KR20000048325A - Method for drying moist material - Google Patents

Abstract

PURPOSE: A method for drying a wet material is provided to dry the wet material without dropping temperature to lower than a dew point while saving energy and to prevent the operation confusion caused by a blockade in a dust-eliminating device of low current. CONSTITUTION: A drying gas is formed by mixing a hot gas generated in a hot gas generator and a second gas. The temperature of the drying gas is measured for controlling the second gas by using the function of the drying gas temperature. Then, the temperature and the dew point temperature of the drying gas leaving a dryer as an autoexhaust are measured. Herein, the autoexhaust volume and the autoexhaust temperature are increased or reduced from a desired autoexhaust temperature by the function of deviation exceeding the initial value of an error or deviation within the autoexhaust temperature. Herein, the desired autoexhaust temperature is decided from the dew point temperature including a safe margin. Moreover, a wet material includes mounting materials such as ore, coal, cokes, and sintering mixture. And, the hot gas is a heated air, heated nitrogen, or burned autoexhaust.

Description

Wet material drying method {METHOD FOR DRYING MOIST MATERIAL}

The present invention relates to a method for drying a wet material using a dry gas in a dryer, wherein the dry gas is formed by mixing a hot gas generated in a hot gas generator with a second gas, and measuring the temperature of the dry gas. And controlling the additional second gas as a function of the dry gas temperature and measuring the dry gas leaving the dryer as wet exhaust gas, the dew point temperature and the temperature of the exhaust gas. The invention also relates to an apparatus for carrying out the invention.

In many of the drying methods currently in use at major industrial scales, the hot gas generator used to produce the dry gas is monitored by monitoring the temperature of the flue gas leaving the dryer and indirect control parameters for the blowers and hot gas generators that can be obtained from this temperature. Adjusted. The drawback to this process is the fact that the parts of the plant connected downstream of the dryer on the gas side will not or only difficultly prevent the exhaust gas from dropping to temperatures below the dew point and as a result caking and clogging. have.

This problem can be avoided especially when the filter is used for dedusting the exhaust gas stream. In this case, the operation of all mechanical filters is adversely affected by the temperature falling below the dew point. The temperature falling below the dew point also results in the formation of concentrates in the piping system, as well as all related problems such as deposition and corrosion phenomena.

The above-described control method can be used without problem only if the material to be dried and the hot gas, as well as the second gas which can be added to the hot gas, show a nearly constant amount of moisture with time.

Thus, if the amount of moisture in the material to be dried fluctuates or rises, for safety reasons the flue gas should be at a very high temperature from the beginning to avoid temperatures falling below the dew point which can cause significant operating disturbances.

Since the atmosphere is usually used as the second gas and is also heated by hot gas or by combustion gas generated by combustion of air and fuel, the amount of moisture in the flue gas fluctuates even if the moisture content of the material to be dried is constant. Therefore, for safety margin, the flue-gas temperature must be higher than the average dew point temperature, and the safety margin must be suitably wide.

Therefore, the energy used to dry is always higher than the level necessary to achieve the desired level of drying and to avoid temperatures falling below the dew point. In particular, in the case of low moisture amounts of the material to be dried and / or the hot gas and / or the second gas, the material to be dried can be over dried and possibly even damaged, for example in the case of combustion materials In the case of spontaneous ignition, the desired value of the flue-gas temperature may not be reset or reset in good time.

JP-A 09-061059 further discloses an apparatus for drying a charging material for the production of iron such as coke or iron ore. In this case, the fuel is burned in the combustion chamber, the combustion gas is mixed with the atmosphere in the mixing chamber, and the charging material is dried in the dryer by this mixed gas. The flue gas leaving the dryer once again mixes with the atmosphere to reduce the amount of moisture in the flue gas and extend the life of the downstream deduster.

This drying apparatus adds tertiary air to the flue-gas, which significantly increases the flue-gas total volume and thus requires a corresponding large dedusting device, which is expensive to set up and operate. In particular, there is no feature that allows an energy saving mode of operation of the combustion chamber.

The object of the present invention is mentioned in the opening paragraph, which allows for good drying of the wetting material in an energy-saving manner and without the possibility of temperature dropping below the dew point of the flue-gas, thus avoiding operating disturbances caused by blockages in downstream dedusting devices. One way is to provide a method.

1 shows an apparatus for drying the wetting material, in which solid lines represent portions of the material flow or installation, respectively, and dotted lines represent signal passages.

2 is a diagram illustrating another adjustment and control method of the present invention.

