The Research On Abetment And Safety Discharge Of Residual Phosphine In Fumigation

The economic losses were caused by storage pests. The successful fumigation is to reduce or avoid this unnecessary loss. Key findings of successful fumigation are affected by dose, length of exposure, temperature and moisture and the suitable fumigation methods. This requires that we clear the fumigant concentration change over time, determine the effectiveness of fumigation according to the change of fumigant concentration, choose the best method of fumigation which could achieve the successful fumigation and use the minimal dosage. In addition, after fumigation, fumigation warehouse contains high concentration of phosphine gas. The usual method is discharging directly into atmosphere; such activity can results in gas concentration which exceeds the short-term exposure limits of 0.3ppm of phosphine. High concentration of residual phosphine not only pollutes the environment and pose a hazard to the health of mammals, it also violate safety discharge law. How to economic, environmentally friendly abatement residual phosphine is notable.In the case of in-store fumigation and stack fumigation, the concentration of phosphine inside and outside of the strips which packed by corrugated box with plastic lining was determined in order to find an optimal fumigation method. After fumigation, the concentration of PH3 was determined to make sure the safety and effective fumigation time. The results indicate that the effect of stack fumigation is better than in-store fumigation. However, the stack fumigation still has leakage. In order to give successful and safety fumigation to strips packed by corrugated box with plastic lining, the whole process of fumigation time should last for 8-9days.Three commercial activated carbons (coal-based) which were modified by ferrite sulfate without calcination, were used to adsorb/oxidize phosphine directly. The characteristics of all those types of carbons were evaluated by means of Boehm titration, thermal analysis, nitrogen adsorption and inductively coupled plasma atomic emission spectrometry. The results show that the SBET (surface area calculated using Brunauer-Emmett-Teller (BET) equation) 1119.26 m2/g, Vt (total pore volume) 0.369 cm3/g and Vmic (micropores volume) 0.470 cm3/g of C2-M were much higher than SBET 941.93 m2/g, Vt 0.336 cm3/g and Vmic 0.449 cm3/g of C2. Moreover, the phosphine breakthrough capacity of C2-M was extended by 25% than before. The results also indicate that activated carbon with slight acidity and a well developed porous structure has higher PH3 breakthrough capacity and longer operational life. Based on the Fourier transformed infrared spectroscopy and thermal analysis, phosphoric acid was the final oxidation product, thus exhausted activated carbons can be regenerated by washing with water.Based on the small scale test in lab, a pilot fixed bed reactor abated phosphine that could achieve the low of safety discharge was designed.