Combustion And Pulverized Coal Firing System

Traditionally, blending coals of differing ranks complicates the combustion system design for boilers and requires oversizing and compromising of optimal performance as individual equipment is required to operate in a nonideal mode. In such a scenario, effectively, the equipment must try to meet the differing needs of both coals at the same time which means that it won’t be operating as efficiently as would otherwise be the case.

Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project 1.1.5 COMBUSTION AND PULVERIZED COAL FIRING SYSTEM 1.1.5.1 In-Furnace Blending Technique July 7, 2014 Traditionally, blending coals of differing ranks complicates the combustion system design for boilers and requires over-sizing and compromising of optimal performance as individual equipment is required to operate in a non-ideal mode In such a scenario, effectively, the equipment must try to meet the differing needs of both coals at the same time which means that it won’t be operating as efficiently as would otherwise be the case B&W has extensive experience with a wide range of coals sourced world-wide and recognizes that for a design that will utilize differing ranks of fuels, such as those proposed here, a better design solution is required For this project, B&W is proposing to utilize an In-Furnace Blending Technique and has designed the equipment to complement this strategy while still providing maximum fuel flexibility for 100% operation on either Coal A or Coal B In practice, B&W has developed a strategy for blending Coal A and Coal B in the furnace rather than in the coal handling system The In-Furnace Blending Technique simplifies the coal handling system and reduces associated costs by eliminating the need for coal blending equipment in the coal yard It also allows the pulverizers to operate more efficiently and reduces the total number required, because the more difficult to grind coal is isolated in particular mills Each coal is fed, without need for blending, to the selected raw coal storage silos All silos can be filled with Coal A, all with Coal B, or any combination of silos with either Coal A or Coal B This provides fuel flexibility while minimizing equipment requirements All feeders, pulverizers, and control hardware remain identical among the six supplied pulverizers This provides for 100% MCR operation firing Coal A and 100% MCR operation firing Coal B Blending is accomplished by distributing the coals into the appropriate number of mills It is envisioned that for the Performance Blend (70% Coal A, 30% Coal B by weight), three mills would handle Coal A and two mills would handle Coal B as shown in Figure below B&W Proposal P-043049 Page of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project July 7, 2014 Figure 1: Example of In-Furnace Blending scenario for performance blend firing The In-Furnace Blending practice will reduce the quantity of pulverizers required from eight to six, while still meeting n-1 operation (one pulverizer out of service) at 100% MCR load firing the Performance Blend All of the low NOx DRB-XCL® burners are also identical and suitable for firing either Coal A or Coal B to the maximum rated heat input All of the burners served by a given pulverizer are situated in a single horizontal row This results in three burner rows on the front wall and three on the rear wall of the furnace In order to provide maximum fuel flexibility, the pulverizers/combustion system is designed to accommodate differences in coal throughput depending upon which coal is in use in a given pulverizer For example, to operate at the same firing rate on the respective burners, the pulverizer(s) using Coal A would operate at approximately 40% higher coal feed rate compared to the pulverizer(s) using Coal B B&W Proposal P-043049 Page of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project July 7, 2014 Typically, certain pulverizer groups and their related coal silos would be dedicated to either Coal A or Coal B, when both coals were simultaneously in use In any case, the differences in coal properties make it clear which pulverizers are operating with which coal Pulverizers operating with Coal A will require much higher primary air temperature into the pulverizer in order to sufficiently dry this coal, due to the higher coal moisture, and due to the higher coal HGI, will demand less power consumption and pressure drop during pulverization The coal/air temperature leaving the mill will be 130-140°F (54 – 60°C) with Coal A Conversely, pulverizers grinding Coal B will operate with higher power consumption and pressure drop, due to the lower coal HGI, and considerably lower mill inlet temperatures for coal/air exit temperatures of 170-185°F (77-85°C) due to