GB2041181A - A flameless combustion method and a boiler utilizing such method - Google Patents

Abstract

A boiler using flameless combustion comprises a central free space (3) supplied with a mixture of fuel and air, a mass of gas permeable heat radiating material surrounding the space (3), and a plurality of radially extending passages (5) for leading the mixture outwardly into the radiant material, there being means provided at the periphery of the central space (3) to heat the mixture to ignition temperature. At least two systems of heat exchanging surfaces (8, 9; 10, 11), are situated at different radial distances from the centre of the boiler. Header chambers (1, 2) situated at opposite ends of the boiler interconnect the two heat exchanging systems. The fuel/air mixture is supplied to the space (3) via an axial passage (6) through one of the header chambers (2). <IMAGE>

Description

SPECIFICATION A method of controlling contact-kinetic flameless combustion and a boiler for carry ing out such method The invention relates to a method of control ling, and equipment for carrying out, the contact-kinetic flameless combustion to heat various masses by means of a radiating mass permeable for gases; such mass usually constitutes a filling of the reaction zone proper, and it can release, on its surface, the bonded heat from gaseous or liquid fuels, whereby the mass itself is heated and heat-processed while being replaced continuously; or it is allowed to assume a state of inaction thus becoming a stable radiating body which radiates the released heat immediately onto other liquid, gaseous or solid masses passing or flowing separately through the reaction zone.

The feasibility of heat transfer by radiation was known as early as the end of the last century; see Stefan (1879), Boltzmann (1881), Planck (1901). Therefore the technicians have always been striving for finding ways of increasing the portion of energy radiated, to the sacrifice of other well-known, commonly used methods of heat transmission.

However, any effort in this field was frutiless due to a gap, which by no means could be bridged at that time, between the limited amount of heat which could be released within a volume unit using combustion processes known at that time, and the high deduction of heat which can be feasibly taken in present practice, using radiation. Last but not least, even mastering the flameless combustion process itself did not bring about any important change leading to a markedly radiation-oriented transmission of heat. The obstacles were low working temperatures, and the inability to bring the intensive combustion zone near the heat-exchanging surfaces while leaving the combustion process undisturbed.

In addition, there were specific, and stringent, prescriptions for the safety and operation sides, promoted by the accepting authorities for newly designed radiation boilers; these specifications were difficult to meet while trying to intensify the combustion process in the preceding generations of radiation boilers. The remaining problems, especially that of heating solid masses by radiation exclusively or predominantly were completely neglected due to the reasons given above.

Attempts at designing a boiler in which liquids would be heated and evaporated by radiation were thwarted either due to a lack of the principal technological conception, very similar to catalytic system of flameless combustion as carried out before the first half of the 20th century; or later on, when contactkinetic flameless combustion had been introduced, there were difficulties in stabilizing the combustion zone and ignition zone, the former having to handle intensive combustion. These zones varied with the boiler thermal pattern, and could not be placed in a position, which would be permanent and advantageous with respect to the heat-exchanging surfaces, owing to their being in fact radiation sources.

Furthermore, the gas flow direction had been such that the gases passed parallel to, or along the heat-exchanging surfaces. Thus there was a problem of the escape of prematurely cooled, and thus not completely burned, residues of the gases lost in this way through the boiler exhausts; another problem was the formation of intensive self-sustained oscillations. Radiation boilers, being very small, do not allow circulation of burning gases to improve combustion efficiency. A partial solution was offered when combustion and radiation zones were partitioned; however, there was a violation of the basic, and determinant, idea of creating a highly intensive radiating body able to retain high and uniform temperature in spite of a high rate of heat deduction.The temperature must be distributed uniformly over the whole surface of the heat exchanging surface, and the radiating body must be able to release, over the mentioned surface, the required heat and to transmit it to the heat exchanging bodies in a direct manner, as a rule, without the hot gases being used as the main carrier to transmit heat.

These shortcomings are coped with using the method dealt with in the invention letter.

The idea is the fact that a homogenous or heterogeneous mixture of fuel and an oxidizer are fed, non-ignited, into the functional central space symmetrically deployed along the axis of symmetry of the reaction space; the former's peripheral area is heated to a working temperature of 800"C or more in a manner that a part of the heat from its surface is deduced in a controlled manner. This internal preheated area in the central space, or cavity, serves to heat the fuel/oxidizer mixture to ignition temperature; the mixture is ignited on the surface of the cavity, the zone of intensive combustion of the complete flow of mixture, as well as intensive temperature zone, are transferred to the space behind the central cavity jacket.As the flow continues, in direction perpendicular with respect to the heat exchanging surfaces, the radiation mass placed in the space adjacent to the heat exchanging surfaces is transformed into a F''- sitionally stable, intensively radiating body, stabilized independently of the changes of the heat pattern of the combustion process.

If liquid fuel is used, it is feasible to have an axial flow of fuel/oxidizer mixture in the central cavity heated by radiation from its peripheral jacket; the radiation is controlled in intensity, and the start of ignition, expressed in terms of over 1 200 C, is locallized in the central cavity space; further increase of combustion temperature until the highest level attainable is achieved, is allowed to proceed gradually as the flow continues.

With gaseous fuel it is feasible to have temperatures in the central cavity below 1 200 C; this is done by limiting the radiation from its peripheral jacket via controlled deduction of heat from the immediate periphery of the central cavity. The combustion is thus temporarily retarded and the intensive combustion zone is transferred to a zone more remote from the axis of symmetry of the reaction space of the radial flow of the mixture, and only then a dramatic increase of the peak combustion temperatures takes place.

To eliminate noise, commonly encountered in all types of units using liquid and gaseous fuels, the fuel/oxidizer mixture is stabilized and equalized before it enters the central cavity protected against flame damping; space-symmetrical heating is then used to bring the mixture to a state which is constant and free of pulsations.

Synthesis or decomposition of chemical agents, the endothermal reactions of which take place partly at the expense of their intrinsic heat, are feasibly effected if a catalyst is used to activate the central cavity jacket.

In cases where the whole reaction space round the axis of symmetry cannot be utilized, the fuel/oxidizer mixture can be fed and conducted in a direction away from the axis of symmetry; combustion and heat passage by radiation can be effected only in some parts of the reaction space related to the axis.

The boiler, as invented, used to heat or evaporate liquids via radiation of heat produced by means of contact-kinetic flameless combustion, with collecting chambers connected by a system of heat exchanging surfaces, with free or forced circulation of the liquid being heated, is typical for the fact that at least one of the two collecting chambers has, in the axis of symmetry of the boiler, a go-through hole connected, on the outside of the boiler, to a feed of the fuel mixture, mouthing inside the free central cavity having peripheral heat-insulated jacket; the cavity is linked, by a system of channels, with a space of the boiler enveloping the central cavity. In this space, intended to be filled with the radiation mass permeable to gases, there are at least two systems of heat exchanging surfaces to heat or evaporate liquids.The passages, or channels, contact the two collecting chambers, each of the systems of heat exchanging surfaces having a greater radial distance from the boiler's axis of symmetry than the system of the heat exchanging surfaces, which precedes the former in realition to the axis of symmetry.

