BRASS AND COPPE
II'UDUST
Cation Exchangers for Metals Concentration from Pickle Rinse Waters F. X. Mc-GARVEY and R. E. TENHOORI, Rohm and H a a s Co., PhiCdeEphia, Pa. R. P. NEVERS, American Brass Co., Waterburg, Conn. T h e concentration and recovery of alloy metals from the dilute pickle rinse solutions encountered in the copper and brass industries has presented a problem for many years which has not been solved by the conventional precipitation and coagulation procedures. Recent stiidies on typical mill rinses have shown that cation exchangers operating in the sodium or hydrogen cycle might be em-
ployed successfully to concentrate copper, zinc, and chromium solutions. The economics of the exchange in the hydrogen cycle indicate that profitable recovery of copper might be accomplished in conjunction with an electrolytic deposition process in the copper pickle itself. Flow rate and influent concentration have a marked effect on the economics.
T
t o clean the metal surface of oxides and other impurities. Sometimes a subsequent sodium dichromate dip is also employed. Following the dipping operation the material is washed free of acid. These running rinse waters vary appreciably in acid and metals content depending on the shape of part, flow rate, method of rinse, age of pickle liquor, and metals to acid ratio of the pickle liquor. This latter factor is dependent on a multiplicity of variables such as prior amount of scale on the metal, strength of acid, area of metal part, and alloy characteristics. It was apparent that establishment of the nature of both the pickle liquor and the wash waters over a representative operating period was essential t o the proper evaluation of a treatment method. In 1948 Bliss ( 4 ) reported an extensive survey of the chararteristics of these wastes in a typical brass plant in the Connecticut Valley. These data are summarized in Table I. Bliss found that on an annual average, 90% of the total metals and 88.5y0 of the acid go to the mill drain in the form of dilute wash waters. The remaining metal and acid constituents are
HE recovery of copper, zinc, and chromium from the copper and brass trade wastes has long been of interest to the industry not only from the pollution abatement standpoint, but also as a copper conservation and cost-saving measure. Various approaches to this problem have been investigated over a period of years by the Yale University chemical engineering group and have been reported by Dodge ( 7 ) , Bliss ( 3 4 ) ,Galloup ( 8 ) , Hilbert ( 9 ) , and others (a). Although the use of zeolites, permutit, and other ion exchange materials was considered for many years ( 1 6 ) as a possible copper recovery method, Beaton and Furnas (1) and Bliss of the Yale University group were the first to do extensive work towards a practical solutioil of this problem. Beaton and Furnas undertook to develop the use of exchangers using simulated pickle rinse solutions and the exchangers available a t that time. The advent of the synthetic exchangers of increased capacity and durability made the ion exchange possipilities as outlined by Beaton and Furnas look applicable, and further studies were conducted by Bliss ( 6 ) and Selke ( I S ) using Table I.
Wash waters Tube mill Rod a n d wire mill Rolling mill Spent acid pickle Tube Rod a n d wire Rolling Bichromate pickle Tube Rod a n d wire Rolling
Pickling and Wash Water Wastes of Typical Brass Company in Connecticut (1940)
Yearly Volume, Gal.
Estd. Av. Flow R a t e / T a n k , Grams
166,000,000 7,660,000 137,000,000
40 3 136
Av. Concentrationsa,____P.P.hI.
HnSOI 86 1390 590
94.4
118, SOOH 3,300 1, 000c
Cu
74 888 34
Zn
' 40 1463 53
A v . Concn., Grams/Liter 9.8
11.6
Cr
23 690 27 0.18
No samples; assumed same as ahox-e 84.9 50.7 10.3
13 ,ZOOc 3,600: 101,000
13.1 27.4 12.15
10.3 36.8 0.5
20.R 43 4 20.5
HnSOi
Yearly Discharge, Lb.b c11 Zn
Cr
115,000 91,100 692,000
98,600 58,000 39,900
53,400 96,000 62,200
30,700 45,100 31,700
93,400
3,500 800
9,700 360 80
11,600 460 100
150 Pienliaible Segligihle
9.300 1,520 6,700 1,015,320
1,440 620 10,200 219,100
1.340 1,100 420 226,620
2,260 1,300 17,300 128,540
a Iron also present a n d analyzed for but not shown here. b
Density corrections are included in computing these figures. Rased on volumes of tanks and frequency of rejection.
actual mill waste solutions. To establish fully the design characteristics of an operating ion exchange plant, data based on actual copper and brass wastes mere necesqary, and this joint study was undertaken for that purpose.
