WO2017072632A1

WO2017072632A1 - Hybrid propylene and absorption chiller system

Info

Publication number: WO2017072632A1
Application number: PCT/IB2016/056298
Authority: WO
Inventors: Joris VAN WILLIGENBURG
Original assignee: SABIC Global Technologies BV
Current assignee: SABIC Global Technologies BV
Priority date: 2015-10-30
Filing date: 2016-10-19
Publication date: 2017-05-04
Anticipated expiration: 2018-04-30

Abstract

The presently disclosed subject matter relates to methods and systems of propylene refrigeration. The subject matter provides a system for propylene refrigeration wherein additional cooling duty is provided to a heat exchanger by a unit which consumes low temperature heat released by reactor effluent (waste heat) produced by cracking and dehydrogenation reactions. The use of waste heat can reduce the compression power required during the refrigeration process.

Description

HYBRID PROPYLENE AND ABSORPTION CHILLER SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Application No. 62/248,705, filed October 30, 2015. The contents of the referenced application are incorporated into the present application by reference.

FIELD

[0002] The presently disclosed subject matter relates to methods of propylene refrigeration.

BACKGROUND

[0003] Propane is often obtained as a by-product of natural gas processing. The hydrocarbon can be converted into propene via propane dehydrogenation which is of great use in the petrochemical industry. However, the equipment in the cold separation section of a propane dehydrogenation unit requires cooling. At a temperature range between -45 °C and 30 °C liquid propane, propylene or a mixture of propane and propylene coolant can be evaporated in heat exchangers at different pressure levels to cool down or condensate process streams. Such cooling systems can require several pressure levels, compressor stages, and energy to drive the refrigeration cycle.

[0004] Meanwhile, steam crackers and propane dehydrogenation units generate waste heat that can often go unused or requires additional energy to dissipate. These processes favor low pressures which are achieved by mixing steam with hydrocarbons. This steam then has to be separated from the reactor effluent, typically by condensation. Condensation releases a significant quantity of low temperature heat and requires additional systems and energy to cool.

[0005] There remains a need in the art for methods and systems for utilizing the low temperature heat waste heat generated by cracking and dehydrogenation. There is also a need in the art for improving the overall energy efficiency of cooling systems for propane dehydrogenation units. The presently disclosed subject matter provides a process of propylene refrigeration utilizing waste heat from the cracking and/or dehydrogenation processes to reduce energy requirements.

SUMMARY OF THE DISCLOSED SUBJECT MATTER

[0006] The presently disclosed subject matter provides for a system and process for propylene refrigeration.

[0007] In certain embodiments, a process for propylene refrigeration can include increasing the pressure of a propylene vapor stream to generate a compressed propylene stream. In certain embodiments, the process can further include condensing the compressed propylene stream to generate a liquid propylene stream. In certain embodiments, the process can further include decreasing the temperature of the liquid propylene stream to generate a cooled liquid propylene stream. In certain embodiments, the process can further include decreasing the pressure of the cooled liquid propylene stream to generate a propylene vapor and propylene liquid mixture. In certain embodiments, the process can further include evaporating the propylene liquid within the propylene vapor and propylene liquid mixture to propylene vapor. In certain embodiments, the process can further include recycling the propylene vapor beginning of the process.

[0008] In certain embodiments, the saturated propylene vapor has a pressure of about 6 bar_a and the compressed propylene vapor stream has a pressure of about 14 bar_a.

[0009] In certain embodiments, the liquid propylene stream has a pressure of about 14 bar_a.

[0010] In certain embodiments, the process can further include cooling the liquid propylene stream to generate a cooled liquid propylene stream at 14 bar_a and a lower third temperature.

[0011] In certain embodiments, the process can further include decreasing the pressure of the cooled liquid propylene stream adiabatically to generate a mixture of propylene vapor and propylene liquid at a lower fourth temperature. [0012] In certain embodiments, the process can further include evaporating the propylene liquid to propylene vapor stream at 6 bar_a.

[0013] In certain embodiments, compression proceeds within a compressor or compressor stage. In certain embodiments, the liquid propylene stream is cooled by a heat exchanger.

[0014] In certain embodiments, the power for the heat exchanger is supplied by an absorption chiller. In certain embodiments, the absorption chiller is a single stage absorption chiller. In certain embodiments, the absorption chiller is a multi-stage absorption chiller. In certain embodiments, the heat exchanger is a single-stage lithium bromide absorption chiller. In certain embodiments, power for the heat exchanger is supplied by an adsorption chiller.

