BEST PRACTICES REPORT (PROCESSING SECTOR)

Transcription

1 BEST PRACTICES REPORT (PROCESSING SECTOR) Supported by RENEWABLE ENERGY & ENERGY EFFICIENCY PROGRAMME (REEE)

2 DISCLAIMER The Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH is implementing the Renewable Energy & Energy Efficiency (REEE) Programme on the basis of a commission from the German Federal Ministry for Economic Cooperation and Development (BMZ). On behalf of Government of Pakistan, Small & Medium Enterprise Development Authority (SMEDA) & National Productivity Organization (NPO) are implementing partners in this project. The opinions and analyses expressed in this report do not necessarily reflect the views and official policies of the REEE Programme. This report is based on the findings of energy efficiency audits and will be updated on a regular basis to include more suitable measures identified in additional energy efficiency audits.

3 TABLE OF CONTENTS INTRODUCTION... 1 BACKGROUND... 1 ENERGY EFFICIENCY (EE)... 1 ENERGY EFFICIENCY (EE) PROJECT... 1 ADVANTAGES / IMPORTANCE OF ENERGY EFFICIENCY... 1 ENERGY SAVING POTENTIALS WORKERS TRAINING ON WATER AND ENERGY CONSERVATION PROBLEM PROPOSED ACTIONS BETTER PROCESS CONTROL PROBLEM PROPOSED ACTIONS INSULATION OF BARE HOT SURFACES PROBLEM PROPOSED ACTIONS REUSE OF STEAM CONDENSATE PROBLEM PROPOSED ACTIONS UPKEEP OF STEAM TRAPS PROBLEM PROPOSED ACTIONS INSTALLATION OF ECONOMIZER ON BOILER FLUE GAS PROBLEM PROPOSED ACTIONS MEASUREMENT OF BOILER EFFICIENCY PROBLEM PROPOSED ACTIONS ENERGY LOSS THROUGH BLOW DOWN PROBLEM PROPOSED ACTIONS INSTALLATION OF WATER SOFTENER/REVERSE OSMOSIS (RO) FOR PROCESS AND BOILER FEED WATER PROBLEM PROPOSED ACTIONS... 15

4 10 FLAME ADJUSTABLE SINGEING MACHINE PROBLEM PROPOSED ACTIONS INSTALLATION OF HEAT EXCHANGER ON HOT WASTEWATER PROBLEM PROPOSED ACTIONS IMPLEMENTATION OF COUNTER CURRENT WASHING AT MERCERIZATION / SOAPER /.BLEACHING PLANT PROBLEM PROPOSED ACTIONS REUSE OF COOLING WATER PROBLEM PROPOSED ACTIONS INSTALLATION OF TEMPERATURE GAUGES/INDICATORS ON HOT MACHINES PROBLEM PROPOSED ACTIONS INSTALLATION OF WATER FLOW METERS ON WATER INLETS PROBLEM PROPOSED ACTIONS ELECTRICAL DISTRIBUTION SYSTEM PROBLEM PROPOSED ACTIONS COMPRESSED AIR SYSTEM PROBLEM PROPOSED ACTIONS LIGHTING PROBLEM PROPOSED ACTIONS REUSE OF CLEAN HOT WATER STREAM OF JETS PROBLEM PROPOSED ACTIONS... 34

5 INTRODUCTION BACKGROUND The Small and Medium Enterprise Development Authority (SMEDA) as well as the National Productivity Organization (NPO) have been supported by the Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH to introduce Energy Efficiency in the Textile Industry. This initiative helps the textile sector address energy losses and related productivity, quality losses. As a first exercise, detailed energy efficiency audits were conducted by national consultants under supervision of international energy efficiency experts in six textile units (two spinning units, two processing units and two integrated units). ENERGY EFFICIENCY (EE) Energy Efficiency (EE) by definition means using less energy to achieve same or better output compared to pre-implementation of the energy efficiency project. Energy Efficiency does not mean rationing or having to do without energy. Rather, energy efficiency means identifying wasteful energy usage, and taking steps to reduce or eliminate that waste without adversely effecting the production and the quality of output. Illustratively, the energy efficiency process is depicted below as ENERGY EFFICIENCY (EE) PROJECT Energy Efficiency (EE) project refers to any process, technique or equipment that helps to achieve reduction in energy consumption to perform a designated operation to achieve same or better level of output while maintaining or improving process time, quality, performance and safety with minimal environmental impact. ADVANTAGES / IMPORTANCE OF ENERGY EFFICIENCY The following are some of the advantages of implementing EE projects: Reduction in energy consumption, thereby adding directly to the profits or bottom line of the company Lowering the vulnerability to energy prices for unit/corporate that has implemented EE projects 1

6 Reducing the need for investment in newer power plants and import of energy Reducing the dependence on conventional resources like oil and natural gas etc. Reducing emissions of air pollutants in most cases 2

