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    Wastewater desalination system utilizing a low-temperature heat pump
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    Abstract:
    A wastewater desalination system based on a low-temperature air source heat pump was developed and studied in this paper. The system consists of 2 main parts: the wastewater flow process and the heat pump cycle. A series of experiments were conducted on the system under different conditions, and the effect of the evaporation temperature was investigated. This system can reach equilibrium at any evaporation temperature using the combination of the compressor and vacuum pump. To treat wastewater with low boiling point organic matter, the system was operated at a low evaporation temperature of 48°C. The organic matter remained in the concentrated wastewater, and the organic removal was approximately 97%. Three kilograms of treated water was produced in 1 hour with an energy consumption of 250 W. The performance ratio (PR) obtained from the experiments ranged from 4.6 to 7.3. The cost for treating 1 kg of water was 0.038 yuan CNY assuming 0.5 yuan CNY per kWh at the compressor frequency of 50 Hz.
    Keywords:
    Boiling point
    Low-temperature thermal desalination
    As climate change intensifies, weather patterns across the globe become far less patterned and more unpredictable. Instances of extreme heat, excessive rain resulting in floods, and droughts that may cause or intensify wildfires have severely stressed centralized water treatment and distribution facilities and compromised access to fresh water for many. Given the vast reserve of saltwater, desalination technologies that can separate the dissolved salts from the fresh water have become essential. Traditional desalination methods use either membrane or thermal-based technologies to separate solutes from salt water and brackish water that have typical concentrations of 35,000 and 1,000 mg/L, respectively. However, they can be unnecessarily energy-intensive for lower salinity conditions. A potential next-generation approach is desalination fuel cells. Desalination fuel cells have the capability to simultaneously desalinate water and produce energy.
    Low-temperature thermal desalination
    Geothermal desalination
    Fresh water
    Citations (0)
    A methodology is proposed to identify improved thermal-based desalination structures. It is based on the notion of superstructure, allowing for the simultaneous representation of numerous feed, brine and vapor routing schemes. By adjusting the flow routings, the superstructure is capable of representing the common thermal desalination structures, as well as an extremely large number of alternate structures, some of which might exhibit advantageous behavior. The superstructure is built around a repeating unit which is a generalization of an effect in a multi-effect distillation system (MED) and a stage in a multi-stage flash system (MSF). The superstructure is proposed as an improved tool for the structural optimization of thermal desalination systems, whereby the optimal selection of components making up the final system, the optimal routing of the vapors as well as the optimal operating conditions are all variables simultaneously determined during the optimization problem. The proposed methodology is applicable to both stand-alone desalination plants and dual purpose (water and power) plants wherein the heat source to the desalination plant is fixed. It can be extended to also consider hybrid thermal–mechanical desalination structures, as well as dual purpose plants where the interface of power cycle and desalination is also optimized for.
    Superstructure
    Low-temperature thermal desalination
    Geothermal desalination
    Citations (41)
    Low-temperature thermal desalination
    Solar still
    Solar Desalination
    Thermal energy
    Geothermal desalination
    Production rate
    Water Desalination
    Citations (138)