EA013851B1 - Bioleaching process control - Google Patents

Abstract

A process of bioleaching a sulphide mineral slurry in a reactor which is controlled by varying the rate of supply of sparging gas to the reactor, and the energy supplied to a motor-driven agitator in the reactor, in response to the measured or inferred oxygen demand of the slurry.

Description

The present invention relates generally to a bioleaching process, in particular to the management of processes of this type, aimed at reducing energy consumption, while these processes are carried out in a tank reactor equipped with a stirrer.

Bioleaching in tank reactors equipped with a mixing device is used to oxidize refractory sulfide gold-bearing concentrates and copper sulfide concentrates; In addition, this method is suitable for the oxidation of nickel and zinc sulphides. In carrying out these operations, the cost of electricity consumed in the compression of air or oxygen supplied to the reactor, and the cost of energy required to disperse the gas in the reactor, represent a significant part of the operating costs.

During the bioleaching process, carried out in a tank reactor equipped with a stirrer, a suspension consisting of water, nutrients and sulphide concentrate is fed to the reactor, where the corresponding microorganisms oxidize the ferrous iron and sulfides. For the oxidation process requires oxygen.

Oxygen is fed to the reactor in a gaseous state in the form of air, air enriched with oxygen, or oxygen. Gas is bubbled into the portion of the reactor below the stirrer, suitable for mixing high viscosity media, which, with stirring, ensures flow from top to bottom, or below the impeller of the radial type. Such a device cuts the suspension and breaks the flow of the incoming gas into small bubbles, which significantly increases the surface area of the gas stream and the rate of oxygen transfer to the suspension.

Oxygen transfer rate is proportional to:

a) the amount of gas supplied, except when the gas flow rate exceeds the capacity of the stirrer to disperse this gas;

b) the partial pressure of oxygen in the gas and

c) the amount of energy transferred to the suspension by the mixing device.

At the same time, the rate of oxygen transfer is inversely proportional to the amount of oxygen dissolved in the slurry.

The consumption of oxygen consumed during the reaction (oxygen consumption) depends on the feed rate of the sulfide material into the reactor, which, in turn, may be affected by the system throughput or the quality of the concentrate.

A typical bioleaching process is usually carried out taking into account a number of boundary conditions, for example, the minimum and maximum dissolved oxygen concentration, gas dispersion restrictions imposed by a mixing device, etc. Within these boundary conditions, there are optimal conditions for the process, depending on the installation location, its size and oxygen consumption. Installations are usually designed based on their design capacity for a certain period of operation of the installation.

In practice, the installation often works in conditions where the quality of the concentrate or the feed rate of the raw materials are significantly different from the design. This is due to a number of factors, for example, changes in the mineralogical composition of the raw materials as the field develops, discrepancies between the calculated and actual parameters of the flotation process of sulfide materials and the processing of other ores, changes in concentrate tonnage due to technological reasons, production rates, etc.

If the oxygen consumption in the reactor drops, then equipment, such as a compressor or a blower, used to supply gas, will operate with less power. FIG. 1 shows the dependence of the energy consumption per kilogram of the sulphide material being processed on the input power of the mixing device for the installation, in which the process is carried out using thermophilic microorganisms, including the primary and secondary reactors. The lower curve represents the above relationship for a full load of sulfide material fed to the installation, while the upper curve represents the same relationship with a decrease in the supply of sulfide material by 50% and with a decrease in power supply for gas, designed to compensate for the above reduction. Obviously, despite the reduction in the gas supply rate to the installation, when compensating for the reduction in the feed rate of sulfide material, the energy consumption per unit of sulfide material being processed increases from 19 to 39%, depending on the power supplied to the mixing device.

FIG. 2 shows similar graphs obtained for an installation with a similar capacity in which the process is carried out using mesophilic microorganisms and air supply. The lower curve shows the total load of sulfide material, and the upper one shows half load. As a result of reducing the load of sulfide material, the energy consumption per unit of sulfide material being processed increases from 26 to 60%.

Thus, in accordance with the data presented in FIG. 1 and 2, it follows that the energy efficiency of the bioleaching process can be significantly increased by reducing the power supplied to the mixing device, under conditions associated with a decrease in oxygen consumption during this process.

- 1 013851

The present invention relates to a control method aimed at reducing energy consumption per unit of sulfide material being processed under the above conditions.