[0015] In certain embodiments, a process for propylene refrigeration can include increasing the pressure of 825 kg/h of a saturated propylene vapor at 6 bar_a to generate a compressed propylene vapor stream of 14 bar_a and 49 °C in a compressor or compressor stage. In certain embodiments, the compression power is 13 kW_meCh- In certain embodiments, the process can further include condensing the compressed propylene vapor stream in a condenser to generate a liquid propylene stream at 14 bar_a and 33 °C. In certain embodiments, the process can further include decreasing the temperature of the liquid propylene stream by a heat exchanger to generate a cooled liquid propylene stream at 14 bar_a and 10 °C. In certain embodiments, said heat exchanger is a single stage absorption chiller and provides 14kW_th cooling duty. In certain embodiments, the process can further include decreasing the pressure of the cooled liquid propylene stream adiabatically to 6 bar_a to generate a mixture of 6% propylene vapor and 94% propylene liquid at 1 °C. In certain embodiments, the process can further include evaporating the propylene liquid to propylene vapor stream at 6 bar_a. In certain embodiments, the process can further include returning the propylene vapor to the compressor or compressor stage.

[0016] In certain embodiments, the absorption chiller consumes waste heat. In certain embodiments, the waste heat is generated by condensation of water from reactor effluent.

[0017] In certain embodiments, the reactor effluent is produced by steam cracking. In certain embodiments, the reactor effluent is produced by dehydrogenation processes.

[0018] In certain embodiments, the subject matter of the disclosure provides for a system for propylene refrigeration comprising a compressor or compressor stage for increasing the pressure of a propylene vapor stream to form a high pressure compressed propylene stream; a condenser coupled to the compressor or compressor stage, for condensing the compressed propylene stream to generate a liquid propylene stream; a heat exchanger, coupled to the condenser for decreasing the temperature of the liquid propylene stream to generate a cooled liquid propylene stream; an absorption chiller, coupled to the heat exchanger to supply cooling duty to said heat exchanger; an expansion valve, coupled to the heat exchanger, for decreasing the pressure of the liquid propylene stream adiabatically to generate a propylene vapor and propylene liquid mixture; and an evaporator coupled to the expansion valve, for evaporating the propylene liquid to propylene vapor, an coupled to the compressor or compressor stage for recycling the propylene vapor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a schematic diagram depicting an exemplary system for a hybrid propylene and absorption chiller refrigeration cycle in accordance with one non-limiting embodiment of the disclosed subject matter.

[0020] FIG. 2 is a schematic diagram depicting an exemplary method for a hybrid propylene and absorption chiller refrigeration cycle in accordance with one non-limiting embodiment of the disclosed subject matter.

DETAILED DESCRIPTION

[0021] The presently disclosed subject matter provides for methods and systems of propylene refrigeration. [0022] The presently disclosed subject matter provides a system for propylene refrigeration that includes a heat exchanger. In certain embodiments, the system can further include an unit, e.g., an absorption or adsorption chiller, that can provide additional cooling duty to the heat exchanger. In certain embodiments, the unit can consume low temperature heat released by reactor effluent (waste heat) produced by cracking and dehydrogenation reactions. In certain embodiments, this use of waste heat reduces the compression power required during the disclosed refrigeration process and results in an overall energy improvement to the both the refrigeration and cracking process.

[0023] In certain embodiments, the waste heat can be produced by cracking and dehydrogenation reactions. For example, during cracking and dehydrogenation processes, steam can be mixed with hydrocarbons to achieve the necessary pressure and prevent coke formation. The steam then must be separated and removed from the reaction, which is typically performed by condensation. In certain embodiments, condensation of the steam occurs at temperatures between about 60 °C and about 100 °C and can result in waste heat. There is limited use for this waste heat in the remaining downstream separation steps of the cracking and dehydrogenation processes and, in certain embodiments, air coolers or cool water are required to eliminate the waste heat. In certain embodiments, the waste heat can be used in the systems and methods of the present disclosure, which can eliminate the need for air coolers or cool water in the cracking and dehydrogenation processes and improve energy efficiency. In certain embodiments, the waste heat source can be the cracking furnace stacks. In certain embodiments, the waste heat source can be from a pyrolysis gasoline (pygas) plant.

