US20070251668A1

US20070251668A1 - High temperature refrigeration cycle method and apparatus

Info

Publication number: US20070251668A1
Application number: US11/691,359
Authority: US
Inventors: Mark Smith
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-03-24
Filing date: 2007-03-26
Publication date: 2007-11-01

Abstract

A refrigeration apparatus for removing heat from a high temperature region. The refrigeration apparatus wherein the high temperature region is a stream of fluid having a temperature above 160 degrees Fahrenheit. The heat from the high temperature region is used to evaporate the refrigerant in a refrigeration cycle.

Description

RELATED APPLICATION

This application claims priority from U.S. Provisional Patent Application No.: 60/785,599, filed on Mar. 24, 2006, which application is incorporated herein by reference.

BACKGROUND

Currently, enormous amounts of waste heat are generated daily by a wide variety of industrial and commercial processes and operations. These range, typically, from waste heat from space heating operations, process steam boiler waste heat, mechanical and electrical system cooling, and the like. Typically, the waste heat is low grade, that is, it is below about 350° F., and often below about 250° F., a value so low that conventional heat recovery systems do not operate with sufficient efficiency to make recovery of energy from such sources economical. The net result is that vast quantities of waste heat are simply dumped to atmosphere, ground or water thereby contributing to the overall greenhouse effect and effectively raising the cost of operations.
Many times the high temperature waste gas and vapor is vented to the atmosphere. For example, in a coal-fired power generator used to produce electricity large amounts of steam or combustion products from burning coal are placed into the atmosphere. Another example is an ethanol plant or a plant used to produce ethanol. Part of producing ethyl alcohol is to form a mash of a biomass material such as corn, or other biomass material. A dryer is used to drive off some of the water thus creating a high temperature moist air stream before further processing the mash into ethyl alcohol or ethanol. Steam is generated by this process which is vented to the atmosphere. It should also be noted that the normal products of combustion include water and carbon dioxide. These waste streams present wasted heat placed into the atmosphere. Placing heat and other waste products in the atmosphere has many disadvantages. One of the main disadvantages is the inefficiencies of the various processes in not recovering some of the heat before venting it to the atmosphere. Also places VOC's into atmosphere

