Tag: wood pellets

How do you keep a 1.2 tonne steel ball in prime condition?

18 January 2018

Power generation

There are 600 giant balls at Drax Power Station. Each one weighs 1.2 tonnes – roughly the same as a saloon car – and is designed for one simple, but very specific, purpose: to pulverise.

Every day thousands of tonnes of biomass and coal are delivered to the power station to fuel its generators. But before this fuel can be combusted, it must be ground into a powder in pulverising mills so it burns quicker and more efficiently. It’s the giant balls that do the grinding.

And although these balls may be incredibly durable, the constant smashing, crushing and pulverising they go through on a daily basis can take its toll. Maintaining the 600 balls across the power station’s 60 mills is a vital part of keeping the plant running as effectively as possible.

Surviving the pulveriser

Each of the six generating units at Drax (three biomass and three coal) has up to 10 mills that feed it fuel, all of which operate at extreme conditions. Inside each one, 10 metal balls rotate 37 times a minute at roughly 3 mph, exerting 80 tonnes of pressure, crushing all fuel in its path.

Air is then blasted in at 190 degrees Celsius to dry the crushed fuel and blow it into the boiler at a rate of 40 tonnes per hour. To survive these extremities, the balls must be tough.

Drax works with a local foundry in Scunthorpe, Lincolnshire to manufacture them. First, they are cast as hollow orbs of nickel steel or chrome iron and then smoothed to within one millimetre of being perfectly spherical.

After 8,000 hours of use, engineers check how rapidly they’re wearing down by measuring their thickness using ultrasound equipment and, if deemed to be too thin (which usually occurs after about 50,000 hours of use), replace them.

For this, they must first remove the top of the mill – including the grinding top ring – and then individually lift out and replace each massive ball. Those that are removed are typically shipped back to Scunthorpe to be recycled.

Transforming for a decarbonised future

When Drax Power Station was first built in the 1970s, the mills were designed to only crush coal, but since it was upgraded to run primarily on biomass, in the form of sustainable wood pellets, they have been adapted to work with the new fuel.

For the most part, this requires only minor changes – the primary difference is that coal is harder to fully pulverise. Coal typically does not get entirely ground down in the first cycle, so a classifier is needed in the mill to separate the heavier particles and recirculate them for further grinding.

The process of switching one mill from biomass to coal takes about seven days and nights. This work was carried out on Unit 4’s mills ahead of this winter, following biomass trials in the spring and summer of 2017. Now that the decision has been made to permanently upgrade that fourth power generation unit, converting one of its 10 mills from coal to biomass later in 2018 will take about twice as long.

Using the same essential equipment and process for both fuels helps to quicken the pace of decarbonisation at Drax Power Station as the UK moves to end the production of unabated coal-fired electricity by 2025. Come seven years from now, one thing will remain consistent at the huge site near Selby, North Yorkshire: the giant pulveriser mills will continue their tireless, heavy-duty work.

Fourth biomass unit conversion

17 January 2018

Investors
RNS Number : 1114C
Drax Group PLC

Drax welcomes the UK Government response to the consultation on cost control for further biomass conversions under the Renewable Obligation scheme, which will enable Drax to convert a fourth unit to biomass.

The response proposes that, rather than imposing a cap on ROC(1) support for any future biomass unit conversions, a cap would be applied at the power station level across all ROC(1) units. This would protect existing converted units and limit the amount of incremental ROCs attributable to additional unit conversions to 125,000 per annum.

The response would enable Drax to optimise its power generation from biomass across its three ROC units under the cap, whilst supporting the Government’s objective of controlling costs under the Renewable Obligation scheme.

Drax will now continue its work to deliver the low cost conversion of a fourth biomass unit, accelerating the removal of coal-fired generation from the UK electricity system, whilst supporting security of supply.

Drax plans to complete the work on this unit as part of a major planned outage in the second half of 2018, before returning to service in late 2018. The capital cost is significantly below the level of previous conversions, re-purposing the existing co-firing facility on site to deliver biomass to the unit.

The unit will likely operate with lower availability than the three existing converted units, but the intention is for it to run at periods of higher demand, which are often those of higher carbon intensity, allowing optimisation of ROC(1) generation across three ROC(1) accredited units. The CfD(2) unit remains unaffected.

