Tri-sector regenerative oxidant preheater pressure zoning
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Solution Overview
Problem
Rotary regenerative oxidant preheaters in oxy-fired pulverized coal combustion systems experience significant oxygen and recycled flue gas leakage from the oxidant side to the gas side, leading to increased operational costs due to the need for additional oxygen production and flue gas purification to meet emission standards, and the risk of oxidant exposure to ash.
Innovation Solution
A tri-sector rotary regenerative oxidant preheater design with a stationary housing and a rotor divided into a flue gas sector, a secondary oxidant sector, and two primary oxidant sectors, where the secondary oxidant sector is interposed between the primary oxidant sectors, minimizing pressure differences and leakage by maintaining the flue gas and primary oxidant sectors at negative pressure and the secondary oxidant sector at positive pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a rotary regenerative oxidant preheater is used to heat combustion air, then heat transfer efficiency is improved, but oxidant leakage from the air side to the gas side increases
Solution Approach 1:
The preheater is divided into three distinct sectors: a flue gas sector, a primary combustion air sector, and a secondary combustion air sector. This segmentation allows different pressure conditions to be maintained in different sectors, with the primary air sector at negative pressure and the secondary air sector at positive pressure, thereby preventing oxidant leakage while maintaining heat transfer efficiency
Solution Approach 2:
The secondary combustion air sector acts as an intermediary buffer zone between the flue gas sector and the primary combustion air sector. By maintaining positive pressure in the secondary air sector, it prevents direct contact and leakage between the negative pressure primary air sector and the flue gas sector, thus eliminating oxidant leakage while preserving the regenerative heat transfer function
2Object-affected harmful factors
If additional oxygen production and flue gas purification systems are added to meet emission standards, then emission compliance is improved, but system complexity and operational costs increase
Solution Approach 1:
The invention converts the potential harmful effect of pressure differential into a beneficial feature by using negative pressure in the primary air sector to prevent oxidant leakage. This eliminates the source of oxygen loss that would otherwise require additional purification systems, thereby reducing system complexity while maintaining emission compliance
3Loss of substance
If oxidant leakage into the gas side is reduced, then oxygen loss is minimized, but the preheater design complexity increases
Solution Approach 1:
Different pressure conditions are applied to different local sectors of the preheater. The primary combustion air sector operates at negative pressure to prevent leakage, while the secondary combustion air sector operates at positive pressure. This localized differentiation of pressure conditions effectively minimizes oxygen loss without requiring complex overall system redesign
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 significantly reduces oxidant leakage from the oxidant side to the gas side, minimizing oxygen loss and reducing the need for additional oxygen production, while ensuring safe handling of high oxygen concentrations and preventing exposure to ash, thereby lowering operational costs and enhancing safety.
Implementation Method 1
Rotary regenerative air preheaters transfer heat indirectly by convection as a heat storage medium is periodically exposed to heat-emitting flue gases and heat-absorbing combustion air
Implementation Method 2
a heat storage medium is periodically exposed to heat-emitting flue gases and heat-absorbing combustion air
Data Source
AI summary
A tri-sector regenerative oxidant preheater apparatus, method and arrangement for utilization with oxy-fired pulverized coal combustion power plants. The preheater includes a stationary housing and a rotor rotatably mounted in the housing. Sector plates are located at the axial ends of the rotor and divide the preheater into a flue gas sector, two primary oxidant sectors, and a secondary oxidant sector interposed between the two primary oxidant sectors. A primary oxidant fan is located downstream of the preheater to create a negative environment in the primary oxidant sectors. During operation of the preheater, the environments of the two primary oxidant sectors and the flue gas sector are at about the same negative pressure, and thus there is very limited leakage between the oxidant side and the flue gas side of the preheater. The environment of the secondary oxidant sector is at a positive pressure and leakage to the negative environment of the primary oxidant sectors will be that of secondary oxidant to primary oxidant with no loss secondary oxidant to the gas side of the preheater.