Appreciating the importance of Vinh Tan Power Center, EVN always directs units to focus on managing and operating EVN’s thermal power plants in Vinh Tan Power Center in a safe and stable manner. However, in the past time, EVN’s thermal power plants have faced many difficulties in consuming ash and slag generated during the operation of thermal power plants.
Lesson 1: Technical parameters of ash and slag are within permissible limits Vinh Tan 4 & Vinh Tan 4 Thermal Power Plants expand to use Bitumen and Sub-Bitium coal as main fuels imported from Australia and Indonesia, with low ash and slag content (only about ≤ 9.8). % of coal consumed). The demand for coal in the operation of the plant is about 5,048,083 tons/year.
Samples of ash and slag generated during the operation phase of Vinh Tan 4 & Vinh Tan 4 extended thermal power plants were analyzed by functional units as regulated such as SGS Vietnam Company, Standard Technical Center. Quality measurement 3, Phuong Nam Center for Environmental Measurement and Analysis.
In order to control the quality of ash and slag, it is necessary to ensure the quality of input coal to meet operational and stable requirements. Accordingly, in addition to requiring the coal supplier to ensure the quality of coal according to the contract, the factory has equipped with control analysis equipment to strictly control the above parameters to ensure the quality. Imported coal conforms to the design of the plant and ensures the quality of ash and slag generated.
At the same time, in order to optimize the operation and stabilize the quality of ash and slag, the plant regularly strictly controls the operation mode of the units, optimizes the combustion mode of the boiler in accordance with the design and process. operation, in order to ensure the quality of ash and slag to meet the needs of the market.
In order to control the quality of ash and slag stored at the yard, the plant has established operating procedures for the ash and slag discharge system and operating procedures for the slag disposal site.
Regarding the ash and slag properties of the extended Vinh Tan 4 & Vinh Tan 4 thermal power plants, compare the analysis results of the fly ash and bottom slag parameters of the extended Vinh Tan 4 & Vinh Tan 4 thermal power plants with QCVN 07: 2009/BTNMT on the threshold of hazardous waste, the parameters are within the allowable limits of current regulations and compare the results of analysis of fly ash parameters according to the standard TCVN 10302:2014 fly ash active additives. used for concrete, mortar and cement, the analytical parameters are within the allowable limits, the factory’s fly ash meets the conditions for use as active admixtures for concrete, mortar and cement. Ash ash of Vinh Tan 4 & Vinh Tan 4 expanded thermal power plants has special advantages compared to ash slag from domestic coal-fired thermal power plants when it has low unburnt carbon content, suitable for cement and concrete production. and other building materials.
Previously, samples of ash and slag generated during the operation phase of Vinh Tan 4 & Vinh Tan 4 extended thermal power plants were analyzed by functional units in accordance with regulations such as SGS Vietnam Company, Technical Center Technical standards for quality measurement 3, Phuong Nam Center for Environmental Measurement and Analysis. Specifically:
The results of analysis of fly ash characteristics of Vinh Tan 4 & Vinh Tan 4 extended thermal power plants analyzed by SGS Vietnam Limited are as follows (Table 1):
Table 1: Parameters of fly ash
| No. | Analytical indicators | Test methods | Unit | Result |
| 1 | SiO2 | ASTM D3682 – 13 | % | 45.68 |
| 2 | High | ASTM D3682 – 13 | % | 4.78 |
| 3 | MgO | ASTM D3682 – 13 | % | 1.60 |
| 4 | Fe 2 O 3 | ASTM D3682 – 13 | % | 13.88 |
| 5 | Al 2 O 3 | ASTM D3682 – 13 | % | 29.45 |
| 6 | MnO | ASTM D3683 – 11 | % | 0.17 |
| 7 | P 2 O 5 | ISO 622: 2016 | % | 0.21 |
| 8 | TiO2 | ASTM D2795: 2001 | % | 1.89 |
| 9 | K2O | ASTM D3682 – 13 | % | 1.00 |
| 10 | Na 2 O | ASTM D3682 – 13 | % | 0.36 |
| 11 | OLD | ASTM D6316-09 | % | 0.96 |
| 12 | SO3 in ash | ASTM D5016: 08e1 | % | 0.84 |
