FI20235526A1

FI20235526A1 - Method and apparatus for converting wax to oil

Info

Publication number: FI20235526A1
Application number: FI20235526A
Authority: FI
Inventors: Tooran Khazraie; Tuomas Närhi; Antti Raiko
Original assignee: Valmet Technologies Oy
Priority date: 2023-05-10
Filing date: 2023-05-10
Publication date: 2024-11-11
Also published as: WO2024231603A1

Abstract

The invention relates to a method and an apparatus for converting wax to oil in a pyrolysis process, wherein a feed (1) comprising plastic is fed to a pyrolysis reactor (2), and the feed is pyrolyzed to form a pyrolysis product (3). At least a wax fraction (16) is separated from the pyrolysis product in a separation unit (10), and the wax fraction can be supplied to a visbreaking unit (13) in which the wax fraction is cracked to form at least an oil product (11) comprising aliphatic compounds.

Description

METHOD AND APPARATUS FOR CONVERTING WAX TO OIL

FIELD

The application relates to a method defined in claim 1 and an apparatus defined in claim 13 for con- verting wax to oil in a pyrolysis process.

BACKGROUND

Pyrolysis products can be produced from dif- ferent raw materials in a pyrolysis process. The raw materials can be pyrolyzed, for example by using a cat- alytic pyrolysis.

To generate positive economic value and de- crease the environment pollution, discarded plastics such as polyethylene and propylene can be converted into chemicals and fuels. As a promising versatile approach to convert discarded plastics into chemicals and fuels, pyrolysis has been recently attractive to scientific and industrial communities. However, the implementation of an efficient pyrolysis process with a feasible produc- tion from a commercial standpoint is a challenge. Addi- tionally, the traditional plastic-to-fuels technology, which requires the consumption of fossil fuels is not an economic way, and it does not make any contribution to plastic circular economy. However, a study of plas- tic-to-fuels technology reveals that the conversion of en discarded plastics into naphtha or plastic monomers is

S a promising approach for manufacturing new plastic in a ro closed loop.

O 30 The first generation of plastic pyrolysis has = been performed in stirring tank reactor (STR) and screw z reactor. There has been extensive studies and conse-

O quently pilot plants working with STR and screw reactors 8 to convert waste recycled plastics to oil. In these

N 35 types of reactors, the residence time of different plas-

N tic carbon chains are controlled, meaning that the smaller the formed compound, the faster it leaves the reactor (Scheirs, J., 2006, Overview of commercial py- rolysis processes for waste plastic, Feedstock Recycling and Pyrolysis of Waste Plastics, p. 381-433).

Fluidized bed reactors could be a good option for scaling up the process. For instance, companies like

Anellotech (Anellotech, 12 April 2022, Plas-TCat™ for mixed plastic recycling, Anellotech, Inc.) or BioBTX (BioBTX, nd, The BioBTX Technology) convert the plastics to oil using the catalytic pyrolysis. The final product from the current catalytic pyrolysis converts the plas- tics to aromatics like benzene, toluene and xylene (BTX) .

Traditional thermal pyrolysis in STR and screw reactors producing aliphatic monomers has the limitation of scaling up. Pyrolysis in the fluidized bed is a good option for commercial-scale pyrolysis units. However, the literature survey and Valmet’s experience showed that fine-tuning the efficient process and narrow-down the final product is quite challenging. Depending on the temperature, a remarkable formation of wax with high viscosity, or high content of non-condensable gas prod- ucts or traces of unwanted aromatics has been observed during thermal pyrolysis in different reactor technol- ogies, especially rise reactors.

The high content of wax or non-condensable gas en compared to the required oil implies a low process yield

S and reduces the plants' profitability. The formed wax

LÖ or non-condensable gases cannot be transported easily = 30 to the refinery plants. Additionally, the refineries are = not interested in buying produced wax. z One way to fine-tune the products from the py-

O rolysis is the catalytic pyrolysis of waste PP/PE using 3 zeolite catalyst. This process forms a high content of

O 35 aromatic compounds including BTX from plastic pyrolysis while it has a niche market. This is due to the fact that the oil refinery companies are more interested in aliphatic hydrocarbons as the feed of their hydrotreat- ers and steam crackers. The aromatic compounds in the 0il result in high coking, high consumption of hydrogen, and poisoning of the catalyst during oil upgrading.

