US2223047A - Method of making mineral wool - Google Patents

Description

Nov. 26, 1940. F, RAMSEYER 2,223,047

METHOD OF MAKING MINERAL WOOL Filed March' 9, 193e 4 sheeis-sheet 1 N 'i L L a gi S S:

/J f/l/// New. 26, 1940.

CL F. RAMSEYER METHOD OF MAKING MINERAL WOOL Filed March 9, 1936 4 Sheets-Sheet 2 Nov. 26, 1940. C, F RAMSEYER 2,223,047

METHOD OF MAKING MINERAL WOOL Filed March 9, 193e 4 sheets-smet 4 1 1 I i l Patented Nov. 26, 1940 UNITED STATES PATENT oFFlcE 9 Claims.

'I'he principal object of the present invention is the provision of a new and improved method of making mineral wool. More specifically, the present invention has for its object a new and improved method o! making mineral wool from a hitherto unused raw material, namely, lcoal ashes. v

By mineral wool is ordinarily meant a fine fibrous wool-like material, made by blowing a small falling stream of molten rock or similar material, such as metallurgical slag, with a jet of steamv or air. The action of the jet of fluid is to blow the molten stream into fine fibrous material Awhich is hardened by the time that the fibers fall to the floor some distance away from the jet of fluid, either steam or air, under pressure.

The commercial form of rock wool in considerable use today is commonly made by melting lar ratio of acid oxides (principally silica and Instead ci' melting rock or the like, sometimes the slags resulting from the smelting of various metallic ores, such as lead and copper, have been found to be suitable for remelting inla cupola and blowing into a mineral wool, the product being usually referred to in this caseas slag wool. Attempts to blow the molten slags directly from the smelters without cooling andy remelting have commonly been unsuccessful, due' .principally to a lack of control ofthe temperature and rate of flow of the slag from the smelting furnaces. Also, slags from iron blast furnaces have been used, but in this case there are 1 sulfldes present with the result that when the wool is later exposed to the moisture in the air chemical reactions take place by which various sulfur acids are formed. These acids are likely )to corrode .anyv metal with which the wool may come into contact, and for this reason iron blast furnace slag wool has a rather limited application in the industry. v

Somel of the disadvantages Aencountered in the production of mineral wool by the processes -mentioned above have been the high cost of production and the dimculty of securing a uniform product. Where the rock has to be quarried and u transported to the mineral wool plant, relatively an argillaceous limestone in which the molecuexpensive fuel (usually coke) purchased to melt `the rock, and steam generated, usually at low emciencies in a small size boiler plant, with which to-blow the molten rock, it will be clear that such mineral wool is a relatively expensive product. Also, since practically the only meth- `od of controlling the temperature, viscosity and chemical content ofthe molten material is by changing theratio of rock or slag to the coke charged in the cupola, it can be seen that the lo control of the lmolten material is very far from being either instantaneous-or automatic, since in most plants it is a matter of hours before the material charged in at the top of the cupola can influence the temperature or composition of the 15 molten material coming from the tap hole.

With these factors in mind, the principal object of the present invention, as stated above, is a relatively great reduction in cost of producing mineral wool and it is a further object of the present Iinvention to improve the quality and uniformity of mineral wool. More particularly, it is an object of the present invention to utilize ashes from coal fired boiler plants and the like, the disposal of which at present is ordinarily an item of expense rather than profit, in the formation of a new and improved product, namely, mineral wool. By the use of the present invention, not only will the cost of the raw material for' the mineral wool be completely eliminated, but the same is true of the cost of the fuel required to melt the raw material in the cupola. Since both of these items of expense are eliminated, the cost of production of the product is very greatly reduced. D

A further important object of the present invention is the provision of new and improvedmeans by which the temperature, and more particulary the viscosity, of the molten stream of material from which the wool is blown can be continuouslyA maintained at any desired predetermined value, thereby insuring the production of wool of uniform characteristics at all times.

Still further, another object of the present invention is the production of a new and improved mineral wool in which, as to chemical content, iron oxide, probably in the ferrous state (Feo),

' can be substituted for the lime and magnesia usually employed at the present time as part of the basic component of an oxide mixture capable of being blown into a mineral wool. As mentioned above, ordinary rock wool available at the present time contains acid oxides, such as silica and alumina, and basic oxides, principally lime and magnesia, in about equal proportions. Bo

far as I am`aware, it is new to employ iron oxide, rather than lime and magnesium oxides, as part of the basic component of the mixture to be blown, with only a small proportion of lime and according to the principles of the present invention I provide other means for controlling the temperature of the molten ash as it runs out yof the furnace, the means being so constructed and arranged that the temperature and viscosity of the molten furnace ash can be accurately adjusted to the most advantageous point for the blowing of the wool'. Therefore, a further object of the present invention is the method of producing mineral wool by melting the raw materials in an oxidizing apparatus, rather than a reducing apparatus as has hitherto been used in the production of rock wool, slag wool and the like.

