Exploring new pathways for Coal-to-Gas Wastewater Treatment: Cyclonic Separation and Coalescence Technology.

Driven by energy security strategic needs, resource endowment advantages, industrial upgrading demands, and the need for clean energy transformation, and guided by the "dual carbon" strategy, China is vigorously developing the modern coal chemical industry. Through continuous technological innovation and capacity expansion, coal is being transformed into high-value chemical products such as coal-based olefins, coal-based gas, coal-based ethylene glycol, and coal-based oils. This shift not only optimizes the national energy structure but also contributes to building strategic energy reserves.

The coal chemical industry comprises an industrial system that converts coal into fuels, olefins, and advanced materials via chemical processes including gasification, liquefaction, and coking. It encompasses both traditional sectors (e.g., coke and synthetic ammonia production) and modern advanced segments (e.g., coal-to-liquids and coal-to-olefins).

Nevertheless, as an energy and water intensive sector, the industry confronts mounting environmental pressures, with wastewater treatment emerging as one of its most critical challenges.

Coal gasification, the core process in coal chemistry, exhibits varying pollution levels depending on the technology route. Although fixed-bed gasification technology (such as the Lurgi furnace) has wide adaptability to raw materials, it suffers from problems such as small single-furnace scale, high steam consumption, and complex composition of gasification wastewater (containing tar, phenols, etc.), making wastewater treatment extremely difficult. While pressurized pure oxygen gasification technology is relatively environmentally friendly, atmospheric pressure gasification and air gasification technologies have been listed as obsolete due to severe pollution.

Research indicates that operational costs in the coal chemical industry are substantial, with wastewater treatment representing a significant portion. Therefore, developing novel treatment technologies that reduce costs, enhance efficiency, and comply with discharge standards has become a critical focus for industry players.

The quench water and wash water produced during the coal gasification process have high oil content and are severely emulsified. In previous treatment processes, the upstream oil removal equipment had insufficient treatment capacity, leading to unstable operation of the ammonia stripping equipment, severely exceeding ammonia nitrogen and COD concentrations in the effluent, significantly increasing the pressure on downstream wastewater treatment, and making it difficult to meet discharge standards. This situation not only restricts the production of enterprises but also poses a potential threat to the environment.

To address these challenges, Brator has developed an integrated solution based on continuous innovation and practical experience, specifically designed for coal gasification wastewater.

This technology primarily utilizes physical oil removal techniques. Compared to traditional chemical oil removal methods, physical oil removal offers the following advantages in the coal chemical industry:

• Lower operating costs with no chemical additives required;

• Purely physical process, introducing no foreign substances, thus avoiding secondary pollution and ensuring compatibility with downstream ammonia stripping;

• High oil recovery efficiency and resource utilization, delivering secondary economic benefits;

• Compact, automated equipment design;

• Low energy consumption, with no electrical power required during operation;

• Fully enclosed, liquid-filled operation, eliminating VOC emissions.

  
  

Gasification wastewater contains fine coal powder and a large amount of oil. The hydro-cyclone utilizes centrifugal separation technology to efficiently separate free oil, dispersed oil, and solid suspended matter such as mechanical impurities and sediment from oily wastewater, enabling pretreatment of the oily wastewater and ensuring efficient subsequent treatment. Thanks to the application of the hydro-cyclone principle, its separation efficiency far exceeds that of inclined plate sedimentation, reaching dozens of times higher.

The coarse-grained filter element can capture dispersed oil droplets larger than 20 microns, promoting their gradual coalescence into larger oil droplets and accelerating oil-water separation; this filter element utilizes a unique and advanced coarse-graining principle, which is a first in China.

The polymer special material coarse-grained filter element, jointly developed with the Institute of Materials Science of the Chinese Academy of Sciences, is specifically designed for oil droplets of 10 microns and above. Due to the oleophilic and hydrophobic properties of the material, this filter element can effectively capture small oil droplets, promoting their coalescence into larger oil droplets, which are then separated from the oil-water mixture and finally collected in the free oil collection device.

The oil-water separator is designed as a single-cylinder, multi-chamber horizontal system, supplied as a skid-mounted integrated unit complete with piping and instrumentation. This modular approach simplifies installation, enhances automation, and facilitates operation and maintenance.

Solving oil removal problems for enterprises, assisting in their development, and achieving a win-win situation for both environmental protection and economic growth is our motivation and vision. We look forward to engaging with more coal chemical enterprises to discuss tailored process solutions and contribute to the sustainable advancement of the industry.