Melt regeneration of waste plastics (2)
Third, the regeneration of granulation
The dried and dried waste is usually granulated before molding. Waste plastics are generally used after the production of varying degrees of aging, the additives also have varying degrees of loss. So before the granulation often need to add some additives, especially soft polyethylene plastic, often need to add plasticizers, stabilizers and so on. As the recycled plastic is often mixed with many different colors of waste, so the general regeneration in the work hours are required to add dark colorants, it should be noted that the addition of additives to consider the use of lower prices varieties, due to regeneration The price of the product is generally low.
Fourth, waste plastic pyrolysis recovery
There are many methods for recovering oil and gas by pyrolysis, such as melt bath method, screw thermal decomposition method, reaction tube evaporator method, fluidized bed reactor method and catalytic cracking method. Different methods can be used for thermal cracking of different kinds of plastic Recycling is now described separately below.
1. Melting tank method
The molten bath method is a method in which a molten salt is used as a heating medium for heating and decomposing the waste plastic, and the decomposed heat vapor is condensed into a decomposing product in a condenser after passing through a power precipitator. This method can be applied to polyethylene, Propylene, polypropylene, polystyrene.
2. Screw thermal decomposition method
Screw thermal decomposition can be used for the recovery of polyethylene, polypropylene, polystyrene, polymethyl methacrylate, a key part of such a device is a screw thermal decomposition reactor. General use of external heating, the temperature of 500 to 550 degrees. The material is preheated with a microwave heater before entering the screw thermal decomposition reactor. Reaction products were light oil, heavy oil recovery.
3. Reaction tube evaporator method
The reaction tube evaporator method is used for homogeneous raw materials and is easy to become liquid monomer waste plastic recycling, applicable waste plastic varieties are random polypropylene (APP), polystyrene and so on.
4. Fluidized bed reactor
Fluidized bed reactor method has a variety of devices for the recycling of waste plastics, this method can be applied to: polypropylene, cross-linked polyethylene, polypropylene, polyvinyl chloride and other plastics.
5. Catalytic cracking method
Catalytic cracking method is the use of appropriate catalyst for low-temperature oil waste plastic method, generally used for a single variety of plastic oil, the applicable plastic polyethylene, polypropylene, polyvinyl chloride and so on. As a result of the use of low-temperature oil, so this method of high oil yield, in addition, the use of the catalyst to make the oil more uniform, the product of the higher price.
Five, waste plastic energy recovery
The energy recovery of waste plastics is through the efficient use of heat energy released during the incineration of the incinerator to achieve the purpose of recycling. Combustion heat is usually used by heat exchangers to convert heat energy into warm water, or by converting the boiler into steam power generation and heating. Waste plastic - broken - burning - heat recovery - smoke treatment
Waste plastic energy recovery of the key issues First, incineration technology, the second is the treatment of combustion waste gas. The former because of the higher calorific value of plastic and waste plastic types are different, so the design of the incinerator have some requirements; the latter due to environmental protection requirements, the exhaust gas requirements of pollution-free, it must be processed.
1. Incinerator for waste plastics
The waste plastic incineration in the design of the following requirements,
1 can be mechanically operated and burned and stabilized
2 can be effectively burned even if it is a mixture of various plastics or mixed with other municipal solid waste
3 to prevent the release of harmful gases to the maximum
4 incineration capacity, less failure
5 burning completely, do not produce dust particles
6 Wastewater discharge should meet environmental requirements
Thermoplastics into the high temperature of the incinerator, part of the plastic quickly melt and rapid composition of the solution or gasification, the results of gas combustion, and the resulting carbon residue burning slower, part of the melt cover its surface, resulting in hypoxia and combustion insufficient. Thermosetting plastic heating is not melting, and the decomposition of combustion and surface combustion, high ignition temperature and burning speed is slow. When the above-mentioned thermoplastics and thermosetting plastics are put into incineration at the same time, frequent combustion of carbonaceous residues and thermosetting plastics occurs, resulting in combustion stagnation. In this case, proper mixing and good ventilation are required in the incinerator, To promote the combustion of solids.
The outer structure of the combustion chamber for the waste plastic incinerator is as follows:
(1) Fire lattice incinerator (2) Bed type incinerator (3) Under the fire lattice incinerator (4) Flowing layer incinerator (5) Tornado incinerator (6) Micro pulverized coal incinerator
2. Waste recycling of waste plastics
The heat of incineration of waste plastics is utilized by the heat exchanger to make water water or steam.
Six, recovery of chemical raw materials
The method of recovering chemical raw materials can be used for the recovery of many kinds of waste plastics. This method is actually a chemical decomposition method. It can obtain more uniform decomposition products than pyrolysis method. However, this method requires a single variety of clean waste, chemical decomposition method Chemical raw materials are mainly hydrolysis and alcoholysis, as follows.
Hydrolysis is a method of recovering raw materials by hydrolyzing a readily hydrolyzable group of polymers. This method is applicable to plastics such as polyesters, polyesters, polycarbonates and polyamides, which are stable under normal conditions, so the hydrolysis must be carried out under special conditions, and the polyurethane is recovered industrially by hydrolysis. Polyester polyol.
Alcoholysis is the use of alcohol alcohols alcoholysis of some polymers to recover raw materials. Alcoholysis method can be used for polyester, polyester and other plastics. The alcoholysis process for a polyester foam is as follows:
Ethylene Glycol - Polyurethane Foam - Crushing - Reactor - Distillation - Polyester Polyol N2
Alcoholysis using ethylene glycol, the reactor with a stirring device, the temperature control in 185 to 210 degrees, the reaction sometimes with organometallic compounds as a catalyst.
Polyester (polyethylene terephthalate) alcoholysis can be obtained Ethylene terephthalate and ethylene glycol, with their production of polyester is not low quality raw materials.
(Source: Alibaba plastic price library)
Shantou Mingfa Machinery Co., Ltd
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