Explanation of symbols on the main parts of the drawings

1: dryer 2: wet material

3: drying gas 4: drying material

5: wet exhaust gas 6: gas mixing device

9: hot gas generator 12, 13: measuring device

14: control unit 15: safety margin

17: temperature measuring device 18: monitoring device

20: conveying device

According to the invention, it is an object of the invention that the flue gas temperature and / or the volumetric flow rate of the flue gas exceeds the deviation or initial error value in the flue gas temperature from the desired flue gas temperature determined from the dew point temperature measured by adding a safety margin. By the fact that it is increased or decreased as a function of

Therefore, when the exhaust gas temperature falls below the desired exhaust gas temperature formed by the sum of the dew point temperature and the safety margin, the volume flow rate and / or temperature of the hot gas is increased. Since the desired dry gas temperature set does not change, the final dry volume flow rate changes by the continuous addition of the second gas to the hot gas.

Using the method of the present invention, it is possible to prevent the possibility of the temperature falling below the dew point of the flue gas from the beginning. Thus, all related problems such as deposition and caking in downstream filter installations as well as concentrates in piping systems are avoided. A further advantage of the method according to the invention is that if the drying parameters, such as the amount of moisture in the material to be dried, are changed, any change in relative atmospheric humidity and fluctuations in the calorific value of the fuel when the combustion chamber is used as a hot gas generator is automatic. It is in the fact that it is compensated by the control method.

The self-regulating effect furthermore makes it possible to maintain the desired value of the flue-gas temperature at a lower level than conventional methods, as a result of which the material to be dried is protected against overheating and further undesirable overdrying is reliably Can be avoided. Thus, the hot gas generator can also operate in an energy saving manner.

The present invention is particularly suitable for drying solid metallurgical charging materials for metallurgical industry, in particular ore, coal, coke and sintering mixtures. In addition to solid metallurgical charging materials for the metallurgical industry, it can be preferably used as a wetting material suitable for the process according to the invention.

According to the invention, the hot gases used are preferably heated air, heated nitrogen, hot combustion flue gases or mixtures of these gases.

Preferably, the second gas used is heated air, heated nitrogen, hot combustion exhaust gas or a mixture of these gases.

In this case, since the second gas is at a temperature lower than the desired temperature of the dry gas, the dry gas at the desired temperature is produced by mixing the second gas and the hot gas.

The appropriate temperature for the drying gas depends on the nature and amount of the material to be dried in the conventional manner, the amount of moisture of the material to be dried, the desired level of drying and in any case the moisture captured by the hot gas.

For example, if coal is to be dried, it is necessary that the temperature selected for the drying gas is not too high. Otherwise, volatile hydrocarbons escape from coal many times.

The hot gas and the gas used as the second gas are mainly selected according to the drying operation to be performed, that is, the characteristics, amount, moisture amount and the desired residual moisture of the material to be dried. For example, wet ore and coal may be dried by warm or hot combustion flue gases which are preferably mixed with air, while the recommended gas for drying plastic particles is, for example, air.

A further important point for selecting hot gases and second gases is the availability of these gases.

According to a preferred embodiment of the method according to the invention, only the volume flow rate of the hot gas changes in case of exhaust temperature which deviates from the desired exhaust gas temperature.

This measurement greatly influences the simplicity of the method according to the invention in terms of control engineering.

According to a further preferred feature, the volume flow rate and / or temperature of the hot gas is adjusted only when the deviation of the exhaust gas temperature from the desired exhaust gas temperature exceeds the initial error value. In this case, the initial error value is at most 20% of the safety margin.

This avoids the need to continuously adjust the operation of the hot gas generator.

The invention also relates to an apparatus for drying a wetting material, said apparatus being capable of supplying a wetting material and allowing the drying material to be discharged and a drying gas to be supplied and released as a wet exhaust gas, and to generate hot gases. A hot gas generator for producing a dry gas so as to supply a dry gas supplied with the hot gas and the second gas and mixed from these components to the dryer, and measuring a dry gas temperature actual value and a corresponding signal Dry gas temperature desired to control the measuring and / or conveying device for controlling the volumetric flow rate of the second gas by the monitoring device in order to supply it to the monitoring device and as a function of the comparison of the dry gas temperature actual / desired value. The value of can be supplied and has a monitoring device connected to the temperature measuring device.

In order to achieve the object set in accordance with the present invention, such a device is characterized in that a control device is provided and connected to the measuring device in order to measure the flue gas dew point temperature and the flue gas temperature actual value and supply a corresponding signal to the control device. Thus, by supplying a safety margin to the control device and forming a sum of the dew point temperature and the safety margin, it is possible to determine the desired value of the exhaust gas temperature, and by the control device and as a function of the exhaust gas temperature actual / desired value comparison, the hot gas generator In particular, it is possible to control the amount of hot gas generated per hour and / or the desired value of the dry gas temperature to be supplied to the temperature- and / or monitoring device.

According to a preferred form of the device according to the invention, the dryer is designed as a cocurrent or countercurrent or cross flow or fluidized bed dryer.

