JPS591934B2 - Automatic control method of heat storage/dissipation system using metal hydrides - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic control method for a heat storage and heat release system that utilizes the heat generated during hydrogen absorption and devolatilization of metal hydrides.

Generally called hydrogen storage metal.

Including the lanthanide (rare earth) and actinide elements, elements from periodic table 3 to
Transition metal elements in the fifth period, or alloys containing these elements, such as TiFe, easily absorb a large amount of hydrogen gas under certain temperature and pressure conditions to form metal hydrides, and in the process they generate heat. However, it is known that hydrogen is devolatilized under certain temperature and pressure conditions, and that it absorbs heat in the process.

By utilizing the above-mentioned properties of hydrogen storage metals, metal hydrides can be used as heat storage bodies to store natural energy such as solar heat, wind power, industrial waste heat, etc., and extract the heat as needed, for example. Research into heat storage and radiation systems for use in heating greenhouses in vegetable gardens in remote areas has become active.

A metal hydride is held, hydrogen gas supplied from a hydrogen gas holder is brought into contact with the metal hydride, hydrogen is absorbed, the heat generated at that time is extracted, heat is given from the outside and the metal is stored, and at that time A heat exchanger that returns the devolatilized hydrogen gas to the hydrogen gas holder is called a reaction tank.

For the above purpose, the reaction tank has a space for holding metal hydride particles and a permeable wall for supplying hydrogen gas to the metal hydride held in the space and recovering the devolatilized hydrogen gas. A hydrogen gas holding space in contact with the metal holding space through the metal holding space, and a heat exchange pipe disposed within the metal holding space or a heat exchange surface as a wall surface of the space for extracting reaction heat during adsorption and devolatilization. S-suck. The reaction heat during devolatilization is recovered by a heat exchange fluid through the heat exchange tube or heat exchange surface. Further, the hydrogen gas holding space is connected to a hydrogen gas holder via a hydrogen gas pipe. One of the characteristics of metal hydrides is that they absorb and desorb hydrogen gas quickly, and this is because they are used for storage and uniform use of hot metal hydrides.

This is a drawback for heat dissipation systems. If hydrogen gas is applied to the metal without any control during the heat dissipation process to absorb hydrogen gas into the metal, a large amount will be absorbed at first, just like water is absorbed by sand, and as time passes, the amount of hydrogen gas absorbed will increase. gradually decreases and saturates, and storage stops. Therefore, the temperature obtained by exchanging the heat generated at that time with the heat exchange fluid is the initial temperature T, as shown by the solid line in FIG. The temperature rises rapidly from the temperature Tmax to reach the maximum temperature Tmax, and then gradually decreases to the temperature Tmax. heat dissipation is complete. For purposes such as heating, it is necessary to obtain heat at a nearly constant temperature Tm over the entire heat dissipation period, as shown by the broken line in Figure 1. It is necessary to control the flow rate of hydrogen gas provided so that the mass of hydrogen gas absorbed by the metal remains constant throughout the heat dissipation period. To control the flow rate of hydrogen gas supplied to the metal, a flow control valve is installed on the hydrogen gas piping connecting the hydrogen gas holder and the reaction tank, and the hydrogen gas pressure in the hydrogen gas holder and reaction tank is adjusted during the heat dissipation process. It is necessary to adjust the mass flow rate to always maintain a constant mass flow rate even if the difference between the two changes. Conventionally, this control has been carried out by detecting the flow rate (mass flow rate) of hydrogen gas using a flow meter (mass flow meter), comparing the detected value with a set value, and then using an electric or gas control type. The flow control valve was driven by a controller.

Therefore, a control gas source or power supply is required, and when using electricity, explosion-proof measures are required because hydrogen gas is handled, which has the disadvantage of complicating the equipment and increasing costs. Ta. This invention provides storage using metal hydrides. It is an object of the present invention to provide an automatic control method that eliminates the above-mentioned drawbacks of the conventional method of controlling a hydrogen gas flow rate control valve in a heat dissipation system and can reliably achieve the objective with a simple configuration.

Hereinafter, the present invention will be explained in detail based on drawings showing embodiments thereof.

