Pure hydrogen reduction rotary kiln ironmaking method

Abstract

The invention discloses a pure hydrogen reduction rotary kiln ironmaking method, and belongs to the technical field of reduced iron smelting. The method solves the technical problems of low smelting efficiency and long time consumption caused by smelting by heating hydrogen and normal-temperature materials in a traditional iron-making method. The pure hydrogen reduction rotary kiln ironmaking method comprises the following steps: step 1, starting a rotary kiln body and a driving device corresponding to an independent rotating spiral structure, and enabling the rotary kiln body and the driving device to independently and reversely rotate; step 2, starting to charge the rotary kiln body; during charging, normal-temperature reducing gas is input through a reducing gas inlet formed in the feeding end of the rotary kiln body; the heating device is used for heating the materials entering the rotary kiln body to the reduction temperature; 3, the materials in the rotary kiln body are subjected to a reduction reaction; and 4, after reduction, discharging a reduced product. The thought of'heating the material without heating hydrogen 'is adopted, and the adopted material is the iron-containing fine ore, so that the reaction time can be shortened, and the production efficiency can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of reduced iron smelting, and in particular to a pure hydrogen reduction rotary kiln ironmaking method. Background Art

[0002] Carbon emissions from the steel industry account for nearly one-fifth of my country's total carbon emissions, and in the traditional blast furnace-converter process, the carbon emission intensity of the ironmaking process accounts for more than 80% of the entire process, and the energy structure is obviously characterized by high carbonization. As a major carbon emitter in the steel process, deep carbon reduction in the ironmaking process has become the key to my country's steel industry. The innovative development of low-carbon technologies and processes is of great significance to emission reduction in the steel industry.

[0003] Hydrogen metallurgy is a new type of smelting process that uses hydrogen as a reducing agent to replace carbon-based fuels for steel production. It has attracted increasing attention in the industry for its advantages such as higher reduction efficiency and less carbon emissions, and is expected to become an important means for the steel industry.

[0004] In the existing technology, both vertical furnace hydrogen metallurgy and hydrogen iron reduction process based on fluidized bed reactor have many problems: First, hydrogen reduction is a strong endothermic reaction. The main idea to solve the heat balance problem is to heat hydrogen through special equipment to supplement the heat gap of the reduction reaction, which leads to many material and technical problems for hydrogen heating equipment and reduction reactor, which is one of the important factors limiting the market promotion of hydrogen vertical furnace in the future; second, there is a serious shortage of high-grade pellets that can be used for vertical furnace hydrogen metallurgy. If the hydrogen-based vertical furnace process is developed on a large scale, the huge potential demand for pellets will bring a new round of challenges of imbalance in the supply and demand structure of raw materials. Although the fluidized bed reaction process has low requirements for high-grade raw materials, its technical maturity is still the main reason affecting its development. It can be seen that the current hydrogen metallurgical process has a series of problems such as high requirements for raw materials, immature technology and equipment, and it is urgent to develop a new process to solve the above problems.

[0005] In addition, when heating hydrogen is currently used to reduce iron-containing materials, there are problems with hydrogen heating equipment, heating equipment materials and heating technology. For example, gas heating in the metallurgical field generally uses a direct-fired tubular heat exchanger. Direct application to hydrogen heating has two problems: First, hydrogen reduction is an endothermic reaction as a whole, and the specific heat capacity of hydrogen is much lower than that of CO. Using pure hydrogen as a reducing agent requires heating to a higher temperature, and at this time, the heat resistance strength of the heat exchange tube is required to be higher; second, hydrogen is highly corrosive at high temperatures and is easy to form hydrocarbons with carbon in the heat exchange tube to cause pitting. At present, the heating temperature of reducing gas (hydrogen-rich gas, H2 content less than 80%) worldwide is 850℃~900℃. The heating temperature of pure hydrogen heating is less than or equal to 400℃. How to meet the high-temperature heating of hydrogen is one of the technical problems that must be solved for pure hydrogen reduction.

[0006] In addition, the traditional hydrogen metallurgical process adopts the idea of ​​heating hydrogen instead of heating the material. When the hydrogen-rich reducing gas reacts with the material, the heat exchange between the hydrogen and the material is relatively slow, and the hydrogen needs to be circulated and heated. Therefore, the reaction time is relatively long. In addition, the raw material used in the traditional hydrogen metallurgical process is pellets. When the pellets react with hydrogen, heat exchange is performed first, and then reaction, and the reduction time is relatively long. Summary of the invention

[0007] In view of the above analysis, the present invention aims to provide a pure hydrogen reduction rotary kiln ironmaking method to solve the technical problems of low smelting efficiency and long time consumption in the traditional ironmaking method which uses heating hydrogen and room temperature materials for smelting.

[0008] The purpose of the present invention is mainly achieved through the following technical solutions:

[0009] In one aspect, the present invention provides a pure hydrogen reduction rotary kiln ironmaking method, the ironmaking method comprising the following steps:

[0010] Step 1, starting the driving devices corresponding to the rotary kiln body and the independently rotating spiral structure, so that the two begin to rotate independently in opposite directions;

[0011] Step 2, starting to load the rotary kiln body with iron ore powder;

[0012] When loading powder, the reducing gas at room temperature is input through the reducing gas inlet provided at the feeding end of the rotary kiln body;

[0013] Step 3, the materials enter the preheating reduction section, constant temperature reduction section and cooling section in the rotary kiln furnace in sequence;

[0014] Step 4: Discharge.

[0015] Further, in step 1, the normal temperature reducing gas is normal temperature hydrogen;

[0016] The rotary kiln body is reduced in a pure hydrogen atmosphere. When the rotary kiln body is first started, inert gas is introduced to replace the air in the kiln.

[0017] Furthermore, in step 2, the particle size of the iron ore powder is 0.05-0.9 mm.

[0018] Furthermore, in step 2, the rotary kiln furnace body includes a preheating reduction section, a constant temperature reduction section and a cooling section from the feeding end to the discharging end, and the material is heated to the preheating reduction temperature and the constant temperature reduction temperature in sequence by a heating device to carry out a reduction reaction.