Waste Characteristics Following annealing of copper and brass wire, tubes, rods, sheet, or fabricated goods, a 10 to 15% sulfuric acid dip is required f
Present address, Dow Chemical Co., Midland, illich.
534
discharged on periodic cleaning of the pickle tanks piior to replenishing with fresh acid. Chcmical precipitation processes for reducing the metals and acid content of the concentrated spent pickle liquor were available. Hoi\evw. these techniques would be cxpensive and mould require considerable space and capital, and no metal recovery viould be accomplished without considerable additional investment. The distinct advantages of ion exchange over neutralization, coagulation, and precipitation for metals recovery and concentration rests in low initial invest-
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 3
-Liquid ment cost, low floor area requirement, and in some cases, reduced chemical expenditures.
Prior Fandamental Data A fundamental study of the ion exchange recovery of copper from copper sulfate solutions was conducted by Beaton and Furnas ( 1 ) in 1941. As indicated, this study utilized pure salt solutions rather than actual wastes. Using a copper sulfate solution approximately 0.16 gram of C u + + per liter (160 p.p.m.), a capacity of 0.1 gram of per dry gram of a sulfonic acid type cation exchanger was reported. Regeneration with 4 N sulfuric acid (20%) achieved a maximum concentration to 650 me. of a++ per liter (20,800 p.p.m. or 2.08%), a 128-fold concentration. Recycling a selected fraction of copper-enriched waste regenerant (4.8% sulfuric acid and 3.1% copper) following a subsequent exhaustion of the same bed achieved build-up to 3.85% copper at peak regenerant concentration or a 221-fold concentration from original solution. The subsequent work indicates that these are optimum concentrates for conventional ion exchange techniques. Bliss in a private communication (6) indicated that Beaton, continuing his *work with Amberlite IR-1, an early synthetic exchanger, was able to pick up about 60% of the copper adsorbed on 12.5 grams of dry resin in the first 25% of regenerant after void displacement. The original regenerant was 20% sulfuric acid enriched with 4.5% copper, and the end product contained 8% copper, These concentrations were considered suitable for recovery by electrodeposition. Computations by Beaton and Furnas showed that under ideal conditions for ion exchange treatment, as previously described, the expenditure of 1 pound of sulfuric acid would give a concentration effect equal to the evaporation of about 4200 pounds of water. Bliss (6) expanded this early work to the sodium and calcium cycles with development emphasis on engineering and design phases, using solutions approaching in composition those found in raw mill wastes. Selke and Bliss ( 1 3 )extended the study using * high capacity cation exchange resins and developed the theoretical aspects of the exchange.
a++
Industrial Wastes-
The reactions proceed according to the rules of chemical equivalency. When the acid is used as regenerant, the effluent will contain the acid from the influent plus an additional amount equivalent to the concentration of copper, zinc, and other divalent metals in the influent. No provision is made to neutralize this acid in the process as shown. Neutralization by lime or some other convenient method may be necessary where close limits on acidity are desired. The resin regeneration step is essentially the reverse of Equa tion 1. The direction of the reaction is changed by using concentrated and excess regenerant chemicals.