The central cavity may be refractory lined, being an internal space inside a body; or it may represent a space demarcated by a ring of pipes carrying heat insulation on the outer surface.

The heat exchanging systems made as pipes are distributed concentrically around the central cavity; the spacing of pipes in the heat exchanging system with a smaller radial distance from the central cavity is smaller than is the spacing of- pipes in the next heat exchanging system, more remote from the central cavity.

The spacing of pipes in the heat exchanging system which is the nearest to the central cavity exceeds the diameter of the pipe itself, and the spacing of pipes of the next heat exchanging system more remote from the central cavity is smaller than the diameter of the pipe.

The heat exchanging system more remote from the central cavity may consist of hollow jackets, in particular shaped as wedge segment cavity, deployed uniformly around the axis of symmetry of the boiler; there are slit intermediate spaces between individual partial jackets, arranged radially over planes placed in the boiler symmetry axis.

Individual heat exchanging systems of pipes may be effected as pipe helices with different spacings between individual adjacent coils The feed of fuel/oxidizer mixture into the functional central cavity, the mixture being free of rough turbulency, and brought into a state of uniformity, is followed by ignition over the internal peripheral surface of the central cavity; the fuel is then ignition-transferred further to reach the external jacket of the cavity. Thus conditions suitable for the control of the contact-kinetic combustion are created; these conditions are free of interference of any factor which might impinge the continuity of the combustion periodically or locally. The overall effect of such arrangement first becomes obvious in that there are no sources of self-sustained oscillations.At the same time safe ignition of the combustible mixture is ensured even in large units with long central cavities; the ignition can be safely monitored and indicated, using any method.

Another feature of the invention is that the peak temperature zone and peak-rate transferof-heat zone are localized into zones where heat exhanging surfaces are purposefully deployed; these surfaces are heated uniformly, within the given reaction space, over the whole area, as the temperatures are distributed and stabilized on isothermal areas congregated around the axis of symmetry. Thus no dangerous stresses are formed due to thermal dilatations of the materials. The combustion is perfect, there is almost zero formation of N oxides, as there is not sufficient time or reaction for these to develop. The high specific transfers of heat bring about lower order of the weight of the reaction space and of the whole unit as constructed on the basis of the invention.

Individual systems of pipes may also be arranged as pipe helices, with varying spacings between the neighbouring coils.

The arrangement, based on the principle of the controlled contact-kinetic flameless com bustion, is designed, first of all, to stabilize, in all the phases of boiler operation, the ignition oriented in direction of the central cavity onto the internal surface of the refractory or onto the heat-insulated layer of cooled pipes demarcating such cavity. Thus the position of the ignition point becomes independent on the changes of the boiler's thermal pattern even in conditions which are highly adverse, e.g. if the flow cross section through which the gases are passing, increases quadratically with radial distance from the central cavity periphery, and tends to shift the ignition point to a zone where there is a lower flow speed.

The temperature of the central cavity is selected constructionally to range between 900 and 1 700 C, depending on the fuel used and purpose for which the unit is intended.

Another important modification in the new arrangement is that the geometric point of intensive combustion and the peak temperature zone is selected "ad libitum", but is mainly positioned at the start of the radiation mass layer immediately behind the external surface of the ceramic layer, or at the space housing the radiation mass behind the set of cooled, heat insulated pipes making a free central cavity. However, in another extreme, the combustion will be controlled in such a way that the point of intensive combustion and radiation can be shifted behind the first system of heat exchanging surfaces.In both instances, however, the intensive combustion zone and peak temperature zone retains, in condition of new reaction space and construction arrangement, as invented, not only a constant radial distance (and thus a constant position with respect to the heat exchanging surfaces); also, there is a constant width of the combustion zone within the whole heat performance range; this could not be attained in the known models of radiation boilers.

There is an advantageous fluctuation of the temperature of the radiating mass, which is particularly desirable in heat transmission by radiation. The cool and hot gases directly meet the cooling effect of the metallic surfaces (as is not the case of the traditional and radiation boiler types) until after having reached the end of the combustion zone; therefore the combustion is complete even in condition of minimal excess of air. The highest volume of released heat is transmitted by radiation directly from the combustion zone, the final cooling being modest as regards heat exchanging surfaces; the boiler as in this invention is a type reducing the volume of the radiating mass vs. the comparable earlier types of radiation boilers, to a mere fraction of the original weight whereby the weight of the whole unit is reduced.In this way the amount of accumulated heat in the radiating mass becomes lower. The range of safety devices for circulation pump failure shrinks to a minimum, being superfluous in a majority of cases. Last but not least, there is a complete absence of the sources of self-sustained oscillation within the whole frequency range because of the free shape of the central free cavity when the fuel mixture is being ignited; this assumes a form of a basic simplification of the control and safety devices. The combustion and radiation take place exclusively in condition of gas flow perpendicularly against the set of tubes whereas the final cooling is effected, as desired, by means of letting the gases flow through the coils, or is modified so that the gases flow repeatedly along pipe walls.Earlier boilers could not control the operation in this manner, there being practically no choice of modifications in such boilers. Another feature worth mentioning is that the boilers as described in this invention can be arranged to make a range of boilers with any desired output characteristics varying in diameter and height.

The invention will now be described, by way of example, with reference to the accompanying drawings showing embodiments in which the process according to the invention may be carried out. In the drawings: Figure 1 is a part of an axial section through the left-hand part of a first embodiment of a reaction space, Figure 2 is a cross-section to Fig. 1, Figure 3 is a part of an axial section through the right-hand part of a second embodiment of the reaction space, Figure 4 is a cross-section to Fig. 3, Figure 5 shows distribution of temperature depending on the radial distance from the axis of symmetry of the reaction space shown in Figs. 1 to 4, Figure 6 is a part of an axial section through a third embodiment of the reaction space, Figure 7 is a cross-section to Fig. 6, Figure 8 shows distribution of temperatures depending on the radial distance from the axis of symmetry of the reaction space shown in Figs. 6 and 7, Figure 9 is an axial section through a watertube boiler designed to heat water and having vertically extending tubes, Figure lOis an axial section through the lefthand part of one embodiment of asteac generating boiler having a combination of vertical tubes and tube coils, and through a right-hand part of another embodiment of that boiler, Figure ii is a part of an axial section through the left-hand part of one embodiment of the central cavity of a hot water pressure boiler having three separate tube coils, and part of an axial section through a right-hand part of the central cavity of that boiler, Figure 12 is a part of a cross-section through a boiler having water tube and jacket heat exchanging surfaces, and Figure 13 shows a part of a cross-section through a boiler having a combination of tube and jacket segments of the heat exchanging surfaces.

Three various examples of the reaction cavity are selected out of an array of potential modifications of practical combustion process based on the functional central cavity; these are presented in Fig. 1-8 and the systems are intended to heat liquids in pipe heat exchanging systems. Same as in other examples, the reaction space houses, in all these examples, a free functional central cavity 3 arranged around the common axis of symmetry o. The functional central cavity 3 is cylindrical, but may also be shaped as a regular prism, cone, pyramid, sphere, cube or regular polyhedron.

