40 Innovative Approaches for Energy Conservation in Modern Spinning Mills

40 Innovative Approaches for Energy Conservation in Modern Spinning Mills

Tapan Sinha1, Shyam Barhanpurkar2, Mufaddal Bagwala3
1Mtech. I.I.T. Delhi, Head of Department, Textile Technology, Shri Vaishnav Institute of Technology and Science, Indore, M.P., India.
2Mtech G.C.T.I., Kanpur, Faculty, Department of Textile Technology, Shri Vaishnav Institute of Technology and Science, Indore, M.P., India.
3Under-Graduate, Department of Textile Technology, Shri Vaishnav Institute of Technology and Science, Indore, M.P., India.

 

Abstract
The textile industry is one of the most complicated manufacturing industries because it is a fragmented and heterogeneous sector dominated by small and medium enterprises (SMEs). 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 a primary concern for spinning plants. There are various energy-efficiency opportunities that exist in every spinning plant, many of which are cost-effective. However, even cost-effective options often are not implemented in spinning plants mostly because of limited information on how to implement energy-efficiency measures, especially given the fact that a majority of textile plants are categorized as SMEs and hence they have limited resources to acquire this information. Know-how on energy-efficiency technologies and practices should, therefore, be prepared and disseminated to spinning plants.

This paper provides information on energy-efficiency technologies and measures applicable to the spinning industry. The paper includes case studies from spinning plants around the India, especially Indore and Rajasthan and includes energy conservation and cost information when available. An analysis of the type and the share of energy used in spinning processes are also included in this paper. Indian industry uses energy more intensively than is the norm in industrialized countries.  Subsequently, “40 Innovative Approaches for Energy Conservation in Modern Spinning Mills” available within some of the major spinning sectors are given with a brief explanation of each measure. The conclusion includes a short section dedicated to highlighting a few emerging technologies in the Spinning industry as well as the potential for the use of renewable energy in the spinning industry.

Keywords: Energy Conservation; Spinning Mills; Specific Energy Consumption (SEC); Variable Frequency Drive (VFD); Original Investment Required; Annual Savings

1. Introduction
As manufacturers face an increasingly competitive global business environment, they seek opportunities to reduce production costs without negatively affecting product yield or quality. For public and private companies alike, rising energy prices are driving up costs and decreasing value added at the plant [1]. 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 [2].

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 [3 and 4]. However, usually there are only limited information sources available on how to improve energy-efficiency, especially for small and medium enterprises (SMEs). Energy-efficiency technologies and practices know-how should, therefore, be prepared and disseminated to industrial plants.

In order to achieve optimal energy-efficiency, a systems energy-efficiency approach is essential. Since around 40 energy-efficiency measures and technologies for the spinning industry are explained in this paper, it can be overwhelming for some readers who are looking for specific information related to their plants [5].

2. Literature Review

2.1 Energy Use in the Textile industry
Energy consumption in the textile industry has augmented with increased mechanization. Energy consumption per unit of output is higher in modern textile units due to technological development, which tends to replace manual labor by electric power. However technological development also offers better productivity and quality that can overcome the efficiency measure. Energy costs vary from 5 to 17% of total manufacturing costs according to the type of process involved [6]. Spinning processes require high amounts of Electrical energy i.e. 41 %, inducing a higher share of energy costs (See Figure 1).

Distribution of Power Requirement in a Composite Textile Mill
Figure 1: Distribution of Power Requirement in a Composite Textile Mill

2.2 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 for preheating the fibers before spinning them together [7]. 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 2 shows the Breakdown of final energy use in a sample spinning plant that has both ring and open-end spinning machines.

Final Energy use in a Spinning Plant

Final Energy use in a Spinning mill
Figure 2: Final Energy use in a Spinning Plant

2.3 Calculation of Specific Energy Consumption (SEC)
Specific energy consumption (SEC) is defined as ratio of kWh of energy consumed to the unit weight of material processed by this energy consumption. It is represented by kilo watt hour per kilogram (kWh/kg) or electrical units per pound (kWh/lb). Specific energy consumption values are different in different countries and mills due to different production variables (delivery speed, twist level, spindle speeds and machines efficiencies) and different linear densities (count) [1, 5 and 7].

The value of Specific energy consumption is known to be high for fine yarn and low for the coarse yarn. The value of Specific energy consumption is also high for high level of twisted yarn (Warp Yarn) and low for low level of twisted Yarn (Hosiery Yarn) for the same yarn count.

Since the highest energy consumption occurs in spinning machines during yarn manufacturing, many studies have been carried out on the energy consumption of spinning machines. One of these studies shows that specific energy consumption in a ring spinning machine can be calculated with the equation given below.

