Document NG1OMn1xG5628YZyDGxMmoM1b

JLR-59 -1, No. 54 Serial Number 18802 Tent. S.W. Process, S.N. 18802-A Prel. Cost Estimates, " " Dr. H. W. Elley (2) Dr. E. K, Bolton (1) Mr. R. J. Goodrich (1) Mr. A. J. Wuertz for I.C.I. for C.I.L. J. L. Piles Dr, 0. Stallmann 0) (1) (2) (1) \1 /^ti i, Mlpi' Cl) E. I. DuPont de Nemours & Company Jackson Laboratory March 2**7**, ' 1 "1p"9F"4 511 T..h..e.....R...e. m--.o...v..a.Vl f-oT"f*..G....r..i.t....f.r..o.m-...W.. e...t...."..M.. .onas..t.r..a...l".....P..r..o...d..u...c. t s Progress Report N. M, Bigelow 9 0. Stallmann Division Head X DUP050041016 The Removal of Grit from Wet "Monastral" Products N. M. Bigelow JLR-59-1, No. 54 Serial Number 18802 Objects of the Investigation; Short Range; to reduce the grit content of "Monastral" pro duct s (in paste and powder form) to passable limits (0.1$). Ultimate: to produce "Monastral" products which are com pletely free of grit* Period Covered by the Report: November 8, 19*0 to March 1, 1945. Historical Background: The uses to which the various "Monastral" products are put make it highly essential that they be as free from grit as possible. The.reasons for this are obvious, and need not be dis cussed here. At present, all of the phthalocyanine pigments on the market contain some grit, regardless of their type or source. DuPont1s "Monastral" pigments are neither strikingly superior or inferior to competing types in this respect. It is certain that the trade requirements as to the grit content of phthalocyanine pigments will become increasingly stringent in the future} and it is also certain that In a competitive field, the fact that one brand of pigment contains relatively less grit than a competing brand may be a critical factor In sales acceptance. When the program described in this report was initiated the specifications for various "Monastral" pigments called for a permissible maximum of 0,25$ to 0.50$ of grit retainable on a 200-mesh screen, on a dry colors basis. Considerable difficulty was being encountered in meeting this standard. Furthermore, it was realized that ultimately this standard would have to be raised. The objects of the investigation were framed with both of these factors in mind. Conclusions: The combined efforts made in laboratory and in the producing areas, and the installation of a settling box of improved design. -1- DUP050041017 have resulted In a reduction of the grit content of the most im portant "Monastral", products to 0.15$ of grit or less. This represents the best attainments in equipment or by methods now known to us, No method of producing completely grit-free "Monastral" products has been found as yet. Summary? The settling box, the vibrating screen and the Dorr Hydroseparator have been investigated as means of removing grit from moist "Monastral" products. The settling box w,as developed to a fairly satisfactory performance, and is now being used in removing grit from CPC Paste Crudes HT, LT, D and SG. This piece of equip ment will reduce the grit content of acid pasted types to about 0,10-0.15$, and of salt-milled types to 0.3$. These figures ap pear to represent the practical limits of this equipment. The vibrating screen removes grit from undispersed pigment suspensions fairly well, and.is being used in the Ponsol Area to reduce the grit content of Polychloro CPC Paste Crude D, The Dorr Hydroseparator is not applicable to our problem. Patent Situation: Nothing of a patentable nature is disclosed in this report. Plans for Future prk:* I, II. III. The Bird Solid Bowl Centrifuge is being studied as a means of removing grit from moist "Monastral" products. Experimental; < The experimental portion of this report is arranged as follows: Part One - The Nature of the Grit in "Monastral" Products Part Two - Grit Removal from Wet "Monastral" Products I, The Settling. Box II. . The Vibrating Screen III. The Dorr Hydro-separator. -2- DUP050041018 Part One The Mature of the Grit In "Monastral" Products Theoretically, it should, be possible to make and keep "Monastral produets free of grit. In actual practice, however, the introduction of grit into the products is inevitable, Phthalic anhydride enters the phthalonitrile converter in gaseous form, free of grit. Even in passage through the catalyst, however, a trace of abraded catalyst is added' to the phthalo nitrile, The drying, premixing and baking operations all intro duce grit