The reaction space houses, or allows to pass, various heat exchanging surfaces, as e.g. the rigid internal system 45 of heat exchanging surfaces, and external system 46 of heat exchanging surfaces. As shown in Fig. 3 and 4, there is another system 47of external heat exchanging surfaces pertaining to the reaction space, whereas the peripheral heat exchanging surfaces 54 in Fig. 1 a 2 do not pertain to the active portion of the reaction space and their purpose is different. The heat exchanging surfaces in these examples are in the form of pipes. The shape and size of the functional central cavity 3 are determined by spacers 4, which separate the gas-permeable grainy or laminar filling of the radiating mass 12 in the reaction zone, marked by cross hatching, from the central cavity 3.The radiating mass 1 2 as well as the spacers 4 are made from a highly refractory material having, if possible, the ability to selectively radiate within the spectral length of IR waves around 6 micrometers. A material suitable for this purpose is for instance corundum, Si carbide, Zr oxide or masses containing slight additions of lithium, or thorium. The spacers 4 are arranged so that there is a circular-ring opening 5. The spacers 4, differing in shape and function, illustrated in Fig. 1 and 2, are wider than those in Fig. 3 and 4, and constitute the jacket proper for the central functional cavity 3 around the axis of symmetry o.The grainy or laminar filling of the radiating mass 12 fills the whole space between the spacers 4 and the internal system 45 of the heat exchanging surfaces and the external system 46 of the heat exchanging surfaces; or, as in Fig. 3 and 4, it reaches as far as the next external system 47of the heat exchanging surfaces, where the action of the reaction space proper comes to an end. In addition to the reaction space Fig. 1 and 2 show a cylindrical partition 51.

The partition 51 is metallic or refractory, often having a catalytically acting surface which serves as-an additional device to ensure complete combustion, to direct the gas flow and to radiate the heat accepted from the gases onto the exposed external system 46 of heat exchanging surfaces and the peripheral heat exchanging surfaces 54. The ex-reaction space also houses a radial partition 52 and jacket 55, which is also shown in Fig. 3 and 4. The jacket 55 may be coated with an external heat insulating layer (not illustrated).

The thick full arrows 48 designate, in the functional central cavity 3, the direction of feeding of the fuel/oxidizer mixture; in the outlet from the radiating mass 12 the arrows 53 show the flowing combustion products.

The doubled, thin arrows 49 show the direction of the entering medium, and the arrows 50, the outlet of this medium, i.e. for instance the heated liquid. Fig. 6 and 7 show a free functional central cavity 3 with no spacers in the jacket; but there is a symmetrically arranged system of auxiliary heat exchanging surfaces 56 which are equipped with a heat insulating layer 57 over their external periphery, gaps 58 being left between individual heat exchanging surfaces 56. The gaps are parallel to the axis of symmetry a The heat insulating layer 57 may be a refractory layer separated from the auxiliary peripheral heat exchanging surfaces 54 by either a free expansion gap, or is fixed onto the surface of the auxiliary heat exchanging surfaces.It is advantageous to use metallic screen of heatresistant steel separated from the surface of the peripheral heat exchanging surfaces 54 either by a regular free gap in which arrangement the screening walls do not lean onto the surface of the heat exchanging surfaces 56, or by a gap filled with a suitable insulating material.

The process occurring in a stabilized heat pattern in the first functional variant of the reaction space as in Fig. 1 and 2 can be described as follows: The spacers 4 are heated up, using some of the known methods suitable for the purpose, to a temperature at which the mixtures are ignited; then the free functional central cavity 3 receives, along its axis of symmetry o, non-preheated and nonignited fuel/oxidizer mixture driven unidirectionally or counter-directionally, as shown by the arrows 48. The mixture is perfectly homogeneous if gaseous fuel is used; or the mixture is perfectly heterogeneous suspension of atomized liquid fuel. The input flow will be laminar or microturbulent. The functional central cavity is free of zones which might extinguish the flame, as e.g. metallic cooling surfaces which would interfere with the uniform heating and ignition of fuel, or with the initial combustion of fuel. The mixture flow is heated uniformly in the symmetrical central cavity 3 owing to the action of uniformly radiating peripheral jacket of the functional central cavity 3; in this process the known non-uniform distribution of vectors of flow in e.g. tubular elements (the central cavity 3 being a variant of such element) is responsible for a slow-down of the flow near the wall of the central cavity 3.The slowed-down current is heated more rapidly to the ignition temperature; as the speed decreases, the direction is changed rapidly and abruptly, the flow beginning to proceed in a direction perpendicular to the internal set 45 of the heat exchanging surfaces and external system 46 of the heat exchanging surfaces and the next external system 47of the heat exchanging surfaces, after initial ignition. In these conditions the fuel/oxidizer mixture flow travelling in the direction indicated by the arrows 48 in the central cavity 3 assumes the peak speed in its centre, where it exceeds several times the frontal speed of flame distribution. Thus the heating time is extended so that in condition of inferior heat penetration of a thicker layer of gases it is retarded in assuming ignition temperature.The surface combustion of the mixture, first in the confined space of the central cavity's peripheral jacket 1 and later on, in the radiating mass 12 in the reaction space, as well as in condition of the selected heat pattern and dynamics of flow in the central cavity 3, brings the mixture ignition to such state in which formation and alternating of self-sustained pressure and under-pressure waves due to alternate ignition and extinguishing of partial volumes of fuel, is completely eliminated. Such pressure oscillations are always accompanied by acoustic phenomena.

The geometry of the central cavity 3 is responsible for all the reverse pressure waves acting simultaneously in radial direction away from the peripheral jacket of the central cavity 3, toward the common axis of symmetry o, thus mutually eliminating their effect. Furthermore, there is a substantial difference between the low frequency of the oscillation source and the high intrinsic frequency of the central cavity 3. For this reason the resultant acoustic frequency is audible neither in cold nor in hot condition and cannot effect the control and regulating organs in the form of oscillations of the system which would produce inaccuracies or failures of these organs.

The passage of gases from the functional central cavity 3 into the radiating mass 12 is provided for by the slit openings 5where the radial flow of ignited gases starts and where the process of flameless combustion proper starts simultaneously. If comparing the greater width of spacers 4 and the greater radial distance of the internal system 45 of the heat exchanging surfaces as in Fig. 1 and 2, with the smaller width of the spacers 4 and the internal system 45 of the heat exchanging surfaces (Fig. 3, 4) which is nearer the central cavity, the functional difference of the two modes of arrangements appears as follows: The internal system of heat exchanging surfaces 45 affects, due to its cooling effect, mainly the development of temperature within the functional central cavity 3.The lower cooling effect of the wider spaces 4 and/or the greater gap between the internal system 45 of the heat exchanging surfaces and the peripheries of these spacers 4, result in a higher temperature of the peripheral jacket of the central cavity 3, reaching to above 1200"C, and in a more vigorous heating of the mixture flow. It is thus advantageously utilized if heterogeneous mixture is fed; here the evaporation of the suspension of liquid fuel is accelerated, by the formation of a transition phase of its pyrogenetic splitting.If the arrangement is somewhat different and, especially if the effect of cooling from the internal system 45 of the heat exchanging surfaces is eliminated by completely removing this system; and if the surface of the spacers is purposefully activated (which may be optional), the functional central cavity 3 and the slit openings 5 may produce catalytic pregassification of dispersed particles of the liquid fuels without there being a transition phase (soot formation) in some types of liquid fuels. In addition to this feature by reducing or eliminating some heat exchanging surfaces, the reaction space may be completely or partly changed into a catalytic system of industrial splitting and gassifying endothermic and exothermic reactions, in which the heat transmission is no longer the main purpose, the aim being production of various gases for chemical industry.

