JP4734769B2 - Cogeneration plant operation method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for operating a cogeneration plant that supplies electric power and steam using a thermoelectric variable cogeneration unit, and in particular, has a visible water vapor prevention device to prevent visualization of water vapor contained in exhaust gas. The present invention relates to a method for operating a cogeneration plant and an apparatus for the same that can minimize the operating cost under constraints.
[0002]
[Prior art]
The thermoelectric variable cogeneration unit, which is composed of a steam-injection gas turbine as the main engine and added with an exhaust heat recovery boiler that generates steam using the exhaust heat of the gas turbine, gasses the steam from the exhaust heat recovery boiler. Since power generation efficiency (power generation capacity) can be increased by inputting to the turbine, not only power and steam can be supplied in parallel, but also the power output amount and steam output amount can be adjusted in a complex manner.
[0003]
As shown in FIG. 7, the cogeneration unit is composed of a steam injection gas turbine 50 and an exhaust heat recovery boiler 51, and the supplied air is compressed by a compressor 53, sent to a combustion chamber 54, and fuel supplied to the combustion chamber 54 And the turbine 55 is driven to generate power by the generator G. The combustion exhaust gas is supplied to the exhaust heat recovery boiler 51 for heat recovery, and the steam obtained by supplying water to the exhaust heat recovery boiler 51 is obtained. While being sent to the demand system 58, a part of the steam is supplied to the combustion chamber 54 as a gas turbine case injection steam and to the turbine 55 together with the compressed air via the nozzle 56 to adjust the amount of electric power and the amount of steam.
[0004]
As described above, the variable thermoelectric cogeneration unit can supply electric power and steam, and increases the power generation efficiency by injecting a part of the steam generated from the exhaust heat recovery boiler into the gas turbine. The amount of steam supplied and the amount of power generation can be made variable.
[0005]
FIG. 6 is a graph showing the fuel-feeding steam amount / power generation amount characteristic of the cogeneration unit.
[0006]
This characteristic diagram shows the characteristics of the amount of steam supplied and the amount of fuel consumed when the power generation amount is 1000 to 6000 kw.
[0007]
The air supply steam amount and the fuel consumption fuel characteristics are determined by the characteristics of the gas turbine and the exhaust heat recovery boiler and the constraint conditions, and the region connected by points A to F is the operation region. Here, the line connecting point A and point B is determined by the upper limit of the amount of steam injected into the gas turbine, and the line connecting point B and point C is determined by the limit of the gas turbine inlet temperature upper limit value. The line connecting D is determined by the limit of the generated steam amount upper limit value, and the line connecting point D, point E, and point F is determined by the gas turbine output lower limit value.
[0008]
Here, if the power demand and the steam demand are determined, even if the same fuel is consumed, the power output amount and the steam output amount can be adjusted in a composite manner by adjusting the injection steam amount as described above. There will be a lot of driving points. In addition, by taking into account the supply of electric power / steam from the outside, the range of operating points is further expanded and the amount of fuel consumption is also different. Therefore, if the operating points are varied, the operating cost will also vary. In addition, since the power demand and the steam demand change constantly, it is difficult to determine the operation point so as to minimize the operation cost.
[0009]
In view of this, the present applicant firstly performed load demand prediction of electric power and steam in Japanese Patent Application Laid-Open No. 2001-212696 (title of the invention; method and apparatus for operating a cogeneration plant). Determine the power and steam output of the cogeneration unit that minimizes the operating cost under the given restrictions, and based on that, create an operation plan schedule under the given restrictions and decide whether to start or stop each cogeneration unit At the same time, we proposed a cogeneration plant operation method that commands start / stop and operation points to the individual control unit of the cogeneration unit.
[0010]
[Problems to be solved by the invention]
By the way, in the operation management system of the conventional cogeneration plant and the invention of the prior application, the operation point at which the operation cost is minimized is determined by giving priority to the operation efficiency of the plant (secondary energy generation amount with respect to the primary energy amount). However, the visible water vapor of exhaust gas discharged from the exhaust heat recovery boiler is not considered.
