CN1117036C - Method for preheating thermal gas for shaft kiln production - Google Patents

Abstract

The invention relates to a method for preheating power gas, which is used for supporting a roasting process when limestone and the like are roasted in an annular shaft kiln. The invention is characterized in that the motive gas is preheated by the waste heat of the exhaust gas drawn off from the annular shaft kiln while continuously flowing through a heat exchanger, and is subsequently finally heated to a temperature below 800 ℃ by means of the combustion gas in one or more combustion chambers and fed to the shaft kiln via injectors.

Description

Method for preheating thermal gas for shaft kiln production

The invention relates to a method of preheating steam gas for supporting the roasting process when roasting limestone and the like in an annular shaft kiln.

For the heat treatment of lumps, for example when limestone or dolomite is roasted to lime, shaft kilns, especially annular shaft kilns are used (DE 3915986 C1 and Zement-Kalk-Gips Nr. 6 (1982), pp. 279-289). In order to support the roasting process, thermal gas is introduced into the bulk roasting product located inside the shaft kiln via a plurality of injectors distributed in at least one cross-section around the shaft kiln. For thermal gas, it is a gas mixture that also contains air. This steam gas can also be mixed with circulating gas, which is taken from the shaft kiln, mixed with steam gas and fed back to the shaft kiln. According to the specification of DE 42 41939C1, the temperature of steam gas should be higher than 800°C, for example, 900°C. This prevents alkali from agglomerating in the shaft kiln.

The object of the present invention is to optimize the calcining process in an annular shaft kiln both with regard to the consumption of fuel energy and at the same time with regard to the quality of the lime produced.

The present invention is based on the knowledge that when the temperature of the steam gas is higher than 800° C., since the density of the steam gas is relatively low in this way, in order to obtain a sufficient injection effect, and for complete combustion, the gas supplied to the shaft kiln is reduced. Fuel has enough residual air quantity to provide and use, and this power gas quantity is just too little.

In order to achieve the objects set forth above, according to the present invention, a method for preheating steam gas is proposed for supporting the roasting process when roasting limestone and the like in an annular shaft kiln, characterized in that the steam gas is continuously When passing through a heat exchanger, it is preheated with the waste heat of the exhaust gas drawn from the annular shaft kiln, then, with the help of gas in one or more combustion chambers, it is finally heated to a temperature below 800 °C, after that, the final heated Steam gas passes through one or more annular pipes laid around the ring shaft kiln, and is fed into the shaft kiln from these ring pipes by means of injectors supplying steam gas. In the case of a central combustion chamber, the final heated steam is fed into the injectors next to the shaft kiln through one or more annular pipes laid around the shaft kiln. In the case of a combustion chamber mounted directly on each injector, the final heated steam gas leaves the relevant combustion chamber at the highest possible velocity and immediately enters the mixing tube of the injector, where it is Perform pulse transmission. The temperature of the thermal gas is preferably in the range of 500 to 800°C, especially in the range of 700 to 800°C. At the same time, steam gas can preferably be compressed to a pressure above 1.5 to 2 bar.

Reached proposed object by method of the present invention:

The mode of operation of the annular shaft kiln can be improved in such a way that, especially when the limestone charge has a calcium carbonate content of more than 93%, sufficient steam gas quantities are available for reliable injector operation. This is required to ensure that the lime produced is of high quality, ie has the highest possible reactivity.

It is also necessary to have a minimum steam gas volume so that sufficient circulating gas volume is available for the lower combustion chamber to avoid premature wear of the refractory lining, especially in the lower combustion chamber.

Furthermore, it is possible to adjust the minimum motive air volume which is necessary for complete combustion of the fuel without formation of CO or soot in the exhaust gas.

Finally, optimization of the overall energy balance is completed by recovering waste heat from the exhaust gases drawn from the shaft furnace.