Therefore, the common catalytic pyrolysis of plastics using zeolites is not a beneficial pathway.

OBJECTIVE

The objective is to solve the above problems.

Further, the objective is to disclose a new-type method and apparatus for treating pyrolysis products after py- rolysis. Further, the objective is to uparade undesired pyrolysis products after the pyrolysis. Further, the objective is to convert wax formed in a pyrolysis to an oil product comprising aliphatic compounds.

SUMMARY

The method and apparatus are characterized by what are presented in the claims.

The method for converting wax to oil in a py- rolysis process comprises feeding a feed comprising plastic to a pyrolysis reactor, pyrolyzing the feed to form a pyrolysis product, separating at least a wax fraction from the pyrolysis product in a separation unit, and supplying the wax fraction to a visbreaking e unit in which the wax fraction is treated to form at

S least an oil product and/or to a pyrolysis unit com-

O prising the pyrolysis reactor. = 30 The apparatus can comprise a pyrolysis reactor = for pyrolyzing a feed comprising plastic to form a py-

E rolysis product, a feeder for feeding the feed to the © pyrolysis reactor, a separation unit comprising at least m one separating device for separating at least a wax

N 35 fraction from the pyrolysis product, and a visbreaking

N unit, into which at least the wax fraction is supplied and in which the wax fraction is treated to form at least an oil product.

BRIEF DESCRIPTION OF THE DRAWING

The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate some embodiments of the invention and together with the de- scription help to explain the principles of the inven- tion. In the drawings:

Fig. 1 is a flow chart illustration of a pro- cess according to one embodiment,

Fig. 2 is a flow chart illustration of a pro- cess according to another embodiment,

Fig. 3 is a flow chart illustration of a pro- cess according to another embodiment, and

Fig. 4 is a flow chart illustration of a pro- cess according to another embodiment.

DETAILED DESCRIPTION

In a method for converting wax to oil in a pyrolysis process, a feed comprising plastic is fed to a pyrolysis reactor, and the feed is pyrolyzed to form a pyrolysis product. At least a wax fraction is sepa- rated from the pyrolysis product in a separation unit, and at least a part of the wax fraction is supplied to en a visbreaking unit in which the wax fraction is cracked

S to form at least an oil product comprising aliphatic

LÖ compounds. In one embodiment, the wax fraction or the = 30 whole wax fraction is supplied to the visbreaking unit. = An apparatus for converting wax to oil in a z pyrolysis process comprises a pyrolysis reactor for py-

O rolyzing a feed comprising plastic to form a pyrolysis 3 product, and a feeder for feeding the feed to the py-

N 35 rolysis reactor. Further, the apparatus comprises a sep-

N aration unit comprising at least one separating device for separating at least a wax fraction from the pyrol- ysis product, and a visbreaking unit comprising at least one visbreaker furnace, into which at least a part of the wax fraction is supplied and in which the wax frac- 5 tion is cracked to form at least an oil product com- prising aliphatic compounds.

In another method embodiment for converting wax in a pyrolysis process, a feed comprising plastic is fed to a pyrolysis reactor, and the feed is pyrolyzed to form a pyrolysis product. At least a wax fraction is separated from the pyrolysis product in a separation unit, and the wax fraction or at least a part of the wax fraction is supplied to a pyrolysis unit comprising the pyrolysis reactor, e.g. to a feed of the pyrolysis re- actor or to the pyrolysis reactor. In one embodiment, the wax fraction is supplied to the pyrolysis unit and to the visbreaking unit in which the wax fraction is cracked to form at least an oil product comprising al- iphatic compounds.

Some embodiments of the method and the apparatus are shown in Fig. 1, Fig. 2, Fig. 3 and Fig. 4.

In this context, the feed comprising plastic means any feed or feed material which comprises at least plastic or plastic material. Further, the feed can com- prise also other materials than plastic. The feed may comprise one or more components. The plastic or plastic en material may be recycled material, residue material,

S waste material or virgin material or their combinations,

LÖ which contains plastic, polymers or mixtures thereof. = 30 In one embodiment, the feed is formed from recycled = material, waste material, residue material and their z combinations. In one embodiment, the plastic may com- © prise any plastic or polymer, such as polyethylene, pol-

O ypropylene, other polymers, or their combinations.

O 35 In this context, the pyrolysis product means any pyrolysis product which is formed by the pyrolysis,

such as by the catalytic pyrolysis. In one embodiment, the pyrolysis product is in a gaseous form. In one em- bodiment, the pyrolysis product is a product vapor.

