Study On Wet Air Oxidation Of Coal Gasification Wastewater

As the coal gas wastewater contains a large amount of organic pollutants and high concentrations of ammonia nitrogen,these pollutants are difficult to deal with biodegradation,resulting in water is difficult to meet the wastewater discharge requirements and standards,the need for advanced treatment and disposal.Advanced oxidation in the removal of sewage difficult to degrade organic matter in a number of advantages,is one of the main methods,so in the water treatment has been widely used.In this paper,the degradation characteristics and reaction mechanism of gas wastewater in wet oxidation reaction system are studied,which can provide effective guidance and useful reference for high temperature and high pressure treatment of gas wastewater.In this paper,we consider coal gasification wastewater as the research object,the wet oxidation is used to treat coal gasification wastewater and study the reaction characteristics.It will provide a theoretical basis for coal gasification wastewater treatment.The main operating factors such as temperature,reaction pressure,residence time,dosage of oxidant and other factors on the treatment effect by wet oxidation of coal gasification wastewater is checked.Wet oxidation of coal gasification wastewater has good treatment effect with adding the adequate oxygen.Wet oxidation technology in the process of reaction to show a good oxidation efficiency and processing capacity,get the best pollutant removal conditions: reaction temperature is 310°C,pressure is 16 MPa,dosage of oxidant is 500 mg/L and residence time is 9 min.The COD removal is up to 82.7 %.Biodegradability of liquid effluents is elevated obviously after coal gasification wastewater treatment by wet air oxidation.The orthogonal results indicate that reaction temperature is the key factor affecting the COD removal.Biodegradability of liquid effluents gets better with rising the temperature.When the temperature is up to 310°C,BOD5/COD is becoming greater than 0.45 and biodegradability is becoming the best at this time.Catalytic wet air oxidation technology can improve the removal rate of pollutants at lower temperature and pressure.In the process of the research,it was found that the alkali and transition metal ion catalysts showed good catalytic activity and activity in the treatment of gas wastewater by wet oxidation process.The test results show that adding a small amount of KOH,K₂CO₃ and KHCO₃ are effective for removal of gas in wastewater COD,adding the removal rate of KOH is higher than KHCO₃,K₂CO₃ and KOH;the most suitable concentration is 400 mg/L,the gas removal rate of COD can reach the maximum value of 88.7%.Metal ion catalyst has good catalytic activity for wet oxidation of wastewater.The overall order of catalytic activity of transitional metal salts is: Fe₂?SO₄?₃>NiSO₄>MnSO₄.COD removal increases as the residence time increases at the presence of Fe³⁺ and Ni2+.The COD removal reaches 99.5% and 97.3% after 9 min with Fe₂?SO₄?₃ and NiSO₄ catalyst,respectively.In order to better investigate the relationship between the various influencing factors,the experimental results show that the effect of pressure,reaction temperature,reaction residence time and oxidant dosage on COD removal rate is relatively large,and the COD removal rate the greatest impact.