The invention relates to an insert unit for improving the combustion efficiency of gas burners, which contains a burner stone that can be connected to the gas burner, where the burner stone has a flow channel, and the burner stone is made of a material containing silicon.

Burner heads suitable for burning fossil energy carriers are used in numerous fields of industry and agriculture. Such burner heads are used, for example, in conveyor furnaces for firing ceramic products. The disadvantage of the commonly used solutions is that in the case of the known burner heads, when natural gas is used it has an unfavourable effect on the energy efficiency of the conveyor, if in the composition of the gas to be burnt the inert content changes significantly, increases by 7-8%, as in this case, while the caloric value of the gas is practically the same, the absolute gas consumption of the furnaces burdened with mass flow can increase by 10-12%. The presence of inert gases inhibits chemical reaction, which - as it takes place at a lower speed - results in a lower number of useful collisions within a time unit.

In order to reach an appropriate number of useful collisions resulting in the undoing of the chemical bond, the natural gas and combustion air flow feed flow must be increased, and by this heat flow suiting the given heat demand can be ensured. Consequently flue-gas loss increases. In order to resolve the problem, a paired burner - catalyst insert having a basic influence on burning and the rate of combustion must be used.

In the field of chemistry it is difficult to determine the speed of chemical reactions or provide an exact description of their mechanism as dynamic processes, and basically even currently they are influenced with the use of empirically selected catalysts. Although there are so-called catalyst libraries, but in application technology the method of testing is the dominant method. Besides the result or output of chemical reactions, an increasingly more essential aspect is the optimum of the energy balance of the gross processes. The amount of energy input or the proportion of energy that can be obtained besides the same product output is an absolutely determinant, important aspect, disregarding that maybe the aim is not to obtain chemical energy, but obviously it also stands for those processes too.

Our aim with the solution according to the invention was to develop a more efficient catalyst suitable for solving the problem outlined above, with the use of which significant amount of energy can be saved, which, in the present case, means that the chemical reaction taking place minimum with the same output is realised at a lower temperature and pressure, in respect of the type of energy used the mechanical (pressure) and/or thermal (temperature) energy demand is lower. If besides this objective the output also improves, then the specific energy input continues to decrease.

The creation of the insert unit according to the invention was the result of performing the following tests and drawing conclusions from them.

A special measurement circuit and measurement arrangement was set up, with the help of which the change of ion current detected in the flame during combustion could be examined. Measurements were performed in a test furnace containing a closed combustion chamber, equipped with a romscliroder ZKIH 150/100R type natural gas burner. During the measurement the pressure in the furnace was kept between 0.5-2 Pa over the ambient air pressure, in order to prevent the introduction of false air. The furnace was equipped with a so-called artificial loading unit in the combustion space, the task of which was to extract heat from the furnace during combustion. Air flew in the tubes to represent thermal load, and by the variation of the air flow rate the amount of the heat to be extracted could also be influenced. In both cases a gas meter was used for measuring the flow rate of natural gas and air. The measured flow rates were necessary fort the determination of the actual air factor. Furnace temperatures were measured at three locations via thermo elements. With the help of computer software the current temperature was registered every 10 seconds. The data acquisition system was designed and built specially for this combustion system with the capability to record flow measured between the electrode extending into the flame and the body of the gas burner.

The measurement system is shown in figure 1. With the potential difference created with the natural gas burner body "F" as a supply source the ions in the flames were forced to migrate. This flow was detected with the voltage intensity on resistance "R" shown in figure 1. Power supply "T" provided a stable direct voltage of 5 V. Resistance "R" was 5 Mohm. The large shunt resistance was needed for detecting the flow in the measuring circuit of the order of μΑ. In the flame the current intensity was changing continuously, it was different at different points in time. Condenser "C" in figure 1 represented a signal integrating member, the task of which was to stabilise the continuously changing current. The capacity of condenser "C" was 4.7pF. The stable voltage intensity obtained was connected to the inputs of A/D converter "A" via Amplifier "E". Amplifier "E" had single amplification, its task was to make the obtained voltage loadable for the following circuits. The task of A/D converter "A" was to convert voltage into a digital code. It was necessary, because the input of computer "S" can receive information only in a digital form. Finally the obtained voltage intensity was processed, displayed and stored with the software installed on computer "S". The sampling rate of data collection, during measuring was 1 sample / 500 msec. During measuring the voltage on resistance "R", the flow rates provided by gas meters "G" and the temperatures measured at six points of furnace "K" were registered. The results were evaluated from the aspect of comparing the results of the magnetic measurement performed after the reference measurement realised besides certain settings, besides the same settings and on the basis of the same principle. The reference and magnetic measurements were performed besides eight air factor settings. The measurement results are shown in figures 2-9.

