B-605 water tube vs Modern Boilers (1).pptx

A boiler

1. 1 UTILITIES UNIT B-605 Comparison with Latest Boilers PRESENTED BY : Abubakar Saeed JE-PRD (UTY) Share The Knowledge

2. Contents Boilers Basic Auxiliary Boiler, B-605 B-605 Comparison with B-4601 Modern Boiler Technology Salient Features of Modern Technology 1 2 3 4 5

3. Is this Boiler

4. Is this Boiler

5. A Boiler is a closed pressurized vessel in which water changes into steam by application of heat, by combustion of fuels or using heat from other sources. Boiler

6. Working Principle of Boiler The chemical energy is converted into heat energy by the combustion process which is absorbed by the boiler Water Boiling Combustion Heat STEAM Boiler As the pressure increases, boiling point of water increases and more energy is required to convert into steam.

7. Boilers are classified on the basis of : Basis of Water Path Allocation Mode of Circulation Of Water Type of Fuel Draught Type Type of Furnace Steam Pressure Classification of Boilers

8. Depending on whether the water or flue gas is in the tube side, boilers can be classified as: Fire tube boilers Water tube boilers Water Path Allocation

9. Fire tube boilers have BFW on the shell side and flue gases at tube side. Fire Tube Boiler

10. Advantages of fire tube boiler are: Low initial investment Occupies less space / Packaged design More fuel efficient Easier to operate Limitations of a fire tube boiler are: Lower capacity (normally < 25 ton/hr) Lower steam temperature / pressure Not suitable for use in large scale process / power plants Fire Tube Boiler

11. Water tube boilers have flue gases on the shell side and BFW at tube side. Water Tube Boiler

12. Advantages of water tube boiler are: Higher capacity Higher steam temperature / pressure Better response to load demand changes Better water circulation ensures uniform cooling of tubes Limitations of a water tube boiler are: Higher capital cost More difficult to operate Higher maintenance cost Water Tube Boiler

13. Classification - Water tube boilers can be classified on basis of tube and drum arrangement; A type D type O type Water Tube Boiler

14. A-type D-type O-type Water Tube Boiler

15. Forced Circulation Boiler If the water is forced through the boiler circuits by an external pump, the ensuing circulation is called positive or forced circulation. Its Advantages include; Steam generation rate is higher Lower scaling problem due to high circulation velocity Greater capacity to meet load variation Quicker start-up from cold Mode of Circulation

16. Mode of Circulation Natural Circulation Boiler The difference in densities of saturated water in the downcomer and the steam-water mixer in the riser brings about natural circulation A baffle separates out the heated riser from the unheated down comer and therefore creates a temperature difference between the two tube systems

17. Type of Fuel Natural Gas / Off Gases Coal Oil Biomass i.e. Baggase / Rice Husk

18. Draught Type Natural Draft (No Fan) Induced Draft (Fan at Exhaust end) Forced Draft Balanced Draft

19. Following main components comprise of a water tube boiler: Steam drum Mud drum Economizer Evaporator Superheater Burner assembly Flue gas stack Water Tube Boiler

20. Steam drum: It is a reservoir of water/steam at the top end of the water tubes. The drum stores the steam generated in the water tubes and acts as a phase-separator for the steam/water mixture. Water Tube Boiler

21. 5” SATURATED STEAM OUTLET SECONDARY SCREEN RISER TUBES Ø5” Ø4 ” FEED PIPE WATER LEVEL PRIMARY SCREEN BAFFLE PANELS FRONT WALL TUBES DRAIN PIPE Ø16 ” MANHOLE BOILER BANK TUBES REAR WALL TUBES REAR WALL TUBES B-605 Steam Drum

22. Mud drum: The lower drum of a boiler. It is used as a settling point for solids contained in the feedwater and as a feedpoint for the lower wall headers and floor tubes. Water Tube Boiler

