JPS62236409A - Perishable food stocker - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a fresh food storage cabinet used for refrigerated storage of vegetables, fruits, etc.

Conventional technology The shelf life of fresh foods can be extended by refrigeration;
Furthermore, it is known that the period can be significantly extended by making the atmosphere low in oxygen and high in carbon dioxide. This type of system is generally called Control
d Atmosphere) storage.

Traditionally, propane fuel has been mainly used in this field. First, when propane fuel is used, the following two methods can be considered. In other words, ■Flushing method that takes in air, burns it, and sends the exhaust gas into the refrigerator; ■Burns fuel with the air inside the refrigerator;
This is a recirculation method that circulates the exhaust gas back into the refrigerator. The former method requires a long time for the oxygen concentration inside the warehouse to decrease, so it is inconvenient when used for the purpose of preserving freshness, and its current popularity is lower than that of the latter recirculation method.

However, the latter recirculation method also requires combustion in the internal air with an oxygen concentration of about 2q6, which means that normal flame combustion is completely impossible in the combustion section and requires the use of large quantities of expensive catalysts. It was something.

Problems to be Solved by the Invention In contrast to these propane gas systems, systems using carbon fuel have also been proposed, but they have not been put into practical use. The reason for this is that it is difficult to achieve complete combustion in an oxygen-deficient state. In addition, the reduction in the amount of combustion caused by oxygen deficiency prolongs the time required to maintain the atmospheric gas concentration to a predetermined level, resulting in poor freshness.

However, carbon fuel is non-explosive, and the safety of the combustion part that communicates with the inside of the closed storage is basically superior to that of propane, and since carbon fuel does not contain moisture in the exhaust gas, it is unlikely that the food in the storage will get wet. This has the advantage that there is no need for a device for removing moisture from the exhaust gas.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides means for detecting the oxygen concentration of the combustion air, and detects the oxygen concentration in the combustion air when oxygen is lacking. i,
In order to prevent the firing temperature from decreasing, the amount of air blown to the air preheater that is linked to the oxygen concentration detection section is increased to preheat the combustion air and achieve complete combustion.

At the start of storage, the oxygen concentration in the chamber is approximately 21%. Under this condition, the carbon fuel can be completely combusted with this 21% concentration of oxygen. However, if combustion continues in this state, the interior of the refrigerator will gradually become deficient in oxygen, and the amount of oxygen contained in the combustion air will also decrease. The combustion of carbon such as coal, charcoal, graphite, etc. has the property that the amount of combustion is determined in proportion to the amount of oxygen sent, but combustion cannot continue if the temperature drops below a certain level. In a state where the oxygen concentration has decreased, although the combustion amount has decreased, the combustion air contains a large amount of carbon dioxide gas with a large specific heat, and the total air amount is 21q6 of oxygen at the start.
It's no different than time.

Therefore, the combustion temperature is lowered. Furthermore, this decrease in combustion temperature makes the reaction between carbon and oxygen inactive, leading to the emission of carbon monoxide due to incomplete combustion and an accelerated decrease in the amount of combustion, leading to extinguishment.

The target oxygen concentration varies depending on the type of food being stored, but is usually 10-2%. For example, at a concentration of 2%, the amount of oxygen is about 1/10 of that in the atmosphere.

At such a low oxygen concentration, combustion cannot be carried out in a simple combustion section, and it is difficult to obtain the target oxygen concentration.

In the present invention, when the oxygen concentration is 21%, combustion air at room temperature is sent to the combustion section to suppress excessive reaction between carbon and oxygen, and when the oxygen concentration is low, the combustion air is preheated and sent to the combustion section at a high temperature. Prevents the combustion temperature from decreasing. Since the temperature of the combustion part is maintained at a high temperature even when the oxygen concentration decreases, the target oxygen concentration can be achieved without causing incomplete combustion or extinguishing the fire due to an accelerated decrease in the amount of combustion. It is.

In the present invention, heat exchange is performed between exhaust gas and combustion air in order to keep the temperature of the combustion section constant in order to prevent changes in combustion due to a decrease in oxygen. In other words, if the oxygen concentration is above a predetermined value, combustion air is supplied at room temperature, and if it is below a predetermined value, high-temperature air is sent to the combustion section via an air preheater by the combustion air switching valve. It is something that exists.

