US3309780A - Process and apparatus for drying wet particulate solids - Google Patents

Description

March 21, 1967 R. R. GOINS 393999789 PROCESS AND APPARATUS FOR DRYING WET PARTICULATE SOLIDS Original Filed April 9, 1962 3 Sheets-Sheet 2 TO BAG FILTER loe N [H4 vENT-\x I 428 -T: loe TC ns -Gi* X WET PELLETS DRYER TREATER cooLER '34 122 H2 |32 L 'S |o4 H6 f r A'R Y coMBusTloN GAS S162 To ElLTxER .'51 Iso r |64 sET PART|ALLY |66 PO'NT I DRIED wET PELLETS I g) PELLETS 15 I --)--5---- RoTARY iDRY 142 DRYER |44 '53 i PELLETS 166 Isa FUEL FURNACE qi S i 156 AlR /NvE/vrof? R. R. GoINs A 7' TORNEVS March 21', 1967 R. R. Goms 3,309,780

PROCESS AND APPARATUS FOR DRYING WETPARTICULATE SOLIDS 192 --ILEJ-POINT EUEL; [Iso 2201 204 m w-7 202 Am- Orignal Filed April 9, 1962 5 Sheets-Sheet 3 wET PELLETS 2:0 To FILTER Q I :82 196lg 212 FIRST IDPYER 214 SET P "1: 208 PolNT kan SEcoND I m4 I DRYER I I is AC Isis l 2|a DRY I N 1/ SETPELLETS 1 I I F/G 4 206 FUEL I SET POINT I l l wET 1 PELLETS I I T l A'RH20 246 r1| I I L l I FuEL H20 248N LJ) DRY 1- L (y) PELLETS T? I I l PEED /NVE/vToR -3- E 2.3. .2 R. R. GolNs T TORNEYS United States Patent Ofiice 3399389 Ptentecl Mar. 2'1, 1967 3,3G9,780 PROCESS AND APPARATUS FOR DRYING WET PARTICULATE SOLIDS Robert R. Goins, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Original application Apr. 9, 1962, Ser. No. 186,038, n ow Patent No. 3,238,634. Divided and this application Jan. 10, 1966, Ser. No. 519,644

6 Clairns. (Cl. 34-10) This is a division of my application S.N. 186,038, filed Apr. 9, 1962, now Patent No. 3,23 8,634.

This invention relates to a process and apparatus for drying wet particulate solids. A specific aspect of the invention pertains to a process and apparatus for drying wet pelleted carbon black.

Various powdered materials are wet pelleted into small pellets Which must be dried before packaging. Carbon black, catalysts, adsorbents, fertilizers, etc., are some of the materials which must be dried in particulate form before storing or packaging. In drying these solids, rotary drum type dryers are conventionally utilized. The drum is rotated around its horizontal axs while feed is introduced to one end and Vdried solids are delivered from the other end. This type dryer is heated by means of hot combustion gas formed in a furnace |under or adjacent the dryer. One of the problems encountered is the control of the shell temperature of the dryer so that the drying is done efficiently without overheating and/or ignitincr the material being dried. When utilizing a drum dryer in drying carbon black pellets, it has been found particularly diflicult to control the heat input to the dryer so as to properly dry the pellets of carbon black without overheating of the black and the dryer.

It has been proposed to dry pellets in a fluidized bed dryer. This drying technique has been more or less successful but due to the vast |heat requirements to vaporize the water from the wet pellets, the dryer must be of large volume capacity in order to allow sufficient heat input. The large capacity dryer requirement means a long residence time of the solids in the dryer which in turn increases the attrition of the solids and the proportion of the solids Which pass out with the effiuent gas :as fines and must be repelleted and recycled to the dryer. This, of course, decreases the efficiency and increases the oost of the drying process.

