| 摘要 |
A composting method accompanying aerobic or anaerobic digestion and a composting device employing the method are provided to utilize a liquid fertilizer which is byproduct of livestock excretion treatment as useful resources, to fix nitrogen in soil for time-release fertilizer and to transform liquid fertilizer into solid fertilizer which is transported or stored more easily by water content control process through mixing liquid fertilizer with hydrophilic absorptive material. A composting method accompanying aerobic or anaerobic digestion comprises: concentration process for liquid fertilizer; water content control process through mixing liquid fertilizer concentration with hydrophilic absorptive material; and solidifying process for the mixture comprising liquid fertilizer concentration and hydrophilic absorptive material. The liquid fertilizer is concentrated to 55-90%. The absorptive material is natural zeolite in the form of stone or clay, or artificial zeolite. A mixing ratio of the liquid fertilizer and zeolite in the mixture is 1:0.5 to 1:2.5 by weight. The concentration degree and the mixing ratio of the liquid fertilizer and the zeolite in the mixture are controlled in order to maintain the water content of the mixture comprising the liquid fertilizer and zeolite as 7-13%. The composting method optionally comprises initial pH control process that comprises adding strong acid to the liquid fertilizer before concentration process. A composting device employing the method comprises: pH control part(1) which controls initial pH of liquid fertilizer; a pressure evaporation part(2) which concentrates the liquid fertilizer from the pH control part(1); an absorptive material mixing part(310) for mixing the concentrated liquid from the pressure evaporation part(2) with absorptive material; a solidifying treatment part(3) which solidifies the mixture from the absorptive material mixing part(310) to produce particulate solid fertilizer; and an energy supplying part(4) comprising a gas boiler(410) and a control valve(420), which controls steam generated from the gas boiler(410) to be supplied for the pressure evaporation part(2). The pH control part(1) comprises a liquid fertilizer retention tank(110) for storing liquid fertilizer from an anaerobic treatment system(5), a storing tank(120) for strong acid, a control valve(130) to control the amount of strong acid for pH control, a liquid fertilizer escort pump(140) which escorts liquid fertilizer in the retention tank(110) to the pressure evaporation part(2), and a detector(150) for the acidity of the liquid fertilizer in the retention tank(110). The pressure evaporation part(2) has plural pressure evaporators(210a,210b,210c), plural heat exchangers(220a,220b,220c) for each pressure evaporator, a recovery line(230) for recycling some water generated from the pressure evaporators(210a,210b,210c) for a heat exchange, condenser(240) for supplying condensed water from water generated from the pressure evaporators(210a,210b,210c), and a cooling tower(250). The absorptive material mixing part(310) comprises a hopper(311) and a feeder(312), and the hopper(311) supplies the feeder(312) with absorptive material. The feeder(312) transports the absorptive material to a pelletizer(320). The solidifying treatment part(3) comprises a pelletizer(320), a drying part(330) and a packaging part(340). |