R (Zn) (Ca)
+
or NaCl
--+ R
(H)
(Ka)
+
(CU ++) (,%++)in excess (2) ( Ca + +) regeneran t
The net effect of these reactions is the expenditure of an amount of regenerant equivalent to the amount of zinc, calcium, and other ions removed by the exchanger bed. Actually a portion of the sulfuric acid will be recovered in the electrolytic step where the electrode reactions are as follows:
Acid used to regenerate other divalent ions must be considered as loss unless these substances can be recovered electrolytically. In general, the amount of acid used by this step will be slight compared to the total amount of acid lost in the rinse effluent. Exact balances on acid usage are extremely hard to obtain and must await plant size evaluation. AC/D MAME-UP
STORAGE ELECTROLYTIC RECOVERY COPPER
.RINSE
WATER SUPPLY
Waterbury Projeot In view of the encouraging preliminary work on laboratory solutions a project was undertaken to: 1. Evaluate the practical value of ion exchange as a recovery and concentration operation on actual rinse waters under plant operating conditions 2. Determine thereby the most favorable design and plant layout for the operating units 3. Ascertain a practical method for reclaiming copper, the most valuable constituent from a volume times unit price standpoint
Emphasis was placed on hydrogen cycle operation since sulfuric acid for pickle liquor make-up could be used, thereby reducing regenerant chemical costs. Preliminary small column work had indicated the likelihood of more complete removal of trivalent chromium and increased regeneration efficiency in sodium cycle operation, so this phase was included. The use of spent acid regenerant as pickle make-up requires the development of an efficient electrolytic procedure for removing copper from the pickle acid bath. Such electrolytic methods have been studied successfully on a commercial scale. Figure 1 describes a schematic picture of the procedure under consideration. During the exhaustion step, the rinse water from the pickling process is passed through the exchanger bed where Reaction 1 will occur; R refers to the resin network.
March 1952
2
DRAIN
Figure 1. Schematic Drawing of System Employing Ion Exchange for Concentration of Copper i n Acid Pickle Rinse Water
The acid to be used as regenerant and as pickle acid make-up passes through the exchanger bed before entering the pickle tank. Recirculation piping for acid is provided to give flexibility during operation. As the acid in the pickle tank is depleted owing to rinse losses, make-up acid is added to the system after passing from the acid storage tank through the ion exchange bed. If the amount of make-up acid should be less than that required to regenerate the bed, only the copper-rich initial portion of the acid would be directed to the pickle tank, whereas the latter portion would be returned to the storage tank for future regeneration and make-up. Rough estimates on the acid requirements indicate that the amounts required for pickle make-up and for regenerant are about equal. A review of Bliss' work (3, 4 ) and plant observation made clear the need for a critical examination of the nature of each individual wash water since, in the plants under study, both concentrated pickle liquor and rinse waters are discharged into a common
INDUSTRIAL AND ENGINEERING CHEMISTRY
535
Liquid Industrial Wastes several rinse units whcrcas the samples used in this study were obtained as grab samples from individual units, P a r t s per Million (Estimated average Exhaustion cycle data selected as most indicative are listed in Calcium flow rate per t a n k = 20 gal./min.) (as CaCOa), Table IV and regeneration characteristics in Table V. Copper Sample H2SObQ Copper Zinc Nickel pH P.P.hI. rinse studies were conducted in the hydrogen cycle only and the 73.7 1.5 0.6 2 0 56 -4-1 624 A-2 58.9 13.0 1.0 0.5 2.7 56 most representative run is outlined in Figures 2 and 3. The 6-3 46.6 39.9 0.8 0.7 3.0 56 0.7 3.7 56 maximum concentration of copper in regenerant was 1.27, A-4 12.3 18.6 1.2 A-5 264.0 41.9 13 O b 0.6 2.4 56 achieved in the first 25% of a 50-pound 66” BE. sulfuric acid per A-6 135.0 24.9 1.0 0.5 2.7 56 Average 190 35 3.1 0.6 , . 