USRE27074E

USRE27074E - Refrigeration process

Info

Publication number: USRE27074E
Authority: US
Priority date: 1969-08-20
Filing date: 1969-08-20
Publication date: 1971-02-23

Abstract

A REFRIGERATION PROCESS COMPRISES EVAPORATING A REFRIGRERANT FROM AN ABSORBENT SATURATED WITH THE REGRIGERANT BY DIRECT CONTACT WITH A HEAT CARRIER WHICH IS READILY SEPARABLE FROM THE ABSORBER AND REFRIGERANT, THEREAFTER CONDENSING THE VAPORIZED REFRIGERANT BY HEAT EXCHANGE

WITH A COLD CARRIER, THEN EVAPORATING THE REFRIGERANT CONDENSATE BY HEAT EXCHANGE WITH A MEDIUM TO BE COOLED WHICH IS READILY SEPARABLE FROM THE REFRIGERANT AND THEN SATURATING THE COOLED ABSORBENT WITH THE REFRIGERANT VAPORS AND RETURNING THE SATURATED ABSORBENT TO THE INTITIAL EVAPORATION STAGE.

Description

Feb. 23, 1971 'E ETAL Re. 27,074

REFRIGERATION PROCESS.

Original Filed Aug. 19, 1964 I l +J l "ABSORBENT wml I REFRIGERANT CARRIER 1 6 I BOILER comma COLUMN TOWER I I a F- I l L J i 5 United States Patent Oflice Reissued Feb. 23, 1971 27,074 REFRIGERATION PROCESS Mikhail Emmanuilovich Aerov, Tatiana Alexandrovna Bystrova, Nina Ivanovna Zeleutsova, and Vera Afauasjevna Kulikova, Moscow, U.S.S.R., by Nauchno: Issledovateljsky Institute Sinteticheskikh Spirtov l Organicheskikh Produktov, assignee, Moscow, U.S.S.R. Original No. 3,312,078, dated Apr. 4, 1967, Ser. No. 390,672, Aug. 19, 1964. Application for reissue Aug. 20, 1969, Ser. No. 855,434

Int. Cl. F25b 15/04 US. Cl. 62-112 7 Claims Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

ABSTRACT OFTHE DISCLOSURE A refrigeration process comprises evaporating a refrigerant from an absorbent saturated with the refrigerant by direct contact with a heat carrier which is readily separable from the absorbent and refrigerant, thereafter condensing the vaporized refrigerant by heat exchange with a cold carrier, then evaporating the refrigerant condensate by heat exchange with a medium to be cooled which is readily separable from the refrigerant and then saturating the cooled absorbent with the refrigerant vapors and returning the saturated absorbent to the initial evaporation stage.

DESCRIPTION OF THE INVENTION The present invention relates to a refrigeration process for processing moderately low temperatures (+10 to 40 C.) in absorption cooling plants.

The known method of producing moderately low temperatures in absorption cooling plants is based on the use of ammonia and water. According to this method the heat exchange between the refrigerant, heat carrier and absorbent is performed through the walls of heat exchange apparatus, that is a boiler, condenser, evaporator, and absorbent cooler which have a large heat exchange surface. Since the difference of temperature of the refrigerant and heat carrier varies from 5 to C., a heat carrier of a higher potential is required. Moreover, the use of a heat exchange device with a large heat exchange surface considerably increases expenses and does not permit the utilization of low potential waste heat as a heat carrier, e.g., the heat of hot water or low pressure steam.

An object of the present invention is to provide a cooling method in absorption cooling plants which enables the production of moderately low temperatures by the utilization of low potential waste heat, e.g. the heat of hot water or low pressure steam.

Another object of the invention is to provide a refrigeration method in which direct heat exchange contact is effected between the refrigerant, the heat carrier and the absorbent.

The above and other objects are attained in a refrigeration process in which an absorbent saturated with refrigerant is passed in direct heat exchange contact in a boiler with a heat carrier while heat exchange between the heat exchanging media is carried out by direct contact.