[0019] Furthermore, in step 2, microwave heating is used in the preheating reduction stage; and medium frequency induction heating is used in the constant temperature reduction stage.

[0020] Furthermore, in step 2, the temperature of the preheating reduction section is 850°C to 1000°C.

[0021] Furthermore, in step 2, the temperature of the isothermal reduction section is 1050°C to 1100°C.

[0022] Furthermore, in step 1, during loading, an upper loading tank and a lower loading tank connected in series are used for alternate loading, and the upper loading tank and the lower loading tank connected in series can prevent air from entering the rotary kiln furnace body during loading.

[0023] Furthermore, in step 4, when discharging, the upper discharging tank and the lower discharging tank connected in series are used to discharge alternately.

[0024] The upper discharge tank and the lower discharge tank connected in series can prevent air from entering the rotary kiln furnace during discharge.

[0025] On the other hand, the present invention also provides a pure hydrogen reduction rotary kiln ironmaking system, which is used to implement the above-mentioned pure hydrogen reduction rotary kiln ironmaking method;

[0026] The ironmaking system includes a rotary kiln reduction device body, a first driving device and a second driving device;

[0027] The rotary kiln reduction device body includes a rotary kiln furnace body and an independent rotating structure; the first driving device is arranged outside the rotary kiln furnace body and can drive the rotary kiln furnace body to rotate;

[0028] The independent rotating structure includes a rotating shaft and an independent rotating spiral plate arranged thereon, the rotating shaft is arranged along the length direction of the rotary kiln furnace body and penetrates the rotary kiln furnace body, and the two ends of the rotating shaft are fixed outside the rotary kiln furnace body and are drivingly connected to the second driving device;

[0029] The rotary kiln body driven by the first driving device and the independent rotating mechanism driven by the second driving device rotate independently in opposite directions.

[0030] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0031] (1) The traditional hydrogen metallurgical process adopts the idea of ​​"heating hydrogen without heating materials". When the hydrogen-rich reducing gas reacts with the materials, the heat exchange between hydrogen and materials is relatively slow, and the hydrogen needs to be circulated and heated. Therefore, the reaction time is relatively long. In addition, the raw material used in the traditional hydrogen metallurgical process is pellets. Compared with the iron-containing fine ore of the present invention, the pellets are first heat-exchanged and then reacted when reacting with hydrogen, so the reduction time is relatively long. Compared with the prior art, the present invention adopts the idea of ​​"heating materials without heating hydrogen", and the material used in the present invention is iron-containing fine ore, which is easier to contact with hydrogen, and the reduction efficiency of room temperature hydrogen and heated iron-containing fine ore is relatively high. Therefore, the reaction time is relatively short and the production efficiency is high.

[0032] (2) The present invention can also significantly reduce the cost of direct reduction iron products in hydrogen metallurgical processes, get rid of the dependence on high-grade iron ore raw materials and foreign equipment and technology, and provide assistance to the promotion and application of pure hydrogen metallurgical technology. Among them, the reduction of the cost of direct reduction iron products in hydrogen metallurgical processes is mainly reflected in the following aspects: First, in terms of raw material costs, compared with the traditional vertical furnace using pellets as raw materials, the present invention directly uses iron-containing powder ore as smelting raw materials, so the construction cost and preparation cost of the pellet production line can be saved; second, in terms of operation, the current rotary kiln needs to be shut down for 1-2 months for maintenance and replacement of refractory linings due to the "ringing" problem, so the production efficiency is low; compared with the prior art, the present invention can forcefully scrape off the high-temperature furnace charge on the inner wall of the rotary kiln furnace body in real time by setting an independent rotating structure and making it rotate independently in the opposite direction with the rotary kiln furnace body, so as to avoid the high-temperature furnace charge from adhering to the furnace wall, and thus avoid the "ringing" phenomenon of the rotary kiln. Therefore, under the same conditions, the production efficiency of the rotary kiln ironmaking system of the present invention is higher.

[0033] (3) The present invention utilizes low-temperature hydrogen that does not participate in the reduction reaction in the rotary kiln furnace body as a cooling protective gas to recover heat from the reduction product. The cooling protective gas after heat recovery is discharged from the furnace body through the reduction gas outlet, and after being dehydrated by a dehydration device and dedusted by a dust removal device, it is introduced into the rotary kiln furnace body through the reduction gas branch pipeline and the reduction gas inlet. The low-temperature hydrogen heated by the reduction product can promote the reduction of iron-containing charge and further improve the metallization rate of the product.

[0034] (4) The present invention uses hydrogen as the cooling and protective gas for the reduction product. The spatial atmosphere in the rotary kiln furnace body will not be destroyed due to the feeding and discharging process. In addition, the temperature of the hydrogen after cooling and heat exchange can reach 50°C to 100°C, and the waste heat of the product can be recycled. Therefore, the waste heat utilization efficiency is relatively high.

[0035] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the embodiments of the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0037] like Figure 1 It is a schematic diagram of the ironmaking process of the pure hydrogen reduction rotary kiln ironmaking method of the present invention;

[0038] Figure 2 This is a structural schematic diagram of a pure hydrogen reduction rotary kiln ironmaking system;

[0039] Figure 3 It is a structural schematic diagram of the rotary kiln furnace body and the driving device corresponding to the independent rotating spiral structure.

[0040] Reference numerals:

[0041] 101-upper loading tank; 102-lower loading tank; 201-rotary kiln reduction device body; 202-microwave heating device; 203-medium frequency induction constant temperature heating device; 204-independent rotating spiral plate; 301-upper discharge tank; 302-lower discharge tank; 401-reduction gas inlet; 402-reduction gas outlet; 5-gear; 6-first drive reducer; 7-second drive reducer; 8-screw drive shaft. DETAILED DESCRIPTION

[0042] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0043] The present invention also provides a microwave-induction coupled heating pure hydrogen reduction rotary kiln ironmaking method, such as Figure 1 As shown, the method comprises the following steps:

[0044] Step 1, starting the driving devices corresponding to the rotary kiln body and the independently rotating spiral structure, so that the two begin to rotate independently in opposite directions;

[0045] In the above step 1, the first driving device and the second driving device are started at the same time. At this time, the first driving reducer 6 rotates through the gear 5 to drive the rotary kiln body to rotate. At the same time, the second driving reducer 7 drives the independent rotating spiral plate 204 to rotate through the rotating shaft, so that the rotary kiln body and the independent rotating spiral structure start to rotate continuously in the opposite direction.

