RU2737795C1 - Shaft furnace for calcination of carbonate raw material on solid fuel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to a shaft furnace for roasting lump material. Furnace comprises heating zone, burning zone, cooling zone, installed vertically along furnace axis metal cylindrical insert with outlet mouth for supply of additional air cooler to cooling zone and means of controlling supply of additional air cooler in form of distributor, wherein said insert for supply of additional air cooler is fixed on furnace upper part by means of spherical hinged connection, and outlet mouth of said insert is arranged at level of nominal height of cooling zone with provision of additional air supply upwards along peripheral part of furnace with possibility of variation of excess air factor value.

EFFECT: higher quality of burnt limestone due to uniform roasting over furnace section, reduced specific fuel consumption while maintaining high degree of lime burning, improving operating reliability of furnace with provision of continuous operation of furnace without local wear of furnace lining.

1 cl, 1 dwg, 1 tbl

Description

The invention relates to shaft furnaces for burning carbonate raw materials on solid fuel.

It is known that the aerodynamic regime of the shaft furnace is due to the mutual arrangement of the draft devices and the resistance of the material layer in the shaft. The upper part of the furnace - the heating zone - communicates with the smoke exhauster, therefore it is under vacuum, gradually decreasing towards the firing zone. In the firing zone, the vacuum reaches a minimum, close to zero, value. The lower part of the shaft - the cooling zone - is under pressure, since cold air is blown into it by a blower fan. As the air moves towards the firing zone, the pressure decreases.

The composition of the gas medium does not significantly affect the quality of firing of lump materials. The value of the excess air coefficient in the firing zone should correspond to the type of fuel burned and the furnace heating system with minimal heat losses from chemical and mechanical underburning and with gases leaving the furnace.

Based on the above, devices are created that provide additional uniform air supply to the firing zone

Known shaft furnace operating on solid fuel, containing a lined shaft with loading and unloading devices and a system for supplying air for combustion of fuel. Most of the air is supplied along the periphery, the smaller part - through the central pipe, which is installed along the vertical axis of the rotating unloading device of the "snail" type and is equipped with openings for air outlet in its upper part under the protective cap.

A charge (a mixture of raw materials and fuel) is periodically fed into the furnace through a charging device. As it descends, the charge is heated by the furnace gases coming from below. In the firing zone, the fuel burns, giving off heat to decompose the raw material.

In the cooling zone, heat exchange takes place between the lime and the air entering the furnace from below. The cooled lime is removed from the kiln using a discharge device.

However, the observed uneven burning of raw materials leads to the production of lime of different activity and partially to losses in the form of "burnout". This is due to the fact that in the furnace in the lower part of the firing zone, near the border with the cooling zone, there is a temperature peak of about 1200-1300 ° C (Tabunshchikov N.P. Lime production. - M .: Chemistry, 1974, p. 53 fig. . 12).

Known shaft furnace, which provides for the installation of an air distributor moved along the axis of the charge, made in the form of a hollow cylindrical insert with perforated cones at the ends (and.with. 476427 USSR class F27B 1/00 1973). The supply of cold air through the insert, moved by the drive, following the position of the temperature peak, the temperature of the boundary region decreases to a certain value.

The disadvantage of this furnace is the unreliability of the insert, since it must move in a dense lumpy filling at a temperature of the order of 1200-1300 ° C. In addition, lifting the device is accompanied by the expenditure of a significant amount of energy.

The aim of the invention is to improve the reliability of the furnace, improve the quality of fired limestone, and reduce fuel consumption for firing.

This goal is achieved by the fact that in a shaft furnace for burning carbonate raw materials on solid fuel, containing a lined shaft, loading and unloading devices, limestone is heated, calcined to obtain lime, and its cooling is carried out in cocurrent and countercurrent. An additional supply of oxidizing air in a controlled mode is supplied to the firing zone through a cylindrical hollow insert made of heat-resistant steel installed in the upper part of the furnace. The insert has a spherical hinge connection with the furnace frame in the upper part (photo 1), which provides flexibility of the connection and, as a result, the lining of the furnace walls is preserved. The supply of additional air volume through the insert is adjustable, which ensures the required fuel combustion mode and temperature stability in the firing zone.

At the interface between the firing and heating zones, there is a so-called "reduction zone" in which the high-temperature furnace gas is no longer oxygen-containing. in contact with the surface of a hot solid fuel. Under these conditions, the reaction of carbon dioxide reduction occurs, which leads to incomplete combustion of the fuel.

Useful furnace height, i.e. the height of the backfill layer of lumpy material is usually 10-20 m. This height mainly determines the nominal length of each of the thermal zones, i.e. heating zones, firing zones and cooling zones. The nominal height of the cooling zone is 15-30% of the working height of the furnace. This height determines the connection of the air distributor outlet to the furnace shaft.

By varying the values of the excess air coefficient, the most favorable firing mode is established, which ensures high quality of the product obtained and increased durability of the walls of the outer and inner mines.Using the proposed firing method and furnace for its implementation allows, in comparison with the known ones, to provide a more uniform distribution of heat loads in the firing zone.

The invention provides the maximum quality of material processing and high productivity,

Usage example:

When firing in a transfer furnace, coal from the Bogatyr open pit of the Ekibastuz deposit was used with a calorific value of 4200 kcal / kg, volatiles content - 28%, ash content 40%, sintering capacity - 1400 ° C. According to the calculation performed, 345 kg of this coal are required to burn a ton of limestone. The effectiveness of the invention is seen in the following table:

Claims (1)

A shaft furnace for roasting lump material, containing a heating zone, a roasting zone, a cooling zone, a metal cylindrical insert installed above the vertical axis of the furnace with an outlet mouth for supplying an additional air cooler to the cooling zone and a means for regulating the supply of an additional air cooler in the form of a distributor, characterized in that The said insert for supplying an additional air cooler is fixed on the upper part of the furnace by means of a spherical hinge, and the outlet mouth of the said insert is located at the level of the nominal height of the cooling zone with the provision of additional air supply to it upward along the peripheral part of the furnace with the possibility of varying the value of the excess air ratio.

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