Brief description of the invention

The present invention relates to a method for carrying out a bioleaching process, which includes the following operations:

feeding the sulphide mineral slurry into the reactor, bubbling the gas through the said slurry in the reactor, mixing the slurry in the reactor with an electric-powered mixing device, which provides biooxidation of the sulfide mineral, and controlling the feed rate of the sparged gas into the reactor and energy supplied to the stirrer drive, depending on at least one of the following factors:

measured oxygen consumption and estimated oxygen consumption, characterized in that the power supplied to the drive of the agitator and / or power supplied to the gas source is reduced if the specified measured or calculated oxygen consumption decreases.

Brief Description of the Drawings

The present invention is further described using an example implementation with reference to the accompanying drawings, where FIG. 1 and 2 relate to the current situation; their description was given above;

FIG. 3 illustrates the energy consumption per unit of sulfide material for compressors and mixing devices for an installation in which the process is carried out using thermophilic microorganisms, with standard quality sulfide material, halved quality sulfide material and halved quality sulfide material with reduced mixing power, respectively;

FIG. 4 illustrates the energy consumption per unit of sulfide material for compressors and mixing devices for an installation in which the process is carried out using thermophilic microorganisms, at full load, load by 2/3 and load by 2/3 with reduced mixing power, respectively;

in fig. 5 is a block diagram of an embodiment of the method according to the present invention.

Description of the preferred embodiments

FIG. 5 of the accompanying drawings is a block diagram of an installation 10 in which the oxidation of a sulfide material is carried out by bioleaching in a tank reactor equipped with a stirrer, in accordance with the principles of the present invention.

Although FIG. 5 shows only one tank reactor 12, this installation includes several tank reactors equipped with a mixing device. Vat reactor includes a mixing device or impeller 14 (in the present description, these terms are interchangeable), driven by an electric motor 16 using methods known in the art. Electric energy is supplied to the engine from source 18.

A gas source 20 is provided at the bottom of the reactor 12 for supplying the bubbling gas to diffusers or similar spraying devices 22. The feed gas may be air, air enriched with oxygen, or substantially pure oxygen. Source 20 may include one or more compressors, air pumps, and the like. For this purpose, you can use traditional devices. The feed rate of gas from the source to the tank reactor is controlled by a sensor 24, information from which is fed to the control computer 26. Input data from other sources is sent to the controller, which can control by changing the gas feed rate from the source to the reactor.

The flow of the suspension 28 in the tub reactor is carried out in a controlled manner. The suspension contains water, nutrients and a sulfide mineral concentrate. The method according to the present invention is not limited to any particular type of mineral and, as a rule, can be used to extract gold, copper, nickel and zinc.

The tank reactor in question is not necessarily a primary reactor; it may be a secondary reactor into which the product from the first reactor is sent for further oxidation.

The tank reactor 12 contains a self-sustaining population of microorganisms that function as a catalyst for the oxidation of bivalent iron and a sulfide mineral. Oxygen is required for these reactions, and, as shown, it comes from a gas source 20.

The concentration of oxygen dissolved in the suspension in the tank reactor 12 is controlled using a suitable sensor 30. The composition of the outgoing gas is determined using sensor 32. Oxygen consumption is calculated either on the basis of gas consumption data in gas supply device 20,

- 2,013,851 stepping from sensor 24 and sensor 32, either using an appropriate algorithm based on power data from information outputs of a mixing device 18, as well as data from information outputs of a gas supply device 20 and sensor 30, or the manual oxygen consumption rate measures the operator.

Calculated or measured, depending on the circumstances, the rate of oxygen consumption is used in the appropriate algorithm to determine the most effective value of the energy supplied to the engine 16, taking into account the total energy consumed for supplying gas to all reactors of the installation, and any gas supply restrictions. The specified algorithm can be implemented as carried out automatically, using the control computer 26, or manually, by entering the source data by a qualified operator. The total energy consumption of all mixing reactors and gas supply compressors is measured and recorded to enable further analysis.

The present invention is to improve the efficiency of the oxidation process by regulating the power supplied to the mixing device, and the amount of gas supplied to the suspension.

