2062
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
During the experiment the compressed gas is discharged a t the desired pressure level into the preheater section of the reaction tube, likewise by water displacement. From the amount of .cvater pumped from the graduated cylinders, the quantity of gas charged and the flow rate may be determined. LIQUID CHARGE. Liquid materials of low vapor pressure are charged from the graduated glass cylinders into the reaction tube by means of the liquid feed pump. Liquids of high vapor pressure or normally gaseous substances rrhich have critical temperatures above the room temperature are also charged by the liquid feed pump from the heavy duty chargers; a t all times there must be a sufficient quantity in the charger to ensure the presence of the liquid phase. In the preheater section of the reaction tube, which is filled with copper punchings or porcelain beads, the gaseous charge and the vapors of the liquid charge mix and pass down through the catalyst zone. The products, after release t o atmospheric pressure through the pressure relcase valvc on the exit end of the reaction tube, pass on to the condenser. Liquid product separates out in the receiver, and the gas passes on through a vvet ice
Vol. 40, No. 11
trap and dry ice-acetone trap in tandem arrangement t o remove any entrained material and condense low boiling products, and finally through a wet-test meter. WEIGHTBALANCES.The weight of the total products obtained from runs of 2 to 4 hours’ duration, after a line-out period of 1 t o 2 hours, will usually fall within the range of 95 to 103Yo of the weight of the total charge. Thc reaction products are investigat,ed by the usual procedures. ACKNOWLEDGMENT
The authors express their appreciation t o E. T. Steele and G. P. Boon for valuable assistance in preparing the drawings. LITERATURE CITED
(1) Ipatieff, V. N., and Nonroe, G . S., J . Am. Chem. Soc., 67, 2188 (1945). (2) I b i d . , 69, 7 1 0 (1947). RECEIVEU December 10, 1947. Presented before the Division of Petroleum CHEMICAL SOCIETY, Kew Chemistry at the 112th Meeting of the AXIERICAN York, X , Y .
PICKLE LIQUOR NEU
ATION
Economic and Technologic Factors RICHARD D. HOAK, CLIFFOKD J. LEVIS’, CHARLES J. SINDLINGER, AND BERNICE KLEIN ikIellon Institute, P i t t s b u r g h , Pa. T h e various economic factors that should be considered in designing a pickle liquor neutralization plant are discussed in some detail. The advantages and disadvantages of low and high cost alkaline agents are compared quantitatively by means of tabulated data and graphs. Preliminary data are presented on the operation of a pilot neutralization plant operated by the Warner Company.
HIS is the fourth paper in a series (1, 9, 3) dealing with the treatment of waste pickle liquor with alkaline agents. The earlier papers were concerned chiefly with reaction rates and sludge characteristics. The major emphasis of the present contribution is on economic factors and the potentialities of alkaline agents normally considered to be wastes by their producers. Spent pickle liquor can be used successfully in a variety of applications-e.g., water purification, sewage treatment, and treatment of many industrial wastes. Unfortunately, however, economy requires that it be used relatively near the plant producing it. I t s corrosive nature and high water content result in costly transportation charges, although i t has been hauled in ordinary steel tanks for distances of 15 miles or more; as the tanks corroded, they were replaced, and, over a period of years, the costs were not excessive. I t s most deqirable component, copperas, can be separated easily, but this compound contains 457; of water of crystallization, and this limits the distance it can be shipped. If this product is dricd t o ferrous sulfate monohydrate, its solution rate is reduced materially. The cost of the additional operation prevents it from competing with other low-cost coagulants. This combination of circumstances necessitates treating pickle liquor as a waste product in most instances, and such treatment is 1
Present address, Warner Company, Philadelphia, Pa.
most economically effected by neutralization with lime or some other cheap alkaline agent,. SELECTION OF ALKALINE AGENT
The choice of the best neutralizing agent in any instance will be governed by the economic position of any given plant. Waste treatment practice varies so widely, because of the inherent complexity of the problems involved, that each installation must, be designed to fit the particular situation of the plant for which it is intended. Although neutralization procedures have become more or less standardized, pickle liquor neutralization plants also must be properly adapted to local condit,ions. Where there is a choice of alkaline agents, it is important t,hat the one best suited t o the purpose be selected. Two types of factors affect the choice of agent: (1) those fixed by the agent itself, such as basicity factor, delivered price, and reactivity; and (2) those set by condit,ions prevailing a t a given mill, such as operating schedule, area available for the treatment plant, and character of the receiving stream or sewer system. Generally, the last-mentioned group of factors will be relatively unalterable and an agent must be selected to meet those requiremenh. Choice of an agent should be based on the following considerations.
