Method for the production of anode paste (options)

 

The invention relates to the field of electrode production and can be used in the manufacture of anodes in aluminium electrolysis cells for the electrolytic production of aluminum. The proposed method involves mixing the coke charge with the pitch and the formation of mass, and the mixture is served or powdered peck particle size less than 2 mm and coke mixture is heated to a temperature of from 50 to 90°C above double the softening temperature of the pitch, or molten tar pitch at a temperature exceeding the softening temperature of the pitch and coke mixture, with the temperature at 15 to 25°C above the temperature of the molten pitch, and the formation of mass in both cases is carried out at a temperature of anode paste, is 100 to 150°C. Technical effect of improving the quality of briquettes and paste: increasing the strength of briquettes, reduced porosity, increased mechanical strength, reduction of destructible in the current CO2. The method allows to process all types of pitches both in solid and in liquid form. 2 S. and 6 C.p. f-crystals, 1 tab., 2 Il.

The present invention relates to the field of electrode production and can be used by the Oia from molten salts.

Currently, with the aim of improving the quality of anodes and improving the environment in the aluminum industry in the production of anode paste involve pitches with a high softening temperature (VKT).

On typical hardware technological lines, which are equipped workshop for the production of anode paste and which was designed under the processing temperature of pitches (STP), processing TPP raises a number of technical difficulties.

Therefore urgent to develop new methods of production of anode paste, allowing you to Refine pitches with a high softening temperature.

Known technical solution according to the patent of Russian Federation №2091511 "method for the production of anode paste for self-baking anodes (From 25 In 11/12, 15.05.95 year), according to which the production of anode paste on the basis of high-temperature pitch (ECP) perform in the "dry" mixing with subsequent briquetting.

Industrial equipment-technological line in the framework of the Smelter is presented on Fig.

The line consists of hopper coke charge of large fractions (nibs) 1, hopper dust fraction of the coke charge 2, the hopper drive powdered pitch 3. From the storage hoppers 1, 2, 3 are fed into the node weight dosing coke charge 7, and peck in the node weight measuring pitch 8. Before mixing coke mixture is heated to the desired temperature in the heater direct heating 9. The heated mixture and the solid crushed peck sent to the mixer 10. Next, via an intermediate heated hopper 11 of the anode mass is sent on the press roller 12, where the mass of bricks falls on cooling in a water bath 13.

The technical essence and the achieved result of the method according to the above patent is taken as a prototype, in which the choice of parameters of the temperature of preparation of the coke mixture before mixing and temperature mixing parameters were aimed at securing the "dry" mix. Also in the prototype it is recommended that the temperature of the mass before briquetting 5-10°C below the melting temperature of the pitch, as ECP in this interval is characterized by sufficient thermal stability.

When testing the method on the prototype using the TPP on industrial equipment and technological lines presented on pic.1, the quality of the briquettes did not meet the requirements for mechanical strength.

This is due mainly to the fact that failed to stabilize temperatures in spiratory softening in the temperature range 5 to 10°C below its melting temperature is less, than VTP, heat stability, therefore, the application of the method on the prototype using the TPP has led to technological violation of the briquetting process, namely, when the temperature of briquetting 10°C, compared with the softening temperature has been difficult briquetted powder mass or decreasing by 5°With the saw sticking in the press. Thus, the temperature range weight before briquetting, it was necessary to narrow, to implement the method according to the prototype when using the PTR, and it is in the current technology is difficult to achieve the task.

In the prototype to ensure the best averaging coke with coal tar pitch in the mode of "dry" mixing peck was crushed to particle sizes less than the maximum particle size of the dust fraction of the coke charge (-1 mm), which, according to the authors, was to increase the total specific surface area of the pitch and provide a better homogenization process. In practice, this has resulted in a negative effect:

- increased pylones peck;

- frequent irregularities in the dosing pitch because it "hangs" in the bunker.

Thus, implementation of the method according to the prototype associated with a number of significant technical difficulties: PR>

The task of the invention is to improve the quality of anode mass on the basis of both the temperature of pitches, and on the basis of pitch with a high softening temperature.