SEC = 106.7 × F1.482× Dr3.343 × n0.917 × αtext0.993

Where,
SEC= Specific Energy Consumption (kWh/kg)
F = Yarn Linear Density (Tex)
Dr = Ring Cup Diameter (m)
n = Speed Spindle (1000 rpm)
αtext = Tex Twist Factor

After realization of high specific energy consumption, a proposal to conduct seven energy saving techniques were selected for the implementation. This study will also focus on potential of annual saving, Original Investment required for the implementation and expected payback period.

3. Methodology
40 Innovative Approaches for Energy Conservation in Modern Spinning Mills consists of following lists of experiments:

3.1 Energy-efficiency Technologies and Measures in the Spun Yarn Spinning Process
Table 1 shows the list of measures/technologies included in this paper for the spun yarn spinning process.

Table 1: List of Energy-efficiency Measures and Technologies for the Spinning Process *

List of Energy-efficiency Measures and Technologies for the Spinning ProcessList of Energy-efficiency Measures and Technologies for the Spinning Process 2

* The energy savings, costs, and payback periods given in the table are for the specific conditions cited. There are also some ancillary (non-energy) benefits from the implementation of some measures. Read the explanation of each measure in the report text to get a complete understanding of the savings and costs.

**Wherever the payback period was not provided, but the energy and cost were given, the payback period is calculated assuming the price of electricity of INR 3750/MWh (INR 3.75/kWh).

3.2 Energy-efficiency Technologies and Measures in the Man-Made Fiber Production
Table 2 shows the list of measures/technologies included in this paper for the man made fiber production.

Table 2: List of Energy-efficiency Measures and Technologies for the Man-Made Fiber production *

List of Energy-efficiency Measures and Technologies for the Man-Made Fiber production

* The energy savings, costs, and payback periods given in the table are for the specific conditions cited. There are also some ancillary (non-energy) benefits from the implementation of some measures. Read the explanation of each measure in the report text to get a complete understanding of the savings and costs.

**Wherever the payback period was not provided, but the energy and cost were given, the payback period is calculated assuming the price of electricity of INR 3750/MWh (INR 3.75/kWh).

4. Results and Discussion

4.1 Spinning Process

4.1.1 Preparatory process

1. Installation of electronic roving end break stop-motion detectors instead of pneumatic systems: In a simplex (roving) machine, the roving end-break system can be converted from a pneumatic suction tube detector to a photoelectric stop-motion system end-break detector in order to save energy.

2. High-speed carding machine: This new carding machine is large and  each machine consumes considerable amounts of electricity. On the other hand, since productivity is high, 1/3 the number of new machines and half the total power can produce the same production capacity as ordinary carding machines.

4.1.2 Ring frame

3. Use of energy-efficient spindle oil: The incorporation of a dispersant additive system to the mineral-based spindle oil may result in energy savings of up to 3% when compared to conventional oils.

4. Optimum oil level in the spindle bolsters: As there is no excess filling of spindle oil into the bolster, it prevents wastage of oil as well as energy”.

5. Replacement of lighter spindles in place of conventional spindles in ring frames: The weight of the spindles is directly related to the energy use of the machine.

6. Synthetic sandwich tapes for ring frames: Synthetic sandwich spindle tapes are made of polyamide, cotton yarn and a special synthetic rubber mix. Sandwich tapes run stable, have good dimensional stability, don’t break, result in less weak-twist yarn, do not cause fiber sticking, and are made of soft and flexible tape bodies [8].

7. Optimization of ring diameter with respect to yarn count in ring frames: A reduction of about 10% in bobbin content lowers ring frame energy intensity by about 10%.

8. False ceiling over the ring frames areas: The energy used by the humidification facility is directly related to the volume of the facility where the spinning process is carried out.  The use of a false ceiling can help to reduce this volume, thereby reducing energy consumption.

9. Installation of energy-efficient motors in ring frames: Even a slight efficiency improvement in ring frame motors could result in significant electricity savings that could pay back the initial investment in a short period.

10. Installation of energy-efficient excels fans in place of conventional aluminum fans in the suction system of ring frames: Energy-efficient excels fans could be installed in place of conventional aluminum fans in the suction system of ring frames.

11. The use of light weight bobbins in ring frames: The heavier the bobbins are, the more energy is required for the rotation of bobbins and hence spindles.

12. High-speed ring spinning machine: This machine has an increased operating speed by 10 – 20% with similar power consumption as compared to conventional equipment.

13. Installation of a soft-starter on ring frame motor drives: In spinning plants, a soft-starter can reduce the costs incurred by yarn breaks on a ring frame when its motor starts after each doff, as smooth starts and gradual acceleration of motors eliminate shocks during starting.

