Fluidized Bed Superheater Steam Temperature Control
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Solution Overview
Problem
Steam turbine power plants face efficiency reductions and blade damage due to premature condensation when load decreases, as reduced thermal energy transfer from fluidized bed material results in lower steam temperatures, leading to inadequate superheating.
Innovation Solution
Introducing additional thermal energy into the fluidized bed material outside the furnace by selectively injecting or burning combustible gas in designated locations, such as the loop seal heat exchanger chamber or combustion chamber, to maintain steam temperature and efficiency even at reduced power plant loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the load of the power plant is decreased, then the fuel consumption is reduced, but the steam temperature drops and efficiency is adversely affected
Solution Approach 1:
The heating function is segmented between the furnace (primary heating) and the external combustion chamber (supplementary heating). This allows independent control of each heating zone, enabling the furnace to operate at lower fuel consumption while the external chamber maintains steam temperature, thus resolving the contradiction between reduced fuel use and maintained efficiency.
Solution Approach 2:
Fluidized bed material serves as an intermediary heat transfer medium. It absorbs thermal energy from both the furnace and the external combustion chamber, then transports this energy to the steam in the superheater. This intermediary mechanism allows decoupling of the steam temperature control from direct furnace combustion, enabling efficiency maintenance with reduced overall fuel consumption.
2Loss of energy
If the load of the power plant is decreased, then the thermal energy transfer from fluidized bed material is reduced, but this causes lower steam temperature leading to premature condensation and blade damage
Solution Approach 1:
The external combustion chamber provides preliminary supplementary heating to the fluidized bed material before it reaches the superheater. This advance heating ensures that even when furnace output is reduced, the fluidized bed material arrives at the superheater with sufficient thermal energy to maintain steam temperature and prevent condensation, thus protecting turbine blades.
Solution Approach 2:
Heating is applied locally at two distinct locations: the furnace (primary zone) and the external combustion chamber (secondary zone). This localized dual-heating approach allows the system to maintain thermal quality in the superheater region even when overall plant load and furnace output are decreased, preventing the thermal deficiency that causes blade damage.
3Temperature
If additional heating is provided outside the furnace, then steam temperature is maintained, but the device complexity increases
Solution Approach 1:
The external combustion chamber is designed to serve multiple functions: it heats the fluidized bed material, provides supplementary thermal energy, and can be integrated with existing plant structures. By making this component multi-functional, the added complexity is justified by the multiple benefits achieved, including steam temperature maintenance and improved operational flexibility.
Solution Approach 2:
The external combustion chamber is merged with the existing fluidized bed circulation system. The fluidized bed material continuously circulates between the furnace, external chamber, and superheater, integrating these components into a unified thermal system. This merging approach minimizes additional complexity by utilizing existing flow paths and structural elements rather than creating entirely separate systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures the steam temperature remains sufficiently high, preventing premature condensation and maintaining electricity production efficiency, without requiring modifications to the steam circulation system.
Implementation Method 1
selectably supplying combustible gas to be combusted in a loop seal heat exchanger chamber (1) or in a combustion chamber (16)
Implementation Method 2
fluidized bed material circulates in the system and transfers thermal energy from the furnace, to elsewhere in the system
Data Source
Figure 1
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AI summary
The solution comprises a method of and a system for maintaining steam temperature and therefore electricity production efficiency with decreased loads of a steam turbine power plant comprising a fluidized bed boiler (12) and a fluidized bed superheater (2) adapted to superheat steam supplied to a steam turbine (3). According to the solution, the steam temperature may be maintained by providing, outside a furnace (10), additional heating to the fluidized bed material in its outer circulation, thereby increasing the amount of thermal energy available in the fluidized bed material to be transferred in the fluidized bed superheater (2) to the steam supplied to the steam turbine (3). Such additional heating may be performed by selectably supplying combustible gas with nozzles (111) into and/or burned with a burner in or in the vicinity of the fluidized bed material outside the furnace (10). As an additional aspect of the disclosed solution, the combustible gas may be produced with a gasifier (4).