In this context, the wax fraction means any fraction comprising at least wax. Further, the wax frac- tion may contain tars and other impurities. In one em- bodiment, the wax fraction comprises at least wax and tars. In one embodiment, the wax fraction comprises wax, oil and tars.

In this context, the oil product means any product which comprises at least aliphatic compounds.

In one embodiment, the oil product is in the vapor form, i.e. the oil product is an oil product vapor.

The feed comprising plastic is treated by a pyrolysis in a pyrolysis reactor. Any suitable pyrolysis reactor can be used in the pyrolysis. In one embodiment, the pyrolysis reactor is a fluidized bed reactor. The feed may be treated by a thermal pyrolysis. In one em- bodiment, the pyrolysis is carried out at low tempera- ture of 500 — 800 °C, in one embodiment temperature of 550 — 700 °C. In one embodiment, the residence time may be 1 - 3 seconds in the pyrolysis reactor.

The feed comprising plastic can be fed using the feeder to the pyrolysis reactor. Any suitable feeder can be used in feeding. In one embodiment, the feeder is a screw feeder or an extruder. < The wax fraction is separated from the pyrol- < ysis product in the separation unit. The separation unit

LÖ comprises at least one separating device. In one embod- = 30 iment, the separation unit comprises more than one sep- = arating device. In one embodiment, a separation unit or = separating device which can separate a desired fraction

O or product based on its boiling point is used for sep- 3 arating the wax fraction. In one embodiment, the sepa-

N 35 ration unit comprises a distillation column, scrubber,

N condensation device, condenser, auench or other suitable separating device. Alternatively, any suitable separa- tion unit or separating device can be used for separat- ing the wax fraction from the pyrolysis product. In one embodiment, the separation unit comprises at least dis- tillation column. In one embodiment, the separation unit comprises at least scrubber and distillation column. In one embodiment, the separation unit comprises at least condensation device or condenser. After the separation, the wax fraction can be supplied to the visbreaking unit.

In one embodiment, the method comprises supply- ing the pyrolysis product to at least one condensation device or condenser in which the pyrolysis product is cooled. The pyrolysis product is cooled in the condensa- tion device or condenser, and a condensed flow comprising wax and/or tars may be separated. In one embodiment, at least the wax fraction, and optionally also gas and/or oil fractions, are separated in the condensation device.

In one embodiment, the apparatus comprises at least one condensation device or condenser for cooling the pyroly- sis product. In one embodiment, the apparatus comprises at least one condensation device or condenser for cooling the pyrolysis product and for separating a condensed flow comprising wax and/or tars from the pyrolysis product.

In one embodiment, the condensation device is arranged to separate at least the wax fraction, and optionally en also gas and/or oil fractions. Any suitable condensation

S device, conderser or the like can be used in the conden-

LÖ sation. In one embodiment, the condensation device is = 30 used as the separating device of the separation unit. = In one embodiment, the method comprises supply- = ing the pyrolysis product to at least one scrubber in

O which the pyrolysis product is cooled. In one embodiment, 3 the method comprises supplying the pyrolysis product to

O 35 at least one scrubber in which the pyrolysis product is cooled and a condensed flow comprising wax and/or tars is separated from the pyrolysis product, and a non-con- densed pyrolysis product is formed. In one embodiment, at least the wax fraction, and optionally also gas and/or oil fractions, are separated in the scrubber or scrub- bers. In one embodiment, the apparatus comprises at least one scrubber for cooling the pyrolysis product. In one embodiment, the apparatus comprises at least one scrubber for cooling the pyrolysis product and for separating a condensed flow comprising wax and/or tars from the py- rolysis product, and for forming a non-condensed pyroly- sis product. In one embodiment, the scrubber or scrubbers are arranged to separate at least the wax fraction, and optionally also gas and/or oil fractions. In one embodi- ment, the scrubber is used as the separating device of the separation unit. In one embodiment, the apparatus comprises at least two scrubbers or scrubber parts. In one embodiment, the apparatus comprises more than two scrubbers, e.g. three, four or more scrubbers. Any suit- able scrubber, gas washing apparatus or the like can be used as a scrubber. In one embodiment, the scrubbers are arranged in series. In one embodiment, temperature of the pyrolysis product is 500 - 600 °C in feeding to the scrubber. In one embodiment, temperature of the condensed flow is 70 - 200 °C, in one embodiment 100 - 150 °C, after the scrubber or scrubbers. In one embodiment, tem- perature of the flow is 250 — 350 °C after the first e scrubber.

