NZ618218B2 - Method and apparatus for energy-efficient processing of secondary deposits - Google Patents
Method and apparatus for energy-efficient processing of secondary deposits Download PDFInfo
- Publication number
- NZ618218B2 NZ618218B2 NZ618218A NZ61821812A NZ618218B2 NZ 618218 B2 NZ618218 B2 NZ 618218B2 NZ 618218 A NZ618218 A NZ 618218A NZ 61821812 A NZ61821812 A NZ 61821812A NZ 618218 B2 NZ618218 B2 NZ 618218B2
- Authority
- NZ
- New Zealand
- Prior art keywords
- plastics
- solvent
- depolymerisation
- reactor
- melt
- Prior art date
Links
- 239000004033 plastic Substances 0.000 claims abstract description 122
- 229920003023 plastic Polymers 0.000 claims abstract description 122
- 239000000463 material Substances 0.000 claims abstract description 52
- 239000002904 solvent Substances 0.000 claims abstract description 51
- 239000000295 fuel oil Substances 0.000 claims abstract description 21
- 238000009835 boiling Methods 0.000 claims abstract description 8
- 239000002699 waste material Substances 0.000 claims abstract description 8
- 150000004945 aromatic hydrocarbons Chemical class 0.000 claims abstract description 5
- 239000000203 mixture Substances 0.000 claims description 10
- -1 polyethylene Polymers 0.000 claims description 7
- 239000010779 crude oil Substances 0.000 claims description 6
- 239000003921 oil Substances 0.000 claims description 6
- 239000004743 Polypropylene Substances 0.000 claims description 4
- 239000007788 liquid Substances 0.000 claims description 4
- 229920001155 polypropylene Polymers 0.000 claims description 4
- 239000004698 Polyethylene (PE) Substances 0.000 claims description 3
- 239000004793 Polystyrene Substances 0.000 claims description 3
- 229920000573 polyethylene Polymers 0.000 claims description 3
- 229920000098 polyolefin Polymers 0.000 claims description 3
- 229920002223 polystyrene Polymers 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 abstract description 7
- 238000004064 recycling Methods 0.000 abstract description 2
- 239000000243 solution Substances 0.000 description 14
- 239000000047 product Substances 0.000 description 11
- 230000002349 favourable Effects 0.000 description 7
- 238000005336 cracking Methods 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 5
- 238000002844 melting Methods 0.000 description 5
- 238000001914 filtration Methods 0.000 description 4
- 238000007872 degassing Methods 0.000 description 3
- 238000004821 distillation Methods 0.000 description 3
- 238000000605 extraction Methods 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 2
- 238000004523 catalytic cracking Methods 0.000 description 2
- 238000004939 coking Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 239000010763 heavy fuel oil Substances 0.000 description 2
- 239000003915 liquefied petroleum gas Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 241001052209 Cylinder Species 0.000 description 1
- 241000196324 Embryophyta Species 0.000 description 1
- 235000011158 Prunus mume Nutrition 0.000 description 1
- 240000002546 Prunus mume Species 0.000 description 1
- 239000007900 aqueous suspension Substances 0.000 description 1
- 230000001174 ascending Effects 0.000 description 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- 239000001273 butane Substances 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 230000003197 catalytic Effects 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002309 gasification Methods 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 239000012456 homogeneous solution Substances 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 239000010805 inorganic waste Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 239000000289 melt material Substances 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 239000003638 reducing agent Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000004227 thermal cracking Methods 0.000 description 1
- 230000001131 transforming Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J11/00—Recovery or working-up of waste materials
- C08J11/04—Recovery or working-up of waste materials of polymers
- C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J11/00—Recovery or working-up of waste materials
- C08J11/04—Recovery or working-up of waste materials of polymers
- C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
- C08J11/12—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by dry-heat treatment only
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
- C10G1/02—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal by distillation
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
- C10G1/10—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal from rubber or rubber waste
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
