Energy Audit

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PT. PLN (PERSERO)

PUSAT PENDIDIKAN DAN PELATIHAN ENERGY AUDIT

1. ENERGY AUDIT

1.1 Types and Methodology

Energy Audit is the key to a systematic approach for decision-making in the area of energy management. It attempts to balance the total energy inputs with its use, and serves to identify all the energy streams in a facility. It quantifies energy usage according to its discrete functions. Power station energy audit is an effective tool in defining and pursuing comprehensive energy management programme.

Energy Audit is defined as "the verification, monitoring and analysis of use of energy including submission of technical report containing recommendations for improving energy efficiency with cost benefit analysis and an action plan to reduce energy consumption".

1.1.1 Need for Energy Audit

In any power station, the three top operating expenses are often found to be energy (both electrical and thermal), labour and materials. If one were to relate to the manageability of the cost or potential cost savings in each of the above components, energy would invariably emerge as a top ranker, and thus energy management function constitutes a strategic area for cost reduction.

Energy Audit will help to understand more about the ways energy and fuel are used in any power station, and help in identifying the areas where waste can occur and where scope for improvement exists.

The Energy Audit would give a positive orientation to the energy cost reduction, preventive maintenance and quality control programmes which are vital for production and utility activities. Such an audit programme will help to keep focus on variations which occur in the energy costs, availability and reliability of supply of energy, decide on appropriate energy mix, identify energy conservation technologies, retrofit for energy conservation equipment etc.

In general, Energy Audit is the translation of conservation ideas into realities, by lending technically feasible solutions with economic and other organizational considerations within a specified time frame.

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The primary objective of Energy Audit is to determine ways to reduce energy consumption per unit of product output or to lower operating costs. Energy Audit provides a " bench-mark" (Reference point) for managing energy in the organization and also provides the basis for planning a more effective use of energy throughout the organization.

Why Conduct Energy Audits?

o Management may be too busy with day-to-day operations to look for efficiencies. o Management may not recognize a need for change.

o Management may not have the tools or resources to capture the insights and ideas of employees.

o Management may need the auditor’s analysis and objective report to sell changes to upper management.

Financial vs. Compliance vs. Operational

Financial Compliance Operational

Objective: Assess the fairness of financial

statements

Determine the adherence to policies, procedures, laws and regulations

Evaluate and improve the effectiveness, efficiency, and economy of operations

Primarily for: Stockholders Regulators Management

Audit Direction: Looking back Looking back Looking present and to the future Audits based on: Financial reporting objectives, such as GAAP Corporate standards of business conduct; internal policies; specific laws and regulations

Mission, vision and objectives of the organization and its management

Examples: Annual audits performed by public accountants

Contract audits; Environmental audits

All other audits, such as those of depart-ments, processes, information systems

1.1.2 Type of Energy Audit

The type of Energy Audit to be performed depends on:  Function and type of power station

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 Depth to which final audit is needed, and

 Potential and magnitude of cost reduction desired

Thus Energy Audit can be classified into the following two types. i. Preliminary Audit

ii. Detailed Audit

1.1.3 Preliminary Energy Audit Methodology Preliminary energy audit is a relatively quick exercise to:

• Establish energy consumption in the organization • Estimate the scope for saving

• Identify the most likely (and the easiest areas for attention

• Identify immediate (especially no-/low-cost) improvements/savings • Set a 'reference point'

• Identify areas for more detailed study/measurement

• Preliminary energy audit uses existing, or easily obtained data

1.1.4 Detailed Energy Audit Methodology

A comprehensive audit provides a detailed energy project implementation plan for a facility, since it evaluates all major energy using systems.

This type of audit offers the most accurate estimate of energy savings and cost. It considers the interactive effects of all projects, accounts for the energy use of all major equipment, and includes detailed energy cost saving calculations and project cost.

In a comprehensive audit, one of the key elements is the energy balance. This is based on an inventory of energy using systems, assumptions of current operating conditions and calculations of energy use. This estimated use is then compared to utility bill charges.

Detailed energy auditing is carried out in three phases: Phase I, II and III. - Phase I - Pre Audit Phase

- Phase II - Audit Phase - Phase III - Post Audit Phase

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A Guide for Conducting Energy Audit at a Glance

Power station-to-power station, the methodology of Energy Audits needs to be flexible. A comprehensive ten-step methodology for conduct of Energy Audit at field level is presented below. Energy Manager and Energy Auditor may follow these steps to start with and add/change as per their needs and power station types.

Ten Steps Methodology for Detailed Energy Audit

Step no. PLAN OF ACTION PURPOSE/RESULTS

Phase I - Pre Audit Phase

Step - 1

- Plan and organize - Walk through audit - Informal overview with

Energy Manager,

Production/Plant Manager

• Resource planning, Establish/organize an Energy Audit Team

• Organize instruments and time frame

• Macro data collection (suitable to type of power plant)

• Familirization of process/plant activities) • First hand observation &assessment of current

level operation and practices

Step - 2

- Conduct of brief meeting/ awareness programme with all divisional heads and persons concerned

• Building-up cooperation

• Issue questionnaire for each department • Orientation, awareness creation

Phase II - Audit Phase

Step - 3

- Primary data gathering - Process Flow Diagram - Energy Utility Diagram

• Historical data analysis, Baseline data collection • Prepare process flow charts

• All service utilities system diagram (ex. Single Line power distribution diagram, water, steam and compressed air distribution)

• Design, operating data and schedule of operation • Annual Energy Bill and energy consumption

pattern (refer to Manual, Log sheet, name plate, interview)

Step - 4

- Conduct survey and monitoring

• Measurements:

Motor Survey, Insulation and Lighting Suevey with portable instrumens for collection of more and accurate data. Confirm and compare operating data with design data.

Step - 5 - Conduct of detailed trials/

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energy guzzlers - 24 hours power monitoring (PF, kWh etc.) - Load variation trends in pumps, fan,

compressor etc.