Will Gardiner, Chief Executive of Drax Group, commented:

“We welcome the Government’s support for further sustainable biomass generation at Drax, which will allow us to accelerate the removal of coal from the electricity system, replacing it with flexible low carbon renewable electricity.”

“We look forward to implementing a cost-effective solution for our fourth biomass unit at Drax.”

Enquiries:

Investor Relations:

Mark Strafford

+44 (0) 1757 612 491

Media:

Ali Lewis

+44 (0) 1757 612 165

 

Website: www.drax.com/uk

Notes

  1. Renewable Obligation Certificate
  2. Contract for Difference

END

 

 

Giving up coal

Tony Juniper, Author, adviser and environmental campaigner

7 December 2017

Opinion
Tony Juniper at Drax Power Station between coal stock and biomass wood pellet storage domes

Tony Juniper* is an environmental campaigner, author and director at Robertsbridge, a consultancy helping advise Drax on its sustainability programmes

Back in 2006 while working as Director at Friends of the Earth I approved a new report to be published in support of our then campaign for a new Climate Change Act. We wanted to show UK government ministers how it would indeed be possible to make cuts in emissions so that by 2050 the UK could progressively have reduced greenhouse gas pollution by 80 per cent compared with emissions in 1990. It was a radical and demanding agenda that we’d adopted and it was important to show the practical steps that could be made in achieving it.

The analysis we presented was based on an electricity sector model that we had developed. Different data and assumptions could be inputted and using this we set out six possible lower carbon futures.

In our best case scenario we foresaw how it would be feasible to slash emissions by about 70 per cent by 2030.

This was based on an ambitious energy efficiency programme and a shift away from fossil energy and toward renewables, including wind and solar power. In that renewables mix was also an important role for biomass to replace coal in the country’s largest power station – Drax.

This was not only crucial for backing up intermittent renewable sources but also a key piece in a future electricity sector that we believed should avoid the construction of new nuclear power stations. In November 2008 our campaign succeeded and the UK was the first country in the world to adopt a new national law for the science-based reduction of greenhouse gas emissions. Since then I’ve been working as an independent sustainability advisor, including with the advisory group Robertsbridge, of which I was a co-founder.

My work has included assisting various companies in meeting the targets set out in that new law. For example, I was the Chair of the industry campaign Action for Renewables which sought government and public support for the large-scale expansion of wind, tidal and wave power.

Different campaigners tried to stop the expansion of these renewable sources of electricity, however, and succeeded in derailing support for on-shore wind power developments.

Although in its infancy, concerns were also raised about proposals for different kinds of tidal power.

In the years after the Climate Change Act I was encouraged to see that Drax began to switch over to wood pellets to generate power but concerned to see that this too had come under attack. The broadly agreed view that sustainable biomass could have a role in the phase out of coal had gone, and in its place were claims  that it was actually worse than burning coal. It was against this backdrop of changed perspectives that myself and Robertsbridge colleagues were pleased to be invited to help Drax in devising a new sustainability plan.

Early on in our conversations with Drax it became clear that part of the challenge with biomass — deciding the extent to which it is a rational choice to help with the process of decarbonisation, is how the answer to that touches so many different issues.

For example, when it comes to the exit from coal, cleaner alternatives must be brought forward to replace it, including wind and solar power.

But although these sources of renewable energy are growing rapidly, they still come with their own challenges, especially because wind can’t generate on still days and solar ceases at night. This intermittency raises issues about what the best electricity storage or complementary clean power sources might be to back them up when needed.

There are important questions about the best sources of biomass and the extent to which long-distance transport of that fuel is desirable. On top of that are issues linked with the management of the forests from which the raw material is sourced, and whether the extraction of wood to generate power can be compatible with carbon neutrality. There is the matter of nature conservation and the extent to which wood fuel demand will affect the status of species and habitats of conservation concern. For example, to what extent might the wood pellet industry be driving the conversion of semi-natural woodlands to plantations?

All of this is bound up with the economic and social conditions prevailing in the landscapes from which the wood is derived and the extent to which those buying wood fuel can pursue positive outcomes for the environment, even when carbon and wildlife are at best of marginal concern to the local forest owners growing the wood.

Then there is the extent to which economic incentives might be linked with the carbon stocks held in the forest. For example, strong demand for wood is held to be the main reason why since the 1950s the volume of carbon stored in standing timber in the forests of the US South has increased by over 100%.