[0046] The present invention can improve the composition of iron-containing materials and their heating uniformity and promote the reduction of iron-containing materials by assembling an independent rotating structure in the rotary kiln body and using two sets of independent driving devices to make the rotary kiln body and the independent rotating structure rotate independently in opposite directions.

[0047] In the above step 1, the rotation speeds of the rotary kiln body and the rotating spiral plate are both 0.3-1.5 r / min. On the one hand, controlling the rotation speeds of the two within this range can meet the requirements of the designed production capacity of the kiln and the real-time metallization rate of DRI; on the other hand, it can achieve sufficient mixing of the material components and promote the reduction process of the material.

[0048] In the above step 1, the rotary kiln body is reduced in a pure hydrogen (H2>99.5%) atmosphere. When the rotary kiln body is first started, an inert gas (for example, nitrogen) is introduced to replace the air in the kiln to prevent explosion after the introduction of hydrogen. The replacement time is based on the kiln tail gas analysis O2 <1%, and then pure hydrogen is introduced to replace nitrogen. The hydrogen gas flow rate is 28m / s-38m / s.

[0049] Step 2, start the reducing gas supply unit and the series tank charging unit, and start to charge the rotary kiln furnace body with iron ore powder; when charging the powder, input the normal temperature reducing gas through the reducing gas inlet provided at the feeding end of the rotary kiln furnace body;

[0050] In the above step 2, the total iron content TFe in the iron-containing ore powder is 55%-68%.

[0051] In the above step 2, in order to prevent the outside air from entering the kiln during the feeding process to cause safety hazards, the present invention adopts a series of tank charging units to charge the rotary kiln body. The specific charging process includes:

[0052] Step 21, first open the upper feed valve, load the iron ore powder into the upper loading tank 101, and then close the upper feed valve;

[0053] Step 22, open the control valve on the first branch pipe and the control valve on the second branch pipe, and fill the upper charging tank 101 and the lower charging tank 102 with hydrogen to keep the pressure in the upper charging tank 101 and the lower charging tank 102 consistent, and close the control valves on the first branch pipe and the second branch pipe to stop filling with hydrogen;

[0054] Step 23, open the upper discharge valve and the lower feed valve, and when all the furnace charge in the upper charging tank 101 is discharged into the lower charging tank 102, close the upper discharge valve and the lower feed valve;

[0055] Step 24, open the lower discharge valve to send the charge into the rotary kiln furnace body, repeat the above process to complete the furnace body feeding.

[0056] In the above step 24, the feed amount is controlled according to the raw material filling rate in the rotary kiln of 6% to 8%.

[0057] Step 3, the materials enter the preheating reduction section, constant temperature reduction section and cooling section in the rotary kiln furnace in sequence;

[0058] In the above step 3, when loading, the microwave heating device 202 and the medium frequency induction constant temperature heating device 203 are turned on simultaneously, and the rapid heating characteristics of microwaves are used to quickly heat the iron-containing material in the preheating reduction section to reach the required temperature for reduction, thereby realizing rapid reduction of the charge as soon as possible; the medium frequency induction constant temperature heating device 203 is used to generate a medium frequency alternating current to perform high-temperature constant temperature heating on the iron-containing charge in the constant temperature reduction section.

[0059] In the above step 3, the temperature of the preheating reduction section of microwave heating is 850°C to 1000°C, and the temperature of the constant temperature reduction section of medium frequency induction heating is 1050°C to 1100°C.

[0060] In the above step 3, the heating and reduction process of the iron-containing material is specifically as follows:

[0061] When iron-containing ore powder is put into the kiln, the microwave heating device 202 and the medium-frequency induction constant temperature heating device 203 are turned on simultaneously. With the continuous addition of charge, under the action of the independently rotating spiral plate 204, the charge gradually moves forward at a uniform speed from the feed end of the rotary kiln body along the axial direction of the rotary kiln body. After passing through the preheating reduction section, the charge is rapidly heated to a predetermined reduction temperature, and iron oxides are pre-reduced under the action of hydrogen. Then, it enters the constant temperature reduction section, and the charge is further reduced to metallic iron.

[0062] Step 4: Discharge.

[0063] In the above step 4, the reduction product is discharged by using a series tank discharge unit, which specifically includes:

[0064] Step 41, when discharging, first open the air inlet and the air outlet on the lower discharge tank 302 and the upper discharge tank 301, then open the control valves on the third branch pipe and the fourth branch pipe, use hydrogen to replace the air in the lower discharge tank 302 and the upper discharge tank 301, and when the pressure in the upper discharge tank 301 and the lower discharge tank 302 is consistent, close the control valves on the third branch pipe and the fourth branch pipe to stop charging hydrogen;

[0065] Step 42, open the upper feed valve, and after the reduced product enters the upper discharge tank 301, close the upper feed valve;

[0066] Step 43, open the upper discharge valve and the lower feed valve, and when all the reduction products in the upper discharge tank 301 are discharged into the lower discharge tank 302, close the upper discharge valve and the lower feed valve; at this time, open the lower discharge valve, and the reduction products are discharged from the rotary kiln furnace body, and repeat the above process to complete the alternating discharge.

[0067] Compared with the prior art, the ironmaking method of the present invention has the following effects:

[0068] (1) The present invention has a wide adaptability to smelting raw materials, and is applicable to high-grade iron ore powder with an iron grade of 55% to 68%, thereby solving the problem of the current hydrogen vertical furnace process requiring high-grade raw materials.

