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Flotation Equipment is realized under highly turbulent flow conditions

April 16, 2018 by mixingtank  

Flotation Equipment is realized under highly turbulent flow conditions, so that turbulence may be process-determining, too. Because the principles of turbulent multi-phase flow have still not been fully worked out, one needs integral quantities to characterize the state of turbulence indirectly.

Models in which the cell contents are partitioned into distinct pulp and froth phases are reviewed critically. The nature of the mixing within the phases is discussed. Multiphase models describing froth column concentration gradients and pulp residence time effects are mentioned. It is shown that at steady state multiphase models can be reduced to the two-phase case. Deficiencies in the models and topics requiring further development are outlined.

Computational domains of Flotation Machine are large, and flow physics are complex involving multi-phase flow turbulence. Even two-phase flow simulations of flotation machines are time consuming and require large computational resources. Some approaches have been used to reduce computational costs for two-phase flow; see, for example, the approach by Tiitinen et al., where sector based simulations were used to reduce the number of grid nodes. Bubble size is one of the most important parameters that affect the air holdup of the pulp phase. A spectrum of bubble sizes exists in flotation machines depending on air flow rate and turbulence parameters. To predict such bubble size distribution, another set of equations that describes a population balance can be solved in the course of CFD simulation. This approach increases the computational demands where transport equation for each size group has to be implemented. A more feasible approach is to conduct a parametric study for different uniform bubble sizes to study their effects on air holdup and rate constant.

 

Froth flotation is extensively used in mineral processing

April 12, 2018 by mixingtank  

Flotation Equipment of native or free gold in a low sulfide ore is often asked about by miners, and can be done in theory, but in practice it is virtually never done commercially. Problems with free gold flotation in a low sulfide ore include the high density of the free gold and the low concentration of the gold in the ore-the low concentrations make for an unstable froth. However, flotation of gold-bearing sulfides such as pyrite or arsenopyrite are done very commonly and can be an alternative treatment to cyanide in areas where cyanide is not permitted.

A very common cyanide-free, gold milling treatment includes a gravity circuit to capture the coarse free gold and a bulk sulfide float to capture any gold in the sulfides. This type of system can give recoveries nearly as high as cyanide in some cases. Dealing with the sulfides is the drawback as finding a ready smelter for smaller amounts of concentrates can be difficult. In some cases, sulfide concentrates produced in this type of circuit can be shipped and treated with cyanide off-site.

Froth flotation is extensively used in mineral processing and can be adapted to a wide range of different metal recovery systems and even some non-metal industrial mineral recoveries since various chemical treatments can selectively alter mineral surfaces to give them the necessary properties for flotation. Froth flotation, properly done, can have excellent recovery rates, with mineral capture efficiencies of up to 90 or 95% being common. The process also produces concentration ratios of feed to concentrates of 10 to 1 and sometimes even higher. The overall costs are normally quite reasonable as compared to other options and so this method is very popular and worth knowing about for the prospector and miner.

Investigations into the Flotation Machine behaviour of single minerals, mineral mixtures and ores at the CSIRO Division of Mineral and Process Engineering have led to the development of sophisticated laboratory flotation testing equipment. Both routine and complicated flotation investigations can be conducted in a precise and reproducible manner using procedures and equipment that have been refined over many years of conducting careful batch flotation testwork. Several important advances in flotation research can be attributed to changes in testing procedure developed as a consequence of the availability of this equipment. The flotation cell and ancillary equipment is described and associated developments and techniques discussed.

 

Improvements in agitation equipment lead to many positive improvements

April 11, 2018 by mixingtank  

Without question, improvements in commercial Agitation Equipment have lead to many positive improvements in the food processing industry over the years.

Any number of different substances require proper mixing techniques to ensure a quality product at the end of the production run. While having the right agitation drive, motor, shaft and impeller for your application are essential, the agitation tank is an incredibly important part of the equation. Without the right tank, your mixing process will be skewed, creating significant problems down the line. This applies to all industries that require liquid blending, solids suspension, dispersion, dissolution, emulsification, heat transfer and other applications. How do you ensure that you have made the right selection in an agitation tank?

The type, size and shape of the tank that you use should be dependent on the viscosity of the substance that you need to mix. However, it should also depend on other factors. For example, if there is a considerable amount of air trapped within the mixed substances (for instance, within slurry), then you need to have an agitation tank shape, size and agitation frequency that will release the air, rather than trapping more within the substance. Too much air (or too little) can be significantly problematic, and can ruin an entire batch.