to the crude product. In'acid pasting, the sulfuric acid solution is screened before drowning; this removes the coarse grit only. Prom the drowning step on, all of the Iron rust, sand and tramp impurities which are introduced accidentally in the finishing steps, remain in the product until it arrives at the last finishing step. If press cakes of semi-finished pro ducts are left in contact with the air, portions will dry to form hard particles which are as troublesome as any other type of grit, ; Since the introduction of grit into "Monastral" pigments is inevitable, a positive means of removing it must be included in the finishing process. When the product is finished in the form of a dispersed paste, its grit content is removed fairly easily by passing the paste through bolting cloth on a vibrating screen immediately before the final packaging. The removal of grit from undispersed "Monastral" products, such as press cakes or undis persed pastes, is much more difficult. The press cakes are too thick to screen. The use of dispersing agents here is not per- missible, because the dispersed product would no longer be suit able for use in flushing pastes or for drying to powder types. Since grit may be introduced into "Monastral" pigments in every operation which is performed upon them, it is obvious the grit removal step should be plaeed as late as possible in the sequence of finishing operations. The last step common to all "Monastral" products is the, ammonia slurry. This appears to be the most logical place to remove grit from all "Monastral" pro ducts. Additionally, dispersed "Monastral" pastes can be screened immediately before packaging (which is done at the present time), and the grit content of "Monastral" powders can be controlled by a suitable combination of fine grinding and size classification. DUP050041019 It was decided, therefore, to attack the problem of grit removal at the ammonia slurry stage for all products, and at the final grinding step in the case of powders. At the time when this investigation was undertaken, the grit content of semi-finished "Monastral" products, defined as materi al retained on a 200-mesh screen by wet screening methods, and referred to a 100$ color basis, was in the order of 0,3$ to 0.6$. The grit content of Polychloro CFG Paste Crude Acid D, the worst offender at the time, occasionally exceeded 1$. The composition of the grit was as follows: 1, Sand and soft coal fly ash. The sand came both from dissolved mortar in tile-lined equipment and atmospheric con tamination; the ash from the latter source. 2. Iron rust, mainly from iron equipment. 3. Dry pigment, formed by allowing press cakes to stand around in the air, or by the re-use of improperly cleaned filter presses. This material is properly classified as grit, since it can scar an engraved copper printing roll almost as badly as silica or iron. 4. Tramp materials, such as window glass, tile, nuts, bolts, etc. Such contamination was avoidable and occurred only occasion ally. The grit came in a complete range of particle sizes, as is shown by the following examinations of representative samples of grit. The first sample is grit separated from CPC Paste Crude HT by passage of the slurry through the settling box. (See JLNB 4259, p.42). To obtain this sample, the scrapings from an empty sett ling box were mixed on a Hamilton-Beach mixer with an excess of Compound 8 and then washed on a 325-mesh screen, to remove all of the dispersible pigment. The residue on the screen was then classified through graduated screens and dried. -4- \ DUP050041020 Table I Composition of Representative Grit from CPC Paste Crude HT Size on 60 mesh Distribution - Screen Mesh Sizes Through 60 Through 100 Through 200 on 100 on 200 on 325 Percent of Total Grit 60.6 Percent Silica and Ash Percent Ferric Oxides 25,2 61,0 Percent Organic (by Difference) Including Dried Pigment * 13.8 16.2 7.46 41.1 51.4 14.4 16.7 40,7 42.6 8.8 2.6 28.1 69.5 The composition of another typical sample' of grit, removed from an undispersed slurry of Polychloro CPC Paste Crude D by passage through. j5Q0-mesh bolting cloth, is tabulated below. In thi3 case the isolated grit was slurried with an excess of Compound #8 and rinsed thoroughly, on a 325-mesh screen to remove adhering wet pigment. Table II j Composition of Representative Grit from Polychloro CPC Paste Crude D Size Distribution Screen Mesh Size