The method of producing calcium carbide

 

(57) Abstract:

The invention relates to the chemical industry and can be used for acetylene. Prepare a mixture of limestone with coarse crystalline marble-like structure (grain size of calcite of 0.1-3 mm) and coke. The charge is loaded into ore-smelting furnace with round bath, having three electrodes with a diameter of 350 mm melting of the charge is carried out at the peripheral resistance of the electrode 1,17-1,67 Omsm. Before draining the melt withstand 5-15 min at peripheral resistance 0,83-1,2 Omsm. Output vysokonatrievogo calcium carbide 280-300 l/kg Can be used electrodes with a diameter of 400-500 mm table 2.

The invention relates to the chemical industry, in particular, to a technology for production of calcium carbide.

A method of obtaining calcium carbide in ore-smelting furnace by melting of the charge, consisting of lime, obtained by pre-calcining of limestone in the kiln, and carbonaceous material (coke), comprising the following stages:

- preparation of the mixture of lime and coke when the ratio of particle size in the range of 1.9 to 2.0;

- loading the obtained mixture in an oven;

- power supply via electronsto calcium carbide, M:Goskomizdat, 1954, S. 26,41,104) (I).

The disadvantages of the method are the complexity of the technological scheme, the instability indicators of quality due to fluctuations in the degree of calcination of limestone (gross volume of the produced calcium carbide 240-295 l/kg).

The closest in technical essence and the achieved result is a method of producing calcium carbide according to the patent of Russian Federation N 1806991, CL 01 31/32 In, Appl. 14.06.90, publ. 07.04.93, B. I. N 13 (III), comprising the following stages:

- preparation of a mixture of crystalline limestone with a grain size of calcite in its particles of 0.001-0.015 mm and coke when the mass ratio of limestone to coke 2,8-3,2 and when the size of the particles 4,5-5,0;

- loading the charge into the furnace;

- the supply of electricity through the electrode;

the fusion mixture while maintaining the specified current electrode and the working capacity of the furnace by moving the electrode and/or the switching speed of the transformer;

draining of the melt and recycle it to marketable products.

The displacement of the produced calcium carbide is 265-275 l/kg

According to the method as calcium maintenanced breed is used pelitomorphic (crystalline) limestone, which at fast Ter the firing belong to I or II classification group. Limestone group III - crystalline marble with a grain size of calcite 0.1 to 3 mm are not thermally stable when heated, decompose into small pieces. This reduces the ratio of sizes of pieces formed of lime and coke (which when heated is not destroyed) to 0.5-1. This is reflected in the results of the heat.

The displacement of the merged calcium carbide is reduced to values that are not valid for commodity calcium carbide (less than 240 l/kg according to GOST 1460-81 with additions). The product yield in terms of conditional carbide - 250 l/kg is 96%. In the foregoing processing of thermally unstable limestone is not economically profitable.

Thus, the disadvantages of the prototype are:

- limitation of the raw material base of production of calcium carbide;

- obtaining the product of the second grade with unstable performance on the quality.

The technical task of the invention is the expansion of raw materials production of calcium carbide and the increase in yield calcium carbide (250 l/kg) by obtaining vysokonatrievogo calcium carbide.

The solution of a technical problem is achieved by the fact that in the known SPEA when the mass ratio of limestone to coke 2,8-3,2 and when the size of the furnace, the melting of the charge while maintaining a given current electrode and the working capacity of the furnace by moving and/or switching speed of the voltage transformer and periodic draining of the melt,

the melting of the charge is carried out at the peripheral resistance of the electrode 1,17-1,67 MSM, and before draining the melt was incubated for 5-15 min at peripheral resistance 0,83-1,2 OSM.

Distinctive features of the proposed method are the size of the peripheral resistance of the electrode at the stage of melting 1,17-1,67 Omsm, the dwell time of the melt before discharge and the magnitude of the peripheral resistance of the electrode at the stage of exposure of the melt 0,83-1,2 OSM.

These differences allow us to expand the raw material base carbide production due to the possibility of processing thermally unstable limestone and increase the release of calcium carbide in terms of conditional carbide for 12-24% by obtaining vysokonatrievogo of calcium carbide in comparison with the processing of thermally unstable limestone in the prototype.

Peripheral resistance is a factor characterizing the technology of smelting of calcium carbide, and is a

K=UD/I OMM,

where U is the voltage on the electrode;

Certain experimentally optimal from the point of view of improving the quality of calcium carbide values of the peripheral resistance of the electrodes carbide furnaces allow you to:

to choose the optimal electric current for vysokonatrievogo product:

- to determine, if necessary, the optimum dimensions of the electrodes, and therefore, the bath of the furnace.

The essence of the method consists in the following.