COST. It is axiomatic that the cheapest agent capable of fulfilling the requirements should be used. Delivered cost per ton is not usually a sound criterion of actual cost, and wherever possihle even cheap agents should be held to specifications by routine analysis of each shipment. land~is available for laSPACEA 4 ~ ~Where h ~little ~ or~no ~ ~ . gooning the sludge from the treatment plant, the agent that yields the most settleable (or dewaterahle) sludge must be used, even though its coFits be comparatively high. Sludge handling may cost several times as much as the actual neutralization, and any agent that will substant,iallg reduce sludge volume will permit the payment of a correspondingly higher price for it.
November 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
equivalent for each agent, and the seventh column the relative cost of each agent, compared with highcalcium quicklime.
TABLE I. COST COMPARISON OF VARIOUSALKALINEAGENTS Price, $/Ton in Grade Container Carloads Flake, 76% Drums 58.00 Sodium hydroxide Dense 56% Bags 25.60 Sodium carbonate 60. OOQ Aqua,’36% Drums Ammonia Anhydrous Tank caL I 59,OO Ammonia Bags 60.00 Powder Magnesium oxide 11.00 Bags Chemical High calcium hydrate Bags 11.00 Chemical Dolomitic hydrate Bags Pressure 13.00 Dolomitic hydrate Bags 12.00 High-calcium quicklime Pulverized Bulk 9.80 High-calcium uicklime Pulverized Bags Ground 12.00 Dolomitic qui&lime Bulk Ground 9.50 Dolomitic quicklime 4.00 Bags High-calcium limestone PulveriEed Bulk Pulverized 3.00 High-calcium limestone Bags Pulverized 4.00 Dolomitic limestone Bulk 3.00 Pulverized Dolomitic limeatone a Price per ton “a, B.s aqua ammo]iia.
Basicity Factor 0.687 0.507 1,647 1.647 1.306 0.710 0.912 0,820 0,941 0.941 1,110 1.110 0.489 0.489 0.564 0.564
Cost, $/Tqn Basicity 84.42 50.49 36.44 35.82 45.94 15.49 12.06 15.85 12.75 10.10 10.81 8.56 8.18 6.13 7.09 5.32
REACTION TIME. The reaction rates of available alkaline
agents mag cover a considerable range. Where reaction time is limited by the space assigned t o the neutralization plant, the most, reactive agents are indicated. Where the dumping schedule of the pickling plant allows relativelv long periods of time to elapse between batches, one of the less reactive, but cheaper, agents, such as pulverized high-calcium limestone, may be used t o a d vantage. PICKLE LIQUORVOLUME.At plants where a large volume of liquor is produced, and there is ade urtte space for the necessary treatment facilities, it may be posszle t o reduce operating costs bv designing a plant of sufficient size to utilize one of the less reactive agents, For example, pickle liquor can be given complete treatment (precipitation of all the iron) with pulverized highcalcium limestone in a plant providing efficient agitation and aeration; several hours’ reaction time is required by this agent as compared with 15 to 20 minutes for lime slurry, but its cost may be a third less, on a basicity factor basis. Operating economies can sometimes be realized by using continuous operation instead of the conventional batch method. WATERSUPPLY. Some mills have a limited supply of process water, and, in consequence, must practice water conservation. Where it is desirable t o re-use the clarified effluent from a pickle liquor treatment plant, it is essential that an alkaline agent be used that will produce the lowest concentration of dissolved salts -e.g., high-calcium lime. Clarified effluent can be used for preparing fresh pickling batches, for lime slaking, or for low-range cooling. Pickle liquor cannot ordinarily be BY-PBODUCT RECOVERY. processed t o recover usable by-products profitably. This results principally from the fact t h a t the spent liquor is a relatively dilute solution of low-cost heavy ehemieals. I n certain localities, however, it should be possible to recover compounds that will pay a substantial part of the cost of operation. For example, if reactive magnesia were to be used as a neutralizing agent, pure magnesium sulfate could be recovered, as well as a n iron oxide suitable for pigments or for conversion to sinter for blast furnace charging. Enterprises of this character should not be. undertaken without making a survey of conditions in local chemical markets, or without the assurance that other producers would not flood the market with a rompetitive compound. AVAILABILITY OF AGEUT. If a plant is designed t o use a partieular agent, it is obvious that the designer should be certain of its long-term availability. This caution applies especially to situations where the most desirable alkaline agent is a waste product of another industry.