S In one embodiment, the separation unit is a

LÖ distillation unit comprising at least one distillation = 30 column in which at least gas, oil and wax fractions are = separated. In one embodiment, the separation unit com- z prises a distillation column for separating fractions

O from the pyrolysis product. In one embodiment, a distil- 3 lation column is used as a separating device of the sep-

O 35 aration unit for separating fractions from the pyrolysis product. The distillation column can fractionate the pyrolysis product depending on the boiling points into different fractions. Further, the distillation column can contain packings and trays. In one embodiment, the gas fraction is recovered from a top part of the distilla- tion column, one or more oil fraction is recovered from a middle part of the distillation column and the wax fraction is recovered from a bottom part of the distil- lation column. In one embodiment, temperature of the wax fraction is 70 — 300 °C, in one embodiment 100 - 200 °C, after the distillation column. In one embodiment, tem- perature of the gas fraction is 20 — 30 °C after the distillation column.

In one embodiment, a distillation column is used as a separating device of the separation unit for separating fractions from the pyrolysis product, and the method comprises supplying the non-condensed pyrolysis product from the scrubber to the distillation column in which at least gas, oil and wax fractions are separated.

In one embodiment, the apparatus comprises at least one line for supplying the non-condensed pyrolysis product from the scrubber to the distillation column in which at least gas, oil and wax fractions are separated. In one embodiment, the distillation column with bottom and top boiling temperatures of about 100 - 150 and 20 - 30 °C, in one embodiment about 100 and 25 °C, respectively, is used in the process. en In one embodiment, the wax fraction or a part

S of the wax fraction is supplied from the separation

LÖ unit, such as from the separating device, e.g. distil- = 30 lation unit or column, scrubber or condensation device, = to the visbreaking unit. In one embodiment, the wax z fraction or a part of the wax fraction is supplied to

O the pyrolysis unit, such as to the pyrolysis reactor or 3 to a feed of the pyrolysis reactor.

N 35 In one embodiment, the wax fraction from the

N separation unit, e.g. distillation unit, and/or the condensed flow from the scrubber are supplied to the visbreaking unit. In one embodiment, the apparatus com- prises at least one line for supplying the wax fraction from the separation unit, such as the distillation col- umn, and/or the condensed flow from the scrubber to the visbreaking unit.

In one embodiment, the wax fraction is recov- ered from a bottom of the separation unit or the sepa- rating device and supplied to the visbreaking unit.

The wax fraction is treated, preferably cracked, in the visbreaking unit. In the visbreaker furnace of the visbreaking unit, the wax fraction is cracked in an in- direct thermal contact with the furnace to lighter prod- ucts with shorter carbon chain length. In one embodiment, the visbreaking unit is based on a mild thermal cracking process. In one embodiment, the wax is cracked to lighter compounds at temperature of 400 — 500 °C. In one embodi- ment, the wax is cracked to lighter compounds at temper- ature of 400 - 500 °C and with residence time which is between 30 s - 30 min, i.e. 30 seconds - 30 minutes, preferably depending on temperature, in a visbreaker fur- nace of the visbreaking unit. In one embodiment, the residence time is 1 - 10 min. In one embodiment, the residence time is below 12 min, in one embodiment below 10 min. Any suitable visbreaker furnace can be used in visbreaking. In one embodiment, the visbreaking unit can en comprise a coil or soaker furnace. In one embodiment,

S temperature of the oil product is 350 — 450 °C after the

O visbreaker furnace. = 30 In one embodiment, the oil product is recircu- = lated from the visbreaking unit to the separation unit, = such as to the separating device, e.g. distillation col- © umn, condensation device or scrubber, or to a feed of the

O separating device. In one embodiment, the oil product is

N 35 recirculated from the visbreaking unit to the separation

N unit or the scrubber. In one embodiment, the oil product is recirculated from the visbreaking unit to the sepa- rating device of the separation unit or the scrubber, which may be arranged before the separating device of the separation unit. In one embodiment, the apparatus com- prises at least one line for recirculating the oil prod- uct from the visbreaking unit to the separation unit, such as the separating device of the separation unit, or to the scrubber, which may be arranged before the sepa- rating device of the separation unit.

