采用超临界技术循环流化床锅炉的里程碑

发布于:2021-11-29 01:10:49

Milestones for CFB and OTU Technology The 460 MWe Lagisza Supercritical Boiler Project Update

Arto Hotta Ari Kettunen James Utt Foster Wheeler Global Power Group Clinton, NJ 08809

Presented at CoalGen Milwaukee, WI USA 8/1/2007

MILESTONES FOR CFB AND OTU TECHNOLOGY – THE 460 MWE LAGISZA SUPERCRITICAL BOILER PROJECT UPDATE
Arto Hotta, Director, R&D FW Global Power Group Ari Kettunen, Manager, R&D FW Global Power Group James Utt, Vice President, Utility Steam Generators, FW Global Power Group

ABSTRACT

When the Lagisza supercritical circulating fluidized bed (CFB), once-through utility (OTU) boiler goes into operation in early 2009, it will be the world's largest CFB

boiler at 460 MWe, and the world's first once-through supercritical CFB boiler. The unit will demonstrate the integrated features of both technologies. The CFB process includes features such as in-furnace sulfur capture

1

by simple injection of crushed limestone, low NOx emissions because of an inherently low furnace temperature and staged combustion, and fuel firing flexibility because of the vigorous mixing resulting from the flywheel of circulating solids. OTU features include the BENSON Vertical evaporator which is designed for low mass fluxes to give a self compensating "natural circulation" characteristic to accommodate heat flux variations within the furnace. Supercritical steam conditions (4000 psia, 1050/1075°F) and a backend gas cooling system that cools the flue gas to 185°F provides high cycle efficiency. Described in this paper are the CFB and OTU design features that make the Lagisza unit a state-of-theart power production facility. The paper describes the 460 MWe supercritical CFB boiler concept and presents the technical solutions of the boiler design with auxiliary equipment. The findings of the dynamic simulations of boiler operation are presented and discussed. An update on the progress of the plant, currently under construction will also be discussed. This remarkable milestone in the development of the CFB technology is continuing to even larger plant sizes. Boiler designs in size range of 600 – 800 MWe are currently being developed.
INTRODUCTION

Higher efficiencies in modern power plants are required not only for economic reasons but also for enhanced environmental performance in terms of reduced fuel needs, quantity of ash generated and pollutants emitted. Cutting CO2 -emissions has become increasingly important subsequent to the Kyoto Protocol and continuing global awareness of the need to reduce greenhouse gases. As coal will remain an important source of energy for many years to come the focus has been on improving the efficiency of coal fired power plants. To achieve this goal, supercritical steam cycles have been applied. Most of the utility power plants built for fossil fuels such as coal and brown coal over the last few years have deployed supercritical steam technology and have been based on pulverized coal (PC) fired oncethrough boiler technology. Circulating fluidized bed (CFB) technology has emerged as an attractive alternative to conventional pulverized coal-fired boilers in energy generation due to its environmental advantages and fuel flexibility. Over the last decade, CFB boiler technology based on natural circulation has reached utility scale. There are several CFB boilers in operation with sizes between 200 – 300 MWe. Among the largest units in operation are two 300 MWe CFB boilers at Jacksonville Energy Authority in Jacksonville, Florida, U.S.A delivered by Foster Wheeler. These boilers are designed to burn either 100% petroleum coke or 100% coal or any combination of the two. Foster Wheeler’s largest units in terms of physical dimensions are three 262 MWe CFB boilers at Turow power plant in