56 cubic foot regenerant level employing 20% acid. a Titration to methyl orange end-point. The brass rinse studies where chromium was h Includes 10 p . p . n i . Zn added. present employed both the hydrogen and sodium cycles, and representative hydrogen cycle runs Table 111. Brass &Till Rinse Waters are outlined in Figures 4 t o 7. The Eodium cycle Parts per Million (Measured flow rate range = Hardness runs were similar to the hydrogen cycle in reduced 57 to 75 ’gal./min.) (as CaCOa), Cr+h, Sample HtSOP Copper Zinc Nickel Cr+3 pH P.P.M. P.P.i\I. acidity in the effluent. These runs are sum4.4 w-1 8.3 0.3 56 613 0 2 1 inarized in Figure 8. A marked reduction in 4.8 8.4 w-2 0.3 608 0 2 15 56 capacity for copper and zinc was found and can w-3 4.8 6.6 0.5 56 778 0 9 205 w-4 4.3 0.5 56 2.6 618 0 9 2 1 be accounted for entirely by a high calciumw--5 4 . 5 5 . 9 684 0.5 0 9 2 1 56 17,8b 8.9C W-6 73 0.1 20 4 d 3 0 56 1 8 magnesium to total divalent cation ratio and to w-7 18.7b 10.7C 154 0.0 21 9 d 2 6 56 0 4 66 0 3 a smaller degree to calcium sulfate precipitation. 8.5 0.3 7.4 Average 503 6 4 The fairly high 20% acid concentration might T o methyl oranqe end-point b Includes 15 p.p:m. Cu a d d e i . also be expected to have an effect on precipitation Includes 10 p.p.m. Zn added. tendency. In both the copper a n d brass hydrogen d Includes 15 p.p.m. Cr + 8 added. cycle, the peak concentration of copper appears to be a linear function of the regenerant acid concentration. The fraction of the column in the copper form is also an important factor and is summarized drain. The pickling units studied TveIe: biass sheet, Goodman in Figure 9. The lower percentage of the bed in the copper form pull-through continuous type nith splay rinse; and copper accounts for the lower copper concentration effect than was wire, batch type with running rinse. These were selected as achieved in initial regeneration cycles by Beaton and Furnas ( 1 ) . representative of newer type equipment. This was believed t o The sodium cycle brass rinse studies are characterized by be important particularly where plant rehabilitation programs efficient regeneration and somewhat higher capacities than those are underway. “Grab” samples of the respective rinses were obtained by acid cycle operation. In these runs the chromium obtained a t intervals over a representative operating period and contents of the influents were increased by addition of Cr+3 analyses are listed in Tables I1 and 111. Flow rates and volume ions to the solutions; approximately 90% removal of this cation were metered and included in the tables. was noted. In both hydrogen and sodiuni cycles 100% removal A considerable variation in composition is shown betn een the of Cu + + and Zn + + was achieved prior to break-through. data reported in Table I and the more recent values in Tables I1 and 111. These differences may be accounted for by recent IDiscnssion of Data improvements in the annealing techniques employed in modern brass and copper mills and by different rinse practices in the These data ale only sufficient t o establish operating conditions various mills. Bliss used a composite sampling technique from over a limited range; however, it is possible to extend these Table 11. Analysis of Copper Rinse Waters
Y
INFLUENT
COMPOSITION: C o P P r R ( p p m as c u ) - ? 3 . 7
REGENERANT C O N C E N T R A T I O N : 2 0 % h/,so+ REOENERATION L E V E L :501bs 66*Be‘HzS0,1fi’ REGENERANT VOLUME: 26.5 GallonslfZ’
as CoC03)-56 SULFURIC Acro(ppm as H,S0,)-62+
HARONESS(pPm
R E G E N E R A T I O LNE V E L :soh$HzSO+lft3 EXHAUSTION
1.2
F L O W4: Gals.Jfts~rn~o.
I 4
Capacrfy
A6
l.8
2.0
f o r Copper, Ibs,CulCt’
Figure 2. Effluent Characteristics of Typical Copper Mill Pickle Rinse Water Treated w i t h Amberlite IR-120
