Transformer machinery structure and characteristics

In the 1960s and the 1970s, China produced a total of nearly 10,000 t PCBs, of which 9 000 t were No. 1 PCBs, mainly trichlorbiphenyl, and 1 000 t were No. 2 PCBs, mainly pentachlorobiphenyl. . No. 2 PCB is used as a paint additive and used as an open entry environment. No. 1 PCBs are used for power transformers and capacitors. Most of them are now abandoned. There are many studies on PCBs in soil, water, sediments, and aquatic organisms. It is still difficult to determine the source of contamination of PCBs in the environment. Leakage of PCBs-containing transformer oil is a major source of PCBs in the environment. When domestic scholars analyze the fingerprints of PCBs isomers in environmental samples, they often use the distribution of American products Aroclor1242 as the main production of trichlorobiphenyl in China. Distribution status. Due to the difference in production process, Jiang Ke et al.

In the study of coplanar dioxin-like PCBs in domestic PCBs, it was found that there are still great differences between domestic trichlorobiphenyls and foreign products. In order to study the distribution characteristics of the domestically produced PCBs, the environmental toxicity, and the differences between them and foreign products, and provide the most basic basis for assessing the environmental toxicity of residual PCBs in China's abandoned transformers/power capacitors, the authors studied the No. 1 transformer oil made in China. Distribution Characteristics of 84 Kinds of PCBs in PCB.

1 Experimental section 1.1 Samples Domestically produced YL/CL/RL series power capacitors and transformer waste oil samples (including domestically produced No. 1 PCBs) were provided by the Shenyang Institute of Environmental Science.

1.2 Reagents and instruments n-hexane, methylene chloride, iso-octane (agrochemical grade, DIKMA); acetone (chromatographic purity, Tianjin Guangfu Chemical Factory); dimethyl sulfoxide (DMSO, 99.7%, produced by Acros organics); Concentrated sulfuric acid (Excellent Grade Pure Chemical Plant). Silica gel (100200 mesh, Merk) was activated by heating at 150°C for 16 h and inactivated by 3.3% water. Anhydrous sodium sulfate (analytically pure, Beijing Chemical Plant) was calcined in a 600°C muffle furnace for 5 hours to remove organic matter therefrom. Secondary deionized water (18.2 M?) was processed by Milli-Q Plus ultrapure water treatment system.

The PCB standards were provided by Accustar, USA. The mixed standard samples consisted of 84 PCB congeners, including 10 Cl 2-PCBs (named according to IUPAC 4-, 5-, 6-, 7-, 8-, 9-, respectively). 10-, 12-, 13-, 15-CB) Cl 3-PCBs of 11 species (16-, 17-, 18-, 19-, 22-, 26-, 28-, 31-, 32-, 33-, 37-CB), Cl 4-PCBs 19 species (41-, 42-, 44-, 45-, 47-, 48-, 49-, 52-, 53-, 56-, 60-, 64-, 66- ,70-,71-,74-,76-,77-,81-CB),Cl 5-PCBs, 19 species (83-,84-,85-,87-,89-,91-,92-,95 -, 97-, 99-, 100-, 101-, 105-, 110-, 114-, 118-, 119-, 123-, 126-CB), 12 species of Cl 6-PCBs (128-, 131-, 132-,135-,138-,144-,149-,153-,156-,163-,167-,169-CB), Cl 7-PCBs, 6 species (170-, 171-, 172-, 174- , 180-, 190-CB), Cl 8-PCBs 5 (194-, 199-, 200-, 202-, 205-CB), Cl 9-PCBs 2 (206-, 207-CB). The standard product was diluted with isooctane to the mother liquor, and the mixed standard mother liquor was gradually diluted with isooctane to prepare a standard working solution with a concentration range of 5.080.0 ng/mL. Agilent 5890/5973 II GC-MS, DB-5MS column (60m×0.25mm×0.25μm, JW Sci. Co product).

1.3 sample processing sample preparation method. 50 μL of the oil sample was dissolved in 10 mL of n-hexane, mixed well, extracted with 15 mL x 4 DMSO, and the DMSO phases were combined. Dissolved in 100 mL of deionized water and back-extracted with 50 mL x 3 n-hexane, the n-hexane phases were combined. Rotary evaporation was concentrated to about 10 mL, washed with 10 mL x 3 concentrated sulfuric acid, and washed with water until neutral. The water was removed over anhydrous sodium sulfate, concentrated to about 12 mL, purified on a silica gel column (3.3% water inactivated silica gel), rotovapped to about 2 mL, and transferred to a KD concentrator flask. Add internal standard PCB204, high-purity nitrogen blow, constant volume 1mL. Transfer to the sample bottle, ready for analysis by GC-MS.

