Partitioned temperature control method for external heating type rotary kiln

Abstract

The invention discloses a partition temperature control method for an external heating type rotary kiln, and belongs to the technical field of metal smelting processes. The external heating type rotary kiln is divided into a first-area combustion chamber, a second-area combustion chamber and a third-area combustion chamber from the feeding end, the first-area combustion chamber, the second-area combustion chamber and the third-area combustion chamber are divided into independent combustion spaces through partition plates, and a first natural gas combustion tail gas pipeline and an electric control valve which are communicated are additionally arranged between the third-area combustion chamber and the second-area combustion chamber. A second natural gas combustion tail gas pipeline and an electric control valve which are communicated are additionally arranged between the third-area combustion chamber and the first-area combustion chamber, and natural gas combustion tail gas exhaust pipelines and electric control valves of the first-area combustion chamber and the second-area combustion chamber are additionally arranged. In order to overcome the defects of a traditional rotary kiln roasting process, the invention provides the external heating type rotary kiln partition temperature control method which is suitable for ultrahigh-copper high-iron low-molybdenum molybdenum concentrate, high in reliability and thorough in molybdenum concentrate oxidizing roasting.

Description

Technical Field

[0001] The invention relates to a zone temperature control method for an externally heated rotary kiln, belonging to the technical field of metal smelting technology. Background Art

[0002] Rotary kiln oxidation roasting of molybdenum concentrate is a traditional process. While the technology is mature and stable, it imposes certain restrictions on the copper impurities in the raw materials, typically requiring a molybdenum grade above 45% and a copper grade below 0.5%. High iron content also significantly impacts roasting. This process is more suitable for concentrates derived from a single molybdenum ore. However, for high-copper and high-iron molybdenum concentrates derived from associated metal ores, the oxidation roasting process faces challenges as copper and iron grades increase. Impurities in molybdenite, particularly copper and iron, are crucial to sintering behavior during roasting, and roasting temperature is also a key factor in initiating sintering. Sintering arises from the formation of low-melting-point eutectics between molybdenum oxide and molybdates, as well as locally elevated temperatures. While magnesium oxide and calcium oxide have a strong sulfur-binding effect during roasting, they can lead to incomplete roasting and increased residual sulfur. Therefore, strict management of impurity elements and reaction temperature is crucial to controlling sintering during molybdenite roasting. When the existing technology uses the traditional rotary kiln oxidation roasting process to treat high-impurity copper-containing molybdenum concentrate, the oxidation is often not complete, the roasted sand is easily sintered and wraps the molybdenum concentrate, and the roasted sand molybdenum ammonia leaching rate is low, only about 85%. In addition, there is currently no direct treatment of ultra-high copper, high iron, low molybdenum molybdenum concentrate in the industry, that is, the ultra-high copper, high iron, low molybdenum molybdenum concentrate has a copper grade of 4% to 16%, an iron grade of 7% to 12%, and a molybdenum grade of 27% to 40%. Therefore, it is urgent to propose a zoned temperature control method for an externally heated rotary kiln to solve the above technical problems. Summary of the Invention

[0003] The present invention is designed to overcome the shortcomings of conventional rotary kiln roasting processes by providing a highly reliable, externally heated rotary kiln zoned temperature control method suitable for ultra-high-copper, high-iron, low-molybdenum molybdenum concentrates, achieving a more thorough oxidation roasting of molybdenum concentrates. A brief overview of the present invention is provided below to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify key or important aspects of the present invention, nor is it intended to limit the scope of the present invention.

[0004] The technical solution of the present invention:

[0005] A zoned temperature control method for an externally heated rotary kiln comprises dividing the externally heated rotary kiln into a first zone combustion chamber, a second zone combustion chamber, and a third zone combustion chamber from a feed end, wherein the first zone combustion chamber, the second zone combustion chamber, and the third zone combustion chamber are separated into independent combustion spaces by partitions, a first natural gas combustion tail gas pipeline and an electric regulating valve are added between the third zone combustion chamber and the second zone combustion chamber, a second natural gas combustion tail gas pipeline and an electric regulating valve are added between the third zone combustion chamber and the first zone combustion chamber, and natural gas combustion tail gas external discharge pipelines and electric regulating valves are added to the first zone combustion chamber and the second zone combustion chamber, and residual heat after natural gas combustion in the three zone combustion chambers is distributed to the first zone combustion chamber and the second zone combustion chamber through the first natural gas combustion tail gas pipeline and the second natural gas combustion tail gas pipeline respectively by controlling the valve opening of the electric regulating valve; when the temperature in the second zone combustion chamber and the third zone combustion chamber is too high, the residual heat is discharged from the natural gas combustion tail gas external discharge pipelines of the first zone combustion chamber and the second zone combustion chamber through the natural gas combustion tail gas external discharge pipeline and the electric regulating valve;

[0006] The number of heating points in the combustion chamber of the externally heated rotary kiln is 9, and the arrangement of the 9 heating points in the combustion chamber is as follows: one heating point in the combustion chamber is set at 12.5%, 25%, 37.5%, 57%, 64%, 71%, 78%, 87% and 96% of the distance from the feed end of the externally heated rotary kiln, respectively.

