Title of Invention

AN IMPROVED BENCH SCALE PRESSURE REACTOR SYSTEM FOR CHEMICAL LEACHING OF MINERALS AT ELEVATED TEMPERATURE AND PRESSURE

Abstract

The invention relates to a method for extraction of minerals and metals at elevated temperature and pressure by adapting a chemical leaching process, in an improved bench-scale pressure reactor system, the method comprising providing a mineral of desired size dried at a predetermined temperature, preparing a liquid alkali of specified concentration, charging the mixture of the mineral and liquid alkali into an improved pressure reactor (1), adjusting a plurality of valves (3 to 5) in the reactor system to ensure respective open or close positions of each valve, switching on a data acquisition means (19) attached to the pressure reactor (1), and commencing data saving including inputting the start time of the process, setting a set-point temperature and pressure adaptable to the process, switching on the heaters on the reactor (1), and adjusting the parameters based on the process requirements, carrying out the process for a scheduled operational time, switching off the heater, and discontinuing the data saving, the already saved data being transferred to a text file, decreasing the set temperature including releasing the pressure inside the reactor (1), and noting the end time of the process, collecting the slurry from the reactor (1) after completion of the process time, and filtering the slurry to collect the filtrate, measuring a plurality of variables namely details of the mineral used, temperature data, cooling water flow-rate, operating temperature and pressure, total operation time, total volume of slurry collected, total amount of filtrate collected, and total number of bleedings, and analyzing the collected data to determine the ash results of the treated mineral. The invention further discloses An improved bench-scale pressure reactor system.

