US2535570A - Continuous batch flash drier having coordinated feed and recycling means - Google Patents

Description

1950 c. w. GORDON 2, 3 70 CONTINUOUS BATCH FLASH DRIER HAVING COQRDINATED FEED AND RECYCLING MEANS Filed Dec. 31, 1946 JNVENTOR. Charles W. Gordon Patented Dec. 26, 1950 CONTINUOUS BATCH FLASH DRIER HAVING COORUIINATED FEED AND RECYCLING MEANS Charles W. Gordon, Glen Ellyn, Ill., asslgnor to Combustion Engineering-Superheater, 1110., a corporation of Delaware Application December 31, 1946, Serial No. 219,346

v terial and 2 Eiaims. (Ci. 241-34) This invention relates to new and useful improvements in drying apparatus and is particularly applicable to flash drying wet materials that are reluctant to give up their moisture.

In the usual flash drying apparatus hereto- However ing.

operation by turbulence.

moisture.

drawings, wherein:

proved flash drying system.

The system preferably omprises a disintegrator such as the cage mill A into which the material to be dried is conveyed in a current of hot gas and in which the material and gas are turbulently and intimately contacted; a separator B in which In the form fore employed, the material to be dried passes the ed. t a y d from e d tethrough the apparatus but once and is in congrator mill in the g t eam is Separated m tact with the hot gaseous drying medium but for a the gas stream and from which the moisturevery small period of time, seldom more than six laden gas is vented; a damper C for deflecting seconds. This short timefor the drying process lo the separated partly-dried material from sepais adequate for most materials when subjected rator B back to the disintegrator cage mill A or to an intimate and turbulent contact with the deflecting the dried material out of the system; drying gases, such as occurs when both the maa feeder D for delivering the raw wet material ses are passed through a cage mill. to be dried to the disintegrator cage mill A; and e are other materials which are l5 a furnace orother heater E for heating the dryrelatively reluctant to give up their moisture, parlng gas. i ticularly the last few percentages of moisture, Reerring to Figure 1, the disintegrator A may, and these require more than one stage of dryas here shown by wayof example, satisfactorily be in the form of a cage mill substantially of the One such system of two-stage drying is shown general type disclosed in thepatent to Gordon in my Patent 2,393,766, wherein two separate 2,149,018 granted February 28, 1939. Suchacage cyclones are used one each for the two stages of mill, shownin cross section, comprises a casing drying. The wet material is partly dried in a I surrounding achamber 2 within which is a first stage while passing through a first cyclone beater 3 mounted for rotation on the overhangwherein it is mixed with the separated drying ing end of a shaft 4 which is supported by beargases taken from a second cyclone, and is thereings 5 outside of the casing I. The casing is proafter carried through a conveyor into the second vided with aninlet 6 for the entry of the wet cyclone in suspension in a stream of hot dry material in suspension ina stream of hot gas and ases taken from an outside source therein and a tangentially placed outlet 1 through which the dried in a second stage to a final moisture conpartly or sufficiently dried material leaves. tent. e mo -E e ases leave the system Shaft 4 is rotated by motor 8 and on the end through the vent of the first cyclone. If deof the shaft extending into the casing l is sired, cage mills, as disclosed in the patent to mounted a hub 9 to which is fastened a circular Gordon 2,149,018 or the like, may be introduced plate in from which there extends across the into the ducts conveying the material to be dried 5, chamber of the casing a plurality of rods ll. into the respective cyclones if a greater tur These rods are arranged in circles concentric bulence is required between the material and hot with the shaft 4. At the periphery of plate in gases so as to effect a greater drying. In genare mounted a multiplicity of fan blades I! which eral, any multi-stage system of hash drying inlike the rods are arranged in a circ'e concentric W lv at least a muhiplicity f y l n inter 40 with the shaft 4 and extend across the chamber connected by conveyors and possiblytheaddition 2 of casing I. In the particular disclosure shown of cage mills, or the like, for improving the drying there are two sets of rods arranged in two concentric circles said circles b ing pc"d radia ly It is an object of thi i v n i n to provid ima art, a similar radial space being provided hel roved and simplified apparatus for flash dryin 1 tween the outermost rods II and the fan blades wet materials that are reluctant to give up their 12. l

Extending into the spaces between the sets of How the foregoing, together with other objects rods II and the fan blades it are other s ts of and advantagesas may hereinafter appear or are rods l3 connected to the casing I. There ar= two incident to my invention are realized, is illussuch sets of rods arranged in concentric circles trated in preferred form in the accompanying with respect to the former rods ll.