1.4 GC/MS experimental conditions DB-5MS column, inlet temperature 250 °C, detector temperature 300 °C, temperature program for 90 °C for 1min, then 15 °C/min to 160 °C, then 3 °C/min Raise to 280°C (hold for 15 min). Constant flow without split injection; carrier gas is high purity helium; flow rate is 1.0mL/min.

Mass spectrometry conditions: EI source, electron energy 70 eV, source temperature 250°C, mass scan range m/z 30450, selective ion monitoring mode (SIM), and internal standard method quantification.

1.5 Quality Assurance and Quality Control (QA/QC) Continuous analysis of 7 standard samples with 5 times the noise, obtained standard deviation (S1), instrument detection limit (IDL) = 1.94 S1, ie 0.0180.048 pg/mL. Analysis of 7 matrices (un-oiled n-hexane) plus standard, spiked at a concentration of 5 times IDL to obtain the standard deviation (S2), method detection limit (MDL) = 1.94 S2, ie 0.061.20 pg/mL. The spike recovery rate was 74% 117%.

2 Results and Discussion 2.1 Results The total concentration of 84 kinds of PCBs in China's transformer oil ranged from 79.8286.6 mg/mL with an average concentration of about 155.9 mg/mL. Figure 1(a) shows PCB isomers in transformer oil in China. The average percentage. It can be seen that out of the 84 PCBs, only 36 PCBs were detected (CB6, CB5+8, CB13, CB18, CB17, CB15, CB16, CB32, CB26, CB31+28, CB33, CB53, CB22, CB45, CB52. , CB49, CB47+48, CB44, CB42, CB37, CB41+71, CB64, CB74, CB70, CB76, CB66, CB56+60, CB110, CB77, CB118, CB105), and mainly based on low-chlorinated PCBs, The content of high-chlorinated PCBs is small, and most of the high-chlorinated PCBs are below the detection limit of the instrument. Of all detected isomers, approximately 17.4% of PCBs were CB-18 (2,2,5-T3CB), followed by CB-33 (2,3,4-T3CB) and CB-31+28. (2,4,5 T3CB+2,4,4T3CB) accounted for 13.5% and 8.3%, respectively, and the highest content was all of trichlorobiphenyl. This was in contrast to the 1st PCB produced in China in the 1960s. The fact that trichlorobiphenyl is consistent.

For comparison purposes, the average percentage of each isomer in Aroclor 1242 produced in the United States is given. The total chlorine content of No. 1 PCB produced in China is about 42.9%, which is very similar to the chlorine content of Aroclor 1242 (chlorine content is about 40% 42%) produced in the United States. In PCBs of Aroclor1242, mainly low-chlorinated PCBs were also used, but the relative percentage differences of the isomers were smaller than that of domestic PCBs. 99 isomers were detected in Aroclor1242 (CB1, CB2, CB3, CB4, CB5, CB6). , CB7, CB8, CB9, CB10, CB12, CB13, CB15, CB16, CB17, CB18, CB19, CB20, CB22, CB23, CB24, CB25, CB26, CB27, CB28, CB29, CB31, CB32, CB33, CB34, CB35 , CB37, CB40, CB41, CB42, CB43, CB44, CB45, CB46, CB47, CB48, CB49, CB51, CB52, CB53, CB54, CB55, CB56, CB57, CB59, CB60, CB63, CB64, CB66, CB67, CB70 , CB71, CB72, CB74, CB75, CB76, CB77, CB81, CB82, CB83, CB84, CB85, CB86, CB87, CB89, CB91, CB92, CB94, CB95, CB96, CB97, CB99, CB101, CB102, CB105, CB109 , CB110, CB114, CB115, CB117, CB118, CB122, CB123, CB124, CB125, CB128, CB132, CB138, CB141, CB149, CB153, CB156, CB158, CB163).

