ADVANCED CLEAN TECHNOLOGY FOR POWER GENERATION

Transcription

1 ADVANCED CLEAN TECHNOLOGY FOR POWER GENERATION ultra supercritical boilers

2 boiler solutions for a world

3 OF ENERGY

4 Burmeister & wain energy a/s...it all began in 1843 Burmeister & Wain Energy A/S is a Danish company with many years of experience as a supplier of high-tech solutions for the power generation industry. The company dates back to a period when Denmark s industrial development had not yet gained momentum. The history of the company began in 1843 when a young and enterprising engineer, Hans Heinrich Baumgarten, was awarded a royal license to establish a machine shop in Copenhagen. In 1846 he went into partnership with Carl Christian Burmeister. Baumgarten retired in 1861 and was succeeded in 1865 by William Wain, and the company Burmeister & Wain was finally founded in 1872 soon becoming the largest and most important enterprise in the iron industry of Denmark. The first once-through Benson boiler was supplied to Masnedø Power Station in 1960 and in 1997 the first Ultra Supercritical (USC) boiler in Europe was supplied to Skærbæk Power Station unit 3. This was followed by the second USC boiler in 1998, Nordjylland Power Station unit 3 - with a net efficiency above 47% establishing a world record. In 2001 the first USC Boiler with a unique multi-fuel firing system was supplied to Avedøre Power Station unit 2. The boiler can utilize coal, HFO, NG and wood pellets as fuel. With the possibility of operating at full load on 73% biomass as fuel input, the unit is the largest biomass boiler in the world. In 1980 Burmeister & Wain Energy A/S (BWE) was established as an independent company, and in 2002 it was acquired by the Italian company STF SpA. The boiler history of Burmeister & Wain has its origins in the second half of the 19 th century when the company supplied steam for the industrial revolution in Denmark in the shape of marine boilers, industrial boilers and power station boilers. Throughout the following century, the company continued to develop the boiler technology and in 1955 a Benson license for once-through boilers was acquired.

5 Vision To remain a leading supplier of boiler and environmental technology through technology supply and engineering services to national and international clients. To be a significant international player in the upgrading of existing boilers for higher efficiencies, lower emissions or for conversion to alternative fuels. To be a significant European player providing services and maintenance to utilities directly or through alliances.. this to ensure and enjoy a better future Advanced Clean Technology in Boiler Design Fossil fuels and especially coal will be the main energy source to cover the increased demand for power generation for many years to come in a growing world. The BWE Advanced Clean Technology in boiler design is an important factor in meeting the world s CO 2 reduction target. By introducing the best available technology both in new power plants and when retrofitting existing, the plant efficiency is increased and consequently the CO 2 emissions are reduced. The BWE Ultra Super Critical Flex Boiler is a solution to utilize fossil and biomass fuels in USC boilers maximizing efficiency, fuel flexibility and use of renewables. BWE benefits from being part of the history of power generation in Denmark Since the energy crisis of the early 70 s, Danish power industry has been focusing on the environment, fuel flexibility and efficiency. The first step to make Carbon Capture and Storage (CCS) viable is to maximize efficiency. The BWE USC Flex boiler and its high efficiency makes the subsequent implementation of the CCS technology feasible. The collaboration of BWE with local utilities has allowed our company to acquire direct experience with different fuels, biomass combustion, co-combustion, high efficiency and load flexibility. BWE is ready to export the Danish example in power generation to the worldwide market.

6 Sub, Super and Ultra Supercritical Boilers The background for the USC process is the well-known Rankine steam cycle which was further developed by BWE during the 1980 s and 90 s in the form of the Benson, once through principle, from the subcritical through the supercritical to the ultra supercritical design. Plant Efficiency (LHV) % BWE references Skærbæk 3* Avedøre 2* Nordjylland 3 Porto Tolle Fyn 7 Staudinger/Rostock** Asnæs 5 Walsum * Natural gas/hfo firing ** Partial scope Year During the transition period from subcritical to USC, the net electrical efficiency has increased from 40% to 49%. This transition process itself has been a step-wise progress and the outcome is now a success on all major technical features, i.e. the water/steam process, pulverized fuel combustion and heat transfer. During the period the steam temperature has increased from 540 C to 600 C and the pressure from 200 bar to 305 bar. Skærbæk Power Station owned by DONG Energy

7 The history of the Benson once-through boiler system -supplied on a license from Siemens since 1955 Asnæs Power Station unit 2 150MWe, 1961 Asnæs Power Station unit 3 250MWe, 1967 Fyn Power Station unit 7 400MWe, 1991 Nordjylland Power Station unit 3 415MWe, 1998 Operational flexibility in modern coal fired power stations Modern coal fired power stations should be able to follow demand changes rapidly and at the same time ensure reliability and availability The Benson Technology and the developed control philosophy follow this need.

