WO2003029384A1

WO2003029384A1 - Pyrolysis apparatus for processing coarse granules made from plastic and rubber scraps

Info

Publication number: WO2003029384A1
Application number: PCT/HU2001/000120
Authority: WO
Inventors: Zoltan Szinay; Ferenc Kiss; Ferenc Czako
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-10-02
Filing date: 2001-11-26
Publication date: 2003-04-10
Anticipated expiration: 2004-04-02
Also published as: HU2291U; HU0100243V0

Abstract

A pyrolisis apparatus for processing coarse granules produced from plastic and rubber scraps and producing hydrocarbon products which has an inner chamber (3) with a vertical axis, serving as a pyrolysis reactor, a combustion chamber (1), an outer reactor case, inlet and outlet elements for the products (17, 18, 20, 24, 9), heating elements (7) and stirring elements (13), wherein the inner chamber (3) is conical at the top and the bottom, it has discrete heat-baffle elements (6) facing the combustion chamber (1), there is a reverse screw mounted on its axis (18) in the pre-feeding tank (17) and the lower blade of its agitator 813) has side scraper elements (14).

Description

PYROLYSIS APPARATUS FOR PROCESSING COARSE GRANULES MADE FROM PLASTIC AND RUBBER SCRAPS

The invention relates to an apparatus for the environment-friendly processing of non-domestic wastes, which are generated continuously and accumulated on a large scale. More particularly, the present invention relates to an apparatus for the processing of coarse granules produced from environment polluting wastes which are difficult to process, namely, plastic and rubber scraps and for the production of hydrocarbon products. The apparatus according to the present invention comprises an inner chamber with a vertical axis, serving as a pyrolysis reactor, a combustion chamber, an outer reactor housing, inlet and outlet elements for the products, heating elements and stirring elements. Throughout the world, it is a main concern that the end-products which cannot be used properly any more lead to environmental pollution due to the lack of appropriate processing industries. Wastes are generally used in power plants, i.e., for energy production. Most traditional heat production processes seriously harm environment. Another danger emerges from the inefficient processing of wastes, i.e., mainly due to the lack of classification, they are burnt under uncontrolled circumstances.

Thus, wastes are generally burnt in power plants or used as secondary raw materials. All kinds of wastes can be burnt in thermal power plants and in cement works, so burning is a general large-scale process.

The reprocessing of plastic and rubber materials has created recycling methods and new branches in this industry. However, due to the diversity of materials, their classification is not satisfactory. So, if the staring materials are not selected according to their manufacturers then the products can seldom get back to their suppliers in order to be used as an equivalent raw material.

The manufacture of rubber products requires specified raw materials. However, in spite of the expensive investments, the large-scale burning technologies are not able to cope with the sewage treatment and the protection of air purity due to the ever more rigorous environmental protection requirements, so the decomposition of wastes during the recycling of industrial rubber products, which represent a minor percentage, should be carried out without polluting the environment.

Since the sixties, several manufacturers have applied partial pyrolytic decom- position and various methods have been developed. For example, Krauss-Maffei, Kiener and Mannesmann pilot plants in Germany have tried to process crumb rubber.

The common features of the above processes were as follows: a) the rubber tires were ground in several steps until an average granule size of 1 to 3 mm was achieved and then the crumb rubber was fed into a drum rector; b) the crumb rubber was decomposed to gases, vapours and carbon black at a temperature of 500° C, but the utilisation of the recycled products was not economical in those days.

However, the commercial plant of TOSCO-GOODYEAR has been still oper- ated in the United States. In this computer-aided complex factory supported by 52 branch works, 300 tons rubber scraps originating from the plant are processed daily in drum rectors, similarly to the German methods mentioned above, under atmospheric pressure and at low temperatures. Each product is recycled to the manufacturing process. The principles of the partial pyrolytic processes mentioned above are well- known, their apparatuses can be constructed. However, their large-scale application is hindered by several factors which can be summarised as follows: • the energy which can be obtained from these scraps by the present commercial processes is less than the energy obtainable from mineral sources; • the drum reactor is expensive, its sealing system is difficult to construct, its energy consumption is high and it works with an expensive crumb rubber;

• the large-scale plant produces a high concentration of air pollution;

• its automating is complicated and the maintenance is expensive; • it requires a rubber collecting network;

• the products need a stable market;

• the products create additional environment protection problems.