Relative Cost 8.36 5.00 3.61 3.54 4.54 1.53 1.19 1.57 1.26 1.00 1.07 0.85 0.81 0.61 0.70 0.53
The variety of basing points, freight allowances, etc., made it impossible t o include delivered costs in this table. This information should be obtained for any given plant location t o provide an accurate cost comparison. REACTIVITY
A condensed summary of the reactivities of certain common agents is given in Table 11. Reactivities were compared under four reaction conditions: (1) room temperature, no aeration; (2) 60” G., no aeration: (3) room temperature, with aeration; and (4)60” C., with aeration.
The neutralizations were made in 4-liter beakers and agitation was provided with laboratory electric stirrers, Where neutralizations were made without aeration a n effort was made t o keep air induced by the stirrers to a minimum; in the other cases, air was introduced through porous diffusers. The pickle liquor used in all tests contained 60 grams of iron per liter, and 200 grams of sulfate per liter, and, in each case, a 57, excess of alkaline agent was added. The data show the iron content of a sample of filtrate, as grams per liter, after a 6-hour reaction time, except where iron is absent in a shorter time. The reactivity of certain alkaline materials is a function of their method of manufacture. The “reactive” magnesia was a chemical grade, the “unreactive” an insulation grade. Cement dust varies widely in reactivity. Figures are given for the most and the least reactive of the several samples of these two materials studied. SLUDGE SETTLEABILITY
The settling character of the sludges from Table I1 is presented in Table 111. The initial settling rate, in per cent of total volume appearing as supernatant per minute in a 100-ml. cylinder, is followed by a figure for the final sludge volume as a percenhge
TABLE11. REACTIVITY O F ALKALINII: AGENTS
The prices in the fourth column are current f.0.b. quotations. The fifth column lists the basicity factors of the agents as grams of calcium oxide equivalent per gram of agent. These factors were determined in the laboratory on representative commercial samples used in the experimental work, except those for sodium hydroxide, sodium carbonate, and ammonia, which were calculated. The sixth column shows the cost of a ton of calcium oxide
WITH PICKLE
LIQUOR (Iron unprecipitated after 6 hours, grams per liter) Conditions of Reaction Agent 1 2 3 4 NaOH n n Na x 0a 0 in 0.75 hr. 0 in 0 . 7 6 hr. 0 in 0 . 7 5 hr. 0 in 0 . 5 hr. 0.72 M g O (reactive) 0 in 3 hr. 0 in 0 . 5 hr. 0 in 0 . 2 5 hr. 11.99 RIgO (unreactive) 14.0s 14.08 2.50 CaO 0 in 0 . 2 5 hr. 0 in 0.25 hr. 0 in 5 min. 0 in 5 min. CaO.Mg0 1.88 3.14 1.04 0.30 Oin0.5hr. O i n O . 5 h r . 0 in 0 . 5 hr. CaiOH)a.hfgO Ca 0 H ) r 0 i n 0 . 5 hr. 0.55 1.23 1.53 0 in 3 . 5 hr. Acetylene sludge 1.66 1.04 Oin3.5hr. 0 in 3 , 6 hr. ICa(OH)zI 2.43 Cement dust (re. 9.44 8.02 0 in 4 hr. active) Cement dust (un13.81 14.00 8.02 3.49 reactive) CaC03, precipi8.95 6.17 0 in 2 hr. 0 in 1 . 5 hr. tated CaCOa, limestone 20.40 18,80 ‘I.95 0.03 “ Reaction practically instantaneous.