on. Through 60 Through 100 Through 60 mesh on 100 on 200 on 325 Percent of Total Grit Percent Silica and Ash 40.6 46.2 Percent Ferric Oxide 36.7 Percent Organic (by Difference)including Dried Pigment 7.1 58.0 '57.9 52.1 / ' 10.0 9.5 59.8 51.0 9.2 2.0 55.1 52.9 14.0 i-R ... DUP050041021 It will be noted that the greatest part of the grit does not pass a 200 mesh 'sieve, and that most of the grit actually is coarser than 60 mesh. This is the dangerous grit, and, fortu nately, the easiest to remove. Our present "Monastral" standards contain enough grit between 100-525 mesh particle size that the deliberate addition of this grit to "Monastral" past Blue B Pow der Std, in amounts up to 10$ does not alter materially Its wedge-grit rating in printing ink. The inks so prepared "showed slightly inferior wedge grit results. However, for practical purposes the differences appear to be negligable" (See JLNB 4259, p,45, and Technical Laboratory Memo 2018, 11-19-45). It appears, therefore, that a pigment free of all grit retainable on a 200 mesh screen will be satisfactory for most present-day applications. However, new uses for "Monastral" pigments are being developed in which higher standard will he required. The pigmenting of plastics which are subsequently extruded Into filaments is a case in point. Therefore, while the immediate grit problem is satisfied by the removal of grit retainablb on a 200 mesh- screen, solution of the ultimate problem will require the removal of al*l grit retainable on a 525 mesh screen. Grit Determination Methods The Technical Laboratory tests for grit by suspending a sample of paste or powder equivalent to 1/4 lb. of 100$ pigment in a liquid medium (water for aqueous pastes; alcohol-water or pure alcohol for powders) and washing the slurry through a stan dard 200-mesh screen with a large excess of water. Undispersed lumps are crushed with the fingertips and then washed through the screen. The screen and its content of grit are then dried for a half-hour at 110j the grit Is then transferred to a sheet of paper and weighed. Grit is reported as milligrams per quarter pound of 100$ pigment. Jackson Laboratory felt that this test relied on too small a sample, and depended too much on the operator's thoroughness. Additionally, there was no provision for recovering the pigment subjected to the test. Accordingly, two tests were developed in Jackson Laboratory. > First Jackson Laboratory Grit Determination Method A sample of press cake equivalent to 150 g. of 100$ pigment is dispersed with an excess of Compound #8 in a Hamilton-Beach mixer ("soda mixer") in two or more installments. The dispersed 6- - DUP050041022 pastes are poured through a standard 200-mesh screen and rinsed through with an excess of Water, The screen and its contents are dried in an oven at 110; then the grit is transferred to a sheet of paper and weighed. Grit is reported as the percent of total solids, 100$ basis. Second Jackson Laboratory Grit Determination Method A sample of press cake equivalent to 500 g. of 100$ pigment is slurried with enough water to give a 5$ suspension. This sus pension is filtered through a specially-prepared screen made by cutting the bottom off a Hamilton-Beach mixer cup and soldering a disc of 200-mesh screen in its place. The 200-mesh screen is protected by a removable disc of coarse screen which lies on top of it. The mixing cup is mounted on a Hamilton-Beach mixer and high-speed agitation is employed during the screening; the agita tor is placed close to the coarse screen but not in contact with it. .The slurry is added to the- cup through a large glass funnel. Another glass funnel is placed below the mixer cup and the screened slurry is run through a rubber hose into a series of buckets, for return to subsequent slurry operations, When the mixture has been screened, the slurry buckets, funnel and mixer cup are rinsed with water until the effluent from the slurry cup is colorless. Cup and contents are then dried at 110. The dried grit is transferred to paper, weighed and reported as per cent on,a 100$ pigment basis. If the material to be tested for grit is already in slurry form, a suitably-sized weighed sample is screened as described above. The effluent is filtered on a large (15 in.) Neutsch. The filter cake is weighed and solids are determined; grit con tent is calculated on the bases of these results. The portion of the