Process Intensification (PI) is a concept in chemical engineering which first defined back in 1970 sparked by the need to reduce capital cost involved in a particular production system This was first pioneered by ICI to reduce plant volume without sacrificing its production capacity [1, Dautzenberg] (Dautzenberg, et al., 2001).
There was a first international conference in 1995, International Conference for Process Intensification in the Chemical Industry. Ramshaw was the early scholar who worked on process intensification philosophical foundation, defined PI as "a strategy for making dramatic reductions in the size of a chemical plant to achieve a given production objective" (Ramshaw, 1995). Process intensification involves dramatic reduction in chemical plant equipments by installation or individual equipment volume as presented by (Ramshaw, 1995) and (Stankiewicz, 2003). By mentioning dramatic reductions, Ramshaw mentions of miniaturizing volume by the order of 100 to 1000.
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This definition by Ramshaw is quite limited and is cited in Stankiewicz (Stankiewicz, et al., 2000) as being too narrow that it discussed more on size reduction. PI can be defined as intensification on particular desired effect and size reduction is one of many desired results that can be achieved through PI. This definition is widened by Stankiewicz definition of process intensification as "any chemical engineering development that leads to a substantially smaller, cleaner and more energy-efficient technology is process intensification" (Stankiewicz, et al., 2000).
BHR Group defines process intensification as: "Process intensification is a revolutionary approach to process and plant design, development and implementation. Providing a chemical process with the precise environment it needs to flourish results in better products, and processes which are safer, cleaner, smaller, and cheaper. PI does not just replace old, inefficient plant with new, intensified equipment. It can challenge business models, opening up opportunities for new patentable products and process chemistry and change to just-in-time or distributed manufacture" (BHR Group, 2003).
This has been widely accepted (try to connect references) as definition of process intensification in chemical industry.
Process intensification can be categorised into two types of approaches which are; (1) methodology-based approach and another one is (2) equipment-based approach.
Figure Process intensfication and its components (from Stankiewicz et al. 2004).
This major categorisation of two approach in process intensification is also presented and some of the latest existing industrial examples are given in an article in The Chemical Engineer journal (King, et al., 2010).
Reaction Engineering involves Sizing and bla bla bla...
Reaction engineers spend a lot of efforts and ingenuity in enhancing reactors performance by studying and implementing any optimum trajectory for the reaction system to be operated (Nicol, et al., 2001). bla bla bla...
In reaction engineering, equipment-driven approach is about reactor improvement of rate of reaction by specific-volume, heat transfer and mass transfer, hence may push chemical process or catalyst performance to achieve the best out of their potentials. Nowadays this is done in terms of enhancing conversion rates and reducing by-products formation by achieving concentration and temperature profiles [4, Multfunct.React. Agar pp. 379-381] (Agar, 2004).
Catalysis is one of examples of process intensification approach by methodology in general sense, as it serves a function to reduce activation energy required for a reaction to occur. In chemical industry there are two major types of catalytic reactor configurations, being the structured and random reactors. These categories are reviewed later in the next section regarding their benefits in reaction engineering process intensification.
Some applications in chemical industry by process-intensifying equipment approach are integrating several unit operations or equipments into one multifunctional reactor, designing a new hybrid separation such as reactive distillation and reactive absorption [2, Trans] (Stankiewicz, et al., 2000).
Integration in between two equipments as examples has been reviewed by Stankiewicz (2003)  Stamicarbon's Urea 200plus technology. In this paper, the reactor is designed incorporated with condenser and known as "pool reactor". Size comparison shown that in this particular case size of equipment reduced to one-fourth of the conventional equipments (Stankiewicz, 2003) .
The best reactor design and configuration is identified in a particular chemical process by knowledge available in its reaction chemistry, contacting pattern in terms of how and when individual elements pass through the reactor and contact one another and how long its identity changes. Furthermore, critical studies in reaction overall kinetics as well as its thermodynamics to which elements are exposed along their reaction trajectory is important in enhancing chemical reactor or in order to integrate reactor with any other unit operations.
