METHOD FOR PYROLYSIS OF WASTE MATERIAL IN THE PRESENCE OF AN AUXILIARY MATERIAL

Abstract

A method for thermally decomposing a carbonaceous waste material including: filling a reactor defined by a reactor wall with the waste material and an auxiliary material, resulting in a reactor content, the auxiliary material including abrasive particles; heating the reactor contents in the absence of oxygen, such that gaseous products are formed by pyrolysis of the waste material and the abrasive particles do not melt or thermally decompose; moving the reactor contents during the pyrolysis, the moving being adapted to mix the reactor contents and to cause the abrasive particles to scrape over at least parts of the reactor wall. The auxiliary material has a composition to include a component adapted to bind halogens present in the gaseous products and/or so that the brittleness of the auxiliary material is greater than the brittleness of the reactor wall.

Claims

1.-15. (canceled)

16. A method for thermally decomposing a carbonaceous waste material, comprising: filling a reactor defined by a reactor wall with said waste material and an auxiliary material, resulting in a reactor contents within said reactor wall, said auxiliary material comprising abrasive particles; heating said reactor contents in the absence of oxygen, whereby gaseous products are formed by pyrolysis of said waste material and said abrasive particles do not melt or thermally decompose; moving said reactor contents with respect to said reactor wall during said pyrolysis, said moving being adapted to mix said reactor contents and to cause said abrasive particles to scrape over at least parts of said reactor wall, wherein said auxiliary material has a composition such that a component is comprised adapted to bind halogens present in said gaseous products and/or such that the brittleness of said auxiliary material is greater than the brittleness of said reactor wall.

17. The method according to claim 16, wherein said auxiliary material has a composition such that a component is comprised adapted to bind halogens present in said gaseous products, said halogens comprising chlorine and/or bromine present in said gaseous products.

18. The method according to claim 16, wherein said auxiliary material has a composition such that a component is comprised adapted to bind halogens present in said gaseous products, said auxiliary material comprising calcium.

19. The method according to claim 16, wherein said auxiliary material has a composition such that a component is comprised adapted to bind halogens present in said gaseous products, said component being integrated within said abrasive particles.

20. The method according to claim 18, wherein said abrasive particles comprise calcium carbonate.

21. The method according to claim 16, wherein said auxiliary material has a composition such that a component is comprised adapted to bind halogens present in said gaseous products and the brittleness of said abrasive particles is greater than the brittleness of said reactor wall, and said abrasive particles are selected from the group of: shells, seashells, broken shells, broken seashells, pieces of coral carcass, pieces of limestone, pieces of a calcium-containing mineral.

22. The method according to claim 16, wherein said auxiliary material has a composition such that a component is comprised adapted to bind halogens present in said gaseous products, said auxiliary material being a mixture of said abrasive particles and slaked lime.

23. The method according to claim 16, wherein the brittleness of said auxiliary material is greater than the brittleness of said reactor wall, and said auxiliary material is selected from the group of: shell material, seashell material, a porous rock.

24. The method according to claim 16, wherein the hardness of said abrasive particles is less than the hardness of said reactor wall.

25. The method according to claim 16, wherein said reactor contents are continuously moved during said pyrolysis.

26. The method according to claim 16, wherein said filling said reactor comprises: feeding said auxiliary material into said reactor, followed by feeding said waste material into said reactor.

27. A system for thermally decomposing a carbonaceous waste material, comprising: a buffer of said waste material and a buffer of auxiliary material, said auxiliary material comprising abrasive particles; a reactor defined by a reactor wall, and a heating system adapted to heat said reactor wall, said reactor and said heating system being adapted to heat said waste material present within said heating reactor in the absence of oxygen to form gaseous products by pyrolysis of said waste material; a supply system adapted to fill said reactor with reactor contents comprising said waste material and said auxiliary material; a mixing system adapted to move said reactor contents with respect to said reactor wall, said moving being adapted to mix said reactor contents and to cause said abrasive particles to scrape over at least parts of said reactor wall; wherein said auxiliary material is adapted not to melt or thermally decompose during said pyrolysis of said waste material, and said auxiliary material has a composition such that a component is comprised to bind halogens present in said gaseous products and/or such that the brittleness of said auxiliary material is greater than the brittleness of said reactor wall.

28. The system according to claim 27, wherein said mixing system comprises an agitator, said agitator comprising a shaft and blades mounted on said shaft.

29. The system according to claims 27, wherein said heating system is an electrical heat source.

30. The system according to claims 27, wherein said reactor is a horizontal mixer adapted to be positioned in flat or inclined condition.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] FIG. 1 schematically illustrates a system and method for pyrolyzing a waste material, according to an embodiment of the invention.