Accordingly, it is an object of the invention to provide an improved process and apparatus for drying particulate solids. Another object of the invention is to provide a process and an apparatus for drying particulate solids Which are highly efiicient and effect a minimum of attrition and production of fines in the solids. A further object is to provide a process and arrangement of apparatus for controlling the drying of partcul-ate solids. It is also an Object of the invention to provide a process and iapparatus for drying particulate solids, such as wet carbon black pellets, which operate more economically than heretofore. Other objects will become apparent to one skilled in the art upon consideration of the accompanying disclosure.

A broad aspect of -the invention comprises utilizing hot off-gas from a carbon black or other type reactor as the drying gas for fiuidizing and drying wet particulate solids, particularly, carbon black pellets. The solids to be dried are either introduced directly into ythe offgas line and transported into a fluidized bed drying zone in the line, or off-gas is taken directly from the off-gas line or smoke header and passed thru a fluidized bed dryer as a fluidizing and drying gas, with efliuent gas from the dryer being passed back into the off-gas line. This technique utilizes sensible heat of the off-gas, thereby reducing the heat costs of the process. When this technique is utilized in drying carbon black pellets, the fines from the dryer pass with the off-gas to the bag filter of the carbon black plant thereby simplifying the recovery process.

In the application of the process in Which smoke is taken from the reactor off-gas line or smoke header, it is advantageous to utilize fluidized bed dryers arranged in series :and to effect most of the drying in the first bed and residual drying in the second bed.V In this manner the major portion of the water (all but about 2-50 Weight percent) is driven from the pellets or other solids at a relatively low bed temperature with higher bed temperature being utilized in the second dryer. Also, the second dryer is made considerably smaller than the first dryer so as to reduce the residence time of the solids therein and reduce the attrition and proportion of solids converted to fines. The operation of two dryers in series is not limited to the use of smoke or yofi-g-as as the drying gas but, on the icontrary, advantages accrue to this technique when utilizing steam, air, C02, and other conventional drying gases.

When drying wet carbon black pellets containing about 43-57 weight percent Water (conventional Water content of wet pelleted carbon black) fines resulting from |abrasion of the pellets run as high as 10 percent or more by weight of the pellets fed to the dryer. These fines must be returned to the pelletizer and recycled thru the dryer as wet pellets which proportionately increases the heat load on the dryer. It has been found that wet carbon black pellets can be dried in two separate beds connected in series With increased efiiciency and less fines loss. To illustrate the advantage of utilizing two fluidized beds for drying carbon black pellets having a moisture content of about 50 weight percent, the following example is presented.

Example Runs Were made utilizing a 12 diameter fluidized bed dryer with different air inlet temperatures. Fines in the dryer efliuent gas Were collected in a cyclone separator. The data obtained -are presented in the table below.

In a similar run utilizing an air inlet temperature of 1400 F., the cyclone product (fines) amounted to a little more than ll) percent of the feed on a dry basis. It should be noted that Operating with a lower drying gas temperature and drying to a lower moisture content such as 3.5 Weight percent as in Run No. 1 produces only 2.7 percent fines :as compared to 6.5% fines when drying to a moisture content of 0.6 weight percent as ill-ustrated in Run 2. By Operating With two beds, the first one under conditions of Run No. 1, and then passing the semi-dry black into the second bed Operating near conditions of Run 2 it is possible to substantially reduce the fines formed in the process. The second bed is operated at a minimum residence time by reducing the relative size of the dryer. Improvemen-ts obtained in this 2-bed operation include 1) efiiciency is increased because most of the drying is done at a lower temperature, (2) abrasion of the pellets is minimized, (3) contact time in the second vessel can be controlled (as well as the temperature) to control the amount of after treating without affecting the efiiciency of the drying operation in the primary dryer, and (4) special atmosphere or treating gas can be utilized in the second dryer for after-treating the black while reducing the moisture content to less than about 1 percent by weight.

Another aspect of the invention comprises drying the wet solids in a first fluidized bed, after-treating the dried solids in a second fluidized bed, and cooling the hot solids from the second bed in a third fluidized bed. In this technique cooling gas passed thru the cooling zone as a fluidizing gas is preheated and passed to the treating zone in admixture with other hot gas to provide the optimum temperature for the after-treating step. The hot treating gas is then passed into the drying zone as fluidizing and drying gas. In this process, a great economy of heat is obtained.

