JPS6014985B2 - Solid heat recovery method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering heat from high temperature solids.

More specifically, when recovering the heat of a high temperature solid in the temperature range of 100 to 600q○, the temperature range of 50 to 20000,
It is brought into direct contact with a dilute aqueous solution of a soluble salt with a concentration of 5% by weight or more, and the heat of the high-temperature solid is used. By converting a dilute aqueous solution of a soluble salt into a concentrated aqueous solution or molten salt with a temperature range of 100 to 500°C and a concentration of 5% by weight or more, and recovering the heat generated when diluting this with water, it can be indirectly extracted from a high-temperature solid. The objective is to provide a method for recovering heat. In recent years, from the perspective of energy conservation, there has been a strong trend toward recovering and effectively using energy that would previously have been discarded.
There is no example of recovering and effectively using waste heat from high-temperature, solid materials such as slabs in steel plants.

The reason why heat from high-temperature solids could not be recovered and used effectively in the past is that in the case of cooling with water, the temperature of the water after cooling is low, which limits the use of energy with low potential. This is because, although the temperature increases to some extent in the case of cooling, the heat transfer coefficient is low and the heat recovery device becomes very large. The inventors of the present invention conducted intensive experimental studies on a method that has a high heat transfer coefficient and can recover heat using small equipment when recovering heat from a high-temperature solid, and found no other similar method and came to propose the present invention.

In the method of the present invention, when recovering heat from a high-temperature solid, a dilute aqueous solution of a soluble salt is brought into direct contact with the high-temperature solid, and the dilute aqueous solution of a soluble salt is converted into a concentrated aqueous solution or a molten salt using the heat possessed by the solid. In the method of recovering the heat generated when diluting this with water, the water used to wash the high-temperature solids after direct contact with the dilute aqueous solution of soluble salts is used to indirectly remove the heat from the high-temperature solids in a non-drainage, i.e., closed system. It is characterized by heat recovery.

Here, high-temperature solids are solids that have a considerable amount of thermal energy during production, such as slabs, wire rods, strips, blast furnaces, cast irons, and forged products in steel mills, and soluble salts are solids that are soluble in water. Salts that generate considerable heat when dissolved in water and whose aqueous solution has a boiling point considerably higher than the boiling point of pure water, such as hydroxides and halides of alkali metal elements or alkali metal elements; Substances such as nitrates and nitrites. For example, temperature 100oo, concentration 5
A sodium hydroxide aqueous solution of 200% by weight was heated to 900oC.
40 when brought into direct contact with a lk9 steel plate heated to 0.
It turned into a molten salt of 9qC, and when it was diluted with water, 28 degrees of steam at 302°C was obtained, making it clear that the heat, which was conventionally discarded, could be sufficiently recovered.

In addition, in the method of the present invention, the temperature range of the high-temperature solid is 10
loo is limited to 0-600℃. If the temperature is below ○, the temperature to generate steam after heat exchange is too low and the merit of heat recovery is small, and if it is above 600°C, the salt in the aqueous solution of soluble salt used for heat recovery may decompose or the salt may be removed by evaporation. This is because the loss will be large. Next, the temperature range of concentrated aqueous solution or molten salt of soluble salt after heat recovery is limited to 100 to 500 oo.
Below 0oo, the temperature is too low to generate steam and recover heat, and the merit of heat recovery is small;
This is because the molten salt of the soluble salt decomposes or the loss of salt due to evaporation becomes large. Next, the reason why the temperature range of the dilute aqueous solution of soluble salt is limited to 50 to 200qo is that below 50℃, the above limited temperature range is 200qo.
The temperature difference is large and the efficiency of heat recovery is too low to raise the temperature to 0.

In addition, at temperatures above 200℃, the temperature difference between the target solid and the target of heat recovery is 4.
This is because the heat exchange amount is small and the device becomes large. Next, the reason why the concentration of dilute aqueous solutions of soluble salts is limited to 5% by weight or more is that below 5% by weight, there is a lot of water.
This is because when heat is recovered from a high-temperature solid, most of the heat is spent in evaporating water, resulting in a very low heat recovery efficiency. Although there is no need to limit the upper limit of the concentration, economically it is preferably 5% by weight or less.

Furthermore, the concentration of the concentrated aqueous solution of the soluble salt is limited to 5% by weight or more because the boiling point of the aqueous solution is at the above-limited temperature 2.
To reach 0000 or more, the concentration must be at least 5% by weight.
This is because it has to be more than that.

In addition, direct contact between the high-temperature solid and a dilute aqueous solution of a soluble salt is possible by immersing the high-temperature solid in a dilute aqueous solution of a soluble salt, or by coating the surface of the high-temperature solid with an aqueous solution of a soluble salt in the form of a film using a sprayer. There are various methods such as coating, and using these methods improves cooling efficiency compared to conventional gas cooling.

Also, some of the aqueous solution of soluble salts adheres to the surface of the high-temperature solid, but since it is soluble, it can be easily washed with water, and this washing water is used to dilute the concentrated aqueous solution of soluble salts or the molten salt. This allows the process to be closed. As explained above, the method of the present invention differs from the conventional methods of recovering heat from high-temperature solids by bringing water, air, etc. into contact with the high-temperature solid as a medium. Using an aqueous solution of salt as a medium,
It is characterized by a combination of a process of concentration or solidification or molten chlorination by contacting the medium with a high-temperature solid, and a process of recovering heat of dilution by contacting the produced concentrated aqueous solution, solid salt, or molten salt with water. It was revealed that this proposal can effectively perform several recovery from high-temperature solids.

