WO2013016929A1

WO2013016929A1 - Preheating start method of aluminum electrolysis cell

Info

Publication number: WO2013016929A1
Application number: PCT/CN2011/084504
Authority: WO
Inventors: 杨建红; 唐新平; 曹鹏; 包生重
Original assignee: 中国铝业股份有限公司
Priority date: 2011-08-04
Filing date: 2011-12-23
Publication date: 2013-02-07
Also published as: CN102234819A; CN102234819B

Abstract

A preheating start method of an aluminum electrolysis cell is provided, which comprises: drilling on the upper surface of the carbon or graphite electrodes and pre-embedding the heating element in the electrode; heating the hearth of the cell according to a roasting curve by using a heating assembly; after arriving at a target temperature, adding solid or liquid electrolyte to a required electrolyte level, then regulating the power of the heating assembly, and primarily establishing heat balance and inner hearth mold required by the electrolysis cell; introducing direct current to preheat electrodes and electrolyzing the electrolyte; gradually replacing the preheating electrodes which carries the heating elements with the electrodes which are normally operating. The method in this invention provides uniform heating, and does not need flexible connection between anodes and bus bars during the preheating process, therefore it can be used to preheat traditional cell having a cathode with an abnormal-shape structure effectively, and also can be used to preheat and start an inert electrode aluminum electrolysis cell effectively, building a stable electrolysis environment, improving current efficiency, and prolonging the service life of the electrode. The preheating electrode can be reused so as to lower the cost of starting the electrolysis cell.

Description

Preheating starting method for aluminum electrolytic cell

Technical field

The invention relates to the technical field of aluminum electrolytic cells, in particular to a preheating starting method for an aluminum electrolytic cell. Background technique

The newly built or overhauled aluminum electrolysis cell undergoes a roasting and start-up process before it enters production. The roasting start-up process of the conventional tank mainly uses the heat generating material placed between the anode and the cathode of the aluminum electrolytic tank to generate heat, so that the temperature of the anode and the cathode (including the lining) of the electrolytic bath rises. The aluminum liquid roasting method and the coke roasting method have different degrees of damage to the cathode, and the roasting of the artificial leg is poor, which adversely affects the life of the groove.

When the electrolysis cell is started, the electrolysis cell is connected to a series of currents to form the basic technical conditions required for the electrolysis reaction, and the main technical parameters of the aluminum electrolysis cell (pole pitch, cell voltage, bath temperature, electrolyte composition) , alumina concentration, etc.) enter the range required for electrolysis. After the start of the roasting, it is necessary to gradually establish energy balance and material balance through a long period of post management.

The roasting start method of the traditional electrolytic cell is prone to current bias current, causing local overheating of the cathode; the aluminum liquid roasting is not suitable for the roasting start of the large preparatory tank due to its own characteristics; the coke grain roasting has poor roasting of the artificial leg, and the electrolyte charcoal residue after starting is required to be removed. Cinder, labor and materials.

In the patent documents currently available, most of the roasting start-up methods still follow the conventional method, but only minor improvements have been made in some aspects, and the main disadvantages of the conventional roasting start-up method have not been overcome. For the inert-electrode aluminum electrolysis cell, the preheating start-up idea basically follows the traditional method.

In Chinese patent 200510031315.3, the inert anode is used for the tank body. The tank body is made of graphite or carbon. The electrode after the installation is like a carbon anode. It can be used during roasting start or pole change to avoid heat, electricity and heat. Corrosive gas impact. After the power is turned on, the can is consumed. When the inert electrode is exposed, the electrode naturally transitions to the working state.

As described in Chinese Patent No. 01820302.7, a vertical current inert electrolytic cell is used, and the electrolytic cell is started by roasting with a carbon anode. After the electrolytic cell is stably operated, it is replaced with an inert electrode group. Chinese patent 200910043018.9 provides a coke grain roasting starting method for a ceramic-based inert anode aluminum electrolysis cell, firstly plating a metallization layer on the surface of the anode, and laying graphite powder or metallurgy between the anode and the bottom of the tank at the start of the operation of the electrolytic cell. The mixture of coke and calcined petroleum coke is used as a heat generating layer; the preheating roasting of the electrolytic cell is controlled at 48-96 hours.