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is pointed out with particularity in the appended claims. However, a more complete understanding of the present invention may be derived by referring to the detailed description when considered in connection with the figures, wherein like reference numbers refer to similar items throughout the figures, and:
FIG. 1 is a schematic diagram of a refrigeration cycle applied to a high temperature waste stream, according to an embodiment of this invention.
FIG. 2 is a schematic of another embodiment of a refrigeration cycle applied to a high temperature waste stream, according to another embodiment of the invention.
FIG. 3 is a schematic diagram of a refrigeration cycle applied to a high temperature waste stream, according to yet another embodiment of the invention.
FIG. 4 is a schematic diagram of yet another embodiment of a refrigeration cycle or refrigeration device applied to a high temperature stream, such as high temperature waste stream, according to an example embodiment.
FIG. 5 is a flow chart of a method for controlling the compressors of a waste stream and a refrigerant, respectively, according to an example embodiment.
FIG. 6 is a block diagram of a computer system 2000 that executes programming for performing the above algorithm or method shown in FIG. 5, according to an example embodiment.
The description set out herein illustrates the various embodiments of the invention, and such description is not intended to be construed as limiting in any manner.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural and electrical changes may be made without departing from the scope of the present invention. The following description is, therefore, not to be taken in a limited sense, and the scope of the present invention is defined by the appended claims.
FIG. 1 is a schematic diagram of a refrigeration cycle 100 applied to a high temperature stream 160, according to an example embodiment of the invention. The high temperature stream 160 can be any type of stream including a high temperature waste stream. Other high temperature streams include streams within a process before venting them to atmosphere. The refrigeration cycle 100 is actually a device which includes an evaporator type heat exchanger that serves as an evaporator 130, a heat exchanger that serves as a condenser 120, a throttling valve 110, and a pump compressor 170. The evaporator type heat exchanger that serves as an evaporator 130 is placed into the high temperature stream. The heat exchanger 130 removes heat from the high temperature stream 160, such as the waste heat stream. As shown in FIG. 1, the high temperature stream includes a portion that is not routed through the heat exchanger that serves as an evaporator 130. This portion represents a portion that might be beyond the capacity of the heat exchanger 130 or a portion that may simply bypass the heat exchanger 130. The heat exchanger 130 or any heat exchanger for that matter, can have capacities related to a volume of gas and vapor or liquid that can be routed through a heat exchanger. A refrigerant R is placed in the refrigeration loop or device 100. The refrigerant R travels in the direction shown by the various arrows in the refrigeration device or refrigeration cycle. The refrigerant R can be any type of refrigerant or any fluid capable of changing phases or even carrying heat in various states as it passes through the refrigeration cycle or refrigeration device 100. The heat exchanger that serves as an evaporator 130 removes heat from the high temperature stream 160, such as any fluid stream in a ethanol plant. At the heat exchanger that serves as an evaporator, the heat may be used to vaporize the refrigerant R. Thus, the refrigerant R may enter the heat exchanger evaporator 130 as a liquid and leave in a gaseous vapor phase in embodiment of the invention. An expansion valve or other throttling mechanism 110 is then used to further expand the gas or regulate the gas vapor. The refrigerant R then enters a heat exchanger condenser 120 where heat is removed from the heat exchanger and placed into a different portion of an industrial process.
The cooled refrigerant R then leaves the heat exchanger condenser as a liquid and is pumped or directed under pressure to heat exchanger evaporator 130 other compressor 170 before reentering the heat exchanger evaporator 130. In essence, the refrigeration cycle or refrigeration device 100 is a device which removes heat from a high temperature stream and places it in a different area needing heat in an industrial process. For example, in the production of ethyl alcohol or ethanol, water and biomass are mixed to form a mash. In many ethanol plants, after a time at least a portion of the water is driven away from the mash for use as animal feed, or the like, and before the mash is further processed. The water driven off is a high temperature stream that, in the past, may have been exhausted to the atmosphere. Using the high temperature refrigeration cycle or refrigeration device 100 shown in FIG. 1, heat can be removed from the high temperature stream 160 and placed into another area of the ethanol plant. For example, heat removed from the high temperature waste stream 160 can be placed or used in the distillation columns of an ethanol plant. Recovering heat and placing it at different areas within a process increases the overall efficiency of the process. It should be noted that the refrigerant R used can be any type of refrigerant. In some instances, water is used as a refrigerant. In other instances, alcohol can be used as the refrigerant and in still other instances liquids designed to be refrigerants can be used. In another embodiment, high temperature azeotrope blends, such as 194 proof ethanol and water, form the refrigerant. An azetrope is a liquid mixture of two or more substances that retains the same composition in the vapor state as in the liquid state when distilled or partially evaporated under a certain pressure.