In one embodiment, a bed material and/or char are separated from the pyrolysis product after the py- rolysis reactor. In one embodiment, the apparatus com- prises at least one cyclone or more than one cyclone for separating a bed material and/or char from the pyrolysis product after the pyrolysis reactor. In one embodiment, the apparatus further comprises a combustor to which at least the bed material, e.g. sand, is supplied and in which the bed material of the pyrolysis reactor is heated.

Any combustor, e.g. a fluidized bed combustor, may be used in the process. The heated bed material can be re- circulated from the combustor to the pyrolysis reactor.

In one embodiment, non-condensable gases from the separation unit, e.g. from the separating device, are recirculated to the pyrolysis reactor, the visbreaking unit and/or a combustor in which a bed material of the pyrolysis reactor 1s treated. In one embodiment, the o apparatus comprises at least one line for recirculating

S non-condensable gases from the separation unit to the

O pyrolysis reactor, the visbreaking unit and/or a combus- = 30 tor in which a bed material of the pyrolysis reactor is = treated. Preferably, the visbreaking unit, the pyrolysis

E reactor and the combustor can get their energy from the

O non-condensable gases. 3 In one embodiment, at least a part of the wax

N 35 separated in the separating device, e.g. condensation

N device or scrubber, is recirculated to the pyrolysis unit, such as to the feed of the pyrolysis reactor. In one embodiment, the apparatus comprises at least one line for recirculating at least a part of the wax separated in the separating device, e.g. condensation device or scrubber, to the feeder of the pyrolysis reactor. In one embodiment, a part of the warm wax, preferably a small portion of the warm wax, is added to the feed to increase the temperature of the feed, and then a required work to heat the feed can be reduced in the feeder. Further, a viscosity of the feed may be decreased.

In one embodiment, the wax fraction is heated before the visbreaking unit by using an indirect contact with flue gas from the visbreaking unit and/or a combus- tor in which a bed material of the pyrolysis reactor is treated. In one embodiment, the apparatus comprises at least one heat exchanger for heating the wax fraction before the visbreaking unit by using an indirect contact with flue gas from the visbreaking unit and/or a combus- tor in which a bed material of the pyrolysis reactor is treated. In one embodiment, temperature of the flue gas is 600 — 800 °C after the visbreaking unit. In one em- bodiment, temperature of the flue gas is 450 — 700 °C after the heat exchanging.

In one embodiment, the method and apparatus are based on a continuous process.

Thanks to the invention, wax and heavy tars en which are formed in a pyrolysis can be converted to oil

S with high content of aliphatic compounds. This increases

LÖ the plant’s efficiency. Further, energy can be saved = 30 when the wax is not cooled down the room temperature and = it is transferred at high temperatures of about 100 °C z to the visbreaking. Flue gases of the visbreaking unit

O can be used to heat the wax, and then efficiency can be 3 increased in the visbreaking unit and the whole process.

N 35 Further, a feed of the pyrolysis can be heated by using

N warm wax which is refluxed to a feeder.

The method and apparatus offer a possibility to convert residue flows to desired products easily, and energy- and cost-effectively in the pyrolysis process.

The present invention provides an industrially applica- ble, simple and affordable way to produce desired prod- ucts from different raw materials. The method and appa- ratus are easy and simple to realize in connection with production processes.

EXAMPLES

Fig. 1, Fig. 2, Fig. 3 and Fig. 4 present some embodiments of the process converting wax to oil in a pyrolysis process.

The apparatus of Figs. 1 - 4 comprises a py- rolysis reactor (2), such as a fluidized bed pyrolysis reactor, for pyrolyzing a feed (1) comprising plastic to form a pyrolysis product (3), and a feeder for feeding the feed to the pyrolysis reactor. Further, the appa- ratus comprises a separation unit (10) comprising at least one separating device for separating at least a wax fraction (16), and a visbreaking unit (13) compris- ing a visbreaker furnace. The wax fraction (16) is sup- plied to the visbreaking unit (13), in which the wax fraction is cracked to form at least an oil product (11) comprising aliphatic compounds. Air (15) can be fed via an air inlet to the visbreaker furnace (13). © The apparatus of Fig. 1 comprises a scrubber (8) < for cooling the pyrolysis product (3) and for separating

O a condensed flow (18) comprising wax and/or tars from the = 30 pyrolysis product, and for forming a non-condensed py- = rolysis product (9). The scrubber (8) of Fig. 2 comprises

E two scrubbers, i.e. first scrubber (8a) and second scrub- © ber (8b). The apparatus of Fig. 4 comprises more than two

O scrubbers, in this embodiment four scrubbers (8c,d,e,f),

O 35 for cooling the pyrolysis product (3) and for separating the wax fraction (16), oil fractions (14a,14b) and gas fraction (12).

