RS59335B1 - Methods for production and use of highly selective adsorbent for simultaneous removal of amine derivative of toluil triazole and sulfur compounds corrosive to silver from mineral transformer oils - Google Patents

Abstract

A process for obtaining a highly selective and efficient adsorbent for the simultaneous removal of sulfur compounds corrosive to silver and the amine derivative toluene triazole from mineral insulating oils consists of obtaining an adsorbent by applying silver ions and ammonium ions to annealed silica, which is then used in silica. steel, by flowing mineral insulating oil through a column filled with adsorbent at a temperature of 50 ° C to 78 ° C, with a flow rate of 1000 to 2000 liters. per hour, and in the case of removal of higher concentrations of sulfur compounds, the process is performed in a narrower temperature range from 68 ° C to 78 ° C. This process effectively removes osmotic sulfur molecules, disulfides and the amine derivative toluene triazole from mineral transformer oils in a wide range of concentrations, including ranges of high concentrations of these molecules and compounds, and thus solves the problem of corrosivity of mineral insulating oils to silver.

Description

Field of technology to which the invention relates

The invention belongs to the field of chemistry in general, namely the subfield of petroleum, petroleum products and petroleum derivatives processing processes (S10) and relates to a process for obtaining an adsorbent for purifying mineral insulating oils used in transformers to remove the corrosiveness of the oil towards silver and to remove the amine derivative toluyl triazole from the oil. According to the International Patent Classification (IPC), the designation is: C10G 53/04.

Technical problem

The invention solves the problem of the corrosivity of mineral insulating oils towards silver while simultaneously removing the amine derivative toluyltriazole from used mineral insulating oils, using a highly selective adsorbent obtained in a special process. Silver, along with copper and iron, is a structural metal of power transformers, and the corrosivity of mineral insulating oils towards silver has become a major problem in the power industry due to the large number of transformer breakdowns caused by this problem.

Corrosion of oils towards silver is most often a consequence of the application of regeneration processes for used mineral insulating oils with adsorbents based on alumina and aluminosilicates ("Bauxite clay", Fuller's earth") in on-line systems when performing the process of reactivating the adsorbent in a high-temperature combustion process that is carried out for its reuse. After this process, the oils become corrosive towards silver, and the octaatomic molecule S8 has been detected as the cause of this phenomenon, as a by-product of high-temperature catalytic cracking of the oil. In addition to the S8 molecule, other sulfur compounds, disulfides and mercaptans can also cause oil corrosiveness towards silver, which is determined by the silver strip corrosion test according to the ASTM D 1275-15 standard.

In practice, it has been shown that the amine derivative of toluyl triazole, which is functionally an oil-soluble metal passivator, does not passivate silver and thus does not solve the problem of silver corrosion, unlike copper where the same compound is used as an effective metal passivator. Treatment methods for oils corrosive to silver using alumino-silicate-based adsorbents are of low efficiency.

This invention solves the problem of the corrosivity of mineral transformer oils towards silver, by simultaneously removing reactive sulfur compounds, the eight-atom sulfur molecule (S8) and disulfide and the amine derivative toluyl triazole, by using a highly selective adsorbent in the oil treatment process by the adsorption-percolation process in a column, which is synthesized in a special process of applying metal ions and inorganic bases to neutralize the acidic by-products of the chemisorption of sulfur compounds. The use of a highly selective adsorbent for sulfur and disulfides in the purification of mineral transformer oils by the adsorption process enables an effective solution to the problem of oil corrosivity towards silver, by removing S8 molecules present in concentrations up to 50 mg/kg, disulfides in concentrations up to 200 mg/kg and simultaneously removing the amine derivative toluyltriazole from the oil as an ineffective silver passivator in concentrations up to 200 mg/kg.

State of the art

Adsorption processes are used in the power industry for purification, i.e. removal of undesirable impurities and contaminants from mineral insulating oils, in order to obtain insulating oils of high stability for use in electrical equipment. The corrosiveness of oils towards construction materials is a very serious problem that can cause transformer failures, due to the deposition of electrically conductive metal sulfides (copper and silver).