7 ENERGY SAVING POTENTIALS 1 WORKERS TRAINING ON WATER AND ENERGY CONSERVATION 1.1 PROBLEM Workers attitude affect processes and environmental performance of the organization. Main reasons for such kind of attitude are generally the lack of education and awareness regarding importance of resource conservation. They are unaware of the fact that their working practices can save substantial resources of the organization with no cost. This awareness and education can be imparted in workers through training which is the basic step towards the implementation of energy efficiency. Following areas are identified where improvements can be achieved through workers training. Excessive use of water is frequent. Sometimes there is no monitoring and record keeping of water consumption. Water keeps on running and wasted from the machines even in case it is stopped. Water hoses, used for floor and equipment washing, are mostly seen lying on the floor with continuous running of water at the time of no use. 1.2 PROPOSED ACTIONS Proposed actions are to conduct trainings of the workers which is considered very important for at source pollution abatement. There is need to create awareness among workers regarding the environmental issues associated with the excessive use of water and improper chemical storage and handling. They should be educated and trained about the importance of resource conservation, best practices and the consequent benefits. Trainings should be conducted in the following areas; General energy awareness Energy Efficiency (EE) specific for the mill Resource conservation measures (water, energy, chemical) 3

8 2 BETTER PROCESS CONTROL 2.1 PROBLEM Normally workers are habitual of carrying out textile processing with conventional techniques, they do not like to change it and consider hard to adopt better practices or any thing different from their natural working style. Due to lack of education and training, they are unable to understand the chemistry behind each process. They can not understand that these chemical processes are based on certain process parameters such as temperature, concentration and ph. Slight variation in these parameters, can result into either excess use of chemicals or deterioration of fabric quality, in most of the cases. In the absence of the feeling of their importance among workers, they consider controlling, monitoring and recording them in daily log sheets useless. 2.2 PROPOSED ACTIONS Following are some of the process control parameters, at each process level, which need to be controlled and recorded for the purpose of better performance: Grey Fabric Reception Get information from the grey fabric suppliers regarding type and quantity of different sizing chemicals applied on the fabric Record information of the grey fabric received from suppliers, including its type, length, width and GSM (gram per square meter). Singeing Record information of the grey fabric received from grey fabric store, including its type, length, width and GSM (gram per square meter). Record production of the singed fabric with all of the fabric parameters mentioned above parameters. Desizing Optimize desizing process recipe on the basis of type and quantity of sizing chemicals present on the fabric Record quantities of chemicals like enzyme, salt and detergents used in the desizing bath Control and record temperature and ph of the desizing bath Record production of the sized fabric with all of the fabric parameters mentioned above. Scouring Optimize scouring process recipe on the basis of type and quantity of sizing chemicals present on the fabric Record quantities of chemicals like caustic soda, sodium carbonate (soda ash),,detergents, and sodium silicate used in the scouring bath Control and record temperature of scouring chemical solution and bath (and 4

9 pressure in case of scouring in kier) Record production of the scoured fabric with all of the fabric parameters mentioned above Bleaching Optimize bleaching process recipe according to the degree of whiteness required (for darker shades, bleaching may be omitted). Record quantities of chemicals like bleaching agent (NaOCl), used in the bleaching bath Control and record temperature of the bleaching bath Record production of bleached fabric with all the fabric parameters mentioned above Neutralization Monitor and record ph of the fabric before neutralization Record quantity of acid used for neutralization Monitor and record ph after neutralization Record production of neutralized fabric with all the fabric parameters mentioned above Mercerization Control and record temperature and concentration of caustic soda bath Control and record percent stretch of fabric Record quantity of caustic soda used for mercerization Record production of mercerized fabric with all the fabric parameters mentioned above Dyeing Record quantities of chemicals like dye, salts, levelers, caustic soda, sodium carbonate, acids etc. Temperature and ph of dye bath in each step Control and record pressure of the dye machine in case of jets Record production of the dyed fabric for each type of dye with all the fabric parameters mentioned above. Boiler Record daily water and gas consumption in the boiler section Record daily steam consumption (if steam flow meter is installed) Monitor and record TDS, ph and hardness of the boiler feed water Monitor and record TDS of the blow down Monitor and record TDS, ph and hardness of the returned steam condensate Record hardness at which regeneration of water softener is carried out with the frequency and quantity of salt used in it (if water softener is installed) Blow Down should be on the basis of Water TDS Steam Distribution System 5

10 Some of the common problems faced by mills in the distribution of steam are briefly described Inadequate capacity of steam generation due to deterioration in boiler capacity or due to expansion of processing without a matching expansion in the boiler plant Large pressure fluctuations at the machine due to use of too small a pipe line Improper design of branch piping particularly after pressure reducers Inadequate draining of the lines Poor lagging Live steam leakages Inadequate pressure at machines due to a large number of machines being trapped from the same branch line Uneven distribution of steam load on different mains or branches Absence of sufficient margin for possible future expansion Wrong inclination of steam mains, branches and other pipe lines Steps Required Minimizing the Problems in Distribution Pipelines During a cold start, steam must be admitted gradually by opening the main valve only slightly to start with, or by opening a small by pass around it. The main valve should be opened fully only after the line has warmed up.( It is estimated that in a well lagged 100 mm line of about 30 m length there can be condensation to the extent of 7kg/hr due to heat loss) Steam separators must be provided where dry steam is desired The pipes and fittings must be lagged properly Pipes should be installed with a downward inclination in the direction of steam flow to avoid water hammering in pipelines. The inclination may be of the order of 10 cm to 20 cm in 100 m length All branches from the steam mains should be taken from above to avoid their acting as subsidiary drains Drain pockets in the form of equal T must be provided on the line to collect the condensate. Suitable steam traps with by-pass must be connected to these drains pockets. The drain pockets should be installed at intervals of about 75 m in lagged pipe lines Why Boiler Feed Water Treatment is Necessary To prevent corrosion, the alkalinity in the feed water and in the boiler water is to be controlled. Dissolved oxygen in the feed water is also liable to cause corrosion. High concentration of dissolved solids in the feed water necessitates excessive blow down from boilers resulting in undue loss of heat. Some boilers, such as the economic boilers, are very sensitive to dissolved solids. Hardness in water causes scale formation in the boiler, resulting in lower thermal efficiency. Scale on the outside or inside of tubes may also result in overheating because of poor heat transfer and in premature failure of tubes. Presence of excessive sodium alkalinity in the boiler water is likely to cause caustic cracking of boiler metal. The tendency for caustic cracking is inhibited by 6