The results of analysis of slag characteristics of the furnace bottom of Vinh Tan 4 & Vinh Tan 4 expanded thermal power plants analyzed by SGS Vietnam are as follows (Table 2):
Table 2: Characteristics of furnace bottom slag
| No. | Analytical indicators | test methods | Unit | Result |
| 1 | SiO2 | ASTM D3682 – 13 | % | 66.07 |
| 2 | High | ASTM D3682 – 13 | % | 4.76 |
| 3 | MgO | ASTM D3682 – 13 | % | 1.88 |
| 4 | Fe 2 O 3 | ASTM D3682 – 13 | % | 11.12 |
| 5 | Al 2 O 3 | ASTM D3682 – 13 | % | 13.72 |
| 6 | MnO | ASTM D3683 – 11 | % | 0.13 |
| 7 | P 2 O 5 | ISO 622: 2016 | % | 0.11 |
| 8 | TiO2 | ASTM D2795: 2001 | % | 0.87 |
| 9 | K2O | ASTM D3682 – 13 | % | 0.86 |
| 10 | Na 2 O | ASTM D3682 – 13 | % | 0.43 |
| 11 | OLD | ASTM D6316-09 | % | 0.86 |
| 12 | SO3 in ash | ASTM D5016: 08e1 | % | 0.06 |
Phuong Nam Environmental Measurement and Analysis Center was certified by the Ministry of Natural Resources and Environment to be eligible to operate environmental monitoring services under the Decisions No. 828/QD-BTNMT dated April 10, 2015, No. 1071 /QD-BTNMT dated May 12, 2016, No. 1896/QD-BTNMT dated August 7, 2017, and No. 1565/QD-BTNMT dated May 16, 2018, of the Ministry of Natural Resources and Environment with code VIMCERTS 075. The results of analysis of fly ash and bottom slag characteristics of the extended Vinh Tan 4 & Vinh Tan 4 thermal power plants analyzed by the Phuong Nam Center for Environmental Measurement and Analysis are as follows (Table 3):
Table 3: Analysis results of fly ash and furnace bottom slag
| No. | Parameter | Unit | Test method | Result (fly ash sample) | Result (coal slag sample) | QCVN 07:2009/BTNMT (Danger Threshold) |
| 1 | pH | – | US EPA Method 9045D6,6 | 6,6 | 9,0 | pH ≥ 12,5 hoặc pH ≤ 2,0 |
| No. | Parameter | Unit | Test method | Result (fly ash sample) | Result (coal slag sample) | QCVN 07:2009/BTNMT (Absolute content – Htc) T = 0.99 |
| 2 | Total Cyanide (CN-) | mg/kg | US EPA Method 9013A + US EPA Method 9010C + US EPA Method 9014 | KPH LOD=5 | KPH LOD=5 | 584,40 |
| No. | Parameter | Unit | Test method | Result (fly ash sample) | Result (coal slag sample) | QCVN 07:2009/BTNMT (Liquid concentration – Ctc) |
| 3 | Antimon (Sb) | mg/L | US EPA Method 1311 + SMEWW 3113B:2012 | KPH LOD = 0,002 | KPH LOD = 0,002 | 1 |
| 4 | Asen (As) | mg/L | US EPA Method 1311 + SMEWW 3113B:2012 | 0,035 | 0,017 | 2 |
| 5 | Bari (Ba) | mg/L | US EPA Method 1311 + SMEWW 3111D:2012 | 1,335 | 0,689 | 100 |
| 6 | Silver(Ag) | mg/L | US EPA Method 1311 + SMEWW 3111B:2012 | KPH LOD = 0,03 | KPH LOD = 0,03 | 5 |
| 7 | Beryn (Be) | ppm | ASTM D5198 – 09 + SMEWW 3111B:2012 | KPH LOD = 0,012 | KPH LOD = 0,012 | 0,1 |
| 8 | Cadimi (Cd) | mg/L | US EPA Method 1311 + SMEWW 3113B:2012 | KPH LOD = 0,0005 | KPH LOD = 0,0005 | 0,5 |
| 9 | Lead(Pb) | mg/L | US EPA Method 1311 + SMEWW 3113B:2012 | KPH LOD = 0,05 | KPH LOD = 0,05 | 15 |
| 10 | Coban (Co) | mg/L | US EPA Method 1311 + SMEWW 3113B:2012 | 0,283 | 0,137 | 80 |
| 11 | Zinc(Zn) | mg/L | US EPA Method 1311 + SMEWW 3113B:2012 | 1,452 | KPH LOD = 0,05 | 250 |
| 12 | Molybdenum (Mo) | mg/L | US EPA Method 1311 + SMEWW 3113B:2012 | 0,452 | 0,369 | 350 |
| 13 | Nickel (Ni) | mg/L | US EPA Method 1311 + SMEWW 3113B:2012 | 0,191 | 0,181 | 70 |
| 14 | Selenium (Se) | mg/L | US EPA Method 1311 + SMEWW 3113B:2012 | KPH LOD = 0,002 | KPH LOD = 0,002 | 1 |
| 15 | Tali (Tl) | mg/L | US EPA Method 1311 + SMEWW 3113B:2012 | KPH LOD = 0,02 | KPH LOD = 0,02 | 7 |
| 16 | Mercury (Hg) | mg/L | US EPA Method 1311 + SMEWW 3112B:2012 | KPH LOD = 0,0005 | KPH LOD = 0,0005 | 0,2 |
| 17 | Chromium (VI) | mg/L | US EPA Method 1311 + US EPA Method 7196A | KPH LOD = 0,01 | KPH LOD = 0,01 | 5 |
| 18 | Vanadium (V) | mg/L | US EPA Method 1311 + SMEWW 3113B:2012 | 0,006 | KPH LOD = 0,003 | 25 |
| 19 | Fluoride salt | mg/L | US EPA Method 1311 + SMEWW 4500B&F:2012 | 0,64 | 0,31 | 180 |
| 20 | Phenol | mg/L | US EPA Method 1311 + US EPA Method 3510C + US EPA Method 8015D | KPH LOD = 0,15 | KPH LOD = 0,15 | 1.000 |
Comparing the results of analysis of fly ash and bottom slag parameters of Vinh Tan 4 Thermal Power Plant above with the standard QCVN 07:2009/BTNMT on hazardous waste thresholds, the parameters are within the allowable limits.