- C10G2300/10—Feedstock materials
- C10G2300/1003—Waste materials
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
- C10G2300/20—Characteristics of the feedstock or the products
- C10G2300/30—Physical properties of feedstocks or products
- C10G2300/301—Boiling range
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
- C10G2300/20—Characteristics of the feedstock or the products
- C10G2300/30—Physical properties of feedstocks or products
- C10G2300/302—Viscosity
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
- C10G2300/40—Characteristics of the process deviating from typical ways of processing
- C10G2300/4081—Recycling aspects
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
- C10G2300/40—Characteristics of the process deviating from typical ways of processing
- C10G2300/44—Solvents
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G2400/00—Products obtained by processes covered by groups C10G9/00 - C10G69/14
- C10G2400/02—Gasoline
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G9/00—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
- Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/62—Plastics recycling; Rubber recycling
Abstract
Specification discloses a method and apparatus for the depolymerisation of plastics material (1), in particular in recycling plastic waste, by means of heat introduction. Plastics material is molten to form a plastics melt and degassed before being passed to a depolymerisation reactor (3) having a heating device (3’). A heavy oil, having a final boiling point of > 300 °C and having a share of aromatic hydrocarbons of at least 25% added to a supply circuit (4) via a solvent introduction device (6’) to improve viscosity of the plastics melt. eating device (3’). A heavy oil, having a final boiling point of > 300 °C and having a share of aromatic hydrocarbons of at least 25% added to a supply circuit (4) via a solvent introduction device (6’) to improve viscosity of the plastics melt.
Description
Method and apparatus for energy-efficient processing of secon-
dary deposits
The invention relates to a method for the depolymerisation of
plastics material, in particular pre- or post-consumer plastics
wastes, by means of heat introduction, wherein the plastics ma-
terial is molten to form a plastics melt and degassed before be-
ing passed to a depolymerisation reactor. The depolymerisation
reactor suitably has a heating device. Described herein is an
apparatus for the depolymerisation of plastics material, in par-
ticular pre- or post-consumer plastics wastes, having a de-
gassing and melting device for transforming the plastics mate-
rial into a plastics melt, and a depolymerisation reactor.
Basically, oiling pre- or post-consumer plastics wastes in
order to recycle the pre- or post-consumer plastics wastes is
already known.
One known type of methods for the recycling of plastics are
high-temperature pyrolysis methods, wherein the plastics mate-
rial is treated in a temperature range of 600 to 1,000 °C; an-
other known type of methods are low-temperature depolymerisation
methods including cracking reactions that are usually performed
in a temperature range of approx. 300 to 450 °C. Especially in
low-temperature depolymerisation, supplying energy to the mole-
cules of the plastics material is difficult because the plastics
melt exhibits high viscosity and plastics are poor heat conduc-
tors in general. As a consequence, only relatively small depoly-
merisation reactors with a turnover volume of up to approx.
6,000 tonnes per year could be created so far; large facilities
have considerable problems regarding heat introduction. More-
over, an economical operation of facilities with a turnover vol-
ume in the range of 6,000 tonnes per year is hardly possible.
On the other hand, catalytic depolymerisation methods
wherein the depolymerisation is performed by catalytic cracking
are known from the publication Shabtai J. et al., Energy & Fuels
11 (1997): 76-87 or US 2002/169223 A1, for example.
An apparatus for the depolymerisation of pre- and post-
consumer plastics wastes is known from the prior art, for exam-
ple WO 95/32262, wherein a circuit system is connected to the
reactor for gently heating the content of the reactor, and the
content of the reactor is passed through an ascending slope in-
tegrated into the reactor for separating coarser particles of
solids with an accordingly high settling speed before entering
an extraction line.
Furthermore, an apparatus for the depolymerisation of or-
ganic and inorganic waste material which is chaffed and mixed
with a solvent before adding water or the like to form a suspen-
sion and then fed into a depolymerisation stage, is known from
US 7,771,699 B2. Thereafter, solids are removed from this sus-
pension.