[0011]
Since this visible water vapor is harmless except for the point that damages the landscape, it has been ignored when operating in a power plant or a facility in a factory with a large site.
[0012]
However, in a cogeneration plant mainly in urban areas, it is an essential condition to prevent white smoke from the chimney so as not to cause inconvenience in the daily life of neighboring residents.
[0013]
Therefore, if a visible water vapor prevention device is added to the operation management system to prevent white smoke, energy loss occurs both when the exhaust gas temperature is raised and when the exhaust gas humidity is lowered. In an operation plan that ignores the characteristics of the water vapor prevention device, problems occur in operation efficiency and load demand followability.
[0014]
In addition, in the case of a system consisting of multiple cogeneration units, if it is operated without considering the energy loss due to the prevention of visible water vapor, there will be a problem that the unit startup will be delayed when the load demand increases and stable supply will not occur .
[0015]
As described above, in an environment where the prevention of visible water vapor is a limiting condition, the operation method that optimizes only the operation efficiency does not necessarily have the minimum operation cost and is not economically advantageous.
[0016]
Therefore, the object of the present invention is to solve the above-mentioned problems, and measure and predict the atmospheric temperature and humidity in addition to the prediction of power demand and steam demand, and perform an optimal operation plan with the constraint of preventing visible water vapor. Another object of the present invention is to provide a cogeneration plant operating method and apparatus capable of improving total energy efficiency and stably supplying power and steam.
[0017]
[Means for Solving the Problems]
In order to achieve the above objectives, it is composed of a steam injection gas turbine as a main engine and a waste heat recovery boiler, and a thermoelectric variable cogeneration unit is equipped with a visible water vapor prevention device, and power and steam are supplied by the thermoelectric variable cogeneration unit. In the cogeneration plant operating method, the load demand amount of power and steam is predicted and the atmospheric conditions of atmospheric temperature and humidity are predicted, and based on the prediction result, the restriction that the water vapor contained in the exhaust gas is not visualized Determine the power and steam output of the cogeneration unit with the lowest operating cost under the control, and based on that, set up an operation plan schedule under the given restrictions, and start / stop each control unit to control each cogeneration unit. stop, upon commanding the operation point, thermoelectric variable Geoje at any atmospheric temperature and humidity conditions Modeling the relationship between the unit's fuel consumption, power generation amount, and generated steam, obtaining the operating point where the fuel consumption, generated steam amount, and power generation amount of the cogeneration unit to meet the power demand and steam demand are determined, and at that operating point Considering whether visible water vapor is generated at the temperature and humidity of the exhaust gas, when performing visible water vapor prevention, determine the operating point that minimizes operating costs by taking into account the heat loss due to the exhaust gas temperature rise due to the visible water vapor prevention device This is a method for operating a cogeneration plant.
[0019]
The invention of claim 2 comprises a steam injection type gas turbine as a main engine and an exhaust heat recovery boiler, and includes a thermoelectric variable cogeneration unit with a visible water vapor prevention device, and supplies electric power and steam by the thermoelectric variable cogeneration unit. Based on the demand and operation condition planning unit that predicts the atmospheric conditions of the atmospheric temperature and humidity, and the prediction result of the demand and operation condition planning unit in the cogeneration plant operation device Based on the plan determined by the optimal operation planning unit and the optimal operation planning unit that determines the power and steam output amount of the cogeneration unit that minimizes the operation cost under the restriction that the water vapor contained in the exhaust gas is not visualized, Establish an operation plan schedule under given restrictions, and start / stop each control unit that controls each cogeneration unit And a separate unit command unit for commanding the operation point, and optimal operation plan unit models the thermoelectric variable cogeneration unit consumption and power generation quantity and generation steam relation fuel at any atmospheric temperature and humidity conditions, power demand In order to meet the demand for steam and steam, the operating point where the fuel consumption of the cogeneration unit, the amount of generated steam and the amount of power generation are planned is obtained, and the visible water vapor is generated considering the temperature and humidity of the exhaust gas at that operating point. This is a cogeneration plant operating device that determines the operating point at which the operation cost is minimized in consideration of heat loss due to the exhaust gas temperature rise caused by the visible water vapor preventing device .
