Technical Field

The present invention relates to radiation burners. Such burners are utilized in chemical, oil processing and oil chemical industries, in metallurgy and other areas where it is necessary to provide an indirect radiation heat exchange.

Background Art One of such radiation burners is disclosed in Soviet Inventors' Certificate No. 954,079. The burner includes an injector with a gas nozzle, a regulating disc, a cylindrical outlet member provided with a reflector and accommodated in a recess of a burner stone fixed in a casing which is arranged with a gap relative to the rear wall of the stone. The above described burner, similarly to other burner devices, has the disadvantage in its low degree of blackness of the refractory burner stone, which at the temperature of 1,520 - 1,550°K is approximately 0.3 - 0.4. This degree of blackness determines a certain density of the heat flow which cannot be increased without the artificial increase of the degree of blackness of the refractory material. Another disadvantage of this burner is that it is not possible to suppress the formation of nitrogen oxides which are quite substantial in the waste products of combustion at temperature of 1,520 - 1,550°K. The ejection of the fuel gas from the burner nozzle with a high speed produces high noise which is another disadvantage of the known burner.

Other radiation burners of this type are disclosed for example in U.S. Patent 3,664,424 and French patent 2,195,328. The radiation burner disclosed in these references includes an injector with a gas nozzle, the burner head and a movable slider. The burner is mounted in a recess formed in a ceramic block which forms a part of the furnace wall. In accordance with another embodiment, the section of the burner which extends outside of the outer surface of the furnace wall is enclosed in a casing provided with a mounting plate which is fixed with a gap to a steel outer plate of the furnace. The casing is provided with a noise-absorbing lining which is held by a perforated sheet. The burner head has a plurality of peripheral longitudinal openings for passing of a prepared gas-air mixture. In order to provide the high quality combustion of the fuel gas of changing content, the burner is provided with air suction of a secondary air. This burner similarly to many other flow burners has the disadvantage that its construction does not permit substantial increase of its output without the increase of its size. For this reason if the minimal output is to be increased three times, it is necessary to replace the injector and the gas head. The second disadvantage of this burner is that it does not permit a high quality flame-free combustion of the fuel gas, since the burner head is located at a substantially great distance from the surface of the ceramic block, and the gas-air mixture which ejects through the longitudinal openings in the burner head in a substantially thick layer does not completely burn at the surface of the furnace wall. As a rule, the final combustion takes place inside the furnace, which leads to an incomplete combustion and excessive consumption of f el.

Finally, a further disadvantage of the burner is that the suction of the secondary air for increasing the combustion degree of fuel gas is obtained only due to the modification in the furnace combustion chamber. This makes its regulation very difficult. The insufficient quantity of air leads to a chemically incomplete combustion and environmental loading with products of incomplete combustion. If the optimal demand for air is exceeded, this leads to the increase in losses with ejected combustion products and ejection of toxic gases.

Disclosure of Invention

Accordingly, it is an object of the present invention to provide a radiation gas burner which is further improvement of the existing burner.

In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a radiation burner which ha a burner stone composed of a refractory material and provided with a passage means; means for supplying a f el through the burner to a front area of the burner stone; means for supplying a primary air into the fuel; means for supplying secondary air into the burner; and means for communicating the passage means in the burner stone with at least one of the primary air supplying means and the secondary air supplying means, preferably to both primary and secondary air supplying means. When the radiation burner is designed in accordance with the present invention, the temperature of flame is substantially reduced and therefore the development of nitrogen oxides is substantially increased.

The novel features which are considered as characteristic for the invention are set forth in

particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

Brief Description of the Drawings

FIG. 1 is a view showing a section of a radiation gas burner in accordance with one embodiment of the present invention;

FIG. 2 is a view showing a section taken along the line II-II in FIG. 1;

FIG. 3 is a view showing a section of the radiation gas burner in accordance with another embodiment of the present invention; and

FIG. 4 is a view showing a section taken along the line IV-IV in FIG. 3.

Best Mode of Carrying Out the Invention

A radiation burner in accordance with one embodiment of the present invention has a mounting plate which is identified with reference numeral 1 and a two-layer burner stone 2 which includes a layer 19 composed of a regular refractory material and a layer 20 composed of a regular refractory material with some additives, particularly metal oxides such that they increase the blackness of the stone front radiating surface. The burner stone 2 has passages 16 and a chamber 17. It is mounted on a mounting plate 1 by bolts 22. A cylindrical bushing 3 is arranged in an opening of the burner stone 2. The cylindrical bushing 3 has one end connected with the mounting plate 1.

