Chemistry: analytical and immunological testing – Including sample preparation – Volumetric liquid transfer
Reexamination Certificate
2000-09-15
2002-08-20
Drodge, Joseph W. (Department: 1723)
Chemistry: analytical and immunological testing
Including sample preparation
Volumetric liquid transfer
C137S001000, C137S571000, C137S572000, C210S097000, C210S205000, C210S088000, C422S062000, C422S081000, C422S129000, C422S131000, C422S110000
Reexamination Certificate
active
06436720
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to chemical processing apparatus, and more specifically, to a module for providing sufficient residence time to ensure that mixtures of reactants supplied to a chemical reactor have sufficient time to completely react with one another before the resulting product is output from the apparatus.
BACKGROUND OF THE INVENTION
Methods of controlling and optimizing the production of chemical substances are well known. The control of parameters such as temperature, pressure, mixing conditions, relative volumes of the reactants, and the use of catalysts are generally well understood. Processing equipment for facilitating chemical reactions can be specifically designed for one particular reaction, or can be designed to facilitate the processing of more than just one specific chemical reaction.
Ideally, equipment designed for processing more than a single specific chemical reaction should be adjustable so that it can be used to facilitate a variety of different chemical reactions of interest. For example, because different chemical reactions require different temperature conditions, chemical processing equipment should enable temperature conditions in the equipment to be varied, so that the optimal temperature for a particular reaction can be provided.
While it is relatively easy to design processing equipment that enables temperature conditions to be adjusted, it is more challenging to design processing equipment that enables all relevant parameters to be adjusted. Reaction time (i.e., processing time) is another parameter that should be precisely controllable. Each different reaction is characterized by having an optimal processing time required to ensure that the reactants have sufficient time to completely react with one another. Ensuring that sufficient processing time is provided in a chemical processing system is critical to achieving good product yields and process efficiency. Providing too little time reduces product yield, because the product will include reactants that have not yet reacted to form the desired product. The processing time required in a given chemical processing system is a function of the specific reaction, the temperature of the reactants, and concentration and volume of the reactants. The amount of processing time provided by a given chemical processing system is a function of the volume of the reactor or reaction chamber within the system, and the flow rate of the reactants into the reactor (or reaction chamber). While the volume of the reaction chamber within a particular chemical processing system is generally fixed, flow rates can typically be varied throughout at least a limited range. Accordingly, the volume of the reaction chamber and the flow rates of the reactants should be selected to ensure that the reactants have sufficient time to thoroughly react.
However, there are instances in which additional processing time may be required for a particular reaction. In this case, it is well known in the art to provide “residence time chambers” or modules down stream of a reaction chamber. Basically, a residence time chamber is a volume into which the already mixed reactants (exiting a reaction chamber or reactor) are diverted. The mixed reactants are held in the residence time chamber for a length of time sufficient to ensure that the desired reaction has been completed before the resulting product and any byproducts are directed into a collection vessel. Thus, residence time chambers can be beneficially incorporated into a chemical processing system when the volume of the reaction chamber and the available reactant flow rates within that chemical processing system cannot otherwise be readily modified to provide sufficient processing time.
Some residence time chambers are integral and unique to specific chemical processing systems and are not designed or intended to be replaceable or usable in other systems. U.S. Pat. No. 5,516,423 (Conoby) describes a chemical processing system in which a residence time is varied by controlling the effective volume of a reaction chamber supplied with a liquid effluent and a treatment chemical. A valve controls an outlet port from the reaction chamber, and a sensor determines whether a desired result has been achieved. Once the desired result has been achieved, the outlet valve is opened and the treated effluent is discharged. Accordingly, the outlet valve is controlled to vary the residence time of the reactants within the reaction chamber. However, new effluent continues to enter the reaction chamber during the residence time, so that the volume of effluent within the reaction chamber is not constant. To maximize product yield and quality, it is preferable to more precisely control the influx of reactants into a reaction chamber and the time of the reaction, rather than simply retaining the reactants in a reaction chamber until a desired result is achieved.
Many chemical processing systems are designed to operate with a constant volume of reactants in the reaction chambers, to ensure that unwanted byproducts caused by varying the relative concentrations of the reactants are not formed. For this reason, the method used to vary the residence time, as described in the above-noted patent, is generally not applicable to many types of reactions, or not desirable. It is preferable to include a separate residence time chamber down stream of the reaction chamber. Residence time chambers of many different types are known. Some residence time chambers are simply unobstructed chambers or fluid paths into which mixed reactants are directed, and the physical dimensions of the chamber or fluid path are such that the time necessary for the mixed reactants to traverse the chamber or fluid path provides the required residence time. Other residence time chambers include baffles or other types of flow restriction elements designed to increase the length of time required for the mixed reactants to traverse the chamber. Such residence time chambers are frequently integral components of chemical processing systems and are not designed to be selectively configurable to provide variable residence times. Furthermore, known residence time chambers typically incorporate a single fluid path, with a volume that controls the additional residence time provided by the residence time chamber.
A simple tube open at both ends can be used as a residence time chamber, and the additional reaction time provided by the device is strictly determined only by the flow rate of the reactants and the volume of the tube. A disadvantage of a simple tube type residence time chamber is that the additional reaction time can be only varied only by changing the flow rate (i.e., by changing the production rate of the chemical processing system, which will generally already have been optimized for a particular chemical production system), or by selecting and installing an appropriately sized tube from a stock of such tubes having different volumes.
It would therefore be desirable and preferable to provide a residence time chamber that is selectively configurable to provide variable residence times without changing to a different residence time chamber. Preferably, such a residence time chamber should incorporate a plurality of fluid paths, and the fluid paths should be individually controllable to provide the same or different residence times. It would further be desirable for such variable residence time chambers to be modular in nature, so that different residence time modules having different ranges of available residence times or other desired properties can be used in a chemical processing system or with a chemical reactor.
Recently, much attention has been directed to the use of microreactors for both research and development work, and the production of chemical products. Microreactors offer several clear advantages over more conventional macro-scale chemical processing systems. Accordingly, it would be desirable to provide a variable residence time chamber adapted to be used with microreactors. The prior art does no
Golbig Klaus
Hohmann Michael
Oberbeck Andreas
Oberbeck Sebastian
Anderson Ronald M.
Cellular Process Chemistry, Inc.
Drodge Joseph W.
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