Poland. The fuel burned in these boilers is brown coal with 45% moisture content, which increases the flue gas flow considerably. Foster Wheeler’s CLECO project in Louisiana, currently under construction, utilizes two (2) 330 MWe natural circulation CFB’s burning a variety of fuels including 100% Petroleum Coke or 100% Illinois 6, Powder River Basin Coal, and Biomass. This “2 on 1” configuration allows for the use of a single 660 MWe reheat steam turbine in conjunction with 2 CFB boilers. Foster Wheeler’s CFB technology has evolved a step further, to larger sizes with supercritical steam parameters and once-through technology. The detailed engineering work for a 460 MWe supercritical CFB boiler for Poudniowy Koncern Energetyczny SA (PKE) in Poland has been finalized. This is a result of continuous and determined development work conducted by Foster Wheeler including an experience database of over 283 reference boilers in operation. Emphasis has been given to mechanical design issues and understanding the process conditions affecting heat transfer, flow dynamics, combustion characteristics, gaseous emission control and thermo hydraulics among others. Understanding of these processes has been verified by the work done in benchscale test rigs, pilot plants, field testing of operating units, model development, and simulation using developed semi-empirical models or more theoretical models. Design criteria’s for larger units have been developed and successfully implemented on the basis of data collected, model development work, and correlations with conventional boiler design.
PKE LAGISZA 460 MW PROJECT - PROJECT OVERVIEW

PKE is located in southern Poland in Katowice and it is the largest utility in Poland, operating eight power plants within a 50 km radius of Katowice. The company has installed capacity of over 5055 MWe, which is approximately 17% of Poland’s total generating capacity. In addition, the company has over 2541 MWth of district heating capacity, which accounts for 16 % of the local heat generating requirements of the Katowice area. In 2001, PKE announced a bidding process for supercritical once-through boiler delivery for 460 MWe unit in their agisza plant, with two alternative combustion technologies: pulverized coal combustion and circulating fluidized bed combustion. Foster Wheeler submitted proposals for both combustion alternatives. Both boiler proposals were based on BENSON technology with vertical tubing and low mass flux. Foster Wheeler was selected as the boiler supplier on December 30, 2002, with both combustion technology options. Ultimately, CFB technology was chosen by PKE for the agisza OTU boiler after an additional two months of detailed technical and economic evaluations with the following conclusions:

2

Total plant investment cost was lower for the CFB alternative. The installation of wet flue gas desulfurization (FGD) and selective catalytic reduction systems (SCR) systems that are essential for a PC-based solution can be eliminated while all emissions requirements are still fulfilled. Overall plant performance is better. Net plant efficiency using CFB technology and an advanced flue gas heat recovery system is approximately 0.3 % better than with PC solution with similar heat recovery system. Fuel flexibility provides a useful reliable operation and economic stability for the future. The unique multi-fuel capability of the CFB boiler provides a wider fuel range and the additional possibility of using opportunity fuels. The new 460 MWe (gross) unit will replace old power blocks of the agisza Power Plant. The existing blocks were erected in the 1960’s and consist of seven units (110-125 MWe each). Two of them will be shut down after the new 460 MWe unit is commissioned. The new boiler will be built adjacent to the old boilers and many of existing plant systems like coal handling and water treatment will be renovated and utilized for the new CFB unit.
INTRODUCTION FOSTER WHEELER SCOPE & CURRENT STATUS



Foster Wheeler’s workscope includes a turnkey boiler island including engineering and design, civil works and foundations for the boiler, boiler house enclosure with steel structures, boiler pressure parts, auxiliary equipment, main steam piping to turbine and reheated steam piping, coal bunkers and fuel feeding equipment, electrostatic precipitator and cold end flue gas heat recovery system, boiler controls, instrumentation, erection, construction, start-up, and commissioning. Full Notice to Proceed (NTP) was received in December 2005. The project is being executed jointly by a consortium of Foster Wheeler Energia Polska sp. z o.o. and Foster Wheeler Energia Oy, both part of Foster Wheeler’s Power Group Europe, with the plant due for commercial operation in March 2009. The engineering phase has been completed and the boiler pressure parts are being manufactured primarily in Foster Wheeler’s factory in Poland. Construction at the site started in February 2006 and as of early June 2007, the boiler island is about 20% completed. There are 350 workers on site at this time and the workforce will peak at 700 later this year for the boiler island work. Other work at site includes a new cooling tower and cooling water system as well as a new steam turbine generator.