A very similar method using an aqueous suspension that is
supplied to the depolymerisation reactor is known from WO
2009/108761 A1.
Moreover, a method and an apparatus for the depolymerisation
of plastics material wherein the reactor has a separating device
for separating liquid plastics material from vaporous plastics
material is known from US 2008/035079 A.
A disadvantage of all known depolymerisation methods and ap-
paratuses is that – as has already been mentioned initially –
heat transferral into the molecules of the plastics material is
difficult, in particular with larger quantities.
As a consequence, the object of the present invention is to
provide a method and an apparatus for the thermal depolymerisa-
tion of the initially mentioned type for improving heat intro-
duction into the plastics material to be depolymerised. Thereby
it should, in particular, be possible to perform depolymerisa-
tion reactions with a larger capacity in a reliable manner and
thus depolymerise plastics material under economically accept-
able conditions. An additional or alternative object is to pro-
vide the public with a useful choice.
According to the invention this is achieved in the thermal
depolymerisation method of the initially mentioned type by add-
ing a crude oil fraction as a solvent to the plastics melt,
wherein the added solvent is a heavy oil having a final boiling
point of > 300 °C and having a share of aromatic hydrocarbons of
at least 25%, thereby lowering the viscosity of the plastics
melt solution supplied to the depolymerisation reactor relative
to the viscosity of the plastics melt. By adding a solvent to
the degassed and molten plastics material, i. e. the heated,
non-solid plastics material, it is possible to lower the viscos-
ity of the plastics melt and thus the heat introduction into the
plastics material in the depolymerisation reactor may be im-
proved. In this way, a thermal depolymerisation is performed
without adding a catalyst, hydrogen or the like. The depolymeri-
sation of the plastics material is thus carried out by thermal
cracking and not by catalytic cracking. Advantageously, the
fraction of crude oil provided as the solvent is residual oil
from distillation and/or cracking facilities in the crude oil
processing industry. During the introduction of the solvent, the
plastics melt preferably has a temperature of at least 120 °C,
in particular between 150 °C and 300 °C; for obtaining a solu-
tion as homogeneous as possible, the solvent has advantageously
been pre-heated to at least 150 °C as well, in particular sub-
stantially 200 °C to 300 °C. Introducing a solution into the de-
polymerisation reactor results in a lower drop of the tempera-
ture gradient over the cross-section of the depolymerisation re-
actor and thus a considerably lower hazard of overheating the
plastics material near the wall of the reactor, which is usually
equipped with a heating device on its outside. In addition, the
hazard of coking is reduced for the plastics material. Further-
more, the lowering of the viscosity with respect to the pure
plastics melt may improve the pumpability of the plastics melt
solution considerably, thus reducing the energy required for the
operation of the depolymerisation reactor. Also, current depoly-
merisation reactors often require providing a central stirring
device, which suffers from the disadvantage that it is subject
to wear by extraneous material in the plastics melt. Lowering
the viscosity has the advantage that the stirring device may be
omitted to simplify operation and maintenance.
In order to obtain a mixing of the plastics material intro-
duced into the depolymerisation reactor, it is advantageous to
continuously pump plastics melt from the depolymerisation reac-
tor and recirculate it into the depolymerisation reactor. Pref-
erably, part of the content of the reactor is extracted in a
lower part of the reactor above a reactor sump, and then recir-
culated into the reactor for further depolymerisation. Regarding
a reliable mixing of the content within the depolymerisation re-
actor and the generation of turbulences inside the reactor, it
is advantageous to continuously pump plastics melt from the de-
polymerisation reactor and recirculate it into the depolymerisa-
tion reactor.
In order to add a solvent to the plastics material that is
recirculated via the supply circuit and thus create more favour-
able conditions for heat introduction in the depolymerisation
reactor, it is advantageous to introduce, preferably inject, the
solvent into the supply circuit. Introducing also the previously
degassed and molten plastics material into the depolymerisation
reactor via the supply circuit guarantees that newly introduced
plastics material and plastics material pumped from the depoly-
merisation reactor via the supply circuit are first brought to-
gether and then the solvent is added to the merged melt material
in order to secure the improved heat introduction in the reac-
tor.
