A METHOD FOR DECOMPOSITION OF HYDROCARBONS

Abstract: In order to prevent fouling during a pyrolytic decomposition of hydrocarbons, where a plasma torch and a reaction chamber are utilized, there is supplied to the torch in its gaps, pipes and openings, together with in the reaction chamber in its walls a gas or vapour which contains oxygen in the form of a compound. CO2 or H2O in gas form are preferably used as the cleansing agent.

Description: A method for decomposition of hydrocarbons The invention concerns a method for the prevention and removal of fouling of apparatus during the decomposition of hydrocarbons. During the process of pyrolytic decomposition of hydrocarbons into hydrogen and carbon, a complete dehydroge.÷ization of the carbon will not always occur, with the result that deposits are very easily formed in the reaction apparatus, both in channels in torches, in the openings between the torch electrodes and in the actual reaction chamber. These deposits can be extremely hard and difficult to remove and they are particularly prevalent in the peripheral areas, i.e. on the walls, partly due to the fact that the temperature is usually lower there, thus leading to a more incomplete decomposition process as well as a greater tendency to form deposits. Such problems are particularly crucial in narrow openings, in pipes and channels which transport the hydrocarbon medium, such as in lead-in tubes, or in the gaps between electrodes, where there is the risk of some intrusion of carbon particles. These problems can lead to a complete blockage of the apparatus, thus causing the decomposition process to be interrupted or to operate in an unsatisfactory manner. For this reason a number of pyrolytic processes can only be conducted intermittently and not continuously, which makes the process considerably more expensive and may even make it unprofitable. The object of the present invention is to provide a method whereby these problems can be avoided. A further object of the invention is to provide a method which thereby can also provide an increase in the yield and to some extent improve the process performed by means of the apparatus. Yet a further object of the invention is to provide a method which prevents fouling, whereby no form of pollution or extra materials are supplied to the process which is being performed. These objects are achieved by a method which is characterized by the patent claims presented. In the invention there is introduced into a pyrolytic burner, and particularly a plasma torch, an atmosphere which does not influence the pyrolytic process, but which is capable of reacting with the carbon deposits or sediments and convert these into volatile materials. In this connection it can be especially advantageous to use CO2 gas as a cleansing agent or cleansing gas, which is supplied to the torch through the channels between the electrodes. A second advantageous alternative for this purpose is the use of H 2 0 in vapour form. Gas supplies of this type will react in the torch with the deposited carbon and convert it to CO gas. In principle, the cleansing process according to the invention is an oxidation of the deposits, but. the unique aspect of the invention is that the oxygen is used in the form of. a compound. A stream of oxygen or air has previously been used in order to remove impurities and to clean channels of this kind, but the obvious disadvantage of this method is that the reaction is too rapid and too strong, which can easily result in a reheating and disturbance of the actual pyrolytic process. Thus it is surprising that by using oxygen in the form of a compound in the invention it is possible to achieve a rapid and effective cleansing of impurities from the channels as well as the removal of already formed impurities without the actual process being thereby affected. In addition there is the advantage that carbon dioxide and naturally also H2O are less dangerous mater¬ ials which are more easily handled, while at the same time carbon dioxide has the advantage that those products which are used for cleaning are an integral part of the actual final product from the pyrolysis. In the following section the invention will be described in more detail by means of an embodiment. In a plasma torch of the type described in the applicant's Norwegian patent application 91 4907, in addition to the supplied medium it will be possible to supply C0 2 gas in limited, suitable amounts in the spaces between the electrodes 2, 3 and 4 and in the space between the lead-in tube 1 and the innermost electrode 2, as well as through the lead-in tube. With such a supply of cleansing agent it will be possible to keep the torch in continuous operation for extended periods.

Claims: PATENT CLAIMS 1. A method for preventing and removal of fouling during pyrolytic decomposition of hydrocarbons, wherein there are utilized a plasma torch and a reaction chamber, characterized in that there is supplied to the torch in its gaps, pipes and openings as well as in the reaction chamber near its walls, oxygen as a compound in the form of a gas. 2. A method according to claim 1, characterized in that CO 2 or H 2 θ are used in gas form as a cleansing agent.

Inventors: HAUGSTEN KJELL, HOX KETIL, HUGDAHL JAN, LYNUM STEINAR, MYKLEBUST NILS, HAUGSTEN, KJELL, HOX, KETIL, HUGDAHL, JAN, LYNUM, STEINAR, MYKLEBUST, NILS
Applicants: KVAENER ENGINEERING A S, KVAENER ENGINEERING A.S.
Application year: 1992
Main classification: C01B3
IPC codes: C01B3, C01B31, C09C1