Another aspect of the invention comprises controlling the heating conditions in a pair of dryers operated in series by sensing the temperature of the efiluent gas from the second dryer and controlling the heat input to the second dryer and simultaneously sensing the Variations in the heat input to the second dryer and utilizing the sensed Variable to control the heat input to the first dryer. This may be accomplished by different apparatus arrangements as more fully set forth below.

A more complete understanding of the inventon may be obtained by consideration of the accompanying schematic drawing of Which FIGURE 1 shows an arrangement of apparatus in accordance -wth one aspect to the invention; FIGURE 2 shows an arrangement of apparatus in accordance With another aspect of the invention; FIGURE 3 shows one arrangement of apparatus and controls for elfecting one aspect of the invention; FIGURE 4 shows another arrangement of controls and apparatus for effecting another aspect of the invention; and FIGURE 5 shows apparatus in accordance with a further embodiment of the invention.

Referring to FIGURE l a pair of carbon black reactors connect with acommon smoke header 12 which feeds intosmoke line 14 leading tocyclone separator 16.Water line 18 connects withline 14 to supply quench water to the smoke.Line 20 connectscyclone 16 withbag filter 22 which feeds black intoline 24 containingpulverizer 26. Off-gas from the bag filter is taken off thruline 28, a portion venting to the atmosphere and another portion being recycled thruline 30 toline 32 leading intoblower 34. Carbon black recovered fromcyclone 16 and frombag filter 22 is deliveredthru lines 24 and 36 topneumatic conveyor 38 for transport tosurge vessel 40. Carbon black fromsurge vessel 40 passes thruline 42 intowet pelletizers 44 which are supplied With water, which may contain additives such as molasses, from aline 46. All of the apparatus thus far described is conventional in modern carbon black pelleting plants.

Wet pellets containing from about 43 to about 57 percent moisture by weight pass thruline 48 intotransport drying line 50 leading into the bottom -offluidized bed dryer 52. Hot smoke for thetransport drying line 50 is drawn fromsmoke line 14 by means oflines 51 and 54. Other gas may be introduced thruline 56 as tempering gas to control the temperature and/or to change the character of the drying gas. Air, steam, C02, etc., may be introduced at this point.

The term smoke, as used in the carbon black art and herein, denotes the hot effluent from a carbon black reactor comprising a suspension of finely divided carbon black in combustion gases.

Efliuent gas fromdryer 52 is passed vialine 60 toline 20 or tobag filter 22. Dried pellets from drier 52 are taken off by means ofconduit 62 which leads into the lower section ofdryer 64. Fluidizing and drying gas fordryer 64 may also be smoke or off-gas obtained fromline 54 thrulines 66 and 68. Here again, additional drying gas of a different character may be introduced thru line 70.

Efiiuent gas fromdryer 64 is passed vialine 72 to finesseparatingcyclone 74 or it may be passed vialine 76 toline 20 for passage tobag filter 22 to separate fines therefrom. In the event the fines are recovered incyclone 74, they are passed thru line 73 topneumatic conveyor 38 for recycle to the pelletizers.

In the event only one fluidized bed dryer is utilized to accomplish the drying step, dried pellets inline 62 are passed vialine 80 directly to bagging or storage. When both dryers are utilized, effluent dry pellets are passed vialine 82 toline 80 for passage to bagging or storage.

The degree of completion of the drying process indryer 52, whendryer 64 is not used, is controlled by manipulation of the flow rate of drying gas to the process by operation ofvalvesV 84 and 86 and by sensing the temperature of the efiluent drying gas inline 60 feeding this signal fromtransmitter 88 totemperature recorder controller 90 which positions motorvalve 92 inwater line 94, thereby manipulating the amount of quench water added to the eflluent smoke and, indirectly, the off-gas temperature inline 60 fromdryer 52.