Full Text

FIELD OF THE INVENTION The invention relates to an improved bench scale pressure reactor system for chemical leaching of minerals at elevated temperature and pressure. More particularly the invention relates to an improved bench scale pressure reactor system in which various minerals and metals can be extracted at elevated temperature and pressure using the process of leaching. BACKGROUND OF THE INVENTION Beneficiation is a variety of processes whereby extracted ore from mining is reduced to particles that can be separated into mineral and waste, the former being suitable for further processing or direct use. Beneficiation may be conducted via a range of techniques including crushing, grinding, magnetic separation, flotation, gravity etc. Beneficiation enables operators to improve the quality of their end product and to enhance the overall processing performance of an ore. Accordingly, physical as well as chemical cleaning (beneficiation) processes have been explored. In physical cleaning, the mineral is crushed into suitable particle size, and the waste is removed in processes based on the differences in their physical properties. In contrast to physical cleaning, chemical processes involve addition of chemical which reacts with the mineral matter or waste and allow it to be easily removed. This includes mainly the process of liquid/solid extraction, also known as leaching, involves the transfer of a solute from a solid, generally employed in particulate form, to a liquid solvent which is termed as the "extract". In this process, the solid imbibes the solvent which dissolves the solute and thereby extracts it from the solid. Leaching is a very old process and a great diversity of apparatuses have been developed over the years to meet the varying requirements of the processes in respect to its widely diverse applications. Leaching processes have been proposed which operate in a batch, semi-batch or continuous mode, and both single-stage and multi-stage contacting techniques are used. Leaching equipment is commercially available for a wide variety of processes, including fixed-bed processes in which solvent is percolated through a stationary bed of solids, moving-bed processes in which the solids are conveyed through the solvent with little or no agitation, and dispersed-solid processes in which the solids are dispersed in the solvent by mechanical agitation. Among the many critical problems involved in the successful operation of a leaching process are those associated with the leaching of solid material which is often quite heterogeneous in character, and therefore exceedingly difficult to treat in an optimum manner. However, most of these reactors are operated at atmospheric pressure only and hence; there is a limit on temperature to which the material can be treated. In most of the cases the maximum temperature limit in such reactors are less than the boiling point of the liquid being used for leaching out the solid materials. Besides, when pressure is applied, uniform mixing of the slurry inside the pressure reactor becomes a difficult proposition because of inadequate provision or lack of stirring. U.S.Patent No. 6613271 discloses an apparatus and method for recovering valuable metals particularly gold using an in line leach reactor. This invention states about the apparatus and method for continuously separating a dense valuable material such as gold from a feed including a grinding mill which directs a crushed feed through hydrocyclones for separation into a light and dense fraction. The dense fraction is concentrated further by in line pressure jigs and the concentrate is leached in a rotating leaching reactor. The resulting pregnant liquor is subjected to electrowinning to recover gold and the spent liquor is recycled. U.S.Patent No. 4824939 discloses a novel leaching process which is useful for leaching a particulate solid material that comprises extractable and nonextractable portions. The process includes the steps of introducing the particulate solid material and a liquid solvent to an extraction zone; agitating the liquid solvent to a degree sufficient to suspend the particulate solid material and effect segregation of particles thereof in relation to their propensity to settle; maintaining contact between the liquid solvent and the particulate solid material for a time sufficient to leach extractable material there from: and selectively withdrawing particles from the extraction zone. In a preferred embodiment, the leaching process is a multi-stage process employing a series of stages in which the selectively withdrawn particles from each stage are introduced to the next successive stage of the series. U.S.Patent No. 5993635 relates to a method of enabling a sulphide mineral composition to be leached at atmospheric pressure instead of above atmospheric pressure which has been hitherto required in order to achieve acceptable rates of leaching. The typical problems usually observed with the existing pressure reactors when the method is conducted near the boiling point of the solution being used for leaching, can be summarized as under: • Substantial vapour generation at the top of the reactor, • Precipitation of the solute/chemical because of substantial loss of vapour while releasing the pressure from the reactor, • Entrainment of liquid chemical droplets with coal particles and carryover of these coal particles, • Slugs of these droplets into the condenser circuit and pressure releasing valve, and • Loss of substantial amount liquid and increase in final filtrate concentration. OBJECTS OF THE INVENTION It is therefore the object of the invention is to propose an improved bench scale pressure reactor system for chemical leaching of minerals at elevated temperature and pressure which eliminates the disadvantages of the prior art. Another object of the invention is to propose an improved bench scale pressure reactor system for chemical leaching of minerals at elevated temperature and pressure which enables evaluating and improving kinetics, thermodynamics and energy requirement of chemical leaching process. A further object of the invention is to propose an improved bench scale pressure reactor system for chemical leaching of minerals at elevated temperature and pressure which reduces slugging and solid carryover. A still further object of the invention is to propose an improved bench scale pressure reactor system for chemical leaching of minerals at elevated temperature and pressure