11 the presence of sodium sulphate or sodium nitrate in adequate concentrations. 3 INSULATION OF BARE HOT SURFACES 3.1 PROBLEM Energy is a major resources of the textile industry, for which mill owners have become more conscious about its saving due to day by day rise in its prices. There are a number of reasons due to which energy losses occur. Uncovering of hot fluid carrying pipelines and machines is one of these reasons. There are different locations in the production hall where either proper insulation is not provided for the heat conservation purposes or present insulation has been damaged and not been repaired. Besides energy losses, uncovered hot surfaces can cause skin burn in case these were touched unintentionally by the workers and visitors. The recommended safe touch temperature range is o C. 3.2 PROPOSED ACTIONS To minimize the energy losses, all the bare steam carrying pipelines and equipments, hot water pipes and condensate return pipes, etc. should be insulated. There are different kinds of insulation material available such as calcium silicate, rock wool and glass wool. At the fluid temperature of up to 650 o C, calcium silicate and rock wool are suitable, whereas, fibre glass wool is useful for temperatures between o C. Fiberglass insulation is recommended for the textile industry. After selecting insulator, its optimum thickness is evaluated because cost of the insulation depends largely on its thickness. In case, thickness is inappropriate, heat losses are not reduced and heat energy is lost to the environment by conduction through insulator. At a certain thickness, called critical thickness, heat losses start decreasing with the increase of thickness. Thickness, above the critical thickness, is the optimum thickness. 7

12 4 REUSE OF STEAM CONDENSATE 4.1 PROBLEM Steam is an important source of supplying thermal energy to the process. Steam is either employed directly or indirectly. Direct usage typically occurs in the form of steam being injected into water or injected on the fabric. Direct usage has the highest possible heat transfer efficiency. Indirect usage requires additional heat exchanges thus reducing the heat transfer efficiency. But this method has the advantage that the condensed steam (condensate) which has transferred its energy can be used again. Steam condensate is a pure and hot water stream, which can be reused for boiler feed water and for the formulation of dye and printing solution. Most of the units waste this important water stream due to non existence of its proper collection and reuse arrangement. Following are the sources from where the steam condensate is generated and ultimately wasted as wastewater stream: Calenders' heaters Drum dryers Kiers heaters Jets' heaters Comfit heaters 4.2 PROPOSED ACTIONS It is better that the industry should make arrangements for the collection of steam condensate streams from all the sources in an appropriate sized insulated storage tank and use for: Boiler feed water Preparation of dye bath Preparation of printing paste Hot water in the process vessels 8

13 5 UPKEEP OF STEAM TRAPS 5.1 PROBLEM Steam traps are the important part of the steam distribution system. In closed circuit, steam after loosing its latent heat, becomes liquid called steam condensate, which has to be removed from the system. In case, steam condensate is not removed, steam system will not work due to its accumulation in the system. As both streams i.e. steam and condensate, are present in the lines, therefore such type of equipment is required which only removes condensate but not the steam. Steam traps are fitted in the steam lines to remove only steam condensate, air and non-condensable gases, not the steam. In case these traps do not work properly due to some reasons or become damaged, they allow both streams of steam and condensate to escape from the system freely. Wastage of steam is not only the economic loss but also makes working environment hot and humid. In most of the textile industries, steam traps are found malfunctioning. Steam leakage, along with the condensate is a regular feature in the production hall. Maintenance crew does not have realization that these malfunctioning traps cause huge energy losses. Most of these traps were fitted in the system, at the start but not replaced or repaired after they became damaged during operation as nobody consider it important entity. 5.2 PROPOSED ACTIONS All the malfunctioning steam traps should be dismantled and checked whether these are workable after minor repair and cleaning or require replacement. Maintenance staff is advised to examine them regularly and take care of their proper repair, maintenance and replacement, if required, on regular basis. A variety of steam traps are available in the market. Some are very expensive with long life whereas the others are cheap and get damaged soon. Thus steam traps selection is important for their uninterrupted operation. Brief description of different steam traps is given in the following section. Float and Thermostatic Float and thermostatic traps consist of a ball float and a thermostatic bellows element. When condensate flows through the body, the float rises or falls and opens the valve according to the flow rate. The thermostatic element discharges air from the steam lines. They are good in heavy, and light loads and on high and low pressure, but are not recommended where water hammer is a possibility. Orifice They contain an adjustable orifice in the body which continually discharges condensate. They are self regulating. When the rate of condensation 9

