Cost Effectiveness Based on Increasing Energy Efficiency Opportunities in Textile Industry

Cost-effectiveness Based on Increasing Energy-efficiency Opportunities in TI (Textile Industry)
Author: Ariful Hasan
Teaching Assistance (TA)
Head of Textile Engineering Department
Daffodil Internatonal University
Email: ariful_1906@diu.edu.bd
Contact: +8801671437822
 
 
 

Abstract
In the present world, various manufacturers face an increasingly competitive global business environment; they seek opportunities to reduce production costs without negatively affecting product yield or quality. Rising energy prices are driving up costs and decreasing value added at the plant. Successful, cost-effective investment into energy-efficiency technologies and practices meets the challenge of maintaining the output of a high quality product despite reduced production costs. This is especially important in the current age, as energy-efficient technologies often include “additional” benefits, such as increasing the productivity of the company or reducing the water and/or materials consumption.

This assignment provides information on energy-efficiency technologies and measures applicable to the textile industry. The assignment includes case studies from textile plants from around the world with energy savings and cost information when available. For some measures the guide provides a range of savings and payback periods found under varying conditions. At all times, the reader must bear in mind that the values presented in this assignment are offered as guidelines. Actual cost and energy savings for the measures will vary, depending on plant configuration and size, plant location, plant operating characteristics, production and product characteristics, the local supply of raw materials and energy, and several other factors. For instance, for some of the energy-efficiency measures, the significant portion of the cost is the labor cost. Thus, the cost of these measures in the developed and developing may vary significantly. Therefore, for all energy-efficiency measures presented in this assignment, individual plants should pursue further research on the economics of the measures, as well as on the applicability of different measures to their own unique production practices, in order to assess the feasibility of measure implementation.

Introduction
TI is a fragmented and heterogeneous sector dominated by small and medium enterprises (SMEs). Energy is one of the main cost factors in the TI. Improving energy efficiency should be a primary concern for textile plants especially in times of high energy price volatility. There are various energy-efficiency opportunities existed in every textile plant. Many of them are cost-effective. However, even cost-effective options often are not implemented in textile plants mostly because of limited information on how to implement energy-efficiency measures, a majority of textile plants are categorized as SMEs and hence they have limited resources to acquire this information.

Energy efficiency is an important component of a company’s environmental strategy. End-of-pipe solutions can be expensive and inefficient while energy efficiency can often be an inexpensive opportunity to reduce emissions of criteria and other pollutants. In short, energy-efficiency investment is a sound business strategy in today’s manufacturing environment. In many countries, government policies and programs aim to assist industry to improve competitiveness through increased energy efficiency and reduced environmental impact. However, usually there are only limited information sources available on how to improve energy-efficiency, especially for SMEs.

Savings and Costs
Wherever available, the energy savings and costs are given per ton of product or as the percentage of energy use by the equipment. However, due to a lack of information, energy savings and costs are given per year or per equipment/year for many measures and technologies. In these cases, especial care should be taken while interpreting the data. The term “average” is used to show that the savings and costs are the average value for the implementation of that measure on similar equipment. The other important issue that needs to be highlighted is nominal costs. Therefore, the time value of the money should be considered.

Energy use in the textile industry
The textile industry, in general, is not considered an energy-intensive industry. However, the textile industry comprises a large number of plants which all together consume a significant amount of energy. The share of total manufacturing energy consumed by the textile industry in a particular country depends upon the structure of the manufacturing sector in that country.

The textile industry uses large quantities of both electricity and fuels. The share of electricity and fuels within the total final energy use of any one country’s textile sector depends on the structure of the textile industry in that country. For instance, in spun yarn spinning, electricity is the dominant energy source, whereas in wet-processing the major energy source is fuels. The U.S. shows that 61% of the final energy used in the U.S. textile industry was fuel energy and 39% was electricity. The U.S. textile industry is also ranked the 5th largest steam consumer amongst 16 major industrial sectors studied in the U.S. The same study showed that around 36% of the energy input to the textile industry is lost onsite (e.g. in boilers, motor system, distribution, etc.)

Energy use in the spinning process
Electricity is the major type of energy used in spinning plants, especially in cotton spinning systems. If the spinning plant just produces raw yarn in a cotton spinning system, and does not dye or fix the produced yarn, the fuel may just be used to provide steam for the humidification system in the cold seasons. Therefore, the fuel used by a cotton spinning plant highly depends on the geographical location and climate in the area where the plant is located. Figure shows the Breakdown of final energy use in a sample spinning plant that has both ring and open-end spinning machines.
Figure . Breakdown of the Final Energy use in a Spinning Plant that has both Ring and Open-End Spinning Machines
For all types of fibers, finer yarn spinning consumes more energy. That said, yarns used for weaving involves more twisting than yarns used for knitting. Also, production speed is low for weaving yarn compared to that of knitting yarn. As a result, with the same yarn count, more energy is consumed for weaving yarn. Also, for the same yarn count, the energy consumption for combed yarn is higher because of the additional production step (combing).