In the apparatus of Fig. 4, the scrubbers are used as the separating devices of the separation unit.

In one embodiment of Fig. 4 the first scrubber (8c) may be optional, and/or any numbers of scrubbers may be used as the third and fourth scrubbers (8e,f). In the appa- ratus of Fig. 4, the wax fraction (16) is supplied via a line from the scrubber (8d) to the visbreaking unit (13).

In the apparatus of Fig. 1 and 2, the separating device (10) of the separation unit is a distillation column in which a gas fraction (12), oil fractions (14a,14b) and the wax fraction (16) are separated. The apparatus comprises a line for supplying the non-con- densed pyrolysis product (9) from the scrubber (8, 8b) to the distillation column (10). Further, the apparatus comprises lines for supplying the wax fraction (16) from the distillation column (10) and the condensed flow (18) from the scrubber (8) of Fig. 1 or from the second scrub- ber (8b) of Fig. 2 to the visbreaking unit (13). The wax fraction (16) is recovered from a bottom of the distil- lation column (10).

In the apparatus of Fig. 3, the separating de- vice (10) of the separation unit is a condensation de- vice in which a gas fraction (12), oil fractions (14a,14b) and the wax fraction (16) are separated. The e apparatus comprises a line for supplying the wax fraction

S (16) or its part from the condensation device (10) to the

O visbreaking unit (13). The wax fraction (16) is recovered = 30 from a bottom of the condensation device (10). Further, = the apparatus may comprise a line for supplying the wax z fraction or its part from the condensation device (10) © to the feed of the pyrolysis reactor (2), and then the

O wax fraction or its part may be supplied from the con-

O 35 densation device to the visbreaking unit and/or pyrolysis unit.

Further, the apparatus of Fig. 2 and Fig. 4 comprises a line for recirculating a part of the wax (22) separated in the first scrubber (8a,8c) to the feeder of the pyrolysis reactor. Further, the apparatus of the

Figs. 1 - 4 comprises lines for recirculating non-con- densable gases of the gas fraction (12) from the separt- ing device (10), such as the distillation column or con- densation device, or from the scrubber (8f) to the py- rolysis reactor (2), the visbreaking unit (13) and/or a combustor (6) in which a bed material of the pyrolysis reactor is treated. The apparatus of Figs. 1, 2 and 4 further comprises a line for recirculating the oil prod- uct (11) from the visbreaking unit (13) to the scrubber (8), and the apparatus of Fig. 3 comprises a line for recirculating the oil product (11) from the visbreaking unit (13) to a feed of the condensation device.

Further, the apparatus of the Figs. comprises a cyclone (4) for separating bed material and/or char from the pyrolysis product (3) after the pyrolysis reactor (2). The apparatus further comprises a combustor (6) in which the bed material (5), such as sand, is heated. The heated bed material (7) is recirculated from the combus- tor to the pyrolysis reactor (2). Air (19) can be fed via an air inlet to the combustor.

Further, the apparatus of the Figs. comprises a heat exchanger (20) for heating the wax fraction (16) en before the visbreaking unit (13) by using an indirect

S contact with flue gas (17) from the visbreaking unit

O (13). Alternatively, an exhaust gas (21) from the com- = 30 bustor (6) is used to heat the wax fraction in the heat = exchanger. 7

O Example 1 3 In this process, wax is converted to oil in a

O 35 pyrolysis process according to Figs. 1 and 2.

A plastic feed (1), which includes waste PP/PE and in which chain length (C) may be 4000 - 40000, is atomized and fed to a fluidized bed riser pyrolysis reactor (2), and the feed is pyrolyzed at temperature of about 500 - 600 °C and with residence time of 1 - 3 s to form a pyrolysis product vapor (3). Sand and/or char are separated from the pyrolysis product in a cy- clone (4) after the pyrolysis reactor. The sand is treated in a combustor which comprises a fluidized bed such that the char burns and warms the sand. The hot sand is re- circulated to the pyrolysis reactor. Air (19) can be supplied to the combustor (6).