- Boiler /Efficiency trials for 4 ÷ 8 hours - Furnace Efficiency trials

- Equipment Performance experiments etc. Step - 6 - Analysis of energy use • Energy and Material Balance Analysis

• Energy loss/waste analysis

Step - 7

- Identification and development of energy conservation (ENCON) opportunities

• Identification & consolidation ENCON measures • Conceive, develop and refine ideas

• Review the previous ideas suggested by unit personil

• Review the previous ideas suggested by energy audit, if any

• Use brainstroming and value analysis techniques. • Contact vendors for new/efficient technology

Step - 8 - Cost benefit analysis

• Assess technical feasibility, economic viability ENCON options for implementation

• Select the most promizing projects

• Prioritise by low, medium, long term measures Step - 9 - Reporting & Presentation to

the Top Management.

• Documentation, Report Presentation to the Top Management.

Phase III - Post Audit Phase

Step - 10

- Implementation and Follow-up

Assist and Implement ENCON recommendation measures and Monitor the performance

• Action Plan, Schedule for Implementation • Follow-up and periodic review

Phase I - Pre Audit Phase Activities

A structured methodology to carry out an energy audit is necessary for efficient working. An initial study of the site should always be carried out, as the planning of the procedures necessary for an audit is most important.

Initial Site Visit and Preparation Required for Detailed Auditing

An initial site visit may take one day and gives the Energy Auditor/Engineer an opportunity to meet the personnel concerned, to familiarize him with the site and to assess the procedures necessary to carry out the energy audit.

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During the initial site visit the Energy Auditor/Engineer should carry out the following actions: - • Discuss with the site's senior management the aims of the energy audit.

• Discuss economic guidelines associated with the recommendations of the audit. • Analyse the major energy consumption data with the relevant personnel.

• Obtain site drawings where available - building layout, steam distribution, compressed air distribution, electricity distribution etc.

• Tour the site accompanied by engineering/production The main aims of this visit are: -

• To finalise Energy Audit team

• To identify the main energy consuming areas/plant items to be surveyed during the audit. • To identify any existing instrumentation/ additional metering required.

• To decide whether any meters will have to be installed prior to the audit eg. kWh, steam, oil or gas meters.

• To identify the instrumentation required for carrying out the audit. • To plan with time frame

• To collect macro data on plant energy resources, major energy consuming centers • To create awareness through meetings/ programme

Phase II- Detailed Energy Audit Activities

Depending on the nature and complexity of the site, a comprehensive audit can take from several weeks to several months to complete. Detailed studies to establish, and investigate, energy and material balances for specific plant departments or items of process equipment are carried out. Whenever possible, checks of plant operations are carried out over extended periods of time, at nights and at weekends as well as during normal daytime working hours, to ensure that nothing is overlooked.

The audit report will include a description of energy inputs and product outputs by major department or by major processing function, and will evaluate the efficiency of each step of the process. Means of improving these efficiencies will be listed, and at least a preliminary assessment of the cost of the improvements will be made to indicate the expected payback on any capital investment needed. The audit report should conclude with specific recommendations for detailed engineering studies and feasibility analyses, which must then be performed to justify the implementation of those conservation measures that require investments.

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The information to be collected during the detailed audit includes: -

a. Energy consumption by type of energy, by department, by major items of process equip ment, by end-use

b. Material balance data (raw materials, intermediate and final products, recycled materials, use of scrap or waste products, production of by-products for re-use in other industries, etc.)

c. Energy cost and tariff data

d. Process and material flow diagrams

e. Generation and distribution of site services (eg.compressed air, steam). f. Sources of energy supply (e.g. electricity from the grid or self-generation)

g. Potential for fuel substitution, process modifications, and the use of co-generation systems (combined heat and power generation).

h. Energy Management procedures and energy awareness training programs within the establishment.

Existing baseline information and reports are useful to get consumption pattern, production cost and productivity levels in terms of product per raw material inputs. The audit team should collect the following baseline data:

- Technology, processes used and equipment details - Capacity utilisation

- Amount & type of input materials used - Water consumption

- Fuel Consumption

- Electrical energy consumption - Steam consumption

- Other inputs such as compressed air, cooling water etc - Quantity & type of wastes generated

- P ercentage rejection/reprocessing - Efficiencies/yield

1.2 Data Collection Hints

It is important to plan additional data gathering carefully. Here are some basic tips to avoid wasting time and effort:

• measurement systems should be easy to use and provide the information to the accuracy that is needed, not the accuracy that is technically possible

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• measurement equipment can be inexpensive (flow rates using a bucket and stopwatch) • the quality of the data must be such that the correct conclusions are drawn (what grade of

product is on, is the production normal etc)

• define how frequent data collection should be to account for process variations.

• measurement exercises over abnormal workload periods (such as startup and shutdowns) • design values can be taken where measurements are difficult (cooling water through heat

exchanger)

“DO NOT ESTIMATE WHEN YOU CAN CALCULATE DO NOT CALCULATE WHEN YOU CAN MEASURE”

1.2.1 Draw process flow diagram and list process steps; identify waste streams and obvious energy wastage

An overview of unit operations, important process steps, areas of material and energy use and sources of waste generation should be gathered and should be represented in a flowchart as shown in the figure below. Existing drawings, records and shop floor walk through will help in making this flow chart. Simultaneously the team should identify the various inputs & output streams at each process step.

1.2.2 Identification of Energy Conservation Opportunities

Fuel substitution: Identifying the appropriate fuel for efficient energy conversion

Energy generation: Identifying efficiency opportunities in energy conversion equipment/utility such as captive power generation, steam generation in boilers, fluid heating, minimum excess air combustion with boilers, optimising existing efficiencies, efficienct energy conversion equipment, biomass gasifiers, Cogeneration etc.

Energy distribution: Identifying Efficiency opportunities network such as transformers, cables, switchgears and power factor improvement in electrical systems and chilled water, cooling water, hot water, compressed air, Etc.

Energy usage by processes: This is where the major opportunity for improvement and many of them are hidden. Process analysis is useful tool for process integration measures.