[0059] FIG. 2 shows two different mixing systems within a reactor, according to possible embodiments of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0060] FIG. 1 illustrates the components included in a system 100 according to an embodiment of the invention, and the steps included in the corresponding method. The system 100 includes a reactor 101 with mixing system 105 and reactor wall 104, a heating system 112, a waste material buffer 102, an auxiliary material buffer 103, and a supply system for supplying waste material 110 and auxiliary material 111 to the reactor 101.

[0061] The waste material is, for example, a mixture of plastic waste, which may contain various types of plastic, for example PE (Polyethylene), PP (Polypropylene), PVC (Polyvinyl Chloride), PET (Polyethylene terephthalate), PS (Polystyrene), etc. Other examples of waste material are organic waste, food waste, slaughter waste, animal feed, rubber, wood, textile, etc. If necessary, a certain pre-treatment of the original mix of waste material can be effected. For example, plastic waste can be selected first, or it can be converted into pellets before entering the buffer 102. In the embodiment shown, the buffers 102 and 103 are silos, in which a supply of waste material, for instance plastic pellets, and auxiliary material, respectively, occur. Furthermore, there may be a provision 108 intended for further processing of the plastic pellets 109 before being fed into the reactor 101. The provision 108 includes, for example, a feed screw, an intermediate storage, a feed belt, and an extruder in which the plastic pellets are melted into a molten plastic mass 110. The auxiliary material 111, which is fed from silo 103 to the reactor 101, includes abrasive particles. The composition of the auxiliary material 111 is discussed further below. A supply line for a direct supply of auxiliary material 111 from the silo 103 can be provided, or provisions such as screw conveyors or conveyor belts can be used for this.

[0062] In the embodiment shown, the reactor 101 is a horizontal reactor, which can be arranged flat or with a certain slope with respect to the ground level. The reactor 101 includes a cylindrical tank, having a reactor wall 104. An electrical heater, consisting of multiple segments 112, is provided to heat the reactor wall 104. The heating elements 112 are shown in FIG. 1 presented purely schematically. The segments 112 can be independently controlled to provide constant and reliable heating of the reactor 101.

[0063] The cylindrical tank contains an agitator 105, which is driven by an electric motor 106. In the embodiment shown, the mixing system is a horizontal mixer, and the agitator 105 is implemented as a ploughshare or plowshare type of mixer, schematically shown in FIG. 1. FIG. 2 shows two possible embodiments of such a ploughshare mixer. The mixer 200 includes a shaft 201 on which blades 202 are mounted. Driving the shaft 201, through the motor 106, causes the blades 202 to move relative to the reactor wall 204, leaving a gap 203 between a blade 202 and the reactor wall 204. When contents are within the tank, the contents are mixed by this movement, and reactor contents are set in motion in the vicinity of the wall 204. In particular, abrasive particles contained in the reactor contents will scrape or scour along the wall 204. In other words, abrasive particles being in contact with the wall 204, move over the wall, thereby rubbing over the wall and scraping it. Similarly, the mixer 205, shown at right in FIG. 2, a shaft 209, and blades 206 moving in the vicinity of the wall 210, with a gap 208 between the blades 206 and the wall 210. The mixer 205 includes centrifugal blades 206 arranged close to the wall 210, and plates 207 arranged close at the shaft 209. The plates 207 promote mixing of the reactor contents.

[0064] At the top of the reactor 101, one or more supply ports are provided, adapted for dosing waste material 110 and auxiliary material 103, as shown schematically in FIG. 1. To monitor the process, a thermometer may be provided to measure the temperature of the reactor contents. A scale may also be present to measure the weight of the reactor 101 and thus monitor the amount of waste material to be pyrolyzed within the reactor.

[0065] At the top of the reactor 101, the gaseous pyrolysis products 117, which result from pyrolysis of the waste material within the reactor 101, are collected, see 107. At the bottom of the reactor 101 there is an outlet port, adapted to collect solid residues 118 of the pyrolysis process, for example ash, inert materials such as glass and sand, and auxiliary material, from the reactor 101.

[0066] Typically the reactor 101 is part of a petrochemical plant. Such plant includes the provisions to further treat and transform the pyrolysis products 117 derived from the reactor 101. Known technology can be used for this. In FIG. 1 schematically represents a cooling provision 114, adapted to convert via cooling the condensable hydrocarbons present in the pyrolysis products 117, for example in the range from C5 to C45, into liquid products 115. The non-condensable hydrocarbons in the pyrolysis products 117, in the range from C1 to C4, result in gaseous products 116. The refrigeration provision 114 may comprise several installations, such as different types of heat exchangers, a quench column, etc.

