The UK’s largest renewable power station has four biomass-fueled generating turbines that produce 2,595 MW.
The plant has an ambition of being carbon negative by 2030. To achieve this, the station has now converted four of its six power generation units to burn biomass in place of coal. Its two coal units ceased commercial operations in 2021 but remain available on standby.
“For the generation of renewable power, biomass pellets are produced using waste wood. It is sourced from sustainably sourced forests in North America. Biomass trains collect 30,000 tonnes of pellets from the Port of Liverpool and deliver to the power station.”
Continuous Emissions Monitoring Requirements
The renewable power production capacity means that compliance with the Industrial Emissions Directive (IED 2010/75/EU) formerly the WI Directive is essential.
The power station underwent an upgrade of the Continuous Emissions Monitoring Systems (CEMS) for both their biomass and coal power generating units.
As defined in the site permit, CEMS are used to continuously collect, record and report emissions data. Industrial process operators that produce emissions to air must respect their permit. CEMS are used to comply with stringent emission limits as regulated by the Environment Agency (EA).
- Space Limit: There is one flue stack which emits controlled emissions to atmosphere. Of which, all six power generating units require a duct within the stack. One of the biggest challenges was to house all six CEM systems within each power generating unit near to the stack using the minimum amount of space.
Each CEM system typically requires:
- A sample probe
- A sample line (umbilical)
- A gas conditioning system
- A calibration gas system
- Housing to accommodate the 19” rack gas analyser
- Logistics of the fluidics, control, power, instrumentation, software, and transportation of the redundancy system
Because of the limited space, site would be unable to accommodate such systems. And therefore a complete re-design of this typical system was required.
- Permit Requirements: Under the IED, the site is required to monitor Oxides of Nitrogen (NOX), Carbon Monoxide (CO), Sulphur Dioxide (SO2), Hydrogen Chloride (HCl), Oxygen (O2) and the Ammonia (NH3) slip while using Selective Non-Catalytic Reduction (SNCR).
New analysers should be certified, for a suitable measurement range, under the EA’s MCERTS scheme. The means of assessing the suitability of the CEM system determines that the certification range must be less than 2.5 times the Emission Limit Value (ELV).
- Redundancy System: Each of the six power generating units required two duty sets of gas analysers. Additional to this, rather than have separate 19” rack standby systems for each duty, a single suitably sized portable standby redundancy system was requested between each of the duty systems.
- Cost Savings: Due to the sheer size of the power plant, one of the challenges was to make cost savings where possible in the engineering of the CEM systems.
The BIOMASS PLANT SOLUTION
- Space Limit Solutions: Fitting so much equipment in the enclosures was only the beginning of the challenge. The whole system was uniquely designed to allow two individual gas analysers to be combined into a single 19” rack enclosure.
A half size portable standby CEM system was also designed to be quickly and easily interchanged between the six systems.
The six shelters had to be uniformly positioned near to the flue stack to limit the heated line lengths and power cables. The benefit shorter lengths reduced sample lag in addition to lower installation costs.
- Permit Requirements: To adhere to their site permit, meet the requirements of IED and EN14181 and accurately measure all the gases at the specified ranges, the MCERTS certified MIR-FTIR multi-gas analyser from ENVEA was chosen.
- Redundancy System: A portable standby redundancy CEM system was designed to be interchangeable between the six systems. This enabled the customer to integrate the portable standby system quickly and easily using hot-swappable ports. This prevented any loss of sample, pressure, or heat.
The redundancy system is always ready. In the event where a duty system has a problem, it can be used straightaway without having to be powered and warmed up.
The design team liaised closely with the software department to re-engineer the signal transfer to the data acquisition software (CDAS). This enabled the flexibility of a portable standby system to be calibrated and maintained so that the Quality Assurance Level (QAL) 3 requirements for EN14181 could be achieved.
- Cost: Thanks to the effective design, it resulted in a huge costing saving for the customer. A single rack system reduced hardware costs. The portable redundancy unit saved the customer from having to invest in a redundancy unit for each of the units.
The project took a lot of ingenuity, experience, knowledge and understanding from the design team, particularly regarding legislative acts. “The design team exceeded the requirements of this project. In doing so, prepared a innovative CEM system redesign for future projects” (Engineering Manager).