Embodiment FIG. 1 is a block diagram showing a storage system of the present invention. In FIG. 1, reference numeral 1 denotes a storage, which has an evaporator 2 inside and an outdoor unit 3 having a compressor and a condenser outside. The air inside the refrigerator is sucked through the air supply pipe 4 and the blower 6, and returns to the inside of the refrigerator through the exhaust pipe 6. The operation of such a device will be described below.

The air sent from the air supply pipe 4 to the combustion section 7 has an oxygen concentration of 21%.
When , valve 8 is open and valve 9 is closed, so air preheater 1o
The combustion air is sent to the combustion section 7 through the combustion air pipe 11 without passing through the air.

The combustion section 7 contains carbon fuel that has been heated in advance by an electric heater 12, and combustion is started by combustion air.

After this exhaust gas is discharged to the exhaust pipe 12, the mixing air pipe 1
3 and flows to the radiator 14 and the catalyst tank 16.

In the catalyst tank 16, a small amount of carbon monoxide produced by combustion of carbon fuel is converted into carbon dioxide.

This catalyst tank 15 is provided with an electric heater 16 to raise the catalyst to a predetermined activation temperature in advance.

In addition, in order to prevent the catalyst from deteriorating at high temperatures, when the temperature of the temperature detection unit 17 is high, the fan of the radiator 14 is turned to lower the exhaust temperature, and when the temperature is low, the electric heater 16 is energized to reduce the exhaust temperature. The tank 16 is maintained at a constant activation temperature.

The amount burned in the combustion section 7 is determined by the amount of oxygen passing through the combustion air pipe 11, the activity of the fuel, the surface area of the fuel, and the temperature. However, if the type of fuel is limited, the amount of oxygen, surface area, and temperature will vary. This is the main element. Therefore, the carbon fuel in the combustion section 7 is combusted according to the amount of oxygen in the air in the combustion air pipe 11, but when there is a large amount of fuel at the beginning, all of the oxygen sent may be consumed. Since the residual oxygen in the exhaust gas in such a case is 0, carbon monoxide is not purified even if the catalyst tank 15 is at a predetermined temperature. Therefore, the mixing air pipe 13 that does not pass through the combustion section 7 always provides residual oxygen and carries the exhaust gas to the catalyst.

Exhaust gas from the catalyst tank 15 passes through the air preheater 1o and enters the cooler 18. When the combustion section 7 is at a sufficiently high temperature, the valve 9 is closed and the combustion air does not pass through the air preheater 1o, so that it is sent to the combustion section 7 at room temperature.

However, as the oxygen in the refrigerator gradually decreases, the number of oxygen meters passing through the combustion air pipe 11 decreases, and the temperature of the combustion section 7 decreases. In carbon fuel, oxygen diffuses onto the carbon surface and first becomes carbon monoxide, then becomes carbon dioxide through a gas phase reaction away from the surface; however, when the temperature of the fuel decreases, this gas The phase reaction becomes insufficient and a large amount of carbon monoxide is emitted. In order to remove this carbon oxide, a large catalyst is required, and if the catalyst deteriorates, it is a safety problem. Furthermore, in such a state, a decrease in the amount of combustion causes a decrease in combustion temperature, which mutually influence each other, leading to accelerated extinguishment.

However, if the oxygen concentration detection unit 19 checks the oxygen concentration in the combustion air to the combustion unit 7, and if the oxygen concentration is lower than the set value, the valve 8 is closed and the valve 9 is opened. It is heated and supplied.

This preheated air raises the temperature of the combustion section 7 again, resulting in complete combustion, and the temperature of the mixing air flowing into the catalyst tank 15 has also risen, which together with the heat of the electric heater 16 prevents a drop in catalyst temperature. can.

Furthermore, the exhaust gas cooled by the cooler 18 is circulated through the exhaust pipe 6 into the refrigerator. Oxygen in air is 21%. If you want to make the inside of the refrigerator 5% oxygen and 6% carbon dioxide, it is not possible just by burning carbon fuel. This is because if oxygen is 6%, carbon dioxide will inevitably be 16%. For this reason, an excess carbon dioxide removal section 20 is required.