[0067] We now describe a method according to an embodiment of the invention, which can be performed with the system 100, for example. Within this embodiment a pyrolysis takes place of a plastic waste material, in which mainly PE and PP occur, with traces of PVC and chlorines from, for example, bleached paper.

[0068] A step within this method involves filling a reactor 101 with waste material 110 and auxiliary material 111, resulting in a reactor contents within the reactor wall 104. Waste material can be in the form of solid pellets at ambient temperature, or may be supplied to the reactor 101 in molten form at a temperature of 200 to 300° C. The auxiliary material 111 comprises abrasive particles, for example broken seashells. Other possible embodiments of the auxiliary material 111 are discussed further. In the embodiment described here, the broken seashells are first fed into the already heated reactor 101. The reactor wall 104 is heated by means of an electric heater 112 and is at a temperature of about 600 to 700° C. By feeding the seashells first, they can act as a bed in the reactor 101, so that waste material 110 fed into the reactor 101 does not come into contact with the hot reactor wall 104 and carbonization is avoided at that time. The seashells are also preheated in this way.

[0069] Furthermore, the method includes heating the reactor contents in the absence of oxygen so that pyrolysis of the waste material occurs. The interior of the reactor 14 can be maintained at atmospheric pressure, or at a certain overpressure to avoid the supply of ambient air to the interior of the reactor 101. In addition, within the method, the reactor contents are set in motion during the pyrolysis by the agitator 105 rotating at 80 rpm in this embodiment.

[0070] In the described embodiment, the pyrolysis is performed in a semi-continuous process. The shells are first introduced into the reactor 101, for example until the reactor 101 is about 10% filled with shells. The temperature of the wall is then approximately 600 to 700° C., and the temperature inside the reactor, for example, approximately 420° C. A temperature within the reactor between 400° C. and 500° C. is recommended to obtain a high fraction of condensable hydrocarbons within the pyrolysis products.

[0071] Waste material 110 is then supplied. Within the reactor 101, the waste material 110 is mixed with the shells present by rotating the agitator 105. The shells thereby distribute themselves between the waste material, and also scrape off waste material that remains stuck to the reactor wall 104. The temperature within the reactor 101 is kept constant at about 420° C. so that pyrolysis of the waste material occurs. Pyrolysis products 117 are thereby formed, which are gaseous at the prevailing temperature, and which are collected in the unit 107. In the meantime, waste material 110 is continuously supplied during the pyrolysis, while both the temperature and the weight of material present within the reactor 101 are monitored. When the feed rate of the waste material 110 is greater than the rate at which degradation occurs within the reactor 101, the level of waste material within the reactor 101 gradually increases.

[0072] When a certain fill level has been reached, for example 70% of the reactor has been filled, the feed of new waste material 110 into the reactor 101 is stopped. The temperature of the waste material present within the reactor 101 can increase further, for example up to about 500° C. During this post-operation phase, pyrolysis of the waste material within reactor 101 continues, forming gaseous pyrolysis products 117. This phase ends when no gaseous hydrocarbons 117 leave unit 107 anymore.

[0073] During the entire pyrolysis process, both during the phase in which waste material 110 is supplied and during the post-operation phase, the agitator 105 continues to rotate, for example at a speed of 80 rpm. The material to be pyrolyzed is continuously mixed and the shells are distributed among the material to be pyrolyzed, so that agglomerations are avoided. In addition, by moving the blades 202, 206 along the reactor wall 104, shells scour along the reactor wall 104, so that the reactor wall 104 is continuously scraped clean. Carbonization of waste material on the reactor wall 104 and the build-up of an insulating layer on the reactor wall 104 are thus avoided.

[0074] After completion of the post-operation phase, solid material 118 remaining within the reactor 101 is removed from the reactor 101 through an outlet port. This concerns the shells that functioned as auxiliary material, ashes that are created from the pyrolysis of waste material, and inert materials such as glass and sand that were between the waste material and do not degrade. A too large amount of inert material would crush the shells while moving in the reactor 101. Optionally, the solid materials 118 may not be removed from the reactor 101 after each post operation. For example, after a post-operation phase has ended, feeding waste material and pyrolyzing it may be immediately restarted, and only after completion of the next post-operation the reactor is freed of solid materials 118. After removing the shells from the reactor 101, they are replaced by new shells to feed into the reactor 101.