the lower coal moisture content It is not possible (or desirable) to operate with Coal A and outlet temperatures over ~60°C, thus making clear to the operator which fuel is in use in a given pulverizer Normally all in-service burners are fired at the same thermal input However, this combustion system is designed to facilitate bias firing to provide even greater fuel flexibility Bias firing refers to operation at somewhat different firing rates (thermal inputs) on different burner rows Bias firing therefore requires the ability to balance combustion air to firing rate on a per burner row (per pulverizer) basis This enables the most efficient operation with minimum NOx emissions Combustion air management is provided by the compartmented windbox burner arrangement shown in Figures and below B&W Proposal P-043049 Page of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project July 7, 2014 Figure 2: Compartmented Windbox with Feeder Ducts and Pitot Grid Array (Typical) As illustrated, all burners fed from a particular pulverizer are located in a single row Each burner row is separated by partition plates from the other burner rows, effectively providing individual windbox compartments for each burner row Feeder ducts supply secondary air to each end of each compartment Each feeder duct is equipped with a pitot grid array to provide an accurate indication of secondary air flow Each feeder duct is also equipped with an automated damper to regulate the secondary air flow per compartment in accordance with the associated pulverizer operating conditions B&W Proposal P-043049 Page of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project July 7, 2014 Figure 3: Compartmented Windbox (outlined orange) with Feeder Ducts (shaded blue) In summary, in-furnace blending provides a more efficient means of handling coals with widely different characteristics It eliminates the need for coal blending equipment in the coal yard, and reduces the necessary grinding penalties on some of the pulverizers In this case it reduced the pulverizer quantity from eight to six, while enabling use of the coals singly or in combination The compartmented windbox burner arrangement provides greater operating flexibility while managing air/fuel on a per-pulverizer basis B&W Proposal P-043049 Page of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project 1.1.5.2 July 7, 2014 B&W’s Burner Technology for Low NOx Combustion Babcock & Wilcox has a long history of innovation and successful application of combustion systems to effectively and reliably reduce NOx emissions on coal-fired boilers B&W has sold more than 115,000 MWe of low NOx combustion equipment since the early 1970’s This includes B&W’s robust and well proven DRB-XCL™ burner design capable of producing low NOx in both staged and un-staged modes of operation with over 22,000 MW of installations The Dual Register XCL burner is B&W’s second generation low NOx burner The DRB-XCL® is mechanically designed for long service life and reliable operation The functional design is very well suited and proven for firing a wide variety of coals, ranging from lignite and sub-bituminous to bituminous This makes the DRB-XCL® particularly well suited for the Duyen Hai project, where coals with widely different characteristics are intended for use The DRB-XCL® is physically arranged as shown in the illustration below The burner nozzle is equipped with Conical Diffuser/Deflector hardware to accomplish the necessary fuel mixing The majority of the pulverized coal (PC) enters the burner nozzle along the outer radius of the B&W Proposal P-043049 Page of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project July 7, 2014 burner elbow due to centrifugal forces The deflector at the entrance of the burner nozzle redirects the PC into the bullet portion of the conical diffuser where the dense stream is dispersed The dispersed PC is shaped by the conical shroud around the bullet to form a fuel rich ring near the wall of the coal nozzle, and fuel lean in the center This fuel pattern serves to improve the rate of ignition and flame stability of the burner The burner is specifically designed to generate rapid heating and high temperatures in the fuel rich flame core This causes more of the coal to burn as volatile matter and releases a larger portion of the fuel nitrogen early in the combustion process, leaving less in the char By limiting available oxygen in the flame core, NOx formation is minimized At the same time, reducing species are generated from the volatile materials These propagate into the flame to aid in reducing NOx formed in the later zones of the flame Char oxidation occurs last at reduced temperature and oxygen concentrations, thereby limiting NOx formation during char burnout NOx ports