Typical Specific Energy Consumption (kWh/kg) for Yarns with Different Yarn Counts and Final Use (Weaving vs. Knitting)

Yarn Count(Tex)


Typical Specific Energy Consumption(Kwh/Kg)

Combed Yarn

Carded Yarn
Knitting
Weaving
Knitting
Weaving
37
1.38
1.63
1.34
1.62
33
1.58
1.88
1.54
1.86
30
1.79
2.12
1.73
2.09
25
2.19
2.60
2.11
2.55
20
3.06
3.64
2.96
3.57
17
3.89
4.62
3.74
4.53
15
4.42
5.25
4.23
5.12
12
5.52
6.81
5.52
6.72
 
Energy use in wet-processing
Wet-processing is the major energy consumer in the textile industry because it uses a high amount of thermal energy in the forms of both steam and heat). The energy used in wet-processing depends on various factors such as the form of the product being processed (fiber, yarn, fabric, cloth), the machine type, the specific process type, the state of the final product, etc.

It can be seen that a significant share of thermal energy in a dyeing plant is lost through wastewater loss, heat released from equipment, exhaust gas loss, idling, evaporation from liquid surfaces, un-recovered condensate, loss during condensate recovery, and during product drying (e.g. by over-drying).

Table: Typical Energy Requirements for Textile Wet- Processes, by Product Form, Machine Type and Process

Table: Breakdown of Thermal Energy Use in a Dyeing Plan

Breakdown of energy use in composite textile plants (spinning-weaving-wet processing)
A composite textile plant is a plant that has spinning, weaving/knitting, and wet-processing (preparation, dyeing/printing, finishing) all on the same site. Figure 9 shows the Breakdown of the typical electricity and thermal energy use in a composite textile plant (Sathaye, et al., 2005). As it can be seen, spinning consumes the greatest share of electricity (41%) followed by weaving (weaving preparation and weaving) (18%). Wet-processing preparation (desizing, bleaching, etc) and finishing together consume the greatest share of thermal energy (35%). A significant amount of thermal energy is also lost during steam generation and distribution (35%). These percentages will vary by plant.


Energy-efficiency improvement opportunities in the TI (Textile Industry)
This analysis of energy-efficiency improvement opportunities in the TI includes both opportunities for retrofit/process optimization as well as the complete replacement of the current machinery with state-of-the-art new technology. However, special attention is paid to retrofit measures since state-of-the-art new technologies have high upfront capital costs, and therefore the energy savings which result from the replacement of current equipment with new equipment alone in many cases may not justify the cost. However, if all the benefits received from the installation of the new technologies, such as water savings, material saving, less waste, less waste water, less redoing, higher product quality, etc. are taken into account, the new technologies are more justifiable economically.

Furthermore, we have tried to present measures for which we could find quantitative values for energy savings and cost. However, in some cases we could not find such quantitative values, yet since some measures are already well-known for their energy-saving value. We believe that the qualitative information given for such technologies/measures can help the textile plant engineers to identify available opportunities for energy-efficiency improvements. However, it should be noted that the energy saving and cost data provided in this assignment are either typical saving/cost or plant/case-specific data. The savings from and cost of the measures can vary depending on various factors such as plant and process-specific factors, the type of fiber, yarn, or fabric, the quality of raw materials, the specifications of the final product as well as raw materials (e.g. fineness of fiber or yarn, width or specific weight of fabric g/m2, etc), the plant’s geographical location, etc. For instance, for some of the energy-efficiency measures, a significant portion of the cost is the labor cost. Thus, the cost of these measures in the developed and developing may vary significantly.