FIG. 2 is a schematic diagram of another refrigeration cycle or refrigeration device 200, according to an example embodiment of the invention. The refrigeration cycle 200 or refrigeration device 200 is applied to a high temperature stream 260. The refrigeration device 200 includes an evaporator or heat exchanger that serves as an evaporator 230, a heat exchanger that serves as a condenser 220, as well as a cascade condenser evaporator 240. The refrigeration device 200 actually includes a first refrigeration loop 201, and a second refrigeration loop 202. The first refrigeration loop 201 includes the heat exchanger that serves as an evaporator 230, a throttling mechanism or expansion valve 210 and a compressor pump 270. The first refrigeration loop 201 also includes a refrigerant R₁. The heat exchanger that serves as an evaporator 230 removes heat from the high temperature stream 260 and turns the refrigerant R₁into a vapor or into a higher temperature vapor, depending upon the refrigerant R₁.
The refrigerant R₁then enters the cascade evaporator/condenser 240. For the first refrigeration loop 201, the cascade evaporator and condenser serve to condense the refrigerant or cooler refrigerant R₁. The liquid refrigerant then passes out of the cascade evaporator/condenser 240 and is revaporized at 230 and again compressed by a pump or other compressor 270 before being routed once again through the heat exchanger that serves as an condenser 240. The refrigerant R₂passes through a refrigeration loop 202 that includes the evaporator/condenser 240, a throttle or other valve expansion valve 212, the condenser heat exchanger 220 and a pump or other compressor 272. At the cascade evaporator condenser, the refrigerant R₂is a liquid being vaporized thus condensing R1 which picks up heat, such as the heat of vaporization. The refrigerant is either moved to a vapor state or to a higher energy carrying state after it passes through the cascade evaporator condenser 240. The refrigerant is compressed, expanded or passed through the condenser 220 and then to throttle 212 before once again picking up the energy needed to vaporize the R2 at evaporator/condenser 240 thus completing the cycle. The refrigerant then passes through the pump 272 or other compressor. Heat is removed from the refrigerant R₂at the heat exchanger that serves as a condenser 220. This heat exchanger that serves as a condenser 220 can be placed at or near any portion of a system that requires additional heat or can benefit from having high quality latent heat. The refrigeration device 200 shows that the refrigeration cycle can be cascaded or can include any number of cascades to recover further heat from the refrigerants or from the high temperature streams. Whether or not to add an additional cascading level is generally a matter of economics. It should be understood that most of the high temperature streams are at 100° F. to 160° F. or above.
FIG. 3 is a schematic diagram of yet another embodiment of a refrigeration cycle or refrigeration device 300 applied to a high temperature stream, such as high temperature stream 160 or high temperature stream 260. The high temperature stream is represented by references C and D in FIG. 3. The refrigeration apparatus 300 utilizes the latent heat of evaporation in a high temperature region, such as a waste stream, to maximize economic benefit. The refrigeration apparatus 300 includes a plate heat exchanger 320 that acts as an condenser evaporator, and a plate heat exchanger 330 that acts as a evaporator condenser. The refrigeration apparatus 300 also includes compressors 301 a and 301 b and a pump 307. The refrigeration apparatus also includes an accumulator 306, a separator 309 and a number of motorized valves 308 a, 308 b, 308 c for controllably adding fluids to the refrigerant in the refrigeration loop that forms the refrigeration apparatus 300. The waste heat stream high temperature region is depicted by the flows labeled (c) and (d) in FIG. 3. A refrigerant is used in a high temperature region to capture latent heat. The refrigerant changes phase from a liquid to a low quality vapor at plate heat exchanger 330. As a result, water is separated out of a gaseous air, CO2 or other inert drying medium. The waste stream enters in counter flow manner at (c) and emerges substantially stripped of water vapor and at lower temperature at the flow arrow (d). The water condensed from the waste stream, represented by the flow arrow (h) is processed to eliminate contaminates at a device 310. Various means are to be utilized within device 310 to neutralize Volatile Organic Compounds (VOC) and particulates and prepare the water for re-utilization within the parent industrial process. This example embodiment uses water as the refrigerant (f′) provided the humidity ratio of the waste stream permits. It should be noted that any type of fluid can be used as a refrigerant. Typically, the refrigerant must be matched to the temperatures of the high temperature region in which the refrigeration apparatus 300 is to be used. Azeotropes, in one example embodiment, are added to the water to alter the condensing temperature and pressures that would allow maximum Coefficient of Performance (“COP”) at lower humidity ratios in the waste stream (c). The low pressure refrigerant vapor is passed through the separator 306 so that no water droplets are allowed to travel into the compressor stage 301 a, or the compressor stage 301 b via flow (f). It should be noted that additional compressor stages may be employed in the refrigeration cycle or refrigeration apparatus 300.
