The present invention relates to the field of solids-fluids contacting operations. More particularly, the present invention relates to incremental countercurrent contacting of solids and fluids that can be used in regenerative heat exchangers, ion exchange and adsorption/desorption columns.
The main bodies of certain classes of process equipment need to be regenerated or renewed after a certain time period of operation. That equipment can include regenerative heat exchangers, regenerative thermal oxidizers, moving bed (simulated or real) chemical reactors/chromatographic separators, adsorption/desorption columns, ion exchange columns and regenerative air dehumidifiers. The regeneration methods include rotating the main body of the equipment or switching on and off a multitude of valves so that different sections of the main body can be contacted by different kinds of fluids at different times. The present invention attempts to optimize continuous countercurrent operation for such a multitude of processes.
For continuous operations of heat transfer or mass transfer from one phase to another, counter-current operation is more efficient than co-current or crossflow operations. The counter-current operation can be easily implemented if both phases are fluids but immiscible to each other, since fluids can be pumped around and flow easily.
If one material is a solid and another material is a fluid, counter-current flow becomes more difficult, since moving solid within a vessel or transporting solid from one vessel to another can present mechanical and efficiency problems.
U.S. Pat. No. 1,746,598 issued to Fredrik Ljungström describes a rotary air preheater that rotates heat storage materials in a cylindrical bed. Hot flue gas flows up in one half of the bed, and cold air flows down in the other half and gets heated up. This technology was credited with saving 4,960,000,000 tons of oil, and was distinguished as the 44th International Historic Mechanical Engineering Landmark by the American Society of Mechanical Engineers.
U.S. Pat. No. 5,676,826 issued to Rossiter and Riley disclosed a fluid-solid contacting apparatus employing a rotary valve to conduct fluid streams to and from the apparatus. The fluid-solid contacting apparatus of such a design comprises a plurality of chambers containing solid, with chambers installed on a turntable. While such a design can achieve counter-current solid-fluid contact, a turntable loaded with chambers may cause mechanical difficulties when the size of chambers becomes large and heavy.
U.S. Pat. No. 6,431,202 describes a rotary valve with mechanical improvement over the apparatus of U.S. Pat. No. 5,676,826, but it still requires a turntable.
U.S. patent application No. 20120111435 discloses a turntableless rotary fluid distributor design which is however mechanically complex, and cumbersome for large fluid flows.
U.S. Pat. No. 8,985,151 discloses a rotary fluid distribution apparatus which does not require a turntable for fluid distribution and direction. However, the solid-fluid contact pattern disclosed are mainly crossflows, not true counter-current flows.
U.S. Pat. Nos. 11,738,286, 11,083,980, and 10,589,190 disclose a number of rotary fluid distribution apparatuses. The counter-current apparatuses use a rotor to direct fluids to multiple stationary columns. By the action of the rotor, counter-current flows of a fluid phase and a solid phase can be achieved for a combined adsorption and desorption cycle, or a combined heating and cooling cycle. The apparatus allows not only countercurrent solid-fluid flows based on columns in series, but also countercurrent solid-fluid flows in the length of each individual column.
Those countercurrent apparatuses require complex routing of fluid phases, and multitude of piping and vessels. The complex flow passages of fluid create in some cases high pressure drops of the fluid phases, and slight reduction of efficiency because of nonoperative volumes in multitude of piping and vessels. Nonoperative volumes refer to volumes within the piping, and volumes of top and bottom open space that does not contain solid heat or mass storage medium in the contact vessels.
It is an object of the present invention to provide an apparatus that minimizes fluid phase pressure drops and nonoperative volumes and achieve true countercurrent contact patterns for solid phases and fluid phases. Another objective is to allow incremental renewal of heat or mass storage medium in the apparatus so that less storage medium is required to achieve the same operational efficiency. Still another objective is to reduce the required sealing area between a hot section and a cold section in a heat exchanger case, or between an adsorption section and a desorption section in an adsorption case.
The present invention is an apparatus comprising two channels for heat or mass transfer operations and multitude of solid blocks that contain solid heat or mass storage medium. A mechanism to push solid blocks back and forth between the said two channels is devised.