536
Regenerant Volume,% of Total
Figure 3. Regeneration History of Amberlite IR-120 Bed Exhausted w-ith Copper MiW Pickle Rinse
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 3
LZquid Industrial Wastes
INFLUENT COMPOSITION C O P P E R ( p p m as c U ) - 4 . 5
&so+
R E G E N E R A N T CONCENTRAtlON t20X R E G E N ERATION L €VEL : 5 0 Ibr 6 6 . 6 ~ ' H,SO+lf+"
Z I N C (ppm a3 Z I N C ) .5.9 HARONESS(PF a s Coco3)- 56.0
R E G E N E R A N T VOLUME:
27.2 Galslf+'
SULFURIC A C l D ( p p m U S Y S 0 9 ) - 6 8 4
REGPNERATIOH L E V E L , 5 0 1 b s 66'6e'lfS' E X H A U S t l a N FLOW :9.0 G a l ~ / f 4 ~ l r n i n
1
OBI
0.2
0 . 3
Capacity f a r Alloy M e t a l s , lbs Cu/ft3
Roqenerant Volume, YOo f T o t a l
Figure 4. Effluent Characteristics of Typical Brass Mill Pickle Rinse Water Treated w i t h Amberlite IR-120
Figure 5. Regeneration History of Amberlite IR-120 Bed Exhausted w i t h Brass Mill Pickle Rinse Water
studies on the basis of data available from the literature. Since the condition of the column during the exhaustion step may be visualized as a series of successive zones depending on the affinities of the various ions, the effect of any ion on the capacity for another ion may be estimated depending on the relative affinity of one ion for another. In the case a t hand the influent ions may be expected to arrange in the following descending order on the bed: (31-13, Cu, Zn, Ca, Mg, Na, H. Since very little difference exists between the chromium, copper, and zinc ions, break-through for these ions is almost simultaneous. However, sufficient difference exists between the copper-zinc zone and the calcium-magnesium zone so that even when the bed is broken for calcium and magnesium, capacity for zinc and copper would still be available. In order to check this effect, the capacity for metals as a function of hardness to total divalent cation ratio has been plotted in Figure 8. The effect of calcium sulfate precipitation on the capacity is probably the explanation of the
lower capacities in hydrogen cycle studies. The effect of flow rate on the copper-zinc-calcium exchange has not been evaluated critically, but on the basis of this and related studies it is likely that 8 gallons per cubic foot per minute is approaching the limit for good operation with optimum probably a t 2 gallons per cubic foot per minute. In several exhaustion runs it was noted t h a t zinc breaks first and a slight enrichment of the effluent occurs, but even a t lower flow rates, no practical fractionation is obtained. It appears that the possibility of selective concentration of copper on the bed cannot be realized with the system under investigation. During the regeneration, the peak concentration obtained is a function of the regenerant strength and also the amount of the component on the bed. In Figure 9 the peak concentration has been plotted as a function of the percentage of copper on the bed -Le., the amount of the capacity in the copper form. The increased effectiveness of the sodium regeneration is shown in the
Table IV.
Exhaustion Cycle Characteristics
(Based on second operational cycle d a t a ; end-point when Cu leakage in efduent = 5 % of influent concentration or 2 p.p.m. Cu, whichever is smaller) Ca acity HzSO? Hardness Kg. (CaC!O)~s)/dd. Sulfuric Copper x 100 Zinc x 100 (as CaCOs), Hardness x l o o Flow, Gal./ Heavy Run Source Regeneration Level (a5P.P.M.) (BM++)% ( B M + + )% P.P.M. (ZM++) % Cu. Ft./Min. nietal Total M + +
5
ZIGa 6-Na, 7-Na
%~~~~
Brass Brass
50 Ib. NaCl/cu. f t . of resin
' '4j.5
137.5 157
18.0
Table V. Run 1-H 2-H 3-H 4-H 5-NE 6-Na 7-Na
Regenerant 20% &SO4
20% NaCl
Regeneration Level Lb./Cu. F t . of Resid 50 lb. 66' BB. HzSOa 50 lb. NaCl
Regeneration Cycle Characteristics Peak Concentration cu Zn 1.2 0.65 0.15 0.22 0:io 1.23 0.20 0.90 0.50 0 53 0.33
.. ..
Av. Concentration, % Composition on Bed, % cu Zn cu Zn 0.46 67 0.28 0.06 0.11 0.34 0.28 0.17
..
*.
0: 20
0.06 0.12 0.12
33
lo 9 46
35 18
.. ..
