Art Domain

This invention concerns method of gas combustion, for example of natural gas or propane, in industrial furnaces, especially glass furnaces or furnaces for metal melting, by the help of oxygen or air and further the invention solves construction of the burner for realization of this method.

Present Prior Art

In the industrial furnaces, there are due to reason of reaching of very high temperatures necessary for thermal treatment of the material, i.e. melted glass or heated metal, used different systems of gas burning by the help of oxygen or air. Combustion systems consist of burners which are placed in the furnace with simultaneous input of the fuel gas and additional gas in the form of oxygen or air. Both these gases react at the temperature over the ignition temperature of the fuel gas, burn and herewith add energy to the process. For accomplishment of optimal heat transfer and at the same time for the protection of heat proof material of the furnace against high temperature of the flame it is necessary to design these burners in the way for the flame to reach good heat transfer in the space of the furnace and simultaneously not to melt heat proof walling of the furnace area. This optimal flame is obtained using specific construction of the burner with accurate setting of the flow and outflow velocity of the gas and oxygen.

The solution of this problem was described for example in files CZ 279526 or WO2007/048429 where with aim to reach improved control of the flame was used setting with one central flow of the gas and one concentric flow of the oxygen.

Yet this solution does not enable setting of outflow velocity in the wide range of values and does not enable to sufficiently control the shape of the flame. Alternative solution is type of the burner with more oxygen and gas inlets as it is described in files EP 0687853 and EP 0762050. According to these solutions it is difficult to properly set the burner and reach optimal conditions for burner performance and at the same time these solutions require use of complicated burner shaped piece. In the device according to the patent US 5,299,929 are used two flows of oxygen which are led through flat slot above and under central flow of the gas with target to create two zones of burning. This solution simplifies control of the burner but does not enable gentle and accurate setting of the gas and reacting oxygen.

In the design according to the file US 6,190,158 was used burner with central flow of the oxygen, which is concentrically surrounded by the gas and the gas is then also surrounded by the oxygen. This solution does enable good gas and oxygen regulation but the presence of oxygen in the central area of the flame decreases radiation efficiency of the burner and negatively influences emission of the nitrogen oxides (NOx). For solution of sufficient regulation ability of the flame was in the patent US 6,685,463 used configuration for burning of the gas by atmospheric air, where the gas is input into through central nozzle and subsequently surrounded by the flow of primary air into which is angle wise added another flow of secondary combustion air. Disadvantage of this solution is use of the air as an oxidation reagent which causes heat efficiency decrease of the burner. Further disadvantage is angle wise input of the secondary air into the burner which causes increase of the turbulence in the flame and increased NOx emissions.

The aim of this invention is to solve above mentioned complications and to design new way suitable for combustion of fuel gas, for example natural gas or propane, by the help of additional gas, preferably oxygen, enabling accurate setting of combustion process with high radiation efficiency and low NOx emission. Likewise is the task of the invention to introduce design of the burner for realization of this method. Essence of the invention

The set goal is reached by an invention, which is the way of gas combustion in industrial furnaces, especially glass furnaces or furnaces for metal melting, by the help of multi nozzle burner with controllable regulation of the flow of fuel gas nozzles as well as of additional gas, where the essence is that the fuel gas is input into cavity of the burner through at least one central gas nozzle with simultaneous input into of two independent flows of the additional gas in the way that the fuel gas is surrounded by concentric flow of primary additional gas which is then surrounded by concentric flow of secondary additional gas.

In preferred design the fuel gas is input into the burner in velocity (Vp) ranging between values 1 to 30 m/s, whereas at first the primary additional gas is input into the burner in controllable capacity amount, which ranges between 10 to 90 weight % necessary for stoichiometric combustion of the fuel gas, in velocity (V ₀ i), whose value is given by relation and also the secondary additional gas is input into the burner in controllable capacity amount, which ranges from 90 to 10 weight % necessary for stoichiometric combustion of the fuel gas, in velocity (V ₀₂ ), whose value is given by relation

In an optimal case the amount and the velocity of the input fuel gas, primary additional gas and secondary additional gas are continuously controllable and as the fuel gas is used methane or propane in mixture with other hydrocarbons and gases and as the additional gas is used oxygen, air or another oxidant with oxygen content over 80 weight %. Next essence of the invention is a burner for gas combustion in industrial furnaces, especially glass furnaces or furnaces for metal melting, containing an injector and a shaped piece of the burner, which is fixed on outfall of the injector, where the injector comprises either from an inner gas nozzle equipped on an infall with a main regulation valve of input of the fuel gas or from the inner gas nozzle and an insertion gas nozzle equipped with an auxiliary valve, whereas the inner gas nozzle is surrounded by a first concentric nozzle equipped on infall with a regulation valve of input of the primary additional gas and the first concentric nozzle is around the perimeter surrounded by a second concentric nozzle, which is equipped with a regulation valve of input of secondary additional gas and which forms the body of the injector.

Likewise is beneficial when between a flow crosscut (0) of the fuel gas, given either by a flow crosscut (0 _r ) of the inner gas nozzle or by sum of flow the crosscut ( 1) of the inner gas nozzle and a flow crosscut (0 ₂ ) of the insertion gas nozzle and a flow crosscut (ø) of the additional gas given by sum of a flow crosscut ( 1) of the first concentric nozzle and a flow crosscut (0 ₂ ) of the second concentric nozzle is valid relation

0 : 0 = 1 : (0,9 to 1,8) whereas under condition ø = Ø! ₊ 0 ₂ is valid relation

01 : 2 = 1 : (0,3 to 2,2).

