Patent Application
20190170442
The devices, systems, and methods described herein relate generally to melting of solids. More particularly, the devices, systems, and methods described herein relate to melting of solids that sublimate at ambient pressures.
Cryogenic solids of various varieties have phase diagrams that do not permit transitions between solid and liquid phases at ambient or near-ambient pressures. Handling these materials as solids is a challenge, as they require the solids handling be done under high pressure conditions, which is logistically difficult and costly. Devices, systems, and methods capable of handling cryogenic materials with minimal solids handling would be beneficial.
Devices, systems, and methods for pressure-regulated melting are disclosed. A vessel includes a solids inlet, a fluids outlet, a cavity, and a melting device. Solids enter the vessel through the solids inlet. The cavity has an internal pressure. The solids inlet has a reducer that produces a first back pressure on the solids in the solids inlet. The melting device heats the vessel, the contents of the vessel, or a combination thereof. The heating rate of the melting device is matched to the feed rate of the solids such that the solids are melted directly to a product liquid at the internal pressure. The product liquid passes through the fluids outlet through a restriction that maintains the internal pressure in the cavity.
The melting device may be an electrically-resistive heater, a hot liquid in a tube, or a combination thereof. The solids inlet may include a screw press.
The fluids outlet may include a heat exchanger that heats the product liquid, producing a heated product liquid. The fluids outlet may further include a gas/liquid separator that receives the heated product liquid from the heat exchanger and separates a final product liquid and a product gas. The gas/liquid separator may include a pump that pumps a portion of the final product liquid from the gas/liquid separator to the vessel, the portion of the final product liquid being the warm liquid.
The restriction may be one or more valves. The reducer may be a concentric reducer, an eccentric reducer, or a nozzle.
The solids may include water, hydrocarbons, ammonia, solid acid gases, or a combination thereof, and wherein solid acid gases comprise solid forms of carbon dioxide, nitrogen oxide, sulfur dioxide, nitrogen dioxide, sulfur trioxide, hydrogen sulfide, or a combination thereof. The warm liquid may include water, hydrocarbons, liquid ammonia, liquid acid gases, cryogenic liquids, or a combination thereof, and wherein liquid acid gases comprise liquid forms of carbon dioxide, nitrogen oxide, sulfur dioxide, nitrogen dioxide, sulfur trioxide, hydrogen sulfide, or a combination thereof.
In order that the advantages of the described devices, systems, and methods will be readily understood, a more particular description of the described devices, systems, and methods briefly described above will be rendered by reference to specific embodiments illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the described devices, systems, and methods and are not therefore to be considered limiting of its scope, the devices, systems, and methods will be described and explained with additional specificity and detail through use of the accompanying drawings, in which:
It will be readily understood that the components of the described devices, systems, and methods, as generally described and illustrated in the Figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the described devices, systems, and methods, as represented in the Figures, is not intended to limit the scope of the described devices, systems, and methods, as claimed, but is merely representative of certain examples of presently contemplated embodiments in accordance with the described devices, systems, and methods.
Many cryogenic solids act in ways seemingly contradictory to that which is expected for solids. Normally, solids melt into a liquid, which then vaporizes into a gas. Many cryogenic liquids, such as carbon dioxide and other acid gases, have phase diagrams that, at ambient pressures, will sublimate from solid directly to gas. In materials handling, liquids are simple to transport when compared to both solids and gases. Gases typically require large equipment to transport similar masses in comparison to liquid. On the other hand, solids have to be moved by conveyance devices that are, with only a few exceptions, open to ambient pressures. The devices, systems, and methods disclosed herein overcome these challenges by avoiding the issue entirely. Cryogenic solids, or any solids that can be melted, are passed into a vessel against a backpressure and met by a warm liquid that is fed at a rate that will melt the solids directly to a liquid as they enter the vessel, resulting in a product liquid. This product liquid then leaves the vessel through a restriction, resulting in an internal pressure in the cavity of the vessel, allowing the solids to transition from solid to liquid instead of liquid to gas. This is due to the pressure increase moving the product to a different portion of the phase diagram—specifically, from the pressure at which solids transition by desublimation to gases to the pressure at which solids transition by melting to liquids. The means by which the solids are passed into the vessel depend entirely upon the solids being passed, whether as fine ‘fluid-like’ solids, or suspended in slurries. Of special note are screw conveyors and peristaltic pumps. Each provides a benefit that traditional systems cannot. In the case of peristaltic pumps, solids are entirely blocked from backing up in the system, and so solids will not be forced backwards. In the case of screw conveyors, specialized filtering screw presses can be used that remove liquids from slurries before forcing the solids into the vessel for melting.