The intensive combustion zone and the position of peak combustion temperatures is stabilized (for arrangements as in Fig. 1 and 2) in zone where the gases passing through the radial slit openings 5 leave the external periphery of the spacers 4 and enter the radiating mass 12. This is due to the abovementioned cooling effect of the internal system 45 of the heat exchanging surfaces, which is responsible mainly for the drop of temperature of the spacers 4, and, especially, due to the increase of the flow-through profile of the reaction space offered for the combustion products; the increase is substantial, being a multiple of the value of the flow-through section at the point where the fuel is ignited on the internal peripheral surface in the functional central cavity 3.

In a zone where the gases come into contact with the exposed surface of the internal system of heat exchanging surfaces 45 a tendency toward cool down and extinguishing of possible residues of unburned gases is practically negligible, because the residues then pass, in forced radial passage of gases, through a hot layer of the radiating mass 12 where they are reheated to ignition temperature and the combustion is completed. The radiating mass 12 then transfers, in conditions specially suited for local heat radiation between two systems of heat exchanging surfaces, to the internal system 45 and external system 46 most of the heat.

Another development of the temperature field takes place in the of arrangement illustrated in Figs. 3 and 4, pertaining to the second functional variant. The main feature is a small width of the spacers 4 with the resultant small depth of the slit openings. The three systems of heat exchanging masses internal 45, external 46 and the further external 47are placed nearer the functional central cavity 3, which remains practically the same as for the first variant in Fig. 1 and 2.

This results in that the cooling effect of the internal system 45 of the heat exchanging surfaces is more pronounced in its action of the temperature of the spacers 4; therefore the temperature of the functional central cavity 1 as in the peripheral jacket drops to less than 1200"C. In this manner the intensity of heat radiation on the mixture flow is reduced whereby the temperature of the flowing mixture drops either.The lower temperature inside the functional central cavity 3 promotes conditions for indication of phenomena occurring in this part of the reaction zone, but also promotes the zone of intensive combustion and peak temperatures being shifted more markedly to the place near the external system 46 of the heat exchanging surfaces. =This is another feature of this system in contrast to the first variant (Fig. 1 and 2); it consists in that the IR radiation of the radiating mass 12 in the second variant (Fig. 3, 4) acts on all the three systems of heat exchanging masses internal system 45, external system 46 and the further external system 47-instead of the two systems as in the first variant.The complete combustion of residues of incidentally and prematurely cooled gases is provided for by two uninterrupted hot belts of radiating mass 12 situated between the heat exchanging systems 45 and 46, and between systems 46 and 47. This arrangement is less suitable for liquid fuel.

Fig. 5 and 6 show the third variant, as one of several instances connected with the existence of the free central cavity. The functional cavity 3 is formed in this case to assume the desired shape, using a set of auxiliary heat exchanging surfaces 56, through which the liquid, entering the heating circle, is being fed. The surface of the auxiliary heat exchanging surfaces 56 (in contrast to the rest of heat exchanging surface systems in any one of the above-discussed variants-Fig. 1, 2, 3, 4, and 6, 7) carries heat insulation 57. The fact is that without the heat insulation 57 the flow of the mixture cannot be induced to combustion in the central cavity 3; even the ignition is precluded. Therefore the combustion will not be transferred behind the periphery of the functional central cavity 3 through axial gaps 58 onto the radiating mass 12.This is due to volume, which is confined, as well as to the metallic or other surface possessing a strong cooling or extinguishing action in heat exchanging surfaces 56. Such behaviour is prevented by heat insulation 57. Having in mind the various levels of heat conductivity of the mentioned types of heat insulation 57 the thickness of these types of insulation is selected so as to keep the temperature on the surface of the heat insulating material 57, in condition of stabilized state of heat, at around 900"C. Thus the flowing mixture is ignited on a limited scale in the central cavity 3, the combustion proper being practically removed behind the orifices 58 into the radiating mass 12.As the flow continues further, the zone of peak combustion temperatures, with the simultaneous stoppage of the combustion proc ess, is removed into the zone between the individual members of the internal system 45 of the heat exchanging surfaces, so that their whole periphery and the close-in half of the periphery of the heat exchanging surfaces of the external system 46 become exposed to a direct action of the IR radiation of the radiating mass 12. This modification is less suitable for liquid fuels and for high and peak output levels.

In Fig. 1 and 2 there are, as an example taken from an array of possibilities-the example being a randomly selected one other functional elements which, however, do not affect the method as invented, but indicate the feasibility of the shape of the reaction space for an efficient final cooling of the combustion products. One of the elements is a cylindrical partition 51, which intercepts the flowing combustion products 53.The partition is metallic or refractory, often possessing catalytically active surface to serve as an additional factor to provide for perfect combustion, but its main purpose is heat transmission; this heat has been withdrawn from the flowing combustion products 53 and is transmitted via two-side radiation at temperature of around 800"C onto the heat exchanging surfaces of the external system 46 and the peripheral surfaces 47. The partition 51 along with the radial partition 52 controls and directs the flow of combustion products 53 from the point where they emerge from the reaction space as far as the space demarcated by the jacket 55 which participates, along with the external heat insulation not indicated in the drawing, in radiating waste heat onto the peripheral heat exchanging surfaces 54. It is only the rest of the heat which is transferred via tangential flow to the convectionrelated heat exchanging surfaces; this portion is almost negligible in contrast to the overall concept of heat transmission by radiation.

In the arrangement illustrated in Figs. 3 and 4 the radiating mass 12 emits more heat than in that shown in Figs. 1 and 2. Therefore it is sufficient to withdraw the combustion prod ucts through free spaces provided between individual members of the next external system 47of the heat exchanging surfaces which are not covered by the radiating mass 12. The flow is coaxial and is shown in Fig. 3. The combustion products are finally coaxially flowed back through space between the rear wall of the next system 47of the heat exchanging surfaces and the jacket 55. This modification requires heavier filling from the radiating mass 12 whereby the heat capacity is increased.

Each of the three variants given in the example are typical, in condition of stabilized heat pattern, for a different heat pattern in the reaction space; such pattern is accompanied by a different heat or temperature trajectory.

The temperature diagrams in Fig. 5 and Fig.

8 show the temperature distribution which is identical in all planes perpendicular to the axis of symmetry o; each point on this curve corresponds to a temperature at a different radial distance from the axis of symmetry o.

