Method for reducing moisture in ore in conveyor belts and transfer chutes

Abstract

The present application relates to a method for reducing moisture in ore in a conveyor belt and a transfer chute. A method of removing ore moisture (2) by exposing ore (2) to a hot drying air stream is described. A conveyor belt (13) and a transfer chute (3) adapted specifically for the above method are also described. The method has, in particular, the function of reducing moisture in such a material prior to the transport phase of the ore (2).

Description

[0001] This application is a divisional application of the invention patent application with the application date of October 4, 2016, application number 201680062394.0, and invention name "Method for reducing ore moisture in conveyor belts and transfer chutes". Technical Field

[0002] The present invention is a method and apparatus for reducing the moisture content of ore prior to ore material handling operations. Background Art

[0003] Conveyor belts and transfer chutes are devices used to transport a variety of materials, in this case, ore.

[0004] The conveyor belt consists of an apparatus essentially formed by an endless belt extending between two drive drums (drive and return) and an internal structure constructed of laminated profiles and juxtaposed rollers, over which the sliding belt enables the movement of the ore located on the belt.

[0005] A transfer chute consists of a device typically used to transfer material between conveyor belts operating in different directions. This basically consists of a funnel configured to mediate the transfer of material, the funnel being formed from associated steel plates and wear material.

[0006] In this case conveyors and transfer chutes are used in particular to transport the ore from the rails to the landing end. After homogenization of the pile and recovery of the ore, it passes through conveyors and transfer chutes to the ship for transportation to the final destination. However, it is not uncommon for such equipment to transport ore with a considerable moisture content, which is a disadvantageous feature for sea transportation.

[0007] The moisture content of the ore brings serious disadvantages to its transportation. The first one is related to the freight costs, since each unit of water transported represents an additional expense, such as a penalty to the supplier when the ore sold is valued on a dry matter basis. In addition, it reduces the ore transport capacity, causing significant losses.

[0008] However, it is well known that the shipping of excessively moist bulk solid cargoes may imply a risk of capsizing and sinking of the cargo ship due to a phenomenon known as "granular load liquefaction", which occurs when the moist ore faces the balance of the ship, the vibration of the ship's engines and the continuous impact of the sea on the hull. When the moisture percentage of the ore exceeds the value corresponding to the flow moisture point (Flow Moisture Point, FMP) and the ore is subjected to such vibration conditions, it may liquefy. When the material liquefies, this viscous mixture may move unduly to the bottom and / or walls in the ship's hold, lose balance, and eventually cause the ship to sink due to the inertial forces acting on the ore cargo / ship.

[0009] In order to prevent the transportation of ore with high moisture content, the government's technical standards establish the TML (Transportable Moisture Limit), which is the maximum amount of moisture the ore must contain to be suitable for transport vessels. In practice, the TML adopts a value equal to 90% of the FMP.

[0010] It is therefore extremely important to use equipment and methods that ensure that the TML requirements regarding ore moisture are met before the material is shipped.

[0011] At the current state of the art, different types of drying equipment can be used, such as rotary kilns. These devices generally have high installation, operation and maintenance costs, mainly due to the high energy consumption. In addition, such drying equipment needs to be installed in series with conveying equipment (especially conveyor belts, chutes). Therefore, changes need to be made in the conveying pipeline for installing such drying equipment, so that the layout-process flow diagram is changed due to the need for more space. However, longer interruption times will be spent in the conveying pipeline for installation, which significantly increases costs and greatly disrupts the production process, and also implies the need for large storage yard areas.

[0012] Therefore, reducing ore moisture using existing state-of-the-art drying equipment implies high costs for equipment purchase, installation, operation and maintenance.

[0013] The state of the art also includes devices for drying or even dehydrating food and other materials. One of such devices is disclosed in document US2395933.

[0014] The device disclosed in US2395933 is configured to generate a hot air flow which is directed into the material being transported by the conveyor belt. Such devices include a conveyor belt, a fan, a heater and specific instrumentation.

[0015] The conveyor belt is set to transport the material along the machine, and the environment is isolated so that the air blown by the fan is retained inside the machine.

[0016] The fan is set to blow air into the device and is mounted in series with the heater. The fan blades are set to direct the air blown by the fan into the conveyed material. These can be oriented in the direction that is most suitable for the process so that all the material present on the belt is dehydrated. Temperature, air humidity and material and other variables involved are also measured.

[0017] Although the device disclosed in document US 2395933 reduces the moisture of the product conveyed on the belt, it is not suitable for reducing the moisture of the ore. The device of the above document does not previously remove moisture from the air used in the process, making it exhibit low efficiency during drying of the material.

