Chemical process miniaturization refers to a philosophical concept within the discipline of process design that challenges the notion of "economy of scale" or "bigger is better". In this context, process design refers to the discipline taught primarily to chemical engineers. However, the emerging discipline of process miniaturization will involve integrated knowledge from many areas; as examples, systems engineering and design, remote measurement and control using intelligent sensors, biological process systems engineering, and advanced manufacturing robotics, etc. One of the challenges of chemical engineering has been to design processes based on chemical laboratory-scale methods, and to scale-up processes so that products can be manufactured that are economically affordable. As a process becomes larger, more product can be produced per unit time, so when a process technology becomes established or mature, and operates consistently without upsets or “downtime”, more economic efficiency can be gained from scale-up. Given a fixed price for the feedstock (e.g. the price per barrel of crude oil), the product cost can be decreased using a larger scale process because the capital investment and operational costs do not normally increase linearly with scale. For example, the capacity or volume of a cylindrical vessel used to produce a product increases proportional to the square of the radius of the cylinder, so cost of materials per unit volume decreases. But the costs to design and fabricate the vessel have traditionally been less sensitive to scale. In other words, one can design a small vessel and fabricate it for about the same cost as the larger vessel. In addition, the cost to control and operate a process (or a process unit component) does not change substantially with the scale. For example, if it takes one operator to operate a small process, that same operator can probably operate the larger process. The economy of scale concept, as taught to chemical engineers, has led to the notion that one of the objectives of process development and design is to achieve “economy of scale” by scaling-up to the largest possible size processing plant so that the product cost can be economically affordable. This disciplinary philosophy has been reinforced by example designs in the petroleum refining and petrochemical industries, where feedstocks have been transported as fluids in pipelines, large tanker ships, and railcars. Fluids, by definition are materials that flow and can be transferred using pumps or gravity. Therefore, large pumps, valves, and pipelines exist to transfer large amounts of fluids in the process industries. Process miniaturization, in contrast, will involve processing of large amounts of solids from renewable biomass resources; therefore, new thinking towards process designs optimized for solids processing will be required. The concept of a microprocess has been defined by S. S. Sofer while a professor at the New Jersey Institute of Technology. A microprocess has the following characteristics:
1) Portability 2) Capable of being mass produced using advanced robotic manufacturing methods 3) Approaching total automation 4) A new technology
Miniaturization of Electronic Devices The microprocess design philosophy has been largely envisioned by historical analysis of the role that component miniaturization has played in the information technology industry. It is the evolution of the miniaturization of computer hardware that has enabled the thinking about process miniaturization, in the chemical engineering design context. Rather than the traditional design objective as “scale-up” of processing to one centralized large processing plant (e.g. the mainframe), one can envision achieving the economic objectives using a “scale-out” philosophy (e.g. multiple microcomputers). Electrical and electronic devices have always played an important role in chemical process plant automation. However, initially, simple thermometers such as those containing mercury, and pressure gauges which were completely mechanical in nature were used to monitor process conditions (such as the temperature, pressure and level in a chemical reactor). Process conditions were adjusted based largely on a human operator's heuristic knowledge of the process behavior. Even with electronic automation installed, many process still require substantial operator interaction, particularly during the start-up phase of the process, or during deployment of a new technology. Process control of the future will involve the widespread utilization of intelligent sensors, and mass-produced intelligent miniaturized devices such as programmable logic controllers that communicate wirelessly to process actuators. Since these devices will be miniaturized to reduce manufacturing cost, this enables the devices to be embedded in structures so that they become invisible to the casual observer. The cost of such sensors will likely be reduced to a point where they either "function or don't function". When that cost threshold has been reached, the repair procedure will be to disable the sensor, and to actuate a redundant working sensor. In otherwords, entire complex control systems will become so low cost, that repair will not be economically viable. The intelligence of the process will be developed using process simulation models based on scientific fundamentals. Heuristic rules will be programmed into the micro-controllers, which will largely eliminate the need for constant monitoring by human heuristic knowledge of the process behavior. Process which can automatically self-optimize through advanced algorithms developed by microprocess engineers will be embedded, and only accessible to the knowledge-owner. This will enable the construction of large networks of autonomous microprocesses.
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