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1.2.3 Technical and Economic feasibility

The technical feasibility should address the following issues:

• Technology availability, space, skilled manpower, reliability, service etc

• The impact of energy efficiency measure on safety, quality, production or process. • The maintenance requirements and spares availability

The Economic viability often becomes the key parameter for the management acceptance. The economic analysis can be conducted by using a variety of methods. Example: Pay back method, Internal Rate of Return method, Net Present Value method etc. For low investment short duration measures, which have attractive economic viability, simplest of the methods, payback is usually sufficient. A sample worksheet for assessing economic feasibility is provided below:

1.2.4 Classification of Energy Conservation Measures

Based on energy audit and analyses of the plant, a number of potential energy saving projects may be identified. These may be classified into three categories:

i. Low cost - high return;

ii. Medium cost - medium return; iii. High cost - high return

Normally the low cost - high return projects receive priority. Other projects have to be analyzed, engineered and budgeted for implementation in a phased manner.

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Projects relating to energy cascading and process changes almost always involve high costs coupled with high returns, and may require careful scrutiny before funds can be committed. These projects are generally complex and may require long lead times before they can be implemented. Refer Table 3.1 for project priority guidelines.

1.3 Energy Audit Reporting Format

After successfully carried out energy audit energy manager/energy auditor should report to the top management for effective communication and implementation. A typical energy audit reporting contents and format are given below. The following format is applicable for most of the industries. However the format can be suitably modified for specific requirement applicable for a particular type of power station.

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PUSAT PENDIDIKAN DAN PELATIHAN COAL HANDLING PLANTS

2. COAL HANDLING PLANTS

2.1 Background

Coal handling plant is one of the important energy consumers in thermal power plants and contains the following energy consuming equipments:

• Crushers • Conveyors • Feeders • Tipplers

• Stacker-reclaimer

2.2 Steps Involved In Conducting The Energy Audit

The energy audit in coal handling plant should emphasise on evaluating specific energy consumption and capacity utilisation and compare with design/PG values pertaining to following

• Overall CHP • Stage wise

• Equipment wise which include conveyor belts, paddle feeders, crushers, vibro feeders, belt feeders, wagon tippler, stacker, reclaimer etc.,

The steps involved in conducting energy audit of coal handling plant are: • Data collection

• Observations and Analysis of - Drives Speed

- Belt tension - Condition of rollers - Condition of belts

- Loading of belts with respect to design value.

- Loss of energy in the coal lying in stockyard due to auto ignition. - System capacity utilization. (To be pushed back)

• Exploration for energy conservation measures • Report preparation

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2.3 Data Collection

2.3.1 Specification Of Coal Handling Plant

Collect the detailed design specifications of coal handling plant, pertaining to the following equipments:

• Design details of overall coal handling plant (Capacity, specific power consumption, etc) • Process flow diagram/Schematic diagram of coal handling plant and description of

system configuration which includes details about different routes (direct bunkering, stacking, reclaiming route, etc) of the key equipment

• Track hopper (Number of track hoppers, length of hopper, capacity, power, capacity, schematic layout, etc)

• Paddle feeders – Ploughs (No of feeders, capacity of each feeder, travel speed, power, etc)

• Wagon tippler details (Number of tipplers, type, capacity, maximum weight of handling, tippler time cycle, number of clamps, motor rating of each tippler)

• Crusher specifications (No. of crushers, type of crushers, Capacity, Maximum coal size at the inlet and outlet, motor rating, power consumption, number of vibrating feeders, etc)

• Coal design parameters and sizes

• Belt conveyers (capacity, number, speed, width, application, motor rating, power consumption)

• Stacker reclaimer (quantity, capacity of reclaimer, travel speed, number of buckets and length of boom, motor rating for travel, slew, bucket wheel, boom conveyor, etc)

• Other equipments – i.e. vibrating feeders, dust suppression system pumps, belt feeder, dust extraction fans, etc

• Compile the Design / PG test values for the above mentioned equipments. The key specification parameters shall be complied as shown below (Refer: Table 2-1)

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Table 2-1 : Key Specification parameters

2.3.2 System data collection

Collect last one year data, month wise given in the Table 2-2 and also for day wise for a period of two/ three weeks when plant is under normal operation.

Table 2-2 : Production and operating data

Parameter Unit

Total coal receipt Lakh tons

Total electrical related load MW

Overall operating load MW

Energy consumption of CHP kWh

Plant equipment operating hours Hrs

Plant utilization factor Hrs

Total gross generation of station MU

Total auxiliary power consumption of the station MU

Equipment reference Capacity Motor input power, kW Speed of driven equipment (rpm or linear) Length (in case of belts) Hours of operation Specific energy consumption Paddle Feeders TPH Belt conveyors TPH Vibro feeders TPH Grizzly feeders TPH Belt feeders TPH Dust extraction fans NM 3 /h Dust suppression system pumps M 3 /h Crusher TPH Stacker reclaimer Other equipment

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Total power consumption by the CHP plant %

% of power consumption of CHP with respect to total auxiliary power

consumption MU

Specific energy consumption, KWh/MT

Equipment wise operating hours 1. 2. 3. 4. 5. 6. 7. 8.

Collect the parameters for coal as given in the Table 2-3. Table 2-3 : Coal Parameters

Unit Design Actual Remarks

Fixed carbon %

Volatile matter %

Moisture %

Ash %

Grindability HGI

Coal calorific value -HHV Kcal/kg Size of the coal to mill mm Total contract fuel fired tph

2.4 Instruments Required

The following instruments are required for conducting the energy audit of coal handling system. • Power Analyzer: for measurement of an electrical parameters such as kW, kVA, pf, V, A

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• Stroboscope: To measure the speed of the driven equipment and motor • Tensiometer

• On line instruments – (calibrated) for coal transfer rates, production, etc

2.5 Measurements & Observation To Be Made

While conducting the audit, the following measurements and observations are necessary: • Equipment operations and throughput, power consumption, loading, comparison with PG

test / design, condition, etc

• Power consumption of the equipments • Drive speed

• Belt speed

• Condition of rollers • Condition of belts

• Loading of belts with respect to the design

• Loss of energy in the coal in stack yard due to auto ignition • Input coal parameters

• Unit load of the plant

• Date & time of measurement • Instruments used for measurement • Frequency of the measurement

2.6 Observations And Analysis

2.6.1 System Familiarisation And Operational Details

Detailed interactions with the plant personnel have to be carried out to get familiarisation for system detail and operational details. Pre visit can be made to get familiarisation with CHP configuration, particularly different routes such as bunkering mode, stacking mode and reclaiming mode.