Another important concern with agitation tank construction is that they should keep your mixture in suspension prior to being pumped out for use in other areas. This will require that the mixer operate at the correct speed and move sufficient volume that the mixture is able to retain your required viscosity without fears of solidification or liquefaction of the substance. It needs to remain at the optimum viscosity for future use. Too much solidification or liquefaction will render your production process problematic, or even ruin the batch entirely.

You will also need to ensure that you have the right mixing equipment mounted to your agitation tank. The right size and shape impeller is vital to keeping your mix in suspension. However, the impeller shaft is also an important consideration. Too thin of a shaft can lead to premature wear and breakage, while too thick of a shaft can also cause issues. The agitation drive is also important, as is the motor-you need sufficient torque and power to keep your mixture in suspension, without worrying that prolonged use will lead to premature wear on the motor or the drive.

The stream which exits the pretreatment enters the primary treatment process which may include clarification by settling, clarification by floating (dissolved, induced air floatation), and physio-chemical treatment (lime addition, phosphate or heavy metal removal). Solids removed during the primary treatment process are taken to sludge Thickening Equipment, sludge dewatering, and final disposal. The water stream which exits the primary treatment process is fed to secondary treatment.

Slow moving agitators that work in the laminar

April 10, 2018 by mixingtank  

Agitation Equipment (excessive motor or verbal activity) can be associated with schizophrenia or bipolar mania, and can further escalate into aggressive behavior and potentially lead to injuries in patients and staff. Medications used to treat agitation include antipsychotics and benzodiazepines, usually administered intramuscularly when rapid action is desired. Loxapine, a first-generation antipsychotic, has recently been reformulated into an inhaled powder that allows for direct administration to the lungs, resulting in rapid absorption into the systemic circulation. Administered via a single-use device, inhaled loxapine was tested in randomized controlled trials in agitation associated with schizophrenia or bipolar mania; doses of 5 mg and 10 mg were found to be efficacious, with an apparent dose response. Separation from placebo on the PANSS-EC was as early as 10 minutes postinhalation, the first time point where this was measured. Dysgeusia was the most commonly encountered spontaneously reported adverse event. Adverse events related to extrapyramidal symptoms and akathisia were relatively rare. Spirometry studies identified the potential for bronchospasm particularly in persons with asthma. Because of concerns over pulmonary safety, inhaled loxapine is restricted to use in hospitals and patients need to be prescreened for the presence of pulmonary disease, as well as monitored for signs and symptoms of bronchospasm for 1 hour postdose administration, as per a Food and Drug Administration-mandated Risk Evaluation and Mitigation Strategy.

Conventional, mechanically agitated, stirred tank reactors may be used for either batch or continuous processes, though the design and operating constraints are different in the two cases. Low viscosity fluids can usually be mixed effectively in baffled tanks with relatively small high speed impellers generating turbulent flows, while high viscosity (typically above about 10 Pa s) and non-Newtonian materials require larger, slow moving agitators that work in the laminar or transitional flow regimes. It is convenient to classify impellers as radial or axial pumping depending on the flow they generate in baffled tanks.

The clinical management of agitation associated with schizophrenia or bipolar mania includes behavioral and psychological techniques, as well as the use of nonspecific sedating agents such as benzodiazepines and/or antipsychotics that also at the same time would be expected to treat the underlying psychiatric condition. Goals of treatment of agitation include calming the patient as rapidly as possible, decreasing the likelihood of harm to self or others, allowing diagnostic tests or procedures to take place, attenuating psychosis, and decreasing the need for seclusion or restraint (a time of high risk for patients and staff injury). Sleep, in itself, is not desirable when evaluating the patient; excessive sedation results in the need for constant observation, assistance in toileting, and excessive burdens being placed on nursing staff resources.

In summary, the literature acknowledges that people with dementia need protection from both overstimulation and sensory deprivation. Empirical research is lacking, however, to establish that interventions designed to create a balance between high-and low-arousal states yield positive outcomes. Accordingly, our purpose in this study is to test the effectiveness of the BACE intervention in decreasing agitation.

