Toolbox 2 ENERGY AUDITING IN INDUSTRY

Transcription

1 APPLIED INDUSTRIAL ENERGY AND ENVIRONMENTAL MANAGEMENT Z. K. Morvay, D. D. Gvozdenac Part III: FUNDAMENTALS FOR ANALYSIS AND CALCULATION OF ENERGY AND ENVIRONMENTAL PERFORMANCE Applied Industrial Energy and Environmental Management Zoran K. Morvay and Dusan D. Gvozdenac John Wiley & Sons, Ltd Toolbox 2 Step-By-Step Guide to Carrying Out an Energy Audit STEP 1 STEP 2 STEP 3 STEP 4 STEP 4.1 STEP 4.2 UNDERSTANDING INDUSTRIAL OPERATIONS PRELIMINARY ENERGY AUDIT IDENTIFICATION OF ENERGY CONSERVATION OPPORTUNITIES (ECO) DETAILED ENERGY AUDIT (DEA) preparing measurement plans and conducting measurements SPECIFICATION OF ENERGY CONSERVATION MEASURES (ECM) PREPARATION AND PRESENTATION OF DEA REPORT AND ACTION PLANS STEP 1: UNDERSTANDING INDUSTRIAL OPERATIONS Developing an understanding of industrial operations is a prerequisite for the analysis of energy efficiency in an organization. In order to achieve that, we start with data on the general characteristics of the business (Checklist 1) followed by data collection on energy use, main utilities and characteristics of energy end-use requirements, as described by Step 2. CHECKLIST 1: GENERAL CHARACTERISTICS Activity Type (sector): Main products: Production capacity [t/y] Capacity utilization [%] NATIONAL OR MULTINATIONAL: History When established: Growth pattern 1

2 2 Cost structure Raw material [%] Labor [%] Energy [%] Other [%] EXTERNAL ENVIRONMENTAL FACTORS Economics Broad economic setting: Development trends: Structure and share of the market: OBJECTIVES AND STRATEGIES General Specific organizational objectives and strategies as defined by management Growth Growth objectives over the next 5 years Investment Policies and plans, main projects STEP 2: PRELIMINARY ENERGY AUDIT (PEA) A PEA is essentially a data gathering exercise which aims to develop an understanding of how energy is used in a factory, and prepare a background for detailed energy audit (DEA) implementation (Fig. 2.1). Questionnaires 1 and 2 will help to guide you through and structure the data gathering process.

3 3 QUESTIONNAIRE 1: Figure 2.1: Flow Chart of Preliminary Energy Audit (PEA) PRELIMINARY ENERGY AUDIT Data on energy consumption and costs Company: Address: General Manager: Contact person: Telephone, Fax, By: Date:

4 4 GENERAL INFORMATION Production program and capacity Production in the year (description and quantities of final products) 1 Raw materials (description and quantities): Short process description (phases) Draft scheme of the production process 1 All quantities shall be given for the same year.

5 5 Electricity, V Steam, 8 barg Industrial Water Cooling Water, 34 o C Compressed Air, 7 barg Waste Water Solid Waste Total annual operating time [h/yr]: Number of shifts per working day: Total number of employees: Number of employees in energy group: Head of group: Total annual cost of production: Total annual cost for energy and water:

6 6 Layout of the factory

7 7 MONTHLY SUMMARY OF FUEL OIL CONSUMPTION AND COSTS Name of fuel: Source: Fuel classification: Average low calorific value [kj/kg]: Year of consumption: Month Deliveries [l] Cost of delivery [ ] Working days in a month Consumption [l] Cost of consumed fuel [ ] I II III IV V VI VII VIII IX X XI XII Total

8 8 MONTHLY SUMMARY OF ELECTRICITY ENERGY AND COSTS Tariff description: Year of consumption Total cost Active energy Reactive energy [ ] Month Consumption Price/unit Consumption Price/unit [kwh] [ /kwh] [kvarh] [ /kvarh] I II III IV V VI VII VIII IX X XI XII Total

9 9 MONTHLY SUMMARY OF ELECTRICITY DEMAND COSTS Month Maximum demand (on peak; partial peak) On peak [kw] Partial peak [kw] On peak Cost [ ] Partial peak Total cost of demand Total cost of energy and maximum demand [ ] [ ] I II III IV V VI VII VIII IX X XI XII Total MONTHLY SUMMARY OF FRESH WATER CONSUMPTION AND COSTS Year of consumption District system Own wells Month Consumption Price/unit Cost Consumption Price/unit Cost [l] [ /l] [ ] [l] [ /l] [ ] I II III IV V VI VII VIII IX X XI XII Total

