A calcium vapor balance control method and device for catalytic carbon reduction magnesium smelting

Abstract

The present invention belongs to the technical field of metal smelting, and in particular relates to a calcium vapor balance control method and device for catalytic carbon reduction magnesium smelting. The calcium vapor pressure in a reaction system is controlled by condensing and evaporating metallic calcium, thereby suppressing the side reactions 2CaO(s)+CaC2(s)=3Ca(g)+2CO(g), CaC2(s)=Ca(g)+2C(s), and Ca(g)+2C(s)=CaC2(s), thereby increasing the yield of magnesium products and calcium carbide products, and extending the service life of carbonaceous materials such as graphite electrodes in the reaction chamber, greatly improving the economic benefits of the method and facilitating the industrialization and promotion of the method.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal smelting, and in particular relates to a calcium vapor balance control method and device for catalytic carbon reduction magnesium smelting. Background Art

[0002] At present, the industry generally adopts silicothermic method or electrolytic method to smelt magnesium. The cost of carbon reducing agent is significantly lower than that of ferrosilicon reducing agent in silicothermic method, and the generated CO waste gas can be used as fuel. In particular, no waste slag is generated when calcined magnesite is used as raw material, and the CaO waste slag generated when calcined white is used as raw material has certain utilization value. Therefore, it is generally believed that carbothermic method of magnesium smelting has obvious economic advantages.

[0003] Patent application CN202080087519.1 proposes a carbon thermal method for magnesium smelting and co-production of calcium carbide using solid-phase calcium carbide as a catalyst. Calcined white is mixed with anthracite, asphalt and calcium carbide, ground into 100 mesh powder and then pressed into balls using a ball press. This method includes two main smelting stages, and the main reaction process is as follows (1.1)-(1.5).

[0004] The first stage is the magnesium smelting stage. Under the smelting process conditions in this stage, the corresponding main reaction (1.1) occurs. During this stage, the CO pressure and calcium vapor pressure both approach zero, and side reactions (1.2) and (1.3) inevitably occur. Side reactions (1.2) and (1.3) consume the magnesium smelting reducing agent CaC2, thereby reducing the magnesium collection rate. Moreover, side reaction (1.3) and reaction (1.4) are mutually contradictory: when the calcium vapor pressure is too low, the CaC2 will decompose and be lost; when the calcium vapor pressure is too high, it will corrode and damage carbonaceous materials such as graphite electrodes. In other words, the calcium vapor pressure cannot be too low or too high.

[0005] The second stage is the calcium carbide smelting stage. The main reaction in the calcium carbide smelting stage is (1.5). During this process, a large amount of CO is produced, which can significantly inhibit the occurrence of reaction (1.2). However, the high temperature conditions in the reaction chamber and the calcium vapor partial pressure tending to zero will lead to the occurrence of side reaction (1.3), which seriously affects the collection rate of the final calcium carbide product, reduces the economic benefits of the method, and hinders the application and promotion of the method.

[0006] CaMgO2(s)+CaC2(s)=Mg(g)+2CaO(s)+2C(s) (1.1)

[0007] 2CaO(s)+CaC2(s)=3Ca(g)+2CO(g) (1.2)

[0008] CaC2(s)=Ca(g)+2C(s) (1.3)

[0009] Ca(g)+2C(s)=CaC2(s) (1.4)

[0010] CaO(s)+3C(s)=CaC2(s)+CO(g) (1.5) Summary of the Invention

[0011] The inventors conducted in-depth research on a carbothermal method for magnesium smelting and co-production of calcium carbide using solid-phase calcium carbide as a catalyst, and found that to solve the above problems, it is necessary to control the calcium vapor pressure in the reaction chamber (system) during the reaction process. Therefore, they designed a method and device for controlling the calcium vapor pressure balance. By timely condensing, collecting and re-evaporating the calcium vapor, the pressure of the calcium vapor in the reaction chamber is controlled, achieving the effect of suppressing side reactions (1.2) and (1.3), thereby completing the present invention.