filter cake left after the determination of solids can be returned to later operations. It must be admitted that the Technical Laboratory and Jackson Laboratory methods do not give closely comparable results. Probably neither method is very accurate, and will probably re quire more study in the future. Jackson Laboratory feels that its methods are more reliable, since they use a larger sample, and also reduce to a more constant degree the physical work done in forcing the pigment through the screen. DUP050041023 Part Two Grit Removal from Wet "Monastral11 Products I. The Settling Box The settling box is a long open wooden tub through which the grit-containing slurry flows, in certain cases over and under a series of baffles and in other cases without baffling. The grit settles to the bottom of the box, while the degritted sus pension flows over a wier out of the box, to be pumped into a filter press. The method removes coarse grit, down to 80-mesh material, very effectively. It is not effective in removing grit finer than 80-mesh in particle size; the highly flocculated, pigment entraps fine grit and prevents its settling. It has the techni cal disadvantages that large amounts of pigment are held up In the settling box, and that the material which settles out con tains much good pigment as well as grit. This material must be accumulated and reworked separately. The principle of the settling box is old. During DuPont's early development of salt milling an arbitrarily designed settling box was used to remove grit from the acid suspension of CPC Paste Crude Acid SG (formerly CPC SG Wet). It proved capable of re moving grit quite effectively, and has since been used for degritting CPC Paste Crude HT suspension, following the ammonia slurry. It was felt that a settling box, designed by" a competent hy draulics engineer on the basis of modern physical principles, might be a more effective means of degritting slurries of phthalocyanine pigments. Accordingly, Mr. T. W. Stricklin was requested to present this engineering problem to Mr. C. E. Lapple of the Technical Division. At Mr. Lapple ' s request, Mr. G. Barnhart of the Miscellaneous Dyes Division determined the viscosities of CPC slurries of various concentrations. (See letter from N, M. Bigelow to Mr. Lapple, dated 12-21-43, which is appended to this report for purposes of record). Mr, Berry's calculations indi cated that the most suitable settling box would be a rectangular trough 10 feet in length, 3 feet in width and 18 Inches in liquid level depth. The slurry was to be introduced through a 3-inch pipe into the bottom of a stilling chamber made by the insertion of a weir 6 inches from the Inlet end of the box. - The suspension -8- DUP050041024 was to flow through the box without agitation or baffling. A baffle suspended from above dipped into the suspension to a depth of 6 inches, 14 inches from the outlet end of the box. The pur pose of this baffle was to hold back foam and floating grit. The suspension flowed under this baffle and then over a 17-1/2 inch wier set into the box 6 inches from the outlet end. The effluent then was to be pumped from the outlet end of the box to a filter press. The box was designed to handle a 1$ pigment suspension pre pared by diluting the usual 5$ ammonia slurry suspension con tinuously with cold water just ahead of the centrifugal pump which transferred the slurry into the settling box. The calcu lated optimum rate was 50 gallons per min., equivalent to 150 lb. of 100$ pigment per hour. (See letter from 0. E. Lapple to N. M. Bigelow, dated 12-23-43, which is appended to this report for purposes of record.) A settling hex was constructed according to the above specifications and placed.in #64 Building of the Semi-Works, adjacent to a 1500 gallon wooden slurry tank and a 30" wooden filter press. 