When the fusion of limestone with coke flow reaction type T: W dissolution of lime and carbonaceous material in the primary carbide melt

CaOTV+(Ca2SAOs)W---> (CaC22 CaOC)W; (1)

WITHcoke+(CaC2SAOs)W---> (CaC22 CaOCvarW(2)

with the accumulation in the furnace bath nischalananda product. Particularly active in this process proceeds in violation of the size of chunks of raw materials (a lot of dust and stuff), the variation in the dosage. For these reasons, it is practically impossible to obtain a stable vysokopetrovsky calcium carbide using thermally unstable rocks of limestone.

At the same time in the melt reactions proceed saturation of the melt carbide To accelerate reactions (3) and( 4) in the melt, it is necessary to raise the temperature in the reaction crucible by reducing the share of energy coming to education nischalananda melt.

This can be achieved:

1) moving the electrode to the area of the melt with a change in electric mode on the electrode or without changes;

2) changing the diameter of the electrode.

The process of obtaining calcium carbide with declared values of the peripheral resistance of the electrodes at the stage of melting and the stage of exposure of the melt, and the dwell time of the melt allows you to get vysokopetrovsky calcium carbide from thermally unstable limestone.

Example 1. For the smelting of calcium carbide at JSC "Cherepovetsky Azot" used limestone from the field Bow (, Nizhny Tagil) of the following composition, wt. %: CaO 55,7; MgO 0,43; SiO20,46; Al2O30,17; Fe2O30,26; P 0,015; S 0,02.

These chemically pure limestones are partially crystalline marble structure with a grain size of calcite 0.1 to 3 mm and not have thermal resistance.

Limestone particle size of 20-60 mm was mixed with coke class 10-25 mm (ash - 12 wt.%, moisture - not more than 5 wt.%, the rest of the carbon mass ratio of 2.8 to 3.2 and when the ratio of particle size of 4.5-5.0.

Melting was performed carbide furnace maximum operating current 14000 And, limit voltage regulation - 48-107 Century

The resulting mixture was loaded into the furnace between the electrodes to the level of the bath of the furnace. The melting process conducted continuously with periodic draining of the melt through 1.6 hours in steel moulds.

The fusion process between plums included the following stage.

1. Rein back calcined mixture after draining the melt omitted when the electrodes.

2. Loading adjustments, if necessary;

3. Download raw mixture to the furnace.

4. The ramp-up and melting at an amperage of up to 10,000 A, the voltage 65-107 W active power 1.1 to 2 MW. At this stage, there is an accumulation of the melt, accompanied by the rise of electrodes 25-30 see the Resulting melt contains <55% carbide (204 l/kg). Peripheral resistance of the electrodes at this stage was 1.17-1,67 OSM.

5. before discharge of the melt was lowered electrodes, increasing the current-carrying capacity up to 14000 and withstood the melt within 5-15 minutes of the Peripheral resistance of the electrodes at the stage of exposure of the melt was 0,83-1,2 OSM.

The results of the experiments are presented in table. 1.

Reducing the current load on the stage of melting to 4136 And leads to high put the Oia capacity between the electrodes, which does not allow to carry out the process in the normal mode through the coal furnace hearth.

Reducing the current load on the heating stage to melt 5495 (increased peripheral resistance to 1.4 Omsm) reduces the amount of heat produced in the melt by passing current through the chain of "electrode - furnace hearth - electrode, increasing the percentage allocated in the charge between the electrodes. When this mode under the electrode melt due to the lack of temperature may partially crystallize, making it difficult to drain from under all three phases.

The increase in current load (at the stage of melting to 7540 And at the stage of exposure of the melt to 9497) and decreases peripheral resistance, respectively, to 1.02 MSM and 0.81 MSM at low power (70 In) accompanied by a decrease in volume of the charge, poplavskii in the reaction space under the electrode. Because of the excess power is overheating and decomposition of part of the calcium carbide, i.e., reduced productivity and quality of calcium carbide.

While reducing exposure of the melt is less than 5 minutes is not achieved stability of indicators of the quality of the product.

Exposure melt more than 15 minutes may result in reduced quality of carbide due to dissoc ECA regardless of the capacity of the furnace allows you to choose the best electric mode to obtain vysokonatrievogo product at different diameters of the electrode, as illustrated in table. 2.

Thus, the claimed method of producing calcium carbide allows you to expand the raw material base for the production of calcium carbide due to the possibility of processing thermally unstable limestone, increase product yield by obtaining vysokonatrievogo product (up to 280-300 l/kg), and also gives the opportunity to determine, if necessary, the optimum dimensions of the electrodes, and hence the bath of the furnace.

The method of producing calcium carbide in ore-smelting furnace, comprising preparing a mixture of limestone and coke, loading the charge into the furnace, the melting of the charge maintaining the desired current and the working capacity of the furnace by moving the electrode and/or switching speed of the transformer and periodic draining of the formed melt, characterized in that the melting of the charge is carried out at the peripheral resistance of the electrode 1,17 - 1,67 Ohm cm, and before discharge of the melt was kept for 5 to 15 minutes when the peripheral resistance of 0.83 - 1.2 Ohms see

 

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