US2560316A

US2560316A - Apparatus for slaking lime

Info

Publication number: US2560316A
Application number: US31120A
Authority: US
Inventors: Robert S Walker
Original assignee: Traylor Engineering & Manufacturing Comp
Current assignee: Traylor Engineering & Manufacturing Co; Traylor Engineering & Manufacturing Comp
Priority date: 1946-02-20
Filing date: 1948-06-04
Publication date: 1951-07-10
Anticipated expiration: 1968-07-10

Description

July 10, 1951 R. s. WALKER- APPARATUS FOR SLAKING LIME Original Fil ed Feb. 20, 1946 mm B B @m 5 mm 5 m 8 E 5 om w 0F 0 N0 3 mm g mm 3 7 8. .E mm 8 1m E Inventor Robcrf 5. Walker W @015 )W Patented July 10, 1951 APPARATUS FOR SLAKI NG LIME Robert S. Walker, Allentown, Pa., a'ssignor to Traylor Engineering & Manufacturing Company, Allentown, Pa a corporation of Delaware Original application February 20, 1946, Serial No. 649,056. Divided and this application June 4, 1948, Serial No. 31,120

4 Claims.

This invention relates to means for producing milk of lime, an object being to produce a milk wherein the particles have the desired physical characteristics as to size and shape, particularly the latter. To this end the invention contemplates separate slaking and diluting steps, the physical characteristics of the particles being determined in the slaking step by maintaining a selected substantially constant slaking temperature. In this connection, it is an object of the invention to produce a milk of lime of desired consistency and particle form by apportioning a total amount of liquid between slaking and diluting functions so that Whatever proportion is supplied in the slakin step, the complement is supplied in thediluting step.

Typical apparatus in accordance with the invention is shown in the accompanying drawing which is a vertical axial section of a lime slaker and appurtenances with parts in elevation.

In the drawing, reference numeral designates a cylindrical shell supported substantially horizontally on rings as at 52 and rollers as at 53 of conventional design. Embracing the drum and fixed thereto is. a ring gear 54 engaged by a gear 55 driven from a motor 56 through a speed reducer 51. At the right or head end the drum is provided with an annular flange 58 defining an opening 59 which is circular on the axis of the drum, the outer margin of the flange bein rimmed by an' outwardly flaring conical lip 6E3. 'At its foot end the drum includes an outwardly tapering coaxial conical portion 6| defining an end opening 62, and a spiral rib S3 is aiiixed to the inner surface of extension 6|. 7

Mounted concentrically within drum 5| in the head end thereof is an inner cylindrical shell or'drum 64, an annular space 65 existing between the two drums. Reference numeral 66 designates a spiral rib affixed to the inner surface 'of drum 5| outwardly of drum 64 with the inner edge of the rib spaced from the latter except that the rib may include spoke-like extensionsfor the support of the inner drum. At its head end the inner drum has a tapered, conical terminal portion 61 whose outer extremity defines an opening 68 circular on the drum axis and is spaced inwardly of the edge of flange 58 so that an annular space exists between the two.

Reference numeral 69 designates a conveyor, here shown as a screw conveyor, in connection with a source of lime, not shown, the conveyor discharging into a spout which extends into the inner drum through opening 68. The conveyor is driven by a variable speed device, for example a motor I I.

Reference numeral 12 designates a pipe leading from any suitable source, not shown, of a slaking and diluting liquid, pipe 12 being connected into a flow meter 13 whose outlet is-in xGil 2 connection with a pipe M which extends into the head end of the inner drum through opening 68, a control valve 15 being interposed in pipe M and the valve being operable by an electric motor l6. Reference numeral ll designates a control member responsive to the driving device 'ii and controlling the flow meter 13 through any suitable connection 18.

Reference numeral 19 designates a thermocouple supported in the head end of the inner drum preferably in a position to be submerged in the reactants, the thermocouple occupyinga fixed position. Wires and 8| connect the thermocouple to a control instrument 82 which has a temperature scale 83 and a manually settable pointer 85, this instrument controlling motor 16 for drive in either direction through a connection 85.