1. Tests with Polyehloro CFO Shortly before the grit removal program was commenced, the grit content of Polyehloro CPC Paste Crude D was excessively high, averaging over 0.5$ (600 mg,), and occasionally exceeding 1$. This material was chosen as the most profitable subject for study. A Tentative Semi-Works Process for the Manufacture of Polyehloro CPC Paste Crude D Special (Low Grit) was written (Serial lumber 18802-A, approved 3-17-44), and a number of ex perimental charges were run. This process combined the standard ammonia slurry of Polyehloro CPC- Paste Crude Acid D and the passage of the slurry through the settling box. A preliminary series of experimental charges proved that under the best con ditions possible (l$ slurry, 15 gal. per min. throughput) the settling box could reduce the grit content of polyehloro CPC Paste Crude D to about 60 mg. (0.05$) by the Technical Labora tory test. Under conditions approaching normal operation, the settling box appeared to be capable of lowering the grit content to about I25 mg. (0.1$). The campaign was not well carried out, due to shortages of labor, Jackson Laboratory supervision and the mechanical short comings of the equipment. It was found im possible to discharge a 5$ slurry from the tub by gravity; and -?- DUP050041025 even when a pump was installed, great difficulty was found in introducing the slurry to. the settling "box at an even rate. Due to variations in feed water pressure, the dilution of the 5$ slurry, with water at an even rate was also impossible without constant attention. Ultimately, it was found necessary to make up the slurry at the concentration at which it was to be put through the settling box. Excluding orienting runs, and false runs, seven runs were made in January, 1944, Under part-time Jackson Laboratory supervision. The data obtained on these runs are tabulated below. Table III Grit Removal from Polychloro CPC Paste Crude Acid D First Campaign Charge No, 12 3 4 5 67 Slurry Concentration, 2.8? Percent Throughput, gal. per. 13, min. Percent Grit in Feed 1.29 Method #1 Percent Grit in Efflu - 1,08 ent, *J,L. Method Percent Grit in Efflu'- 0.17 ent, T.L. Method Tech. Lab. Grit Rat- 190. Ing, Mg. per Quart er Pound 3.04 0.92 0,95 7.- 13. 17, 0.72 2.50 1.52 0.39 0.54 0,60 0,055 0.044 62.. 50. 0.88 8.7 1.62 1.46 0.11 125, 1.65 1.50 6.8 15,5 2.06 1,27 1.13 1.09 0.13 0.12 152, 140. This experimental lot was used in the preparation of "Monastral" Fast Green GF Paste; this particular material had to be used because of an acute shortage of Polychloro CPC Paste Crude D. Since the finished paste received the usual screening, no report can be made as to the grit content of the lot as a whole. Later in the spring the Sales Division placed an order for the production of ,2000 lb, of low grit "Monastral" Fast Green G Powder, to be prepared by use of the settling box. Before this material could be produced, the grit content of Polychloro CPC Paste Crude Acid D'was reduced sharply. A lead-lined steel drowning tank had been used in the acid pasting of the crude pig ment. Seams had developed in, the lead lining of this tub, and -10- DUP050041026 the exposed steel was contributing heavily to the grit in the pro duct. Ultimately the tub was r eplaced by a tile-lined drowning tub, and the grit content of the Polychloro CFG Paste Crude Acid D dropped at once to about 120 mg, (Technical Laboratory method). Thus, the quality of the starting material was already.equal in quality to the anticipated product. However, the paste was ammonia slurried and passed through the settling box. As might be expected, there was no appreciable reduction of its grit con tent. The actual performances on individual runs are tabulated below. Table IV Grit Removal Prom Polychloro DEC Paste Crude Acid i) Second Campaign Charge 10 11 12 13 14 15 16 17 "Grit- Content* 110 62 80 70 ' 60 50 110. 170** Charge 18 19 20 21 22 23 24 Grit Content 268** 100 150 128 130 * 100 105 *Milligrams per quarter pound, Tech. Lab. method, **The ''hold up" in the settling box was recirculated in these charges, 'accounting for the.abnormally high grit content. The Polychloro CPC Paste Crude D so prepared wds dried and standardized as "Monastral" Fast Green G Powder, Lot 10.1, Two grit determinations on this lot at the Technical Laboratory indicated total grit contents of 230 and 280 mg., and magnetic grit contents of 60 and 20 mg. Since this lot was no higher in quality than other lots prepared at the same time, it was released to the trade without special treatment, and accepted without comment. 