Referring to FIGURE 2, a fluidized dryer is provided With a wetpellet inlet line 102, inlet dryinggas line 104, and aneffluent gas line 106. Dried pellets are taken off thruline 108 and passed to the lower section offluidized treater 110. Fluidizing gas fortreater 110 is supplied thruline 112 and effluent gas is passed thruline 114 toline 104 as drying gas todryer 100. Combustion gas is added thruline 116 as needed to supplement the drying gas fromline 114 in sufficient volume to provide a fluidizing flow rate and at sufiicient temperature to provide the desired drying gas temperature indryer 100. Efiiuent treated pellets fromtreater 110 are passed thruline 118 to cooler 120 for cooling to a temperature satisfactory for bagging or storing of the pellets.

Air or other gas for cooling the treated pellets is introduced to cooler 120 t-hru line 122. Off-gas fromdryer 100 may be passed thruline 124 intoline 122 to supplement the cooling gas when desired. This off-gas may also be recycled toeffluent line 126 from cooler 120 thruline 128. All or any part of the gas inline 126 may be passed toline 112 as treating gas thruline 130. A substantial portion of the treating gas inline 112 is supplied fromline 132, preferably as combustion gas or superheated steam. Cooled pellets are withdrawn from cooler 120 thruline 134.

Fluidizing vessels and the depth of the fluid beds therein are sized to give proper hold up time and to provide as well as to require compatible volumes of gases as needed in the diierent steps. Such beds are relatively deep and only a few feet in diameter. Integrated gas temperature and volume controls are used to maintain proper conditions in the beds. Volume controls are needed to produce the necessary fluidization velocities in the beds. Temperatures within the beds are principally controlled by manipulation of the inlet temperatures of the gases to each of the beds. Desired compositions of the gases used in the drying and treating beds can be achieved by recycle of off-gas from the dryer to the cooling bed. To further reduce oxygen (if desired) the air used in the cooling bed can be used as combustion air for the treater and dryer. Cyclones may be required on the gas efiiuent from each of the beds to remove small amounts of fines.

Drying in the arrangements shown in FIGURE 1 can be accomplished in the first fluidized bed at bed temperatures in the range of about 275 to 300 F. with short residence time; and drying to around 3.5 percent moisture can be elfected at about 175O F. as shown in the illustrative example above. Drying is done in the first fluidized bed preferably in the temperature range of to 300 F. Pellets are then passed to the sec-ond drying and/or treating ybed where temperature is raised to the range of about 500 to 1200 F. to complete vthe drying and to control the properties of the black. Carbon black.

5. pellets then pass to the cooling bed (FIG. 2) for cooling to the range of about 200 to 500 F. and, preferably, below 400 F. for bagging or storage.

Referring to FIGURE 3, arotary dryer 140 is provided With a wetpellet inlet line 142 and a driedpellet effluent line 144. Burners or burner means 146 below the dryer drum are supplied air and fuel gas fromline 148. These burners or burner means may be radiant burners located either outside or inside of the dryer shell. Off-gas is vented throughstack 150 or any portion thereof may be passed vialine 151 toline 160 to Supplement the drying gas inline 160. A second dryer in the form of afluidized bed dryer 152 is connected withline 144 to receive -partially dried pellets. Hot drying and fluidizing gas is supplied =by burning an air-fuel miXture in furnace 154, supplied throughfuel line 156 andair line 158. The hot combustion gas is introduced to the bottom ofdryer 152 vialine 160. Off-gas fromdryer 152 passes throughline 162 to the filter of the carbon black plant.

