Carbonaceous boiler

#This invention relates to furnaces and boilers and more specifically relates to furnaces and boilers utilizing impervious, low permeability silicon carbide as a medium for efficiently absorbing infrared radiation.

#In processes for heating and vaporizing liquids and gases there are many types of boilers or furnaces that perform specific functions within a well-defined set of parameters such as upper heat limits and pressure levels. All boilers are either directly or indirectly energized by chemical or fossil fuels which may be in the form of liquids, gases or solids. All of these boilers generate pollution and, with the exception of nuclear boilers, are limited to relatively low heat levels and pressure limits. Further, these prior art boilers have been characterized as having a less than optimum efficiency.

#Furthermore, in many processes ranging from the debarking of logs in the production of pulp paper and firing furnaces for steel mills to the burning of fuels for internal combustion engines, substantial quantities of waste heat are generated which are never fully utilized. To make use of the emission of waste heat many types of heat exchangers have been developed, an example of which is disclosed in Cushman U.S. Pat. No. 3,404,731. These prior art heat exchangers have a primary purpose of capturing heat from a waste heat source, conducting that heat to a liquid or gas medium which transfers the latent heat absorbed in the exchanger process to another medium. To make such a waste heat exchanger desirable for an end use, the exchanger must have a second medium which can efficiently utilize and convert the waste heat to a useful end.

#Other objects, features and advantages of the present invention will become more fully understood from the following detailed description of the preferred embodiment, the appended claims and the accompanying drawings in which:

#FIG. 1 is a perspective illustration of the preferred embodiment of a carbonaceous boiler of the present invention;

#FIG. 2 is an end elevation view of the carbonaceous boiler of FIG. 1 with adjacent counter flow tubular block, constructed of silicon carbide;

#Refer now to FIG. 1 where there is disclosed a perspective view of the preferred embodiment of the present invention. A block of silicon carbide 11 having relatively large side surface areas 12 and having a relatively small or narrow depth dimension is fixedly positioned on a metal mount 14 which in turn is fixedly secured to a point intermediate the ends of a metal frame 15. The carbonaceous block may be formed of any suitable low permeability, impervious graphite or carbon material but in the preferred embodiment, the carbonaceous block is formed of KT silicon carbide which is manufactured by the Carborundum Corporation. Such a block can operate at working temperatures up to 3000.degree. F in an oxidizing atmosphere and up to 4,200.degree. F in an inert atmosphere and has a thermal conductivity in excess of 700 BTU 1 hr./sq.ft./.degree. F/in. In addition, KT silicon carbide is impermeable, has excellent thermal shock characteristics and can contain liquid or gas at pressures in excess of 2,000 psig.

#As illustrated, a single pass channel 13 is formed in the carbonaceous block 11 with the single pass channel 13 having a grid structure so that the fluid or gas passing through the channel is exposed to a maximum of the heat energy absorbed by the carbonaceous block at the sides thereof.

#To each side of the carbonaceous block are positioned sources of infrared energy 16, 17 which are movable to within one-half inch with respect to the carbonaceous block on the metal frame 15. The sources of infrared energy are shown in schematic form for ease of illustration since such sources are well known in the art. In the preferred embodiment the infrared energy is generated by fossil fuel heating means known in the art. A series of infrared radiation sources may be formed wherein infrared rays of progressively increasing energy are directed onto the block 11 from the bottom thereof to the top. Thus, for example, the infrared source 18 may provide infrared rays which are directed onto the lower portion of the carbonaceous block 11 for heating the fluid passing through channel 13 to a temperature of, for example 500.degree. F. The infrared radiation provided by source 19 may, for example, generate temperatures in the fluid passing through the channel 13 which range between 500.degree. F and 1,000.degree. F while the upper infrared source 20 provides radiation for heating the fluid in channel 13 to a level above 1,000.degree. F. As aforementioned, the infrared sources may be of any suitable type, gas or electric, known in the art for generating the aforementioned or other temperature levels.