Process Intensification In Chemical Engineering

Shefali Kapgate¹ ,Bhairavi Mudholkar² , Mrs Swarda Mote³

^1,2Student of final year, B.Tech in Chemical Engineering, Priyadarshini Institute of Engineering and Technology,Nagpur

³Associate Professor,Chemical Engg Department, Priyadarshini Institute of Engineering and Technology,Nagpur

¹shefalikap29@gmail.com

²bhairavimudholar@gmail.com

³swarda_mote@rediffmail.com

Abstract:

Process intensification is now well known among the world of chemical engineers. The development of new chemical routes and of innovative modular technologies may lead to some breakthrough progress. Today, we are witnessing important new developments that go beyond “traditional” chemical engineering and engineers are working on novel equipment and techniques that potentially could transform our concept of chemical plants and lead to compact, safe, energy-efficient, and environment-friendly sustainable processes which is called as Process Intensification. In Process Intensification an  approach  has been around for quite some time but has truly emerged only in the past few years as a special and interesting discipline of chemical engineering. In this paper an attempt has been made to review process intensification in details, recent developments, applications and few case studies.

Keywords: Process Intensification,Ecofriendly,Energy-efficient

I. INTRODUCTION

PROCESS INTENSIFICATION is a modern approach that aims to shrink size of chemical plants,but at the same time increase their efficiency. These can be achieved by compressing the size of individual pieces of equipment and number of unit operations or apparatus involved. Emerging equipment, processing techniques, and operational methods and combining separate unit operations such as reaction and separation into a single piece of equipment provide improvements in process plants,by reducing their size and boosting their efficiency,increase in production capacity, ,decrease in energy consumption per ton of product, or even reduction in wastes or by-products formation and an economical manufacturing process. At the molecular level, this enhance mixing, which improves mass and heat transfer, reaction kinetics, yields.These results in reduction in process complexity, minimize cost and risk in chemical industries .It is generally divided into two areas:

Process-intensifying equipment:

reactors,heat and mass transfer devices

Process –intensifying methods: integration of reaction and separation,heat exchange and phase transition .( Stankiewicz A, Moulijn JA (2000))PI simply means using much LESS to produce MUCH more and BETTER, in which less is related to investment, space, time, raw materials, energy etc. It is about revolution rather than evolution.( Ben-Guang Rong(2015))

II. Principles for PI

A. Maximize effectiveness of intramolecular and intermolecular events :  This principle deals with changing the kinetics of the process.(example: dynamically changing conditions to attain kinetic regimes with higher conversion and selectivity)

B. Uniform treatment for every single molecule in the process: Process where every single molecule undergoes same process condition.This produce uniform product with minimum waste. (example: plug flow reactor with uniform)

C. Optimize driving forces at all scales and maximize the specific surface areas to which this forces apply : This principle is about transport rates across the interface .Optimization is not always maximization of driving force required.The output needs to be maximized .(Gerven and Stankiewicz 2009).

III. STRUCTURE OF PROCESS INENSIFICATION

III PROCESS-INTENSIFYING EQUIPMENTS

A. Novel reactors: Process intensification tools,offer several benefits due to well-defined high specific interfacial area available for heat and mass transfer,which increases the transfer rates,and also enhances the safety of the process.

B. Intensive mixing: Intensive mixing and intensive mixers has replaced the traditional ring through mixer.

C. Heat transfer devices:.The aim of thermal intensification is to reduce the distance by supplying or removing the heat almost as rapidly as it is absorbed or generated by the reaction.As a result this technology may offer better safety and by-product reduction.

D. Mass transfer devices: An intensified mass transfer device is the rotating liquid-liquid extractor.

IV PROCESS-INTENSIFYING METHODS

The most process-intensifying methods fall into three well-defined areas: integration of reaction and one or more unit operations into so-called multifunctional reactors,for example,reactive distillation is a combination of reaction and separation (Fig.a) and a membrane reactor is a combination of reaction and in situ removal of a reactant or product ( Fig.b).

