A method for producing fuel for diesel engines from tyres or the like waste rubber material

Abstract

 The invention relates to a method of producing fuel from spent tyres or the like waste rubber material for use in diesel engines or the like particularly for the production of electricity and heating energy. The method firstly includes the step of shredding and breaking down the tyres or the like into crumb rubber material to be fed into a reactor. Then liquid hydrocarbons, preferably in the form of diesel oil, heavy fuel oil or lubricating oils, are fed into the reactor and mixed with the rubber material under a pressure of 3-50 bar, preferably 15-30 bar. The mixture in the reactor is further heated to a temperature of 300-405 °C, preferably 320-385°C, to decompose the solid hydrocarbons and crack the long chained compounds into oils to thereby create a homogenous mixture. A cryogenic process may be used to cool the tyres to glasification temperature after shredding thereof, whereby improper materials like steel wires and textiles can be removed before feeding of the remaining rubber material into the reactor. The homogenous mixture is suitably pumped out of the reactor and cooled to be ready for use as fuel oil in diesel engines.

Description

[0001] This invention relates to a method for producing fuel from tyres or the like waste rubber material in accordance with the preamble of claim 1.

[0002] In a known process shredded tyres are mixed with spent lubricating oil to obtain a mixture for further processing in a gasifier. The gasifier generates low energy gas to be used in a gas turbine for power generation. This process includes a number of complex process steps, such as the removal of steel and textile material from the tyre material, and the use of a high pressure and temperature gasifier with sulphur absorption and gas cleaning making it costly. Therefore this known process is applicable only in larger plants.

[0003] The disposal of spent tyres constitutes a severe environmental problem. Although it is well known to recycle rubber from tyres, it is usually required that the quality of the finished rubber product should be similar to the original virgin product. This can be achieved by making use of a cryogenic process, known as such, where shredded tyres are cooled to glass transition temperature and the product is thereafter milled and classified with separation of steel wires and textile material from the tyres.

[0004] Rubber that does not meet the quality requirements either has to be burnt in a boiler or dumped on a land fill. Rubber from spent tyres has an energy content of approximately 8 MWh/ton and is constituted by styrene butadiene or similar, carbon black as filler, zink oxide, sulphur and small parts of various additives.

[0005] Also plastics of different kinds constitute an environmental problem and must be recycled either for reuse or converted for energy production. The energy content is similar to that of rubber.

[0006] An aim of the invention is to create a new way of processing spent or scrap tyres or the like waste products so as to provide fuel for diesel engines to be further converted, for example, into electricity and heat. A further aim is to avoid the drawbacks of known techniques and to provide a less complicated and more cost effective way of putting into practice such an energy conversion process.

[0007] The aims can be met with a method according to claim 1 and the sub claims.

[0008] In accordance with the basic concept of the invention, liquid hydrocarbons, such as diesel oil, heavy fuel oil, lubricating oils, and/or other organic oils, such as vegetable oils, together with crumb rubber and possibly plastics are mixed and cracked in a chemical process so as to provide a homogeneous liquid having an appropriate viscosity to enable it to be pumped into a diesel engine and having an energy content similar to original diesel fuel oil. The oils referred to above for mixing with the rubber material can be virgin or used oils and these waste products can with advantage be recirculated.

[0009] An embodiment of the invention will now be described in more detail, by way of example only, with particular reference to the accompanying drawing, the sole figure of which schematically illustrates a plant for producing fuel from used tyres or other waste material.

[0010] In the drawing there is shown a shredding plant for shredding tyres and plastics materials. The shredded tyres are fed to a cryogenic plant for cooling to the glass transition temperature to produce crumb rubber and this together with the shredded plastics material are fed to a reactor, e.g. through a sluicing system such as a so-called lock-hopper system. A separate pipe feeds oils through a pump into the reactor. There is a pressure of from 3 - 50 bars, preferably 15-30 bars, in the reactor where the rubber and oils are mixed together. The reactor is heated by steam or a hot oil system to a temperature of approximately 300-405 °C, preferably from 320-385 °C. A decomposition of the solid hydrocarbons takes place in the reactor and the long chained compounds are cracked in the oils thereby creating a homogenous mixture which is pumped out from the bottom of the reactor.