[0069] (2) The present invention adopts the medium frequency induction constant temperature heating device 203 as the heat source of the constant temperature reduction stage, which can overcome the disadvantages of microwave high temperature constant temperature power consumption and reduce the energy consumption per ton of iron.

[0070] (3) In the conventional rotary kiln, the charge is slightly melted and adheres to the kiln wall during the constant temperature reduction stage, resulting in a "ringing" phenomenon. However, the present invention uses an independently rotating spiral plate 204 to force the charge to scrape, reduce the adhesion of the charge, and avoid the occurrence of the ringing phenomenon.

[0071] (4) The present invention utilizes low-temperature hydrogen that does not participate in the reduction reaction in the rotary kiln furnace body as a cooling protective gas to recover heat from the reduction product. The cooling protective gas after heat recovery is discharged from the furnace body through the reduction gas outlet 402, and after being dehydrated by a dehydration device and dedusted by a dust removal device, it is introduced into the rotary kiln furnace body through the reduction gas branch pipeline and the reduction gas inlet 401. The low-temperature hydrogen heated by the reduction product can promote the reduction of iron-containing charge and further improve the metallization rate of the product.

[0072] (5) In the prior art, the pellets after hydrogen-rich metallurgical reduction are generally cooled with nitrogen, and the nitrogen after cooling is directly discharged, and the waste heat utilization efficiency is low. Compared with the prior art, the present invention uses hydrogen as the cooling protection gas for the reduction product, and the space atmosphere in the rotary kiln furnace body will not be destroyed by the feeding and discharging process; in addition, the temperature of the hydrogen after cooling and heat exchange can reach 50℃~100℃, and the waste heat of the product is recycled, so the waste heat utilization efficiency is high.

[0073] (6) The traditional hydrogen metallurgical process adopts the idea of ​​"heating hydrogen without heating materials". When the hydrogen-rich reducing gas reacts with the materials, the heat exchange between hydrogen and materials is relatively slow, and the hydrogen needs to be circulated and heated. Therefore, the reaction time is relatively long. In addition, the raw material used in the traditional hydrogen metallurgical process is pellets. Compared with the iron-containing ore powder of the present invention, the pellets are first heat-exchanged and then reacted when reacting with hydrogen, so the reduction time is relatively long. Compared with the prior art, the present invention adopts the idea of ​​"heating materials without heating hydrogen", and the material used in the present invention is iron-containing ore powder, which is easier to contact with hydrogen, and the reduction efficiency of room temperature hydrogen and heated iron-containing ore powder is relatively high. Therefore, the reaction time is relatively short and the production efficiency is high.

[0074] In order to realize the above-mentioned ironmaking method, the present invention provides an ironmaking system, such as Figure 2 and Figure 3 As shown, the system includes a rotary kiln reduction device body 201, a first drive device and a second drive device; the rotary kiln reduction device body 201 includes a rotary kiln furnace body and an independent rotating structure; the first drive device is arranged outside the rotary kiln furnace body and can drive the rotary kiln furnace body to rotate; the independent rotating structure includes a rotating shaft and an independent rotating spiral plate 204 arranged thereon, the rotating shaft is arranged along the length direction of the rotary kiln furnace body and passes through the rotary kiln furnace body, the two ends of the rotating shaft are fixed outside the rotary kiln furnace body and are transmission-connected to the second drive device; the rotary kiln furnace body driven by the first drive device and the independent rotating mechanism driven by the second drive device rotate independently in opposite directions.

[0075] Specifically, the rotary kiln body of the present invention is a spiral rotary kiln, which is used to carry iron-containing raw materials and reduce the iron-containing raw materials; the first driving device includes a gear 5 and a first driving reducer 6, the gear 5 is installed on the outer shell of the rotary kiln body, and the first driving reducer 6 can drive the rotary kiln body to rotate by driving the gear 5. The independent rotating structure of the present invention includes a rotating shaft, the length of the rotating shaft is greater than the length of the rotary kiln body, the rotating shaft penetrates the rotary kiln body along the length direction of the rotary kiln body, the two ends of the rotating shaft are located outside the rotary kiln body and connected to the second driving device, the second driving device includes a second driving reducer 7 and a spiral driving shaft 8, the second driving reducer 7 can drive the rotating shaft to rotate through the spiral driving shaft 8, and then the rotating shaft drives the independent rotating spiral plate 204 to rotate. When the rotary kiln ironmaking system starts to work, the first drive device and the second drive device are started at the same time, the rotary kiln furnace body and the independently rotating spiral plate 204 rotate continuously in the opposite direction, and the charge moves from the feed end to the discharge end of the furnace body under the guidance of the independently rotating spiral plate 204. At the same time, the independently rotating spiral plate 204 can forcefully scrape the inner wall of the rotary kiln furnace body in real time, thereby preventing the high-temperature material from adhering to the inner wall of the furnace to form a ring.

[0076] Compared with the prior art, the present invention can improve the composition of iron-containing materials and their uniformity of heating, and promote the reduction of iron-containing materials, by assembling an independent rotating structure in the rotary kiln body and using two sets of independent driving devices to make the rotary kiln body and the independent rotating structure rotate independently in opposite directions.

[0077] The present invention uses iron-containing ore powder as raw material for smelting, and the iron-containing ore powder includes one or more of vanadium-titanium magnetite, high manganese ore, and laterite-nickel ore; and also includes various iron-containing dust muds generated in the process of steel and non-ferrous metal smelting. The present invention solves the demand for high-grade iron-containing raw materials (need to be made into iron-containing pellets) in the current hydrogen-based vertical furnace process, and eliminates the ring formation problem faced by the current traditional rotary kiln.