Thus it follows that each cylindrical surface drawn coaxially about the axis of symmetry o represents an isothermal plane.

The temperature diagrams have temperature levels on the y-axis; radial distance is on the x-axis. The diagram in Fig. 5 with the cross-hatched area delimited by the solid line, refers to the first embodiment shown in Figs.

1 and 2. The temperature trajectory in Fig. 5, indicated by the dashed line, pertains to Figs.

3 and 4, but is transferred mirror-like into the first diagram. The basic points a, b, c, d, e, f, g, h in the first diagram can be compared with the points a', b', c', d', e', f', g', differing only in the latter's being indexed, with the other, dashed curve. The different position of two points marked with an identical letter means that the shift in radial direc tin ever the x-axis-indicates a condition of different progress of combustion; the differences in height over the y-axis show a different distribution of the thermal field. This can serve to assess the range of intensity of heat radiation existing in the two systems being compared at any point of the reaction space.

The temperature diagram in Fig. 8 shows another modification of the progress of the heat pattern, as it follows from the changed conditions of the progress in the third embodiment. The conditions are apparent from Figs.

6 and 7. The diagram ends at the letter "h" as the reaction space illustrated is free of final cooling of combustion products; a zone which would reduce the temperature of the flowing combustion products 53 approximately copying the trajectory of the dashed curve between points "h" and "i".

Each of the reaction spaces illustrated in Figs. 1, 2, 3, 4 and 6, 7 can be halved, or divided into conical sectors by one or more planes through the axis of symmetry o. A purposeful extension of the newly developed formation produced from the original central cavity 3 would make it functionally fully adaptable to it and would make it equal to it. Then these partial segments of the reaction space can release and transmit heat by radiation independently in the sense as intended by the invention; such segments can be introduced, on a group basis, into asymmetrical blocks, as is the case of heating solid masses differing in shape and dimensions, such as metallurgical products, engineering semis, etc.

Another field of an efficient utilization of the methods according to the invention in basic symmetrical reaction spaces or in modified block formations, in which the two variants of the reaction spaces are adapted in shape to suit the given purpose, are technologies of heating and drying loose, spilly masses and gases; heating to very high temperatures in this way is particularly feasible in several other industries. A specific field of application of this method would be melting, sintering and roasting of ore and non-ore raw materials or metals, as well as ore reduction. In an extreme case the radiating mass 12 would act as a sole heat exchanging surface, being also the heat-treated medium.

The boiler shown in Fig. 9 is a water tube type, vertical boiler, with a vertical axis of symmetry 0, which represents schematically a heat exchanger for heating water; it is designed to heat water and is shaped as a cylinder. The construction is as follows: between the upper collector 1 and the upper passage 7, and between the lower collector 2 and the lower passage 6 which is conical, is, in the axis of symmetry o, a hollow vertical cylinder made of refractory spacers 4. The cylinder acts as a peripheral jacket of a free functional central cavity 3. The individual spacers 4 are from refractory material, arranged as multiple sectors of an annulus to eliminate the effect of heat stress and non-uniform expansion. The spacers 4 are arranged so as to define horizontal slit openings 5 between adjacent spacers 4.The materials suitable for the spacers 4 is e.g. corundum, Si carbide, Zr oxide or masses containing slight additions of lithium, or thorium. The upper and lower collectors 1 and 2 have removable fronts permitting access from the upper and lower ends to the two systems of boiler tubes, first and second system 8 and 9, respectively, and to the two systems of preheating tubes of the system 10 and to the other system 11. These connect parallelly the two collectors 1 ano and are preferably parallel to the axis of symmetry o; however, for expansion may be connected obliquely or arch-like.All the systems in the example are, for simplicity, arranged as one-row sets of tubes positioned in concentric cylindrical surfaces with different radial distances, the free distances between individual tubes of the first system 8 of the boiler tubes being generally greater than the external diameter of the tubes, and filled with a layer of radiating mass 12 whereas the distances between the tubes of the second system 9 of the boiler tubes radially more distant from the axis of symmetry oare smaller than the diameter of its tubes hindering the penetration of the radiating mass 12 behind these tubes.The layer of radiating mass 12 which can consist of the same material as the spacers 4, is delivered into the boiler through the upper hole 7which serves also as a reserve of the radiating mass 12 which, shaped as hollow cylinders, fills the space between the column of the spacers 4, passes through the space between the tubes of the first system 8 of the boiler tubes, and completely clogs the intermediate space as far as the second system 9 of the boiler tubes, where the radiating mass 12 ends on the internal surface area of these tubes. The part of the boiler comprising the space from the free central cavity 3 as far as the second system 9 of the boiler tubes and being filled with a layer of radiating mass 12, with the exception of the central cavity 3, constitutes the radiation space proper in the boiler.In this space complete combustion and transmission of a substantial part of the heat by radiation, takes place.

The first and second systems of preheating tubes 10 and 11 are preheating tubes connected, at liberal spacing, with the two collectors 1 and 2; these are interlinked by weldedon ribs-first, 16 and second, 17, producing the first and second membrane tube wall. The first ribs 16 are connected only to the upper collector 1, but their ends do not reach as far as the lower collector 2, thus providing openings for a free passage of gases between the preheating tubes 10 and the collector 2; these openings lie in front of the mouths of the tubes 10 into the lower collector 2.The opposite arrangement is provided for the second weld-on ribs 17so that these ribs do not reach as far as the upper collector 1 whereby openings are provided here for a free passage of gases along the whole periphery of the boiler, now in the opposite zone of the boiler.

With perpendicular tube systems the space between the weld-on ribs 16 and 17 is feasibly filled with granular refractory material 13; this material differs functionally and in composition from the radiating mass 12.

The entrance of the returning water through the socket 18 is effected tangentially into the lid of the upper collector 1 and the water circulates along its periphery above the first 10 and second 11 system of preheating tubes, as it is separated by means of a separator ring 19 from the space containing warm water, the outlet socket for which is also placed in the lid of the upper collector 1. The upper passage opening 7 is sealed with a flange of water-cooled insert 22 comprising a watchhole 21 and ignition and securing devices (not shown). The lower passage opening 6 is conical; to its flange are connected the lid of the lower collector 2, a socket 14 for feeding the fuel mixture, and a socket with a conical homogenizing and protective mesh 15.The boiler has a jacket 23to which is connected a collector ring 24 to collect combustion products, and socket 25 through which combustion products are withdrawn, is connected to a fan (not shown), making the whole boiler exposed to underpressure constantly in this case.

The boiler is activated and operated as follows: the feed of fuel and oxidizer through the socket 14 is set so as to allow 1/10-1/4 of the volume of mixture per the nominal output of the boiler. The mixture is underpressure-fed; the underpressure is produced by the fan action connected to the socket 25 withdrawing the combustion products. The mixture is fed via the homogenization and protective mesh 15, into the lower passage opening 6 shaped as a nozzle, where it is stabilized and the turbulence, induced earlier, is eliminated. It then penetrates into the adjacent free central cavity 3. The igniting device (not shown), ignites the freely flowing mixture in the central cavity 3; it burns as naked flame in condition of the starting low speed.