TABLE 111. SLUDGE SETTLEABILITY“
COST COMPARlSON OF 4LKALINE AGENTS
Selection of the proper alkaline agent should be based on three criteria: cost per ton of available basicity, reactivity, and character of sludge produced. The weight given t o each of these will depend .on local conditions, as outlined above. Table I presents a tabulation of the relative costs of a number of common neutralizing agents.
2063
Agent NaOH NagCOa MgO (reactive) g g 0 (unreactive)
Conditions of Reaction 2 3 4 0.03- 83 0.04-79 0.03-84 0.00- 96 4 . 4 - 16 3 . 6 -22 5.6- 1 4 2.4 20 0.22- 58 0.55-44 0.18-44 0.00-100 1
-
b
0.01- 91 0.00-100 0.07- 68 0.03- 71 0.13- 76 1.73- 62
0.07-69 0.10-70 0.13-70 0.10-57 0.27-69 1.33-58
0.67- 63
0.63-65
0.05-51 0.01-93 0.67-48 0.67-70 1.26-70
0.011.330.050.030.000.271.24-
0.13-72 0.57-46
0.2 67 0.13- ‘77
0.01-92
b b
81 11 57 95
60 80 67
-
a Figures show initial rate in % per min.-final sludge volume, % original. Final sludge volume attained in 17 to 20 hours. b Settling rate meaningless because of small fraction of iron precipitated.’
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 40, No. I1
the cheap agent by using it to perform the major proportion of the neutralization and a more reactive material to complete the treat, ment. This technique is similar to the split treatment, but here the primary agent is required to do a much larger part of the job, and the secondary agent becomes, more accurately, a polishing agent. Figure 1, in which dolomitic lime appears a* the prototype of the primary agent, illustrate5 the degree to which the reaction approache5 completion for several stirring times, and a range of lime additions as a percentage of the, stoichiometric requirement of the liquor. Preparation of a plot of this kind for any agent will permit, by economic balance, a determination of the optimum proportions of the primary and secondary agents for the mixing time available a t a given plant. It is assumed that the polishing agent will complete the reaction almost Figure 1. Polishing Requirement us. Time and Proportion o f instantaneously. Lime, Using Dolomitic Lime as Primary Agent Pulverized high-calcium limestone, precipitated chalk, dolomitic quicklime or hydrate, and cement dust may be cited as examples of possible primary agents. Sometimes a survey of the region in which the af the original slurry volume, for each agent under the four replant is located will disclose an enterprise that produces a Rction conditions. In some cases the sludge compacted t o its suitable alkaline material as a waste product. Such source,' final volume in several hours, in others a number of days were often yield a satisfactory agent that may be had for little more required. Certain of the agents were so unreactive that only a t,han the cost of transportation. relatively small proportion of the iron was precipitated; in these Polishing agents comprise a group of very reactive alkaline eases the settling data were not recorded. materials that can be used without serious handling problems Treatment was discontinued in all cases as soon as iron was and whose cost is not excessively high. Caustic soda, highabsent in a filtered sample. With reactive agents, had aeration calcium quicklime, and hydrate are examples of suitable polishrrs. been continued for the full 6-hour period, sludge settleability would have been improved. Where pickle liquor is treated with caustic soda and held a t the boiling point for a short time, the iron oxide is converted to magnetic iron oxide, which settles rapidly to a very small volume.
