Review of recycling of plastic packaging material waste in various countries (8)

(4) Japan actively promotes the use of waste plastic solid waste fuel.

The RDF technology was originally developed by the United States. In recent years, due to the shortage of landfills and the incinerator's treatment of chlorine-containing waste plastics, the problem of hydrogen chloride corrosion to boilers and the generation of dioxin-contaminated environment in tail gas has been exploited in recent years. All kinds of combustible waste (including waste paper, sawdust, fruit shells, sewage sludge, etc.) are made into a RDK with a calorific value of 5000 kcal/kg and a uniform particle size, so that the chlorine can be obtained as an oleolysis to improve the power generation efficiency, and it is also easy to store. Transportation and supply of substitute coal for other boilers and industrial kilns. The main development and application are as follows:

· With the support of the Ministry of Health, the resource regeneration company jointly invested by ITOCHU Corporation and Kawasaki Steel Corporation has mass-produced RDF, increasing the steam parameters of the waste power plant from <300°C to about 450°C, and increasing the power generation efficiency from 15% to 15% 20~25%. Japan is combining the overhaul to change some of the small garbage incineration stations to RDF production stations so that it can concentrate on continuous and efficient scale power generation.

· Tokushima Environmental Power Generation Company, which is mainly composed of Takomo Corporation, is building a 220,000 kW combined heat and power unit and burns RDF. It purchases RDF at 3 Yen/kg and can still sell electricity at a price of 10 Yen/kW·h. Profit.

· With the assistance of the Ministry of International Trade and Industry, the Power Supply Development Corporation is conducting a test of RDF fuel combustion in a fluidized-bed boiler. The target of power generation efficiency is 35%. The 1500kW unit is in the middle of the test.

· Under the support of the Ministry of International Trade and Industry, the Comprehensive Development Agency for New Energy Industry Technology is organizing the development project for the use of waste plastic scraps and RDF for the production of cement rotary kilns. Chichibu Onoda Cement Co., Ltd. has succeeded in burning RDF on a rotary kiln instead of using coal, and ash has also become a useful component of cement, which is better than power generation. Cement plants are actively promoting.

5.4 New Developments in Recycling Technology

Due to ecological and economic reasons, the recycling of plastic waste (also known as recycling) has become the focus of global attention. Plastic recycling process is diverse, technology varies, features vary, and evaluation varies. However, it has been proved that the best method for recovering the polymer, whether it is single component or homogeneous mixing, or known or low-mixed polymer materials, is the material method recycling. The material recycling method is the highest energy recovery method. Assuming that the recycled material can replace the new material by a 1:1 ratio, the “substitution coefficient” is set to 1, which means that the recycled material can meet the performance standards of the new material. Under such circumstances, the material recycling method consumes less energy than other recycling methods, and the amount of exhaust emissions is also low. These advantages of the material recycling method will decrease as the substitution coefficient decreases.

5.4.1 Sorting Technology of Plastic Waste

There are many kinds of plastics. Their raw materials for production are different, and the products after waste degradation are also different. The influence of the mixing of different impurities on the performance after recycling is also not the same. The differences in the physical and chemical properties of various plastics and the incompatibility make it The processing performance of the directly recycled mixture is greatly affected. In order to increase the use value of recycled products, the collected waste plastics are generally categorized and screened first, and then treated with different recycling technologies according to different materials and different requirements. In the past 20 years, the separation and separation of waste plastics has mainly focused on five main plastics such as PE, PP, PVC and PS, and polyethylene terephthalate (PET). A computer automatic sorting system has been developed abroad to achieve continuous automation of the sorting process. Our country still adopts the most primitive manual selection method, relying on manual sorting, which is inefficient and labor-intensive. The Bueher company in Switzerland uses four kinds of filters to identify the halogen light as a strong light source. The PC386 computer can separate PE, PP, PS, PVC and PET waste plastics with a separation capacity of 1t/h. The density of PE and PP is less than 1.0g/cm3, the density of PVC and PET is greater than 1.3g/cm3, and the density of PS is between 1.0~1.1g/cm3. Therefore, flotation can be performed according to different plastic densities. PE and PP are separated from other plastics, but because PE and PP are close in density, it is difficult to separate them by re-selection.

The separation rate of the small suspension separation unit of Japan Plastics Processing Promotion Association can reach 99.9%. The Dow Chemical Company of the United States has also developed a similar separation technology, using liquid hydrocarbons instead of water to separate mixed waste plastics, and achieved better results. Kellogg and the Rensselaer Polytechnic Institute have jointly developed a solvent selective separation and recovery technology to separate mixed waste plastics without manual sorting, adding chopped waste plastics to certain solvents. At different temperatures, solvents can selectively dissolve different polymers and separate them. Tokyo Metropolitan University has successfully developed a new technology for high-efficiency sorting of waste plastic sheets, which applies a strong magnetic force to the waste plastic chips in the water tank. Separation occurs due to different magnetic fields of different plastics and different depths of float sinks. In addition, some new separation techniques such as electromagnetic heating and reactive blending have also been reported. Electromagnetic rapid heating method can recover and separate metal-polymer components, and reactive blending method can realize the recovery and separation of waste bumpers with paint layer.

(to be continued)