Gas separation: processes – Solid sorption – Including reduction of pressure
Reexamination Certificate
1999-08-27
2001-06-26
Spitzer, Robert H. (Department: 1724)
Gas separation: processes
Solid sorption
Including reduction of pressure
C095S106000, C095S107000, C095S115000, C095S138000, C096S123000, C096S128000, C096S130000
Reexamination Certificate
active
06251164
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process and system for selective separation of at least one of a plurality of fluidic components from a stream of feed fluid containing the plurality of fluidic components. More preferably, this invention relates to a gas separation process and system for selective separation of one or more gaseous components from a gas comprising a plurality of gaseous components, wherein the selective separation is accomplished by an adsorbent entrained in a fluid stream.
BACKGROUND OF THE INVENTION
Conventionally known gas separation methods include, for example, (i) chemical absorption, (ii) cryogenic separation, and (iii) adsorption. Although these methods have been widely used, each has merits and demerits.
The chemical absorption method (i) has been used for the removal of hydrogen sulfide or carbon dioxide gas and has also been put to trial use for the desulfurization of exhaust gases. However, this method is defective in that, in the case of using an organic compound as an absorbent, there are problems in treatment of waste fluid, treatment of harmful substances resulting from decomposition of the absorbent, etc. Further, in the case where an acidic gas is treated using a hot aqueous alkali solution as an absorbent, the consumption of heat energy is large.
The cryogenic separation method (ii) has been used, for example, for the separation of air and the separation of hydrocarbon gases such as natural gas. However, this method is disadvantageous in that a large-sized, costly freezing equipment is required. Therefore, practical use of the cryogenic separation method is limited to applications in which separation by the other methods is difficult.
The adsorption method (iii) has been extensively used because it is simple, and the unit used therefor can have a size ranging from small to relatively large. Known types of units for this method include fixed bed type and fluidized bed type.
In adsorption, the amount of a gas adsorbed onto an adsorbent becomes larger with increasing pressure and decreasing temperature, and becomes smaller with reducing pressure and increasing temperature. The adsorption method utilizes this phenomenon in conducting the adsorption step, where a gas is adsorbed onto an adsorbent and the desorption step, where the adsorbed gas is desorbed from the adsorbent. Adsorption separation units of the fixed bed type can utilize the above phenomenon by being provided with a means for changing pressure and temperature. However, in the case of adsorption separation units of the conventional fluidized bed type in which fluidized adsorbent particles circulate in the unit, a pressure difference is rarely utilized in the adsorption-desorption operation. However, a slight pressure is applied as a driving force for circulating the adsorbent particles, and to enable smooth migration of adsorbent particles between the desorption part and the adsorption part. For these reasons, the adsorption-desorption operation in conventional units of the fluidized bed type utilizes a temperature difference only. In the case of adsorption separation units of the fixed bed type, since a larger bed height results in an increased pressure loss, the area of the adsorbent bed should be increased, or the whole unit should be enlarged, in order to heighten treating capacity. However, the possible unit size is limited. Furthermore, size increase of switch valves is also limited.
With a recent increase in the amount of chemical products produced in a single plant in the chemical industry, large amounts of gases need to be treated by gas separation. Therefore, there is a need for an adsorption method capable of coping with such large amounts of gas.
The power consumption in these adsorption processes has been mainly mechanical/electrical type energy. Further, prior art moving bed adsorption processes exhibit an undesirable rate of attrition of the adsorbent particles compared to the fixed and/or stationary bed processes. Additionally, the heat and mass transfer of such processes can be undesirably low. Furthermore, the processes can require an unduly high inventory of expensive adsorbent (particularly as newer sophisticated adsorbents are developed). These and other factors have led to an undesirably high cost of running such prior art processes.
SUMMARY OF THE INVENTION
The object of this invention is to provide improved processes for separation of at least one component from a plurality of components in a feed stream of fluids, such as gas or liquids. For simplicity, the description of the invention hereinafter will generally be in relation to selectively separating at least one component of a plurality of gaseous components in a stream of gas; however, it is to be recognized that the invention is equally applicable to selective separation of components from gases or liquids, but preferably gases.
Another object of this invention is to provide a process and system for selective separation of a gaseous component from a stream of gases using adsorbent powder that primarily can utilize thermal energy, particularly waste thermal energy.
A further object of this invention is to provide a process and system, which can require a reduced inventory of selective adsorbent material and still provide a process and system with improved mass and heat transfer. Yet, another object of this invention is to provide a selective gas separation process and system that can reduce the operational costs of the process and system.
A still further object of this invention is to provide a selective gas separation process and system which can be operated as either a temperature swing absorbent (TSA) process, a pressure swing adsorbent (PSA) process or a combination of the two. An even still further object of the invention is to provide a selective gas separation process and system which can produce high purity gas, such as oxygen, nitrogen or argon gas and the like, and also which can selectively remove environmentally undesirable components from waste gas to be discharged into the atmosphere.
In one aspect, the present invention relates to a selective separation process and system in which adsorbent powder is entrained and suspended in a stream of feed gas of multiple gaseous components to selectively adsorb at least one of the gaseous components from the feed gas stream. In another aspect of this invention, the selective separation process and system employ waste heat as energy to operate the process and system.
In the invention, the term “unloaded adsorbent” means adsorbent which has no gas adsorbed thereon or from which gas has been completely or substantially completely desorbed therefrom.
The present invention comprises a process for selectively removing from a feed gas at least one of a plurality of gaseous components present in a stream of the feed gas, which process comprises:
(a) providing the stream of feed gas at a first temperature;
(b) providing unloaded selective adsorbent powder and entraining said adsorbent powder in the stream of feed gas to provide a mixture of adsorbent powder suspended in the stream of feed gas, said selective adsorbent powder adapted to selectively adsorb at least one of the plurality of gaseous components from the stream of feed gas;
(c) cooling the mixture of the adsorbent suspended in the stream of feed gas to a lower second temperature whereby said selective adsorbent powder selectively adsorbs the at least one of the plurality of gaseous components from the stream of feed gas; separating the adsorbent powder from the cooled suspension of adsorbent in the stream of feed gas to provide:
(1) separated adsorbent powder having adsorbed thereon the at least one selectively adsorbed gaseous component from the stream of feed gas, and
(2) as a first gaseous product, a stream of feed gas having selectively removed therefrom the at least one selectively adsorbed gaseous component;
(d) providing a secondary gas stream and introducing the separated adsorbent powder of (c)(1) into the secondary gas stream;
(e) heating the separated adsorbent powder in
Notaro Frank
Nowobilski Jeffert John
Zadeh Dariush Habibollih
Follett Robert J.
Praxair Technology Inc.
Spitzer Robert H.
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