To make sure that the plastics material dissolves in the
solvent, it is favourable for the solvent to be heated to pref-
erably approx. at least 150 °C, in particular substantially 200
°C to 300 °C, before being added to the plastics melt.
Here, it is particularly advantageous to add a heavy oil as
the solvent. Heavy oil (heavy fuel oil (HFO) and its components)
is residual oil from distillation and/or cracking plants in the
crude oil processing industry, which is currently sold mainly as
fuel for diesel engines of ships and as combustible. Sales of
heavy oil, however, are declining, which leads to excess capaci-
ties. Because of this, heavy oil may be used as a low-cost and
also efficient solvent and/or viscosity-reducing agent for de-
polymerising plastics material. Furthermore, some heavy oils
contain fine-grained residues of catalysts, which could have a
favourable effect on the cracking behaviour during depolymerisa-
tion.
To prevent the solvent from vaporising immediately after in-
troducing the plastics melt solution into the depolymerisation
reactor, it is advantageous for the solvent to have a higher fi-
nal boiling point than the operating temperature in the depoly-
merisation reactor. Accordingly it is advantageous for the heavy
oil to have a final boiling point of > 350 °C.
It has been found to be especially advantageous to use a
heavy oil having a share of aromatic hydrocarbons of at least
% as the solvent. In particular, a heavy oil or a mixture of
different heavy oils having no. 265-xxx-x or no. 270-xxx-x ac-
cording to the EINECS (European Inventory of Existing Commercial
Chemical Substances) classification system may be used here,
with x being a placeholder. Particularly preferred heavy oils
are selected from a group consisting of EINECS Nos. 2656,
2653, 2656, 2652, 2658, 2659, 270
6, 2654.
In order to improve heat introduction by lowering viscosity,
it is favourable to reduce the viscosity of the plastics melt
solution by at least 30%, preferably by at least 50%, in par-
ticular by at least 80%, with respect to the plastics melt with-
out solvent at a temperature of substantially 180 °C to 240 °C.
In order to obtain products that can be reused for the in-
tended purpose by depolymerisation, it is advantageous to pre-
sort the plastics material used in the method according to the
invention, so only special plastics materials are supplied to
the depolymerisation reactor. Here, it is favourable to use
polyolefines, in particular polyethylene and polypropylene,
and/or polystyrene as the plastics material.
A suitable temperature for the depolymerisation of pre- or
post-consumer plastics wastes is reached once the plastics mate-
rial is depolymerised in the depolymerisation reactor at approx.
300 °C to 500 °C, preferably 350 °C to 450 °C.
Regarding further appropriate processing of the plastics ma-
terial depolymerised in the reactor, it is favourable to extract
the depolymerised plastics material in an upper section of the
depolymerisation reactor in the form of vapour. The product mix-
ture, which is preferably extracted at the head of the depoly-
merisation reactor, may then be supplied to a downstream separa-
tion column, wherein it is particularly advantageous to separate
the vaporous, depolymerised plastics material into several prod-
ucts, preferably a gas flow, liquid gas and naphtha as well as a
product similar to gas oil.
In order to make the heat introduction into the plastics ma-
terial as efficient as possible, it is advantageous to heat the
plastics melt solution before introducing it into the depolymer-
isation reactor. In this way, a substantial part of the heat re-
quired for the endothermic cracking reactions as part of depoly-
merisation may be supplied to the plastics melt solution already
before introducing the plastics melt solution into the depoly-
merisation reactor.