[0007] Preferably, the length ratio of the first zone combustion chamber, the second zone combustion chamber and the third zone combustion chamber is 2:1:1.

[0008] Preferably, the first zone combustion chamber, the second zone combustion chamber and the third zone combustion chamber respectively include three combustion chamber heating points in sequence.

[0009] Preferably: when the temperature of the combustion chamber in zone 1 and the combustion chamber in zone 2 is too high, cold air is sent into the combustion chamber in zone 1 and the combustion chamber in zone 2 through the combustion air duct at the heating point of the combustion chamber to cool the combustion chamber in zone 1 and the combustion chamber in zone 2.

[0010] Preferably, the rotation speed of the externally heated rotary kiln is controlled to be 0.28-0.36 r / min, and variable frequency regulation and natural gas external heating are adopted.

[0011] Preferably, the temperature of the combustion chamber in zone one is controlled at 430-490°C, the temperature of the combustion chamber in zone two is controlled at 450-500°C, and the temperature of the combustion chamber in zone three is controlled at 600-630°C.

[0012] The present invention has the following beneficial effects:

[0013] 1. The present invention strictly controls the impurity elements and reaction temperature in the high-copper, high-iron, low-molybdenum molybdenum concentrate to avoid the occurrence of sintering during the roasting process of molybdenite, making the externally heated rotary kiln suitable for the oxidative roasting of ultra-high-copper, high-iron, low-molybdenum molybdenum concentrate;

[0014] 2. The present invention avoids the drawback of conventional externally heated rotary kilns in which the first, second, and third combustion chambers 2, 3, and 4 are all constantly ignited to maintain production temperatures. The present invention rationally distributes the residual heat from the combustion of natural gas in the third combustion chamber 4 after the roasting reaction in the first combustion chamber 2 begins, eliminating the need for ignition and temperature increase in the first and second combustion chambers 2 and 3, effectively saving natural gas consumption.

[0015] 3. The present invention can raise or lower the temperature of each zone of an externally heated rotary kiln. Since the oxidation roasting of molybdenum concentrate is a highly exothermic process, the present invention can finely control the temperature of each zone of the externally heated rotary kiln.

[0016] 4. The present invention is also beneficial for the separation and recovery of rhenium during the oxidation roasting of rhenium-containing molybdenum concentrate, can reduce the volatilization of molybdenum, and the process is stable and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural diagram of a zone temperature control method for an externally heated rotary kiln;

[0018] Figure 2 This is a diagram of the coordinated installation of the first natural gas combustion exhaust gas pipeline and the second natural gas combustion exhaust gas pipeline;

[0019] Figure 3 It is a side view of a zoned temperature control method for an externally heated rotary kiln;

[0020] In the figure, 1 is an externally heated rotary kiln, 2 is a combustion chamber in the first zone, 3 is a combustion chamber in the second zone, 4 is a combustion chamber in the third zone, 5 is a second natural gas combustion tail gas pipeline, 6 is a first natural gas combustion tail gas pipeline, and 7 is a heating point in the combustion chamber. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the present invention more clearly apparent, the present invention is described below using specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely illustrative and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0022] The connections mentioned in the present invention are divided into fixed connections and detachable connections. The fixed connection refers to a non-detachable connection, including but not limited to conventional fixed connection methods such as hem connection, rivet connection, adhesive connection, and welding connection. The detachable connection refers to but not limited to conventional detachable connection methods such as threaded connection, snap connection, pin connection, and hinge connection. When the specific connection method is not clearly specified, it is assumed that at least one connection method can always be found among the existing connection methods to achieve the function. Those skilled in the art can choose according to their needs. For example, a welded connection is selected for a fixed connection, and a hinge connection is selected for a detachable connection.

