MANUFACTURE OF TEXTILES # 29

Background:

The textile industry in India is not only one of the oldest, but the third largest among all industries. Each year, the industry produces 5,231,100,000 square meters of printed cloth, which consumes about 136 million liters of kerosene per year. Of this amount, approximately 122 million liters of kerosene evaporate into the atmosphere during the printing drying process. This results not only in enormous amounts of air pollution, but also in huge waste of kerosene. The United States, Japan and countries in Europe have replaced the kerosene emulsion printing with a synthetic thickener (kerosene substitute). But printing conditions in India are not similar to Europe, the United States and Japan, and the practical problems are many and varied. Because of brilliant prints and ease of application, etc, printing units in India prefer to use kerosene in printing. Hence, the substitution of kerosene is moving at a much slower pace.

Based on a quick study conducted in 18 mills, it was found that 72% of the surveyed mills were still using kerosene emulsion. The remaining 28% have only partially substituted kerosene. The hydrocarbon vapor recovery system reported to be used for hydrocarbon handling vessels in the United States is based on a compression and chilling technique. This is a very costly process for the textile printing industry.

The principle objectives of this project were to:

Cleaner Production Principle:

Recovery, reuse and recycling

Cleaner Production Application:

The Bombay Textile Research Association (BTRA) started developing the thin kerosene vapor recovery system in November 1995. After extensive studies in the laboratory as well as on the shop floor, BTRA decided to set up a plant at M/s. Dhanlaxmi Fabrics Ltd., near Mumbai, in collaboration with the Petroleum Conservation Research Association (PCRA). This printing plant consumed about 1500 liters of kerosene per day on printing.

After a thorough study, BTRA decided to develop a direct water cooling system along with an electronically controlled vapor delivery technique for thin kerosene vapor recovery. Subsequently, the newly designed system was erected on site and put on stream by BTRA. The BTRA recovery plant uses a combination of vapor control and cooling through the use of water. The plant has an electronically operated vapor delivery system. From the drier of the printing machine, the kerosene vapors above 120°C are transferred to the main header through the exhaust fans operating under precisely controlled electronic signals from the kerosene sensor's. The  electronic signals are controlled depending on the vapor concentration inside the machine drier. The above controlled inlet vapors are lead to the recovery column by the differential pressure of vapors between the header and the recovery column. The entering vapor is sprayed with water by spray nozzles. The mist of water absorbs heat from the hot air inlet, which vaporizes the water, thereby, partially cooling the hot vapors. These vapors are then further passed through specially designed baffle plates and clean the vapors through contact with the circulating water. About 1000 liters of water is used in the recovery column for circulation. Nearly 80% of the vapors at this stage are condensed into fine droplets and results in kerosene mixed water, which accumulates at the bottom of the recovery column. The minor traces of uncondensed kerosene vapors are released to the atmosphere through the outlet. The de-mister pad, fitted on the top of the recovery column, prevents moisture from being carried out with the airflow. This way the temperature of the inlet air is maintained below 40°C. A level controller monitors the water level at the bottom of the recovery column and replenishes it from the fresh water supply through the solenoid valve. The water used for cooling of inlet vapor is cooled and recirculated to the system. The kerosene-water mixture is transferred to the settling tank, where top layer kerosene is automatically drained out into the kerosene tank.

From BTRA’s studies on loss of kerosene evaporated at different stages of printing, it was found that about seventy-five percent of the kerosene used comes from only the printing machine drier to the recovery column. Of this part, eighty percent of the kerosene vapors are recovered through the new system. The percentage of recovery may vary depending on the dwell time, temperature maintained for drying, speed of the machine, etc. At present, the recovered kerosene is reused for printing. The commissioning of this new system has resulted in fuel conservation, thereby minimizing environmental pollution. Designing of a fully automated kerosene vapor recovery plant is being planned.

Environmental and Financial Benefits:

The recovered kerosene obtained from this new system is superior in quality. The lower hydrocarbon fractions are missing in the recovered kerosene, since these are lost before entering the printing machine drier. The project benefits include:

To date, there is no synthetic thickener, which equals the performance of kerosene emulsion. This is because, in the case of emulsion thickener, both the kerosene and water are completely evaporated, leaving behind clear binder film containing pigments. In the case of synthetic thickeners, the amount of thickener used in the preparation of print paste gets entrapped in the binder film, resulting in less brilliancy and a coarse texture. Based on the present plant vapor recovery of kerosene and reported total consumption, the country could save a minimum of 70,000,000 liters of kerosene per year for the Indian textile industry.

Additionally, this system can be utilized for treating other gaseous pollutants from textile finishing.

Capital investment: US$ 40,000

Payback period without any incentives: 6 years*

*The above payback period is calculated without taking into consideration two factors:

Therefore, by considering these two benefits, the actual payback period will be less than two years.

Constraints:

The kerosene vapors are explosive in nature above 0.7% of concentration, thus, for safety reasons, the machine drier exhaust is maintained within 0.5% kerosene vapor level. Therefore, the recovery of this diluted vapor is a very difficult task. Based on the bulk trials, efficiently, the plant can recover 80% of the inlet vapors.

The balance of kerosene vapors can be recovered by making the plant fully automated, or by cooling the vapors below 25°C.

Contacts:

Mr. Joseph Zacharia, Head

T.E. & Q.C. Section

Bombay Textile Research Association

Lal Bahadur Shastri Marg

Ghatkopar (West)

Mumbai 400 086

India

Tel: +91 22 500 2652; Fax: +91 22 500 0459

Review Status:

This case study was submitted as part of a Bombay Textile Research Association project. It was edited for the ICPIC diskette in January 1999. It has not undergone a formal technical review by UNEP IE.

Subsequently, in March 1999 the case study underwent a technical review by Dr. Prasad Modak, Environmental Management Centre, Mumbai, India.