Study On The System Protective Performance Of Air-purifying Respirator Against Sulfur Dioxide

Sulfur dioxide is a typical acidic and toxic gas commonly found in industrial production,and when its concentration in the environment reaches a threshold,it can damage the human respiratory system and cause harm to human life safety.Whether in daily protection or emergency rescue,air-purifying respirator is an important protective equipment to protect the human body from toxic and harmful gases,and its research can reduce the psychological burden of workers and provide a theoretical basis for the revision of relevant standards,which has certain practical significance.This paper takes gas masks,a typical representative of air-purifying respiratory,as the research object and firstly studies the protection mechanism of SO₂by activated carbon,which mainly plays the role of adsorption in gas masks.The dynamic adsorption experiments of four types of activated carbon on SO₂at different concentrations,airflow ratio,airflow relative humidity and bed temperature were conducted with coconut shell-based carbon（AC-1）,coconut shell-impregnated carbon（ASZMT-1）,coal-based carbon（AC-2）and coal-impregnated carbon（ASZMT-2）.The results showed that the protection time became shorter as the concentration,specific velocity and temperature increased,and the protection time of the two impregnated carbons became longer as the relative humidity increased,while the protection time of the two base carbons was basically unchanged.Four apparent adsorption kinetic models were used to fit the adsorption curves nonlinearly,and the changes of the rate-controlling step in the adsorption process under different conditions were discussed.Most of the results showed that the Mckay quasi-secondary adsorption kinetic model was the best fit,indicating that the surface oxidation reaction was the rate-controlling step.Then,the protection performance of the core component of the gas mask,the canister,against SO₂at different concentrations,airflow ratio,relative humidity and bed temperature was studied and compared with the protection performance law of activated carbon against SO₂to analyze the correlation and consistency between the two.The results showed that the protection performance of the canister filled with coal-impregnated carbon（ASZMT-2）against SO₂under different conditions was consistent with that of coal-impregnated carbon（ASZMT-2）against SO₂.Among them,the two have good linear correlation at different concentrations,flow rates and humidity,and poor linear correlation at different temperatures.In the same concentration,specific velocity,temperature and relative humidity conditions,the protection performance of activated carbon against SO₂was better than that of the canister against SO₂,mainly because the ratio of cross-sectional area to cross-sectional area of the inlet of the canister was relatively small,resulting in insufficient gas diffusion and the filling process.Finally,the system protective performance platform of the gas mask was used to test the protection performance of the gas mask against different concentrations of SO₂under pulse airflow and constant airflow,and the results showed that the protection performance of pulse airflow was better than that of constant airflow,mainly because constant airflow was more likely to destroy the stability of the carbon bed layer under the same flow rate.In the scope of this experimental study,the protection performance under pulse airflow is about 1.28 times of that under constant airflow.