Processes and plants for removing the corrosiveness of mineral insulating oils towards silver using adsorbents based on alumina and aluminosilicates (Bauxite, Fuller’s earth) are applied, but their efficiency is low, which means that the removal of reactive components towards silver is sometimes not feasible or possible with very long treatment times (AVV experiences) in a limited range of low concentrations of reactive components. Often the reactive component is an octaatomic molecule of sulfur (S8), with typical concentrations of 6 to 10 mg/kg and sometimes 10 to 15 mg/kg. Cases of completely ineffective use of adsorbents of this type have also been reported, such as the experience of “National Grid”, G. Wilson and M. Dahlund, ABB (paper “Understanding the Presence of Corrosive Sulfur in Previously Non-Corrosive Oils Following Regeneration”, 77th Annual International Double Client Conference, 2010) and published in CIGRE TB 625: “Sorper Sulphide Long-term Mitigation and Risk Assessment”, July 2015, where treatment with over 40 oil passes through the adsorbent without results is reported, where the S8 molecule was not removed, and the corrosivity of the oil towards silver remained positive. The application of these processes is carried out in an on-line mode, while the transformer is in operation, at the operating temperatures of the transformer, by continuous oil circulation between the oil treatment machine and the transformer, which further extends the treatment time because the treated oil is constantly mixed with a large amount of untreated oil. One of the reasons for the low efficiency of the adsorbent is the low selectivity of the adsorbent based on aluminum oxide and/or aluminosilicates towards components reactive towards silver and the competitive adsorption of other polar oil degradation products. Existing processes and adsorbents are of limited efficiency in solving the problem of corrosiveness of mineral insulating oils towards silver, primarily for the removal of the osmoatomic sulfur molecule (S8) and are completely ineffective for the removal of high concentrations of the osmoatomic sulfur molecule (S8).

Exposition of the essence of the invention

The process for obtaining a highly selective adsorbent for the simultaneous removal of oil corrosivity towards silver and the amine derivative toluyl triazole from mineral transformer oils due to the presence of elemental sulfur and disulfide in the oil in a wide concentration range and the use of the synthesized adsorbent in the column consists of two technological units.

The first technological unit represents a process for obtaining a highly selective adsorbent based on silicon oxide with incorporated silver and ammonium ions and consists of three phases:

1. heating (annealing) of the adsorbent

2. application of silver ions to the adsorbent with an aqueous solution of silver nitrate for the chemisorption of sulfur compounds corrosive to silver and

3. application of ammonium hydroxide base in the form of an aqueous solution to the adsorbent in order to neutralize acidic by-products after chemisorption of sulfur compounds on the adsorbent.

The key part of the process is the second and third phases of the first technological unit, because the application of the above components results in an adsorbent with high selectivity and efficiency for removing the corrosiveness of oil towards silver.

The second technological unit consists of using the obtained highly selective adsorbent with incorporated silver ions and ammonium ions for the simultaneous removal of the amine derivative toluyl triazole and reactive sulfur compounds, corrosive to silver, and obtaining purified mineral insulating oil with good characteristics for further use. The process is carried out by flowing the oil through a stainless steel column at a flow rate of 1000 to 2000 liters/hour under pressure, with a packed bed of adsorbent at a certain mass ratio of adsorbent to oil, from 2% to 10% and at operating temperatures from 50°С to 78°С. In the case of removing high concentrations of reactive sulfur compounds (up to 50 mg/kg S8, up to 200 mg/kg dibenzyl disulfide) and 200 mg/kg of the amine derivative toluyl triazole, the treatment is carried out in a narrower temperature range from 68 to 78°C and possibly in a two-stage process, i.e. with two portions of fresh adsorbent in the total amount relative to the oil, maximum up to 10% by weight. The efficiency of this process compared to existing processes is reflected in the binding of silver ions to the adsorbent that has functional acid centers - Si-O-H-, which in a chemical reaction with reactive compounds and sulfur molecules perform their efficient removal from the oil, and the ammonium ion performs effective neutralization of acidic by-products of chemisorption of sulfur compounds on the adsorbent. Compared to existing processes, this process is more efficient, removing corrosive sulfur compounds, elemental sulfur at high concentrations of up to 50 mg/kg S8, disulfides at concentrations of up to 200 mg/kg and the amine derivative of toluyl triazole at concentrations of up to 200 mg/kg, as determined by oil testing according to methods IEC 62697 part 1 and part 2 (for determining the concentration of the octoatomic sulfur molecule and dibenzyl disulfide), ASTM D 1275-15 (for determining the corrosivity of oil to silver) and IEC 60666 (for determining the concentration of the amine derivative of toluyl triazole).

