JPS6094198A - Treatment of geothermal hot water - Google Patents

Abstract

PURPOSE:To reduce Al and Fe, etc. contained in the geothermal hot water and to prevent formation of scale effectively by adding liquid contg. silica gel and/ or colloidal siica by adding such liquid to geothermal hot water and by maintaining the temp. and pH at >=40 deg.C and 6-9. CONSTITUTION:A liquid contg. silica and/or colloidal silica is added to geothermal hot water, and the dissolved silica is polymerized to form colloidal solution by maintaining the temp. at >=40 deg.C and the pH at 6-9. Elemental Al, Fe, Ti and Mg coexisting in the geothermal hot water is simultaneously fixed. The silica liquid is alkali silicate soln. or one prepd. by removing alkali from alkali silicate soln. by neutralizing previously with acid or ion exchange resin. Further, the colloidal silica liquid. is any soln. in which presence of polymerized silica is recognized by gel chromatography. Preferred content of total silica after mixing with geothermal hot water is 0.05-5%.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention allows dissolved silica in geothermal hot water to be precipitated as a stable silica colloid, while at the same time coexisting A-6,
This invention relates to a geothermal hot water treatment method for fixing Fa, T1, and Mt elements into silica colloid.

Geothermal energy is utilized by ejecting high-temperature hot water from underground together with steam, separating the steam and hot water, and using the steam for power generation, and using the hot water to generate secondary steam by flash evaporation as needed. It is well known that after the pressure is lowered, the heat is used for heating, etc., and is then returned to hot springs or underground, and is actually practiced in six places.

In this geothermal use, the hot water that erupts dissolves a large amount of silica in rocks depending on the temperature underground, resulting in several hundred ppm of silica.
Contains more than silica.

As the temperature of the hot water after steam separation decreases, the solubility of silica decreases, and a portion of the dissolved silica becomes supersaturated. This supersaturated dissolved silica is unstable and has a strong adhesive force, so it forms schools and precipitates on the wetted parts of equipment. In addition, scale precipitation is caused not only by the temperature drop mentioned above, but also by
Fe, Ti.

This is promoted by elements such as Mt. Such scale precipitation causes serious troubles such as a reduction in the performance of each device and even the inability to use it.

Various methods are being considered to counter this silica problem. For example, there is a method in which lime is added to hot water to produce calcium silicate and precipitated, and a method in which A1 or Fe 2 compound is added as a flocculant to produce colloidal silica. However, these methods may not always be able to sufficiently prevent scale precipitation;
There were problems such as being economically disadvantageous.

In order to solve the above problem, the present inventors have conducted repeated research on the above elements that promote the polymerization and scale precipitation of supersaturated dissolved silica.

As a result, under certain conditions, the addition of the silica solution and/or silica colloid-containing solution causes dissolved silica to polymerize in a short period of time, producing a stable silica colloid that does not precipitate as scale. It was discovered that it can be efficiently immobilized on colloids.

That is, the method for treating geothermal hot water of the present invention involves adding a surface containing silica liquid and/or silica colloid to geothermal hot water at a temperature of 40°C.
As mentioned above, while keeping the pH in the range of 6 to 9 and polymerizing dissolved silica to make it a colloid, A and Fa coexist in the geothermal hot water.

The T1 and Mt elements are immobilized on the χ silica colloid.

The substance that promotes colloid formation is silica liquid and/or silica colloid liquid. More specifically, the silica liquid is
This is an alkali silicate solution or an alkali silicate solution that has been previously neutralized with an acid or dealkalized with an ion exchange resin.

Further, the silica colloid liquid may be one in which the presence of polymerized silica is recognized by gel chromatography. Of course, commercially available silica colloid solutions containing silica colloids of 4 mμ or more can also be used.

The total amount of silica in the mixed solution after mixing the above seeds and geothermal hot water is 0.05% (500PPm) to 5%.
It is desirable that it be within the range of %.