The thin surface layer of the internal jacket of the central cavity 3, consisting of the ceramic spacers 4, is rapidly heated above the ignition temperature as for the fuel mixture (to 800-900"C). During this period of heating, which lasts for about 30 s, the spacer 4 mass remains cold inside, but the boiler output may be smoothly increased so that after another 1.5-2 minutes full-scale operation is achieved in the boiler. This is also the determinating factor for the operation control of the boiler operation; a difference lies in that the boiler with above-ignition temperature inside the central cavity 3 has the control period dependent solely on the discriminating power of the controls.

Toward the end of the period of heat up of the central cavity 3 as the boiler is started up, the visible flames disappear spontaneously, the burning changes into flameless combustion and is concentrated exclusively onto the internal peripheral surface of the spacers 4 where ignition takes place of that part of the fuel mixture, which flows in the direction indicated by the arrows. In this particular instance the direction is upward through the central cavity 3. However, the ignition takes place only in that portion of the fuel mixture flow, which comes into an immediate contact with the internal jacket of the central cavity 3, the rest of the volume of gas mixture flowing inside the confined space, i.e, the central cavity 3, non-ignited; its speed is higher than that in the flame front. The high speed also means that all the flowing medium cannot be radiation-heated to the ignition temperature due to the shortness of the travel of the medium. Therefore the peripheral ignition moves further into the slit openings 5; in zones where these openings 5 mouth into the subsequent layer of radiating mass 12 the fuel mixture flares flamelessly in conditions of kinetic combustion and of the contact with the indented mass 12. Here also intensive combustion and peak temperature zone can be localized; no change is induced by boiler output as the start of ignition is determined by the unchangeable surface on the internal periphery of the central cavity 3.The position of the intensive combustion zone depends on the surface temperature of the internal periphery of the central cavity 3 and this, in turn, depends on the deduction of apart of the heat from the space where the refractory spacers are placed; the smaller the radial distance of the spacers 4 from the first system 8 of boiler tubes, the higher the deduction of heat. Provided there is absolutely close distance between the first system 8 of boiler tubes and the spacers 4, the main combustion migrates through the gaps between the adjacent tubes, filled with radiating mass, as far as the radiation mass layer 12 placed in-between the two systems of the boiler tubes (8, 9).

Such situation represents, however, an extreme, but not a rarity. The construction arrangement given as an example in Fig. 9, is conducive to only a mean temperature in the central cavity, i.e. around 1200"C. The layer of radiating mass 12 between the first 8 and second 9 system of boiler tubes is uninterrupted and free of elements impairing the combustion, or even interrupting it. Therefore this zone, be it a zone functioning as an extreme zone of intensive combustion, or be it a zone in which, in a majority of cases, the random residues of fuel are final-burnt, behaves as a protective zone to block leakage of unburnt components of the fuel with combustion products; thus, this in the first instance ever brought into practice in the field of protection of environment in boilermaking techniques. However, this is not merely the main function.The perfectly burnt and strongly cooled fumes pass through a system of narrow vertical slits between the boiler tubes of the second system 9; the welded-on first ribs 16in the first system 100f boiler tubes deviate the cross flow of the combustion products, marked with thickline arrows, making it pass downward along the membrane tube intermediate wall. As the first rib 16 does not reach as far as the lower collector 2, the combustion products penetrate through the gaps, which are formed, into space between the systems of preheating tubes 10 and 11; and as the preheating tubes of the second system 11 are connected with the tube intermediate wall by means of second welded-on ribs 17, the combustion products flow along these, in upward direction.As the second ribs 17 do not reach, in this instance, the upper collector 1 either, the combustion products pass through openings, similar to those mentioned above, which are in the upper portion of the boiler, to enter the space behind the tube intermediate wall of the second system 11 of preheating tubes, to reach the cylindrical boiler, and to flow downward into the collector ring 24 for combustion product accumulation; thence they are piped off by means of a fan (not shown). The piping is connected to the socket 25.

The effect of cooling of combustion products between the first and second system of preheating tubes 10, 11 is enhanced if this space a hollow cylinder with wall thickness equal to the radial distance of welded-on ribs, first 16 and second 17-is filled with coarsegrain refractory material 13, which has, at 250"C, a higher coefficient of radiation than is the level of the total heat passage coefficient for gas-to-pipe wall direction. In addition, the presence of the refractory material 13 produces turbulence on the wall of tubes of the preheating system of the first 10 and second 11 type, whereby the heat passage coefficient by convection is increased.The radiation effect of the surface-indented refractory material 13 is the most important, taking a substantial part in reducing the heat exchanging surfaces even in condition of low temperatures of the waste fumes, which are operationally tolerated and rated economically tolerable. The filling material 13 is, for clarity, represented by cross-hatching only in the right-hand half of the Fig. 9. The left-hand half shows welded-on ribs of the first 16 and second 17 type; however, these are presented free of the refractory material 13 in Fig. 9.

It should be pointed out here that no changes take place in the design of boilers shown in Fig. 9, 10, 11, 12, 13, if the boiler is connected to a system of overpressure feed of fuel mixture; it means that the spaces of these boilers can operate in condition of overpressure as well as underpressure, with no need for modifications.

The circulation of water or another liquid to be heated in the boiler proceeds so that the cool liquid is piped into the boiler via a neck 18 for the entrance of return water; the neck mouths tangentially into the lid of the upper collector 1 and the return water circulates between the external periphery of the upper collector 1 and the dividing ring 19, being regularly divided into branches leading it to the two systems of preheating tubes of the first 10 and second 11 system; here it proceeds to the lower collector 2 and the upward pressure produced by the heated liquid in the boiler systems 8 and 9 forces it upwards into the upper collector 1 where it is divided by the dividing ring from the input cool liquid.In addition, there may be an internal spontaneous circulation in which a part of less heated liquid from the first system 8 of boiler tubes returns partly through the second system 9 of boiler tubes, because the dividing ring 19 is made adequately permeable to gases and liquids in its upper and lower periphery.

All the sensor heads intended to control and protect the boiler are inserted, while packed in separate tubes, into the central cavity 3 via water-cooled collar 22. The water cooled collar also has a watchhole 21. All these appliances can also be placed in the lower hole 6 and to zone closely adjacent to it.

If liquid fuel is used, special atomizing and mixing and directing unit is placed into the lower passage hole 6; the unit produces a perfectly homogeneous aerosol, which is not covered by this invention and is not sketched.

Its function is, however, adapted, and is bound to co-act with the function of the central cavity 3, not being able to operate in a free space in the existing classical boilers.

Fig. 10 shows another modification of the radiation boiler; it is presented diagrammatically, in the form of a vertical section as a boiler designed to generate dry or super heated steam. It is clear at the first sight that here, too, the dominant feature is the cavity 3; there is, however, a difference in that the left-hand side indicates the potential use of refractory spacers 4, whereas the right-hand side shows the central cavity 3 bordered by a set of auxiliary tubes 28, carrying surface heat insulation. These two possible modifications of the central cavity 3 bring about certain construction modifications of the otherwise identical concept of the atom boiler. The common feature of both are the two collectors, upper 1 and lower 2; these are, however, appreciably smaller in contrast to those illustrated in Fig.

