Migration and diffusion of unsteady-state flow of volatile organic compounds on activated carbon adsorption beds under reverse ventilation.

Despite increasing attention to the influence of unsteady-state volatile organic compounds (VOCs) on the adsorption of activated carbon, studies in this regard are rare. Therefore, in this study, an investigation into the migration and diffusion of unsteady-state VOCs on activated carbon adsorption beds under reverse ventilation was conducted. Here, reverse clean air was introduced when the activated carbon bed reached the penetration point. The influence of reverse ventilation temperature, reverse superficial gas velocity, activated carbon filling height, and different ventilation modes on the adsorption of unsteady toluene by activated carbon were studied. Our experimental results show that when the reverse ventilation temperature increased from 20 °C to 60 °C, the quasi-first-order desorption rate constant increased from 0.00356 min-1 to 0.00807 min-1, an increase in the reverse superficial gas velocity led to a higher rate constant, and at greater reverse superficial gas velocities, the stripping capacity increased. It was observed that the maximum stripping capacity was achieved at a reverse superficial gas velocity of 0.3 m/s. For different activated carbon filling heights, following reverse ventilation, the stripping capacity of a 5 cm and 30 cm activated carbon bed accounted for 41.43% and 65.85% of the original adsorption capacity, respectively. The study concludes that concentration of toluene first increased and then decreased with time under forward ventilation, whereas the concentration gradually decreased under reverse ventilation.

The migration and diffusion of unsteady-state VOCs flow on activated carbon adsorption beds.

ABSTRACTTraditionally, in engineering applications, VOC (volatile organic compound) emissions are usually under non-steady states due to intermittent emissions and concentration fluctuations, which adversely affects the stable and reliable operation of many existing purification systems and may constitute a safety hazard. However, previous studies on VOC adsorption by adsorbents have mostly focused on the adsorption performance and properties of different modified adsorbents. Few studies of VOC adsorption have focused on adsorption or movement for unsteady-state VOCs using activated carbon adsorption beds. This study investigated three common and important factors (load time ratio, load mode and no-load flow rate) that affect the adsorption of unsteady-state VOCs by activated carbon. This allowed the migration and movement of VOCs between activated carbon adsorption beds under different factors to be analyzed, which provides important insights in understanding VOC adsorption and can promote the development of homogeneous buffering technology for non-steady state VOCs. In addition, this information provides support for the development of pollution control processes for tidal VOCs discharge airflows that result from storage and transportation operations, and also provides parameters that could support practical applications of activated carbon to adsorb unsteady-state VOCs.

[Operation and Maintenance of Cost-Effective Volatile Organic Compounds Abatement Alternatives].

Presently, volatile organic compounds (VOCs) pollution control in China has entered the deep-water zone, facing difficult challenges. The cost-effectiveness of VOCs abatement alternatives will determine the final environmental benefits. Screening of abatement alternatives with good cost-effectiveness and performance is important to form a sound basis for VOCs emission abatement work to create sustainable and stable alternatives. In this study, 12 typical emission scenarios are set up based on the emission characteristics of pollution sources, such as emission concentration, airflow volume, continuous or intermittent emissions, and fluctuations in concentration. Based on these typical scenarios, the operation costs of current mainstream emission abatement alternatives is estimated, and a cost-effectiveness comparison is made using the unit abatement cost (UAC, yuan·kg-1, VOCs) as the index. The results obtained can provide a reference for choosing appropriate VOCs abatement alternatives according to the characteristics of VOCs emission. Results show that for low concentration VOCs, the UAC of emission abatement is normally more than 8 yuan·kg-1. The concentration in the process plays an important role in reducing UAC. Therefore, the reasonable collection of VOCs gas, resulting in smaller emission volume and higher concentration, has a significant impact on the subsequent emission abatement cost-effectiveness. Enhancing the classification collection of VOCs to improve resource attributes of the recovered VOCs liquid is also an effective way to improve the cost effectiveness of VOCs abatement.