From the cyclone (4) the pyrolysis product va- por (3), at temperature of about 500 °C, is supplied to a scrubber (8) in which the pyrolysis product vapor is cooled and a condensed flow (18) comprising wax and/or tars are separated from the pyrolysis product, and a non- condensed pyrolysis product (9) is formed. Temperature of the condensed flow (18) may be about 100 °C after the scrubber. In the process according to Fig. 2, tempera- ture of the flow may be about 300 °C after the first scrubber (8a) and about 100 °C after the second scrubber (8b). The non-condensed pyrolysis product (9) is supplied from the scrubber (8) or the last scrubber (8b) to the distillation column (10) in which gas (12), oil (14a, 1l4b) and wax (16) fractions are separated. Temperature of the e wax fraction (16) is about 250 °C after the distillation

S column.

O The wax fraction (16) is supplied from a bottom = 30 of the distillation colum to a visbreaker furnace (13) = in which the wax fraction is cracked to form an oil z product comprising aliphatic compounds. The wax fraction © (16) comprises at least wax and tars, in which chain

O length C may be below 100 — 200. The condensed flow (18)

N 35 from the scrubber can be combined to the wax fraction

N flow (16), and the combined flow can be supplied to the visbreaker furnace. The wax fraction or the combined flow can be heated in a heat exchanger (20) before the visbreaker furnace by using an indirect contact with flue gas (17) from the visbreaker furnace (13) and/or exhaust gas from the combustor (6). Temperature of the flue gas (17) may be about 700 °C after the visbreaker furnace and about 500 °C after the heat exchanger. In the visbreaker furnace, the wax fraction is cracked to form the oil product (11). The wax can be cracked to lighter compounds at temperature of 400 — 500 °C and with resi- dence time of between 1 — 10 min in the visbreaker fur- nace. Air (15) can be supplied to the visbreaking (13).

Temperature of the oil product may be about 400 °C after the visbreaking. The oil product (11) may be recirculated from the visbreaker furnace to the scrubber.

The non-condensable gases (12), such as light gases, from the distillation column (10) may be recircu- lated to the pyrolysis reactor (2), the visbreaker fur- nace (13) and/or the combustor (6). Temperature of the non-condensable gases may be about 25 °C after the dis- tillation column.

In the process according to Fig. 2, a part of the wax separated in the first scrubber (8a) can be re- circulated to the feed of the pyrolysis reactor (2). Then warm wax may be used to heat the the plastic feed (1), e.g. in the beginning of the extruder.

N

S The pyrolysis reactors, combustors, scrubbers,

LÖ distillation columns and visbreaker furnaces, and other = 30 devices and eguipments of the process used in Figs. 1 - = 4 are known per se in the art, and therefore they are

E not described in any more detail in this context.

O The method and apparatus are suitable in dif- 3 ferent embodiments for producing desired products from

N 35 different raw materials and for converting wax fractions

N of the products.

The invention is not limited merely to the ex- amples referred to above; instead many variations are possible within the scope of the inventive idea defined by the claims.

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Claims

1. A method for converting wax to oil in a pyrolysis process, characterized in that the method comprises - feeding a feed comprising plastic to a pyrolysis reactor, and pyrolyzing the feed to form a pyrol- ysis product, - separating at least a wax fraction from the pyrol- ysis product in a separation unit, and - supplying at least a part of the wax fraction to a visbreaking unit in which the wax fraction is cracked to form at least an oil product comprising aliphatic compounds.

2. The method according to claim 1, char - acterized in that the method comprises supplying the pyrolysis product to at least one condensation device in which the pyrolysis product is cooled.

3. The method according to claim 1 or 2, characterized in that the method comprises sup- plying the pyrolysis product to at least one scrubber in which the pyrolysis product is cooled and a condensed flow comprising wax and/or tars are separated from the pyrolysis product, and a non-condensed pyrolysis product is formed.

4. The method according to claim 3, char - acterized in that a distillation column is used en as a separating device of the separation unit for sepa- S rating fractions from the pyrolysis product, and the LÖ method comprises supplying the non-condensed pyrolysis = 30 product from the scrubber to the distillation column in = which at least gas, oil and wax fractions are separated.