[0078] In addition, the present invention can also significantly reduce the cost of direct reduction iron products in hydrogen metallurgical process, get rid of the dependence on high-grade iron ore raw materials and foreign equipment technology, and provide help for the promotion and application of pure hydrogen metallurgical technology. Among them, reducing the cost of direct reduction iron products in hydrogen metallurgical process is mainly reflected in the following aspects: First, in terms of raw material cost, compared with the traditional vertical furnace using pellets as raw materials, the present invention directly uses iron-containing ore powder as smelting raw materials, so the construction cost and preparation cost of the pellet production line can be saved; second, in terms of operation, the current rotary kiln needs to be shut down for 1-2 months for maintenance and replacement of refractory lining due to the "ringing" problem, so the production efficiency is low; compared with the prior art, the present invention can force the scraping of high-temperature furnace charge on the inner wall of the rotary kiln furnace body in real time by setting an independent rotating structure and making it rotate independently in the opposite direction with the rotary kiln furnace body, so as to avoid the high-temperature furnace charge from sticking to the furnace wall, and thus avoid the "ringing" phenomenon of the rotary kiln, so under the same conditions, the production efficiency of the rotary kiln ironmaking system of the present invention is higher.

[0079] In order to fully scrape the inner wall of the rotary kiln body and prevent the high-temperature materials from adhering to the furnace wall to form rings, the radial length of the independently rotating spiral plate 204 of the present invention is equal to the radial distance between the rotating axis and the inner wall of the rotary kiln body; in addition, the axial length of the independently rotating spiral plate 204 is equal to the length of the rotary kiln body.

[0080] Specifically, when the independently rotating spiral plate 204 and the rotary kiln body rotate relatively independently and in the opposite direction, there is a certain relative speed between the two, so that the material is subjected to a certain stirring intensity in the circumferential direction of the furnace body. The independently rotating spiral plate 204 can not only stir the material in the circumferential direction of the furnace body to make the material composition more uniform, but also, when the material is spirally advanced at a set speed under the action of the independently rotating spiral plate 204, the independently rotating spiral plate 204 can play a role of forced scraping to prevent the high-temperature material from adhering to the kiln wall, and finally prevent the high-temperature material from forming a circle on the kiln wall. In addition, the length of the independently rotating spiral plate 204 is equal to the length of the rotary kiln body, which can play a role in fully mixing and scraping the material.

[0081] It should be pointed out that the independently rotating spiral plate 204 of the present invention includes a special-shaped spiral blade, which is made of a steel plate with excellent high temperature resistance and hydrogen corrosion resistance. The present invention installs the special-shaped spiral blade on the rotating shaft instead of the inner wall of the rotary kiln furnace body, which can reduce the production cost of the recycling ironmaking system. This is because: if the special-shaped spiral blade is installed on the inner wall of the rotary kiln furnace body, it is necessary to install a special-shaped low-refractory brick (that is, the refractory material needs to be specially made and customized according to the shape of the spiral). Compared with the conventional cylindrical refractory bricks installed in the present invention, the production and installation of special-shaped low-refractory bricks will inevitably increase the production cost and installation cost of low-refractory bricks, and will also increase the difficulty of installing refractory bricks, ultimately increasing the production cost of smelting iron in the rotary kiln furnace body; in addition, the present invention installs the special-shaped spiral blade on the rotating shaft instead of the inner wall of the rotary kiln, which can form relative rotation with the rotary kiln furnace body, thereby increasing the degree of stirring of the material, improving the uniformity of the material, and providing convenient conditions for the subsequent reduction reaction of the material.

[0082] It should be noted that the pure hydrogen reduction rotary kiln ironmaking system of the present invention also includes a reducing gas supply unit; a reducing gas inlet 401 is provided at the feed end of the rotary kiln furnace body, and a reducing gas outlet 402 is provided at the discharge end; the reducing gas supply unit is connected to the reducing gas inlet 401 through a reducing gas main pipeline, and the reducing gas supply unit is used to provide room temperature reducing gas to the rotary kiln furnace body.

[0083] Specifically, in view of the endothermic property of hydrogen metallurgical reduction reaction, the present invention adopts "room-temperature hydrogen for high-temperature iron-containing material reduction", that is, a heating device (including a microwave heating device 202 and a medium-frequency induction constant temperature heating device 203) is first used to heat the iron-containing ore powder instead of heating hydrogen, and when heated to the set temperature, room-temperature reducing gas is introduced for reduction treatment. This operation can avoid the technical problems faced by the prior art using high-temperature hydrogen for heating.

[0084] It should be noted that the reducing gas supply unit of the present invention also includes a reducing gas branch pipeline, which is connected to the reducing gas inlet 401 at the feed end of the rotary kiln furnace body through a dehydration device and a dust removal device, wherein the dehydration device is used to dehydrate the unreacted reducing gas discharged through the reducing gas outlet 402, and the dust removal device is used to remove the dust from the unreacted reducing gas discharged from the rotary kiln furnace body, and the hydrogen after dehydration and dust removal is introduced into the rotary kiln furnace body through the reducing gas branch pipeline and the reducing gas inlet 401.

[0085] The reducing gas outlet 402 at the discharge end of the rotary kiln body is connected to the reducing gas inlet 401 through a reducing gas branch pipeline.

[0086] In order to heat the iron-containing ore powder, the rotary kiln furnace body of the present invention includes a preheating reduction section, a constant temperature reduction section and a cooling section from the feeding end to the discharging end; the preheating reduction section is provided with a microwave heating device 202; the constant temperature reduction section is provided with a medium frequency induction constant temperature heating device 203; the microwave heating device 202 and the medium frequency induction constant temperature heating device 203 are both used to heat the iron-containing material.

[0087] In the prior art, when using traditional blast furnace smelting, a hot blast furnace is used to heat the air and then spray it into the blast furnace for reduction; when using traditional hydrogen-based vertical furnace and hydrogen-based fluidized bed smelting, hydrogen is first heated and then the iron-containing material is reduced. Compared with the prior art, the present invention uses both microwave heating and induction heating as heat sources in a rotary kiln to heat the iron-containing material, solving the problems of hydrogen heating equipment and many materials and heating technologies faced by the current process.

[0088] It should be noted that the microwave heating device 202 and the medium frequency induction constant temperature heating device 203 of the present invention are both used to heat iron-containing ore powder. The purpose of heating is to reduce the high-temperature iron-containing ore powder using normal temperature reducing gas.