14 decreases, the condensate temperature increases due to the presence of steam. It causes throttling in the orifice and reduces capacity due to steam flashing on the downstream side. An increased load decreases flashing and the orifice capacity becomes greater. There is possibility that on light loads, these traps pass live stream. They can become clogged due to the build up of particulates in the orifice. These impurities can cause erosion and damage the orifice size, causing escape of steam. Inverted Bucket They have a bucket that rises or falls as steam and/or condensate enters the trap body. When steam is in the body, the bucket rises and closes the valve. When condensate enters, the bucket sinks down, and opens the valve and allows the condensate to drain. These traps are ideally suited for water hammer conditions. Thermodynamic They have a disc that rises and falls depending on the variations in pressure between steam and condensate. Steam tends to keep the disc down or closed. When condensate builds up, it reduces the pressure in the upper chamber and allows the disc to move up for condensate discharge. This trap is good where steam pressures remain constant. It can handle superheat and water hammer but is not recommended for process, since it has a tendency to air bind and does not handle pressure fluctuations well. Two of the most common causes of trap failure are over sizing and dirt. Over sizing causes traps to work too hard. In some cases this can result in blowing of live steam. Dirt is always created in the steam system. Excessive build up can cause plugging or prevent a valve from closing. Dirt is generally produced from pipe scale or from over treating of chemicals in the boiler. Mostly inverted bucket types are used in the textile mills. 10

15 6 INSTALLATION OF ECONOMIZER ON BOILER FLUE GAS 6.1 PROBLEM Flue gas discharged in the atmosphere at a temperature of o C from the steam boiler contains substantial thermal energy, which is being lost in the atmosphere presently. 6.2 PROPOSED ACTIONS Flue gas thermal energy should be recovered and used to heat boiler feed water by the installation of economizer. Economizer comprises of shell and tubes and attached with the boiler stack. The hot flue gas passes through the shell side and fresh water is pumped through the tubes of the economizer. Use of preheated water in the boiler reduces fuel consumption in the boiler. Special care has to be taken when using economizers at boilers fuelled by heavy oil fuel or charcoal/lignite. During the combustion of these higher amount of sulphuric acid is generated. The chimney must be able to handle the acid without getting damaged. 11

16 7 MEASUREMENT OF BOILER EFFICIENCY 7.1 PROBLEM There is much more worry about the efficiency of the steam boilers, mainly because of the day by day rise in the energy price. The more efficient the boiler is, the lesser its fuel consumption will be. Industry should install water, steam and gas (where gas is the fuel) flow meters to measure consumption of these utilities and consequently enable measurements of boiler performance or efficiency. Ignorance of boiler performance monitoring and evaluation is a serious concern with respect to energy conservation and environmental pollution. 7.2 PROPOSED ACTIONS The boiler feed water consumption is monitored to estimate the steam production of the boiler. The boiler stack emissions should be analyzed to review the combustion efficiency of the boiler. The analysis parameters are given below: Boiler Stack Analysis Parameter Temperature of flue gas Sulfur dioxide (SO 2 ) Nitrogen Oxides-NOx (NO 2 +NO) Nitric Oxide (NO) Nitrogen dioxide (NO 2 ) Carbon monoxide (CO) Carbon dioxide (CO 2 ) To keep an optimal air-fuel ratio at different loads, an automatic lambda control system can be used 1. Boiler efficiency can also be calculated with the following relation: Efficiency Actual energy consumed to produce 'x' quantity of steam x 100 (%) = Theoretical energy required to produce 'x' quantity of steam For steam monitoring, steam flow meter can be installed at the boiler. However, if installation of steam meters is not possible due to their high price, then water and gas meters can be used to measure boiler efficiency, which are relatively cheap. One cubic meter of water and 90 m 3 of natural gas at 80% combustion 1 A system for retrofitting burners with lambada control is offered under 12

17 efficiency generate about one ton of steam at 150 Psig. 13

18 8 ENERGY LOSS THROUGH BLOW DOWN 8.1 PROBLEM Blow down discharged in the environment at a very high temperature from the steam boiler contains substantial thermal energy, which is normally lost in the atmosphere. 8.2 PROPOSED ACTIONS Two types of blow downs are conducted - intermittent and continuous. The frequency of intermittent blow downs is normally three-four times a day with an estimated flow rate of 1 m 3 /day. In most of the textile mills, normal practices of blow down rate is about 13% of the boiler feed water, which is higher than the normal range of 6% to 8%, but can be as high as 10% when boiler feed water has a high solid contents. Reason for such high blow down is the higher concentration of TDS in the boiler feed water. For this one must utilize the substantial thermal energy from blow down. 14