can be added when further NOx reduction is required Typical B&W DRB-XCL® Burner Staged & Unstaged Low NOx Sliding Air Damper Conical Diffuser Air Measuring Pitot Grid Stationary Vane Outer Zone Adjustable Vane Inner Zone Adjustable Vane Pulverized Coal and Primary Air Inlet Secondary Air (SA) flow to the burner is regulated by a sliding air damper The slide damper can be positioned by an automated actuator (as illustrated for use in open windboxes) or by a ratchet jack device for use in compartmented windboxes An impact/suction pitot tube grid is located in the burner barrel to provide a local indication of secondary air flow for each burner With this information, the secondary air can be more uniformly distributed among all the burners in a given compartment, by appropriately adjusting the sliding air dampers B&W Proposal P-043049 Page of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project July 7, 2014 Downstream of the pitot tube grid are the inner and outer air zones Adjustable vanes in the inner zone impart sufficient swirl to stabilize ignition at the burner nozzle tip The outer zone, the main SA path, is equipped with two stages of vanes The upstream set is fixed and improves peripheral air distribution within the burner The downstream set is adjustable and provides proper mixing of this secondary air into the flame The DRB-XCL® is designed for long service life and reliability This framework and structure was first developed by B&W in the 1980’s and has proven to reliably withstand the rigorous conditions prevalent in utility coal fired boilers The DRB-XCL® benefits from experience and refinements incorporated into the mechanical design over many years The burner nozzle is lined with ceramic tile to protect the nozzle from erosion The conical diffuser and deflector are constructed from nitride bonded silicon carbide and provide excellent resistance erosion All of the front end elements of the burner are fabricated from high quality stainless steel to protect against overheat damage The structure of the burner includes a system of longitudinal stiffeners to accommodate thermal expansion, while avoiding distortion or loss of function Each burner is equipped with shop-installed thermocouples to provide indications of front end burner temperatures to guard against overheat An Advanced Over Fire Air System is integrated with the DRB-XCL® burners for this project The rugged, adjustable Dual Zone NOx ports supply the remaining over-fire air (OFA) necessary to complete combustion Correct separation between the OFA system and burners provides time for more NOx reduction, and provides more complete char burnout ahead of the OFA system The DRB-XCL® burners were sized for the Duyen Hai application by considering the specified Coal A and Coal B being fired in setting the optimum burner velocities The range coals as well as the additional coals specified in Section 1.1.1 were considered in order to check that acceptable velocities were also attained while firing these coals The adjustable Dual Zone NOx ports were sized by considering the performance design coal being fired in setting the optimum burner velocities at an overall design burner zone stoichiometric ratio of 0.95 The range coals as well as the coals listed in Section 1.1.1 were considered in order to check that acceptable jet penetration velocities were also attained through the Dual Zone NOx ports while firing these coals at the expected design stoichiometric ratio B&W Proposal P-043049 Page of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project 1.1.5.3 July 7, 2014 Burners and NOx Ports Each unit will be supplied with thirty (30) Babcock & Wilcox Dual Register DRB-XCL® coal burners, ten (10) heavy fuel start-up oil burners, and one level of ten (10) Babcock & Wilcox Overfire Air Ports Each burner includes the following:  Ceramic-lined coal elbow at inlet  Coal nozzle with conical silicon carbide diffuser  Silicon carbide deflector for optimum distribution of coal in the nozzle  Adjustable inner and outer air zone spin vanes to control air swirl  Air slide disk, with manual actuator, to adjust burner air flow and to permit burnerto- burner air balancing  Local burner air flow indicator  Class I ignitor with high energy spark system  Flame detector sighting tube  Observation door Each of the lowest level of burners will also be supplied with the following:  One heavy fuel oil start-up burner B&W Dual Zone NOx ports of the Advanced OFA system are designed and arranged to reduce NOx emissions by air staging The unique dual zone design improves mixing capability, in order to reduce NOx while minimizing unburned combustibles A sliding sleeve, is manually adjustable to optimize, regulates airflow to each port The air then proceeds to either