JPS59202396A - Heat-recovering method - Google Patents

Abstract

PURPOSE:To enhance heat-recovering efficiency, by a method wherein thermal energy of an exhaust gas is recovered by an aqueous solution of a salt, and thermal energy of the solution is indirectly used for heating water. CONSTITUTION:Counterflow-type gas-liquid contact towers 2, 4 are provided, and an aqueous solution of a salt contained at the bottom of each of the towers is drained through a lower part of the tower. An exhaust gas is passed upward through the tower 2 from a lower part of the tower 2, while air is passed upward through the tower 4 from a lower part of the tower 4, and is introduced into a packed tower 6 in which pure water is circulated by a pump 7. By this, thermal energy of the exhaust gas is recovered by the aqueous solution, and thermal energy of the solution is used indirectly for heating water through air. Accordingly, heat-recovering efficiency can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to high energy gases (high temperature, high humidity or both).
The present invention relates to a heating method.

The high-energy gas mentioned here includes various types of dryers (
These include exhaust gas from box dryers, tunnel dryers, drum dryers, 7-rush dryers, tower dryers, spray dryers, etc., and exhaust gas from combustion furnaces, heating furnaces, and boilers.

Conventional technology Methods of using the energy of exhaust gas to preheat water; methods of indirect heat exchange such as in boiler economizers; There are so-called direct contact type heating towers for waste heat recovery that are used in The former belongs to unit operations that utilize heat conduction, or more specifically, heat flow, and the latter includes mass transfer and heat transfer that involve special heat transfer to wash away microscopic water droplets generated by cooling. Regarding the latter, to be more specific, it is thought that heat is recovered by heat transfer from the atomized gas phase to the liquid phase (water).

The present invention utilizes a method different from the above-mentioned known heating tower to utilize the heat possessed by the exhaust gas into a salt liquid (which has a lower vapor pressure than water) (therefore, the so-called boiling point rises, and the steam at that boiling point is superheated steam). This is a new method of directly contacting the human body.

OBJECTS OF THE INVENTION An object of the present invention is to provide a method for recovering the thermal energy of exhaust gas using a salt solution and using the thermal energy of the salts indirectly for heating water.

The principle of heat recovery of the present invention will be explained with reference to the humidity chart shown in Fig. 1 and Fig. 2.

As is well known, the adiabatic cooling line (1'l: such as the line AA on the lower right in the figure) is as follows under a total pressure of 1 atm, assuming that the water temperature is kept at a constant value (ts). This diagram shows the process by which unsaturated air becomes saturated with water vapor evaporated from water, with humidity on the vertical axis and temperature on the horizontal axis. On this line, from the gas phase to the liquid phase (there is evaporation of water vapor equivalent to the amount of heat transferred to the water village, so the gas phase (in other words, per dry air)
The enthalpy is constant, the temperature of the aqueous phase in contact takes a constant value ts, and 78 is the adiabatic saturation temperature.

From this, for example, point X on this line (see Figure 2)
If the moisture in the air with the humidity H1 and the temperature t is liquefied and removed using an appropriate method, it will be exposed to the adiabatic cooling line and exhibit a temperature of 1 and a temperature of t1, which is indicated by xl.

In the present invention, salts (Mg01
2, LiBr, etc.) is used.

That a salt water bath can be used as a deliquefaction agent is evident from the boiling point increase phenomenon generally observed when non-volatile substances are dissolved.

Now, for the sake of simplicity, regarding a dilute solution, the boiling point rise △TB is expressed as (for example, W, J, Moore; Physical Chemistry
try, p. 132, Prentice-Hall
(see 1962). In other words, the boiling point increase phenomenon means a decrease in vapor pressure, which results in the effect of dehydration (liquefaction removal).

Figure 2 shows water, 34% MEO12 aqueous solution, and 50% LiBr.
It shows the normal temperature of the water bath liquid at the temperature of the master.

These aqueous salt solutions are excellent in that they have a large vapor pressure lowering effect, do not precipitate solids, have little toxicity, and are stable.

Specific Examples of the Invention (Embodiments) In FIG. 3, heat source gas is passed from the conduit (1) to the bottom of the packed tower (2), which is an example of a countercurrent gas-liquid contact device, Ql< (2
A saline solution (e.g. MIF-12 3
A 4% aqueous solution) is cooled and discharged from the stack (2b) through extensive heat exchange involving water transfer between the liquefied gas phase and the liquefied gas phase. Assuming that the adiabatic saturation temperature of the heat source gas is 60°C,
Regardless of temperature or humidity, the enthalpy of the dry air standard (hereinafter referred to as ffl6'J enthalpy)
ld 109 (kcal/kg% gas, hereinafter this dimension will be omitted), and the stack (2b)
If the adiabatic saturation temperature of the exhaust gas released from is 31°C [for example, 50°C, humidity 0.018 kg water/kg dry gas], the wet enthalpy is approximately 25 kcal.
/kg dry gas.

In the packed tower (2), the aqueous salt solution contacts the heat source gas countercurrently and rises in temperature while falling down the tower, for example, to 45°C at the top of the tower.
88°C at the bottom of the tower), is drawn out by the pump (3) and rinsed from the upper part of the packed tower (4), and the temperature is reduced by air blown from the blower (5) (for example, by blowing air at 15°C, The temperature of the air leaving the column top (4b) is 80° C.). The aqueous salt solution (45° C.) accumulated at the bottom of the packed tower (4) is drawn out by the pump (d) and, as described above, is poured down from the top of the packed tower (2), and the circulation is repeated.