10 10 MONTHLY SUMMARY OF WASTE WATER COSTS Year of consumption Total cost of Sewerage system Total cost water Month Consumption Price/unit Cost [l] [ / ] [ ] [ ] [ ] I II III IV V VI VII VIII IX X XI XII Total

11 11 QUESTIONNAIRE 2: PRELIMINARY ENERGY AUDIT Specifications of main utilities ENERGY TRANSFORMERS Boiler Room STEAM to process BOILER No.1 BOILER No.2 Feed Water Pumps Blow Down Make Up Water Oil Preheater Heavy Fuel Oil FEED WATER TANK EXAMPLE Return condensate app. 65 % Figure 2.2: Draft Scheme of the Boiler Room Number of boilers: Total capacity: Total annual production of heat energy [TJ/yr]: Total annual fuel consumption [h/yr]: Total annual operating time [h/yr]: Total annual quantities of water supplied to the system [h/yr]:

12 12 Steam Boiler Figure 2.3: Draft Scheme of the Steam Boiler Type of boiler: Design capacity [t/h]: Fuel: Total annual operating time [h/yr]: Age [years]: Rated capacity [t/h]: Annual fuel consumption [yr]: Annual operating period: Pressures and Temperatures Steam pressure at boiler outlet [kpa] Steam temperature at boiler outlet [ o C]: Water temperature at boiler inlet [ o C]: Combustion air temperature [ o C]: Temperature of gas leaving the boiler [ o C]: Fuel temperature [ o C]: Flue Gas Analyses CO 2 : O 2 : CO: N 2 : Excess air:

13 13 Electric Power Figure 2.4: Draft Single-Pole Scheme of the Transformer Station s Connection Annual need for electric power satisfied by: Distribution system [%] Your own CHP plant [%] Voltage of the power supply system [kv] Voltage transformation [kv] Number of transformer stations Number of transformers Total installed capacity [kva] Installed capacity per units [kva] ENERGY END-USERS A/C systems A/C systems used: Number of independent systems: Total design quantity of the A/C air output [m 3 /h]

14 14 A B C D E OEF OEF AEF AEF m 3 /h m 3 /h m 3 /h m 3 /h PREMISES 24 o C 50 % PREMISES 24 o C 50 % PREMISES 24 o C 50 % PREMISES 24 o C 50 % PREMISES 24 o C m 3 /h 825 kw AHU SA RA m 3 /h 1943 kw AHU SA RA m 3 /h 605 kw AHU SA RA m 3 /h 170 kw AHU SA RA SA m 3 /h CFU FA m 3 /h FA m 3 /h FA 3150 m 3 /h FA m 3 /h 1512 kw OAHU 1 & m 3 /h 66 kw OAHU 3 OAHU 4 FRESH AIR FRESH AIR FRESH AIR FRESH AIR Figure 2.5: Draft Scheme of the System Age [years] Total design capacity of air cooling [MJ/s] Annual operating time (describe all relevant facts and characteristics, such as changes in working conditions, seasonal and other) Daily operating time (describe): Air temperature [ o C] Type of regulation

15 15 Compressed air system Compressed air system used in a building: 100A 100A CFU-1 40A AIR SUPPLY 50A/75A 200A 65A DOMNICK AO 15/ Pre Filter DRY-1 DC5600 AF0.9 After Filter Flow Adjust 65A 65A PQ 200A 150A /100A 20A 150A /100A Ball Valve 40A AIRSUPPLY 50A/75A 100A 10A 15A 100A 65A DOMNICK AO 15/ Pre Filter DRY-2 DC5600 AF0.9 After Filter Flow Adjust 65A 65A PQ 40A AIR SUPPLY 15A 75A 65A DOMNICK AO 15/ PreFilter DRY-3 DC5600 AF0.9 After Filter Flow Adjust 65A 65A PQ 40A AIRSUPPLY 15A 75A 100A 200A PreFilter 65A After Filter FQ 100A 100A 100A 40A AIR SUPPLY 15A 75A 200A PreFilter 65A 200A PreFilter 65A After Filter FQ After Filter FQ Unload 100A 20A 25A 25A 15A Air Tank WWT. Auto Tabe Cleaning R-3 200A PreFilter 65A After Filter FQ 40A 15A 10A Seperator SequenceControl in Control room 40A Unload 80A Pre Filter 50A DOMNICK 40/30/ DRY FQ After Filter PCC1200 AF Flow Adjust 80A 40A 50A Figure 2.6: Draft Scheme of the Compressed Air System Number of compressors: Total capacity [nm 3 /min] Capacity per unit [nm 3 /min] Output pressure [kpa] Total capacity of electric motors [kw] Unit capacity of electric motors: [KW] Volume of the tank [m 3 ] Type of regulation Air cooling system Parameters Working pressure of machinery [kpa] Entering air temperature [ o C] Daily operating time (system): Daily operating time (compressors):

