JPS6258813B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a sensible heat recovery device for a continuous casting machine. As is well known, in continuous casting machines, molten steel is poured into a bottomless mold, a thin solidified shell is formed around the molten steel within this mold, and then cooling water is injected onto the surface of the solidified shell in a water spray zone directly below the mold. Then, the solidified shell is grown by air cooling and pulled out by pinch rolls to produce a slab. Since the inside of the slab is not solidified between the mold and the pinch rolls, the slab must be guided and supported by the rolls to prevent the solidified shell from breaking. The wider the slab to be cast, the greater the stress and strain values generated in the shell due to the molten steel pressure acting on the shell. For the quality of slabs, this stress and strain must be suppressed above a certain value. Therefore, the wider the slab, the narrower the roll spacing must be. In addition, the closer the roll is to the mold, the closer the roll spacing must be. In such continuous casting, solidification heat is radiated to the outside until the slab hardens, and recovering this radiant heat is important for saving energy and lowering steel manufacturing costs. By the way, even if you try to install heat recovery tubes between the rolls, the rolls are arranged closely, so it is difficult to cover the slab with the tube, and a considerable amount of the heat dissipated by the slab is absorbed by the rolls. It will be done. For this reason, in the past, heat was left unrecovered between the roller apron and the pinch rolls. This invention was proposed in view of the above circumstances, and its purpose is to provide a sensible heat recovery device capable of recovering radiant heat at the roller apron section and the pinch roll section and performing slow cooling. There is a particular thing. The sensible heat recovery device according to the present invention provides a refrigerant passage inside the rolls of the roller apron and the pinch rolls, and divides these roll groups into a plurality of stages, each of which has a refrigerant circulation pipe having a steam/water separation drum and a circulation pump. At the same time, each air-water separation drum of the refrigerant circulation pipe is connected by a connecting pipe having a water supply pump, and the refrigerant is configured to pass from the roll group on the downstream side to the roll group on the upstream side in order. In the downstream refrigerant circulation system, the water is first converted to low-pressure hot water, and then
High-temperature, high-pressure steam is obtained through a refrigerant circulation system on the upstream side. The present invention will be described below based on an illustrated embodiment. As shown in FIG. 1, a large number of roller aprons 2 are arranged in a curved manner between the mold M and the pinch roll 1, and each of these roller aprons 2 has a plurality of guide rolls 3. Guides and supports the slab S. The pinch roll 1 and each guide roll 3 are provided with a refrigerant passage 4 that penetrates from one end to the other end (see Fig. 2), and a header 5 that communicates with this refrigerant passage 4 is connected to each roller apron. Each is also connected to the pinch roll 1. In the pinch roll 1 and roller apron 2 having such a configuration, these roll groups are divided into two stages, a downstream roll group 6 and an upstream roll group 7,
A downstream refrigerant circulation line 8 having a steam/water separation drum 13 and a circulation pump 14 and an upstream refrigerant circulation line 9 having a steam/water separation drum 16 and a circulation pump 17 are connected to these roll groups 6 and 7, respectively.
These air-water separation drums 13 and 16 are connected to the water supply pump 1.
They are connected by a connecting conduit 10 having 2. In the downstream refrigerant circulation pipe 8, pure water is supplied from the water tank 11 to the downstream steam/water separation drum 13 by the water pump 12, and the downstream circulation pump 14
The pure water is circulated between the rolls 1 or 3 of the downstream roll group 6 and the drum 13, and the pure water absorbs the radiant heat of the slab by thermal conduction while passing through the coolant passage 4 of the rolls 1 or 3. and becomes low-pressure hot water. The low-pressure hot water in the drum 13 is supplied to the upstream steam/water separation drum 16 of the upstream refrigerant circulation pipe 9 through the connecting pipe 10 by the water supply pump 15 . The hot water in this drum 16 is transferred to an upstream circulation pump 17
The steam is then sent to the roll 3 of the upstream roll group 7, where it is further heated to a high temperature, and then returned to the drum 16 to recover the high pressure steam St. Although the water supply and drainage to the headers 5 are arranged in parallel, the present invention is not limited to this, and adjacent headers may be connected in series. Furthermore, the water supply to the rolls 1 or 3 may be provided by parallel or series piping. In the present invention, since the downstream roll group 6 first generates low-pressure hot water and then supplies it to the upstream roll group 7, there is no need to raise the temperature from the normal ambient temperature in the upstream roll group 7. , high temperature and high pressure steam can be obtained. Furthermore, another advantage of the present invention is that the slab can be cooled slowly (soft cooling). Recently, in order to save energy, a continuous casting line is directly connected to a blooming line and slabs are exposed at high temperature. However, in conventional equipment, cooling water is passed inside the roll to protect the roll. Therefore, the average temperature of the roll surface is
The temperature is kept low at 200-300℃, and a considerable amount of heat is removed from the slab by the rolls. Therefore, since the slab is rapidly cooled at the contact portion with the rolls, surface cracks may occur depending on the steel type. In the present invention, by circulating hot water inside the rolls 1 and 3, the surface temperature of the rolls is inevitably raised by the temperature of the hot water, and the amount of heat removed from the slab is lower than in the past, and the cooling degree is will also decrease. As a result, the slab is slowly cooled and surface cracks are prevented. Next, explanation will be given using specific numerical examples. This is an example of continuous casting under the following conditions.