Hydrostatic testing of the pressure parts is scheduled for early 2008, while commissioning activities will begin in the fall of 2008.
FUEL TYPE

The primary fuel for the boiler is bituminous coal. The source of fuel consists of 10 local coal mines with wide range of coal parameters, proving once more the fuel flexibility of the CFB technology. Table 1 presents make up of the design fuel and overall fuel range. Further, the boiler design is optimized for combustion of additional fuels. The main additional fuel is a coal slurry that is available in large amounts from the local coal mines. Due to CFB technology characteristics, wet coal slurry can be combusted with the primary fuel at up to a 30% share by fuel heat input. Coal washing rejects can also be burned in the form of dry coal slurry granulates. The boiler is also designed to utilize biomass fuels up to 10% by weight of fuel input. The biomass feeding equipment is included in the delivery as an option.

3

Table 1 Fuel specification
Bituminous Coal Design fuel LHV (a.r.) MJ/kg Btu Moisture Ash (a.r.) Sulfur (a.r.) Chlorine (dry.) % % % % 20 8600 12 23 1.4 < 0.4 Range 18 – 23 7700 -9900 6 – 23 10 – 25 0.6-1.4 < 0.4 Coal Slurry Range 7-17 3000 7300 27-45 28-65 0.6-1.6 < 0.4

sulfur molar ratio of 2.0 - 2.4. The nitrogen oxide emissions are reduced with inherently low combustion temperature and staged combustion. There are also provisions made for a simple ammonia injection system (a selective non-catalytic reduction system), however that is not required for the design coals. Particulate emissions are controlled by an electrostatic precipitator. Table 3 Emission limits Emission (6% O2, dry) SO2 NOx Particulates mg/m3n 200 200 30 Lb/mBtu 0.14 0.14 0.02

a.r. = as received
Steam Parameters

The steam parameters for the boiler were specified by the customer. The selected steam pressure and temperature are proven in other supercritical units and conventional boiler steel materials can be used. Table 2 presents the main steam parameters of this 460 MWe CFB boiler. Table 2 Steam parameters at 100 % load SH flow SH pressure SH temperature RH flow RH pressure Cold RH temperature Hot RH temperature Feed water temperature kg/s MPa °C kg/s MPa °C °C °C 361 27.5 560 306 5.48 315 580 290 kpph psig °F kpph psig °F °F °F 2859 3989 1040 2424 798 599 1076 554

AGISZA CFB BOILER DESIGN

General The boiler design for the agisza CFB is based on well proven Foster Wheeler CFB technology. It utilizes the experience of over 283 reference units starting from the first generation of CFB boilers. Furnace heat flux in CFB boilers is considerably lower and much more uniform than in PC boilers. Detail studies have confirmed that in CFB boilers, conditions for proper cooling of the evaporator wall tubes is achieved at wide load ranges See Figure 1 100%

50%
OVERALL PLANT EFFICIENCY

EMISSION REQUIREMENTS

The net plant efficiency is dictated by the selected steam parameters, steam cycle configuration, cooling tower conditions and boiler efficiency. In the agisza design the boiler efficiency is improved by the flue gas heat recovery system, which cools the flue gases down to 85°C thus improving the plant net efficiency. The calculated net plant efficiency for agisza is 43.3% on an LHV basis and 41.6% on an HHV basis and net power output is 439 MWe. The emission requirements for the agisza boiler are in accordance with European Union Large Combustion Plant Directive (see Table 3). The emissions for sulfur dioxide are controlled by limestone feeding into the furnace. With the design coal, a sulfur reduction of 94% is required and is easily achieved with a calcium to

0%

Figure 1 – CFB Furnace Heat Flux
Water / Steam side

The water and steam side design in based on the low mass flux BENSON once-through technology licensed by Siemens AG, Germany. This technology is