An outlet pipe 4 is coaxially arranged inside the cylindrical bushing 3 so as to form an annular gap ' . A reflector 6 is mounted on the end of the outlet pipe 4 coaxially therewith by means of radial plates 5. The reflector 6 has a cylindrical portion A formed as a disc, and also a portion H formed as a body of revolution with a concave generatrix substantially corresponding to a truncated cone with a greater base at the end of the portion H. The portion H of the reflector is located inside the outlet pipe 4 and together with it forms an annular outlet nozzle i through which gas-air mixture can exit. The concave generatrix of the reflector 6 is smooth and made by a radius. It is formed so that the gas-air mixture which exits through the nozzle eye smoothly flows along the concave inner wall of the reflector and then is directed exactly parallel to the front surface of the front wall of the burner. For this purpose the reflector is formed so that a tangent to the concave generatrix at the rear side of the portion A of the reflector extends substantially parallel to the front surface of the front part of the burner. A ring 8 is arranged at the outer side of the outlet pipe 4 in its front part by means of pins 7 so as to form a gap S' for passage of a secondary air and combustion products.

The burner further has an injector 9 which is mounted to the outlet pipe 4 by a flange 10 and pins 11. The pins 11 are fixed in the mounting plate 1. The burner also has a regulating device 12 formed as a noise absorbing casing which is mounted on the pipe 13 so that it can move along its axis to change the gap between the device 12 and the front surface of the injector 9. Thereby the regulation of consumption of the supplied primary air is obtained. The pipe 13 is

also provided with a nozzle 14 for supplying a fuel gas. The regulating device 12 has a noise absorbing insulation 15 reducing the noise during operation of the burner. The above described radiation burner operates in the following manner. A fuel gas is supplied into the burner through the pipe 13, exits from the gas nozzle 14 as a compressed jet and entrains a primary air which is mixed with the gas so as to form a unitary gas-air jet. This jet moves through the injector 9, outlet pipe 4 to the reflector 6, it is guided by the portion H of the reflector, and exits from the portion 4 substantially parallel to the working surface of the burner stone 2. The jet of the mixture of the fuel gas and primary air has a certain speed, it passes through the annular outlet nozzle i and sucks in the secondary air which is supplied through the annular gaps S and S'. The secondary air, in turn, sucks in the combustion products which are supplied through the passages 16 and the chamber 17 provided in the burner stone 2 , and then through the openings 18 provided in the cylindrical bushing 3. The thusly produced recirculation of some quantity of combustion products into the combustion zone reduces the combustion temperature and results in significant reduction of the nitrogen oxides. The mixture which is formed from the fuel gas with the primary air, the secondary air, and partially dissolved with the combustion products, is distributed over the working surface of the burner stone 2 and is burnt there in a thin layer. Thereby the working surface of the burner stone 2 is heated to high temperature and radiates the heat energy into the combustion area of the furnace.

The increase of the degree of blackness of the radiation part of the burner stone significantly

increases the density of the heat stream, intensifies the heat exchange in the combustion area, and as a result reduces the consumption of fuel gas.

The outer cylindrical bushing 3, in addition to reliably fixing the burner in this horizontal position, also together with the mounting plate 1 and the pins 22 provide such a mounting of the burner stone 2, that it is no longer necessary to have a big casing with a double bottom as in the first mentioned reference. Therefore, the metal consumption of the burner is significantly reduced. Moreover, the mounting and demounting steps are substantially simplified. For example, in order to exchange the reflector 6 which has a diameter not exceeding the diameter of the ring 8, it suffices to screw the nuts on the pins 11 and remove the inner part of the burner from the cylindrical housing 3. Such steps can be performed even when the furnace is in operation.

Since the burner has a self-regulating suction of the secondary air, it provides efficient combustion of gases of both permanent and changing content. Thus, when the density of the fuel has increases, consumption is also increased; therefore, the necessary quantity of injecting primary air must increase as well. However, this does not happen since the speed of ejection of gas from the nozzle remains constant. The insufficient quantity of the primary air is compensated by the secondary air, since when the consumption of gas increases, the speed of ejection of the gas-air mixture from the annular nozzle is increased and therefore the greater quantity of secondary air is sucked in. As a result, the incomplete fuel combustion is prevented.

When the density of the fuel gas reduces, its consumption is also reduced and therefore the speed of

ejection of the gas-air mixture from the annular nozzle is reduced. Despite this, the flame does not jump into the burner due to screen which is formed by the secondary air and the recirculated combustion products.

