JPS5875691A - Heat-exchanging method - Google Patents

Abstract

PURPOSE:To utilize the latent heat of evaporation of a hyrocarbon effectively and contrive energy conservation, by a method wherein a refrigerant (water or a brine containing calcium chloride) heated by being used in a cooling step is cooled in an evaporating step of a liquefied lower hydrocarbon, and thereafter it is recirculated into the cooling step. CONSTITUTION:Liquefied ethylene is fed into an ethylene evaporator 3 through an inlet 1 thereof, and is evaporated to be a gas, which is fed out through an outlet 2 of the evaporator 3 and is fed to plants where it is used. Water is circulated to the evaporator 3 in a required amount through a circulating line 4 for cold water, return cold water of a higher temperature is received from a return cold water line 14 as a heat source required for evaporating liquefied ehtylene, and after cooling, it is fed to a cold water tank 8 through a cold water feed line 7 under level control. Cold water is fed to a cold water using appratus 10 through a cold water feed line 9, is heated in the apparatus, and is returned to a refrigerator suction tank 12 through a cold water return line 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat exchange method using liquefied lower hydrocarbons.

Liquefied low hydrocarbons are generally vaporized and used in gaseous form, but the common method for vaporizing liquefied low hydrocarbons is to install a heat exchanger and use steam as the heat source. be.

This method not only requires steam as a heating source, but also does not utilize any latent heat when the liquefied lower hydrocarbons are vaporized.

Furthermore, in chemical factories, cold water or calcium chloride prine is used as a refrigerant in various manufacturing equipment, such as vinyl chloride manufacturing equipment, but these refrigerants are currently cooled using refrigeration equipment.

Therefore, the inventors of the present invention have completed the present invention as a result of intensive studies on methods for evaporating liquefied lower hydrocarbons.

That is, in the present invention, a refrigerant selected from water or calcium chloride prine, which has been used in the cooling process and whose temperature has been raised, is cooled by introducing it into the vaporization process of liquefied lower hydrocarbons and exchanging heat, and then cooled by the cooling process. This is a heat exchange method characterized by circulation throughout the process.

The liquefied lower hydrocarbons used in the present invention are mainly composed of hydrocarbons having 1 to 4 carbon atoms, such as liquefied ethylene, liquefied natural gas (LNG), liquefied petroleum gas (LPG),
Examples include liquefied propane.

Further, the refrigerant used in the present invention is selected from water or calcium chloride prine, and sodium chloride prine is not suitable because it causes equipment corrosion.

The cooling process is a process that has equipment that requires cooling, and specifically includes a process that has vinyl chloride polymerization equipment, a caustic soda cooler, etc., and the refrigerant is circulated therethrough.

In the case of water, the temperature of the refrigerant that is heat-exchanged and cooled in the vaporization process of liquefied lower hydrocarbons is preferably 2.
-30°C, more preferably 3-15°C, and preferably -5-30°C in the case of calcium chloride prine. As a method for achieving such thermal fatigue, there is a method of adjusting the flow rate of the refrigerant.

As the heat exchanger used in the process of vaporizing the liquefied lower hydrocarbons, any known heat exchanger can be used, such as an open rack type heat exchanger, a flooded type corrugated tube type heat exchanger, and the like.

In the vaporization step, the liquefied lower hydrocarbon absorbs heat corresponding to the heat of vaporization and vaporizes, while the refrigerant releases the heat to be cooled and sent to the cooling step.

Next, as an embodiment of the present invention, a case where water is used as the refrigerant and liquefied ethylene is used as the liquefied lower hydrocarbon will be described with reference to FIG.

It becomes a gas from the evaporator outlet 2 and is sent to each ethylene gas single-use factory.

The water is circulated in the amount necessary for the evaporator through the cold water circulation line 4, and high-temperature return cold water is received from the ethylene evaporation return cold water supply line 14 as a heat source necessary to evaporate the liquefied ethylene. After cooling, the water is sent to a cold water tank 8 from a cold water supply line 7 under level control.

The cold water is sent from the cold water supply line 9 to the cold water using equipment 1°.
The warmed cold water is returned to the refrigerator suction tank 12 from the cold water return line 11.