4

densities and finally the heat transfer with gas temperatures. The furnace has one single fluidizing grid under which there are four separate air plenums introducing primary air to furnace. The primary air flow for these four air plenums is measured and controlled separately to insure equal air flow to all sections of the grid and uniform fluidization. The single continuous fluidizing grid ensures simple control as well as a stable and uniform operation of the furnace. Figure 2 Water Steam Circuitry The lower ideal for both CFB and PC boilers since it utilizes vertical furnace is tapered which provides high internal turbulence furnace tubes as opposed to the spiral wound tubing used of the fluidized bed and enables efficient mixing of fuel in many other once-through designs /1/. Vertical tubing and secondary air. The operation of the furnace has been is a typical arrangement in natural circulation boiler verified with measurements in the largest units in designs and hence the similar design can now be used for operation as well as with 3D computer modeling, (see supercritical, once-through boilers. Figure 3). The furnace is very insensitive to operational The furnace heat flux (heat absorbed per surface disturbances such as unbalanced fuel feeding. area) in CFB boilers is very low and uniform compared to Solids separator design pulverized coal (PC) boilers. In addition, BENSON low The solids separator system for the agisza CFB boiler is mass flux design provides a unique “self protecting” designed with steam cooled panel wall construction. The feature reducing the risk of overheating any one tube. design is optimized for high collection efficiency with Much like a natural circulation design, if any one tube low flue gas pressure loss. The Foster Wheeler design receives a higher heat flux, the water/steam flow will has evolved into the use of water- and steam-cooled naturally increase, cooling the tube and minimizing the cyclones which eliminate the need for thick refractory increase in the tube metal temperature. This effect is a linings as well as eliminating some or all expansion joints direct result of the increased buoyancy characteristic of between the combustion chamber and separator, the steam/water mixture in the low mass regime. depending on unit size and configuration. This Fluid temperatures after each evaporator tube development integrates the solids separator with system were analyzed at different load conditions. Due to combustion chamber. The first of the compact integrated inherently low and uniform heat flux of the CFB furnace cyclone CFB boilers was commissioned in 1992 and and the BENSON low mass flux technology the fluid thereafter the number and size of this design has grown temperatures are very uniform /1/. steadily. The largest CFB boilers utilizing the integrated Key Advanced Design Features furnace/cyclone technology are the units delivered to the Furnace Turow power plant in Poland for units 4, 5 and 6. The power output of these units is 262 MWe. The flue gas side of the agisza CFB boiler design The use of this unique technology allows for larger is based on extensive analysis of the fuels and limestones CFB boilers (especially greater than 400 MWe) to that are going to be used. This analysis has produced the incorporate integrated cyclones on opposite furnace walls. required data for the design models to make predictions This reduces the plan area while still maintaining for circulating material particle size distribution, solids excellent performance. See Figure 2.

5

m /s

CFD Model

Same Separation Efficiency

FWCompact Solids Separator

FW Conventional Cyclone Separator

(firing rate). Steam after the high pressure turbine is brought back to the boiler for reheating. The first stage reheater is located in the heat recovery area convection pass. The reheater I (RH I) is equipped with a steam side bypass which is used for reheat steam temperature control. At higher loads part of the reheat steam bypasses RH I, which reduces the heat pick-up and hence the inlet steam temperature to RH II is decreased. This patented reheat steam control method avoids adding water spray to the reheat steam side and therefore does not cause a decrease in plant efficiency. There are over 20 CFB boilers utilizing this control method, e.g. Turow CFB boilers in Poland. In agisza the final reheater stage is located in INTREX heat exchanger similar to the final superheater.
Flue Gas Heat Recovery System

