HARMONIC ADSORPTION RECUPERATIVE POWER SYSTEMS AND METHODS
20170370251 · 2017-12-28
Assignee
- Battelle Memorial Institute (Richland, WA)
- Rockwell Collins Inc. (Cedar Rapids, IA, US)
- EthosGen, LLC (Wilkes-Barre, PA, US)
Inventors
- B. Peter McGrail (Pasco, WA)
- Radha Kishan Motkuri (Richland, WA)
- Jeromy J. Jenks (Hines, OR, US)
- Paul Roege (Wilkes-Barre, PA, US)
- William Abrams (Simpsonville, SC, US)
Cpc classification
F01K25/00
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F25B37/00
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
International classification
Abstract
A new power generation thermodynamic cycle is described that eliminates need for bulk liquid condensation and vaporization steps required in conventional ORC power systems. An exemplary harmonic adsorption recuperative power cycle system offers more efficient power generation as compared with conventional ORC systems. A multibed adsorption system is used to provide thermal compression for the cycle. An adsorption compressor contains a sorbent with strong adsorption affinity for the working fluid in the pores while well outside the P-T conditions needed to condense the liquid phase, allowing the adsorption compressor to reduce operating pressure exiting the expander.
Claims
1. A thermal compression power generation system, comprising: a working fluid; an engine driven by the working fluid; a heat exchange fluid; and a thermal compression system comprising two or more independent adsorbers each containing a sorbent; wherein the working fluid passes through the adsorbers and is adsorbed and desorbed by the sorbent; wherein the heat exchange fluid passes through the thermal compression system and transfers energy to and from the working fluid while being desorbed and adsorbed by the sorbent; and wherein the working fluid remains in vapor phase while in the thermal compression system without condensing into liquid phase.
2. The system of claim 1, wherein the adsorbers alternate between an adsorption phase and a desorption phase in a harmonic cycle, wherein during the desorption phase output pressure of the adsorbers falls to a minimum value while adsorber temperature rises to a maximum temperature, and during the adsorption phase the adsorbers begin at a lowest pressure in the cycle and pressure increases up to a maximum value.
3. The system of claim 1, wherein the two or more independent adsorbers operate out of phase with one another, such that at least one adsorber is adsorbing the working fluid while at least one adsorber is desorbing the working fluid.
4. The system of claim 3, wherein working fluid exiting the engine flows into one of the adsorbers in an adsorption phase, and working fluid entering the engine flows from one of the adsorbers in a desorption phase.
5. The system of claim 1, wherein the thermal compression system comprises four or more independent adsorbers.
6. The system of claim 5, wherein the four or more independent adsorbers alternate between a pre-cooling phase, an adsorption phase, a pre-heating phase, and a desorption phase, in harmonic cycles.
7. The system of claim 1, wherein the system lacks a condenser.
8. The system of claim 1, wherein the system lacks an evaporator.
9. The system of claim 1, wherein the system lacks a working fluid pump.
10. The system of claim 1, wherein the thermal compression system comprises at least one adsorber having a tube-and-shell configuration.
11. The system of claim 1, wherein at least one of the adsorbers comprises a tubular body having a cylindrical wall and fins projecting radially inwardly from the cylindrical wall, with the sorbent positioned between the fins.
12. The system of claim 11, wherein a vapor channel is defined radially inside of the fins, and the working fluid passes through the vapor channel in contact with the sorbent.
13. The system of claim 11, wherein an outer shell is positioned around the cylindrical wall and the heat exchange fluid flows between the outer shell and the cylindrical wall.
14. The system of claim 1, where at least one of the adsorbers comprises a plurality of tubular adsorption beds containing the sorbent, and an outer wall positioned around the tubular adsorption beds, wherein the working fluid passing through the tubular adsorption beds and the heat exchange fluid passes between the tubular adsorption beds and the outer wall.
15. The system of claim 1, wherein the sorbent comprise a metal organic framework with a strong chemical affinity for the working fluid.
16. The system of claim 1, wherein the sorbent comprise a covalent organic framework with a strong chemical affinity for the working fluid.