As described herein, an apparatus of the initially mentioned
type is characterised in that a solvent introduction device is
provided for adding a fraction obtained from crude oil as a sol-
vent to the plastics melt, thereby lowering the viscosity of the
plastics melt solution supplied to the depolymerisation reactor
relative to the viscosity of the plastics melt. Using the appa-
ratus according to the invention, it is possible – as in the
method according to the invention described above – to reduce
the viscosity of the melt introduced into the depolymerisation
reactor and thus improve heat introduction. In order to avoid
repetitions, reference is made to the advantages discussed in
detail in conjunction with the method according to the inven-
tion.
For a simple melting and gasification of the plastics mate-
rial and an efficient introduction of the solvent it is advanta-
geous to provide an extruder as the degassing and melting device
and for the solvent introduction device to have at least one
dosing pump.
In order to obtain a twist flow in the depolymerisation re-
actor and thus a continuous mixing of the content within the re-
actor, it is advantageous to connect to the depolymerisation re-
actor a supply circuit line via which part of the plastics melt
within the depolymerisation reactor is pumped out and recircu-
lated into the depolymerisation reactor. Here, it is favourable
to connect the degassing and melting device and/or the solvent
introduction device to the supply circuit line since this guar-
antees that the solvent is added to plastics material that is to
be introduced newly into the reactor as well as to plastics ma-
terial pumped out of the reactor via the supply circuit line,
thereby improving heat introduction into the plastics melt.
Provided that a heat exchanger is connected to the supply
circuit line, the plastics melt solution may be pre-heated using
the heat exchanger already before introducing it into the de-
polymerisation reactor, in turn improving the efficiency of the
energy introduction.
In the following, the invention will be explained in more
detail by means of a preferred exemplary embodiment illustrated
in the drawing, however, without being limited to it.
The sole figure of the drawing shows a schematic set-up of
the method according to the invention and/or the apparatus ac-
cording to the invention.
It can be seen from the sole figure of the drawing that pre-
sorted plastics material, which is composed in particular of
polyolefines, preferably polyethylene and/or polypropylene, and
polystyrene, if applicable, is supplied to an extruder provided
as an introduction device and/or a degassing and melting device
2. The plastics material is compacted, degassed and molten in
the extruder 2. The plastics melt leaving the extruder 2 is not
supplied to a depolymerisation reactor 3 directly, but passed
into a supply circuit line 4. Via the supply circuit line 4,
part of the plastics material within the reactor 3 is extracted
from above a reactor sump located in the lower portion of the
reactor 3 using a pump 5. By introducing a solvent 6 into the
supply circuit line 4, the solvent 6 is thus added to the plas-
tics melt extracted from the reactor 3 as well as to the plas-
tics melt supplied by the extruder 2. Before adding the solvent
6 to the plastics melt, the solvent 6 is supplied to a solvent
introduction device 6', in which the solvent 6 is pre-heated to
approx. 200 °C to 300 °C, in particular approx. 250 °C.
By introducing the solvent 6 into the supply circuit line 4
via the solvent introduction device 6', which mainly includes
nozzles not specified in more detail for injecting solvent 6
into the plastics melt via at least one dosing pump, it is pos-
sible to lower the viscosity of the plastics melt which is in-
troduced into the depolymerisation reactor 3. Preferably, pre-
heated heavy oil (HFO) is added here in order to obtain a homo-
geneous solution. Preferably, a heavy oil having an EINECS
(European Inventory of Existing Commercial Chemical Substances)
Number or CAS (Chemical Abstracts Service) Number selected from
Table 1 below and/or a mixture of a variety of these heavy oils
is added.
EINECS Number
CAS Number
Table 1
Tests have revealed that the viscosity in the solution intro-
duced into the depolymerisation reactor 3 relative to the pure
plastics melt is significantly lowered by adding such a solvent.
