SU1283510A1 - Method for controlling process of roasting material in rotary tube furnace - Google Patents

Abstract

The invention relates to methods for controlling the process of calcining materials in a tubular rotary kiln. The purpose of the invention is to improve the quality of the material to be calcined and to prevent the formation of the present formation under the conditions of a varying azodynamic regime in a rotary tube furnace. The essence of the invention is that the material is loaded into the furnace and is heated by feeding fuel and air into the furnace. During the firing period, the nominal specific consumption of gas and air is established, which ensures a given temperature regime in the furnace. During various periods of operation of an electric furnace operating in conjunction with a rotary kiln, the pressure in the discharge head of the rotary kiln changes, resulting in a change in the aerodynamic mode. In the period of decreasing pressure in the discharge head, the specific fuel consumption is reduced by 2-5% of the nominal value without changing the air flow, then after the pressure is restored in the period equal to Г / 20-1 / 10 the duration of the material in the furnace, the specific fuel consumption increases 5-10% of the nominal value and at the same time reduce air consumption by the same amount. 1 tab. (L

Description

112

The invention relates to the heat treatment of materials, specifically to methods of controlling the process of firing a mixture of chrome ore and limestone in a rotary tube furnace.

The aim of the invention is to improve the quality of the material to be calcined and to prevent the formation of a slurry under the conditions of the changing aerodynamic regime of the rotating tube furnace.

The method is carried out as follows.

Material with a predetermined quantitative ratio of the components (chrome ore and lime continuously loaded

The gas is heated into a rotary tubular furnace heated by a gas.

The calcined material through the open gate of the hopper through chutes from the rotating tube furnace enters continuously into the smelting furnace. The vacuum in the discharge head of the rotary tube furnace during this period is 0.1-0.5 Pa.

For this firing period, the nominal specific gas flow rate and the nominal air flow rate are established to ensure the specified temperature in the furnace.

During the warm-up period, the ore-limestone melt in the electric furnace and the melt being blown out of the furnace is closed.

In the discharge head, the vacuum increases by 1-4 Pa due to the free flow of air through the open gate of the bunker.

During the period of overlap of the material supply path to the electric furnace and the increase in vacuum in the discharge head by 1-4 Pa, the specific gas consumption is reduced by 2-5% without changing the air flow.

Reducing the specific fuel consumption prevents overheating of the lining in the zone of maximum temperatures.

The calcined mixture maintains an optimal calcination temperature without overburning.

i

The reduced specific fuel consumption at a constant established air flow rate is maintained throughout the entire period of increasing the vacuum in the discharge head of the rotary tube furnace.

After turning on the electric furnace, the calcined material from the hopper is loaded

0

into the electric furnace and then again continuously supplied from the rotating tube furnace through the open gate of the hopper.

After the aerodynamic regime has been restored for a period equal to 1 / 20-1 / 10 of the duration of the material in the kiln, the specific fuel consumption is increased by 5-10% of the nominal, reducing air consumption by the same amount.

This increases the specific heat flux from the torch to the material and the lining in the burning zone and burns the accumulated material, the thickness of which exceeds the nominal value to 20%.

After this period, a stationary thermal regime is established in the rotary kiln, maintaining dynamic thermal equilibrium in the burning zone. Specific fuel consumption, as well as air consumption, is maintained nominal in accordance with the regime card.

An example of a specific implementation.

An industrial testing of the method was carried out on a burning rotary kiln with a diameter of 3.6 m, a length of 75 m, lined with aluminosilicate products with joint calcination of chrome ore and limestone. The natural groove was burned in a turbulent head.

The output of the rotary kiln rotary kiln is 20 t / h. The natural gas consumption for loading is 2000, air is 18000 nm / h.

With the established thermal and aerodynamic regimes of the furnace rarefaction; in the discharge head was 0.2 Pa.

five

0

0

The ratio of fuel to air in the burner was 1: 9, and in the furnace due to suction - 1: (11.28-12.69).

The residence time of the material in the furnace was 2 hours and 40 minutes, of which, for 2 hours and 15 minutes, the calcined material was continuously fed to the electric furnace.