Next, an example of an embodiment of the present invention will be explained with reference to FIG.

In FIG. 1, high-temperature solids are supplied from line 1 and dilute aqueous solutions of soluble salts are supplied from line 2 to solid-liquid contacting device 3, where the high-temperature solids and the dilute aqueous solutions of soluble salts are brought into direct contact, and the high-temperature solids are The heat it possesses converts a dilute aqueous solution of a soluble salt into a concentrated aqueous solution or molten salt.

As a contact method here, there is a method of applying a dilute aqueous solution of a soluble salt to the surface of the high temperature group in the form of a film by spray dipping. Concentrated aqueous solutions of soluble salts or molten salts are sent from line 4 to tank 5, and heat-recovered solids are sent to line 6.
The cleaning device 7 is then connected to the cleaning device 7. In cleaning device 7, line 6
The soluble salt attached to the target solid supplied from the line 8
The cooled solids are sent to the next step via line 9. Wash water containing a small amount of soluble salt is supplied from line 11 and a concentrated aqueous solution or molten salt of soluble salt is supplied from line 10 to a heat generating device 12, where the concentrated aqueous solution or molten salt containing a small amount of soluble salt is supplied to a heat generating device 12. It is diluted with washing water and the heat generated at that time is recovered by heat exchange. Note that as a method of recovering this generated heat, a method of directly utilizing the steam generated during dilution can also be applied. An example of a method of utilizing this recovered heat is a method in which a steam generation tube is provided in the heat generation device 12, and water therein is converted into steam and recovered as energy.

The diluted solution in the heat generating device 12 is circulated through line 2. As described above, the heat of the high temperature solid is continuously recovered.

Next, examples of the present invention will be shown. Example 1 The present invention was carried out using a lk9 steel plate heated to 500q0 as a high temperature solid and a sodium hydroxide solution prepared by dissolving 70 parts of sodium hydroxide in 130 parts of water as a dilute aqueous solution of a soluble salt.

When 200 tons of 8,000 sodium hydroxide solution was brought into contact with 1 portion of sand between 50,000 lk9 of steel plate, the steel plate decreased from 500q○ to 246oo, and the sodium hydroxide solution was 18,700 7t% hydroxide. It turned into a sodium solution.

When the calorific value obtained when 1009 yen of this concentrated sodium hydroxide solution was added with 100 yen of water was recovered using a heat exchanger, 7 yen of water vapor with 13% of 0 was obtained. Example
2 A lk9 steel plate heated to 600oo as a high-temperature solid,
Also, as a dilute aqueous solution of soluble salt, magnesium chloride 6
The present invention was carried out using a magnesium chloride solution prepared by dissolving 0.0 parts in water and 14 parts in water.

When 200 tons of 80qo magnesium chloride solution was brought into contact with 600qo steel plate lk9 between 1 inkstone sand, the strength of the steel plate decreased from 600qo to 29300, and the magnesium chloride solution changed to 203qo 61M% magnesium chloride solution. did.

If 100 liters of this concentrated aqueous solution and 75 q0 of water are added, and the heat generated is recovered by a heat exchanger, 149
Water vapor of 7 o'clock in the afternoon was obtained. Example 3 A 3K9 steel plate heated to 550°C was used as a high-temperature solid, and 100 parts of sodium hydroxide was mixed with 100 parts of water as a dilute aqueous solution of soluble salt.
The invention was carried out using sawn sodium hydroxide solution.

When a 55,000 lk9 steel plate was brought into contact with 200 ml of a 100 oz sodium hydroxide solution, the steel plate turned into a 409 qo molten salt.

When the calorific value when 80 kg of 90 qo water is added to 100 kg of this molten salt and the heat is recovered using a heat exchanger, it is 30,200 kg.
28 hours of water vapor was obtained. As described above, the present invention has the advantage that solid heat, which was previously discarded, can be effectively recovered by using an aqueous solution of a soluble salt as a coolant.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing one embodiment of the apparatus used in the present invention. 1... High temperature solid supply line, 2... Dilute soluble salt solution line, 3... Solid contact device, 5...
...Concentrated salt solution tank, 7...Cleaning device, 8
...Washing water line, 9...Cooling solid line, 10...Concentrated salt liquid line, 1 1...
・Soluble salt-containing cleaning water, 12... Decontamination generator.

Claims (1)

[Claims] 1 High-temperature solid in the temperature range of 100 to 600°C in the temperature range of 5
Direct contact with a dilute aqueous solution of a soluble salt with a concentration of 5% by weight or more at 0 to 200℃, and use the heat of the high temperature solid to turn the dilute aqueous solution of the soluble salt into a concentrated aqueous solution or melt at a temperature range of 100 to 500℃ with a concentration of 50% by weight or more. In a method of recovering the heat generated when converting the salt into a salt and diluting it with a liquid, the liquid is used as the liquid to wash the high-temperature solid after direct contact with the dilute aqueous solution of the soluble salt. A method for recovering solid heat, which is characterized by recovering heat.