9, because there is no part designed to feed the return liquid, demarcated by the dividing ring 19. The boiler tubes of the first 8 and second 9 system are on the right-hand side more remote from the axis of symmetry 4 which is due to the fact that the intensive combustion zone is shifted, owing to the action of the set of auxiliary tubes 28 with surface heat insulation, as far as the first 8 and second 9 system of boiler tubes; therefore the radiating mass layer must reach as far as the boiler tubes (and behind them) of the second system 9, the radiating mass 12 in the left-hand side in Fig. 1 ending at a point between the two systems 8 and 9.

The common features of the boiler in Fig.

10 are that the return water entrance socket 1 8 is connected to the first tube coil 27, free of, or with, ribs, which heats the return water and feeds it via feed pipes 29 into the lowest point in the lower collector 2, distributing it as indicated by arrows. The steam, which is accumulated above the surface of the water in the upper collector 1 is withdrawn via tube coil 26, which can also be made as a multiple bundle of tube coils, toward the steam outlet tube 30, where it leaves the system in the form of dry or preheated steam. The preheating of steam is more advantageous as indicated in the right-hand side of the Fig. 10, where the radiating filling 12touches the second tube coil 26.

The boiler shown in Fig. 10 has a neck 14 to feed fuel mixture connected to the upper area of the functional central cavity 3, and the feed is directed into spiral mixer 33tangentially with respect to the axis of symmetry o, making the fuel mixture rotate around the homogenizing and protective mesh 15, passes through it, and flows through the centre of a water cooled collar 22 into the central cavity 3. For this reason all the operation, monitoring, control and measuring sensors are inserted separately through one or several throughgoing tubes 32 in the lower collector 2, but the watchhole 21 is at the highest point of the boiler. As shown in Fig. 10, the fan 31 acts as a base for upright boiler. The remaining reference numerals in all Figures are identical for the functionally and dimensionally identical components, and are not repeated in the text.

Another variant of the boiler is shown in Fig. 11. It shows a typical central portion of boiler body designed to make pressurized water or another liquid with an increased useful temperature; the mentioned portion has been modified to comply with the principles of radiation boiler concept as invented.The typical features are that the systems of tube coils 8, 9, 10, 11 as in Fig. 9, and also the systems of tube coils 26 and 27 as in Fig. 10 are replaced with three series-connected. tube coils-first, 34; second, 35 and third, 36,--of identical cross section; the coils are coiled coaxially with the axis of symmetry 4 and differ in different radial distances from the axis of symmetry o, as well as in different pitch of the coils whereby technically necessary gaps are produced between the tubes as discussed above; the gaps differ in width. For explanation see the text describing the boiler illustrated in Fig. 9.The lower part of Fig. 11 shows the arrangement of the central cavity 3 with refractory spacers 4; the central part of Fig. 3 shows the possibility to replace them with a set of auxiliary tubes 28 carrying surface heat insulation. The direction of flow of liquids and gases, indicated by means of arrows, corresponds to the description of the earlier Figs. 9, 10. Obviously, the axis of symmetry oas in Fig. 11 can assume any position same as is the case of all boilers as in Fig. 9 and 10, if construction-oriented modifications and prerequisites are created to provide for a correct circulation of the liquid within the whole system.

A special position n the construction concept of boilers is assumed by jacket boilers as illustrated in Fig. 1 2 and 1 3. This denomination, however, refers only to those parts of the boilers, which are placed in the external periphery of the reaction space proper, but the whole section of cooling is involved. This means that around the functional central cavity 3, which is, by way of an example, given in Fig. 1 2 as a regular quadrangular prism, is a jacket from sectional spacers 4, square in profile, spaced by means of slit gaps, not visible in the Fig. 1 2. Depending on how the position of the future combustion zone is selected, the radial distance of the first system of boiler tubes 8 is determined.The function of these tubes is the same as that in Fig. 10 and 9. However, the second system of boiler tubes 9 in Fig. 9 and 10 is replaced by internal hollow spaces 43 and with the hollow peripheral jacket 44 through which water flows, because they are, along with the first system of boiler tubes 9, connected with the collectors on the upper and lower ends; the collectors are not given in Fig. 12. All or most of the inter-spaces 37, produced either between the neighbouring internal hollow spaces 43 or between these spaces 43 and the hollow peripheral jacket 44, are wedgeshaped, narrowing in the direction toward the boiler periphery and are filled with a layer of refractory material 13, the space from the jacket of the central cavity 3 as far as the first system 8 of boiler tubes being filled with radiating mass 12. They are not differentiated by cross hatching in this instance.The interspaces 37 are, in fact, zones in which final cooling of combustion products takes place; these zones open into vertical channels 38, from which they are taken for withdrawal.

The modification of a rotary boiler, shown in Fig. 1 3 as a plan of the section, is a parallel to the boiler shown in Fig. 12; a difference is that the functional central cavity 3 is bordered by a set of auxiliary tubes 28, with a partial surface heat insulation in this case, the insulation facing the inside of the central cavity 3, which produces even stronger final cooling action than do the tubes with an insulating layer along their whole periphery. Thus the controlling action on the contact-kinetic flameless combustion is strengthened; the action in this instance becomes apparent by localising the intensive combustion zone and peak temperature zone mainly into the first system 8 between the boiler tubes or closely behind them in direction away from the axis of symmetry o.The peripheral jacket of the boiler is equipped, along its periphery, with a plurality of wedgeshaped hollows 39 with markedly rounded hollow tip; these are filled with water except for the flat smoke ducts 40. The hollows 39 are divided by a partition 41, dividing the hollows 39 into spaces of different sizes; these spaces are independent. The greater space nearer the boiler jacket 23 houses water; this is return water, which flows downward and is heated by a current of combustion products from the flat smoke ducts 40.

The smaller space in the tip of the hollows 39 houses warm water flowing upward; this water is separated by the partition 41 and flows from the lower collector-not illustrated- into the upper collector 1. The interspaces 37 as illustrated in Fig; 1 2 serve for final cooling and are filled with refractory mass 13. The reaction space proper is filled with radiating mass 12; these two spaces are presented as cross hatched and undifferentiated. From the interspaces 37 almost cooled combustion products flow into the peripheral collecting space 42; then they proceed coil-wise between the boiler jacket 23 and the rear walls of the hollows 39 to be directed into the flat smoke ducts 40 and further on to the fume exhaust. These parts are not illustrated in Fig.

13.

In connection with Fig. 10, 11, 12, 13 it was stated how the main construction principles, given in detail in the example in Fig.