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[0022]
FIG. 1 shows a cogeneration plant operating apparatus according to the present invention.
[0023]
First, there are a plurality of cogeneration units 10 to supply desired power / steam to the power / steam demand plant 11, and these may have the same capacity or different capacity.
[0024]
Each of the cogeneration units 10 and 10 is controlled by an individual control device 12. The cogeneration unit 10 includes a visible water vapor prevention device 13 for preventing white smoke, and the individual control device 12 can also control the visible water vapor prevention device 13.
[0025]
The power / steam demand plant 11 receives power / steam supply from the cogeneration units 10, 10 to satisfy the power demand / steam demand according to the operation status, and steam from the auxiliary boiler 14, and power from the power company 15, etc. Receive the supply.
[0026]
The power demand / steam demand of the power / steam demand plant 11 is output to the cogeneration overall control device 16.
[0027]
The cogeneration integrated control device 16 includes a demand and operation condition planning unit 17, a cogeneration plant constraint setting unit 18, an individual constraint setting unit 19, an optimum operation calculation unit 20, and an individual unit command unit 21.
[0028]
The demand and operating condition planning unit 17 plans changes in operating conditions based on changes in electric power demand / steam demand and changes in atmospheric temperature and humidity from the present to a certain time ahead. The power demand / steam demand plan may be a method of automatically predicting from past results, a method of manual input by an operator, or a method of inputting a plan planned in advance. Changes in atmospheric temperature and humidity are predicted based on weather forecast data or past results. A method of manual input by an operator or a method of inputting a plan planned in advance may be used.
[0029]
The cogeneration plant operation restriction setting unit 18 sets a restriction condition for operating the plant. As an example, the power supply from the electric power company 15 or the like is set to a constant value, and other constraint conditions for operating the plant are set.
[0030]
The individual unit constraint setting unit 19 sets constraint conditions in the individual cogeneration unit. As an example, information such as a plant that is out of control due to a manual mode or a failure, a plant that must be stopped after a predetermined time for maintenance or the like is set.
[0031]
The optimal operation calculation unit 20 generates power / steam generated by the cogeneration unit 10 based on the power demand / steam demand plan from the demand and operation condition planning unit 17 and the atmospheric prediction and the constraint conditions from the cogeneration plant operation constraint setting unit 18. A combination of supply power and supply steam from the outside of the electric power company 15 or the auxiliary boiler 14 is derived, and based on this, the number of operating units / operating points of the cogeneration unit 10 is calculated. In this case, the optimum operation calculation unit 20 calculates the one that minimizes the operation cost in consideration of the operation state of the visible water vapor prevention device 13 in each cogeneration unit 10.
[0032]
The individual unit command unit 21 selects a plant to be operated based on the start / stop from the optimum operation calculation unit 20 and the operation point based on the individual unit restrictions and the total operation time and the latest stop time in the individual cogeneration unit 10. The individual unit control device 12 is instructed to start / stop and operate points. In this case, by considering the total operation time, for example, the operation time of each cogeneration unit 10 can be made uniform, and a maintenance schedule can be established.
[0033]
FIG. 2 shows details of the optimum operation calculation unit 20, which models the relationship between the fuel consumption, the amount of delivered steam, and the amount of power generation of the cogeneration unit 10, and further includes an auxiliary boiler 14 and the like. Minimum cost according to the characteristics of the gas turbine cogeneration unit to meet the power demand and steam demand based on the input air temperature / humidity, power demand, steam demand, fuel cost, water supply cost, power purchase cost at the plant Plan the operation pattern (steam amount, power generation amount, number of units operated, gas turbine thermoelectric ratio, auxiliary boiler steam amount, purchased power amount).
[0034]
The optimum operation plan based on the characteristics of the gas turbine cogeneration unit means that the gas turbine inlet temperature and the amount of injected steam are constrained, and the minimum cost operation pattern that satisfies the target power generation amount and steam generation amount under the restricted conditions is searched. It is to be.
