Recovery of Ferrous Sulfate Crystals From Pickling Liquor Citation Yang, Kai-Jin (1926) Recovery of Ferrous Sulfate Crystals From Pickling Liquor. Bachelor's thesis, California Institute of Technology. doi:10.7907/2ZVZ-8361. https://resolver.caltech.edu/CaltechETD:etd-01032005-112533 Abstract No abstract. Item Type: Thesis (Bachelor's thesis) Subject Keywords: Chemistry ; Chemical engineering Degree Grantor: California Institute of Technology Division: Chemistry and Chemical Engineering Major Option: Chemistry Minor Option: Chemical Engineering Thesis Availability: Public (worldwide access) Research Advisor(s): Unknown, Unknown Thesis Committee: None, None Defense Date: 1 January 1926 Record Number: CaltechETD:etd-01032005-112533 Persistent URL: https://resolver.caltech.edu/CaltechETD:etd-01032005-112533 DOI: 10.7907/2ZVZ-8361 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 6 Collection: CaltechTHESIS Deposited By: Imported from ETD-db Deposited On: 05 Jan 2005 Last Modified: 03 Oct 2019 22:55 Thesis Files Preview PDF (Yang_kj_1926.pdf) - Final Version See Usage Policy. 860kB Repository Staff Only: item control page

RECOVERY OF FERROUS SULFATE CRYSTALS PROM PICKLING LIQUOR Thesis by Kai-Jin Yang In partial fulfillment of the requirements for the degree of Bachelor of Science in Chemical Engineering. CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 1926 RECOVERY OF FERROUS SULFATE CRYSTALS FROM PICKLING LIQUOR I. INTRODUCTION Pickling liquor is nothing more than dilute sulfuric acid used in the iron and steel industry for removing scales on the surface of iron work which is to be further treated. The reaction for pickling may be represented by the equation Fed + HESO4 = Fes04 + Hod. ‘Thus we see from this equation that H2S04 is gradually used up and FeS04 formed during the process. It is evident,then, after a certain “length of time, Hg504 will be too weak for further pickling, and the amount of FeSO, will oe too valuable to cast away. This Fes0, may be converted into an oxide which is a pigment, or taken out in the form of FeS04.7H20 crystals. The latter is the purpose of this work. FeS04.7H20 has the following uses: photography; writing ink; Prussian blue; preparation of iron oxide for illuminating gas purifi- cation; water purification; mediciene; disinfectant , textile and leather industries; analytical reagent; making other iron salts. II. PROPERTIES OF FeSO, Aqueous solutions of FeS0, are easily oxidized. In a neutral solution the reaction may be represented by (1), and in acid solu- tion by (2): | (1) 4FeS0, + Op + 2Ho0 = 4¥e(0H)S0, (2) 4FeS0, + Oo + 2H2S0, = 2Feg(S04)3 + 2Ho0 . ' Metallic iron, if present in a neutral solution, will be oxidized into oxides; but if present in an acid solution it has a reducing ten- dency. Thus we have Feo(S0,)3 + Fe = 3FeS04. Crude Fe804.7H20 crystals contain Feo(S0,)3 which gives tne crystals a decidedly green color. ‘They are also frequently coated with a layer of yellowish basic salt. By washing with absolute alcohol this salt, being soluble, is removed and the crystals are thus rendered permanent. Hydrates of FeS0, having 1H20, 2He0, 3H20, $400 and 6H90 are known, but the one having TH90 is the only one stable at room temperature. It will, however, effloresce at 33°C. The solubilities of FeSO, are shown in the following table: ( According to Handbook of Solubility by Arther M. Comey) .t = temperature in degrees Centigrade, © = parts of FeS0, in 100 parts of water. t 0 5 LO 15 20 25 30 35 C 7.9 12.0 16.2 20.4 24.7 29.0 33.5 38.0 t 40 45 50 es) 60 65 70 75 Cc 42.6 47.1 51.9 56.7 61.7 65.7 64.3 64.0 t 380 85 90 95 100 G 62.3 §9.8 56.2 51.0 42.6 III. EXPERIMENTAL WORK The experimental work on pickling liquor consists of 1. evapora- tion, 2. filtration, 3. crystalization, 4. drying crystals and 5. analysis. Evaporation was carried out in open beakers in laboratory scale, in steam jacketed enamal kettles in engineering scale. Steam was ad- mitted at 20 pounds pressure, the temperature of the Liquor was 100.5°C. Metallic iron in the form of iron filing was used to react with the free acid in the liquor. Evaporation was stopped when the solution