Control method for steam generator, steam generator, and steam generator system

Abstract

To provide a control method of a steam generator which can reduce steam with a simple approach and can enhance energy use efficiency, and a steam generator and a steam generation system.SOLUTION: According to an aspect of the present invention, a control method of a steam generator 30 is provided, the steam generator 30 comprising: a can body 31 having an input port 31A into which an adsorbent is input and a discharge port 31B for discharging adsorbent; a steam supply line 32 for supplying steam to the can body 31; and a heat exchanger 33 arranged in the can body 31. The adsorbent exhibits adsorption of micropore-filling type, and a flow rate of steam which is supplied to the can body 31 is controlled to be at a flow rate which is determined on the basis of Expression (1): ((minj=mad×(qeq-q0) ...(1)), In Expression (1), minj is the flow rate (kg / h) of the adsorbent, mad is the flow rate (kg / h) of the adsorbent when it is completely dry, qeq is an equilibrium adsorption amount (%) of the adsorbent at a temperature at which liquid boils, and q0 is an adsorption amount (%) of the adsorbent when it is input.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control method for a steam generator, a steam generator, and a steam generator system. [Background technology]

[0002] In waste treatment facilities, waste heat is generated when waste is incinerated, and currently, utilizing this waste heat is considered important. While it is possible to transport the waste heat through pipes, this becomes difficult over long distances.

[0003] Therefore, a zeolite boiler has been proposed that uses this waste heat to degas water vapor from zeolite, and then supplies steam to the zeolite from which the water vapor has been degassed at a location with a heat demand to generate heat (see Non-Patent Literature 1). The zeolite boiler utilizes the principle that zeolite generates heat when it adsorbs moisture. With this zeolite boiler, it is possible to degas water vapor from the zeolite using waste heat, and the problem of long-distance transport can also be solved.

[0004] In recent years, from a carbon neutrality perspective, efforts have been made to reduce fuel (steam) consumption and improve energy efficiency in zeolite boilers. In zeolite boilers, it has been thought that maximizing steam adsorption on the zeolite leads to better energy efficiency, as the zeolite releases more heat when it adsorbs more steam. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Shoichi Fujii et al., "Design of zeolite boiler in thermochemical energy storage and transport system utilizing unused heat from sugar mill", Applied Energy, March 15, 2019, Vol. 238, pp. 561-571

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in a zeolite boiler of an indirect heat exchange method that generates steam while continuously flowing zeolite and generates steam by heat exchange between the heated zeolite and water, the zeolite is discharged at a high temperature. That is, the zeolite is discharged with excess heat. Therefore, when the zeolite adsorbs steam to the maximum extent, the energy utilization efficiency is low. In addition, in order to improve the energy utilization efficiency, performing complex numerical analysis requires a great deal of effort.

[0007] The present invention has been made to solve the above problems. That is, an object of the present invention is to provide a control method for a steam generator, a steam generator, and a steam generation system including the same, which can reduce steam by a simple method and can increase energy utilization efficiency.

Means for Solving the Problems

[0008] [1] A control method for a moving bed type steam generator comprising a can body having an inlet for continuously feeding an adsorbent at the upper part and an outlet for continuously discharging the adsorbent at the bottom, a steam supply line having one end connected to the can body for supplying steam to the adsorbent in the can body, and a heat exchanger disposed in the can body through which a liquid flowing from the bottom of the can body toward the upper part exchanges heat with the heated adsorbent, wherein the adsorbent exhibits micropore filling type adsorption, and the flow rate of the steam supplied to the can body is controlled to be a flow rate determined based on the following formula (1), m inj =m ad ×(q eq -q0) …(1) In the above formula (1), m inj is the steam flow rate (kg / h), m ad is the flow rate (kg / h) of the adsorbent at absolute dryness, q eq is the equilibrium adsorption amount (%) of the adsorbent at the temperature at which the liquid boils, and q0 is the adsorption amount (%) of the adsorbent at the time of feeding, a control method of a steam generator.

[0009] [2] The control method of the steam generator according to [1] above, wherein the adsorbent is an adsorbent conforming to the Dubinin-Astakhov formula or the Langmuir formula.

[0010] [3] The control method of the steam generator according to [2] above, wherein the adsorbent is at least one of zeolite, silica gel, and activated carbon.

[0011] [4] The control method of the steam generator according to any one of [1] to [3] above, wherein the liquid is water.

