which is preferably employed in the introduction into the firebox of the desired amount of water-vapor.

In the drawings, 1 is the shaft of a lime-kiln, having the stack 2 and the hopper or cooler 3, with winged bottom 4 for the removal of the calcined stone.

air containing its normal conthere occurs to certain 5 is the fire-box, having the grates 6, the bridge-wall 7, the fire-door 8, and the ash-pit door 9.

in Fig. 2.) The water-supply pipe 'is equipped with a valve 17 to regulate the amount of water. Referring to Fig. 2, the atomizer 16 will be seen in section with the diagonal openings 21, serving to direct streams of water against one another, whereby a spray of a. very fine character is pro duced.

18 .is an air-inlet connected with the conduit 10 and is provided with a suitable damper 19. The conduit 10 is also provided with a damper 20.

In carrying out my process with the apparatus as above described I draw from the opening 11 through the chamber 14 and pipe 10 a continuous stream of products of combustion, mix therewith through the opening 18 a quantity of air, whereby the'proportion of carbon dioxid in the mixture is main-v tained at from about four per cent, to about eight per cent, and force this mixture by the fan-blower'13 into the ash-pit of the fire-box 5. Simultaneously with the withdrawal of the stack-gas through the opening 11 there is admitted through the atomizer 16 a quan-- tity of water-vapor, (also supplied continuously) Which water-spray is immediately converted into: a vapor and is impelled with the other gases into theash-pit. This mix ture travels through the fuel-bed on the grate-bars 6, and some slight decomposition of the components of the draft-current, due ,to their reaction on the carbon of the fuel. instance, is in part split up into carbon monoxid, while water-vapor is to a certain slight extent converted into hydrogen and carbon monox'id. Both of these reactions are endothermic and serve to cool the fire, so that there is lesstrouble from clinkering than is the case with a'fire fed by a supply of fresh air. Ordinarily the fire-bed is thin, so that sufficient oxyen traverses it. unchanged and permits 0 the completion of combustion above the fire-bed. The retarding action of the endothermic constituents of the draftcurrent the steam and the carbon dioxidupon combustion is sufficient to permit the draft-current to be passed through the thinbed of fuel faster than the fuel can react thereon.

Carbon dioxid, for

Thereby can be obtained a body of gas containing unchanged air, unchanged products of combustion, and unchanged steam, all in timately commingled with carbon monoxid and hydrogen resulting from the chemical action of the draft-current upon the fuel; but it is evident that should the fire-bed be of such depth that insuflicient oxygen reaches the ripper part of the bed to provide for a fairly complete combustion above said bed that air may be introi'htced from other sources to supply the deficiency. Ordinarily, however, asabove stated, the thin fuelbed which is customarily carried permits of the'passage through the fire of suflicient oxygen to'complete combustion beyond the upper surface of the fuel-bed. The shaft-kiln ordinarily constructed for burning lime permits of considerable air passing into the cooler in the lower part of the kiln, which air is usually suffic-ient for making up any deficiency in the air supplied to the fire-box. Along flame, relatively cool, is thereby produced in the shaft of the kiln 1 and burns the lime uniformly, rapidly, and efficiently. The water-vapor supplied through the agency of the atomizer 16 reacts in some subtle way with the limestone and greatly accelerates its decomposition. of this catalytic action the investigations made up to the present time are insuflicient to determine precisely. I content myself, therefore, with simply noting the fact withou t endeavoring to explain the modus operandi of this obscure phenomenon.

The proportions of diluent gas, water-vapor, and air are in part determined by the composition of the stack-gases. There is some variation inthe gas from time to time, owing to the disturbances produced through the charging and withdrawing the lime-rock and lime, respectively. However, the gases will on an average contain twenty-five to thirty per cent. of carbon dioxid and perhaps five per cent. of oxygon, the balance being nitrogen. As from four to eight per cent. of carbon dioxidis ordinarily desired in the draftcurrent admitted to the ash pit, a diluti on with five or six parts of air is necessary. The quantity of water-vapor introduced should be such that at least one-half per cent, and preferably two to four per cent, of vapor is present in the draft-current. It should be borne in mind that the gases leaving the kiln through the opening 1 1 may have a temperature of from 600 Fahrenheit to 1,000 Fahrenheit, depending on the height of the kiln, &c., andeonsequently have a great capacity for moisture.- The addition of the moisture in the form of water-spraythat is to'say, practically as a liquidresults in some cooling of these gases, inasmuch as the water has to be converted into steam and raised to the mean temperature ot the mixture, whereby heat is. absorbed. Subse- As to the exact nature fresh air admitted as to prevent 'tion of water during transit, as suc precipiof volatilization of liquid holding water, may be compensated byincreased volume. In any event it is desirable to so roportion the amount of water-vapor intro uced with reference to the temperature of the stack-gases and the amount of recipitatoo great a cooling acto the high latent heat water. It is of course possible to admit hot air through the inlet 18, thereby increasing the amount of water which may be introduced as a vapor into the fire. It is also possible to admit the water-vapor above the fire-as, for instance, over the bridge 7, through'pipe w, either in the form of spray, or as ordinary steam,or as superheated steam. Flooding the ash-2 it with water is an uncertain and undesirable means of introducing the vapor.

My invention effects important economies in the burning of lime, owing to the catalytic action of water-vapor, as aforesaid, in conjunction with the beneficial flame control attendant on the use ofdiluent gas. The amount of Water-vapor admitted is not sufficient to cause the loss at the stack as sensible heat, &c., of any appreciable amount of fuel. It is evident, of course, that a large amount of moisture or steam would cause a loss in this way, and therefore only such quantity of. water-vapor should be admitted tated water may have tion on the fire, owing through addition of air can react therewith,

as is sullicient to secure the desired catalytic action.

What I-claim is 1. The herein-described process of calcining limestone, &c., which consists in passing a shallow bed of ignited fuel an accelerated draft-current of commingled air, water-vapor and diluent as at a rate greater than the fuel can react tfierewith-and burning the resultant gaseous mixture in contact with limestone.

2. The process of calcining limestone, &c., which consists in passing through a shallow bed of ignited fuel an accelerated draft-current of commingled air, water-vapor and limekiln-ga'ses at a rate greater than the fuel and burning the resultant gaseous mixture in contact with limestone.

3. The process of calcining limestone, &c'., which consists in passing through a shallow bed of ignited fuel an accelerated draft-current of .commingled air, water-vapor and limekiln-gases, the water-vapor being present in not to exceed four per cent. and burning the resultant mixture in contact with limestone.

4. The process of calcining limestone, &c.,' which consists in mixing .a predetermined amount of water with hot products of combustion, whereby said water is vaporized, adding a predetermined amount of air, passing the resultant mixture through a shallow bed of ignited fuel'at a rate greater than said fuel can react therewith and burning the resultant mixture in contact with limestone.

5. The process of calcining limestone, &c., which consists in mixing a redetermined amount of water with hot fimekiln-gases, whereby said water is vaporized, adding a predetermined amount of air, passing the resultant mixture through a shallow bed of ignited fuel at a rate greater than said fuel can react therewith and burning the resultant mixture in contact with limestone.

, Signed at New York, in the county of New York and State of New York, this 5th day of December, A. D. 1905.

oARiJEToN ELLIS.

Witnesses:

FLETCHER P. SCOFIELD, FRED 1. SMITH.

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