19 9 INSTALLATION OF WATER SOFTENER/REVERSE OSMOSIS (RO) FOR PROCESS AND BOILER FEED WATER 9.1 PROBLEM Generally the groundwater is the source for process and boiler feed water in the textile mills. This water contains calcium, magnesium and other metals which have certain impacts in textile processing in terms of additional water and chemical consumption and product quality deterioration. High mineral laden water also leads towards additional energy requirements. The use of such water also results into scale formation in the machines and conveyance system which affects their life and efficiency. In case of boiler, scale formation on the heating surfaces affects the boiler efficiency and may lead to damages of the boiler tubes. To cope with the situation, boiler water conditioning chemicals are dosed in heavy quantities, which is expensive in terms that salt deposition increases at the bottom of boiler body and removed ultimately from the system through blow downs. Excessive blow downs are one of the sources from where thermal energy is lost extensively. 9.2 PROPOSED ACTIONS It is recommended to install water softener for the treatment of process and boiler feed water, mainly to remove calcium and magnesium salts. Industries facing problem for iron contents, water softener for the iron can also be considered. Major consumption of the soft water will be for boiler feed water and for preparation of following process water: Desizing Scouring Bleaching Mercerization Dyeing Printing Water Softener Ion exchange removes unwanted ions from the raw water by transferring them to a solid material, called an ion exchanger, which accepts them while giving back an equivalent number of a desirable species stored in it. The most commercial ion exchangers are synthetic plastic materials, such as copolymers of styrene and divinyl benzene. Cat ion exchanger (used to exchange cat ions of calcium and magnesium with sodium) called sodium zeolite is generally used. The ion exchanger has a limited capacity for storage 15

20 of ions, called its exchange capacity. Due to its limited capacity, ion exchanger eventually becomes depleted 16

21 of its desirable ions and saturated with unwanted ions. It is then washed with a strong regenerating solution containing the desirable species of ions (sodium chloride salt solution), and these then replace the accumulated undesirable ions, returning the exchange material to a usable condition i.e. the unwanted calcium and magnesium ions on the surface of exchanger are washed/removed by exchanging themselves with the sodium ion of salt solution during regeneration process. Zeolite softening is the oldest and the simplest of the ion exchange process. It removes hardness from water, including iron and manganese, if these constituents can be kept in the reduced ionic form. The equipment design is simple consisting of a steel shell holding the ion exchange bed and provided with piping and valves to permit the essential operations of softening, backwash, brining and rinsing. If storage capacity is provided for softened water, a single unit may be adequate for the plant needs. In larger plants, it is common to have more than one unit, so that one can be taken out of service for regeneration without interrupting the flow of soft water. Reverse Osmosis (RO) Reverse Osmosis (RO) plants are used to reduce dissolved solids in the process water. In RO, driving force, the differential pressure across the membrane, causes water to flow from the stronger solution (high TDS water) to the weaker (low TDS water). The most widely used membrane materials are cellulose acetate, triacetate and polyamide polymer. The type of the membrane has to be adapted to the particles size in the water. 17

22 10 FLAME ADJUSTABLE SINGEING MACHINE 10.1 PROBLEM Most of the textile industries have installed singeing machines with burners fixed to certain length. Grey fabric subjected to singeing treatment varies in width (from 1 to 2 meter). Fabric of any width, whether wide or small, has to pass over the full width of burners. This is due to the fact that the burners' width is fixed and can not be adjusted according to the width of the subjected fabric. This is one of the areas where substantial energy is lost PROPOSED ACTIONS It is recommended to modify the existing fixed burners of the singeing machine and convert them into adjustable form. For adjustable burners, their width will be controlled or adjusted according to the width of the fabric to be singed. Extra burners will be turned off in case shorter width fabric is subjected to singeing. 18

23 11 INSTALLATION OF HEAT EXCHANGER ON HOT WASTEWATER 11.1 PROBLEM Extensive hot washes are carried out in the textile industries to wash impurities, undesired chemicals and unfixed dyes and pigments. Hot wastewater from these washes contains substantial amounts of thermal energy which costs millions of rupees per year. These wastewater streams are discharged at a temperature of o C from various processes: Desizing wash water at 50 o C to 70 0 C Washing water discharged from kiers at 50 o C to 70 0 C Mercerization hot wash water at 50 o C to 80 0 C Soaper hot wash water at 50 o C to 80 0 C 11.2 PROPOSED ACTIONS Thermal energy from the wastewater streams should be recovered. It is not practicable to recover energy from all the wastewater streams but there are few from which energy can be recovered effectively. Major factors for evaluating the viability and effectiveness of heat transfer are the temperature and the flow of the stream under consideration. For the effective heat recovery, following are the suitable waste streams: Hot mercerization washes Hot soaper washes Hot bleaching plant washes Heat energy of the above hot washes can be recovered by installing shell and tube heat exchanger. For the implementation of this option, hot washes are first collected in a small covered storage tank. It is then pumped into the heat exchanger while passing through the strainer, in the tube side, whereas fresh water, which will be used as hot washing water, flows in the shell side. Fresh water is heated and used in the washings. Under such arrangement less quantity of steam will be required to heat up the washing water up to the required temperature as it is already pre-heated. 19

