Gas separation: processes – Solid sorption – Including reduction of pressure
Reexamination Certificate
2001-04-30
2003-01-21
Simmons, David A. (Department: 1724)
Gas separation: processes
Solid sorption
Including reduction of pressure
C095S116000, C095S115000, C096S126000
Reexamination Certificate
active
06508862
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and apparatus for separation by thermally cycled sorption and desorption.
INTRODUCTION
Separation of fluid components from fluid mixtures has been a topic of great scientific and economic interest for more than 100 years. This invention concerns methods and apparatus for separating fluid components from fluid mixtures by thermally cycled sorption and desorption. Our experimental work, and much of the following descriptions, concern separating hydrogen gas. In its broader aspects, however, this invention is applicable to any fluid, either gaseous or liquid including supercritical fluids.
Purified hydrogen has long been and continues to be used in a variety of industrial processes. For. example, petroleum refineries are using increasing quantities of hydrogen to meet regulatory requirements on diesel, gasoline, and other petroleum products. Hydrogen-based treating processes are expected to grow substantially because fuel regulations in North America, Europe, and other regions are becoming increasing stringent. For example, the sulfur levels in U.S. diesel fuels must decrease from the current level of 250 ppm to 15 ppm by 2007. While several options exist for lowering sulfur levels, all of commercially available processes require a hydrogen input stream.
Another major use of hydrogen is in upgrading crude oil to make gasoline. To meet the world's increasing demand for gasoline, it has been necessary to develop poorer grades of crude oil that are denser and require hydrogenation for upgrading to gasoline.
Additionally, for more than 10 years there have been intense research and development efforts directed toward hydrogen as a clean power source for fuel cells. Compared to conventional power systems, hydrogen-powered fuel cells are more energy efficient, more robust, and less polluting. Fuel cells can totally eliminate ozone and nitrogen oxides, the most noxious precusors of smog. However, problems such as excessive cost, equipment size, and process complexity have prevented hydrogen-based fuel cell technology from replacing most conventional power sources.
The present invention provides apparatus and methods for separating fluids. The invention can be used, for example, to purify hydrogen formed in a steam-reforming reaction (typically a gas containing hydrogen, carbon monoxide and carbon dioxide). Compared to conventional fluid separation technology, many of the configurations and procedures of this invention are relatively simple, scaleable over a broad range, including small, and are amenable to cost-effective mass production.
SUMMARY OF THE INVENTION
In a first aspect, the invention provides a method of separating a fluid component from a fluid mixture including at least two steps. In the first step, a fluid mixture passes into a flow channel at a first temperature. The flow channel comprises a sorbent within the channel, and flow through the flow channel is constrained such that in at least one cross-sectional area of the channel, the height of the flow channel is 1 cm or less. Heat from the sorbent is transferred to a microchannel heat exchanger. The fluid mixture contacts the sorbent without passing through a contactor. Then, in a second step, energy is added and the temperature of the sorbent is increased. A fluid component is desorbed from the sorbent at a second temperature and a fluid component that was sorbed in the first step is obtained. The second temperature is higher than the first temperature.
In a second aspect, the invention provides another method of separating a fluid component from a fluid mixture that includes at least two steps. In a first step, a gas mixture passes into a flow channel at a first temperature. The flow channel comprises a sorbent within the channel, and flow through the channel is constrained such that in at least one cross-sectional area of the channel, the height of the flow channel is 1 cm or less. Then, in a second step, energy from an energy source is added and the temperature of the sorbent is increased. A fluid component is desorbed at a second temperature and a fluid component that was sorbed in the first step is obtained. The second temperature is higher than the first temperature. The first and second steps, combined, for a non-condensed fluid mixture (i.e., a gaseous or supercritical fluid) take 10 seconds or less and wherein at least 20% of the gaseous component sorbed in the first step is desorbed from the sorbent; or for a liquid mixture take 1000 seconds or less and wherein at least 20% of the fluid component sorbed in the first step is desorbed from the sorbent.
In a third aspect, the invention provides another method for separating a fluid component from a fluid mixture. In this method, a fluid mixture passes into a first sorption region at a first temperature and first pressure, wherein the first sorption region comprises a first sorbent and wherein the temperature and pressure in the first sorption region are selected to favor sorption of the fluid component into the first sorbent in the first sorption region. Heat from the first sorption region is transferred into a microchannel heat exchanger. A fluid component from said fluid mixture is selectively sorbed, thus resulting in a sorbed component in the first sorbent and a fluid mixture that is relatively depleted in said component. The relatively component-depleted fluid mixture is passed into a second sorption region at a second temperature and second pressure, wherein the second sorption region comprises a second sorbent and wherein the temperature and pressure in the second sorption region are selected to favor sorption of the fluid component into the sorbent in the second sorption region. Heat transfers from the second sorption region into a microchannel heat exchanger. The fluid component is selectively sorbed from said relatively component-depleted fluid mixture thus resulting in sorbed component in the second sorbent and a relatively more component-depleted gas mixture. The second temperature is different than the first temperature. Heat is added to the first sorbent, through a distance of about 1 cm or less to substantially the entire first sorbent, to raise the first sorbent to a third temperature and the component is desorbed from the first sorbent. Heat is added to the second sorbent, through a distance of about 1 cm or less to substantially the entire second sorbent, to raise the second sorbent to a fourth temperature and the component is desorbed from the second sorbent; and the component desorbed from the first and second sorbents is obtained.
In a fourth aspect, the invention provides a fluid separation apparatus that includes: a flow channel comprising a porous sorbent, the flow channel having at least one dimension of 1 cm or less, wherein, in at least one cross-section of the flow channel the porous sorbent occupies at least 90% of the cross-sectional area; and a microchannel heat exchanger in thermal contact with the flow channel. The invention also provides a use of this apparatus to purify a fluid component from a fluid mixture.
In a fifth aspect, the invention provides a fluid separation apparatus including: a first array of flow channels, a second array of flow channels, at least one fluid conduit connecting the outlet of the first array to the inlet of the second array; and a valve capable of controlling the flow through the fluid conduit. The first array of flow channels includes: at least two flow channels, each of which includes an inlet, an outlet and a sorbent disposed between the inlet and the outlet. Each of the at least two flow channels are in thermal contact with a microchannel heat exchanger and have at least one dimension of 1 cm or less. This dimension is in a direction toward a microchannel heat exchanger. The first array also includes at least one array inlet and at least one array outlet. The second array of flow channels includes: at least two flow channels, each of which includes an inlet, an outlet and a sorbent disposed between the inlet and the outlet. Each
VanderWiel David P.
Weller, Jr. Albert E.
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