Storage by the metal hydride explained earlier. For heat dissipation system}
When the flow rate of hydrogen gas is controlled to be constant, the pressure of the hydrogen gas in the hydrogen gas holder and reaction tank changes as shown in FIG. 2 during heat radiation and heat storage processes.

In Fig. 2, the horizontal axis shows time, the vertical axis shows hydrogen gas pressure, a is the time when heat radiation starts, b is the time when heat radiation ends and heat storage starts, and c
indicates the end of heat storage. In the figure, the solid line indicates the hydrogen gas pressure in the hydrogen gas holder, and the dashed line indicates the hydrogen gas pressure in the reaction tank. The control method of the present invention includes heat radiation. The present invention is characterized in that the operation of the hydrogen gas flow rate control valve is controlled by utilizing such pressure changes within the hydrogen gas holder during the heat storage process.

FIG. 3 shows a storage system to which the control method of the present invention is applied. It is a piping system diagram of a heat radiation system.

In the figure, a flow rate (mass flow rate) control valve 2 is provided between hydrogen gas pipes 15 and 16 that connect the hydrogen gas holder 1 and the reaction tank 8. The valve body 21 formed as a needle valve of the flow rate control valve 2 is located at the lower end, and the valve stem 22 penetrates the valve body 23 while maintaining airtightness with the gland packing 24, and then the upper end thereof is slid into the cylinder 3. It is attached to a movably arranged piston 31. A bellows 4 is provided between the ground surface of the piston 31 and the inner surface of the upper end of the cylinder 3, and the internal space 41 of the bellows 4 and the hydrogen gas holder 1 are connected by a pipe 17. The pipe 17 is provided with a stop valve 13 . A compression spring 5 is provided between the lower surface of the piston 31 and the inner surface of the lower end of the cylinder 3.
1 is pressed upward. A manual start device 6 is attached to the valve stem 22. Inside the reaction tank 8, there is provided a container 12 composed of an air-permeable wall for holding metal hydride particles, and inside the container 12 there is provided a heat exchange fluid pipe 9 whose both ends extend outside the reaction tank. ing. Also, bellows 4 and stop valve 1
A hydrogen gas pipe 17 between pipes 1 and 3 has a stop valve 10 and a pressure reducing valve 11 in order to fill this system with hydrogen gas.
8 to which a hydrogen gas cylinder 7 is connected and, if necessary, to extract hydrogen gas from this system.
A pipe 19 with a stop valve 14 is connected.

In the flow regulating valve 2, when the gas pressure inside the bellows and the gas pressure inside the valve box 23 both exceed a certain pressure P1, the push-up blade of the spring 5, the push-up blade of the valve body 21 due to the gas pressure P, and the push-up blade of the bellows 4 are activated. The valve is designed so that the force of the gas pressure in the bellows pushing the piston 31 downward is greater than the total force of mechanical forces such as elasticity and frictional force of the gland fitting 24, and the valve is closed. has been done. Moreover, the flow rate coefficient Cv of the flow rate adjustment valve 2 changes even if the difference between the pressure of the hydrogen gas holder 1 and the pressure of the reaction tank 8 changes as shown by the difference between the curves a and b in FIG. , designed to have a constant mass flow rate. A storage configured as described above. The control action of the heat dissipation system will be explained below.

(The pressure state before the start of heat radiation is that the pressure inside the hydrogen gas holder is approximately P,5, which is much higher than the pressure P2 in the reaction tank 8, and the force of the gas in the valve box 23 pushing up the valve body 21 is small. The flow rate regulating valve 2 is in a closed state.
(The pressure P1 is determined by the type of metal and the temperature of the heat used.) When starting heat radiation, when the manual start device 6 is manually operated to open the valve 2, the hydrogen gas holder 1 The hydrogen gas flows through the hydrogen gas pipe 15, square 2, and pipe 16 inside, and flows into the reaction tank 8.

