Study On Adsorption Atmospheric Water Collection Based On Activated Carbon Fiber

It can provide living and drinking water in islands and remote areas by using solar energy or other low heat sources to supply energy to extract moisture from the air.At present,the thermal cycle process of the atmospheric water catchment system is complex,the energy utilization rate and heat transfer efficiency are not high,and the adsorption and desorption performance still needs to be improved.In order to solve this problem,a high-efficiency composite adsorbent was prepared by single impregnation or mixed impregnation of polyvinyl alcohol,lithium chloride and calcium chloride with different concentrations and the activated carbon fiber was used as a carrier.Based on the prepared adsorbents,an atmospheric water harvesting system was designed and constructed.The system relies on the adsorbent to capture water vapor in the atmosphere at night,and resolves the liquid water in the adsorbent by solar energy during the day.Then the vapor water condenses on the surface of the condenser to form liquid fresh water.The adsorption and desorption processes work independently.The experimental study was carried out under the winter climate conditions of Kunming.The adsorption of water at below 20 °C and the efficient desorption of water at close to 60 °C or over 60 °C were achieved.Compared with the conventional water collection method,the atmospheric water collection system broadens the water source and changes the water collection method.It can draw fresh water at a high dew point without consuming electricity,and is clean and convenient.The main research contents of this paper are as follows:(1)According to the working principle and heat transfer process of the atmospheric water catchment system,the enthalpy-humidity diagram was described.The physical property changes of the internal air were theoretically analyzed,showing the performance evaluation index of the water catchment system.The results show that: increasing the adsorption capacity,increasing the desorption temperature,and improving the heat transfer performance can increase the water production of the system.(2)The performance of the composite adsorbent was analyzed from the microscopic level and macroscopic characteristics.From the SEM image,it is found that the voids of pure activated carbon fibers are more obvious.As a result,the voids of pure activated carbon fibers can carry a large amount of hygroscopic salts.Compared with pure activated carbon fiber and single-impregnated hygroscopic salt,the composite adsorbent prepared by mixed impregnation has stronger adsorption properties.And a unit mass of composite adsorbent material can absorb 1.28 g of water.At the same time,the void change of the composite adsorption material was tested by the specific surface area and pore size analyzer,in which the specific surface area,porosity and pore size all decreased,while the adsorption characteristics were enhanced.Compared with several other adsorption materials,the composite adsorption material(APLI)made of composite activated carbon fiber,polyvinyl alcohol and lithium chloride has the best adsorption and desorption performance,which can complete the adsorption in the environment below 20 °C,and complete the desorption at close to 60 °C or higher than 60 °C.Finally,the adsorption equilibrium equation fitted based on the Polanyi principle established a theoretical basis for the subsequent research on atmospheric water catchment.(3)By simulating the heat transfer performance of different fin spacing,fin thicknesses,and fin lengths,an adsorption-type atmospheric water catchment system with optimal size parameters is optimized.Under the winter conditions of Kunming,the adsorbent was placed in the atmospheric water collection system for experiments.The results showed that the system using APLI for the outdoor experiment of atmospheric water collection had the best water collection performance,and the200mm×200mm×250mm box could produce 68.15 g of water.To some extent,the atmospheric water catchment system experiment can provide theoretical guidance for the use and promotion of water-deficient areas in various places.