Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Bench scale
Reexamination Certificate
2000-02-03
2003-03-25
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Bench scale
C422S091000, C422S105000, C422S129000, C422S131000, C422S138000
Reexamination Certificate
active
06537506
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to a miniaturized chemical processing apparatus, and more specifically, to a miniaturized chemical processing apparatus assembled from stacked plates that cooperate to provide fluid channels for conveying reactants and other fluids.
BACKGROUND OF THE INVENTION
Methods of controlling and optimizing processes for producing chemical compounds 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. Traditionally, newly discovered chemical compounds and processes involving either the production of such compounds, or processes involving the use of such compounds, have been initially carried out by researchers in “bench-scale” environments. Particularly promising chemicals or processes may ultimately be produced in quantity by application to industrial scale processes. Often, problems are encountered in scaling up a process from the laboratory to industrial scale production.
Problems associated with moving from bench-scale production to industrial scale production often involve changes in process conditions between the bench-scale environment and the industrial environment. For example, the temperature of the reactants within a small beaker or flask in a laboratory is much easier to keep constant than the temperature within a production tank having a capacity of hundreds of liters, as is often the case in a chemical processing plant. Variations in other process conditions within a large tank are also more difficult to control, and frequently effect the quality and yield of the desired product.
Another aspect of laboratory development of processes to produce chemical compounds is that often potentially dangerous chemicals are used to create the desired product. Fires and explosions in research laboratories and concomitant injury to personnel and property are well known risks in the chemical research industry. The risks are not limited only to research only, as industrial chemical production facilities also may experience fires and explosions related to chemical production using dangerous chemicals. Often, due to the quantities of chemicals used in industrial scale processes, such accidents are significantly more devastating in an industrial setting than similar accidents in a research setting.
Recently, much attention has been directed to the use of micro-scale reactors for both development and production of chemical processes. These types of reactors offer several advantages. As noted above, the control of chemical processes within very small reactors is much simpler than control in a large-scale production tank. Once a reaction process has been developed and optimized in a micro-scale reactor, it can be scaled up to industrial production level by replicating the micro-scale reactors in sufficient quantity to achieve the required production output of the process. If such reactors can be fabricated in quantity, and for a modest cost, industrial quantities of a desired product can be manufactured with a capital expenditure equal to or even less than that of a traditional chemical production facility. An additional benefit is that because the volume of material in each individual reactor is small, the effect of an explosion or fire is minimized, and with proper design, an accident in one reactor can be prevented from propagating to other reactors.
Safety in the research setting is also improved, as such reactors generally require less exposure to hazardous substances and conditions by research personnel than traditional “wet-chemistry,” which typically requires that the researcher physically handle chemicals in a variety of glass containers, often in the presence of an open flame and/or other heat sources. Any accident in such an environment is likely to increase the risk that the researcher will be exposed to hazardous chemicals, as well as the risk of causing significant damage to the laboratory. In contrast, small scale or microreactors can be designed as self-contained units that minimize the researcher's potential exposure to chemical substances. Since when using a microreactor, the researcher is not required to physically manipulate containers of chemical materials to carry out a desired reaction, the reactor can be located in an area so that if an accident should occur, any resulting fire or explosion can be relatively easily contained.
Another area in which microreactors offer an advantage over conventional chemical process development and production is in the mixing of reactants. A mixing channel of the proper scale encourages a laminar flow of the reactants within the channel and is readily achievable in a microreactor. A laminar flow enhances mixing by diffusion, which eliminates the need to expend energy to physically stir or agitate the reactants and is an extremely fast and efficient mixing technique.
Microreactors particularly offer great promise to the pharmaceutical industry, which engages in chemical research on many new chemical compounds every year, hoping to find a drug or chemical compound with desirable and commercially valuable properties. Enhancing the safety and efficiency of such research is valuable in and of itself. And, when coupled with the potential that these reactors offer for eliminating the problems of moving from bench-scale production to industrial production, it will be apparent that a microreactor suitable for use in carrying out a variety of chemical processes and having an efficient and low-cost design will be in high demand.
Several different designs for microreactors have been investigated. For example, such reactors are described in U.S. Pat. No. 5,534,328 and U.S. Pat. No. 5,690,763 (both listing Ashmead as the inventor). These patents describe reactors structures for chemical manufacturing and production, fabricated from a plurality of interconnected layers. Generally, each layer has at least one channel or groove formed in it and most include orifices that serve to fluidly connect one layer to another. These layers are preferably made from silicon wafers, because silicon is relatively inert to the chemicals that may be processed in the reactor, and because the techniques required to mass produce silicon wafers that have had the required channels and other features etched into their surfaces are well known.
A disadvantage of the reactors described by Ashmead stems from the rather expensive and complicated process for manufacturing the devices. While silicon wafer technology is advanced to the state that wafers having desired surface features can readily be mass produced, the equipment required is capital intensive, and unless unit production is extremely high, the substantial costs are difficult to offset. While Ashmead does suggest that other materials can be used to fabricate the layers, such as metal, glass, or plastic, the surface features required (grooves, channels, etc.) must still be formed in the selected material. The particular surface features taught by Ashmead require significant manufacturing steps to fabricate. For instance, while forming an opening into a material is relatively easy, forming a groove or channel that penetrates only part way through the material comprising a layer is more difficult, as the manufacturing process must not only control the size of the surface feature, but the depth, as well. When forming an opening that completely penetrates through a material comprising a layer, depth control does not need to be so precisely controlled. Ashmead teaches that not only openings that completely penetrate the layers are required, but also that surface features (grooves/channels) that do not completely penetrate the individual layers are required. Hence, multiple processing steps are required in the fabrication of each layer, regardless of the material selected. Accordingly, it would be desirable to develop a microreactor comprising layers that do not require such detailed fabrication.
A patent issued to Bard (U.S. Pat. No. 5,580,5
Dittmann Bernd
Georg Petra
Golbig Klaus
Hohmann Michael
Oberbeck Andreas
Anderson Ronald M.
Cellular Process Chemistry, Inc.
Handy Dwayne K.
Warden Jill
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