[0024] For the purpose of illustration and not limitation, FIG. 1 is a schematic representation of an exemplary system according to the disclosed subject matter. In certain embodiments, the system 100 can include one or more compressors with multiple stages, one or more condensers, one or more evaporators and one or more vessels. [0025] In certain embodiments, a system 100 for propylene refrigeration can include a first compressor 103. In certain embodiments, the compressor 103 can be a single stage compressor or a multiple stage compressor. For example, and not by way of limitation, the compressor can have one stage, two stages, three stages, four stages or more. In certain embodiments, the first compressor 103 can be a first compressor stage. In certain embodiments, the first compressor or compressor stage 103 can be used to compress the propylene refrigerant.

[0026] "Coupled" as used herein refers to the connection of a system component to another system component by any means known in the art. The type of coupling used to connect two or more system components can depend on the scale and operability of the system. For example, and not by way of limitation, coupling of two or more components of a system can include one or more joints, valves, transfer lines or sealing elements. Non-limiting examples of joints include threaded joints, soldered joints, welded joints, compression joints and mechanical joints.

[0027] In certain embodiments, the first compressor 103 can be coupled to a condenser 105, e.g. , via a transfer line. In certain embodiments, the condenser 105 is further coupled to a heat exchanger 107, e.g., for reducing the temperature of the compressed refrigerant. The heat exchangers of the processes and systems of the present disclosure can be of various designs known in the art. In certain embodiments, the heat exchangers can be double pipe exchangers. In certain embodiments, the heat exchangers can include a bundle of tubes housed in a shell, such that fluids to be warmed or cooled within the heat exchanger flow through the shell and/or bundle of tubes. In certain embodiments, the heat exchangers can include corrosion-resistant materials. In certain embodiments, the heat exchangers can include an alloy, e.g., steel or carbon steel. In certain embodiments, the heat exchangers can include brazed aluminum. [0028] In certain embodiments, the heat exchanger 107 is coupled to unit which can provide cooling power generated by waste heat. For example, and not by way of limitation, the unit can be an adsorption chiller or a absorption chiller. In certain embodiments, the incorporation of an adsorption chiller or a absorption chiller can reduce the amount of mechanical work required to be performed by the compressor.

[0029] In certain embodiments, the absorption chiller is a single stage absorption chiller, e.g. , a single stage lithium bromide absorption (LiBr) chiller. In certain embodiments, the absorption chiller is a multi-stage absorption chiller, e.g., a multi-stage LiBr absorption chiller or an ammonia absorption chiller. In certain embodiments, there is sufficient waste heat available and the absorption chiller can replace condenser 105. In certain embodiments, the absorption chiller can condense the propylene refrigerant directly from first compressor or first compressor stage 103 and replace the condenser 105. In certain embodiments, the absorption chiller can be replaced with an adsorption chiller.

[0030] In certain embodiments, waste heat utilized by the absorption chiller can be generated by different sources along the steam cracking process. In one non-limiting example, a source of waste heat can be heat produced from the cracking furnace stacks in the temperature range of 80-120 °C by cooling and/or partially condensing the flue gases. In certain non-limiting embodiments, the source of waste heat can be heat from a pyrolysis gasoline plant, furnace flue gasses or low pressure (e.g., from about 0.5 to about 1 bar_a) steam from a steam turbine exhaust or stage extraction.

[0031] In certain embodiments, the heat exchanger 107 can be coupled to an expansion valve 109, e.g. , for reducing the pressure of the compressed refrigerant. In certain embodiments, the expansion valve 109 is in turn coupled to an evaporation unit 112, e.g. , to vaporize the liquid refrigerant exiting the expansion valve 109. In certain embodiments, the evaporation unit 112 is coupled to the first compressor stage 103 to create a closed-loop propylene refrigeration system. For the purpose of illustration and not limitation, FIG. 2 is a schematic representation of methods according to non-limiting embodiments of the disclosed subject matter. In certain embodiments, a method of propylene refrigeration 200 is carried out using system 100 of the disclosed subject matter. In certain embodiments, the propylene refrigerant used in the disclosed systems and methods can further include propane. For example, and not by way of limitation, the propylene refrigerant can include from about 1% to about 10% propane, e.g., about 5% propane.