2.6.2 Measurements & Evaluation a. Power parameters:

Measure the power input i.e. electrical parameters such as kW, kVA, Current, Voltage, power factor, for all drives for no load and load conditions

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b. Coal throughput rate:

Study track hopper management/coal unloading. It is also desired to study time-motion study. Note the coal throughput using coal totalisers or other alternative methods.

c. Evaluation of equipment loading and specific energy consumption

• Determine equipment wise % loading (i.e. actual TPH / rated TPH) as well as the motor % loading (i.e. Actual kW / Rated kW)

• Also make a table (as shown in Table 2-4), for each of the euipment and their actual & design electrical parameters like KW, PF, V, A. Also provide remarks and calculations. • Obtain operating hours

• Operational constrains to achieve the optimum loading

Table 2-4 : Power Consumption & Throughput

Direct Bunkering (Rated capacity …….tph, Average capacity ………tph, hour operation ….) Equipment Rated

kW No load Average load

Specific Energy Consumption No load Average Rated

A kW A kW kW /MT kW /MT kW /MT

Remarks on throughput, condition, power consumption, operating hours, operational controls for energy efficiency, specific energy consumption, operational constrains etc.

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Reclaiming (Rated capacity …….tph, Average capacity ………tph, operating hours ….) Equipment Rated

Stacking (Rated capacity …….tph, Average capacity ………tph, hour operation ….) Equipment Rated

d. Calculation of Specific Energy Consumption

• Calculate kW /MT for existing operations i.e. bunkering, stacking, and reclaiming both activity wise & equipment wise for last one year for each CHP.

• Based on energy meter reading & coal receipt data, calculate month wise kWh / MT for last one year.

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e. Coal Sample Analysis

Send 2-3 samples of coal taken from the belts feeding to the crushers for sieve analysis to determine extent of coal particles below 20 mm size.

f. Drive Speed Analysis & Belt Tension

• Measure drive speed N1 (with the help of tachometer), Diameter of drive and driven pulley (D1 and D2.

• Calculation theoretical value of

driven rpm (N2) : N1D1 = N2D2

• Measure actual driven rpm (Na) by tachometer. • Calculate liner speed of the belt (Sb)

• Sb = p D2N2

• Measure actual linear speed of belt (Sa) • Calculate slip = Sb -Sa

• Tolerances of slips should be < 4% for conveyor belts. • Recommendations may be made accordingly.

g. Lub Oil Inspection

• Collect the lube oil sample. • Get the sample analysed.

• If the metal traces are found beyond permissible limits, recommend for complete oil change or inspection of bearings / Gear internals.

h. Performance of Crushers

• Observe and compare the operation of crushers and its throughput, hours of operation, power consumption, etc

• Carryout the sieve analysis and compare with the design or optimum values

Sieve size (mm) -20 mm -25 mm + 25 mm

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2.6.3 Study of coal feeding circuits

Study the different coal feeding circuits routes. The details of feeding circuits of coal handling system to be given in the report along with the specifications and schematic layout indicating equipments.

Comparative study of various coal feeding circuits has to be made. The measured and calculated specific energy consumption data for these circuits need to be compiled and compared. The merit order studies for energy consumption of various paths, which indicates scope for energy conservation, need to be identified.

2.6.4 Exploration of energy conservation possibilities

While conducting the energy audit of the CHP, the following need to be explored in detail to arrive at an appropriate energy conservation measures.

• Performance improvement options:

- Possibilities in Improving the throughput - Reduce the idling time

- Increase the loading

- Modifications and changes in coal feeding circuits - Need for automation and controls

• Explore Installation of power saver device in major LT motors. (Conveyor belt etc.): Major HT /LT motors i.e. conveyors, crushers etc. are often partially loaded & also there is frequent starts /stops. Explore the possibility of providing power saver devices (soft starters) in major motors.

• Power factor correction possibility: Induction motors are characterized by power factors less than unity, leading to lower overall efficiency (and higher overall operating cost) associated with a plant’s electrical system. Capacitors connected in parallel with the motor are typically used to improve the power factor. The impacts of PF correction include KVA demand (and hence reduced utility demand charges), reduced I2R losses in cable upstream of capacitor (and hence reduced energy charges), reduced voltage drop in cables (leading to improved voltage regulation), and an increase in the overall efficiency of the plant electrical system.

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• Explore the possibility of using chemicals for reduced water spray: Mixing of chemical compounds in water for suppression of dust provides much better atomization of water spray, by way of reduction in surface tension of water. Thus for the given application of dust suppression, lesser quantity of water is sprayed which also results into lesser wastage of latent heat in the steam generator.

• Maximum Mechanical Handling: Minimum Bulldozing: Sequence of coal handling operations like receipt, unloading, stacking and reclaiming and the selection of machinery is to be made in such a way that all the handling operations are accomplished without the use of semi mechanized means like bulldozers which are more energy intensive equipments. However Principal of “FIRST IN FIRST OUT” is to be adopted for coal receipt & consumption and at any time coal need not to be stocked in yard for more than incubation period (duration between coal mined and getting self ignited)

• Reduced Number of Fillings: Live storage capacity of raw coal bunkers and the filling pattern of bunkers is so planned that 24 hours coal requirement of the generating units is met by not more than two fillings per day. This will eliminate frequent starting and stopping of the CHP

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PUSAT PENDIDIKAN DAN PELATIHAN BOILER

3. BOILER

3.1 Background

In a thermal power plant, boiler is used to produce steam at the high pressure and temperature required for the steam turbine that drives the electrical generator. The Boiler has Furnace, Steam drum, Super heater coils, Reheater coils, Economizer and Air Pre Heaters. The air and flue gas path equipment include Forced draft fan (FD), Induced draft fan (ID),Air pre heaters (APH),Boiler furnace, fan, fly ash collectors (Electrostatic precipitator or bag house) and the flue gas stack. Brief schematic diagram of a typical Pulverized Coal fired subcritical Boiler is given in the Figure 3-1.