Referring now to the Figures,
A melting device 144 provides a portion of the heat required to melt the solid stream 156. The melting device 144 may be an electrically-resistive heater, a hot liquid in a tube, or other devices that provide heat to the interior or exterior of the vessel 102. A warm fluid stream 164 passes through the vessel fluids inlet 118 into the vessel 102, providing the remainder of the heat required to melt the solid stream 156. The inlet pressure of this warm fluid stream 164 from pump 110 contributes to the backpressure on the solid stream 156 in the solids inlet 116, and therefore on the slurry stream 150 in the filter screw press 104. In this example, the warm fluid stream 164 may be liquid carbon dioxide. As the warm fluid stream 164 encounters the solid stream 156, the solid stream 156 is melted, resulting in a first product liquid stream 158. The vessel outlet 120 is restricted, in this case downstream by valves 112 and 114, such that an internal pressure is maintained in the cavity of the vessel 102. The warm fluid stream 164 is pumped into the vessel 102 at a rate that matches the rate required to melt the solid stream 156 and at an inlet pressure that will maintain the internal pressure of the vessel 102 in a range that the solid stream 156 can transition directly from solid to liquid. Deviation from pressure can result in sublimation rather than melting, which can be dangerous and inefficient. Also, impurities, such as isopentane from the filter screw press 104, can be introduced into the vessel 102 if the melting rate and pressure are not balanced.
The first product liquid stream 158 leaves through the vessel outlet 120 and is heated passing through a first heat exchanger 106, resulting in a warmed product stream 160. Warmed product stream 160 enters a gas-liquid separator 108, splitting into a second product liquid stream 166 and a product gas stream 168. Product liquid stream 166 leaves through valve 112 and product gas stream 168 leaves through valve 114. A portion 162 of product liquid stream 166 is diverted through pump 110 and passed into the vessel 102 as the warm fluid 164, as described above.
In other embodiments, a lesser amount of liquid may be removed from the filtering screw press 104, resulting in some contamination of the product liquid stream 158 by the liquid.
Referring to
The slurry 150 is conveyed through the filtering screw press 104 by screw 236, driven by rotor 237. The slurry 150 is pushed through the outlet, solids inlet 116. Solids inlet 116 is restricted, in this case, an orifice, resulting in a first back-pressure on the slurry 150 in the screw press that drives the liquid out of the slurry and through the filter 238. The liquid leaves out of the liquid outlet 234 as a substantially pure liquid stream 154. Some portion of the liquid and the solid may leave in the gas phase through gas outlet 232. The solid stream 156 passes through solids inlet 116 and is met by warm fluid stream 164, which melts the solid stream 156 at the rate it enters the vessel 102. The warm fluid stream 164 also provides a portion of the backpressure on the solids inlet. The resultant first product liquid stream 158 passes out the vessel outlet 120, which is restricted, providing the internal pressure on the first product liquid stream 158.
Referring to
Referring to
Pressure transmitter 442 and temperature transmitter 444 measure pressure and temperature, respectively, in vessel 402, and transmit the information to a process controller 446. Flow meters 444 and 446 measure flow in their respective streams and transmit this information to the process controller 446. Process controller 446 evaluates this information and then controls the heating rate of melting device 440 and flow rates for solid stream 456 and warm liquid stream 464 and balances these against valve 412 to maintain pressure, temperature, and melting rate in vessel 402.
Referring to
Referring to
In some embodiments, the solid and the warm liquid are the same compound. In other embodiments, the solid or liquid stream may include impurities or be varying mixtures of compounds.
In some embodiments, the solids may include water, hydrocarbons, ammonia, solid acid gases, or a combination thereof, and wherein solid acid gases comprise solid forms of carbon dioxide, nitrogen oxide, sulfur dioxide, nitrogen dioxide, sulfur trioxide, hydrogen sulfide, or a combination thereof.
In some embodiments, the warm liquid may include water, hydrocarbons, liquid ammonia, liquid acid gases, cryogenic liquids, or a combination thereof, and wherein liquid acid gases comprise liquid forms of carbon dioxide, nitrogen oxide, sulfur dioxide, nitrogen dioxide, sulfur trioxide, hydrogen sulfide, or a combination thereof.
This invention was made with government support under DE-FE0028697 awarded by the Department of Energy. The government has certain rights in the invention.