In addition, since the silica colloid after polymerization promotion is stable, there are no particular restrictions on the particle size of the silica colloid, but it is not preferable to grow it to a sedimentary gel.

The conditions for fixing the above elements to the silica colloid during the production process of the silica colloid are a temperature of 40° C. or higher and a pH of 6 to 9. When the temperature is less than 40°C, colloid formation is slow and at the same time the deposition of the above elements is also slow. Further, if the pH is less than 6, the above elements will not be deposited on the silica colloid, and if the pH exceeds 9, the silica colloid will dissolve and at the same time the above elements will also dissolve.

In the geothermal hot water, the above-mentioned Al1. Fs, TI and M
In addition to the t element, Na, K, Ll+ ca, F,
C.I.J.

804, B, As, etc. have been confirmed. Although some of the other substances such as Na and Ni were immobilized on the silica colloid under the above conditions, most of them remained on the liquid side and had no selectivity. Especially F, which exists as an anion.
s CIJ s S One B and A8 were selectively present on the liquid side.

On the other hand, since A4 m Fe s T l and Mt have the following properties, they promote silica scale precipitation or are immobilized in silica colloid.

l) The coordination number of oxides and hydroxides is 4, which is the same as that of silica, making it easy to form compounds with silica.◇ 11) Solubility near neutrality is extremely low, making it easy to form nuclei.

iii) Since ions and hydroxides or oxides have a positive charge, they easily combine with negatively charged silica.

1v) Schulty-Hardy's law (the larger the valence of the cation, the higher the coagulation force for the colloid), making it easier to aggregate silica colloids.

According to the present invention, a stable silica colloid is produced by a relatively simple operation, and at the same time A-e and F dissolved in the liquid are produced.
e, Ti and M? Since the elements are reduced, scale prevention can be effectively achieved. Furthermore, it can be said that the present invention effectively utilizes the above-mentioned elements, which originally promoted scale precipitation, for stable silica colloid production. The silica colloid produced by the present invention is stable and does not dissolve again, so it can be returned to the reinjection well as it is, but if necessary, it can be separated and recovered using an ultra membrane, reverse osmosis membrane, etc. .

Furthermore, the separated silica colloid can be used as a seed.

Although A-g, Fe, Ti, and Ml are elements confirmed in geothermal hot water, other elements having properties similar to these elements may also be immobilized in the silica colloid. Many of these elements belong to the following ranges.

1) Elements with an electrostatic valence (value divided by the valence by the coordination number) of 0533 to 0.67 when converted into an oxide 11) Ionization potential (value divided by the ion radius) of 2 to 0.67 Elements in the range 7) The isoelectric points of oxides and hydroxides (the pH value of the water bath solution at which the surface charge becomes zero) are in the range of 4 to 13. Demonstrate specific effects.

Preparation method for hot water simulated coagulation Solution A2: Dissolve sodium silicate 2θ8t with a silica concentration of 24 wt% in 100 KPK of pure water to make diluted sodium silicate with a silica concentration of 0.05 wt%. - IB) diameter 1OCrn filled with 51,
The lysate was passed through a column of length 200 crn at a speed of SV5 and 100 crn of silicic acid solution at 0.05 vrt.
d was prepared. This 0.05 wt% silicic acid solution 100
．． 4 contains 99.5% potassium chloride, 99.5% sodium chloride, 95.0% calcium chloride, 99.5% sodium thiosulfate, 99.5% boric acid, 99.5% sodium arsenite, 5-hydroxide Add sodium etc. to silicic acid solution 1
K 118M Na 752mg Ca 14.6 reports MP 0.44 ■ Layer 1.0 ■ Fe 1O,OQ 'l'i 12.511f/ B 7.1 ~ As 1.62 ■ 8 67.7 reports ( A mock coagulant solution was prepared so as to have a concentration of 1,000 μl.This is hereinafter referred to as solution A.