The technical result of the proposed method is to improve the quality of briquettes and paste: increasing the strength of briquettes, reduced porosity, increased mechanical strength, reduction of destructible in the current CO2that, as a consequence, in the process of electrolysis reduces the specific consumption of the anode mass, energy, etc. Also, the proposed method allows to process all types of pitches, both in solid and in liquid form.

This object is achieved in that in the method of production of anode paste, comprising preparing a polydisperse coke charge, pre-heating and dispensing, preparation and dispensing of pitch, mixing coke mixture with peck and molding masses, mixing powder serves peck particle size less than 2 mm and coke mixture is heated to a temperature of from 50 to 90°C above double the softening temperature of the pitch. In another embodiment, the mixing serves molten tar pitch at a temperature exceeding the softening temperature of the pitch and coke mixture with tempera in the case of supply of molten pitch mixing of the components of the paste is carried out in the regime of turbulent mixing with counterflow, when this powder peck in the mixer serves evenly, and dosing of the components of the charge is performed with accuracy of ±0.5%, and molding is carried out at a temperature of anode mass 100 to 150°With extrusion or pressing, the pressing is performed with the use of water.

The technical essence of the present invention is as follows.

It is known that the mixing quality carbon filler (coke) and hydrocarbon binder (pitch) depends on two processes: the wetting coke peck and homogenization of the mixture. Good wetting facilitates the impregnation with pitch then coke, and therefore, decrease the porosity of the anode mass and, consequently, improve its physico-chemical properties after firing. Homogenization of the mixture provides a uniform material throughout the volume, which is necessary for forming a homogeneous anode and stabilization of the process of electrolysis.

With the aim of creating the most favorable conditions of wetting and impregnation of coke peck in the process of mixing powdered pitch with coke, the authors propose to heat the coke mixture to a temperature of from 50 to 90°C above double the softening temperature of the pitch. Due to the high temperature coke peck quickly Perea to a high temperature, sharply reduced, which results in good wetting and impregnation of coke peck. Low viscosity pitch interlayer provides rapid homogenization of the mixture.

To ensure the high temperature coking of the charge, the authors propose to carry out heating in an electric heater direct heating, i.e. by passing current through the charge. This provides a quick and uniform heating of the coke particles in the entire volume, and such heating is high efficiency.

Also the authors suggest mixing to produce in unheated vortex mixer in a counter created multidirectional rotation of the plate of the mixer and turbulence, which provides a higher degree of homogenization compared with vane and screw mixers. In addition, when mixing the heated coke from hard coal tar pitch in unheated mixer is a slight reduction in the temperature of the coke, which leads to the compression of air in the pores of the coke and the emergence of "suction". This further improves the impregnation.

Due to the fact that plants supply peck both in solid and in liquid form, the method also includes the option of filing for mixing molten pitch. In Dan is the softening temperature of the pitch, and the pitch is heated to a temperature exceeding the temperature of its softening. When such preliminary thermoadhesive components paste mixing process is also implemented as described above for powdered pitch mechanism.

As when using powder and molten pitch, the authors do not recommend heating the mixture above 260°C, since otherwise significantly increases the low-temperature distillation fractions, which is not desirable in the mixing process.

Achieved in the proposed method, a higher degree of impregnation of coke pitch and homogenization of the mass at an elevated temperature coke and its vortex mixing can improve the operational characteristics of the anode mass (porosity, strength, resistivity and destructible in CO2).

Side of the positive effect of the proposed method is the reduction of energy consumption on special technological operation of melting the solid pitch.

The authors declare the following distinctive features of the prototype characteristics:

1) if "...mixing serves powdered pitch, coke mixture is heated to a temperature of from 50 to 90°C above double the softening temperature of the pitch" and the EU the coke charge is heated to a temperature of 15 to 25°C above the temperature of the molten pitch" (see PP.1 and 2 claims).

The fulfillment of the above conditions is provided by mixing a good wettability coke pitch and homogenization of the mixture, since, unlike the prototype, the mixing is performed in a mode of liquid mixing, which allows for the impregnation, and the "vortex" mixing when mixing mass in a plastic condition intensifies the process of homogenization.