The nonstandard design problem that has to be solved to be able to build such equipment was solved using a step-by-step approach: the first step was to build a large laboratory Thickening Equipment unit and determine the parameters of the process under laboratory conditions; the second step entailed constructing a three-dimensional hydrodynamic model that could be used to build a specimen suitable for factory tests.

Flotation equipment varies widely from one technology to another

April 9, 2018 by mixingtank  

Depending on the separation efficiency requirements, a system can be designed to fit the specific need of an offshore application. “There are enough options to design Flotation Equipment based on the desired level of performance required, what a company is willing to invest, and the amount of space that can be sacrificed,” Walsh said. Some other variations of flotation parameters in the industry are total cost, schedule, operability, and after-sales service. However, separation efficiency remains the most difficult to predict for an operator or designer, Walsh said. In relationship to efficiency and overall cost, flotation equipment varies widely from one technology to another.

The poppy seed recovery test is a simple and inexpensive means of determining the effectiveness and consistency of any particular botanical flotation system. By adding a known number of charred poppy seeds (Papaver somniferum) to a sample before it is processed, archaeologists can check for loss, damage, and inter-sample contamination. Different systems, equipment, methods, and personnel tested since 1976 yield recovery rate percentages ranging from 6% to 98%. Such percentages provide a basis of comparison among widely differing flotation systems and enable the archaeologist to decide which flotation system to use under particular logistical constraints.

Froth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in mineral processing, paper recycling and waste-water treatment industries. Historically this was first used in the mining industry, where it was one of the great enabling technologies of the 20th century. It has been described as "the single most important operation used for the recovery and upgrading of sulfide ores". The development of froth flotation has improved the recovery of valuable minerals, such as copper- and lead-bearing minerals. Along with mechanized mining, it has allowed the economic recovery of valuable metals from much lower grade ore than previously.

A flotation process is one method used throughout the industry to recover gold. It's a very cost-effective method for concentrating gold, and is a desirable process used for the upgrading of low-sulphide and refractory ore for further gold recovery treatment. Froth flotation is a process used to selectively separate hydrophobic materials from hydrophilic materials. Air bubbles can only stick to the desired mineral particles if they can displace water from the mineral surface, and can only continue to support the mineral particles at the surface if they can form a stable froth achieved by using floatation reagents.

Flotation Machine is a secondary process installed downstream of primary separators. It is typically capable of capturing smaller drops than primary separation and hydrocyclones. “The reject flow rate and oil concentration must be accounted for in the overall process flow,” Walsh said. This means that the separators must be large enough to handle the flotation reject flow rate. According to Walsh, the preferred process lineup ultimately allows the reject from a primary separation to capture the oil contained in the oily water recycle. By routing flotation reject to a slop tank for chemical treating and settling time, operators can reduce recycled chemical. This also provides additional oil/water separation before recycling into the rest of the system.

The key to ensuring the quality of the flotation product

April 8, 2018 by mixingtank  

Flotation is used to separate the ash-forming mineral matter and the carbonaceous materials of fine coal below 0.5 mm in size. This process is widely applied in countries such as China, USA, Australia, Canada and India. Flotation columns are extensively studied and used as an efficient coal Flotation Equipment due to many advantages, including the simplicity of construction, lack of moving parts, and low energy consumption, among others. According to the different structures and separation principles, flotation columns mainly include the Leeds column, Microcel column, packed column, Flotaire column, hydrochem column, Jameson column and cyclonic micro-bubble column.

As part of a systematic programme for correlating mineral engineering process variables1,2, flotation machines are now being investigated. There is no need to stress the engineering importance of the flotation process. First applied more than fifty years ago for the recovery of fine sulphide minerals from Australian gravity plant tailings, to-day it is the only method for treating the major base metal sulphide ores, and is becoming of increasing importance for non-metallic ores and coal. As a mineral engineering operation, it is often second only to fine grinding in power consumption. Despite this, empiricism largely prevails from choice of equipment to control of process variables.

Hydrodynamic and gas dispersion parameters, obtained from industrial flotation cells on South African Platinum concentrators, are reviewed in this paper. Hydrodynamic results show that power intensities are slightly higher than those typically observed in industrial flotation cells while impeller tip speeds and Froude numbers are within the range found in industrial cells. Gas dispersion results show that air flow rates, air flow numbers and air flow velocities vary significantly from cell to cell but are within the range typically found in industrial flotation cells. Gas dispersion results also show reasonably broad variations in bubble size, gas holdup and superficial gas velocity, although bubble surface area fluxes are shown to lie within a fairly narrow range of 50–70/s.

