Removal of' Inert Material from Bone Char JAMES
hl. 1).
h o W K A N D WATSON
A.
FIQURE 2. FEEDCONTROL, DUSTCOLLECTOR. AND D i s c ~ ~ x c e
~EwIs
Revere Sugar Refinery, Charlestown, Mass.
I
N THE caue sugar refining industry of the United States the amount of bone cliar in active circulation in the refineries is probably in excess of 50,OfK)t(1ii.i. In addition there is a tremendous aniount in constant use in tlic corn products and kindred industries; rnialler quantities are employed in the refining of petrolatnms, the filtration of imaffin, and the Iliaking of niedic.in:il nliite oils. i t s t l i i s product is generally the only decolorizing agent used, it is importallt that it be kept at its mxirnulri degree of efficiency hot11 in asli and color adsorption ability. It ii. rather strange, in so far as tlic sugar industry is concerned, that lit.& practical research uii this problem has been done. This is probably due to the fact that tlie ninjority of tlie refineries have an excess of boric char over tlreir actual requirements and because it is difficult to int.erpret the cornplex reactions of bone char in ternis uf refinery practice. Impurities having no adrorptivc ndne collect in the bone char system continually; the usual nietliod of screening or air separation removes only the dust and smaller particles which Irave a high adsorption value bot are likely to hinder filtration, and leaves behind the useless imrt material such as iron scale from the char containers, hard poreless portions of bone having little or no adsorptive value, axid pieces of glass, concrete, sand, sinal1 gravel, small pieces of tramp iron, and other di.bris. All of these for some unaccountable reason appear to gravitate to the bone owing to the practice of reniovirig only the smaller particlcs by screening, accniriulate over a period of years to a sisahle portion of tlie total volume of bone char in service. BONE CIiAR SEPARATOR
Magnetic pulleys have soinetirnes been used to remove tramp iron: but the authors have found that this is only a
niirior portion of tlie undesirable inaterial present in service char. This o ~ ~ i p a has i ~ yinstalled and is operating as part OS its bone char equipment a specific gravity char separator designed and built by Sutton, Steele alii1 Steele, Inc., of Ualla., Texas. With tlie aid of this apparatus material can be reniosed froin tlie bone cliar tein \vhich is of absolntely llo value tl, prescllce of wiiich is a continual and appreciable itciri of expense owing to waste of l)o.irer and circu,sting, Ill tl,e scl)arai~,r a grassliopper conveyor plus an adjustable screened deck through wllicli po,~,erful currellt of air ~ 1 deck , ~ consists of a perForated plate tliroirgh wliich air is blown a t the rate of lTOO tu 3100 cubic feet per minute, the rate being ileter.iiiImll by tl,e type of cl,ar to be cleaned, I,eck baBes diout one inch apart run practically tlie entire length of-the deck. The deck moves ahont inch longituilinally four a ririIil~te, rate is variable between :%30 and 400 vibrations per niinute.) The sidewise and endwise slopes of the are variable, The bo,le char is fed onto tlie deck and tlic dust i s collected at the receiving end tllrough a dlist fan, and lighter of bone are raised by current of air liigl, el,ougl, to drift over baBes and tlie particles, iiidependent of size, move toward the far end aiid are tllere as discitrci, ~h~ good l)ol,e c.,ar is diScharged over the side of tho apparatus and returns to the system. Operation of tile apparatus requires no labor after the machine has been adjusted for whatever bone cllar it is desired to clean, Tlie rnte of removal of discard bone and tl,e weigllt per unit volume are determined by the volume of air, rate of feed, degree of end and side slopes, and quantity of heavy particles contained in the entering bone char. The quantity of dust collected is determined by the fineness desired. The amount of air nsed to convey this material is regulated h y a
918
I N D U S T R 1 A I, A Y D E N G IN E I?. I< I N G C H E M I S T R Y
S'~,,tlrnbrr 1931
sliding ilaiiijrer. A &liorsepower motor is required to operate ttia entire nnit,. Iione chars of varying densities and degrees tif activity may be obtained at will by varying the lateral or longitudinal tilt of the table and hy varying tlie air flow through the perforated deck. The fineness of the dust removed may be controlled and varied by raising or loneriiig the dust hood and by varying, with tlie damper, tlie voliime of air smked into the dust-collecting system. T . ~ EI.