In this connection it should b'e mentioned that, as a part of the present invention, andparticularly as the part thereof which contemplates making use of a by-product that at the present time requires money to be spent for its disposal, I make use of wet-bottom or slag-tap furnaces. Furnaces of. this type have been de veloped within the vlast few years and are particularly adapted to use pulverized coal. In furnaces of this type, the temperature is kept lhigh enough vso that the ash of the coal collects on the floor of the furnace in a molten condition and can be drawn or tapped oif at will, either continuously or at intervals as may be desired.

Ordinarily, the pulveri'zed coal is blown into the furnace, this method of firing being particularly advantageous with coals having a` low fusion point ash, such low fusion point frequently being due to the presence of iron oxide in the ash, th'e iron oxide being originally present in the coal, largely as iron disulde or pyrites' (FeSz). Therefore, according to the present invention, I

make use of the molten slag or ash from fur.

naces of this 'type,'in which the slag or ash is relatively high in iron oxides in the production of an improved mineral wool.

An additional object of the present invention is the provision of a small furnace or container so constructed and arranged to receive the molten ash from the boiler plant, which may or may not be a wet-bottom furnace or the like, and to control the temperature and viscosity of the molten material so as to facilitate the subsequent blowing of the same into mineral wool. Buch small orintermediate furnace, whichmay be termed a conditioning furnace. may. be heated in any suitable manner, either by fuel. or electricity,preferably the latter. According to the principles of the present invention, heat is generated inthe molten ash bypassing an electric current through it, whereby .the molten ash itself acts as the -`resistance in the circuit transforming the electric'current into heat. By virtue of a conditioning furnace, the proper viscosity of themolten material may be maintained at all times for producing the best quality of wool. Y

A further object of the present invention, halving particularly to do with the form and construction of the conditioning furnace, is the provision of new and improved means for passing a current through the molten coal ashes, which means includes water cooled electrodes. In this way -the corrosive action of the iron oxide content of the molten ash-will be eliminated as `much as possible. Other, features and advanr'tages ofthe conditioning -furnace will be apparent from the detailed description thereof.

A further object of the present invention is a new and improved means for controlling the -viscosity of the molten ash or material. Accord- `ing to the principles of the present invention,

the molten material itself is used as theresistance element in the heating circuit, this mak-I ing it possible to maintain substantially constant viscosity by maintaining the resistance of the slag in the conditioningv furnace substantially constant. 'Ihis is due to the fact that the viscosity of a molten oxide mass or mixture is "directly related to itselectrical resistivity. It is recognized that the viscosity of the (slag at' the time the blast from the blowing nozzle'sstrikes the same is one of the most important variables determining the quality of the mineral wool, and

thus by virtue of the present invention, which contemplates keeping' the viscosity' of the molten ash constant, variations in the chemical 4composition of the molten material which ordinarily would affect the` quality ofthe wool are rendered substantially harmless.

These and other .objects-.and advantages of 'I the present invention will be apparent to those skilled in the art after a consideration of the following detailed description;

In the drawings: y Figure 1 is a'view lshowing a portion of the iioor of a wet-bottom coal iired furnace and a' portion of a conditioning or intermediate furnacefreceiving the molten slag or ashfrom the wet-bottom furnace; Figure 2 is a larger view of the intermediate or conditioning furnace; f

Figure 3 is a section taken substantially alonl the 'line 3--3 of Figure 2;

through one of the insulated cooling `Jackets: and j Figure 8 is aview illustrating one method of blowing the mineral wool by tiltingthe conditioning furnace about an axis substantially coin- -eidental with the pouring spout of the furnace. Referring now more particularly to Figure l, the furnace which the present invention makes use of is-indicated in its entirety by the reference numeral l and-includes more or less conventional water tubes 2 and I and a furnace floor l upon which the slag or ashes from the combustion of the pulverized coal collect-in `molten state, as indicated at I. Buch furnaces are provided with a slag hole I, either in the bottom or side of the furnace, through which the molten ash iiows, more or less continuously. The

intermediate or conditioning furnace is indicated in Ithis entirety by the reference numeral Il and includes suitable framework I2 carryinl a refractory container i3., which willl be referred to may be arranged for conducting a flow of molteny as h from the furnace I- to the'lnlet opening I8 of the conditioning furnace I0. If desired, there fili best indicated in Figure '1.

