Limonite coal-based oxidation-reduction roasting system

Abstract

The utility model relates to a limonite coal-based oxidation-reduction roasting system which comprises an oxidation roasting system, a reduction roasting system, a cooling slurrying system and a hot air circulating system which are connected in sequence, and the oxidation roasting system comprises a constant feeder, a rotary kiln and a combustor; the reduction roasting system comprises a first screw feeder, a reducing agent bin, a reducing agent screw feeder, a reduction reactor, a discharge chute, a second screw feeder and a feeding chute; the cooling pulping system comprises a sealed stirring tank, a slurry pump and a spraying system, and the hot air circulating system comprises a water bath dust remover, an air return fan and an air conveying pipeline. The system has the advantages that the system enables limonite coal-based oxidation and reduction roasting to be performed in sections according to process requirements without mutual interference, the reduction reactor adopts an internal spiral reactor and is easy to seal, a certain pressure in the reactor is ensured, and the reduction efficiency is improved. The spiral rotating speed of the reactor is adjustable, and reduction time can be adjusted according to reaction requirements.

Description

Technical Field

[0001] The utility model belongs to the technical field of metal mineral beneficiation and reduction roasting, and more specifically, relates to a limonite coal-based oxidation-reduction roasting system. Background Art

[0002] At present, the coal-based reduction roasting process mainly uses a rotary kiln for roasting. A burner is arranged at the head of the rotary kiln for heating the materials in the rotary kiln. The materials to be roasted are fed into the rotary kiln from the tail after adding pulverized coal in proportion. In theory, the reduction roasting is completed through two technological sections of preheating and reduction. However, in actual production, when a single rotary kiln is used for magnetic reduction roasting, the production is unstable, the indexes are poor, and the production line is mostly in a stagnant state. The main reasons for the failure of this process include the following aspects: (1) Reduction and heating are carried out in one rotary kiln. The head of the kiln is in an oxidation atmosphere, and the middle and tail of the kiln are in a reduction atmosphere. And air passes through the cavity from the head to the tail of the kiln, so the atmosphere is difficult to control, and the reduced materials are partially re-oxidized after passing through the oxidation atmosphere at the head of the kiln; (2) In the reduction atmosphere, the low-melting-point substances in the materials to be roasted and pulverized coal are easy to liquefy and form rings; (3) Due to the difficult control of the atmosphere in the kiln, local combustion occurs, the temperature is too high, and there is an over-burning phenomenon; (4) The temperature of the materials in the rotary kiln fluctuates greatly, and the reduction time of the materials cannot be guaranteed at the effective reduction temperature. Summary of the Invention

[0003] The purpose of the utility model is to provide a limonite coal-based oxidation-reduction roasting system. The purpose of the utility model is realized through the following technical solutions:

[0004] A limonite coal-based oxidation-reduction roasting system of the utility model is characterized in that it includes an oxidation roasting system, a reduction roasting system, a cooling and pulping system and a hot air circulation system which are connected in sequence,

[0005] The oxidation roasting system includes a metering feeder, a rotary kiln and a burner. The discharge port of the metering feeder is connected to the feed port of the rotary kiln, and the burner is arranged at the head of the rotary kiln;

[0006] The reduction roasting system includes a first screw feeder, a reductant bin, a reductant screw feeder, a reduction reactor, a discharge chute, a second screw feeder and a feed chute. The first screw feeder is arranged at the bottom of the head of the rotary kiln, the feed port of the first screw feeder is connected to the discharge port of the rotary kiln, the reductant screw feeder is arranged at the upper side of the first screw feeder, the feed port of the reductant screw feeder is connected to the reductant bin, the discharge ports of the first screw feeder and the reductant screw feeder are both connected to the feed port of the reduction reactor through a chute, one end of the second screw feeder is connected to the discharge port of the reduction reactor through the discharge chute, and the other end is connected to the feed chute;

[0007] The cooling pulping system comprises a sealed stirring tank, a slurry pump and a spray water system. The spray water system is provided in the sealed stirring tank. The feed chute is connected to the feed port of the sealed stirring tank and inserted into the sealed stirring tank. The slurry pump is connected to the lower discharge port of the sealed stirring tank.

[0008] The hot air circulation system includes a water bath dust collector, a return air fan and an air transmission pipeline. One end of the exhaust pipe of the cooling pulping system passes through the top cover of the sealed stirring tank and is connected to the sealed stirring tank, and the other end is connected to the air inlet of the water bath dust collector. One end of the return air fan is connected to the air outlet of the water bath dust collector, and the other end is connected to the exhaust pipeline. The end of the exhaust pipeline is connected to the kiln head of the rotary kiln and is arranged at the upper end of the burner of the oxidation roasting system.

