INTRODUCTION TO MINERAL PROCESSING FLOWSHEET DESIGN PDF

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INTRODUCTION TO MINERAL PROCESSING FLOWSHEET DESIGN Introduction • The flowsheet shows diagrammatically the sequence of operations in the plant. • Most flowsheets use symbols to represent the unit operations • The flowsheet is the “road-map” of a process, • It serves to identify and focus the scope of ...

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INTRODUCTION TO MINERAL PROCESSING FLOWSHEET DESIGN

Introduction • The flowsheet shows diagrammatically the sequence of operations in the plant.

• Most flowsheets use symbols to represent the unit operations • The flowsheet is the “road-map” of a process, • It serves to identify and focus the scope of the process for all interested and associated functions of the project. • Flowsheets/flow diagrams are fundamental engineering documents used by everyone on a facility • As the mineral processing flowsheet design project progresses, the various engineering

disciplines read their portions of responsibility from the flowsheet, although they may not understand the process or other details relative to some of the other phases of engineering.

Introduction

In this flowsheet (+) indicates oversized material returned for further treatment and (−) undersized material, which is allowed to proceed to the next stage.

Introduction Definition Arrangement of processes in order to execute a certain technology for the efficient recovery of a known mineral • A Flowsheet has to be designed for each mineral deposit that need to extracted • It is commonly known that no two ores are identical even if they occur only a few meters apart • The technology and the plant have to be concluded only after a thorough understanding of the processing characteristics of the ore • Minerals occur in nature more or less closely associated with impurities. Hence making the composite minerals less useful to mankind • Therefore the purpose of Flowsheet design is to recover the useful mineral commodity from a given ore body or reduce impurities associated in the ore body to an acceptable levels at a minimum possible cost • Flowsheet design is a major and vital part of the design process, and the correct choice of flowsheet is crucial to the technical and financial success of the plant to be built.

Importance of Good Plant Design 1. A good plant design can minimize capital expenditure and maximize on long term profits. 2. A good plant design can greatly contribute towards: easing commissioning problems, and ensure that the plant is brought into production in time. 3. Maximize design capacity efficiency, and operate within budget. 4. Ease control and monitoring during plant operations 5. For future upgrading of the process plant 6. eliminate delays in commissioning which is extremely costly exercise in terms of profit loss due to loss of production 7. A good designed process flowsheet pictorially and graphically identifies the chemical process steps in proper sequence

OBJECTIVES OF MINERALS PROCESSING PLANT FLOWSHEET DESIGN 1. Efficient performance in order to save on investment and avoid risk on investment 2. Earn profit by optimizing extraction process 3. Provide a framework for plant control and monitoring

TYPES OF FLOWSHEETS There are several types of flowsheets as described 1.Block Diagram • This is usually used to set forth a preliminary or basic processing concept without details. • The blocks do not describe how a given step will be achieved, but rather what is to be done. • These are often used in survey studies to management, research summaries, process proposals for steps, and to talk-out a processing idea.

1.Block Diagram • In the block flow diagram below all operations of similar character are grouped together • “comminution” deals with all crushing and grinding. • The next block, “separation,” groups the various treatments incident to production of concentrate and tailing. • The third, “product handling,” covers the shipment of concentrates and disposal of tailings.

Figure: An example of a block flow diagram

2. Process Flow Diagram • A Process Flow Diagram (PFD) illustrates the relationships between major components of a processing plant • They can present the heat balance and material balance of a process.

• They may be in broad block form with specific key points delineated, or in more detailed form identifying essentially every flow, temperature, and

pressure for each basic piece of process equipment or processing step. •

They usually include auxiliary services to the process, such as steam, water, air,

fuel gas, refrigeration, circulating oil, and so on.

2. Process Flow Diagram In general, the following information is shown on a PFD • Process piping above a certain size, such as 2 inches

• Process flow directions • Major equipment

• Bypass and circulation lines • Control valves and process-critical block valves • Connections between systems located on other PFDs.