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The brief specifications of a typical boiler used in 210 MW plant is given in the Table 3-1 Table 3-1 : Brief specifications of Boiler

In addition to the above, there are several other important specifications, which are discussed later. Conducting energy audit of boiler is a very complex activity involving several measurements and observations; hence the study should be comprehensive and include all the aspects, pertaining to:

• Boiler aspects

• Coal quality - composition and calorific value • Coal milling aspects

• Combustion and excess air • Reheaters

• Heat recovery units – Economizers, air preheaters, etc. • Insulation aspects

• Boiler blow down aspects • Soot blowing aspects

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• Operation and maintenance features which affect the energy efficiency • Condition & status of boiler and their internals

• Feed water system aspects • Air and flue gas system aspects • Several others

3.2 Steps Involved In Conducting the Energy Audit

The steps involved in conducting energy audit of boiler are:

• Data collection

• Observations and Analysis

3.3 Data Collection

The first step in energy audit of boiler is to collect the design/PG test parameters pertaining to boiler, economiser, air preheaters, coal and coal milling, soot blowing and other key associated equipments.

The following data sheets give brief specifications to be collected. It is suggested to obtain the comprehensive technical specifications of boilers and its associated equipment.

3.3.1 Specifications of boiler and associated equipment a. Boiler

Collect the detailed design specifications of the boiler. The following Table 3-2 gives the list of specifications to be collected for energy audit study in addition to following specific details.

b. Economiser

Collect the specifications given in the Table 3-3 for economiser. c. Air preheater

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Table 3-2: Design Specifications of boiler

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Table 3-4: Specifications of air preheater (APH)

Collect the parameters for exhaust gas as given in the Table 3-5: Table 3-5: Exhaust gas temperature profile

Collect the parameters for coal as given in the Table 3-6: 6. Table 3-6: Coal parameters

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Collect the heat balance parameters of the boiler (as shown in Table 3-7:7) Table 3-7: Heat balance of Boiler

Collect the recommended feed water limits (as shown in Table 3-8 :).

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Collect the design specifications of mill and burner performance (as shown in Table 3-9: 9). Table 3-9: Mills and Burners Performance

In addition to the above collect the individual mill specifications and design coal parameters: Mill specifications:

Type of mill: Make :

Capacity : __________tph at coal ________grind Fineness : ___________% through ________mesh Motor rating :____________kW

Motor voltage :________ V No of mills :__________

Running /Standby :_________/________ Design coal parameter

Moisture :_____% Ash :_____%

Volatile matter :_____% Fixed carbon :______% HGI :_____%

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Collect the information of soot blowers (Table 3-10: 10). Table 3-10: Soot blowers

3.4 Instruments Required

The following instruments are required for conducting the boiler energy audit.

• Power Analyser: Used for measuring electrical parameters such as kW, kVA, pf, V, A and Hz

• Temperature Indicator & Probe

• Stroboscope: To measure the speed of the driven equipment and motor • Sling hygrometer or digital hygrometer

• Anemometer

• Available On line instruments at the site ( Calibrated )

• Digital Manometer of suitable range and appropriate probes for measurement of pressure head and velocity head.

• Additional pressure gauges with appropriate range of measurement and calibrated before audit.

• Flue gas analysers / orsat apparatus • Infrared pyrometers

• Pressure gauges

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3.5 Measurements & Observations to Be Made

While conducting the audit, the following measurements and observations are necessary • Average GCV of coal

• Coal composition – ultimate and proximate • Coal consumption details

• Performance parameters of coal mills • Heat rate- kcal/kWh

• Steam parameters of main steam, reheat, super heater, LTSH (flow, • pressure and temperature)

• Air – flow, temperature, pressures

• Flue gas – Flow, temperature and pressure • Flue gas analysis

• Coal consumption pattern • Ambient temperature • Boiler loading

• Motor electrical parameters (kW, kVA, Pf, A, V, Hz, THD) • Surface temperatures of insulation and boiler surfaces • Unburnt composition

While conducting the measurement or performance evaluation any system simultaneously the following need to be noted

 Unit load of the plant

 Date & time of measurement  Instruments used of measurement  Frequency of the measurement

3.6 Observations and Analysis

3.6.1 System familiarization and operational details

Detailed interactions with the plant personnel have to be carried out to obtain familiarisation of system and its operational details. The brief details of the system have to be given in the report along with the specifications.

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During the familiarization, boiler, plant key performance data has to be collected pertaining to the following:

• Availability factor PLF

• Coal consumption (tons and kg/kWh) • Oil consumption in ml/kWh

• Boiler efficiency • Others

During the familiarization on power plant and its operation, plants observation and past data should be obtained pertaining to the :

• Past performance trends on boiler loading, operation, PLF, efficiency

• Major constrain in achieving the high PLF, load or efficiency (Input from plant personnel) • Major renovation and modifications carried out in the recent past

• Coal – quality and calorific values aspects

• Operational failures leading to in efficient operation such as tube failures, constraints for efficient heaters operation,

• Soot blowers operation • Tripping

• Performance of economiser, air preheaters, LP / HP heater from past record • Combustion control system – practice followed

• Mills performance

• If plant has online and off line tools for performance evaluation of main equipment and BOP equipment – then details of these tools

• Plant side initiatives to improve the performance and efficiency of the boiler

The data and information collected to be consolidated and the same has to be given in the report for reference. For all major observations arrived at during the discussions, which affect the performance and energy efficiency of the boiler; it is suggested to verify the records and history.

3.6.2 Operating efficiency of the boiler

The boiler efficiency trial has to be conducted to estimate the operational efficiency under as run conditions. The efficiency evaluation by and large follow the loss components mention in the

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reference standards for Boiler Testing at Site using indirect method namely, BS 845: 1987 and USA Standard is ASME Power Test Code Steam Generating Units.