Chinese patent 200910243383.4 provides a preheating start method for an inert anode aluminum electrolytic cell, mainly using an electric heating assembly in which the furnace is laid in accordance with the number of electrode groups, filled with electrolyte in the furnace, and heated to melt the electrolyte to continue to be added. The electrolyte is at the desired level. After that, reduce the power of the heating unit and simulate the heat generation of the electrolytic cell during normal operation. After the technical parameters are stabilized, gradually replace the heating resistor with the inert electrode.

As described in US 6,537,438, the protective layer is overcoated on the cathode during the preheating of the electrolysis cell. The innermost layer of the protective layer contacts the carbon cathode with a titanium boride layer, the intermediate layer is a metal aluminum or alloy, and the outermost layer is carbon. The gas is calcined, and the anode is a cermet anode. The protective layer of the anode is derived from oxidation during the calcination to oxidize its surface layer.

For aluminum cells with inert electrodes, the firing start method of conventional cells has been completely unsuitable. Because of the poor anti-disturbance properties of the inert anode, it is apparent that the inert heat of the inert electrode cannot be used to heat the electrolyte during the firing. This necessitates a stable electrolysis environment for the inert electrode before the cell is started so that the electrode can be placed in the cell for immediate production. Summary of the invention

The technical problem to be solved by the invention is to provide an aluminum electrolysis which can effectively and uniformly heat the electrolyte, is beneficial to the protection of the cathode, increases the life of the tank, shortens the post management time, and provides a stable electrolysis environment before the inert electrode is operated normally. The preheating start method of the tank.

In order to solve the above technical problem, the present invention provides a preheating starting method for an aluminum electrolytic cell, comprising:

The carbon or graphite electrode block is drilled downward from the surface, and the heating element is pre-buried into the bore of the carbon or graphite electrode to form an electrolysis cell preheating electrode;

The preheating electrode equipped with the heating element is placed in the electrolytic cell, and the preheating electrode is fixed on the large busbar of the electrolytic cell by the clamp; the solid electrolyte is filled in the furnace, and the heating component is first connected to the alternating current, and the heating component is used according to the baking curve. Heating the furnace; After the furnace reaches the target temperature, the solid or liquid electrolyte is added to the required electrolyte level, and then the power of the heating assembly is adjusted until the energy input of the electrolytic cell is normal, and the heat balance required for the electrolytic cell and the inner shape of the furnace are established;

When the electrolytic cell reaches the expected heat balance state and the inner shape of the furnace, the electrolysis cell is supplied with direct current, and the preheating electrode starts to electrolyze; the heating element power is adjusted or the alternating current heating state is stopped, and the electrolyte temperature is stabilized at the target temperature;

After the cell voltage and the electrolysis temperature are stabilized, the preheating electrode carrying the heating element is replaced with the normal operating electrode one by one to complete the preheating start of the electrolyzer.

The preheating starting method of the aluminum electrolytic cell provided by the invention can solve the main shortcomings of the conventional aluminum electrolytic baking start, and the heating is hooked, and the soft connection between the anode and the bus bar is not required during the preheating process, and the cathode can be effectively preheated into a special structure. The traditional trough can improve the life of the traditional aluminum electrolysis cell; it can also effectively preheat the inert electrode aluminum electrolysis cell (vertical current electrolyzer or horizontal current electrolyzer) to establish a stable electrolysis environment before the inert electrode works, improve current efficiency, and increase Electrode life. The preheating electrode can be reused to reduce the startup cost of the cell. DRAWINGS

1 is a schematic structural view of a preheating electrode for a preheating start of a conventional aluminum electrolytic cell according to an embodiment of the present invention;

2 is a schematic view showing the structure of a preheated anode for a vertical inertial electrode aluminum electrolytic cell according to an embodiment of the present invention. detailed description

The preheating starting method of the aluminum electrolytic cell provided by the embodiment of the invention is as follows: Step 10: The electrolytic cell preheating electrode is drilled on the surface of the carbon or graphite electrode, and the heating element is embedded in the electrode. The number and power of the heating elements can be determined according to the size of the electrolytic cell and the required heating power. The number of preheating electrodes is the same as that of the normal operating electrode of the electrolytic cell, and the structure is similar in size, and can be connected to the large busbar of the electrolytic cell like the normal operating electrode.

