1. Field of the Invention
This invention relates to a burner for introducing a combustible mixture comprising hydrocarbon fuel, free oxygen-containing gas, and optionally a temperature moderator (liquid or vapor) into a free-flow partial oxidation synthesis gas generator.
2. Description of the Prior Art
In the partial combustion of a hydrocarbon with oxygen, or air enriched with oxygen, in the presence of steam and/or carbon dioxide, temperatures between 1,100.degree. and 1,500.degree. C. are often reached. Special requirements are therefore placed on the design and the material from which the burner is constructed to avoid damage to the latter.
An essential requirement in burner construction of the type contemplated is that they be cooled or otherwise protected from the high temperature environment. This is most often achieved by circulating water or a similar coolant through the unit. Thus, by constructing the burner both internally and externally with coolant passages, a sufficient amount of heat transfer to the circulating cooling fluid can be achieved to minimize and stabilize the temperature which the burner itself reaches.
Normally, the oxidizing flame which combusts the mixture, introduces the hot flame as well as the products of combustion into a reactor or generator. The latter is lined with a suitable refractory material to avoid damage as a result of the high temperatures that will be reached and sustained.
A relatively vulnerable part of the burner is that section which is continuously exposed for extended periods of time to the high reactor temperatures. Although means have been provided for cooling internal segments of the burner, the problems which result from the high temperature still persist.
For example, external walls of the burner are generally surrounded with a cooling coil or the like which circulates a liquid such as water to effectuate a cooling action. Further, the lower or flame end of the burner is provided with internal passages which permit coolant to be internally circulated to maintain a desired temperature range.
In either instance, the forward most vulnerable face of the burner, can reach certain temperatures, or range of temperatures within which accumulations of particular slag or ash will tend to cling to the exposed burner face. Such a slag build-up will cause a reduction in burn efficiency and eventually impairment of operation and eventual unit shutdown.
These accumulations are prompted generally by back mixing of the combustible particles or ash as the particles enter the reactor. Here they are caught up into the violently turbulent flows of the gas as associated with the high velocity flame.
More specifically it is found that if the temperature on the exposed burner face is in excess of 750.degree. to 900.degree. F., ash particles will be prone to stick thereto. If, on the other hand, the temperature is kept lower than 750.degree. to 900.degree. F. on the face of the burner, the ash sticking will be substantially avoided.
In burners that function as required, it is found that a particle build-up along the burner face will generally commence at the lip of the discharge opening or nozzle. Thereafter, the build-up will progress radially outward from the nozzle and gradually cover a substantial segment of the exposed face. Slag will also build upon itself due to progressive insulation from cooling coil/channel.
One way for precluding or at least limiting this slag build-up along the burner face is to inject steam directly into the combustible mixture within the burner itself. This step will facilitate the avoidance of undesired build-ups at the discharge lip. It will not, however, completely preclude the accumulations as herein mentioned.
For example, the back mixing and flow of the particulated matter as a result of the turbulence immediately inside the reactor, will continue to cause or prompt a certain degree of build-up at the burner face.
Toward overcoming the above stated problems, the present invention is addressed to means for providing a fluid, dynamic shield which protects the entire burner face. The shield is provided in the form of one or more jets of a fluid such as steam, which are projected transversely of the face from a point at the burner periphery.
A number of fluids such as steam, CO.sub.2 or even water could serve as the protective dynamic shield. For the present disclosure, however, the fluid will be considered to be steam.
Physically, one or more high velocity steam jets are caused to sweep the burner face. The jets first of all form a barrier which precludes the hot particles from getting to, or contacting the face. Secondly, the fluid jet is so aligned that it will flow parallel to the face, or will contact or impinge against the face preferably adjacent to the discharge lip. This creates a thermal radiation/convection shield to keep burner face below 750.degree. to 900.degree. F. Thirdly, the flow will thus clear the face of any accumulation that might be initiated.
It is therefore an object of the invention to provide a burner which is adapted for use in combusting a coal-oxygen mixture to achieve a partial oxidation of the gaseous product. A further object is to provide a burner of the type contemplated that is capable of withstanding undesired particulate depositions along the burner exposed face. A still further object is to provide a burner of the type contemplated wherein one or more high velocity fluid jets are directed to sweep the burner face and maintain it free of accumulated particulate matter and to concurrently protect the face by establishing a fluidized radiation/convection shield thereacross.