CS223071B1 - A method of preparing an injection system with a controlled gel time - Google Patents

Abstract

The invention describes an injection system with a controllable gelation time. It is based on alkali metal silicates and a regulator consisting of salts of organic or inorganic acids. The system can be applied in the isolation of soils against water seepage, mainly in the construction of waterworks.

Description

The present invention relates to a process for the preparation of an injection system having a broad controllable gel time based on silicone compounds with high technical and economic efficiency.

In order to impregnate the rocks in order to achieve their impermeability to the liquid s-a, they have developed a number of chemical methods. In practice, the process is carried out by injecting successively two solutions into the soil at the desired depth, which in contact form an insoluble substance and this fills the voids. A disadvantage of this method is the formation of clots at the point of solution formation. It is preferable to inject a single solution which, after a period of time, forms a sealing clot, most often gel-like.

Alkali metal silicates, mainly sodium silicate, with different molar ratios of silica: sodium oxide (modulus) are most commonly used as the main gelling agent.

An example of the preparation of a simple composition that cuts at a predetermined time is described in U.S. Pat. According to the example, 40% sodium silicate (modulus = 3.2) was diluted with water to a density of 1171 kg.m ^-3 to give a solution containing 10.1% sodium silicate. This solution was added to a dilute hydrochloric acid solution with vigorous stirring. The concentrated acid (10 parts by volume, 10 to 20 parts by weight) is mixed with 12 to 70 parts by water after adding 10 to 75 parts by volume of dilute water glass (19.2% by weight), starting to gel at 0.5 to 25 parts by volume. hours at 49 ° C.

Gelling can also be influenced by ammonium bicarbonate. The gel is prepared by the tetraethyl silicate Si (C ₂ H _{5) 4} by adding dilute hydrochloric acid. Silicates may also be directly coagulated with weak bases (NH ₄ OIT - ammonium hydroxide, pyridine, piperidine), also with solar and organic acids. Ammonium sulfate is also recommended (U.S. Pat. No. 2,208,766). Also described is the use of adsorption clay insulating solutions, often called celite, dialomite, bentonite, (U.S. Pat. 2,053,562, 2,025,948). For pH stabilization, it is sometimes preferred to use phosphorus pentoxide hydrates (e.g., ΗθΡΡΡΟ, H ₄ P ₂ O ₇ ). These types of acids are used in the presence of limestone, preferably work also in the presence of organic acids and at a pH of from 1 to 3. At that time gel times of 0 to 1 hour are achieved (U.S. Pat. No. 2,281,010).

The disadvantages of these processes are that gels are formed at hardly reproducible boundaries and in most cases there is a high rate of gel formation, which limits the processing of ready-to-use solutions. Typically, these mixtures do not fulfill an important stability condition for the pH holding capacity of the β solution with the permeable soil. Some of the known methods use flammable liquids, for example lower carboxylic acid esters, which is disadvantageous from the fire and safety point of view. Some of the organic impurities used are non-biodegradable in the system and may compromise groundwater quality.

The above drawbacks are overcome by a process for the preparation of an injection system having a controlled gel time based on silica compounds using regulators according to the invention, where an aqueous solution of sodium hexametaphosphate having a concentration of 6 to 12% by weight is added. at least one partial ethanolamine and / or sodium citric acid] at a concentration of 2 to 8 wt. prepared in an aqueous solution in an amount to adjust the reaction of the injection mixture to a pH of 6 to 9 and to this mixture a water glass solution having a density of 1300 to 1400 kg.m ^-3 in an amount of 20 to 32% by weight is added.

Among the main advantages of the process according to the invention is the relatively high accuracy of the setting of the gel time while maintaining good reproductive properties. This advantage also applies to the possibility of setting longer gel times, which allows more efficient application and reduced losses. The prepared system is non-flammable, does not contain toxic additives and the components are well biodegradable, so there is no contamination of soil from the ecological point of view. Winding all the components to be incorporated is readily available economically and commercially.

The following examples illustrate the process according to the invention.

Example 1

To 720 L of an aqueous solution of hexametaphosphate at a concentration of 10 wt. a partial salt of di- and triethanolamine sodium citric acid prepared by dissolving and reacting at normal temperature 6 kg of citric acid with 1.4 kg of a mixture of di- and triethanolamine (1: 1 ratio) and 4 kg of 40% Na is added gradually with vigorous stirring OH in the amount of 74 liters. To this mixture of substances is added under stirring 206 liters of 1350 kg water glass. m ' ³ . The coagulation of this mixture is 120 minutes.

Example 1 a d 2

Procedure as in Example 1, except that 66 L of a partial salt of citric acid adjusted to pH 7 and 250 L of 1350 kg water glass are added to 720 L of hexametaphosphate solution. m ^-3 . The coagulation of this mixture is 240 minutes.

Example 3

Procedure as in Example 1 except that 70 L of a partial salt of citric acid adjusted to pH 8 and 270 L of 1350 kg of water glass are added to 720 L of hexametaphosphate solution.

. rcr ³ . The coagulation of this mixture is 320 minutes.

Claims (1)

SUMMARY OF THE INVENTION A method for preparing an agitating system with adjustable gel-based gelling time using regulators comprising concentrating the aqueous sodium hexametaphosphate solution. 6 to 12 wt. add, under vigorous stirring, an aqueous solution of at least one of the partial ethanolamine and / or sodium salts of citric acid (2 to 8% by weight). in an amount to adjust the reaction of the injection mixture to pH 6-9 and a solution of waterglass of 1300 to 1400 kg is added to the mixture. m-3, in an amount of 20 to 32 wt.