which restricts the loss of liquid chemical and improves the concentration of the final filtrate. SUMMARY OF THE INVENTION Accordingly there is provided an improved bench scale pressure reactor system, in which substantially higher quantity of ore/minerals can be treated. This helps in optimization as well as scaling up the chemical leaching process at elevated temperature and pressure. In the present case, an example has been given for brief methodology to be followed for carrying out chemical leaching of coal using alkali and acid leaching method. However, the invented system can be used for chemical leaching process of various other minerals using any other inorganic chemical including acid and alkalis. This system can be used for evaluating data representing detail kinetics, thermodynamics and energy requirement for extraction of minerals using existing chemical leaching processes, and further for implementing new processes for extraction of other minerals using this leaching technique. Methodology, scientific background and few important test results using this system have been discussed in the subsequent sections. The invention addresses the problem of existing location of the compressed air inlet (pressure input point) of prior art, by optimally relocating the pressure input point so as to suppress slugging and solid carryover. A new control strategy has been adopted which enables determining the liquid-solid equilibrium and minimum filtrate concentrations to be maintained during the process- implementation. BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS Figure 1: Schematic diagram of an improved bench scale pressure reactor system for carrying out chemical leaching of minerals Figure 2: Schematic diagram of a condensor adapted in the system according to the invention Figure 3: Schematic diagram of the pressure control means disposed inside the reactor of the invention. Figure 4: Schematic diagram of data acquisition and control means for the reactor of the invention Figure 5: Graphical representation of the change in temperature of vapour with time Figure 6: Graphical representation of the change in temperature of Condensate with time Figure 7: Graphical representation of the change in temperature of Cooling water inlet and outlet with time. Figure 8: Graphically illustrates the variation in energy consumption during implementation of the method of the invention with time. Figure 9: Graphically illustrates the variation in energy consumption during implementation of the method of the invention with pressure Figure 10: Graphical representation of the variation in energy consumption during implementation of the method of the invention with temperature. DETAIL DESCRIPTION OF THE INVENTION A schematic diagram of the improved bench scale pressure reactor system for carrying out chemical leaching at elevated pressures and temperatures is shown in Fig. 1. The system essentially comprises a batch reactor of substantially equal to 5.0 litres capacity with heating and continuous mixing means; two condenser units, means for applying pressure at least up to 10 bar; and data acquisition and control means. The batch reactor (1) is of diameter ~ 7.0 inch and height ~ 10.0 inch, and having a conical bottom. The reactor (1) is made up of SS-316 or equivalent material. The feed materials are charged inside the reactor through a charging funnel (2) disposed at the top of the reactor (1) by opening a first valve (3). The products after completion of the reaction time are taken out by opening a second valve (4) located at the bottom of the reactor (1). Pressure can be applied inside the reactor (1) through an air inlet pipe (6) by opening a third valve (5). Pressure can be applied by using compressed air, nitrogen or argon. The inlet pipe (6) through which pressure is applied is having side arms (not shown) at different angles inside the reactor (1) and is extending up to the end of the cylindrical part of the reactor (1). The side arms and inlet pipe (6) are having perforations through which pressure is applied inside the reactor (1). This configuration helps in continuous agitation and mixing of the reactants inside the reactor (1). A plurality of baffles (not shown) are fitted at 60 degree angle at the entrance and exit points of the reactor (1) so that entraihment and carryover of the solid particles can be avoided. At least two numbers of shell and tube condensers (7) are fitted at the top of the reactor (1) in series as shown in Fig. 1. The schematic diagram of the condenser (7) is depicted in Fig. 2. Either one or both the condensers (7) can be used at the time of implementing the process. Both the condensers (7) have a plurality of tubes (23) each inside the shell (24). Vapour flows through the shell side and cooling water flows (23) through the tube side. Water flow rate to the condensers (7) can be controlled by adjusting the position of a plurality of ball valves (8). All the pipe lines connected to the reactor system are of nearly 9 mm thickness. At least five numbers of thermowells (9) have been fitted at various locations in the pipelines to measure the temperature using a thermometer or RTD (10). The pressure inside the reactor (1) is controlled by control elements called solenoid valves (11), which act as ON-OFF control. At least two solenoid valves (11) are fitted after each condenser (7) for releasing pressure incase pressure inside the system becomes higher than the set point pressure. A pressure sensor (12) is connected at the middle of the at least two solenoid valves (11) to control the pressure inside the reactor (1). A separate line is taken out from the main line and mercury is filled in the extended pipe. The pressure sensor (12) is fitted after the mercury filled part so that the sensor (12) is not exposed to steam or vapour. This is important as the pressure transmitter (14) or sensor (12) should never be exposed to very high temperature. The reactor (1) is heated with two heating coils (13) of 1- kilowatt capacity each of which are fitted outside the circumference of the reactor (1). A Resistance Temperature Detector (RTD) (10) is mounted inside the reactor (1) to indicate and control temperature. There are at least two heating coils (13) each of lkw capacity to raise the temperature inside the reactor (1). These two heating coils (13) are mounted on the circumference of the reactor (1), which are well insulated from the surrounding. The RTD (10) is connected to a first PID