Utility Systems in Composite Textile Mills

In a composite textile mill, the core operations are yarn production (spinning), fabric preparation (weaving/knitting) and processing (wet/mechanical finishing). To run them, the mill needs electricity, compressed air, water, gas and steam. A team of engineers provides these, and this forms the utility department. The department also controls humidity and temperature in the spinning and weaving departments. Its main job is to ensure uninterrupted supply while keeping costs under control, which makes well-run utility systems in textile mills a foundation of textile operational excellence.

It carries out regular preventive maintenance of compressors, boilers, chillers, air conditioning, water pumps, RO plants and the captive power plant. It also ensures that the quality of air released into the atmosphere stays within the norms set by government bodies.

Power Generation System

Power generation is a key area of textile mill energy management. A gas-fired power plant burns natural gas to generate electricity. It combines efficiency and flexibility with low emissions, and it provides a great amount of power in a reduced site, so it can be placed close to consumption nodes. A gas turbine converts natural gas into mechanical energy that drives a generator. Used with a steam turbine in a combined-cycle power plant, it creates power extremely efficiently.

A diesel power plant uses a diesel engine as the prime mover. As diesel costs high, it is not suitable for large-scale power production. It is used for small-scale production, or where no other alternative is easily available.

Sample design for a 50,000-spindle spinning mill: Four 1,500 kW gas generators run continuously, with one more as standby. At 85% load each gives 1,275 kW, so the total running load is 5,100 kW against a required process load of 5,000 kW. Supporting equipment includes cooling towers (250 RT, 5 sets), cooling water pumps, plate heat exchangers and ventilation fans.

The sample 1,500 kW gas generator is offered in two forms: "K" (optimized for robustness and low CAPEX) and "R" (optimized for high total efficiency). The K version gives 1,500 kW at 40.9% electrical and 86.6% total efficiency (50 Hz). The R version gives 1,560 kW at 43.3% electrical and 87.1% total efficiency.

Electrical Transmission and Distribution

The distribution system covers LT switchgear, power BBT transmission for machinery, lighting power BBT, DB/SDB and other switching, and LT cable distribution. In captive power generation, the LT sub-station synchronizes the total power from all running generators and transmits it by segregation according to load.

Busbar trunking (BBT) distributes power through copper or aluminium busbars in a protective enclosure. Beyond what cables do, it can tap off power to switchgear through tap-off boxes, replacing both cables and floor-level distribution boards. It can run vertically, horizontally or both. Compared with cables, BBT offers:

• Better finishing and aesthetics
• Power feeding to multiple floors from a single system
• Power tap-off from one system, where a load change needs only a higher-rated tap-off box (cables need additional runs)
• Lower voltage drop
• Lower cost
• DB/SDB-free transmission

Tap-off boxes plug into the busway track slot and connect with a 90-degree twist. They typically contain circuit breakers and outlets, in capacities from single-phase 120 V to three-phase 415 V. They are easy to install, maintain and replace, user friendly, and offer a long life and high cooling efficiency.

Chilling and Cogeneration Systems

A chiller removes heat from a liquid, which then cools equipment or air. Chilled water is used to cool and dehumidify air in industrial facilities. Two types are commonly used:

• Vapor compression chillers use a compressor to pump the refrigerant, which extracts unwanted heat from a process. The system has an evaporator, a condenser and an expansion unit.
• Vapor absorption chillers use a heat source (hot water or steam) instead of a compressor. They have an absorber, a pump and a generator in its place.

Cogeneration (combined heat and power, CHP) generates electricity and useful heat at the same time, using fuel more efficiently because otherwise-wasted heat is put to productive use. Trigeneration (CCHP) uses the waste heat for both heating and cooling, typically in an absorption refrigerator. It can reach higher overall efficiency than cogeneration or traditional power plants.

A heat recovery steam generator (HRSG) uses hot exhaust gases from gas turbines or reciprocating engines to generate steam, which drives a steam turbine or serves industrial processes. In an exhaust gas boiler, exhaust heat passes through several stages: water heating, low-pressure steam, and saturated steam that goes on to a super heater. If steam is not required, the boiler entry is closed and a bypass line is opened.

The jacket-water heat recovery system raises overall plant efficiency and lowers fuel demand, which supports textile mill energy management. Waste Heat Recovery Units (WHRUs) turn the waste heat in the generator jacket water into chilling.