`furnace to the other the continuous flow of molten coal ashes 5 may be accommodated.

'Iurning now to Figures 2 to 6, which best illus- Vtrate the details of one form of conditioning furnace which has been found to be successful in carrying out the principles of the present invention, the furnace I0 consists of end walls 20 and 2| and side walls 22 and 23, and a bottom wall 24 sloping downwardly toward a tap hole 28. The bottom, side and end walls are formed of refractory material, commonly employed where highv temperatures are encountered, and preferably the side and end walls 20, 2| and 22, 23 are water jacketed so as to prevent overheating. The bottom 24 is not water jacketed but is moreheavily lined with refractory brick or similar material, due to the possible danger of the formation and collection of molten iron in the furnace. When iron does collect, the plug 28 (Figure 3) may^be removed and the molten iron drawn 'off through the 'slag tap 28. The roof |4 of the furnace is also formed of refractory material, such as nre brick or the like, and is provided with the inlet or receiving opening. l5, as best shown in Figures land 5. It may be water jacketed if necessary. The water Jacketing of the sides and ends of the furnace may be accomplished in any known manner, such as a `iacket 21 adapted to contain water or other cooling medium and surrounding the ends and sides with openings 23 and 23 for the Jacketed electrodes, to be referred to later.

According to the present invention, operatively disposed plate electrodes 3|, 32 and 33, v34 are disposed on opposite /side walls 22.and 23 of the furnace on the inside thereof and in the openings 28 and 23 in thefurnace Jacket` 21. I'hese plate electrodes are insulated from each other and are provided with conducting bars 31 (Figure 7) which connect the plate electrodes both thermally and electrically with the water Jacket inserts indicated at 40, 4| and 42, 43. These water jacket inserts are insulated with respect to the other portions of the cooling Jacket system, as In this figure the water Jacket inserts 42 and 43 have insulating strips 45 and 48 secured to the upper -and lower edges by bolts 49 and 80, and the two water jacket inserts at one side of the furnace, thus insulated from one another, are bolted together as at 5| and to the upper water jacket 21 and a lower attaching plate 52 by bolts 53 andl4 (Figure 4). It is to be noticed that the conductor bars 31 connecting the contact plates with the insulated water jacket inserts pass through the refractory material making up the side of the furnace. The bars 31 are so proportioned as to conduct heat from the contactor plate to the water Jacket at a predetermined rate sufficient to maintain the contact plates'3l, 32 and 33, 34 at a temperature low enough to prevent destruction by the molten material in the furnace. In other words. to maintain the electrodes within thev desired temperature limits, depending on the viscosity required, the refractory material resists to a certain extent the flow of heat from the plates 3|, 32, 33 and 34 to the associated water jackets,

while the heat conducting bars 31 passing through the refractory material conduct a certain amount of heat from the inner plates to the outer water jackets.

Cooling water is directed to and withdrawn from the furnace shell 21 by means of water connections 80 and 8| (Figure 2), the upper ends ends of the flexible copper metal hose sections l 84 and 88. Bus bars 10 (Figure 2) are electrically connectedwith the copper hose sections adiacent -the points where the latter are supported on the frames 83, and at the same point suitable water pipes 12 (Figure 8) are connected through supporting and insulating sleeves 13 carried on the frame 83. The water supply connections include pipes 14 leading Ito a supply main `18. Obviously, of course, other forms of supply, both as to cooling water and electrical current, may be employed where desired. Also, while I have shown only two .iacketed electrodes on opposite side walls for purposes of illustration, a greater number is preferably used.

The furnace I0 is mounted for tiltingl movement on the frame I2 so that the furnace may be tilted for discharging its load of molten coal ash. As best shown in Figure 3, the end wall 2| ofthe furnace I0 is provided with a pouring hole 80 provided with a spout 3|, and as best indicated in Figures 1 and 3 the furnace includes a trunnion shaft 85 which is mounted "in bearings 88 and 81 forming a part of the supporting framework i2. The shaft 85 passes close to the pouring spout 8|, and as indicatedin Figure 3 the curvature of the lower wall of the pouring opening 80 and the adjacent portions of the spout 3| is substantially arcuate about the axis of the trunnion shaft 85. The frame or pedestal l2 is of more or less conventional construction, being built up of angle irons welded or bolted together I .and fastened to the floor .by any suitable means,

such as lag screws or expansion bolts 83. Clips 90 are welded or bolted to the framework i2 so as to support the furnace i0 in level position. The furnace itself carries a quadrant |00, best indicated in Figure 8, which is secured to the furnace shell in any suitable manner, such as by angle irons |0| orthe like, and the quadrant |00 is preferably, but not necessarily, made up of a section of tubing split longitudinally and bent to the proper radius.