[0089] It should be emphasized that the present invention couples microwave heating and induction heating as two heat sources and applies them to the rotary kiln to heat the iron-containing material. The rapid heating characteristics of microwaves can be used to quickly heat the iron-containing material to the temperature required for reduction, and the medium-frequency induction constant temperature heating device 203 is used to maintain the high temperature, ultimately achieving the purpose of reducing production costs and operating costs. This is because: the advantage of microwave heating is fast heating speed, but its disadvantage is that the power consumption is relatively high when maintaining a high temperature, resulting in high production costs, while the speed of induction heating is not as fast as that of microwave heating, but its power consumption at the same temperature is lower than that of microwave heating. Through the cooperation of the two heating methods, the purpose of rapid heating and reduction of the furnace charge can be achieved, and the operating cost can be reduced.

[0090] The inclination angle of the rotary kiln body of the present invention is 0°; that is, the rotary kiln body is arranged in a horizontal direction.

[0091] Specifically, the rotary kiln furnace body of the present invention is provided with an independent rotating spiral plate 204, which can realize active rotating discharge, that is, the charge can be discharged automatically without setting an inclination angle.

[0092] Compared with the prior art, the present invention can avoid the problems caused by the tilting of the rotary kiln body, reduce the difficulty of installing the furnace body, improve the stability of the furnace body, and reduce the energy consumption and safety hazards of the furnace body.

[0093] In order to ensure a pure hydrogen environment in the rotary kiln body and prevent outside air from entering the kiln during the feeding process to create a safety hazard, the pure hydrogen reduction rotary kiln ironmaking system of the present invention also includes a series tank charging unit; the series tank charging unit includes an upper charging tank 101 and a lower charging tank 102 connected in series; the series tank charging unit is arranged at the feeding end of the rotary kiln body; the series tank charging unit is connected to the feeding port of the rotary kiln body, and can provide iron-containing ore powder to the rotary kiln body.

[0094] Specifically, the upper loading tank 101 of the present invention is provided with an upper feed valve and an upper discharge valve, the lower loading tank 102 is provided with a lower feed valve and a lower discharge valve, and both the upper loading tank 101 and the lower loading tank 102 are provided with an air inlet and an air outlet; the upper loading tank 101 is connected to the reducing gas main pipeline through a first branch pipe, and the lower loading tank 102 is connected to the reducing gas main pipeline through a second branch pipe, and control valves are correspondingly provided on the first branch pipe and the second branch pipe. When feeding into the rotary kiln furnace body, first open the upper feeding valve, load the iron ore powder into the upper charging tank 101, then close the upper feeding valve, open the control valve on the first branch pipe and the control valve on the second branch pipe, and fill the upper charging tank 101 and the lower charging tank 102 with hydrogen, so that the pressure in the upper charging tank 101 and the lower charging tank 102 are kept consistent, close the control valves on the first branch pipe and the second branch pipe to stop filling with hydrogen; open the upper discharge valve and the lower feeding valve, and when all the charge in the upper charging tank 101 is discharged into the lower charging tank 102, close the upper discharge valve and the lower feeding valve; open the lower discharge valve, send the charge into the rotary kiln furnace body, repeat the above process to complete the alternating feeding.

[0095] Compared with the prior art, the present invention can prevent air from entering the rotary kiln during the feeding process of the furnace body by arranging an upper loading tank 101 and a lower loading tank 102 connected in series and corresponding control valves, thereby ensuring a pure hydrogen environment in the furnace.

[0096] Similarly, in order to ensure a pure hydrogen environment in the rotary kiln and prevent outside air from entering the kiln during the discharge process to create a safety hazard, the pure hydrogen reduction rotary kiln ironmaking system of the present invention also includes a series tank discharge unit; the series tank discharge unit includes an upper discharge tank 301 and a lower discharge tank 302 connected in series; the series tank discharge unit is arranged at the discharge end of the rotary kiln body; the series tank discharge unit is connected to the discharge port of the rotary kiln body, and can discharge the material smelted in the rotary kiln to the outside of the furnace.

[0097] Specifically, the upper discharge tank 301 of the present invention is provided with an upper feed valve and an upper discharge valve, the lower discharge tank 302 is provided with a lower feed valve and a lower discharge valve, and both the upper discharge tank 301 and the lower discharge tank 302 are provided with an air inlet and an exhaust port; the upper discharge tank 301 is connected to the reducing gas main pipeline through the third branch pipe, and the lower discharge tank 302 is connected to the reducing gas main pipeline through the fourth branch pipe, and control valves are correspondingly provided on the third branch pipe and the fourth branch pipe.

[0098] When discharging the rotary kiln furnace body, first open the air inlet and exhaust port on the upper discharge tank 301 and the lower discharge tank 302, then open the control valves on the third branch pipe and the fourth branch pipe, use hydrogen to replace the air in the upper discharge tank 301 and the lower discharge tank 302, so that the pressure in the upper discharge tank 301 and the lower discharge tank 302 is consistent, and then close the control valves on the third branch pipe and the fourth branch pipe to stop filling with hydrogen; then, open the upper feed valve, and after the reduction product fully enters the upper discharge tank 301, close the upper feed valve, and open the upper discharge valve and the lower feed valve at the same time, until the reduction product in the upper discharge tank 301 is completely discharged into the lower discharge tank 302, close the upper discharge valve and the lower feed valve; at this time, open the lower discharge valve, and the reduction product is discharged from the furnace body, and repeat the above process to complete the alternating discharge.

[0099] Compared with the prior art, the present invention can prevent air from entering the rotary kiln body during the discharge process and ensure a pure hydrogen environment in the furnace by providing an upper discharge tank 301 and a lower discharge tank 302 connected in series and corresponding control valves.

[0100] Example 1

[0101] In this embodiment, iron concentrate powder with an iron content of 56% is used as raw material, and the raw material loading amount is calculated according to the raw material filling rate of 6% in the rotary kiln furnace body.