Demand for wood might seem counter-intuitive as a positive factor in maintaining tree cover, but in the US South it has been a big part of the picture.

On top of all this is the question of what would happen if there were no demand for wood fuel. In landscapes that have seen volatility in demand arising from the decline in newsprint in favour of digital devices and the slowdown in US house building following the 2008 financial crisis, this is not easy to answer.

Although seeking answers is a complex task, our advice to Drax was that it should work with its many stakeholders in finding the best possible fit between its business planning and these and other questions.

One way of doing that would be to set out the different issues in an accessible manner and hence the production of the film that can be seen here.

It’s called ‘The biomass sustainability story’ And while most of us can agree with the basic idea that we have to stop burning coal, it seems the big questions are about what might be the best ways to do it? Might biomass have a role? I believe it does.

Have a look at the film and see what you think, especially if you feel as though you’ve already made up your mind.

How lasers reduce emissions

25 July 2017

Power generation
Drax laser

Of the air that makes up our atmosphere, the most abundant elements are nitrogen and oxygen. In isolation, these elements are harmless. But when exposed to extremely high temperatures, such as in a power station boiler or in nature such as in lightning strikes, they cling together to form NOx.

NOx is a collective term for waste nitrogen oxide products – specifically nitric oxide (NO) and nitrogen dioxide (NO2) – and when released into the atmosphere, they can cause problems like smog and acid rain.

At a power station, where fuel is combusted to generate electricity, some NOx is inevitable as air is used in boilers to generate heat. But it is possible to reduce how much is formed and emitted. At Drax Power Station, a system installed by Siemens is doing just that.

It begins with a look into swirling clouds of fire.

Not your average fireplace

“Getting rid of NOx is, at heart, a problem of getting combustion temperatures to a point where they are hot enough to burn fuel effectively. Too hot and the combustion will form excess amounts of NOx gases. Too cool and it won’t combust efficiently,” says Julian Groganz, a Process Control Engineer who helped install the SPPA-P3000 combustion optimisation system at Drax. “Combustion temperatures are the result of the given ratio of fuel and air in each spot of the furnace. This is our starting point for optimisation.”

An industrial boiler works in a very different way to your average fireplace. In Drax’s boilers, the fuel, be it compressed wood pellets or coal, is ground up into a fine powder before it enters the furnace. This powder has the properties of a gas and is combusted in the boilers.

“The space inside the boiler is filled with swirling clouds of burning fuel dust,” says Groganz. Ensuring uniform combustion at appropriate temperatures within this burning chamber – a necessary step for limiting NOx emissions – becomes rather difficult.

Heat up the cold spots, cool down the hotspots

If you’re looking to balance the heat inside a boiler you need to understand where to intervene.

The SPPA-P3000 system does this by beaming an array of lasers across the inside of the boiler. “Lasers are used because different gases absorb light at different wavelengths,” explains Groganz. By collecting and analysing the data from either end of the lasers – specifically, which wavelengths have been absorbed during each beam’s journey across the boiler – it’s possible to identify areas within it burning fuel at different rates and potentially producing NOx emissions.

For example, some areas may be full of lots of unburnt particles, meaning there is a lack of air causing cold spots in the furnace. Other areas may be burning too hot, forcing together nitrogen and oxygen molecules into NOx molecules. The lasers detect these imbalances and give the system a clear understanding of what’s happening inside. But knowing this is only half the battle.

A breath of fresher air

“The next job is optimising the rate of burning within the boiler so fuel can be burnt more efficiently,” explains Groganz. This is achieved by selectively pumping air into the combustion process to areas where the combustion is too poor, or limiting air in areas which is too rich.

“If you limit the air being fed into air-rich, overheated areas, temperatures come down, which reduces the production of NOx gases,” says Groganz. “If you add air into air-poor, cooler areas, temperatures go up, burning the remaining particles of fuel more efficiently.”

Drax Laser 2

It’s a two-for-one deal: not only does balancing temperatures inside the boiler limit the production of NOx gases, but also improves the overall efficiency of the boiler, bringing costs down across the board. It even helps limit damage to the materials on the inside the boiler itself.

Thanks to this system, and thanks to its increased use of sustainable biomass (which naturally produces less NOx than coal), Drax has cut NOx emissions by 53% since the solution was installed. More than that, it is the first biomass power station to install a system of this sophistication at such scale. This means it is not just a feat of technical and engineering innovation, but one paving the way to a cleaner, more efficient future.

