Internal Reuse of Methanol-to-Olefin Wastewater Based on Micro-Channel Separation Coupling Hydrocyclone Regeneration

Abstract

Methanol-to-olefin (MTO) is a typical example of the new coal chemical industry. Due to the large volume of generated wastewater, complex composition, and heavy environmental hazard, wastewater recycling is critical for sustainable industrial development and ecological protection. Herein, a swirl regenerating micro-channel separation (SRMS) technology integrating deep filtration and hydrocyclone-enhanced regeneration was proposed. A small-scale experimental investigation was first conducted to verify the feasibility of the MTO wastewater treatment. A pilot SRMS device with a treatment capacity of 20 m3/h was constructed, and the continuous operation effect and stability of the device were comprehensively evaluated. The separation performance of the SRMS device at different solution pH values and the effect of the hydrocyclone-enhanced regeneration of separation media were discussed in detail. At low solution pH values (<7), the SRMS device exhibits an average separation efficiency of 92.0% for fine particulate matter in wastewater, and the median particle size, d50, decreases from 1.55 to 0.6 μm. As the solution pH increases, the repulsive energy barrier for the medium-contaminant and contaminant-contaminant increases, inhibiting the deposition behavior of particulate pollutants. In addition, hydrocyclone desorbs contaminants deposited on the separation media and the average contaminant residual rate decreases from 3.3 to 0.2 wt.%. Based on the experimental results, we propose an industrial application for the treatment and reuse of MTO wastewater (200 m3/h) using the SRMS technology. The costs of the wastewater treatment process are as low as 0.25 CNY/m3, and the wastewater reuse rate is over 97%, without chemical consumption. This work can provide an environmentally friendly and economically sustainable approach to the source management of MTO wastewater.

Keywords: MTO, waste catalyst, micro-channel separation, XDLVO theory, media enhanced regeneration