JPS6342320Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a heat recovery device for powder particles, and more particularly to a device for effectively recovering heat from high-temperature iron-containing reduced pellets produced in iron works.

In steel plants, tens of thousands of tons of dust are generated each year at each step of the iron and steel manufacturing processes, and this dust contains 30 to 60% iron (Fe).
These dusts are collected, converted into reduced iron by a direct reduction method using carbon C as a reducing agent, and then fed into a blast furnace as a raw material for steel, thereby saving resources.

FIG. 1 shows an outline of the direct reduction method. In the figure, a raw material 1 passes through an inlet 2 and reaches a rotary kiln 3, where it is heated to about 1050° C. by a burner 4 in a reducing atmosphere and reduced. In order to prevent re-oxidation, the reduced particles (hereinafter referred to as "reduced pellets") are put into a water tank 5 within a very short time after being reduced and cooled to near room temperature. A large amount of steam is generated from the water tank 5 by cooling the reduced pellets, but
This steam is released into the atmosphere, causing environmental pollution, and the heat contained in the reduced pellets is completely wasted. For this reason, a method of forming a fluidized bed for cooling the reduced pellets can be considered, but it is necessary to use an inert gas that has no risk of oxidation as the cooling gas, and the injection speed of these inert gases must be controlled to ensure fluidization. It is necessary to maintain it above a certain value, which increases the power cost, making it uneconomical overall. Further, by fluidizing the reduced pellets, the reduced pellets may collapse into powder, which may cause inconvenience in handling. Furthermore, when nitrogen is used as the inert gas, there is also the problem of nitridation. Generally speaking, fluidized bed cooling is technically and economically difficult to achieve, but is an effective method.
Development of a device is desired.

The purpose of this invention is to eliminate the above-mentioned problems and provide an apparatus that can effectively recover the heat retained in reduced pellets without changing the properties of the particles.

In short, this device is a device in which a moving layer of reduced pellets is formed and a heat pipe is placed in this moving layer.

Examples of this invention will be described below.

In FIG. 2, a moving layer forming casing 12 (hereinafter simply referred to as casing 12), which forms a moving layer 7 made of reduced pellets inside, is disposed at the outlet of a rotary kiln 3, which is a reduced pellet manufacturing device. A quantitative feeder 10 such as a shaking conveyor or a rotary feeder is arranged at the bottom of the casing 12. The water tank 5 is connected to the casing 12 via this quantitative feeder 10.

A heat recovery element 8 is disposed within the casing 12 to recover heat from the high temperature reduced pellets forming the moving layer. Since this heat recovery element has the function of recovering heat from the reduced pellets and transmitting it to the outside, it may be, for example, a water pipe of a boiler. However, in the case of a boiler water pipe, if the water pipe were to break, a large amount of boiler feed water would flow into the moving bed, so a heat pipe is most suitable as the heat recovery element.

FIGS. 3 to 5 show a structure for a casing when a separate type heat pipe in which an evaporating section and a condensing section are separated is used as a heat pipe. Reference numeral 13 denotes a tube constituting the evaporation section of the separate heat pipe, and both ends of the plurality of tubes arranged in parallel are connected to the header 1.
4 and 15 to form a panel, which is arranged in multiple stages within the casing 12. In this case, each panel is arranged diagonally with respect to the horizontal plane at a predetermined angle so that the vapor of the enclosed working medium rises and the condensate returned from the condensing section easily descends. 17a, 17b, 1
7c is a manifold for each panel group, and each panel group is connected to each manifold via a communication pipe 18. 19a, 19b, and 19c are communication main pipes that connect each manifold to a condensing section (heat dissipation section) not shown. The condensing section may be located in the heat recovery section, for example, in the boiler drum 9, as shown in FIG. 2, and may directly heat the water supplied within the drum.

In the above structure, a moving layer 7 is formed in the casing 12 by the high-temperature reducing pellets 20 in a reducing atmosphere. The heat of the reduced pellets is transferred to the evaporation tube 1.
At step 3, the internal working medium evaporates, and the generated steam S is transferred to the outside as latent heat via the header 14 and the connecting pipe 18, and reaches the condensing section via each manifold and the connecting main pipe, where it condenses and radiates heat. The condensed liquid L mainly descends along the inner wall surface of the tube and returns to the evaporation tube. Heat is recovered by circulating and flowing the working medium in this manner. In this case, even if any of the tubes 13 were to be damaged, the amount of working medium pre-filled in the tube is the length of one tube and is not very large, so it will not have a major effect on the reduced pellets. Further, a plurality of nozzles 21 for supplying inert gas and/or reducing gas are provided in the lower part of the casing 12 to create a reducing atmosphere inside the casing to prevent the pellets from being oxidized.

By implementing this idea, heat can be effectively recovered without exposing the reduced pellets to an oxidizing atmosphere.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram of a plant including a cooling device for reduced pellets according to the conventional method, and Fig. 2 shows an arrangement in which a heat recovery device is installed at the outlet of a rotary kiln showing one embodiment of this invention. 3 is a partially enlarged view of FIG. 2 when the evaporation part of the separated heat pipe is provided in the moving layer of reduced pellets; FIG. 4 is a cross-sectional view taken along line AA in FIG. 3; Fifth
The figure is a sectional view taken along line BB in FIG. 3. 3...Rotary kiln, 7...Moving layer, 12...
...Moving bed forming casing, 13...Evaporation section, 2
0... Reduction pellet, 21... Nozzle.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. In a reduced pellet heat recovery device that recovers heat possessed by reduced pellets using a heat recovery element,
A casing for forming a moving layer of reduced pellets is disposed in the discharge section of the reduced pellet manufacturing device, and a plurality of gas supply means for supplying inert gas or reducing gas are provided in this casing, and 1. A heat recovery device for reduced pellets, characterized in that an evaporating section of a heat pipe is disposed, and a condensing section of the heat pipe is disposed in a heat recovery section to recover heat from the reduced pellets. 2 Utility Model Registration Scope of Claim 1. The reduced pellet heat recovery apparatus according to claim 1, wherein the heat pipe is a separate heat pipe.