The carbon dioxide removal unit 20 is filled with a carbon dioxide adsorbent such as activated carbon or zeolite, and when the carbon dioxide concentration indicated by the gas concentration meter 21 inside the refrigerator is higher than a predetermined value, the valve 22 is closed and the valve 23 is closed.
It opens to adsorb carbon dioxide gas in the exhaust gas, and sends low-oxygen air that does not contain carbon dioxide gas into the refrigerator. In addition, this removal section 19 closes the valve 23 to regenerate the internal adsorbent, depressurizes the interior with a vacuum pump, desorbs carbon dioxide gas, and discharges excess carbon dioxide gas to the atmosphere through the carbon dioxide gas exhaust pipe 24.

The pressure inside the warehouse and the entire path is reduced by this discharge volume, but the pressure inside the warehouse returns to atmospheric pressure due to outside air that enters intentionally or unavoidably through a gap in the warehouse. The oxygen contained in this infiltrated atmosphere is consumed again in the combustion section 7. By repeating this process, the concentration inside the refrigerator reaches the target value.

After reaching the target value, the stored plants are said to enter a state of suspended animation. Therefore, although it maintains its freshness for a long period of time, it still breathes a small amount, and the amount of carbon dioxide inside the refrigerator increases more than the target value, albeit slowly. At this time, only the carbon dioxide removal section 2o is operated without combustion.

As described above, by using the air preheater 10, combustion can be sustained down to a low oxygen concentration, but as the oxygen concentration decreases, the oxygen a supplied to the combustion section 7 also decreases. . Since the amount of carbon fuel combusted is proportional to the amount of oxygen supplied, deterioration of the combustion zone in low-oxygen air is unavoidable. This is undesirable because it prolongs the time it takes for the gas concentration in the refrigerator to reach the target value.) To address this problem, the amount of air blown by the blower may be increased in response to the decrease in oxygen slippage.

For example, it is conceivable to control the blower 6 according to the oxygen concentration measured by the oxygen concentration detection section 19.

Of course, if a large air volume with low oxygen is sent to the combustion section 7, the fuel will further cool down and become difficult to burn, but in this case, as mentioned above, if the capacity of the air preheater 1o is sufficient, the combustion temperature will not drop. It is something.

Although it is desirable to control the amount of air blown linearly in inverse proportion to the oxygen concentration, block control may be performed in several stages depending on the oxygen concentration.

Furthermore, the opening and closing of the valve of the air preheater 10 may be similarly controlled by block control or linear control.

f;□ In the former case, it is sufficient to set the opening/closing time of each valve according to several levels of oxygen concentration. For example, when the oxygen concentration is 16 to 10%, valve 8 is open and valve 9 is closed.
0 second, valve 8 closed, valve 9 open for 10 seconds, 10 to 7%, 5 seconds and 16 seconds, respectively. In the latter case, the first The amount of air in the air supply passage and the second air supply passage shall be switched to IJ near, and the valve angle may be set in advance according to the oxygen concentration.

Effects of the Invention As described above, according to the present invention, it is possible to completely burn carbon fuel, which has an advantage in safety, at a low oxygen concentration. In order to handle fresh food by adjusting the gas atmosphere inside the refrigerator using a recirculation method,
Concentration adjustment at the start of storage is quick, and food remains fresh for a long period of time because moisture in the exhaust gas is not released into the warehouse.

[Brief explanation of drawings]

The figure is a system diagram of a fresh food storage warehouse according to an embodiment of the present invention. 1...Storage, 4...Air supply pipe, 6...
...Blower, 6...Exhaust pipe, 7...
・Combustion section, 8, 9... Valve, 10... Air preheater, 11... Combustion air pipe, 19...
...Oxygen concentration detection section.

Claims (2)

[Claims] (1) A carbon fuel combustion section, a first air supply path that sends combustion air from inside the refrigerator to the combustion section, and a second air supply path that sends combustion air to the combustion section from inside the storage via an air preheater. an air supply path, a path for discharging exhaust gas from the combustion section into the refrigerator via the air preheater, and an oxygen concentration detection section for the combustion air,
A fresh food storage unit including a valve that increases the amount of air blown through the second air supply path when the oxygen concentration decreases. (2) The fresh food storage facility according to claim 1, wherein the amount of combustion air blown is increased when the oxygen concentration decreases.