[0009] Preferably, a flue gas treatment system is also provided at the kiln tail of the rotary kiln, and the flue gas treatment system comprises a hot air exhaust duct, a bag filter and a main exhaust fan.

[0010] Preferably, the exhaust pipe end is arranged 100 mm above the burner of the oxidation roasting system.

[0011] Preferably, the reduction reactor is an internal spiral reactor, comprising a driving device, a cylinder, a stirring main shaft, spiral blades arranged on the stirring main shaft and sealing mechanisms arranged at both ends of the stirring main shaft, lifting plates are arranged at intervals on the sides of the spiral blades, a feed port for entry and an input port for passing the reducing agent are arranged at the top of the reduction reactor, a discharge chute for discharging is arranged at the right end of the reduction reactor, and a temperature sensor is also arranged on the chute.

[0012] The advantages of the utility model are:

[0013] 1) The system can make the oxidation and reduction roasting of limonite coal-based be carried out in sections according to process requirements without interfering with each other.

[0014] 2) The reduction reactor uses an inner spiral reactor, which is easy to seal, ensures a certain pressure in the reactor, and improves the reduction efficiency. The reactor spiral speed is adjustable, and the reduction time can be adjusted according to the reaction requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of a coal-based redox roasting process and equipment of an exemplary embodiment of the utility model.

[0016] Figure 2 Schematic diagram of the reactor structure.

[0017] Figure 3 Schematic diagram of the inner spiral.

[0018] Description of Reference Numerals

[0019] 11 - Quantitative feeder, 12 - Rotary kiln, 13 - Burner, 141 - Hot air exhaust pipe, 142 - Bag filter, 143 - Main exhaust fan, 21 - First screw feeder, 22 - Reduction reactor, 23 - Discharge chute, 24 - Second screw feeder, 25 - Feeding chute, 26 - Reducing agent bin, 27 - Reducing agent screw feeder, 28 - Temperature sensor, 31 - Sealed mixing tank, 32 - Slurry pump, 33 - Exhaust pipe, 41 - Water bath dust collector, 42 - Return air fan, 43 - Gas transmission pipeline, 221 - Driving device, 222 - Cylinder body, 223 - Inner spiral blade, 224 - Lifting plate, 225 - Central shaft, 226 - Sealing mechanism. Detailed implementation mode

[0020] The present utility model will be described in detail below in conjunction with embodiments.

[0021] A limonite coal-based oxidation-reduction roasting system of the present utility model is characterized in that it includes an oxidation roasting system, a reduction roasting system, a cooling and pulping system, and a hot air circulation system connected in sequence.

[0022] The oxidation roasting system includes a quantitative feeder 11, a rotary kiln 12, and a burner 13. The discharge port of the quantitative feeder 11 is connected to the feed port of the rotary kiln 12, and the burner 13 is arranged at the kiln head of the rotary kiln 12.

[0023] The reduction roasting system includes a first screw feeder 21, a reducing agent bin 26, a reducing agent screw feeder 27, a reduction reactor 22, a discharge chute 23, a second screw feeder 24, and a feeding chute 26. The first screw feeder 21 is arranged at the bottom of the rotary kiln head. The feed port of the first screw feeder 21 is connected to the discharge port of the rotary kiln 12. The reducing agent screw feeder 27 is arranged at the upper side of the first screw feeder 21. The feed port of the reducing agent screw feeder 27 is connected to the reducing agent bin 26. The discharge ports of the first screw feeder 21 and the reducing agent screw feeder 27 are both connected to the feed port of the reduction reactor 22. One end of the second screw feeder 24 is connected to the discharge port of the reduction reactor 22 through the discharge chute 23, and the other end is connected to the feeding chute 25.

[0024] The cooling and pulping system includes a sealed mixing tank 31, a slurry pump 32, and an exhaust pipe 33. A spray water system is arranged in the sealed mixing tank 31. The feeding chute 25 is connected to the feed port of the sealed mixing tank 31 and inserted into the sealed mixing tank 31. The slurry pump 32 is connected to the lower discharge port of the sealed mixing tank 31.

[0025] The hot air circulation system includes a water bath dust collector 41, a return air fan 42 and an air delivery pipeline 43. One end of the exhaust air pipe 33 of the cooling pulping system passes through the top cover of the sealed stirring tank 31 and is communicated with the sealed stirring tank 31, and the other end is connected to the air inlet of the water bath dust collector 41. One end of the return air fan 42 is connected to the air outlet of the water bath dust collector 41, and the other end is connected to the exhaust pipeline 43. The end of the exhaust pipeline 43 is connected to the kiln head of the rotary kiln and is arranged above the burner 13 of the oxidation roasting system, connecting each system into a closed loop.