The amine derivative of toluyl triazole is a mixture of two isomers: N,N-bis(2-ethylhexyl)-4-methyl-1 H-benzotriazole-1 -methylamine and N,N-bis(2-ethylhexyl)-5 -methyl-1 H-benzotriazole-1-methylamine, which most often cannot be separated under the test conditions of the above standard method.

Brief description of the draft images

Figure 1. - shows the change in the concentration of the osmoatomic sulfur molecule with the number of oil passes through a column packed with a highly selective adsorbent in the treatment of oil with typical concentrations of S8, Example 1

Figure 2. - shows the change in the concentration of the amine derivative toluyl triazole with the number of oil passes through a column packed with a highly selective adsorbent in the treatment of oil with typical concentrations of ATTA, Example 1

Figure 3. - shows the appearance of a silver plate after the oil corrosion test using the silver strip method according to ASTM D 1275-15 before and after treatment of oil with typical S8 concentrations by passing it through a column packed with a highly selective adsorbent, Example 1

Figure 4. - shows the change in the concentration of the osmoatomic sulfur molecule with the number of oil passes through a column packed with silica without incorporated silver ions and ammonium ions in the treatment of oil with typical concentrations of S8, Example 1

Figure 5. - shows the change in the concentration of the amine derivative toluyl triazole with the number of passes through a column packed with silica without incorporated silver ions and ammonium ions in the treatment of oil with typical concentrations of ATTA, Example 1

Figure 6. - shows the appearance of a silver plate after an oil corrosion test - silver strip method according to ASTM D 1275-15 before and after treatment of oil with typical S8 concentrations by passing through a column packed with silica without incorporated silver ions and ammonium ions, Example 1

Figure 7. - shows the design of a stainless steel column with a height (L)/diameter (D) ratio of 2.3 to 3 packed with a highly selective adsorbent.

Detailed description of the invention

The process for obtaining a highly selective adsorbent used in a stainless steel column for the treatment of mineral insulating oils, corrosive to silver, and the simultaneous removal of the amine derivative toluyl triazole consists of two technological units.

I. In the first technological unit there are three phases:

• First stage - annealing of the adsorbent

• Second stage - application of silver ions

• Third stage - applying ammonia

First stage - Annealing the adsorbent

The adsorbent based on silicon oxide (94-98%), with a granulation of 200 μm to 1200 μm, is heated at a temperature of 150°C for 18-24 hours at atmospheric pressure to remove adsorbed moisture.

Second stage — Activation of the adsorbent by applying Silver ions

The prepared, calcined silica is treated with 4-10% by weight of silver nitrate relative to the mass of the adsorbent, by applying an aqueous solution of silver nitrate to the adsorbent. Then, the water is gradually evaporated from the adsorbent in the following way:

• Heating at a temperature of 30°C and a pressure of 40 - 45 mBar for 2 hours • Heating at a temperature of 40°C and a pressure of 70-75 mBar for 2 hours • Heating at a temperature of 50°C and a pressure of 120 - 130 mBar for 2 hours, followed by annealing at a temperature of 120°C to 130°C and atmospheric pressure for 18 to 24 hours.

Third phase - Neutralization of acidic by-products

The adsorbent silicon dioxide with incorporated silver ions, with the chemical composition: Si (30 - 40%, 20 - 33 at. %), O (60 - 65 %, 74 - 80 at. %), Ag (3 - 6 %, 0.50 - 1.15 at. %), Sa (0.25 - 0.80 %, 0.10 - 0.40 at. %), is treated with an aqueous solution of ammonia, with a concentration of 5% to 10% relative to the mass of the adsorbent, depending on the concentration of corrosive compounds to be removed and acidic by-products. Then, gradual evaporation of water at atmospheric pressure is carried out, for 5 hours, from 30°C to 120°C with a temperature increase of 0.3°C per minute. In the second step, the adsorbent is additionally calcined at a temperature of 125°C to 130°C for 18 to 24 hours.

