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Report | December 2016

Simple steps to save energy

In the textile industry, appreciable amounts of energy could be saved or conserved by regulating the temperature in the steam pipes, adjusting the air/fuel ratio in the boilers, and installing heat exchangers using warm waste water, says Dr P Senthilkumar.

The conservation of energy is an essential step towards overcoming the mounting problems of the worldwide energy crisis and environmental degradation. In particular, developing countries are interested to increase their awareness on the inefficient power generation and energy usage in their countries. However, usually only limited information sources on the rational use of energy are available.

The know-how on modern energy saves and conservation technologies should, therefore, be disseminated to governments and industrial managers, as well as to engineers and operators at the plant level in developing countries. It is particularly important that they acquire practical knowledge of the currently available energy conservation technologies and techniques.

The rational use of energy calls for a broad application of energy conservation technologies in the various industrial sectors where energy is wasted. One of these energy intensive industrial sectors to be considered to improve efficiency through the introduction of modern energy conservation technologies is the textile industry. In the textile industry, appreciable amounts of energy could be saved or conserved by regulating the temperature in the steam pipes, adjusting the air/fuel ratio in the boilers, and installing heat exchangers using warm waste water.

Characteristics of energy consumption

Types of energy used in the textile industry: In general, energy in the textile industry is mostly used in the forms of electricity, as a common power source for machinery, cooling and temperature control systems, lighting, office equipment, etc., oil as a fuel for boilers which generate steam, liquefied petroleum gas, coal, and city gas.

Production process and energy use for each specialised technical field: The major operations and sources of energy use evolved in the production process of each specialised technical field, as a necessary component of the overall production of apparel goods, are schematically as follows:

Energy use and rational use of energy in process-specific technologies: Progress in production rationalisation is achieved through the implementation of a comprehensive set of measures, including energy conservation technologies as the centerpiece measure, along with time management, labour saving, natural resources saving and space saving. It has been frequently pointed out that, along with management techniques described earlier, the improvement and development of process-specific techniques on energy conservation greatly contribute to the rationalisation of production. Here, process-specific techniques relating to energy saving are summarised for each specialised technical field.

Fibre production: Exhibiting relatively large-scale structural forms in the textile industry, this division has already reached a high level of production rationalisation, as seen from Figures 1-5. As well known it is technologically aiming at diversification into such high value added goods as super extra-fine fibre and inorganic functional fibre, commonly referred to as shingosen. In particular, the following techniques relate to energy saving:

  • Raw material production process: Implementation of energy saving through improvements in the process and reaction conditions
  • Polymerisation process: Reduction’ in polymerisation time by means of high efficiency catalysts, polymerisation methods, etc.
  • Spinning process: Promotion of energy saving through combining the POY (pre-oriented yarn: Yarn with some stability with its molecules partially having gone through orientation) and DTY (Draw Textured Yam: false twisted yarn produced while drawing POY yarn) methods and an expanded use in multi-folded spinning yarn.
  • Newly-built factories: The factories built during the high growth period have large margins and allowances for production increase so that high losses would result if production decreased. Therefore, suitably sized factories should be constructed.
  • Spinning: Regarding technological trends in spinning, moves towards high speed and large package size have been investigated in order to achieve labor saving through as much automation as possible (Figures 6 & 7). Ring spinning operation: For the fine spinning operation, electricity is consumed in driving the spindles, packaging, spinning, drafting, and operating the lifting and cleaning mechanisms. It is desired to curb the increase of electricity consumption as much as possible by setting an optimal condition for each of these electricity usages.
  • Air-conditioning: Although as an ideal working environment a room temperature less than 30°C is desirable, in cases where the working environment has been drastically improved in most other aspects with work load also reduced, a slightly increased room temperature may be permitted. As has been reported, there was a case where raising the regulated temperature from 30°C to 32°C resulted in a reduction in the electric power demand of a carrier with a contract demand of some 8,000 kW by 190 kW. Also, there are many instances of seasonal switch-over from a damper to a pulley as a means of readjusting the blown air volume; this is in order to recycle the air sucked from the processing machine for each operation through a filter back to the same room, and it is therefore necessary to recheck the locations of fans for suction and returning.

Textured-yarn production: While synthetic-fibre textured-yam is mostly produced with false twisting machines, its history of rationalisation is characterised by challenges for high speed operation (Figure 8). As their operating speeds increased, driving and heat-curing motors and other peripheral equipment became larger, accompanied by an inevitable increase in electricity consumption. Although this may be acceptable as long as the production improvement resulting from a high speed operation covers the increase in electricity costs, reductions in energy cost would surface as an avoidable urgent task, should a sharp increase in electricity charge occur. It can reasonably be said that the major form of energy consumed in the production of synthetic finished-yarn is electricity. Although the amount of electricity consumed in each piece of equipment varies with factory scale and the type of false twist machine, and therefore cannot be treated in a standardised manner, generally accepted average values may be taken as 3.5 kW h/kg for a single heater system and 5.0 kWh/kg for a double heater system-as one report suggests. Of all the energy consumed in finished-yam production, 70 per cent is accounted for by false twist machines.

Weaving: Rationalisation in fabric production is such that while various improvements in machinery aimed at high speed operation and labor saving have been carried out, the amount of energy use per unit of the product has gradually increased (Figure 9). Regarding loom design, high productivity shuttleless looms such as water jet, rapier and gripper types have successfully been introduced, with air jet models put in practice in the production area of industrial fabric material. The amount of energy consumed by each loom during its weaving operation can be estimated from the motor capacity and weaving speed.