[0018] Other devices included in the state of the art are disclosed in document US 2415738. This document presents a device for partially dehydrating cellulose-containing products, food products and other industrial materials. This type of device consists of a conveyor belt group in an isolated environment in which hot gases are injected.

[0019] The equipment includes a conveyor belt, an exhaust pipe, a gas chamber, a pump and a monitoring system. The environment in which the conveyor belt is located is isolated so that the gas remains inside, and the pump is set to inject hot gas into the isolated environment.

[0020] The inlet pipe is responsible for admitting the gas, while the exhaust pipe is set to remove excess gas from the internal environment. The exhaust pipe also allows the removed gas to be reused, returning it to the drying chamber.

[0021] Measuring process-related variables such as gas temperature and flow rate. Variable monitoring systems allow machine settings to be changed to ensure optimal functioning.

[0022] Similar to patent document US2395933, document US2415738 discloses a device for reducing the moisture contained in industrial materials conveyed in a belt, however, this device is not suitable for reducing the moisture of ores. The device of the above document previously did not remove moisture from the air used in the process, so that it exhibited low efficiency and high energy consumption during drying of the material.

[0023] According to the equipment described in these documents, in the state of the art there is no method or equipment for reducing the moisture content of an ore to a percentage below the TML with low installation, operation and maintenance costs. Summary of the invention

[0024] The present invention is directed to a method for reducing the moisture content of ore in conveyors and transfer chutes with low installation and operating costs.

[0025] The present invention is also directed to an apparatus for reducing the moisture content of ore in conveyors and transfer chutes with low installation and operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention is described in detail based on the corresponding figures:

[0027] Figure 1 - depicts a front view of a conveyor belt adapted for use in the method defined by the invention.

[0028] Figure 2 -Describe Figure 1 A cross-sectional front view of the belt revealed in FIG.

[0029] Figure 3 - depicts a front view of a transfer chute adapted for use in the method of the invention.

[0030] Figure 4 -Describe Figure 3 Cross-sectional front view of the transfer chute in FIG.

[0031] Figure 5 - Depicting a front view of a transfer chute and conveyor belt combination modified by the method of the present invention.

[0032] Figure 6 -Describe Figure 5 A cross-sectional elevation view of the setting disclosed in FIG.

[0033] Figure 7 - A flow chart showing the method of implementation of the present invention in its preferred use setting. DETAILED DESCRIPTION

[0034] like Figure 7 The invention disclosed in the invention consists of a method for reducing the moisture content of an ore 2, said method comprising the following steps:

[0035] Step 1 - inserting ore 2 into a closed environment;

[0036] Step 2 - Removing moisture from atmospheric air;

[0037] Step 3 - heating the atmospheric air from step 2;

[0038] Step 4 - Blowing the dry hot air from step 3 into the closed environment containing the ore 2 of step 1.

[0039] The removal of moisture from the atmospheric air depicted in step 2 is preferably carried out by condensing the water vapor present in the air by means of an evaporator unit consisting of a cooling system (see Figure 2 and 4 ).

[0040] As is known, the cooling system consists of an evaporator unit, a condenser unit, a compressor and an expansion valve, which operate in a closed thermodynamic cycle. The coolant fluid circulates between the four elements, being injected into the compressor, which performs work on the fluid, thus increasing its temperature. After the compressor, the fluid passes through the condenser, which is intended to condense it, thus cooling the fluid. Furthermore, this fluid passes through the expansion valve, where it is subjected to a sudden pressure and temperature reduction. The evaporator is responsible for evaporating a portion of the liquid produced during the expansion of the fluid, ensuring that the gas / liquid mixture is completely evaporated and returned to the compressor in gaseous form, completing the thermodynamic cycle.

[0041] The spray coolant fluid reaches extremely low temperatures when passing through the expansion valve. In the evaporation unit, the fluid passes through a serpentine tube that surrounds a mesh of metal fins, the function of which is to increase the efficiency of heat exchange. The water vapor in the atmospheric air passing through the evaporator coil condenses when it contacts the fins and serpentine tubes contained in the evaporation unit of the cooling system.

[0042] For this reason, the atmospheric air in contact with the evaporation unit of the cooling system loses moisture and its temperature decreases. Generally speaking, this is the beginning of the drying of the atmospheric air carried out in step 2 of the moisture reduction method of the invention.

[0043] To heat the drying air coming from step 2, it passes through a circuit of resistors or heat exchangers such as boilers, direct or indirect contact gas burners, etc. This heating of the cold drying air is the third step of the method defined by the invention.

[0044] The fourth step is to expose the ore 2 to the hot dry air from step 3. This exposure uses the principles of heat and mass transfer to cause this hot dry air injected into the closed environment to remove a portion of the moisture from the ore body 2.

