AFBC boilers firing coal are not competitive with oil or gas .. versa. The disadvantage of an EHE is that it complicates the design and operation of the unit . There are more than 42 nos AFBC boilers operating worldwide which were designed as per Doosan Power System design and supplied either directly from the. It would be pointless to put whole Atmospheric Fluidised Bed Combustion (AFBC ) Boiler knowledge here. But from a quick search within Quora and Google you.

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Radian Corporation Under Contract No. Environmental Protection Agency, and approved for publication as received from the Radian Corporation.

Approval does not signify that the contents necessarily reflect the views and policies of the Operstion. Environmental Protection Agency, nor does mention of trade namesorcommercial products constitute endorsement or recommenda- tion for use.

DOE Development Programs 3. Several vendors are offering industrial FBC steam generators on a commercial basis. Competing with FBC technology are two other options for burning coal in the industrial setting and meeting applicable emission limits: The overall objective of this study is to evaluate the development status of FBC systems and the influence of alternative S02 emission limits on the economic competitiveness of FBC relative to the two competing S02 control options.

This overall objective has been expanded into three specific sub-objectives: The emphasis of this update will be on S02 emissions but nitrogen oxide NOX and particulate matter PM emissions will also be considered; 2. To evaluate the economic competitiveness of FBC technology relative to the two competing Operatoin control options and determine how this competitiveness would be affected by alternative emission limits; 3.

To determine boilerr what conditions, if any, FBC operatkon would be economically favored over the two competing control options. Although this report will build on the ITAR, it is intended to serve as a stand-alone document.

Therefore, if material is covered adequately in the ITAR, that discussion is only summarized here; the emphasis in this report is on new information not covered in the ITAR. Section 2 of this report contains an Executive Summary of the study’s findings. An evaluation of the development status of F8C technology is presented in Section 3. Emissions and performance data related to both SO- control and N0x and particulate matter PM control are discussed in Section 4.

Section 5 describes the development of the FBC cost algorithm and compares algorithm projections with independent vendor cost estimates.

While the primary emphasis of this zfbc is on operafion S02 control capabilities of FBC technology, NO envisions, PM emissions, and boiler performance parameters have also been examined. Commercial Availability Atmospheric fluidized bed combustion AFBC boilers have developed rapidly over the past four years and are now offered commercially in several different configurations.

Design alternatives which are currently available include the conventional bubbling fluidized bed with or without solids recyclestaged fluidized beds, circulatory fluidized beds, and staging of combustion air for N0x control.

Pressurized FBC technology has been under development for several years, but it is not a likely candidate for commercial applications in the industrial boiler segment except for very large-scale industrial boilers.

Pressurized FBC boilers are not considered further operwtion this study. Many vendors offer system guarantees covering performance in such areas as steam quality and boilsr, emissions, and combustion efficiency. A majority of the existing and planned units in the U.

Many units are designed to burn multiple fuels, either separately or in combination. This fuel feedstock flexibility is an advantage that FBC boilers enjoy over conventional boilers as a result of their high thermal inertia. Of the 80 existing or planned units in the U. Excluding boilers that are test, demonstration, undisclosed, or uncompleted units reduces this number to 8 commercially-operated, coal-fired AFBC units.

The S02 reduction capabilities that have been demonstrated by AFBC boilers boile the industrial size category are summarized below: This unit is a utility type design, however, with a higher freeboard than typical industrial boiler designs. The results may not be directly applicable to the industrial setting.


Performance results are afbbc on continuous emission monitoring CEM data collected over two periods of 12 and 15 hours duration; Georgetown Boileer conventional FBC boiler: Opedation operation of the FBC unit was not achieved during the tests.

West German circulating FBC boiler: Test method and duration were not specified. For those industrial units for which data are available, FBC NO boilerr have been consistently below 0. Staged-beds and circulating FBC boilers appear to have the greatest potential for reducing NO emissions below this A level.

However, the major emphasis in FBC research to date has been on optimizing combustion efficiency and S02 control. Although the exact mechanism is not currently understood, test unit data indicate a definite tradeoff between SO- and NO emission control for the use of staged booler air.

The afbx between S02 and N0x must be further defined to establish optimum overall performance. Fabric filters have been used more widely for commercial applications than ESPs due to the low resistivity of entrained solids from FBC boilers.

PM emissions of less than 0. FBC Algorithm A cost algorithm has been developed for estimating operstion and annual costs for conventional FBC systems over a wide range of boiler sizes and operating conditions. A comparison of the ITAR design with current operating system parameters shows that the design is representative of AFBC systems being offered commercially to industrial plant owners.

Two-stage and circulating FBC designs agbc not considered due to the lower market penetration expected for these systems abfc the next five years. This is due primarily to the conservative nature of the industrial boiler market and the fact that these two designs are in an earlier commercialization stage than the conventional bubbling bed design. Cost Comparisons Among Independent Estimates The FBC algorithm design basis and methodology have been validated in part by comparison with independent estimates developed by five other organizations, four of which currently offer industrial-size FBC boilers on a commercial basis.