' r Y m . ~ r . :\vtm.m
AX.ALISW i\CTlihL OrERATroX
O W ~ . U X ~ V ~,WOM
919
arc inactive; tlierefore R screeniiig separator is iiot depend-
:&le. These discard. particles arc extremely liard and therefore (lo not wear down RS do the usual particles of bone char and so do not become fine enough to he screened out. On the contrary, be.cause of their Iiardness and abrasive action, they cause the active particles to wear down more rapidly than \i.ould he the case if they had not been allowed to aceinnulate. This material, in occupying space in tlie char filters that might be replaced by active bone char, cuts down the efficieney of the hone char system. The liigh content of bone phosphate indicates tliat the discard particles are composed mostly of dense, poreless, iniictive hone fragments accomulated over a period of years. Tests have sliown that this material has a high degrce of reUnder present operating conditions Che discard aniounts one ton of material having color and as11 adsorption d u o s of 10 and 5 per cent, respectively, and onehalf ton of line dust per 24 honrs. A feed of 7000 p o i i n d s per hour has been experinientally used on this machine and a satisfactory separation obtained, Iiut a feed of 3OOO pounds per hour with a discard rate of t h e e per cent and a dust reinoval of 1 per cent gives a eonsist,ent maximum weight ger cubic foot with low adsorption ralues for the discard material. Tlie discard is controlled by k e e p i n g the weiglit between 86 t,o about
O n 10
on
14
On 20 o n 28
o n :a5 O n 48
Tiwoimh 4h
iuo.0
100.0
oniaiNni. ssn-
H u n No. 1 Weight. lb./e?. it. 58 COlOi naaorgt,n,,. ?ih !)I Aair ndaointimi, % Direnrd.%oifead d l Lh. />or hnnr ieed 3:WV
8 :7
78 71 4.!1
I800
1
77 19 17
6.U
1200
7 80 17
it.:' ?200
81
17 12 :i.O lLU0
B
q
9
x:i
87
88 12 7
16 I2
:37 ?lUO
1'3 3
4 0 :iUCNl
4:i :3W0
12-\ 90 8 5 I ? lXKI
w c i l TlONr. Crux
56 !I4 :44
.. ..
D~~~ neI10ViiD
40 1. u ''
IFigures 1 to 4 s h o w tlie table in operation. Figure 1 is taken from above and sliows tlie dust liood in tlie upper center; tile feeder is under the riglit-hand end of tlie dust liood. Tlie volume of tlie o\-crR o w is d i s t i n c t l y &mil as the bone c h a r Hmvs into the liopper on the left-liaiid side of tlie m a c l ~ i r r e . T h e disc a r d trongli is over tlie receiving bag shoirn at the lower riglit. Taiile IIgives the results of test runs aivina . discard char at v a r y i n g w e i g h t s per unit volurne. Figure 5 sliom the average color a.nd ash ailsorption values of ilifEercnt portions of service cliar at varying weights per cubic foot as obtained by the use of the bone char separator. It has been demonstrated that particle size is not necessarily a nieasure of tlie quality of bone c h a r , altliougli the discard consists mostly of the larger particles as shown by the scrcen tests; it is equally true ihat not all large prticles
ciibic foot. Bone char of this density has adsorption values of approximately 10 per cent color and 5 per cent a s h a d -
scrptitiii. Tlie above d i s c a r d r a t e s were o b t a i n e d on a service char wliicli has been in use over a period of years. The bone lilack replacement under ordinary operating c o n d i t i o n s should amount Lo less tiiaii 0.5 per cent of the boiie char revivified. The ash and color rernoval values are determined by heati n g t o g e t h e r in a flak submerged in awater bath at 170" I:. a weight of char equivalent to the solid content of a sugar s o l u t i o n of 47.5" Brix for 4 Iiours. Tlie flasks are shaken at oach half-hour period with a rotaryinotiou. Tlie results are compared witti a bone char Iiaving a definite, liigli-adsorption value wiiicli is r e g a r d e d as s t a n d a r d by this laboratory. (All a d s o r p t i p n values are c,alciilatedby using the results o b t a i n e d on tlic s t a n d a r d laboratory cliar and laboratory sugar solution under the usual routine adsorption procedure in use in this laboratory.)
