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 automous microprocesses.
Process Miniaturization for Knowledge-based Businesses
Advanced process control systems for process miniaturization
will increase the need for controlling the security and ownership of process
intelligence in a knowledge-based business. It will become more difficult to
control intellectual property through the traditional method of patents;
therefore, trademarks, brand recognition, and copyright laws will play a more
important role in value security for knowledge-based businesses of the future.
Techno-economic analysis, as taught in traditional chemical
process design, will also dramatically shift from a conservative viewpoint of
utilization of historical trend economics and cash flow analysis. Economic
viability of a given enterprise will be more linked to acquisition of real-time
economic information, that can rapidly change based on empirical observations
created by an emerging discipline of microprocess development systems;
therefore, the models will be more based on "what can be?" rather
that "what has the past shown?"
Process Miniaturization for Future Societies Based on
Renewable Materials
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, future fuel and materials will be based on renewable biomass.
Process Miniaturization for Microbial Fuel Cells
The conversion of biomass into energy is perhaps more
challenging to the technologist than energy from fossil fuels. Water, dissolved
organic and inorganic compounds, and solid particulates of various size can be
present in biomass processes. It is perhaps the development of microbial fuel cells where the philosophical
thinking of process miniaturization will play a wider role. Distribution of
knowledge, in a fashionable, intriguing style through miniaturized devices, can
be substantially enhanced (accelerated) by low power consuming devices (such as
smart phones). A rethinking of "what is a powerplant?" can create
enormous innovations, given recent advances in membrane materials of
construction, immobilized whole cell methodologies, metabolic engineering, and nanotechnology.
The challenges of microbial fuel cells relate mainly to
finding lower cost manufacturing methods, materials of construction, and
systems design. Bruce
Logan from the Penn State University has described in several research
articles and reviews these challenges.
However, even with existing designs which generate low
power, there are applications in distribution of
electrical recharging systems to remote areas of Africa, where smart phone,
can enable access to the vast information of the internet, and to provide
lighting. These systems can run on agricultural, animal and human waste streams
using naturally occurring bacteria.
Process Miniaturization for mini Nuclear Reactors
Nuclear power is considered "green technology" in
that it does not produce carbon dioxide, a green house gas, as do traditional
natural gas or coal-fired power plants. The economics of the deployment of mini
nuclear reactors has been discussed in an article in "The Economist".
The advantages of mini nuclear reactors has also been
discussed by Secretary of Energy, Steven Chu.
As discussed by Chu, the reactors would be manufactured in a factory-like
situation and then transported, intact by rail or ship to different parts of
the country or world. Economy of scale by size is replaced by economy of scale
by number. Many companies are not willing to accept the risk of investing $8B
to $9B dollars in single large reactor, so one of the most attractive feactures
of process miniaturization is a reduction in the risk of capital investment,
and the possibility of recovering investment by reselling and relocating a
functional turn-key microprocess to a new owner - a major economic advantage of
the portability of microprocesses.
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