Biomass as Fuel in Small Boilers (PDF 6.4 - APO Asian Productivity ...

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Biomass as Fuel in Small Boilers - Fuel savings = 526,800-154,280 = USD3,72,520 - Investment for purchase of new rice husk-fired boiler = USD50,000 - Simple payback period = 1.6 months 5.3 CHECKLIST FOR ENHANCING BOILER EFFICIENCY 5.3.1 Periodic tasks and checks outside of the boiler • All access doors and plate work should be maintained airtight with effective gaskets. • Flue systems should have all joints sealed effectively and be insulated where appropriate. • Boiler shells and sections should be effectively insulated. Is existing insulation adequate? If insulation was applied to boilers, pipes, and hot water cylinders several years ago, it is almost certainly too thin even if it appears in good condition. Remember, it was installed when fuel costs were much lower. Increased thickness may well be justified. • At the end of the heating season, boilers should be sealed thoroughly, internal surfaces either ventilated naturally during the summer or very thoroughly sealed with tray of desiccant inserted. (This is only applicable to boilers that will stand idle between heating seasons.) 5.3.2 Safety and monitoring • Explosion relief doors should be located and/or guarded to prevent injury to personnel. • Safety valves should have self-draining discharge pipes terminating in a safe location that can be easily observed. • Installed instruments should be maintained in working order and positioned where they can be seen easily. • Provide test points with removable seal plugs in the flue from the boiler, to enable flue gas combustion tests to be carried out. • Do you check boiler combustion conditions periodically? CO2 or O2 readings and exit temperatures can be obtained using relatively inexpensive portable equipment. Adjusting combustion by optimizing the fuel/air ratio costs nothing and can lead to substantial savings. • Do you monitor exit temperatures? There should be a steady rise between boiler flue-duct cleaning intervals, and this should not be allowed to exceed, say, 40 ºC. Try to clean based on temperature indications, rather than on the calendar. - 38 -
Retrofitting of Coal-/Oil-Fired Boiler with Biomass and Checklist for Enhanced Boiler Efficiency • If you have more than one boiler, do you isolate boilers which are in excess of load requirements? Automatic flue isolation should be used, if possible, to prevent excessive purging by chimney draughts during idle periods. • In multi-boiler hot water installations, are the boilers hydraulically balanced to ensure proper sharing of the load? • Consider fitting heat exchangers/recuperators to flues; these can recover 5-7% of the energy available. 5.3.3 Boilers: Extra items for steam-raising and hot-water boilers • Check regularly for buildup of scale or sludge in the boiler vessel; or check TDS of boiler water each shift, but not less than once per day. Impurities in boiler water are concentrated in the boiler, and the concentration has limits that depend on type of boiler and load. Boiler blow-down should be minimized, but consistent with maintaining correct water density. Recover heat from blow-down water. • With steam boilers, is water treatment adequate to prevent foaming or priming and consequent excessive carryover of water and chemicals into the steam system? • For steam boilers: Are automatic water level controllers operational? The presence of interconnecting pipes can be extremely dangerous. • Have checks been made regularly on air leakages around boiler inspection doors, or between boiler and chimney? The former can reduce efficiency; the latter can reduce draught availability and may encourage condensation, corrosion, and smutting. • Combustion conditions should be checked using flue gas analyzers at least twice per season, and the fuel/air ratio should be adjusted if required. • Both detection and actual controls should be labelled effectively and checked regularly. • Safety lock-out features should have manual re-set and alarm features. • With boiler plant, ensure that the fuel used is correct for the job. With solid fuel, correct grading or size is important, and ash and moisture content should be as the plant designer originally intended. • Ensure that the boiler operators are conversant with the operational procedures, especially any new control equipment. • Have you investigated the possibility of heat recovery from boiler exit gases? Modern heat exchangers/recuperators are available for most types and sizes of boiler. • Do you check feed and header tanks for leaking make-up valves, correct insulation, or loss of water to drain? - 39 -
Page 1: From: Biomass as Fuel in Small Boil
Page 5 and 6: CONTENTS List of Tables v List of F
Page 7 and 8: LIST OF TABLES 1-1 Residue from maj
Page 9 and 10: 1. INTRODUCTION TO BIOMASS AS FUEL
Page 11 and 12: - 3 - Introduction to Biomass as Fu
Page 13 and 14: Figure 1-3 Various biomass energy s
Page 15 and 16: 2. BIOMASS PREPARATION, STORAGE, HA
Page 17 and 18: Biomass Preparation, Storage, Handi
Page 25 and 26: ( ... Continued) Draft Conditions B
Page 27 and 28: Biomass-based Fluidized Bed Combust
Page 37 and 38: - 29 - Performance Evaluation of Bi
Page 39 and 40: i. Percentage heat lost due to dry
Page 41 and 42: Solution: Step 1) Find the theoreti
Page 43 and 44: 5. RETROFITTING OF COAL-/OIL-FIRED
Page 45: Retrofitting of Coal-/Oil-Fired Boi
Page 49 and 50: 3. Close drain cock 4. Close steam
Page 51 and 52: ( ... Continued) Air leaks on water

Biomass as Fuel in Small Boilers (PDF 6.4 - APO Asian Productivity ...

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