Technical Field

The proposed engineering solution comprises equipment for recycling of plastics by recovering hydrocarbons from the plastics.

Background Art

Waste plastics must be disposed of in ways which involve minimum impact on the environment. This means primarily landfilling, incineration or recycling. Since waste plastics have a potential to provide valuable raw materials, and their reuse appears to be the most environmentally friendly option, recycling of plastics has become today's trend. One recycling method involves making products from crushed plastics by partial melting and consolidation of the granulated plastic material. Using moulding processes, drainage troughs, flower pots, and other products can be made.

An economically and environmentally sound option is the recovery of hydrocarbons from waste plastics. It is accomplished by heating the waste plastics to a very high temperature in the absence of air (oxygen). Condensation of the gasified waste plastics produces oil which can be used, for instance, as fuel for diesel combustion engines.

One type of equipment and process for recycling plastics by recovering hydrocarbons is outlined, for instance, in the JP2015057500 patent file. The disadvantage of the equipment described therein is its poor operating safety which is given by its design. As a consequence, incidents have been recorded where melted waste plastics and the resulting gases ignited during out-of-standard operation regimes. These disadvantages are eliminated by the engineering solution proposed herein.

Disclosure of Invention

The engineering solution consists in the design of equipment for continuous recycling of plastics. The equipment comprises at least one heating system, at least one evaporation tank, a feeder system, a closed-circuit cooling system, a distribution system that supplies inert gas to the equipment's interior, and an air separation device for removing air from the plastics in the process. The air separation device is installed between the feeder system, which is in the form of a pre-heating extruder, and the evaporation tanks. In the evaporation tank, at least one level sensor is provided for checking the level of the tank's content. The sensor output is connected to the control unit of the feeder system drive. By this means, the waste plastics feed rate to the process can be controlled accurately - with respect to the evaporation rate. The heating system comprises an array of electrical heating ceramic elements.

With respect to operating safety, it is advantageous when the evaporation tank is fitted with a pressure relief valve whose outlet leads to the cooler. If the pressure relief valve activates, the hot gas is safely reduced in the cooler and cannot escape uncontrollably outside the process.

It is also advantageous when the equipment is provided with a backup electrical power source and an after-cooling system with at least one coolant reservoir connected to the cooler. In the event of an electrical power supply failure, the backup power source activates automatically. In addition, a shutdown sequence activates in order to keep running the after- cooling system and all devices that are required for safe shutdown. By this means, uncontrollable local overheating of the equipment, which could pose a severe fire risk, will be prevented in case of an electrical power supply failure.

In a configuration which is advantageous for flexible deployment, the equipment is built into a portable and closable transport container. Given its favourable dimensions, it can be easily transferred directly to a plastics sorting facility to enable the plastics to be processed at the point of sorting. Such an arrangement is both economically and environmentally beneficial. With respect to fire safety, it is advantageous to install distribution piping for an automatic fire extinguishing system in the interior of the transport container.

Brief Description of Drawings

An example embodiment of the proposed solution is described with reference to the drawings which show the following.

Fig. 1 - Side view of the equipment;

Fig. 2 - Front view of the equipment. Best Mode for Carrying Out the Invention

In this case, the equipment for continuous recycling of plastics contains a heating system in the form of an array of electrical heating ceramic elements. Thanks to this method of heating the waste plastics, the plastics neither burn nor suffer degradation. Furthermore, the equipment comprises two evaporation tanks 6, feeder system 1 , closed-circuit cooling system 9 with anti-freeze coolant, and distribution system 8 that supplies process inert gas to the equipment interior.

Sorted waste plastics are transported to the feeder system 1, which has the form of a preheating extruder. In here, they are heated gradually and then forced to the downstream parts of the equipment. The liquid phase released from the waste plastics descends by gravity through air separation device 2 which acts as a siphon trap. By this means, the air is prevented from passing from the input section to the downstream assemblies of the equipment, while, at the same time, flammable vapours from the melted plastics are kept from entering the input section of the equipment where they could mix with air. Due to high temperature, the latter occurrence would pose a severe fire risk. The liquid phase is then heated in pre-heating device 3 in the absence of air and transferred to balancing tank 4. The first gaseous phase passes from the balancing tank via the first condenser with a filter to cooler 9. The remaining liquid phase flows through the inlet piping 5, which is installed below the operating level of the content, to the evaporation tanks 6, where it continues to be heated. Inside evaporation tank 6, at least a level sensor is provided for checking the level of the content of evaporation tank 6, and this sensor's output is connected to the control unit of the drive of the feeder system L In evaporation tanks 6, the liquid phase is separated into solid and gaseous phases. The second gaseous phase passes to condensing tanks 7, where long hydrocarbon chains split into short chains.

The resulting oil gas is conducted via evaporation piping 12 to primary cooler 9, in which it cools rapidly, thanks to the closed-circuit cooling system, and eventually condenses into liquid oil. Together with the process inert gas, the liquid oil flows into a separator made of glass, in which the process gas is separated from the oil and, upon passing through water, the gas enters the gas filter and can be collected in a reservoir for reuse. The oil is then clarified and poured into a tank from which it is pumped to external storage vessels.

To provide operating safety, the evaporation tank 6 is fitted with a pressure relief valve whose outlet leads to the cooler 9. The equipment is provided with a backup electrical power source and an after-cooling system with at least one coolant reservoir which is connected to the cooler 9. The equipment configuration enables it to be built into a portable and closable transport container. The interior of the container is fitted with distribution piping for an automatic fire extinguishing system.

This equipment is unique primarily thanks to its compact arrangement, and fire safety. The plastics recycling process is fully automated and places only minor requirements on the operating staff. The operating staff only visually supervises the operation of the equipment and prepares the input stock.

The best mode for carrying out the invention is shown in Figs. 1 and 2.

List of reference symbols

1 - feeder system

2 - air separation device

3 - pre-heating device

4 - balancing tank

5 - supply piping

6 - evaporation tank

7 - condensing tank

8 - distribution system for application of process inert gas

9 - cooler

12 - evaporation piping