8 Decades of experience designing and manufacturing once-through USC boilers The main design features of the Ultra Supercritical boiler are: One pass tower type design Superheaters and economizers in horizontal tubing Tangential firing system with circular burners This design is chosen because it gives the most compact, material-saving design. Process and operational wise, it also gives the advantage of a symmetrical and well defined flue gas flow, which will lead to a more homogeneous temperature profile of the flue gas and of the water/steam. In order to control the steam outlet temperatures in an economical way, an FGR (Flue Gas Recirculation) system can be installed. The BWE design consists in a fully drainable tower type boiler for Ultra Supercritical installations adaptable both for the single and for the double reheat water/steam cycle. For efficiency reasons BWE recommends the single train air/gas flue gas path. The boilers are equipped with a complete BWE multi-fuel Low-NOx firing system and an SCR system capable of bringing the NOx emission as far down as 50 mg/nm 3. Avedøre Power Station, owned by DONG Energy

9 Standard size BWE USC boilers BWE has three 400 MWe size USC references. Using the design and operation experience from these, BWE has developed a standard coal fired 400 MWe net USC Boiler. 3D model of a standard 660 MWe size boiler island. BWE has also developed a standard 660 MWe size boiler. 3D model of a standard 400 MWe size boiler island. Due to its long experience with USC boiler design and available engineering resources, the company is also qualified for the supply of larger size boilers, such as the 800 and 1100 MWe class

10 Best Available Technology The plant efficiency can be increased by: raising live steam parameters (temperature and pressure) reducing the condenser pressure by means of a cold and effective cooling media - preferably sea water using reheat or maybe double reheat optimizing the feed water temperature selecting the single train mono component solution for the air/flue gas path and thereby reducing the auxiliary power increasing the boiler efficiency The boiler efficiency can be increased by: reducing the flue gas exit temperature by means of an effective air preheater reducing Unburned Carbon (UBC) in the fly ash by an effective combustion reducing the air excess and thereby obtaining a reduced flue gas loss reducing the leakage in the air preheater reducing the pressure loss of the water/steam cycle The USC boiler with a PF combustion system will still be the simplest and most efficient way of using coal for power generation.

11 Combustion system The design idea of the combustion system is to establish the best possible conditions for Low NOx combustion. The circular burners are placed in the corners of the furnace. Above each burner are OBA (Over Burner Air) openings, and at the top of the furnace OFA (Over Furnace Air) openings, which together with the air split in the burners establish the air staging. Tangential firing Up to 6 burner levels n*4 Low NOx BWE Circular Burners (3 air stages) Single Burner Concept (full control of coal / air ratio) Low Air Excess 1.15 (full load) OBA (protection of membrane walls) OFA (air staging)

12 Low NOx Combustion and a wide range of fuels The BWE Low NOx burner can be applied for fuels in fluid, gaseous and pulverized form. One burner may operate on any of the 3 types of fuels. BWE has references on hard coal, HFO, NG, pelletized peat & biomass (wood & straw).

13 Improved SCR built in The installation of an SCR becomes mandatory. Tower type boilers are suitable for easy installation of SCR. The split ECO improves SCR operation (320 to 400 C) in full load range. The design of an SCR without bypass prevents leakage in bypass dampers and results in proper heating of SCR during start up. In addition a flue gas recirculation system improves SCR operation at low load.

14 Regenerative Air-preheaters and Gas-Gas heaters Regenerative heat exchangers play an important role in fossil fuels steam power plants as air preheaters (APH) and as gas-gas heaters (GGH) in emission control plants such as FGD plants and tail-end SCR plants. The BWE APH and GGH heat exchangers operate according to the rotating, regenerative, counterflow principle. Heat transfer elements placed as a matrix in an open rotor transfer heat from one gas sector to another when slowly rotating. The heaters are equipped with various sealing systems in order to minimize the leakage of air to flue gas or untreated gas to treated gas. Quad sector type APH and single train solution The secondary air section is divided into two sections embracing the primary air section which reduces the air leakage. This single train train design can improve the overall efficiency of approximately 0.2%.

15 Improved sealing system for APH & GGH Automatic leakage control system In order to minimize the leakage between the gas flows which is not beneficial for the overall plant efficiency, BWE has developed a highly efficient sealing system for the radial sector seal plates. The Active Leakage Control is an important feature for rotating regenerative heat exchangers and BWE s inductive system has proved to be particularly suited for this application. Cold condition Hot condition The system: is insensitive to gas properties and fly ash content requires very little maintenance being a none contact system has proved to have a very high reliability has been in continuous development since 1978

16 High pressure piping design BWE has a long-standing experience in design, manufacturing and delivery of high pressure piping systems including spherical TEEs and hangers. Highly sophisticated software tools with integration between 3D modeling (PDMS) and pipe stress analysis (RORHII) ensure an efficient and reliable design according to state-of-the-art design codes like EN and ASME B31.1. Safety valve arrangement The boilers are equipped with safety valve arrangements according to EN x HP combined controlled bypass and safety valve (Hydraulic Spring loaded) 2 x RH safety valves (Hydraulic Spring loaded) Spherical TEE The 100% combined HP bypass and safety valves secure sufficient cooling of the RH heating surfaces during turbine trip. Furthermore, the arrangement of the steam lines is simplified. Pipe routing in 3D system (PDMS) The LP-bypass valves dumping the steam to the condenser normally have a capacity of 60-70%.