920
t N D U S T 11 I A 1, A N D E N G I N E E 11 I N G C H E M I S T R Y A sniall quaiitity of inert bone particles is present in new char and may he s e p a r a t e d with this machine before the c h a r is p u t in service or renroved in the routine m a n n e r f r o m the s e r v i c e char after the addition of the new hone c h a r t o the service cliar. A sufficient number of tests on this phase of tho question to supply evid e n c c convincing enoueli to determine whicgmethod is the 11,oj-e economical have not yet been made.
Vol. 26, No. 9
FIGURE 5. AVERAGECOLORAND ASH ADSORPTIONIN RELATION TO WEIGHT PER CUBICFOOT
ADVANTAGES OF INSTALLATION
FIGURE 4. NAKEDTOP DECKOF A P P A R A T U ~
The following advantages, which tend to increase the efficiency of the bone char system, may be attributed to the use of this installation: removal of useless debris from bone char; removal of inert bone char and its replacement with new active bone char; increase in active area per bone char filter: savinlr in heat and power: inhibition of attrition of Of dust. active particles; and this machine bone char may be graded into Or from various service chars in the bone char system, or, as mentioned, a definitely determined portion may be continuously from One char to another without loss Of time Or bone I
The separator has run with practically no attention (except changing the bags as filled), and the results obtained have ~ 1 deck , ~is swept clean daily as a prebeen hone char slivers whit], havc * cautionaFy measure tendency to embed themselves in the openings of the screen and should be brushed out before they become too firmly embedded. The performance of the apparatus has been so consistent that it is possible to take off any portion of bone char with the deflectors and obtain comparable figures for density and weight over the full weekly period of operation of the a p paratus and also to transfer char from primary to secondary service char in this manner, using a slow constant rate and thus insuring even distribution of the transferred portion.
service
ACKNOWLED~MENT The authors are deeply grateful to Sutton, Steele and Steele, Inc., and to Ashley L. Sheppard of that company for the time and effort they have expended in helping to work out details and problems connected with the adaptation of this unit to the requirements of the bone char system. RWBIVD ~ u n e 11.1834.
MEXICANSUGAR INDUSTRY IN STRONG POSITION The Strict eontroi exercised by the Sugar Producers Amoeiation of Mexico in connection with production and sale of sugar in t.hat country has plil~edthe local sugar industry in the most iavorabio position it has knom for years, according to a report to the Commerce Department from Assistant Commercial Attach6 Glover, Mexico City. The association was organized in 1932 following the crisis in the Mexican sugar industry whioh began in 1930, in which year production ivns in excess of consumption, selling pricee below production costs, arid sugar producers unable to obtain finances. Since the associbtion was organized st tho i tnnce of tho Mexican Government, it has had complete supervi on over sales. Last year, it, exported surplus sugsr to t,he amount of 100,000t.ons, after wbicli it, managed to st,rhilise prices on the home market. The assmintion also orgmiaed a irurik t,o advance money to grow01s. This greatly relieved the financial crisis existing in the sugar industry. Mcxico's norrml coiisumptian of sugw amounts to approximateiy 200,000 tons annually, but, nov thit conditions are good
in all txctions of the country, coiisumption will probably be
inoreased. The s u e r association has recently taken steps to incrwse domestic consumption by means of a well-planned educat,iorral campaign throughout the country, a movement which undoubtedly will meet with at least a fair degree of success in view of the favorable economic situation at present prevailing there.
&,;because
of early grinding during tho latter pa& oi the year. Mexioo is a high-cost sugar-producing country, and for that reason it is essential for tho welfare of the sugar industry to regulnte eonsumption t o meet the domestic demand, ss it is impossible for Mexican ~ u m rsuuccossfuliv to comoete in world
markets.