FIG. 4 is a schematic diagram of yet another embodiment of a refrigeration cycle or refrigeration device 400 applied to a high temperature stream, such as high temperature waste stream 460. The high temperature waste stream 460 can be any stream of waste water. In one embodiment, the high temperature waste stream 460 is a waste stream from a drum drying apparatus. The refrigeration device 400 includes a heat transfer device 402, such as an evaporator heat exchanger. The waste stream includes steam having a pressure and temperature. The high temperature refrigeration device includes a compressor 410 for compressing the waste stream 460. The waste stream 460 may include superheated steam. The compressor 410 in the waste stream 460 can then be used to control the pressure associated with the steam in the waste stream. In other words, the compressor 410 is used to adjust the boiling point of the waste stream. By increasing the pressure in the waste stream 460, the boiling point of the fluid in the waste stream can be increased. The high temperature refrigeration device 400 also includes a refrigeration loop 430. The refrigeration loop includes a refrigerant, R1, and also includes a compressor 420 that is used to compress the refrigerant, R. The compressor 420 in the refrigeration loop 430 can then be used to control the pressure associated with the refrigerant in the refrigeration loop 430. In other words, the compressor 420 is used to adjust the boiling point of the refrigerant. The compressors 410, 420 are used to place both the waste stream and the refrigerant R in a state where the latent heat of transfer can occur for both fluids within the heat transfer device 402. In the case of a heat exchanger, the latent heat of transfer is occurring for both fluids at a plate or plates within the heat transfer device 402. When the latent heat of transfer is occurring for a fluid is being transferred at a plate or plates within the heat transfer device 402 the fluid is said to be at a pinch point. The strategic use of liquid de-superheaters in both waste heat stream 460 and refrigerant R1 streams arc used to further refine the pinch point. The pinch point is a realm where there is sufficient temperature difference to move heat across the plate or plates in the heat transfer device 402. More specifically, one fluid must be at a state where it can transfer the latent heat and the other fluid must be at a state where it is capable of absorbing the heat given up by the other fluid. In this particular embodiment, the steam in the waste stream 460 must be in a state where it is able to condense and transfer the latent heat to the heat exchanger and the refrigerant R must be in a state where the latent heat can be absorbed by vaporization. This provides for an efficient transfer of heat from the waste stream 460 to the refrigerant 402. The compressors 410, 420 are used to place the two streams, the waste stream 460, and the refrigerant in the refrigeration loop 430 in a state where the efficient heat transfer can occur in the heat transfer device 402.
In one embodiment, the compressors 410, 420 are controlled to place the steam from the waste stream 460 at a pinch point and the refrigerant in the refrigeration loop 430 at a pinch point. The pinch points of each fluid are matched to provide for an efficient transfer of heat from the steam from the waste stream 460 to the refrigerant in the refrigeration loop 430. In one embodiment, the compressors 410 and 420 are dynamically controlled. The condition of the waste stream 460 can change. The compressors are controlled to condition or place the steam from the waste stream 460 in a state where it is ready to release its latent heat, and to condition the refrigerant so that it can absorb the latent heat from the steam of the waste stream 460. It should also be noted that in some embodiments of the HTBR system, as the temperature-pressure rises in the refrigerant stream, increases in energy efficiency result in the form of lower compressor energy.
FIG. 5 is a flow chart of a method 500 for controlling the compressors 410, 420 of the waste stream 460 and the refrigerant respectively. The waste stream 460 condition is monitored using sensors for temperature and pressure, and the like, as depicted by reference numeral 510. The refrigerant condition is monitored using sensors for temperature and pressure, and the like, as depicted by reference numeral 512. The condition of the waste stream 460 is then placed in a state where the latent heat can be freely released (i.e. at the pinch point of the steam in the waste stream 460) by varying the pressure in the waste stream 514 using the compressor 410 and modifying the superheat temperature using de-superheaters. At the same time, the refrigerant is then placed in a state where the latent heat from the waste stream 460 can be absorbed by the refrigerant. The pressure on the refrigerant can be varied 516 using the compressor 420 and modifying the refrigerant superheat temperature with de-superheaters. The sensed conditions are continuously monitored using sensors. The data from the sensors is used in a feedback control loop for the condition of the waste stream 460. Data from sensors sensing the condition of the refrigerant is used in a feedback control loop for the condition of the refrigerant in the refrigeration loop 430. In one embodiment, a computer 600 controls the compressors 410 and 420 and de-superheaters to keep both the refrigerant and the waste stream 460 in a condition at their respective pinch points to allow for efficient heat transfer. Of course, the transferred heat can be used in other portions of a system.