16 16 STEP 3: IDENTIFICATION OF ENERGY CONSERVATION OPPORTUNITIES (ECOs) During inspection of the plant, as a part of PEA activities, opportunities for energy conservation have to be identified. The following checklist should serve as a reminder as to where to look for ECOs. Based on the ECOs identified, measurement plans will be prepared and measurements executed during the DEA, in order to evaluate the potential for energy performance improvement by individual ECOs. ELECTRICAL SYSTEM GENERAL Use demand limiters where applicable and where cost benefits exceed installed cost without creation of unacceptable environmental conditions or limitations in manufacturing production. Replace oversized motors and replace old motors with new energy-efficient motors. Investigate power factor improvement. Use two- or three- speed motors on pumps and fans when reduced flow is desired. Improve maintenance for all equipment. Reduce lighting levels where this will not reduce manufacturing production or quality or sales efficiency. Turn off lights when not needed. Replace present lighting with more efficient lighting sources. In manufacturing processes control warm-up time and turn off time. Reschedule production or other operations to spread out the electrical load and thus improve the load factor. When possible, modulate a load rather than turning it off and on. Install small electric boilers for local requirements rather than operating a complete steam system. In manufacturing plants, install sub metering for manufacturing sections. This has the effect of making a manufacturing subsection an energy profit centre. Use variable-speed drives. Installation of electrical-peak-shaving generators. The largest savings of electrical energy by electrical energy management will come from the basic principle: WHEN YOU DON'T NEED IT, TURN IT OFF AIR CONDITIONING Turn off air conditioning in all unoccupied areas. Ensure that the air conditioning system is in good working order; keep filters, coils and blowers clean. Use spot coolers when spaces are occupied only at various and irregular times. Clean refrigerant condensers to reduce compressor horse power. Utilize humidity controlling systems which will allow humidity to rise to the highest acceptable setting systems that use re-heat are particularly beneficial. Minimize the heat created by lights, machinery or equipment which are left on when not required. Leave storm doors and windows in place during the summer to prevent outside heat from coming in. Use water cooled lighting fixtures if possible. If the office is completely vacated after normal closing hours, turn off air conditioning at least one hour before quitting time.

17 17 If possible, use heat-producing equipment such as photocopiers in the early morning or late afternoon. Use awnings or shades to reduce heat gain from insulation. Urge employees to wear lighter clothing in order to accustom themselves to slightly higher office or plant temperatures. Consider a spraying system or other means of evaporating water on the roof in order to reduce the air conditioning load. Size air handling grills, ducts and coils in order to minimize air resistance. LIGHTING Turn off all unnecessary lights. Replace low efficiency light sources with fluorescent, mercury, sodium or high intensity direct lighting. Keep bulbs and fixtures clean and free of light-blocking dirt. Remove lights selectively and ballasts where lighting levels exceed established standards. Reduce or eliminate decorative lighting. Install photocells in order to control outdoor or perimeter lighting. Utilize direct sunlight as a light source wherever possible. Employ a lower wattage of lighting where possible. Use light colors on ceilings and walls, floors and furnishings. Install timers on lights in little used areas of the plant. Use automatic switches in order to ensure that plant lighting is extinguished after the last shift leaves. Provide light switches in office areas so that individual lights may be turned off. Place lighting switches in prominent places. Move to task lighting wherever possible. Eliminate inefficient electric lamps from plant stocks and catalogs. Consider turning off plant lights during lunch breaks. INDUSTRIAL BOILERS Look to stack gas temperatures as a running indicator of boiler performance. Carry out frequent checks of boiler performance. If more than one boiler is in use, sequence boiler use in decreasing order of efficiency. Keep as many boilers as possible operating near full load (rather than having a greater number operating at partial capacity). Keep all heat transfer surfaces clean. Improve boiler control systems. Reduce excess air in order to increase boiler efficiency. Look to waste heat boilers and/or economizers in order to utilize hot stack gases. Utilize boiler blow-down as flash steam or in a blow-down heat exchanger in order to preheat make-up water. Reduce blow-down through feed-water control. STEAM Fully insulate all steam and condensate lines, and process equipment. Cover and insulate condensate tanks. Repair or replace faulty steam traps. Repair all other sources of steam leakage including flanges and high pressure reducing stations. Maintain steam jets used for vacuum system. Ensure that boilers are operating at peak efficiency.