It can be seen that the PCBs of Aroclor1242 mainly consist of trichlorin and tetrachlorobiphenyl, accounting for 45% and 31% of the total, followed by dichloro and pentachlorobiphenyl, accounting for 13% and 10%, respectively; The PCBs contained in transformer oil are mainly trichlorobiphenyls, with 63% in the measured total, followed by tetrachlorinated and dichlorinated biphenyls, which account for 24% and 9%, respectively, and transformer oils produced in China. The distribution characteristics of the PCBs in the PCBs are similar to those of the Aroclor 1242 products in the United States. They are based on trichlorobiphenyl, but the content of tetrachlorobiphenyl is lower than that of Aroclor1242 in the United States. In addition, the content of pentachlorobiphenyl in transformer oil produced in China is much lower than that of Aroclor1242 in the United States, and its content in the measured PCBs is only 3% of the total; high-chlorinated biphenyls such as hexachloro and heptachlor are The content of PCBs in China's transformer oil is minimal.

2.2 DISCUSSION Assessing the environmental toxicity of PCBs requires not only the total content and congeners but also the presence of the most toxic isomers. The toxicity of PCBs has a lot to do with the location of the chlorine atom substitution, there is no ortho-chlorine substitution, or only 12 ortho-chlorine-substituted PCBs homologues are toxic, called dioxin-like PCB. Coplanar PCBs with no chlorine substitution in the ortho-position were more toxic, especially PCBs with bi- and more than two lateral chlorine substitutions were the most toxic, such as CB77, CB81, CB126, and CB169, and their structures were closest to 2, 3,7,8-TCDD. Visible, domestic PCBs, the content of coplanar PCBs only accounted for 1.6% of the total determination, of which the highest content of CB-77, the largest contribution to TEQ, accounting for 72% of 6 highly toxic PCBs, followed by CB-105 and toxicity The strongest CB-126 accounted for 15% and 8% respectively. Domestic PCBs did not detect CB-169, Jiang et al.

In the study of domestic PCBs and their incineration of dioxin-like PCBs in soot, CB-169 was not detected. The TEQ values ​​of domestically produced PCBs were lower than those of foreign products and corresponded to only 15% of Aroclor1242, but no acute toxicity was detected in Aroclor 1242. In CB-126, Aroclor 1242, 84% of the toxic contribution came from CB-77, followed by CB-105, accounting for about 13%. From the distribution of isomers, the domestic No. 1 PCBs and Aroclor1242 in the United States are relatively large. The difference.

The results of atmospheric studies on PCBs contaminated areas in China indicate that PCBs detected in gaseous or particulate matter are all low-chlorinated PCBs, and high-chlorinated PCBs have not been detected. PCBs in atmospheric particles reported in foreign countries are tetrachlorinated. And the fact that the six chlorinated PCBs are predominant, the fact that the capacitor oil used in our country is mainly low-chlorinated PCBs is consistent. According to the survey, the dismantling of waste capacitors and the loss of capacitor oil are the sources of local PCB pollution. The content of PCB-31+28 in the air of polluted areas is as high as 95.35 ng/m 3 , while PCBs used in domestic transformer oil/power capacitor oils are heterogeneous. The content of PCB-31+28 in the body is as high as 12.97 mg/mL, indicating that the leakage of waste oil containing PCBs has seriously polluted the local ecological environment. At the same time, the dismantling of waste power containers/transformers and the arbitrary discharge of waste oil are revealed in the local environment. The main source of PCBs. Ren et al.

Studies have shown that PCBs contamination in soils in China is dominated by low-chlorinated PCBs, with the highest trichloro-PCBs content (34%), which is consistent with the isomer distribution of PCBs used in domestic transformer/power capacitor oils. It shows that the leakage of PCBs waste power capacitors/transformer oil has become the main source of PCBs contamination in China's environment.

3 Conclusions 3.1 PCBs in China's transformer oil are mainly based on low-chlorinated PCBs, and the content of trichlorobiphenyl in the measured total is as high as 63%, followed by tetrachloro and dichlorobiphenyl, accounting for 24% and 9% respectively. .

3.2 Distribution Characteristics of PCBs Congeners in Transformer Oils Made in China are similar to Aroclor1242 products in the United States. The total chlorine content of domestic PCBs is about 42.9%, and that of Aroclor 1242 (chlorine content is about 40% 42%) produced in the United States. The amount of chlorine is very similar.

3.3 In domestic PCBs, the content of coplanar PCBs only accounted for 1.6% of the total determination. Among them, the highest content of CB-77 contributed the most to TEQ, accounting for 72% of 6 highly toxic PCBs, followed by CB-105 and toxicity. The strongest CB-126 accounted for 15% and 8%, respectively.

3.4 CB-169 was not detected in domestic PCBs, and the TEQ value of domestic PCBs was only 15% of Aroclor1242.