[0012] [5] A can body having an inlet for continuously feeding an adsorbent at the upper part and an outlet for continuously discharging the adsorbent at the bottom, a steam supply line having one end connected to the can body for supplying steam to the adsorbent in the can body, a heat exchanger disposed in the can body through which a liquid that exchanges heat with the heated adsorbent flows from the bottom to the upper part of the can body, and a control unit for controlling the flow rate of the steam flowing through the steam supply line. The adsorbent exhibits micropore filling type adsorption, and the control unit controls the flow rate of the steam so that the flow rate of the steam supplied to the can body becomes a flow rate determined based on the following formula (1), m inj =m ad ×(q eq -q0) …(1) In the above formula (1), m inj is the flow rate of the steam (kg / h), m ad is the flow rate of the adsorbent at absolute dryness (kg / h), q eq is the equilibrium adsorption amount (%) of the adsorbent at the temperature at which the liquid boils, and q0 is the adsorption amount (%) of the adsorbent at the time of feeding. A steam generator.

[0013] [6] The steam generator according to [5] above, wherein the adsorbent is an adsorbent that follows the Dubinin-Astakhov equation or the Langmuir equation.

[0014] <00001​​​​​​​​​​​​​​ According to the control method for a steam generator, the steam generator, and the steam generation system of the present invention, steam can be reduced using a simple method, and energy utilization efficiency can be improved. [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 is a schematic diagram of the steam generation system according to the embodiment. [Figure 2] Figure 2 is a graph showing the relationship between temperature and adsorption amount at the location of the zeolite boiler in simulation examples 1 to 4. [Modes for carrying out the invention]

[0019] The following describes the control method for a steam generator, the steam generator, and the steam generator system according to the present invention. Figure 1 is a schematic diagram of the steam generator system according to this embodiment.

[0020] <<<Steam generation system>>> The steam generation system 10 shown in Figure 1 comprises two steam generators 20 and 30, and a steam mixer 40 that mixes the steam generated by the steam generators 20 and 30. Steam generator 30 is located downstream of steam generator 20.

[0021] <<Steam Generator>> An existing steam generator can be used as the steam generator 20 located in the preceding stage. The steam generator 20 is equipped with a steam discharge line 22, one end of which is connected to the boiler 21 of the steam generator 20 and the other end of which is connected to the steam mixer 40. The steam discharge line 22 is equipped with a valve 22A, etc., for adjusting the flow rate of steam supplied to the steam mixer 40.

[0022] The steam generator 30 located downstream uses the adsorbent AD and a portion of the steam generated by the upstream steam generator 20. The steam generator 30 is of the movable bed type and indirect heat exchange type. The steam generator 30 mainly comprises a boiler 31, a steam supply line 32, a heat exchanger 33, and a control unit 34. The steam generator 30 may further include a liquid supply line 35 for supplying liquid to the heat exchanger 33, a steam discharge line 36 for discharging the steam generated by the heat exchanger 33 to the boiler 31, and a steam separator 37 located between the steam discharge line 36 for separating steam (e.g., water vapor) and liquid (e.g., water).

[0023] The adsorbent AD used in the steam generator 30 exhibits micropore-filling type adsorption. If the adsorbent AD exhibits micropore-filling type adsorption, then equation (1) described later can be applied. Whether the adsorbent AD exhibits micropore-filling type adsorption can be determined from the adsorption isotherm data of the adsorbent AD. Examples of adsorbent AD exhibiting micropore-filling type adsorption include adsorbents that conform to the Dubinin-Astakhov equation or the Langmuir equation. Examples of adsorbents that conform to these two equations include zeolites, silica gel, and activated carbon. Among these, zeolites are preferred because they have high heat of adsorption and high heat storage density as a heat storage material, and among zeolites, zeolite 4A and zeolite 13X are preferred because they have high differential heat of adsorption and high heat storage density.

[0024] <Can body> The container 31 has an inlet 31A at the top of the container 31 for continuously feeding in the adsorbent AD, and an outlet 31B at the bottom of the container 31 for continuously discharging the adsorbent AD. Specifically, the inlet 31A is located on the top surface of the container 31, and the outlet 31B is located on the bottom surface of the container 31.

[0025] <Steam supply line> The steam supply line 32 has one end connected to the boiler body 31 and supplies steam to the adsorbent AD placed inside the boiler body 31. Preferably, one end of the steam supply line 32 is connected to the top of the boiler body 31. Preferably, a portion of the steam generated by the steam generator 20 is used. In this case, the other end of the steam supply line 32 is connected to the steam generator 20. The steam supply line 32 is equipped with a valve 32A or the like for adjusting the flow rate of steam supplied to the boiler body 31.