The absorbent is constituted by a liquid heavy parafiin hydrocarbon having 6 to 10 carbon atoms per molecule. The refrigerant is constituted by a light paraffin such as ethane, propane and butane. The heat carrier is constituted by waste water or low-pressure steam. In the process, the refrigerant is vaporized in the boiler and escapes from the boiler and passes into a conljdenser, where it is condensed by contact with a] denser, where it is condensed by contact with a cold carrier, e.g., water. The thus condensed refrigerant passes [into an evaporator, 'where i it evaporates [in direct contact] into an evaporator, where it evaporates in' direct contact with the medium to be cooled. The refrigerant vapors then pass into an absorber, where they saturate absorbent from the boiler which has been cooled. The thus saturated absorbent is then returned to the boiler to complete the process.

The described process may comprise one or more of the aforementioned stages each stage including such steps as boiling, condensing, evaporating, absorbing and absorbent cooling steps. All of said stages carry out direct contact between the heat exchanging media at least in the above-mentioned stage of evaporation of the refrigerant in the boiler. The medium to be cooled may be slightly soluble in the [afrementioned] aforementioned hydrocarbons, but must be readily separable therefrom. The same is true of the cold carrier. The medium to be cooled may for example, be water or an aqueous solution of calcium chloride (brine). The hydrocarbons which are dissolved in the cold carrier are removed by blowing through with a gas which may be slightly soluble in the cold carrier, e.g. a methane-hydrogen fraction.

The direct contact between the refrigerant, the absorbent, the heat carrier and cold carrier, enables maintaining temperature differences as low as 1 to 3 C., which permits the use of hot water as a heat carrier and the utilization of low pressure steam more effectively. Moreover, the direct contact permits the use of simple vessels instead of heat exchangers, thus reducing the expense and the power requirements of refrigeration.

The nature of the invention will appear more clearly from the appended flow diagram illustrating a contact type heat-exchange apparatus[:] comprising boiler 1, condenser 2, evaporator 3, absorber 4, absorbent cooler 5, column 6, cooling tower 7, low pressure pump 8, high pressure pumps 9, 10, and 11, and

throttle valves

12 and 13.

According to the method of the invention, refrigeration is produced in the following way.

The absorbent saturated with refrigerant is delivered into the boiler 1 by the pump 11, the heat carrier (hot water or low pressure steam) is also delivered into the same boiled by the pump 9. In the boiler 1 the refrigerant is vaporized from the absorbent by the heat exchange with the heat carrier. Heat exchange is efleeted by direct contact between the heat carrier, refrigerant and absorbent in boiler 1. The refrigerant vapors escaping from the boiler 1 are condensed in condenser 2 by direct contact with the cooling water supplied from the cooling tower 7 by the pump 8. The refrigerant condensate formed in the condenser is throttled through the throttle valve 12 and is then directed either to the point where it is being consumed, or to the contact-type evaporator 3 where it evaporates in direct contact with the medium to be cooled, thus cooling the latter.

The heated absorbent flows from the boiler 1 to the absorbent cooler 5 where it is cooled by coming into direct contact with water delivered from the cooling tower 7. Then the cooled absorbent and the refrigerant vapors from evaporator 3 are supplied to the absorber 4, the cooled absorbent having passed through the throttle valve 13. The heat of absorption in the absorber 4 is removed by the cooling water in direct contact with the hydrocarbons. Then the saturated absorbent is transferred from the absorber 3 to the boiler 1 and the whole cycle is repeated.

When butane vapors are used for cooling water, bydrates may form; however, it has been found by experionce that they do not clog the apparatus. Propane hydrates can be decomposed in the presence of electrolytic aqueous solutions which are supplied in this case as a.

[refrigerant] medium to be cooled to the evaporator 3 withsmall amounts delivered at the same'time to the" throttle 12. The cooling water, leaving the condenser 2, absorber 4, and cooler 5, will contain small amounts of hydrocarbons. In order to avoid the objectionable odor of these hydrocarbons (C and up), the water flowing from the condenser 2, absorber 4 and cooler is blown through with the methane or methane hydrogen fraction in column 6.

For the production of brine having a temperature from 20 to 40 C. by the proposed method, a twostage plant is used where a second stage of a condenser, an evaporator, an absorber and [a] an absorbent cooler are supplied with water or brine already cooled in a first stage.,The invention will next be described in conjunction with the following specific examples.

EXAMPLE 1 This example is directed to the production of cold water with a temperature of +5 C. using the heat of hot water at a temperature of +90 C.