A tilting cable |08 is fastened at its lower end to the forward portion of. quadrant |00 and at its upper end is connected to a cable |08 passing over a sheave |01 and extending downwardly to a fixed point |08. A counterbalancing cable ||0 is also fastened to the flexible section |0ll` and passes over suitable pulleys H2 and H3 where the end of the cable I i0 supportsa counterweight H8. The sheave |01 is carried at the lower end of a plunger I 20 which passes into a' cylinder |2| which has suitable connections |22 to a source of fluid pressure. m-ay be directed into the cylinder |2I to raise the plunger |20 and shift the furnace I0 from the position shown in Figure 8 in full lines to the position shown in dotted unes, menthe-.rur-

,nace about the axis of the shaft Il. Molten material within the furnace il will therefore be poured out of thespout il.4

As best show n in Figure 1, a steam supply connection |30 leads to a blowing-nozzle ifi disposed atone side of the stream issuing from the pourmg nozzle u) The rate' of nowzof the blowing fluid, such as steam under pressurefand the rate Y of tilting of the furnace are so controlled that the iluid pressure blows the entire molten stream laterally, as at |32, forming the product commercially known as mineral wool.

` The bus-bars 10 are connected in any suitable manner with a source ofcurrent and suitable controls serve to maintain a ow of current. providing that the furnace contains molten slag or` coal ash, from one pair of contacts or plates to the other. Itv was mentioned above that the viscosity of a molten oxide bath is vdirectly related to its electrical resistivity. By the use of suitable electrical controls, the resistance of'the slag in the furnace may be maintained constant and by virtue thereof the viscosity ofthe mass of molten material inthe furnace will also be maintained constant. This is an important feature On the other hand, if the resistance across the two sets o'f contactor 'plates falls, a lowering of the power input will immediately permit the slag bath to cool off slightly so that both its resistance and viscosity will again increase.

One of the important advantages-of using `molten coal ashes, entirely aside from .their availability as a by-product of novalue at the present time, is that the mineral wool produced from coal: ashes ,contains an appreciable percentage of iron oxides and is much softer than the ordinary commercial 'rock wool in which the. basic constituent is composed practically wholly of the lighter metal oxides, as for example, calcium oxide and magnesium oxide. The molten material containing basic oxides in which the major portion is lmatie up of iron oxides will best about 3 microns.

flow freely at about atemperature o f 2400 F., and if blown at this temperature the best results are secured, the fibers being soft and flexible and have an average diameter, I have found, offrom 2 to 6 microns. the average-diameter usually being 'I'he proportion between the acid and basic oxidesA of a mixturecapable of being blow into a mineral wool will, of course, vary with the type ofcoalburned in the furnace and talso to vsor'ne extent upon the conditions under .which the furnace operates. For exampleby using a given coal with a given furnace, I produced minerai wool from boiler coaLash-having approximately '54% silica and alumina oxides and approximately 46% iron oxides (FezOz). In ordinary commercial rock wool, the iron oxide content amounts to not more than 2 or 3% by weight.

I have also found -that the mineral wool that I have produced by the above process scarcely ever contains as muchas one tenth of 1% of sulphur. As a matter of fact, usually the sulphur content lof the molten ash from the' furnace rarely conaosaosz talns any more sulphur than the above amount, and even this small amount is not stable and is apparently oxidized and driven out in heating and blowing of the molten material. 4 While it is true that many coals may contain up to 5% sulfur, and -it would seem that the coal ash 'coming lfrom the furnace might Ialso contain appreciable quantities of sulphides, yet, however, this is not the case, for sulphides are stable only under reducing conditions and in basic slags, whereas a boiler furnace is a fuel oxidizing, not reducing,

apparatus. For this reason, since practically all commercial .coal ashes form acid, rather than` basic slags, such small amounts of'sulfur as may initially enter the slag are rapidly driven therefrom.

