Forced-Flow Steam Generator Bulkhead Heating Surface
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Solution Overview
Problem
Once-through steam generators face challenges in achieving higher steam parameters due to material limitations, leading to complex and costly manufacturing and assembly processes for high-temperature applications, especially when using materials like martensitic 9-12% chromium steels or Ni-based alloys, which require heat treatment and have high procurement costs.
Innovation Solution
Incorporating a bulkhead heating surface made from high-quality materials like martensitic, austenitic, or nickel-based alloys between the upper edge of the burner and the lower edge of the secondary heating surface to absorb excess heat, reducing the thermal load on the enclosing walls and allowing the use of commercially available, weldable 2.25-2.5% chromium steels that do not require post-weld heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If higher steam parameters (above 650°C) are achieved to improve efficiency, then steam temperature increases, but material strength becomes insufficient and complex heat treatment processes are required
Solution Approach 1:
The steam generator is divided into different zones with different material requirements. The bulkhead heating surface uses high-temperature resistant materials (martensitic 9-12% chromium steels or Ni-based alloys) while the enclosing walls use more economical 2.25-2.5% chromium steels. This segmentation allows each zone to be optimized for its specific thermal load.
Solution Approach 2:
A bulkhead heating surface is introduced as an intermediary component between the combustion chamber and the enclosing walls. This bulkhead absorbs excess heat through its high-temperature resistant materials, acting as a thermal buffer that protects the enclosing walls from direct exposure to maximum temperatures, thereby eliminating the need for complex heat treatment processes.
2Temperature
If martensitic 9-12% chromium steels or Ni-based alloys are used for enclosing walls to withstand high temperatures, then temperature resistance improves, but manufacturing and assembly costs increase due to heat treatment requirements
Solution Approach 1:
Different material qualities are applied to different locations within the steam generator. The bulkhead heating surface (exposed to combustion chamber heat) uses high-temperature resistant martensitic 9-12% chromium steels or Ni-based alloys, while the enclosing walls (lower thermal load) use more economical 2.25-2.5% chromium steels that do not require post-weld heat treatment.
Solution Approach 2:
The invention replaces expensive, complex-to-manage high-temperature materials in the enclosing walls with more economical 2.25-2.5% chromium steels. These cheaper materials suffice for the enclosing walls' thermal conditions and eliminate the need for expensive post-weld heat treatment facilities and procedures.
3Productivity
If steam parameters are increased to reduce CO2 emissions, then efficiency improves, but material strength characteristics become insufficient
Solution Approach 1:
The thermal load is segmented and distributed to different components. The bulkhead heating surface absorbs the excess heat from high-efficiency combustion, while the enclosing walls operate at reduced temperatures that 2.25-2.5% chromium steels can withstand without requiring expensive high-temperature alloys.
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 simplifies manufacturing and assembly, reduces material and operational costs, and maintains efficiency by controlling the temperature of the enclosing walls within safe limits for existing materials, avoiding the need for complex heat treatment and high-cost alloys.
Implementation Method 1
a bulkhead heating surface (8) which covers part of the enclosing walls (4) in the area of the combustion chamber (2) and by its surface area on the combustion chamber side determines the heat absorption of the enclosing walls (4)
Implementation Method 2
the tubes (5) of which contain the working medium water/steam
Implementation Method 3
the combustion chamber has at least one burner
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a forced-flow steam generator for using steam temperatures of above 650°C. Said forced-flow steam generator (1) comprises a combustion chamber (2) and a waste gas flue (3) connected to the upper end thereof, and peripheral walls (4) surrounding said flue. Said walls (4) are formed from tubular walls (5), the tubes thereof guiding the water/steam working medium. The combustion chamber (2) comprises at least one burner (6), and downstream heating surfaces (7) are arranged in the waste gas flue (3). Part of the peripheral walls (4) is covered in the region of the combustion chamber (2) by at least one bulkhead heating surface (8), the size of which on the surface side being determined such that the heat absorption of the peripheral walls (4) and therefore the temperature thereof are reduced to a value enabling the formation of the peripheral walls (4) from modified, heat-resistant 2.25-2.5% chrome steel that does not require any heat aftertreatment following the welding treatment thereof.