Flotation

Measuring the specific gravity of a pulp in concentrating plants is a relatively simple procedure, but the desired accuracy is often difficult to attain. Many plants use the system of weighing a known volume of the pulp on a scale. In many cases, this method is quite accurate, but obtaining a true sample presents quite & problem.

The first density meter was made of glass tubing using rubber tubing for connections, with pinch valves for regulating the volume of air to each bubble tube through the sight bubblers. Our first problem became very apparent. Even though we were using low pressure air (3 psi), we found that the system had to be absolutely leakproof. This laboratory model was finally redesigned, using iron pipes and copper tubing.

In the laboratory, we found that the density meter gave us reliable results on liquids of various densities and, also, on pulps kept in suspension by small agitators. Our next problem was how to sample a moving pulp. We found that by bleeding off a portion of the flow through a 2-inch pipe, we were able to get a representative sample of the pulp to be measured.

The density meter and sampler were installed in the plant.

The question of automation of concentrator operations with computer control is under increasing consideration. Some of the problems involved will be discussed from the viewpoint of the availability of the requisite, detailed knowledge of the unit operations. The justification for full-scale automation of a mill must ultimately be economic an increase in profitability over and above the cost of instrumentation and development.

For the sake of clarity, a hypothetical porphyry copper mill will be used to illustrate the problems. Its flowsheet will involve: mine-crushing-storage-grinding and classification flotation-product de-watering and disposal. Ore supply and crushing are invariably discontinuous, and connected to grinding-flotation indirectly through storage. Hence, the direct tie-in of crushing to a continuous control system for grinding/concentration may be difficult and probably unnecessary.

Storage after crushing brings up the basic problem of ore supply uniformity. The need for elaborate control methods is due primarily to the existence of unpredictable and uncontrollable disturbances to a process which affect its performance. If there were no such disturbances, a process once set to run at an optimum set of conditions would continue to do so, barring equipment deterioration. In the case of beneficiation plants, the major disturbance is the quality of the ore supply as

The essential foundation upon which to build an effective marketing program in industrial minerals is the ability to produce competitively mineral products meeting precise customer specifications and to ship them promptly and on schedule. Without this prerequisite, all the other factors in a second marketing program creative sales management, energetic solicitation, advertising, technical service, new products, etc. are without meaning. The primary image to be created in the mind of customers is that of the reliable and prompt supplier of mineral products at competitive prices and of standard, uniform quality.

Product Specifications

Product specifications include all or part of the following;

1. Chemical analysis
2. Physical properties (screen analysis, color, bulk density, viscosity, hot strength, green strength, shrinkage, oil absorption etc.)
3. Freedom from specific objectionable impurities
4. Method of packaging (bulk, multiwall bags, pallets, hopper cars, box cars, truck)

Item number 1 above is normally straight-forward. Item number 2 very often becomes an impenetrable jungle, in which case selling and buying become a mixture of art, science, economics, habit, opinion, idiosyncracy, and prejudice. As an example, observe the manufacturer who, in spite of well developed and standard techniques for screen analyses, performs his screen analysis by hand methods, weighing out a standard quantity onto

Flotation Plant Instrumentation can help recover ilmenite from the finer size fraction of the ore that cannot foe efficiently treated in the main gravity-magnetic separation process. It was later expanded to handle the regrind middlings from the tables wetherill magnetic separators.

The flotation feed is conditioned at high density with tall oil, fuel oil, sodium fluoride, frother, and sulfuric acid. There are two parallel banks of rougher flotation cells, followed by one scavenger bank, and one bank each of cleaner and recleaner cells. The scavenger concentrate, cleaner tails, and recleaner tails are pumped back to the head of the rougher cells. The final concentrate is thickened, filtered, and blended with the wetherill ilmenite for shipment in open hopper cars.

The diversion of the feed out of the conditioner circuit had an adverse effect on the flotation operation. For a period of a half to three-quarters of an hour after sampling the circuit would be erratic because the reagents added to the conditioners, were not stopped while the feed was taken out and therefore a surge of feed with excess reagents would come through and upset the circuit balance. One sample every two hours could not keep up with the surges in the

Floating “fines” differs from floating “sands” because the fines have a much larger surface area compared to their mass. The forces that arise from this large specific surface are the key to under standing the behavior and treatment of fine particles. Though the nature of these forces is not thoroughly understood, enough work has been done to give a qualitative picture of what is happening in a flotation cell. It is the purpose of this chapter to re-examine some of the more recent theoretical work and-to indicate its importance.

Dynamic Double Layer

Consider a submerged air bubble in an aqueous solution containing an ionogenic surfactant. The bubble is at rest with respect to the fluid. At the surface of the bubble, i.e., at the air water interface, there is a transistion region. At this interface there will be an excess of the surface-active compared to its concentration in the bulk liquid. The adsorbed constituent carries a charge, negative. The surfactant adsorbs so that, the charged end remains in the water and the hydrocarbon end into the air. Because of the adsorption, of this ionogenic agent, the surface of the bubble contains a net charge on the surface. This charge draws

This paper presents the results of a study in which commercially available forms of various reagents were used as flotation frothers. Flotation procedures which would conform in general to those employed in a large number of commercial coal flotation plants were utilized.