Thus, according to the present invention, I am enabled to take a waste by-product, that is, mlten coal ashes which is not only of little -or no value at the present'time but is usually an item of expense on account of the need for disposal thereof, and convert this waste by-product into a highly useful and valuable by-product in the form 'of a mineral wool of uniform quality and superior characteristics, and at a cost'far lower than any of thegpresent methods for making a similar grade of mineral wool. Specifically, by

` the utilization of the waste molten ashes from slag bottom pulverized fuel fired boilers, the entire cost of quarrying, transporting and melting rock or slag for the production of mineral wool is avoided; dueto the substitution of iron oxides for calciumand similar oxides in the composition of the mineral wool,l I obtain a softer, more desirablel product than the ordinary commercial rock wool type of mineral wool and without excessive temperature requirements in the blowing of the molten material? and d ue to the use of a heat-controllable intermediate furnace for holding and conditioning the molten raw material ,placed'between the melting furnace and the blowing nozzle, I amable t'o control thev uniformity of the product without any appreciable time lagand much more accurately and continuously than ithas been possible to do in the previous state of Y the art. A

While I have described above the details of my new and' improved method of making mineral 'wool, it is to be understood that they are not limiting, but illustrative, and that all vvariations 50 thereinas fall within the scope and purport of the appended claims are to be considered as part of my invention.

What I claim, therefore, and desire to secure by Letters Patent is: u

l. Themethod of producing mineral lwool from coal without substantial addition of other material, which comprises burning coal containing a useful percentage of iron in an' oxidizing atmosphere and at a temperature which fuses the in-v combustible ash content, collecting the fused ash in fluid form, and forming the fused ash into WOOL 2. The method of' producing mineral wool from coal without substantial addition of other mau terial, which comprises burning soft coal in powdered form in an oxidizing atmosphere at a temperature sumcient to reduce the ash to molten form, collecting theA moltenA ash whilel still fluid,

and forming v.the fluid ash into mineral wool. 10-

3. The method .of claim 2 characterized by. adding heat to the molten ash after it has been collected to bring it to,l substantially a predetermined temperature and'viscosity, and maintaining the temperature .and viscosity-l constant. 'Il

whereby .its viscosity is substantially uniform during the formation of the mineral wool.

4. The method of producing mineral wool from coal substantially without the addition of other material, which comprises burning finely divided coal which has a low fusion point ash while suspended in a current of air, the combustion being carried on in an oxidizing atmosphere and at a temperature which melts the ash, collecting the molten ashwhile it -is in iluid form, and converting the molten ash into libers to form mineral wool.

5. 'I'he method of claim 4 characterized by bringing the molten ash after it has been collected to substantially a predetermined temperature and viscosity, and maintaining the temperature and viscosity constant, whereby its viscosity is rendered substantially uniform for blowing.

6. The method of producing a mineral wool from coal without substantial addition of other materials, the ash of which contains from 25 to 50% iron oxides and approximately 50% or more oxides of silicon and aluminum, which comprises burning the coal in powdered form in an oxidizing current of air at a temperature high enough to reduce the ash to iiuid form, collecting the molten ash while in fluid form, adding heat -to the molten ash after it has been collected to bring it to a predetermined temperaturewhereby the viscosity is predetermined, and forming the molten ash into mineral wool while it is at said predetermined viscosity.

7. The method of producing a mineral wool from coal. the ash of which contains acid oxides and basic oxides in approximately equal proportions with iron oxides forming the major portion .of the basic oxides, without substantial addition of other materials, which method comprises burning the coal in powdered form in an oxidizing current of air at a temperature high enough to reduce the ash to fluid form, collecting the molten ash While in fluid form, adding heat to the molten ash after it has been collected to bring it to a predetermined temperature, whereby the viscosity is predetermined, and forming the molten ash into mineral wool while it is at said predetermined viscosity.

8. The method of producing mineral wool from coal without substantial additions of other materials, the ash of which has a low fusion point and contains acid and basic oxides with iron oxides, including both ferrous and ferric oxide, forming the major portion of the basic oxides, which method comprises burning the coal in pulverized form in an oxidizing currentl of air at a temperature high enough to reduce the ash to fluid form and without reducing the iron oxides to metallic iron, collecting the molten ash while in iluid form, adding heat to the molten ash after it has been collected to bring it to a predetermined temperature, whereby` the viscosity is predetermined. and forming the molten ash into mineral wool at said predetermined viscosity.

9. 'I'he method of producing mineral wool from coal without substantial addition of other material, which comprises burning a (coal, the ash of which is fusible and contains silica and iron,

-in powdered form in an oxidizingI atmosphere and

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