(441a) Process Intensification: A Novel Approach for Development of Smaller, Cleaner and Energy Efficient Technologies

Process Intensification, in brief, can be defined as development processes which are smaller, cleaner, safer and highly energy efficient. Likewise any “multidimensional concept, process intensification is not easily defined [1]”. Although experts have provided diverse definitions on process intensification “the common thread among these definitions is a focus on new schemes and equipment that create improved processes by combining, controlling and or enhancing the chemistry and transport phenomena in a chemical process [1]”. As per European road map, one of the main objectives of process intensification is innovative process and equipment design which can ensure enhancement in efficiency in processes and reduce both capital and operating expenses[1]. Although“Process Intensification efforts have lagged in US for last forty years compared to other parts of the world, industry and academia in Europe have already embraced developments in Process Intensified Technologies [2]”. In this context, it is worth mentioning that an institute named as RAPID (Rapid Advancement in Process Intensification Deployment) has been set up in US to spearhead the research and development activities in Process Intensification technologies.In India, some process intensification works have been carried out. A notable example may be development of Micro-Fluidic device such as Micro-Coiled Flow Inverter (MCFI) which provides enhanced heat transfer characteristics [3]. Process Intensification may be considered as a revolutionary approach to process design, development and implementation as it has potential to give birth to better products and processes which are safer, cleaner, smaller and cheaper. It may also lead to manufacture of new products which could not be produced by conventional process technologies. Intensified processes can result in to reduction in size of plant or equipment by 10 to 100 times. Process Intensification, when implemented in plant level will lead to de-compartmentalization of chemical unit processes and will advocate their integration into one whole.

Fundamentally, Process Intensification of a chemical plant can be accomplished by enhancing the transfer co-efficient or the driving force for mass and heat transfer. The prime reason for large distillation and absorption towers is that the inter-phase mass transfer rates are governed by gravity. One way to enhance the transfer rates considerably is to replace the gravitational field with centrifugal field which is higher by few orders of magnitude. Applying this principle, compact size Spinning Disk Reactors, Rotating Packed Bed Separators and Centrifugal Absorbers have been developed. Conventionally, for gas separations, large and expensive cryogenic distillation systems are used. In order to achieve gas separations in compact size equipment, moving bed adsorption technology can be effectively used which ensures utilization of the entire bed due to counter current contact of adsorbent solid and the gases. The counter current contact leads to increase in mass transfer driving force by ensuring non-equilibrium between fluid and solid phases and due to high mass transfer rate, the size of the equipment can be reduced to a large extent. Since, absorbers and extraction columns sizes are governed by flooding velocities, use of porous medium for the solvent may be useful in effecting large throughput through a compact size column.

Process Intensification goals can also be achieved by combining reaction and separation and carrying out the same in one equipment if the reaction improves the separation substantially by means of enhanced mass transfer or the separation leads to higher reaction rate. Reactive Distillation, Reactive Absorption technologies are the examples in this regard.

Clathrate hydrates or gas hydrates are crystalline water based solids in which small non-polar gaseous molecules such as CH₄, H₂ , CO₂ etc.,can be trapped inside the cages of the H- bonded water molecules mostly under cryogenic conditions or at high pressures. Clathrate hydrates are not chemical compounds as the gaseous molecules are not bonded to the lattice. Clathrate hydrates can be decomposed easily by either reducing the pressure or increasing the temperature. Thus large quantities of hydrocarbon gases (CH₄, C₂H_6, and C₃H₈) and H₂ might be stored as hydrates under appropriate conditions and can be used as solid fuels which can be decomposed by reducing pressure for combustion. Deposits of Clathrates of methane have been found to occur naturally (around 6.4 trillion tones) on deep ocean floor. Such deposits have been found on the Norwegian continental shelf in the northern head wall flank of the Storegga Slide. Use of these natural gas hydrates may prove to be economical in near future once cost effective technology for their extraction is developed.

Finally, Process Intensification, now a day, is a proven way for size reduction of process equipment and in turn the entire process plant can be miniaturized. It may eventually lead to lower CAPEX (capital expenditure) and OPEX (operating expenditure) due to substantial reduction in equipment sizes and enhancement in energy efficiencies. It also leads to inherently safer designs by virtue of creation of smaller equipment. In conclusion, development initiatives in process intensification field are extremely encouraging and miniaturization of process equipment and process plants is a reality today.

Literature cited

(1) James Bielenberg and Michelle Bryner, CEP, March 2018, pp. 41-45

(2) T. Walsh, CEP, March 2018, pp. 40

(3) K.D.P. Nigam et al., Chemical Engineering and Processing, 86 (2014), pp.78-89