The test method employed is based on the abbreviated efficiency by the loss method (or indirect method) test, which neglects the minor losses and heat credits, which are covered in full text version. The major losses covered are:

• Heat loss due to dry flue gas losses • Heat loss due to moisture in fuel

• Heat loss due to hydrogen (moisture of burning hydrogen) • Heat loss due to combustibles in refuse

• Heat loss due to radiation

• Un accounted losses as per the contract with the Boiler Supplier

Indirect method is also called as heat loss method. The efficiency can be arrived at, by subtracting the heat loss fractions from 100. The standards do not include blow down loss in the efficiency determination process. While conducting the efficiency evaluation, the following need to be ensured (Trials are conducted at least for two hours and measurements are to be taken every fifteen minutes):

• Load on the boiler to be by and large constant and represent average loading and normal operation

• No soot blowers are operated during the evaluation period • No intermittent blow down is given

• A team of 3-4 members are required for simultaneous measurements and data collection of various parameters. These members should be trained/ explained prior to the test in their assignments in measurements and observations.

• Before conducting the actual measurement for the evaluation, it is suggested to carry out a demo exercise for one set of measurement and observation

Measurement locations:

During the test, the power plant under the coordination of energy auditor may organize the collection and analysis of samples at the following locations:

• Flue gas analysis at air preheaters inlet/outlet • Temperature of flue gas at air preheaters inlet/outlet

• Fly ash sampling at the economizer outlet and ESP hoppers for unburnt carbon in fly ash • Sample of bottom ash from hopper or scrapper

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• Sample of raw coal from RC Feeder of the mill for proximate and ultimate analysis of fuel and gross calorific value.

• Pulverized coal samples from each mill for sieve analysis. Sample of mill rejects for GCV.

The following Table 3-11: gives the data sheet for measurements and observations for conducting as run test for boiler efficiency evaluation

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In the above data sheet, steam parameters, proximate analysis, load details are given, and these are not used in the efficiency evaluation; however these are very important since these parameters required for comparison, whether the operating parameters are at par with normal operation.

The following can be used for estimating the losses: a. Dry Flue gases Ldfg:

b. Loss due to unburnt carbon in ash, Luca

c. Loss due to moisture in fuel, Lmf

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e. Loss due to moisture in air, Lma

f. Loss due to carbon monoxide, Lco

During the flue gas analysis when CO is obtained in ppm, then losses can be obtained. Loss due to carbonmonoxide Lco

Lco =

g. Radiation and un-accounted losses

Consider these losses as given in the PG test / Design documents. Alternatively, the radiation losses can be estimated by measuring the surface temperatures and surface areas of the boiler section. Normally surface loss and other unaccounted losses are assumed based on the type and size of the boiler.

However it can be calculated if the surface area of boiler and its surface temperature are known as given below:

Once after estimating the individual components, the losses need to be tabulated and compared with the PG test value or best achievable values.

While comparing the losses, the deviations need to be highlighted and factors contributing for these deviations need to be arrived at.

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The following Table 3-12: gives the tabulation sheet for boiler efficiency on Table 3-12: Efficiency evaluation of the boiler

All loss components should be thoroughly examined for the deviations, since in most of the plants, the actual GCV of the fuel and composition of the fuel does not match with design specifications, and the above losses need to be corrected for the present fuel.

3.6.3 Coal Mills

The major objectives of coal mill energy audit are:

• To evaluate specific energy consumption of the mills. (kWh/ton of coal) • To establish air to coal ratio of the Mills (ton of air per ton of coal) • To evaluate specific coal consumption of the unit (kg /kWh) • Compare the actual consumption with design/PG test values

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• Suggest ways to optimize energy consumption

• To discuss on general health of equipment and review maintenance practices which affect energy consumption.

The energy audit of coal mills has to be commenced by obtaining a overview of system which include mills, RC feeders, PA fans, seal air fans, mill reject handling system and associated ducts, piping, valves and dampers, lubrication system, thermal insulation status of mills/PA fans ducts/piping etc. While monitoring the general health of various installations identify noticeable leakages of coal, air, oil and also to check condition of thermal insulation etc.

During the audit obtain samples of raw coal, pulverized coal, mill rejects, mill gearbox oil, fly ash and bottom ash analyse for the various parameters.

Raw Coal: GCV, ash content, volatile matter, fixed carbon, total moisture, and HGI value of coal.

Pulverized Coal: Mill fineness (% passing through 200 mesh), Running hours of mill grinding elements with material composition of each part. Individual RCF coal integrator readings should be compared with overall coal integrator readings.

Mill Reject Coal: Ash content and gross calorific value of mill rejects, Fly Ash, Bottom Ash and Combustibles in fly ash and bottom ash & GCV.

Mill Gear Box Oil: Viscosity, moisture, mechanical impurities and appearance of lubricating oil of mill gearboxes.

• Carry out power measurements of mills, PA fans, seal air fans, etc,.In the absence of energy meters, take readings from on-line panel instruments for current, voltage, power factor etc. For LT equipment, portable instrument can be used for power measurements.

• Coal flow to also be established by dirty Pitot tube test (to be carried out on Pulverized coal lines). This also helps to identify unbalancing/choking is occurring in flow in the Pulverized Coal lines. The on line coal flow values if available, may also to be taken by appropriate coal feeder calibration.

• Airflow to be established per PA fan by clean air Pitot tube method or by Aerofoil DP where available.

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Based on above observations, Auditor may draw Inference as follow:

• Specific power consumption kWh per tonnage of coal handled • Coal fineness and its impact on the unburnt & air to fuel ratio.

For a typical coal fired boiler, the design indicates that 70% passing through 200 mesh is ideal. Similarly, these values need to be obtained and compared with the actual. The following Table 3-13: can be used as data sheet for mill fineness analysis.

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Table 3-13: Coal fineness

Observe the mill rejects with respect to the quantity and calorific value: Tabulate the results as shown in Table 3-14:

Table 3-14: Mill rejects

Carryout the detailed analysis of mill rejects, compare with the other mills and coal quality. The variation in mill rejects (among the mills) could be due to variation in performance of mill due to mill internals status, fuel handling, etc.