24 12 IMPLEMENTATION OF COUNTER CURRENT WASHING AT MERCERIZATION / SOAPER /.BLEACHING PLANT 12.1 PROBLEM Post mercerization/bleaching/soaper washes, which are in different numbers, consume large quantity of water and steam. Normally washing pattern is such that each wash box acts as an individual chamber where water and steam is supplied at one side and hot wastewater is discharged through overflow pipe from the other side PROPOSED ACTIONS To avoid large consumption of water and energy in the current post mercerization washes, the current washing pattern of each chamber, acting individually, will be changed to counter current sequence (one unit), which allows water and energy savings. In the counter current washing, water flow is designed in such a way that the clean fabric makes contact with the clean water and dirty fabric with the dirty water. Fresh clean water is supplied in the last box from where clean fabric comes out after washing. This water, from the last box, overflows to the next box and so on. The overflow pipes are arranged in such a way that the overflow pipe at the last box is placed at the highest level whereas it is at the lowest level at the first box. This difference in levels of overflow pipes establishes gradient by which water flows from the last box to the first. From the first box, water is discharged as wastewater. In this way, wastewater of one box is used as feed water for the next and so on. In case of hot wastewater, its energy is utilized in washing, too. 20

25 13 REUSE OF COOLING WATER 13.1 PROBLEM Fresh water is used in machines and pumps to cool mechanical seals and other moving parts in order to avoid overheating. Typical examples of this type of machinery are: Compressors Thermo oil boiler pumps Ammonia chillers After absorbing heat, cooling water is discharged as wastewater. It is a clean warm water stream which can be used at various processes. Compressors are used at a number of machines where pneumatic control is required such as rotary printing and stenters. Thermo oil boilers are used with those machines where high temperature is required, which can not be attained with saturated steam such as stenters, dryers and agers. Ammonia chiller is used to keep caustic soda at lower temperatures for the effective cold mercerization process PROPOSED ACTIONS Cooling water stream, discharged from any of the above mentioned machines, should be collected in a storage tank attached with a pump, which can be used according to the requirement at suitable machine or process. It is preferred that this water should be used for the washing of vessels, containers, machine parts etc instead of using in the process because sometimes it becomes contaminated with iron particles and oil and grease contents. 21

26 14 INSTALLATION OF TEMPERATURE GAUGES/INDICATORS ON HOT MACHINES 14.1 PROBLEM Energy monitoring is the first step in the energy management. In most of the industries, no actions have been taken to reduce energy losses by the management due to a lack of awareness about the energy conservation and its benefits. A number of areas have been identified where energy is not being monitored. Temperature is not monitored for the hot washing baths such as desizing, bleaching, scouring and dyeing processes. Workers keep on injecting steam in the baths to heat up water, even after attaining the required temperature. Since there is no temperature indication and automatic shut off valves for steam, temperature is being controlled by visual judgment. The lack of energy monitoring results in energy wastage and its excess and unnecessary use at various levels of production processes PROPOSED ACTIONS Energy monitoring and recording is the first step towards energy management. All the machines where hot water or chemical solutions are used should be fitted with temperature gauges/indicators to monitor temperature. On the basis of temperature, steam supply to these machines should be controlled. The areas where temperature indicators are required to be fitted are shown below: Desizing machine Continuous bleaching machine (Bleaching and scouring saturators) Continuous washing machine or wash boxes of continuous bleaching machine Rope washing machines Kier Open jiggers Jets Pressure jiggers 22

27 15 INSTALLATION OF WATER FLOW METERS ON WATER INLETS 15.1 PROBLEM In general, water is abundantly available and easily accessible in Pakistan. No direct cost is borne for it. Workers, in general, consider this commodity as cheap and invaluable. Even management is not much concerned about the excessive use of water in different processes, especially in washing. Mostly, these washes are continuous, where water is supplied at one end and discharged from the other. Excess use of water is not only the direct loss of natural resource but also it results into excess use of chemicals in the process vessels because most of the textile chemicals are fed in the process vessels on the basis of water quantity. If more chemicals are added in the process vessels, there will be more pollution in the washing wastewater at the end PROPOSED ACTIONS Resources can only be conserved when water consumption is the optimum in an industry. Water optimization can not be implemented without water monitoring. For water monitoring and its controlled use, water flow meters of appropriate size and types will be installed at the tube wells inlets and at all the major water utility machines and areas. 23

28 16 ELECTRICAL DISTRIBUTION SYSTEM 16.1 PROBLEM Proper electric distribution systems are important for the reduction of energy losses. The electrical power distribution system, from the source to utilization points, consists of electric lines of varying sizes, switches and circuit breakers, transformers and protective equipment. The voltage in an electric circuit will drop in proportion to the circuit resistance. Resistance varies with wire size, temperature and metallic material. When conductor losses increase, the current necessary to deliver a given amount of power increases at any point in the circuit, as power derives from the product of the voltage and current. This principle applies likewise to switches, circuit breakers and protective equipment. Generally the electrical distribution system losses are due to voltage unbalance, over and under voltage, low power factor, undersized conductors, leakage to ground, and poor connections. Losses due to poor connections represent one third of the total loses. Electrical Motors After electrical distribution system, electrical motors play an important role in the energy saving. The electric motors are the main consumers of the electricity. More than 90% of the electricity is consumed by the electric motors. Major savings of electricity can be achieved by improving the motors performance. Following are the concerns regarding electrical motor performance: - Old class III motors - Operation of motors at low load - Abnormal operation of motors Old Class III Efficiency Motors Mostly, different types of motors are installed. Some motors are purchased from the local market and some received as attached with the imported machines. The local motors are of Class III efficiency whereas for the imported motors, the efficiencies are not known. Class III efficiency motors operate at lesser efficiencies and consume more energy. Operation of Motor at Low Load When a motor has a greater rating than the machine requirement, motor operates at partial load. In this state, the efficiency of the motor is reduced. Generally oversized motors are used in the industry due to following reasons: Actual load of the machine is not known and electrician s select oversized motor to be on the safe side. Designers and suppliers of the machines want to ensure that their units have ample power so they suggest a driver that is substantially 24