Although both the froth depth and reagent dosage significantly influence the result of flotation, these variables are typically not adjusted simultaneously due to the coupling between variables and the hysteresis of the flotation process. For coal preparation plants that contain a distributed control system (DCS), operators typically determine which variable must be adjusted in real time and change the set point according to observation and experience. In the actual operation process, with the aim of ensuring product quality, we prefer to reduce the reagent dosage rather than adjust the froth depth, and we prefer to adjust the froth depth rather than increase the dosage. The coordinated adjustment of these two variables is the key to ensuring the quality of the flotation products and reducing the costs. To select an appropriate controller within a reasonable time frame, the hybrid model should be able to execute a reasonable and timely switch of the controllers using auxiliary variables. Thus, controllers for different manipulated variables are used according to different condition parameters. In this case, the determination of switching points is critical.

In Flotation Machine, the operation takes place in a highly turbulent flow. Therefore, the modelling as well as the optimization of a flotation process necessitate the application of essential results of the statistical turbulence theory, where an extensive simplification of the complicated laws is typical for the application in processing. Three effects of turbulence are important in flotation: the turbulent transport phenomena (suspension of particles), the turbulent dispersion of air and the turbulent particle–bubble collisions. While the transport phenomena are mainly caused by the macroturbulence, the microturbulence controls the two last-named microprocesses. In the paper a brief introduction of the theoretical background is given as far as it is necessary for modelling. The effect of turbulence damping by fine particles is also discussed. Models of the microprocesses air dispersion and particle–bubble collisions are presented, and it is clearly demonstrated that the particle–bubble attachment almost exclusively occurs in the zone of high energy dissipation rates, i.e., in the impeller stream. Further on, it is shown that the entrainment of fine particles into the froth lamellae is a result of the suspension state and, therefore, can be influenced by the design of the turbulence generating system (impeller–stator system). Finally, it is demonstrated that there is no feasibility to achieve optimum hydrodynamics for all particle sizes simultaneously. For coarse particle flotation, the power input should be minimized (generation of coarser bubbles; stronger buoyancy and lower turbulent stresses acting on the particle–bubble agglomerates!). In contrast to this, fine particle flotation requires high turbulent collision rates, i.e., a higher power input.

Should computer software be classified as an equipment

April 4, 2018 by mixingtank  

In accounting terms, an intangible asset is something of value that is not of physical nature. On the other hand, property, plant and Classifying Equipment are just as the name suggests. PPE refers to physical long-term assets, such equipment that is vital to a company's operations and has a definite physical component. Under most circumstances, computer software is classified as an intangible asset because of its non physical nature. However, accounting rules state that there are certain exceptions that permit the classification of computer software as Property Plant and Equipment (PPE).

Some of the statements that have rules concerning the classification of software include: Financial Accounting Standards Advisory Board (FASAB) Statement of Federal Financial Accounting Standards (SFFAS) No. 10, Accounting for Internal Use Software; Governmental Accounting Standards Board (GASB) Statement No. 42, Accounting of Costs of Computer Software Developed or Obtained for Internal Use; There are two general rules that are applied to determine whether or not software must be capitalized as PPE or expensed. If software meets the criteria of property, plant and equipment, meaning it will be used in providing goods and services, then it can be classified as PPE. For example, a computer company would capitalize computer software as PPE because it is used in a major part of the company's operations that is intended to provide profits. However, software that provides a means for a warehouse to efficiently perform inventory management duties would not be incorporated as PPE. The second capitalization criterion is based on cost. If an individual copy of the software package costs more than $100,000 it is classified in the PPE category. The software would then be amortized, like other assets, over its useful life. However, as a general rule, if two software copies are purchased for $150,000 they are accounted for as intangible assets. If the two preceding conditions are not met, then the software, whether purchased or created internally would be considered an intangible asset. The basic nature of the business and the stage of software development also play a significant role in the classification decision.

For some years now, growing numbers of strategy instructors at business schools worldwide have been transitioning from a purely text-case course structure to a more robust and energizing text-case-simulation course structure. Incorporating a competition-based strategy simulation has the strong appeal of providing class mem- bers with an immediate and engaging opportunity to apply the concepts and analytical tools covered in the chapters and to become personally involved in crafting and exe- cuting a strategy for a virtual company that they have been assigned to manage and that competes head-to-head with companies run by other class members. Two widely used and pedagogically effective online strategy simulations, The Business Strategy Game and GLO-BUS.