 A. Reactive (catalytic) distillation- In this case, the multifunctional reactor is a distillation column filled with catalytically active packing,chemicals are converted on the catalyst while reaction products are continuously separated.The advantages consist mainly of reduced energy requirements and lower capital investment (Stankiewicz A, Moulijn JA (2000))

B. Membrane Reactor – Membrane can be used for selective insitu separation of the reaction products.It also can be applied for a controlled distributed feed of some of the reacting species, either to increase overall yield or selectivity.(Stankiewicz A, Moulijn JA (2000))

IV. CASE STUDY IN PROCESS INDUSTRIES

CASE 1 :Fixed Bed Catalytic Reactor

Benefits:

• 37% increase in yield-saving$1/2m per annum
• Improved reactor control-no polymer fouling

Problem

• Poor reaction stability,Exothermic gas/liquid reacrtion
• Contaminated catalyst fig 3 (a) show before deign safety reactor

Solution:- Retrofit design of reactor,produced in 4 days

Features:-

• Pre-mix gas/liquid to achieve saturation
• Raised catalyst bed to provide an even reaction front,Jet mixing in bottom of column.fig 3 (b) show design modification

Case study 2-Polymerisation

Benefits:-

• CAPEX reduction from 6m to 1 m
• OPEX reduced by using less pure feedstock

Problem:-Scale up of an exothermic reaction was  needed to meet market demand for the product .A conventional approach would have required a 60m³ reactor.

Solution:- The conventional batch vessel was replaced  by a continuous statix mixer based reactor.fig 4 show the retrofit deign of pilot plant

Case study 3 – Batch to Continuous

The Challenge – A chemical manufacturer wanted to move from a batch regime to continuous flow and utilise the benefits of Process Intensification.

Make significant energy and operating cost saving by-

removing one component completely from the process by exploring higher temperatures and mixing energies and potentially eliminating the need for downstream energy separation processes such as distillation and  full-scale reaction time from hours in batch reaction to seconds in continuous flow.

The Benefits- Understanding the minimum mixing energy required for adequate mass transfer.  Deriving a rate expression to model process behaviour. 

V. ADVANTAGES OF PROCESS INTENSIFICATION:

Case Study 4-Integrated Methyl Acetate Column          

A. Economical benefits

• capital cost reduced by 60%,
• 70% plus reduction in energy usage and hence substantial reduction in operating cost,

B. Technical(operational) benefit

• improved product propertiesand process safety,
• 90% reduction in impurity levels resulting in significantly more valuable product.

C. Environmental benefits

• less energy consumption,
• reduced waste and  solvent used,

Other benefitsare in some cases the number of process operations can be reduced, leading to fewer transfer operations and less pipework (which can be a source of leaks).Many incidents are associated with process transients such as start-up and shutdown. These are reduced during continuous (and intensified) processes. (J C Etchells)

VI. APPLICATIONS

• Applications for PI technologies crosscut energy-intensive industries with opportunity space in chemicals, petroleum refining, plastics, forest products, oil and gas production, and food industries among others.
• PI innovation could deliver solutions to energy security, environmental, and economic challenges in areas ranging from stranded gas recovery, carbon capture, and water treatment.
•  In these application areas, where environmental regulations are main drivers for innovation, PI approaches may prove productive.
• As the cost reduction due to more efficient use of energy and water resources is achieved, it also reduces the waste and has a positive impact on the environment, making the process thereby more sustainable.(Van Gerven,Tom and A. Stankiewicz(2009))

VII. CONCLUSION

Process intensification improves the performance of an existing process as well as improves the design of a new process in terms of economic and environmental improvements. It is imperative that chemical and biochemical manufacturers remain competitive through the design of economically viable, innovative, more sustainable processes. Therefore, PI plays an important role in identifying the more sustainable and innovative process designs. In this respect the three-stage approach of process synthesis stage, process design (and analysis) stage, and innovation stage (process intensification) where new (or novel) hybrid/intensified unit operations could be generated, could become an important tool.

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