29 larger than the real requirement When replacement of motor is required and if there is no exact rating motor available in the industry, electricians install the next larger motor available in the store. Later on, when correct sized motor is purchased, they do not replace it and oversized motor continues to be in use. A large motor is selected for some unexpected increase in the driven equipment load which is not materialized. Process requirements are reduced but oversized motors are not replaced. Abnormal Operation of Electrical Motors Sometimes motors consume more energy due to their abnormal operation. It should be in the mind of maintenance crew and the electricians that the smooth energy transfer from one form to other like electricity to the output shaft speed, belt transmission etc. should not produce abnormal heating, heavy noise, spark etc. Spark in motors is produced in case of contactor switching, loose joints etc. Heat is produced in motors due to friction, metal to metal touch, poor lubrication and misalignment. Sound is produced from the equipment in the form of vibration, mounting on bed, noise from belts, bearings, metal to metal contact etc. In case, faulty motors are kept on running, these will consume much energy. Motors bearings and their alignment play an important part in their abnormal operation. In more than 50% cases, the failure of motor is a mechanical cause due to improper alignment and the failure of bearings PROPOSED ACTIONS Maintenance of Transformer It is recommended priority for the maintenance of transformers. Generally 3% transformer losses are unavoidable whereas about 1-2% losses can be reduced by good transformer maintenance. Efficiency of the transformer is affected when transformer oil is hydrated (absorbs moisture), which requires dehydration for the moisture removal. Proper placement with clean surrounding is also necessary. Energy Efficient Motors Energy efficient motors are available from a broad selection of companies. These motors are the class I and class II motors. Comparative efficiencies are given in Table. Efficient motors save energy. Presently class I motors are not available in the Pakistan. These will have to be imported and become very expensive when taxes are added in their prices. Class II efficiency motors are manufactured by Siemens and ABB. Replacing old efficiency class III motors by class II will save energy. However, it is not wise to replace all the old motors but in stages like when one old motor is out of 25

30 order, it could be replaced. 26

31 Comparison of Motor Efficiency Efficiency of Different Class Motors kw EFF3 EFF2 EFF1 1.1 < 76.2 >= 76.2 >= < 78.5 >= 78.5 >= < 81.0 >= 81.0 >= < 82.6 >= 82.6 >= < 84.2 >= 84.2 >= < 85.7 >= 85.7 >= < 87.0 >= 87.0 >= < 88.4 >= 88.4 >= < 89.4 >= 89.4 >= < 90.0 >= 90.0 >= < 90.5 >= 90.5 >= < 91.4 >= 91.4 >= < 92.0 >= 92.0 >= < 92.5 >= 92.5 >= < 93.0 >= 93.0 >= < 93.6 >= 93.6 >= < 93.9 >= 93.9 >= 95.0 Removal of Oversized Motors First of all, plant management should ensure that the over sized motors are not used in the plant. For that, regular motor load monitoring will have to be carried out for all the motors at different production loading. The recording wattmeter is the most useful instrument for this purpose to analyze the load over a representative period of time. Also, management must ensure that the factors mentioned due to which over sized motors are installed, should be avoided. Replacement of under loaded motors with smaller motors will allow a fully loaded smaller motor to operate at higher efficiency. This arrangement is generally most economical for larger motors, and only when they are operating at less than one third to one-half capacity. Larger motors are typically installed at the filters and air conditioning units. Maintenance of Motors and Equipment A reduction in motor load is one of the best means of reducing electricity costs. Proper maintenance of equipment will also reduce motor load by eliminating friction losses from such sources as the misalignment of equipment and belt drag. Proper lubrication of all moving parts such as bearings and chain drives will minimize friction losses. 27

32 Motor cooling fans should also be of proper size because these also consume energy. Though these are fitted with the motors by the manufacturer, still their working can be monitored and can be improved and adjusted if required. Motors maintenance includes: Regular checking of motor load Timely oiling and lubrication Appropriate ventilation Cleaning of motor body Monitoring of motors with regard to noise, vibration and heating Frequent alignment checking It is recommended that the mechanical and electrical staff should have the checklist for regularly monitoring the maintenance and upkeep of motors. Placement of Inverters on Motors For those machines operating at variable loads, it is recommended that the inverters should be placed on them to save energy. Inverters should be compatible with the motors. Most of the old motors can not be operated with the inverters. Where inverters are placed, high peak voltages can be experienced at the motor terminals especially when the distance between the inverter (drive) and the motor exceeds about 15 meters. Some additional heating to the motor windings will inevitably occur because of the inverter's "synthesized" AC wave form. In case, motors are very old then the first choice should be to replace them, one by one, if it is feasible. It is not advisable to invest on older motors and place inverters. The best use of inverter is for variable flow applications. In case of air conditioning plants, the flow is changed by changing the angles of the fans. When the flow is reduced, motor takes less amperes but it operates at less efficiencies. The better way to control the flow is through changing the speed of motor by using frequency inverters. 28