4.1.3 Windings, doubling, and yarn finishing process

14. Installation of variable frequency drives on Autoconer machines: The installation of variable frequency drives (VFD) on an Autoconer’s main motor can help maintain a constant vacuum and save energy.

15. Intermittent modes of the movement of empty bobbin conveyors in Autoconer/cone winding machines: This measure results in not only substantial energy saving but also results in maintenance cost savings and waste reduction.

16. Using a modified outer pot for two-for-one (TFO) machines: In two-for-one twisting machines, the balloon tension of yarn accounts for about 50% of total energy consumption. The balloon diameter can be reduced with a reduction in yarn tension by providing a modified outer pot [9].

17. Optimization of balloon settings in TFO machines: It has been observed above that that TFOs consume less electricity at lower balloon settings.

18. Replacing electrical heating systems with steam heating systems for yarn polishing machines: The electrical heaters can be replaced by steam heaters which can reduce overall energy use.

4.1.4 Air conditioning and humidification system

19. Replacement of nozzles with energy-efficient mist nozzles in yarn conditioning rooms: The type of nozzles used for spraying the water can effectively influence the electricity use of the yarn conditioning system.

20. Installation of variable frequency drives (VFD) for washer pump motors in humidification plants: In humidification plants, an inverter can be installed on washer pump motors with auto speed regulation, which can be adjusted to meet the required humidity levels.

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: Fans with FRP impellers require lower drive motor ratings and light duty bearing systems. Fans with FRP impellers consume less electricity compared to fans with aluminum alloy impellers under the same working conditions [10 and 11].

22. Installation of VFD on humidification system fan motors for flow control: VFDs can be installed on flow controls; these devices control fan speed instead of changing the dampers’ position.

23. Installation of VFD on humidification system pumps: In place of throttling valves, variable frequency drives can be installed for controlling relative humidity, and thereby the speed of the pumps can be reduced.

24. Energy-efficient control systems for humidification systems: The control system consists of variable speed drives for supply air fans, exhaust air fans and pumps in addition to control actuators for fresh air, recirculation and exhaust dampers.

4.1.5 General energy-efficiency measures in spinning plants

25. Energy conservation measures in overhead traveling cleaner (OHTC): It is imperative for textile plants to have control over waste removal out of the processing area to ensure best yarn and fabric quality [12].

  1. Timer-based control system for overhead traveling cleaners (OHTC): An energy-efficient control system using timer circuits can be introduced in addition to a main contactor provided in the control box to start and stop the OHTC whenever it touches the ends of the ring frame over which it moves in a linear path.
  2. Optical control system for overhead traveling cleaners (OHTC): An optical sensor to sense the position of the OHTCs on the ring frames can also be used. This system will start running the blower fan of the WCS only during the required operation time.

26. Energy-efficient blower fans for overhead traveling cleaners (OHTC): Existing blower fans of OHTCs can be replaced by energy-efficient fans with smaller diameters and less weight.

27. Improving the power factor of the plant (reduction of reactive power): There are many electric motors in a spinning plant that can cause reactive power. Therefore, reducing reactive power by improving the power factor of the plant is an important measure in reducing energy use and costs.

28. Replacement of ordinary ‘V – belts’ with cogged ‘V – belts’ at various machines: Ordinary V-belts can be replaced with cogged v-belts to reduce friction losses, thereby saving energy.

4.2 Man- Made Fibre Production

29. Installation of variable frequency drives (VFD) on hot air fans in after treatment dryers in viscose filament production: The new system consists of the installation of variable frequency drives (VFD) for a group of motor driven hot air fans and these fans are grouped based on the zones, as shown in Figure 3. In the initial stage (zone 1, 2, 3) where the amount of moisture is high, the VFDs are operated at higher speeds (RPMs) to deliver more hot air flow and thus reduce the moisture content. As the yarn passes through the second stage (zone-4) the speed of the motors is reduced as the moisture removal is reduced from that of the initial stage. In the final stage (zone-5) the amount of moisture is very minimal and thus the speed of the hot air fans is further reduced as, shown in the figure [13]. Fan speed reduction using a variable frequency drive for a group of motors has resulted in significant energy savings.

Zones in an After Treatment Dryer (Before Modification)
Figure 3(a): Zones in an After Treatment Dryer (Before Modification)
Zones in an After Treatment Dryer (Modified System)
Figure 3(b): Zones in an After Treatment Dryer (Modified System)

30. The use of light weight carbon reinforced spinning pots in place of steel reinforced pots: Steel reinforced spinning pots can be replaced with carbon reinforced spinning pots in synthetic fiber production plants (Figure 4) [14].