[0035]
Here, the optimum operation calculation unit 20 can calculate the exhaust gas temperature and the exhaust gas humidity in an arbitrary operation state from the gas turbine cogeneration unit model. It is also possible to limit the exhaust gas temperature and exhaust gas humidity and to plan an operation pattern that minimizes the cost under the constraint conditions.
[0036]
The visible water vapor prevention condition is to measure or calculate the temperature and humidity of the exhaust gas, and determine whether the water vapor in the exhaust gas released into the atmosphere is visualized from these and the atmospheric temperature and humidity. Specifically, in the middle of transition from the exhaust gas temperature / humidity condition to the atmospheric temperature / humidity condition, the operation is performed so as not to pass the inside of the saturated water vapor curve.
[0037]
FIG. 3 is a diagram showing changes in state due to the visible water vapor prevention condition and the visible water vapor prevention device.
[0038]
In the air diagram of FIG. 3A, it is assumed that the state (temperature, humidity) of the exhaust gas discharged from the cogeneration unit is at point p and the state of the atmosphere is at point q. If the exhaust gas at this point p is released to the atmosphere as it is, as shown by the line l, it passes through the saturated water vapor curve s (liquid phase side) and is visualized to generate white smoke. Therefore, when the temperature of the exhaust gas to be discharged is raised and the absolute humidity is lowered and released to the atmosphere at the point r, it passes through the outside of the saturated water vapor curve s (gas phase side) as shown by the line m, and the visualization water vapor prevention operation Can be done.
[0039]
When water vapor is visualized at the actual control level of the cogeneration unit 10, the locally controlled visible water vapor prevention device 13 is activated to limit the heat recovery from the exhaust gas in the exhaust heat recovery boiler, and the exhaust gas temperature to be released Visualized water vapor prevention operation is performed by raising. That is, as shown in the air diagram of FIG. 3B, the temperature of the exhaust gas is raised from the state of the point p without changing the absolute humidity to the state of the point t, and then released into the atmosphere in that state. As shown by n, it passes through the outer side (gas phase side) of the saturated water vapor curve s, and the generation of visualized water vapor can be prevented.
[0040]
FIG. 4 shows a specific example of the visible water vapor prevention device 13 in the cogeneration unit 10.
[0041]
First, exhaust gas from the gas turbine 25 passes through the primary exhaust heat recovery boiler 26, passes through the secondary exhaust heat recovery boiler 27, and is exhausted by the collecting chimney 28. The primary exhaust heat recovery boiler 26 and the secondary exhaust heat recovery boiler are then exhausted. It is assumed that the steam generated at 27 is supplied from the drum 29 to the plant side as an air supply steam 30 and partly as nozzle steam or case steam to the gas turbine 25 to control the gas turbine thermoelectric ratio.
[0042]
As shown in FIGS. 4A and 4B, the visible water vapor prevention device 13 includes a bypass circuit 31 that bypasses the exhaust gas from the primary exhaust heat recovery boiler 26 to the collecting chimney 28, as shown in FIG. 4), a damper 32 is provided on the inlet side of the bypass circuit 31, and the exhaust gas from the primary exhaust heat recovery boiler 26 is exhausted to the collecting chimney 28 through the bypass circuit 31, and FIG. As shown, a damper 33 is provided on the outlet side of the bypass circuit 31, and the exhaust gas from the primary exhaust heat recovery boiler 26 is mixed with the exhaust gas that has passed through the bypass circuit 31 and passed through the secondary exhaust heat recovery boiler 27. There are things that exhaust to the chimney 28.
[0043]
In addition to the illustration, the visible water vapor prevention device 13 has a condenser installed downstream of the exhaust heat recovery boiler. However, since visible water vapor prevention using only the condenser requires a cooling cost, the temperature rises. The method of using together is preferable.
[0044]
The visible water vapor prevention device 13 determines the exhaust gas temperature so that the water vapor in the exhaust gas released into the atmosphere is not visualized from the humidity of the exhaust gas (calculated from the gas turbine operating conditions if direct measurement is not possible) and the atmospheric temperature humidity. Calculate and, if the current exhaust gas temperature is lower than this value, raise the exhaust gas temperature that is activated to release visible water vapor.
