1. No category

DEPOLYMERIZATION
GTE INTERNATIONAL s.r.o.
SNP 29,
990 01 Veľký Krtíš
Slovenská republika
1.1 Low-temperature catalytic depolymerization
1.1.1 The significance of plastic waste
The various synthetic polymer derivatives became the most important structural materials
of humanity. The use of plastics has increased significantly over the last hundred years and in
the result of wastes also appears increasingly the different types of polymers. The
manufacture of polymers requires large amounts of fossil fuels because the main raw
material in the production is oil. For this reason, it is important to regard the waste polymers
as a secondary source of raw materials.
1.1.2 The depolymerization process and description
The thermal decomposition means chemical breakdown of polymer chains at oxygen-poor
or oxygen-free environment in a properly designed reactor. In this way, the energy content of
plastic waste is recovered better efficiency. Also a big advantage is that the resulting liquid,
gas and solid products can utilize as primarily energy source and secondly the chemical
industry can use as secondary raw materials. In this case the depolymerization means the
processing of waste plastics (polymers) in inert atmosphere at the temperature range of 350450 °C. The effect of higher temperature cracks the long carbon chains into smaller ones and
depending on this formed a variety of useful hydrocarbons fuels. It is important that during
the process should create oxygen-free atmosphere, so without generating environmentally
hazardous combustion products (CO2, CO, SO2, NOx, etc).
It is not a process of combustion or pyrolysis, but the low-thermo catalytic decomposition
of the material. This unique technology brings a different view of polymer processing.
Depolymerization is a cracking process with the addition of a catalyst, lowering the
transformation reaction temperature to the level of 350-450°C.
The low-temperature catalytic depolymerization line is a process facility for the
depolymerization (decomposition) of polymers to carbon products which are synthetic gas,
synthetic oil and solid residue (carbon with inert material fraction). Thanks to their
composition and energy value, the output products are similar to light fuel oil, natural gas and
bituminous coal.
In this way of recycling the plastics can be produced a lot of valuable chemical raw
material and fuel like:
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C1-C5 gas products (good quality combustible gas with which the technology of heat
demand partly be covered)
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C5-C14 gasoline type liquid products,
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C10-C28 diesel fuel products,
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C25-C37 heavy oil fractions and,
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C38+ can be defined as fuel oil, cracking residual etc.
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DEPOLYMERIZATION
GTE INTERNATIONAL s.r.o.
SNP 29,
990 01 Veľký Krtíš
Slovenská republika
Qualitative and quantitative distribution of products can be significantly influenced with the
temperature, residence of time and the catalyst. Processes illustrated in the simplified flow
chart of the depolymerization process.
1. Simplified flow chart of the depolymerization process
1.1.3 The devices of technology and a description of the method
The device is designed as a simple aggregate, the ease of which provides a long life and
easy operation. Ease of the device is compensated by larger building area; however, the
failure is minimal.
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DEPOLYMERIZATION
GTE INTERNATIONAL s.r.o.
SNP 29,
990 01 Veľký Krtíš
Slovenská republika
The device consists of a dosing system, bucket conveyor of material to receiver, dosing
system of catalyst, screw conveyors of material, depolymerization reactors, heating of
reactors, dry scrubber, and system of condensers, fuel tanks for Poly-fuel, cooling system,
outlet and deposit of the solid residue of Poly-carbon and the gas containers for Poly-gas. The
whole procedure illustrates the so-called schematic diagram of the apparatus
depolymerization.
2. Schematic diagram of the apparatus depolymerization
Depolymerization line consists of 2 identical parts. Each part contains two double skin
depolymerization reactors mutually connected in series. Material enters the depolymerization
reactor through the dosing system and receiver. Receiver is equipped with a pair of sliding
gate valves working in polar mode at the inlet and outlet; therewithal the ingress of
atmospheric oxygen into the technology is eliminated. To limit the entry of oxygen, the
gaseous nitrogen is let-in into receiver at regular intervals. The amount of oxygen in the
receiver is controlled by the oxygen detector.