During the period when the melt was released from the electric furnace, the burned material entered the receiving bin. The shutter in the heat, j in the path of the material in the electric furnace was closed. After the gate was closed, the vacuum in the discharge head was set at 4 Pa and the specific fuel consumption was reduced by 3.5% with J00

3

to 96.5 mixture, keeping the air flow 18000.

The fuel to air ratio in the burner was 1: 9.33, and in the furnace it was 1: (9.78-10.2) due to the reduction in the amount of air to be sucked out due to the blocking of the living section of the bunker shutter.

A vacuum of 4 Pa in the discharge head was maintained during the entire period of melt injection from the electric furnace (l5 min).

After the end of the production, the melt switched on the electric furnace, the whole mixture of chrome ore and lime was loaded into the electric furnace and the continuous loading of the mixture of materials was resumed.

The vacuum in the discharge head was 0.2 PA. The specific fuel consumption for the kiln was increased by 7.5% from the optimal mix to 107.5, the air flow was reduced to 16650, i.e. on. 7.5%.

The ratio of fuel to air in the burner was 1: 7.74, and in the furnace - 1: (9.86-11.4) due to the increase in suction through the open valve

O

five

0

five

The duration of the kiln with increased specific fuel consumption was 10 minutes.

Then installed on the kiln nominal specific fuel consumption and air flow. We carried out two more campaigns on the proposed method of controlling the process of continuous firing of the material with a decrease in specific fuel consumption by 2 and 5% without changing the established air flow during the period of increasing vacuum and increasing the specific fuel consumption by 5 and 10% with a corresponding decrease in air flow by 5 10% during the recovery period of the vacuum in the discharge head.

For comparison, the campaign was carried out according to the method chosen for the prototype.

The main indicators of the firing campaign, conducted with various changes in fuel and air consumption during the process, as well as in the prototype, are shown in the table.

The table shows that in three campaigns, the quality of the calcined material meets the requirements of the technology; the deviations from the stabilized composition in terms of the CaO content in lime were ± 0.5%.

In the prototype campaign, the content of CaO in lime changed from 88 to 98.7%; moreover, after the dilution was restored in the discharge head, the quality of lime was unsatisfactory due to the underburning of lime, and during the period of increasing the dilution, due to overdraft.

The total amount of the mixture, poorly quality, is -15%.

In the three campaigns of the proposed method, the formation of a software prototype was ruled out. In a furnace, an overgrowth was formed in the zone of maximum temperatures (1250 ° C).

With an increase in the vacuum in the discharge head of a rotating tube furnace, a decrease in specific fuel consumption by less than 2% without changing the established air flow leads to the formation of maximum temperatures in the zone, and with a decrease of more than 5%, to a low-quality roasting of the material with a high content of residual CO.

During the period of aerodynamic recovery in a rotating tube furnace, an increase in specific fuel consumption of less than 5% and a decrease in air consumption of less than 5% result in poor-quality firing of the material, and an increase in fuel consumption of more than 10% and a decrease in air of more than 10% overheating of the lining and the formation of wall accretions.

With a subsequent increase in specific fuel consumption and a decrease in

air flow is less than 1/20 of the material being kept in the furnace, poor-quality firing occurs - the material is not burned; if the material is kept in the furnace for more than 1/10, the lime is overbaked, and nastier formation occurs in the maximum temperature zone.

The method according to the invention allows to improve the quality of the calcined material and eliminate the formation of wall accretions.

-,

Claims (1)

Invention Formula The method of controlling the firing process in a rotary tubular furnace, including the flow of air into the furnace and the change in fuel consumption depending on the amount of feed material, characterized in that, in order to improve the quality of the calcined material and to prevent the formation of the material under conditions of varying aerodynamic conditions of rotating tube furnace; the pressure in the discharge head of the furnace is additionally measured; it is compared with the specified value and during the period of pressure reduction with respect to the specified value fuel consumption is reduced by 2-5% from the nominal value without changing the air flow rate, then after the aerodynamic regime has been restored in the period of 1 / 20-1 / 10 the duration of the material being in the furnace, the specific fuel consumption is 5-10% of the nominal value and at the same time reduces air consumption by the same amount.