[0023] Specific implementation method 1: Combination Figure 1-Figure 3 The present embodiment is described. The present embodiment is a zone temperature control method for an externally heated rotary kiln, comprising dividing an externally heated rotary kiln 1 from a feed end into a first zone combustion chamber 2, a second zone combustion chamber 3, and a third zone combustion chamber 4. The first zone combustion chamber 2, the second zone combustion chamber 3, and the third zone combustion chamber 4 are separated into independent combustion spaces by partitions. A first natural gas combustion tail gas pipeline 6 and an electric regulating valve are added between the third zone combustion chamber 4 and the second zone combustion chamber 3. A second natural gas combustion tail gas pipeline 5 and an electric regulating valve are added between the third zone combustion chamber 4 and the first zone combustion chamber 2. The natural gas combustion exhaust gas discharge pipes and electric regulating valves of the zone 2 combustion chamber and the zone 2 combustion chamber 3 distribute the residual heat after the natural gas combustion in the zone 3 combustion chamber 4 through the first natural gas combustion exhaust gas pipe 6 and the second natural gas combustion exhaust gas pipe 5 to the zone 1 combustion chamber 2 and the zone 2 combustion chamber 3 respectively by controlling the valve opening of the electric regulating valve. When the temperature in the zone 2 combustion chamber 3 and the zone 3 combustion chamber 4 is too high, the residual heat is discharged from the natural gas combustion exhaust gas discharge pipes of the zone 1 combustion chamber 2 and the zone 2 combustion chamber 3 through the natural gas combustion exhaust gas discharge pipes and the electric regulating valve;

[0024] The number of combustion chamber heating points 7 of the externally heated rotary kiln 1 is 9, and the arrangement of the 9 combustion chamber heating points 7 is as follows: one combustion chamber heating point 7 is set at 12.5%, 25%, 37.5%, 57%, 64%, 71%, 78%, 87% and 96% of the distance from the feed end of the externally heated rotary kiln 1 respectively.

[0025] The length ratio of the first zone combustion chamber 2, the second zone combustion chamber 3 and the third zone combustion chamber 4 is 2:1:1.

[0026] The zone 1 combustion chamber 2, zone 2 combustion chamber 3 and zone 3 combustion chamber 4 respectively include 3 combustion chamber heating points 7 in sequence, that is, the zone 1 combustion chamber 2 includes the 1st to 3rd combustion chamber heating points 7 in sequence from the feed end, the zone 2 combustion chamber 3 includes the 4th to 6th combustion chamber heating points 7 in sequence from the feed end, and the zone 3 combustion chamber 4 includes the 7th to 9th combustion chamber heating points 7 in sequence from the feed end. Arranging the combustion chamber heating points 7 in this position can effectively heat each zone separately; because the zone 3 combustion chamber 4 is the highest during the rotary kiln roasting process.

[0027] When the temperature of the first zone combustion chamber 2 and the second zone combustion chamber 3 is too high, cold air is sent into the combustion air duct through the combustion chamber heating point 7 to cool the first zone combustion chamber 2 and the second zone combustion chamber 3.

[0028] The rotation speed of the externally heated rotary kiln 1 is controlled to be 0.28-0.36 r / min, and variable frequency regulation and natural gas external heating are adopted.

[0029] The temperature of the zone 1 combustion chamber 2 is controlled at 430-490°C, the temperature of the zone 2 combustion chamber 3 is controlled at 450-500°C, and the temperature of the zone 3 combustion chamber 4 is controlled at 600-630°C. Since the material needs to undergo different stages such as dehydration, decomposition, and crystal transformation during the heat treatment process, the low-temperature section of the zone 1 combustion chamber 2 can remove free water and part of the crystalline water to avoid direct vaporization at high temperature and causing the material to explode; the medium-temperature section of the zone 2 combustion chamber 3 triggers the decomposition reaction; the high-temperature section of the zone 3 combustion chamber completes deep reactions, such as oxidation, sintering or lattice reconstruction, to ensure the thoroughness of the reaction. Such a design can gradually increase the temperature to adapt to the phase change of the material, avoid reaching high temperature too early to trigger side reactions, such as sintering and ringing of the material, and at the same time reduce the instantaneous release of harmful gases and improve the purity of the product.

[0030] Specific implementation method 2: Combination Figure 1-Figure 3 This embodiment is described based on the first embodiment. The embodiment of this embodiment is a zone temperature control method for an externally heated rotary kiln, comprising the following steps:

[0031] Step 1: Select an externally heated rotary kiln 1 with a length of 24 m and a diameter of 1.2 m;

[0032] Step 2: The rotation speed of the externally heated rotary kiln 1 is controlled to 0.28-0.36 r / min, variable frequency adjustment is possible, and natural gas is used for external heating;

[0033] Step 3: Turn on the induced draft fan and combustion-supporting fan connected to the inside of the externally heated rotary kiln 1, start the externally heated rotary kiln 1 and adjust the speed, ignite and heat the combustion chamber 2 in zone 1, the combustion chamber 3 in zone 2 and the combustion chamber 4 in zone 3, evenly add the ultra-high copper, high iron and low molybdenum molybdenum concentrate into the externally heated rotary kiln 1, and start oxidative roasting. Qualified molybdenum roasted sand can be produced after 8 hours.

