JP2001064789A - Sludge concentration separation method and apparatus - Google Patents

Abstract

(57) [Problem] To provide an inexpensive and effective method and apparatus for concentrating and separating sludge in a pickling tank of a stainless steel plate. When an acid solution containing sludge is supplied from an acid solution supply port (2) of a spirally formed pipe and discharged from an acid solution discharge port (4), a concentrated sludge provided on the outer peripheral side of the spiral shaped body. The acid solution containing the concentrated sludge is discharged from the liquid outlet 3, and the acid solution after the concentrated acid solution containing the sludge is removed is discharged from the acid solution outlet. An apparatus for carrying out this method, comprising an acid solution supply port, a concentrated sludge liquid outlet, and an acid solution discharge port as main parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a pickling process,
The present invention relates to a method for concentrating and separating sludge contained in an acid solution used in an acid washing step performed for removing oxides on a stainless steel surface, and an apparatus therefor.

[0002]

2. Description of the Related Art Pickling of stainless steel plates, stainless steel pipes, etc. is usually carried out by passing them through a pickling tank containing a pickling solution. As the pickling solution, a mixed acid of nitric acid and hydrofluoric acid is used. And nitric acid is used.

[0003] In this pickling tank, chromium oxide or the like, which is hardly soluble in acid, remains at the bottom as sludge.
In pickling of a stainless steel plate, this sludge is bitten between the immersion roll and the steel plate, causing problems such as indentation flaws in the steel plate. In order to solve this problem, the line is normally stopped to perform a removal operation, which is a factor that greatly reduces productivity.

Therefore, Japanese Patent Application Laid-Open No. Hei 6-158370 proposes a method of sucking and discharging sludge accumulated in an acid pickling tank. However, the tank capacity is usually 2
Since it is as large as 0 m ³ or more, there is a drawback that the amount of emission is large and the equipment cost is high.

[0005] Further, ordinary pickling equipment is provided with a filter for protecting a circulating pump for pickling liquid to remove sludge. However, there is no ability to remove the entire amount of sludge. Since filter clogging frequently occurs, the filter is often circulated through a bypass line, and it is desired to establish an inexpensive and effective sludge removal measure.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and concentrates and separates sludge in a pickling tank used for pickling to remove oxides on the surface of stainless steel. And to provide an inexpensive and effective method and apparatus for removal.

[0007]

The gist of the present invention resides in the following method (1) for sludge concentration and separation and (2) an apparatus therefor.

(1) An acid solution containing sludge is supplied from an acid solution supply port provided at one end of a spirally formed pipe, and the acid solution is supplied from an acid solution discharge port at the other end. A method of concentrating and separating sludge in the pickling solution by discharging, wherein an acid solution containing concentrated sludge is discharged from a concentrated sludge liquid outlet provided on the outer peripheral side of the spiral shaped body, and the acid solution is discharged. A sludge concentration separation method for discharging the acid solution after the acid solution containing the concentrated sludge is removed from an outlet.

(2) An apparatus for performing the method described in (1) above, wherein an acid solution supply port for supplying an acid solution containing sludge is provided at one end of a spirally formed pipe. The concentrated sludge liquid outlet for discharging the acid solution containing the concentrated sludge on the outer peripheral side of the spiral shaped body, after the acid solution containing the concentrated sludge is removed at the other end of the pipe. A sludge concentration / separation device having an acid solution outlet for discharging an acid solution.

Here, the term "spiral shaped body" refers to a shaped body in which a pipe is formed in a spiral shape. In addition, the "outer peripheral side" is, in the radial cross section of the spiral shaped body,
The outer side, that is, the side in the direction where centrifugal force acts. The exact outer range is not specified. As will be described later, the centrifugal force acts to collect a large amount of sludge having a large specific gravity, that is, a portion through which an acid solution containing concentrated sludge passes.