Figure: Process Flow Diagram

Figure: Pictorial Flow Diagram establishes key processing steps: Cement manufacturing

Figure: Process Flow Diagram

Purposes of a Process Flow Diagram A Process Flow Diagram has multiple purposes: •To document a process for better understanding, quality control and training of employees. •To standardize a process for optimal efficiency and repeatability. •To study a process for efficiency and improvement. It helps to show unnecessary steps, bottlenecks and other inefficiencies. •To model a better process or create a brand-new process. •To communicate and collaborate with diagrams that speak to various roles in the organization or outside of it.

3. Mechanical Flow Diagram or Piping and Instrumentation Diagram (P&ID)

• This presents “mechanical-type” details to piping and mechanical vessel designers, electrical engineers, instrument engineers, and other engineers not directly in need of process details. • They show all the process lines in a unit, including valves, material specifications, and

insulation detail.

3. Mechanical Flow Diagram or Piping and Instrumentation Diagram (P&ID) • They include vessels (columns and tanks), pipe sizes, schedule (thickness), materials

of construction, all valves (sizes and types), pumps, heat exchangers, reactors, furnaces, compressors, expanders, relief and drain valves, traps, filters, conveyors,

hoppers, purchased subsystems, sensors, insulation requirements (thickness and type), controllers (flow, pressure, temperature, level), spares, and other manufactured items, all in a logical configuration. • They do not include piping lengths and bends. • In some engineering systems, detailed specifications cannot be completed until this flowsheet is basically complete.

Figure: Example of P&ID

4. Combined Process and Piping Diagram • • • • • •

This is used to serve the combined purpose of both the process and the piping flowsheets. Often opens data to larger groups of persons who might misinterpret or misuse it. Some companies do not allow the use of this sheet in their work primarily because of the confidential nature of some of the process data. Where it is used, it presents a concise summary of the complete process and key mechanical data for assembly. This type of sheet requires more time for complete preparation It is an excellent record of the process as well as a worksheet for training operators of the plant.

5. Utility Diagrams • Utility line diagram (ULD) includes hardware details of the steam, water piping, and control

systems. • Used to summarize and detail the interrelationship of utilities such as air, water (various

types), steam (various types), heat transfer mediums, process vents and purges, safety relief blow-down, and so on to the basic process. • The amount of detail is often too great to combine on other sheets, so separate sheets are prepared. • They identify the exact flow direction and sequence of tie-in relationships for the operating and maintenance personnel.

Figure: Utility Flow Diagram

6. Special Diagrams • From the basic process containing flowsheet, other engineering specialties can develop their own detailed Flowsheets. •

For example, the Instrument Engineer often takes the requirements of the process and prepares a completely detailed flowsheet which defines every action of the instruments, control valves, switches, alarm horns, signal lights, and so on. This is his/her detailed working tool.

• Likewise, the Electrical Engineer takes basic process and plant layout requirements and translates them into details for the entire electrical performance of the plant.

7. Supplemental Aids – Plot Plans • Typical process area plot plan • Plot plans are necessary for the proper development of a final and finished

process, piping, or utility flowsheet. •

After overall layout decisions are made, the detailed layout of each processing area is necessary in determining the realistic estimate of the routing, lengths, and sequence of piping and other supporting facilities

General Procedure for Plant Design 1. Process Design: Entails determining processing activities workflow, equipment needs, and requirements for a particular process and uses a number of tools including flowcharting, process simulation software, etc. 2. Flow sheet Design: Diagrammatic representation of the requirements specified in the design criteria on how will be executed 3. Process Plant Simulation: Is the simulation of the designed plant using a computer software model-based representation of chemical, physical, and other technical processes and unit operations for the purpose of visualizing or demonstrate how the plant will run. 4. General Arrangement Drawings: Detail indication of the location of all process units, equipments, material handling and storage, power distribution, utilities, and overall outline of the plant layout.