【table】

[Table] When the roll was conventionally cooled through industrial water, the roll inner surface temperature was kept at 40 to 60°C and the average roll surface temperature was kept low at 200 to 300°C, but in the present invention, the roll When the inner surface temperature is 170 to 250℃, the average roll surface temperature is 250 to 400℃,
Compared to the conventional method, the amount of heat removed from the slab and the degree of cooling are lower, allowing for gradual cooling. In this embodiment, the roll group is divided into two stages, but the roll group is not limited to this and may be divided into three or more stages. In addition, when controlling the hot water temperature of the downstream roll group 6 so as not to significantly exceed 100°C, the water supply pump 12 and the downstream air-water separation drum 13 are unnecessary, and as shown in FIG. , the water supply tank 11 can be used instead of the drum 13. It should be noted that an accident may occur in which the solidified shell of the slab ruptures directly under the mold M and the molten metal flows out of the shell. At this time, operations must be stopped and the roller apron repaired. Therefore, mold M
A group of several roller apron rolls directly below may be used for preheating (to 100° C. or less) pure water to be supplied to the water supply tank 11. If you do this,
This system uses water piping rather than boiler piping, and damage can be minimized. Further, the same effect can be obtained by using not only pure water but also fluorocarbon or the like as the refrigerant. As described above, according to the present invention, the roll group is divided into multiple stages for heat recovery, so that the radiant heat of the slab can be effectively recovered. Furthermore, the slab can be cooled slowly, and surface cracks can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing a sensible heat recovery device according to the present invention, FIG. 2 is a system diagram of a similar device, and FIG. 3 is a system diagram of a different circulation system of a downstream roll group of the same device. be. 1...pinch roll, 2...roller apron,
3...Guide roll, 4...Refrigerant passage, 5...
Header, 6...Downstream roll group, 7...Upstream roll group, 8...Downstream refrigerant circulation pipe, 9...Upstream refrigerant circulation pipe, 10...Connection pipe, 11...Water tank , 12...Water pump, 13...Downstream side air-water separation drum, 14...Downstream circulation pump, 1
5... Water supply pump, 16... Upstream side air-water separation drum, 17... Upstream side circulation pump.

Claims (1)

[Claims] 1. A refrigerant passage is provided inside the rolls and pinch rolls of the roller apron, and these roll groups are divided into multiple stages, each of which is connected to a refrigerant circulation pipe having a steam separation drum and a circulation pump,
Each of the air-water separation drums of the refrigerant circulation pipe is connected by a connecting pipe having a water supply pump, and the refrigerant is sequentially passed from the roll group on the downstream side to the roll group on the upstream side. Sensible heat recovery device for casting machines.