was sa- turated and anhydrous FeS0, began to appear. Ordinary suction filter was used for filtration in laboratory scale, filter leaf with the add of diatomaceous earth in engineering scale. Centrifugal machine was used for separating the crystals in the latter case. Both slow cooling and rapid cooling with running water have been tried. The significance of them will be seen in the table. All crystals were dried at atmospheric temperature, and no me- chanical devise was attempted. For determining free HyS0, in the pickling liquar, the liquor was titrated with standard KOH using methyl orange as indicator. Its Fe50,4 content was ascertained by determining Fe** with Kim0, of known streng- th. The Fet** content in F804. 7H20 is determined as follows: 40 grams FeS0,.7H20 made up 1O5cc. solution. 100 cc. of it was heated to 60°C, 5cc. HCl was added. Sec. of SnGlg whose strength was deter- mined with KMn0, was then added. Back titrate the excess SnCly with | Tg whose ratio to SnGl, was determined in each experiment, starch used for indicator. The other 5Scc. of FeSO,-7Hg0 solution was diluted to 50cc. Its Fet* was determined with KMm0,. Knowing the amount of Fe*** and Fe** their relative percentage can be figured out. These results are shown in the following table: of exp. No.of Condition for evapor. Appear. % yield % Fet** crops | of cry. “1 Lst. excess iron filing large, dirty 53.5 0.10 and neutral solution a 23.5 3rd " " t " _10. 5 87.5 2 lst theoretical amt of Fe “ clean 41.0 0.06 and neutral solution " dirty 34.5 3rd ‘ " n tt 20.0 9525 3 lst less than theor. Fe " clean 62.5 0.00 and acidie solution " " 22.5 3rd " " " " 13.5 98.5 4 lst less than theor. Fe " " 58.5 0.00 end acidic solution " " 31.5 0.05 3rd " " " " 5.0 0.068 95.6 5 1st 2/3 theoretical Fe " " 48.6 0.00 2nd " " " 34.7 0.02 3rd Ys " " " "11.5 0.08 94.8 6 lst 2/3 theoretical Fe small" 49.0 0.6 and 1/4" " " 31.4 0.0 ard ij" " " 12.1 (0.0 92.9 7 C.P. FeS04.7H20 from stock room 0.0 8 commercial " " " 0.02 9 lst 19/20 theor’tical Fe small clean 50.8 0.0 sed (evap. in enamal kettle) SS and acidic solution in ket. " " 15.0 0.0 3rd ; tt " % nt " 6. 2 oO. fa) 4th " " beaker " " 4.6 0.0 2.4 0.0 5th w tw Ly ri] Reaction rate of Fe in the form of 10 iron nails and HpS0, . At room temperature At 90°C Time in days Normality of Ho50, Time in min. Norm. of HeS04 ) 0.59 0 0.62 1 0.20 15 0.42 2 0.00 30 0.22 45 0.13 30 0.02 100 0.00 Corrosion test of H5504 upon cast iron: We of CI plate Dif. in wt Surface of Norm. of Time Rate of cor. before After gin plate in® acid hrs. gia/in®/nr. 12.795 12.563 0.232 2.193 0.36 16.4 0.00648 13.517 13.262 0.255 2.393 0.36 16.4 0.00658 Iv. A PLAN FOR PRODUCING 2 TONS FeSO,.7He90 DAILY. This plan is based upon the experimental results as far as they are serviciaole. When experimental data is lacking, theoretical con- sideration is relied upon. Experiments show that a solution containing the reaction product of iron filings and saturated with FeS0,, is very difficult to filter. This is probably due to the carbon content of the iron filings and the formationof massive anhydrous iron salts, both of which tend to block the openings of the filtering medium. Fortunately the foregoing table shows that as long as the evaporating Liquor is slightly acidic and crystals quickly collected, the crystals are clear and not excessive in Fe*+* content. It has also shwon that that the reaction between Fe and H250, can be complete in two days at room temperature. Accord- ing to Alexander Smith, the carbide and graphate content of steel and cast iron will not react with eold dilute p50, Take these facts in- to consideration, it seems best to let the iron react with the free acid of the liquor at room temperature for two days in wooden tank; and then after a process of sedimentation and decantation, the liquor is submitted for filtration | Evaporation van be conducted in cast iron vessel, for the liquor will be practically neutral when it comes to this stage. Steam coil is to be used for supplying heat. Air stream will be directed against this coil in order to prevent the formation of anhydrous salts due to local and excessive heat in