According to a preferred variant of the device according to the invention, the hot gas generator is formed by a combustion chamber, in which the fuel, for example natural gas, fuel oil or CO- and / or H ₂ containing reducing gas and oxygen containing gas, ie Air and / or oxygen can be supplied. In this case, the fuel supply and / or the supply of the oxygen containing gas can be controlled by a control device and by an adjustable measuring and / or conveying device, for example a valve, a pump or a blower.

According to a further preferred variant of the device according to the invention, the hot gas generator is formed by a heat exchanger, which can supply heat exchange fluids, for example steam, hot water, hot combustion flue gas or process gas and gas to be heated. In this case, the supply of the heat exchange fluid and / or the supply of the gas to be heated can be controlled by the control device and by the adjustable measuring and / or conveying device.

The above-described process gas is a partially or fully consumed reducing gas, for example extracted from a reduction furnace for reducing ore.

The apparatus according to the invention as well as the method according to the invention are described in more detail below with reference to the embodiment shown in FIGS. 1 and 2.

The wetting material 2 is placed in the dryer 1. The drying gas 3 is further supplied to the dryer 1, and the wet material 2 is dried in the dryer 1 and discharged from the dryer 1 as the drying material 4. Dry gas 3 is extracted from the dryer as exhaust gas 5 which is now wet.

Upstream of the dryer 1, there is a gas mixing device 6 to which the hot gas 7 and the second gas 8 are supplied. In the gas mixing device 6, the hot gas 7 and the second gas 8 are mixed so that the dry gas 3 (hot gas temperature> dry gas temperature> second gas temperature, for example 1000 ° C.> 200 ° C.) 100 ° C.) is then fed to the dryer 1.

The hot gas generator 9 for generating the hot gas 7 is arranged upstream of the gas mixing device 6. The hot gas generator 9 is designed in the case of the present invention as a combustion chamber to which oxygen-containing gas 10, for example air and fuel 11, for example natural gas or fuel oil, is supplied. The fuel 11 is burned in the combustion chamber and the hot gas 7 formed therein is supplied to the gas mixing device 6.

The measuring device 12 for measuring the exhaust gas dew point temperature and the measuring device 13 for measuring the actual exhaust gas temperature value are arranged in the flow of the wet exhaust gas 5 downstream of the dryer 1. The measuring devices 12 and 13 supply the corresponding signals to the control device 14. The control device 14 also defines a predetermined safety margin 15, and the desired value of the exhaust gas temperature is determined from the sum of the measured dew point temperature and the safety margin 15. The flue gas temperature actual / desired value comparison is performed by the control device 14. The operating mode of the hot gas generator 9, in particular the amount of hot gas generated per unit time preferentially, is controlled as a function of actual / desired value comparison.

For the purposes of the present invention, an adjustable measuring and / or conveying device 16, for example a blower, is provided whereby the oxygen containing gas 10 and the fuel 11 are supplied to the hot gas generator 9. do. The control device 14 regulates the operation of the measuring and / or conveying device 16 as a function of the flue gas temperature actual / desired value comparison, so that, for example, if the flue gas temperature actual value falls below the flue gas temperature desired value. , A larger amount of hot gas 7 is generated per unit time.

In order to control the operation of the gas mixing device 6, a temperature measuring device 17 for measuring the dry gas temperature actual value is provided in the stream of dry gas 3 and a corresponding signal is provided to the monitoring device 18. Supplied. The dry gas temperature desired value 19 can also be input to the monitoring device 18. The measuring and / or conveying device 20, for example a blower, is again regulated by the monitoring device 18 as a function of the dry gas temperature actual / desired value comparison, and the measuring and / or conveying device 20 is arranged in a second manner. The supply of the gas 8 to the gas mixing device 6 is controlled.

In the case of the operating principle of the method according to the invention shown in FIG. 2, the moisture content is shown in ordinate. The measuring point 21 corresponds to the measuring temperature of the wet flue gas, the measuring point 23 corresponds to the dew point temperature, and the measuring point 22 corresponds to the corresponding absolute moisture amount. The safety margin 24 is added to the dew point temperature, in which way the exhaust gas temperature desired value is formed.

In this case, the exhaust gas temperature actual and the desired values do not initially deviate from each other, and the exhaust gas actual values are above the dew point temperature by the value of the safety margin 24, so that no part of the installation risks the temperature falling below the dew point. .

If the moisture content of the wetting material to be dried is increased in comparison with the original moisture content, only the absolute moisture content of the flue gas is first raised to, for example, a value (25). The safety margin 24 is again added to the new dew point temperature 26, resulting in a new exhaust gas temperature desired value 28. The control device 14 can then be used to control the operation of the hot gas generator 9 so that a larger amount of hot gas is produced or to increase the dry gas temperature desired value 19 supplied to the monitoring device 18. Can be. In the former case, the original dry gas temperature is set again in the gas mixing device 6 by adding the second gas 8, but the volume flow rate of the dry gas is increased. Therefore, the moisture content of the flue gas again falls to a level lower than that at the measuring point 25. In the latter case, the exhaust gas actual temperature will also rise to the temperature of the dry gas until the exhaust gas temperature actual value and the desired value finally correspond again.