. of cage mill disclosed, only two sets of circularly- Figure 1 is a diagram showing the arrangement arranged rods ll rotate together with the fan and interconnections of the apparatus of my imblades l2. The remaining sets of circularly-arranged rods l3 remain stationaiy.

This general type of cage mill, as herein used in disintegrator A, is not novel and in some forms both sets of rods M and it may be arranged to rotate but in opposite directions. The fan blades !2 act to propel the material and gases through the system. When drying some materials a multibladed fan may be used instead of the disin tegrator cage mill and provide sufilclent turbulence to satisfactorily eirect drying.

In the illustrative system represented said disintegrator mill A is supplied with wet material in flotation in a stream of hot gas through conduit it which connects to thedisintegrator inlet 6. The wet material is dropped into said conduit it through a conduit i5 into which said material is delivered by means of feeder D. Feeder D, which may be of the type shown in which belt or other conveyor it travels under a hopper l l which con tains the wet material to be dried, functions to withdraw the material from said hopper at a predetermined rate. The feeder is driven by a motor it.

Upon falling into the conduit Ed the wet mate= rial is conveyed by flotation in the stream of hotv gas coming from the heater E into the disintegrai tor mill A. After being turbulently mixed with the hot ases within mill A the material is do livered from the disintegratcr mill outlet through conduit 59 into separator B. Device B may be cyclone separator of the welldrnown type having avent 29 at the top for discharge of the moisture laden gases separated from the material therein and an outlet ill for removal of the partially dried or insufiiciently dried material therefrom. [iduct 22 connected to the outlet it of separator E de livers the partially dried material from the outlet to the hot gas conduit is leading to the inlet cf disintegrator mill A. Anotherduct 23 is con nected to the outlet M of separator B and removes the sufficiently dried material from the system.

Means such as damper C comprising adivider vane 24 is provided at the outlet of separator B and so arranged with respect toducts 22 and 23 that by the proper damper setting the partially dried material may be all deflected back into the hot gas conduit it viaduct 22 or, if the material is sufficiently dried it may be all deflected intoduct 23 and thence from the system. Such a damper may be a flap divider vane 2t which, when in the position shown in the drawing, will deflect all of the partially dried material throughduct 22 back to the mill A for recirculation and further drying, and which when rotated to the right will deflect all of the sufficiently dried material from the system throughduct 23.

In operation, when starting the system up, thedividervane 24 is set to return all oi. the material passing out of the separator B back into the disintegrator mill A viaduct 22 and conduit M. The disintegrator mill A is then placed into operation by starting motor 8. The feeder D is then started and operated for a short time to feed raw wet material into the system via conduits i5 and 14. When a predetermined amount of material has been fed to the system the feeder D is stopped.

The material thus introduced into the system passes through the disintegrator mill A, then through conduit i9 to separator 3 wherein it is separated from the gas and is thence returned via.duct 22 and conduit l4 into disintegrator mill A to pass through a second stage of drying and may thus be recycled through a number of subsequent stages, the number of stages of drying being predetermined for each material to be stages thedivider vane 24 is set to discharge the suificiently dried material from the system throughduct 23.

Simultaneously feeder D is started again to recharge the system and the cyclic operation is repeated as before until the subsequent batch is sufficiently dried and removed from the system. These cycles are repeated as often as is necessary to dry all of the material to be dried.

Preferably the operation of damper Cs divider vane 25 is made automatic and correlated with the operation'of the feeder D so that when the sufliciently dried material is being discharged from the system the feeder will operate to refill the system and when the partially dried material is being recirculated the feeder will be stationary so as not to admit additional material into the system.

One form of such automatic control may include a clock-operatedswitch 26 which in timed intervals will make or break the electric current tosolenoids 21 and 28. Upon energizing the solenoids, the divider M is drawn against a compression spring in into position (vertical as shown) to recirculate the material through the system and the switch contact 25 is opened (against gravity) to stop the feeder motor l8. Upon deenergizing the solenoids, thedivider vane 24 is returned by the aforesaid compression spring into position (its top rotated to the right) to discharge the dried material from the system and theswitch contact 29 is closed (by gravity) to start the feeder motor It so as to recharge the system with wet material.