" 6
NEUTRALIZATION TECHNIQUES
Three techniques may be used to noutraline pickle liquor with 811 alkaline agent-namely, conventional, split treatment, and conventional with polishing. These are discussed in detail below to provide a basis for determining the procedure best adapted to a specific case. This technique is practiced CONVENTIONAL KEUTRALIZATIOX. almost universally where pickle liquor is treated n ith an alkaline agent. It comprises mixing the proper amount of agent JTith thc liquor until the reaction is complete. In this treatment, it is important that quicklime be properly slaked (or hydrate wetted) for maximum efficiency in utilizing the agent. SPLITTREATMENT. I n localities where pulverized high-calcium h e s t o n e , or a similar low-cost agent, can be purchased at a relatively low price per ton of equivalent calcium oxide, economie.; can be realized by using the limestone to neutralize the free acid and precipitate the ferric fraction of the iron, and a more reactive (but more costly) agent to compIete the treatment. The proportion of the treatment borne by eachagens will be determined by local conditions. If both compounds were pure, it would be economical to substitute pulverized stone for quicklime whcrc the former could be bought for less than 56% of the price of the latter. In practice the break-even point is about 61%. This procedure is discussed in detail in a previous publication ( 2 ) , but it must be emphasized here that dolomitic limestone is unsuitable for this application. POLISHING TREATWWT.Where a cheap, but relative unreactive agent is available, operating schedules or limited space for the neuCralization plant usually prevent its use bemuse of the relatively long time required to complete the reaction. I n a case of this kind it is possible to obtain much of the economy of
94
YO
L,
88
-
8.8
-
8.4
-
82-
86
-
7.6
1
0
I I I I 1 I 40 80 120 160 200 240 280 A L K A L I N E A G E N T ADDED, PER C E N T OF STOlCHlOMETRlC
Figure 2. Titration of Pickle Liquor with Caustic Soda and Soda Asb
November 1948
2065
INDUSTRIAL AND ENGINEERING CHEMISTRY
Soda ash, which would appear to be suitable, cannot be used effectively because it will not readily produce a sufficiently high pH (9.3) for complete precipitation of ferrous iron. Heat and aeration are necessary to remove the carbon dioxide formed by the soda ash reaction, and this adds an unnecessary operating cost, I n addition, it is substantially less reactive than the other agents cited. Figure 2 shows titration curves for sodium hgdroxide and sodium carbonate, and illustrates the ineffectiveness of the latter compound.
5 I\
0
Room Temp. without aeration 0.00
I
100
EVALUATION OF VARIOUS AGENTS
Every neutralization plant will differ from another in some respect, on account of local conditions. Selection of the proper alkaline agent may be the determining factor in the final plant design. I n this section the significant characteristics of the most likely agents are discussed in detail. CAUSTICSODA. Thiq is the most reactive of all of the common agents, but its high price will normally preclude its use in all but exceptional circumstances. It has, however, certain definite advantages which must be weighed in reaching a decision. Its high reactivity and the small volume of sludge it yields, especially where the reaction is carried out near the boiling point, means that plant size will be small per unit volume of pickle liquor. In addition, the relatively pure hydrated iron oxide can be recovered and sintered for blast furnace charge, and pure sodium sulfate, either anhydrous or Glauber salt, can be produced from the iron-free supernatant. These recoveries will partly offset its high price, as will the compactness of the plant itself. Mills which use caustic soda degreasing baths, or have sodium hydride pickling installations, should investigate such sources of caustic for possible application in a pickle liquor neutralization plant. The possibility of obtaining ?elatively impure by-product caustic, either as a solid or as a moderately dilute solution, from a nearby chemical plant should be explored to reduce over-all operating costs. In general, however, this compound would find its major field of usefulness as a polishing agent in combination with a much cheaper alkaline material. SODAASH. This compound is not only costly but much less reactive than caustic soda and it is unsatisfactory as a polishing .agent. It would appear to have no place in the pickle liquor neutralization field. AMMONIA. High in price, this agent will not precipitate iron completely because of the formation of a soluble iron-ammonia complex. Special equipment is required t o realize the full effectiveness of ammonia, and its use is uneconomical except, under special conditions, in large mills. LIMES. High-Calcium. The high reactivity and low cost of both high-calcium quicklime and hydrate point to these compounds as the most universally desirable agents for pickle liquor treatment. For full effectiveness it is important that quicklime be properly slaked, and the hydrate thoroughly wetted before use. These products have been dealt with in detail previously (9). The supply of high-calcium limes is limited a t present, and is likely t o continue so for several years. It is reported that the available supply is insufficient to treat more than a small fraction of the pickle liquor requiring neutralization. Combined with a cheap primary agent, high-calcium lime can be used in relatively -small proportion a8 a polishing agent. Dolomatac Lime. Less reactive than the equivalent highcalcium products, dolomitic quicklime and hydrate are in somewhat better supply, but accelerated construction of dwellings may reduce their availability. These products have higher basicities than their high-calcium counterparts, and, as they sell for approximately the same price, provide basicity a t a lower unit cost. Low reactivity is the principal objection t o dolomitic materials, but this disadvantage can be overcome by adoption of the techniques previously described ( 3 ) . Figure 3 relates iron removal to I wwtion time for dolomitic lime under four conditions of opera-
1
I
0
I
2
3
I 4
I
1
5
6
T I M E , HOURS
Figure 3.