17. The system of claim 1, wherein the sorbent comprise a hierarchical porous carbon with a strong chemical affinity for the working fluid.
18. The system of claim 1, wherein the sorbent comprise a zeolite or mesoporous silica framework with a strong chemical affinity for the working fluid.
19. The system of claim 1, wherein the sorbent comprises a composite combination of two or more of a metal organic framework, a covalent organic framework, a hierarchical porous carbon, and a zeolite or mesoporous silica framework, and wherein the sorbent is in the form a core-shell, a yolk-shell, or a mixed matrix with a strong chemical affinity for the working fluid.
20. The system of claim 1, wherein the adsorbers can achieve at least 98% of a theoretical liquid density of the working fluid in pores of the sorbent while the working fluid remains in vapor phase.
21. The system of claim 1, wherein the thermal compression system comprises a harmonic adsorption recuperative power (HARP) system.
22. The system of claim 1, wherein the thermal compression system achieves a compression ratio of at least 30:1.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0010]
[0011]
[0012]
[0013]
[0014]
[0015]
[0016]
[0017]
[0018]
[0019]
[0020]
[0021]
[0022]
[0023]
[0024]
[0025]
DETAILED DESCRIPTION
[0026] Disclosed herein are exemplary non-condensing power generation systems and methods that include adsorption-based compression systems and provide improvements in cost and/or efficiency as compared with standard ORC systems. The disclosed systems can modify or eliminate the need for a condenser and an evaporator, and can eliminate the need for pumps that pump liquid working fluid through an ORC system, such as the Rockwell Collins system used in the analysis of the embodiments disclosed herein. The disclosed systems can produce at least 40% more power, and can produce power at higher ambient temperature conditions for lower driving temperatures. The disclosed systems solve the problems of, among others, operation at high ambient temperature and eliminating some components in a standard ORC system.
[0027]
[0028]
[0029]
[0030] Because the adsorption beds in the disclosed HARP systems undergo thermal and pressure cycling, the system can benefit from minimizing the pressure/temperature swings experienced by the output engine to maintain a steady power output and can reduce mechanical fatigue on the components. Configuring the adsorbing and desorbing beds to be out of phase during the cycle helps dampen the fluctuations across the output engine. It is also advantageous to use a multi-bed configuration to optimize timing of the pressure and temperature swings of each adsorber/desorber bed in the system to generate the maximum working fluid flow rate per kg of sorbent. For example, during a desorption cycle, it is advantageous to allow the output pressure to fall to a minimum value while the bed temperature rises to its maximum temperature as this will minimize the amount of working fluid left in the sorbent bed at the end of the desorption cycle. This can be facilitated by simultaneously adsorbing to a fully regenerated bed that is at the lowest temperature and pressure in the cycle. As working fluid is adsorbed during the adsorption cycle, the pressure is allowed to increase up to a maximum value, which maximizes the working fluid loading in the sorbent. The net result is an oscillating absolute pressure at the engine inlet and outlet but a constant or approximately constant pressure differential across the engine.