2. Tests with CPC Paste Crude SG In connection with the study of the Bird Centrifuge which is now in progress, the grit content of CPC Paste Crude Acid SG, which is regularly, passed through the new settling box, has been determined. The grit content of three representative charges, made after a regular ammonia slurry, were 0.32$, 0.32$ and ,0.34$. -11- DUP050041027 This probably represents the optimum performance of the settling box with this material under normal operating conditions. Tests on the Original Settling Box with CPC Paste Crude ;HT The Technical Laboratory and the Semi-Works have tested the performance of the older settling box on CPC Paste Crude HT, by measuring the grit contents of each individual charge and of each lot of "Monastral"`Fast Blue BF Press Cake into which they were composited. Preliminary grit figures were predicted for each lot of press cake by calculating weighted average grit figures for every component charge. The results indicate first, that the original settling box may .be keeping gross contamination ' ; in check, but is not making a particularly satisfactory-product; and second, that the grit detection test now used by the Techni cal Laboratory is not accurate. In the table below, grit is reported as milligrams per quarter pound, dry basis. Table V Grit Content of "Monastral" Fast Blue BF Press Cake After Passage Through the Settling Box Charge Grit Rating Prelim. . Final Charge Grit Rating Prelim, Final 96 324 93 112 505 190 99 100 101 ' 102 300 280 254 158 90 165 400 285 113 475 114 ' 470 115 407 116 120 170 360 220 245 103 280 250 104 423 260 117 118 250 230 105 196 250 119* 130 106 156 200 120 165 107 134 222 121 72 108 - 120 150 122 172 109 550 175 110 283 169 123 124 * / 185 30? 111 124 155 125 164 *In charges 119 to 125, the solids content of the ammonia slurry was lowered from 5^-6$ to 3$, with the object of determining whether this would increase the effectiveness of the settling box. No marked effect was apparent, and the change in process was dropped. "12 DUP050041028 Cost of Grit Removal in the Settling Box The added cost of removing grit from P.olychloro CPC Paste Crude D by means of a settling box in the Semi-Works at a rate of 3,700 lb, per month, 100$ basis has been estimated at $10.85/ cwt., 100$ basis. Details may be found in Jackson Laboratory Cost Estimate, S.N. 18802-A, and in a letter from Dr. 0, Stallmann to Dr. H. A. Lubs, dated 3-29-44. It is believed that in suitable equipment this cost could be reduced to about $5.00/cwt. 100$. II, 'The Vibrating Screen For some years the Ponsol Area has passed at least-part of its Polychloro CPC Paste Crude D slurry through a 50-mesh vibrating screen prior to filtration. According to their ex perience this was not a successful operation; the grit either wore holes in the screen or plugged it, causing later additions of slurry to flood over the screen, rather than to filter through It. Moreover, the useful effect of a 50-mesh screen would not be very pronounced, even if its use were not connected with so much difficulty. A 100-mesh vibrating screen would be far more effective in grit removal, and it appeared desirable to determine exactly what sort of pigment could be produced by such a treatment. The Ponsol Area was unwilling to undertake the problem; their main concern was to maintain the production of Green, and they felt that passing'the Green slurry through a 100-mesh vibrating screen would slow up production excessively. The Basic Colors Area, however, had suitable equipment, consist ing of a mild steel tank, a screen and a filter press, which was not in'constant use, and arrangements were made to carry out the tests, (See JLNB 4259, p. 7.5*) A typical ammonia slurry was prepared (7,4$ solids concentration) and passed through the vibrating screen. The screen plugged badly, and after two hours' operation water wa3 added to the slurry, reducing its solids content to 5.2$. This slurry passed through the vibrating screen without difficulty, at the estimated rate of about 150 lb, of 100$ pigment per hour. The material was filtered and washed without difficulty. The material remaining on the screen was accidentally dis carded by the operator. An attempt was made to pass a separate dilute ammonia slurry of green (3<7$ solids) through 300-mesh bolting cloth on a vibrating screen* This proved to be impracticably slow, and -13- DUP050041029 the charge was finally passed through the 100-mesh vibrating screen. Again no difficulty was encountered. Samples of the press cake, dried in the laboratory, con tained 20-40 rag. of grit per quarter pound by the Technical Laboratory test. This is an excellent rating, inspection of the grit recovered from the screen indicated,that 0.37 lb. of grit was removed from 100 lb. of 100$ pigment. The particle size