23. STEAM DRUM LOWER DRUM BOILER BANK TUBES FLOOR TUBES FRONT WATER WALL BOILER SIDE WALL UPPER SIDE WALL DISTRIBUTION HEADERS BOILER REAR WALL TUBES SIDE WALL HEADERS SAT. STEAM OUTLET SUPERHEATER ROOF RISER TUBES STEAM OUTLET HEADER ACCESS DOOR AIR INLET PLENUM BURNERS AIR SUPPLY DUCT BURNERS ASSEBMLY WINDBOX ASSEMBLY FURNACE FLOOR TILES CROSS FLOW BAFFLES MINERAL FIBER BLANKET FURNACE ROOF TUBES RIBBED CASING B-605

24. TANGENTIAL FIRING - creates a single rotating flame envelope (or vortex) for a uniform and consistent heat profile BURNER ASSEMBLY BURNER ASSEMBLY IMAGINARY CIRCLE B-605

25. B-605 B-4601 Manufacturer Combustion Engineering, USA Machhi , Italy Capacity 70 Ton/hr ( MCR ) 77 Ton/hr (Peak) 120 Ton/hr ( MCR ) 132 Ton/hr (Peak) Design Pressure 105 kg/cm 2 Max. Allowable 122 kg/cm 2 115 kg/cm 2 Max. Allowable 122 kg/cm 2 Design Temperature 510 °C 515 °C Type Water Tube Natural Circulation Forced Draught Water Tube Natural Circulation Forced Draught Fuel Natural + Purge + Syn. Gas Natural + Off gas Efficiency % 78.6 (80.9 in TMP’2020 ) 82.7 (77.1 in TMP’2020 ) B-605 VS B-4601

26. B-605 B-4601 Expansion Boiler is placed on foundation, steam drum expansion occurs upward. The boiler is hanged typed i.e. It is structurally supported from the top and expansion occurs downward when the boiler is put in service as compared to B-605 Burners 04 - Tangential Firing 04 - installed on the front wall for fuel combustion Drum Steam + Mud Drum No Mud Drum Steam Drum Internals Baffle Plates and Screens Cyclone Separators and Demister Pads Super heaters Vertical Horizontal B-605 VS B-4601

27. STEAM DRUM PRIMARY SUPERHEATER INLET SEC. SUPERHEATER OUTLET WATER WALL FURNACE ECONOMIZER OUTLET BOILER EXHAUST LOWER DISTRIBUTION HEADERS WATER COLLECTION HEADER SATURATED DSTEAM OUTLET BOILER STRUCTURE UPPER DISTRIBUTION HEADER DE-SUPERHEATER PRIMARY SUPERHEATER OUTLET BURNERS (04 EA) GAS DEFLECTOR SEC. SUPERHEATER INLET DOWNCOMERS RISERS

28. Interlocks bypass Philosophy The MOS bypass system allows inhibiting maximum two interlocks. In case more than 2 securities are bypassed simultaneously, complete boiler trip will be generated. Low Level Drum Security 03 level switches on steam drum and tripping on 2oo3 logic. As per NFPA clause, Low level security should not have time delay. B-605 low level trip 2oo3 logic modification is under study. B-601/602 also have only one level switch. B-4601 or Latest Boilers BMS have following additional features. B-605 VS B-4601

29. Natural Draft Sequence When boilers trips on FD fan security (low speed or low P) natural draft sequence starts for 15 mins Burners damper full open during this sequence The purpose of natural draft sequence is to provide some time for dispersion of gases and pulling in some air to reduce combustion chamber temperature. During this time, FD fan can not be started. B-605 VS B-4601

30. Natural Gas Leak Test After completion of Purging, Fuel gas header block valve is opened and vent valves are closed. FIC is opened while burner block valves are closed. Fuel gas pressure is maintained ≥1 kg/cm 2 . In case of the Natural Gas pressure remains stable, the leak test is completed. If during the control time the fuel gas pressure increases/decreases, the sequence will be automatically stopped. Emergency Shutdown Boiler tripping from HMI in addition to BMS panel and field push button, through interlock. Suggested by Vendor but not Incorporated. B-605 VS B-4601