[0026] The utility model also provides a flue gas treatment system at the kiln tail of the rotary kiln 2. The flue gas treatment system includes a hot air exhaust pipeline 141, a bag filter 142 and a main exhaust fan 143.

[0027] The end of the exhaust pipeline 43 of the utility model is arranged 100 mm above the burner 13 of the oxidation roasting system.

[0028] The reduction reactor 22 of the utility model is an internal spiral reactor, which includes a driving device 221, a cylinder body 222, a stirring main shaft 225, spiral blades 223 arranged on the stirring main shaft 225 and sealing mechanisms 226 arranged at both ends of the stirring main shaft. Lifting plates 224 are arranged at intervals on the side surface of the spiral blades 223. A feed inlet for entry and an input port for passing the reducing agent are arranged at the top of the reduction reactor. A discharge chute 23 is arranged at the right end of the reduction reactor, and a temperature sensor 28 is also arranged on the chute pipe. Refractory bricks or castables are arranged on the inner wall of the cylinder body 222. The lifting plates 224 arranged on the inner spiral blades 223 can lift the materials to the highest point of the spiral. The stirring main shaft 225 and the rotating surface of the cylinder body 222 adopt a sealing mechanism 226 to ensure the airtightness inside the cylinder body 222. The driving device 221 is a variable frequency speed regulating motor, ensuring that the materials stay in the reactor 4 for 50 minutes. The pitch of the inner spiral blades 223 is designed according to two factors: the materials can stay for 50 minutes when the driving device 221 is at 30 HZ, and the fullness of the materials in the cylinder body 222 reaches 90%. The temperature sensor 28 is arranged to control the feeding temperature of the reducer.

[0029] Taking a certain limonite, the iron grade of the raw ore is 35 - 55%, crushed to a particle size of -3 mm, and the used coal is a certain raw coal from Shaanxi, with a calorific value of 6500 kcal, a volatile content of 28%, an ash content of 24%, and a fixed carbon of 65%. The coal is prepared into 40% powder of -200 mesh by a pulverizer. The above-mentioned limonite coal-based oxidation-reduction roasting system is used for coal-based oxidation-reduction roasting of limonite, and the specific steps are as follows:

[0030] Step 1 Oxidation roasting operation

[0031] The limonite is fed into the feed inlet of the rotary kiln 12 by the metering feeder 11, and the burner 13 sprays fire into the kiln body for heating. The limonite undergoes three stages of drying, preheating, and calcination in the rotary kiln 12. The temperature of the material in the oxidation section is controlled at 700°C ± 25 to achieve the preheating, oxidation, and roasting of the material. The hot flue gas generated in the rotary kiln 12 is discharged into the flue gas treatment system through the hot air exhaust pipe 141, the bag filter 142, and the main exhaust fan 143.

[0032] Step 2: Reduction roasting operation

[0033] After oxidation and roasting, the limonite is fed into the reduction reactor from the discharge port of the rotary kiln through the first screw feeder. The reducing agents are oxygen enhancer, calcium hydroxide, and pulverized coal. The ratio of the three raw materials is by weight: 7 parts of coal, 2.5 parts of oxygen enhancer, and 0.5 part of calcium hydroxide. They are mixed proportionally by the wet method. The reducing agents form a CO reduction atmosphere inside the reduction reactor. 10 kg of reducing agents are added per ton of limonite in proportion.

[0034] The reduction reactor 22 adopts an internal spiral reactor. The rotation of the internal spiral ensures the full mixing of the reducing agents and the material. The driving device 221 of the reduction reactor adopts a variable frequency speed regulating motor to ensure that the residence time of the material in the cylinder is 50 min. The specific designed residence time is determined according to laboratory tests. The lifting plate 224 on the spiral blade 223 lifts the material to the highest point of the spiral, which is conducive to the full reaction of the material with the reducing gas, and the oxidized ore is reduced to magnetite. The temperature of the material discharged from the reduction reactor 22 after roasting is 600°C.

[0035] Step 3: Cooling and pulping operation

[0036] The reduced magnetite is fed into the sealed stirring tank 31 through the discharge chute 25. The spraying water system in the sealed stirring tank 31 directly water-quenches the material and stirs and mixes it into a pulp with a concentration of 40%. Then it is transported to the subsequent grinding and separation operation system through the slurry pump 32.