Moreover, the retail industry's success is dependent on market forces that make it experience more fluctuations than perhaps any marketplace. This report attempts no only to answer the areas mentioned below, but also to explore the economic factors and their implications to the retail industry such as: an increase of cautious consumer spending, increased competition, varying consumer fashion taste, and the global financial crisis. Although clothing is a basic need, people have wide discretion as to when they update their wardrobes and how much they spend. When times are good, apparel sales are usually brisk, but during periods of economic uncertainty and contraction, clothing is an area where people can easily trim outlays.

Hydrometallurgy Equipment consists of a series of separations that begins with leaching of ores or concentrates and ends with fairly pure, marketable cathodes, powders, or compounds recovered from solution. Intermediate separations are conducted to recover by-products, isolate impurities, or enhance the productivity of subsequent unit operations. There is a constant search for new technologies that will: (1) increase the productivity of parts of the process; (2) reduce operating costs; (3) reduce adverse environmental impact of effluents from the process; and (4) (in the case of the need for new plant capacity) develop new, simpler, cleaner, more economic processes.

Passes hydrometallurgy equipment are being more widely used

April 2, 2018 by mixingtank  

"Material" means property that may be consumed or expended during the performance of a contract, component parts of a higher assembly, or items that lose their individual identity through incorporation into an end-item. Material does not include Classifying Equipment, special tooling and special test equipment. The qualifiers for the definition of material are: incorporated, consumed, or expended. The descriptors include parts, assemblies, components, raw and processed materials, liquids, and other items. Examples of material are nuts, bolts, screws, washers, gasoline, oil, paint, solvents, chemicals, wire, switches, circuit boards, cable, sheet metal, bar stock, copper tubing, etc. Parts may also include more complex items such as starters, fuel injectors, radios, radar, sonar, and jet engines provided they are to be incorporated into the next higher assembly of the finished end item.

Most writers classify regime types with reference to both their dispositional properties (whether there is a president and/or a prime minister, whether or not they are popularly elected and whether or not they serve for a fixed term) and their relational properties (the actual patterns of executive politics in the political system). It is argued that this juxtaposition of dispositional and relational properties creates a conceptual ambiguity. As a result, it is concluded that classifications of regime types should be made on the basis of either dispositional or relational properties but not both together. It then shows that writers who classify regime types with reference to relational properties are likely to make highly contestable assumptions about how power is actually exercised. This is because the question of where executive power lies in a particular country is often subject to not just one incontestable interpretation but to a number of contestable and mutually exclusive interpretations. Therefore, it is concluded that the classification of regime types should be made with reference to dispositional properties alone.

This significant issue-the unauthorized disclosure of classified intelligence—has been extraordinarily resistant to correctives. It will never be solved without a frontal assault on many levels, and an essential one is US law. It advocates a range of legal solutions that have not been tried before, some of which are controversial. The views expressed here are my own.

"The advantage of having classifieds linked to a social network is that you know something about the seller," said Charlene Li, an analyst at Forrester Research. "You are less likely to buy a lemon from someone who is a friend of yours."

With each year that passes Hydrometallurgy  Equipment are being more widely used to recover base metals from ores and  concentrates. Generally these processes involve liquid-solid separation of  metal-bearing liquors from barren residues. This may be done by countercurrent  decantation, thickening and filtration, or filtration or centrifuging only.  Choice of method is governed by chemical and physical characteristics of the  pulps; cost of labor, power, materials, and waste disposal; and even by the  amount of capital available when building plans are under way. Since all these  controlling factors change with time and location and with technological  advances, the separation method must be re-evaluated when new plants or  expansion programs are contemplated.

Flotation is an important part of coal preparation

March 29, 2018 by mixingtank  

Selecting Flotation Equipment is like buying a vehicle, Walsh said. Proper selection depends on the specific needs of a project and the equipment features. There are models that provide 95% separation efficiency. "This equipment is very large and heavy," Walsh said. He said that these systems have been installed offshore, but with the penalty of weight and space. More compact systems are available that provide only 50% separation efficiency. There is also equipment that provides separation efficiency in the range of 20% to 40%, which is extremely compact and relatively inexpensive.