The counter-current apparatus uses multitude of solid blocks to carry mass storage or heat storage medium to two opposite sides of mass and heat transfer operations. The said multitude of solid blocks are pushed in a clockwise or counterclockwise pattern incrementally through two channels. The energy of sensible heat or mass of selected species from a first fluid stream transfers into the solid blocks in a first channel and is stored in the solid storage medium within. Those solid blocks loaded with energy or specific mass from the first channel are pushed one by one to a second channel in which the energy or specific mass stored within is released to a second fluid stream. The solid blocks after releasing energy or specific mass in the second channel are pushed back into the first channel, continuing the heat transfer or mass transfer cycle. Counter-current flows of the fluid phase and the solid phase are achieved in both channels, for a combined adsorption and desorption cycle, or a combined heating and cooling cycle.
The present invention is a solid/fluid counter-current contact apparatus having two parallel channels containing a plurality of solid blocks within their internal volume for mass or heat transfer, wherein ends of the two parallel channels are aligned at both sides of the two parallel channels. The plurality of solid blocks are positioned so as to line up inside the two parallel channels. A first middle section connects the two parallel channels at one side, and a second middle section connects two parallel channels at an opposite side. The plurality of solid blocks comprise a solid block that occupies the first middle section and another solid block that occupies the second middle section. A first set of plungers are positioned at respective ends of the two parallel channels. The first set of plungers are adapted to push solid blocks from one channel of the two parallel channels to another channel of the two parallel channels through the first middle section and second middle section. A second set of plungers are positioned at respective ends of the two parallel channels adapted to push solid blocks along respective lengths of the two parallel channels between the first and second middle sections.
In an embodiment, the plurality of solid blocks have non-porous side frames and a porous interior for fluid flow. The solid blocks may have screens at front and back ends thereof. The solid blocks may comprise particulate solid matter.
In an embodiment, the solid blocks comprise an assembly of solid materials. The assembly of solid materials may be selected from a group consisting of: steel plates, steel mesh, steel fiber, ceramic plate, ceramic honeycomb, plastic plate, plastic strips and plastic fiber.
In an embodiment, the two parallel channels and the first and second middle sections form a rectangular shape, wherein the first set of plungers are directed in opposite and parallel directions, wherein the second set of plungers are directed in opposite and parallel directions.
In an embodiment, the current contact apparatus has a first inlet positioned at one end of a first channel of the two parallel channels and a first outlet positioned at an opposite end thereof, such that a process stream can be directed through the first channel from the first inlet to the first outlet. A second inlet is positioned at one end of a second channel of the two parallel channels and a second outlet positioned at an opposite end thereof, such that a regeneration stream can be directed through the second channel from the second inlet to the second outlet, said process stream flowing in an opposite and parallel direction than said regeneration stream.
In an embodiment, each of the plurality of solid blocks have a width and a depth, or a diameter, wherein each of the two parallel channels has an interior width substantially equal to the width of a solid block, or the diameter, such that the solid block substantially fills the width of the channel and prevents fluid flow therebetween, wherein each of the first and second middle sections has an interior width substantially equal to the depth of a solid block, such that the solid block substantially fills the width of the middle section and prevents fluid flow therebetween.
In an embodiment, the first and second middle sections are longer than the width of a solid block to prevent fluid leaking through the interior of the solid block.
The present invention is also a method of providing solid/fluid counter-current contact comprising the following steps: providing a loop of channels comprising a first parallel channel, a second parallel channel and first and second middle sections connecting the first parallel channel with the second parallel channel; arranging a plurality of solid blocks in the loop of channels, the plurality of solid blocks snugly fitting with the loop of channels; flowing a process stream through the first parallel channel, the process stream flowing through the plurality of solid blocks; flowing a regeneration stream through the second parallel channel, the regeneration stream flowing through the plurality of solid blocks; and moving the plurality of solid blocks through the loop of channels in a direction opposite a direction of the flow of the process stream.
In an embodiment, the method further includes positioning plungers at corners of the loop of channels, the step of moving being accomplished by sequential operation of the plungers.
In an embodiment, an interior of the loop of channels is capable of holding a number n of solid blocks, wherein n-2 blocks are arranged within the interior of the loop of channels.
In an embodiment, the plurality of solid blocks have non-porous side frames and a porous interior for fluid flow. The plurality of solid blocks may comprise particulate solid matter, the plurality of solid blocks having screens at front and back ends for containing the particulate solid matter.
In an embodiment, the solid blocks may comprise an assembly of solid materials. The assembly of solid materials may be selected from a group consisting of: steel plates, steel mesh, steel fiber, ceramic plate, ceramic honeycomb, plastic plate, plastic strips and plastic fiber.
In an embodiment, the process stream is a hot fluid stream for heat transfer operations, or a rich material stream for mass transfer operations.