[0037] Step 4: Hot air circulation operation

[0038] The excess flue gas in the reduction reactor 22 undergoes a primary water bath in the sealed stirring tank 31 for primary dust removal, and then the dust and water vapor in the flue gas are secondary purified by the water bath dust collector and then transported to the kiln head of the rotary kiln for waste gas combustion by the return air fan. The dust-containing slurry in the water bath dust collector returns to the stirring tank to form a closed-loop cycle. In this way, the waste heat is fully utilized, and at the same time, it plays a good environmental protection role.

[0039] The utility model is also applicable to the coal-based oxidation-reduction roasting of hematite and siderite.

[0040] Implementation effect

[0041] A certain limonite ore, without undergoing an oxidation-reduction roasting process, is directly fed into an 1800G wet drum magnetic separator, and effective separation cannot be carried out.

[0042] Calculated at 6500 kcal, using a traditional single-stage rotary kiln reduction roasting system: 50 kg of coal is allocated per ton of limonite ore for reduction and fed into the rotary kiln through a metering feeder. The residence time of the material in the kiln is 50 min, and 30 kg of coal is used for combustion. The temperature of the high-temperature section is controlled at 800 °C. The discharged material is directly quenched with water, and the prepared pulp is also fed into an 1800G wet drum magnetic separator. For the single-stage rotary kiln of the present utility model, internal coal distribution is not required, 40 kg of coal is used for combustion per ton of limonite ore, and 10 kg of reducing agent is used and fed into the reduction reactor. The comparison of the implementation results with the present utility model patent is shown in Table 1:

[0043]

[0044] The above are only the preferred embodiments of the present utility model. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the technical principle of the present utility model, several improvements and substitutions can be made, and these improvements and substitutions should also be regarded as the protection scope of the present utility model.

Claims

1. A limonite coal-based oxidation-reduction roasting system, characterized in that: It includes the oxidation roasting system, reduction roasting system, cooling pulping system and hot air circulation system connected in sequence. The oxidation roasting system comprises a quantitative feeder, a rotary kiln and a burner, wherein the discharge port of the quantitative feeder is connected to the feed port of the rotary kiln, and the burner is arranged at the kiln head of the rotary kiln; The reduction roasting system comprises a first screw feeder, a reducing agent bin, a reducing agent screw feeder, a reduction reactor, a discharge chute, a second screw feeder and a feeding chute, wherein the first screw feeder is arranged at the bottom of the rotary kiln head, the feed inlet of the first screw feeder is connected to the discharge outlet of the rotary kiln, the reducing agent screw feeder is arranged at the upper side of the first screw feeder, the feed inlet of the reducing agent screw feeder is connected to the reducing agent bin, the discharge outlet of the first screw feeder and the discharge outlet of the reducing agent screw feeder are both connected to the feed inlet of the reduction reactor, one end of the second screw feeder is connected to the discharge outlet of the reduction reactor through the discharge chute, and the other end is connected to the feeding chute; The cooling pulping system comprises a sealed stirring tank, a slurry pump and a spraying system. The sealed stirring tank is provided with a spraying water system. The feed chute is connected to the feed port of the sealed stirring tank and inserted into the sealed stirring tank. The slurry pump is connected to the lower discharge port of the sealed stirring tank. The hot air circulation system includes a water bath dust collector, a return air fan and an air transmission pipeline. One end of the exhaust pipe of the cooling pulping system passes through the top cover of the sealed stirring tank and is connected to the sealed stirring tank, and the other end is connected to the air inlet of the water bath dust collector. One end of the return air fan is connected to the air outlet of the water bath dust collector, and the other end is connected to the exhaust pipeline. The end of the exhaust pipeline is connected to the kiln head of the rotary kiln and is arranged at the upper end of the burner of the oxidation roasting system.

2. The limonite coal-based oxidation-reduction roasting system according to claim 1, characterized in that: A flue gas treatment system is also provided at the kiln tail of the rotary kiln. The flue gas treatment system includes a hot air exhaust pipe, a bag filter and a main exhaust fan.

3. The limonite coal-based oxidation-reduction roasting system according to claim 1, characterized in that: The end of the exhaust pipe is arranged 100 mm above the burner of the oxidation roasting system.

4. The limonite coal-based oxidation-reduction roasting system according to claim 1, characterized in that: The reduction reactor is an internal spiral reactor, including a driving device, a cylinder, a stirring main shaft, spiral blades arranged on the stirring main shaft and sealing mechanisms arranged at both ends of the stirring main shaft. Lifting plates are arranged at intervals on the sides of the spiral blades. A feed inlet for entry and an input inlet for passing the reducing agent are arranged on the top of the reduction reactor. A discharge chute for discharging is arranged at the right end of the reduction reactor, and a temperature sensor is also arranged on the chute.

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