On the basis of the results obtained from these measurements the following conclusions could be drawn: for a combustion scenario in a furnace with a closed combustion chamber there was a substantial difference in the intensity of the ion current measured in the flame, depending on the placement or non-placement of a permanent magnet on the incoming fuel line, i.e. on the natural gas pipe. When placing a magnet on the natural gas pipe the intensity of the current flow was always higher than without a magnet. In this way the magnetic catalytic effect in chemical reactions could be basically modelled and measured. Catalysts are very useful materials, they are used almost everywhere. About 85% of current industrial chemical processes involve the use of catalysts. On the basis of the above, considering an average activation energy level, the energy efficiency of catalytic chemical reactions can be improved by 15-25%, with the optimum exploitation of the available possibilities.

On the basis of the above one could conclude that magnetic catalysis and heterogeneous catalysis are analogue processes. Their main point is that they take place with a lower thermal input and faster than heating without a magnet or chemical reactions without catalysts. Change in the ion current is suitable for further study of magnetic catalysis, e.g., for determining an increase in the reaction speed and - similarly - the decrease in the necessary activation energy. Consequently, in the case of catalytic chemical reactions the effect of the catalysts influencing the above two parameters can also be characterised by a change in the ion current.

The main point of the improvement method was that in catalytic chemical reactions ion current must be determined in the reactor space, and its extent must be allocated to the current catalyst besides measuring other common parameters. Furthermore, the parameters characterising the magnetic behaviour of the given catalyst system are also recorded. The use of different catalysts in the same chemical reactions results in varying energy input and energy release, so energy transfer is the essential function of catalysts, the extent of which depends on the catalyst used.

On the basis of the above, the requirements determined with respect to catalysts can be redefined and supplemented with the essential aspect that from the point of view of energy they should be able to enable processes approaching the optimal by placing catalyst development on new grounds. At the same time we can set a new aim to develop and use catalysts during the release of energy from chemical energy carriers, which improve energy efficiency making them more economic and reduce the emission of harmful substances.

On the basis of the measurements and studies the solution according to the invention was based on the following ideas. On the one part, determining ion current and its changes is already known from patent description no HU 225.933 and its 3 ^rd claim, as well as its use for studying the process and energy features of chemical reactions. It turns out from this that the process of chemical reactions can be characterised with an electric signal, which can provide important information on the process. It was also recognised that during the combustion reactions of fuels a magnetic catalysis indicated with a change in the ion current can be detected, and that analogy can be identified between catalysis and magnetic catalysis from the aspect of energy mechanisms.

In the end, as it can be deduced from the basic ideas, the solution according to the invention was based on the recognition that if the burner head is given a burner stone having a specific material composition, at least a part of the surface of which is coated with a catalyst layer other than the ordinary selected for the given purpose, then in respect of the gas consumed it starts to react with oxygen at a lower temperature, so even despite the increasing of the proportion of inert gases the fossil energy carrier can be burnt with the desired efficiency, and so the task can be solved.

In accordance with the set aim the insert unit according to the invention for improving the combustion efficiency of gas burners - which contains a burner stone that can be connected to the gas burner, where the burner stone has a flow channel, and the burner stone is made of a material containing silicon - is constructed in such a way that the burner stone is made of a silicon carbide based material with an open porosity of at least 10%, and at least a part of the external delimiting surface of the burner stone and/or at least a part of the internal delimiting surface of the burner stone is coated with a catalyst layer. A further feature of the insert unit according to the invention may be that an insert piece having openings is inserted in the flow channel of the burner stone, where the insert piece is made of a silicon carbide based material with an open porosity of at least 10%, and at least a part of the external delimiting surface of the insert piece and/or at least a part of the internal delimiting surface of the insert piece is coated with a catalyst layer.