17 Improved design and material development The improvements in the steam cycle and the related development of new materials have also been accompanied by major improvements in the design of boilers, turbines and other main components of the power plant. The main design challenge in USC boilers can be found in the thick walled steam headers, the superheaters and the furnace walls. The challenges are connected with the selection of materials and manufacturing methods. In drum boilers, it is possible to make the boiler pressure system in normal ferritic materials. For the higher pressures and temperatures in the USC boiler, new ferritic/ martensitic high-temperature steels like the P91 and P92 have been developed for commercial use. For the final stages in the superheaters, a line graine austenitic material like TP347HFG or Super304 has been selected as having the necessary creep rupture strength and high temperature corrosion resistance. By only using the austenitic materials in the relatively thin walled tubes, the problem with thermal fatigue is minimized.

18 Nordjylland Power Station Unit State of the art Clean Coal Technology USC Coal fired Boiler - double RH 415 MWe Nordjylland Power Station near Aalborg (Denmark), owned by Vattenfall, represents the latest technological development with respect to coal fired units and consists of an Ultra Supercritical (USC) boiler with full flue gas cleaning, i.e. NOx, dust and SO2 removal. In addition to producing electricity to the public grid, the plant also supplies heat to local district heating companies. The plant was put into commercial operation in Operational results: Size 415 Type Tower RH Cycle Double FW temperature 298 C HP pressure 290 bar HP/RH temperature 582/580/580 Plant efficiency 47% More than 65,000 of operational hours have proven: Plant efficiency > 47% Availability > 98%

19 Boiler The boiler of Nordjylland Power Station unit 3 is a supercritical, once-through tower boiler of the Benson type with double reheat. The furnace walls are designed as membrane walls with helical tubing. By using special materials, it has been possible to design the boiler to very advanced steam data. A flue gas recirculation system (FGR), including reheat of the flue gas in a special sector in the quad sector air heater, is installed as part of the control of the IP outlet temperature. Low-NOx tangential firing system single train solution The USC boiler of Unit 3 was designed with special attention to minimizing the emission of nitrogen oxides (NOx). The tangentially fired boiler with four levels of burners includes Over Burner Air (OBA) nozzles above each burner and Over Fire Air (OFA) nozzles above the upper level of burners. This concept of air staging brings the NOx level below 475 mg/nm 3.

20 Avedøre Power Station Unit USC Multi fuel Boiler 415 MWe Avedøre Power Station Unit 2, owned by DONG Energy, is one of the most efficient, fuel flexible, and environmentally friendly power plants in the world. In addition to generating electricity, the plant supplies heat to the Copenhagen district heating network as well. The main plant of Avedøre Power Station is the Ultra Supercritical (USC) unit incorporating a BWE once-through, Benson, tangentially fired boiler. The plant has a total output of 415 MWe. Of these more than 300 MWe can be achieved by biomass firing (wood pellets). Operational results: Size 415 Type Tower RH Cycle Single FW temperature 320 C HP pressure 305 bar HP/RH temperature 582/600 Plant efficiency 49%

21 Boiler The boiler of Avedøre Power Station unit 2 is a supercritical, once-through tower boiler of the Benson type with single reheat. The furnace walls are designed as membrane walls with helical tubing. By using special materials, it has been possible to design the plant to the very advanced steam data (HP: 305 bar, 582 C and RH: 74 bar, 600 C with the biomass boiler in operation). Multi Fuel Firing System The USC boiler of Unit 2 has been designed with a unique multi-fuel firing system which makes it possible to utilize: coal, HFO, NG and wood pellets as fuels. All these fuels can be burned in the same burners. These are placed at four levels in the corners of the large furnace, having a low thermal loading. The air staging is carried out through the burners as primary, secondary and tertiary air and above the burners as Over-Burner-Air (OBA) as well as Over-Fire-Air (OFA). This concept of air staging ensures the low primary formation of NOx.

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24 STF S.p.A. Via Robecco, Magenta (MI) Italia Tel: Fax: BWE Burmeister & Wain Energy A/S Lundtoftegårdsvej 93A DK-2800 Kgs. Lyngby - Denmark Tel: Fax: info@bwe.dk BWE Energy India Pvt. Ltd No. 43, KB Dasan Road Teynampet Chennai TamilNadu, India Tel: /2 Fax: info@bweenergy.in