M-Type Boiler U-Shaped Flue for Ultrahigh Steam Temperature
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Solution Overview
Problem
The development of advanced ultra-supercritical thermal power generating units with ultrahigh steam temperatures faces challenges such as the high cost of nickel base alloy materials and the complexity and cost of double-reheat systems, which limits the efficiency and application of these units.
Innovation Solution
The M-type pulverized coal boiler design features a middle flue that forms a U-shaped circulation channel between the hearth and the tail downward flue, allowing high-temperature flue gas to flow at a lower elevation, reducing the length and cost of high-temperature steam pipelines and enabling the use of double-reheat technology with improved efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If nickel base alloy material is adopted for high-temperature pipelines, then the steam temperature can reach 700°C or above, but the manufacturing cost increases significantly (from 300 million RMB to 2.5 billion RMB for four pipelines)
Solution Approach 1:
The patent introduces a middle flue between the hearth and tail downward flue, creating a new spatial dimension for flue gas circulation. This U-shaped circulation channel allows flue gas to flow through a lower elevation path, enabling the placement of high-temperature heating surfaces at lower heights where standard materials can be used instead of expensive nickel base alloys, thus resolving the contradiction between achieving high steam temperature and controlling manufacturing cost.
2Productivity
If double-reheat system is adopted, then the unit efficiency increases significantly, but the system complexity and investment increase greatly
Solution Approach 1:
The patent merges the functions of multiple heating surfaces (superheaters and reheaters) into a integrated flue gas circulation system within the middle flue. By utilizing the U-shaped circulation channel, the system achieves double-reheat functionality through a unified design approach, reducing system complexity while maintaining the efficiency benefits of multiple reheating stages.
3Use of energy by moving object
If high-temperature heating surfaces are arranged at high elevation to access high-temperature flue gas, then heat transfer efficiency improves, but the length and cost of steam pipelines increase
Solution Approach 1:
Instead of placing high-temperature heating surfaces at high elevations to access hot flue gas, the patent inverts this approach by creating a downward flue gas flow path through the middle flue. The U-shaped circulation channel directs flue gas to flow through lower elevation areas, allowing high-temperature heating surfaces to be positioned at lower heights where shorter steam pipelines can connect to the turbine, thus resolving the contradiction between heat transfer efficiency and pipeline length.
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 design reduces manufacturing costs, improves unit efficiency, and allows for the adoption of ultrahigh-temperature steam parameters, making it feasible to implement ultrahigh-temperature steam conditions and double-reheat systems in large-scale thermal power generating units.
Implementation Method 1
a middle flue communicated between the hearth and the tail downward flue, and the middle flue comprises: a hearth outlet downward flue and an upward flue of which the bottoms are mutually communicated and the upper ends are respectively communicated with the upper end of the hearth and the upper end of the tail downward flue to form a U-shaped circulation channel
Data Source
AI summary
The disclosure provides an M-type pulverized coal boiler suitable for ultrahigh steam temperature. The pulverized coal boiler comprises a hearth of which the bottom is provided with a slag hole and a tail downward flue of which the lower part is provided with a flue gas outlet. The pulverized coal boiler further comprises a middle flue communicated between the hearth and the tail downward flue, wherein the middle flue comprises an upward flue and a hearth outlet downward flue of which the bottoms are mutually communicated and the upper ends are respectively communicated with the upper end of the hearth and the upper end of the tail downward flue to form a U-shaped circulation channel. In the pulverized coal boiler provided by the disclosure, the middle flue which extends downwards and can make flue gas flow along the U-shaped circulation channel is arranged between the outlet of the hearth and the tail downward flue, so that high-temperature flue gas from the hearth can be introduced into a position with low elevation through the downward flue, and final-stage convection heating surfaces (such as a high-temperature superheater and a high-temperature reheater) can be arranged at positions with low height, and the length of ultrahigh-temperature steam pipelines between the high-temperature superheater and a steam turbine, and between the high-temperature reheater and the steam turbine can be greatly reduced. Therefore, the manufacturing cost of a boiler unit is obviously reduced.