PLEASE DO Nar REMOVE FRG1 LIBRARY iRIi 8846 Bureau of Mines Report of Investigations/1984 Evaluation of Methods for Recovering Potash From Carnallite Ore By D. G. Foot, Jr., and J. L. Huiatt UNITED STATES DEPARTMENT OF THE INTERIOR Report of Investigations 8846 Evaluation of Methods for Recovering Potash From Carnallite Ore By D. G. Foot, Jr., and J. l. Huiatt With an Economic Evaluation by D. A . Kramer UNITED STATES DEPARTMENT OF THE INTERIOR William P. Clark, Secretary BUREAU OF MINES Robert C. Horton, Director Library of Congress Cataloging in Publication Data: Foot, D. G. (Donald G.) Evaluation of methods fo r recoverin g potash from carnal lire ore . ( Report of in ves ti gati ons; 8846) Includes bibliographical re ferences. Supt. of Doc s . no. : I 28.23:8846. 1. P o tas h. 2. Carn a llite . 3. F lota ti on. [. lJu iarr, J. L. [I. T i· tl e . II[. Series: Report of investigations (United Stares. Bureau o f Mines ) ; 8846. TN23.U43 [TN919] 622s [622' .36361 83·600310 CONTENTS Abs tract ••••••. 1 Introduction ••• 2 Acknowledgment .....•......•....•.......• 2 Sample description........................ • ••.•. 2 Continuous flotation unit design and operation ••••••••• 3 Design for insoluble-slimes flotation... ••••••••• 3 Design for direct flotation............. • ••••••••• 4 Operation •••.••••••••••••••.•••.•.•••••• 4 Sampling and data analysis •••••••••••••• 5 Experimental results ••••••••••••••••••••• '. 5 Material balance and economic evaluation •• 6 Summa.ry and conclusions................... .................. 6 Appendix.--Economic evaluation by D. A. Kramer ••••••.•••••••.••.••••••. 7 ILLUSTRATIONS 1. Overall view of continuous flotation unit •••••••••••••.••••••••••••••••.• 4 A-l. Insoluble-slimes flotation: Ore preparation section ••••••••••.• 11 A-2. Insoluble-slimes flotation: Flotation section •••••••••••••••••. 12 A-3. Insoluble-slimes flotation: Potash flotation section •.•••••••••••••.•••• 13 A-4. Insoluble-slimes flotation: Concentrate debrining and drying section •• 14 A-5. Insoluble-slimes flotation: Tailings debrining section ••••••••.••••••. 15 A-6. Direct flotation: Ore preparation section ..••..........•.....•......... 16 A-7. Direct flotation: Potash flotation section •.••..••••••••••••••••••. 17 A-8. Direct flotation: Concentrate debrining and drying section •••••• • • • 18 A-9. Direct flotation: Tailings debrining section ••••••••••••••••••.•.•.•.••• 19 TABLES 1. Chemical analysis of carnallite ore •................•.......•........... 2 2. Screen analysis of carnallite ore •••••.••••••••••••••.••.••••••••••• 3 3. Reagent schemes used in continuous flotation unit •.••••••••••••.••••• 5 4. Flotation results for continuous flotation unit.... ••••••.• 5 5. Screen analysis of final KC1 products.............. •••••••• 6 A-l. Estimated capital cost, insoluble-slimes flotation....... • ••••• 7 A-2. Estimated capital cost, direct flotation •••••••.••••.•••• 8 A-3. Estimated annual operating cost, insoluble-slimes flotation •••..• 9 A-4. Estimated annual operating cost, direct flotation •••.•••••..••••••••••••• 10 UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT °B e/ degree Baum{ lb/d pound per day d/wk day per week lb/h pound per hour d/yr day per year Mgal thousand gallons h hour min minute hid hour per day MMBtu million British thermal units in inch pct percent kW·h kilowatt hour ton/d ton per day Ib pound EVALUATION OF METHODS FOR RECOVERING POTASH FROM CARNALLITE ORE By D. G. Foot, Jr., 1 and J. L. Huiatt 2 ABSTRACT The Bureau of Mines investigated two methods for recovering potash from carnallite ore in continuous 100-lb/h flotation units. In the insoluble-slimes flotation procedure, insoluble slimes were removed by flotation prior to potash flotation. In the direct flotation method, insoluble slimes were depressed and the potash floated directly without prior removal of the insoluble slimes. Seventy-three percent of the potash in the ore was recovered in a leached final KCl product contain­ ing 59.1 pet K20 using the insoluble-slimes flotation method. The di­ rect flotation method recovered 74.5 pct of the potash in a final product containing 60.2 pet K20. The rate of return on the investment was calculated at 13 pct for the insoluble-slimes flotation method and 15 pct for the direct flotation method, based on a Bureau economic evaluation. lGroup supervisor. 2Research supervisor. salt Lake City Research Center, Bureau of Mines, salt Lake City, UT. 2 INTRODUCTION The Bureau of Mines conducted research potassium used in fertilizers. Current on techniques for recovering potash val­ domestic demand for potash is 6.0 million ues from high-insoluble-slimes-bearing tons of K20. However, only approximately domestic carnallite ores. In the first 1.8 million tons of K20 are produced in phase of the study, two techniques were this country. The balance of the domes­ devised: (l) a method where the insolu­ tic demand is supplied by Canadian ex­ ble slimes were depressed during potash ports. 