[0032] In certain embodiments, the method 200 includes increasing the pressure of a propylene refrigerant vapor to generate a compressed propylene vapor 201. In certain embodiments, the propylene vapor has a flow rate from about 500 kg/h to about 1000 kg/h. In certain embodiments, the propylene vapor has a flow rate from about 750 kg h to about 900 kg/hr. In certain embodiments, the propylene vapor has a flow rate of at least about 825 kg h. In certain embodiments, the propylene vapor has a pressure from about 1 to about 10 bar_a (bar absolute). In certain embodiments, the propylene vapor has a pressure from about 3 to about 7 bar_a. In certain embodiments, the propylene vapor has a pressure of about 6 bar_a.

[0033] In certain embodiments, the saturated propylene vapor is compressed to generate a compressed propylene vapor having a pressure of about 5 bar_a to about 20 bar_a, e.g., in a compressor or compressor stage. In certain embodiments, the compressed propylene vapor has a pressure of about 10 bar_a to about 15 bar_a. In certain embodiments, the compressed propylene vapor has a pressure of about 14 bar_a. In certain embodiments, the required compression power, i.e., for compressor or compressor stage 103, is from about 5 to about 25 kWmech (kW mechanical work). In certain embodiments, the required compression power is from about 10 to about 25 kWmech. In certain embodiments, the required compression power is about 13 kWmech. In certain embodiments, superheated propylene vapor is generated at a first temperature. In certain embodiments, the first temperature is from about 35 °C to about 65 °C. In certain embodiments, first temperature is from about 45 °C to about 55 °C. In certain embodiments, the first temperature is about 49 °C.

[0034] In certain embodiments, the method can include condensing the compressed propylene vapor to generate a propylene liquid 202. In certain embodiments, the propylene liquid is at second temperature, which is lower than the temperature of the compressed propylene vapor. In certain embodiments, the second temperature is slightly below the boiling point of propylene. In certain embodiments, the second temperature is from about 25 °C to about 45 °C. In certain embodiments, the second temperature is about 30 °C to about 40 °C. In certain embodiments, the second temperature is about 33 °C. In certain embodiments, the propylene liquid 106 has a pressure from about 5 bar_a to about 20 bar_a. In certain embodiments, the propylene liquid 106 has a pressure from about 10 bar_a to about 15 bar_a. In certain embodiments, the propylene liquid 106 has a pressure of about 14 bar_a.

[0035] In certain embodiments, the temperature of the liquid propylene can be reduced to generate a cooled propylene liquid 203 having a third temperature. In certain embodiments, the third temperature can be from about 1 °C to about 40 °C. In certain embodiments, the third temperature can be from about 1 °C to about 20 °C. In certain embodiments, the third temperature can be from about 10 °C. In certain embodiments, the cooled propylene liquid can have a pressure from about 5 bar_a to about 20 bar_a, e.g., the cooled propylene liquid can have the same pressure at the liquid propylene. In certain embodiments, the cooled propylene liquid can have a pressure from about 8 bar_a to about 16 bar_a. In certain embodiments, the cooled propylene liquid can have a pressure about 14 bar_a.

[0036] In certain embodiments, the temperature of the liquid propylene can be reduced via heat exchanger. In certain embodiments, an adsorption unit or an absorption unit can provide the cooling duty required for the heat exchanger.

[0037] In certain embodiments, about 65% of the thermal heat input generated by cracking or dehydrogenation is converted to thermal cooling duty by a chiller, an absorption chiller or an adsorption chiller. In certain embodiments, about 70% of the thermal heat input is converted to thermal cooling duty by the chiller. In certain embodiments, at least about 70% of the thermal heat input is converted to thermal cooling duty by the chiller. In certain embodiments, heat exchanger 107 utilizes from about 5 to about 25 kWth cold, i.e., generated from a chiller. In certain embodiments, heat exchanger 107 utilizes from about 10 to about 20 kWth cold generated from a chiller. In certain embodiments, heat exchanger 107 utilizes about 14 kWth cold generated from a chiller.