[0012] Therefore, in the first aspect, the present invention provides a calcium vapor balance control device for catalytic carbon reduction magnesium smelting, which includes a reactor, a vacuum pipe connected to the outside of the reactor, a crucible, insulation material and a calcium liquid condensation screen inside the reactor, a calcium liquid conduit connecting the bottom of the reactor located between the calcium liquid condensation screen and the insulation material and a calcium liquid tank, a calcium vapor conduit connecting the crucible and the calcium liquid tank, and a heating device embedded in the bottom of the calcium liquid tank.

[0013] In one embodiment, the heat-insulating material is disposed between the crucible and the calcium liquid condensation screen.

[0014] In one embodiment, the upper portion of the thermal insulation material is provided with openings to allow calcium vapor and magnesium vapor to flow out.

[0015] In one embodiment, the calcium liquid tank is located below the reaction furnace.

[0016] In one embodiment, the calcium liquid conduit extends below the calcium liquid level in the calcium liquid tank.

[0017] In one embodiment, the calcium vapor conduit is in contact with the reaction materials within the crucible.

[0018] In one embodiment, the device further includes a PLC device for controlling the temperature of the calcium liquid tank by controlling the heat load of the calcium liquid tank heating device, thereby controlling the speed (pressure) at which the calcium liquid re-evaporates into the crucible, thereby achieving the purpose of controlling the pressure of the calcium vapor in the crucible in the reaction furnace.

[0019] During metal smelting using the calcium vapor balance control device of the present invention, calcium vapor and magnesium vapor pass through openings in the insulation material. The calcium vapor, upon contacting the calcium liquid condensation screen, condenses into calcium liquid, flows into the bottom, and then enters the calcium liquid tank through the calcium liquid flow guide pipe. The magnesium vapor, due to its lower melting point, continues to escape in gaseous form along the vacuum pipe. After the calcium liquid tank is heated to a certain temperature, the calcium liquid evaporates again, passes through the calcium vapor conduit, and enters the crucible, thereby achieving the effect of controlling the calcium vapor pressure balance in the reactor.

[0020] In another aspect, the present invention provides a method for controlling calcium vapor balance in catalytic carbon reduction magnesium smelting, the method comprising:

[0021] In the first stage, calcined white, calcium carbide and anthracite fine powder are mixed and pressed into balls and placed in a crucible. The temperature T1 of the first stage magnesium smelting is set, and the system equilibrium pressure P is calculated according to formula (1):

[0022] T1=0.0687*lg 3 P+5.3738*lg 2 P+130.01*lgP+1482.4 Formula (1);

[0023] Then according to formula (2), we can get the calcium vapor partial pressure P 钙 ,

[0024] P 钙 =3 / 5P formula (2);

[0025] Set the calcium vapor pressure P1 in the reaction chamber to be slightly greater than P 钙 , calculate T2 according to formula (3):

[0026] lgP1=-9415.2 / T2+11.445-6.2151×10 -4 T2 formula (3)

[0027] T2 is used as the temperature control basis of the calcium liquid tank in the magnesium smelting stage to obtain the product magnesium;

[0028] In the second stage, the temperature T3 of the second stage calcium carbide smelting is set, and the system equilibrium pressure P2 is calculated according to formula (4):

[0029] T3=35*lg 2 P2+161*lgP2+1080 formula (4);

[0030] At this time, the system pressure is equal to the calcium vapor partial pressure. The calcium vapor pressure P3 in the reaction chamber is set to be slightly greater than P2. T4 is calculated according to formula (5):

[0031] lgP3=-9415.2 / T4+11.445-6.2151×10 -4 T4 formula (5)

[0032] T4 is used as the basis for controlling the temperature of the calcium liquid tank in the calcium carbide smelting stage, and the product calcium carbide is obtained by reaction.

[0033] In one embodiment, the raw materials of calcined white, calcium carbide and coke are first ground into 80-200 mesh fine powder, and then pressed into balls using a double-roll ball press.