Polymer processed within depolymerization reactors is moved by a spiral feed. The heat is
provided by flue gases generated in heat generators (this is indirect heating of the polymer).
The flue gases provide heat to the depolymerization process. Subsequently, the flue gases are
transferred through a chimney into the air. Dual burners are used for combustion of gas or oil
in the heat generators. A liquid fuel of equivalent diesel is used for the first start of the line.
Synthetic gas produced in depolymerization process is burnt for the line operation itself.
Synthetic gas will be also used as a fuel for start of the line after service downtimes.
The hydrocarbon gas is generated in the depolymerization reactors during
depolymerization process. It flows through cyclone separator (removing heavy hydrocarbon
fractions from the gas – waxes, which are transported to a first depolymerization reactor
where they undergo depolymerization again), and then through the pre-heater to the
condensers where the gaseous phase of the hydrocarbon is transformed into a synthetic oil.
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DEPOLYMERIZATION
GTE INTERNATIONAL s.r.o.
SNP 29,
990 01 Veľký Krtíš
Slovenská republika
The oil is collected in the oil receiver from where it is re-pumped into the phase separator
column. The produced oil is further purified by the filter device (centrifugal oil cleaner), and
hence it is possible to carry it to final storage tanks for further use.
The non-condensed hydrocarbon gas – synthetic gas flows through a dry scrubber into the
gas container. From gas container, the synthetic gas is distributed as a fuel in heat generators
to the burners of heat generators. A proportioning burner – flare stack (as a safety device) is
inserted in gas train. It can also burn low calorific value hydrocarbon gas produced at start of
the line. A method of dry scrubbing is used to clean the synthetic gas, when a limestone or
granulated activated carbon is used as a sorbent.
The catalyst used in the depolymerization process is a multicomponent modern catalyst
PECAT, which the manufacturer of the line produces and supplies. The dosage of the catalyst
is carried out automatically by its addition to the depolymerization reactor during dosing of
input polymer. The amount of catalyst is depending on the input polymer material.
Pre-heaters are placed in the system for maximum utilization of the calorific energy. They
ensure mainly preheating of combustion air whereby they reduce consumption of gas for
heating of depolymerization reactors, for heating tanks and oil distribution system and
possibly for heating of the space where the technology is placed. The entire heating system
will be charged with a mixture of glycol and water. A closed cooling circuit is a part of the line
and it will contain the mixture of glycol and water.
Depolymerization cycle lasts 6 hours, and is repeated 4 times per day. The cycle is
terminated by carrying of solid carbon residue out from the depolymerization line in bags (big
bags) or in some kind of containers.
The plan view of installed depolymerization plant can be seen on Figure 3. You can see
clearly the compact size of design due to good space utilization of the plant.
3. Top plan view of the depolymerization plant
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DEPOLYMERIZATION
GTE INTERNATIONAL s.r.o.
SNP 29,
990 01 Veľký Krtíš
Slovenská republika
Smooth operation of depolymerization line is automatically controlled by the
measurement and control system. Measured values can be seen in the visualization on
switchboards, central control board, or at a remote message. Automation system ensures
starting of the line, shutting down before servicing, alerts (visual and acoustic alarms), safe
shutting down of the line in case of critical failures.
1.1.4 Storage of products
Liquid products (gasoline and diesel-type hydrocarbon fraction) are stored in first step at
temporary storage tank. The ultimate storage can be predictable depending on application
requirements and available tonnage.
The gas products can be stored in 500 m3 gas storage tanks. From without residual energy
will be used in the cogeneration unit.
4. Cogeneration unit (CHP)
The solid residue (activated carbon) can be stored in special storage bags at dry place and
will be sold as by product after storage. This is not accumulating during the process. It has
high carbon content and can be used for energy purposes, can be easily sold.
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