GENERAL PROCEDURE FOR MINERAL PROCESS PLANT DESIGN AND DEVELOPMENT 1. Ore sampling and testing for process definition 2. Production of basic Flowsheet, 3. Production of piping and instrument drawings 4. Production of general arrangement drawings and conceptual models 5. Equipment selection and specification 6. Costing and preparation of definitive budget 7. Production of final Flowsheet 8. Production of detailed design drawings and models 9. Construction 10.Commissioning 11.Decommissioning

Mineral Extraction Process Design Stages 1. Collection of a representative sample from the ore body 2. Characterization of the ore body - WE HAVE TO KNOW THE ORE FULLY 3. Mineral separation tests – Bench and pilot plant test 4. PROCESS SELECTION - Cheaper and more efficient processing route. 5. PROCESS OPTIMISATION – Basing on design criteria evaluation

1. Collection of a representative sample from the ore body • When developing a process flowsheet, the risks in achieving positive financial outcomes are minimized by ensuring representative metallurgical samples and high quality testwork. • The quality and type of samples used are as important as the testwork itself. • The key characteristic required of any set of samples is that they represent a given domain and quantify its variability • There is a need to consider both in-situ and testwork sub-sample representativity • Early ore characterization and domain definition are required, so that sampling and testwork protocols can be designed to suit the style of mineralization in question.

2. Characterization of the ore body - WE HAVE TO KNOW THE ORE FULLY Using various instruments and methods it is possible to generate adequate knowledge of the ore for designing a suitable processing flowsheet to treat the ore. A detailed mineralogical study to define the minerals present, their proportions ( composition by elements is done through chemical analysis – gravimetric analysis and AAS and XRF. Composition by minerals is done using mineralogical techniques such as ore microscopy using thin sections and polished surfaces). Granulometric analysis – usually determined by sieving analysis using standard sieves. • The liberation size of the values • Grain study for physical description e.g. shape of minerals, color, etc. • Properties of the different minerals – shape of minerals, colour ,density, magnetic, solubility in reagents etc. • Potential problem areas in processing will be highlighted and likely achievable grades and recoveries are indicated.

3. Mineral Separation Tests – Bench and pilot plant test • These are conducted using laboratory size separation equipment such as density separation using liquids such as TBE, Bromoform, Methylene iodide, Clerici solution , jig, shaking table, magnetic separator, electrostatic separator, froth flotation cell, amalgamation, cyanidation, etc. • Batch tests Bench test) are those which require small quantities of sample for a unit operation. • Using the results obtained from batch separations, pilot scale tests may be applied. • Pilot scale tests are semi continuous tests using a larger sample of say 30 tones depending on the ore. • Provides more detailed data on the treatment flowsheet. • Also provide sample products for further examination regarding usability for other purposes such as smelting etc.

4. PROCESS SELECTION - Cheaper and more efficient processing route

• It is based on the logical decision that this is the most ideal process for effecting the separation. • Always look for a cheaper and more efficient route.

5. PROCESS OPTIMISATION – Basing on design criteria evaluation

• The evaluation criteria are examined to establish the best conditions for the process to give the best results. • These are the optimum conditions e.g. reagent consumption, grinding size etc.

Process Design Criteria A statement of what the plant will be required to do and the framework in which it will have to accomplish it. • The design criteria document evolve through preliminary studies and conceptual designs. • It Provide source of design information • It acts as bases for any assumptions. • It acts as the governing codes and standard for each discipline

Process Design Criteria Basic design criteria includes: • Description of the project • Scope of work • Location • Meteorological data • Site and Soils description • Utilities • Applicable laws and codes • The capacity of the plant • Material to be treated • The sources of feed • The product • Time schedule for the commissioning of the various stages

DESIGN CRITERIA ESSENTIALLY DEALS WITH: • What the plant is to achieve • Basic directive to the plant designer • Setts limits within which the designer should operate and targets that must be attained.

Process Design Criteria Table: Example of a gold plant design criteria

Process Design Criteria Table: Example of a TSF design criteria

CRUSHING PLANT DESIGN • •

• • • •

Crushing is the first mechanical stage in which the main objective is the liberation of valuable minerals from the gangue. The run off mine ores are usually big and have to be crushed to reduce them to a size amenable for grinding or any next process before extraction process from them. Crushing plants usually consist of set of machines that are put together to form a process to gradually reduce the size of the processed material until the desired output size is reached. The ore has to pass various crushing stages, depending on the chosen process, each reducing the ore to a certain size. The desired particle size of determines the number of stages of crushing (primary, secondary and tertiary) and the type of crusher to be used The quantity of material entering the crusher determines the size and type of the crusher to be selected.