Flotation has promoted a wide scope of research activities ranging from fundamental chemistry and hydrodynamic studies to studies of industrial operations. In general, fundamental studies have been mainly related to ideal situations. In recent years, however, large efforts have been focusing on achieving a better insight into the actual sub-processes provided by the development of new and more sophisticated instrumentation. Since the massive incorporation of flotation columns, around 15 years ago, a renewed interest in flotation fundamental studies, process modelling and new cell designs have been observed worldwide. The key role of the froth has been recognized as an independent and sometimes rate limiting process step. Thus, separation of pulp and froth process stages seems the most appropriate in terms of process modelling, diagnostic, design and scale-up purposes.In relation to Flotation Equipment development, until the middle of the 1970’s, only the sub-aeration mechanical cells were dominant. Since the 1980’s, the use of pneumatic cells and forced air mechanical cells has emerged strongly. Also, in the last decade, flotation equipment has shown a dramatic increase in size, reaching values of 200m3 in unitary mechanical cells and more than 300m3 in columns.

Flotation is an important part of coal preparation, and the flotation column is widely applied as efficient Flotation Equipment. This process is complex and affected by many factors, with the froth depth and reagent dosage being two of the most important and frequently manipulated variables. This paper proposes a new method of switching and optimizing control for the coal flotation process. A hybrid model is built and evaluated using industrial data. First, wavelet analysis and principal component analysis (PCA) are applied for signal pre-processing. Second, a control model for optimizing the set point of the froth depth is constructed based on fuzzy control, and a control model is designed to optimize the reagent dosages based on expert system. Finally, the least squares-support vector machine is used to identify the operating conditions of the flotation process and to select one of the two models (froth depth or reagent dosage) for subsequent operation according to the condition parameters. The hybrid model is developed and evaluated on an industrial coal flotation column and exhibits satisfactory performance.

Flotation is a complex multifaceted process that is widely used for the separation of finely ground minerals. The theory of froth flotation is complex and is not completely understood. This fact has been brought many monitoring challenges in a coal processing plant. To solve those challenges, it is important to understand the effect of different parameters on the fine particle separation, and control flotation performance for a particular system.

In Flotation Machine, the operation takes place in a highly turbulent flow. Therefore, the modelling as well as the optimization of a flotation process necessitate the application of essential results of the statistical turbulence theory, where an extensive simplification of the complicated laws is typical for the application in processing. Three effects of turbulence are important in flotation: the turbulent transport phenomena (suspension of particles), the turbulent dispersion of air and the turbulent particle-bubble collisions. While the transport phenomena are mainly caused by the macroturbulence, the microturbulence controls the two last-named microprocesses. In the paper a brief introduction of the theoretical background is given as far as it is necessary for modelling. The effect of turbulence damping by fine particles is also discussed. Models of the microprocesses air dispersion and particle-bubble collisions are presented, and it is clearly demonstrated that the particle-bubble attachment almost exclusively occurs in the zone of high energy dissipation rates, i.e., in the impeller stream. Further on, it is shown that the entrainment of fine particles into the froth lamellae is a result of the suspension state and, therefore, can be influenced by the design of the turbulence generating system (impeller-stator system). Finally, it is demonstrated that there is no feasibility to achieve optimum hydrodynamics for all particle sizes simultaneously. For coarse particle flotation, the power input should be minimized (generation of coarser bubbles; stronger buoyancy and lower turbulent stresses acting on the particle–bubble agglomerates!). In contrast to this, fine particle flotation requires high turbulent collision rates, i.e., a higher power input.

Liquid-solid separation factors in hydrometallurgical leach circuit design

March 26, 2018 by mixingtank  

With each year that passes Hydrometallurgy Equipment are being more widely used to recover base metals from ores and concentrates. Generally these processes involve liquid-solid separation of metal-bearing liquors from barren residues. This may be done by countercurrent decantation, thickening and filtration, or filtration or centrifuging only. Choice of method is governed by chemical and physical characteristics of the pulps; cost of labor, power, materials, and waste disposal; and even by the amount of capital available when building plans are under way. Since all these controlling factors change with time and location and with technological advances, the separation method must be re-evaluated when new plants or expansion programs are contemplated.