3.6.4 Combustion control, excess air and cold air infiltration While conducting the study, the following need to be verified:

• Present excess air and comparison with PG test or design value

• Combustion control systems installed and status of operation, calibration systems

• Monitoring and controlling mechanism for oxygen, excess air and reporting systems in place • Effect of excess air on boiler performance

• Excess air with respect to boiler load variation

• Cold air infiltration in to the system – observe the present method of measurement, estimation, frequency of measurement for estimating the losses and control mechanisms initiated. The air infiltration also increases load on the ID fan and hinders the capacity of the boiler.

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The best way to identify the cold air infiltration is to measure the oxygen profile across the flue gas path. The following data sheet (Table 3-15:) can be used for excess air and combustion control system.

Table 3-15: Data sheet for estimating air infiltration

The above data sheet will help in identifying the suitable improvement options. If there is any increase in oxygen content then carryout the following:

• Quantity of air in filtered (the exhaust gas quantity can be measured / estimated based on the oxygen content)

• Heat losses due to infiltration (impact on boiler efficiency) • Sources for air filtration

• Suggest the measures to reduce the cold air infiltration into the system. Typical acceptance value for a 210 MW power plant, to increase oxygen by 3% across the APH inlet to ID fan inlet). However, there are very good monitoring systems are available the increase in oxygen is less than 3%.

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• Recommend suitable monitoring system for oxygen profile in flue gas path and suggest instruments required for the monitoring along with suggesting ideal locations for sensors installation

• Estimate the energy saving benefits in the following equipment by having very good cold air infiltration controlling mechanism

o Improvement in boiler efficiency o Improvement in APH

o Reduction in ID/PA and FD fan power consumption

o Increase in boiler loading / PLF

3.6.5 Performance of air preheaters

Air preheater is one of the critical equipment in the boiler and its performance has direct effect on boiler efficiency. “A run test” has to be carried out to assess the performance of the air preheaters.

Air heater leakage and air heater gas side efficiency has to be carried out to check the performance of APH. Air heater leakage in APH is weight of air passing from the airside to gas side of the air heater. This is an indicator of the condition of the air heater’s seals, as the air heater seals wear, air heater leakage increase. The increase in air heater leakage increases the power requirements of the forced draft and induced draft fans, increasing the unit net heat rate and possibly limiting the unit capacity.

Air heater gas side efficiency is defined as the ratio of temperature drop, corrected for leakage, to the temperature head and expressed as a percentage. This is an indicator of the internal condition of the air heater. As conditions inside the air heater worsen (baskets wear, ash plugging, etc.), the air heater gas side efficiency decreases. This is generally accompanied by an increase in exist gas temperature and decrease in air heater outlet temperature.

Air leakage estimation:

The following gives the air leakage in to the air preheaters (APH) system if the Oxygen % is measured at the entry and exit of the air preheaters (APH). APH leakage %:

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Alternatively, if the CO2% is measured in the exhaust gases then the air leakage is estimated by

APH leakage %,

(CO % in the gas entering the APH - CO % in the gas leaving APH)

AL = x 100%

CO % in the gas leaving APH

Gas side efficiency:

The gas side efficiency is defined as the ratio of the temperature drop, corrected for leakage, to the temperature head and expressed as percentage.

Temperature drop is obtained by subtracting the corrected gas outlet temperature from the inlet. Temperature head is obtained by subtracting air inlet temperature from gas inlet temperature. The corrected gas outlet temperature is defined as the outlet gas temperature for no air leakage and is given by the following:

Air leakage estimation and gas side efficiency estimation are important while evaluating the performance of the air heater.

The measured data and estimated parameters need to be tabulated for comparison with the design or best-run values. The following Table 3-16: gives the data sheet for filling the parameters

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Table 3-16: Data sheet for air preheaters (APH)

Unit Design/PG _test Actual _Deviation% Remarks Total combustion air tph

Oxygen content in flue gas

before APH %

Excess air % in flue gas

before APH %

Air heater leakage % Quantity of air in filteration tph Temperature of the air

entering the APH

O

C Temperature of the air leaving the APH

O

C Air temperature at fan outlet OC Temperature of the gas

leaving the APH

O

C Gas outlet temperature

corrected for no leakage

O

C

Note: Auditor can identify the following. Loss parameters from the above Data of leave/Observations 1) Increase in FD and ID fan power consumption

2) Air preheater performance

3.6.6 Controllable losses due to unburnt in ash

Collect the fly ash and bottom ash samples, during the efficiency test period for the analysis of unburnt carbon. It is also suggested to verify the past data pertaining to:

• Ash quantities – bottom ash and fly ash • Unburnt analysis

• Coal used, coal mill performance parameters, unit load, etc (for the dates pertaining to the unburnt analysis

• It is also suggested to see the trend if the plant monitors the unburnt regularly by plotting the graph. For this purpose collect the historical data of analysis.

• Work out boiler efficiency and impact on coal consumption, for every raise of 0.1% in unburnt

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Use the following data sheet Table 3-17: for tabulating unburnt values. Table 3-17: Unburnt – reported values

After collecting the data, it is suggested analyze for the high (if any) and suggest suitable options to reduce the same.

3.6.7 Operation of soot blowers

List the number and type of soot blowers installed along with their operating condition. The data sheet for soot blowers is given in Table 3-18:

Table 3-18: Data sheet for soot blowers

The disfunctional soot blowers cause clinker build up, loss of heat transfer, leads to break downs, higher flue gas high steam temperature at the super heater zone, higher de-super heater spray, etc.

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Table 3-19: Comparison of actual and normative spray consumption

If the actual super heater spray is more than normal, then this will affect the unit performance and heat rate. Identify causes for disfunctioning of soot blowers of each zone and possible remedies. Check the following:

• Soot blower piping. • Poppet valves servicing.

• Functioning of rotary and traverse motor.

• Positioning of split cam assembly, shifting of nozzle position. • Retract limit switches.

• Sleeves condition.

• Positioning of concentricity of swivel tube in respect of wall • Other parameters which affect the performance f soot blower

During the study, observe for these causes due to dysfunctional soot blowers.

3.6.8 Water Treatment

Water quality influences the performance of the boiler internals; observe the present water treatment parameters pertaining to type and rated capacity, operating capacity of the internal and external treatment methods

• Water quality parameters – design vs. comparison

• Control of blow down Present instrumentation, its condition and operational status • Condensate polishing unit

• The higher the boiler operating pressure, the greater will be the • Sensitivity to impurities.