[0102] When charging, first open the upper feed valve, load the iron ore powder into the upper charging tank 101, and then close the upper feed valve; open the control valve on the first branch pipe and the control valve on the second branch pipe and fill hydrogen into the upper charging tank 101 and the lower charging tank 102, so that the pressure in the upper charging tank 101 and the lower charging tank 102 are kept consistent, then close the control valves on the first branch pipe and the second branch pipe to stop filling hydrogen; then, open the upper discharge valve and the lower feed valve, and when all the charge in the upper charging tank 101 is discharged into the lower charging tank 102, close the upper discharge valve and the lower feed valve; finally, open the lower discharge valve to send the charge into the rotary kiln furnace body, repeat the above process, and complete the furnace body feeding.

[0103] While loading, 700m 3Pure hydrogen is continuously sprayed into the kiln from the reducing gas inlet 401 as a reducing agent. After being heated by the microwave heating device 202, the temperature of the iron-containing charge rises to 850°C. By setting the rotation speed of the rotary kiln body and the independent rotating spiral plate 204 to 1.5r / min, the residence time of the charge in the preheating reduction section (microwave heating section) is maintained at 10min. Subsequently, the charge gradually moves from the microwave heating section to the medium frequency induction constant temperature heating section at a uniform speed along the axial direction of the kiln under the guidance of the independent rotating spiral plate 204. The charge is heated from 850°C to 1020°C by the medium frequency induction constant temperature heating device 203 and reduced at a constant temperature for 40min. At the current stage, the iron-containing charge is further reduced to metallic iron. After the reduction is completed, the charge moves at a uniform speed to the second half of the rotary kiln under the guidance of the independent rotating spiral plate 204 and is gradually cooled. Then, it is discharged from the tail of the kiln into the series tank discharge unit for discharge.

[0104] When discharging, the material is first discharged into the upper discharge tank 301 in which the air has been replaced with hydrogen. After the upper discharge tank is full, the upper feed valve on the upper discharge tank 301 is closed and the upper discharge valve is opened to discharge the material into the lower discharge tank 302 and exchange heat with the room temperature hydrogen introduced into the lower discharge tank 302, so that the 700°C direct reduced iron powder is discharged after the temperature drops to 50°C. The metallization rate of the reduced direct reduced iron powder is greater than or equal to 92%.

[0105] The reduced hydrogen is discharged from the reducing gas outlet 402, treated by a dehydration device and a dust removal device, and then recycled by being sprayed into the kiln. In addition, the temperature of the hydrogen after heat exchange through the lower discharge tank 302 is 200°C-220°C, and is directly sprayed into the rotary kiln furnace body through a pipeline, which improves the utilization efficiency and reduction efficiency of hydrogen and reduces production costs.

[0106] Example 2

[0107] In this embodiment, iron concentrate powder with an iron content of 62% is used as raw material, and the raw material loading amount is calculated according to the raw material filling rate of 7% in the rotary kiln furnace body.

[0108] When charging, first open the upper feed valve, load the iron ore powder into the upper charging tank 101, and then close the upper feed valve; open the control valve on the first branch pipe and the control valve on the second branch pipe and fill hydrogen into the upper charging tank 101 and the lower charging tank 102, so that the pressure in the upper charging tank 101 and the lower charging tank 102 are kept consistent, then close the control valves on the first branch pipe and the second branch pipe to stop filling hydrogen; then, open the upper discharge valve and the lower feed valve, and when all the charge in the upper charging tank 101 is discharged into the lower charging tank 102, close the upper discharge valve and the lower feed valve; finally, open the lower discharge valve to send the charge into the rotary kiln furnace body, repeat the above process, and complete the furnace body feeding.

[0109] While loading, 700m 3Pure hydrogen is continuously sprayed into the kiln from the reducing gas inlet 401 as a reducing agent. After being heated by the microwave heating device 202, the temperature of the iron-containing charge rises to 900°C. By setting the rotation speed of the rotary kiln body and the independent rotating spiral plate 204 to 1.0r / min, the residence time of the charge in the preheating reduction section (microwave heating section) is maintained at 20min. Subsequently, the charge gradually moves from the microwave heating section to the medium frequency induction constant temperature heating section at a uniform speed along the axial direction of the kiln under the guidance of the independent rotating spiral plate 204. The charge is heated from 900°C to 1050°C by the medium frequency induction constant temperature heating device 203 and reduced at a constant temperature for 60min. At the current stage, the iron-containing charge is further reduced to metallic iron. After the reduction is completed, the charge moves at a uniform speed to the second half of the rotary kiln under the guidance of the independent rotating spiral plate 204 and is gradually cooled. Then, it is discharged from the tail of the kiln into the series tank discharge unit for discharge.

[0110] When discharging, the material is first discharged into the upper discharge tank 301 in which the air has been replaced with hydrogen. After the upper discharge tank is full, the upper feed valve on the upper discharge tank 301 is closed and the upper discharge valve is opened to discharge the material into the lower discharge tank 302, and heat is exchanged with the room temperature hydrogen introduced into the lower discharge tank 302, so that the 730°C direct reduced iron powder is discharged after the temperature drops to 50°C, and the metallization rate of the reduced direct reduced iron powder is greater than or equal to 94%.

[0111] The reduced hydrogen is discharged from the reducing gas outlet 402, treated by a dehydration device and a dust removal device, and then recycled by being sprayed into the kiln. In addition, the temperature of the hydrogen after heat exchange through the lower discharge tank 302 is 200°C-220°C, and is directly sprayed into the rotary kiln furnace body through a pipeline, which improves the utilization efficiency and reduction efficiency of hydrogen and reduces production costs.

[0112] Example 3

[0113] In this embodiment, iron concentrate powder with an iron content of 68% is used as raw material, and the raw material loading amount is calculated according to the raw material filling rate of 8% in the rotary kiln furnace body.