Through this reactor design concept, the most suitable reactor configuration is selected, e.g., ideal plug flow, packed-bed and etc.
Overall kinetics bla.. bla.. bla..
In considering thermodynamics, heat transfer within or across the boundaries of reactor is a crucial consideration to establish optimised reaction in multifunctional reactor, based on their activation energy needed for raw materials to react. In multifunctional reactor this is the scope where energy would be supplied or removed from an endothermic or exothermic main reaction to maintain a forward drive of chemical reaction. Energy balances are important at this stage and establishing temperature profile is needed from analysis for purpose of chemical reaction intensification. Methods of heat transfer are also reviewed as there are categories of heat transfer methods known to be efficient in a particular reaction.
This is the normal and widely accepted procedure
Individual reactor design such as static mixer reactor, monolithic reactor, spinning disk reactor and etc, are examples of equipment-driven approach in process intensification (Stankiewicz, 2003). This examples are actually concepts revolves on developing component design and improvement of a particular reactor.
Modelling of process intensification.
MAIN PARTS a
PI Area of Concern in Reaction Engineering Applications.
Heat exchange in reaction engineering
Reactor usually contains high amount of energy namely heat as reaction is progressing with reactor usually being operated at the highest temperature compare to other equipment upstream and downstream. This is essential to the reactions as thermal energy required for molecular bond to form or dissociate.
Heat exchange in reaction engineering design has been studied extensively as heat transfer plays a significant role in all chemical reactions. Agar D.W. (2004) (Agar, 2004) has categorised heat transfer into four categories, namely convection, recuperation regeneration and reaction (Figure ??). This categorisation helps a lot in providing the best heat transfer solution in knowing which the best reactor configuration is in adding or removing heat.
Figure Heat transfers for manipulating temperatures and concentration profiles
in chemical reactors (from Agar, 2004).
Convection is additional or removal of side-streams which intentionally limits the availability of one reactant, hence, improving selectivity, e.g.; cold-shot reactor. In recuperation heat transfer there is an external heat transfer sources and sinks which operates to generate temperature differences in between reaction phase and heating medium by taking in or removing heat somewhere else, e.g.; cooling towers, fin fan coolers, heat exchangers and etc. Regeneration heat transfer makes use of the reactor internals, usually beds or packings as an accumulation of heat and mass in order to establish temperature profile and also concentrations. This temperature could not increase when in steady-state operation (Agar, 2004). Reaction is a straight-forward combination of main reaction with compatible supplementary reaction either thermally or materially, e.g.; oxyhydrogenation (Agar, 2004).
Operating temperature is achieved in reactor by one of these heat exchange approaches using various kinds of reactors accessories in multifunctional reactor such as heat jacket, tubes heat tracing or less commonly by heating coil.
Mass transfer in reaction engineering
Integration of mass transfer and catalyst has been studied (since, whom, what are achievement so far....???) and prominently applied in reactive distillations which will be reviewed in details below.
Multifunctional reactors development. - e.g; Pool reactor, reactive distillation column, heat exchanger reactor
Multifunctional reactors are reactors that serve many functions of unit operations in single equipment. These reactors usually combined with separators either distillation or absorber, or with heat transfer equipments such as cooler, heater or condenser. Some of the examples are:
Pool reactors (reactor-condenser)
Reactive distillation columns
Pool reactor were discussed in Stankiewicz 2003  (Stankiewicz, 2003), where combination of reactor and condenser yielded a novel equipment. World's first pool reactor is known developed by DSM Research back in 1945.
A type of multifunctional reactor in which combined reactor and condenser was studied in details by Ben Amor et al (1999) (Ben Amor, et al., 1999) took methanol synthesis from its raw material, syngas in prototypes as main scope.
(Add a bit of elaboration for advancement & achievement).
This is further developed and analysed in Haut, et al (2004) (Haut, et al., 2004)
Heat exchanger reactor is designed by combining reactor, heat exchanger and scrubber by the
PI in multifunctional reactor design.