In the case of a possible version of the insert unit the burner stone is made of recrystallised silicon carbide with an open porosity of at least 16%.

From the aspect of the invention it may be favourable, if the catalyst layer contains a metal oxide belonging to the iron group, favourably cobalt oxide.

The insert unit according to the invention has numerous advantageous characteristics. One of the most important advantages that due to the burner stone having a material structure unlike the ordinary and provided with a specific coating, it is possible to improve energy efficiency significantly when used with gas burners during releasing energy from chemical energy carriers, energy consumption can be realised in significantly more economical way, and the emission of harmful materials can also be reduced.

A further advantage of the insert unit according to the invention is that when it is used in firing technology, when burning natural gases with an inert content above 1%, it counterbalances the combustion reaction damping effect by accelerating the burning process of the combustible components, which improves the efficiency of energy use even further.

Another advantage is that if the use of the novel insert unit is combined with enriching the combustion air with oxygen, then the combustion rate can be increased at such an extent that its effect will be practically the same as the heat engineering capacity of natural gas with an inert content below 1%, i.e. of a favourable composition, as a result of which natural gases with a higher inert content and even biogases can be burnt even with ordinary natural gas burners supplemented with the insert unit according to the invention.

It must also be regarded as a general advantage that during the elaboration of the given insert unit a general procedure suitable for developing catalysts was also elaborated, which is based on that in the case of catalytic chemical reactions ion current must be determined in the reactor space, its extent must be allocated to the current catalyst besides measuring other common parameters, and the catalyst optimised for the given purpose must be created in this way, as the use of different catalysts in the same chemical reactions results in varying energy input and energy release, so the essential function of catalysts is energy transfer, the extent of which depends on the catalyst used.

Below the insert unit according to the invention is described in detail in connection with a construction example, on the basis of drawings. In the drawings

Figure 1 is the schematic representation of the measuring arrangement of the burner head also containing the insert unit according to the invention.

Figure 2 is a graph drawn during measuring, indicating changes in ion flow intensity in the flame depending on the air factor, in the cases of using the magnet and without magnetising the gas,

Figure 3 is a graph drawn during measuring, indicating changes in the furnace temperature depending on the air factor at the first measuring point, in the cases of using the magnet and without magnetising the gas,

In figure 1 - besides the measuring arrangement described above - the insert unit according to the invention can also be seen. It can be seen that natural gas burner "F" contains the burner stone 1 of the insert unit, which has a flow channel 2. The flow channel 2 is surrounded by the internal delimiting surface lb of the burner stone 1. The insert piece 4 is also situated in this flow channel 2, and in the present case it has openings 4c. The openings are covered by the internal delimiting surface 4b of the insert piece 4, while the external delimiting surface 4a of the insert piece 4 contacts the flow channel 2 of the burner stone 1. In the present case the material of the burner stone 1 is made of recrystallised silicon carbide (RSiC), which has an open porosity of at least 10%, but 16% in this case. Besides the burner stone 1 of the insert system the insert piece 4 has a similar material structure, so the insert piece 4 is also made of recrystallised silicon carbide (RSiC), which has an open porosity of at least 10%, but 16% in this case.

In the case of this version of the burner stone 1 and the insert piece 4 the internal delimiting surface lb of the burner stone 1 and a part of its internal delimiting surface lb, the internal delimiting surface 4b surrounding the openings 4c of the insert piece 4 and a part of the external delimiting surface 4a of the insert piece is covered with a catalyst layer 3. The catalyst layer 3 is at least one molecule thick, so it covers the given surfaces as a layer in the nanometre dimension range. Here the catalyst layer 3 contains cobalt oxide, but a nano layer containing another metal oxide belonging to the iron group is also possible.

The nano particles forming the catalyst layer 3 form a high-blackness virtual mirror coating on the catalyst or catalyst carrier and by doing so they are able to take on the heat energy from the flame and radiate it from their surface, which also explains the outstanding catalytic effect experienced when creating the invention.

When studying the insert unit having the burner stone 1 and the catalyst layer 3 described above, the following could be observed.