[0026] <Heat exchanger> The heat exchanger 33 is located inside the boiler body 31, and a liquid flows through it that exchanges heat with the heat-generating adsorbent AD. The liquid flowing through the heat exchanger 33 flows from the bottom to the top of the boiler body 31. When the liquid exchanges heat with the heat-generating adsorbent AD, it boils and turns into steam. Water is one example of the liquid. If the liquid is water, for example, if the discharge steam pressure is 0.2 MPa, the steam will be about 120°C.

[0027] <Liquid supply line, steam discharge line, steam separator> One end of the liquid supply line 35 is connected to the heat exchanger 33. Preferably, the liquid supply line 35 is equipped with a pump 35A that pumps liquid to the heat exchanger. One end of the steam discharge line 36 is connected to the heat exchanger 33 and the other end is connected to the steam mixer 40. A steam separator 37 is interposed in the steam discharge line 36. From the viewpoint of reuse, it is preferable that the liquid separated by the steam separator 37 is returned to the liquid supply line 35.

[0028] <Department Head> The control unit 34 is for controlling the flow rate of steam supplied to the boiler 31. Specifically, the control unit 34 is electrically connected to the valve 32A and is capable of controlling the flow rate of steam supplied to the boiler 31.

[0029] The control unit 34 controls the valve 32A, etc., so that the steam flow rate becomes the flow rate determined based on the following equation (1). Alternatively, the control unit 34 may determine the steam flow rate based on the following equation (1) and control the valve 32, etc., so that the steam flow rate becomes the determined flow rate. m inj =m ad ×(q eq -q0) …(1) In the above formula (1), m inj This is the steam flow rate (kg / h), and m ad is the flow rate (kg / h) of the adsorbent AD when completely dry, and q eq Q is the equilibrium adsorption amount (%) of adsorbent AD at the boiling point of the liquid, and q0 is the adsorption amount (%) when adsorbent AD is added. In this specification, "absolutely dry adsorbent" means a state in which the moisture content of the adsorbent is 0%. Equilibrium adsorption amount q of adsorbent AD at the boiling point of the liquid eq The amount of adsorption q0 when the adsorbent AD is introduced is, for example, the amount of water adsorbed.

[0030] Flow rate of adsorbent AD when completely dry m ad This can be calculated using the following equation (2).

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[0031] Equilibrium adsorption amount q of adsorbent AD at the boiling point of the liquid eq This refers to the maximum capacity that can adsorb vapor at the boiling point of the liquid. The boiling point of the liquid is determined by the vapor pressure being supplied.

[0032] Specifically, for example, in an adsorbent that follows the Dubinin-Astakhov equation, the equilibrium adsorption amount q eq This can be expressed by the following equation (3). q eq =ρW eq …(3) In the above equation (3), ρ represents the adsorbed phase density, and W eqW represents the equilibrium adsorbate volume. eq This is expressed by the following equation (4).

number

number

[0033] Furthermore, in adsorbents that follow the Langmuir formula, q eq This can be expressed by the following equation (6).

number

[0034] Equilibrium adsorption amount q of adsorbent AD at the boiling point of the liquid eq This varies greatly depending on the type of adsorbent AD, but for example, when zeolite 4A or zeolite 13X is used as the adsorbent AD, q eq This is generally around 20% to 30%.

[0035] The amount of adsorption q0 when the adsorbent AD is introduced can be measured, for example, as follows: First, a fixed amount (for example, several kg) of the completely dry adsorbent is filled into a quantitative container and its weight is measured. Then, the adsorbent to be introduced into the steam generator is filled into the same quantitative container and its weight is measured. This weight is then compared with the weight of the completely dry adsorbent measured above to determine the amount of adsorption q0 when introduced. Accuracy is ensured by securing a fixed amount (for example, several kg). Alternatively, the amount of adsorption q0 when the adsorbent is introduced can be measured by sampling the adsorbent to be introduced into the steam generator and measuring the weight change while increasing the temperature using a thermogravimetric differential thermal analyzer (TG-DTA). The above measurement method can also be applied to measuring the amount of adsorption when the adsorbent is discharged.

[0036] The amount of adsorption q0 when adsorbent AD is introduced varies depending on the water vapor desorption (heat storage) conditions of the adsorbent and also differs depending on the type of adsorbent AD. However, in the case of zeolite 13X, if q0 is generally 10% or less, sufficient heat can be obtained and steam can be generated, so q0 of 10% or less is preferable. Furthermore, if the amount of adsorption q0 when adsorbent AD is introduced is 6%, the discharge pressure of the liquid supply line is preferably 0.4 MPa or less from the viewpoint of further demonstrating the fuel reduction effect.