[0075] Within the described embodiment, the gaseous pyrolysis products 117 leaving the unit 107 at a temperature of about 400° C. are cooled to about 70° C. Various types of liquid oils can be formed, such as, for example, parafins, isoparafins, aromatics, fuel similar to diesel, etc. The condensate, at a temperature of about 70° C., is collected, for example, in a crude oil tank.

[0076] In the above-described embodiment, use is made of broken seashells or seashells as auxiliary material. For example, the broken seashells have a size of a minimum of 0.2 mm and a maximum of 13 mm, preferably a minimum of 1 mm and a maximum of 10 mm, this dimension being the diameter of a circle surrounding a shell. The use of broken seashells as an auxiliary material is advantageous because of the combination of a number of characteristics. First, the seashells function as abrasive particles, which scour along the reactor wall 104 during the pyrolysis, so that the wall 104 is continuously kept clean.

[0077] In addition, the seashells consist of a fragile material, in particular a porous material with a brittleness greater than the brittleness of a typical steel reactor wall. The breaking of the shells during their presence within the reactor 101 causes the size of the shells to adapt to the size of the present gap 203, 208, and the dimensions need not be chosen very restrictively. The shells themselves therefore form a waste material that does not need to be recovered after use in the reactor. In addition, the shells cause no or minimal damage to the reactor wall 104 or agitator 105 when hit against them. The sharp edges of broken shells also contribute to a better scouring or scraping effect.

[0078] Finally, the seashells contain Calcium Carbonate (CaCO3), whereby the Calcium will react with halogens present in the gaseous pyrolysis products 117. In the described embodiment, the pyrolysis gases 117 contain HCl and HBr, and the reactions that occur are: [0079] CaCO3+2 HCl.fwdarw.CaCl2+CO2+H2O [0080] CaCO3+2 HBr.fwdarw.CaBr2+CO2+H2O

[0081] The salts CaCl2 and CaBr2 formed are discharged along with the other solid residual materials 118 through an outlet port of the reactor 101.

[0082] The CaCO3 present in the seashells thus ensures a direct binding of halogens in the pyrolysis products 117: the moment HCl or HBr are released, they are immediately bound, at the place where they are formed. This ensures an efficient removal of pollutants from the pyrolysis products in a simple way.

[0083] In one embodiment, the removal of chlorins using CaCO3 in the reactor can be supplemented by other measures, such as the use of halogen binding additives in the extruder 108. This makes it possible to have a very low Cl content in the resulting oil, for example at most 50 mg/kg by pyrolysis of a plastic mixture (PE, PP) with 0.1% to 1% PVC.

[0084] Besides the use of broken seashells as auxiliary material, other embodiments are also possible. For example: [0085] The component adapted for binding halogens can be an element other than Calcium, for example a metal such as Aluminum, or Magnesium (Mg) present as Magnesium Carbonate (MgCO3) in the auxiliary material. [0086] The auxiliary material can be a brittle material, without the presence of a halogen-binding component, for example a porous rock such as pumice stone or a mineral rock. [0087] The auxiliary material can comprise a halogen-binding component, without being a brittle material. For example, the auxiliary material can be a mixture of abrasive particles, e.g. sand, and a halogen-binding component, e.g. Ca(OH)2 in powder form. This mixture can be made in advance and thus being fed into the reactor. [0088] The auxiliary material can be a brittle material and comprise a halogen-binding component, for example pieces of coral carcass, pieces of limestone, pieces of a calcium-containing mineral, or the aforementioned (broken) seashells.

[0089] While the present invention has been illustrated by specific embodiments, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention can be practiced with various modifications and modifications. modifications without departing from the scope of the invention. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being described by the appended claims and not by the foregoing description, and any modifications falling within the meaning and scope of the claims, are therefore included here. In other words, it is understood to include all modifications, variations or equivalents that fall within the scope of the underlying basic principles and whose essential attributes are claimed in this patent application. In addition, the reader of this patent application will understand that the words “comprising” or “comprising” do not exclude other elements or steps, that the word “a” does not exclude a plural. Any references in the claims should not be construed as limiting the claims in question. The terms “first”, “second”, “third”, “a”, “b”, “c” and the like, when used in the description or in the claims, are used to distinguish between like elements or steps. and do not necessarily describe a consecutive or chronological order. Likewise, the terms “top”, “bottom”, “over”, “bottom” and the like are used for purposes of description and do not necessarily refer to relative positions. It is to be understood that those terms are interchangeable under appropriate circumstances and that embodiments of the invention are able to function in accordance with the present invention in sequences or orientations other than those described or illustrated above.