[0045]
In this visualization prevention method, since the absolute humidity of the exhaust gas does not change, in order to reduce energy loss, the cogeneration integrated control device 16 (see FIG. 1) needs to reduce the amount of steam injected into the gas turbine.
[0046]
The normal steam generation amount (air supply steam amount) is determined by Equation 1, but the steam generation amount (air supply steam amount) during operation of the visualized water vapor prevention device 13 is Equation 2.
[0047]
Generated steam amount = Generated steam from boiler-Injection steam amount of gas turbine Formula 1
Steam generated = Steam generated in boiler-Gas turbine injection steam-Steam that should have been generated by bypassed exhaust gas Equation 2
The optimal operation calculation unit 20 performs the following processing when considering prevention of visible water vapor.
[0048]
(1) Draw a tangent line from the atmospheric temperature / humidity to the saturated water vapor curve to set the allowable range of exhaust gas temperature / humidity.
[0049]
(2) Add the gas turbine exhaust gas bypass model to the operation plan. That is, with the exhaust gas bypass amount as a variable, the exhaust gas temperature rise relative to the bypass amount and the decrease in the amount of steam generated from the exhaust heat recovery boiler are added to the operation evaluation formula.
[0050]
(3) Under the constraint of the original gas turbine cogeneration unit and the constraint of (1), a solution that minimizes the evaluation formula (operation cost calculation formula) is searched for in the operation pattern that takes into account (2).
[0051]
(4) A plan that takes into account future operating conditions is performed by using atmospheric temperature, humidity, power demand, and steam demand as predicted values.
[0052]
In addition, when the visualization water vapor prevention is not an absolute condition, how far the exhaust gas temperature / humidity state is from the tangent line of (1) can be added to the evaluation formula.
[0053]
Next, a specific example of the optimum operation plan under the visualization water vapor prevention condition will be described with reference to FIG.
[0054]
In FIG. 5, the area surrounded by points A, B, C, D, E, and F is the original gas turbine characteristics (fuel-steaming steam amount / power generation amount characteristics) of the cogeneration unit described in FIG. When visualizing water vapor is taken into account, the characteristics in any given atmospheric condition are the points A ′, B ′, C, D, E, and The region surrounded by F ′.
[0055]
The calculation of the operating point by the optimum operation calculation unit 20 is performed as follows.
[0056]
(A) Now, for a certain power demand / steam demand, the optimum operating point not considering the prevention of visible water vapor is point H in the fuel-sending steam amount / power generation amount characteristic diagram of the cogeneration unit in FIG.
[0057]
(B) When the prevention of visible water vapor is taken into consideration, first, the range in which the gas turbine can be operated is narrowed within the region surrounded by A ′ to F ′ in FIG. 5 due to exhaust temperature / exhaust humidity restrictions.
[0058]
(C) To make the power generation amount the same as the point H in this range, the fuel is increased along the power amount constant line.
[0059]
(D) In this case, the amount of heat to the exhaust heat recovery boiler also increases. By using the increased amount of exhaust gas to increase the exhaust gas temperature, the amount of generated steam is eliminated, and the visible water vapor prevention condition is set. Make it easier to establish. However, since the fuel flow rate, exhaust gas bypass amount, exhaust temperature, and exhaust humidity are calculated as simultaneous equations, these values are uniquely obtained.
[0060]
(E) As a result, the (apparent) operating point I of the gas turbine cogeneration unit is determined. The actual generated steam is the same as the H point by the exhaust gas bypass.
[0061]
The operation point I is operated by the individual control unit 12 from the individual unit command unit 21 to operate the cogeneration unit 10 based on the operation point I (fuel consumption, water supply amount, thermoelectric power adjustment) and visible water vapor. The bypass steam amount is controlled by the prevention device 13, and power load tracking / steam load tracking according to demand prediction is performed automatically or semi-automatically by giving an instruction to the operator.
[0062]
In addition, since the optimum operation point constantly changes due to the demand prediction change and the atmospheric prediction change, an optimum plan is created every time and the operation point is searched for operation.