[0034] In one embodiment, P1 is greater than P 钙 Large 4Pa.

[0035] In one embodiment, P3 is 37 Pa greater than P2.

[0036] In one embodiment, the temperature T1 of the magnesium smelting stage is in the range of 1350-1450°C.

[0037] In one embodiment, the temperature T3 of the calcium carbide smelting stage is in the range of 1700-1800°C.

[0038] Technical Effects

[0039] The calcium vapor balance control method and device for catalytic carbon reduction magnesium smelting of the present invention controls the calcium vapor pressure by condensing and evaporating metallic calcium in the reaction system, thereby achieving the purpose of suppressing the side reactions 2CaO(s)+CaC2(s)=3Ca(g)+2CO(g), CaC2(s)=Ca(g)+2C(s) and Ca(g)+2C(s)=CaC2(s), thereby increasing the yield of magnesium products and calcium carbide products by more than 20%.

[0040] In particular, due to the occurrence of the side reaction Ca(g)+2C(s)=CaC2(s), the excessive calcium vapor pressure in the reaction furnace will damage the carbonaceous material devices in the furnace. The device and method of the present invention effectively extend the service life of carbonaceous materials such as graphite electrodes in the reaction chamber by controlling the calcium vapor pressure, greatly improving the economic benefits of the method and contributing to the industrial promotion of the method.

[0041] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic structural diagram of a device for catalytic carbon reduction magnesium smelting according to a preferred embodiment of the present invention;

[0043] Figure 2 This is a working diagram of a device for catalytic carbon reduction magnesium smelting according to a preferred embodiment of the present invention.

[0044] Figure numerals: 1-vacuum pipe; 2-reaction furnace; 3-calcium liquid condensation screen; 4-calcium steam conduit; 5-calcium liquid box; 6-insulation material; 7-crucible; 8-calcium liquid conduit; 9-heating device. DETAILED DESCRIPTION

[0045] The following describes several preferred embodiments of the present invention with reference to the accompanying drawings to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0046] In the drawings, components with identical structures are denoted by the same reference numerals, and components with similar structures or functions are denoted by similar reference numerals. The size and thickness of each component shown in the drawings are arbitrary and are not limited by the present invention. For clarity, the thickness of components in some places in the drawings is appropriately exaggerated.

[0047] Example 1

[0048] Figure 1 The present invention shows a calcium vapor balance control device for catalytic carbon reduction magnesium smelting. The device includes a reactor 2, the outside of which is connected to a vacuum pipe 1. The reactor 2 is internally provided with a crucible 7, insulation material 6, and a calcium liquid condensation screen 3. A calcium liquid conduit 8 connects the bottom of the reactor 2, located between the calcium liquid condensation screen 3 and the insulation material 6, and a calcium liquid tank 5, extending below the calcium liquid level in the calcium liquid tank 5. A calcium vapor conduit 4 connects the crucible 7 and the calcium liquid tank 5 and contacts the reaction materials in the crucible 2. A heating device 9 is embedded in the bottom of the calcium liquid tank 5. The insulation material 6 is disposed between the crucible 7 and the calcium liquid condensation screen 3. An opening is provided on the top of the insulation material 6 to allow calcium vapor and magnesium vapor to flow out. The calcium liquid tank 5 is located below the reactor 2.

[0049] The device also includes a PLC device (not shown) for controlling the temperature of the calcium liquid tank 5 by controlling the heat load of the calcium liquid tank 5 heating device, thereby controlling the speed (pressure) of the calcium liquid re-evaporating into the crucible 7, thereby achieving the purpose of controlling the pressure of the calcium vapor in the crucible 7 in the reaction furnace 2.