In order to adapt to the extreme fluctuations in the moisture content or volume of the material to be dried, the control device 14 can also interfere simultaneously with the operation of the hot gas generator 9 and the monitoring device 18.

The same adjustment method described also applies with the necessary changes in case the moisture level falls to the low level 27.

The invention is not limited to the illustrative embodiments shown in FIGS. 1 and 2 but also includes all means known to those skilled in the art and that can be used to practice the invention.

Using the method of the present invention, it is possible to prevent the possibility of the temperature falling below the dew point of the flue gas from the beginning. Thus, all related problems such as deposits and caking in downstream filter installations as well as concentrates in piping systems can be avoided. In addition, by changing the drying parameters, such as the amount of moisture in the material to be dried, any changes in relative atmospheric humidity and fluctuations in the calorific value of the fuel when the combustion chamber is used as a hot gas generator can be compensated by the automatic adjustment method. It is also possible to operate the hot gas generator in an energy saving manner.

Claims (12)

The dry gas is formed by mixing the hot gas generated in the hot gas generator with the second gas, measuring the temperature of the dry gas, controlling the additional second gas as a function of the dry gas temperature, and drying the dryer as a wet exhaust gas. A method for drying a wet material using a dry gas in a dryer, the method comprising measuring the leaving dry gas and the dew point temperature and the temperature of the flue gas, The flue gas temperature and / or the volumetric flow rate of the flue gas is increased or decreased as a function of the deviation in the flue gas temperature from the desired flue gas temperature determined from the measured dew point temperature plus the safety margin, or a deviation exceeding the initial error value. How to. Process according to claim 1, characterized in that the wetting material comprises metallurgical industry charging materials, in particular ore, coal, coke and sintering mixtures. The method according to claim 1 or 2, wherein the hot gas is heated air and / or heated nitrogen and / or combustion exhaust gas. The method of claim 1, wherein the second gas is heated air and / or nitrogen and / or combustion exhaust gas. The volume flow rate of the hot gas only varies in the case of a deviation or in the case of a deviation exceeding the initial value of the error in the exhaust gas temperature from the desired exhaust gas temperature. How to. 6. A method according to any one of claims 1 to 5, wherein the initial error value is at most 20% of the safety margin. The wet material 2 can be supplied and the drying material 4 can be discharged and the drying gas 3 can be supplied and can be discharged as and as the wet exhaust gas 5 and to generate hot gas. A gas mixing device for producing a dry gas 3 so as to supply a high temperature gas generator 9 for supplying a dry gas to which a high temperature gas 7 and a second gas 8 are supplied and mixed from these components to a dryer. (6) and for measuring the dry gas temperature actual value and supplying a corresponding signal to the monitoring device and for adjusting the volume flow rate of the second gas by the monitoring device as a function of the comparison of the dry gas temperature actual / desired value. Wet material 2, which may be supplied with a dry gas temperature desired value 19 so as to control the measuring and / or conveying device 20 and having a monitoring device 18 connected to the temperature measuring device 17. In the device for drying the In order to measure the flue gas dew point temperature and the flue gas temperature actual value and to supply a corresponding signal to the control device 14, a control device 14 is provided and connected to the measuring devices 12 and 13, so that the control device 14 is safe. By supplying the margin 15 and forming the sum of the dew point temperature and the safety margin 15, the exhaust gas temperature desired value can be determined, and by the control device 14 and as a function of the exhaust gas temperature actual / desired value comparison, A device characterized in that it is possible to control the hot gas generator, in particular the amount of hot gas generated per hour and / or the dry gas temperature desired value to be supplied to the temperature- and / or monitoring device. 8. Device according to claim 7, characterized in that the dryer (1) is designed as a cocurrent or countercurrent or crossflow or fluidized bed dryer. 9. Apparatus according to claim 7 or 8, characterized in that the hot gas generator (9) is formed by a combustion chamber, capable of supplying fuel (11) and oxygen containing gas (10) to the combustion chamber. 10. The fuel supply according to claim 9, characterized in that the fuel supply and / or the oxygenous gas supply can be controlled by the control device 14 and by an adjustable measurement and / or transport device 16. Device. 9. An apparatus according to claim 7 or 8, characterized in that the hot gas generator (9) is formed by a heat exchanger, capable of supplying heat exchange fluid and gas to be heated to the heat exchanger. 12. The device according to claim 11, wherein the supply of heat exchange fluid and / or the supply of gas to be heated can be controlled by the control device (14) and by an adjustable measuring and / or conveying device.