In order to solve the above problems, the present inventors have paid attention to the fact that sludge in a pickling tank is mainly composed of an oxide of a metal element and precipitates when left in the pickling tank. That is, sludge, which is the object to be removed from the pickling tank, has a specific gravity greater than 1,
If centrifugal force is used, sludge having a large specific gravity should be efficiently concentrated and separated.

Therefore, as a result of various studies on a method of applying a centrifugal force to the sludge in the pickling tank with a simple device, it was found that simply passing an acid solution containing the sludge through a spirally formed pipe, It was confirmed that concentration and separation were possible, and the present invention was accomplished.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for concentrating and separating sludge of the present invention (the method of the present invention) and an apparatus therefor (the apparatus of the present invention) will be specifically described.

According to the method of the present invention, as described above, an acid solution containing sludge is supplied from an acid solution supply port provided at one end of a spirally formed pipe and the acid solution at the other end is supplied. A method of concentrating and separating sludge in the pickling liquid by discharging an acid solution from a discharge port, wherein the sludge is concentrated by the action of centrifugal force from a concentrated sludge liquid discharge port provided on the outer peripheral side of the spiral shaped body. And discharging the acid solution containing the concentrated sludge from the acid solution discharge port.

The reason why the spirally shaped pipe is used is to apply a centrifugal force to sludge in the pickling liquid passing therethrough. While the acid solution passes through the pipe, a large amount of sludge having a large specific gravity collects and concentrates on the outer peripheral side of the spiral shaped body, that is, on the side where the centrifugal force acts.

It should be noted that the pipe used here usually has a circular cross section which is easy to manufacture and process, but is not necessarily limited to this. A pipe having a cross section of an elliptical shape, a square shape, or another special shape, for example, a pipe having a shape in which centrifugal force acts on sludge and is easily concentrated on the outer peripheral side may be used.

The flow rate (flow rate per unit time) when the acid solution containing sludge is supplied from one end of the spirally formed pipe and discharged from the other end is not particularly limited. This is because the concentration of sludge increases as the flow rate increases and the concentration efficiency increases as shown in the examples described later, but the concentration effect is recognized even when the flow rate is small. However, the upper limit of the flow rate is naturally determined from the viewpoint of the performance of the pump or the suppression of wear caused by sludge on the inner surface of the pipe.

As described above, since the sludge is concentrated on the outer peripheral side of the spiral shaped body, in the method of the present invention, the acid solution containing the concentrated sludge is discharged from the outer peripheral side of the spiral shaped body. The acid solution containing the concentrated sludge is usually discharged from the outer periphery of the pipe at or near the acid solution discharge port (the side corresponding to the outer periphery of the spiral shaped body). The discharge position may be any position in the length direction of the pipe as long as the sludge is thickened by the action of the force, and is not limited to a specific position. In addition, it may be discharged from a plurality of places.

The method of discharging is not particularly limited. For example, as described below, a branch pipe is attached to the outer peripheral side of a spirally formed pipe (the side corresponding to the outer peripheral side of the spirally formed body), and It is convenient to discharge through

FIG. 1 is a view showing the configuration of a main part of an example of an apparatus (the apparatus of the present invention) for carrying out the method of the present invention. This is an example of a case where the processing is performed from a nearby outer peripheral side. (A) is a longitudinal sectional view, (b) is a plan view.

As shown in the drawing, the apparatus (main part) has a pipe 1 formed in a spiral shape, and one end of the pipe 1 is supplied with an acid solution for supplying an acid solution containing sludge. An outlet 2 is provided near the other end, and an outlet (hereinafter, referred to as a “concentrated sludge liquid outlet”) 3 provided on the outer peripheral side for discharging an acid solution containing concentrated sludge is provided.
And an acid solution outlet 4 for discharging the acid solution from which the acid solution containing the concentrated sludge has been removed. That is, the so-called main pipe that leads to the acid solution discharge port 4,
A branch pipe communicating with the concentrated sludge liquid outlet 3 is attached. If the flow in the spiral becomes turbulent,
Since the effect of concentrating the sludge by the centrifugal force is weakened, the acid solution supply port 2 has a straight pipe portion 5 for preventing the occurrence of turbulence.
Is desirably provided.

