JPS61150707A - Water treatment method by ozone in cooling water used for rolling - Google Patents

Abstract

PURPOSE:To stabilize the residence time of O3 and to keep the O3-concentration of headers at a prescribed value, by installing a branch pipe at the downstream just before water-spraying headers, and controlling the amount of water in the O3- residence-time zone of a cooling-water piping into which the gaseous O3 is injected at the upstream into a constant value. CONSTITUTION:A gaseous O3 injecting pipe 17 is parallelly connected to a water- supplying piping 10 at the outlet side of a cooling tower 7. A gaseous ozone generating and supplying device 15 is connected to the pipe 17 to supply gaseous O3 by an ejector 16, and high-pressure cooling water is supplied to the ejector 16 by an ejector pump 18. For controlling the flow rate of cooling water, a cooling-water extracting pipe 20, branched from the pipe 10 in the vicinity of headers 14, is connected to the return pipe 21 of a discharged-water receiving tank 5. A flow regulating valve 22 is provided to the pipe 20, and a flow meter 23 is attached to the pipe 10 at the upstream side of the connecting point of pipe 20. The valve 22 is controlled by a flow-rate signal outputted from the meter 23, to maintain the constant flow-rate of cooling water at the O3-residence-time zone of pipe 10, that is between the ozone injecting point A and the connecting point B of pipe 20.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to the treatment of roll cooling water in a cold rolling mill, and relates to the treatment of roll cooling water in a cold rolling mill. This invention relates to treatment for preventing slime formation in roll cooling water for maintaining friction at an appropriate value and cooling rolls and rolled materials below a predetermined temperature.

(Conventional technology) Conventionally, there are two types of roll cooling methods for cold rolling mills: recirculation method and direct method. In the former method, a large amount of emulsion liquid in which rolling oil is added to cooling water is rolled. It circulates and supplies the rolls and the material to be rolled for lubrication and cooling at the same time. On the other hand, in the latter direct method, as shown in FIG. 6, rolling oil is injected from a lid 2 into the metal strip 1, which is the material to be rolled, by a nozzle, so that the work roll 3 and the metal strip 1 The work rolls 3 are cooled by being injected with cooling water from the nozzles of the roll cooling water header 4. The cooling water and rolling oil after injection are collected in a drainage tank 5, and after removing impurities such as oil and iron powder by a water purification device 6, they are cooled by a tower 7, and then discharged from a new water supply pipe 8 to a new water supply pipe 8. Pipe 10 is supplied with water by pump 9
The cooling water is supplied to Hesogou 4 through , and is used for circulation. On the other hand, the oil separated by the water purification device 6 is regenerated in the re-main device 11 and temporarily stored in the tank 12, where it is replenished with new oil as needed.
The rolling oil is supplied to the rolling oil header 2 through the rolling oil supply pipe 14 and used for circulation.

However, in the conventional direct roll cooling method as described above, microorganisms propagate within the water supply pipe 10 and form slime, resulting in the water supply pipe 10 being blocked or slime peeling off from the inner wall of the water supply pipe. There was a problem in that the water was sprayed from the nozzle of the roll cooling water header together with the cooling water, causing scratches on the surfaces of the rolls and metal strips.

Conventionally, as a countermeasure to such problems caused by slime,
The following methods are used to suppress slime generation.

(1) By replenishing fresh water in an amount of 40 to 60% of the water supply, the cooling water is kept clean and the growth of microorganisms is suppressed.

(2) Chlorine or sodium hypochlorite is added to the cooling water, and its sterilizing effect suppresses slime generation.

(Problems to be solved by the invention) However, method (11) has the problem of large water consumption, and method (2) increases the chlorine concentration in the cooling water during circulation, resulting in poor surface quality of the metal strip. There were problems such as not only having a negative impact on the environment but also high drug costs.

(Means for Solving the Problems) An object of the present invention is to provide a roll cooling water treatment method that solves the above problems.

The present inventor has discovered that when performing roll cooling using the direct method,
It has been confirmed that the generation of slime can be suppressed by injecting ozone into the cooling water so that the ozone concentration in the cooling water at the cooling water injection part to the roll is 0.1 pp+i or more.

Ozone not only has a higher bactericidal effect than conventionally used chlorine, but also has the advantage that it decomposes into oxygen in a relatively short time and has no effect on metal strips. A new problem arises due to the fact that ozone has a lifespan (half-life).

