CN1133602C

CN1133602C - Continuous two-step process for preparing magnesium sand by electric smelting

Info

Publication number: CN1133602C
Application number: CNB00110800XA
Authority: CN
Inventors: 孙守刚
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-08-17
Filing date: 2000-08-17
Publication date: 2004-01-07
Anticipated expiration: 2020-08-17
Also published as: CN1280961A

Abstract

The present invention relates to a technique for producing fused magnesia by a continuous two-step method. Decomposition and smelting in a technique for producing fused magnesia by smelting magnesite ore as raw material by an electric arc furnace is divided into two steps. Firstly, ore is crushed into blocks of 8 to 12 centimeters, put into a reflection vertical kiln and roasted at the temperature of 900 to 1100 DEG C preferably to the degree that the ore is thoroughly roasted but not broken; the temperature of kiln discharge material is from 800 to 900 DEG C, and the kiln discharge material is immediately put into the electric arc furnace and smelted. The power consumption is only from 2000 to 2200 kilowatt hours /ton. The present invention has the advantages of short period of 7.5 hours and low cost.

Description

Method for producing fused magnesia by continuous two-step method

The present invention relates to a magnesite (magnesium carbonate MgCO as main component)₃) The electric arc furnace is used for decomposing and smelting magnesite as a raw material, and particularly relates to the technical field of continuous two-step method production of electric smelting magnesite by respective decomposition and smelting.

At present, the method for producing the fusedmagnesia by taking magnesite ore as a raw material comprises two steps:

decomposing and smelting magnesite

The magnesite ore is crushed into small blocks of 1-5 cm, and the small blocks are put into an electric arc furnace to be decomposed and smelted to produce the fused magnesite. The method has the defects that the energy consumption is high, and each ton of finished products consume 3250-3300 kilowatt-hour; the smelting period is long, and the output of each furnace is 6.5-6.7 tons (1600 kVA of the electric furnace transformer matched with the furnace) and each furnace lasts for 10-10.5 hours. The reason for the high energy consumption and long melting period is that both decomposition and melting are carried out in an electric arc furnace. The electrode arcing temperature in the electric arc furnace is 2800-3000 ℃, and the decomposition temperature of the magnesite is only 900-1100 ℃. Therefore, most of the heat generated by the electric energy of the electric arc furnace is dissipated outside the furnace, and the waste is wasted. The stones in the furnace are small, the edges and corners are hard, the gaps among the stones are large, the heat conduction is poor, and therefore the smelting period is long.

Smelting with light-burned magnesia

The light-burned magnesia is prepared by roasting magnesite. Is a magnesium product. During smelting, the light-burned magnesia is continuously put into an electric arc furnace for smelting to produce the fused magnesia. Compared with the former method, the method has the advantages that: the power consumption of finished products per ton is reduced by about 800 kilowatt-hours. The method has the disadvantages of high power consumption and long smelting period. In addition, the smelting of the powdery light-burned magnesium oxide has poor air permeability and higher operation technical requirements.

The invention aims to provide a method for producing fused magnesia by a continuous two-step method, which can further save energy and has short smelting period.

The invention is realized by the following technical scheme:

the present invention makes key improvement on the existing fused magnesia producing technology to reach the aims of saving energy greatly, shortening smelting period and raising single furnace yield. The existing production method of fused magnesite consists of the procedures of mineral separation, crushing, decomposition and smelting, natural cooling, crushing and sorting. The present invention only divides the decomposition and smelting into two steps and continuously carries out the decomposition and smelting, namely, the magnesite is decomposed by a common reflection shaft kiln (a vertical kiln which is usually used as a bitter earth kiln), and the decomposed massive magnesia is sent to an electric arc furnace to be immediately smelted when the magnesia is hot. Other process contents are not changed.

The specific content of the invention is as follows:

the decomposition and smelting of magnesite ore are carried out in two steps.

The first step is as follows: decomposition of magnesite

Magnesite ore with low impurity and over 46% magnesia is selected, and the calorific value of the coal for combustion needs to be over 4500 kilocalories/kilogram. The roasting process comprises the steps of crushing ores into blocks of 8-12 cm, putting the blocks and coal into a reflecting shaft kiln layer by layer, and roasting at 900-1100 ℃, wherein the weight ratio of coal to stone is 1: 7-9. The roasting is carried out until the ore blocks are burnt completely and cannot be broken (a small amount of raw materials and powder materials exist). The coal used for magnesite decomposition is 0.25 ton/ton magnesia. The upper layer in the reflecting shaft kiln is a preheating zone, the middle layer is a roasting zone, and the lower layer is a roasting zone. Discharging the material from the lower part of the kiln after the material is sintered (the material temperature is 800-900 ℃ when the material is taken out of the kiln), and supplementing magnesite stones and coal to the upper part according to the weight ratio of the coal and the stone so as to keep the height of the charge level in the kiln. The process is carried out cyclically. And immediately feeding the magnesium oxide blocks discharged from the kiln at 800-900 ℃ into an electric arc furnace for smelting. The feeding method comprises the following steps: 1. can automatically flow in through a slope groove-shaped channel connecting the discharge port of the shaft kiln and the feeding part of the electric arc furnace. 2. The conveying is carried out by a mechanical hopper which is hung on a support and can move in an oriented way and turn over.

The first step is as follows: the decomposition is a chemical reaction. The reaction equation is as follows:

the closer the distance between the roasting kiln and the electric arc furnace is, the better, so as to avoid the temperature reduction of the materials by long-distance transportation.