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Table 3-20: Feed water and condensate parameters

Check scope for improving the control systems.

3.6.9 Visual survey and insulation survey of the boiler system

It is suggested to make a visual survey and measurements of the ducting and insulation system for:

• Insulation status (measure the surface temperature with the aid of surface thermocouple/ infrared pyrometer or by using thermal imaging cameras)

• Physical condition of insulation

• Identification of locations where action is required to improve the insulation (provide with detailed techno-economics)

• Improvement options

• Procedure for conducting the energy audit of insulation is given separately.

3.6.10 Exploration of energy conservation possibilities

While conducting the energy audit of the boilers, the following need to be explored in detail to arrive at appropriate energy conservation measures

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• Boilers

o Steam and water parameters (flow, pressure and temperature) o Air and gas parameters (flow, pressure and temperature) o Burners operation

o Primary and secondary air ratios and temperatures o Air infiltration in to boilers

o Unburnt loss reduction

o Combustion control – boiler excess air, O2 Measurement

o inaccuracy or unbalance, o Dry flue gas losses o Insulation

o Air infiltration to flue gases o Blow down and its control o Water quality & its control

o Coal quality and performance of coal mills o Super heater and reheater performance

o Super heater temperature, slagging of furnace water walls and tubes, Fouling on the pendant and horizontal convection tubes, soot blowers performance

o Boiler control systems

o Limitation on Performance of associated equipment (pumps, fans, heaters, soot blowers, mills, etc.) affecting boiler loading and efficiency

o Loading on ID, FD and PA fans

o Operation of dampers/inlet guide vanes/speed controllers of fans o Fouling of boiler heating surfaces

o Installation of energy saving retrofits o DM water consumption

• Air preheaters o Air Infiltration o Gas side efficiency

o Performance of air preheaters • Economizer

o Pressure drop o Performance

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3.6.11 Key observations and Analysis

This forms the major component of energy audit system the details should be given in details pertaining to the section mentioned in the earlier sections:

Detailed observations and their description pertaining to the following, which include,  Energy consumption pattern (fuel consumption, specific

 consumption, heat rate, plant load factor, operating hours,  efficiency, energy metering and monitoring aspects)  Boiler loading pattern and unit load

 Major O&M aspects affecting the boilers

 Boiler efficiency and heat balance, loss components  Combustion and control

 Water and steam quality & control aspects  Soot blowers

 Insulation aspects  Economizer  Air preheaters  Air infiltration

 Mills and performance aspects  Fuel quality aspects

 Burner operation and performance  Recent modifications carried out  Observation on visual survey  Make up water aspects  Blow down aspects

 Since energy audit is case specific activity hence, In addition to the above there will be several other components, which affect the energy efficiency. The audit should also cover these points.

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PUSAT PENDIDIKAN DAN PELATIHAN THERMAL INSULATION

4. THERMAL INSULATION

4.1 Background

Detailed study of thermal insulation for consideration of energy loss is a part of any energy audit, since thermal insulation condition is an indicative parameter for the potential thermal energy savings. The study aims at not only to judge the potential thermal energy saving by insulation up gradation but also to plan for proper maintenance schedule keeping in view equipment and personnel safety.

In addition to this, periodic insulation survey should be carried out to initiate the measures by maintenance personnel to prevent these heat losses.

This document gives a standard procedure for energy audit of thermal insulation of boiler, turbine and piping and it is generic in nature and can be customized as per the actual site conditions.

4.2 Steps Involved In Conducting the Energy Audit

The scope of insulation study includes:

• To carry out temperature profile survey of insulated surfaces in areas of boiler, steam pipes, ducts & turbine etc. Thorough thermal scanning of all related surfaces for identifying hot spots with poor insulation.

• Identification of areas of poor/damaged insulation, contributing to excess heat losses. • Estimation of extra heat loss/revenue loss due to the hot spots because of damaged or

poor insulation.

The steps involved in conducting energy audit of Insulation system are: • Data collection

• Measurements and observations • Estimation of heat losses (controllable)

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The following instruments are required for conducting the energy audit survey of the thermal insulation.

• Non-contact type infrared pyrometer • Measuring tape

• Distance measuring instrument (for the pipes)

4.3 Data Collection

Single line diagram of all the insulated lines/ surfaces of the plant with their dimensions. • Dimensional sketches of other hot surfaces of boiler, turbine, vessels etc.

• Details of insulating material and cladding used (type of insulation, pipe sizes, type of cladding, emissive of cladding, thickness etc).

• Also collect the following:

- Emissivity (refer the instruction manual of the instrument)

- Permissible allowed surface Temperature (o C) (Tsa) = Tambient + Ä T allowed - Generation (Last one year) in Million Units

- Calorific value of Fuel (Kcal/Kg) - Price of fuel (Rp/Ton) at station end - Boiler Efficiency (%)

- Cost of reinsulation (Rp/m2)

4.4 Measurements & Observation to Be Made

• Record average unit load in MW and ambient temperature (Ta) in ºC prevailing at the time of survey.

• Scan and record the temperatures at various locations of the insulated surface at the interval of 1-2 meters, with the help of non-contact type thermometer or thermo vision camera.

• Typical format is shown in the following table (Table 4-1) by taking one section of the boiler as an example. Similarly of measurement can be carried out for other sections/equipment.

• After recording the temperature and tabulating, highlight the measurements where temperatures are above acceptable level.

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Table 4-1: Typical format for recoding the surface temperature

• If the plant uses the thermal vision camera, it is suggested to enclose the printout of measurements. Typical printouts are given in the following Table 4-2.

Table 4-2: Typical thermal images Thermal Image of 8 meter level:

Down comer line RHS

Thermal imager of 8 meter level: 2 & 3 corner rear side (channel below APH)

• Carryout physical survey and make a list of defective insulation areas indicating along with type of defect i.e. insulation damaged/poor insulation/cladding missing/cladding loose/un-insulated or any other) along with description of location and approximate area of defect.