That is, while the cold rolling mill is placed indoors, water treatment equipment such as the water purification device 6 and the cooling tower 7 are usually placed outdoors, and therefore the water supply pipe 10 becomes very long. There are many cases. Therefore, when ozone is supplied upstream of the water supply pipe 10, the time required for the roll cooling water injected with ozone to reach the roll cooling water header 4 at the end from the ozone supply position, that is, the residence time becomes longer; is also influenced by the flow rate of roll cooling water.

Generally, the flow rate of roll cooling water in a cold rolling mill is controlled according to the rolling speed, so the flow rate of cooling water flowing through the water supply pipe 10 to the header 4 fluctuates, and as a result, the residence time fluctuates greatly and As shown in Figure 2, the ozone concentration at

Therefore, the ozone concentration in the roll cooling water header 4 at the end of the residence time zone is set to a predetermined value, that is, 0.1 p
There is a problem in that it is difficult to efficiently maintain an appropriate amount of ozone injected over pm.

The present invention provides a method for solving the above problem.According to the present invention, in order to cool the rolls of a cold rolling mill, as shown in FIG. When ozone treatment is performed by injecting cooling water supplied to the header 4 from the ozone generation supply device 15 through the ejector 16, the residence time of ozone from the ozone injection point to the roll cooling water header is stabilized, and ozone treatment at the end is stabilized. The flow rate of cooling water is controlled to be constant at least during the ozone residence time period so as to stabilize the ozone concentration.

(Function) As described above, according to the present invention, the ozone concentration in the cooling water is stabilized by controlling the flow rate of the cooling water in the water supply piping and stabilizing the residence time of ozone.
This makes it possible to maintain a predetermined ozone concentration value in the lug to the roll cooling water at the end of the water supply pipe.

(Embodiment) In the embodiment of the present invention shown in FIG. 1, an ozone injection pipe 17 is connected in parallel to the water supply pipe 10 on the outlet side of the cooling tower 7, and
The ejector 16 is connected to supply ozone from the ozone generation and supply device 15 to the ozone injection pipe 17, and the ejector pump 18 is configured to pass cooling water from the water supply pipe 10 to the ejector 16 at high pressure.

19 indicates an oxygen supply device. In order to control the flow rate, a cooling water take-out pipe 20 is connected to the water supply pipe 10 upstream from the end of the water supply pipe, preferably near the header 4, and this take-out pipe 20 is connected to the return pipe 21 of the wastewater receiving tank 5. A flow rate adjustment valve 22 is provided in the outlet pipe 20, and a flow meter 23 is installed in the water supply pipe 10 upstream from the connection point of the outlet pipe 20.
The flow rate regulating valve 22 is controlled by the flow rate signal from the flow meter 23.
ozone residence time in the water supply pipe 10 by controlling the opening degree of the water supply pipe 10,
That is, from the ozone injection point A to the connection point B of the extraction pipe 20
Keep the flow rate of cooling water constant between the two.

(Effects of the Invention) According to the present invention, it is possible to achieve an effect that economical and stable water treatment using ozone can be performed without being influenced by the amount of water in the roll cooling water header.

[Brief explanation of drawings]

Figure 1 is a system diagram of a water treatment system that ozone-treats roll cooling water that cools the rolls of a cold rolling mill by the direct method, and Figure 2 shows the relationship between the flow rate of cooling water in the water supply pipe and the ozone concentration. A graph showing the relationship, FIG. 3, is a circulation system diagram of roll cooling water that cools the rolls of a conventional cold rolling mill by a direct method. ■・・・Metal strip 2-Rolling oil header 3...
-Work roll 4- Roll cooling water header 5・
- Drainage tank 6 - Water purification device 7 - Cooling tower
8-New water supply pipe 9-Water supply pump 10--Water supply pipe 15--Ozone generation and supply device

Claims (1)

[Claims] 1. When treating water by injecting ozone into the cooling water that is injected from the roll cooling water header installed at the end of the water supply pipe to the rolls of the cold rolling mill at the base end of the water supply pipe,
Ozone-generated water for rolling cooling water, characterized in that the cooling water is taken out in a controlled amount from the water supply pipe at a position upstream from the end of the water supply pipe, and the flow rate of the cooling water is controlled to be constant during the ozone residence time period in the water supply pipe. Processing method.