The foot end of the outer drum extends into a chamber 88, through a suitable seal, the chamber including a sump 81 which can be opened for ischarge. A conduit 88 connects chamber 81 with the inlet of a fan casing 89. The casing has a vertical outlet conduit 90 extendin into the bottom of a chamber 9! in which is disposed a series of conical baffies 92 aligned with conduit 9B. A stack 93 surmounts chamber 9|.

Branched from pipe 14 in advance of valve 15 is a pipe as which through a riser portion 95 is in connection with a vertical header 96 into which are connected pipe sections 91 which extend into chamber 9| and have downwardly directed delivery openings above baffles 92 respectively. A pipe 98 leads from the bottom of chamber 9| into the foot end of the outer drum. With the drums rotating, as driven from motor 56, conveyerBQ is driven so as to deliver a constant quantity of lime into the head end of the inner drum. In order to produce a milk of lime of desired consistency a total amount of liquid proportional to the amount of fed lime must be supplied and flow meter i3 is adjusted so that the required total quantity is delivered to pipe 14. Should the speed of the variable speed driving device ll be changed, thus varying the output of conveyor 69, the setting of the flow meter 13 will be correspondingly changed through controller H and connection 18, so that the correct proportion of water to lime will be maintained.

Depending on the desired characteristic of the ultimate particles of slaked lime, a certain slaking temperature must be maintained. This temperature will be somewhat between and 200 F. Due to the variables encountered, no definite temperatures of general application can be specified but as soon as the plant is set up, the required temperature can be readily determined. In order to produce a particle of granular form, and this will be the form demanded-if the slaker output is to be centrifuged as later described, the slaking temperature may, for example, be required to be 186 F. In that case, pointer 84 is set at this figure on the scale 83 and valve '16 will assume an adjustment such that sufficient slaking liquid will be supplied to the inner drum to maintain the set temperature. This may require, for example, approximately one-third of the metered amount of liquid.

In order to obtain the required cooling effect it is always necessary to supply more slaking liquid than the minimum necessary for the completion of the reaction and, consequently, the resultant, or reaction product, will always be of a viscous putty-like consistency instead of in a dry condition. The resultant, or reaction product moves toward the foot end of the slaking chamber defined by the inner drum under the combined influences of the rotation of the drum 64 and the continued feed of lime and liquid at the head end. The slaking chamber is long enough with respect to the rate of feed so that the reaction will be completed therein and the product will break down to the viscous putty-like consistency above-mentioned.

This consistency will, of course, vary under different conditions. For example, if the slaking liquid is relatively cold, less will be required for cooling than as though it were relatively warm, the quantity of fed lime remaining constant. However, there is always an excess of liquid beyond the minimum required for the reaction but the excess will be far short of that required to produce a milk and, hence, the slaked lime will emerge from the foot end of the slaking chamber in the aforesaid viscous or putty-like consistency and will drop into the outer chamber defined by drum 5|.

Such 'of the metered liquid as is not passed by valve 15 enters pipe 94, and goes to the sprays 91 for'discharge on the baflles 92, thus serving to condense steam pulled by the fan from drum 5| and discharged into chamber 9|. The liquid flows from member 9| through pipe -98 into the foot end of driun 5| as diluting liquid.

The slaked lime and diluting liquid fiow with mixing action over the spiral rib 66 toward the head end of drum 5|, and a well dispersed product overflows through opening 59 and over lip (it into a surge tank 99 whence the milk may be lead away through a pipe N30 or may go to a centrifuge NH. 59 is below the lowest point of opening 52 at the foot end of the conveyor so that overflow will occur only at the head end. The spiral rib 63 in the foot end of the outer drum serves to convey tailings through opening 82 to the sump 81. The pitch of the

spirals

66 and 63 is such that the drum is normally rotated in a counterclockwise direction, looking toward the right-hand or head end thereof. Hence, grit, tailings, and other foreign matter, precipitated from the suspension flowing toward the right will be positively mechanically fed toward the left where it will be picked up by the rib 63 and discharged through opening 62, as noted above.

