Patent Application
20190193027
A system that uses single or multiple elements arranged in a single unit or multiple arrays for the extraction, purification, and concentration of lithium and other constituents from a brine that can be constructed in a mobile unit.
Constituents are targeted by arranging the following unit operations using an interdependent multiple array concept: extraction columns, purification membranes, and concentration membranes.
Conventional methods of separating lithium and other constituents from brines depend upon a specific sequence of variable concentration streams. These streams are run through different types of equipment, most commonly packed bed columns. Lithium specifically is selectively adsorbed onto the internal packing of the packed bed column. The internals, made up primarily of treated material in the form described below is operated using a specific sequence set of steps. The sequence of flows is required to displace various residual streams minimizing impurities and maximizing concentration of the targeted constituent for isolation, the conventional system performance is limited by the ability to increase the concentration of the targeted constituent and decrease concentration of the undesired impurities. Conventionally, streams dilute in the targeted constituent have to be recycled thus creating specific sequences and column arrangements that require large volume internal components and flow. Large volume internals which may include sorbent particles, sorbent fibers, separation membranes, plates, and other known separation materials must be arranged such that a sharp distinct difference in the concentration of the stream flowing through the equipment containing the internals is present to enable the mass transfer of the targeted constituent to the internals. These internals are the extracting materials.
An example of the conventional approach is described by the following sequence. A column of sufficient diameter to support the needed flowrate and of a height with a ratio of diameter to height of 1 to 3 filled with a particle that has been treated to capture and extract a specific constituent present in the flow is fed brine at an appropriate rate. The targeted constituent is held on sites on the extracting material, in this case, the particle. Saturation occurs once the extracting material has reached a point that all available extraction sites have been filled by the targeted constituent. A second stream is flowed through the column to displace the residual liquid from the initial flow. This lowers the impurities, or the non-targeted constituents. A third flow comprised of an appropriate constituent concentration removes the targeted constituent from the extracting material. This is known as product flow. The sequence duration and specific makeups of each of these streams determine the performance of the column. In many cases streams of dilute concentration of the targeted constituent are used in the sequence. This requires the equipment to be large volume, therefore affecting the stability of the sharp concentration profile needed to drive mass transfer. There are many other possible sequences including intermediate arrangements of the columns as well. There are also many other methods of extracting the targeted constituents including using the extraction material sites to grab the unwanted impurities. Other methods include steps not addressed here which could be wash, breakthrough, backwash, and regeneration.
This invention simplifies the column sequence, reduces the needed volume, reduces the dynamic shock on the internals, and makes use of post column concentration methods not available previously in conventional systems. An embodiment of the invention is described by the following sequence. A stream containing a concentration of lithium or another targeted constituent is fed into an array of small diameter columns on the order of one fifth to one twentieth diameter of conventional columns with a height to diameter ratio in the range of two to ten. The columns are arranged in a parallel flow array thus allowing a combined feed manifold and a number of parallel single elements arranged in the array to behave as one flow unit. This enables an extremely sharp concentration profile presented to the extracting material in each of the single elements. This arrangement using single elements in an array with a distribution manifold acting as one flow unit can be constructed of dimensions that allow its fitting to a standard mobile container. These can be many types. Since many economically recoverable constituents are located at remote sites, the ability to bring a mobile system to extract those constituents is novel and useful. Such an array cannot support the complex valving required for conventional sequencing. The number of valves and the complexity of the piping would create not only technical barriers due to the hydraulic action and dynamics that would destroy the internals but it would also be economically prohibitive.
In addition to the benefits described above, this invention solves problems with the mechanical dynamics that are present in the conventional approach. In the conventional approach, the internals are subjected to great dynamic movement, vibration and surface to surface interaction. These dynamics grind the internals such that particles or structures become smaller and smaller. As the packed bed of internal vibrates, the ground smaller pieces fill the previously open interstitial spaces and the pressure drop increases. A specific application of this invention is for lithium. To capture lithium, the internals must be constructed of size exclusion material, typically one of many types of alumnosilicates, that has a high surface area and that has been activated by one of many methods using various chemicals. For a lithium example, the activation is completed with a hydroxide and acid sequence to develop the sites for lithium capture, then build a structurally stable particle to make up the internals of the packed bed. The use of these materials is much more susceptible to damage due to hydraulic dynamics as opposed to conventional ion exchange resin which usually has a more robust structure. This invention solves the problem associated with the brittle and friable nature of the alumnosilicates in lithium extraction applications. An increased pressure drop reduces the flow that can be obtained trough the system, thus reducing the capacity of the system. The reduced capacity and higher pressure drop leads to more dynamic action as more flow is attempted to processed through the column thus exacerbating the griding, and exponentially increasing the reduction of the interstitial space. At some point the column is rendered in operable. The invention reduces this dynamic destruction of the internals by reducing the stress on the internals and keeping the pressure drop low. The lower pressure drop reduces the grinding and allows much more capacity of the system. This in (urn increases internal useful life and allows for continued lower cost operation.