9, would find application in practice, and how a combination of some construction elements can provide for an array of variants and modifications using a unified system of the reaction space constituted by some of the given types of peripheral area of the central cavity with surfaces arranged in a manner specified by the laws of the system, as far as the zones where the combustion ceases, as well as the intensive heat radiation. There is no need for grouping several small boiler units to provide for a considerable output; thus it is not necessary to connect such small units by means of costly controls, as the boilers as invented can be controlled in output within a range of 1:10.The useful effect of the boiler when operated at peak output at which the temperatures of the smoke gases do not exceed 240"C, does not drop below 92%; as the load on the boiler decreases, the efficiency rises up to as much as 96% which is promoted, in addition to the well-known conditions, by the reduced weight of the radiation boilers, reduced radiating area along with perfect combustion with minimum excess air, the latter factors being of primary importance. For these reasons the method according to this invention offers ample possibilities for making boilers of all categories, starting from individual, central or block heating of flats and settlements to industrial systems low-, medium- and high-pressure and systems for heating water, generation of steam, using various heat-exchanging media.In these a,"li- cations water, various oils, liquid Na etc. can be used to transmit heat. As these boilers are mobile and low-weight, and small in dimensions, and can be rapidly brought to full-rate operation, they can act as integrated units combined with other equipment such as solar or wind-oriented sources of energy, and can participate in accumulating periodically occurring excess sources of thermal energy, etc.

The basic construction elements of the invented system can be utilized, in harmony with the basic method of application, to reconstruct and innovate majority of the conventional flue boilers and other types of boilers, which have symmetrical combustion space and at least the first system of the heat exchanging surfaces deployed symmetrically around this space. The modification is easy; there are usually no final-cooling smoke duct systems, so that the shape, appearance and dimensions of the boiler are usually conserved. The heat output rises at least two-fold, but fourfold of the original nominal output is not an exception after modifying the final cooling system in harmony with some of the manners described in the invention. As the efficiency of the equipment as invented will achieve high levels in all instances mentioned above, there are promising possibilities, in light of the existing miniaturization, in the field of classical and novel systems of traction motors such as Stirling, Minto, steam drives, turbines and, last but not least, novel cascade hybride heat generators with advantageous operational parameters and substantially higher efficiency, while the construction becomes simpler; of importance is the freedom of a necessity to control the combustion by means of intricate electronic systems.

Claims (14)

1. A method of controlling contact-kinetic flameless combustion for heating substances by means of radiation of a radiating mass permeable to gases, such mass releases, on its surface, bonded heat from a gaseous or liquid fuel, wherein this heat either heats the mass itself, with simultaneous heat treatment of the mass, the mass being continuously replaced, or the mass is stabilized to become a stable radiating body immediately radiating the released heat onto liquid, gaseous or solid substances separately flowing or passing through the reaction space wherein homogeneous or heterogeneous mixture of fuel and oxidizer is introduced non-ignited into the functional central cavity symmetrically deployed round the axis of symmetry of the reaction space, peripheral surface of this cavity is heated to working temperature of 800"C or more via a change of heat deduction, on partial basis, from the surface of the peripheral area, on this internal preheated surface of the central cavity the fuel as introduced is heated to ignition temperature and is simultaneously ignited on the surface of the cavity, while the intensive combustion zone for the whole flow of the mixture, and intensive temperature zone, are transferred as far as the space behind the external periphery of the jacket of the central cavity and further flow, directed across the heat exchanging surfaces, brings the radiating mass placed within the zone of these heat exchanging surfaces to a state of position-stable intensive heat radiating body, stabilized independently of the changes of the thermal pattern of the combustion process.

2. A method as claimed in Claim 1, wherein the axial flow of the mixture of fuel and oxidizer within the central cavity is heated by radiation from the peripheral jacket, the radiation being controlled in its intensity and the start of ignition, at a temperature above 1200"C, is localized already in the central cavity and further increase of combustion temperature up to peak attainable temperature is allowed to take place gradually during the subsequent flow.

3. A method as claimed in Claim 1; wherein the temperatures in the central cavity is reduced to below 1200"C via reducing the radiation from the cavity's. peripheral jacket by means of controlled deduction of heat from the immediate periphery of the central cavity when the combustion is temporarily slowed down and the intensive combustion zone is transferred as far as the zone more remote from the axis of symmetry of the reaction space in which the mixture flows radially and only there an abrupt rise of peak temperature of combustion takes place.

4. A method as claimed in any one of Claims 1 to 3, wherein the flow of fuel/oxidizer mixture is stabilized and equalized before entering the central cavity protected against a flame extinguishing effect and then exposed to spacesymmetrical heating to assume a constant, pulsation-free state.

5. A method claimed in any one of Claims 1 to 4, wherein a catalytic action is induced in the central cavity jacket.

6. A method claimed in any one of Claims 1 to 4, wherein the fuel/oxidizer mixture is directed away from the axis of symmetry, the combustion and heat transmission by radiation taking place only in some partial zones of the reaction space pertaining to it.

7. A method of controlling flameless combustion for heating substances by means of radiation of a radiating mass permeable to gases substantially as herein described with reference to any one of the figures of the accompanying drawings.

8. A boiler for carrying out a method of controlling flameless combustion for heating substances by means of radiation of a radiating mass permeable to gases, the boiler being substantially symmetrical about an axis and comprising a body including a heat insulating jacket defining a central free cavity substantially symmetrical about said axis, the cavity communicating through a plurality of transverse passages with the space in the body encircling the central cavity, at least two systems of heat exchanging surfaces for heating or evaporating liquids being situated in said space at different radial distances from said axis, mass permeable to gases being situated in said space, said mass, in operation of the boiler, radiating heat, a first collector being situated at one end of the body and a second collector being situated at the opposite end of the body, the said systems interconnecting the two collectors and providing communication therebetween, at least one of the collectors defining an axial passage communicating with a fuel mixture feeder outside the boiler.

9. A boiler according to Claim 8 wherein the central cavity is a hollow in a refractory body.

10. A boiler according to Claim 8 wherein the central cavity is a space delimited by a set of tubes carrying surface heat insulation.

11. A boiler according to Claim 8, 9 or 10 wherein the heat exchanging systems include tubes concentrically distributed around the central cavity, the spacing between these tubes and the heat exchanging system radially less distant from the central cavity being greater than the spacing between the tubes of the heat exchanging system radially more distant from the central cavity.

1 2. A boiler according to Claim 11 wherein the spacing between the tubes of the heat exchanging system radially less distant from the central cavity is greater than the diameter of the individual tubes, and the spacing between the tubes of the heat exchanging system radially more distant from the central cavity is smaller than the diameter of the individual tubes.

1 3. A boiler according to any one of Claim 8 to 10 wherein the heat exchanging system more remote from the central cavity is.

composed of hollow jackets which are evenly distributed around the axis of symmetry, there being radially arranged slit interspaces between the individual partial jackets.

14. A boiler according to Claim 1 3 wherein the hollow jackets are in the shape of segment wedge-shaped cavity.

1 5. A boiler according to Claim 8, 9 or 10 wherein the individual heat exchanging systems include tube coils, the pitch or gaps between the individual turns in one coil being different from that in the other.

1 6. A boiler constructed, arranged and adapted to operate substantially as herein described with reference to and as shown in any one of the figures of the accompanying drawings.