Further then is advantageous when the regulation valve of inflow of the primary additional gas and the regulation valve of inflow of the secondary additional gas are via a control unit of the additional gas connected into a block of control of combustion process where, also via a control unit of the fuel gas, is connected the main regulation valve of inflow of the fuel gas with the auxiliary regulation valve, whereas the block of the control of combustion process is connected to an evaluating and control block equipped with control elements. With this presented solution is reached new and higher effect herein that through quite simple construction lay out is possible to achieve accurate setting of combustion process with high radiation efficiency and low NOx emission. Continually controllable infalls of the fuel gas and the additional gas the enable accurate and gentle setting of shape and kinetic of the flame and enable sufficient regulation ability of the luminescence of the flame and influence over NOx production.

Description of figures on enclosed drawings

Particular examples of invention design are schematically illustrated in enclosed drawings where: fig. 1 is lengthwise schematic cut of basic design of the burner, fig.2 is lengthwise schematic cut of an alternative design of the burner with two gas nozzles, fig.3 is scheme of a flame structure in basic design of the burner according to the fig.1 and fig.4 is lengthwise schematic cut of the alternative design of the burner from the fig.2 with illustrated connection of the regulation valves of particular nozzles to the block of control and operating of combustion process.

The drawings which illustrate introduced invention and subsequently described examples of particular designs do not in any case limit scope of the protection mentioned in definition, but only clarify essence of the invention. Examples of carry out of the invention

In a basic design illustrated in fig. 1 the burner consists of an injector 1 and a shaped piece of the burner 2, which is fixed on outfall of the injector and is formed in way that the diameter of its inner cylindrical cavity 21 basically corresponds with outer diameter of the body of the injector 1. The injector 1 consists of three coaxially placed pipe nozzles H , 12 and 13. The inner gas nozzle 11 is equipped on infall with a main regulation valve HI of inlet of the fuel gas and is surrounded by a first concentric nozzle 12 equipped on infall with a regulation valve 121 of inlet of the primary additional gas. This first concentric nozzle 12 is around its perimeter surrounded by a second concentric nozzle 13 which is equipped with a regulation valve 131 of inlet of the secondary additional gas and which forms the body of the injector 1. As it is visible from the fig. 4 both regulation valves 121 and 131 are via a control unit 4 of the additional gas connected to a block 5 of control of combustion process, where is also via a control unit 6 of the fuel gas connected the main regulation valve HI of inlet of the fuel gas. The block 5 of the control of the combustion process is then connected to an evaluation and control block 7, which is equipped with non-illustrated control units and preferably contains computer.

In an alternative design of the burner illustrated in the fig. 2 the injector 1 is also equipped with an additional insertion gas nozzle 14 equipped with an auxiliary regulation valve 141, which is then connected via the control unit 6 of the fuel gas into the block 5 of the control of combustion process.

The injector 1 is then made in the way to have between a flow crosscut (0) of the fuel gas, given in case of basic design of the burner by a flow crosscut (0i) of the inner gas nozzle 11 and in case of alternative design of the burner or by sum of the flow crosscut (0i> of inner gas nozzle 11 and a flow crosscut (0 ₂ ) of the insertion gas nozzle 14 and a flow crosscut (ø) of the additional gas given by sum of a flow crosscut (0i) of the first concentric nozzle 12 and a flow crosscut (0 ₂ ) of the second concentric nozzle 13 valid relation

0 : 0 = 1 : (0,9 to 1 ,8) whereas under condition ø = 0i + 0 ₂ is valid relation

01 : 02 = 1 : (0,3 to 2,2).

During performance of the burner of basic construction design according to the fig. 1 the fuel gas is blown at velocity VP. ranging between 1 to 30 m/s from the inner gas nozzle 11 into the central part of the cavity 21 of the shaped piece 2 of the burner where it is mixed with the primary additional gas inlet from the first concentric nozzle 12 at outflow velocity Q! whose value is given by relation whereas the primary additional gas is into the cavity 21 inlet in controllable capacity amount, which ranges between 10 to 90 weight % necessary for stoichiometric combustion of the fuel gas. During the flow through the cavity 21 of the shaped piece 2 comes to, thanks to temperature conditions in an industrial furnace, into which is the burner installed, to ignition of the fuel gas and reaction CH ₄ with oxygen of the additional gas to formation of C0 ₂ and H ₂ 0. With regard to relatively low velocity of the fuel gas and the additional gas there is no significant turbulent flow which results in decreased temperature of the flame and in forming of the zone rich in exhaust gas surrounding the flow of the fuel gas depleted of oxidant, thus oxygen. This phenomenon causes slow down of the burning and due to radiation from the space of the furnace comes to formation of carbon radicals in the area of the reacting flame. The structure of the flame for basic design of the burner from fig. 1 is then illustrated in fig. 3.

Simultaneously there is from the second concentric nozzle 13 blown into the cavity 21 of the shaped piece 2 secondary additional gas, which surrounds the reacting fuel gas and the primary additional gas and enables perfect combustion of all reactive products. The secondary additional gas is again inlet in controllable capacity amount, which ranges between 90 to 10 weight % necessary for stoichiometric combustion of the fuel gas, whereas controllable outflow velocity \/Q2 of the secondary additional gas is with regard to outflow velocity E of the fuel gas given in relation.

Continually controllable infalls of the fuel gas into the nozzles 11, 12, 13, 14 equipped with the regulation valves HI, 111, 131, 141 enable accurate and gentle setting of the kinetic of the flame and enable its sufficient controllability with possibility of influence of NOx emission. As the fuel gas is according to the area of use of the burner preferably used methane or propane in mixture with other hydrocarbons and gases. As the additional gas is preferably used oxygen, air or another oxidant with oxygen content over 80 weight %.

Industrial usability

The way of gas combustion for example of natural gas or propane, namely by the help of oxygen or air, and the burner for performance of this method is aimed for use in industrial furnaces, above all glass furnaces or furnaces for metal melting.