According to a preferred configuration of the invention, the final heating of the steam gas takes place in one or more combustion chambers. It is also possible in such a way that the thermal gas is finally heated in an assembly of always one combustion chamber directly connected to the injector, in this case next to the shaft kiln there are several of the same kind with one of its own Combustion chamber connected injector assembly.

Figure 1 schematically shows the preheating of the steam gas and the final heating in the central combustion chamber and the delivery of the steam gas to the annular shaft kiln.

The thermal gas continuously introduced into the heat exchanger 2 along the arrow direction 1 is preheated to about 200 to 250° C. by the about 300° C. kiln hot exhaust gas fed into the heat exchanger along the arrow direction 3 . After the kiln exhaust gas has substantially transferred its waste heat to the steam gas in the heat exchanger 2, it flows out of the heat exchanger in the direction of the arrow 4.

The preheated power gas enters the central combustion chamber 6 from the heat exchanger 3 through the pipeline 5 . Fuel is fed into one or more burners 8 in the direction of the arrow 7 . The power gas is finally heated to a temperature lower than 800° C. through combustion gas in the combustion chamber 6 .

The final heated steam gas is fed through the pipe 9 into an annular pipe 11 laid around the annular shaft kiln 10, from where it flows to injectors 12 distributed around the shaft kiln 10, only one of which is shown in the figure .

FIG. 2 schematically shows the preheating and final heating of the steam gas and its delivery to the annular shaft kiln via injectors each combined with a combustion chamber.

The thermal gas continuously introduced into the heat exchanger 2 along the arrow direction 1 is preheated to about 200 to 250° C. by the about 300° C. kiln hot exhaust gas fed into the heat exchanger along the arrow direction 3 . After the kiln exhaust gas has substantially transferred its waste heat to the steam gas in the heat exchanger 2, it flows out of the heat exchanger in the direction of the arrow 4.

The preheated steam gas passes from the heat exchanger 2 through the pipeline 9 to an annular pipeline 11 laid around the annular shaft kiln 10, from where the steam gas flows to the structural injectors 12 distributed around the shaft kiln 10 and The assembly of the directly connected combustion chamber 13, only one of the injector and combustion chamber assemblies is shown in the figure. Fuel is supplied to each combustion chamber connected to the injector by means of one or more burners.

Claims (8)

1. the method for preheating power gas, the preheating power gas is used for supporting roasting process when ring-shaped shaft kiln roasting Wingdale and analogue, it is characterized by: when power gas is crossed a heat exchanger in Continuous Flow, carry out preheating with the waste gas residual heat of extracting out from ring-shaped shaft kiln, then, finally be heated to temperature below 800 ℃ by means of the combustion gas in one or more combustion chambers, afterwards, finally Jia Re power gas centers on the circulating line that ring-shaped shaft kiln is laid through one or more, and imports shaft furnace by means of the injector of supplying power coal gas from these circulating lines.

2. it is characterized by in accordance with the method for claim 1: power gas finally is heated to temperature in 500 to 800 ℃ scope.

3. it is characterized by in accordance with the method for claim 2: power gas finally is heated to temperature in 700 to 800 ℃ scope.

4. according to the described method of one of claim 1 to 3, it is characterized by: the power gas that is heated to outlet temperature is to be input to the other injector of shaft furnace in 1.5 to 2 Palestine and Israels with pressure.

5. according to the described method of one of claim 1 to 3, it is characterized by: the final heating of power gas, at a central chamber or in the combustion chamber that a plurality of dispersions are provided with, mix realization by the hot waste gas with the fuel formation that infeeds the combustion chamber.

6. according to the described method of one of claim 1 to 3, it is characterized by: the final heating of power gas, realize in one or more combustion chambers.

7. it is characterized by in accordance with the method for claim 5: the longitudinal center line of central chamber flatly or vertically extends.

8. in accordance with the method for claim 5, it is characterized by: power gas finally heating in subassembly with the direct-connected combustion chamber of injector always, in this case, at the other subassembly that is provided with a plurality of similar injectors that are connected with the combustion chamber of oneself of shaft furnace.

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