Packing towers (2) and (4) are filled with Raschig rings and other packing materials. The hot air (80°C) exiting from the top of the packed tower (4) is then transferred to the lower part of the packed tower (6) (
6a) and discharged from the upper part of the column (6b) (3 (1°C). Pure water (not directly) is circulated in the column (6) by a pump (7) as shown in the figure. The air and water are in direct contact with each other, and the thermal energy of the hot and humid air is recovered through the transfer of both heat and matter (water temperature at the bottom of the tower: 20°C, water temperature at the bottom of the tower: 55°C).

Feed water (15°C) for heat recovery enters the system from the conduit (11), and in the indirect heat exchanger "'4, the circulating water (!: heat exchanges to 48°C, for example, of the packed tower 16), and the water is heated to 48°C, for example, Tower (
2) solution circulation path (the bottom solution of the column (2) is pumped (8)
), cooled by heat exchanger 1, and flowed down from the top of tower (2). ) is further heated (81°C) by the heat exchanger in
It is sent to and used as a product.

In this example, when calculating for 100 tlOkφ of dry air, the heat input is 109 x 109 kcal (insulation I1 phase temperature 60°C), and the amount of heat of the exhaust air exiting the top (2b) of the packed column 12) is 25 x 109 kcal (adiabatic saturation temperature 31° C.), the temperature of each part shown in the above example is expected, 12.7 t/h of 81° C. hot water can be produced, and the energy efficiency is 77%.

Next, FIG. 4 shows another embodiment.

The packed tower (2) and the packed tower (4) function substantially the same as in the embodiment described above. That is, high-energy gas (adiabatic saturation temperature due to water 60°C) enters the column from the lower part (2a) of the packed tower (2) through the conduit (1) and is released from the upper part (2b) of the column (adiabatic saturation temperature 31 ℃
).

On the other hand, the liquid is secreted from the upper part of the packed tower (2) (45°C), and the liquid accumulated at the bottom of the tower (88°C) is pumped (3).
) and heat the feed water (water to be heated) in a heat exchanger (66.5°C), then the air ( 1.5℃
) in the same flow, dehydrated and refined (at 45°C), pulled out from the bottom of the column by a pump (6'), and then pumped down from the top of the packed column (2). . The saline pericardial fluid is dehydrated and diluted in the packed tower (1), and reduced in the packed tower (4) to maintain a balance of 7L. Air for pongee is released from the upper m (4b) of the packing tower (4) (62°C)
.

In the case of this example, dry air 10t)00 kF! 7h
Then, the heat input is 109 x 109 kca.
l (adiabatic saturation temperature Ji 6Q'C), filling 4 (2)
The amount of heat of the exhaust air leaving the tower top (2b) is 25 x 10
kcal (insulated gun phase temperature gin°C), the above-mentioned temperatures at each part are expected, 14t/h of water can be heated from 50°C to 80°C, and the recovery rate is 38. It's a crow.

In addition to the packed tower, the countercurrent gas-liquid contact device also has a tray tower,
Disturbing roots and others are well known.

Structure of the Invention As described above, including the principle of the invention and its effects in the examples, the present invention comprises two units: a countercurrent gas-liquid contact device (2) and a countercurrent gas-liquid contact device-4). Using a counter-current gas-liquid contact device (2), 741 pieces of salt water was poured from the upper part of the counter-current gas-liquid contact device (4). ) is included in the circulation type gas-liquid contacting device (2).
), and air is passed through the self-flow gas-liquid contact device (4) to stabilize the roughness of the salt aqueous solution. It is characterized in that it includes a configuration in which natural energy is transferred from the feed water to the water supply using an indirect heat exchange method.

[Brief explanation of the drawing]

Fig. 1 is a well-known mixed coal chart for explanation, Fig. 2 is an explanatory humidity chart that is an enlarged version of the Hatochi humidity chart, Fig. 3 is a process diagram of one embodiment of the present invention, and Fig. 4 is a diagram of another embodiment of the present invention. It is a process diagram of an example. (2)... Packed tower, (3)... Pump, (4)...
...Filled tower, (5)...Blower, (6)...Filled tower, (1 smell...Indirect heat exchanger, state...Indirect heat exchanger, u')...Indirect heat exchanger.

Claims (1)

[Scope of Claims] 1 Countercurrent gas-liquid contact tower (2) and countercurrent gas-liquid contact device (4
), the aqueous salt solution that has passed through the cocurrent gas-liquid contact tower (fi+) is brought down from the upper part of the countercurrent gas-liquid contact tower (4), and the bottom liquid of the countercurrent gas-liquid contact tower (4) is obtained. Countercurrent gas-liquid contact tower (2)
The counterflow type gas-liquid contact tower (2) has a circulation path for the salt aqueous solution that is returned to the upper part of the tower and is thus circulated. Air is passed through the gas-liquid contact tower (4) from the bottom to the top to concentrate the aqueous salt solution, and these two towers are used together to prevent changes in salt concentration, and the circulating salt aqueous liquid is transferred to an indirect heat exchanger method. A heat recovery method that involves transferring thermal energy to water to be heated. 2. The method according to claim gg1, wherein the aqueous salt solution is an aqueous magnesium chloride solution. 3. The method according to claim 1, wherein the aqueous salt solution is an aqueous lyticum bromide solution.