JPH0751681A - Treatment of silica-containing solution - Google Patents

Abstract

PURPOSE:To rapidly treat a silica-contg. soln. such as geothermal hot water with a simple apparatus at a low cost while preventing the precipitation of silica scale and to recover high purity silica. CONSTITUTION:An org. capturing agent and a polymer flocculant are added to a silica-contg. soln. to flocculate and precipitate the silica and this precipitated silica is recovered or removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a silica-containing solution, and more particularly to a method for removing or recovering silica from a silica-containing solution such as geothermal hot water or hot spring water.

[0002]

2. Description of the Related Art Geothermal power generation has been conventionally developed, but in geothermal power plants, a large amount of hot water is often ejected in addition to steam used for power generation. Since the geothermal reservoir in the deep underground has high temperature and high pressure, silica is not present in the geothermal water.
It is generally dissolved in about 400 to 1200 ppm.
When jetted to the ground, the pressure drops, and the silica becomes supersaturated, and silica scale begins to precipitate.
This scale is a major obstacle for geothermal power generation because it clogs the pipeline for transferring hot water and the return well for returning hot water to the deep underground, so effective and quick scale prevention is possible. Law is required. Further, in the case of recovering silica, the treatment of a large amount of silica sludge becomes a problem. Therefore, since this silica sludge is regarded as a silica resource and has a large specific surface area and a large pore volume, it is important to utilize it.

Conventionally proposed or practiced methods for treating silica-containing solutions such as geothermal hot water are (1) spontaneous deposition method, (2) addition of secondary components such as calcium and magnesium, and reaction formation Secondary component addition method for recovering substances
59-16588, JP-A-59-13919), (3) Aggregation and precipitation method (JP-A-59-86864, JP-A-62-158111), (4) by suspending silica Floating separation method for selective separation ("Examination and utilization technology feasibility study of geothermal water inhibiting components", New Energy Development Organization, 1985), (5) Ultrafiltration membrane method (Japanese Patent Laid-Open No. 63-1495, There are various methods such as JP-A-63-2805).

[0004]

However, each of the above methods has its own problems. That is, the natural deposition method of (1) is a simple method, and it is estimated that the silica to be recovered is also high in purity, but since a precipitation time is long, a large-scale retention tank is required, and hot water after treatment is required. There is a problem that a considerable amount of silica remains inside and the problem of scale precipitation cannot be completely solved. The second component addition method (2) has a drawback that it cannot be used as silica because it is recovered as a compound, and its use is narrow. If the use of the product is established, it can be produced at low cost,
If not established, sludge treatment is the biggest drawback.

Furthermore, in the coagulating sedimentation method (3), when an inorganic scavenger is added, sludge treatment becomes a problem,
Practical application is difficult unless promising applications are established. Also,
Inorganic scavenger such as aluminum compound disclosed in JP-A-59-86864 is used in combination with organic polymer flocculant to precipitate as hydroxide sludge, and hydroxide is dissolved with acid after recovery. However, the method of recovering silica has the drawbacks that the cost of the acid is high, impurities are left over by a single acid treatment, and the purity does not increase unless this step is repeated several times. Further, the polyethyleneimine disclosed in JP-A-62-158111 has a slow floc sedimentation rate, weak floc aggregation degree, and efficient silica recovery is difficult in addition to the agent of the present invention. The chemical cost is about 5 times.

In the flotation method of (4), although the purity of the recovered silica is high, a large amount of bubbles are generated in the flotation and sorting process, a large amount of chemicals is required for the treatment, and a large amount of it is required. Since a large number of devices are required to process the hot water of
There are drawbacks such as the need for a vast site and increased costs. Further, the ultrafiltration membrane method of (5) requires a large number of ultrafiltration membranes when processing a large amount of geothermal hot water,
High cost. Furthermore, it takes time to process, and there is a problem that scales adhere to the filtration membrane.

As described above, the conventional techniques for removing and recovering silica from a silica-containing solution such as geothermal hot water require large-scale equipment and materials, and silica scale is generated in the treatment process. There are various problems such as precipitation and clogging, recovery of high-purity silica, complicated process and high cost. The present invention has been made in view of the above problems,
Its purpose is to be able to process silica-containing solutions such as geothermal hot water quickly and at low cost using a simple device, prevent precipitation of silica scale, and recover highly pure silica. It is to provide a processing method.

[0008]

Means and Actions for Solving the Problems The gist of the present invention for achieving the above-mentioned objects is to add an organic scavenger and a polymer flocculant to a silica-containing solution to cause the silica to flocculate and precipitate. A method for treating a silica-containing solution, which comprises recovering or removing silica.

As a means for achieving the above object, the present invention is characterized in that a specific organic scavenger and a polymer flocculant are combined and added to a silica-containing solution in a fixed amount range. It is a thing. The organic scavenger used in the present invention is a long-chain alkylamine-based surfactant, which is widely commercially available, treated with acetic acid, in which the alkyl composition is C14: C16: C18 = 4: 30. Most preferred are those with: 66. And, as the addition amount thereof, 20 to 150 ppm is suitable, and if an amount exceeding this range is added, white turbidity remains in the supernatant of the solution and the silica collecting ability is lowered.

Next, as the polymer coagulant used in the present invention, it is desirable to use an anionic polymer coagulant in which a part or all of polyacrylamide is replaced with sodium acrylate. And the addition amount is 0.5-5
ppm is preferred. This is because if the amount added is less than this, the flocculation property of silica becomes weak and the sedimentation rate becomes slower.If the amount added is more than this, silica flocs are formed but many flocs that do not settle and float. Because it will be.