Step 20: In the preheating stage, the preheating electrode equipped with the heating component is placed in the electrolytic cell, and the preheating electrode is fixed to the large busbar of the electrolytic cell by using a clamp. Fill the furnace with solid electrolyte, first The heating element is energized by alternating current, and the heating element is used to heat the furnace according to the firing curve.

Step 30: After the target temperature is reached, the solid or liquid electrolyte is added to the desired electrolyte level, and then the power of the heating element is adjusted until the energy input of the electrolytic cell is normal, and the heat balance and the furnace internal type required for the electrolytic cell are initially established.

Step 40: When the electrolytic cell reaches the expected heat balance state and the inner shape of the furnace, the electrolysis cell is supplied with direct current, and the preheating electrode starts to electrolyze. Through the control system, the heating element power is adjusted or the AC heating state is stopped to stabilize the electrolyte temperature at the target temperature, and the electrolytic cell gradually enters the electrolysis and self-heating state.

Step 50: After the cell voltage and the electrolysis temperature are stabilized, the preheating electrode carrying the heating element is replaced by the normal running electrode (the conventional electrolytic cell uses a carbon anode, and the inert electrolytic cell uses an inert electrode), and the electrolysis cell preheating starts smoothly. End.

The aluminum electrolytic cell preheating starting method of the invention, for the conventional aluminum electrolytic cell, the preheating electrode can adopt the carbon anode for production; for the vertical inert electrode aluminum electrolytic cell, the preheating electrode comprises a preheating anode and a preheating cathode, Carbon or graphite electrodes with the same or similar appearance as inert electrodes (including inert anodes, inert cathodes); For vertical current inertial electrode aluminum cells, the preheating electrodes can be made of carbon or graphite electrodes of the same or similar shape as the inert anodes.

In the aluminum electrolytic cell preheating starting method of the present invention, before the preheating electrode is placed, the solid electrolyte is filled in the furnace or the solid electrolyte is not filled; the pole pitch of the preheating electrode is the same as or different from the normal electrode pole pitch. The vertical inert electrode aluminum electrolytic cell preheating electrode is composed of carbon or graphite electrode, heating element, corrosion resistant material protective layer, plate bus bar and guide rod. The electrode heating assembly exposes the graphite electrode portion and the guide rod is wrapped by a protective layer of corrosion resistant material. The protective layer of corrosion resistant material is high alumina porcelain, corundum, corrosion resistant castable, boron nitride, and silicon carbide.

In the aluminum electrolytic cell preheating starting method of the present invention, before the power is turned on, the furnace is filled with aluminum water or not filled with aluminum water; the preheating cathode has heating elements or no heating elements.

The application of the aluminum electrolytic cell preheating starting method provided by the embodiment of the present invention will be described in detail below with reference to Figs.

Example 1

A conventional 300KA aluminum electrolytic cell uses a carbon anode to make a preheating electrode. The upper surface of the carbon anode 1 is drilled and placed in the heating element 2. The anode does not need to be connected to the busbar by a soft connection, and the fixture is preheated. The electrode bus bar 3 is fixed on the aluminum bus bar, and the number of preheating electrodes is the same as the number of anodes in normal production. The furnace is filled with solid electrolyte, and cryolite and soda ash are added to the tank and anode to maintain heat and avoid anodization. The heating element is connected to the alternating current, and heating is started according to the heating system. When the furnace temperature is heated to 950 ° C, continue to add solid electrolyte until the electrolyte level is 25 cm, add fluoride salt, adjust the electrolyte composition, adjust the heating component power to simulate the electrolysis state heat input, when the electrolyzer reaches the expected thermal equilibrium state and the furnace In the case of type, disconnect the alternating current and apply direct current to make the preheating electrode enter the electrolysis state. At this time, the electrolysis cell stops the heating state of the heating element, enters the electrolysis and self-heating state, and adjusts the pole pitch to stabilize the cell voltage and the electrolysis temperature at 3.8V and 935 °C. In the next 48 hours, the preheating electrode was replaced one by one using the normal production carbon anode, and the warm-up start was successfully completed.