This is how you unload a wood chip truck

30 June 2017

Sustainable bioenergy
Truck raising and lowering

A truck arrives at an industrial facility deep in the expanding forestland of the south-eastern USA. It passes through a set of gates, over a massive scale, then onto a metal platform.

The driver steps out and pushes a button on a nearby console. Slowly, the platform beneath the truck tilts and rises. As it does, the truck’s cargo empties into a large container behind it. Two minutes later it’s empty.

This is how you unload a wood fuel truck at Drax Biomass’ compressed wood pellet plants in Louisiana and Mississippi.

What is a tipper?

“Some people call them truck dumpers, but it depends on who you talk to,” says Jim Stemple, Senior Director of Procurement at Drax Biomass. “We just call it the tipper.” Regardless of what it’s called, what the tipper does is easy to explain: it lifts trucks and uses the power of gravity to empty them quickly and efficiently.

The sight of a truck being lifted into the air might be a rare one across the Atlantic, however at industrial facilities in the United States it’s more common. “Tippers are used to unload trucks carrying cargo such as corn, grain, and gravel,” Stemple explains. “Basically anything that can be unloaded just by tipping.”

Both of Drax Biomass’ two operational pellet facilities (a third is currently idle while being upgraded) use tippers to unload the daily deliveries of bark – known in the forestry industry as hog fuel, which is used to heat the plants’ wood chip dryers – sawdust and raw wood chips, which are used to make the compressed wood pellets.

close-up of truck raising and lowering

How does it work?

The tipper uses hydraulic pistons to lift the truck platform at one end while the truck itself rests against a reinforced barrier at the other. To ensure safety, each vehicle must be reinforced at the very end (where the load is emptying from) so they can hold the weight of the truck above it as it tips.

Each tipper can lift up to 60 tonnes and can accommodate vehicles over 50 feet long. Once tipped far enough (each platform tips to a roughly 60-degree angle), the renewable fuel begins to unload and a diverter guides it to one of two places depending on what it will be used for.

“One way takes it to the chip and sawdust piles – which then goes through the pelleting process of the hammer mills, the dryer and the pellet mill,” says Stemple. “The other way takes it to the fuel pile, which goes to the furnace.”

The furnace heats the dryer which ensures wood chips have a moisture level between 11.5% and 12% before they go through the pelleting process.

“If everything goes right you can tip four to five trucks an hour,” says Stemple. From full and tipping to empty and exiting takes only a few minutes before the trucks are on the road to pick up another load.

Efficiency benefits

Using the power of gravity to unload a truck might seem a rudimentary approach, but it’s also an efficient one. Firstly, there’s the speed it allows. Multiple trucks can arrive and unload every hour. And because cargo is delivered straight into the system, there’s no time lost between unloading the wood from truck to container to system.

Secondly, for the truck owners, the benefits are they don’t need to carry out costly hydraulic maintenance on their trucks. Instead, it’s just the tipper – one piece of equipment – which is maintained to keep operations on track.

However, there is one thing drivers need to be wary of: what they leave in their driver cabins. Open coffee cups, food containers – anything not firmly secured – all quickly become potential hazards once the tipper comes into play.

“I guess leaving something like that in the cab only happens once,” Stemple says. “The first time a trucker has to clean out a mess from his cab is probably the last time.”

Forests, sustainability and biomass – the expert’s view

Matthew Rivers, Director of Corporate Affairs, Drax, Group Special Advisor

6 October 2016

Opinion

It was a forestry catastrophe that first inspired Matthew Rivers’ interest in forests.

Dutch Elm trees, an iconic part of the UK landscape for over 250 years were becoming infected with a fatal and fast-spreading disease. The race was on to save them.

A schoolboy in North London at the time, Rivers joined the after curricular school team tasked with saving its trees – first by injecting them with insecticide, and when that didn’t work, by felling and replanting them. It was an early foundation in how forests work and the challenges of keeping them healthy.

Decades later, Rivers is Director of Corporate Affairs at Drax. It’s a role he finds himself in following a career as a forester, helping to manage forestry businesses, and supporting the setting up of wood product manufacturing plants.

His own estimation of his working life is a humble one, however. “I think I’m probably a failed farmer,” he says.

“A forester always plants in hope.”