Treatment of Pickle Liquor with Dolomitir Lime
tion. Complete precipitation of iron is normally effected with high calcium lime in about 15 minutes. Aeration of the reaction mixture is the most effective means for reducing the time for complete iron removal with dolomitic lime. Table IV shows the effect of aeration on a pickle liquor trested with dolomitic lime a t room temperature. These data show thai oxidation has little effect in the early stages of the reaction, but. as the rate of iron precipitation decreases, the oxidation rate increases relatively faster than the rate of iron precipitation, reduces the p H of the mixture, and provides the driving force for completion of the reaction, by increasing the tendency of the alkaline agent to dissolve. I n many localities dolomitic lime will be found t o be a n excellent primary agent, which, because of its low cost per basicit: unit, can be combined with an expensive polishing agent to provide economical treatment. PULVERIZED HIGH-CALCIUM LIBIESTONE.This is a cheap agent that is usually in plentiful supply but, unfortunately, it;reactivity is low. The reactivities of limestones from different sources vary widely, however, and a stone should be selected only after making comparisons in trial neutralizations. Data on a group of pulverized limestones appear in a previous paper ( 8 ) . Dolomitic limestone is too unreactive for pickle liquor treatment. There probably are a number of localities where one of the more reactive limestones will provide economical complete treatment. This would normally be the case where the volume of pickle liquor is small and ample reaction time can be provided. The split limestone-lime method has shown operating economies in commercial practice, and limestone plus a polishing agent should reduce treatment costs similarly. PRECIPITATED CHALK. More reactive than natural calcium carbonate and selling a t only a slightly higher price where it is a by-product of chemical manufacture, this compound may find expanded uses for neutralization. Its reactivity in pickle liquor is shown in Figure 4. CEMENTDUST. Experimental work on this by-product of portland cement manufacture was limited t o two samples from different sources. Its reactivity varies considerably and would
TABLEIV. EFFECTOF AERATION Time, Hours 0.083 0.25 0.6 1 2 3 5 6
Unaerated Fe, g./l. P 13 4.71 6.9 3.15 7.1 2.46 7.0 1.90 7.0 1.40 6.9 1.40 7.0 1.18 7.1 0.56 7.5
Aerated ______ Fe, K./’l. 4.15 2.88 2.53 1.12 0.08
... ... ...
PH 5.1 4.8 4.2 2.7 4.2 0
.
..,
...
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INDUSTRIAL AND ENGINEERING CHEMISTRY I
I
I
1 4
I
S e t t l i n g Rote D o t o
IE
Initio1 %/min. Room Temp wlthaut aeration 0.67
u\ X
A'
Final volume
original 63
65
0.63
60T.without a e r a t i o n
0 Room
Temp. w i t h aeration
0.13
0 60'C
with a e r a t i o n
0.2
57
w
72
i
Vol. 40, No. 11
BfAGNESIh. The high price of this compound limits its value as a neutralizing agent. I t s high basicity, and the possibility it offers for recovering pure iron oxide and magnesium sulfate, would reduce its ncb cost. It might find a useful application i n areas where there is a steady demand for magnesium sulfat,e. Commercial magnesias vary in reactivity, depending on the method of manufacture. The reaction rates €or the mopt and the least reactive of the four magnesias st,udied are shown in Figures 7 and 8.
PILOT PLANT STUDIES
Thc desirability of investigating neutralization react,ions on a scale t'hat would provide practical design data has been recognized for a long time. But the exigencies of the war and the current scarcity of equipment prevented the instal1at)ion of a suitable pilot plant until recently. Through cooperative cffoit by the Columbia. Steel and Shafting Company, the Tolhurst Centrifugals Division of American Lfachine and Metals, Inc., and the \Framer Company, a pilot neuiralization plant was complct,ed iu June 1947 on the site of the high-magnesium limc plant, of the Warner Company at Devault, Pa. The pilot equipment currently consists of the following: TIME, HOURS
Treatment of Pickle Liquor with Precipitated Chalk
Figure 4.