Figure 3 Comparison of Solids Separator Designs
INTREX

Foster Wheeler’s patented INTREXTM is a fluidized bed heat exchanger extracting heat from the hot circulating bed material that is collected by the solid separators. Additional bed material is directed to INTREX chambers directly from the lower part of the furnace. This provides sufficient bed material over a wide load range. The agisza boiler design incorporates a total of eight INTREX heat exchangers, one for each solids separator.
Steam Temperature Control

The main steam temperature is trimmed with a twostage feed water spray and by adjusting fuel feeding

The flue gas heat recovery system (HRS) improves the boiler and power plant efficiency by decreasing the flue gas temperature to 85°C. The system recovers heat from the flue gases which results in an improvement of 0.8%-points in total plant efficiency. The HRS is located in the clean gas area after the electrostatic precipitator and induced draft fan. The cooling of the flue gas takes place in a heat exchanger made of PF-plastic tubing to avoid corrosion problems. After the HRS, the flue gas flows to the cooling tower via glass fiber duct. A primary water circuit transfers the recovered heat from the HRS to the combustion air system and heat is transferred to both primary and secondary air. As the combustion air temperature before the rotary air preheater is increased, the air is not able to absorb all of the heat available from the flue gases. Therefore part of the flue gas is directed to a separate low-pressure bypass economizer where the heat from the flue gas is used for heating of the main condensate, see Figure 5.
Boiler materials

The material requirements for most sections of the boiler are conventional and normal boiler materials can be used. For example furnace and solids separator panels can be manufactured of materials that do not require postweld heat treatment. Material for INTREX heat exchangers is austenitic steel material, TP347HFG. This material has been successfully used in many existing Foster Wheeler CFB Boilers.

Figure 4 - INTREX

Combustion air systems for the agisza boiler consist of primary and secondary air systems with a separate air system for fluidizing the INTREX heat exchangers and sealing devices. Radial fans with inlet guide vane control are used for primary and secondary air fans, (2 each). For induced draft (ID) fans two axial fans are used.

Auxiliary equipment

6

Foster Wheeler has continued to expand it’s capability to simulate transient behavior of CFB boilers and power plants during the past fifteen years /2/. For the Lagisza design, the simulations have been applied for the analysis of boiler transients and control system responses, The above mentioned load change test program, which will be performed during commissioning phase, has already been demonstrated in a process simulator environment. The dynamic simulation models have shown that the unique control features of a CFB boiler combined with standard control can be used to make the CFB OTU comparable to conventional PC boilers for step and Figure 5 Flue Gas Heat Recovery System ramp load changes. Unique to the CFB OTU is that it can accommodate Downstream of the economizer flue gases are disturbances from the process (fuel rate and quality) cooled in a tri-sector rotary air heater and in a parallel bybecause of the stabilizing effect of the inventory and pass economizer. The tri-sector air heater was selected flywheel of circulating solids. over a quad-sector alternative due to its smaller diameter Further, the following abnormal process transients of heating surface, shorter sealing length and better have been simulated: mechanical rigidity. An Electrostatic precipitator (ESP) with four – Automatic boiler runbacks electrical fields in series is used to control dust emissions to 30 mg/mn. The separated fly ash is conveyed to fly Turbine trip ash silo using a dense phase ash conveying system. Fuel handling equipment includes a coal screening Primary air fan trip and crushing station located at the fuel yard. The coal feeding system consists of four similar Secondary air fan trip fuel feed systems; two fuel feed systems at both of the long walls of the furnace. ID fan trip The coal slurry feeding system includes a slurry preparing station where coal slurry is homogenized by HP heater outage adding water and fed to two buffer silos. Prepared coal slurry is then pumped with piston pumps to feeding – Blackout nozzles in the furnace walls. The slurry system is similar to those used in CFB boilers Foster Wheeler has delivered Protection of evaporator tubes during to Elektrownia Jaworzno S.A. and EC Katowice S.A. in blackout (loss of feed water pump) Poland. The simulations have proven that with a tightly LOAD FOLLOWING CAPABILITY AND DYNAMIC controlled balance between firing rate, heat transfer, SIMULATIONS water/steam flow and properly coordinated turbine and It is essential that utility power plants meet current boiler controls, the agisza CFB boiler is able to fulfill demands for the load following capabilities, load cycling, the response requirements of the electrical grid authority. fast start-ups and high availability. For the Lagisza power plant the electrical grid operator has set up a specified test SCALING UP ONCE-THROUGH SUPERCRITICAL CFB program for the verification of unit capability for the BOILERS TO 800MWe primary and secondary controls (electrical grid frequency After the agisza 460 MWe CFB boiler is in control) and for the tertiary control (scheduled load operation, the next logical step is to design for even larger changes). boiler sizes and higher plant efficiencies with even lower Contemporary dynamic process models were used emissions, such as CO2. Recent trends show an increasing to develop control systems and to analyze the dynamic demand for boilers in the size range of 600 to 800 MWe, behavior of various types of boilers and power plants.