2) "...the molding is carried out at a temperature of anode mass 100 to 150°C".

In the prototype, and in the proposed method, after mixing, use a heated intermediate bunker for thermal stabilization of the anode mass, but the level of thermal mass before briquetting different. When the temperature of the mass before briquetting 100 to 150°With the proposed method is guaranteed continuous receipt of quality and durable briquettes. In the prototype for briquetting lots with temperature for 5-10°C below the softening temperature of the pitch. This leads to reduced ductility pitch in strips of coke during pressing, and therefore, to obtain briquettes with low mechanical strength.

In the proposed method, the temperature of the mass before briquetting 100 to 150°C, i.e. approximately 20°below double temperate briquette in the process of pressing.

Temperature before briquetting specified intervals taking into account the entire range of pitches (STP, VKT), arriving for processing. To 100°With the cooled mass-based STP, up to 150°C is based on the TPP.

3) "...mixing powder serves peck particle size less than 2 mm...".

As mentioned above, pereselenie pitch prototype worsened some of the process indicators, namely: inaccurate dosing by hovering pitch in the hopper and high dusting when electric current is applied to the mixer.

(4) Paragraph 3 of the formula of the invention relates to a method of powdered pitch.

The basic requirement for filing is uniform to prevent the formation of lumps when the volley filing pitch, because the formation of lumps can lead to stop the mixer running at the "vortex" of mixing. The authors recommend to download pitch during one revolution of the plate of the mixer.

5), Paragraph 4, of the formula, the authors emphasize the versatility of the proposed method, as the mixing in liquid mode and the ability to vary the temperature before molding allows you to mould the mass of a pressing roller in the press, and traditional extrusion, and to improve the quality of brikettanlagen.

6), Paragraph 6, of the formula, the authors emphasize the need for accurate dosing of the components of the paste during mixing. Announced the dosing accuracy of ±0.5% is achievable precision on modern weight batchers and quite satisfying the need of the proposed method.

When all the conditions expressed in the claims, achieves the objective - increasing and stabilizing the quality of the anode mass on the binder with different softening temperature.

The main common feature of the proposed method and how the prototype is used in the production of anode paste of pitch with a high softening temperature. But the proposed solution is more progressive, as it allows the same apparatus and process line process pitches with different softening temperature. This proposed technical solution is significantly different from the prototype.

Therefore, this technical proposal meets the criteria of the invention is a "novelty".

For the definition of "prior art" conducted a search of the patent and scientific literature.

The analysis of existing methods of production of the coke in the mixture before mixing Pekoe-coke composition the reception is known and occurs in a number of inventions:

- The United Kingdom, application No. 1426794, MKI With 01 In 55/00, publ. 03.03.76, a method of obtaining a carbon-containing briquettes;

- A. S. of the USSR №1726453, 04 35/52, publ. 26.12.89, the Method of preparation of the electrode mass.

The result of pre-heating the coke charge in each of the inventions is a coding gain and increase efficiency smeeling machines, mixing the mass due to the pressure in the faucets that you create a special design of the screw. Data screw mixers processing Pekov the TPP is not possible, so as to obtain the temperature, twice exceeding the softening temperature of the TPP, it is not possible, and therefore, it is impossible to carry out the process in the mode liquid mixing.

In the proposed solution, the heating temperature of the coke charge significantly exceed double the softening temperature of the pitch coke and heat have enough to do the mixing process in liquid mode in turbulent mixing apparatus, such as a firm "Aurich";

2) processing methods VTP known:

- A. S. of the USSR №1034994, 01 31/02, publ. 15.08.83,

- The Federal Republic of Germany, application No. OS 3432887, N 05 In 7/085. A method of manufacturing graphite electrodes, high power.

- Japan, application No. 61-24326, 01 Whateley thermal before mixing known:

- A. S. of the USSR №223367, 22, publ. 02.07.68,

In this case, coke and pitch are mixed in the cold and the mixture pictires, i.e. heat treatment Pekoe-coke composition is completely absent.

