Marine desulfurated wastewater

Introduction of marine Exhaust Gas Cleaning Systems

Marine exhaust cleaning system usually is divided into open, closed and hybide system.

  -Open Loop System

  In an open-loop system,exhaust gas is washed with sea water in the scrubber. The process water is discharged to the sea directly after treatment.

   -Closed-Loop System

   In a closed-loop system, exhaust gas is washed with sea water in the scrubber. The process water is recirculated in the system after treatment.

    -Hybrid System

   Ahybrid system can run in either closed or open loop mode. The process water can be recycled or discharged directly to the sea.

Marine washing water treatment system

  In order to meet the discharge standards of washing water, a number of solution providers provide different solutions. In summary, they are basically divided into centrifugal method and membrane method.

  Centrifugation:

Principle of Centrifugation: when liquids of different densities rotate around a central axis at a high speed, the moving object will receive centrifugal force. The higher the rotation rate, the greater the centrifugal force received by the moving object. At the same rotational speed, substances of different sizes and densities in the liquid will settle at different rates. If the particle density is greater than the liquid density, the particle will gradually move away from the central axis along the direction of centrifugal force. After a period of centrifugation, the effective separation of substances of different densities can be achieved.

Membrane:

Membrane method principle: Membrane method through physical filtration to achieve the treatment of washing water. For the composition of washing water, the basic choice of microfiltration membrane can meet the relevant discharge requirements, and can save energy.

    At present, the Marine industry mainly uses silicon carbide membrane or alumina membrane. Comprehensive comparison, silicon carbide membrane in hardness, flux, life, acid and alkali resistance are better than alumina membrane, silicon carbide membrane should become the trend of The Times.

    The washing water treatment system adopts silicon carbide ceramic membrane filtration technology to realize the wastewater treatment produced by ship wastewater desulfurization system.

    After quenching and tempering treatment, the raw water is filtered through silicon carbide ceramic membrane. After filtration, the raw water can be directly discharged in accordance with EPC.259(68), and the impurities produced by filtration are filtered and packed for storage.

   The washing water treatment system adopts modular design, which is provided with a feeding module, a treatment module and a pressure filter module. The feed module is provided with a coarse filter and a centrifugal pump to supply raw water to the treatment module; The treatment module is provided with a control system, a membrane treatment module, a cleaning module and a sewage discharge module to treat the washing water; The filter press module is equipped with a sludge tank, a diaphragm pump and a filter press to separate the concentrated water from the solid liquid.

 Working principle:

 The circulating cross-flow filtration is adopted to filter the pretreated water. In the filtration process, the backwash pump is used to backwash the membrane regularly to maintain the membrane flux. When the pressure difference between the two ends of the membrane filtration is too large, the system is cleaned chemically with a cleaning pump to recover the membrane flux.

The equipment uses silicon carbide membrane to treat the washing tower waste water, and physically separates the suspended solids such as ash and particles in the waste water. The separated waste water is directly discharged overboard or Holding Tank after qualified monitoring by the water quality monitoring equipment. The device adopts membrane separation technology, which is different from the traditional purification system, and has the advantages of small footprint and high efficiency.

At present, there are two kinds of water treatment schemes in ship desulfurization market. Both schemes have their own characteristics:

◾ Centrifugation method occupies a relatively small area, the cost is relatively low, the waste liquid is less that requires a small waste liquid tank. However, the water quality after treatment is sometimes not guaranteed, and the control process is more difficult. At present, there is mature control technology on the market for Alfalaval and a French enterprise, but Alfalaval's WCU is not for sale, resulting in a very small choice of centrifugal method. And if emissions standards are tightened further in the future, upgrading may not be easy.

◾ Membrane method is relatively large in area, high in cost and large in volume demand of waste liquid tank, but filter cake can be made by filter press scheme. The treated water quality is generally stable. Later, if emissions standards are tightened, it will be easier to upgrade. In addition, it can achieve a higher degree of automation and requires less maintenance.