Greenbank Terotech, in partnership with our Joint Venture R&D company GAIM Ltd (Greenbank Advanced Instrumentation and Measurement), have developed a revolutionary non-intrusive rope breaker for Pulverised Fuel (FP) called a VARB. Greenbank’s VARB technology can be utilised as a retrofit or an integral part of new build projects for super efficient coal fired plant.

The purpose of a Greenbank VARB device is to break the ‘rope’ (the tight formation of coal dust in air) and diffuse the PF which is a common condition when transporting coal from mills to burners. This is particularly useful for many older power stations which often have one or two large pipes coming from the mill that split to deliver fuel to 6 or 8 burners. Due to rope formation, coal does not split as equally as the air at these pipe junctions, which results in poor fuel to air distribution.

By applying the Greenbank VARB system the client can correct and optimise performance of low NOx burners via their fuel / air diet. Also with improved fuel flow you can enhance combustion efficiency burning more carbon and by design reduce unwanted emissions.In summary the Greenbank VARB system offers massive potential in the enhancement and performance improvement on front wall boilers that experience poor combustion.

Greenbank collaborate with GAIM engineers to analyse each application individually using bespoke Computational Fluid Dynamics (CDF) programmed to mimic the existing flow conditions then, in turn, engineer the best application for the chosen VARB device. GAIM Engineers have now designed and patented several generations of VARB devices which are suitable for differing situations.

There are two main VARB products, the VARB and the HVARB. A third, S-VARB [Special VARB], has been designed for dealing with more aggressive spinning or rotating flows after bends in the vertical plane or on slight inclines. The VARB [Standard VARB] is designed for spinning or rotating flows after bends in the vertical. The H-VARB or Horizontal VARB is designed primarily for horizontal pipes and involved with lifting PF off the bottom of pipes.

H-VARB devices have been installed just before a Trifurcator (3-way) splitter in an attempt to improve the PF coal flow balance going into the boiler. The adjacent graph shows how the split was pre H-VARB, then what difference the introduction of the H-VARB did to improve the PF split.

Initially there is extreme unbalance between the outlets D and E Mills. The introduction of the H-VARB device equated that balance. In addition to the H-VARB device is the control gate. This device allows a fine tuning of splits to allow the customer to get as close as possible to the perfect split.

Greenbank have installed an S-VARB into an inclined vertical riser before primary and secondary riffle assembly (4-way) splitters. The S-VARB was installed to improve the overall pulverised fuel balance at the quadrafurcator. The standard VARB proved less effective in simulation, so alterations were made to make the S-VARB more “aggressive” providing a much greater pulverised fuel mixing.

The S-VARB improved the split by~2% which was a significant saving despite the additional pressure drop imposed by the aggressive SP-VARB. Patent Ref No’s 050723.4 / 2498333 Refer.