the first place, and secondly to increase the rate of evaporation. It will increase the oxidation but this dis- . advantage may be more than offset by its advantages. In order to produce two tons of crystals daily, the percentage yield at each stage of evaporation must be definitely known. From this percentage the volume of the pickling liquor has to be handled each day can be ascertained. Since the experimental data concerning this percentage do not agree with each other, the theoretical solubility of Fe504 will be taken as a starting point fot the following caiculations. By analysis of pickling liquor Fe50, resulting from free acid 41 grams per litre “ " "Fett content 178 grams per litre Total Fe504 219 grams per litre. Assuming the evaporation is to be at 100°C: Solubility of FeSO, at 100°C is 42.6 parts per 100 parts of water, " "at 2006 is 24.7 parts " * * 4 f According +0 experiment, when 45.2 grams of FeS0,.7H20 which is equi- valent to 24.7 grams of FeSO, was added to 100 cc. of water the final volume was 121 cc. Water added to the final volume from water of Crystallization is 45.2 (126/276) = 20.6 cc., 126 being the molecular 7 weight of 7H\0, and 276 being the molecular weight of FeS04.7H20. To simplify the calculation, we can assume that the increase in volume due to the addition of FeS50, is negligible. That is to say when 24.8 grams of ¥es0, is added to 100 cc. of H90 the final volume is still 100 cc. | Sturting with 1000cc. of this liquor the saturated volume at 100°C is 21.9/42.6 = 515 cc. Water to be evaporated is 1000 - 515 = 435 cc. Let X be the FeS04 in grams which we should get when the saturated liquor cools down to 20°C. Each gram of Fes0, separating out from the liquor will take up 126/152 = 0.83 cc. of water as water of crstalli- zation, 152 being the molecular weight of FeS0,. We have then the following relation: (219 - X)/0.247 = 515 - 0.33X = saturated volume at 20°C. X= 116 grams. The percentage crystallization is 116/219 = 0.528 or 52.8%. FeSO, left in the solution is 219 - 116 = 103 grams. Volume to start for the second evaporation is 515 - 0.83 (116) = 419 cc. Saturated volume after the second evaporation is 419 (24.7/42.6) = 243 cc. Again (103 - X)/0.247 = 243 - 0.83X X= 54 grams of FeS0,4. FeS04 left in the liquor is 103 - 54 = 49 grams. In the same way the calculations go on for the third, fourth, and the fifth evaporation. These results are tabulated as follows: Theoretical Volumes and Yields Based on Solubility. Basis; 1000 cc. of liquor contains 173 gm FeSO4 and 0.537N free acid giving a total of 219 gm FeS04 per litre. ( The first evaporation including the reaction of Fe with free acid. Sobubility of Fe504 at 100°C is 42.6 and at 20°C is 24.7 parts per 100 parts of H20. Symbols used: (a. = volume to start evaporation in cc. o «= saturated volume at 100°C. c¢ = H90 in ce. evaporated. 4 = volume after separating crystals and saturated at 209°C. e = Fe504 in grams f = 4% crystallization (crystals obtained/total FeS04 in 1000 cc.) g = & crystallization (crystals obtained/total FeS04 in the solution at that stage) Evap.No. lst and 3rd 4th Sth a 1900 419 193 94 44.4 c 485 176 33 39.5 18.6 a) S15 243 115 54.5 2523 d 419 198 94 44.4 al. b/a 0.515 0.58 0.58 0.58 0.58 c/a 0.485 0.42 0.42 0.42 0.42 a/b 0.815 0.315 0.815 0.815 0.815 6 116 54 25.8 12.2 5.3 f 52.3 24.6 11.3 5.5 2.64 g 52.7 52.7 52.7 D207 52.7 d/a 0.419 0.473 0.473 0.473 0.473 Solution left 2lcc. FeSO, in the solution = 5 gm or 2.3%. From the foregoing table a schedule for a month's run can be figured out as follows: _Two tons of Fe504.7H20 is equivalent to 1.092 tons of Fe504. To produce 1.092 tons of FeS04 the theoretical amount of pkckling liquor needed is (1.092)(2000)(454)/116 = 8560 litres. 2260 gallons. =(8560)(0.264) = If we take 2660 gals. for the first day, according to the foregoing table, we sh=1l have to evaporate 2660(0.485) = 1285 gais. 9 Volume left after the first evaporation is 2550 (0.419) = 1115 gals. The amount of crystals we should have from the first evaporation is theoretically 2 (26660/2260) = 2.350 tons. Assuming 90% of this amount is obtainable practically, we have 2.350(0;9) = 2.10 tons FeS04.7H20 for the first day's run. For the second day we take in another 2660 gals. of liquor and have another 2.120 tons of product. For th third day we combine the two portions of liquor left over during the last two days which is 2230 gals. Water to be evaported is 2230 (0.42) = 936. Volume left for the next evaporation is 2230(0.473) = 1,055 gallons. The amount of crystals we should have is . 