[0031] An additional advantage is avoidance of requirement to physically condense the working fluid in the disclosed systems. However, by using a sorbent within the adsorbers with a very strong chemical affinity for the working fluid, near liquid phase densities can be achieved in the adsorption beds. By avoiding the need for condensation, the disclosed HARP systems can also impose a larger pressure drops across the engine and generate more power. The impact of this enhanced pressure drop can be quantified with a simple energy balance calculation. Power generation (P) is given by:
P=η.sub.e{dot over (m)}.sub.r(h.sub.r.sup.1−h.sub.r.sup.o) (1)
where η.sub.e is the efficiency of the expander (engine), {dot over (m)}.sub.r is the working fluid mass flow rate, h.sub.r.sup.1 and h.sub.r.sup.o are the outlet and inlet enthalpy across the engine, respectively. Heat flows across an adsorption bed are given by:
(1−η.sub.h)[{dot over (m)}.sub.rΔH.sub.at.sub.c+(m.sub.Alc.sub.p.sup.Alm.sub.sc.sub.p.sup.s+m.sub.vc.sub.p.sup.v)(T.sub.h−T.sub.L)]={dot over (m)}.sub.w(h.sub.w.sup.1−h.sub.w.sup.o) (2)
where η.sub.h is the recuperation efficiency between beds, ΔH.sub.a is the heat of adsorption, t.sub.c is the bed cycle time, m.sub.Al, m.sub.s, and m.sub.v are the masses of aluminum, sorbent, and refrigerant vapor in the adsorption bed, c.sub.p.sup.i are the corresponding heat capacities, and T.sub.h and T.sub.L are the high and low temperatures of the bed during a cycle. The right hand side of Equation (2) represents the balancing heat rejection to the environment through either cooling water or an air-cooled heat exchanger. The sorbent mass required can be estimated from:
[0033] Achieving the power increase estimates with the disclosed HARP system can be obtained by having a high performance sorbent material that allows cycle times and refrigerant loadings consistent with the t.sub.c and f.sub.r values shown in Table 1.
[0034] Three exemplary sorbents that are well suited for the HARP system are: 1) metal organic frameworks (MOF), 2) covalent organic frameworks (COF), and 3) hierarchical porous carbon (HPC) materials.
[0035] Another example class of sorbents are COFs. Specific examples of COFs are COF-3 and COF-4 comprised of aromatic phenyl/biphenyl rings connected through stable covalent C—C, C—H, and C—N bonds to form highly porous and controllable structures with high surface areas. These COFs showed the highest gravimetric sorption capacities for fluorocarbons (up to ˜200 wt %) but their low packing densities gives only medium volumetric capacities.
[0036] The aromatic character of the sorbent framework can be more favorable towards fluorocarbon adsorption via C—F . . . π interactions. Consequently, some preferable sorbents can comprise monomer building units with more conjugated/aromatic character. The monomer unit can provide suitable reactive groups such as OH, CN, CHO, NH.sub.2 that can be selected/tuned according to the chosen polymerization reaction and the required synthesis conditions. The degree of polymerization significantly depends upon the reaction conditions, choice of solvent, choice of catalyst and amounts, and ratios between the monomer and catalyst. The ratio can greatly influence the formation of the porous framework with different pore volume, surface area, and pore-size distribution. Consequently, reaction conditions can be optimized to achieve COFs that possess similar sorption characteristics compared to COF3/COF4 materials illustrated in
[0037] Another sorbent class is HPC materials where textural properties and porosities can be tuned into microporous (<20 Å), mesoporous (20-500 Å) and macroporous (>500 Å) respectively. One example HPC is a commercially available activated carbon (e.g., KBB or Ketjenblack manufactured by AkzoNobel) that has both macropores as well as mesopores with a surface areas up to 1300 m.sup.2/g. These HPCs are thermally stable and can be tuned to get more ordered (graphitic) carbon. KBB shows moderate to high sorption capacities both volumetrically and gravimetrically. These sorbent examples are not meant to be limiting in any way. Any sorbent material with sufficiently high adsorption capacity and adsorption kinetics can be used in embodiments of a HARP system.
TABLE-US-00001 TABLE 1 Exemplary HARP System Heat Balance Parameters Parameter Value Units η.sub.e 0.9 T.sub.h 140 ° C. T.sub.L 30 ° C. h.sub.r.sup.o 427 kJ/kg h.sub.r.sup.1 415 kJ/kg {dot over (m)}.sub.r 0.65 kg/s tc 60 s fr 130% wt % m.sub.s 30.1 kg m.sub.v 0.96 kg ΔH.sub.a 350 kJ/kg m.sub.Al 24.1 kg c.sub.p.sup.v 1.1 kJ/kg .Math. K c.sub.p.sup.s 0.9 kJ/kg .Math. K c.sub.p.sup.Al 0.9 kJ/kg .Math. K η.sub.h 0.7
[0038] A thermal compressor driven by heat is created by the adsorbers of the HARP system and provides the motive force to transport the working fluid through the expansion engine. In various embodiments, the internal structures of thermal compressors created by the adsorption systems can take on different geometrical dimensions. Some exemplary embodiments are illustrated herein. Power generation applications based on the disclosed HARP systems can withstand high pressures and a very large number of thermal cycles without failure due to the thermal compressor architecture. Embodiments can be manufactured using various different techniques, including casting, brazing, extruding and additive manufacturing (3D printing) of parts. A combination of all or some of these methods can also be used.