[0050] Figure 2 The schematic diagram of the calcium vapor balance control device for catalytic carbon reduction magnesium smelting according to the present invention illustrates the operation of the device. During the metal smelting process, calcium vapor and magnesium vapor pass through openings in insulation material 6. The calcium vapor condenses into calcium liquid upon contact with calcium liquid condensation screen 3, flows into the bottom, and then enters calcium liquid tank 5 through calcium liquid flow conduit 8. Due to its lower melting point, magnesium vapor continues to escape in gaseous form through vacuum conduit 1. After calcium liquid tank 5 is heated to a certain temperature, the calcium liquid evaporates again and enters crucible 7 through calcium vapor conduit 4, thereby achieving the effect of controlling the calcium vapor pressure balance within reactor 7.

[0051] Example 2

[0052] The raw materials of calcined white, calcium carbide and coke are ground into 80-200 mesh fine powder, pressed into balls by a double-roller ball press, and put into the reaction furnace.

[0053] The temperature T1 of the first stage of magnesium smelting is set to 1623K (1350℃), and T1 is substituted into the relationship (1) to obtain the system equilibrium pressure:

[0054] T1=0.0687*lg 3 P+5.3738*lg 2 P+130.01*lgP+1482.4 Formula (1)

[0055] P≈10.8758Pa, and the calcium vapor partial pressure P is obtained from formula (2): 钙

[0056] P 钙 =3 / 5P Formula (2)

[0057] Get P 钙 =6.52548Pa. In order to suppress the reaction 2CaO(s)+CaC2(s)=3Ca(g)+2CO(g), the calcium vapor pressure in the reaction chamber should be slightly greater than P 钙 , so take P1 = 10Pa, and substitute P1 into equation (3) to obtain T2:

[0058] lgP1=-9415.2 / T2+11.445-6.2151×10 -4 T2 formula (3)

[0059] It is found that T2≈955K (682℃), which is used as the basis for controlling the temperature of the calcium liquid tank in the magnesium smelting stage, and the magnesium product is finally obtained.

[0060] The temperature T3 of the second stage of calcium carbide smelting is set to 1973K (1700℃). Substituting T3 into equation (4) yields the system equilibrium pressure (i.e., calcium vapor pressure) P2:

[0061] T3=35*lg 2 P2+161*lgP2+1080 Formula (4)

[0062] P2≈313Pa, take P3=350Pa, substitute P3 into equation (5) to get T4:

[0063] lgP3=-9415.2 / T4+11.445-6.2151×10 -4 T4 formula (5)

[0064] It is obtained that T4≈1150K (877℃), and this T4 is used as the basis for controlling the temperature of the calcium liquid box in the calcium carbide smelting stage, and the final product calcium carbide is obtained.

[0065] Example 3

[0066] The raw materials of calcined white, calcium carbide and coke are ground into 80-200 mesh fine powder, pressed into balls by a double-roller ball press, and put into the reaction furnace.

[0067] The temperature T1 of the first stage of magnesium smelting is set to 1723K (1450℃), and T1 is substituted into the relationship (1) to obtain the system equilibrium pressure P:

[0068] T1=0.0687*lg 3 P+5.3738*lg 2 P+130.01*lgP+1482.4 Formula (1)

[0069] It is obtained that P≈53Pa, and the calcium vapor partial pressure P is obtained from formula (2) 钙

[0070] P 钙 =3 / 5P Formula (2)

[0071] Get P 钙 =31.8Pa. In order to suppress the reaction 2CaO(s)+CaC2(s)=3Ca(g)+2CO(g), the calcium vapor pressure in the reaction chamber should be slightly greater than P 钙 , so take P1 = 50Pa, and substitute P1 into equation (3) to obtain T2:

[0072] lgP1=-9415.2 / T2+11.445-6.2151×10 -4 T2 formula (3)

[0073] It is found that T2≈1034K (761℃), which is used as the basis for controlling the temperature of the calcium liquid tank in the magnesium smelting stage, and the final magnesium product is obtained.