(The starting device may be driven by a signal such as the pressure of the reaction tank 8 or the temperature of the metal hydride or heat exchange fluid therein.) When hydrogen gas flows, the pressure inside the holder 1 increases. When the temperature reaches P1', which is slightly lower than P1, the starting device 6 is released. After releasing the starter device 6, the pressure in the hydrogen gas holder 1 decreases over time as shown by the solid line between A and b in FIG.
The internal pressure increases over time as shown by the chain line. Accordingly, the opening degree of the flow rate regulating valve 2 is adjusted by the spring 5,
The total number of push-up blades of the valve body 21 gradually increases, the push-down blade of hydrogen gas in the bellows 4 gradually becomes smaller, and the smaller the pressure difference between the holder 1 and the reaction tank 8, the more the valve 2 opens. increases, and the flow rate of the valve (
mass flow rate) is always kept constant. Therefore, during that time, the metal in the reaction tank 8 stores a certain mass of hydrogen, and heat at a certain temperature is recovered by the heat exchange fluid through the heat exchange fluid pipe 9 and used for heating the greenhouse or the like. When the heat dissipation process is completed, the pressure in the hydrogen gas holder 1 and the pressure in the reaction tank 8 are reduced to the second level.
Shown at point b in the figure. Will the temperature Pm be the same as that?
Or almost the same temperature. The heat storage process in which the hydrogen absorbed in the metal is returned to the original holder 1 is to transfer heat obtained from wind power, solar heat, and industrial waste heat into the reaction tank 8 through the heat exchange fluid pipe 9 using a heat exchange fluid. It is done by giving it to the metal.

At this time, since the valve 2 is in an open state, the pressure inside the holder 1 increases together with the pressure inside the reaction tank 8. Therefore, between b and c in FIG. 2, the solid line curve and the dashed line curve overlap. As the heat storage process progresses, the holder 1 and the reaction tank 8
The pressure continues to rise, and when the pressure exceeds P1, valve 2
is in a closed state, the pressure in the holder 1 does not rise any further, and the heat storage process ends.

When the supply of heat to the reaction tank 8 is stopped at this point (c in FIG. 2), the metal inside the reaction tank 8 cools down and the pressure inside the tank returns to the pressure P2 at the start of the heat dissipation process.

Moreover, the pressure inside the holder 1 also decreases due to the cooling of the hydrogen gas, and returns to the starting pressure. If heat is to be recovered from the system again, the above steps can be repeated.

As described above, according to the control method of the present invention, except for manually operating the starting device at the time of starting, no storage is required. Utilizing the changing gas pressure of the hydrogen gas holder during the heat dissipation process,
Since the opening/closing and opening degree of the flow control valve is controlled, a controller is not required, and a pressure gas source or power source to operate it is not required.Since no electricity is used, there is no need for explosion-proof measures, and the structure is simple. It is simple and effective in reducing costs.

As mentioned above, since no other facilities such as a power source are required, this system is particularly advantageous when used for local energy use in remote areas where there is no electricity supply, such as heating greenhouses in vegetable gardens. .

[Brief explanation of the drawing]

Fig. 1 is a curve diagram showing the heat dissipation characteristics of the heat storage/dissipation system using metal hydrides when the hydrogen gas flow rate is not controlled and when the hydrogen gas flow rate is controlled, and Fig. 2 is a curve diagram showing the heat dissipation characteristics of the above system with the hydrogen gas flow rate controlled. FIG. 3 is a diagram of a pressure change curve in a hydrogen gas holder and a reaction tank during a heat storage process, and a piping system diagram of an example of a heat storage/dissipation system implementing the method of the present invention. 1...Hydrogen gas holder, 2...Flow rate adjustment box, 8.
... Reaction tank, 9... Heat exchange fluid pipe, 12... Metal hydride container.

Claims (1)

[Claims] 1 The metal hydride held in the reaction tank is brought into contact with hydrogen gas supplied from a hydrogen gas holder to absorb hydrogen, and the heat radiated at this time is recovered and used by a heat exchange fluid, and the metal hydride is removed after the heat radiation is completed. Hydrogen gas piping connecting the gas holder and the reaction tank in an automatic control method for a heat storage and release system in which heat is applied to a hydride from the outside to store the heat, and hydrogen gas devolatilized at the time is recovered in the hydrogen gas holder. 1. An automatic control method characterized in that a flow rate adjustment valve is provided in the holder, and the opening/closing and flow rate adjustment of the valve is controlled by utilizing the fluctuating pressure of hydrogen gas in a hydrogen gas holder during heat storage and heat release processes.