[0039] The thermal compressor/adsorption beds can take various different structural configurations, such as tube-in-shell configurations, microchannel structures, plate-type systems, etc.
[0040] In such thermal compressors, volumetric refrigerant loading and cycle time can be significant. The cycle time can be directly proportional to the size of the thermal compressor. Additionally, refrigerant loading kinetics for a given sorbent can play a major role in that time.
[0041]
[0042] In some embodiments, the thermal compression system can achieve a compression ratio of at least 30:1, such as 30 bar to about 1 bar for example. In some embodiments, the compression ratio can be about 15 bar to about 5 bar, for example. The cycle times can be about 90 seconds to about 100 seconds, for example.
[0043]
[0044] In one example, a 40 kW nominal standard ORC system can be upgraded with a HARP thermal compressor, such as using the MOF sorbent. Such an upgraded system can produce a power increase output and can provide more cost efficient power compared to normal ORC systems, especially with a relatively low temperature heat source.
[0045] The disclosed systems can be used with medium and low-temperature geothermal reservoirs, including geo-pressured and produced water from oil & gas operations, and other geo-pressured resources, such as are present in several areas of the United States, ranging from California and the Dakotas to Texas, Louisiana and Alabama. Hot brine (90 to 200° C.) often saturated with methane is recovered from wells at depths of 3 to 6 km. Co-produced resources consists of hot water and hydrocarbons produced concurrently during oil and gas extraction. Produced water can be difficult to handle, incurs pumping costs, and has to be reinjected at an additional cost for permitting and injection wells. For every barrel of oil produced, nearly 100 barrels of hot water are co-produced. In Texas alone, over 12 billion barrels of waste water are produced as a byproduct of oil and gas extraction. If even a small fraction of the geo-pressured and co-produced resource fluids can be used to provide power using the disclosed systems, economically, it could easily quadruple the nation's geothermal energy production output. Additional exemplary applications for the disclosed systems can include low temperature geothermal resources, waste heat sources such as heat delivered from combination diesel engine/electric generator systems (i.e., gensets), solar thermal sources, on maritime vessels, military bases, and other remote locations such as in Alaska, Arctic and Antarctic locations. Economic benefit can vary significantly based on existing electrical power rates.
[0046]
[0047]
[0048]
[0049]
[0050]
[0051]
[0052] For purposes of this description, certain aspects, advantages, and novel features of the embodiments of this disclosure are described herein. The disclosed methods, apparatuses, and systems should not be construed as limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The methods, apparatuses, and systems are not limited to any specific aspect or feature or combination thereof, nor do the disclosed embodiments require that any one or more specific advantages be present or problems be solved.
[0053] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.
[0054] Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed methods can be used in conjunction with other methods.
[0055] As used herein, the terms “a”, “an”, and “at least one” encompass one or more of the specified element. That is, if two of a particular element are present, one of these elements is also present and thus “an” element is present. The terms “a plurality of” and “plural” mean two or more of the specified element. As used herein, the term “and/or” used between the last two of a list of elements means any one or more of the listed elements. For example, the phrase “A, B, and/or C” means “A”, “B,”, “C”, “A and B”, “A and C”, “B and C”, or “A, B, and C.” As used herein, the term “coupled” generally means physically or chemically coupled or linked and does not exclude the presence of intermediate elements between the coupled items absent specific contrary language.
[0056] In view of the many possible embodiments to which the principles of the disclosed technology may be applied, it should be recognized that the illustrated embodiments are only examples and should not be taken as limiting the scope of the disclosure. Rather, the scope of the disclosure is at least as broad as the following claims. We therefore claim all that comes within the scope of the following claims.