distribution, expressed as percent of pigment, dry basis, was as follows: over 60-mesh 0.36$; 60-100 mesh, 0,013$. The grit contained 25$ f203 and 59$ silica, the remainder being dried pigment,, wooden splinters, etc. These two special charges of Polychloro CPC Paste Crude D were dried and standardized as "Monastral11 Past Green G Powder Lot 96. The Technical Laboratory reported (letter from Dr. K. C. Johnson to Mr. C. F. Schaumann, dated 1-11-44) that "the lot, which was dried in the Semi-Works and micropulverized at G&M, shows somewhat higher grit (85 mg.) than the laboratory, dried material, but lower than standard and very much lower than recent production," The Basic Colors Area estimated that the process outlined above would add $l2,26/cwt. 100$ to the current cost of Poly chloro CPC Paste Crude (see letter from Mr. C. J. Darling to Dr. 0. Stallmann, dated 3-8-44). No commercial use has been made of this method for pro'ducing low-grit material. The abrupt improvement in the quality of Ponsol Area Paste Crude made a separate de-gritting operation less imperative, in addition, Jackson Laboratory found that the ammonia-ammonium chloride slurry was definitely corrosive to mild steel, which made it unadvisable to use the Basic Colors equipment for this operation, III. The Dorr Hydroseparator The Dorr Company has recently developed a machine for the continuous and semi-automatic classification of solids in aqueous .suspension which is based on the differential settling rates of its various components through an ascending column of water. Mr. C. E. Berry of the Technical Division arranged a test program at the Dorr Company's laboratories, and a sample of Polychloro CPC Paste Crude D was sent there'Under the code designation MDD-869. The visit was made on September 21, 1944, A few settling experi- -14- DUP050041030 ments convinced Mr. G. M. Darby of the Dorr Company that Poly chloro CPC Paste Crude D was too highly flocculated to be amenable to grit separation in the Dorr Hydroseparator. For details, see the letter from Mr, T. , Stricklin to Dr. H. A. Luba, dated 9-27-44. Submitted for typing - May 2, 1945 Typed - May 7, 1945 AES i H DUP050041031 COPT APPENDIX CC: Dr. Dr. I, E. Gubelmann 0. Humphery Orchem Dr. H. A. Lubs, Orchem Mr, C. F, Schaumann Dyestuffs Mr. T. A. Martone Dr. Wm. Kirk, Mgr., Dye Works Att: Mr. J. K. Reed Dr. E. F. Hitch Mr. G. H, Schuler, Dir., T. L. . Att: Dr. C. K. Black Dr, K. C. Johnson Mr. J, M. Tinker, Dir., J. L. Att: Mr. T. -W. Stricklin, Jr, Mr. C. J, Darlington December 21, 1943 DR. A, P. TANBERG, DIRECTOR EXPERIMENTAL STATION ATT: MR. C. E. LAPPLE GRIT REMOVAL FROM "MONASTRAL" PRODUCTS As promised in our conference of November 19 at the Experi mental Station, and confirming yesterday1s telephone conversa tion, we, herewith, submit the experimental data which you have requested in order to make the necessary calculations for de signing an improved settling box. These data were obtained by determining the rate of fall of spherical glass beads through suspensions of CPC Paste Crude D (drip drowned) and CPC Paste Crude HT (drowned at high turbulence). The suspensions were taken' from the ammonia slurry tub and are representative of the material that will be passed through the proposed settling box. The determinations were made by Mr. G. Barnhart. The glass beads which were used had the following dimensions: specific gravity 2.334; diameter 3.50-3.63 mm.; average weight CPC Paste prude D Slurry; specific gravity at 3.6$ solids concentration, 1.028. -16* DUP050041032 CPC Content of slurry, $ nil (water). 2.27 2.60 2.92 3.25 3.60, Bate of Settling, Feet per Min. 57 43 39 35 29.5 14.3 CPC Paste Crude HT Slurry; specific gravity at 6.5$ solids concentration, 1.030. CPC Content of slurry, $ nil (water) 1.0 2.0 3.0 . 