In the example shown in FIG. 1, the acid solution supply port 2 is located at the upper part, and the acid solution discharge port 4 and the concentrated sludge liquid discharge port 3
Is formed so as to be located at the lower part, but is not limited to this, and is formed so that the acid solution supply port 2 is located at the lower part, and the acid solution outlet 4 and the concentrated sludge liquid outlet 3 are located at the upper part. And the direction of rotation (winding direction) when forming into a spiral may be either right-handed or left-handed.

Although the concentrated sludge liquid outlet 3 is provided at one place in the illustrated example, it may be provided at a plurality of places. For example, in a spirally formed pipe having three turns, the concentrated sludge liquid discharge port 3 is attached to the outer peripheral side of the end of the spiral of the third turn corresponding to the end (opening) on the discharge side. It may be attached to the outer peripheral side of the end of the spiral of the second winding. An acid solution containing sludge having a higher specific gravity can be extracted from a discharge port attached to the outer peripheral side of the end of the spiral of the second turn.

The size of the spirally formed pipe, that is, the size of the spirally shaped body is not particularly limited, but the maximum radius is 100 times or less the diameter of the pipe constituting the spirally shaped body. It is desirable to do. on the other hand,
There is no particular limitation on the minimum radius. This is because the smaller the radius, the higher the efficiency of sludge concentration and separation. In the example shown in FIG. 1, the diameter of the spiral shaped body is the same from the upper part to the lower part, but it is not always necessary and may be different. In addition, the spiral shaped body is
It is not necessary to have a three-dimensional shape as shown in FIG.
A part or the whole may be formed into a spiral shape in a plane.

There is no particular limitation on the number of turns of the spiral in the spiral shaped body. However, since the efficiency of concentration and separation of the sludge increases as the number of turns increases, it is generally preferable that the number of turns is 3 or more. . On the other hand, if the number of windings is too large, the effect tends to be saturated as shown in the examples described later. Therefore, the upper limit is preferably set to about 5 windings.

The material of the pipe constituting the spiral shaped body is not particularly limited as long as it is not affected by the acid solution to be treated, does not easily wear by sludge, and is easy to process. A pipe made of vinyl chloride or the like satisfies these requirements and is inexpensive, and is therefore preferable.

The cross-sectional shape of the pipe is usually circular as described above, but is not necessarily limited to this.

By using the apparatus of the present invention having the above-mentioned spiral shaped body as a main part, the above-mentioned method of the present invention can be easily carried out.

In the case of the apparatus having the configuration shown in FIG. 1, an acid solution containing sludge sucked by a pump from the lower part of the pickling tank may be supplied to the acid solution supply port 2 and used. The sludge contained in the acid solution supplied from the acid solution supply port 2 and passing through the spirally formed pipe is as follows:
Since the specific gravity is large, a large amount is gathered at the portion near the inner wall on the outer peripheral side of the pipe (the side corresponding to the outer peripheral side of the spiral shaped body)
It is thickened. Therefore, the acid solution discharged from the concentrated sludge liquid discharge port 3 contains concentrated sludge, and the sludge can be concentrated and separated.

Further, foreign matter having a specific gravity smaller than 1 can be separated by using the apparatus of the present invention. At this time, the foreign matter is concentrated and discharged from the acid solution discharge port 4.

The sludge after concentration and separation can be further recovered as a solid by an appropriate method, and can be effectively used as a source of chromium and nickel when melting steel. In addition, the acid solution after separating the sludge may be reused as it is in the pickling tank, or may be reused after being reduced to a sludge concentration that does not cause any problem by an appropriate method depending on the concentration of the sludge. be able to.

According to the method of the present invention described above, the acid solution containing sludge is supplied from one end of the spirally formed pipe and discharged from the other end in the pickling tank by a simple method. The sludge can be concentrated and separated, and the sludge recovery device can be reduced in size to greatly reduce equipment costs. This method can be easily performed by the apparatus of the present invention.