13 12 12 14.8 10
-
Metal Recovered, % cu Zn 99 84 100 lloa 119a 102" 104"
.. .. 1Os' 72.5 134 61
a Estimated variation from 100% within experimental error
March 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY
537
Liquid lrPcdustsiarrC Vl‘astes
1‘0
LNFLUENT COHPO5lllON COPPERfppm aS c u ) - / ? ’ e ~ t ~ c ( p pas m z ~ ) - B , s C H R O M I U M (ppm
019
as C r j - 2 0 4
TOTAL H A R D N E S S ( P p 7 asCac0, - 5 6 SULFURIC A C I D fppm as I&SO,]- 7 5
1.4
h6
REGENERANT CONCENTRATION-.?^% H,SO+ REGENERANTL E V E L5016s 66’Be H2S0,1ft3 R E G E N E R A N T VOLUME
< I, 2
I
1. 8
C apacrfy f o r Alloy Metuls(lbs. Cu/f+’)
I
I
25
50
Reqenerant
2 6 8 GolsJff3
75
Volume & o f Tofa
Figure 6. Effluent Characteristics of Typical Brass Mill Pickle Rinse Water (with Chromium) Treated with Amberlite IR-120
Figure 7. Regeneration History of Amberlite IK-120 Bed Exhausted with Brass Mill Pickle Rinse Water (with Chromium)
approsiniate 30yodifference in strength between the sodium and hydrogen regenerant curves. These peak concentration zones are always found in the first 20y0of the regenerant. These data may be applied to calculations involving the fractionation of regenerant for selective recovery, but it is unlikely that such a technique caii be applied to this problem. rUthough 11 o significant correlation between hydrogen ion content aiid capacity was found between the pH range of this study (2.0 t o : 3 , i ) , l’ii.ot and Carlson ( l a ) shon-ed that xith Anibeilile
IR-1 the capacity for copper increased twentyfold when the 1’1 i of the influent solution was increased from 1.1 to 5.3. Srlson and Walton ( 1 1 ) found a sharp increase in the capacity of ii suifonated coal exchanger for copper, zinc, and nickel when thi: 111-I was increased from about 2.7 t,o about 11.5; this may lie ilue t o metal precipitation atbove pH 5.0. For practical application of ion exchange techniques 011 picliling rinse water a niinirnum p I I of 1.95 is estimated. These runs show little evidence for the accumulation of cliromiuni on the exchanger bed. The tendency for such fouling has been reduced greatly by the use of large amounts of regcnerant. The nldity of chromium to form complex salts has inntie t h e
Tobsal Hordness/Oivalent C c r f i o n s
Figure 8. Relative Efficiency of Amberlite IR-120 in Sodium and Hydrogen Cycles with Copper and Brass Mill Rinse Water
538
Figure 9. Concentration Efficiencies of Sodium Chloride and Sulfuric Acid with Amberlite IR-120 (Copper)
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44. No. 3
-LZqrid exchange of this ion very uncertain. The leakage certainly depends on the form of the chromium. Apparently state of chromium and temperature of regenerant have a marked effect on regeneration efficiency. An occasional regeneration with hot solution may be necessary to ensure successful long-term operation.
flowing at high rates have flow rate limitations as the basis of design. As the concentration increases, capacity becomes the limiting factor, In this analysis, an 8-hour daily cycle and an 8 gallon per cubic foot per minute limitation is assumed.
t
Economics ef Operation The practical aspects of this study can be evaluated fully only if an analysis is made of the economics. A comparison of the economics may be made for various conditions if the depreciation in capital investment, labor costs, chemical costs, and power costs are evaluated for each condition. Recommended methods for carrying out such a comparison appear frequently in the literature ( 3 , 14). For successful operation, the total operating costs must be balanced a t least by an equal return in value of copper recovered.
Industrial Wastes
-
C CATION~
- STEELTANKS
E D S
C IO*
-
Initial Costs Sufficient information is available from the work of Monet (10) and Bliss ( 3 ) t o permit an estimate of initial equipment costs. Figure 10 shows the variation of unit cost as a function of exchanger bed volume. These cost values include: rubber-lined tank; Everdur solo valves; regenerant tanks; regenerant educator; and ion exchange resins. An analysis of these costs indicate that they may be represented by the expression
’
Unit costs = 340 (V)O (dollars)
(4)
The depreciation on the equipment and the resin may be based on a &year life and a 300-day working year so that the depreciation per cycle based on a I-cycle day becomes, 340 Cost of depreciation/cycle = ___ (V)O.? 5 X 300 No interest rates have been applied to the capital investment nor are insurance and tax rates included since these considerations cannot be generalized sufficiently to allow a practical evaluation of their effect on total operating costs. However, a relatively conservative depreciation rate has been applied to compensate for these values. Space rental should be considered but the cost involved is quite smallin comparison with other quantities. Pumping charges and other power requirements have not been included because of the variables of operation location, and power load although these charges are usually quite low.
Labor Costs An arbitrary value for labor of $2.00 per cycle regardless of unit size has been selected. This sum is based on a rate of $2.00 per hour assuming hour for the regeneration steps. Actually, less time is required if the operators can do other jobs while the various resin conditioning steps are in progress. This value is probably too high on small units and low for large units.