Annual cost comparisons among the FBC algorithm projections and the three available estimates show very good agreement. All five vendor capital operztion estimates are in agreement with the algorithm projections.

This comparison of five independent estimates with the FBC algorithm projections lends added validity to the algorithm as a cost estimating tool.

FBC costs are estimated with the cost algorithm described above. Lime spray drying has been chosen as the FGD technology over wet scrubbing systems because 1 the technology is being widely applied for SCL control among industrial boilers; 2 spray drying costs are representative of costs for wet FGD technologies throughout the studied size range; and 3 the” technology is similar to FBC technology in its use of a calcium sorbent and production of a dry waste product.

Costs for the competing SCL control options are estimated with analogous model boiler cost algorithms. The purpose of these comparisons is to identify trends related to the relative competitiveness of the three options as S02 emission levels become more stringent. Cost differences are felt to be significant if they exceed these limits. These cost differences are also dependent on the technical and economic assumptions that form their basis and thus should be used with caution in view of this and the overall accuracy level.

The S02 emission levels chosen for examination are 1. Removal efficiency levels for FBC and FGD are specified on the basis of the target emission level and coal fuel properties; compliance coals are selected to meet the emission levels assuming continuous S02 monitoring without the use of SO- control equipment. Emission levels for N0x and PM are consistent for all S02 control altenratives examined.

The annual cost differences between options do not exceed 15 percent, which is within the overall accuracy of the annual cost estimates. When FBC and FGD annual costs are compared at equal S02 reduction efficiencies between 65 and 90 percent, the results follow the same trend identified above: FBC competitiveness vis-a-vis FGD remains relatively unchanged over the studied range of S02 percentage removal requirements.


Absolute economic competitiveness among these options will be sensitive to site-specific parameters and decided on a case-by-case basis. Given the small cost differences among S02 control options, it is unlikely that economics alone will be the deciding factor when a choice is made. Rather, less tangible factors such as operator requirements for fuel flexibility and preference for risk are likely to play a major role in the decision process.

To be significantly favored over competing S02 control options, the algorithm costing analysis indicates that FBC systems should be approximately 15 percent less expensive on an annual cost basis. To achieve the same competitive edge over compliance coal combustion, low sulfur coals prices would have to rise almost 65 percent relative to high sulfur coal, or FBC relative capital costs would have to decline by over 60 percent, or a combination of the two shifts would have to occur.

The likelihood of cost changes of this magnitude occurring in the foreseeable future as a result of coal market or technological changes is quite remote. Relative changes of a similar magnitude would be required for other boiler sizes and emission limits. The coal price sensitivity of annual costs for the three S02 control alternatives are equivalent for practical purposes.

This section will focus on the technology developments concerning new bed configurations and improvement of emissions control, especially S02 and NOX emissions. The advances which have resulted from both governmental and private research and development programs will be reviewed.

First generation units were based on a stationary bubbling bed design. Since the ITAR was published, a significant amount of development work has been conducted to more thoroughly investigate the beneficial effects of recycling elutriated bed material.

Pressurized fluidized bed combustion PFBC has been under development for several years, but has not yet been used in commercial applications. Therefore, the following discussion will focus on AFBC technology.

Atmospheric Fluidised Bed Combustion Boiler (AFBC)

In the conventional bubbling bed system presented in Figure 3. The limestone is added for S02 removal. The fluidized bed consisting of unreacted, calcined, and sulfated limestone particles, coal, and ash is suspended in a stream of combustion air blowing upwards from an air distribution plate.

Bed material is drained from the bed to maintain the desired bed depth. Some bed material is also elutriated from the bed with the combustion gas. This entrained material is separated from the flue gas by cyclones and a baghouse or electrostatic precipitator. The material is then discarded as a solid waste.


All or part of this material is then fed back to the fluidized bed. The net effect operatiob solids recycle is an increased fuel and sorbent residence time opeeation the bed, with improvements in combustion efficiency and S02 and N0x control. A substoichiometric amount of air is added at the fluidizing air primary air injection point.

The balance of the air needed to achieve adequate combustion efficiency is added above the bed. This allows combustion to be completed in the freeboard i.

Early testing with staged combustion air showed N0x reductions of up to 50 percent. Refer to Section 4. In this arrangement, one bed is stacked on top of the other. The lower bed is fed only coal and is operated at substoichiometric air conditions to reduce N0x formation. Limestone is fed to the upper bed where operaion and final combustion occur. Also, the distribution plate for the upper bed acts as a baffle, reducing fines elutriation from the lower bed. This lowers the freeboard requirements for both beds.

Similar technology was originally used in other applications such as fluidized catalytic cracking of petroleum feedstocks. This creates a stable fluidized bed of solid particles with a well-defined upper surface. As a result, a physically well-defined bed is not formed; instead, solid particles coal, limestone, ash, sulfated limestone, etc.