18 18 Keep boiler tube surfaces clean. Return condensate to boiler or use pre-softened cooling water from compressors, etc. as feed-water in order to minimize both blow-down and overall energy and water consumption. Monitor boiler blow-down chemical analysis. Recapture blow-down energy using heat exchangers or flash tanks. Use air heaters and/or economizers to recover heat from boiler flue gases. Minimize the distance that steam must travel by re-arranging process equipment and eliminating straggling steam laterals. Use insulation valves to split up the steam distribution system. Operate steam-heated processes at the lowest permissible temperature. Lower steam pressures wherever possible. Use steam traps and/or balance pressure air vents in order to eliminate air films in steam lines. Put flash steam to work in lower pressure applications. Where clean condensate cannot be returned to the boiler, use it for washing or other processes. Turn off steam tracing during mild weather. Look to glycol tracing systems to replace steam. Consider replacing electric motors with back pressure steam turbines and use exhaust steam for process heat. Operate distillation columns at minimum quality requirements. Operate distillation columns at near flooding conditions for maximum separation efficiency. Determine correct feed plate location on distillation columns in order to increase efficiency and minimize steam consumption. Consider switching selected steam stripping distillation units from direct (live) steam to indirect (dry) stripping. Use steam traps of a correct size. Evaluate replacing condensing steam turbine rotating equipment drives with electric motors, if your plant has a power generating capability. Add traps to distillation column in order to reduce the reflux ratio. Minimize boiler blow-down with better feed-water treatment. Use waste heat low pressure steam for absorption refrigeration. Replace barometric condensers with surface condensers. Shut off steam traps on superheated steam lines when not in use. Optimize the operation of multi-stage vacuum steam jets. Use insulation of optimum thickness. Use reflux ratio control or similar control instead of flow control on distillation towers. Substitute hot process fluids for steam. FURNACES, KILNS AND OVENS Calculate and plot boiler efficiency daily. Establish a definite burner maintenance schedule. Adjust burners regularly for the most efficient operation. Heat oil to a proper temperature for good atomization. Eliminate combustible gas in flue gas. Reduce combustion air flow to an optimum level. Replace obsolete burners with more efficient ones. Use waste and by-products as fuel wherever possible. Limit and control secondary combustion air in furnace operations. Calculate a heat balance for all combustion equipment in order to better understand where energy is dissipated or used. Utilize hot stack gases as an energy source. Insulate furnaces, kilns and ovens in order to minimize heat loss.

19 19 Control infiltration of cold air into furnaces. Shut down idle combustion whenever possible. Consider cam controllers or other systems in order to control the shut down cycle on combustion equipment. Schedule plant operations for full load operations on combustion equipment. Minimize energy loss during loading and unloading (cycling). Eliminate over-design in equipment and practices. Analyze flue gases regularly. Look into using automatically controlled flue dampers. COMPRESSED AIR Make an optimized selection of a central compressor versus a number of smaller zone compressors. Choose the compressor with the highest efficiency. Select an air intake location that provides dry, clean air. Maintain compressor driving belts, and all other critical parts. Ensure that water cooling ducts are not blocked. Use larger or extra receivers on existing compressors. Investigate automatic control systems. Provide basic instrumentation in order to gauge system efficiency. Repair all line leaks promptly as part of a regular maintenance program. Use long radius bend and welded joints wherever possible in piping. Incorporate strainers and lubricators in each air-operated device. Maintain air operated equipment regularly as well as conditioning units filters, pressure regulators and lubricators. Do not operate equipment above the manufacturer's recommended operating pressure. Reduce air pressure to the lowest feasible level. Consider using double acting air cylinders. Use hot air from remote receiver tanks close to cylical loads. Use hot air from air cooled compressors for space heating wherever economically available. Cooling water from water cooled compressors has many potential uses within the plant.