The analysis showed that fundamentally individual characteristics of the object are known, but the combination of known and unknown characteristics specified in the claims, allows you to reach a new level in the development of promising universal method for the production of anode paste, including on the basis of pitch with a high softening temperature. Thus, the proposed solution meets the criteria of the invention is "prior art".

Below are examples of industrial application of the proposed method of production of anode paste. All examples are implemented in hardware processing line shown in Fig. 2.

Apparatus and process line consists of a series of storage volume: bunker large coke fractions 1, dust bin 2, bin solid pitch 3, a pressurized tank of liquid pitch 4. From the storage bins coke charge through the respective weighing batchers 5, 6 is sent to the electric heater coke charge 7. Next is the complete method:

1) feed mixing of solid pitch through weighing batcher solid pitch 8;

2) supply to the mixing liquid pitch through weighing batcher liquid pitch 9.

Mass from the mixer is sent to probortunity hopper 11.

You may receive the paste in two forms: in the form of pellets or in the form of three-dimensional form corresponding to the form of the installed nozzles. In the first case through probortunity auger 12 mass is fed into the press roller 14. In the second case, the mass is passed through probortunity auger with Villeroy 13 and then to a water-cooled conveyor 15.

I. 1.1. Raw materials for the preparation of anode paste:

- pitch coke - 73%;

- pitch with a high softening temperature (90°C) - 27%.

1.2. Coke mixture was prepared according to the specified composition and desirables with an accuracy of ±0.5% in elektroobogrevatel. The granulometric composition of the coke charge:

nibs - 50%;

- dust - 50%.

1.3. The temperature of the coke charge - 247°C.

1.4. The preheated coke mixture was fed to the vortex mixer company "Aurich".

1.5. Solid peck crushed to a fraction-2mm and dispenser solid peck served in a vortex mixer evenly over one complete revolution of the drum mixer. Filing peck was implemented in the ass is setele, usually within 2-3 minutes.

1.7. Anode mass at the outlet had a temperature of 189°C, and it was unloaded into the intermediate hopper, where the temperature of the mass was reduced to 140°C.

1.8. The resulting mass was going on a roller press, and from there to the warehouse.

II. 2.1. Raw materials for the preparation of anode paste:

- pitch coke - 73%;

- STP with a softening temperature 67°C - 27%.

2.2. Similarly 1.2.

2.3. The temperature of the coke charge - 155°C.

2.4. Similarly 1.4.

2.5. Peck is heated to a temperature of 135°C and through the pressure tank and the weight of the dispenser of liquid pitch was served in a vortex mixer in a predetermined ratio.

2.6. Intensive mixing was carried out to stabilize the current load on the mixer, as a rule, stabilization occurred within 1.5-2 minutes from the start of mixing.

2.7. Anode mass at the outlet had a temperature of 140°C, and it was unloaded in the intermediate cooling bunker, where its temperature was reduced to 110°C.

2.8. Similarly 1.8.

As a result of experiments in both embodiments of the proposed method has been briquettes paste with high consumer properties (see table).

2. The method according to p. 1, characterized in that the mixing of the paste is carried out in the regime of turbulent mixing with counterflow, with the supply of powdered pitch in the mixer carry out evenly.

3. The method according to p. 1, characterized in that the molded anode paste is performed by pressing or extrusion.

4. The method according to p. 1, characterized in that the weight dosing of the components of the paste is performed with accuracy ±0.5 percent.

5. Method for the production of anode paste, comprising preparing a polydisperse coke charge, pre-heating and dispensing, preparation and dispensing of pitch, mixing coke mixture with peck and molding mass, characterized in that the mixing serves molten tar pitch at a temperature exceeding the softening temperature of the pitch and coke furnace with temperature n the Sy 100 to 150°C.

6. The method according to p. 5, characterized in that the molded anode paste is performed by pressing or extrusion.

7. The method according to p. 6, characterized in that the pressing of the anode mass is performed with the use of water.

8. The method according to p. 5, characterized in that the weight dosing of the components of the paste is performed with accuracy of ±0.5%.



 

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