Use method of gravity double-tube microwave-assisted grinding device capable of controlling ore thickness

A use method of a gravity double-tube microwave-assisted grinding device, wherein the gravity double-tube microwave-assisted grinding device comprises a microwave heating device and a conveying platform;

• the microwave heating device comprises a microwave source, a tuner, a waveguide, and a water load;
• an output end of the microwave source is connected with one end of the tuner, another end of the tuner is connected with the waveguide, the water load is arranged at a tail end of the waveguide along a radial direction and absorbs an excess microwave energy, and a circular through hole is formed in a middle of a horizontal section of the waveguide;
• the conveying platform comprises a feeding bin, a feeder, a feeding hopper, a choke coil, a metal tube, a quartz tube, and a discharger;
• an inlet end of the feeding bin is connected with an upstream process product feeding system for storing materials fed from an upstream process, an outlet end of the feeding bin is connected with an inlet end of the feeder, and the feeder conveys ores from the feeding bin to the feeding hopper, and a speed of the feeder and a speed of the discharger are controlled to be matched with each other so as to prevent overflow of the materials from the feeding hopper;
• an outlet end of the feeder is located above the feeding hopper, an outlet end of the feeding hopper is connected with an upper end of an upper section of the metal tube, a lower end of the upper section of the metal tube is connected with one end of the quartz tube, another end of the quartz tube passes through the circular through hole in the waveguide and is connected with one end of a lower section of the metal tube, another end of the lower section of the metal tube is connected with an inlet end of the discharger, an outlet end of the discharger is connected with a downstream grinding equipment, and the discharger is a star discharger for controlling the speed of the discharger, so as to control a heating time of the ores;
• an outer surface of the upper section of the metal tube, an outer surface of the waveguide and an outer surface of the lower section of the metal tube are wrapped with the choke coil, so as to limit escape of a microwave energy;
• and a through hole allowing the waveguide to pass through is formed in the choke coil, shooting devices are respectively mounted at a microwave input end and a microwave output end of the waveguide, so as to monitor macro phenomena and temperature during ore irradiation,
• wherein the method comprises the following steps:
• step 1, estimating a metal mineral content of the ores according to a proportion of a metal mineral area on surfaces of the ores, wherein the metal mineral content is classified into a high content (>50%), a medium content (10-50%) and a low content (<10%);
• step 2, calculating a penetration depth of the ores, testing dielectric constants of massive samples and granular samples of the ores respectively by a vector network analyzer in a laboratory, and substituting a real part and an imaginary part of a dielectric constant of massive ores into an equation (1) to calculate Dp, wherein at this time, a penetration depth Lb of the massive ores is equal to Dp;
• substituting a real part and an imaginary part of a dielectric constant of granular ores into the equation (1) to calculate Dp, wherein at this time, a penetration depth Lp of the granular ores is equal to Dp;
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• wherein Dp is the penetration depth, λ0 is a wavelength, ε′ is a real part of the dielectric constant, and ε″ is an imaginary part of the dielectric constant;
• step 3, determining a feeding size by using an on-site estimation method and a test method;
• (1) the on-site estimation method:
• performing estimation according to the metal mineral content and a metal mineral structure on the surfaces of the ores:
• for the high content and a massive distribution of the metal mineral structure, estimating that the feeding size is a size of finely-ground products (<14 mm);
• for the medium content and a punctate distribution or vein distribution of the metal mineral structure, estimating that the feeding size is a size of medium-ground products (<50 mm);
• and
• for other cases, selecting the test method for determination;
• (2) the test method:
• the penetration depth Lb of the massive ores, calculated according to step 2;
• when the penetration depth Lb of the massive ore samples is less than 10 mm, determining that the feeding size is the size of the finely-ground products (<14 mm);
• when the penetration depth Lb=(10-50) mm of the massive ore samples, determining that the feeding size is the size of the medium-ground products (<50 mm);
• and
• when the penetration depth Lb of the massive ore samples is greater than 50 mm, determining that the ores are not suitable for microwave-assisted ore grinding;
• step 4:
• determining a material thickness, wherein according to the feeding size determined in step 3, the material thickness is classified into two categories:
• (1) when the feeding size is the size of the medium-ground products, determining that the material thickness is 20 cm;
• and
• (2) when the feeding size is the size of the finely-ground products, determining that the material thickness is 10-20 cm;
• when the feeding size is the size of the finely-ground products, and the penetration depth Lp of the granular ores is less than 5 cm, determining that the material thickness is 10 cm;
• step 5:
• determining a discharging speed Vp0 (kg/s) of the feeding hopper, given a feeding speed Tm (kg/s) of the feeding bin, the discharging speed Vp0 is calculated by an equation (2);
• Vp0=Tm (2)
• step 6, determining an outer diameter of an inner tube of the microwave-assisted grinding device,
• wherein when the feeding size calculated in step 3 is the size of the medium-ground products, a metal inner tube of the upper section of the metal tube, a quartz inner tube and a metal inner tube of the lower section of the metal tube are not provided, the gravity microwave-assisted grinding device adopts a single-tube structure consisting of a metal outer tube of the upper section of the metal tube, a quartz outer tube and a metal outer tube of the lower section of the metal tube, a heating cavity is formed in an inner hole of the metal outer tube of the upper section of the metal tube, the quartz outer tube and the metal outer tube of the lower section of the metal tube, and outer diameters of the metal outer tube of the upper section of the metal tube, the quartz outer tube and the metal outer tube of the lower section of the metal tube are respectively 20 cm;
• when the feeding size calculated in step 3 is the size of the finely-ground products, the metal inner tube of the upper section of the metal tube, the quartz inner tube and the metal inner tube of the lower section of the metal tube are provided, and the gravity microwave-assisted grinding device adopts a double-tube structure consisting of the metal outer tube of the upper section of the metal tube, the quartz outer tube, the metal outer tube of the lower section of the metal tube, the metal inner tube of the upper section of the metal tube, the quartz inner tube and the metal inner tube of the lower section of the metal tube;
• and the outer tube and the inner tube form the heating cavity, outer diameters of the metal inner tube of the upper section of the metal tube, the quartz inner tube and the metal inner tube of the lower section of the metal tube are 5 cm, and when the penetration depth Lp of the granular ores is less than 5 cm, the outer diameters of the metal inner tube of the upper section of the metal tube, the quartz inner tube and the metal inner tube of the lower section of the metal tube are increased to 10 cm;
• and
• step 7, conveying the ores, and performing heating, wherein the ores fall from the feeding hopper and pass through the heating cavity under an action of self-gravity, a microwave power of the microwave source is 100 kW, the ores are transferred into the heating cavity through the waveguide, the microwave energy is limited in the heating cavity under an action of the choke coil to prevent the microwave energy from escaping, the microwave energy in the heating cavity is used to heat the ores in a heating process of the ores, and in the heating process of the ores, if a spark phenomenon is severe, the feeding size of the ores is reduced;
• if a temperature distribution of the ores is becoming seriously polarized, the material thickness of the ores fed is reduced;
• in the heating process of the ores, high-speed cameras are used for shooting the macro phenomena during the ore irradiation, infrared thermal imagers are used for observing the temperature distribution of the ores, and the feeding size of step 3 and the discharging speed of step 5 are optimized;
• the heated ores enter the discharger and then enter the downstream grinding equipment through the discharger;
• if poor ore damage situations have no effect on ore grinding, an irradiation time are prolonged by reducing the discharging speed, and meanwhile, excess ores in the feeding bin are discharged from other outlets into another gravity double-tube microwave-assisted grinding device;
• and if ore sintering has a negative effect on the ore grinding, the microwave power is reduced.