Patent Application
20230235963
Direct contact cooling is used in industrial processes to cool hot gas streams for use in downstream processes, for example, cooling of flue gases for post-combustion carbon capture. The direct contact between the hot gas and the cooling media, typically water, leads to efficient heat transfer due to high amounts of heat transfer area and to the removal of an intermediate heat transfer media (i.e. the materials typically used to separate process streams).
External cooling duties for the direct contact cooling process are often provided by the use of evaporative cooling, especially when the hot gases are to be cooled temperatures near local ambient dry bulb temperatures. Evaporative and blowdown losses from evaporative cooling processes can be significant and place a strain on local water resources.
Direct contact cooling processes can minimize unnecessary consumption of water by evaporative cooling processes by more efficiently allocating cooling duties between air cooled processes and evaporative cooled processes.
A multistage direct contact cooling process may include a multistage direct contact consist of a high temperature stage and a low temperature stage.
In a first aspect of the present disclosure, which may be combined with any other aspect listed herein unless specified otherwise, the hot process gas enters the high temperature stage of the direct contact cooler where it is cooled by contact with water. The water being contacted in the high temperature stage of the direct contact cooler is cooled using an air cooling device such as air cooled heat exchangers, chiller packages, or air-to-gas exchangers. The high temperature stage is designed such that cooling duty thereof is maximized and can be cooled in a practical manner via the use of air-cooled heat exchangers or other cooling devices. In practice, this means the cooling water supply temperature of the high temperature stage is above a local design dry bulb temperature plus approach temperature limitations of air-cooled heat exchangers. The approach temperature of the cooling water supply and the cooled saturated process gases leaving the high temperature stage should be minimized to ensure that the amount of cooling duty performed by the air-cooled heat exchangers is maximized. This results in a net reduction in the amount of cooling demand on the low temperature stage, and therefore reduces water losses in the evaporative cooling process.
In a second aspect of the present disclosure, which may be combined with any other aspect listed herein unless specified otherwise, the cooled saturated process gas enters the low temperature stage of the direct contact cooler where it is further cooled by contact with water via an evaporative cooling device. The water being contacted in the low temperature stage of the direct contact cooler is cooled using an evaporative cooling process. The evaporative cooling process allows the cooling water to be cooled near the ambient wet bulb temperature. The low temperature stage is designed to perform the remaining cooling duty required to cool the process gases to the temperature required in the downstream process.
In a third aspect of the present disclosure, which may be combined with any other aspect listed herein unless specified otherwise, an additional air-cooled process can be incorporated upstream of the evaporative cooling process. The addition of the air-cooled process upstream of the evaporative cooling process further reduces the cooling demand on the evaporative cooling process, and therefore reduces water loss due to evaporation and blowdown. In this arrangement, the evaporative cooling process operates as a trim cooler, performing the remaining required cooling duty that the air-cooled process was not able to perform. This arrangement takes advantage of variations in ambient conditions, which allows the air-cooled process to perform higher relative amounts of the required duty when ambient dry bulb temperatures are lower (i.e due to seasonal or daily variations).
Additional features and advantages of the disclosed devices, systems, and methods are described in and will be apparent from the following Detailed Description and the Figures. The features and advantages described herein are not all-inclusive and in particular many additional features and advantages will be apparent to one of ordinary skill in the art in view of the figures and description. Also, any particular embodiment does not have to have all of the advantages listed herein. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and not to limit the scope of the inventive subject matter.
Understanding that the figures depict only typical embodiments of the invention and are not to be considered to be limiting the scope of the present disclosure, the present disclosure is described and explained with additional specificity and detail through the use of the accompanying Figure.
The detailed description is to be construed as exemplary only and does not describe every possible embodiment, as describing every possible embodiment would be impractical, if not impossible. One of ordinary skill in the art could implement numerous alternate embodiments, which would still fall within the scope of the claims. To the extent that any term is referred to in a manner consistent with a single meaning, that is done for the sake of clarity and illustration only, and it is not intended that such claim term be limited to that single meaning.
The hot process gases are sent to the high temperature stage 102 of the direct contact cooler. In the high temperature stage 102, the hot process gases may be cooled via direct contact with cooling water. The process gases are saturated with water and leave the high temperature stage 102 as partially cooled saturated process gases.
The partially cooled saturated process gases then enter the low temperature stage 103 where the partially cooled saturated process may be further cooled via direct contact with cooling water to the temperature required by the downstream process 104. The process gases are saturated with water and leave the low temperature stage 103 as cool saturated process gases.