Conventional shuttle looms are based on the weft-insertion method, incorporating a shuttle zooming to and fro with a large inertia mass (about 400) and mounted with extra weft, and they also use energy consuming pirns as an integral part of the machine. For this reason, the shuttleless looms’ contribution to energy saving cannot be regarded as too high.

On the other hand, as a large amount of energy is consumed in sizing, as one of the preparatory operations for weaving, the introduction of foam and solvent sizing operations are being investigated. Furthermore, long fibre fabrics using nonsizing filaments have been developed, eliminating the sizing process altogether. In a reported example, the introduction of a new heat exchanger into a sizing machine with a very poor sealing capability achieved more than 40 per cent of energy saving.

Knitting : The share of energy cost in the total cost of production is not necessarily high for the knitting process (Figure 10). However, of the main production facilities for this process, knitting machines have also been undergoing a shift towards high speed and large capacity and fine gauge features; the current industry trend is for high added-value goods and multi-line, small-volume production based on advanced systems such as computer-controlled pattern making mechanisms. Therefore, a potential tendency for increased energy consumption should be taken into account. As a result, it is desirable to conduct a comprehensive re-examination of the production schedule along with the implementation of actual energy conservation measures in order to reduce or restrain the share of energy cost in the total production cost.

Dyeing and finishing: It is very important to advance energy conservation in the dyeing and finishing field, which has a high energy consumption share in terms of both the amounts of money and energy used (Figures 11-19). The dyeing and finishing process consists of many interwoven unit operations, and it is well known that the process generally goes through repeated wet and dry operations. The heat balance of a unit operation can mainly be considered as the difference between the total supplied heat on the one hand and the sum of the heat required by the system and various forms of heat losses on the other.

  • High speed processing of unit operations: As long as the product turnout is maintained, continuous processing with a large machine will be more effective in achieving energy conservation.
  • Elimination or merger of unit operations: Through omitting or merging some of the unit operations according to the usage of the product and considering the characteristics of the coexisting synthetic fibres, it becomes possible to achieve energy conservation.
  • Reduction in processing bath ratio: It is easy to understand that a reduction in water use will contribute to energy conservation in the dyeing process which consists of various wet treatment and drying unit operations.
  • Treatment with low bath ratio
  • Utilisation of low bath ratio processing equipment
  • Utilisation of low add-on equipment
  • Extension of foam processing technique

Clothing manufacturing: The energy consumption share of the clothing manufacturing division which consists of large numbers of small-sized companies and their employees in the overall textile industry is not necessarily low, but the ratio of energy cost to the total cost is relatively low (Figure 13). However, the energy cost forecast is inevitably a gradual increase under circumstances where the production of high value-added goods is required, along with the implementation of labor saving measures, as a result of the challenging market environment characterised by personalised and diversified consumer needs, high demand for quality goods, short product cycles, etc. Therefore, it is desirable that a comprehensive rationalisation programme be investigated apart from reductions in energy consumption

Conclusion

There is no panacea for achieving energy conservation in the textile manufacturing industry. With the actual implementation of an energy conservation program, it is important to grasp the current level of energy consumption and its actual conditions in detail, set goals (energy consumption and corresponding cost), and achieve the goals through a company-wide effort as far as possible. In the textile manufacturing industry, it is important to thoroughly understand that, depending on the trend of the market, the company is targeting, consumer requirements for the textile products to be supplied differ, thereby urging the implementation of energy conservation measures which are relevant to the production of the goods that suit the market.

Therefore, it is necessary to expect that, when multi-line, small-volume production type high value-added goods are produced, energy consumption may increase rather than decrease with production rationalisation, in contrast with mass-production type goods.

When differentiated goods are produced, the share of energy costs in the overall production cost should be given importance rather than energy consumption. It is reasonable to consider that ultimately desired energy conservation promoting techniques will depend on the development and practical application of innovative technologies in each specialised technical field.

References

  • Handbook of Energy Conservation, UNIDO, 1992
  • Palaniappan C et al., Proceedings of the 2nd International Workshop on Renewable Energy Application to Plantation and Other Industries (REAPOI–97). Renewable Energy Applications to Industries . April 1997. Chennai, India.
  • Kumar.S et al., 1999. Energy and Environmental Indicators in the Thai Textile Industry, School of Environment, Resources and Development, Asian Institute of Technology, Pathumthani, Thailand
  • Norms for the Textile Industry, 1991. Northern India Textile Research Association (NITRA), New Delhi, India.
  • Norms for Spinning Mills, 1993, The South India Textile Research Association, Coimbatore, India.
  • Kalyanaraman. A.R.,1998. ‘Power Cost’, Programme on Cost Control in Spinning Mills(August 28-29), South India Mills Association – HRD Centre, Coimbatore, India.
  • Muthukumaraswamy et al., 1999. Economics of Energy efficient equipment and Inter-Mill Study on Power Consumption: Costs and yarn quality: A quality inter mill study of key factors?, Article 23/ 189-195. SITRA Focus: Energy Conservation measures in Spinning Mills.,Vol.16/No.6.
  • P Senthilkumar and R.Murugan, “Energy conservation in spinning mills”, Spinning Textiles, Vol. 10, No. 1, pp. 4-8, Jan-Feb 2016.

Dr P Senthilkumar is Assistant Professor (Sr. Gr) with Department of Textile Technology, PSG College of Technology, Coimbatore – 641004. He can be contacted at: Email: senthiltxt11@gmail.com

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