Main process
Food waste pre-treatment process includes reception, automatic separation, solid-liquid separation, slurry heating and oil extraction. After receiving and weighing, food waste is poured in receiving hopper whose bottom is equipped with a three-screw feeder because there are lots of water and impurities in food waste. The bottom plate of hopper is of porous structure, and a leachate collection pool is arranged at the bottom of the receiving hopper, which is used to collect organic slurry leached during transportation
Food waste in receiving hopper is lifted by the screw conveyor into the automatic sorter. Main function of the automatic sorter is to separate the plastic, fabric, hard and non-fragile inorganic materials such as metal and other sundries in food waste. Sorted material is pumped to slurry heater which helps oil easily separated in solid-liquid separator. There are mainly two functions of slurry heating process: firstly, it is beneficial to maximize efficient of oil recovery process; secondly, solid organic matter in the crude material can be maximally separated via action of high temperature and agitation and enter liquid phase in next process. Separated solid slag is output by screw. The hopper leachate is mixed with extrusion slurry and enters oil extraction unit after sand removal and impurity removal.
Slurry is pumped into slurry heater after gravel and scum removal, temperature in heating tank is raised to 80℃ via steam heating and kept for a certain time. Heated slurry is sent to three-phase oil extractor to separate grease, organic solid phase and organic liquid phase in slurry. The organic solid and liquid phase separated are mixed and then pumped to the anaerobic tank for anaerobic digestion; moisture content of crude oil separated by the three-phase oil extractor is less than 3%, which can be directly sold as industrial raw materials.
Biogas produced by organic slurry is used for steam boiler partly after pre-treated, rest can be used for power generation or natural gas production. After anaerobic effluent treated dehydration system, biogas residue is transported out for disposal, biogas liquid is pumped into wastewater treatment system.
Advantages
Large volume is designed for receiving hopper to cope with limited receiving time.
Large-particle inorganic phase can be avoided entering anaerobic digestion system by pretreatment process.
1. Improving system adaptability and reliability to deal with large or hard food waste.
Since composition of food waste is complex, receiving hopper is provided with a three-screw structure, which is dual-purpose and standby, so as to improve system stability. The positive and negative reversal measures are adopted to avoid blocking of large items. The high-speed rotating paddle is used in automatic separator to crush the waste, and special structure of paddle can deal with complex and variable components of food waste. Ordinary organic matter can be broken into slurry, and large heavy inorganic matter will be separated and discharged when it cannot be broken, so as to avoid obstacles to subsequent processes.
2. Organics and light impurities (plastics, fibers, etc.) can be effectively separated
Plastics and other light sundries are separated by automatic sorter. The unique internal design structure can prevent plastic from being broken, and effectively prevent winding and blocking of plastic, fabric and other tough materials. At the same time, because pulp leaves drive the plastic to rotate at a high speed, organics and sewage adhered on the plastic can be separated by centrifugal action. The separated plastic is clean and convenient for subsequent transportation and landfill. Low organics loss rate also conducive to full recovery for anaerobic gas production.
3. Organic matter and heavy inorganic inert matter can be separated effectively.
After slurry is heated, solid-liquid separation is carried out. Most inorganic inert materials will remain in solid phase, realizing separation with organic matter. At the same time, heating and solid-liquid separation are also conducive to the transformation of organic matter into liquid phase.
Key equipment has strong wear resistance
Automatic sorter blades are made of high wear-resistant alloy steel. In addition, unique internal structure of automatic sorter ensures wear reduction in process of sorting food residues. Blades of all material screw conveyor adopt thickening design.
