SU1629722A1 - Method for adjusting lime calcination in fluidized bed kiln - Google Patents

Abstract

The invention relates to the processing of bulk materials, mainly for calcining lime and can be used in the metallurgical, chemical industry, in the production of building materials. The purpose of the invention is to increase the productivity of the furnace. The essence of the invention is that before unloading the material from the burning zone to the discharge transfer device, it is heated by 50-60 ° C relative to the burning zone due to the additional supply of fuel to the burner group near the transfer zone and maintaining this temperature difference by controlling the fuel consumption to this group of burners. 1 il.

Description

The invention relates to the processing of bulk materials primarily for the calcining of limestone and can be used in the metallurgical, chemical industry and in the production of building materials.

The purpose of the invention is to increase the productivity of the furnace.

This goal is achieved by creating and using a store of physical heat in the material being calcined before unloading it into the discharge outflow device.

The drawing shows a multi-zone fluidized bed furnace for the implementation of the method, a general view.

The furnace consists of a charging chute 1, the first along the material of the heating zone 2, the second heating zone 3, the burning zone 4, and the cooling zone 5.

The transfer of the material from zone to zone and its unloading is carried out with the help of valve diverting devices 6-9. The burners, combined into groups, through separate piping with regulating valves 10-14 supply fuel and autonomously, through the Venturi pipes, heated air from the superlayer space of zone 5. The control of fuel consumption for these burners is carried out using controller 15, executive mechanism 16. control valve 17 according to the temperature measured in the layer of the firing zone of the thermal converter 18 and the secondary device 19. The desired temperature is set using the setting device 20.

The burners adjacent to the discharge flows 8 are combined into a separate group with autonomous fuel consumption control using the controller 21, the actuator 22, the control valve 23 on the temperature difference of the layer in the discharge flows (heat generator 24, the secondary device 25) and the firing zone (heat converter 18} in accordance with the task set on the setting device 26. This task is set within 50 ... 60 ° C.

A decrease in the temperature difference below 50 ° C does not bring the desired effect due to insufficient heat reserves for dissociation, and an increase in this difference over 60 ° C is undesirable due to an increase in the temperature of flue gases and the associated overgrowth of the openings of the gratings of these zones This phenomenon is explained by the so-called fusible dust extract, when, at a high temperature of the exhaust gases, fine dust particles soften and intensively pour onto the surface of the heating zone grids, which results; stopping the oven for cleaning. Thus, maintaining the temperature in the material layer of the burning zone near discharge flows by 50-60 ° C above the material temperature in the layer of this zone allows creating the necessary heat in the lime discharged from the burning zone, the temperature level of which significantly exceeds the limestone dissociation temperature.

Example. The implementation of the method on a lime kiln with a fluidized bed with a capacity of 1000 tons / day.

In an amount of 84 t / h, it is known through the loading chute 1 to the first heating zone 2 along the material, where it is heated to 450 ° C, then it is transferred to the second heating zone 3 via the downstream device 6.

Heated to 750 ° C. Limestone from the second heating zone 3 is transferred via a percolating device 7 to the burning zone 4, where it is calcined at 950 ° C. Calcination of limestone occurs during the combustion of fuel in the layer of the burning zone with the help of bottom burners distributed over the cross section of the furnace and combined into six groups. From the burning zone, the lime is transferred to the zone 5, where it is cooled to 450 ° C, via a percolating device 8, which simultaneously serves as an adiabatic holding chamber. Air from the over-bed space of zone 5 is fed to the burner units, where 7000 m / h of natural gas is supplied.

Gas distribution among the burner groups is carried out using control valves 10-14. Gas flow control by burner groups is carried out using controller 15, actuator 16, control valve 17 c.

depending on the temperature change in the firing zone layer, measured by the thermoconverter 18, by the secondary measuring device 19, in accordance with the task

master 20.

Depending on the fractional composition of the loaded limestone, the limestone calcination temperature is set within 940 ... 980 ° С,

Burner devices adjoining

to the discharge flows, they are grouped in a separate group, the gas flow rate to which they regulate with the help of the controller 21, the actuator 22, the control valve 23 on the temperature difference of the layer in the discharge flows (thermal converter 24, secondary device 25) and the temperature of the firing zone ( thermal converter 18) in accordance with

task on the gauge 26.

Reducing the temperature of lime before unloading from the burning zone below 990 ... 1030 ° С to the overflow devices that serve as an adiabatic holding chamber,

no effect due to the small amount of physical heat in the lime pieces. Increasing the temperature of lime before unloading into overflow devices above 1000 ... 1040 ° С leads to fusible dust removal, overgrowing of the grids, and increased fuel consumption.

At the temperature of lime in the overflow devices 990, .. 1040 ° C, lime is languishing, i.e. in the unburned core of lime pieces, due to the store of physical heat, a dissociation reaction occurs and lime is transferred to lime, which has reduced the residence time in the calcination zone from 40 minutes to 35 minutes, increasing

most performance of the furnace by 2-3%.

Claims (1)

Invention Formula The method of controlling lime burning in a fluidized bed furnace includes measuring the temperature of the material in the bed in the burning chamber, measuring the air and fuel consumption to the groups of burners placed in the bottom of the burning chamber, with the aim of increasing furnace productivity, In addition, the temperature of the material in the discharge outflow channels from the firing chamber to the cooling chamber is measured, compared to the temperature of the material in the firing chamber, and the difference is kept within 50., 60 ° C by measuring the flow rate fuel per group of peripheral burners adjacent to the discharge outflow channels. R / | o o o o o "