An enormous amount of rubber and plastic scraps is produced continuously in the developed countries. This fact urges the experts of the energy sector to de- velop a comprehensive strategy and method. The high-pressure and high- temperature processes require high initial and operational costs, thus, they do not solve the problem.

Therefore, apparatuses requiring low initial costs and inexpensive maintenance and using a simple technology are to be developed which are able to produce energy carriers at low temperatures, under low pressures, i.e., with reasonable operational costs, economically, together with increased environment protection.

The above requirements have been met by the apparatus described in Hungarian utility model No. 1 853.

The said utility model is based on the discovery that, due to the large dimen- sions of the traditional drum reactors, the reaction space is almost totally filled with the gases and vapours emerging from the decomposition of the fine-grained granules which are continuously fed into the reactor, further, non-desired condensations, the precipitation of impurities or lengthy downs may occur due to the feeding errors, heating errors or other operational disorders. However, a charge of granules which almost fills the chamber can be fed into a vertical reactor, therefore, if a crumb rubber having a high granule size and, in consequence, a loose structure, is to be processed, the flue-gases flowing turbulentfy in the reactor, which is continuously stirred at a controlled rate and heated intermittently, can intensively transfer their heat- content to the great mass of the moving material. The uniform generation of the gases and the removal of the gases/vapours are not hindered and take place under a stable pressure, so an end-product of the required quality is produced under the set parameters.

The main feature of the above utility model is that it has a vertical pyrolysis reactor with a top inlet and a bottom outlet.

The reactor is preferably indirectly heated by the burners mounted horizontally and tangentially at the lower part of the combustion chamber.

The above apparatus has various advantages, however, its processing capacity has not proved to be sufficient. Therefore, the object of the present invention is to improve the process according to Hungarian utility model No. 1 853 and to eliminate the drawback mentioned above.

It was found that the performance of the apparatus can be significantly improved by certain structural modifications. The present invention comprises an inner chamber with a vertical axis, serving as a pyrolysis reactor, a combustion chamber, an outer reactor housing, inlet and outlet elements for the products, heating elements and stirring elements, wherein the top and bottom of the inner chamber are conical, the inner chamber has discrete heat-baffle elements facing the combustion chamber, there is a reverse screw mounted on its axis in the pre-feeding tank and the lower blade of the agitator has side scraper elements. Instead of the traditional fire-clay wall, the apparatus has a heat-resistant steel outer case.

The heating elements are preferably arranged tangentially and diagonally to each other. Further, the bottom of the combustion chamber of a preferable embodiment is provided with a fire-clay lining while the outer case has a ceramic thermal insulator.

The sectional drawing of the reactor according to the invention is shown in Figure 1 in order to facilitate understanding.

Naturally, the scope of the invention is not limited to the figure. With reference to Figure 1, inner chamber 3 with a vertical axis (pyrolysis reactor) is surrounded concentrically by combustion chamber 1. The lower boundary element of inner chamber 3 is bottom plate 2 which is shared by combustion chamber 1; thus, bottom plate 2 closes both inner chamber 3 and combustion chamber 1. Bolt lock 15 and outlet pipe 20 for the products are located on dome cover 5. The upper boundary element of combustion chamber 1 is rimmed cover 4 which is fastened to the rim of the outer case and to the neck rim of inner chamber 3 by a screwed connection in the preferred embodiment according to the figure. Agitator 13 is located in the centre of the bottom part of inner chamber 3. It is equipped with side scraper elements 14. Opening 23 for inserting axis 12 and opening 9 for carbon black removal are also located in the centre of the bottom part of inner chamber 3. The apparatus is driven by a cross drive mechanism. Tangential heating elements 7 which are arranged diagonally to each other, in this case block burners mounted on fire tubes, are located in the lower third of combustion chamber 1. Bolt lock 15 mounted on dome cover 5 and lower bolt lock 16 of feeding tank 17 form a gate and the feeding device is formed together with a reverse axis, single-shaft screw mounted on axis 18 above the gate. The lower boundary section of inner chamber 3 is bolt lock 8 for slag removal.