If the amount of cold water is greater than the amount of cold water returned from the ethylene evaporator in line 7, the cold water refrigerator 13 is operated to make up for the shortage. Also, when the cold water using equipment 1° is stopped, or when the heat load is less than the amount required by the ethylene evaporator 3, steam is blown directly into the cold water warmer 5 from the steam line 6,
Secure the heat necessary to evaporate ethylene.

Next, the second example shows the case where calcium chloride prine is used as the refrigerant and liquefied ethylene is used as the liquefied lower hydrocarbon.
As shown in the figure. Each step is the same as in the case of FIG. 1, but
A prine cooler 13 is used instead of a cold water refrigerator, and Freon is circulated between a Freon refrigerator 15, a liquid Freon line 16, a return gas 7, and a Leonine line 17.

If the amount of calcium chloride brine used in the calcium chloride brine using equipment 1o is greater than the amount of calcium chloride brine returned from the ethylene evaporator, the brine cooler is operated to make up for the shortage.

According to the present invention, it is possible to effectively utilize the latent heat when the low-grade hydrocarbonized water is vaporized, and the cost of utilities such as steam necessary for heating the liquid can be saved or eliminated.
Furthermore, the power of a refrigerator for cooling water or calcium chloride brine can be saved or eliminated.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Using the equipment shown in Figure 1, the ethylene evaporation amount was 4,000.
The operation was carried out at 0 kg/H, an ethylene evaporator feed water temperature of 32°C, and an ethylene evaporator outlet cold water temperature of 5°C. The amount of cold water produced was 20.5t/H.

The liquefied ethylene temperature at the ethylene evaporator inlet was -96°C (ethylene evaporator pressure 12 kg/c4·G), and the outlet ethylene gas temperature was 5°C.

Energy saving effect compared to conventional steam heating method: Steam reduction: 9 s Okg/Hs Chilled water refrigeration power saving lid: 170 kwH/H% Chilled water circulation pump power increase: 2
It was 0kvJH/H.

Therefore, compared to the conventional method using steam,
', f-! , the amount saved is 238 kg/It of ethylene.

The amount of power saved was 37.5 kwH/1 t of ethylene.Example 2 Using the equipment shown in Figure 1, ethylene evaporation was performed for 8,00 t of ethylene.
The operation was carried out at 0 kg/H, an ethylene evaporator feed water temperature of 15°C, and an ethylene evaporator outlet cold water temperature of 4°C. The amount of cold water produced is 9
It became 9t/H. The liquefied ethylene temperature at the inlet of the ethylene evaporator was -96°C, and the ethylene gas temperature at the outlet was 5°C.

Compared to the conventional steam heating method, the energy saving effect is 1.900 kg/h of steam reduction.

The amount of power saved for the cold water refrigerator was 340 kwH/Hz, and the power for the cold water circulation pump was increased by 20 hours.

Therefore, compared to the conventional method using steam, the amount of steam saved is 238 kg/It of ethylene.

Power saving amount is 40. OkwH/1 ton of ethylene became 0

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of equipment showing an embodiment of the present invention using water as the refrigerant and liquefied ethylene as the liquefied lower hydrocarbon, and Figure 2 is a schematic diagram of equipment showing an embodiment of the present invention using water as the refrigerant and liquefied ethylene as the liquefied lower hydrocarbon. 1 is a schematic diagram of equipment using liquefied ethylene. 1... Liquefied ethylene evaporator inlet 2... Ethylene gas evaporator outlet 3... Ethylene evaporator 4... Cold water or calcium chloride prine circulation line 8
...Cold water tank 10...Equipment using cold water or calcium chloride brine 1
3...Cold water or calcium chloride brine refrigerator patent applicant Toagosei Chemical Industry Co., Ltd.

Claims (1)

[Claims] 1. The refrigerant selected from water or calcium chloride prine, whose temperature has been raised during the cooling process, is guided to the liquefied lower hydrocarbon vaporization process and cooled by heat exchange, and then circulated to the Mayuki cooling process. A heat exchange method characterized by: