Device for producing a hot propellant jet

Abstract

There is disclosed a device for producing a hot propellant jet intended to atomize, and subsequently vitrify, liquid inorganic melts such as, for instance, slags or glass, including a burner chamber. The burner chamber has inlet openings for water and/or vapor distributedly arranged in the axial direction and about the periphery of the flame in a wall surrounding the burner axis and forming an annular chamber with the wall of the burner chamber. A lance including a nozzle is connected to the burner chamber.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to a device for producing a hot propellant jet intended to atomize, and subsequently vitrify, liquid inorganic melts such as, for instance, slags or glass, including a burner chamber.

[0003] 2. Prior Art

[0004] To granulate and disintegrate liquid slags, it has already been proposed to eject the same into granulation spaces by the aid of vapor or a propellant gas, it having also been proposed to carry out further comminution in jet mills using a propellant jet. Departing from slag temperatures of between 1400° C. and 1600° C., the use of conventional propellants, due to the relatively high temperature difference between the propellant jet and the liquid slag, entails the risk of the formation of more or less large agglomerates as well as the danger of thread formation, which, as a result, will raise comminution expenses and considerably reduce the cooling speed. The known proposals, therefore, primarily aimed to effect the cooling of liquid slags as rapidly as possible. According to another proposal, the liquid slag was ejected into a granulation space along with combustion offgases in order to reduce the risk of obstruction of a slag outlet opening from a slag tundish by solidifying slag. By such a mode of procedure, the slag particles injected into the granulation space will reach a consecutively arranged cooling zone at a substantially higher temperature, the higher temperatures resulting in a reduced slag viscosity and a reduced surface tension of the slag droplets so as to enable a finer division of slag droplets at the entry into the cooling zone. The fine dispersion of slag droplets causes the formation of extremely small droplets with relatively high specific surfaces, which allows cooling in relatively short-structured cooling chambers. In such a device in which combustion offgases are used as propellants, vapor and/or water under pressure is subsequently directed against the slag jet within the cooling chamber in order to ensure accordingly rapid cooling.

SUMMARY OF THE INVENTION

[0005] The invention now aims to provide a device for producing a hot propellant jet, by which it is feasible in a simple and cost-effective manner to form a vapor and a vapor-gas mixture for such a propellant jet, in which the temperature of the propellant may be adjusted and controlled within wide limits. It is known that high propellant temperatures result in an extremely fine atomization of the slag particles, whereby the diameters of the slag droplets can be kept at below 15 μm. At lower temperatures such as, for instance, temperatures ranging between 600° C. and 1350° C., the maximum slag diameter attainable will change exponentially, maximum particle diameters of 110 μm being observed, in particular, at propellant jet temperatures of about 600° C. as opposed to a maximum particle diameter of 15 μm to be obtained in a propellant jet of about 1350° C. If the temperatures of the propellant vapor or propellant gas jet are even lower, the initially mentioned thread formation will occur. Such a thread formation may be intended, though, if, for instance, slag wool, glass fibers or insulating wool are to be produced.

[0006] In order to provide a structurally simple device of the initially defined kind, which allows for a wide range of control of the temperature of the propellant jet, the configuration according to the invention essentially is characterized in that the burner chamber comprises inlet openings for water and/or vapor distributedly arranged in the axial direction and about the periphery of the flame in a wall surrounding the burner axis and forming an annular chamber with the wall of the burner chamber, and that a lance including a nozzle is connected to the burner chamber. By providing an additional wall in the interior of the burner chamber, it is feasible, on the one hand, to arrange the inlet openings for water and/or vapor, which are formed, for instance, by bores or slots, in a suitable manner to effect the nozzling of water and/or vapor into the propellant jet and, in particular, into the flame of the burner, while, at the same time, an annular chamber is formed, which is accordingly cooler than the flame on account of the water under pressure or vapor supplied. As a result, the interior of the burner chamber, in which the fuels are burned by means of a flame, may be cooled by radiation cooling, whereby a major portion of the burner chamber can, thus, be efficiently cooled and hence be formed of simpler materials. An additional refractory lining or configuration with a refractory material such as, e.g., alumina, magnesite, silica, zirconium, quartz, silicon carbide or silicon nitride may be required merely in the lower part of a burner chamber of this type in case the water or vapor supply is adjusted such that relatively high propellant jet temperatures will result. By the controlled introduction of water under pressure or vapor into the annular chamber, the desired temperature may be adjusted within wide limits, the burner chamber system corresponding to some type of an internally fired steam superheater. Thermodynamically, such a configuration yields an optimum efficiency of nearly 100%, whereby a short heat transition period may be realized by appropriate turbulences in the burner chamber such that a relatively small-structured and extremely compact cost-effective design will do as compared to conventional superheater systems. The combustion enthalpy of the vapor burner chamber may be recovered to the major extent at a lower temperature level in the subsequent cooling and vitrification chamber into which the liquid inorganic melts are ejected, thus ensuring a high energetic efficiency.