The inlet temperature of the hot gas entering disintegrator mill A may be controlled by temporing air dampers 38 which control the influx of cold air through conduit 3! into the hot gas conduit it. The tempering dampers are located one each in the conduits H and 3| and are interconnected by arod 32 so that as one damper closes the other opens. The control of said dampers may be made responsive tothermostat 33 located in theoutlet conduit 20 of separator B. The

no variation in pressure due to the expansion of a gas in the thermostat is conveyed bytube 34 to a diaphragm motor 35 for moving the dampers.

Furthermore the said thermostat may control the amount of fuel to the furnace E in order to 59 control the temperature of the hot gases entering conduit M, either alone of supplementary to the aforesaid damper control. In this case the tube {it will lead either directly fromthermostat 33 to thediaphragm motor 36 of the fuel control valve 31 or it will lead to both. thediaphragm motors 35 and 36.

By my improved system of drying wet materials that are reluctant to give up their moisture, I accomplish the drying with a simple apparatus W comprising only a single disintegrator mill and a 55 tion has been shown and described, it will be dried. At the conclusion of the drying cycles or 7 understood that changes in construction and organization of parts may be made without departing from the spirit and scope of the invention as claimed.

What I claim is:

1. In a. system for removing water from materials havins a high moisture content, the combination of a disintegrator mill, a fan and a separator through which the material being dried flows in series; a. source of hot gases; a conduit for. conveying the hot gas from said source and said material in suspension therein into said mill; feeder means for delivering the wet material to be dried into said hot gas conduit; a conduit through which said delivered material is carried in suspension in said gas from said mill through the fan and to said separator; a vent on said separator for removing therefrom the portion of said gas that is therein separated from said material; an outlet on said separator for removing the separated material together with the remaining portion of said gas that does not pass out of said vent; a first duct connecting said outlet directly with said hot gas conduit for returning partly dried material in flotation in the aforesaid remaining gas portion from said separator to said mill for further drying a second duct connected to said 0 outlet for removing sufficiently dried material from the system; a divider vane effective when in a first position to direct all of the partially dried material and said remaining gas portion from said outlet through said first duct into said hot gas conduit for recirculation through and further drying in the system and effective when in a second position to remove all of the sufliciently dried material through said second duct from the system; means including a control device for placing said divider vane alternately in its first and second positions for predetermined periods of time; and means also governed by said control device for causing said feeder means to be inoperative while the divider vane occupies said first position to effect the aforesaid recirculation of the partly dried material, and causing said feeder means to operate while the divider vane occupies said second position to effect the aforesaid removal of the sufliciently dried material from the system.

2. In a system for removing water from materials having a high moisture content, the com bination of a disintegrator mill and fan and a cyclone separator through which the material being dried flows in series, a source of hot gas, a conduit for conveying the hot gas from said source and said material in suspension therein into said mill, a feeder for delivering the wet material to removing therefrom the portion of said gas that is therein separated from said material, an outlet on said cyclone for removing the separated material together with the remaining portion of said gas that does not pass out of said vent, a first conduit connecting said outlet directly with said hot gas conduit for returning partly dried material in flotation in the aforesaid remaining gas portion from the said cyclone to said mill for further drying, a second duct connected to said outlet for removing sufliciently dried material from the system, divider apparatus at said separator outlet effective under a first control condition to direct all of the partially dried material and said remaining gas portion from said outlet through said first duct into said hot gas conduit for recirculation through and further drying in the system and effective under a second control condition to remove all of the sumciently dried material through said second duct from the system, automatic means including a timing device for subjecting the aforesaid divider apparatus alternately to said first and second control conditions during predetermined periods of time, and means also governed by said timing device for stopping said feeder during said first-control-condition time periods while the partly dried material is recirculating and operating the feeder during said alternate second-control-condition time periods while the sufllciently dried material is removed from the system.

7 CHARLES W. GORDON.

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

UNITED STATES PATENTS Great Britain Dec. 2, 1931

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