SU811050A1 - Blast furnace air-duct apparatus - Google Patents

Description

one

The invention relates to metallurgical heat engineering, namely to the heat exchange between the high-temperature gas-air flow and the heat-receiving surface, in particular hot air flowing in the air duct of the blast furnace, and cooled air heater valves.

A device is known for lining a cylindrical air duct for transporting hot air heated in air heaters to a blast furnace consisting of a metal air duct, a cushioning material, and a refractory cylindrical brickwork 1.

It is also known to arrange a lined cylindrical air duct with a flange connection for accommodating a shut-off cooled valve, for example, a hot blast, comprising a metal air duct, gasket material, flanges and a refractory lining of a few (3-4) okates 2.

A disadvantage of the known device is that when a high-temperature gas-flow flows through the duct and the washing of the heating surfaces of the valve, the convective component of the heat exchange is significant and leads to a significant heat release by the valve and the temperature of the hot air is reduced by 12-14 ° C in the heater mode.

The aim of the invention is to reduce the heat load on the valve by reducing the heat exchange component.

The goal is achieved by the fact that

The lining on the inlet side of the hot air flow into the valve is made in the form of a small base (narrowing) diffuser, passing into the cylinder, followed by a sharp expansion towards the valve, and the narrowing cross section forms an expansion of the flow in such a way that a flow separation zone from the surface is created valve along its entire length, created by the central angle of constriction,

equal to 16-20 °, and the ratio of the areas of the orifices of the restriction and the valve is 0.6-0.7. .

Ratio of the areas of the throat narrowing and valve 0.6-0.7 is chosen from the following considerations: when a gas jet emanates from the nozzle, followed by a sharp flow expansion, there is a gradual expansion until it covers the entire cross section of the large duct (duct). In this case, the boundary radius of any jet section is calculated from the ratio

I X + R ,,

where a is the experimental expansion constant of the gas flow of the jet, equal to 0.09; X is the distance from the nozzle section downstream to any cross section of the gas jet; RO is the radius of the constriction (nozzle).

From the above it follows that for a valve with a through diameter of 1100 mm, with a distance between the flanges attached to the duct of 500 mm, the maximum radius at which the connection widened out of the gas flow will occur in the zone of the flange farther from the edge, or the ratio of the radius of the contraction to the radius of the duct .RQ 0.9. However, in this case, the convective composition of the convective part and its heat exchange at the far part of the valve will not be removed. This indicates that it is advisable to accept this radius ratio less than 0.9, namely, 0.6-0.7. At the same time, a decrease in the last ratio less than 0.6-0.7 will entail a sharp increase in the hydraulic resistance of the section.

It is known that the angle of constriction of the diffuser should exclude zones of stagnation of the gas flow and create a minimum hydraulic resistance of the site. This is provided by a central tapering angle of 16 ° -20 °.

Thus, the creation of a zone with a separation of flow from the wall (heating surface) with the aid of, and narrowing allows to reduce the heat transfer coefficient of the convective component ush by reducing the speed of movement of the flow in the zone of separation of flow.

FIG. Figure 1 shows the general view of the proposed air duct with the installation of a cooled shut-off valve between the flanges, for example, a hot blow; in fig. 2 — node I of FIG. one.

The air duct has a casing 1, which serves to transport the gas-air flow and perceive internal overpressure from the air and the weight of the masonry 2, which serves to enclose the casing 1 from heating, a shut-off cooled valve 3 to separate the heater from the duct, a smooth transition 4 designed to change the larger diameter air duct into a smaller, cylindrical restriction 5 for compressing the flow and separating it from the walls of the heating surfaces of the valve 3, a sharp expansion 6, which serves to create a pressure differential during expansion and the zone of flow separation from the walls.

High-temperature gas-air flow under excessive pressure washes

laying 2, protective casing 1 from heating. When the flow enters transition 4, the velocity of its movement increases and in the cylindrical restriction 5 it reaches its maximum value. At the entrance of the stream

into a sharp expansion, the flow separates from the heat-receiving surfaces of the valve 3 and a zone is created in which the heat transfer coefficient of convection decreases, the heat load on the claian,

and the thermal direction of the metal is reduced.

Upon further movement, the flow structure is restored to the characteristics that occur before it enters

in a smooth transition.

The narrowing of the constriction in front of the flow entry into the valve area allows the heat load to be reduced by reducing the convective heat transfer component.

Claims (2)

1. Air duct device for blast furnaces, including air duct, flanges, cooled valve, lining, characterized in that, in order to reduce the heat load on the valve by reducing the convective component of heat exchange, the lining is made in the form of a confuser, which passes into the cylinder and then expands towards the valve. 2. The device according to claim 1, characterized in that the confuser is made with a central angle 16-20 and the ratio of the flow areas of the narrowing of the confuser and the valve is 0.6-0.7. Sources of information taken into account in the examination 1. Instructions for lining and drying blast furnaces and their auxiliary devices. PI-30651. M., Gipromez, 1974, p. 64, fig. 43. FIG.