The second step is that: melting is a physical change. Smelting 800-900 ℃ blocky magnesium oxide from a reflecting shaft kiln in an electric arc furnace, wherein the smelting technical conditions are related to the furnace type specification of an electric plate furnace and the capacity of an adopted electric furnace transformer. The comparative description is given in the examples.

Experiments prove that: the continuous two-step method for producing the fused magnesia by the fused magnesia has low energy consumption, and the power consumption of each ton of finished products is only 2000-2200 kilowatt-hour. And (3) smelting period: the smelting period is within 7.5 hours by using a furnace type (an electric furnace transformer 1600 kilovolt-ampere) with the diameter of 1.8M multiplied by 1.7M.

The invention has the advantages of low energy consumption, short smelting period and low product cost.

The invention has no figure.

Example 1:

test types are as follows: industrial testing

Number of test furnaces: 3 heats

Specification of electric arc furnace: phi 1.8M x 1.7M iron sheet furnace

Specification of electric furnace transformer: 1600 kilovolt-ampere

Operating current: 10000-11500A

10.7 tons of magnesia (formed by roasting magnesite containing 46.9 percent of magnesia) containing 92.4 percent of magnesia is fed into each furnace, and the material temperature is 860 ℃ when the magnesia is fed.

After smelting, the mixture is naturally cooled (95 hours), crushed and sorted to obtain 20.1 tons of products with the content of magnesium oxide and MgO being more than 96 percent.

The product grading conditions were as follows:

the content of magnesium oxide MgO is more than or equal to 98 percent and is 10.1 tons, accounting for 50.2 percent;

the content of magnesium oxide MgO is more than or equal to 7.03 tons with the content of 97 percent, and themagnesium oxide MgO accounts for 35 percent;

2.97 tons of magnesium oxide Mg0 with the content of more than or equal to 96 percent, accounting for 14.78 percent;

the smelting period is 7.5 hours, the electricity consumption of each ton of product is 2050 kilowatt hours, and the product quality meets the industrial standard ZBD 5001-90. 5.829 tons of auxiliary materials are also produced.

Example 2:

test types are as follows: industrial testing

Number of test furnaces: 2 heats

Specification of electric arc furnace: same as example 1

Specification of electric furnace transformer: same as example 1

Operating current: 11000 to 12000A

The magnesia block used contained 92% magnesia (calcined with magnesite containing 46.6% magnesia) 870 ℃ blocks (of which there was 5% lining).

The first furnace was charged with 10.5 tons and the second 10.45 tons.

After the mixture is refined, the mixture is naturally cooled (97 hours), crushed and sorted, and 13.1 tons of finished products with the content of magnesium oxide and MgO being more than 96 percent are obtained.

The product grading conditions were as follows:

6.55 tons of magnesia with MgO content more than or equal to 98 percent and accounting for 50 percent

4.716 tons accounting for 36 percent of MgO with the content of more than or equal to 97 percent, and 1.834 tons accounting for 14 percent of MgO with the content of more than 96 percent.

The electricity consumption of the product per ton is 2040 kilowatt hour, the smelting period is7 hours and 26 minutes, and the product quality meets the industrial standard ZBD 52001-90. 3.9 tons of auxiliary materials are produced.

Example 3:

test types are as follows: industrial testing

Number of test furnaces: 2 heats

And (3) smelting period: 7.5 hours

Specification of electric arc furnace: phi 1.5M x 1.7M

Specification of electric furnace transformer: 1250 kilovolt-ampere

Operating current: 5000-8000A

The charging amount of 870 ℃ blocky magnesium oxide (containing 10 percent of powder) with the content of 92.9 percent in each furnace is respectively 7.3 tons and 7.2 tons, and the blocky magnesium oxide is respectively smelted and discharged after smelting. The material lump is naturally cooled, crushed and sorted to obtain 9.1 tons of fused magnesia with the content of more than 96 percent.

The product rank distribution is as follows:

3.185 tons of magnesia with MgO content more than or equal to 98 percent and accounting for 35 percent;

4.095 tons of magnesia with MgO content more than or equal to 97 percent, accounting for 45 percent;

1.82 tons of magnesia with MgO content more than or equal to 96 percent, accounting for 20 percent;

the power consumption of each ton of product is 2100 kilowatt hours, and the product quality meets the industrial standard ZBD 52001-90. The auxiliary material yield is 2.71 tons.

Claims

1. A continuous two-step process for preparing electrically fused magnesite clinker includes such steps as ore dressing, breaking, decomposing smelting, natural cooling, breaking and sorting,

firstly, crushing magnesite ore into blocks of 8-12 cm, putting the blocks and coal into a reflective vertical kiln layer by layer, roasting at 900-1100 ℃ at a coal-stone weight ratio of 1: 7-9, discharging from the lower part of the kiln after sintering at a discharging temperature of 800-900 ℃, putting the magnesia of 800-900 ℃ into an electric arc furnace, replenishing the ore blocks and coal at the upper part of the vertical kiln according to the coal-stone weight ratio to protect the charge level in the kiln,

and step two, immediately smelting the magnesium oxide lump material at 800-900 ℃ from the shaft kiln, and discharging the magnesium oxide lump material after smelting is finished.

2. The continuous two-step process according to claim 1, wherein the shaft kiln feeds the electric arc furnace by means of a sloping trough-shaped channel connecting the shaft kiln outlet to the electric arc furnace inlet.

3. The continuous two-step process according to claim 1, characterized in that the electric arc furnace is fed from a shaft kiln, using a mechanical hopper which is suspended from a support and can be moved in an oriented manner and turned over.