[0033]

EXAMPLE A helical formed body (600 mm in diameter) having the structure shown in FIG. 1 was prepared using a vinyl chloride pipe having an outer diameter of 200 mm. The number of windings was changed in the range of 1 to 10 windings with 5 windings as standard. In each case, a pipe made of vinyl chloride having an outer diameter of 60 mm was attached in a tangential direction on the outer peripheral side of a pipe made of vinyl chloride having an outer diameter of 200 mm, and used as a concentrated sludge liquid outlet. In addition, a straight pipe portion having a length of 1000 mm was attached to the acid solution supply port in order to prevent turbulence in the spiral pipe.

A test was conducted in which an acid solution containing sludge was passed through the helical formed body made of the vinyl chloride pipe, and the degree of sludge thickening was examined.

As the acid solution containing sludge, sludge is collected at the time of sludge removal work in an actual pickling tank, and after washing with water, the solid content of the sludge is 1% by weight.
% Sludge-containing water was used by adding water to adjust the water content.

The flow rate of the sludge-containing water was changed to a range of 2000 l / min based on 1000 l / min.

The test results are shown in FIG. 2 and FIG. FIG. 2 shows the effect of the flow rate of the sludge-containing water flowing through the pipe, and FIG. 3 shows the effect of the number of turns of the vinyl chloride pipe. The evaluation of the sludge thickening is performed by filtering the sludge thickened liquid discharged from the concentrated sludge liquid outlet, measuring the weight of the obtained sludge after drying, and obtaining the solid content (% by weight) of the sludge. It was done by doing.

As shown in FIG. 2, the sludge concentration increased as the flow rate increased, and the concentration efficiency increased. Also,
As shown in FIG. 3, the enrichment efficiency increased as the number of turns of the spiral shaped article increased. Moreover, within the range of the above test, the sludge concentration exceeded 2% by weight under any of the conditions, and it was found that the sludge concentration could be doubled or more.

[0039]

According to the method of the present invention, an acid solution containing sludge is supplied from one end of a spirally formed pipe and discharged from the other end by a simple method. Can be concentrated and separated. As a result, the size of the sludge collection device can be reduced, and the equipment cost can be significantly reduced. This method can be easily performed by the apparatus of the present invention.

[Brief description of the drawings]

FIG. 1 is a view showing a configuration of a main part of an example of an apparatus for carrying out a method of the present invention, wherein (a) is a longitudinal sectional view and (b) is a plan view.

FIG. 2 is a diagram showing the effect of the flow rate of sludge-containing water sent through a pipe on the concentration of sludge, as a result of an example.

FIG. 3 is a graph showing the effect of the number of pipe turns on sludge concentration in the results of the example.

[Explanation of symbols]

 1: spirally formed pipe 2: acid solution supply port 3: concentrated sludge liquid discharge port 4: acid solution discharge port 5: straight pipe portion

Claims (2)

[Claims] 1. An acid solution containing sludge is supplied from an acid solution supply port provided at one end of a spirally formed pipe, and the acid solution is discharged from an acid solution discharge port at the other end. The concentrated sludge in the pickling liquid by discharging the concentrated sludge from a concentrated sludge liquid outlet provided on the outer peripheral side of the spiral shaped body, and discharging the acid solution. A sludge concentration and separation method, comprising discharging an acid solution after the acid solution containing the concentrated sludge is removed from an outlet. 2. An apparatus for carrying out the method according to claim 1, wherein an acid solution supply port for supplying an acid solution containing sludge to one end of a spirally formed pipe is provided. A concentrated sludge liquid outlet for discharging the acid solution containing the concentrated sludge on the outer peripheral side of the spiral shaped body, the acid solution after the acid solution containing the concentrated sludge is removed at the other end of the pipe. A sludge concentration / separation device, comprising an acid solution discharge port for discharging water.