If in normal operation one-third of the metered liquid is required for slaking, it will be evident that two-thirds of the liquid will be used for diluting. In view of the head provided by the riser 95 there will always be preferential delivery through valve '15 so that of the total quantity of liquid required to produce a milk of lime of the desired consistency, the slaking requirement is first satisfied and the balance is used for dilution. If there The lowest point of opening,

4 is a change in the temperature of the metered liquid, for example, if it becomes colder, less will be required in the slaking chamber and valve 16 will operate to reduce the supply appropriately, the

thus increased balance serving for dilution. Likewise, if the output of conveyor 69 drops, less slaking liquid will be required for the maintenance of the slaking temperature and valve 15 will be closed to the appropriate extent.

The described apparatus is usable with great advantage as a causticizingsystem. In that case, pipe 72 is in connection with a source of green liquor with the slaking and diluting operations following in the same manner as above described. Where the slaker output is to be centrifuged, as herein particularly contemplated, the slaking temperature is maintained at a point such that slaked lime and calcium carbonate particles'of substantially granular form and appropriate size will be produced. Granular particles, as opposed to flake particles, are heavier per unit of surface area, will settle readily and, by the same token, can be separated out of the white liquor by centrifuging, whereas such separation is impossible with concentrated white liquor which has been causticized :by prior art methods. With the surge tank 99 in connection with the centrifuge I01, white liquor will be delivered at 32 and the calcium carbonate sludge at H3. The centrifuge may be of any suitable type, for example, such as is shown in Patent No. 2,085,538, S. C. Lyons, June 29, 1937.

A thoroughly causticized discharge will ordinarily emerge at opening 59. However, if necessary, an auxiliary causticizer I04, which may be simply a paddle mixer, or equivalent device. can be provided. A valved pipe H15 leads-from tank 99 to the inlet of the mixer and a pump I06 is in connection with the outlet for delivery to the centrifuge. The auxiliary causticizer is by-passed when not needed.

The invention thus provides not only an improved apparatus or system for the production of milk of lime but, in particular, an improved causticizing system. The two-stage procedure with determination of the particle form in the first stage is the best mamier known to me for the certain production of the granular particle form essential to successful centrifuging of the suspension. However, I do not necessarily limit myself to this particular procedure in the preparation of a centrifugeable prod-uct. Other variations in procedure and variations in apparatus are contemplated under the invention as defined in the following claims.

This application is a division of my prior filed application, Serial No. 649,056, filed February 20, 1946, for Method and and Means for Producing Milk of Lime and for Producing White Liquor and Lime Carbonate Sludge, and is directed to the apparatus phase of the invention originally shown,

described and claimed therein.

I claim:

1. Apparatus for slaking lime and producing milk of lime comprising concentric inner and outer drums arranged for rotation in unisonon a substantially horizontal axis, means for feeding unslaked lime at a predetermined constant rate to the head end of the inner drum, means for supplying slakingliquid at a predetermined, constant rate, proportional to the fed lime to produce a milk of lime of desired consistency, means for delivering a portion of the supplied liquid to-the head end of the inner drum for admixture therein with the total of the fed lime to produce a slaked lime of viscous consistency, the foot end of the inner drum being open for the discharge of the material into the outer drum, a combined dust collector and steam condenser in communication with the foot end of the outer drum, means causing a draft of air, steam, and dust through the drums for discharge into said collector, means for continuously spraying the remainder of the fed liquid into said collector, means for conducting the sprayed liquid into the foot end of the outer drum for admxiture with the slaked lime, to produce a milk of lime of the desired consistency, and means for discharging the milk of lime from the head end of the outer drum.