Multifunctional reactor has been a good example of process intensification by equipment-driven approach. ...
Process intensification in multifunctional reactors were presented in
Pros: Examples in practiced
"Several "functions" or processes are designed to occur simultaneously in multifunctional reactors". One of many examples of these reactors is fluidised catalytic cracker (FCC) that has two reactions occur in one unit operation namely cracking and another is removal of coke in hydrocarbon (Dautzenberg, et al., 2001).
MAIN PARTS b
Chemical reactors often used catalysts in its operations as they provide easier path for reaction to happen that the activation energy is lowered with their presence in reaction phase. Two general categories of catalytic reactor configuration are random catalytic reactor and structured catalytic reactor.
Structured catalysts has been paid attention
Reactive distillation is one of many examples of process intensification in multifunctional reactor.
One of many good examples in process intensification by integration of unit operations is the reactive distillation in which reaction phase is put together with separation phase in single equipment. This has been call as 'pool reactor' (Stankiewicz, 2003 ) (Stankiewicz, 2003). Reactive distillations uses column packing which made by the catalyst material as the reactants pass through the column will react and the separation takes place along the column throughout the packing
This was initiated by the studies..?????? where column internals which use conventional packing shape with materials that could probably be replaced with catalytically compatible materials to bring forward reaction equilibrium for more yields.
An example of this ground-breaking new packing is Super X-pack (structured packing) designed and manufactiured by Nagaoka International Corp., able to reduce size of column down to five times smaller compares to conventional column and much lower pressure drop across the packing. This dramatic reduction of equipment size was illustrated as comparison to conventional applications by Stankiewicz (2003)  (Stankiewicz, 2003) as shown in figure (Figure ??).
Figure Super X-pack - revolutionary packing for
distillation columns by Nagaoka International Corp.
Sulzer Chemtech developed KATAPAK-S packing as catalytic packing and this is packing has been studied in details regarding the geometry of flow channel, hydrodynamics and mass transfer performance in Behrens et. al. (2006)  (Behrens, et al., 2006). Modelling of liquid hold-up, pressure drop and mass transfer were conducted specifically based on this Sulzer's KATAPAK-S as the main focus in this publication. This knowledge is crucial for further developments and applications. Stankiewicz (2003) (Stankiewicz, 2003) is also cited in this paper in terms of combining reactors and separators.
Future researches on these Super X-pack and Sulzer's KATAPAK-S are potential development of catalytic version of this packing. From process-intensification point of view this could possibly be the breakthrough shift in vast reduction of column size and a key step up in reactive distillation that will bring a extensive benefits in chemical industry.
Parkinson (2000), Drip drop in column internals
Applications in Chemical Industry.
Catalytic reactive distillation has been commercially used in chemical industry (DeGarmo J.L., 1992)  (DeGarmo, et al., 1992). One of the examples of applications in chemical industries is the Methyl Acetate separative reactor technology development by Eastman Chemicals. This is presented by Siirola (1995)  (Siirola, J. J.; Eastman Chemical Company, 1996). This has been cited in Stankiewicz (2003)  to reflect the extensive reduction in plant size. This massive plant size of seven tasks is integrated into single piece of equipment. Distillation, extractive distillation, reaction, reactive distillation are the discrete tasks which have been combined into one column. As the result, numbers of equipment are reduced to 3 from conventional plant that has 28 equipments. This is shown in figure (label figure below)
Figure 4 Plant integration in methyl acetate separative reactor process by Eastman Chemical
(from Siirola 1996 ).
Benefits (to relate this point of integration benefits in between [5, Stankiewicz], [Ramshaw,1999] cost reduction and [6, Hendershot] safety regarding integrated unit operation e.g.; pool reactor, in reactive distillation)
Cost reduction on the major plant item was the primary objective of PI, but other benefits comes along with this reduction of costs such as structural work, earth/civil work for large vessel foundations, installations and labour as well as less pipe work needed (Ramshaw, 1999).