Steel Reinforced and Carbon Reinforced Spinning Pots
Figure 4: Steel Reinforced and Carbon Reinforced Spinning Pots

31. Installation of variable frequency drives in fresh air fans of humidification systems in man-made fiber spinning plants: The speed of all the fans can be controlled by changing the frequency of the VFD as to meet the requirement for fresh air by measuring the temperature as well as the relative humidity (RH) of the ambient air in the production process.

32. Installation of variable frequency drives on motors of dissolvers: The dissolvers normally run with a fixed speed, while the speed could be adjusted based on the process requirements.

33. Adoption of pressure control systems with VFDs on washing pumps in the after treatment process: The energy consumption of washing pumps can be optimized by varying the speed of the pumps as per the variation in the denier (thickness) of yarn.

34. Installation of lead compartment plates between pots of spinning machines: Lead compartment plates can be installed between each spinning pot to overcome the cross current of air between the pots (Figure 5).

35. Energy-efficient high pressure steam-based vacuum ejectors in place of low pressure steam-based vacuum ejectors for viscose Deaeration: Two stage high pressure steam-based ejectors can be installed in place of low pressure steam-based ejectors.

Installation of Lead Compartment Plates between Pots of Spinning Machines
Figure 5: Installation of Lead Compartment Plates between Pots of Spinning Machines

36. Optimization of balloon setting in TFO machines: Research has shown that TFO (two-for-one) twister machines consume less electricity at lower yarn balloon settings.

37. Solution spinning high-speed yarn manufacturing equipment (for filament other than urethane polymer): This equipment achieves high-performance and energy savings while employing new technology for the manufacture of yarn. In conventional equipment, 16 filaments can be spun from each machine, whereas with this equipment, an efficient electric motor providing high-speed spinning has been adopted to permit the spinning of 24 filaments per machine [15].

38. High-speed multiple thread-line yarn manufacturing equipment for producing nylon and polyester filament: This equipment is different from the one explained above and it melts and spins nylon and polyester filament to spin fully drawn filament (FDY) or partially oriented filament (POY) at a high speed of 6,000m/min.

39. Reduction in the height of spinning halls of man-made fiber production through the installation of false ceilings: Since the spinning halls of almost all man-made fiber production processes needs air conditioning and humidification systems, the volume of the hall has a direct effect on the energy [16].

40 Improving motor efficiency in draw false-twist texturing machines: The energy efficiency of the draw false-twist texturing machines can be improved by the use of combined transistor-VFD systems for the speed control of the motor (Figure 6).

5. Case Study
To check the feasibility of the 40 innovative approaches for energy conservation mention in this paper, the energy-efficiency technique number 14 -“Installation of Variable Frequency Drive on Autoconer machine”  was experimented in two renowned spinning mills –“Spinning Mill A” & “Spinning Mill B” in Indore, Madhya Pradesh. The experiment resulted in high savings of energy and capital for both the spinning mills. Figure 7 and Figure 8 shows the images of original receipt received from the manager of both the mills. The result of these two case studies shows the feasibility of above stated 40 innovative energy-efficiency techniques.

The Thyristor System and the Transistor-Inverter Control System
Figure 6: The Thyristor System (Fig.a) and the Transistor-Inverter Control System (Fig.b)
Using DANFOSS Variable Frequency Drive (VFD) in Autoconer – Murata make (CASE STUDY 1)
Figure 7: Using DANFOSS Variable Frequency Drive (VFD) in Autoconer – Murata make (CASE STUDY 1)
Using DANFOSS Variable Frequency Drive (VFD) in Autoconer – Murata Machoner (CASE STUDY 2)
Figure 8: Using DANFOSS Variable Frequency Drive (VFD) in Autoconer – Murata Machoner (CASE STUDY 2)

6. Conclusion
Energy is one of the main cost factors in the spinning industry. Especially in times of high energy price volatility, improving energy efficiency should be one of the main concerns of spinning plants. There are various energy-efficiency opportunities in spinning plants, many of which are cost-effective. However, even cost-effective options often are not implemented in spinning plants due mainly to limited information on how to implement energy-efficiency measures, especially given the fact that the majority of spinning plants are categorized as SMEs. These plants in particular have limited resources to acquire this information.

This paper provides information on energy-efficiency technologies and measures applicable to the textile industry. The paper includes case studies from spinning plants from the Indore with energy savings and cost information. For some measures the paper provides a range of savings and payback periods found under varying conditions. The level of reduction in Specific Energy Consumption depends on the use of technology by the mills and amount of investment. It is also anticipated that implementation of energy saving techniques on 12 spinning mills can saves the energy equal to run a small capacity spinning mills. This can be a turning point to control the energy crisis of India. Also this paper can be used as guidebook to setup various energy-efficiency technologies an SMEs as well as MNCs.

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