In one embodiment of the method 500, superheat water vapor from a source, such as a superheated drying apparatus, is condensed by an evaporator associated with a high temperature balanced refrigeration device. This heat energy in the form of superheated water and latent heat is transferred to either a refrigerant or condensate from a steam process. In the method 500, the pinch points are matched by manipulating refrigerant properties or changing pressure in the superheated waste stream to the evaporator. Another embodiment of the method 500 is used in a ethanol plant. In this other embodiment of the method 500, a distillation condenser is used in place an evaporator of a high temperature balanced refrigeration device as part of a closed loop balanced refrigeration cycle. A pinch effect is made by using the correct azeotrope for the refrigerant thus allowing maximum heat transfer at the condenser and the lowest compression power for one or both of the compressors 410, 420. The higher energy refrigerant is condensed at the distillation reboiler.
Part of production of ethanol may include cooking of a liquid slurry. Liquid slurry cooking in systems that have matched heat demand (condenser) and cooling (evaporator) loads present another application for a high temperature balanced refrigeration (“HTBR”) system. The energy needed for cooking comes from the slurry cooling section and a compressor raises the temperature to a level to provide the delta temperature needed for the cook. The system is balanced except for superheat at the compressor and system line heat losses.
Another application for an HTBR system is a molecular sieve. Molecular sieves may be altered to remove the waste heat discharged at the product condenser and by transferring this energy to a properly matched and conditioned refrigerant. The properly matched refrigerant is vaporized in the HTBR system. A compressor is used to increase the energy level to meet the delta temperature for evaporating the fluid to be processed in the molecular sieve.
Also contemplated is an HTBR system for balancing the energy within an entire ethanol production facility. Such a system includes at least one HTBR loop at the distillation or stripper and rectifier with its concurring superheat gain. The heat from the distillation or stripper and rectifier will substantially supply the energy for the entire process. The entire system is balanced after the ethanol production facility is started up. Energy that here to for has been dumped, if in a latent vapor phase, can be extracted and its value (temperature) raised to provide heat for many industrial and commercial processes with system COP's of from 3-12:1 ratios. This system, called High Temperature Balanced Refrigeration manipulates vapor pressure in a refrigerant (using various azeotropes) closed loop at much higher temperatures than is standard practice. Heat is transfered from the dumped stream to the refrigerant stream using plate heat exchangers and setting the thermodynamics of each stream to maximize phase change latent heat transfer. The heat energy is then given a higher value via compression to match the need of the industrial process and disbursed via another heat exchanger.
FIG. 6 is a block diagram of a computer system 2000 that executes programming for performing the above algorithm or method 500 shown in FIG. 5. A general computing device in the form of a computer 2010, may include a processing unit 2002, memory 2004, removable storage 2012, and non-removable storage 2014. Memory 2004 may include volatile memory 2006 and non-volatile memory 2008. Computer 2010 may include, or have access to a computing environment that includes, a variety of computer-readable media, such as volatile memory 2006 and non-volatile memory 2008, removable storage 2012 and non-removable storage 2014. Computer storage includes random access memory (RAM), read only memory (ROM), erasable programmable read-only memory (EPROM) & electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD ROM), Digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium capable of storing computer-readable instructions. Computer 2010 may include or have access to a computing environment that includes input 2016, output 2018, and a communication connection 2020. One of the inputs could be a keyboard, a mouse, or other selection device. The communication connection 2020 can also include a graphical user interface, such as a display. The computer may operate in a networked environment using a communication connection to connect to one or more remote computers. The remote computer may include a personal computer (PC), server, router, network PC, a peer device or other common network node, or the like. The communication connection may include a Local Area Network (LAN), a Wide Area Network (WAN) or other networks.
Computer-readable instructions stored on a computer-readable medium are executable by the processing unit 2002 of the computer 2010. A hard drive, CD-ROM, and RAM are some examples of articles including a computer-readable medium. For example, a computer program 2025 capable of providing a generic technique to perform access control check for data access and/or for doing an operation on one of the servers in a component object model (COM) based system according to the teachings of the present invention may be included on a CD-ROM and loaded from the CD-ROM to a hard drive. The computer-readable instructions allow computer system 2000 to provide generic access controls in a COM based computer network system having multiple users and servers.
A machine-readable medium that provides instructions that, when executed by a machine, cause the machine to perform operations including the controlling of either the entire energy conversion process or various subprocesses associated with the refrigeration device 400, and more specifically the control of the compressors 410 and 420 for conditioning the waste stream 460 and the refrigerant associated with the refrigeration loop 430 (see FIG. 4).
The Abstract is provided to comply with 37 C.F.R. §1.72(b) to allow the reader to quickly ascertain the nature and gist of the technical disclosure. The Abstract is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Claims

