Good Practice in Pellet Storage and Handling

Andrew Leslie, Forever Fuels Ltd

Usewood fuel Scotland and WHA Seminar 2015Dunblane, 26 November

Bulk Storage

Screening plant

Satellite Depots

Purpose built Pellet Tanker

Nationwide Delivery Capability

Design

• Pre-fab or custom: pre-fab recommended*

• Detailed instructions for types of:

– Small pre-fab stores

– Small custom stores

– Large stores

* Big provisos: assumes manufacturers know what they are doing…

Truck Access

• Road width > 3.5m, height > 4(.5)m

• Gradient & condition of road in winter

• Restrictions from other parked vehicles

• Turning circle & Gross Vehicle Weight

• Legal parking space, not obstructing other road users

• Consider noise (e.g. neighbours)

• Line of sight from truck to connectors

Pipes and connectors• Delivery and suction connectors accessible by

driver and enough clearance (20cm) to connect– Max. height 1.8m (or platform required)– Recommended height 1.5m

• 100mm internal diameter at connector• Robust construction (not flue pipe)• Fewest bends possible (prefer Wolfson advice)• Storz 110A or national equivalent (Camlock)• Connectors labelled (In/Out). No blowing through

suction connector.• Conductive and earthed• Vented caps on connectors

Store Cleaning & Inspections• Frequency as per ENPlus Handbook. • Precautions:

– Minimise frequency of entry into store (e.g. size)– Turn off boiler and fuel-feed systems– Second person outside store (to call for help, NOT rescue)– Well-fitting dust-mask & goggles + skin covered– Industrial vacuum (Class M filter); no sweeping– Personal CO monitor for underground and large (>10t)

stores (multi-gas?)– Ventilate for ≥ 15 mins. before entering– Follow manufacturer’s instructions (what if they are BS?)

• Design store to avoid dust build-up (e.g. flat surfaces) + suitable, safe access. Confined-spaces qualified only?

Access

Burner Fire

Burn back, CO & explosion risk

Wasted space

Badly-fixed connectors

Ladders?

Shoddy workmanship

Poor delivery pipe runs

Poor transfer pipe runs

Inlet obstructions

Access hatches

Impact mats

Sweeping arms

Fines and “dusty” pellets

• Particle-size segregation

• Fines (<3.15mm) vs dust (airborn)

• Sampling methodology (representative sample)

• ENplus limit: 1% on loading, 4% delivered IF

– store was nearly empty before delivery

– blowing distance < 30 metres

– store designed according to the UKPC guide

Fines

• Factors:– Length and bends in the pipework

– Inadequate or badly-positioned impact mats

– Obstacles in the route of the pellets

– High pellet velocity

– Low solids loading factor

– Particle-size segregation

– Fuel-feed system

• “Dusty” face does not mean pellets are out of spec. Only valid test set out in ENplus Handbook.

Testing

• Problem? Test the fuel, don’t blame the fuel

• If fuel passes standard tests, fix your system, don’t blame the tests

• “It looks dusty”, close-up photos, unrepresentative samples, etc. are not objective tests

• Biomass heating reputation: installer blames the fuel, fuel supplier blames the installation

• No business if reputation worsens

Conclusions• Early lessons learnt (e.g. floor angle)• Increasing use of pre-fab stores helps, but some mistakes

built into pre-fab too• Widespread lack of technical competencies e.g.

– particle-size segregation, – augers: angle vs RPM, and constant vs variable pitch– suction transfer: pressure drop, distance, bends, gradient– pressure/flow-rate/velocity/degradation in delivery

• Average size stores getting smaller!• Minimal progress on impact mats• Little knowledge of store cleaning requirements• No training on bulk solids handling in MCS/HETAS courses• Still mostly Amateurville

UKPC storage guidehttp://www.pelletcouncil.org.uk/storage

UKPC / Wolfson Centre Installer Day Courses

http://www2.gre.ac.uk/about/faculty/engsci/research/groups/wolfsoncentre/coupro/sc/UKPC

Where to find competent installers

http://www.pelletcouncil.org.uk/consumer-information/installers

Thank you for your attention

Forever Fuels Ltd, 225 Blackamoor Lane, Maidenhead, Berks. SL6 8RTwww.forever-fuels.com 01628 509690