FI104560B - Electrode consumption in plasma torches - Google Patents

Description

104560

The invention relates to a method for reducing electrode wear in plasma burners in the process of hydrocarbon processing and decomposition.

DD 292 920 discloses a process for the preparation of high quality carbon black by pyrolysis of hydrocarbons in a plasma reactor. The hydrocarbon feed may be in the form of gas, solution, or solid. The plasma may consist of hydrogen or an inert gas such as argon, or a mixture of hydrogen and hydrocarbon gas, or hydrocarbon gas only. However, it has not been explained that the use of hydrocarbon gas and hydrogen gas as plasma forming gas reduces electrode wear or in some way affects wear in the plasma reactor.

GB 1 400 266 discloses a process for the preparation of carbon black by pyrolysis of hydrocarbons in a plasma reactor. The device consists of two electrodes which are coaxially opposed. The hydrocarbons in the gas space 20 are fed to form plasma. In order to better utilize the heat generated by the plasma and improve the yield, the hydrocarbons can be further fed to the reaction chamber. However, it has not been explained that the use of hydrocarbon gas as plasma gas reduces the wear of the electrode .. or in some way affects the wear in the plasma reactor.

During the process of natural gas processing and decomposition in the plasma burner, the electrodes wear out and the electrodes must therefore be replenished or replaced after a certain period of use. This wear is detrimental because wear causes process stoppages which can be time consuming and cause production interruptions in addition to wasting expensive electrode material.

One alternative has been the use of renewable, graphite or carbon electrodes 35, which can be continuously replenished and do not 104560.

dirt decomposition products. This is cheaper than using wear-free electrodes, which are more complex and expensive in addition to dirty products.

It is an object of the present invention to provide a method for reducing the wear of electrode material in plasma torches for the decomposition and processing of hydrocarbons, regardless of whether the electrodes are renewable or consumable.

This object is solved by a method known from the claims.

It has surprisingly been found that burner-disintegrating hydrocarbons can be used to reduce electrode wear by mixing them with the respective plasma gas. When mixed directly with plasma-15 gas, the hydrocarbons decompose into hydrogen and carbon black in the actual flame zone where the electrodes wear, and the carbon black formed precipitates in the same area where the wear occurs. In this way, there is growth on the surface of the electrodes, which completely or partially offsets the wear, and greatly prolongs the life of the electrodes.

By controlling the mixing amount of hydrocarbons, e.g. methane, and possibly also the gas supply area and temperature, it is possible to control the deposition on the electrodes and thereby achieve this advantageous effect.

25 The advantage of using "spoilage" of electrodes in this way is very surprising. In the use of plasma torches, this considerable deterioration of the electrodes has been a major problem up to now. But by operating according to the invention, this contamination is controllable and controllable to a desired range by mixing natural gas with the respective plasma gas. In this way, the electrode life can be extended without resorting to expensive means because of the availability of affordable, natural gas. The effect is particularly advantageous when prehydrogen as a plasma gas is used to ensure that there are no post-growth changes in the plasma gas composition.

• Tests have been conducted on both copper and graphite electrodes which have the same effect on both types of electrodes. The effect achieved by the Applicant's own experiments is illustrated in the drawing, which shows the wear of the electrode as a function of the percentage of methane mixed with hydrogen plasma gas.

In a simple manner, the invention has thus achieved a considerable improvement in the use of plasma torches. A further advantage obtained is that the mixing of the hydrocarbon gas can reduce the thermal load on the electrodes. This effect is particularly evident when using hydrogen as plasma gas.

Thus, the use of electrode wear when using carbon electrodes in the manufacture of pure decomposition products can, by means of the invention, partially or completely reduce the hydrocarbon gas by controlled and controlled mixing of the hydrocarbon gas with plasma gas. In order to control the growth of the electrode 20 at the wear point, the amount of natural gas doping can be appropriately controlled based on the control parameters calculated from the arc voltage of the plasma torch.

• ·

Claims (4)

A process for reducing electrode consumption in plasma torches during processing and degradation of hydrocarbons for the production of carbon black and hydrogen, especially from natural gas or methane, wherein hydrogen is measured in the plasma burner as a plasma forming gas, characterized in that in the plasma source the gas is mixed 2-10% of natural gas or methane and the amount of natural gas or methane mixed is regulated according to the calculated electrode consumption on the basis of operating parameters of the beaker in the plasma burner. Process according to Claim 1, characterized in that the natural gas can be preheated to a certain temperature. Method according to claim 1, characterized in that the natural gas is introduced into the plasma gas by means of separate introductory tubes. 4. A method according to claim 1, characterized in that the natural gas is added to the plasma gas to reduce the thermal load on the electrodes. • · · * * ·