[0037] The temperature at which the adsorbent AD is introduced is not particularly limited, but is room temperature (e.g., 20°C to 25°C). Furthermore, the flow rate of the adsorbent AD when completely dry varies significantly depending on the size of the steam generator 30.

[0038] If the control unit 34 is equipped with a computer, then the input means of the computer will be used to communicate via m ad , q eq Enter the value of q0, and the entered m ad , q eq , from q0, m is calculated within the computer's calculation means based on the above equation (1). inj You may also calculate m based on the above formula (1). inj The value of may be input via the computer's input means. In this case, the control unit 34 will input the value of m calculated by the calculation means. injor m entered via input means inj The steam flow rate is controlled based on this.

[0039] In the steam generation system 10, first, adsorbent AD is introduced at a predetermined flow rate from the inlet 31A of the boiler 31, and a portion of the steam generated by the steam generator 20 is supplied into the boiler 31, bringing the steam into contact with the adsorbent AD within the boiler 31. At this point, the control unit 34 determines the steam flow rate based on the above equation (1) and controls the valve 32A so that the steam flow rate becomes the determined flow rate. When the adsorbent AD comes into contact with the steam, it adsorbs the steam and generates heat. Meanwhile, liquid is supplied from the liquid supply line 35 to the heat exchanger 33 inside the boiler 31. Since the adsorbent is generating heat, it exchanges heat with the liquid flowing through the heat exchanger 33, causing the liquid to boil and turn into steam, which is then discharged from the boiler 31 via the steam discharge line 36.

[0040] The temperature of the steam generated by the steam generator 30 may be higher or lower than the temperature of the steam generated by the steam generator 20. If the temperature of the steam generated by the steam generator 30 is lower than the temperature of the steam generated by the steam generator 20, the amount of steam generated by the steam generator 30 will be greater than the amount of steam generated by the steam generator 20, thus achieving a fuel reduction effect.

[0041] In a moving-bed type indirect heat exchange steam generator, the adsorbent is discharged at a high temperature because, before the liquid boils, the balance between the heat capacities of the adsorbent and the liquid prevents the heat from being recovered from the adsorbent down to room temperature, and the adsorbent also generates heat due to excess steam at the bottom of the boiler. On the other hand, if too little steam is supplied to the adsorbent, the amount of heat adsorbed by the adsorbent will be small. Therefore, by supplying only enough steam to the adsorbent to complete the heat generation at the point where the liquid boils (the point where the temperatures of the adsorbent and the liquid are closest), the amount of steam can be reduced and the energy utilization efficiency can be maximized. According to this embodiment, the steam flow rate is determined from the above equation (1), and the steam flow rate is controlled based on the determined steam flow rate, so that only enough steam is supplied to complete the heat generation by the adsorbent AD. This reduces excess steam and maximizes the energy utilization efficiency. Furthermore, equation (1) above is a simplified equation using the flow rate of adsorbent AD when completely dry (kg / h), the equilibrium adsorption amount of adsorbent AD at the boiling point of the liquid (%), and the adsorption amount when adsorbent AD is added (%). Therefore, it is possible to reduce steam using a simple method and improve energy utilization efficiency.

[0042] <Simulation> A simulation was performed using the steam generation system with the configuration shown in Figure 1. Figure 2 is a graph showing the relationship between temperature and adsorption amount at the location of the zeolite boiler for simulation examples 1 to 4.

[0043] In the simulation, Zeolite 13X was used as the adsorbent. The flow rate of the zeolite when completely dry was m ZEO The vapor pressure was set to 1500 kg / h, the adsorption amount q0 of zeolite at the time of introduction was set to 6%, the discharge vapor pressure was set to 0.2 MPa, the boiling temperature was set to 120°C, and the water flow rate of the liquid supply line was set to 350 kg / h. From the boiling temperature and water flow rate, the equilibrium adsorption amount q of zeolite was calculated. eq When we find the equilibrium adsorption amount q, eq The percentage is 22.3%, and the flow rate of the above zeolite when completely dry is m ZEO And the calculated equilibrium adsorption amount q eqThen, using the adsorption amount q0 when the above zeolite is added, the flow rate m of water vapor can be obtained from equation (1) above. inj To find the flow rate of water vapor m inj The flow rate of water vapor was 245 kg / h. inj When a simulation was performed with a rate of 245 kg / h, the graph shown in Figure 2 was obtained (Example 1). In Figure 2, the axial position x on the vertical axis is represented with the steam injection point into the boiler as 0.0m, and positions further away from that point towards the bottom of the boiler as +. The temperature of the zeolite is set to "T ZEO ", the water temperature is "T W The water absorption capacity of the zeolite was represented as "q".