If a specific flocculant and a polymer flocculant as described above are combined and added to a silica-containing solution in a certain amount and treated, a silica floc is rapidly formed, so that it is precipitated. Separation and recovery can be performed efficiently. The separated and recovered silica sludge is washed with water, dried, and then heated at a temperature of 600 ° C. or higher for about 30 minutes to thermally decompose the attached organic collector and polymer coagulant. Can be removed by high-purity silica having a purity of 97 to 98%.

Next, the result of processing according to the present invention will be shown as an example. 48 ° C. containing 629 ppm silica
Beef tallow propylene, which is one of the organic scavengers satisfying the above conditions, was added to the geothermal hot water in 1) in varying amounts, and 1 ppm of the polymer flocculant satisfying the above conditions was further added. As a result of the treatment, as shown in Table 1, 4
It can be seen that when 0 ppm is added, a high removal capacity of 98% is exhibited. Further, as shown in Table 2, it can be seen that a small amount of the added drug is sufficient as compared with polyethyleneimine which has been conventionally said to exhibit a high silica-collecting ability. Further, in the both cases, the cost of the present invention is about ⅕ as low as the comparison of the equivalent drug costs.

[0013]

【Example】

Example 1 Beef tallow, which is one of the organic scavengers satisfying the above conditions, was prepared by placing geothermal hot water having a silica concentration of 629 ppm and a temperature of 48 ° C. in a precipitation tank made of acrylic resin having a radius of 30 cm and a volume of 40,000 cm ^3. Propylene was added in an amount varying from 10 to 200 ppm, and 1 ppm of a polymer flocculant satisfying the above conditions was added and treated. As a result, as shown in Table 1, the amount of the organic scavenger added was 40 ppm. In case of 98%, 50p
It was possible to remove 100% of the silica at pm. When treated with polyethyleneimine under the same conditions, it showed a silica removal ability of 64% at 40 ppm addition and 94% at 50 ppm addition.

EXAMPLE 2 Geothermal hot water having a silica concentration of 629 ppm and a temperature of 48 ° C. was placed in a precipitation tank made of an acrylic resin having a radius of 30 cm and a volume of 40,000 cm ³ , and one of the organic scavengers satisfying the above-mentioned conditions. As a result of adding 50 ppm of beef tallow propylene, and further adding a polymer flocculant having the above-mentioned conditions in various amounts, and precipitating it in about 30 seconds in the addition amount range of 0.5 to 5 ppm. However, if the amount of addition is less than this amount, the flocculation property of silica is weak and the sedimentation speed becomes slow. Therefore, it took 1 minute or more to complete sedimentation. When the amount added was more than this, silica flocs were formed, but many flocs floated without settling.

Example 3 Geothermal hot water having a silica concentration of 629 ppm and a temperature of 48 ° C. was placed in a precipitation tank made of an acrylic resin having a radius of 30 cm and a volume of 40,000 cm ³ , and one of the organic scavengers satisfying the above conditions. As a result of adding 50 ppm of beef tallow propylene and 2.5 ppm of a polymer flocculant satisfying the above conditions, the sedimentation was completed in 35 seconds. Then, the precipitated silica flocs were collected, dried, and further heated at 600 ° C. for 30 minutes, and as a result, silica having a purity of 98% was obtained.

[0016]

[Table 1] Comparison of collection power with changes in the amount of organic collection agent added

[0017]

[Table 2] Comparison of collecting power between beef tallow propylene and polyethyleneimine

[0018]

INDUSTRIAL APPLICABILITY The present invention combines a silica-containing solution such as geothermal hot water with a specific organic scavenger and a polymer flocculant,
A method for treating a silica-containing solution, which comprises adding minute amounts of silica to remove it by coagulating and precipitating, or recovering the precipitated silica.
Silica in a silica-containing solution such as geothermal hot water can be removed or recovered rapidly and at low cost by a relatively simple device and process. And since the efficiency of removal and recovery is high and it is possible to prevent the adhesion of lyca scale,
It is possible to greatly improve the obstacles due to the deposition of silica scale on the pipes and plants in geothermal power plants, etc., and extend the life of the plant. In addition, the recovered silica is 98
%, High-purity silica can be obtained, so that it is expected to be effectively used as a silica resource.

Claims (6)

[Claims] 1. A method for treating a silica-containing solution, which comprises adding an organic scavenger and a polymer coagulant to the silica-containing solution to coagulate and precipitate the silica, and recover the precipitated silica. 2. A method for treating a silica-containing solution, which comprises adding an organic scavenger and a polymer flocculant to the silica-containing solution to cause the silica to flocculate and precipitate, and to remove the silica. 3. The organic scavenger is a long-chain alkylamine-based surfactant treated with acetic acid, and the polymer flocculant is an anionic scavenger in which a part or all of polyacrylamide is replaced with sodium acrylate. The method for treating a silica-containing solution according to claim 1, which is the polymer coagulant according to claim 1. 4. An anionic polymer flocculant in which 20 to 150 ppm of an organic scavenger obtained by treating a long-chain alkylamine-based surfactant with acetic acid and a part or all of polyacrylamide are replaced with sodium acrylate. 0.5-5p
The method for treating a silica-containing solution according to claim 1 or 2, characterized in that it is added in a proportion of pm. 5. A long-chain alkylamine-based surfactant treated with acetic acid has an alkyl composition of C14: C1.
The method for treating a silica-containing solution according to claim 3, wherein 6: C18 = 4: 30: 66. 6. The method for treating a silica-containing solution according to claim 1, 2, 3, 4, or 5, wherein the silica-containing solution is geothermal hot water containing silica.