[0045] In order to avoid thermal power loss in step 4, the environment should preferably be covered with an upright material that is non-porous and has thermal insulation capabilities.

[0046] The method disclosed above should be carried out on a conveyor belt 13 and / or a transfer chute 3 or an environment that allows continuous flow of ore 2 and dry hot air.

[0047] This article Figure 1 and 2 The conveyor belt 13 disclosed in the invention comprises an insulated duct 1 and a dry hot air supply unit 5, the dry hot air supply unit comprising an evaporator unit 15 (configured for water vapor condensation in the environment), a heating unit 16 and a forced ventilation unit 14. Preferably, the dry hot air supply unit 5 is connected to the inner part of the insulated duct 1 through a feed duct 4.

[0048] For the purpose of defining the scope of protection of the present invention, it should be understood that any device capable of removing moisture from the atmospheric air by condensation of water vapor may serve as evaporator unit 15. This definition includes air conditioners, fan coil type units and other industrial refrigeration equipment that use a membrane of cooling gas or even a fluid, usually chilled water (obtained using a chiller), to reach the wet bulb temperature of the atmospheric air.

[0049] To obtain a more accurate and efficient ore moisture removal method, the conveyor belt 13 in its preferred configuration comprises at least one measuring device 9 and an automated controller 7. The measuring device 9 consists of electronic accessories such as: thermometer / dry bulb thermocouple and wet bulb, pressure gauge, anemometer, air humidity meter, ore moisture meter and infrared contact thermometer for measuring the ore and conveyor belt surface temperature.

[0050] The above-mentioned measuring device 9 is connected to an automation controller 7, which consists of a control panel installed close to the conveyor belt 13. The automation controller 7 processes the information from the measurement results obtained by the measuring device 9 and automatically changes it into the functions of all the elements of the conveyor belt 13 system, with the main changes concentrated in the dry hot air supply unit 5. The historical data of the information obtained in the system are also recorded and archived.

[0051] Such changes are made to control key process parameters so that the conveyor belt 13 operates under optimum process conditions, which are continuously monitored to achieve the best results in reducing the moisture content of the ore.

[0052] A more efficient method of removing moisture from the ore than on the conveyor belt 13 is to remove moisture in the transfer chute 3 .

[0053] Generally speaking, for the purposes of defining the scope of the present invention, a transfer chute may be defined as a sealed vessel configured to convey minerals by gravity, comprising an ore inlet 17 in an upper portion, an ore outlet 18 in a lower portion, and a central chamber 21 .

[0054] As in this article Figure 3 and 4 As can be seen in the figure, the operating principle of the transfer chute 3 of the present invention is almost the same as that of the conveyor belt 13. However, the moisture reduction method in the transfer chute 3 is generally more efficient than that in the conveyor belt 13, because the exposure area is significantly increased due to the fluidization of the belt-like ore bed, so that the contact surface between the transported ore and the air from the dry hot air supply unit 5 is larger. This type of equipment can produce a fast drying method because the mineral particles are exposed to the dry hot air for only a few seconds.

[0055] The dry hot air passes through the dry hot air supply unit 5 combined with the feed pipe 4, through the air inlet 19, and is blown into the transfer chute 3 in countercurrent with the ore. The dry hot air supply unit 5 also includes an evaporator unit 15, a heating unit 16, a forced ventilation unit 14 and a cooler type water cooling unit.

[0056] When the hot dry air contacts the ore 2 in the transfer chute 3, a cloud of suspended particles is created, referred to as "particulate material". The distribution of particulate material in the atmosphere can cause unnecessary loss of material and also generate air pollution if not properly handled.

[0057] To solve this problem, the transfer chute 3 comprises, in its preferred configuration, an exhaust pipe 6 which connects the air outlet 22 with the compartment 11. The exhaust pipe 6 is configured to remove the air containing the particulate matter and transfer it to the compartment 11, which is subjected to a cyclonic separation process. The cyclonic separation allows the particulate matter to be collected, making the air clean before returning to the atmosphere. The collected particulate matter can be incorporated into the dry ore 2 remaining in the transfer chute 3 or into the ore already stored in the stockyard. A circulating load of a certain amount of particulate matter can be formed to prevent the accumulation and subsequent disposal of this material.

[0058] The exhaust system of the conveyor belt 13 consists of only one exhaust hole 6' which is arranged to allow saturated moist air to be removed naturally from the insulated pipe 1, as particulate matter on the belt is not significantly exhausted. It should be noted that on the conveyor belt 13, the air flow can be operated countercurrent and / or cocurrent with the ore on the conveyor belt. For the transfer chute, the flow is only in countercurrent.