[0074] The temperature T3 of the second stage of calcium carbide smelting is set to 2073K (1800℃). Substituting T3 into equation (3) yields the system equilibrium pressure (i.e., calcium vapor pressure) P2:

[0075] T3=35*lg 2 P2+161*lgP2+1080 Formula (4)

[0076] We get P2≈610Pa, take P3=650Pa, and substitute P3 into equation (5) to get T4:

[0077] lgP3=-9415.2 / T4+11.445-6.2151×10-4 T4 formula (5)

[0078] It is found that T4≈1193K (920℃), which is used as the basis for controlling the temperature of the calcium liquid tank in the calcium carbide smelting stage, and the final product is calcium carbide.

[0079] Compared with the existing carbon thermal magnesium smelting technology, such as the technology described in CN202080087519.1, the device and method of the present invention can achieve a magnesium product yield of 80-85%, and a calcium carbide product yield of about 75%, thereby increasing the magnesium collection rate by more than 20%.

[0080] The preferred embodiments of the present invention have been described in detail above. It should be understood that numerous modifications and variations based on the concepts of the present invention are possible without inventive effort by those skilled in the art. Therefore, any technical solution that can be derived by one skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A calcium vapor balance control device for catalytic carbon reduction magnesium smelting, the device comprising a reactor, a vacuum pipe connected to the outside of the reactor, a crucible, insulation material, and a calcium liquid condensation screen provided inside the reactor, a calcium liquid conduit connecting the bottom of the reactor between the calcium liquid condensation screen and the insulation material and a calcium liquid tank, a calcium vapor conduit connecting the crucible and the calcium liquid tank, and a heating device embedded in the bottom of the calcium liquid tank.

2. The calcium vapor balance control device according to claim 1, wherein: The upper portion of the heat-insulating material is provided with openings.

3. The calcium vapor balance control device according to claim 1, wherein: The calcium liquid conduit extends to below the calcium liquid level in the calcium liquid tank.

4. The calcium vapor balance control device according to claim 1, wherein: The device also includes a PLC device for controlling the heat load of the calcium liquid tank heating device.

5. A method for controlling calcium vapor balance in catalytic carbon reduction magnesium smelting, using the calcium vapor balance control device for catalytic carbon reduction magnesium smelting according to any one of claims 1 to 4, the method comprising: In the first stage, calcined white, calcium carbide and anthracite fine powder are mixed and pressed into balls and placed in a crucible. The temperature T1 of the first stage magnesium smelting is set, and the system equilibrium pressure P is calculated according to formula (1): T1=0.0687*lg 3 P+5.3738*lg 2 P+130.01*lgP+1482.4 Equation (1); Then according to formula (2), we can get the calcium vapor partial pressure P 钙 , P 钙 =3 / 5P formula (2); Set the calcium vapor pressure in the reaction chamber to P1, P1 is higher than P 钙 4Pa, calculate T2 according to formula (3): lgP1=-9415.2 / T2+11.445-6.2151×10 -4 T2 formula (3) T2 is used as the temperature control basis of the calcium liquid tank in the magnesium smelting stage to obtain the product magnesium; In the second stage, the temperature T3 of the second stage calcium carbide smelting is set, and the system equilibrium pressure P2 is calculated according to formula (4): T3=35*lg 2 P2+161*lgP2+1080 formula (4); At this time, the system pressure is equal to the calcium vapor partial pressure. The calcium vapor pressure in the reaction chamber is set to P3, which is 37 Pa greater than P2. T4 is calculated according to formula (5): lgP3=-9415.2 / T4+11.445-6.2151×10 -4 T4 type(5) T4 is used as the basis for controlling the temperature of the calcium liquid tank in the calcium carbide smelting stage, and the product calcium carbide is obtained by reaction.

6. The calcium vapor balance control method according to claim 5, wherein: The raw materials of calcined white, calcium carbide and coke are ground into 80-200 mesh fine powder and pressed into balls using a double-roller ball press.

7. The calcium vapor balance control method according to claim 5, wherein: The temperature T1 in the magnesium smelting stage ranges from 1350 to 1450°C.

8. The calcium vapor balance control method according to claim 5, wherein: The temperature T3 in the calcium carbide smelting stage ranges from 1700 to 1800°C.

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