2. Apparatus in accordance with claim 1 characterized by the inclusion of means for determining the temperature of the material in the inner drum, and means responsive to said temperature for proportioning the delivery of the fed quantity of liquid between the head end of the inner drum and the foot end of the outer drum.

3. Apparatus in accordance with claim 1 characterized by the inclusion of means for determining the temperature of the material in the inner drum, and means responsive to said temperature for proportioning the delivery of the fed quantity of liquid between the head end of the inner drum and said dust collector and steam condenser.

4. An apparatus for slaking lime and producing milk of lime, comprising inner and outer concentric, open-ended drums journalled for rotation on a common, substantially horizontal axis, means for deliveringunslaked lime at a substantially constant predetermined rate to the head end of the inner drum, means for supplying slaking liquid at a constant predetermined rate to produce a milk of lime oi the desired consistency, means for delivering a portion of the supplied liquid to the head end of the inner drum to produce a slaked lime of viscous consistency therein for, delivery from the foot end of the inner drum to the interior of the outer drum, a chamber in communication with the open foot end of the outer drum having baffles therein, means for causing a flow of steam and dust from the drums into said chamber, means for spraying the remainder of the supplied liquid into the chamber to condense steam and collect dust, means for conducting the sprayed liquid from said chamber to the foot end of the outer drum for admixture with the slaked lime for the production of milk of lime of the desired consistency, and means for causing the milk of lime to flow toward the head end of the outer drum for discharge therethrough.

ROBERT S. WALKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 18,510 Green July 5, 1932 1,018,404 Baxter Feb. 27, 1912 1,917,300 Hardinge July 11, 1933 1,945,652 Martin Feb. 6, 1934 2,020,098 Bird Nov. 5, 1935 2,041,544 Hammond May 19, 1936 2,047,202 Hardinge July 14, 1936 2,149,269 Brooks Mar. 7, 1939 2,365,736 Warner Dec. 26, 1944 2,375,499 Shigley May 8, 1945

Claims

1. APPARATUS FOR SLAKING LIME AND PRODUCING MILK OF LIME COMPRISING CONCENTRIC INNER AND OUTER DRUMS ARRANGED FOR ROTATION IN UNISON ON A SUBSTANTIALLY HORIZONTAL AXIS, MEANS FOR FEEDING UNSLAKED LIME AT A PREDETERMINED CONSTANT RATE TO THE HEAD END OF THE INNER DRUM, MEANS FOR SUPPLYING SLAKING LIQUID AT A PREDETERMINED, CONSTANT RATE, PROPORTIONAL TO THE FED LIME TO PRODUCE A MILK OF LIME OF DESIRED CONSISTENCY, MEANS FOR DELIVERING A PORTION OF THE SUPPLIED LIQUID TO THE HEAD END OF THE INNER DRUM FOR ADMIXTURE THEREIN WITH THE TOTAL OF THE FED LIME TO PRODUCE A SLAKED LIME OF VISCOUS CONSISTENCY, THE FOOT END OF THE INNER DRUM BEING OPEN FOR THE DISCHARGE OF THE MATERIAL INTO THE OUTER DRUM, A COMBINED DUST COLLECTOR AND STEAM CONDENSER IN COMMUNICATION WITH THE FOOT END OF THE OUTER DRUM, MEANS CAUSING A DRAFT OF AIR, STEAM, AND DUST, MEANS THE DRUMS FOR DISCHARGE INTO SAID COLLECTOR, MEANS FOR CONTINUOUSLY SPRAYING THE REMAINDER OF THE FED LIQUID INTO SAID COLLECTOR, MEANS FOR CONDUCTING THE SPRAYED LIQUID INTO THE FOOT END OF THE OUTER DRUM FOR ADMIXTURE WITH THE SLAKED LIME, TO PRODUCE A MILK OF LIME OF THE DESIRED CONSISTENCY, AND MEANS FOR DISCHARGING THE MILK OF LIME FROM THE HEAD END OF THE OUTER DRUM.