CRUSHING PLANT DESIGN

The number of crushing stages necessary to reduce ore to the proper size varies with the type of ore. Hard ores like gold, iron, and molybdenum ores, may require as much as a tertiary crushing. To design a good crushing plant one has to follow these three steps: 1. Crusher selection 2. Crusher layout and 3. Process design

CRUSHING PLANT MAJOR EQUIPMENT

• Crushing plant usually include the following major equipment: 1. Size reduction machine( crushers) 2. Separation Machines ( screens) 3. Transporting machines( conveyer belts and feeder) 4. Storage equipment( Bins or stockpiles)

AUXILIARY EQUIPMENT IN A CRUSHING PLANT Crushing plant usually include the following auxiliary equipment:

1. Rock breaker 2. Overhead crane 3. Freight elevator 4. Service air compressor 5. Sump pump 6. Air vacuum clean system 7. Rock grapple 8. Conveyor belt magnets 9. Conveyor belt metal detectors 10.Belt monitoring systems 11.Belt feeders 12.Screw feeders 13.Bin ventilators 14.Apron feeder to the primary crusher

15.Service trolleys 16.Conveyor gravity take-up service winch 17.Conveyor belt rip detector 18.Conveyor belt weight scales 19.Vibratory feeders 20.Sampling stations 21.Dust collection/suppression system 22.Eccentric trolley removal cart 23.Man-lift elevator 24.Air cannons 25.Water buster pumps

Crusher Selection • The choice of crusher depends on the type and amount of material to be crushed • The factors that affect the size and type of crusher for specific process flowsheet include the following: • • • • • •

Plant throughput, ore delivery schedule Size of feed Desired product size for downstream processing Ore characteristics; hard rocky, clay, gravel, variability, etc. Climatic conditions Downstream processes

MAJOR CRUSHER There are many types of crushers but the major ones are: 1. The jaw crusher 2. The gyratory and 3. The cone crusher.

Crusher Sizing • Jaw crushers are sized on the basis of the maximum particle size to be crushed or the tonnage rate to be crushed. • Maximum particle size should not exceed 80% of the gape. • For example, a 400- by 600-mm crusher will accept a maximum lump size of 400 by 0.8 = 320mm. • In actual operations, the crusher will occasionally accept particles up to the gape size, as long as bridging does not occur.

Crusher Sizing •

The size of a jaw crusher is usually described by the gape and the width, expressed as gape × width.

• These dimensions vary as individual manufacturers have their own specifications and their catalogues are a good guide to the geometry and design of individual makes.

Capacity of jaw crusher

Gyratory Crusher Sizing • Gyratory crushers are sized by the size of the gape and the size of the mantle at the discharge. • For Example 1,600 mm×2,900 mm (gape × mantle diameter)

Crusher Layout • Layout must suit the design criteria, flowsheet and selected equipment in the most possible economical configuration • It should minimize structural cost • It must accommodate easy maintenance and operation • It should be simple • The best design are developed using the basic approach: site visit, discussion with mine personnel, sketches, and cut and paste layouts

Process Design Process Design Criteria The information required to develop crusher process design criteria will include; • Geographical data • Civil design Criteria • Structural design criteria • Mechanical design criteria • Climatic data • Process design data( Process description, ore characteristics) • Electrical/instrumentation design criteria

Bond Work Index for Energy Consumption of Crusher • The energy required to grind one tonne of an ore from a given feed size to a specified product size is a material property that needs to be determined for different ore deposits. • The Bond work index is a measure of ore resistance to crushing and grinding and is determined using the Bond grindability test. • Its value constitutes ore characteristic and is used for comminution plants designing. • Determining the Bond work index value is quite complicated, time-consuming and requires trained operating personnel and therefore is subjected to errors. • Numerically, the work index represents the energy (kWh/sht) required to reduce the material of one short ton from a theoretically infinite feed size to size at which 80 percent of mate...