controller (16) through which the temperature inside the reactor (1) can be controlled using a relay switch (25) connected to the heaters (13). A second PID controller (15) is used to control the pressure inside the reactor (1). The pressure transmitter (14) sends the signal to the pressure controller (16) which in turns sends the signal to the solenoid valves (11) to open or close. A tank (17) half filled with water having measurement facility is placed at the pressure release outlet so that amount of non-condensable gas at the end of the process can be measured using water displacement method. There is a current sensor (18) to sense the amount of current passing through the "Live wire" which provides electricity supply to the at least two heating coils (13). The output from a data acquisition device (19) is sent to a host computer (20) for measuring the total cumulative energy consumption during the process using the calculations as mentioned below. Power (kwhr) = Power (kwhr) + Voltage (volt)* Current (ampere) Energy= (Power)* time The temperature, pressure and current data from data acquisition module (19) can be seen on the host computer (20) through a graphical user interface developed particularly for this system. The details of the microprocessor based interfacing for data acquisition is described later. The data acquisition modules (19), PID controllers, (15,16) current sensor (18) and batteries (21,22) are placed inside a panel. Schematic views of the pressure control arrangement and data acquisition and control means along with circuit diagram for the unit are shown in Fig. 3 and Fig. 4 respectively. Different Sensors and Modules that were used during the process- implementation Sensors: RTD temperature Sensor (10): The RTD (10) is a sensor that operates on the principle that the resistance of a metal like platinum increases with an increase in temperature at a specific rate. The Resistance Temperature Detector is often selected when accurate temperature measurements are required. RTD's could be made of Copper, Nickel or Platinum. Currently, Platinum is the industry standard for the material use in making RTD's. As long as the temperature relationship with resistance is predictable, smooth, and stable, the phenomenon can be used for accurate temperature measurement. To ensure high accuracy, the resistance effects due to impurities must be small and the resistance versus temperature curve must be known and repeatable. Platinum RTD's are suitable for use from -50C to 550C, when long-term temperature stability and repeatability is required. They offer virtually a linear response over this range. The details of the two data acquisition module used in the present case is described below. The Pressure Sensor (12) The pressure sensor (12) is a sensor that operates on the principle of capacitance. It consists of a diaphragm and two parallel plates. An insulating fluid has been used to insulate the diaphragm from the reactor's vapour. Here mercury is used as insulating fluid because its density is higher than normally used fluid. It can sense pressure range from 0-100 kg/cm2. When the reactor pressure acts on the insulating fluid it transmit the pressure to the diaphragm which changes the capacitance between the two plates. And due to the change in capacitance a change in potential difference develops across the plates that in turn give rise a change in output voltage. The Solenoid valve (11) The solenoid valve (11) is the final control element in this process. It works on the principle of Magnetic Induction Effect and is consisting of a plunger and a coil. It operates in ON-OFF mode (i.e., at one time it is either ON or OFF). The operating voltage is 22-24 V dc. The moment voltage is applied the coil get energized and it pull the plunger inside. And as the applied voltage is removed the coil gets de-energized and releases the plunger to reach its original position. This effect is used to release and maintain pressure in side the reactor according to the control signal generated by the pressure controller. Modules 1. 7520 Module (19) This module provides the necessary serial bus protocol conversion from PC standard RS 232 to a 2 wire RS 485 interface. This module connects to all other modules on the RS 485 network. Its specification is: Input: RS 232C protocol Output: RS 485 protocol (2 wires, D+,D-) Baud Rate: "Self Tuner" auto switching baud rate, 300 to 115200 bps. Modules: 256 modules maximum without repeater. 2. 7017 Module (19) The 7017 (19) is a 8-Channel Voltage and 4-20mA Input Module. It takes in an analog input. Eight different inputs can be given to this module at a time at Channel 0 to Channel 7. Its specifications are Input type: mV, V, mA Input Range: +/-150 mV, +/-500mV, +/-1 V, +/-5V, +/-200mA Sample Rate: 10 samples per second Bandwidth: 13.1 Hz Accuracy: 0.01% or better Methodology followed for chemical leaching of minerals in the bench scale pressure reactor system of the invention In the present case, an example has been given describing a brief methodology to be followed for carrying out chemical leaching of coal using alkali and acid leaching method with this pressure reactor system. Here, West Bokaro fine clean coal was taken as a feed sample for this process. The feed sample can be taken directly or can be crushed to desired size fraction for improving the kinetics of the process. This West Bokaro fine clean coal is referred as feed coal in the subsequent section of this write up and the clean coal produced from this process is referred as Product. Sample Preparation: 200-300 gm of coal is taken through coning quartering method from the received West Bokaro fine clean coal. This coal sample is dried in an oven at 105°C. Chemicals: Commercially available sodium hydroxide (NaOH) in combination with sulphuric acid (H2SO4) and HCI were used in the present method. The treatment process The process for chemical leaching were carried out in the reactor assembly using two steps. In the first step, feed coals (200-300 gm) were treated with varying concentration of alkali (NaOH) (2-3 lit) at varying temperatures under different pressure conditions upto 10 bar for particular length of time in the reactor system described hereinabove. The treated coal is then washed repeatedly with water and/or HCI and then dried. Then, the treated coal is filtered, washed with water and dried before sending for their chemical, Theological and petrographical properties. The coal to slurry ratio can be