In addition, Hoang Son Fly Ash and Cement Joint Stock Company – Southern Branch (partner of ash and slag consumption of Vinh Tan 4 & Vinh Tan 4 expanded thermal power plants) has hired a consultant (Technical Center to quality measurement standards 3) take samples of fly ash from the factory to evaluate the quality of fly ash according to the standard TCVN 10302:2014 fly ash active additive for concrete, mortar and cement. The results of the analysis are as follows (Table 4.5).
Table 4: Quality criteria of fly ash for concrete and mortar
| No. | Analytical indicators | Unit | Result | TCVN 10302:2014 | |||
| a | b | c | d | ||||
| 1 | Total oxide content SiO 2 + Al 2 O 3 + Fe 2 O 3 | % | 85,4 | ≥70 | |||
| 2 | Sulfur content, compound sulfur conversion out SO 3 | % | 0,4 | ≤3 | ≤5 | ≤3 | ≤3 |
| 3 | Free calcium oxide content CaOtd | % | 0,5 | – | – | – | – |
| 4 | Loss content when heating MKN | % | 0,3 | ≤12 | ≤15 | ≤8 | ≤5 |
| 5 | Harmful alkaline content (alkaline dissolve) | % | 0,36 | ≤1,5 | |||
| 6 | Humidity | % | 0,01 | ≤3 | ≤3 | ≤3 | ≤3 |
| 7 | The residual amount of sieve 45 m | % | 19,4 | ≤25 | ≤34 | ≤40 | ≤20 |
| 8 | Amount of water required compared to the sample control | % | 98,8 | ≤105 | ≤105 | ≤100 | ≤105 |
| 9 | Cl ion content | % | <0,01 | ≤0,1 | – | – | ≤0,1 |
Table 5: Technical parameters of fly ash for cement
| No. | Fecal criteria volume | Unit | Result | Result | TCVN 10302:2014 |
| 1 | Amount of loss when heating MKN | % | 0.3 | 0.3 | 8 |
| 2 | Retention content sulfur, fit sulfur convertibility SO3 | % | 0.4 | 0.4 | 3.5 |
| 3 | Jaw quantity free calcium oxide CaOtd | % | 0.5 | 0.5 | 1 |
| 4 | Jaw quantity alkaline harmful (alkali dissolve) | % | 0.36 | 0.36 | 1.5 |
| 5 | Humidity | % | 0.01 | 0.01 | 1 |
According to table 1 above, fly ash with CaO content = 4.78%, according to TCVN 10302:2014 fly ash of Vinh Tan 4 Thermal Power Plant belongs to acid ash (F).
Comparing the analysis results of fly ash parameters of Vinh Tan 4 thermal power plant according to the standard TCVN 10302:2014 fly ash active additives for concrete, mortar and cement, the analytical parameters are within the limits. allowable, the factory’s fly ash meets the conditions for use as active admixtures for concrete, mortar and cement.
The collection, transportation and storage of ash and slag from Vinh Tan 4 and Vinh Tan 4 expanded thermal power plants at Vinh Tan 2 slag dumping site is being carried out strictly according to the process approved by the People’s Committee of Binh Thuan province in Document No. 1767/ People’s Committee-KTN dated May 26, 2016, in compliance with the approved environmental impact assessment reports of Vinh Tan 2, Vinh Tan 4 and Vinh Tan 4 extended thermal power plants, ensuring safety, stability and assurance. environment.
Thus, with the composition and properties of the fly ash generated by the plant, it meets the national technical regulations on active additives for concrete, mortar and cement.
