Variable Wall Thickness Cooling Screen for Gasifier Pressure Management
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Solution Overview
Problem
Entrained-flow gasifiers face challenges in maintaining pressure equality and thermal stability across the cooling screen, leading to potential corrosion and mechanical stress due to the limitations of existing designs, which compromise the durability and efficiency of the gasification process.
Innovation Solution
A cooling screen design with varying tube wall thickness and a conical shape to manage thermal loads and mechanical strength, combined with a specific arrangement of claws and ceramic fiber mats for pressure equalization and dust prevention, ensures reliable operation and efficient heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the cooling screen diameter and height are increased to achieve higher gasifier output, then productivity is improved, but the resistance to pressure differentials across the cooling screen walls deteriorates
Solution Approach 1:
The cooling screen tubes are designed with variable wall thickness: thicker walls at the ends (where pressure differential resistance is most critical) and thinner walls in the middle section (where thermal stress is highest). This local differentiation allows the cooling screen to maintain high pressure differential resistance across the entire structure while enabling larger dimensions for higher gasifier output.
2Temperature
If thin tube walls are used to improve heat transfer from the reaction chamber to the cooling water, then heat transfer efficiency is improved, but the differential pressure resistance of the cooling screen deteriorates
Solution Approach 1:
The tube wall thickness is optimized locally: thinner walls in the middle section maximize heat transfer efficiency where thermal stress is highest, while thicker walls at the ends provide sufficient differential pressure resistance. This local differentiation resolves the contradiction between heat transfer efficiency and pressure resistance.
3Adaptability or versatility
If elastic fiber mats are used to allow free movement of the cooling screen, then adaptability to thermal expansion is improved, but the limitation of dust passage from the reaction chamber into the back chamber deteriorates
Solution Approach 1:
A purge gas system is introduced as an intermediary measure: inert gas is fed into the back chamber to create a protective atmosphere that prevents dust and reaction gases from entering through the annular gap, while the fiber mats continue to provide mechanical flexibility for thermal expansion.
4Reliability
If a corrugated pipe compensator is used to close the gap and route purge gas, then pressure equalization is improved, but device complexity and cost increase
Solution Approach 1:
The complex corrugated pipe compensator structure is removed and replaced with a simpler direct purge gas injection system. The essential function of pressure equalization and dust prevention is maintained by feeding inert gas directly into the back chamber through simplified piping, eliminating the need for expensive compensators and complex pressure equalization lines.
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
The design enhances the cooling screen's mechanical strength and heat transfer capabilities while maintaining pressure equality, reducing the risk of corrosion and mechanical stress, thus extending the lifespan and performance of the gasification system.
Implementation Method 1
good heat transfer from the reaction chamber to the cooling water is necessary to prevent damage
Implementation Method 2
The resulting back chamber 10 (also referred to as the cooling screen gap) is purged with an inert gas and exhibits pressure equalization with the reaction chamber
Implementation Method 3
This purging is intended to prevent hot gasification gas from flowing back into the cooling screen gap during pressure fluctuations
Data Source
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AI summary
For an entrained-flow gasifier for gasification of fuels in dust or liquid form using a gasifier agent containing free oxygen, at pressures between atmospheric pressure and 8 MPa and gasification temperatures between 1200 and 1900°C, there is proposed a liquid-cooled cooling screen of which the cooling pipes in the central cylindrical section have thinner walls than the cooling pipes in the lower and upper conical sections. The invention provides a cooling screen design having sufficient strength under high pressure difference over the cooling screen wall, a pipe wall thickness which ensures reliable operation of the cooling screen and high heat throughput, and pressure equalization between the cooling screen gap and the reaction chamber under all operating circumstances.