Rivers studied forestry at university in Scotland before taking up jobs in the forestry industry across the UK, Uruguay and Finland. Working in this industry, he says, is one that requires patience.

“In the UK we’re talking about 30- or 40-year growth cycles. The trees I planted at the start of my career are only just coming to maturity now,” he explains.

But more than the long investment of time, being a forester relies on faith. “A forester always plants in hope,” he says. When a forester plants a tree, he or she most commonly does not know who the end customer will be.

So when the call came from Drax for a forestry expert to help guide the company through an important transformation – upgrading the power station from coal to biomass – the challenge was one he was ready to take.

“Drax already had ambitions of converting three boilers to run on biomass. That would mean consuming tonnes of compressed wood pellets,” he says. The business needed a supply, and Rivers was drafted in to set this up.

As part of the supply solution, and Chaired by Rivers, Drax set up Drax Biomass, a pellet manufacturing business in the USA that makes and supplies compressed wood pellets to Drax Power Station.

Setting up its own manufacturing plant not only means Drax needs to rely on fewer external suppliers, but also that it can use the learnings about the technologies, the economics and the sourcing of the process to continually hone its supply chain.

To operate responsibly and receive governmental support, Drax has to be sustainable, and this is particularly important when it comes to where and how it sources its fuel. This comes with its own challenges.

No universal definition of sustainability

“To my understanding, there is no universal definition of sustainability,” says Rivers. So how do you proof your business for an unclear entity?

“At its heart, sustainability is about not doing anything today that would prejudice doing the same thing for the next generation or generations to come.”

A responsibly managed forest is one that is as healthy, productive, diverse and useful in 100 or 500 years’ time as it is today. They key to this, is to think of forests as a whole.

Rivers explains: “Think about a single tree – you fell it and use it to heat your home over one winter. But it’s going to take perhaps 30 years for that tree to grow back,” he says. “What do you do for the next 30 years?”

“In a sustainably managed forest you have all different ages of tree represented – one thirtieth devoted to each age- and, when you use an older tree to warm you in winter, you plant a replacement. That way, for every year you’ll have trees reaching maturity ready to provide your power.” It’s a cycle that, if managed responsibly, keeps delivering a useful resource as well as maintaining the health of the forest.

Rivers continues: “Sustainability is the very nature of what a forester does; because if we don’t take care of our forests, and ensure we have a crop to harvest year after year, we lose our livelihood.”

forests_trees_growing_for_winter_heating_smh4nj

Becoming a private forester

Two decades ago, Rivers completed a loop he started decades ago amidst the Dutch Elm crisis and became a forest owner himself. In Scotland, he bought, and now manages, his own private forest.

“We’ve had kids’ birthday parties, we’ve dug out a pond, we harvest chanterelles in the autumn – there’s a millennium capsule buried somewhere,” he says.

It’s not only a family heirloom. It’s a place for him to exercise a passion – maintaining and managing a responsible and healthy forest.

 

Inside the dome

Sustainable bioenergy

There are four storage domes at Drax Power Station and each of them can hold 80,000 tonnes of compressed wood pellets. It’s these biomass pellets, a sustainable fuel, that Drax is being upgraded to run on and produce renewable electricity.

Wood pellets are an incredible fuel that can match coal for efficiency – the challenge is you just need more of them as the density and calorific value of coal is greater. However, storing such large quantities in a confined space presents risks that have to be managed, 24/7.

Atmospheric control

The crucial difficulty with storing the pellets is their chemical volatility. Wood, which the pellets are made from, emit carbon monoxide (CO). In a confined space such as the storage dome, this CO can build up and – due to CO’s extreme flammability – require the entire internal atmosphere to be regulated by a set of highly sophisticated engineering solutions.

As long as materials are emitting more heat into the atmosphere than they are storing in themselves, there is no risk of combustion. A single wood pellet in a fuel store poses no fire risk. Nor does a small pile. But when thousands upon thousands are piled together, the pressure builds up and causes the pellets to heat up.

Gradually, the rate of temperature increase speeds up, and before you know the flashpoint threshold has been crossed and there’s potential for danger.

However, remove or limit the oxygen supply in the silo and purge the CO that’s emitted from the pellets, and the risk of a thermal event is substantially reduced. The challenge for the engineers at Drax constructing the domes was finding a way to manage temperatures within the dome.