Regenerant Costs Normally, regeneration costs represent a large fraction of the total operating costs; however, since the spent regenerant is used as’pickle acid make-up, no cost is assigned to this acid. Actually a small net usage of acid results depending on the composition of the rinse water. Generally, this usage is small compared t o the amount of acid required for the pickle make-up and is reduced further by acid generated in the electrolytic recovery of copper. The actual removal of copper by electrolytic deposition requires a power cost. This cost has not been evaluated as yet for a large scale installation. The design of copper recovery equipment must be based on either a flow rate or a capacity limitation. Very dilute solutions
March 1952
I
I
10
100
I
loo0
I a n Exchange Bed Volume, cubic feet.
Figure 10. Cost of Ion Exchange Units
If an 8-hour cycle is to be used, then
If on the of,her hand, the capacity is to be used as the basis, then
- 8 X [CUI X G X O Bed capacity
(7)
The capacity value may be derived in a approximate mannw from Figure 8 if i t is assumed that a straight line relationship exists between capacity and water hardness to divalent ion ratio. Capacity, q = 2.8
[1-
-+I
H
Operation costs, O.C., is defined as unit depreciation plus labor charges. 340 Vo.7 O.C. = ___ 5 X 300
+
2.00
(9)
If flow rate is the limitation in design, Equation 9 reduces to
O.C. =
+ 2.00
0.052 GO.’
(10)
If capacity is the limiting factor, Equation 9 may be reduced to terms of operational condition by substituting Equation 8 in Equation 7 . (11)
+
Since ZM + + is the sum of (Cu) H ; some simplification in calculation may be obtained by rearranging Equation 12 and calculating H in terms of pounds of copper per gallon.
INDUSTRIAL AND ENGINEERING CHEMISTRY
539
-Liquid
Xndustrial Waste-
T i t h this technique, regeneration of the sulfuric acid pickle for re-use as well as recovery of virtually all copper is achieved. Where brass rinses are concerned, a build-up of zinc and chromium
17-
I6
-
146
-
IZO-
im
C o n c e n t r a t i o n o f Alloy M e f u / s , p p m
CIS
Cu
Figure 11. Economics of Copper Recovery with Cation Exchange Resins
BREAK EVEN
y:s E a
m-
B
60-
eJ1
CURVE3
d 40-
E3 20-
Such a curve is shown in Figure 12. These curves are based on a copper value of 23 cents per pound. The zero gain curves may also be obtained analytically by equating the total value to the operating cost function.
OO
I
I
I
100
200
300
400
500
C o n c e n r r a f r o n o f Alloy M e f a k , ppm as C u
600
-Liquid acid and thus more effective use of acid. Although a crane truck will be required, one man can be trained to handle all the units in a single mill with consequent less training and supervisory expense and better control of metals content to streams. The cartridge method is generally to be preferred within its operational limitations. On the other hand, where very wide variance in rinse flow rates and copper content from tank to tank exists within a mill or where there are less than four tanks per mill, the fixed unit should be more practical.
operational factors, including labor costs, might then be made t o establish the merits of any particular process.
Acknowledgment The authors wish t o acknowledge the helpful suggestions of Harding Bliss of Yale University and J. C. Winters, Rohm and Haas Co., and the helpful cooperation of C. E. Potts and members of the staff of the American Brass Co. laboratory, where these studies were carried out.
Nomenclature
Conclusions
.