In the operation of the dryers of FIGURE 3, the temperature of the efiiuent gas inline 162 is sensed and a signal is emitted bytransmitter 164 to temperaturerecorder-controller 166 which manipulatesmotor valve 168 in response to the signal received so as to add more fuel upon sensing a lower temperature and cut down on the rate of fuel flow When a higher temperature is sensed than a predetermined Operating temperature. In this arrangement the flow of air in line 58 is maintained substantially constant by means ofmotor valve 170,controller 171, and flowtransmitter 172. In order to proportion the drying load between the two dryers (140 and 152), the flow rate of fuel inline 148 is also manipulated by means of temperature-recorder-controller 174 which is in control ofmotor valve 176 and receives a measurement signal fromtransmitter 178 in response to the sensed temperature of the gas inline 160. In order to protect the equipment,temperature transmitter 175 senses the shell temperature of the rotary dryer and acts throughcontroller 174 to limit fuel gas flow throughline 148 viavalve 176 to prevent exceeding the maximum set temperature for the safe operation of the dryer.

To illustrate the operation of the control system of FIGURE 3, when the drying load on the system (dryer 140 and dryer 152) changes (for example, increases) by an increase in the feed rate of wet pellets or by an increase in the initial water content of the pellets, this effect passes todryer 152 by virtue of a higher water content of the pellets inline 144 which subsequently' causes the temperature of the off-gas inline 162 to decrease, since more water enters the dryer via the pellets but the rate of heat input vialine 160 has not yet been increased.

This change in temperature inline 162 is sensed and the control system changes the heat input to both dryers. In response to this off-gas (line 162) temperature de- Grease,controller 166 increases the opening ofvalve 168, thus increasing the fuel gas flow rate, which raises the combusted gas temperature and thereby increases the heat input todryer 152 vialine 160. This increased heat input dries the pellets discharged byline 153 to a greater degree, thereby increasing the temperature of the offgas inline 162 toward its desired value (set point to controller 166). The increase in combusted gas temperature inline 160 over its previous value (which was equal toTRC 174 set point), indicating that an increase in drying load had taken place, is then used by TRC 174 (in cooperation with its set point) to increase the fuel gas flow rate to rotary drier 140 so as to transfer at least a portion of this increased drying load 'from the fluid bed dryer to the rotary dryer. This system is doubly advantageous in that (l) it brings about load sharing of two serially operated units performing the same general function and (2) the rapid changes in drying load are compensated for in the unit which canwbe manipulated more rapidly, and the slower-occurring drying load changes,

which persist for some period of time, are first corrected by the fluid bed dryer, with the increased load being transferred (gradually during a period of time) to the greater drying capacity unit (rotary dryer) thus leaving the faster correcting fluid bed unit in the middle of its drying capacity range ready to compensate for the next drying load transient condition.

When the heat load on dryer decreases because of lower feed rate of wet pellets or lower water content, the opposite adjustment is made invalves 168 and 176 by the control system. In the arrangernent shown in FIGURE 3,dryer 140 may also be a fluidized bed dryer (as illustrated in FIGURE 4) with a diiferent set of controls.

Referring to FIGURE 4, afirst dryer 180, which may be either a rotary or a fluidized bed dryer, is supplied wet pellets throughline 182 and heat for drying throughline 184 fromfurnace 186. Air at a constant rate is fed tofurnace 186 vialine 188 and -fuel gas vialine 190 under the control ofmotor valve 192. Eflluent drying gas is vented throughline 194 or passed to the filter, and efuent semi-dry pellets are passed vialine 196 to secondfluidized Ibed dryer 198. Fluidizing and heating gas is passed into the bottom ofdryer 198 through line 200 which connectsvwith furnace 202. This furnace is supplied an air-fuel mixture throughline 204 under the control ofmotor valve 206. Eflluent dry pellets are recovered throughline 208 and effluent drying gas from the second dryer passes to the filter Vialine 210.

The control system for operation of the dryer of FIG- URE 4 comprises atemperature transmitter 212 responsive to the temperature inline 210 and emitting a signal proportional to the sensed temperature toTRC 214.lnstrument 214controls valve 206 in response to the sensed temperature so as to increase the flow rate of combustible mixture tofurnace 202 when the sensed temperature is below the desired (set point) temperature of the gas inline 210 or to decrease the flow rate tofurnace 202 When the sensed temperature is above normal Operating temperature. The heat input to dryer is simultaneously controlled by an arrangement of instruments comprisingflow transmitter 216 and flowrecorder controller 218 which is in control ofmotor valve 192 so that upon an increase in flow rate inline 204, the flow rate of fuel in line is also increased to proportion the heat loads on the two dryers. The opposite adjustment is made when the temperature inline 210 is too high, indicating above-normal heat input to the dryers for the drying load imposed thereon.