[0034] Process control 1: During the roasting process of the externally heated rotary kiln 1, the oxygen concentration of the sulfur dioxide flue gas is controlled at 5% to 10%.

[0035] Process control 2: The temperature of the combustion chamber 2 in zone 1 is controlled at 430-490°C, the temperature of the combustion chamber 3 in zone 2 is controlled at 450-500°C, and the temperature of the combustion chamber 4 in zone 3 is controlled at 600-630°C.

[0036] Table 1 is a comparison of technical indicators before and after implementing a zoned temperature control method for an externally heated rotary kiln according to this embodiment.

[0037] Table 1

[0038]

[0039] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be permuted and combined. Those skilled in the art can exhaust all possibilities based on the mathematical knowledge of permutations and combinations. Therefore, the present invention will no longer describe the technical solutions after permutations and combinations one by one, but it should be understood that the technical solutions after permutations and combinations have been disclosed by the present invention.

[0040] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A zone temperature control method for an externally heated rotary kiln, characterized in that: The invention comprises dividing an externally heated rotary kiln (1) into a first zone combustion chamber (2), a second zone combustion chamber (3) and a third zone combustion chamber (4) from a feeding end, wherein the first zone combustion chamber (2), the second zone combustion chamber (3) and the third zone combustion chamber (4) are separated into independent combustion spaces by partitions, adding a first natural gas combustion tail gas pipeline (6) and an electric regulating valve connected between the third zone combustion chamber (4) and the second zone combustion chamber (3), adding a second natural gas combustion tail gas pipeline (5) and an electric regulating valve connected between the third zone combustion chamber (4) and the first zone combustion chamber (2), and adding a first zone combustion chamber (2) and a second zone combustion chamber (3) to connect the first zone combustion chamber (2). The natural gas combustion tail gas exhaust pipe and the electric regulating valve of (3) are used to distribute the residual heat after the natural gas combustion in the three-zone combustion chamber (4) through the first natural gas combustion tail gas pipe (6) and the second natural gas combustion tail gas pipe (5) to the first zone combustion chamber (2) and the second zone combustion chamber (3) respectively by controlling the valve opening of the electric regulating valve. When the temperature in the second zone combustion chamber (3) and the third zone combustion chamber (4) is too high, the residual heat is discharged from the natural gas combustion tail gas exhaust pipe of the first zone combustion chamber (2) and the second zone combustion chamber (3) through the natural gas combustion tail gas exhaust pipe and the electric regulating valve; The number of combustion chamber heating points (7) of the externally heated rotary kiln (1) is 9, and the arrangement of the 9 combustion chamber heating points (7) is as follows: one combustion chamber heating point (7) is set at 12.5%, 25%, 37.5%, 57%, 64%, 71%, 78%, 87% and 96% of the distance from the feed end of the externally heated rotary kiln (1), respectively.

2. The method for controlling temperature by zones of an externally heated rotary kiln according to claim 1, wherein: The length ratio of the first zone combustion chamber (2), the second zone combustion chamber (3) and the third zone combustion chamber (4) is 2:1:

1.

3. The method for controlling temperature by zones of an externally heated rotary kiln according to claim 2, wherein: The first zone combustion chamber (2), the second zone combustion chamber (3), and the third zone combustion chamber (4) respectively include three combustion chamber heating points (7) in sequence.

4. The method for controlling temperature by zones of an externally heated rotary kiln according to claim 3, wherein: When the temperature of the first zone combustion chamber (2) and the second zone combustion chamber (3) is too high, cold air is sent in through the combustion air duct at the combustion chamber heating point (7) to cool the first zone combustion chamber (2) and the second zone combustion chamber (3).

5. The method for controlling temperature by zones of an externally heated rotary kiln according to claim 4, wherein: The rotation speed of the externally heated rotary kiln (1) is controlled to be 0.28-0.36 r / min, and variable frequency regulation and natural gas external heating are adopted.

6. The method for controlling temperature by zones of an externally heated rotary kiln according to claim 5, wherein: The temperature of the first zone combustion chamber (2) is controlled at 430-490°C, the temperature of the second zone combustion chamber (3) is controlled at 450-500°C, and the temperature of the third zone combustion chamber (4) is controlled at 600-630°C.

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