Electron beam flue gas treatment process for purification of exhaust gases with high SO 2 concentrations

Transcription

1 Electron beam flue gas treatment process for purification of exhaust gases with high SO 2 concentrations Andrzej G. Chmielewski 1, Janusz Licki 2 1 Department of Nuclear Methods in Process Engineering, Institute of Nuclear Chemistry and Technology, 16 Dorodna Str., Warsaw,, Poland. 2 Department of Nuclear Energy,Institute of Atomic Energy, Otwock-Świerk, wierk, Poland. Tel: (+4822) Fax: (+4822) licki@cyf.gov.pl INTERNATIONAL CONFERENCE ON RECENT DEVELOPMENTS AND APPLICATIONS OF NUCLEAR TECHNOLOGIES SEPTEMBER 2008, BIAŁOWIEśA, POLAND Main tasks The application of the electron-beam process for purification of flue gases with w high SO 2 concentrations was the purpose of this paper. The experimental studies were concentrated on the purification of exhaust gases 1. from combustion of high sulphur coal heavy fuel oil 2. and from copper smelter. The other aim was determination of the conditions for obtaining the highest SO 2 and NO x removal efficiencies from above exhaust gases. Table 1. Main parameters of industrial e-beam installations Parameter Flue gas flow rate Inlet flue gas temperature Inlet SO 2 concentration mg/nm concentration mg/nm Inlet NO concentration x SO 2 removal efficiency NO x removal efficiency Electron beam parameters Unit Nm 3 /h 0 C % % Chengdu TPP China kev, 320 kwx2 Hangzhou TPP China kev, 320 kwx2 Pomorzany EPS Poland kev, 260 kwx4 1

2 Fig. 1. Technological scheme of the industrial plant at EPS Pomorzany Fig. 2. Schematic flow diagram of the pilot plant at TPP Kawęczyn Fig. 3. Flow diagram of INCT laboratory plant equipped with stand for burning of mazout C thermostated fuel oil 2. oil burner 3. particulate and soot filters 4. orifice 5. dosage of water vapour 6. gas sampling point - process inlet 7. ammonia injection 8. process vessel 9. electron beam accelerator 10. retention chamber 11. bag filter 12. gas sampling point process outlet 13. induced - draught fan 14. stack 15. concrete shielding wall 16. concrete shielding door 2

3 Fig. 4. Flow diagram of INCT laboratory plant with gas-fired boilers 1. two gas-fired boilers, 2. orifice, 3. SO2 dosage, 4. NO dosage, 5. water vapour dosage, 6. gas sampling device, 7. NH3, dosage, 8. irradiation chamber, 9. electron accelerator, 10. retention chamber, 11. bag filter, 12. gas sampling device, 13. draught fan, 14. chimney, 15. shielding walls, 16. shielding door. α NH 3 Effect of absorbed dose Fig. 4 presents the dose dependence of SO 2 and NO x removal efficiency. Dose dependence of SO 2 removal from gas mixture with extemely high SO 2 concentration: SO 20 : 10% vol., H: 14.5% vol., α NH3 : , T inlet : C Effect of ammonia stoichiometry 3

4 Effect of gas temperature at inlet to proces vessel Effect of flue gas humidity Experimental conditions: SO 20 : 10 % vol, H: % vol., α NH3 : , T inlet : C Effect of inlet high SO 2 concentration SO 2 + *OH + M HSO 3 + M HSO 3 + O 2 SO 3 + HO 2 * NO + HO 2* NO 2 + *OH NO 2 + *OH + M HNO 3 + M 4

5 Conclusions Flue gases from combustion of high sulphur fossil fuels can be effectively purified by the electron beam process. The SO 2 removal efficiency above 95 % and NO x removal above 75 % were obtained in the optimal treatment conditions. High removal efficiencies can be obtained by firstly properly controlling the temperature and humidity of flue gas in a dry bottom spray cooler. Then a near stoichiometric amount of NH 3 should be added to gas before its inlet to a process vessel. Thirdly, the mixture should be irradiated with adequate irradiation dose in the process vessel. The improvement in NO x removal is achieved by multi-stage irradiation and by adequate dose distribution between irradiation stages [5]. The gas humidity and temperature, ammonia stoichiometry and irradiation dose up 8 kgy strongly influence SO 2 removal efficiency. The synergistic effect of high SO 2 concentration on NO x removal was indicated. The collected by-product was the mixture of ammonium sulphate and nitrate. The content of heavy metals in the byproduct was many times lower than the values acceptable for commercial fertilizer. In addition the formation of a valuable product in large quantities might further reduce the operating cost of the EBFGT process depending on the market value of fertilizer by-product. Thank you for your attention! INTERNATIONAL CONFERENCE ON RECENT DEVELOPMENTS AND APPLICATIONS OF NUCLEAR TECHNOLOGIES SEPTEMBER 2008, BIAŁOWIEśA, POLAND 5