[0007] Advantageously, the device according to the invention is further developed in a manner that the inlet openings for water and/or saturated vapor are arranged in a substantially bell-shaped or conical wall provided in the interior of the burner chamber. By such substantially conical or bell-shaped wall parts delimiting the externally arranged annular chamber towards inside, the expansion of the vapor upon entry into the flame space is taken into account, whereby the transfer of the cooling vapor into the burner space in a particularly simple manner may be effected via a perforated or slotted sheet metal, conventional materials such as, for instance, materials employed in the construction of gas turbines being usable therefor. In a particularly advantageous manner, the configuration is devised such that the bell-shaped or conical wall encompasses the burner of the burner chamber concentrically with the generating lines of the wall being designed to diverge from the burner nozzle towards the flame tip of the burner.

[0008] In order to take into account the rapid expansion of the vapor after the transition into the burner chamber, the configuration alternatively also may be devised such that the inlet openings for water and/or saturated vapor are arranged in a substantially cylindrical wall concentrically surrounding the axis of the burner, the clear widths of the openings differing from one another in different cross sectional planes and increasing, in particular, towards the tip of the flame. The temperature of the hot burner flame, which is about 2400° C. at an adiabatic combustion, may in any event be adjusted to the required target temperature of, for instance, between 120° C. and 1350° C. by the addition of wet or saturated vapor, the burner chamber being directly or indirectly cooled by wet vapor or saturated vapor.

[0009] Suitable adjustment or control of the respectively desired operating parameters is feasible in that a relief valve controllable in a pressure-dependent manner is connected to the annular chamber, which relief valve is controllable by the supply pressure of the propellant jet. In this manner, the pressure prevailing within the annular chamber, which becomes active as an evaporator or superheater chamber, may be controlled accordingly and relieved with a view to enabling, for instance, the preheating of fuels by the aid of the thus lowered pressure so as to impart the respective supply pressure on the same. Advantageously, controlling also may be effected in a manner that the feed of water, vapor, combustion air and/or fuels to the burner chamber is conducted via a control valve capable of being controlled as a function of the pressure and/or temperature of the propellant jet. In this manner, it is feasible in any event to maintain a defined pregiven supply pressure in the burner lance connected thereto and adjust the desired temperature according to demands.

[0010] The transition from the burner chamber into the consecutively arranged lance advantageously may be realized in a manner that the burner chamber is connected with the lance via a funnel, which offers fluidic advantages and provides the option to obtain the respective pressure and temperature measurements required for controlling, in the region of the funnel or at the funnel outlet.

[0011] The device according to the invention advantageously is used in a manner that liquid inorganic melts and, in particular, slags or glass are ejected through a nozzle into a consecutively arranged cooling or vitrification chamber, the lance having to be adjustable relative to the nozzle to eject the liquid inorganic melts. To this end, the configuration advantageously is devised such that the burner chamber is mounted so as to be adjustable in the height direction together with the lance. In order to safeguard the respective thermal resistance of the lance in the region of the hot slag, the configuration advantageously is devised such that the lance is comprised of an oxide-dispersive superalloy, in particular Fe or Ni base material with Al, Cr and less than 1 wt.-% Y2O3. Y2O3 raises the high-temperature creep resistance, while admixtures of aluminum and chromium offer a protection against hot corrosion and, in particular, oxidation in the region of the mouth of the lance.

