Role of CLRI Chemical Engineers in Leather Processing
The physical and chemical phenomena associated with the leather making processes are complex and highly interactive. From the thermodynamic viewpoint, materials are rarely taken to complete or near equilibrium state. The action of a number of active substances of hide/ skin matrix is less well understood from a chemical engineering point of view. The underlying kinetic and heat/ mass transport phenomena have analogs in better understood chemical and biological systems. The basic concepts of chemical process analysis, synthesis, optimization, modeling and control, chemical plant design and project engineering have relevance to leather processing. Keeping in view these potentials, the chemical engineering area was created in 1986 at CRLI with the following functional sections:
- Engineering for Modernization (EFM)
- Hazard and Risk Assessment of chemical, leather and allied industries (CISRA)
Engineering for Modernization (EFM)
One of the important and critical requirements of the Indian leather sector has been identified to be modernization of tanneries in the country. Modernization of tanning industry in the country for enhanced productivity is essential for the survival of the leather sector in India , in emerging global market and economies.
The benefits of tannery modernization (environmental cleanup, improved labour productivity, material quality and consistency in reduction of land and water pollution, better work environment and improved productivity etc.) were demonstrated in identified tanneries.
The chemical engineering group is equipped with a Design and Engineering Cell , which provides the following, based on the technologies developed at CLRI.
- Pre-design cost estimates and Techno-Economic Feasibility Reports
- In-plant Studies, Detailed Project Reports and Revival Studies for Sick Units
- Basic and Extended Basic Engineering Packages for Commercial Plants (Chemical and Tanneries).
CLRI Chemical Engineering Design Team has undertaken modernization programme involving highly traditional vegetable tannin extraction concept. CLRI established its first multi-stage pilot tannin extraction plant with microprocessor controls. Chemical Engineering Design Team provided the basic engineering package for a state of the art tannin extraction plant and a couple of years back the plant had gone into production
Process Design Engineering Packages for Tannery Modernization
- Leather Process Control and Automation
- Plant Layout Design and Development of Standard Layout for Modern Tannery
- Concept of Leather Complexes and Development of Indian Leather Sector
Leather Process Control and Automation
The present century carries on with the irresistible march of progress of electronics and its invasion of various sectors of world industry. Leather industry is no exception. Microprocessor control systems have already become popular in the automation of leather finishing operations. The Indian Leather units have already started reaping these benefits. Beam house and other wet operations in Indian Tanneries are however lagging behind in process control and automation. They continue to be operated on traditional lines. Commercially these operations are carried out in batch mode by contacting hides/ skins with finite amount of chemical formulations. For application of microprocessor control systems for tannery wet operations, the following aspects have been identified as important under Indian context:
- In process quality control of leather
- Controlled chemical and water dosages
- Drum operation control
The chemical engineering team at CLRI has taken major initiatives in this field. The first large scale Indian tannery commissioned microprocessor control systems for its wet operation in October 1989 and for its beam house operations in 1993. Process know-how, design and project engineering have been developed with appropriate control systems for small scale tanneries in the country for beam house operations.
Process Control Systems have been established in tanneries which includes Khizar Hussain and Sons, Ranipet; Kings International Pvt. Ltd., Amin & Sons Ltd., Asian Tannery, Kanpur and Avanti Leather, Tada, AP State to reduce consumption of water, chemicals, time of processing, to improve the quality of leather, to get consistent results and to reduce the pollution load in the effluents.
Standard Layout for Modern Tannery
Modern layout of machineries provided easy flow of materials and decreased processing time by 20%. A good layout results in reduced manufacturing cost and higher profit. Standard layouts for tanneries processing from raw to finish were developed for various capacities (1000/ 2000/ 5000 skins or equivalent hides per day). Unit based Layouts were developed for relocation of Sixty Tanneries to the proposed Kolkata Leather Complex and presented to tanneries.
Design of Leather Complexes and Development of Indian Leather Sector
Since environmental regulations are becoming more stringent in several states in India , a new thinking has opened up avenues for the setting up of Leather Complexes and the proposal for a large Leather Complex near the city of Kolkata is a landmark decision. The relocation of about 500 tanneries in a 400-hectare of leather city will revitalize the entire leather sector of Eastern India and provide significant environmental improvement to a huge area. Various State Governments including Maharashtra , Madhya Pradesh, Gujarat , Uttar Pradesh, Andhra Pradesh and Tamil Nadu followed this. Database developed on the list of tanneries, their processing capacity, open and built up area, water and chemical requirement, etc. for Tamil Nadu, Kolkata, Kanpur and Andhra Pradesh is being maintained.
Process analysis, Scaleup and Technology Development
A thorough understanding of the complex structure of animal skin/ hide and its reactive ability is essential for assessing the rates of various kinetic and mass transport process. The concepts of diffusion and chemical reaction in porous catalyst particles, swelling phenomena in polymer films/ fibres, thermodynamics of chemical reactions and solid-liquid phase equilibria are relevant to leather process applications. The pore structure of hides/ skins, fibrous network at interfibre, interfibril and intrafibril levels and their spatial variation needs extensive experimental investigations. A specialist team of the chemical engineers is currently engaged at CLRI in these studies. Experimental facilities are available for diffusion and kinetic studies. They include diffusion cells, macropore volume measuring facility, automatic titration units and other supporting equipment.
Leather Process Modelling and Simulation
This is an area of practical importance and thrust research activity at CLRI for improving the efficiency of serious unit operations and processes associated with the leather making. Leather process modeling has attracted the attention of process engineers inspite of the mathematical constraints in precisely simulating the acting of complex and crying structure of animal skins and their behavior towards chemical agents. The reported models are nevertheless based on simple and macroscopic concepts with not so adequate emphasis on their physical validity.
Mathematical models (Continuum) based on species balance across a moving boundary on a three layered hide/ skin matrixes are being formulated to describe most of the leather process operations in the wet section. The phenomena of swelling and size shrinkage of hides/ skins, evolution and shrinkage of their pore structure and time variant diffusion and kinetic processes are being investigated through academic research programmes.
Scale up and Development of Chemical Processes (Laboratory & Pilot Scale)
Bench and Pilot Scale development of chemical processes for the leather industry form the major output from the Chemical Engineering group. The group has a full-fledged process development cell. The chemical engineering group has successfully scaled up processes for the preparation of Thiram and Ziram, commercially known fungicides, Blended vegetable tannin extracts, Acid stable fat liquor based on oxidative sulfonation of fish oil, preparation of keratin fillers (and retanning agents) from poultry wastes, etc. The chemical engineering laboratory/ pilot plant facilities consist of stirred reactors, gas-liquid contractors, liquid-liquid and solid-liquid extractors, bubble columns with recycle facilities, dryers, evaporators, filters, centrifuges, etc. The process development group gets the support from the property evaluation group for the experimental and theoretical estimation of physical, thermodynamic and transport properties of chemicals.
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