B liquid silicon dispersion l! 109 Proverbs Na 11]9m5 Ca 32.7g Ml 0.27plexy Binding 0.5doory Fs 25.0 Shouldery T133゜3xy B 23.3xy As 1.631+y 8 536 report C A mock coagulated solution was prepared in the same manner as Solution A except that the concentration was adjusted to 1700*y. This will be referred to as liquid B hereinafter.

Example I To 100 J of Solution A, 18 t of a colloidal solution having a silica concentration of 30 wt % and a silica colloid with a particle size of 119 A was added to make the total silica concentration 554 ppm. p at this time
H was 8.7. Then, while maintaining the temperature at 80°C,
After heating continuously for a minute, this liquid was mixed with a molecular weight cutoff of 6o.
P liquid 9B7 was obtained by ultraf filtration through an ultrafiltration membrane of oo.

Example 2 To liquid B 1001, colloidal liquid 161 having a silica concentration of 30 wt and a particle size of 120 particles was added to make the total silica concentration 548 ppm. p at this time
H was 7.4. Then, while maintaining the temperature at 80°C,
After heating continuously for a minute, this liquid was mixed with a molecular weight cutoff of 60.
The solution was ultrafiltered through a 00 ultramembrane to obtain P solution 99.8 g.

Example 3 Sodium silicate solution 502 with a silica concentration of 24 wt was added to liquid B 100-e to bring the total silica concentration to 620.
It was set as ppm. The pH at this time was 7.9. Next, after heating was continued for 10 minutes while maintaining the temperature at 80° C., this liquid was subjected to ultrafiltration using an ultrafiltration membrane having a molecular weight cut off of 6000 to obtain P liquid 991.

Example 4 Colloidal liquid 1 having a silica colloid with a particle size of 119 people at a silica concentration of 30 wt'Ji for A liquid 1001
8t and 24 wt% silica concentration of sodium silicate 30
t was added to give a total silica concentration of 625 ppm. The pH at this time was 9.0. Next, after heating for 10 minutes while maintaining the temperature at 80°C, this liquid was passed through an ultra membrane with a molecular weight cut off of 6000 for an ultraviolet period to obtain a P liquid of 98. I got it.

Comparative Example I For 100J of liquid A, 0. IN sulfuric acid 60〇 and 30
Particles at wt% silica concentration! 18 tons of colloidal solution containing 119A silica colloid was added to bring the total silica concentration to 55%.
It was set to 0 ppm. The pH at this time was 5.0. Next, after heating continuously for 10 minutes while maintaining the temperature at 80°C, this liquid was ultrafiltered through an ultramembrane with a molecular weight cut off of 6000 I7) to obtain f3 liquid 98! I got it.

Comparative Example 2 Liquid A! Colloidal liquid 1 having a silica colloid with a particle size of 119A at a silica concentration of 3o w*qb for (jO)
82 was added to give a total silica concentration of 554 ppm. The pH at this time was 8.7. Then, it was cooled to 20°C and held for 10 minutes.

This liquid was ultrafiltered using an ultrafiltration membrane of fraction molecule i 6000 to obtain 98 ml of liquid e.

The compositions of the i+j liquids of each of the Examples and Comparative Examples obtained as described above were analyzed to determine the residual rate. The results are shown in the table below.

This shows that the present invention can sufficiently reduce the dissolved silica concentration in the liquid, as well as the amounts of Fe, AA, T, and M#.

The concentrations of various elements were measured according to the following methods: OK, Na: Flame photometric method As, 5 (naso4): Ionometric method Cj = Potentiometric titration method

Claims (1)

[Claims] 1. Add the silica liquid and/or the silica colloid-containing liquid to the geothermal hot water and maintain the temperature at 40°C or higher and the pH in the range of 6 to 9 to polymerize the dissolved silica and make it colloid, while at the same time coexisting in the geothermal hot water. AA, Fe, TI and M
A treatment method for geothermal hot water that is immobilized into t-element silica colloid.