[0012] The burner itself may be operated with hot air, for instance in a temperature range of between 800° C. and 1200° C., as well as natural gas but also crude oil and carbon dust, whereby CO2, H2O and nitrogen oxides are formed in the burner chamber and a relatively high nitrogen portion remains, taking into account the hot air employed. When cooling with saturated vapor at 2 bars within the burner chamber, cooling to 900° C. will yield extremely superheated water vapor having a relatively high nitrogen portion such that a largely inert propellant jet is formed. Such a mode of operation in subsequently provided physical vitrification procedures offers the particular advantage that the N2 portion contained in the propellant jet substantially decreases the dew point and possible undesired condensation procedures in the cooling system are more readily avoided. Hot air may be produced in a conventional manner in regenerative heat exchangers.

[0013] For economic reasons, the atomization of liquid blast furnace slags may preferably be effected by the aid of hot blast and, for instance, natural gas, the respectively desired particle size being adaptable to the respective requirements by adjusting the temperature of the propellant gas and accordingly adjusting the lance in the slag exit nozzle. Because of the option to adjust the vapor temperature within wide limits, also different melt temperatures of the inorganic melts, which usually range between 1180° C. and 1560° C. in the case of oxidic slags, may be taken into account.

[0014] By the burner chamber according to the invention, it is, for instance, feasible to produce, and use as a propellant jet, 1000 g vapor at a temperature of 1350° C. under a pressure of 2 bars, using 17 g hydrogen and 136 g oxygen as well as 848 g vapor at 2 bars and 145° C. Alternatively, 10 g hydrogen and 81 g oxygen may yield a target quantity of 1000 g vapor at a temperature of 800° C. and 2 bars, using 909 g vapor at 2 bars and 145° C., the vapor fed at 2 bars at first being relieved to the pressure of the burner chamber via the perforated walls and subsequently being again superheated by the flame.

BRIEF DESCRIPTION OF THE DRAWING

[0015] The device according to the invention for producing a hot propellant jet will now be explained in more detail by way of an exemplary embodiment schematically illustrated in the drawing, wherein:

[0016] FIG. 1 illustrates a burner chamber including a lance connected to the burner chamber, and

[0017] FIG. 2 is a detailed view of the arrangement of the vapor lance within the slag outlet.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0018] FIG. 1 depicts a burner chamber 1 whose external wall is denoted by 2. The burner is supplied with O2, air or hot air via a duct 3 and with fuels such as, e.g., H2, CH4, CO, natural gas, crude oil or carbon via a duct 4, in order to form a flame 5, which flame 5 is surrounded by a conical wall 6 comprising inlet openings 7 for water and/or vapor, which are distributedly provided about the periphery of the flame 5. Between the conical wall 6 and the external wall 2 of the burner chamber 1 is thus formed an annular chamber 8 into which wet or saturated vapor or water is introduced through a connection means 9. The vapor or water introduced into the annular chamber 8 rapidly expands due to the heat radiated off the flame 5, whereby further superheating of the vapor up to 1350° C. is attained in that the vapor is ejected from the annular chamber 8 into the immediate region of the flame 5 through the openings 7. In doing so, the flame 5 is cooled from a temperature of approximately 2400° C. to the required target temperature of between 120° C. and 1350° C.

[0019] The burner chamber via a funnel-shaped lower part 10 lined with a refractory material is connected with the vapor lance 11 which opens within a slag jacket 13 emerging through a slag nozzle 12. A pressure measuring means 14 as well as a temperature measuring means 15 are provided to control and adjust the parameters of the vapor jet. To this end, a relief valve 17 to be controlled in a pressure-dependent manner is triggered via a control line 16 to relieve the annular chamber 8, the supply of O2, air, hot air and combustible to the burner being controlled via a control line 18 and valves 19 installed in ducts 3 and 4 as a function of the pressure and temperature values.