Industrial Wastes-
The recovery and disposal of copper and brass alloy metals from wash waters prior to passage into streams might be accomplished successfully by employing high capacity cation exchangers such as Amberlite IR-120. Either the sodium or hydrogen cycle may be used; however, current operation using spent regenerant acid as pickle make-up points t o a considerable economy if the hydrogen cycle is used. I n many cases a considerable saving might be realized. The major factor influencing capacity for copper and zinc is the relative amount of calcium and magnesium hardness in the raw water supply. This factor is particularly important where the copper concentration in the rinse water is relatively low. Where the elimination of metals is the primary concern without considering recovery, sodium cycle operation should be considered. Sodium cycle operation has the advantage of a greater capacity, less sensitivity to total hardness in rinse water, greater concentrations of toxic metals in the regenerant, more complete removal of trivalent chromium, and reduced acidity. Copper, zinc, and chromium could be precipitated from the waste chloride regenerant b y sodium carbonate. The precipitated metals may be recovered by chemical means or dumped. These studies have served t o emphasize the problems existing in the treatment of pickle rimes with ion exchange. It is suggested that a survey be made of the flow rates and copper contents of pickling rinses in representative brass &ndcopper sheet, rod, wire, and tube mills. Once these data are available, a n over-all cost estimate for each firm could be determined and plant designs suggested. A large scale pilot plant study to fully determine
v
= Bed volume, cubic feet
P
= Capacity, pounds of copper per cubic foot
EM++ O.C. Cu ZMo++
= Total divalent cations, p.p.m. as CaCOa
G
H
= Flow rate, gallons per minute = Hardness of water, p.p.m. as CaCOa = Operation costs, dollars = Pounds of copper per gallon = Total divalent cation, pounds of copper per gallon
Literature Cited (1) Beaton, R. H., and Furnas, C. C., IND.ENG.CHEM.,33,‘1500
(1941). (2) Beohnor, H.L., and Mindler, A. B., Ibid., 41,448 (1949). (3) Bliss, H., Chem. Eng., 54, No. 5, 128; No.6 , 100 (1947). (4)Bliss, H.,Chem. Eng. Progress, 44, 887 (1948). (5) Bliss, H.,Connecticut State Water Commission, Metal Inds. Memo., No. 42,43, 44 (1940). (6) Bliss, H., personal communication (February 1, 1949). (7) Dodge, B. F., Connecticut State Water Commission, Metal Inds. Memo. No. 23, 25, 27-35, 37-41. ( 8 ) Galloup, C . F., “Electrolytib Treatment of Brass Mill Waste Pickling Liquors,” doctoral dissertation, Yale (1941). (9) Hilbert, L. E.,Connecticut State Water Commission, MetaE Inds. Memo. No. 36. (10) Monet, G., Chem. Eng., 57, No. 3, 106 (1950). (11) Nelson, R.,and Walton, H. F., J . Phys. Chem., 48, 406 (1944). (12) Piret, E. L., and Carlson, R. W., Proc. Minn. Acad. Sci., 9, 70 (1941). (13) Selke, W.A,, and Bliss, H., Chem. Eng. Progress, 46,’509(1950). (14)Tyler, C., “Chemical Engineering Economics,” New York, McGraw-Hill Book Co.. 1938. (15) Vessalovski, V. S.,and Seligliei, I. A., Chemie & industrie, 35, 875 (1936). RECEIVED for review August 11, 1951. ACCEPTED January 2, 1952.
Sulfuric Acid Recovery from Waste Liquors F. J. BARTHOLOMEW, Chemical Conetructi~n Corp., 488 Madi8on Am., New York 22, N. Y. T h e current shortage of sulfur and sulfuric acid has prompted industry to give serious consideration to recovering acid from products that are now going to wastefor example, the iron sulfate-sulfuric acid solutions from steel mills and titanium pigment plants. A practical method is described for recovering the sulfuric acid of such solutions by concentrating the free acid, removing the iron sulfate by salting out, and then decomposing the sulfate for the recovery of the acid value it carries. The process is a development resulting from years of work on this
problem in conjunction with designing and constructing plants for the manufacture of sulfuric acid and other heavy chemicals and for the recovery of sulfuric acid from industrial wastes. Cost of water evaporation has always been a major cost in pickle liquor recovery. A new method of supplying heat to concentrate the liquor improves fuel efficiency and makes the recovery possibilities somewhat more attractive. The economic aspects of these problems are stressed because of increased prices of sulfur and sulfuric acid arising from their short supply.
A
dence of the importance of thiR basic chemical. So closely is ita production tied to the national economy that its sale is used as a measuring stick, like car loadings, to gage prosperity. In many of its applications sulfuric acid is completely consumed and be-
BOUT 75% of the sulfur that is mined or obtained in other ways is used for the manufacture of sulfuric acid. In 1950, more than 12,000,000 tons of sulfuric acid (100% HB04 equivalent) were consumed in the United States; this is sufficient evi-
March 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY
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