The expansion of renewable energy generation driven by our need to meet our Paris agreement commitments, has meant that coal-fired power plants designed for base-load operation are increasingly operating in flexible modes such as low load, load following, on/off cycling, and extended layups. These changes to coal-fired generation present significant technical challenges but also substantial commercial reward for plant that successfully manages this transition.
Flexible Operation
Challenge
Solution
HRL provides the platform from which the commercial imperative of plant flexibility and related issues can be evaluated and managed through:
- understanding safety, risk and plant integrity
- determining plant limitations/bottlenecks, including mills and coal quality
- developing ways to enable faster load changes, ramping up/down
- improvement in low load operation
- optimising combustion and boiler tuning to maximise efficiency and fuel consumption
- statutory compliance within different regulatory environments
- allowing the station to respond to the market needs, capture high pricing and avoid low pricing
HRL offers the following service pathways for assisting plant owners with flexible operation:
1. Understand probable future flexible operating scenarios.
- Steady state operation
- full load
- low load
- Transient operation
- daily
- weekly
- random
- rapid loading
- hot banking
2. Complete a desk-top evaluation.
- review plant records, drawings, engineering reports, operating logs
- assess operational data from various loads and load changes, hot, warm, cold starts and trips
- conduction discussions with engineering and operational staff
- boiler and turbine modelling including Steam Pro, Thermoflex and CFD modelling
3. Detailed analysis of pinch-points.
- A desk-top study will identify:
- missing information and data
- areas of plant that are susceptible to damage when cycling
- fuel and combustion issues that limit flexible operation
To quantify these issues and determine methods to overcome any limitations these have on flexible operation, more detailed analyses are undertaken, which include:
- Finite Element Analysis (FEA) of pressure equipment and Piping Stress Analysis to evaluate stresses, thermal gradients and component lives. Outcomes are determining maximum heating ramp rates for safe operation, risk-based inspection plans and maintenance requirements.
- Combustion analysis looking at coal quality, mill testing, combustion stoichiometry, combustion stability at low loads, air ingress/egress, back-end metal and gas temperatures, etc.
- Evaluation of control instrumentation
4. Plant trials and performance testing
- "Measurement and Testing" is an important step post Step 3 as this will test the operation and performance of the plant under the various proposed ramp rates and operating scenarios.
- Testing of current plant limits, boiler stability, turbine performance and measurement of key plant operating parameters.
- Testing and evaluation of control systems.
5. Safety and risk mitigation
- Review and update of operating, inspection, maintenance and repair procedures to capture learnings and to enshrine best practice in order to maintain plant integrity, manage plant life and to ensure safe operation.