While looking into process intensification from safety point of view this equipment integration ..... (Hendershot, 2004)
This can reduce the risk of reaction stage while in operation as reducing the size of the plant means minimising hazardous material usage concept proposed by Kletz (Kletz, 1996). The possible opportunity for chemical fugitive through pipe connection in between unit operations is also eliminated as 'what you don't have cant leak' (Kletz, 1978). This simpler plant is the result one looking for in achieving the objective in process intensification. Smaller plant is one of the objectives in process intensification and parallel with the concept of mentioned above in introduction (Stankiewicz, et al., 2000).
Potentials of further development of reactive distillation:
Pool reactor was started as R&D program by DSM Research back in 1945 and after 51 years, the technology was established and patented in 1996 in urea production known as Urea 2000plusâ„¢ technology. The first commercial plant was commissioned in 1998 when start-up of first Urea 2000plusâ„¢ pool reactor plant.
Stamicarbon's Urea 2000plusâ„¢ technology reduced the size of installed equipments from early establishment at total height of 78 metres ..... (Bakker, 2004).
Urea 2000plusâ„¢ technology
Conventional urea technology
C:UsersdynaPicturesMP Navigator EX2010_10_03Urea 2000Plus Pool Reactor2.jpg
Figure 5 Reduction of size by integration of reactor, condenser and scrubber featured in Stamicarbon's
Urea 2000plusâ„¢ technology (from Bakker, 2004).
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Modelling of process intensification.
Modelling of Krishna & Taylor (2000)
MAIN PARTS d
Process intensification for safety.
In establishing a chemical plant nowadays, there are massive lists of safety legislations need to be adhered. One of the best practices in chemical industry is to construct a plant with elements of inherent safety. Inherent safety and intrinsic safety mean the same and would be used interchangeably from this point onwards. Process intensification is an important aspect that needs to be implemented in achieving an inherently safer chemical process and plant.
Process intensification for inherent safety concept has long been establish has been
Intrinsic safety in reactor configuration and operation is a crucial element since reactor is a heart of a chemical manufacturing plant. Being the centre of a process containing various components of chemicals as raw materials are introduced and as reactions took place there would be mixture of products and normally more than two by-products. Reactor also traditionally contains high amount of energy namely heat as operating with usually being operated at the highest temperature compare to other equipment upstream and downstream. This is where energy would be supplied or removed as stated before in the introduction.
From the point of equipment integration reviewed before, reactor combination with other unit operations such as distillation, condenser, scrubber or heat exchanger is another approach in process intensification, i.e; equipment-driven approach (King et. al. 2010) .
MAIN PARTS e
Barriers and potential prospects of process intensification in reaction engineering.
Besides wide-ranging advancement in PI in reaction engineering, there are several difficulties known in holding back the research and implementation of technologies. This occurs especially in upscaling from lab or pilot scale to commercial scale.
In 1998 AIChE's Center for Waste Reduction Technologies organised two workshops that has recognised barriers for reactive/hybrid separations and as agreed there were three categories of technical and nontechnical difficulties which are:
Technical gaps, such as lack of simulation and scale-up capability, lack of validated thermodynamics and kinetic data, lack of materials (compatible materials, e.g., integrated catalysts/sorbents, membrane materials) as these materials have to be developed specifically for the purpose of new process chemistry, and lack of high-level process synthesis methodology.
Technology transfer barriers, lack of experts in multidisciplinary team in process integration approach, lack of communality of problems (each application has unique technology) and lack of models/prototypes on a reasonable scale (most of the studies still regarded as science which involves small-scale researches).
General barriers, such as higher standards, to require implementation of new technologies, as opposed to conventional technologies, lack of process economics (as new technologies have not been proved to be feasible as there is no commercial model available) and fear of risk in operating new technologies.
Besides those difficulties, future opportunities
The implementations of process intensifications transform conventional chemical engineering unit operations into a revolutionary process technology whether by integration of several unit operations or by altering intrinsic chemical process elements to eliminate unnecessary process bottlenecks. Changes usually measured by the substantially cost improvement, progress delivery/process time, - [3, Re-Engineering chem]
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