JP5225904B2 - Combustion state monitoring method - Google Patents

Description

  The present invention relates to a combustion state monitoring method, and more particularly, to a method for monitoring the combustion state of fuel in a calcining furnace in a cement manufacturing process.

  A conventional cement manufacturing method is disclosed in Patent Document 1. In this manufacturing method, in order to manage the decomposition degree of the cement raw material in the preheater, based on the measurement result of the decomposition degree of the cement raw material sampled on the downstream side of the calcining furnace, the downstream side of the calcining furnace in the steady state The gas temperature is controlled.

JP 2000-272940 A

  In recent years, however, the use of recycled raw fuel and low-grade coal as fuel for cement production has increased due to environmental awareness and rising coal prices. When such a fuel is used, the combustion characteristics in the calcining furnace change, which makes it difficult to manage the decomposition degree of the cement raw material based on the gas temperature in a steady state. That is, even if the gas temperature in a steady state is constant, the decomposition degree of the cement raw material changes due to the change in combustion characteristics, so the measurement result of the gas temperature is not necessarily an indicator of the decomposition degree. Moreover, since combustibility deteriorates depending on the combination of the recycled raw fuel and the amount of coal used, it may be necessary to use more fuel in order to keep the degree of decomposition of the cement raw material constant.

  The present invention has been made to solve such problems, and even if the combustion characteristics of the fuel used in the cement manufacturing process change, a combustion state monitoring method capable of keeping the degree of decomposition of the cement raw material constant. The purpose is to provide.

A combustion state monitoring method according to the present invention is a combustion state monitoring method for burning recycled raw fuel and main fuel in a calcining furnace in a cement manufacturing process, and is a gas that is more gas than the calcining furnace or the calcining furnace. Changing the amount of the recycled raw fuel supplied to the upstream side as a flow of or changing the amount of the main fuel supplied to the calciner, and the temperature of the combustion gas in the calciner and measuring, from the combustion gas temperature measurement result of the steps of calculating the temporal change of the temperature change of the recycle raw fuel to said main said combustion gas change amount per unit amount of fuel supplied, is calculated And comparing the time-dependent change with the time-dependent change of the temperature change of the combustion gas for the various recycled raw fuels or the main fuels prepared in advance.

  According to the present invention, since the change in the combustion characteristics of the fuel can be recognized by comparing the calculated change over time with the change over time prepared in advance, even if the combustion characteristics of the fuel used in the cement manufacturing process change. The degree of decomposition of the cement raw material can be kept constant.

It is the schematic of the cement manufacturing apparatus for implementing the cement manufacturing process which concerns on embodiment of this invention. It is a graph which shows the time-dependent change of the temperature change of combustion gas when supply_amount | feed_rate is changed about various coal and recycle raw fuel. It is a graph which shows an example of a time-dependent change of the temperature change of combustion gas when changing supply_amount | feed_rate about recycled raw fuel. It is the schematic of the database which recorded the combustion characteristic for every kind of main fuel and recycle raw fuel.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
In FIG. 1, the schematic of the cement manufacturing apparatus for implementing the cement manufacturing process which concerns on this embodiment is shown. The cement manufacturing apparatus includes a preheater 1, a calcining furnace 2, a rotary kiln 3, and a clinker cooler 4.

  The calcining furnace 2 is provided with an inlet 12 for feeding the recycled raw fuel into the calcining furnace 2, and a recycled raw fuel supply device 11 for supplying a recycled raw material is connected to the inlet 12. Moreover, the calciner 2 is provided with a burner 17, and a coal supply device 13 is connected to the burner 17 so as to supply coal as a main fuel. A fineness setting device 14 for adjusting the fineness of supplied coal is connected to the coal supply device 13.

  The preheater 1 is composed of a multistage cyclone in which a plurality of cyclones 1a to 1e are connected in multiple stages. A duct 1f connecting the uppermost cyclone 1e and the second cyclone 1d from the top is provided with an inlet 1g for supplying cement raw material, and a cement raw material supply device 16 for supplying the cement raw material is provided at the inlet 1g. It is connected. A fan 5 that attracts exhaust gas from the cyclone 1e is connected to the cyclone 1e. Further, a temperature detector 6 for measuring the temperature of exhaust gas from the cyclone 1a is provided in a duct 1h connecting the lowest cyclone 1a and the second cyclone 1b from the bottom. The cyclone 1a and the rotary kiln 3 are communicated via a chute 18, and the cyclone 1a and the calcining furnace 2 are communicated via an upper duct 1J.

