Yellow Phosphorus Tail Gas Catalytic Oxidation To Purify The Series Of Catalyst Research And Development

This thesis is about research and discussion of purification of yellow phosphorus off-gas at low temperature and low oxygen content.Firstly, experiments were conducted to select carrier of catalyst, to assess the efficiency of catalyst regeneration, and the influencing factors which were related with purification of yellow phosphorus off-gas. Activated carbon was an efficient adsorbent for both PH₃ and H₂S, and therefore chosen as carrier of catalyst. HCl, Na₂CO₃ and CuAc₂ were selected to be used as impregnants for phosphorus-remove catalyst, sulfur-remove catalyst and phosphorus-sulfur-remove catalyst respectively. When phosphorus-remove catalyst was used to remove PH3, it was 5% and 1% (vol%) for the appropriate concentration of HC1 and oxygen content respectively; and it was physic adsorption in anoxic atmosphere with 20℃ as appropriate temperature, and chemical reaction and adsorption in aerobic atmosphere with 70 ℃ as appropriate temperature. When sulfur-remove catalyst was used to remove H₂S, it was 7%, 0.4% (vol%) and 90℃ for the appropriate concentration of Na₂CO₃, oxygen content and reaction temperature respectively; the higher the temperature was the higher the removal efficiency was. When phosphorus-sulfur-remove catalyst was used to remove PH₃ and H₂S, for PH3 the superiority order was temperature > oxygen content > parch temperature > impregnant concentration (Cu²⁺) > flow rate > diameter while for H₂S it was reaction temperature > oxygen content > impregnant concentration > parch temperature > diameter > flow rate. And the optimum experiment parameters for both PH₃ and H₂S were reaction temperature, 95℃; impregnant concentration (Cu²⁺), 0.25 mol/L; diameter of catalyst, 3.5 mm; oxygen content, 1%; parch temperature, 300 ℃ and flow rate, 0.4 L/min. Regeneration of phosphorus-sulfur-remove catalyst was effective for PH₃ but not compelling for H₂S.Secondly, experiments were carried out to acquire thermodynamic parameters and to assess the influence of internal and external diffusion on removal efficiency. When sulfur-remove catalyst was used to remove H₂S, it was -1 and 23.77kJ/mol for the average reaction order and average activation energy. When phosphorus-remove catalyst was used to remove PH₃, it was -2 and 61.3kJ/mol for the average reaction order and averageactivation energy. When phosphorus-sulfur-remove catalyst was used to remove PH₃ and H₂S, reaction orders were -0.8 and -0.76 for PH₃ and H₂S respectively; and average activation energies were 1247.6 J/mol and 134.4 J/mol for PH₃ and H₂S respectively. Purification of yellow phosphorus off-gas could be primarily identified as a chemical process through these values of activation energies. Decrease of diameter of catalyst and increase of flow rate could dramatically increase the average reaction rate.Thirdly, onsite experiments were conducted to investigate the practical purifying efficiency of catalyst on phosphorus off-gas in Jianglin Corporation; and SEM, TG/DTA, BET adsorption and XPS were used to characterize the performance of catalysts and to illustrate the reaction mechanism. When sulfur-remove catalyst was used to purify phosphorus off-gas, total impurity content was lower than 10mg/Nm³ in 200 minutes with better selectivity on H₂S. When phosphorus-sulfur-remove catalyst was used to purify phosphorus off-gas, total impurity content was lower than 10mg/Nm³ in 300 minutes with better selectivity on H₂S and PH₃. Analysis of pore size distribution, TG/DTA and SEM primarily indicates that, during purification, H₂S and PH₃ were firstly reacted with oxygen to produce sulfur and sulfur oxides or phosphorus and phosphorus oxides, and then adsorbed on sulfur-remove catalyst or phosphorus-remove catalyst. Analysis of XPS, TG/DTA and pore size distribution indicates that, during purification, H₂S and PH₃ were firstly reacted with oxygen to produce S and P₂O₅, and then adsorbed on phosphorus-sulfur-remove catalyst.Finally, models were established according to reaction mechanism, and calibrated and validated through experiment data. Parameters of models of phosphorus-remove catalyst and sulfur-remove catalyst were attained through fitting of experiment data. When they were used to forecast the outlet concentration, the relativity coefficients were 0.99354 and 0.99136 for PH₃ and H₂S respectively. Model of phosphorus-sulfur-remove catalyst was solved numerically. When it was used to forecast outlet concentration, the relativity coefficients were 0.9976 and 0.9919 for PH₃ and H₂S respectively.