The refrigerant is butane. The high-boiling absorbent [component] is a mixture of parafiins which contains 7 to 8 carbon atoms per molecule. Pressure in the boiler is 4.5 kg./sq. cm., in the condenser 24.5 kg./sq. cm., in the evaporator 3 and absorber 4-1.3 kg./ sq. cm., in the [coler] cooler 54.5 kg./sq. cm. The temperature of the water leaving the cooling tower 7 is C., of the water supplied to the boiler 1 is +90 C., of the refrigerant condensate at throttle 12 is +4 C., of the water before entering column 6 is C., and of the cooled water at the outlet of the apparatus is +5 C.

The minimum temperature differences are 12 C., condensation pressure is 4.5 kg./ sq. cm., evaporation pressure is 1.3 kg./sq. cm. Butane concentration in mole percent is as follows: in the absorbent discharged from the boiler-%, in saturated absorbent-50%, and in refrigerant99% EXAMPLE 2 This example is directed to the production of brine at a temperature of 30 C, in the two-stage plant using the heat of hot water at a temperature of +90 C The refrigerant is propane. The absorbent corresponds to that in Example 1. The assembly of

elements

2, 3, 4 and 5 is supplied with brine having a temperature of +5 C., said brine having been obtained in a first stage by using butane as the refrigerant, according to Example 1.

In the second stage the condensation pressure is 6.5 kg./sq. cm., the evaporation pressure is 2 kg./sq. cm., propane [condensation] concentration in mole percent in absorbent discharged from the boiler in the second stage is 22%, in the saturated absorbent34%, in the refrigcram-100%.

What is claimed is:

1. A method of effecting refrigeration in absorption tcoioling' plants comprising evaporating a refrigerant from an absorbent saturated with said refrigerant by heat exchange with a heat carrier which is readily separable from said absorbent and refrigerant, said refrigerant being a light parafiin hydrocarbon, said absorbent being a liquid, 5 heavy parafiin hydrocarbon, condensing the vaporized refrigerant by heat exchange with water'as a cold carrier, evaporating the refrigerant condensate by heat exchange with a medium to be cooled which is readily separable from the refrigerant, saturating cooled absorbent with the refrigerant vapors and returning the saturated absorbent to the initial evaporation stage, the steps of the heat exchange between said absorbent, said heat carrier, said cold' carrier, and said refrigerant being carried out by direct contact.

2. A method as claimed in claim 1 wherein said heat carrier is hot water.

3. A method as claimed in claim 2, wherein said heat carrier is low pressure steam.

4. A method as claimed in claim 1 comprising blowing through the water serving as a cold carrier [through] a gas which is not soluble in the cold carrier to remove any dissolved hydrocarbons.

5. A method of effecting refrigeration in an absorption cooling plant comprising evaporating a refrigerant from an absorbent saturated with said refrigerant by heat exchange with a heat carrier which is readily separable from said absorbent and refrigerant, said refrigerant being a light paraffin hydrocarbon the absorbent being a liquid, heavy paraffin hydrocarbon; condensing the vaporized re- 30 frigerant by heat exchange with cooling water constituting a cold carrier, evaporating the refrigerant condensate by heat exchange with the medium to be cooled; cooling the absorbent after the heat exchange with the heat carrier; saturating the thus cooled absorbent with vaporized re- 35 frigerant produced after contact with the medium to be cooled and recirculating the thus saturated absorbent to the initial stage of evaporation whereby a continuous process is obtained, said steps of heat exchange between said absorbent, said heat carrier, said cold carrier and 40 said refrigerant being carried out by direct contact at least at the above-mentioned initial stag of evaporation. 6. A method as claimed in claim 5, wherein said heat carrier is hot water.

7. A method as claimed in claim 5, wherein said heat carrier is low pressure steam.

References Cited The following references, cited by the Examiner, are of record in the patented file of this patent or the original patent.

UNITED STATES PATENTS 2,041,741 5/1936 Bichowsky 621l2 2,045,204 6/1936 Shagoloff 62102 2,290,506 7/1942 Thomas 62-402 2,667,764 2/1954 Turner 62-101 WILLIAM E. WAYNER, Primary Examiner