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Process Miniaturization

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 processes, and perform scale-up of these 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 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 a single design template

3) Approaching total automation

4) A new technology

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).

Rather than one large central plant, that has to be fed a large amount of feedstock, such as a refinery that can unload a tanker shipment of petroleum if located next to an ocean, the discipline of process miniaturization envisions the distribution of the process technology to areas where the feedstock is not readily transportable in large quantities to a large centralized processing plant. The miniaturized process technology may simply involve transformation of solid biomass materials from multiple distributed microprocesses into more easily manageable fluids. The fluids can then be transported or distributed to larger-scale intelligent processing nodes using conventional fluid transport technology.

Historically, small processes or microprocesses per se have always existed. For example, small vineyards and breweries have produced feedstock, processed it, and stored product in what could be considered “microprocess” when compared to processes designed based on the petrochemical industry model or, for example, large-scale production of beer. Small villages in India and other places in the world have learned to produce biogas from animal manure in what could be considered small-scale microprocesses for the production of energy. However, microprocesses and process miniaturization as a design philosophy includes the notion of approaching total automation and is a new technology which has been enabled by computer hardware miniaturization, for example, the microprocessor. It is easy to envision processes which can be mass produced and transported. For example, many appliances such as air conditioners, domestic washing machines, and refrigerators could be considered microprocesses.

The design philosophy of process miniaturization envisions that “scale-down” of complex processes involving multiple process unit operations can be achieved, and that economy of scale will be more related to the size of a network of distributed autonomous microprocesses. Since failure of one autonomous microprocess does not cause shutdown of the entire network, microprocesses will lead to more economically efficient, robust, and stable production of products that have traditionally been produced for a petroleum-based society. Since fossil fuels by definition are being consumed and are non-renewable, the future existence of modern society will be based on renewable materials such as biomass. It is that future in which the designers of microprocess technology will be required.

References

"Microprocesses - Sometimes Smaller is Better", S. S. Sofer, Chemical Processing, May 1987