Comparison and selection of smash pretreatment scheme before dehydration in large scale for water hyacinth

Abstract: Water hyacinth (Eichhorniacrassipes) is a noxious weed that has attracted worldwide attention due to its fast spread and congested growth, which lead to serious problems in water way transportation, irrigation, and power generation. On the other hand, it can be a valuable resource with several unique properties. Water hyacinth contains more than 95% water but due to its fibrous tissue and a high energy and protein content, it can be used for a variety of useful applications. In order to achieve theoretical basis for large-scale treatment and disposal project that have overall solution of low cost and high efficiency with water hyacinth, a comparative study of different engineering pretreatment before dehydration and analysis of the processing cost were studied as the test platform of pilot demonstration project of water hyacinth. In this paper, the process of instant smash instant dehydration was used, and two kinds of water hyacinth salvage and water transportation (the water hyacinth loaded directly into the cabin, and the water hyacinth after coarse crushing for salvage ship loaded into 1 m3 nylon bags and transported to the shore by ship), two modes of shore transfer (tower crane airlines and shore based crane) and three methods of crushing (coarse crushing of salvage ship, smash again by turning the machine two times, and smash again after coarse grinding on salvage ship)were designed and experimented in this study. The results showed that the pretreatment method of two times after the salvage of coarse powder was helpful to reduce the energy consumption of processing dehydration of water hyacinth. The treatment of per tons for water hyacinth needed about 2.5 kW·h. Through analysis of energy consumption of different crushing methods, the results showed that the method of two times after the salvage of coarse powder reduced the transportation cost, along with the need for shore crushing. It improved the grinding and dehydration treatment ability, reduced operation cost and the volume by 70.61%, and increased the transport capacity by 3.4 times for the method of salvage ship coarse powder. After the separation of water hyacinth, the content of N and P were the main nutrients in the extrusion residue, while the K value was the main factor in the extrusion juice. With the increase of the degree of grinding for water hyacinth, the N, P, K nutrient in the extrusion residue was gradually transferred to the juice. The solid-liquid separation effect of water hyacinth after anaerobic fermentation was better than that of water hyacinth direct solid-liquid separation in terms of residue water content reduction and nutrient recovery, and the moisture content of the dewatering residue was reduce to 62.89%, and it was only about 0.06 hours and about 0.7 kW·h after dehydration of per tons with water hyacinth. The results of this study have laid a solid foundation for the final design of the water hyacinth treatment and disposal, which is the treatment scheme of "rough grinding of salvage-transfer-twice crushing-dehydration".