Energy-efficiency technologies and measures in the spun yarn spinning process
  1. Installation of electronic roving end break stop-motion detectors instead of pneumatic systems
  2. High-speed carding machine
  3. Use of energy-efficient spindle oil
  4. Optimum oil level in the spindle bolsters
  5. Replacement of lighter spindles in place of conventional spindles in ring frames
  6. Synthetic sandwich tapes for ring frames
  7. Optimization of ring diameter with respect to yarn count in ring frames
  8. False ceiling over the ring frames areas
  9. Installation of energy-efficient motors in ring frames
  10. Installation of energy-efficient excel fans in place of conventional aluminum fans in the suction system of ring frames
  11. The use of light weight bobbins in ring frames
  12. High-speed ring spinning machine
  13. Installation of a soft-starter on ring frame motor drives
  14. Installation of variable frequency drives on Autoconer machines
  15. Intermittent modes of the movement of empty bobbin conveyors in Autoconer/cone winding machines
  16. Using a modified outer pot for two-for-one (TFO) machines
  17. Optimization of balloon settings in TFO machines
  18. Replacing electrical heating systems with steam heating systems for yarn polishing machines
  19. Replacement of nozzles with energy-efficient mist nozzles in yarn conditioning rooms
  20. Installation of variable frequency drives (VFD) for washer pump motors in humidification plants
  21. Replacement of existing aluminum alloy fan impellers with high efficiency FRP (fiberglass reinforced plastic) impellers in humidification fans and cooling tower fans of spinning mills
  22. Installation of VFD on humidification system fan motors for flow control
  23. Installation of VFD on humidification system pumps
  24. Energy-efficient control systems for humidification systems
  25. Energy conservation measures in overhead traveling cleaner (OHTC)
  26. Timer-based control system for overhead traveling cleaners (OHTC)
  27. Optical control system for overhead traveling cleaners (OHTC)
  28. Energy-efficient blower fans for overhead traveling cleaners (OHTC)
  29. Improving the power factor of the plant (reduction of reactive power)
  30. Replacement of ordinary ‘V – belts’ with cogged ‘V – belts’ at various machines
Energy-efficiency technologies and measures in the weaving process
  1. Evaluation and enhancement of the energy efficiency of compressed air systems in air-jet weaving plants
  2. General measures to save energy in weaving plants
Energy-efficiency technologies and measures in wet-processing
  1. Combine preparatory treatments in wet processing
  2. Cold-pad-batch pretreatment
  3. Bleach bath recovery system
  4. Use of counter-flow currents for washing
  5. Installing covers on nips and tanks in continuous washing machines
  6. Installing automatic valves in continuous washing machines
  7. Installing heat recovery equipment in continuous washing machines
  8. Reduce live steam pressure in continuous washing machines
  9. Introducing point-of-use water heating in continuous washing machines
  10. Interlocking the running of exhaust hood fans with water tray movement in yarn mercerizing machines
  11. Energy saving in cooling blower motors by interlocking motors with the fabric gas singeing machine's main motor
  12. Energy saving in shearing machine blower motors by interlocking motors with the main motor
  13. Enzymatic removal of residual hydrogen peroxide after bleaching
  14. Enzymatic scouring
  15. Use of integrated dirt removal/grease recovery loops in wool scouring plants
  16. Installation of variable frequency drives on pump motors of Top dyeing machines
  17. Heat insulation of high temperature/high pressure (HT/HP) dyeing machines
  18. Automated preparation and dispensing of chemicals in dyeing plants
  19. Automated dyestuff preparation in fabric printing plants
  20. Automatic dye machine controllers
  21. Cooling water recovery in batch dyeing machines (jet, beam, package, hank, jigger, and winches)
  22. Cold-pad-batch dyeing systems
  23. Discontinuous dyeing with airflow dyeing machines
  24. Installation of VFD on circulation pumps and color tank stirrers
  25. Dyebath reuse
  26. Equipment optimization in winch beck dyeing machines
  27. Equipment optimization in jet dyeing machines
  28. Single-rope flow dyeing machines
  29. Microwave dyeing equipment
  30. Reducing the process temperature in wet batch pressure-dyeing machines
  31. Use of steam coils instead of direct steam heating in batch dyeing machines (winch and jigger)
  32. Reducing the process time in wet batch pressure-dyeing machines
  33. Installation of covers or hoods in atmospheric wet batch machines
  34. Careful control of temperature in atmospheric wet batch machines
  35. Jiggers with a variable liquor ratio
  36. Heat recovery of hot waste water in autoclaves
  37. Reducing the need for re-processing in dyeing
  38. Recovering heat from hot rinse water
  39. Reuse of washing and rinsing water
  40. Reduce rinse water temperatures
Energy-efficiency improvements in cylinder dryer
  1. Introduce mechanical pre-drying
  2. Selection of hybrid systems in cylinder dryer
  3. Recover condensate and flash steam in cylinder dryer
  4. End panel insulation in cylinder dryer
  5. Select processes for their low water add-on characteristics
  6. Avoid intermediate drying in cylinder dryer
  7. Avoid over drying in cylinder dryer
  8. Operating cylinders at higher steam pressures in cylinder dryer
  9. Reduce idling times and using multiple fabric drying in cylinder dryer
  10. Maintenance of cylinder dryer
  11. The use of radio frequency dryers for drying acrylic yarn
  12. The use of low pressure microwave drying machines for bobbin drying instead of dry-steam heater
  13. High-frequency reduced-pressure dryers for bobbin drying after the dyeing process
  14. Utilization of heat exchangers for heat recovery from wet-process wastewater
  15. Heat recovery from the air compressors for use in drying woven nylon nets
Energy-efficiency technologies and measures in man-made fiber production
  1. Installation of variable frequency drives (VFD) on hot air fans in after treatment dryers in viscose fiber production
  2. The use of light weight carbon reinforced spinning pots in place of steel reinforced pots
  3. Installation of variable frequency drives in fresh air fans of humidification systems in man-made fiber spinning plants
  4. Installation of variable frequency drives on motors of dissolvers
  5. Adoption of pressure control systems with VFDs on washing pumps in the after treatment process
  6. Installation of lead compartment plates between pots of spinning machines
  7. Energy-efficient high pressure steam-based vacuum ejectors in place of low pressure steam-based vacuum ejectors for viscose deaeration
  8. The use of heat exchangers in dryers in viscose filament production plants
  9. Optimization of balloon setting in TFO machines
  10. Solution spinning high-speed yarn manufacturing equipment (for filament other than urethane polymer)
  11. High-speed multiple thread-line yarn manufacturing equipment for producing nylon and polyester filament
  12. Reduction in the height of spinning halls of man-made fiber production through the installation of false ceilings
  13. Improving motor efficiency in draw false-twist texturing machines
Energy-efficiency improvement opportunities in compressed air systems
Instrumentation consumes large amounts of compressed air at many individual locations in a textile plant, but these uses are susceptible to leakage. Most such leaks are at threaded connection points, rubber hose connections, valves, regulators, seals, and in old pneumatic equipment. Air leaks from knitting operations are very common and can be quite large; these exact a large invisible cost, and the reduced pressure may impair the operation of the dyeing and finishing machines. Integrated mills that contain knitting operations should check the compressed air systems in knitting as well as in the dyeing and finishing areas.