maintained at 1:10 or 1:5 keeping the total volume 2-3 litres. The moment the feed is fed to the reactor (1), the heaters (13) are switched on and then the data acquisition means (19) is switched on. The readings are checked in the host computer (20) using the GUI to ensure proper working of the sensors. Once checked, the data are captured using the save command which saves the data to a text file. Pressure is applied inside the reactor (1) by opening the inlet valve (5) for pressure as desired for the particular process. The treated coal samples are collected at the end of the process only once pressure inside the reactor (1) is released. The sample can be washed with water and/or 10-20% HCI/H2SO4 solution. These samples are dried and analyzed for various properties. Multi-stage processes can also be carried out using the invented system. The detail work instructions for carrying out these experiments is given below. An Example of Chemical leaching 1. Providing 200-300 gm coal sample of desired size as per requirement of the process. 2. Preparing 2.0-3.0 litre of alkali of desired concentration. 3. Charging the mixture of coal and alkali solution into the pressure reactor (1). 4. Checking position of all the valves (3 to 5) to ensure position of the valves (3,4,5) which are supposed to remain close during starting of the process. 5. (a) Switching on the data Acquisition means (19). (b) Setting a set point pressure and set point temperature, (c ) Switching on the heater (13). (d) Checking that all the incoming data are being displayed properly. (e) Commencing the saving of data and noting the starting time of the process. 6. Running the process for total operational time as per designed criteria. 7. Following the heating schedule and increasing the pressure set point as per requirement of the process. 8. a) When the total operation time is about to over, all the operating data are noted. b) Switching off the heater (13). c) Stopping the saving of data through the data acquisition means (19) and saving the text file with proper file name. d) Decreasing the temperature set point to 60 deg. C. e) Closing the valves (3,4,5) of the cylinder and pressure inlet valve (5) through which pressure is applied inside the reactor (1). f) Releasing the pressure inside the reactor (1) by reducing the set point pressure gradually at 1 bar at a time. g) Noting the end time of the process. 9. Measuring the following variables and noting the following data at particular time interval as mentioned below. (a) Sample Details i) Coal Name- ii) Coal Size- iii) Coal Quantity- iv) NaOH Concentration- v) NaOH Quantity- vi) Coal: Slurry Ratio- (b) Temperature Data: (Data to be noted every 30 minutes from the start of the Experiment): i) Vapour Temperature: ii) Condensate Temperature: iii) Cooling Water Inlet: iv) Cooling Water Outlet: (c) Cooling Water Flow Rate: (Data to be noted every 60 minutes from the start of the Experiment including at the beginning i.e. Time = 0): Noting the time taken to collect 1 litre of water from the cooling water outlet pipe. Take at least two readings and take their average. Total amount of water consumed: (d) Operating Temperature and Pressure: i) Maximum Set Point Pressure: ii) Maximum Pressure Applied: iii) Maximum Set Point Temperature: iv) Maximum Operating Temperature: (e) Total Operation Time: (f) Total Volume of Coal slurry Collected: (g) Total Amount of Filtrate Collected after filtration: (h) Total no of Bleedings: (At the end of the process while pressure release from the reactor takes place) (i) Change in the volume of water content inside the Tank after the Release of Pressure: (Where pressure release line is dipped) (j) Remarks/Any other observation during the experiment: (k) Plots of trend of various operating variables during the. experimentation 10.Collecting the coal slurry after reaction by opening the outlet valve very slowly. Ensuring that the pressure inside the reactor is nil (0.0) before taking out the product. Dividing the total volume of reacted coal slurry in to six equal parts and naming them A,B,C,D,E and F. Filtering the six parts separately in six different conical flask, funnel and filter paper assembly. A, B: Washing with only water C,D: Washing with 10% HCI (100ml), (water + 50 ml 10% HCI + Water + 50 ml 10% HCI + water) E, F: Washing with 20% HCI (100ml) (water + 50 ml 20% HCI + Water +50ml 20% HCI + water) 11.Analysing the dried coal sample for ash content as per standard test procedure. Conducting ash analysis for each of the sample A,B,C,D,E and F twice at least. However, if there is a difference of more than 1% is found for a particular sample, repeating them again. 12.Collecting the remaining coal sample after drying in a polythene bag with proper tag and sending them for chemical, rheological, petrographical and other morphological analysis as per requirement. An exemplary data sheet for chemical leaching process under high pressure is given below. Exemplary Test Data Sheet for Pressure Reactor process. (j) Sample Details i) Coal Name- West Bokaro Fine Clean Coal (WB Fine C/C) ii) Coal Size- (-72) mesh (0.021 mm) iii) Coal quantity- 300 gm iv) NaOH Concentration-40% v) NaOH Quantity-1.2 kg vi) Coal:SIurry Ratio-l:10 (I) Cooling Water Flow Rate: (Data to be noted every 60 minutes from the start of the Experiment including at the beginning i.e. Time = 0): i) 0.0 hr-1000 ml/55 sec ii) 1.0 hr-1000 ml/60 sec iii) 2.0 hr-1000 ml/60 sec iv) 3.0 hr-1000 ml/60 sec v) 4.0 hr-1000 ml/60 sec Total Amount of water consumed: ~ 240 litres (m) Operating Temperature and Pressure: i) Maximum Set Point Pressure, bar: 10.0 ii) Maximum Pressure Applied, bar: 8.4 iii) Maximum Set Point Temperature, deg. C: 175 iv) Maximum Operating Temperature, deg. C: 175 at 7.4 bar pressure (n) Total Operation Time: 4.0 hr (o) Total Volume of Coal Slurry Collected: 2.6 litres (including coal) (p) Total Amount of Filtrate Collected after filtration: (q) Total no of Bleedings: 82 (At the end of the experiment while pressure release from the reactor takes place) (r) Change in the volume of water content inside the Tank after the Release of Pressure: (Where pressure release line is dipped) If two ash results of a particular sample are not matching and differ by more than 1%, repeating the analysis and noting them as A3, A4 etc. (h) Remarks/Any other observation during the process (j) Trends of various operating variables during the process The variations in vapour temperature and condensate temperature