[0059] Recent experiments have shown that for the specific case of iron ore having an initial moisture content of approximately 10-12%, the present invention is able to reduce the moisture of the ore by 0.5-1.8 percentage points on the conveyor belt 13 and by 0.5-2.0 percentage points in the transfer chute 3, depending on the temperature and air flow conditions used. The experimental equipment exhibited an installed power of 180kw.h, providing approximately 650,000kJ / h of energy to the system.

[0060] These values ​​obtained for the moisture reduction in the iron ore are very significant because it takes much higher energy to achieve the same moisture percentage when it is only hot air or only dry cold air to remove moisture. In other words, it can be said that the sum of the evaporator unit 15 to the heater unit 16 contained in the dry hot air supply unit 5 shows unexpected results because the combined effect of the two is greater than the sum of these parts when taken separately.

[0061] That is, the use of dehumidification mechanism and air heating mechanism when used in separate forms exhibited lower efficiency in reducing the moisture content of iron ore, since the combined form uses heat and mass transfer principles. Therefore, it can be experimentally observed that the use of dry hot air in the combined mechanism resulted in a greater percentage increase in ore body water removal.

[0062] The combination of a transfer chute 3 and a conveyor belt 13 clearly provides more significant results than using a single chute 3 or belt 13. For this reason, a preferred configuration of the invention comprises at least one transfer chute 3 associated with a conveyor belt 13, such as Figure 5 and 6 The presented.

[0063] Finally, it can be concluded that the present invention achieves all the objectives it set out to achieve, disclosing a method and an apparatus for reducing ore moisture on conveyors and transfer chutes with low installation and operating costs.

[0064] Having described some examples of preferred implementations of the present invention, it is noted that the scope of protection possessed herein encompasses all other alternative forms suitable for implementing the present invention, being defined and limited only by the contents of the appended claim forms.

Claims

1. A method for reducing the moisture content of an ore, the method comprising the following steps: a) conveying the ore in an isolated enclosure which allows the ore and drying air to flow continuously therethrough, The housing includes an inlet and an outlet defining at least a portion of an ore conveying path therebetween; b) removing moisture from atmospheric air by condensation of water vapour, said atmospheric air being supplied to a dry hot air supply unit; c) heating said atmospheric air from step b); and d) blowing the dry hot air from step c) into the closed enclosure containing the ore.

2. A method of reducing ore moisture according to claim 1, wherein the moisture is removed from the atmospheric air by using an evaporator unit consisting of a cooling system.

3. A method of reducing moisture in ore as claimed in claim 1, wherein moisture is removed from the atmospheric air by using a fan coil type unit.

4. A method for reducing the moisture content of an ore according to claim 1, wherein step c) is performed by using an electrical resistance for heating purposes.

5. The method for reducing moisture in ore according to claim 1, wherein step c) is performed by using a heat exchanger comprising a boiler.

6. A method of reducing moisture in ore as claimed in claim 1, wherein step c) is carried out by using direct and / or indirect contact gas burners.

7. The method of reducing moisture in an ore according to claim 1, wherein the isolation enclosure further comprises an insulated duct surrounding the conveyor belt.

8. The method of reducing ore moisture according to claim 1, wherein the isolation shell further comprises an outer structure of a transfer chute, the transfer chute comprising: an ore portal; an air intake; an ore outlet; as well as a central chamber; The central chamber is placed between the ore inlet and the ore outlet; and the air inlet is configured to be filled with hot dry air that undergoes a condensation and heating process before entering the central chamber of the chute.

9. A method for reducing the moisture content of an ore according to claim 8, wherein the transfer chute also comprises an exhaust pipe, which is configured to remove the air injected into the transfer chute after it comes into contact with the ore (2) contained in the transfer chute (3) and transfer the air to a compartment, which performs a cyclone separation process.

10. A method of reducing the moisture content of an ore as claimed in claim 9 wherein the compartment in which the cyclonic separation process is carried out removes particulate material from the air contacting the ore.

11. The method for reducing ore moisture according to claim 1, wherein the isolation housing of step a) further comprises an isolation pipe, which is radially installed around the conveyor belt structure and is configured to isolate the conveyor belt from the external environment, and the conveyor belt also includes a dry hot air supply unit; and a feed pipe, which is configured to connect the internal environment of the isolation pipe with the dry hot air supply unit.

12. The method for reducing moisture in ore according to claim 11, wherein the hot drying air supply unit comprises at least one heating unit.

13. The method of reducing ore moisture according to claim 11, wherein the hot drying air supply unit comprises at least one evaporation unit.

14. The method for reducing moisture in ore according to claim 11, wherein the hot drying air supply unit comprises at least one forced ventilation unit.

15. The method of reducing ore moisture according to claim 11, further comprising a vent hole configured to naturally remove humid air from within the insulated conduit.

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