The cooling water circulated in the high temperature stage 102 is cooled by dry cooling 105. In some embodiments, the dry cooling 105 comprises an air cooling device utilizing air cooling, such as an air-cooled heat exchangers. In alternative embodiments, a chiller package is used to cool the cooling water. In a further embodiment, ambient air could be used as the cooling medium with a gas-to-air heat exchanger. The cooling water supply temperature for the high temperature stage 102 is designed such that it can be practically achieved via the use of air-cooled heat exchangers. For example, if the dry-bulb design temperature is 90° F., the cooling water supply temperature for the high temperature stage may be set at 110° F., allowing for a 20° F. approach temperature. The approach temperature can be reduced to as low as approximately 8° F. with more heat transfer area.
The cooling water circulation rate and the contact volume size of the high temperature stage 102 are designed to result in a close approach temperature (<10° F.) between the cooling water supply temperature and the partially cooled saturated process gases leaving the high temperature stage 102. These design considerations maximize the cooling duty performed in the high temperature stage 102 which in tum reduces evaporative and blowdown losses associated with the evaporative cooling process 107 of the low temperature stage 103.
The cooling water circulated in the low temperature stage 103 may be cooled by the evaporative cooling process 107 to a temperature of approximately 5-15° F. above wet-bulb temperature. The evaporative cooling process 107 utilizes an evaporative type cooler such as a cooling tower or other suitable device. In processes where the desired cooling water supply temperature is near or below the dry-bulb temperature, evaporative cooling processes may be required. Dry cooling processes (i.e. air-cooled heat exchangers) are limited to by the approach to the ambient dry-bulb temperature, whereas evaporative cooling processes are limited by the approach to the ambient wet-bulb temperature which is lower than the ambient dry-bulb temperature.
The duty of the evaporative cooling process 107 is designed to achieve the required outlet temperature for the cool saturated process gases. Evaporative and blowdown losses are related to the duty and the allowable concentration of contaminants in the cooling water loop. Reductions in the required cooling duty of the evaporative cooling process 107 will result in reductions in evaporative and blowdown losses.
Additional dry cooling 106 can be incorporated upstream of the evaporative cooling process 107 to reduce the duty of the evaporative cooling process 107. The dry cooling 106 performance will vary with ambient dry-bulb temperatures, and can be designed to accommodate 100% of the low temperature stage 103 cooling duty at a specified dry-bulb temperature. The evaporative cooling process 107 performs any residual cooling duty not performed in the dry cooling 106.
All percentages expressed herein are by weight of the total weight of the composition unless expressed otherwise. As used herein, “about,” “approximately” and “substantially” are understood to refer to numbers in a range of numerals, for example the range of −10% to +10% of the referenced number, preferably −5% to +5% of the referenced number, more preferably −1% to +1% of the referenced number, most preferably −0.1% to +0.1% of the referenced number. All numerical ranges herein should be understood to include all integers, whole or fractions, within the range. Moreover, these numerical ranges should be construed as providing support for a claim directed to any number or subset of numbers in that range. For example, a disclosure of from 1 to 10 should be construed as supporting a range of from 1 to 8, from 3 to 7, from 1 to 9, from 3.6 to 4.6, from 3.5 to 9.9, and so forth.
As used in this disclosure and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “an ingredient or “the ingredient” means “at least one ingredient” and includes two or more ingredients.
The words “comprise,” “comprises” and “comprising” are to be interpreted inclusively rather than exclusively. Likewise, the terms “include,” “including” and “or” should all be construed to be inclusive, unless such a construction is clearly prohibited from the context. Nevertheless, the compositions disclosed herein may lack any element that is not specifically disclosed herein. Thus, a disclosure of an embodiment using the term “comprising” includes a disclosure of embodiments “consisting essentially of” and “consisting of” the components identified. A composition “consisting essentially of” contains at least 75 wt. % of the referenced components, preferably at least 85 wt. % of the referenced components, more preferably at least 95 wt. % of the referenced components, most preferably at least 98 wt. % of the referenced components.
The terms “at least one of” and “and/or” used in the respective context of “at least one of X or Y” and “X and/or Y” should be interpreted as “X,” or “Y,” or “X and Y.” For example, “at least one of honey or chicory root syrup” should be interpreted as “honey without chicory root syrup,” or “chicory root syrup without honey,” or “both honey and chicory root syrup.”
Where used herein, the terms “example” and “such as,” particularly when followed by a listing of terms, are merely exemplary and illustrative and should not be deemed to be exclusive or comprehensive. The many features and advantages of the present disclosure are apparent from the written description, and thus, the appended claims are intended to cover all such features and advantages of disclosure. Further, since numerous modification and changes will readily occur to those skilled in the art, the present disclosure is not limited to the exact construction and operation as illustrated and described. Therefore, the described embodiments should be taken as illustrative and not restrictive, and the disclosure should not be limited to the details given herein but should be defined by the following claims and their full scope of equivalents, whether foreseeable or unforeseeable no or in the future.
The present application claims the benefit of priority to U.S. Provisional Application No. 63/303,687 filed Jan. 27, 2022, the entirety of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63303687 | Jan 2022 | US |