  The temperature detector 6, the recycled raw fuel supply device 11, the coal supply device 13, and the fineness setting device 14 are each electrically connected to a control device 15 that controls the operation of the cement manufacturing device. The control device 15 includes a storage unit 15a that stores in advance a change with time in the temperature change of the combustion gas when the supply amounts of various coals and recycled raw fuels are changed, and a storage unit from the data received from the temperature detector 6 A calculation unit 15b that calculates a change over time similar to the change over time stored in 15a, a comparison unit 15c that compares the change over time stored in the storage unit 15a with the change over time calculated by the calculation unit 15b, and a coal supply And a control unit 15d electrically connected to the device 13 and the fineness setting device 14, respectively.

  FIG. 2 shows an example of a graph of change over time stored in the storage unit 15a. FIG. 2 is measured by the temperature detector 6 when the supply amount is increased by 1 ton / hr (unit supply amount) for each of the three types of coal and the four types of recycled raw fuels, based on the increase of the supply amount. It shows how the temperature change of the temperature changes (time-dependent change).

Next, operation | movement of the cement manufacturing apparatus based on Embodiment of this invention is demonstrated based on FIG.
The recycled raw fuel supplied by the recycled raw fuel supply device 11 is input to the calcining furnace 2 through the input port 12. The coal whose fineness is adjusted by the fineness setting device 14 is supplied to the burner 17 by the coal supply device 13. The recycled raw fuel charged into the calciner 2 is burned by a burner 17 that burns with coal as fuel. The combustion gas generated by the combustion in the calcining furnace 2 enters the cyclone 1a via the upper duct 1J and flows upward in the preheater 1. That is, the combustion gas sequentially flows through the cyclones 1a to 1e.

  On the other hand, the cement raw material supplied by the cement raw material supply device 16 is input into the duct 1f through the input port 1g. The input cement raw material moves downward in the preheater 1. At this time, the cement raw material is preheated by exchanging heat with the combustion gas flowing upward in the preheater 1, and calcium carbonate, which is the main component of limestone in the cement raw material, is decomposed into calcium carbide and carbon dioxide gas. Here, the degree of decomposition of the cement raw material means the degree of progress of the decomposition reaction in which calcium carbonate is decomposed into calcium carbide and carbon dioxide gas.

  The combustion gas that has circulated to the cyclone 1e is attracted by the fan 5 and discharged from the cement manufacturing apparatus. On the other hand, the cement raw material preheated by the preheater 1 enters the rotary kiln 3 and is fired to become a cement clinker, which is sent to the clinker cooler 4. The cement clinker sent to the clinker cooler 4 is cooled by exchanging heat with the cooling gas.

Next, a combustion state monitoring method when the recycled raw fuel is burned in the calciner 2 will be described.
Usually, management is performed so that the measurement value obtained by the temperature detector 6 is constant (a certain set temperature). For example, when the control device 15 recognizes that the measured value by the temperature detector 6 has decreased, the control unit 15d operates the fineness setting device 14 to reduce the fineness of coal, or the coal supply device 13 The measured value by the temperature detector 6 is adjusted to the set temperature by increasing the coal supply amount by operating the or by combining them.

  However, as described above, when recycled raw fuel or low-grade coal is used, the combustion characteristics in the calcining furnace 2 may change. When the combustion characteristic changes, the relationship between the measured value by the temperature detector 6 and the degree of decomposition of the cement raw material also changes, so that the measured value by the temperature detector 6 becomes the conventional set temperature even though the combustion characteristic has changed. Even if it manages so that it may become, the decomposition degree of a cement raw material cannot be kept constant. Therefore, it is necessary to determine whether or not the combustion characteristics in the calciner 2 have changed.

  In order to determine whether or not the combustion characteristics in the calcining furnace 2 have changed, first, the amount of recycled raw fuel supplied by the recycled raw fuel supply device 11 is changed. Changing the supply amount of recycled raw fuel does not only include intentionally changing the supply amount, but when changing the lot of recycled raw fuel, the supply amount is inevitably and temporarily changed. It also includes changes.

  For example, when the supply amount of recycled raw fuel is increased, combustion in the calcining furnace 2 becomes intense, and the measured value by the temperature detector 6 gradually increases, so the supply amount of recycled raw fuel increases. The temperature difference between the measurement value obtained by the temperature detector 6 and the measurement value obtained by the temperature detector 6 gradually increases. Based on the measured value by the temperature detector 6, the calculation unit 15b in the control device 15 changes with time of this temperature difference per unit supply amount of the recycled raw fuel, that is, the combustion gas per ton / hr of the recycled raw fuel. Calculate the change in temperature over time.