Practically all hydrometallurgical processes involve leaching of solids to dissolve valuable constituents. This usually is followed by a liquid‐solids separation before producing the final product. The liquid‐solids separation step requires careful investigation because:

1. Soluble values must be recovered to a very high degree for economic purposes.

2. Final liquor volume must be minimized to reduce capital and operating costs of later steps.

3. Usually large amounts of gangue solids are associated with the digested pulp requiring care in minimizing wash volumes.

4. The colloidal solids are strongly dispersed by retention times and pH conditions in leaching. This necessitates flocculation investigations to achieve desired results.

5. Operation must be dependable under severe conditions of pH, abrasion, fast settling solids, temperature, etc. Equipment must have flexibility to allow efficient operation under even abnormal fluctuations.

6. An appreciable percentage of initial investment is required for this portion of the plant.

The two common liquid-solids separation methods-countercurrent decantation and filtration with cake washing, are discussed. Investigation and correlation procedures for prediction of full scale results and design requirements are stressed. Emphasis is given to the influence of particle size distribution, temperature, pH, flocculation, repulping, solids concentration, and filter cake permeability.

Pregnant liquors are separated from the barren leach residues in a thickener-filter liquid-solids circuit. The decision to use this type of separation was based on a summation of economic factors during the pilot plant and design stages. Although countercurrent decantation was not incorporated in the refinery flowsheet, the problems solved in thickening the leach residues and the experience gained in operating the commercial plant are pertinent to countercurrent decantation, particularly where it is applied to slow-settling leach slurries or slurries having a relatively high vapor pressure of a valuable, obnoxious, or poisonous vapor. The nickel sulfide concentrate is leached under pressure with air and ammonia to dissolve the nickel, copper, and cobalt and most of the sulfur, leaving a residue of iron and siliceous material to be discarded.During a subsequent distillation stage to recirculate part of the ammonia used for leaching, copper is recovered from the solution as a high-grade sulfide. After further purification to remove traces of copper and undesirable sulfur compounds, the nickel is precipitated by hydrogen under pressure at an elevated temperature. The cobalt, together with unreduced nickel, is precipitated as a mixed metal sulfide by hydrogen sulfide for eventual cobalt recovery. The end solution is then evaporated to produce a crystalline ammonium sulfate byproduct.

Hydrometallurgy is a widely studied recovery process to recover NiMH battery, but the large chemical consumption restricted its application in industry. To achieve a low chemical consumption recovery process of NiMH battery anode alloy, an integrated process with selective leaching and multistage extraction was designed. In selective leaching, the leaching procedure was divided into four stages. The acid used could be reacted with the battery anode alloy totally except in the last stage. The metal components of the alloy have different reaction activities with acid, and they were leached into liquor by the sequence La > Pr > Nd > Ce > Al > Mn > Co > Ni. Hence, the selectivity of metals was achieved to make the following extraction much easier. The total chemical consumption was calculated by the ratio of UMAC/UMACmin and S, which in this integrated process was 60% less than in traditional recovery process. Through this recovery process, the recovery rate of rare earth elements (REEs) reached 90.5%, and the purity of the rare earth oxide (REO) product exceeded 99%. This integrated process was considered as a practical approach to recover the waste alloy.

A process and apparatus for hydrometallurgical leaching of unseparated, crushed mineral ores using a vessel having liquid stream forming nozzles in the lower portion thereof which operate to direct a stream of leaching liquid into solids in the lower portion of the vessel and to create a highly agitated interaction zone above which solids are settling under gravity and through which liquid from the lower portion rises upwardly in counter-current flow. The vessel is sufficiently high that an overflow of low solids content liquid is taken from the top. Outlets, as for example discharge piping or sumps, are provided in the bottom of the vessel for the controlled removal of solids therefrom. In multistage operation, the solids content of the overflow liquid is removed and the liquid content of the underflow is removed and combined to yield a mineral pregnant liquor which serves as the leaching liquid for a preceding stage where less depleted solids are being processed. Solids removed from a stage are passed to a subsequent stage where less pregnant leaching solution is used, so that the solids not only are processed in each stage in counter-current flow to the leach solution, but the interstage progression of the solids and leaching liquid is also counter-current.

Single stage continuous operation is also disclosed in which solids having passed downwardly through the reactor are discharged periodically through a discharge trap formed in the lower portion of the vessel so as to minimize the amount of liquid discharged with the solids.

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