31. MODERN TECHNOLOGY

32. These boilers, in contrast to recirculation or natural circulation units, are characterized by continuous flow paths from the evaporator inlet to the superheater outlet without a separation drum in the circuit. Once Through Boiler (Drum less)

33. Once Through Boiler Characteristics Once-through boilers are able to produce steam at higher pressures and temperatures than drum boilers. Raising steam conditions (pressure and temperature) can enable efficiency gains in power generation equipment, allowing an operator to reduce its fuel consumption and CO 2  emissions. They have high load response characteristics due to the fact that it does not have a drum and has a much lower water inventory.

34. Once through boilers of super-critical pressure boilers have higher efficiency. However in the sub-critical range there is no difference in efficiency when compared to the drum type design. The water quality level is much more stringent than drum type boilers. Normally a condensate polishing unit is employed in once through units Once through boilers capital cost is approx. 2–4 % more than the drum type units due to high grade material required. Once Through Boiler

35. Drum Boilers In a drum boiler, the circulation of water is produced through the density difference of water in the down comer pipe and the water/steam mixture in the furnace tubes. Cold start-up takes much more time in drum type units as the metal temperature difference across the thickness dictates this. Drum type units do not find application in super-critical pressure power plants. The water chemistry is maintained within a band and can accommodate some variations when compared to once through type boilers.

36. Sub-Critical Boilers Super-Critical Boilers Once Through Boiler

37. Super Critical Technology P V Critical point Latent Heat At Critical point, no Latent heat is required

38. Super Critical Technology Critical Point The critical point of a substance is the temperature and pressure at which that substance can behave like a gas and a liquid at the same time, hence indistinguishable gas and liquid phases occur. That is because the density of the gas phase and the liquid phase is equal at this point. Critical Temperature The  critical temperature  of a substance is the temperature at and above which vapor of the substance cannot be liquefied, no matter how much pressure is applied. Critical Pressure The critical pressure of a substance is the pressure required to liquefy a gas at its critical temperature.

39. The critical pressure and critical temperature of water / steam are 22.12 MPa (225.5 kg/cm 2 ) and 647.14 K (373.9 °C) , respectively. Any boiler that operates below the critical point is called a subcritical boiler, and one that operates above the critical point is known as a  Supercritical   boiler. Super Critical Technology

40. Higher efficiency compared to the typical subcritical cycle. Less fuel consumption Less carbon emissions Less water consumption Low NOx emissions There is no bubble formation in Super critical boilers Salient Features of SC Technology

41. Operational flexibility Better temperature control and load change flexibility Shorter startup time More suitable for widely variable pressure operation Controls only Feed water flow Higher the steam pressure lesser the volume which would save piping, turbine volume thereby saving equipment weights and costs. Salient Features of SC Technology

42. Subcritical VS Supercritical Boilers Description Sub-Critical Super Critical Temperature < 530 °C 550 – 650 °C Pressure < 218 kg/cm 2 > 224 kg/cm 2 Water Circulation Natural or Forced Forced Circulation Ratio 3 - 20 1 Overall Cycle Efficiency 30 – 36 % 40 – 46 % Steam Dum Yes No Startup time More Less Blowdown water loss More Less Comparison

43. The steam separator acts similar to a drum in a natural circulation boiler. The fluid from this separator is recycled to the economizer inlet where it mixes with feedwater to maintain the minimum flow through the boiler furnace during startup. This system provides the maximum amount of heat recovery back to the boiler during startup allowing for rapid startups with the least amount of thermal stress on the components Steam Separators

44. Fuel Flexibility Modern Boilers have dual firing system i.e. Natural gas with Coal or Oil, Coal with Biomass. Flue Gas Cleaning System Removal of Dust, SOx and NOx. Dust is removed by Electrostatic Precipitators. Dry scrubbers are used for De- sulphurization Selective Catalytic Reduction (SCR) for NOx removal. Cyclones for Ash removal (in case of solid fuel) Additional Features of Latest Boilers