1. A heat exchange apparatus comprising:

a fluid stream in the range of 100 degrees Fahrenheit to 200 degrees Fahrenheit;

a refrigeration apparatus that includes an evaporator positioned in the fluid stream, the evaporator removing heat from the fluid stream.

2. The heat exchange apparatus of claim 1 wherein the refrigeration apparatus further comprises a compressor for compressing the refrigerant.

3. The heat exchange apparatus of claim 1 wherein the refrigeration apparatus further comprises a plurality of compressors for compressing the refrigerant.

4. The heat exchange apparatus of claim 1 wherein the refrigerant is water.

5. The heat exchange apparatus of claim 1 wherein the refrigerant is an azetrope.

6. The heat exchange apparatus of claim 1 wherein the refrigerant is an azetrope of ethanol and water.

7. The heat exchange apparatus of claim 1 wherein the refrigerant is an azetrope that is a mixture of two fluids, wherein the ratios of the two fluids in the refrigerant is selected to evaporate in a given fluid stream.

8. The heat exchange apparatus of claim 1 wherein the condensor includes a heat exchanger, the heat removed at the condensor being used to heat another fluid.

9. The heat exchange apparatus of claim 1 wherein the refrigeration apparatus is used to generate steam.

10. A plant for the production of ethanol comprising:

a fluid stream having a temperature in the range from 100 degrees Fahrenheit to 400 degrees Fahrenheit; and

a heat exchanger in the fluid stream, the heat exchanger including a closed loop system for removing heat from the fluid stream.

11. The plant of claim 10 wherein the closed loop system includes a refrigerant.

12. The plant of claim 10 wherein the plant includes a dryer for driving water from a mash, the fluid stream including water and heat from the dryer.

13. The plant of claim 10 wherein the heat exchanger includes a first refrigeration loop and a second refrigeration loop.

14. The plant of claim 13 wherein the first refrigeration loop is cascaded with the second refrigeration loop.

15. The plant of claim 13 further comprising a heat exchanger, the heat exchanger acting as the condensor for one of the first refrigeration loop or the second refrigeration loop and acting as the evaporator for the other of the first refrigeration loop or the second refrigeration loop.

16. The plant of claim 10 wherein the refrigeration loop is associated with a distillation portion of the ethanol plant.

17. The plant of claim 10 wherein the refrigeration loop is associated with a distillation portion of the ethanol plant.

18. The plant of claim 17 wherein a latent vapor phase is extracted and the temperature is raised to provide heat for another processes with system COP's of from 3-12:1 ratios.

19. The plant of claim 10 wherein the compressor has increased energy efficiency in the form of lower compressor energy as the temperature-pressure rises in the refrigerant stream.