Neutral nitrogen

To do this they created a system to automatically inject nitrogen into the storage dome. While nitrogen isn’t a truly inert gas, it is much less reactive than CO and oxygen.  With this pumped into the dome’s atmosphere it is a much safer environment.

To get a steady supply of nitrogen, regular air from our atmosphere – which is 78% nitrogen – is passed through a molecular filter, which removes the larger oxygen molecules. The gas collected at the other end is 96% nitrogen.

This nitrogen-rich air is then injected from underneath the dome and continually distributed around it. Not only is this a fire prevention method, but also a firefighting one that can be pumped in larger quantities in the event of combustion. Separate to the above measures which are there to manage fuel temperatures, the dome is also fitted with a carbon dioxide (CO2) injection system and water deluge system which are there as fire extinguishing precautions.

The big ear inside the dome

The next problem facing the designers was how to accurately monitor the quantity of compressed wood pellets inside the dome. To achieve this, each dome is fitted with a sonar system – which sounds a bit like a chirping bird – that provides continuous feedback on how full the dome is.

The sonar monitoring system provides level, profile and volume information which is translated into a 3D image of the stored biomass. This method of volumunetric measurement allows the operators to view and monitor in ‘real time’ the effects of their actions when filling and unloading domes, so they can target specific areas particularly when unloading and for fuel accounting purposes.

Other tools and tricks

Five thermocouple arrays measure the pile temperature and provide feedback in real time to the operators to allow them to assess the status of the dome and effectively plan material filling and reclaim. Gas monitors measure the levels of CO and CO2 as well as O2 depletion within the head space of the dome.

A dome breather vent (a two way acting valve, which as its name suggests, allows the dome to breathe) is fitted to the top of the dome and acts as a vacuum breaker maintaining a relatively even pressure allowing air in during unloading and releasing head space gasses during nitrogen inserting.

The final piece of the atmospheric control puzzle is regulating pressure. At the top of each dome is a controllable aperture called a slide gate which is closed unless the dome is being filled to allow material to enter. A dome aspiration system is installed here to filter and remove displaced air from within the head space during filling, but also allow a route for CO and other offgassing products to escape.

All the hidden systems within these four huge white domes allow the operator to effectively control their atmospheric conditions and crucially to store massive amounts of potentially volatile biomass safely on site.

Find out more about these giant storage domes – read the story about how they were constructed. 

The single biggest transformation of our century

Sustainable bioenergy

At the turn of the millennium, Drax was facing a serious issue. Demand for electricity was high and increasing, but so was the desire for sources of power that were less harmful to the environment than coal, at that time Drax’s fuel.

To continue to meet demand in a cleaner and more sustainable way, an alternative approach was needed. Drax had a legacy in this field – in 1988, it was the first coal-fired power station to install flue-gas desulphurisation technology, which removes 90% of coal’s harmful sulphur dioxide (SO2) emissions.

In the two decades that followed, however, the sustainability conversation moved beyond how to make coal cleaner. Instead, the focus was finding a truly viable alternative fuel.

Finding a new fuel

In those early days, the idea of converting a fully coal-fired station to another fuel seemed outlandish to say the least.

“We made a lot of people’s heads hurt with this project,” says Drax Strategic Projects Engineering Manager Jason Shipstone. “No one had the answers. It was a bit like going for a walk but not knowing where you’re going.” Back then it was all about experimentation.

Jim Price, Alternative Fuel manager at the time, explains: “Initially, we found a few distressed cargos of wood pellets and sunflower husks that someone had ordered but didn’t want. We mixed that with coal at very low concentration.”

Price and his team found they could use the plant-based fuel alongside coal at low percentages without it detrimentally affecting the boilers. It was a long way from being a new business model, but it was a start. They spent the next year working with willow wood, a subsidized energy crop that proved difficult to turn into a fuel that could be used efficiently to power a boiler.

Then in 2005, after building a prototype plant and finding a way to pulverise the willow into a fine powder – called wood flour – and combine it with coal dust, the team hit its first key milestone. It was able to power a Drax boiler.

“That was the Eureka moment,” says Price.

“No one had the answers. It was a bit like going for a walk but not knowing where you’re going.”

A change in attitude

The response to the success was immediate. Senior management support for the project had been in place from the beginning, but now there was a change across the whole company. “People started to think maybe it can be done,” says Price.