In one embodiment, the implementation of the present invention, a method aimed at solving the above problem. In particular, a method is proposed for carrying out a bioleaching process, which includes the following operations:

feeding the sulphide mineral slurry into the reactor, bubbling the gas through the said slurry in the reactor, mixing the slurry in the reactor with an electric-powered mixing device, which provides biooxidation of the sulfide mineral, and controlling the feed rate of the sparged gas into the reactor and energy supplied to the stirrer drive, depending on at least one of the following factors:

measured oxygen consumption and estimated oxygen consumption, characterized in that the power supplied to the drive of the mixer, and / or the power supplied to the gas source is reduced if the specified measured or calculated oxygen consumption decreases.

FIG. 3 shows three points characterizing the course of the process, namely, point 40 of normal operation, point 42, showing the effect of reducing the quality of sulfide material by half in the absence of reducing the power of the mixing device, and point 44, showing the effect of reducing the quality of sulfide material by half with a corresponding decrease in the power of the mixing device .

From FIG. 3, it can be seen that with the quality of the sulfide material reduced by half, the energy consumption, i.e. the energy consumed by the engine 16 and the source 20 of gas, about 35% more than in the case when the power supply to the mixing device is reduced. However, with a decrease in energy consumption, the energy consumption per unit of sulphide material processed increases by about 21%.

By reducing the quality of the sulfide material, the efficiency of the oxidation process decreases, as indicated in the explanatory notes to FIG. 1-3. It should be borne in mind that for installations in which processes using microorganisms are carried out, a reduction in the quality of the material does not always lead to a decrease in the process time at the same predetermined percentage of the valuable mineral that should be achieved after extraction.

Often it is a decrease in concentrate loading leads to a decrease in plant performance. FIG. 4 shows the capacity of the plant during normal operation (point 48), with operation by 2/3 of the design capacity with (point 50) and without (point 52) reducing energy consumption by the mixing device. Reducing the feed rate of the concentrate leads to an increase in energy consumption per unit of sulphide material being processed by 24% while reducing only the power consumed by the gas source 20. However, if the processor 30 is used to optimize the operation of the engine 16 and the source 20 to regulate the energy expended in mixing and the energy expended on aeration, the increase in energy consumption per unit processed sulfide material is approximately 14%.

The present invention is directed to the optimization of the bio-leaching section of the plant. Aspects related to the control of energy consumption can be implemented by using electric drives with variable speed, which, as a rule, are made with the possibility of automatic control. Also, to optimize the entire process or parameters of an individual reactor, you can use measured or calculated oxygen consumption rates along with mathematical correlation and the use of mathematical models. With regard to optimizing the parameters of a separate reactor, it should be borne in mind that the invention is described on the example of a separate reactor or vat, but in practice a group of reactors is used.

Thus, the present invention provides an increase in overall efficiency with a corresponding reduction in energy consumption.

Reducing energy consumption is achieved by using the interdependence between energy,

- 3 013851 supplied to the engine, and the energy supplied to the gas source. At the same time, the cumulative amount of energy supplied is optimized, in contrast to the optimization of energy consumption of one engine only.

The information received during the process is processed automatically or can be transferred to the management staff, who can then perform the appropriate regulatory actions manually.

Claims (4)

1. A method of carrying out a bioleaching process, which includes the following operations: feeding a suspension of sulfide mineral into a reactor, bubbling gas through a suspension in a reactor, mixing the suspension in a reactor with an electric stirring device, providing a biooxidation process of said sulfide mineral, and speed control supply of bubbling gas to the reactor and energy supplied to the stirrer drive, depending on the oxygen consumption rate determined by m nshey least one of the following factors: the measured oxygen consumption and the calculated oxygen consumption, characterized in that the power supplied to the stirrer drive and / or the power supplied to the source gas is reduced, if said measured or calculated oxygen consumption decreases. 2. The method according to claim 1, including the operation of collecting data characterizing the feed rate of the bubbling gas into the reactor and the composition of the gas leaving the reactor, as well as the calculation of oxygen consumption based on the obtained data. 3. The method according to claim 1, characterized in that the oxygen consumption depends on the power developed by the stirring device with an electric drive, the feed rate of the bubbling gas into the reactor and the content of dissolved oxygen in the suspension. 4. The method according to claim 1, including the operation of reducing the feed rate of the suspension into the reactor while reducing the quality of the sulfide material from which the suspension is obtained.