[0044] Also, instead of 245 kg / h, the water vapor flow rate m inj When simulations were performed with the flow rate set to 225 kg / h, 255 kg / h, and 266 kg / h, the graphs shown in Figure 2 were obtained (Examples 2-4). Note that in Examples 2-4, the water vapor flow rate was m inj All other conditions were the same as in Example 1.

[0045] As shown in Figure 2, Example 2 uses a water vapor flow rate m that is lower than the optimal water vapor flow rate. inj Therefore, the amount of heat adsorption generated and the amount of fuel reduction were smaller compared to the case with the optimal steam flow rate. Also, in Examples 3 and 4, the steam flow rate was greater than the optimal steam flow rate m inj Therefore, the temperature of the zeolite located at the bottom of the tank was high, and heat generation from the zeolite located at the bottom of the tank was observed. In contrast, in Example 1, the water vapor flow rate m based on the above equation (1) inj Therefore, the water vapor flow rate was optimal, the temperature of the zeolite located at the bottom of the tank was low, and no heat generation from the zeolite at the bottom of the tank was observed. Furthermore, since Example 1 has a lower water vapor flow rate than Examples 3 and 4, it was confirmed that water vapor can be reduced and energy utilization efficiency is high. [Explanation of Symbols]

[0046] 10…Steam generation system 20, 30... Steam generator 31…Can body 32... Steam supply line 32A…Valve 33...Heat exchanger 34…Control Unit 35…Liquid supply line 36... Steam discharge line 37... Steam separator 40... Steam mixer

Claims

1. A control method for a movable-bed type steam generator comprising: a boiler having an inlet at the top for continuously introducing an adsorbent and an outlet at the bottom for continuously discharging the adsorbent; a steam supply line having one end connected to the boiler for supplying steam to the adsorbent inside the boiler; and a heat exchanger disposed inside the boiler through which a liquid that exchanges heat with the heated adsorbent flows from the bottom to the top of the boiler, wherein The adsorbent exhibits micropore filling type adsorption, The flow rate of the steam supplied to the boiler is controlled to be the flow rate determined based on the following formula (1). m ｉｎｊ =m ａｄ ×(q ｅｑ -q ０ ) …(1) In the above formula (1), m ｉｎｊ This is the steam flow rate (kg / h), and m ａｄ is the flow rate (kg / h) of the adsorbent when completely dry, and q ｅｑ q is the equilibrium adsorption amount (%) of the adsorbent at the boiling temperature of the liquid, and q ０ A control method for a steam generator, wherein is the amount of adsorption (%) when the adsorbent is introduced.

2. The control method for a steam generator according to claim 1, wherein the adsorbent is an adsorbent that conforms to the Dubinin-Astakhov formula or the Langmuir formula.

3. The control method for a steam generator according to claim 2, wherein the adsorbent is at least one of zeolite, silica gel, and activated carbon.

4. The control method for a steam generator according to claim 1, wherein the liquid is water.

5. A movable-bed type steam generator comprising: a boiler having an inlet at the top for continuously feeding in an adsorbent and an outlet at the bottom for continuously discharging the adsorbent; a steam supply line having one end connected to the boiler and supplying steam to the adsorbent inside the boiler; a heat exchanger disposed inside the boiler through which a liquid that exchanges heat with the heated adsorbent flows from the bottom to the top of the boiler; and a control unit for controlling the flow rate of the steam flowing through the steam supply line, The adsorbent exhibits micropore filling type adsorption, The control unit controls the flow rate of the steam supplied to the boiler so that the flow rate of the steam is determined based on the following formula (1). m ｉｎｊ =m ａｄ ×(q ｅｑ -q ０ ) …(1) In the above formula (1), m ｉｎｊ is the flow rate of the steam (kg / h), and m ａｄ is the flow rate (kg / h) of the adsorbent when completely dry, and q ｅｑ q is the equilibrium adsorption amount (%) of the adsorbent at the boiling temperature of the liquid, and q ０ A steam generator, where is the adsorption amount (%) when the adsorbent is introduced.

6. The steam generator according to claim 5, wherein the adsorbent is an adsorbent that conforms to the Dubinin-Astakhov formula or the Langmuir formula.

7. The steam generator according to claim 6, wherein the adsorbent is at least one of zeolite, silica gel, and activated carbon.

8. The steam generator according to claim 5, wherein the liquid is water.

9. A steam generation system comprising a steam generator according to any one of claims 5 to 8, and a steam generator positioned upstream of the steam generator and to which the other end of the steam supply line is connected.

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