[0063]
【The invention's effect】
In short, according to the present invention, the prevention of visible water vapor is a limiting condition, and the optimum operation plan is performed so that the operation cost is minimized under the restriction, thereby increasing the total energy efficiency and the power / steam according to the demand. Can be stably supplied.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of the present invention.
2 is a detailed diagram of an optimum operation calculation unit in FIG. 1. FIG.
FIG. 3 is an air line diagram for explaining the state change by the visible water vapor prevention condition and the visible water vapor prevention device in the present invention.
FIG. 4 is a diagram showing a specific example of a visible water vapor preventing apparatus according to the present invention.
FIG. 5 is a diagram for explaining an example of an operation plan under a visible water vapor prevention condition based on a fuel-send steam amount / power generation amount characteristic diagram in the present invention.
FIG. 6 is a diagram showing a fuel-sending steam amount / power generation amount characteristic diagram of a thermoelectric variable type gas turbine.
FIG. 7 is a diagram showing a cogeneration unit.
[Explanation of symbols]
10 Thermoelectric Variable Cogeneration Unit 12 Individual Control Device 13 Visible Water Vapor Prevention Device 17 Demand and Operating Condition Planning Unit 20 Optimal Operation Planning Unit 21 Individual Control Unit Command Unit

Claims (2)

In the operation method of the cogeneration plant, which is composed of a steam injection type gas turbine and a waste heat recovery boiler, the thermoelectric variable cogeneration unit is equipped with a visible water vapor prevention device, and the thermoelectric variable cogeneration unit supplies electric power and steam. Predicting the load demand for electric power and steam and predicting atmospheric conditions of atmospheric temperature and humidity, and based on the prediction results, the operating cost under the restriction that the water vapor contained in the exhaust gas is not visualized is minimized upon determining the power and steam output of cogeneration units, based thereon, sets a driving schedule schedules under given restriction, the individual control device for controlling each of the cogeneration unit, start / stop commands the operation point , Fuel consumption and power generation of thermoelectric variable cogeneration unit under any atmospheric temperature and humidity conditions・ Modeling the relationship between the generated steam and obtaining the operating point where the fuel consumption, generated steam amount and power generation amount of the cogeneration unit to meet the electric power demand and steam demand are calculated and visualized with the temperature and humidity of the exhaust gas at that operating point Considering whether water vapor is generated and performing visible water vapor prevention , the co-generation is characterized in that the operating point at which the operation cost is minimized is determined in consideration of heat loss due to the exhaust gas temperature rise by the visible water vapor prevention device. How to operate the plant. In a cogeneration plant operating device that consists of a steam injection gas turbine as a main engine and a waste heat recovery boiler, a thermoelectric variable cogeneration unit is equipped with a visible water vapor prevention device, and electric power and steam are supplied by the thermoelectric variable cogeneration unit, The demand and operating condition planning unit that predicts the load demand of electric power and steam and the atmospheric conditions of atmospheric temperature and humidity, and the water vapor contained in the exhaust gas based on the prediction results of the demand and operating condition planning unit The optimal operation planning unit that determines the power and steam output of the cogeneration unit that minimizes the operating cost under the restriction that does not visualize the operation, and the operation under the given limitation based on the plan obtained by the optimal operation planning unit Establish a plan schedule and specify start / stop and operation points for individual control devices that control each cogeneration unit. And a separate unit command unit, and optimal operation plan unit that models the thermoelectric variable cogeneration unit consumption and power generation quantity and generation steam relation fuel at any atmospheric temperature and humidity conditions, the power demand and steam demand When preventing the visible water vapor by obtaining the operating point where the fuel consumption of the cogeneration unit to satisfy, the amount of generated steam and the amount of power generation are planned and considering whether the visible water vapor is generated at the temperature and humidity of the exhaust gas at that operating point In addition, an operating device for a cogeneration plant is characterized in that an operating point at which the operation cost is minimized is determined in consideration of heat loss due to an increase in exhaust gas temperature by the visible water vapor prevention device.

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