223061/0.264) (54/0.419) (1/454x2000) (278/152) (0.9) = 1.970 tons. The rest of the month can be figured im:thesame way, and we shall have three grades of grades of crystals as shown in the following: j “4 Ist 2ovo” Pe St! Aged) a red 4 : *¥e ~o An 2230 — - St) 2600 | ons . - PEO p92 t, 2600: (2¥S @ ang. 4930 7 ard — 7tf0 - 8 hae acer jars Fost 260. | KS : ‘ 19 and 2230 1! jst: 2500. | i7%S ee ° oO. (xd _ 34Z0- —yilo | 7009, Roe | | aTs it Qebo | : pars pedo , aves) | =% wp dn’ bens XOOU: tate ware | ilo abbo | a9 aboo. aes. | jaws - 729 abou ars Abobo {aes Za 2600 pte | and net 2nd . ‘Bvap. i Volume Hand ted (gals Schedole Da IN Va ah a se and - Fe =< y) 3 Algo i an “1970 2170. q 36 G36 73h 936 — F36 | 99h S40 — 936 936 S36 9430 936 - 10fo . ye Yolamre after cagstal (gatr ; rs WS (Oss 1S Is. 1085 (aS Wis | Ws 05S HS (0585 hs ys. — 1055 [1s furs is. Hts. has. 1055 (yaad —{rbo ; 1osS- [000 : / VOSS. HS }O00. $000 arb 3 id. {9° Fesg- 70 Cry A ANS (FOS 2120 21)9 zo abe? G7? B+ 7O | 1 yo. pro ry lro° : 147° ayo 240: 1972 2'xO- 2 lro 1-470 1-440 “1g70 1390 177° (97° 1°$470 197? 3330 woo 2g ard 3 paren e 2 n | Y, a vt -} | iid per f the volume left. frm 15% 3rd, 4> yd ad, 5% and ll The next chart shows the operating prosess and the relative length of time for each operation. The one succeeding list show some of the equipment to be used. | Take in 2660 gallons of liquor on the 23th of the month before, add iron filings, and let it react at room temperature, and then allow it to settle. On the first of the month, the liquor is to be filtered early in the morning. Evaporate bn the same day. Crystallization would take place in the night. Early the next morning, the crystals are to be separated with a centrifugal machine; the mother liquor goes to tank No. 1, and the crystals go to the drying process. Evasoration and cry- stallization are the same on the second day as on the first. On the third day, tne crystals formed during the night are to be centriguged early in the momming; the mother liquor together with that in tank No. 1 goes to the evaporation process during the day time. The rest ‘of the procedure is the same exce:t that the mother liquor left from this coming separation is to go to tank No. 2. / aiid AA A KLA KAA A KY > | | i 4 DB 0424S | | | | | PS a fe PA TR EF “aS &= & ne < R KK’ k- K~ ¥~ & a a a Sy a KF F ; + | | BUMALT SON 2ERL04S Pyner7 | rs LI | | | | buen 0 fia $22 por 1// fA) SN en ee ee ee ee ee aed oat ell ond soloed ae ol oat mel voll ool cael onl ool oe ce 91pOe ofwv“rd and and znd —+- 3rd 3rd _ pnd \oad —— avd gnd and ard ard on yp Osg/ Ag Lyra | ; - | | i i | | G04 00 2F ¥ 4 2 ae | Ty ee a A list of equipment : Article Purpose Capacity Material made 2 Tanks reaction 3000gal cypress with . asphalt paint 1 Tank decantation 3000 " 1 Tank liquid stor- : age No.1 3000. " 1 Tank liquid stor- age No.2 5000 " l Evap- Evaposation 3000 body - cast orator w iron wita coil - monel steam metal coil ¥ilter § filtration cloth 2 Grys- erystallize.lus tal. zation 2000 cypress wood tanks 2 Gen- trifu. separating L8Qfous crystals per Buhy.:. cast iron l drier dry crystals 2.4tons wooden tray per 8 hrs. Barrels shipping Auxiliary Boiler steam generation Motors fan in drier. 13 Renmark Let the Fe react with free acid at room temperature for 48 hrs. & let solution sediment for 24 hrs. - To hold soln. left from lst evaporation. Big enough to hold soln. from poth 2nd & 3rd evaporation. Leaf filter with dia- tomaceous earth. Talhust Machine Work's self Balancing cen- trifuge, dia=26" Max. load = 30#,nor- mal RPM=1000,approx floor space 37°x44". Tannel & trucks type described on p.542. Prin. of Chem. Eng. by Walker, Lewis, & ~ McAdams, can be used. centrifuge, compressed air of agitation and stirrer,