7

The basic design parameters of the plant are presented in Table 7.

as existing power plants are aging and new replacement capacity is required. CFB technology is now emerging as an alternative for facilities of this size. Foster Wheeler, together with a group of other interested companies from Germany, Greece, Finland and Spain has initiated a study for an 800 MWe power plant centered around CFB technology. The group is working on a conceptual boiler design to better understand the feasibility of a large scale CFB design. Imported bituminous coal has been used as the base fuel in the study.

Table 7. Design parameters of 800MWe CFB once through boiler.
US Equiv. SH RH 4499 3873 4351 653 1112 1148 554 64

Steam Flow SH Pressure SH Temp. Feedwater Tenp. Cooling Water Temp.

kg/s bar °C °C °C

SH 568 300 600 290 18

RH 489 45 620

kpph psig °F °F °F

Figure 6 Design of 800 MWe CFB Once Through Boiler
The boiler design for 460 MWe agisza power plant is based on proven solutions that are already used in other large CFB boilers delivered by Foster Wheeler. Only a modest scale-up has been required. It can be concluded that CFB technology is today commercial viable to boiler sizes of 500 MWe and programs exist for the rapid scale-up of the technology to 800 MWe.
REFERENCES

The actual scale-up of the dimensions and size of plant components required is quite moderate, due to the modular approach adopted for the boiler design. Currently the basic design of the boiler island and dimensioning of auxiliary systems have been completed (Figure 6). A more detailed study of an 800 MWe CFB power plant covering an optimized steam cycle, boiler design, emission performance, dynamic behavior, and economical feasibility is in progress.
CONCLUSIONS

/1/

R. Lundqvist, R. Kral, P. Kinnunen, K. Myhnen: “The Advantages of a Supercritical Circulating Fluidized Bed Boiler”, presented at PowerGen 2003, Düsseldorf, Germany A. Kettunen, T. Hyppnen, A-P. Kirkinen, E. Maikkola: “Model-based Analysis of Transient Behavior of Large-Scale CFB Boilers”, presented at 17th International Conference on Fluidized Bed Combustions, May 18-21, 2001, Jacksonville, USA

CFB boiler technology has established its position in the market place as a utility scale boiler technology. This “state of the art” technology is now ready to demonstrate successful operation utilizing supercritical steam cycles and larger boiler sizes. The Polish utility company PKE has shown confidence in Foster Wheeler’s technology by placing an order for a 460 MWe supercritical CFB boiler for their agisza power plant. This will be the first operational supercritical oncethrough CFB boiler in the world as well as the worlds largest CFB. With supercritical once through technology CFB boilers are able to provide a basis for a high efficiency, fuel flexible, environmentally sensitive power plant with reduced emissions, including CO2. The CFB boiler for agisza power plant will utilize a wide range of coals and is also able to burn coal wastes in the form of coal slurry and granulates while cofiring biomass.

/2/

8


相关推荐

最新更新

猜你喜欢