In an embodiment, the regeneration stream is a cold fluid stream for heat transfer operations, or a lean material stream for mass transfer operations.
The apparatus of the present invention uses solid medium to extract thermal energy or selected material from a process stream and use a regeneration stream to regenerate the used solid medium. The thermal energy or selected material is transferred eventually from the process stream to the regeneration stream, with the solid as the mass transfer or heat transfer medium. The process stream can be a hot fluid stream for heat transfer operation, or a rich material stream for mass transfer operation. The regeneration stream can be a cold fluid stream for heat transfer operation, or a lean material stream for mass transfer operation.
Referring to
While the apparatus is shown with a rectangular configuration, it is within the concept of the present invention that the apparatus may take the form of other loop or looped structures through which the solid blocks pass.
In comparison of this technology with traditional rotational regenerative heat exchangers, such as Ljungström air preheater as described by the landmark U.S. Pat. No. 1,746,598, this invention could have better efficiency and requires much less solid thermal energy storage medium. This technology requires as little as 5-10% thermal storage mass of Ljunström's rotary bed technology.
The reason behind this difference in solid mass requirements between the present invention versus Ljungström technology is in the different ways of solid-gas contacting. As the bed rotates with Ljungström technology, an increment of solid is rotated into the cold section from the hot section, and at the same time an increment of solid is rotated into hot section from the cold section. The incremental movement of solid, however, is not opposite to the flow direction, rather, it is perpendicular to the flow direction.
In Ljungström, as an incrementally small pie section of the bed from the cold section enters the hot section via the axle rotation, the whole vertical depth of the small pie section enters the hot section at the same time. After rotation of 180° or after time duration of half a period, the whole depth of this pie section would exit the hot section at the same time. Except for temperature changing as a function of time or as a function of rotation, this pie section is not interacting with other solid sections and is not moving in vertical direction. This is equivalent to heating a single column of solid medium of the same area and same depth, from time zero to the time of ½ period (turning 1800) without moving solid at all.
Whereas in the present invention, as shown in the example of
Another issue that needs to be considered is the purging of solid beds. Solid beds have void within to allow fluid flow, and open space at the top and bottom for solid support, fluid introduction and collection. The existing fluid in those volumes needs to be displaced by the new incoming fluid when switching from cold to hot or hot to cold.
Since the Ljungström air preheater switches the whole depth of the bed, more gas volume needs to be displaced at each switching step. The system and method of the present invention switches only a small fraction of the bed depth, resulting in more efficient purging.
A comparison study of the technology of the present invention with Ljungström technology is shown in Table 1.
Different total mass of solid medium and different period are used to calculate efficiencies and outlet temperature of a hot gas. The hot gas comes in at 232° C., and the cold gas comes in at 27° C.
The operating conditions, physical and heat transfer parameters are listed in Table 2.
It can be seen from Table 1 that an incremental counter-current (ICC) heat exchanger is not sensitive to bed mass, and it functions well with extremely low bed mass. As bed mass is increased from 5 kg to 50 kg, only a slight improvement in efficiency is made. On the other hand, a Ljungström heat exchanger requires much more bed mass for energy storage and release. It does not function well without enough mass such as 5 kg cases. At 5 kg bed mass, either the thermal efficiency is bad with 80 seconds period, or the purge efficiency is bad with 10 seconds period. Once enough mass is used, such as in the 50 kg case, the Ljungström heat exchanger is able to match the performance of an incremental counter-current (ICC) heat exchanger at 5 kg.
The technology of the present invention requires bed mass of only 5-10% of that of Ljungström APH, is easier to seal and leaks less than Ljungström APH, because only two blocks are switched at each synchronized push cycle, in contrast to Ljunström APH which needs to seal a large bed.
This apparatus causes minimal fluid phase pressure drops because the fluid passages are straight through. There is no nonoperative volume because each solid block does not have an entrance zone or an exit zone as is required for a solid bed in a vessel, and there is no piping between solid blocks as is required for apparatuses of U.S. Pat. Nos. 11,738,286, 11,083,980, and 10,589,190.
The present application claims priority to U.S. Provisional Application No. 63/551,385, filed Feb. 8, 2024.
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1404626 | Mathy | Jan 1922 | A |
1746598 | Ljungström | Feb 1931 | A |
5676826 | Rossiter et al. | Oct 1997 | A |
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20120111435 | Antonetti | May 2012 | A1 |
Number | Date | Country | |
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63551385 | Feb 2024 | US |