E 5. The method according to any one of claims 1 O or 4, characterized in that the wax fraction 3 from the condensation device, distillation column and/or N 35 scrubber and/or the condensed flow from the scrubber are N supplied to the visbreaking unit.

6. The method according to any one of claims 1 to b, characterized in that at least a part of the wax separated in the separating device is recircu- lated to the feed of the pyrolysis reactor.

7. The method according to any one of claims 1 to 6, characterized in that the wax fraction is recovered from a bottom of the separation unit and supplied to the visbreaking unit.

8. The method according to any one of claims 1 to 7, characterized in that a bed material and/or char are separated from the pyrolysis product af- ter the pyrolysis reactor.

9. The method according to any one of claims 1 to 8, characterized in that the oil product is recirculated from the visbreaking unit to the separation unit or scrubber.

10. The method according to any one of claims lto 9, characterized in that non-condensable gases from the separation unit are recirculated to the pyrolysis reactor, the visbreaking unit and/or a combus- tor in which a bed material of the pyrolysis reactor is treated.

11. The method according to any one of claims 1 to 10, characterized in that the wax fraction is heated before the visbreaking unit by using an indi- rect contact with flue gas from the visbreaking unit o and/or a combustor in which a bed material of the pyrol- S ysis reactor is treated. LÖ

12. The method according to any one of claims = 30 l to 11, characterized in that the wax is = cracked to lighter compounds at temperature of 400 — 500 E: °C and with residence time which is between 30 s — 30 min O in a visbreaker furnace of the visbreaking unit. 3

13. An apparatus for converting wax to oil in N 35 a pyrolysis process, characterized in that the N apparatus comprises

- a pyrolysis reactor (2) for pyrolyzing a feed (1) comprising plastic to form a pyrolysis product (3), and a feeder for feeding the feed to the pyrolysis reactor, - a separation unit (10) comprising at least one sep- arating device for separating at least a wax frac- tion (16) from the pyrolysis product, and - a visbreaking unit (13) comprising at least one visbreaker furnace, into which at least a part of the wax fraction (16) is supplied and in which the wax fraction is cracked to form at least an oil product (11) comprising aliphatic compounds.

14. The apparatus according to claim 13, characterized in that the separation unit (10) is a distillation unit comprising at least one distilla- tion column in which at least gas, oil and wax fractions are separated.

15. The apparatus according to claim 13 or 14, characterized in that the apparatus comprises at least one scrubber (8) for cooling the pyrolysis prod- uct (3) and for separating a condensed flow (18) compris- ing wax and/or tars from the pyrolysis product, and for forming a non-condensed pyrolysis product (9).

16. The apparatus according to claim 15, characterized in that the apparatus comprises at least one line for supplying the non-condensed pyrol- en ysis product (9) from the scrubber (8) to the distilla- S tion column in which at least gas, oil and wax fractions LÖ are separated. = 30

17. The apparatus according to any one of = claims 13 - 16, characterized in that the ap- z paratus comprises at least one line for supplying the wax O fraction (16) from the separating device of the separa- 3 tion unit (10) and/or the condensed flow (18) from the O 35 scrubber to the visbreaking unit (13).

18. The apparatus according to any one of claims 13 to 17, characterized in that the apparatus comprises at least one line for recirculating at least a part of the wax separated in the separating device to the feeder of the pyrolysis reactor (2).

19. The apparatus according to any one of claims 13 to 18, characterized in that the apparatus comprises at least one cyclone (4) for sepa- rating a bed material and/or char (5) from the pyrolysis product (3) after the pyrolysis reactor (2).

20. The apparatus according to any one of claims 13 to 19, characterized in that the apparatus comprises at least one line for recirculating the oil product (11) from the visbreaking unit (13) to the separation unit (10) or scrubber (8).

21. The apparatus according to any one of claims 13 to 20, characterized in that the apparatus comprises at least one line for recirculating non-condensable gases (12) from the separation unit (10) to the pyrolysis reactor (2), the visbreaking unit (13) and/or a combustor (6) in which a bed material (7) of the pyrolysis reactor is treated.

22. The apparatus according to any one of claims 13 to 21, characterized in that the apparatus comprises at least one heat exchanger (20) for heating the wax fraction (16) before the visbreaking unit en (13) by using an indirect contact with flue gas from the S visbreaking unit (13) and/or a combustor (6) in which a ro bed material of the pyrolysis reactor is treated. o 7 NN O & &