To prevent the first dryer's temperature from becoming excessive, as heretofore mentioned, each pair of transmitters 175-178 and 216 and 217 in FIGURES 3 and 4 may operate through a 'low pressure selective relay included withinTRC 174 andFRC 218, to select the lower signal (temp) and pass it to its respective controller. Taylor Instrument Co., Model SK 11359 is an illustration of this type of instrument.

An alternative control system on the first dryer of FIGURE 4 is illustrated byline 220 which connectsTRC 214 directly withmotor valves 192 and 206 (eliminatingtransmitter 216 and controller 218) so that the signal fromTRC 214 simultaneously either increases or decreases the flow through the lines Iwhich these valves control to change the heat requirements of the process and simultaneously proportion the loads on the two dryers.

FIGURE 5 shows afluidized bed dryer 230 positioned directly insmoke line 232 directly downstream of one or more carbonblack reactors 234. Wet pellets are fed into the lower section ofdryer 230 throughline 236 and dry pellets are withdrawn throughline 238 from the top of thefluidized bed 240. It is also feasible to introduce the pellets throughline 242 directly intosmoke line 232 sufiiciently upstream ofdryer 230 to provide substantial transport drying of the pellets prior to their introduction todryer 230.

Temperature control of the smoke todryer 230 is effected by sensing the eflluent gas temperature lby conventional means and transmitting the sensed temperature by means oftransmitter 244 tocontroller 245 which operatesmotor valve 246 in water quenchline 248. In this manner the effluent temperature from the dryer is regulated by regulating the amount of -quench water introduced to the smoke stream.

When utilizing smoke from a carbon black reactor as drying and fluidizing gas, the temperature of the smoke is usually controlled (by Water quench) in the range of 500 to 1500 F. and preferably 800 to l500 F., but temperatures up to reactor outlet temperature may be used. The gases from the dryer which contain fines from the pellets, as well as most of the original loose black from the smoke, pass through the smoke line to the plant filters and thus eliminate the need for a separate filter for the dryer oT-gas.

Advantages of the use of smoke as the driyng gas include (l) elimination of need for fuel gas and equipment for burning same to produce hot gas, (2) smoke is completely inert (no free 02), (3) no extra filter and no extra load on regular filters of the plant, and (4) the dryer acts as an elutriator to remove fines so that product has less dust than product from a rotary dryer.

It is feasible to utilizesmoke line 232 as a transport dryer to effect substantially the entire drying process and utilizevessel 236 as a cyclone separator to remove the dried pellets. In fact, drying of any wet particulate solids may be etfected wholly by transport drying followed by separation of the dried particles from the hot transport gas in a cyclone separator, bag filter, or other suitable separation means.

In the drying of particulate coal (being transported in a slurry) before feeding same to a furnace, stack gas from the furnace can be utilized etfectively as the drying gas in accordance with this invention. Transport drying is effective in this application.

Certain modifications of the inventon Will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

I claim:

1. A process for drying wet pellets compacted from carbon black which comprises the steps of:

(1) entraining said pellets in a stream of hot drying gas comprising essentially smoke from the carbon black reactor wherein the carbon black was produced, water-quenched to a temperature in the range of 500 to 1000 F. to form a suspension of said pellets in said gas;

(2) passing the suspension 4of step (1) through an elongated transport drying zone of substantial length to dry same substantially;

(3) passing said pellets from the zone of step (2) upwardly into a fluidized bed dryer of expanded lateral dimension relative to the zone of step (2), said gas being the fluidizing gas;

(4) maintaining said pellets in fluidized condition in the dryer of step (3) so as to further dry said pellets to a relatively low moisture content; and

(5) separately withdrawing gas and dried pellets from the dryer of step (3).