More than 85% of the electrical energy input to an air compressor is lost as waste heat, leaving less than 15% of the electrical energy consumed to be converted to pneumatic compressed air energy . This makes compressed air an expensive energy carrier compared to other energy carriers. Many opportunities exist to reduce energy use of compressed air systems. For optimal savings and performance, it is recommended that a systems approach is used. In the following, energy saving opportunities for compressed air systems are presented

Replacement of old inefficient boiler feed pumps with energy-efficient pumps
Boiler feed pumps are used to feed the hot water to boilers. In a textile plant in India a boiler feed pump with a power consumption of 12.9 kW was replaced by an energy-efficient pump that consumed only 9.88 kW. Annual electricity savings is reported to be about 27 MWh/year with an investment cost of about US$3000

Foam technology
The application of foam processing leads to considerable savings in the energy required for heating, drying, thermo-fixing, and steaming because the water content is greatly reduced (Prince, 2008). In the foam process the liquor is diluted using air instead of the water that is normally used to apply the textile chemicals over the textile materials. In foam finishing, most of the water is replaced by air which leads to a reduction of energy requirements in the drying processes, resulting in substantial savings in energy cost.

Use of renewable energy in the textile industry
  1. Installation of turbo ventilators that rotate using wind blowing over roofs
  2. Use of direct solar energy for fiber drying
  3. Use of solar energy for water heating in the textile industry
Conclusions
Energy is one of the main cost factors in the textile industry. Especially in times of high energy price volatility, improving energy efficiency should be one of the main concerns of textile plants. There are various energy-efficiency opportunities in textile plants, many of which are cost-effective. However, even cost-effective options often are not implemented in textile plants due mainly to limited information on how to implement energy-efficiency measures, especially given the fact that the majority of textile plants are categorized as SMEs. These plants in particular have limited resources to acquire this information. Know-how regarding energy-efficiency technologies and practices should, therefore, be prepared and disseminated to textile plants.

References
  1. Abdel-Dayem, A.M. and Mohamad, M.A., 2001. “Potential of solar energy utilization in the textile industry-a case study”. Renewable Energy 23 (2001) 685–694.
  2. Barclay, S.; Buckley, C., 2000. Waste Minimization Guide for the Textile Industry. Available at: http://www.c2p2online.com/documents/Wasteminimization-textiles.pdf
  3. Barnish, T. J., M. R. Muller, and D. J. Kasten., 1997. “Motor Maintenance: A Survey of Techniques and Results”. Proceedings of the 1997 ACEEE Summer Study on Energy efficiency in Industry.
  4. American Council for an Energy-Efficient Economy, Washington, D.C.
  5. www.energystar.gov/.../industry/.../EE_Guidebook_for_Textile_industry 
 

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