[0011] The high temperature in the reactor makes the solid hydrocarbons and the oils give off gases which may be released from the top of the reactor. However, to obtain favourable diesel fuel features, it is important to keep as much as possible of the gases dissolved in the fuel. This can be achieved by using a low temperature cracking process of catalysts containing, for example, nickel and/or molybdenum. The released gases can be used together with fuel oil as fuel in a steam boiler or a hot oil system for heating the reactor.

[0012] The liquid fuel produced is cooled and can be fed directly to a diesel engine for power and heat generation or stored in an intermediate tank for later consumption.

[0013] The diesel engine should of course be of a type which is able to operate, when necessary, also on heavy fuel oils or the like, and it should also be equipped with appropriate facilities for cleaning of diesel exhaust gases in order to meet local emission standards.

[0014] By making use of the cryogenic process, the quality of the crumb rubber and milled rubber is better suited for processing in the reactor, and it makes it easier to separate in a classifier the steel wires, textiles and other impurities of the tyres before the rubber material is fed into the reactor. Thus, the reactor can be continuously used without the need to periodically clean it to remove the steel and textile. However, in some cases and in a smaller scale utilization of the process, it may be of advantage to directly feed the shredded tyres into the reactor so as to save the costs of a cryogenic plant, although this entails cleaning the reactor of steel, textile and possibly larger unprocessed rubber parts.

[0015] The shredding of the spent tyres to produce crumb rubber may be performed in any known manner. For example, shredding to produce fragmented rubber may be achieved in a mechanical shredder or by the use of high pressure water jets as is known per se.

[0016] The invention is not limited to the embodiment shown and described but several modifications are feasible within the scope of the attached claims.

Claims

1. A method of producing fuel from spent tyres or the like waste rubber material for use in diesel engines or the like, e.g. for the production of electricity and heating energy, characterised in that it includes the steps of:

(a) fragmenting said tyres or the like waste rubber material and feeding the fragmented waste rubber material into a reactor;

(b) feeding liquid hydrocarbons into the reactor and mixing them with said rubber material under a pressure of from 3 to 50 bar; and

(c) heating the mixture in the reactor to a temperature of from 300 to 405 °C to decompose the solid hydrocarbons and crack the long chained compounds into oils to thereby create a homogenous mixture.

2. A method according to claim 1, characterised in that the waste rubber material is fragmented prior to being fed into the reactor by shredding and breaking down said tyres or waste rubber material to produce crumb rubber material.

3. A method according to claim 1 or 2, characterised in that the liquid hydrocarbons comprise diesel oil, heavy fuel oil and/or lubricating oil.

4. A method according to claim 1, 2 or 3, characterised in that the pressure in the reactor is from 15 to 30 bar.

5. A method according to any of claims 1 to 4, characterised in that the mixture in the reactor is heated to from 320 to 385°C.

6. A method according to claim 2 or any one of claims 3 to 5 when dependent on claim 2, characterised in that in step (a), after shredding, the tyres or the like waste rubber material are cooled under a cryogenic process to the glass transition temperature.

7. A method according to any one of the preceding claims, characterised in that, in step (a), unwanted materials, for example steel wires and textiles, are removed before feeding of the remaining rubber material into the reactor.

8. A method according to any one of the preceding claims, characterised in that in step (b), fragmented, e.g. shredded, waste plastic materials are also fed into the reactor.

9. A method according to any of one of the preceding claims, characterised in that the mixture in the reactor comprises from about 40-60% of material from said tyres or the like waste rubber material.

10. A method according to any of the preceding claims, characterised in that in step (c) catalysts, preferably containing nickel and/or molybdenum, are added to the reactor to keep as much as possible of any gases dissolved in the fuel mixture.

11. A method according to any one of the preceding claims, characterised in that gases released in the reactor in step (c) are recovered separately and used as fuel for heating of the reactor.

12. A method according to any one of the preceding claims, characterised in that after step (c) the homogenous mixture is pumped from the reactor and cooled so as to be ready for utilisation as fuel oil in diesel engines or the like.

Drawing