appear to be generally similar t o t h a t of pulverized high-calcium limestone. I t should be available a t a low price. It is unlikely- that this material could be used for complete treatment of pickle liquor because of its lorn- reaction rate, but where a reactive dust is available a t low cost it could be used as a primary agent if aeration and heat could be provided. The reaction rate of the more reactive sample is shon II in Figure 5. ACETYLENE SLUDGE.A trade waste from acetylene generation, this material is a n impure hydrated high-calcium lime which is available in many areas a t a low price. Less reactive toward pickle liquor than high-calcium hydrate, this material could be used successfully in a split treatment or n i t h a polishing agent. Its reactivity is illustrated in Figure 6. 20,
I
I
1
I
I
Settiing Rate Data I n i t i a l Final voiume % / min. Yo or i q I n o I -____ *-Room Temp. without aeration
1.73
X-6OoC. without a e r a t i o n
1.33
0 - R o o m Temp. with aeration
1.26
0-60°C.with oetation
1.24
62 58 70 67
Wood tank, 6 X G feet in diameter, for pickle liquor storage. Robinson Ribbon agitator for batch slaking quicklime, or slurrying hydrated lime; capacity, 80 pounds of quicklime per hatch. Wood tank 4 X .1. feet in diameter d h a,gitator, for storing inilk of lime; capacity 375 gallons. Wood niixing tank 6 X 6 feet in diameter with turbo-type agi1,ator for reacting pickle liquor and lime. %-inch perforat,ed basket, batch type, Tolhurst suspended centrifuge of iron and steel construction, with drop bottom and rack and plow unloader. Wood tank, 4 x 4 feet in diameter, equipped for admission of steam and compressed air, for storing centrifuge effluent.. Niagara portable pilot filter, supplied by Siagara Filter Corporation. Le Val pilot filter, supplied by the Whiting Corporation. Miscellaneous pumps, flowmeters, and control instruments. Because of the recent, installation of thc pilot plant, all runs made to date must be regarded as exploratory. Among the many qualitative observations t.hat have been xilade is the significant one that bhere appears to be a mass action cffcct that reduces the difference in relat,ive react,ivitp between dolomitic and high-calcium limes with pickle liquor. This effect was not' observed in the laboratory work, and it map be attributable to the larger scale of the present, studies. Further work will be 1,equired before this point, can be substant iated.
I
I
Settling R a t e Dal I n i t i a l Final volur %/min. %arigina Room Temp. without oeration 0.13 75 I
--
withoul aeration 0 Room Temp. with a e r a l i o n
I
I
I
2
I 3
I 4
X 6O'C.
0.27
69 70
0 60'C. w i t h aerotion
0.67 0.27
80
I 5
T I M E , HOURS
Figure 5 .
Treatment of Pickle Liquor with Cement Dust
Figure 6.
Treatment of Pickle Liquor with Acetylene Sludge
DEWATERING OF HIGH-CALClUhI TABLEv. CENTRIFUGAL , 0 LIMESLUDGE Overation Feed t o centrifuge, min.:sec. Slow speed drain, min. :see. High speed drying, min.:sec. Cake plow-out, min. : s e a Total time, min.:sec. Weight of cake, lb. Moisture at 105’ C., 70
T-LE
2067
INDUSTRIAL A N D ENGINEERING CHEMISTRY
November 1948
1
0:55 3:15 1o:o
1:0 15:lO 100 43.09
2
Cake Number -, 2 6 1:15 0345 6:O 8:0 21:o 12:o * 1:30 0:40 29: 45 21:25 114 95 41.08 42.69
LIVE VI. AINALYSISOF LIQUORFROM HIGH-CALCIUM
NEUTRILIZATION Sludge Centrifuge Filter Supernatant Effluent Effluent Parts per Million 10 10 60 Color Chem. Chem. Chem. Odor 10 120 60 Turbidity 3720 4280 4140 Total solids 580 780 660 Total volatile solids 3140 3500 3480 Total fixed solids 70 20 50 Suspended solids 10 30 30 Volatile suspended solids 40 10 20 Fixed suspended solids 52 69 70 Oxygen consumed 0.4 0.02 0.05 Settleable solids (1 hour), ml./l. 0.8 2.0 1.6 Iron, a8 Fe 11.4 11.2 11.4 53 64 68 gEchemica1 oxygen demandD * B.O.D. of original pickle liquor could not, be determined accurately.