4 About 84 pct of the domestic flotation and (2) a method where insolu­ production is from bedded deposits in the ble slimes were removed by flotation pri­ Carlsbad, NM, area. This area has been a or to potash flotation. Reports of the source of high-grade sylvinite (a mixture first phase of the research3 described of KCl and NaCl) ores during the last 40 batch- and locked-cycle, bench-scale years. Depletion of high-grade ores testing of the two techniques. This re­ makes low-grade sylvinite and carnallite port describes results of the second ores major potash sources. Insoluble phase of the research: (1) operation of slimes in these ores create processing a continuous 100-lb/h flotation unit de­ difficulties. Discarded insoluble slimes signed to technically evaluate the two occlude valuable potash minerals and methods and (2) an economic evaluation of adsorb significant amounts of amine col­ t he two me thods • lectors used in flotation. Methods com­ patible with existing commercial potash Potassium is one of three basic chemi­ processes must be devised to remove or cal ingredients used for promoting plant treat these insoluble slimes before po­ growth. Refined potash salts, obtained tash flotation to improve potash recover­ from ei~her ores or brines, are the only ies and reduce processing costs. economically significant sources of ACKNOWLEDGMENT The authors wish to acknowledge cooper­ Carlsbad, NM, for providing the carnal­ ation from the National Potash Corp., lite samples used in this investigation. SAMPLE DESCRIPTION Over 25 tons of minus 4--in, run-of-mine kainite (KCI·MgS04 ·3H20), leonite (MgS0 4 ore was received for testing in the con­ ·K2S04 ·4H20), and polyhalite (MgS04 ·K2S04 tinuous flotation unit. A partial chemi­ ·2CaS04·2H20) were also present. The cal analysis of the ore is given in table 1. Petrographic and X-ray diffraction TABLE 1. - Chemical analysis of carnal­ analysis of the carnallite ore indicated lite ore that halite (NaCI), ' carnallite (KCI·MgCI 2 wt pct ·6H20), and sylvite (KCI) were the most abundant minerals. Minor amounts of K2 O. " " " " " " " " " " " " " " " " " " " " " " " " " " " " 12.8 Na" " " " " " " " " " " " " " " " " " " " " " " " " " " " " " 23.4 3Foot, Jr., D. G., and J. L. Huiatt. Mg " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " 4 Direct Flotation of potash From Ca" " " " " " " " " " " " " " " " " " " " " " " " " " " " " " • 2 Insoluble-Slime-Bearing Sylvinite and 8°4 " " " " " " " " " " " " " " " " " " " " " " " " " " " " " 2.5 Carnallite Ores. Pres. at AIME Annual C1 2 " " " " " " " " " " " " " " " " " " " " " " " " " " " " " 46 Meeting, Chicago, IL, Feb 22-26, 1981, Water insolubles •••••.•••.•••••• 3.5 preprint 81-74, 8 pp. Foot, Jr., D. G., C. E. Jordan, and 4Searls, J. P. potash. Sec. in Bu­ J. L. Huiatt. Direct Flotation of potash Mines Mineral Commodity Summaries, 1983, From Carnallite. BuMines RI 8678, 1982, pp. 118-119. 11 pp. 3 water-insoluble fraction of the ore con­ through 3/4-in size using a hammer mill. tained abundant magnesite, chlorite, and The ore was screened at 10 mesh, the lib­ illite. Some carnallite and sylvite con­ eration size for the sylvite and tained minor amounts of occluded hema­ carnallite minerals. The oversize was tite, which gave the minerals a distinct processed in a rod mill. Dry screen red color. analysis of the crushed ore, given in ta­ ble 2, indicated that 23.4 pct of the Carnallite ore was prepared for feed to total weight was coarser than 10 mesh. the continuous flotation unit by crushing CONTINUOUS FLOTATION UNIT DESIGN AND OPERATION DESIGN FOR INSOLUBLE-SLIMES FLOTATION circuit. Insoluble-slimes flotation rea­ gents (Superfloc 127 and Aeropromoter Circuit design was based on data ob­ 870)5 were added ahead of flotation in tained from bench-scale, locked-cycle a Denver No. 7 Sub-A flotation machine. testing. The flow diagram presented in No conditioning was required. Total appendix figures A-I through A-5 was insoluble-slimes flotation time was ap­ adopted for the method using insoluble­ proximately 10.5 min. slimes flotation. Minus 3/4-in material was fed to a 10-mesh vibrating screen. Deslimed pulp was conditioned for 2 min Screen oversize was processed in a rod with MRL-201 insoluble-slimes blinder and mill operating at 50-pct-solids pulp den­ an emulsion of Armeen TD and Barrett's sity. The screen undersize was slurried oil. Conditioned pulp was fed to a bank with saturated brine and mixed with of three Denver No. 5 Sub-A flotation rod mill discharge. The combined slurry machines. Potash rougher flotation time