45. Reheater System Reheater is installed in path of flue gases after superheater. Exhaust steam from Turbines exhaust is superheated again through flue gases. It increased cycle thermal efficiency. Air Pre-heater Pre-heats combustion air with flue gases. Two stage Attemperators Fine control of superheater steam final temperature. Additional Features of Modern Boilers

46. Sub-critical Boiler with Natural water Circulation Fuel: Pulverized Coal, Natural Gas, Off Gas

47. Once Through Boiler for Super-critical application Fuel: Pulverized Coal, Natural Gas, Off Gas

48. Circulating Fluidized Bed Boilers Bubbling Fluidized Bed Boilers Other Types of Boilers Fluidization is an operation in which fine solids (fuel) is transformed into fluid like state through contact with gas (air) The chief advantage of fluidization is that the solid is vigorously agitated by the fluid passing through the bed, and the mixing of the solid ensures that there are practically no temperature gradients For Solid Fuels

49. Fluidized bed Boilers Advantages Low environmental impact Preferred in Co-firing system In normal boilers, temperatures inside the furnace reaches 1400 – 1500 °C, While temperatures inside a CFB are in the low range of 800 – 900 °C Thus, inhibiting the generation of thermal nitrogen oxides (NOx whose production is dependent on combustion temperature).

50. Biomass Fuel-fired Boilers A wide range of biomass mixed co-firing rates can be realized by applying coal/biomass dual system (coal pulverizer /burner) to coal-fired power generation technologies. Biomass co-firing rates can be adjusted without major changes of equipment. In addition, it is possible to have 100% biomass firing in a boiler by adding a small amount of coal ash

51. Bubbling Fluidized Bed (BFB) Boilers A bubbling fluidized bed (BFB) boiler is a boiler that can also handle fuels that are difficult to pulverize or less combustible. The fuel is introduced into a mixture of sand flowing at high temperatures, allow The release of pollutants such as nitrogen oxides (NOx) can be reduced due to sufficiently low-temperature combustion (~900℃). ing the fuel to be efficiently combusted. Circulating fluidized bed (CFB) boilers from Mitsubishi Power are able to combust a wide range of fuels, including bituminous coal, brown coal, anthracite, petroleum coke, wood biomass, paper sludge, RPF (refuse paper & plastic fuel) and waste tires, and have high combustion efficiency. Low environmental impact As for temperatures inside the furnace, while a regular boiler reaches 1,400-1,500°C, temperatures inside a CFB are in the low range of 800-900°C, thus inhibiting the generation of thermal nitrogen oxides (NOx whose production is dependent on combustion temperature). Further, with the use of two-stage combustion, NOx generation can be limited to less than 100 ppm

52. Sub-critical Boiler with Natural water Circulation Fuel: Natural Gas or Off Gases

53. Sub-critical Boiler with Natural water Circulation Fuel: Pulverized Coal

54. Fire tube boiler Water tube boiler Package boiler Stoker fired boiler Pulverized fuel boiler Waste heat boiler Fluidized bed boiler Types of boiler

55. B-605 PARTS LIST STEAM DRUM LOWER DRUM BOILER BANK TUBES FLOOR TUBES FRONT WATER WALL BOILER SIDE WALL UPPER SIDE WALL DISTRIBUTION HEADERS BOILER REAR WALL TUBES SIDE WALL HEADERS SATURATED STEAM OUTLET SUPERHEATER ROOF RISER TUBES STEAM OUTLET HEADER ACCESS DOOR AIR INLET PLENUM BURNERS AIR SUPPLY DUCT BURNERS ASSEBMLY WINDBOX ASSEMBLY FURNACE FLOOR TILES CROSS FLOW BAFFLES BOILER BUCKSTAY MINERAL FIBER BLANKET FURNACE ROOF TUBES RIBBED CASING RISER TUBES