during the process are shown in Fig. 5 and Fig. 6 respectively. Variations in cooling water inlet and outlet flow rate are shown in Fig. 7. Change in energy consumption during the process with time, pressure and temperature are shown in Fig. 8, Fig. 9 and Fig. 10 respectively. Plot can also be made for cooling water flow rate vs. time if there is a change of cooling water flow rate during the course of experiment. However, since the flow rate was maintained at a nearly same level during the process,, no plot is shown for this parameter. Few important ash results are depicted below for West Bokaro fine clean coal at 40% NaOH concentration and various operating pressures. The original sample has ~ 14% ash content. With the development of the present bench scale pressure reactor system, the chemical cleaning process can be carried out at high temperature and pressure using a bigger size reactor with jacketed steam heating or electric heating arrangement as described above. Detail thermodynamic and kinetic study as well as energy requirement for this process can be evaluated using the bench scale unit. This will help in optimization as well as scaling up the chemical leaching process to commercial scale and low ash coal can be produced economically for coke making. However, this system can also be used for detail kinetics, thermodynamics and energy requirement studies for extraction of any other minerals using existing chemicazl leaching processes and also for development of new processes for extraction of other minerals using this leaching technique. We claim 1. An improved bench scale pressure reactor system for chemical leaching of minerals at elevated temperature and pressure, the method comprising: - providing a mineral of desired size dried at a predetermined temperature, - preparing a liquid alkali of specified concentration, - charging the mixture of the mineral and liquid alkali into an improved pressure reactor (1); - adjusting a plurality of valves (3 to 5) in the reactor system to ensure respective open or close positions of each valve; - switching on a data acquisition means (19) attached to the pressure reactor (1), and commencing data saving including inputting the start time of the process; - setting a set-point-temperature and pressure adaptable to the process, switching on the heaters on the reactor (1), and adjusting the parameters based on the process requirements; - carrying out the process for a scheduled operational time, switching off the heater, and discontinuing the data saving, the already saved data being transferred to a text file; - decreasing the set temperature including releasing the pressure inside the reactor (1), and noting the end time of the process; - collecting the slurry from the reactor (1) after completion of the process time, and filtering the slurry to collect the filtrate; - measuring a plurality of variables namely details of the mineral used, temperature data, cooling water flow-rate, operating temperature and pressure, total operation time, total volume of slurry collected, total amount of filtrate collected, and total number of bleedings; and - analyzing the collected data to determine the ash results of the treated mineral. 2. An improved bench scale pressure reactor system for chemical leaching of minerals at elevated temperature and pressure, the system comprising: - a batch reactor (1) with heating means (13) mounted on the circumference of the reactor (1), the reactor (1) comprising a charging funnel (2) controllable by a first valve (3), a pressure application means (5, 6), and an outlet valve (4); - at least two condensers (7) disposed on the top of the reactor (1) and having a plurality of valves (8) to control the flow of cold water and vapour; - at least five thermowells (9) provided at different locations of the tubular network of the system to measure temperature by using a thermometer (10); - at least two solenoid valves(ll) connected to one each condenser (7) to control pressure inside the system; - a pressure sensor (12) and a pressure transmitter (14) provided to control the pressure inside the reactor (1); - at last two PID-Controllers (15,16), a first Controller (16) to control the temperature inside the reactor (1) via a relay switch (25), and a second Controller (15) to control the pressure inside the reactor (1); - a current sensor (18) to sense the current date; and - a data acquisition means (19) collecting the process data for displaying in a host computer (20) for further analysis to determine the ash-results of the mineral treated in the system. ABSTRACT Title: An improved bench scale pressure reactor system for chemical leaching of minerals at elevated temperature and pressure The invention relates to a method for extraction of minerals and metals at elevated temperature and pressure by adapting a chemical leaching process, in an improved bench-scale pressure reactor system, the method comprising providing a mineral of desired size dried at a predetermined temperature, preparing a liquid alkali of specified concentration, charging the mixture of the mineral and liquid alkali into an improved pressure reactor (1), adjusting a plurality of valves (3 to 5) in the reactor system to ensure respective open or close positions of each valve, switching on a data acquisition means (19) attached to the pressure reactor (1), and commencing data saving including inputting the start time of the process, setting a set-point temperature and pressure adaptable to the process, switching on the heaters on the reactor (1), and adjusting the parameters based on the process requirements, carrying out the process for a scheduled operational time, switching off the heater, and discontinuing the data saving, the already saved data being transferred to a text file, decreasing the set temperature including releasing the pressure inside the reactor (1), and noting the end time of the process, collecting the slurry from the reactor (1) after completion of the process time, and filtering the slurry to collect the filtrate, measuring a plurality of variables namely details of the mineral used, temperature data, cooling water flow-rate, operating temperature and pressure, total operation time, total volume of slurry collected, total amount of filtrate collected, and total number of bleedings, and analyzing the collected data to determine the ash results of the treated mineral. The invention further discloses An improved bench-scale pressure reactor system.