II. In the second technological unit, oil treatment is carried out by the percolation process, by passing oil under pressure, at an operating temperature of 50 to 78°C, with a flow rate of 1000 to 1800 liters per hour, through a stainless steel column with a height/diameter ratio of 2.3 to 3 and filled with a highly selective adsorbent, whereby chemisorption of silver-corrosive compounds and the amine derivative of toluyl triazole from the oil is carried out on the highly selective adsorbent. A narrower temperature range of 68 to 78°C is used to remove high concentrations of silver-corrosive sulfur compounds and the amine derivative of toluyl triazole.

A highly selective adsorbent consisting of silica with incorporated silver ions and ammonium ions has industrial application for the purification of mineral insulating oils used in power transformers, in order to remove undesirable compounds that cause corrosion of silver as one of the structural metals of power transformers. Additionally, the amine derivative toluyl triazole is removed from the oil, which is added as a metal passivator via an oil solution to the transformer, but has proven in practice to be ineffective for passivation of silver, and it can be removed with the oils. Using the obtained highly selective adsorbent, it is possible to effectively remove compounds corrosive to silver from oil, in high concentrations of up to 50 mg/kg of the eight-atom sulfur molecule (S8), dibenzyl disulfide up to 200 mg/kg and the amine derivative toluyl triazole up to 200 mg/kg.

By applying this process, in addition to eliminating corrosivity towards silver, the insulating characteristics of the oil are obtained: dielectric loss factor, oil-water interfacial tension, acid number, satisfactory for further application in power transformers.

Example 1: Treatment of oil with typical concentrations of elemental sulfur and the amine derivative toluyltriazole

The treatment of oil containing 14 mg/kg of the eight-atom sulfur molecule S8 and 50 mg/kg of the amine derivative toluyl triazole was carried out at a temperature of 50-70°C, in a stainless steel column filled with a highly selective adsorbent of the chemical composition: Si (30 - 40%, 20 - 33 at. %), O (60 - 65 %, 74 - 80 at. %), Ag (3 - 6 %, 0.50 - 1.15 at. %), Sa (0.25 - 0.80 %, 0.10 - 0.40 at. %), with an oil flow of 1800 liters per hour at a mass fraction of the highly selective adsorbent of 2.8% relative to the mass of the oil.

Tables l.A. and 1.B. show the results of oil treatment with typical concentrations of the eight-atom sulfur molecule and the amine derivative toluyl triazole, using a highly selective adsorbent with incorporated silver ions and ammonium ions, while Tables 1.C. and 1.D. show the results of oil treatment with typical concentrations of the eight-atom sulfur molecule and the amine derivative toluyl triazole using calcined silica of the chemical composition: Oxygen - O (60-65%, 70-74% at.) and silicon Si (30-35%, 20-24% at.).

Legend: DBDS - dibenzyl disulfide

tg δ - dielectric loss factor of oil σ - oil-water interfacial tension Nb - oil acid number

TTAA - amine derivative of toluyl triazole n.d. - not detected

Legend: S8- eight-atom sulfur molecule DBDS - dibenzyl disulfide

tg δ - dielectric loss factor of oil σ - oil-water interfacial tension Nb - oil acid number

TTAA - amine derivative of toluyl triazole n.d. - not detected

Example: 2 - Treatment of oil with high concentrations of the osmolar sulfur molecule, dibenzyl disulfide, and the amine derivative toluyltriazole

The treatment of mineral insulating oils containing high concentrations of sulfur compounds corrosive to silver, namely the octaatomic sulfur molecule (S8) and dibenzyl disulfide (DBDS) and a high concentration of the amine derivative touyl triazole consists of two experiments:

• Experiment A: mineral insulating oil containing the octaatomic sulfur molecule S8 in a high concentration of up to 50 mg/kg and the amine derivative toluyl triazole of 100 mg/kg was treated in a column packed with a highly selective adsorbent of the chemical composition: Si (30 - 45%, 20- 33 at. %), O (60 -70 %, 74 - 80 at. %), Ag (3 - 6 %, 0.50 - 1.15 at. %), Sa (0.25 - 0.80 %, 0.10 - 0.40 at. %), with an oil flow of 1800 lit. per hour, a mass ratio of adsorbent to oil of 8%, at a temperature of 68 to 78°C (results shown in Table 2A).