The reagents employed have been grouped into the following chemical classes;

1. aliphatic alcohols
2. terpines
3. glycols (synthetic water-soluble alcohol type frother)
4. neutral hydrocarbons
5. phenols
6. mixture of aliphatic alcohols with neutral hydrocarbons

Following grinding, the coal was transferred to a Fagergren laboratory flotation cell and diluted to the flotation pulp density, which was normally 9.7% solids. Impeller speed was 1520 rpm and the temperature of the pulp was maintained between 24 – 26°C for all tests. The pH was maintained between 7.2 – 7.4.

Close examination of the data does show that methyl isobutyl carbinol (MIBC) is superior to the other reagents tested on an ash-yield basis. However, the data also show a number of other reagents which closely approach the results obtained with MIBC.

The data were replotted in graphs showing yield and ash against frother dosage and from these graphs, the dosages required for yields of 70, 80, and 90% were read. It is apparent from the data that, although the reagent

The flotation behavior of quartz in the presence of alkyl ammonium acetates as a function of alkyl chain length has been interpreted in terms of hemi-micelle formation at the solid-liquid interface. The van der Waals cohesive free-energy that is responsible for hemi-micelle formation has been found from these results to be 1.02 kT per CH2 group.

Basic Principles

In 1955, the marked changes in electrokinetic potentials of quartz in dodecylammonium acetate (DDA) solutions were postulated to result from the association of adsorbed collector ions into two-dimensional aggregates, called hemi-micelles.

In dilute solutions alkyl ammonium and related salts behave as ordinary-strong electrolytes, but at a certain concentration there is a marked change in physical properties of the solutions, e. g., in equivalent conductance, transport number, freezing point lowering, and viscosity. To account for these phenomena, McBain introduced the concept of micelles, which are aggregates of long chain ions. It is believed that the ionic heads of the constituent ions of the micelle are in contact with water, whereas the nonpolar groups turn away from it and are in contact with each other.

Theoretical treatments of micelle formation by Shinoda and Phillips and others lead to the following expression for the concentration at which

In the operation of today’s large scale ore-processing mills, it is extremely important to have some way of making an objective evaluation of the performance of the available flotation reagents. While Reagent Testing the use of Statistics is necessary for Result Analysis.  Attempts to do this may often result in inconclusive findings since the magnitude of the difference in the mill results for any two reagents is apt to be quite small compared to the variability introduced by the process and the analytical procedures used to measure them. In cases where two reagents give vastly different mill results, evaluation becomes a simple matter and as such deserves no further attention here. A question of primary concern, however, is how a mill can go about evaluating the performance of two reagents which may, for example, give a difference of only 0.0017, copper in the tailings or of 0.2% in copper recovery. The casual observer may feel that such small differences may be of little importance, but in a mill whose daily tonnage is between 30 and 40 thousand, these differences could mean a substantial savings.

Any comparison which is made regarding the metallurgical performance of two reagents will be made on

For the flotation of mineral solids the fluids of interest are water and air, the latter partially or completely saturated with water vapor. A necessary condition for application of the process is a small contact angle, usually obtained by the selective effect of specific reagents on one or more ore minerals. A number of exceptions to this requirement have been recognized, the evidence being either flotation or manifestation of contact angle without reagent treatment of the mineral.

Experimental Procedures

The mineral specimens, molybdenite (Ontario) stibnite (Portugal and Japan) were obtained from Ward’s Natural Science Establishment, Rochester, New York, and the graphite (Ceylon) from Asbury Graphite Mills, Asbury, New Jersey. Cleavage specimens of molybdenite and graphite were gifts of the American Museum of Natural History and the Geology Department, Columbia University.

Contact angles were measured with a Leitz Goniometer which is a modification of the original Taggart-Taylor Ince bubble machine Each value reported is the average of at least a dozen measurements. Flotation test data were obtained in a modified Hallimond tube with a fritted glass disk of medium porosity to provide air flow, a glass coated magnetic stirrer and a glass flowmeter.

Experimental Results

The effects of pH variation on contact

The Coal Research Bureau of the School of Mines at West Virginia University, using a modified design of a Russian flotation device, was able to obtain a clean coal product containing 7.64 percent ash with 94 percent yield and 97 percent coal recovery. This favorable performance was obtained with the semi-pilot scale flotation cell operating as a simulated three stage unit on slurry taken from the fine coal circuit of a coal preparation plant.

This experimental device, consisting of a sheet metal cyclone-like unit mounted on a U-shaped uplift pipe, uses a combined flotation and cyclone action to beneficiate the minus 14 mesh partially cleaned feed product. In addition to providing comparable analytical results, the airlift-cyclone possesses other attractive features among them being a low capital expenditure, utilization of moderate plant floor space, efficient operation on high density feed slurry, and absence of moving parts.

The Coal Research Bureau’s semi-pilot scale airlift-cyclone is constructed of standard 1½ inch diameter U-shaped pipe with a 0.77 cubic foot capacity integrally mounted cyclone unit made from 18-gauge sheet metal and 10-mesh wire screen. Air is injected into the uplift pipe through a standard ½