Lynemouth Power Station, located on the coast of Northumberland in North East England, features three biomass-fired generating units, each producing 140 MW. Originally coal-fired, the power station began co-firing with biomass in 2003. In 2011, it was announced that the station would convert to 100% biomass white pellets. Today, the power station operates exclusively on biomass white pellets, utilising MB 195 series vertical spindle mills equipped with new port rings and dynamic classifiers.
EnFloTech became involved when the Lynemouth Power Station plant faced several challenges:
- Poor boiler controllability due to inconsistent fuel flow to the furnace
- Biomass fuel hang-ups requiring manual mill cleaning, indicating poor purge ability
- Biomass fuel agglomeration and compacting within the spring-loaded mill loading system
- Ineffective classification control with the dynamic classifier
CFD/Numerical phase
EnFloTech approached the project by focusing on a critical aspect of milling: the interface where the pneumatic conveying medium (air) meets the material to be transported (ground biomass flakes). This interface is located at the port ring of a vertical mill.
Upon analysing the baseline port ring (PR), it was discovered that the vane angle and the venturi design of the PR combined to create an angled vector directed into the mill’s grinding zone.
The swirling flow induced large centrifugal forces on the particles, resulting in suspended clouds of particles at the mill’s loading system (spring) level and just before the dynamic classifier (DC).
EnFloTech then modelled a V5 high-performance port ring designed to eliminate swirling flow and prevent the formation of suspended particle clouds. The analysis showed that a modular replacement port ring addressing the swirl issue would resolve most of the problems experienced with the mills.
The numerical analysis revealed significant particle deprivation to the burners due to the suspended particle clouds inside the mill. These clouds also caused blockages, necessitating manual intervention to purge (clean) the mill.
The results demonstrated a significant improvement in particle throughput to the burners, as the V5 port ring prevented the mill from holding back inventory. It is believed that the accumulation of inventory led to the formation of particle clouds. As these clouds became saturated, they released pockets of material to the boiler, causing flame instabilities.
Performance of trial EnFloTech V5 PR
The loading frame is subjected to high-velocity pulverised coal, which is extremely abrasive and causes premature wear, risking its useful life and mechanical integrity. Combined with the limited ergonomic design, this presents a significant problem given the cost, lead time, and threat to the plant’s reliability.
EnFloTech installed a trial V5 port ring (PR) at Lynemouth Power Station, which yielded the following results:
- Reduction in suspended particle clouds inside the mill
- Decreased particle clouds and reduced particle residence time inside the mill, providing stable fuel flow to the boiler and ensuring stable firing
- Particle fineness within specification, resulting in stable firing, low unburnt carbon, and normal back-end temperatures
- Reduction of 0.8 to 1 kPa in mill differential pressure (dP), indicating the elimination of particle suspension
EnFloTech is now the proud mill port ring OEM of Lynemouth Power Station in the UK. The station mills are now fully converted to EnFloTech’s technology.