Work continued on the project and – after more experiments – Drax eventually settled on compressed wood pellets. This form of biomass ultimately required investment in four vast storage domes that between them store 80,000 tonnes of pellets.

Then there was the issue of supply and delivery. Materials were sourced from the US, shipped to the UK, then freighted to the plant in specially designed covered train wagons, each carrying up to 7,600 tonnes.

“Everything else had to carry on as normal. This had to be seamless. We had to work the same as Drax has always worked – reliable and available,” says Shipstone.

Jason Shipstone, Drax Strategic Projects Manager, played an instrumental role in upgrading Drax.

Jason Shipstone, Drax Strategic Projects Manager, played an instrumental role in upgrading Drax.

The final hurdle

In 2009 the team overcame one of the final challenges, and successfully adapted the boilers to combust the new fuel, proving that co-firing (the process of using two fuels powering one boiler – in this case wood pellets and coal) could work. It was enough to show there was a future in wood pellets and it could work at scale.

Although nothing was fully built yet, but Dorothy Thompson, CEO of Drax, was convinced. Shipstone remembers the conversation after Thompson signed the contract to begin the transition in earnest. “’So we can do 10%. What does it take to get to 50%?’ she asked,” recalls Shipstone. His response? No problem. “It was the right answer,” he says.

Toward a coal-free future

Fast forward to 2016, and Drax is Europe’s largest decarbonisation project – reducing emissions by at least 80% of the 12 million tonnes of carbon dioxide that the three, now converted, former coal generation units would have released per year. Although only half of Drax’s six units have been upgraded from coal to use compressed wood pellets, 65% of the electricity generated at the power station is the result of a renewable, rather than a fossil fuel. Its three biomass units produce enough electricity to power the equivalent of four million homes – or more than half of all residential properties in northern England.

Given the challenges the world faces regarding the future of energy production, decisive action is required if we’re to meet carbon reduction targets. In the UK the government has voiced ambitions of phasing out coal by 2025. Drax has aims of doing it quicker. Thompson has spoken of plans that see all coal units taken off the Drax system by 2020, if not before.

The story of energy since the dawn of the Industrial Revolution has been one of fossil fuels. This simply has to change. By finding a way to ease the transition away from coal, Drax is helping to write the next chapter.

The biggest balls of electricity generation

Power generation

When making a cup of tea, it’s unlikely you consider the industrial equipment kicked into action the moment you switch on your kettle. And of all of the activity going on behind the scenes, it’s even more unlikely you think about a 1.2-tonne steel ball.

But without a number of 1.2-tonne balls and the electricity they help generate, your kettle would be nothing more than a fancy jug.

How do giant balls help to generate power?

The answer lies in the way fuels like coal and compressed wood pellets are used to power boilers and generate electricity. Drax started its life as a coal power station, but today it is in the process of upgrading to run on biomass. Progress has already been made – three of the station’s six units already run on compressed wood pellets, Drax’s biomass fuel, generating around 20% of the UK’s renewable electricity.

To generate enough power to supply 8% of the UK’s demand – as Drax does – a lot of fuel is needed. Hundreds of thousands of wood pellets are delivered to Drax every day, arriving on custom-built trains travelling from the Ports of Tyne, Hull, Immingham and Liverpool.

The pellets pass through a system of conveyor belts until they arrive at one of four massive conical storage domes, located on site in Yorkshire. Before the wood pellets can be converted into fuel, they need to be crushed: this is where the balls come into play.

The pulveriser

The wood pellets used at Drax are compressed and dried wood that is formed into small capsules the size of a child’s crayon. But, like with coal, to get the best results in the power station’s huge boilers, the material needs to be turned into a very fine powder in pulverising mills. When very fine, the fuel burns as efficiently and as quickly as a gas.

Inside each mill are 10 giant steel balls that grind down either the wood pellets or coal. Each ball is three quarters of a metre in size, made of hollow cast steel alloy and weighs roughly 1.2 tonnes – equivalent in weight to British-made Jaguar XE mid-sized saloon car or an entire football team.

And to make sure that each one is up to the task of extreme pulverisation, they need to be hard. Each one is heat treated during manufacture to make sure they’re up robust enough to consistently crush raw fuel.

The benefit of this durability is that they can readily pulverise fuel to feed Drax boilers, to power kettles across the country – a big responsibility for a big ball.