[0038] In certain embodiments, the pressure of the cooled propylene liquid is decreased, e.g. , adiabatically decreased, to produce a mixture of propylene vapor and propylene liquid 204. For example, and not by way of limitation, the pressure of the cooled propylene liquid 108 is adiabatically decreased, e.g., using an expansion valve, to produce a mixture of propylene vapor and propylene liquid. In certain embodiments, the pressure is decreased from 14 to 6 bar_a. In certain embodiments, the pressure is decreased by at least 2 bar_a. In certain embodiments, the pressure is decreased by at least 5 bar_a. In certain embodiments, the pressure is decreased by at least 8 bar_a. In certain embodiments, the pressure is decreased by at least 10 bar_a. In certain embodiments, the temperature of the propylene vapor and propylene liquid mixture is a fourth, lower temperature, e.g. , from about -15°C to about 10°C. In certain embodiments, the fourth temperature is from about -5°C to about 5°C. In certain embodiments, the fourth temperature is about 1 °C. In certain embodiments, the mixture contains from about 1% to about 25% vapor. In certain embodiments, the mixture 110 contains about 2% to about 15% vapor. In certain embodiments, the mixture 110 includes about 6% vapor. In certain embodiments, the mixture includes about 75% to about 98% propylene liquid. In certain embodiments, the mixture is from about 85% to about 97% liquid. In certain embodiments, the mixture includes about 96% liquid. [0039] In certain embodiments, the propylene liquid within the propylene vapor and propylene liquid mixture 110 is evaporated 205, which can then be combined with the propylene refrigerant vapor to generate a closed-loop propylene refrigeration method. In certain embodiments, the remaining liquid 110 is evaporated in an evaporation unit, and returned to the first compressor, e.g., the first compressor or compression stage. In certain embodiments, the amount of energy that can be used to evaporate the propylene liquid within the propylene vapor and propylene liquid mixture can be from about 75 kWth to about 100 kWth. In certain embodiments, the evaporation energy can be from about 80 kWth to about 90 kWth. In certain embodiments, the evaporation energy can be from about 81 kWth.

[0040] The term "about" or "substantially" means within an acceptable error range for the particular value as determined by one of ordinary skill in the art, which will depend in part on how the value is measure or determine, i.e., the limitations of the measurement system. For example, "about" can mean a range of up to 20%, up to 10%, up to 5% or up to 1% of a given value.

[0041] In addition to the various embodiments depicted and claimed, the disclosed subject matter is also directed to other embodiments having other combinations of the features disclosed and claimed herein. As such, the particular features presented herein can be combined with each other in other manners within the scope of the disclosed subject matter such that the disclosed subject matter includes any suitable combination of the features disclosed herein. The foregoing description of specific embodiments of the disclosed subject matter has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosed subject matter to those embodiments disclosed.

[0042] It will be apparent to those skilled in the art that various modifications and variations can be made in the compositions and methods of the disclosed subject matter without departing from the spirit or scope of the disclosed subject matter. Thus, it is intended that the disclosed subject matter include modifications and variations that are within the scope of the appended claims and their equivalents.

[0043] The following example is merely illustrative of the presently disclosed invention and should not be considered as a limitation in any way. EXAMPLES

Example 1: Propylene refrigeration.

[0044] This example provides a process of propylene refrigeration using an absorption chiller.

[0045] In this example, a saturated propylene vapor is 825 kg/h of saturated propylene vapor at 6 bar_a. The vapor is compressed to 14 bar_a. The required compression power for the compressor (FIG. 1; 103) is 13 kWmech. The outlet condition of the compressor is superheated propylene vapor of 14 bar_a and at 49 °C (FIG. 1; "2"). In a condenser (FIG. 1; 105), the condensation heat is discharged to cooling water. The outlet conditions are propylene liquid at 33 °C and 14 bar_a(FIG. 1; "3"). The liquid propylene is sub cooled by a heat exchanger (FIG. 1; 107) which utilizes 14 kWth cold generated from an absorption chiller. The absorption chiller unit has a coefficient of performance of 0.7 (kWth cold generated / kWth heat required). The heat utilized by the absorption chiller originates from low temperature waste heat from a steam cracking process.

[0046] The outlet conditions of the heat exchanger are propylene liquid at 10 °C and 14 bar_a (FIG. 1; "3"')- The pressure of the propylene liquid is adiabatically decreased over an expansion valve (FIG. 1; 109) to a mixture of 6% propylene vapor and 94% propylene liquid at 6 bar_a and at a temperature of 1 °C (FIG. 1; "4"). The remaining liquid is evaporated back to a saturated propylene vapor (FIG. 1; "1").

[0047] The evaporation energy of 81 kWth (kW thermal) originates from the process that requires the cooling and equals the cooling duty provided by the described cooling cycle. [0048] The temperature difference for liquid propylene is 4 °C, as compared to a standard propylene refrigeration process, and the described cooling cycle provides 81 kWth cooling at 4 °C.