33 17 COMPRESSED AIR SYSTEM 17.1 PROBLEM Most of the industries are using piston type compressors but screw type is more efficient. Comparison of Reciprocating and Screw Type Compressors Generally piston type compressors are not considered energy efficient as compared with rotary type compressors. Piston type compressors have 8-10 compression parts in comparison with 2-4 compression parts of the screw type compressors. The energy and cost savings are dependent on the size of the compressor, the load factor, and the number of hours during which the compressor is used. The load factor is the average fraction of the rated load at which the compressor operates. The load factor is fairly constant for compressors that operate only when they are actually compressing air. Most reciprocating compressors are operated in this manner. When on, they operate with fairly constant power consumption, usually nearly equal to their rated power consumption; when they are cycled off, the power consumption is zero. Screw compressors are often operated in a different manner. When loaded (i.e. actually compressing air), they operate near their rated power, but when compressed air requirements are met, they are not cycled off but continue to rotate and are unloaded. Older screw compressors may consume as much as 85% of their rated power during this unload state. Therefore, if a screw compressor is to be operated continuously, it should be matched closely to the compressed air load that it supplies. Often, plant personnel purchase compressors having several times the required power rating. This may be done for variety of reasons, but often in anticipation of expansion of the facility and a commensurate increase in the compressed air requirements. Pressure Gauges Mostly pressure gauges are not installed on the machines or even if installed then they might not be calibrated. Auto Drains Mostly, no auto drain is installed in any of the receiver tanks of the compressors to control compressed air quality. Due to this, air moisture is not removed effectively. Air Leakages Air leaks around valves and fittings in compressor air lines may represent a significant energy cost for the mill. Sometimes up to 20% of the work done by the compressor is to make up for air leaks. The energy loss as a function of the hole diameter at an operating pressure of 6-7 bar is shown in Table 29

34 Hole Diameter (mm) Energy Loss from air Leaks Energy Wasted per Leak (kwh/h) Free Air Wasted (m3/year)by a Leak of Air at 7 bar 9.5 2,500, ,100, , , , Mostly, for cleaning compressed air is used through large 8.5 mm diameter pipe, resulting into energy losses PROPOSED ACTIONS Pressure Monitoring It is recommended to install pressure gauges at all the lines to monitor pressure and assess the areas where pressure drops occur. There should be the calibrated gauges. Delivery temperature should also be checked in accordance with the manufacturer specifications at specified pressure to know the efficient working of the compressor. Air Leakages Maintenance crew should survey the air distribution system and identify all the leaking points. These points should immediately be rectified to avoid energy losses. This measure does not require investment. Cleaning Points For reducing air consumption, it is recommended that the pipes of 8.5 mm diameter or more, used for the air cleaning, should be replaced with the 6 mm diameter with air guns. It will allow reduction in air use and ultimately the energy consumption. Investment for this measure is nominal. Air Quality Use of moist air in the machines and the compressor affects their performance. Manual bleeding off the receiver tanks is not a good practice as it wastes too much compressed air. It is recommended to install auto bleeders on these tanks to avoid this loss. For the better quality air, management should also use dryers and line filters. Alternate Compressor Option It is recommended to replace piston type compressors with screw type. Excess pressure results in higher leakages and degraded compressor 30

35 performance. 31

36 18 LIGHTING 18.1 PROBLEM Magnetic Ballasts In most of the units 40/36 watts tube lights are used. These tube lights consume more energy as compared with the 36/28 watts tube lights with the same lumens. These tube lights are attached with the conventional magnetic ballasts which are not considered energy efficient. These ballasts waste energy in heat and noise PROPOSED ACTIONS Effective Lighting Generally, two most common causes of lighting energy waste are excessive illumination levels and failure to locate fixtures in relation to the activity area. It will be helpful in improving lighting intensity if more lights are placed over the machines not on that places like aisle and idle places. Lighting can also be improved by reducing the height of the tube lights fixtures. Electronic Ballasts It is recommended to replace 40 watts tube lights with the 36 watts lights to reduce electricity consumption. Tube light of 36 watts is available in two types with different lumens. Detail of 40 and 36 watts tube lights is given in Table. Detail of Tube Lights Typeof Tube Light Lumens Lamp life (Hours) Unit Price (Rs) TL 40 Watt 2,500 6, TLD 36/54 Watt 2,650 13, TLD 36/80 Watt 3,350 15, watt tube light with ballast consumes about 52 watts whereas 36 watts tube light with ballast consumes 44 watts i.e. 10 watts less. About Rs. 150 can be saved per year per tube light by replacing 40 watts tube light with 36 watts. It is also recommended to replace conventional magnetic ballasts with the efficient electronic ballasts for the tube lights. By replacing magnetic ballasts with electronic ballast, up to14 watts can be saved per ballast. The cost of the electronic ballast (EB-E) is Rs For effective lighting, following are the recommendations: Turn off the lights during break hours or when no body is present at work place 32