the central core zone or the outer air zone The core zone provides an axial jet of air to penetrate and mix with flames further out in the furnace Air through the outer zone is swirled to better mix with flames and gases closer to the wall B&W Proposal P-043049 Page of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project July 7, 2014 Each Dual Zone NOx port includes the following:  Manual actuator to adjust secondary airflow through the sliding sleeve  Manually adjustable disk to regulate airflow to the core zone  Manually adjustable vanes in the outer zone  Pitot grid to locally indicate NOx port airflow Typical Dual Air Zone NOx Port With Total Air Flow Control B&W Proposal P-043049 Page 10 of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project 1.1.5.4 July 7, 2014 Heavy Fuel Oil System Each burner will be equipped with one oil-fired retractable igniter The total capacity of all thirty (30) igniters will be approximately 12% of BMCR heat input Each burner of the bottom row will be equipped with one oil-fired burner The total capacity of all ten (10) oil start-up burners will be approximately 30% of BMCR heat input The fuel flow to a group of igniters will be set using control valves A safety shutoff valve will be provided to isolate the fuel flow to the igniters in the event of a trip condition Each oil burner will be controlled the same, but individually not as a group A high energy spark will be used to initiate igniter flame The igniters will continue to fire until coal firing and or oil burner is established, or until stopped by the operator The scope of supply will include the following: 1.1.5.5  Thirty (30) Class l igniters with steam atomization and HEI igniters  Ten (10) oil start-up burners with steam atomization  Thirty (30) Flame scanners  Valves, piping, and instrumentation within the boiler island  x 100% scanner cooling fans B&W Roll Wheel Pulverizer Since its introduction in 1972, B&W’s Roll Wheel type pulverizer has demonstrated reliable and durable operation With over 1,100 mills in operation worldwide, B&W has the proven experience that makes this Roll Wheel pulverizer the equipment of choice for power plant owners The B&W Roll Wheel Pulverizer is described in detail in this section In summary, B&W’s pulverizer design features and enhancement translate into:       B&W Proposal P-043049 Reduced operating and maintenance costs Extended capacity and fineness ranges Reduced pressure drop Extended turndown range Controlled low-load vibration Increased wear life of pulverizer components Page 11 of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project July 7, 2014 B&W’s 98G pulverizer, which is proposed for this project, successfully demonstrates these benefits These pulverizers are used at the 425 MW Millmerran units in Australia, which fire a very high ash content erosive coal Comments from the Millmerran plant manager, excerpted here, support B&W’s claim for the Roll Wheel Pulverizer as the finest coal pulverizer on the market today For our particular application, we have found that the B&W coal Pulverizer can accommodate a wide range of fuel quality, since coal for this plant is mined from a narrow seam strip that often includes a significant amount of overburden The pulverizers continue to operate smoothly with no vibration, and the capacity and fineness predictions for these mills continue to be achieved I am pleased to recommend the B&W-98 Coal Pulverizer for any boiler unit requiring this size mill Sincerely yours, Mal Gamble Plant Manager The B&W type pulverizer employs the roller principle of grinding The required capacity is provided by large, low speed grinding elements The grinding elements of wear resistant VAM 20 materials consist of three rollers and a lower grinding ring The B&W pulverizer is designed to accept a raw coal feed sized to pass through a 1-1/2 inch ring Operation, maintenance, and performance of the pulverizers may be affected if coal provided exceeds this size B&W Proposal P-043049 Page 12 of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project July 7, 2014 Raw coal enters the pulverizer through a downspout in the center of the pulverizer, flows radially outward due to centrifugal force where it is pulverized between the rollers and grinding ring segments A stream of preheated primary air picks up the partially pulverized coal from the grinding zone and carries it to the Dynamically-Staged, Variable-Speed DSVS™ classifier There the coarse particles are separated from the fines and returned to the grinding zone while the fines are air borne through the coal-air piping to the burners DSVS™ Classifier Preheated air of the required temperature is obtained by proportioning hot and cold primary air to each individual pulverizer B&W Proposal