Example 2

The traditional 400KA aluminum electrolytic cell has a cathode and a diversion structure. Drilling the upper surface of the carbon anode 1 into the heating element 2, the anode does not need to be connected to the busbar by a soft connection, and the preheating electrode busbar 3 is fixed to the aluminum busbar by a clamp, and the number of preheating electrodes is the same as the number of anodes in normal production. . The furnace is filled with solid electrolyte, and the heating element is connected to alternating current, and heating is started according to the heating system. When the furnace temperature is heated to 960 ° C, add liquid electrolyte until the electrolyte level is 23cm, inject 10cm of aluminum water, add fluoride salt, adjust the electrolyte composition, adjust the heating component power to simulate the heat input of the electrolysis state, when the electrolyzer reaches the expected When the heat balance state and the furnace inner type, the AC power is disconnected, and the direct current is supplied to make the preheating electrode enter the electrolysis state. At this point, the electrolysis cell stops heating the heating element, enters the electrolysis and self-heating state, and adjusts the pole pitch to stabilize the cell voltage and electrolysis temperature at 3.82V and 937 °C. In the next 72 hours, the preheating electrode was replaced one by one using the normal production carbon anode, and the preheating start was successfully completed.

Example 3

The vertical inertial electrode aluminum electrolytic cell, the "preheating anode" comprises a graphite electrode 4, a heating element 5, a corrosion resistant material protective layer 6, a plate busbar 7, and a guide rod 8. The upper surface of the graphite electrode 4 is drilled and placed in the heating assembly 5; the preheating electrode heating assembly is wrapped around the exposed graphite electrode portion and the guide rod 8 by the corrosion resistant material protective layer 6. The graphite electrode 4 is connected by a guide bar 8 and a plate bus bar 7. The "preheated cathode" is also made of a graphite electrode, the structure is the same as the "preheated anode", but it is not drilled and there is no heating element. The preheating electrode and the preheating cathode are fixed in the electrolytic cell by means of "one yin, one yang, one yin and one yin". Two electrolytic cells, each containing 9 preheated anodes and 10 preheated cathodes. The preheating electrode is connected to the aluminum bus bar, and the preheating electrode pole pitch is smaller than the normal operating electrode pole pitch. The furnace is filled with solid electrolyte, and the heating element is connected to alternating current, and heating is started according to the heating system. When the furnace temperature is heated to 800 °C, continue to add solid electrolyte until the electrolyte level is 40cm, add fluoride salt, adjust the electrolyte composition, inject 2cm of aluminum water, adjust the heating component power to simulate the heat input of the electrolysis state, when the electrolyzer reaches the expected When the heat balance state and the furnace inner shape are disconnected, the alternating current is turned on, and the direct current is supplied to make the preheating electrode enter the electrolysis state. At this time, the electrolysis cell stops the heating state of the heating element, enters the electrolysis and self-heating state, and adjusts the pole pitch to stabilize the cell voltage and the electrolysis temperature at 3.65V and 800°C. In the next 24 hours, the inert anode was used, and the inert cathode was replaced one by one with the preheated anode and the preheated cathode, and the preheating start was successfully completed.

Example 4

Vertical inertial electrode aluminum electrolytic cell, "preheating anode" includes graphite electrode 4, heating element 5, corrosion resistant material protection layer 6, plate busbar 7, guide rod 8. The upper surface of the graphite electrode 4 is drilled and placed in the heating assembly 5; the preheating electrode heating assembly is wrapped around the exposed graphite electrode portion and the guide rod 8 by the corrosion resistant material protective layer 6. The graphite electrode 4 is connected by a guide bar 8 and a plate bus bar 7. The "preheating cathode" is also made of graphite. Like the "preheated anode" structure, the "preheating cathode" is also drilled with holes and placed in the heating element; the preheating electrode and the preheating cathode are "one yin_yang" The _Yinyi method is fixed in the electrolytic cell, and there are 4 electrolytic cells, each of which contains 12 preheating anodes and 13 preheating cathodes. The preheating electrode is connected to the aluminum bus bar, and the preheating electrode pole pitch is the same as the normal running electrode pole pitch. The furnace is filled with solid electrolyte, and the heating element is connected to alternating current, and heating is started according to the heating system. When the furnace temperature is heated to 800 ° C, continue to add liquid electrolyte until the electrolyte level is 38 cm, add fluoride salt, adjust the electrolyte composition, adjust the heating component power to simulate the electrolysis state heat input, when the electrolyzer reaches the expected thermal equilibrium state and inside the furnace In the case of type, direct current, preheating electrode electrolysis. The power of the heating element is adjusted by the control system to stabilize the electrolysis temperature at 800 °C. In the next 36 hours, the preheated anode and the preheated cathode were replaced one by one with an inert anode and an inert cathode, and the preheating start was successfully completed.