  Subsequently, the comparison unit 15c compares the calculated temporal change with the temporal change stored in the storage unit 15a. Here, the temporal change stored in the storage unit 15a is a temporal change obtained when the supply amount of the same type of recycled raw fuel is increased. When the time-dependent change of both has shifted | deviated as a whole, the comparison part 15c determines with the combustion characteristic in the calcining furnace 2 having changed.

  For example, as shown in FIG. 3A, the calculated temperature change (broken line) is different from the time change (solid line) stored in the storage unit 15a in the final temperature difference (gain). If there is no increase in the temperature change, the measured value by the temperature detector 6 does not change in the steady state compared to before increasing the supply amount of recycled raw fuel. Therefore, since the conventional management method cannot recognize that the combustion characteristics have changed, the change in the decomposition degree cannot be recognized until the decomposition degree of the cement raw material is actually measured.

  Further, for example, as shown in FIG. 3B, the calculated temporal change (broken line) is larger in overall temperature change than the temporal change (solid line) stored in the storage unit 15 a. If at least one of the supply amount of recycled raw fuel, the supply amount of coal, and the fineness of coal is not changed, the supply amount of recycled raw fuel is increased in a steady state. The measured value by the temperature detector 6 is higher than before. In this case, since the combustion characteristics in the preheater 1 have changed, the relationship between the measured value by the temperature detector 6 and the degree of decomposition of the cement raw material has also changed. However, in the conventional management method, it is impossible to determine whether the measured value by the temperature detector 6 has simply deviated from the set temperature or whether the combustion characteristic has changed, and the measured value by the temperature detector 6 is set. In order to adjust the temperature, the supply amount of coal, the fineness of coal, or the supply amount of recycled raw fuel is changed. Then, as described above, since the decomposition degree of the cement raw material changes, it is necessary to reset a new set temperature.

  In order to calculate a new set temperature, a database recording combustion characteristics for each type of main fuel and recycled raw fuel is prepared. As shown in FIG. 4, this database is a collection of data actually measured during operation of the cement manufacturing apparatus according to this embodiment. From this database, the relationship between the measured value by the temperature detector 6 and the degree of decomposition of the cement raw material can be found under various conditions, whereby a new set temperature can be calculated.

  Specifically, the gain, dead time, and time constant are read from the change over time in the temperature change caused by the change in the supply amount of recycled raw fuel. If the read dead time or time constant becomes longer than the dead time or time constant in the database, it means that the combustibility has deteriorated. increase. On the other hand, when the read gain is larger than the gain of the database, it means that the combustibility is improved, and therefore the set temperature is lowered. However, apart from flammability, there is an optimum temperature range for the degree of decomposition, and if it falls outside that range, the contribution rate to the degree of decomposition of combustion heat will decrease significantly, so the setting is managed so that it falls within that range . In this way, the degree of decomposition can be kept constant.

  In this way, the change in the combustion characteristics of the fuel can be recognized by comparing the change over time calculated by the calculation unit 15b with the change over time stored in the storage unit 15a, so that the combustion of the fuel used in the cement manufacturing process can be recognized. Even if the characteristics change, the decomposition degree of the cement raw material can be kept constant.

In this embodiment, the temperature detector 6 is provided in the duct 1h. However, the temperature detector 6 is not limited to this form, and may be provided anywhere in the preheater 1.
Further, in this embodiment, the calcining furnace 2 is provided with the input port 12 for the recycled raw fuel, but the input port 12 is provided upstream of the calcining furnace 2 as a gas flow (for example, the kiln bottom 19). If it is the structure which provides, flammability can be evaluated. The combustion characteristics of the calcining furnace 2 change due to the combustion of the input recycled raw fuel, and this change can be measured as a change in the combustion characteristics of coal. When the combustibility deteriorates due to the use of recycled raw fuel, the combustibility of coal itself deteriorates.

  Furthermore, in this embodiment, in order to determine whether or not the combustion characteristics in the calciner 2 have changed, first, the supply amount of the recycled raw fuel by the recycled raw fuel supply device 11 is changed. The amount of coal supplied to the burner 17 may be changed.

  2 Calciner.

Claims (1)

In a calcining furnace in a cement manufacturing process, a combustion state monitoring method when burning recycled raw fuel and main fuel,
Changing the amount of the recycled raw fuel supplied to the upstream side as the gas flow from the calcining furnace or the calcining furnace, or changing the amount of the main fuel supplied to the calcining furnace When,
Measuring the temperature of the combustion gas in the calciner;
From the measurement result of the temperature of the combustion gas, a step of computing the time course of temperature change of the recycle raw fuel to the combustion gas per amount of change in the unit supply amount of the main fuel,
And comparing the calculated time-dependent change with time-dependent changes in the temperature change of the combustion gas for the various recycled raw fuels or main fuels prepared in advance.

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