P-043049 Page 13 of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project July 7, 2014 B&W 98 Roll Wheel Pulverizer Pulverizer isolation for maintenance or inerting purposes is accomplished by closing the primary air isolation guillotine damper in the primary air connection to each mill, closing the feeder and mill seal air valves, and closing the feeder discharge valve The hot and tempering air dampers and burner line automatic shut-off valves are closed by the burner control system Manual knife gate valves are provided in the burner lines at an elevation near the burners and are closed during pulverizer maintenance for additional isolation and protection B&W Proposal P-043049 Page 14 of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project July 7, 2014 The B&W Roll Wheel Pulverizer offers a number of advantages:  No loss of capacity with wear The unique loading system on the roll wheel assemblies allows the rolls to move in two (2) different directions, along the axis of rotation and perpendicular to that axis in a pendulum-like motion This second motion allows the roll to adjust to the contour of the coal bed and the grinding track The same pressure is exerted on the coal bed Therefore, the capacity and particle size distribution to the classifier remains constant over the life cycle of the grinding elements With over 1,100 mills running on a wide variety of fuels, this company claim is accepted by the utility industry Confident application of B&W mills without need for over-milling for capacity loss provides good control range and eliminates the need for frequent classifier adjustment to compensate for changes in the product leaving the grinding zone Typically, the final adjustment by the start-up engineer is the last classifier adjustment needed, unless the coal quality changes B&W Proposal P-043049 Page 15 of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project  July 7, 2014 Superior maintenance access The B&W mill is designed with a single large maintenance door in the intermediate housing All maintenance on the interior of the mill can be accomplished through this door There is no need for an owner to provide for access on all sides of a mill with either a circular monorail or temporary cribbing over surrounding auxiliary equipment B&W Proposal P-043049 Page 16 of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project  July 7, 2014 Reduced mill down time during maintenance A roll wheel handling device (also called a “pogo stick”), as shown in the illustration below, is used to remove the roll wheels instead of overhead cranes The B&W mill is designed with a removable gear drive There is no need to unstack the mill to remove the drive Therefore, downtime is minimized B&W Proposal P-043049 Page 17 of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project  July 7, 2014 Minimum downtime for maintenance The normal maintenance schedule calls for getting inside the mill every 3000 hours Changing the roll wheel oil, making adjustments and general inspections require a tenhour shift with a two (2) man crew The B&W pulverizer is a very reliable, relatively maintenance free piece of equipment which will run 4-5 months between inspections  Conservatively designed gear drives Bearing selection will provide an L10 life of 100,000 hours or more based on the installed motor horsepower Gear rating will be based on AGMA standards with a minimum service factor of 2.2  Low speed, low vibration with a clean interior design The B&W 98G pulverizer has a grinding ring rotational speed of 22.8 RPM and a very clean interior design Areas where coal can collect or stagnate and promote fires are minimized These are eliminated entirely in areas swept by high temperature primary air This prevents unnecessary wear from local turbulence and is important to eliminating inservice fires  Good control of oversize particles The check-valve type discharge assembly from the classifier minimizes backflow of air and resulting re-entrainment of coarse classifier rejects B&W Proposal P-043049 Page 18 of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project  July 7, 2014 Ability to handle foreign material B&W recommends exercise of maximum care in preventing foreign material from entering with the raw feed Failure to control foreign material may eventually lead to damage to mill internals Recognizing the inevitability of foreign material under the best of conditions, B&W has designed the mill with massive grinding parts and low speed to provide maximum resistance to damage from tramp material  Automatic adjustable loading system - Improves turndown - External adjustment - Accommodates oversized coal, rocks and tramp materials For applications such as Duyen Hai where the flexibility to increase fineness and