Cl o 2. The process ofclaim 1 wherein a selected Withdrawn gas temperature from step (5) to effect drying' to a moisture content of not more than 3.5 weight percent is maintained by controlling the flow rate of said drying gas and by sensing the temperature of said withdrawn gas, injecting aqueous quenching fluid into said smoke as it flows directly from said reactor, and controlling the fiow rate of said quenching fluid in response to the sensed temperature to maintain said selected withdrawn gas temperature.

3. Apparatus for forming and drying wet carb-on black pellets comprising in combination (a) a carbon black reactor having an efiluent hot smoke line; (b) an upright fluidized bed dryer having an unobstructed drying zone, an inlet in its lower section, a gas outlet in its upper section, and a pellet outlet from an intermediate section; (c) an elongated transport and dryer conduit of substantial length connected at its downstream end to the inlet of (b) for substantially drying said pellets therein; (d) pellet inlet means connected to the upstream end of the conduit of (c); and (e) a line connecting the smoke line of (a) with the upstream end of the conduit of (c) for supplying smoke as a drying, transport, and fluidizing gas to said conduit. 4. The apparatus of claim 3 including a pellet cooler connected by conduit means with the pellet outlet of (b).

5. The apparatus of claim 3 including carbon black recovery means connected with the gas outlet of (b), a wet pelletizer connected by conduit With said recovery means, and a transport line for wet pellets connecting said pelletizer with an upstream section of the conduit of (c).

6. The apparatus of claim 5 including (f) a quench line connected with the hot smoke line of (a) having a motor valve therein;

( g) means for sensing the temperature of the gas from the gas outlet of (fb) and emitting a signal proportional to the sensed temperature;

(h) and a temperature controller connected to receive the emitted signal of (g) and operate the motor valve of (f) to control said outlet gas temperature.

References Cted by the Examiner UNITED srATi-:s PATENTS 2,55o,374 4/1951 Palmer 34-57 X 2,s43,942 7/1958 whitsei 34-47 x 2,s5o,sos 9/1958 Jones ei a1. 34 57 3,028,68l 4/1962 Jorman et al. 34-57 FOREIGN PATENTS 624,375 7/1961 canada.

DONLEY J. STOCKING, Primary Examiner.

FREDERICK L. MATTESON, JR., Examiner.

D. A. T AMBURRO, Assistant Examner.

Claims (1)

1. A PROCESS FOR DRYING WET PELLETS COMPACTED FROM CARBON BLACK WHICH COMPRISES THE STEPS OF: (1) ENTRAINING SAID PELLETS IN A STREAM OF HOT DRYING GAS COMPRISING ESSENTIALLY SMOKE FROM THE CARBON BLACK REACTOR WHEREIN THE CARBON BLACK WAS PRODUCED, WATER-QUENCHED TO A TEMPERATURE IN THE RANGE OF 500 TO 100*F. TO FORM A SUSPENSION OF SAID PELLETS IN SAID GAS; (2) PASSING THE SUSPENSION OF STEP (1) THROUGH AN ELONGATED TRANSPORT DRYING ZONE OF SUBSTANTIAL LENGTH TO DRY SAME SUBSTANTIALLY; (3) PASSING SAID PELLETS FROM THE ZONE OF STEP (2) UPWARDLY INTO A FLUIDIZED BED DRYER OF EXPANDED LATERAL DIMENSION RELATIVE TO THE ZONE OF STEP (2), SAID GAS BEING THE FLUIDIZING GAS; (4) MAINTAINING SAID PELLETS IN FLUIDIZED CONDITION IN THE DRYER OF STEP (3) SO AS TO FURTHER DRY SAID PELLETS TO A RELATIVELY LOW MOISTURE CONTENT; AND (5) SEPARATELY WITHDRAWING GAS AND DRIED PELLETS FROM THE DRYER OF STEP (3).

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