High-efficient clean, high-variable load rate coal-fired power generation system and operation method thereof
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Solution Overview
Problem
Coal-fired power generation units face challenges in maintaining optimal SCR catalyst temperature across varying load conditions, leading to reduced denitration efficiency and increased operational costs due to frequent low-load operations and integration with renewable energy sources.
Innovation Solution
A high-efficient coal-fired power generation system incorporating a thermal storage medium heater, economizer, and internal thermal source SCR denitration catalytic module, with a temperature adjustment mechanism using thermal storage tanks and variable frequency pumps to maintain the SCR catalyst within the optimal 300° C to 400° C activity range, allowing for optical temperature adjustment and efficient denitration across all operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the coal-fired unit operates at low load, then the proportion of power generation decreases to accommodate renewable energy, but the temperature of flue gas at the SCR catalyst outlet decreases and approaches the edge of the high activity range, reducing denitration efficiency
Solution Approach 1:
The thermal storage medium heater pre-heats the thermal storage medium before it enters the SCR denitration catalytic module. This preliminary heating action ensures that even when flue gas temperature is low at part load operation, the catalyst maintains its operating temperature in the optimal range, preserving denitration efficiency while accommodating renewable energy integration
Solution Approach 2:
A thermal storage medium is introduced as an intermediary between the flue gas and the SCR catalyst. This thermal storage medium absorbs heat from the flue gas when temperatures are high and releases heat when temperatures are low, acting as a thermal buffer that maintains catalyst temperature stability regardless of load conditions or renewable energy fluctuations
2Temperature
If the flow direction of working fluid inside the coal-fired unit is changed or heating surface is reduced to maintain SCR catalyst temperature at low load, then the catalyst temperature is maintained, but the device complexity increases due to reconstruction requirements
Solution Approach 1:
The system is segmented into distinct functional modules: the flue gas pathway, the thermal storage medium circulation loop with separate heater and cooler, and the SCR catalyst module. This segmentation allows the thermal storage system to be added as a standalone temperature control mechanism without requiring complex reconstruction of the boiler or flue gas flow paths
Solution Approach 2:
The thermal storage medium acts as an intermediary that simplifies temperature control compared to directly modifying flue gas flow or heating surfaces. Instead of complex boiler modifications, the system uses a relatively simple external circulation loop with a heater and cooler to maintain catalyst temperature, reducing overall system complexity
3Loss of energy
If economic operation is prioritized with frequent low-load operations, then operational costs are reduced, but the SCR catalyst cannot maintain optimal temperature, leading to reduced denitration efficiency
Solution Approach 1:
The system changes the thermal parameters of the SCR catalyst by introducing a controlled thermal storage medium circulation system. The heater and cooler adjust the thermal storage medium temperature based on real-time catalyst temperature feedback, enabling the catalyst to maintain optimal operating temperature across a wide range of load conditions and economic operating scenarios
Solution Approach 2:
The system implements feedback control where the actual temperature of the SCR catalyst is monitored and used to adjust the thermal storage medium temperature. When catalyst temperature drops below the optimal range, the heater activates; when it exceeds the optimal range, the cooler activates. This feedback mechanism ensures denitration efficiency is maintained regardless of load conditions or economic operating priorities
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 expands the denitration operation range, increases the ramp rate of the coal-fired unit, and improves boiler efficiency by maintaining SCR catalyst activity and efficiency across all operating conditions, enhancing operational flexibility and power output.
Implementation Method 1
a thermal storage medium heater, an economizer and an internal thermal source selective catalytic reduction (SCR) denitration catalytic module are distributed in a flue which is located at a tail portion of the boiler along a flow direction of flue gas in sequence
Implementation Method 2
the cold thermal storage medium port of the internal thermal source SCR denitration catalytic module is connected with a first port of a low temperature storage tank through a second thermal storage medium pump and a first thermal storage medium control valve
Implementation Method 3
SCR (selective catalytic reduction) denitration catalyst has high activity and high denitration efficiency in the range of 300° C. to 400° C.
Data Source
AI summary
In a high-efficient clean, high-variable load rate coal-fired power generation system, through the internal thermal source SCR denitration catalytic module coupled with high temperature and low temperature storage tanks, the operating temperature of the internal thermal source SCR denitration catalytic module is controlled in a range of 300° C. to 400° C., ensuring that the SCR catalyst has high activity in full-working conditions. Moreover, the high temperature and low temperature storage tanks are coupled with the high-pressure heater group for steam turbine regenerative system, so that when the coal-fired unit needs to increase load rate, the thermal storage energy is quickly converted into output power. In addition, energy stored in the high temperature and low temperature storage tanks come from both the internal thermal source SCR denitration catalytic module and the thermal storage medium heater within the boiler, the operational flexibility and the boiler efficiency are improved.