turndown is recommended in order to cover the range of varying HGI and fuel constituents, a dynamic classifier (DSVS™) is provided along with the adjustable loading system B&W Proposal P-043049 Page 19 of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project  July 7, 2014 Excellent erosion protection The B&W mill uses high alumina content ceramic tile liners to resist Cera-VAMTM Lined Turret Cera-VAMTM Lined Classifier Cone erosion in the grinding area, classifier and top of the turret in the mill for long life and reliable operation Cera-VAMTM Lined Housing Liners Cera-VAMTM Lined Roll Wheel Bracket Wear Plate 1.1.5.6 Pulverizer Sizing Pulverizers are selected such that BMCR load is met while firing 70% Coal A and 30% Coal B by weight via In-Furnace Blending for the Performance case, 100% Typical Coal A, or 100% Typical Coal B with five of the six B&W 98G pulverizers in service This approach optimizes unit performance for the Performance case across the boiler load range The resulting equipment also provides for BMCR load capability on all six pulverizers for the Coal A and Coal B range fuels B&W Proposal P-043049 Page 20 of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project 1.1.5.7 July 7, 2014 Inerting The inerting and clearing procedure is used to reduce the possibility of a pulverizer fire or explosion The inerting and clearing procedure is not required after a normal pulverizer shutdown where the pulverizer is swept clean of coal However in the case where the pulverizer trips unscheduled, it is required, and the pulverizer must be isolated against air infiltration before the inerting procedure can be initiated Steam is used as the inerting medium The rate at which it is admitted is such as to reduce the oxygen level in the mill to a non-explosive level within two minutes To maintain an inert atmosphere, an additional volume of media equivalent to the protected volume must be injected at the same rate approximately every thirty (30) minutes Notes: • • • Type “A” - fire extinguishing connections Type “B” - Inerting connection * - denotes pulverizer isolation system components Water spray nozzles are provided in the pulverizer windbox, pyrite box transition chute, and primary air duct near the pulverizer inlet for the purpose of clearing the coal from the pulverizer after a trip from load to reduce the possibility of fires and explosions In addition, water fogging nozzles are provided in the pulverizer windbox to reduce the migration of coal dust back into the primary air duct following a pulverizer trip from load B&W Proposal P-043049 Page 21 of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved Sumitomo Corporation for EVNGENCO1 Duyen Hai Extension, x 660 MWnet Power Project 1.1.5.8 July 7, 2014 Firefighting A water deluge connection is provided on the top of the pulverizer turret for fire extinguishing purposes 1.1.5.9 Coal Piping and Valves The pulverizer coal piping from the pulverizers to the burners will be of 10 mm nominal thickness carbon steel in the straight sections All changes in direction that are greater than 15 degrees will be lined with 12 mm think ceramic wear resistance material The ceramic wear resistant material extends meter downstream of the bend tangent The burner coal nozzles are partially lined with 12 mm think ceramic wear resistance material The piping will be designed to maintain maximum velocities in the range of 23 to 28 m/sec at maximum pulverizer load Provisions will be made to permit pulverized coal (PC) samples to be taken from each PC pipe Two ball valves and fittings will be installed per PC pipe Two dustless connectors will be provided per pulverizer Each PC pipe will be complete with a pneumatically operated barrier valve located at the pulverizer outlet In case of a pulverizer trip these valves will automatically close so that the mill can be isolated As specified by NFPA 85, pulverized fuel systems, each PC pipe is also supplied with a manually operated dust tight valve upstream of the burner inlet B&W Proposal P-043049 Page 22 of 22 PROPRIETARY AND CONFIDENTIAL Copyright © 2014 Babcock & Wilcox Power Generation Group, Inc All rights reserved ... certain pulverizer groups and their related coal silos would be dedicated to either Coal A or Coal B, when both coals were simultaneously in use In any case, the differences in coal properties make... due to the higher coal HGI, will demand less power consumption and pressure drop during pulverization The coal/ air temperature leaving the mill will be 130- 140 F (54 – 60°C) with Coal A Conversely,... Technology for Low NOx Combustion Babcock & Wilcox has a long history of innovation and successful application of combustion systems to effectively and reliably reduce NOx emissions on coal- fired boilers