[0114] When charging, first open the upper feed valve, load the iron ore powder into the upper charging tank 101, and then close the upper feed valve; open the control valve on the first branch pipe and the control valve on the second branch pipe and fill hydrogen into the upper charging tank 101 and the lower charging tank 102, so that the pressure in the upper charging tank 101 and the lower charging tank 102 are kept consistent, then close the control valves on the first branch pipe and the second branch pipe to stop filling hydrogen; then, open the upper discharge valve and the lower feed valve, and when all the charge in the upper charging tank 101 is discharged into the lower charging tank 102, close the upper discharge valve and the lower feed valve; finally, open the lower discharge valve to send the charge into the rotary kiln furnace body, repeat the above process, and complete the furnace body feeding.

[0115] While loading, 700m 3Pure hydrogen is continuously sprayed into the kiln from the reducing gas inlet 401 as a reducing agent. After being heated by the microwave heating device 202, the temperature of the iron-containing charge rises to 950°C. By setting the rotation speed of the rotary kiln body and the independent rotating spiral plate 204 to 0.7r / min, the residence time of the charge in the preheating reduction section (microwave heating section) is maintained at 30min. Subsequently, the charge gradually moves from the microwave heating section to the medium frequency induction constant temperature heating section at a uniform speed along the axial direction of the kiln under the guidance of the independent rotating spiral plate 204. The charge is heated from 950°C to 1100°C by the medium frequency induction constant temperature heating device 203 and reduced at a constant temperature for 70min. At the current stage, the iron-containing charge is further reduced to metallic iron. After the reduction is completed, the charge moves at a uniform speed to the second half of the rotary kiln under the guidance of the independent rotating spiral plate 204 and is gradually cooled. Then, it is discharged from the tail of the kiln into the series tank discharge unit for discharge.

[0116] When discharging, the material is first discharged into the upper discharge tank 301 in which the air has been replaced with hydrogen. After the upper discharge tank is full, the upper feed valve on the upper discharge tank 301 is closed and the upper discharge valve is opened to discharge the material into the lower discharge tank 302 and exchange heat with the room temperature hydrogen introduced into the lower discharge tank 302, so that the 760°C direct reduced iron powder is discharged after the temperature drops to 50°C, and the metallization rate of the reduced direct reduced iron powder is greater than or equal to 96%.

[0117] The reduced hydrogen is discharged from the reducing gas outlet 402, treated by a dehydration device and a dust removal device, and then recycled by being sprayed into the kiln. In addition, the temperature of the hydrogen after heat exchange through the lower discharge tank 302 is 200°C-220°C, and is directly sprayed into the rotary kiln furnace body through a pipeline, which improves the utilization efficiency and reduction efficiency of hydrogen and reduces production costs.

[0118] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A pure hydrogen reduction rotary kiln ironmaking method, characterized in that: The following steps are involved: Step 1, starting the driving devices corresponding to the rotary kiln body and the independently rotating spiral structure, so that the two begin to rotate independently in opposite directions; Step 2, starting to load the rotary kiln body with iron ore powder; When loading powder, the reducing gas at room temperature is input through the reducing gas inlet provided at the feeding end of the rotary kiln body; Step 3, the materials enter the preheating reduction section, constant temperature reduction section and cooling section in the rotary kiln furnace in sequence; Step 4: Discharge.

2. The pure hydrogen reduction rotary kiln ironmaking method according to claim 1, characterized in that: In step 1, the normal temperature reducing gas is normal temperature hydrogen; The rotary kiln body is reduced in a pure hydrogen atmosphere. When the rotary kiln body is started for the first time, inert gas is introduced to replace the air in the kiln.

3. The pure hydrogen reduction rotary kiln ironmaking method according to claim 1, characterized in that: In step 2, the particle size of the iron ore powder is 0.05-0.9 mm.

4. The pure hydrogen reduction rotary kiln ironmaking method according to claim 1, characterized in that: In step 2, the rotary kiln furnace body includes a preheating reduction section, a constant temperature reduction section and a cooling section from the feeding end to the discharging end, and the material is heated to the preheating reduction temperature and the constant temperature reduction temperature in sequence by a heating device to carry out a reduction reaction.

5. The pure hydrogen reduction rotary kiln ironmaking method according to claim 4, characterized in that: In step 2, the preheating reduction stage adopts microwave heating; the constant temperature reduction stage adopts medium frequency induction heating.

6. The pure hydrogen reduction rotary kiln ironmaking method according to claim 5, characterized in that: In step 2, the temperature of the preheating reduction section is 850°C to 1000°C.

7. The pure hydrogen reduction rotary kiln ironmaking method according to claim 5, characterized in that: In step 2, the temperature of the isothermal reduction section is 1050°C to 1100°C.

8. The pure hydrogen reduction rotary kiln ironmaking method according to claim 1, characterized in that: In step 1, during loading, an upper loading tank and a lower loading tank connected in series are used for alternate loading, and the upper loading tank and the lower loading tank connected in series can prevent air from entering the rotary kiln furnace body during loading.

9. The pure hydrogen reduction rotary kiln ironmaking method according to claim 1, characterized in that: In step 4, when discharging, the upper discharging tank and the lower discharging tank connected in series are used to discharge alternately. The upper discharge tank and the lower discharge tank connected in series can prevent air from entering the rotary kiln furnace body during discharge.

10. A pure hydrogen reduction rotary kiln ironmaking system, characterized in that: Used to implement the pure hydrogen reduction rotary kiln ironmaking method according to any one of claims 1 to 9; The ironmaking system comprises a rotary kiln reduction device body, a first driving device and a second driving device; The rotary kiln reduction device body comprises a rotary kiln furnace body and an independent rotating structure; the first driving device is arranged outside the rotary kiln furnace body and can drive the rotary kiln furnace body to rotate; The independent rotating structure comprises a rotating shaft and an independent rotating spiral plate arranged thereon, wherein the rotating shaft is arranged along the length direction of the rotary kiln furnace body and penetrates the rotary kiln furnace body, and both ends of the rotating shaft are fixed outside the rotary kiln furnace body and are drivingly connected to the second driving device; The rotary kiln body driven by the first driving device and the independent rotating mechanism driven by the second driving device rotate independently in opposite directions.

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