Example 5

Vertical current type inert electrode electrolyzer, preheating electrode adopts carbon anode, drilled in carbon anode, put heating element, fix preheating electrode on aluminum busbar with clamp, preheating electrode number and normal The number of anodes is the same during production, and the pole pitch is slightly smaller than the normal operating electrode pole pitch. The furnace is filled with solid electrolyte, and the heating element is connected to alternating current, and heating is started according to the heating system. When the furnace temperature is heated to

At 850 °C, add liquid electrolyte until the electrolyte level is 25cm, add fluoride salt, adjust the electrolyte composition, adjust the heating component power to simulate the heat input of the electrolysis state, when the electrolyzer reaches the expected heat balance state and the inner shape of the furnace, direct current, Preheat electrode electrolysis. The heating element is adjusted by the control system to stabilize the electrolysis temperature at 800 °C. In the next 24 hours, the preheating electrode was replaced one by one using a ceramic-based or metal-based inert anode, and the warm-up start was successfully completed. The present invention has been described in detail with reference to the accompanying drawings, and the embodiments of the invention It is intended to be included within the scope of the appended claims.

Claims

Claim

A preheating start method for an aluminum electrolytic cell, comprising:

The preheating electrode equipped with the heating element is placed in the electrolytic cell, and the preheating electrode is fixed on the large busbar of the electrolytic cell by the clamp; the solid electrolyte is filled in the furnace, and the heating component is first connected to the alternating current, and the heating component is used according to the baking curve. Heating the furnace;

After the furnace reaches the target temperature, the solid or liquid electrolyte is added until the required electrolyte level, and then the power of the heating assembly is adjusted until the energy input of the electrolytic cell is normal, and the heat balance required for the electrolytic tank and the inner shape of the furnace are established;

2. The preheating start method for an aluminum electrolytic cell according to claim 1, wherein: for a conventional aluminum electrolytic cell, a carbon anode for an aluminum electrolytic cell is used to prepare a preheating electrode.

3. The preheating start method for an aluminum electrolytic cell according to claim 1, wherein: the carbon or graphite electrode block is a preheating electrode for a vertical inert electrode aluminum electrolytic cell, comprising a preheating anode and a preheating cathode.

4. The aluminum electrolysis cell preheating start method according to claim 1, wherein: the furnace reaches a target temperature of 800 ° C to 960 ° C.

5. The aluminum electrolysis cell preheating start method according to claim 1, wherein the required electrolyte level is 23 cm to 40 cm.

6. The aluminum electrolysis cell preheating start method according to claim 1, wherein: the stabilized electrolyte temperature is at a target temperature of 800 ° C to 937 ° C.

7. The aluminum electrolysis cell preheating starting method according to claim 1, wherein: the preheating electrode comprises a preheating electrode heating component, a carbon or graphite electrode, a corrosion resistant material protective layer, a plate bus bar and a guiding rod. The preheating electrode heating assembly exposes the graphite electrode portion and the guide rod The coating is covered by a protective layer of corrosion resistant material; the graphite electrode is connected by a guide bar and a bus bar.

8. The aluminum electrolytic cell preheating starting method according to claim 1, wherein the corrosion resistant material protective layer is one of high alumina ceramic, corundum, corrosion resistant castable, boron nitride, and silicon carbide.

The method for preheating and starting the aluminum electrolytic cell according to any one of claims 1-8, further comprising:

Before the power is turned on, the furnace is filled with aluminum water or not filled with aluminum water; the preheating cathode has heating elements or no heating elements.

The method for preheating and starting the aluminum electrolytic cell according to any one of claims 1-8, characterized in that:

The preheating electrode carrying the heating element is replaced with the normal running electrode one by one within 24 hours to 78 hours after the tank voltage and the electrolysis temperature are stabilized, and the preheating start of the electrolytic cell is completed.