20 20 STEP 4: DETAILED ENERGY AUDIT (DEA) A detailed energy audit aims at establishing actual energy performance of selected end-users and processes. Based on identified of energy conservation opportunities during the preliminary audit. At the heart of a DEA is a specific metering campaign which usually takes a week or two according to a carefully prepared measurement plan (see Examples 1 and 2 below). The measuring results are analyzed in order to establish energy balances, specify performance improvement measures (Step 4.1) and carry out an economic and financial analysis of performance improvement projects (Fig. 2.7) Figure 2.7: Flow Chart of Detailed Energy Audit (DEA) The Economic and Financial Evaluation of energy performance improvement measures includes cost-benefit analysis, calculation of economic and financial internal rates of return (EIRR and FIRR) and a discounted cash flow analysis. It is described in Toolbox III-3 and includes a spreadsheet program (Software No. 3, Toolbox III-3), for carrying out such calculations. The audit results have to be summarized in a report, together with an action plan containing the priorities for the implementation of performance improvement projects, as specified in Step 4.2.

21 21 Example 1: Preparing the measurement plan for a steam boiler M1 M2 M3 M4 M5 M6 M7 Combustion air: - Temperature, t FA [ o C] - Relative humidity, RH FA [%] Fuel consumption: - Fuel flow rate, mf [l/h, t/h, nm 3 /h.] - Temperature, t F [oc] Steam (saturated): - Pressure, p S [bar] Feed water: - Mass flow rate of feed water, m FW [t/h] - Temperature, t FW [ o C] - Conductivity, Cond FW, [µs/cm] Flue gas: - Flue gas temperature, tfg [ o C] - Oxygen content, O 2 [%] - CO content, CO [ppm] Blow-down: - Mass flow rate of blow-down water, m BD, [t/h] Boiler water: - Conductivity, CondBW, [µs/cm] Example 2: Preparing measurement plan for a a Sterilization Process (Retorts) M1 Mass flow rate versus time kg/h Temperature o C Pressure Bar Duration min M2 Mass flow rate of water versus kg/h time Temperature o C M3 Mass flow rate f condensate kg/h Temperature o C M4 Mass flow rate of water kg/h Temperature versus time o C M5 Mass of product in kg Temperature o C M6 Temperature o C

22 22 STEP 4.1: SPECIFICATION OF ENERGY CONSERVATION MEASURES All of the measures or performance improvement projects have to be specified to the level of a conceptual engineering design (see the example below). Project: CHP Scheme and position of NEW PLANT ECM #2: Gas Engine Installation Investment specification: Design and installation Supervision EQUIPMENT Gas engine and generator (electrical output 1,819 kw e ) Absorption chiller Capacity 861 kw R ; hot water 88/83 o C Heat exchanger for engine cooling (767 kw H ) Heat exchanger for flue gases (1148 kw H ) Transformer 0.4/20 kv Cooling tower Energy cost reduction: m$us/y Simple pay back period: 7 years Reduction in co 2 emission: 31.1 % LOCATION PREPARATION Site preparation 5000 Adoption the existing installation Gas connection installation 7500 MISCELLANEOUS 10 % of equipment cost TOTAL: $US

23 23 STEP 4.2: PREPARATION AND PRESENTATION OF DEA REPORT AND ACTION PLANS 1. Recommended chapters for DEA report Executive summary General data on factory and processes Observations and comments on operational, housekeeping and maintenance practice Current level of production and energy consumption and energy balances Specifications of identified energy performance improvement measures Expected values of energy cost savings Investment analysis: Economic aspects: Payback period and EIRR Financial aspects: Cash flow and FIRR Quantitative target for improving energy performance Implementation plan for achieving the set targets Technical details and specifications must be attached 2. Approach to preparing an energy action plan The order of consideration of energy conservation measures: i. Improvement of maintenance practices, ii. Improvement of operation practices, iii. Improvement of equipment efficiency, iv. Improvement of process efficiency. The order of priority for the implementation of energy conservation measures: i. Introduction of systematic energy management practices (including awareness, training and motivation programs) ii. Improvement of energy metering, control and monitoring (provide data for continuing improvement of efficiency) iii. iv. Improved housekeeping and maintenance Implementation of energy performance improvement projects with a short payback period 3. Selling of energy action plan to management i. Organize the session as a formal presentation to be attended by general, technical, production, financial and maintenance managers ii. Establish the relevance of energy costs iii. Explain the opportunities for cost reduction iv. Avoid technical jargon and detail v. Provide comparisons or benchmarks within the industry group vi. Provide a time scale in order to achieve results vii. Provide targets for the coming years viii. Specify investment requirements