Documents:

1550-KOL-2008-(28-05-2012)-ABSTRACT.pdf

1550-KOL-2008-(28-05-2012)-AMANDED CLAIMS.pdf

1550-KOL-2008-(28-05-2012)-AMANDED PAGES OF SPECIFICATION.pdf

1550-KOL-2008-(28-05-2012)-DESCRIPTION (COMPLETE).pdf

1550-KOL-2008-(28-05-2012)-DRAWINGS.pdf

1550-KOL-2008-(28-05-2012)-EXAMINATION REPORT REPLY RECEIVED.pdf

1550-KOL-2008-(28-05-2012)-FORM-1.pdf

1550-KOL-2008-(28-05-2012)-FORM-2.pdf

1550-KOL-2008-(28-05-2012)-OTHERS.pdf

1550-KOL-2008-(28-08-2012)CORRESPONDENCE.pdf

1550-kol-2008-abstract.pdf

1550-kol-2008-claims.pdf

1550-KOL-2008-CORRESPONDENCE 1.1.pdf

1550-kol-2008-correspondence.pdf

1550-KOL-2008-CORRESPONDENCE1.2.pdf

1550-kol-2008-description (complete).pdf

1550-kol-2008-drawings.pdf

1550-KOL-2008-EXAMINATION REPORT.pdf

1550-KOL-2008-FORM 1 1.1.pdf

1550-kol-2008-form 1.pdf

1550-KOL-2008-FORM 18.pdf

1550-kol-2008-form 2.pdf

1550-KOL-2008-FORM 3.1.pdf

1550-kol-2008-form 3.pdf

1550-kol-2008-gpa.pdf

1550-KOL-2008-GPA1.1.pdf

1550-KOL-2008-GRANTED-ABSTRACT.pdf

1550-KOL-2008-GRANTED-CLAIMS.pdf

1550-KOL-2008-GRANTED-DESCRIPTION (COMPLETE).pdf

1550-KOL-2008-GRANTED-DRAWINGS.pdf

1550-KOL-2008-GRANTED-FORM 1.pdf

1550-KOL-2008-GRANTED-FORM 2.pdf

1550-KOL-2008-GRANTED-SPECIFICATION.pdf

1550-KOL-2008-OTHERS.pdf

1550-KOL-2008-REPLY TO EXAMINATION REPORT.pdf

1550-kol-2008-specification.pdf

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