I
RoomTemp.without aeration X 60%. without aeration
RoomTemp. with aeration Cl 6OoC. with aeration
0
r
OO
TABLSVII.
CENTRIFUGAL
DEWATERING OF DOLOMITIC LIhfE SLUDGE
Operation
1
Feed to centrifuge, min. : s e a . Slow speed drain, min. :sec. High speed drying, min. :see. Cake plow-out, min.:sec. Total time, min. :sec. Weight of cake, lb. Moisture at 105’ C., %
1:30 3:30 4:O
TABLE VIII.
0:37
9:37 89.5 35.00
3 1:30 4:O 5:30 0:40 11:40 93 38.13
LIQUOR FROM DOLOMITIC LIME XEUTRALIZATION
-4NALYSIS O F
Color Odor Turbidity Total solid? Total volatile solids Total fixed solids Suspended solids Volatile suspended solids Fixed suspended solids Oxygen consume Settleable solids hr.), ml./l. Iron, as F e
8
%chemical
0:40
9:40 91 33.72
Cake Number 2 1:30 4:O 3:30
oxygen demandn
Sludge Centrifuge Supernatant Effluent Parts per Million 100 90 Caustic ,Musty 1000 80 4680 6240 1020 1160 5080 3660 220 580 120 100 460 120 102 1.59 0.4 8.5 36 3.4 11.3 8.3 148 100
Filter Effluent 10 Aromatic 10 3680 700 2980 15 :1 77 0.02 0.2 8.2 88
B.O.D. of original pickle liquor could not be determined accurately.
%. 0 22
Room Temp. without a e r a t i o n X 60.C. without aeration 0.55
3
4
5
TIME, HOURS
Treatment of Piclde Liquor with Unreactive Magnesia
The pilot plant runs have shown that by varying the type of lime and the method of mixing it with pickle liquor, sludges of widely different dewaterability can be produced. Repeated runs have shown that for a given set of conditions, the same type of sludge is always produced. I n view of the exploratory nature of this investigation, relatively few pertinent data are yet available. A later paper dealing exclusively with the pilot plant work is planned. Enough runs have been made, however, to permit the inclusion of data on two typical studies of sludge dewatering to indicate the results currently being obtained. High-calcium lime was used to treat conventional pickle liquor supplied from the batch pickling operation of Summerill Tubing Division of Columbia Steel and Shafting Company. The sludge, representing 182 pounds of dry solids was dewatered in the centrifugal in three portions. The results are given in Table V. Sanitary chemical analyses of sludge supernatant, centrifuge effluent, and filtered centrifuge effluent are given in Table VI. In a typical run using dolomitic quicklime as the neutralizing agent for the same kind of pickle liquor, the sludge, representing 176 pounds of dry solids, gave the results shown in Table V I I . Sanitary chemical analyses of the effluents are given in Table VIII. ACKNOWLEDGMENT
% oriainol 58 44
0 Room Temp. with oerotion
0.18
44
0 60.C.
0.00
100
with aeration
Figure 8.
2
I
This study was presented as a part of the research program of the Stream Pollution Committee of the American Iron and Steel Institute through the Multiple Industrial Fellowship it has sustained at Mellon Institute since 1938. Credit is also due to the companies whose cooperation has made possible the pilot plant in which neutralization procedures are currently being investigated. LlTERATURE CITED
(1) Hoak, R.D., Lewis, C . J., and Hodge, W. W., IND.ENO.CHEM.,
36, 274 (1944).
Ibid., 37, 553 (1945). (3) Hoak, R. D., Lewis, C. J., Sindlinger, C. J., and Ibid., 39, 131 (1947). (2)
TIME, HOURS
Figure 7.
Treatment o f Pickle Liquor with Reactive Magnesia
Klein, Bernice,
RECEIVEDOctober 16, 1947. Presented before the Division
of Water, Sewage, and Sanitation Chemistry a t the 112th Meeting of the AMERICAN CH~PMICAL SOCIETY,New York, N. Y.