Example 1:
Samples with adding rates of 0 per cent by weight, 50 per cent
by weight, 70 per cent by weight and 100 per cent by weight were
prepared from pure polypropylene granulate and solvent („clari-
fied slurry oil“, EINECS no. 2656). The mixtures were
heated in a nitrogen atmosphere and kept at a preferred process
temperature for the depolymerisation method of approx. 360-390
°C for a short time (a few minutes) in order to take into ac-
count process conditions as well as to obtain a homogenisation
of the samples as complete as possible. Thereafter the dynamic
viscosity was measured at the individual measuring temperatures
using a cylinder rheometer (type: Bohlin Visco 88 Viscometer) at
various reaction rates in the medium setting range of the cylin-
der.
The following values have been detected consistently and al-
most independent from shear rates (at medium rates) (the viscos-
ity of the pure solvent could not be determined as the viscosity
was out of the measuring range):
Adding rates of solvent (%)
Measuring 0
temperature (= pure plastics
[°C] melt) 50 70 100
180 1.9 0.17 0.03 n/a
200 0.6 0.12 0.02 n/a
220 0.46 0.09 0.02 n/a
240 0.37 0.06 0.01 n/a
Table 2: Viscosities of mixtures [Pa*s]
Advantageously, adding a solvent and thus obtaining a lowering
of viscosity also result in higher turbulences within the de-
polymerisation reactor 3, thereby improving in particular the
heat introduction into the molecules of the plastics material.
In addition, the drop of the temperature gradient along the ra-
dius of the reactor may be reduced in this way, in turn leading
to a lower hazard of overheating in the region of the outer
frame of the reactor 3 near a jacket-shaped heating device 3' of
the reactor and reducing the hazard of coking for the plastics
material.
In order to also make the heat introduction for depolymeri-
sation more efficient, a heat exchanger 5' is also provided in
the supply circuit line 4, heating the plastics melt solution
already before introducing it into the depolymerisation reactor
The plastics material is then depolymerised in the depoly-
merisation reactor 3 in a temperature range of approx. 350 °C to
450 °C and under substantially atmospheric pressure. Here, a va-
porous product is created and extracted from the reactor 3
through an extraction line 7 via the head. The required heat
supply for triggering the endothermic cracking reaction for the
depolymerisation is obtained by means of the heating device 3'
of the depolymerisation reactor 3, on the one hand, and by means
of the heat exchanger 5', on the other hand, before introducing
the mixture of plastics melt/heavy oil and/or the solution of
the supply circuit 4 into the depolymerisation reactor 3.
Furthermore, the residue remaining in the reactor 3 is
pumped into a filtering circuit line 8 in the sump of the reac-
tor using a pump 9. The plastics residue that has not been
transformed and the coke created during depolymerisation are
filtered from the sump product, which is partially recirculated
into the depolymerisation reactor 3, by means of filters 10. The
plastics material transported in the filtering circuit line 8
may also be heated in a heat exchanger not specified in more de-
tail before being recirculated into the reactor 3. An especially
high-boiling part is branched off from the filtering circuit
line 8 as a side product 11.
The vaporous product mixture extracted via the extraction
line 7 at the head of the reactor 3 is supplied to a downstream
separation column 12. In the separation column 12 the product
mixture is separated into three product flows by distillation.
Substantially, it is separated into a gas flow 13, liquid gas
(LPG – liquefied petroleum gas), i. e. propane, butane and their
mixtures, and a naphtha-containing product 14 as well as prod-
ucts 15 similar to gas oil.
By adding the solvent 6 to the plastics melt, it is possible
to operate a comparably large depolymerisation reactor with a
turnover volume of much more than 6,000 tonnes per year, pref-
erably more than 100,000 tonnes per year, in an economically
profitable manner, wherein the lowering of the viscosity of the
plastics melt does not only allow an improved heat introduction
into the plastics material, but also makes it possible to reduce
the energy consumption for the operation of the pumps 5, 9 of
the lines 4, 8 of the supply circuit and the filtering circuit.
Another advantage is that a stirring device in the reactor may
also be omitted to reduce energy consumption even further.