• Experiment B: mineral insulating oil containing dibenzyl disulfide in a concentration of up to 200 mg/kg and the amine derivative of toluyl triazole of 100 mg/kg was treated in a column packed with a highly selective adsorbent of the chemical composition: Si (30 - 45%, 20 - 33 at. %), O (60 - 70 %, 74 - 80 at. %), Ag (3 - 6 %, 0.50 - 1.15 at. %), Sa (0.25 - 0.80 %, 0.10 - 0.40 at. %), with an oil flow of 1800 lit. per hour, at a mass ratio of adsorbent to oil of 8%, at a temperature of 68-78°С (results shown in Table 2B).

Legend: S8- eight-atom sulfur molecule DBDS - dibenzyl disulfide

TTAA - amine derivative of toluyl triazole n.d. - not detected

Claims (5)

Patent claims 1. Adsorbents containing silicon oxides and used for the purification of mineral insulating oils, characterized in that the highly selective adsorbent with a particle size of 200 to 1200 μm for the removal of eight-atom sulfur molecules, dibenzyl disulfide and the amine derivative toluyl triazole consists of silicon, Si of 30 - 40%., oxygen, O of 60- 65% and calcium of 0.25 - 0.8% with incorporated silver ions of 3% -6% wt. in ionic and elemental form, bound to acid centers Si-O-H and ammonium hydroxide in a concentration of 5-10% relative to the mass of the adsorbent. 2. A method for preparing and obtaining an adsorbent according to claim 1, characterized in that the first phase of the process consists of annealing silicon dioxide of the composition, Si of 30 - 40%, oxygen, O of 60-65% and calcium of 0.25 - 0.8%, at a temperature of 150°C, for 18-24 hours and atmospheric pressure, followed by a second phase consisting of depositing silver ions in an amount of 4 to 6% by weight. from an aqueous solution of silver nitrate with evaporation of water by heating at a temperature of 30°C and a pressure of 40 mBar for 2 hours, then at 40°C and a pressure of 74 mBar for the next 2 hours and finally at 50°C and a pressure of 120 - 130 mBar for the last 2 hours, with final annealing at a temperature of 120°C to 130°C and atmospheric pressure for 18-24 hours and completed with a third phase consisting of applying an aqueous solution of ammonium hydroxide in a concentration of 5 to 10% by weight. relative to the mass of the adsorbent, followed by gradual evaporation of water at atmospheric pressure for 5 hours, from 30°C to 120°C at a rate of 0.3°C per minute and additional annealing of the adsorbent for 18 to 24 hours at atmospheric pressure and a temperature of 125°C to 130°C. 3. A method for removing sulfur compounds corrosive to silver and the amine derivative of toluyl triazole from mineral insulating oils using an adsorbent according to claim 1, characterized in that the removal of sulfur compounds corrosive to silver means the removal of the osmoatomic sulfur molecule or dibenzyl disulfide or other sulfur compounds corrosive to silver and the removal of the amine derivative of toluyl triazole and is carried out by circulating the oil through a stainless steel column filled with adsorbent with a height to diameter ratio of the column from 2.3 to 3 at a temperature of 50 to 78°C at a flow rate of 1000 to 2000 lit./h and an initial concentration of the osmoatomic sulfur molecule up to 15 mg/kg, dibenzyl disulfide up to 200 mg/kg and the amine derivative of toluyl triazole up to 100 mg/kg. 4. A method for removing high concentrations of sulfur compounds corrosive to silver and the amine derivative of toluyl triazole from mineral insulating oils using an adsorbent according to claim 1, characterized in that the removal of sulfur compounds corrosive to silver means the removal of the osmoatomic sulfur molecule or dibenzyl disulfide or other sulfur compounds corrosive to silver and the removal of the amine derivative of toluyl triazole and is carried out by circulating the oil through a stainless steel column filled with adsorbent with a height to diameter ratio of the column of 2.3 to 3 at a temperature of 68 to 78°C at a flow rate of 1000 to 2000 lit./h and an initial concentration of the osmoatomic sulfur molecule of up to 50 mg/kg, dibenzyl disulfide of up to 200 mg/kg and the amine derivative of toluyl triazole up to 200 mg/kg. 5. A process according to claim 3 and 4 for removing sulfur compounds corrosive to silver and the amine derivative of toluyl triazole from mineral insulating oils using the adsorbent according to claim 1, characterized in that the removal of the osmoatomic sulfur molecules, dibenzyl disulfide, and the amine derivative toluyl triazole are produced simultaneously.