[0020] FIG. 2 is an enlarged view of the arrangement of the vapor lance 11 within the slag nozzle 12 and the slag jet 13 ejected in the form of a hollow cylinder. It is apparent that the end of the vapor lance 11 is configured as a nozzle 20 so as to ensure the optimum atomization of the melt. The acceleration due to gravity causes the gradual diminution of the wall thickness of the hollow slag cylinder 13 until the latter starts to divide itself into individual skeins in region 21. It has proved to be advantageous if the mouth of the nozzle 20 is approached to closely before of the region of skein formation. This will be extremely beneficial to the slag atomizing procedure. Another decisive parameter aimed at an efficiency increase is the length of the free jet, which has a particular influence on the specific propellant consumption. The length of the free jet is defined as the length between the exit of the propellant vapor from the lance nozzle 20 and the point of impact of the propellant jet on the hollow melt cylinder 13. This length in the instant case is to be kept as small as possible. The vapor lance 11 is arranged to be adjustable in the height direction in the sense of double arrow 22 so as to enable the precise adjustment of the point of impact of the vapor jet on the hollow slag cylinder and the minimization of the length of the free jet.

Claims

1. In a device for producing a hot propellant jet intended to atomize, and subsequently vitrify, liquid inorganic melts such as, for instance, slags or glass, of the type including a burner chamber containing a burner having a burner axis and constructed to produce a flame within said burner chamber and a burner chamber wall defining said burner chamber, the improvement comprising a further wall surrounding said burner axis and forming an annular chamber with said burner chamber wall, a plurality of water and/or vapor inlet openings arranged in said further wall in a manner distributed in the direction of said burner axis and about the periphery of said flame, and a lance including a lance nozzle and connected to said burner chamber.

2. A device as set forth in claim 1, wherein said vapor is saturated vapor and said further wall including said plurality of water and/or vapor inlet openings is a substantially bell-shaped wall arranged in the interior of said burner chamber.

3. A device as set forth in claim 1, wherein said vapor is saturated vapor and said further wall including said plurality of water and/or vapor inlet openings is a substantially conical wall arranged in the interior of said burner chamber.

4. A device as set forth in claim 2, further comprising a burner nozzle and wherein said substantially bell-shaped wall encompasses said burner of said burner chamber concentrically with the generating lines of said substantially bell-shaped wall being designed to diverge from said burner nozzle to the tip of said flame produced by said burner.

5. A device as set forth in claim 3, further comprising a burner nozzle and wherein said substantially conical wall encompasses said burner concentrically with the generating lines of said substantially conical wall being designed to diverge from said burner nozzle to the tip of said flame produced by said burner.

6. A device as set forth in claim 1, wherein said vapor is saturated vapor and said further wall including said plurality of water and/or vapor inlet openings is a substantially cylindrical wall concentrically surrounding said burner axis, and said water and/or vapor inlet openings have clear widths respectively differing from one another in different cross sectional planes.

7. A device as set forth in claim 6, wherein the clear widths of said water and/or vapor inlet openings increase towards the tip of said flame.

8. A device as set forth in claim 1, further comprising a relief valve connected to said annular chamber and capable of being controlled in a pressure-dependent manner by the pressure of said hot propellant jet.

9. A device as set forth in claim 1, wherein said burner chamber is provided for the supply of at least one of water, vapor and combustion air, and further comprising a control valve capable of being controlled as a function of at least one of the pressure and the temperature of said hot propellant jet, wherein said supply of said at least one of water, vapor and combustion air to said burner chamber is conducted via said control valve.

10. A device as set forth in claim 1, further comprising a funnel means constructed to connect said lance with said burner chamber.

11. A device as set forth in claim 1, wherein said burner chamber is mounted so as to be adjustable in height along with said lance.

12. A device as set forth in claim 1, wherein said lance is comprised of an oxide-dispersive superalloy.

13. A device as set forth in claim 12, wherein said oxide-dispersive superalloy comprises a base material selected from the group consisting of Fe and Ni, admixed with Al, Cr and less than 1 wt.-% Y2O3.