Sample cogenerated chilling system for a 50,000-spindle mill: three steam-fired chillers (630 USRT each) and two hot-water-fired chillers (530 USRT each) give a total of 2,530 USRT at 85% load. Cooling is provided by six 1,000 RT box-type cooling towers.

Air Conditioning and Humidification

Air conditioning, a major part of composite textile mill utilities, controls temperature, humidity, cleanliness and distribution of air. System capacity is directly proportional to heat load, which combines almost constant internal heat with transmission heat that varies by season. The maximum heat load occurs during summer afternoons, and the roof heat load accounts for 25% to 30%.

Natural and manufactured fibers are hygroscopic. Proper humidity control increases the strength of yarn and fabric during processing. Too high a humidity causes problems in spinning, while lower humidity may induce static electricity that is harmful to production.

In partial saturation systems with recirculation-air bypass, the temperature of the "leading" zone (zone 1) controls the outside, exhaust and recirculation dampers through a cascade control system. If any zone is too cold (4 °C below the set point, adjustable), its humidity control is disabled. Each zone has its own humidity controller, and the zone with the greatest negative deviation from the required humidity sets the pump or water throttle damper.

Sample ring-spinning plant: an area of 6,272 m² with a 4.0 m clear height. The guaranteed conditions are 50 ± 2.5% RH and 28 ± 1 °C. The plant has three air-washer units and three control zones, with a supply air flow of 1,150,000 m³/h (45.8 air changes per hour) and refrigeration capacity of 4,721.6 kW (1,341.4 RT).

Compressed Air System

Compressed air and steam systems in textile plants need careful design and regular upkeep, because both are used across many processes. A compressed air system has a supply side (compressors, air treatment and primary storage) and a demand side (distribution piping, secondary storage and end-use equipment). Its main components are:

• Air intake filter
• Air compressor: reciprocating, rotary screw or rotary centrifugal
• Aftercooler
• Air receivers
• Air dryer

Compressed air is sometimes considered the "fourth utility," yet in many facilities these systems are the least energy-efficient equipment. Producing one unit of mechanical output takes about 10 units of electrical energy at the compressor. Decisions should therefore be based on life cycle cost rather than first cost. Direct drive electrical motors should be considered first. Where compressed air is used, it should be at the minimum quantity and pressure necessary, for the shortest possible duration. Chronic air leaks should be repaired.

Sample calculation for a 50,000-spindle mill: the total air consumption is 24.20 m³/min. Compressors are 90 kW screw type units of 15.4 m³/min each. About 1.57 run at peak, with one on standby, so three are required. Three dryers are required at 23.1 m³/min each (1.5 times the compressor capacity), at a maximum operating pressure of 10 bar.

Water Supply and Treatment System

Within utility systems in textile mills, water treatment optimizes water-based industrial processes such as heating, cooling, processing, cleaning and rinsing. Poor treatment lets boilers and cooling towers scale up or corrode, which requires more fuel, and untreated cooling towers can encourage bacterial growth. Treated effluent can be reused in other processes, which lowers water consumption, effluent disposal and energy costs.

• Coagulation/flocculation: alum or polymer makes fine dirt particles form flocs.
• Sedimentation: the flocs settle as sludge.
• Filtration: layers of sand and gravel, and in some cases crushed anthracite, remove suspended impurities. The filters are cleaned by backwashing.
• Disinfection: chlorine destroys disease-causing microorganisms.

Sample 60 m³/hr plant (manual operation, 40 hours of operation and 1 hour for backwash and regeneration): raw water of hardness 42 ppm, TDS 450 ppm and iron 0.5 ppm is treated to less than 5 ppm hardness and 0.3 ppm iron. The equipment is an iron removal filter (IRF-1800), a multigrade sand filter (MGF-1800) and a softener (SF-1600) with 2,500 litres of resin, regenerated with 375 kg of NaCl. For best results, the plant should run without interruption.

Conclusion

Composite textile mill utilities must be managed as an integrated engineering system rather than a collection of independent services. Power generation, electrical distribution, heat recovery, chilling, air conditioning, compressed air and water treatment directly influence plant availability, production stability, energy consumption and operating cost. The design examples show the importance of adequate capacity, standby provision, preventive maintenance, efficient distribution and recovery of otherwise wasted energy. A coordinated utility strategy supports reliable production, strengthens textile operational excellence and creates opportunities for improved energy and resource efficiency through sound textile mill energy management.