The volume of fluid that takes up the space of one column is called a bed volume. In column extraction it is helpful to think of the sequence for loading the targeted constituent on the extraction material sites and collecting, or stripping, the targeted constituent off the extraction material sites in terms of bed volumes. The extraction array in combination with purification and concentration membrane units makes use of a simplified sequence that maximizes the collected mass of the target constituent. At saturation the targeted constituent concentration on the extraction material is at its peak and the liquid in the column contains one bed volume of loading, or feed, solution worth of impurities.
At saturation in the conventional method the residual impurity liquid bed volume is displaced with a dilute stream and the residual impurity liquid bed volume is sent to spent solution. Next the bed volume of dilute stream is displaced with a bed volume of clean stream containing a part per million concentration of targeted constituent also known as strip solution. The same happens in the invention for these two displacement step in the sequence. In the conventional method the bed volume of displaced dilute stream is either recycled or sent to spent solution so as not to dilute the concentrated target constituent stream that will be stripped off the sites. In the invention the bed volume of displaced dilute stream can be recycled or pushed forward to the purification and concentration membrane units because the units can readily concentrate dilute and clean target constituent streams. In the conventional method the strip solution is pushed for a limited number of bed volumes to capture a clean and concentrated stream of targeted constituent. The conventional method does not have the advantage of the purification and concentration membrane units and has to stop the flow of strip solution when the targeted constituent falls below a concentration level. The invention allows a greater number of bed volumes of strip solution to run through the columns resulting in a higher mass of collected targeted material. This material, known as the product cut, will be clean of impurities, but more dilute than the conventional method. The invention's product cut can be more dilute because the invention utilizes the purification and concentration membrane units. Additionally, in the invention the extraction material sites in the column are more available than the conventional method because more of the targeted constituent was released, or stripped, from the extraction material sites. The next step of the sequence is to repeat the load step pushing the impurity and constituent laden feed solution back into the column. Because the invention can remove more of the targeted constituent, resulting in a greater number of available extraction material site, a greater number of bed volumes can be loaded back onto the columns than in the conventional system. The invention can operate without the need for recirculating loads. This results in a simple time based sequence without complex valving conventionally required for high purity product cuts.
As mentioned, the invention product cut is dilute compared to conventional methods. To overcome this challenge a concentration membrane is used to remove the solvent, in most cases water, from the stream containing the desired constituent. Concentration membranes are susceptible to impurity materials affecting the performance of the separation. This challenge is overcome by using a purification membrane prior to the concentration membrane. In a typical embodiment, a cross flow membrane. Cross flow meaning the way the liquid is presented to the membrane. The cross flow membrane allows the targeted constituent and solvent to pass, or permeate, as it rejects the undesired impurities. An example would be lithium in a chloride brine as the targeted constituent and solvent with divalent cations, most commonly calcium and magnesium, being rejected. Other constituent combinations exist. Purification membranes typically reduce the levels of impurities to the parts per million level. Purification membranes typically are operated at a pressure between 100 and 400 psig.
To complete this invention's purification and concentration of the targeted constituent the product stream that passed through the purification membrane is now fed into a system containing a concentration membrane. In this unit the solvent, most commonly water, passes through the membrane and the targeted constituent is rejected, thus concentrates in the reject stream from the concentrating membrane unit. An embodiment of this concentrating membrane is reverse osmosis. Concentration membranes operated as reverse osmosis systems typically concentrate the targeted constituent to weight percentage levels. Concentration membranes operated as reverse osmosis systems are limited by the osmotic pressure of the solution and the practical limits of the pressure ratings of the single element components. Concentration membranes typically operate between 200 and 1200 psig.
Both the purification membrane units and the concentration membrane units are made up of single elements arranged in arrays. Similar to the extraction array, purification and concentration membrane units can be arranged in arrays and fitted to mobile systems. This allows the mobile deployment of these unit operations for recovery of targeted constituents.
The mobile configuration of RO units and ion exchange units is not new, however, the arrangement of selective absorbent, which is a particle which is described as one of the possible internals above, in a mobile configuration is new and novel and previously unavailable in a small single element configuration due to the previous limitation of the management of the dilute streams and the recirculating loads. The conventional lithium extraction system columns are very large diameter and very large heights. This invention, and its use of the post extraction membrane purification and concentration methods enables the unique and novel use of this configuration to deliver the benefits of the invention.
The invention can include the collection of the purified and concentrated lithium rich brine for use in post extraction product conversion systems. These systems benefit from the purity of the lithium rich brine and the ability to avoid further raw purification processes to prepare the brine for unit operations including electrolysis, splitting and recovery.
The invention makes use of membrane technology to also isolate CO2 from a feed gas stream which could be simply air, ore as complex as a discharge from a power plant. The CO2 is used to produce the final Li2CO3 product by reacting the lithium rich brine stream with the separated CO2. In the case of LiOH production, the raw purification and concentration system allows the direct feed to a lithium hydroxide electrolysis system. The purified product will meet the raw purification requirements and the system will only require the secondary purification system to prepare the brine for electrolysis to LiOH. In both these product cases, lithium is the targeted constituent, but other elements may behave in a similar fashion using the same scheme.
Provisional Patent Application 62/577,554 is incorporated in this application in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62577554 | Oct 2017 | US |