4.0 *5.0 6.0 6.5 Bate of Settling, Feet per Min. 57 ' 57 57 57 55 50 34 27 CPC SG Slurry] (suspension formed by extracting a saltmilled mixture of 1.0 part of CPC and 4 parts of sodium chloride with 25 parts of 1$ sulfuric acid). CPC Content of slurry, $ nil 5.0 Bate of Settling, Feet per Min. 57 42 At present we have no data on the ammonia slurry of Polychloro. CPC Paste Crude D; but preliminary observations indi cate that it will resemble CPC Paste Crude D in its properties. We trust that the information given above will enable you to carry out the calculations you have offered to make in .order to arrive at recommendations as to the designing of an improved settling box. We should appreciate it if you would give this problem your earliest possible consideration. -17- DUP050041033 If for any reason you should be unable to take care of this matter promptly, please notify us, since the removal of grit from current production of "Monastral" colors is an emergency problem of such urgency that ve shall have to go ahead with the construction of a settling box not later than a week from now. JACKSON LABORATORY NMBjmnr N. M. Bigelow DUP050041034 COPY CC: Mr. S. I. Winde, I. E. D., D, . Att: Mr. W. 0. Jewett Mr. J, M. Tinker, Jackson Lab, Att: Mr. T. W. Stricklin, Jr. December 23, 1943 DR. N, M. BIGELOW (.3) JACKSON LABORATORY DYE WORKS' GRIT REMOVAL PROM C.P.C. COLORS I. .. ." '.. L,. '.< IHI'H . .t l W ! '. ' I ". Confirming our telephone conversation, attached is a sketch giving the suggested size of a settling box, to handle a C.P.C. Paste Crude D slurry at the rate of 150 lb./hr. of dry color. Based on the settling rate data for 3.6 mm, glass beads in a C.P.C. Paste Crude D slurry at 25C. , we have estimated the apparent viscosity as follows: Slurry Concentration Weight % Settling Rate ft./min, Apparent Viscosity Antipoises 0.00 2.27 .2.60 2.92 3.25 3.60 57 1 43 39 35 29.5 14.3 0.9 4.0 5.5 7.8 12.9 37.4 These values of apparent viscosity should be regarded as giving only the relative order of magnitude and may be in con siderable error for the following reasons:1 2 (1) For the relatively large beads, settling velocity is not very sensitive to viscosity, whereas for the fine particles (under 100 mesh), the settling velocity is directly proportional to the fluid viscosity. (2) If the slurry shows plastic properties, the apparent viscosity will'vary depending on the conditions so that it may be impossible to settle very fine particles under the action of gravity iependiiij &n IshS field stress 6f the 9lbhry -19- DUP050041035 (3) The settling tests were conducted at 25C, At the higher operating temperatures, the viscosity may he much differ ent (either higher or lower) depending on the relative effect of temperature on degree of solids flocculation and fluid viscosity. Despite their very approximate character, however, these data (when plotted) show that for solids contents of-over ifo the slurry shows a very rapid increase ih apparent viscosity. It is therefore suggested that the settling chamber be operated with a Vfo rather than the usual 2.- 5% slurries by introducing the re quired amount of water ahead'of the centrifugal pump leading from the mixing tank to the settling box. On this basis, the settling box shown on the attached,sheet is estimated to remove particles larger than 325 mesh and having a specific gravity greater than 210 when handling 30 gal .-/min. of a slurry by weight, -This estimate assumes the absence of any plastic prop erties, such as a yield point, in the case of a 1$ slurry. It will be noted that, with the exception of the baffles, the suggested box is not much different than the existing box. We feel that-thedilution of the slurry is the critical factor in securing satisfactory settling and the increased liquor vol umes, to be handled are far more than compensated for by the re duced viscosity resulting from dilution. It is furthermore suggested that the present box be equipped with a water feed at the pump intake to determine the effect on pigment quality when diluting the slurry from the mixing tank to 1$ with hot and with cold water. In preparation for any further required improvements in degrit ting, it is suggested that the settling t.es.ts be conducted with the 90 micron sand which we shipped to you yesterday using water and various coneentratibns of .each slurry. We would suggest that a known wet volume of this sand be fed to the settling tube. After a specific time, the sand that has passed through the bottom trap can be separated from the slurry by washing through a 325 mesh screen and then measuring the sand thus settled out volumetrically. Since the sand is not entirely uniform in size, this will give a means of estimating the mean settling velocity. The settling velocity of the sand is estimated as 1 to 4 ft./min, in water at room temperature. We trust this meets your immediate needs end will be pleased to offer any further assistance in the solution of this problem. TECHNICAL DIVISION /s/ C. E. Dapple -20- DUP050041036