Claims (20)
1. A method for the depolymerisation of plastics material, in particular pre- or post-consumer plastics wastes, by means of heat introduction, wherein the plastics material is molten to form a plastics melt and degassed before being passed to a depolymerisation reactor, wherein a crude oil fraction is added to the plastics melt as a solvent, wherein the added solvent is a heavy oil having a final boiling point of > 300 °C and having a share of aromatic hydrocarbons of at least 25%, thereby lowering the viscosity of the plastics melt solution supplied to the depolymerisation reactor relative to the viscosity of the plastics melt.
2. The method according to claim 1, wherein the added solvent is a heavy oil having a final boiling point of > 350 °C.
3. The method according to claim 1 or 2, wherein part of the plastics melt within the depolymerisation reactor is pumped out and recirculated into the depolymerisation reactor via a supply circuit.
4. The method according to claim 3, wherein plastics melt is continuously pumped from the depolymerisation reactor and recirculated into the depolymerisation reactor.
5. The method according to claim 3 or 4, wherein the solvent is introduced into the supply circuit.
6. The method according to claim 5, wherein the solvent is injected into the supply circuit.
7. The method according to any one of claims 3 to 6, wherein the plastics melt to be depolymerised is introduced into the depolymerisation reactor via the supply circuit.
8. The method according to any one of claims 1 to 7, wherein the solvent is heated to at least about 150 °C before it is added to the plastics melt.
9. The method according to claim 8, wherein the solvent is heated to substantially 200 °C to 300 °C before it is added to the plastics melt.
10. The method according to any one of claims 1 to 9, wherein a heavy oil having no. 265-xxx-x or no. 270-xxx-x in the EINECS classification system, with x being a placeholder, is added, in particular a heavy oil selected from a group consisting of EINECS Nos. 2656, 2653, 2656, 2652, 265 8, 2659, 2706, 2654 and/or a mixture thereof.
11. The method according to any one of claims 1 to 9, wherein the viscosity of the plastics melt solution is reduced by at least 30% with respect to the plastics melt without solvent at a temperature of substantially 180 °C to 240 °C.
12. The method according to claim 11, wherein the viscosity of the plastics melt solution is reduced by at least 50% with respect to the plastics melt without solvent at a temperature of substantially 180 °C to 240 °C.
13. The method according to claim 12, wherein the viscosity of the plastics melt solution is reduced by at least 80% with respect to the plastics melt without solvent at a temperature of substantially 180 °C to 240 °C.
14. The method according to any one of claims 1 to 13, wherein polyolefines, in particular polyethylene and polypropylene, and/or polystyrene are used as the plastics material.
15. The method according to any one of claims 1 to 14, wherein the plastics material is depolymerised in the depolymerisation reactor at about 300 °C to 500 °C.
16. The method according to claim 15, wherein the plastics material is depolymerised in the depolymerisation reactor at 350 °C to 450 °C.
17. The method according to any one of claims 1 to 16, wherein the depolymerised plastics material is extracted in an upper section of the depolymerisation reactor in the form of vapour.
18. The method according to any one of claims 1 to 17, wherein the vaporous, depolymerised plastics material is separated into several products. 19. The method according to claim 18, wherein the vaporous, depolymerised plastics material is separated into a gas flow, liquid gas and naphtha as well as a product similar to gas oil.
19. The method according to any one of claims 1 to 18, wherein the plastics melt solution is heated before introduction into the depolymerisation reactor.
20. The method according to claim 1, substantially as herein described with reference to any embodiment disclosed.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
ATA632/2011 | 2011-05-05 | ||
ATA632/2011A AT511772B1 (en) | 2011-05-05 | 2011-05-05 | METHOD AND DEVICE FOR THE ENERGY EFFICIENT PREPARATION OF SECONDARY STORES |
PCT/AT2012/000127 WO2012149590A1 (en) | 2011-05-05 | 2012-05-04 | Method and apparatus for energy-efficient processing of secondary deposits |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ618218A NZ618218A (en) | 2015-02-27 |
NZ618218B2 true NZ618218B2 (en) | 2015-05-28 |
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