[0049] The compression power required for the compressor is reduced. Less power is require due to the 14 kWth cold supplied by the absorption chiller which powers the condenser. The energy efficiency a propylene refrigeration process is therefore improved.

Claims

1. A process for propylene refrigeration comprising:

a) increasing the pressure of a propylene vapor stream to generate a compressed propylene stream;

b) condensing the compressed propylene stream to generate a liquid propylene stream;

c) decreasing the temperature of the liquid propylene stream to generate a cooled liquid propylene stream;

d) decreasing the pressure of the cooled liquid propylene stream to generate a propylene vapor and propylene liquid mixture;

e) evaporating the propylene liquid within the propylene vapor and propylene liquid mixture to propylene vapor; and

f) returning the propylene vapor of step e) to step a).

2. The process of claim 1, wherein the saturated propylene vapor has a pressure of about 6 bar_a and the compressed propylene vapor stream has a pressure of about 14 bar_a.

3. The process of claim 2, wherein the liquid propylene stream has a pressure of about 14 bar_a.

4. The process of claim 3, wherein step c) further comprises cooling the liquid propylene stream generate a cooled liquid propylene stream at 14 bar_a and a lower third temperature.

5. The process of claim 4, wherein step d) further comprises decreasing the pressure of the cooled liquid propylene stream adiabatically to generate a mixture of propylene vapor and propylene liquid at a lower fourth temperature.

6. The process of claim 5, wherein the propylene vapor stream at 6 bar_a.

7. The process of claim any one of claims 1 to 6, wherein step a) proceeds within a compressor or compressor stage.

8. The process of claim any one of claims 1 to 6, wherein in step c), the liquid propylene stream is cooled by a heat exchanger.

9. The process of claim 8, wherein power for the heat exchanger is supplied by an absorption chiller.

10. The process of claim 9, wherein the absorption chiller is a single stage absorption chiller.

11. The process of claim 9, wherein the absorption chiller is a multi-stage absorption chiller.

12. The process of any one of claims 8 to 11, wherein the heat exchanger is a single-stage lithium bromide absorption chiller.

13. The process of claim 8, wherein power for the heat exchanger is supplied by an adsorption chiller.

14. A process for propylene refrigeration comprising:

a) increasing the pressure of 825 kg/h of a saturated propylene vapor at 6 bar_a to generate a compressed propylene vapor stream of 14 bar_a and 49 °C in a compressor or compressor stage, wherein the compression power is 13

b) condensing the compressed propylene vapor stream in a condenser to generate a liquid propylene stream at 14 bar_a and 33 °C;

c) decreasing the temperature of the liquid propylene stream by a heat exchanger to generate a cooled liquid propylene stream at 14 bar_a and 10 °C, wherein said heat exchanger is a single stage absorption chiller and provides 14kW_th cooling duty;

d) decreasing the pressure of the cooled liquid propylene stream adiabatically to 6 bar_ato generate a mixture of 6% propylene vapor and 94% propylene liquid at 1 °C;

e) evaporating the propylene liquid within the propylene vapor and propylene liquid mixture to propylene vapor stream at 6 bar_a; and f) returning the propylene vapor of step e) to the compressor or compressor stage of step a).

15. The process of any one of claims 1 to 14, wherein the absorption chiller consumes waste heat.

16. The process of claim 14, wherein the waste heat is generated by condensation of water from reactor effluent.

17. The process of claim 14, wherein the reactor effluent is produced by steam cracking.

18. The process of claim 14, wherein the reactor effluent is produced by dehydrogenation processes.

19. A system for propylene refrigeration comprising:

a) a compressor or compressor stage for increasing the pressure of a propylene vapor stream to generate a high pressure compressed propylene stream;

b) a condenser coupled to the compressor or compressor stage, for condensing the compressed propylene stream to generate a liquid propylene stream;

c) a heat exchanger, coupled to the condenser for decreasing the temperature of the liquid propylene stream to generate a cooled liquid propylene stream; d) an absorption chiller, coupled to the heat exchanger to supply cooling duty to said heat exchanger;

e) an expansion valve, coupled to the heat exchanger, for decreasing the pressure of the cooled liquid propylene stream to generate a propylene vapor and propylene liquid mixture; and

f) an evaporator coupled to the expansion valve, for evaporating the propylene liquid within the propylene vapor and propylene liquid mixture to propylene vapor, and coupled to the compressor or compressor stage of step a) for recycling the propylene vapor of step e).