During the measurements, in the reference unit we used a known natural gas burner "F" having a SiSiC burner stone used with BIC-type burners, and natural gas with a low inert content of 1%, while in order to ensure the suitability of the insert unit according to the invention, "as bad quality natural gas" we burnt natural gas with an inert content of 17V/V% (16 V/V% C0 ₂ , 1 V/V% N ₂ , 82.3 V/V % CH ₄ , 0.7 V/V% C ₂ H ₆ ). As a catalyst we placed an insert unit consisting of a burner stone 1 made of reciystallised silicon carbide - RSiC - and an insert piece 4 in the reference BIC-type natural gas burner "F". In the case of an inert content of 17 V/V% the combustion rate dropped by 26.4%, as compared to the reference gas, considering the combustion rate of methane as a base of comparison.

The heat engineering parameters of the flue gas leaving the burner indicated evident changes when using the insert unit with a catalytic effect. As compared to the version with a SiSiC burner stone used with the reference BIC burner, in the case of the version with an RSiC burner stone 1 according to the invention the reduction of the combustion rate was compensated to an extent of about 62%.

In the case of using a burner stone 1 with different catalyst layer 3 coatings, and low current resistance insert pieces 4 in the flow channel 2 of the burner stone 1 , in different variations, even 80%) compensation could be reached. In every case an increase in the ion current could be observed, proportional to the increase in the combustion rate. During the use of insert units consisting of a burner stone 1 and catalyst layer 3 according to the invention with natural gas of a normal inert content below 1%> minimum 15% energy was saved in a ceramic burner continuous furnace. The same effect could be reached in respect of gas mixtures with a high inert content. When using a catalyst, for example, in the case of natural gas with an inert content of 7-8 V/V%>, the loss due to the inhibiting effect of the inert content was compensated to a minimum extent of 60% on the one part, and the combustion rate of the combustible components improved by a minimum of 15%, with which an energy saving of about 21% could be achieved.

It must be pointed out here that in firing technology the purpose of using insert units - catalysis - and the reaction-kinetic reason for using them is practically the same as the pre-heating of combustion air (maybe fuel) or the oxygen enrichment of combustion air, as in the case of the latter two the combustion rate is higher, and the so-called energy self-consumption of the reaction is lower, as there is no need for using some of the energy deriving from undoing chemical bonds to ensure the energy proportion needed for converting the mixture into a reactive state. All this can be realised at a lower initial energy level.

Consequently, when using the insert unit according to the invention made with a burner stone 1 and a catalyst layer 3, the possibility of energy saving is supplemented with a new method, and with solutions ensuring better results when combined with oxygen enrichment procedure or with air preheating mentioned above. For example, when combined catalysis with oxygen enrichment, an extreme extent of 35-45% energy saving can be reached. The additional advantages of using the insert unit containing an RSiC-based burner stone with the oxygen enrichment technology are that on the one part the possibility of use up to 2,000 °C makes it possible to increase the extent of oxygen enrichment, and on the other part, as it has a 15-20% positive effect on the burning of the combustible components too, lower oxygen enrichment can also produce good results, if for example technological obstacles or higher oxygen prices occur. In respect of the utilisation of biogases, the use of the insert unit containing an RSiC-based burner stone and, in a given case, an insert piece 4 combined with oxygen enrichment results in a completely satisfactory solution which makes the use of biogases equivalent to the use of good quality natural gas with no inert content, and they can be burnt with traditional gas burners.

Besides the above, their use with natural gases with a low inert content is also advantageous on the basis of the above, as their use results in 15-20% energy saving.

The insert unit according to the invention can be favourably used in several fields of practical life, i.e. in the industrial, agricultural and communal sectors, where thermal energy is produced from natural or artificially produced energy carriers, and the aim is the significant improvement of energy efficiency. List of references

1 burner stone la external delimiting surface lb internal delimiting surface flow channel

3 catalyst layer

4 insert piece 4a external delimiting surface

4b internal delimiting surface 4c openings

"A" A/D-converter "C" condenser 'Έ" amplifier "F" natural gas burner "G" gas meter "K' ¹ furnace "R" resistance "S" computer "T" power supply