Because of the specific shape of the reflector 6 and in particular of its concave generatrix with a tangent to the outlet point extending parallel to the front surface of the burner, the fuel-gas mixture is uniformly spread over the front surface of the burner and the final combustion takes place immediately near the front wall of the burner and not inside the furnace, therefore providing a complete combustion and a lower consumption of fuel. The possibility of self-regulation of the ratio of the primary and secondary air provides the possibility of increasing the coefficient of working regulation of the burner output. This ratio is a ratio of the nominal output to the minimal output. In the burner in accordance with the present invention it is equal to substantially 9, while in the known injection burners it is equal to substantially 3.

A radiation gas burner in accordance with another embodiment of the present invention shown in FIGS. 3 and 4 has a mounting plate which is identified with reference numeral 31 and provided with a flange 40 which can be welded to it. A bush 33 is screwed into the flange 40 at one side, and a ring support 32 for an injector 39 is screwed into the flange 40 at another side. The ring support 10 has slots for passage of secondary air and pipes 49. The cylindrical bush 33 has openings for communication of passages 38 provided in a burner stone 2, with an annular gap S for passage of the secondary air. The bush 33 also has openings for insertion of bent ends

of the pipes 49 for communication with passages 17 provided in the burner stone 32.

A short pipe 34 is screwed into an outlet part of the injector 39, and a reflector 36 including a cylindrical part A formed as a disc and a part H formed as a body of revolution with a concave generatrix is mounted in the pipe 34 by radial strips 35. The part H of the reflector is located inside the outlet pipe 34 and in cooperation with it forms an annular outlet nozzle i for exiting a gas-air mixture. A ring 38 is mounted upwardly of the pipe 34 in its front part by pins 37 with a gap S' for exiting the secondary air and combustion products.

The radiation burner is further provided with a control device 42 formed as a noise absorbing casing mounted on a pipe 43 so that it can displace axially in order to change the gap between the device 42 and the front surface of the injector 39. Thereby a regulation of the supplied primary air is performed. A nozzle 44 is arranged on the pipe 43 for supplying a fuel gas. The regulating device 42 is provided with noise-absorbing insulation 45 for noise reduction during the operation. Sleeves 52 are mounted in a rear part of the ejector 39 and connected by nuts 41 with the pipes 49 for supplying recirculated combustion products.

During the operation of the fuel gas is supplied through the pipe 43 and exits the nozzle 44 as a compressed jet so as to inject the primary air flowing through the gaps B and B' . During this process, sucking (injecting) of combustion products from the front area of the burner is performed through the passages 47 in the burner stone and the pipe 49. this jet which is a mixture products, the primary air and the fuel gas is supplied through the injector 39 and

the outlet pipe 34 to the reflector 36, directed by the part H of the reflector and exits along the part A substantially parallel to the front working surface of the burner stone 32. This jet which flows with high speed through the annular nozzle i forms in this area a radification which provides the injection of the secondary air through the passages S and S'. This radification provides the injection of the combustion products supplied through the passages 46 and 48 from the combustion chamber. Through the gap Si a mixture of the secondary air and combustion products is supplied.

Therefore in the burner the combustion products or the combustion gas is recirculated so as to ballast both the primary air and the secondary air with the products of complete combustion of fuel. In accordance with important feature of the present invention, the passages 16 are arranged at such a distance from the burner axis, where a complete combustion of fuel has been performed. In other words, non-combustible products are supplied into the passage 46. Due to the ballasting of the primary and secondary air the temperature of fuel combustion or in other words, the temperature of flame is reduced, and thereby the content of the nitrogen oxides (NO _s ) is substantially reduced.

As can be seen, in the radiation burner in accordance with the present invention, the ballasting of the primary air is performed only by the combustion product and not by a mixture with the secondary air which usually has still not completely combusted products, and therefore the ballasting in accordance with the present invention substantially reduces the flame temperature. The pipes 49 are arranged so that the secondary air which passes through the gap S flows

around the pipes and then the primary air which passes through the gap B flows around the pipes, sot hat the pipes are cooled and their service life is increased. The ballasting of the primary air and secondary air with the combustion products is very efficient.

As can be seen from FIG. 3, the burner stone 32 has a front part 32' and a rear part 32". The front part is composed of refractory with an increased degree of blackness. For example the front part 32' can be provided with metal oxides which increase the degree of blackness of the burner stone and therefore increase the emissivity, so as to substantially increase the heat exchange.

While the invention has been illustrated and described as embodiment in a radiation gas burner, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.