The starting material is fed by an individual conveyor to feeding tank 17 and, after opening bolt locks 15 and 16 by a level-control, it is loosened continuously due to gravitation and to the operation of the reverse screw mounted on axis 18. Thus, the agglomerating and compacting of the material can be avoided and it can be fed quickly.

After feeding, bolt locks 15 and 16 close. Combustion chamber 1 is heated to the pre-set temperature by burners 7 mounted on the fire tube. The diagonal arrangement of the burners leads to favourable air engineering characteristics and the burners do not disturb the operation of each other in contrast with other arrangements. The desired operation pressure is achieved by agitating the charge by the periodic movement of side scraper elements 14 of agitator 13. Due to the agitation, the amount of the material to be decomposed increases on the heat transfer surface. The oil vapours generated by the decomposition of coarse granules transfer a part of their heat content to the loosened charge which means a secondary heat transfer. Inner chamber 3 according to the present invention comprises lower and upper cy- lindrical elements, in contrast with cylindrical reactors or those with only an upper conical part, and this shape is more suitable for increasing the surface and processing the charge than those of known reactors.

The moving of the charge is favourably influenced by crossbar 19 which is fastened to axis-end 12 and holds side-wing (scraper element) 14 fastened to the lower scraper blade with a screwed connection.

At the end of the cycle, the slag remaining on bottom 2 is mainly carbon black. If the starting material does not comprise metallic reinforcing materials its residues are removed together with carbon black when lower bolt lock 8 is opened; then upper bolt locks 15 and 16 are closed. The intensive heat transfer between combustion chamber 1 and inner chamber 3 is favourably increased by baffles 6 welded on the wall of inner chamber 3 and facing combustion chamber 1. They also facilitate the spiral flow of the hot flue gases which leave combustion chamber 1 at smoke-pipe 25. The heat storage of the apparatus is provided by the fire-clay lining (not shown in the figure) covering the bottom of combustion chamber 1. The slow heat response of the apparatus is not influenced by the warming up of ceramic thermal insulation 21, 22 mounted on the outer case. This light insulation is fixed by a plate cover.

Each operation of the apparatus is automated, thus, the latency between the consecutive cycles is the opening and closing of the disconnecting elements. The inner chamber according to the present invention is 2,5 times larger than that of Hungarian utility model No. 1 853. Therefore, the amount to be fed and the amount of charge to be processed are increased by the same factor.

The increase of the capacity is facilitated by the fact that inner chamber 3 has a conical shape also at the bottom and it allows a greater amount of material to con- tact simultaneously the heat transfer surface along the inner envelope.

The application of baffles 6 has the same effect; they improve heat transfer, prevent the turbulent flow of the flue gases and enable the spiral flow of the gases in combustion chamber 1. It was also found that the efficiency of heat transfer may improve in a smaller combustion chamber. It is further increased by the heat resistant outer steel case which is used instead of the fire-clay wall and directs radiated heat to the walls of inner chamber 3.

The change of the heat resistant walls leads to a further advantage, namely, the heat storage of the furnace does not generate a fire hazard, and the apparatus can be heated and cooled quickly.

Side scraper elements 14 of the lower scraper blade of agitator 13 lead to a more intensive moving on the heat transfer surface.

The feeding of the material to be treated is improved by the reverse screw on axis 18 mounted into feeding tank 17; the screw prevents the clogging of feeding opening 24 as it loosens the granules agglomerating in the centre by lifting them and sprinkles them towards the envelope, thus, the feeding is fast and free from clogging.

Claims

1. A pyrolysis apparatus for processing coarse granules produced from plastic and rubber scraps and producing hydrocarbon products which has an inner chamber (3) with a vertical axis, serving as a pyrolysis reactor, a combustion chamber (1), an outer reactor case, inlet and outlet elements for the products (17, 18, 20, 24, 9), heating elements (7) and stirring elements (13), wherein the inner chamber (3) is conical at the top and the bottom, it has discrete heat-baffle elements (6) facing the combustion chamber (1), there is a reverse screw mounted on its axis (18) in the pre-feeding tank (17) and the lower blade of its agitator (13) has side scraper elements (14).

2. The apparatus according to Claim 1, wherein the heating elements (7) are arranged tangentially and diagonally to each other.

3. The apparatus according to Claim 1 or 2, wherein the bottom of the com- bustion chamber (1) is provided with a fire-clay lining while the outer case has a ceramic thermal insulation.