Changing the fuel to fit the plant

A new biomass processing system could be “a game-changer” says Chas Fritz

Credit: Active Energy

As emissions rules become more stringent worldwide, operators of coal-fired power plants are increasingly considering retrofitting their plants to burn biomass – but the costs are significant. Tildy Bayar spoke with one company which believes it has come up with a low-cost alternative

New standards are “hitting the global power industry really hard against coal,” says Chas Fritz, chief executive of Active Energy Coalswitch.

The company is a joint venture between UK-based Active Energy Group, a supplier of wood fibre products and biomass-for-energy (BFE) fuels and processing systems, and US-headquartered Biomass Energy Enhancements LLC (BEE), which has developed a chemical process that it claims improves the quality of biomass used for fuel.

“So we’re analyzing the costs to replace coal-fired power to allow biomass,” Fritz continues. “It’s a fairly large cost in many cases, because you have to change the material handling, have to change the mill, have to change the grinding and the actual furnace temperatures.”

Indeed, a recent exemplary coal-to-biomass conversion project profiled in these pages (Making the switch from coal to biomass, February 2015) featured the installation of new unloading and feeding systems, the addition of biomass storage facilities, and many changes to the mill’s grinding system and associated controls, fuel classification system, fuel transport system, and the 24 burners designed to burn bituminous coal. Changes to the burners included new primary air tubes, a new core nozzle and new secondary air swirl inlets.

In addition, the operating parameters of the firing system needed adjusting to deal with the properties of biomass. The project was begun in summer 2013 and the converted plant came online in March 2014 after four trial runs.

Fritz says a new biomass fuel processing system, which BEE has been developing for the past seven years, could prove to be a game-changer for a global power generation industry dealing with the need for expensive and complex retrofits.

For the first time, he says, it enables biomass fuel to be used in traditional coal-fired power plants as a direct replacement for coal – as well as being mixed with coal in co-firing operations – without requiring plant owners to invest in expensive and time-consuming furnace, handling and storage modifications.

No boiler upgrades, changes in material handling equipment, or changes to the ball mill or injection system are needed, Active Energy claims, because its biomass fuel stream “has the same characteristics as coal”.

The company says its processing system cleanses the raw biomass material by removing salts, minerals and other contaminants that can damage power plant furnaces, and converts it into feedstock that lacks the low and medium volatiles of other biomass fuels, such as ‘white pellets’.

According to Fritz, “biomass as a general energy source for coal plants doesn’t work well as it sits today”, because the characteristics of biomass include these volatiles that could cause a mill fire, such as potassium, chlorides and sulfates.

“So we solve that problem by basically beating up the fibres through a handful of technologies that explode out the fibre cells – called steam explosion,” he explains. “After that we reduce the ‘nasty stuff’, some down over 90 per cent, some over 80 per cent, some over 70 per cent.”

“We like biomass to come into our platform one-quarter inch minus in size. If it’s sawdust then it’s even better,” he continues. “We do not add any chemicals or anything to the process. We use natural processes to weaken the cellular structure of the biomass, both the intercellular structure and the cell itself, because that’s where a lot of the water and what’s called entrained salts reside.”

Biomass processing test results

Source: Active Energy

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Biomass processing test results

Source: Active Energy

This beneficiation process can handle 40 tonnes per hour, with two tonnes in producing one tonne out. “We put it through a couple of pre-processing steps in a system which is closed-loop, and very efficient at the energy balance,” Fritz continues. “We wash out all the salts – it’s the potassium that typically causes a lot of slagging and fouling, but we also don’t want sulfur, chlorine or chlorides.”

The biomass can then be blended with coal or coal fines, a waste product from coal mining which can be used as a cheaper alternative to coal. “In some parts of the world there’s a coal tax placed on plants,” Fritz explains, “but in some places they don’t tax the fines because it’s a waste stream.”

Rather than modifying the plant, Fritz says, “all we’re doing is changing the feedstock to look like coal.” This includes all material handling, grindability and friability as well as decreasing low volatile issues. Fouling and slagging are also reduced, Fritz claims. “At the end of the day,” he says, “we have a drop-in fuel that can either be blended with coal using a natural binder called lignin, or just a one-to-one replacement.”

At the plant level, Active Energy says its solution requires only “very minor” modifications, and that the goal is “zero to very minimal” plant changes. “There might be a small adjustment to temperatures and blowers,” Fritz says. Active Energy plans to do a deposition burn test early this year “with a major lab”, the results of which will be published in the first quarter, and the firm says it has already done 50 to 60 tests.

The characteristics of the biomass fuel “are in the bituminous and sub-bituminous coal range, hitting 23 gJ and consistently hitting 10,000 to 11,000 BTU per pound”, Fritz notes. The fuel can be delivered in a range of compacted formats including pellets, granules, briquettes and bales, and Active Energy says it can be handled and processed at power stations using the same equipment currently used to handle and prepare coal. In addition, the fuel is hydrophobic – it doesn’t absorb water – which means the pelletized biomass can be stored outdoors, eliminating the need for a covered storage area. “Nothing is 100 per cent, but it is good enough, especially if you pelletize or briquette it,” Fritz says.

Works on waste

Active Energy says its process can be used on any plant- or wood-based raw biomass material, and also on previously unusable or economically unviable waste timber, such as that produced from forestry and wood chip processing activities; contaminated or redundant industrial residues, such as sawdust, demolition and construction materials; and chemically-treated wood, such as railroad ties.

Coal fines, with a maximum particle size of less than one-sixteenth of an inch, are usually put into a slurry or back into the mine and are “pretty cheap” according to Fritz. When they are mixed with biomass waste streams such as bark, tree limbs and sawdust, the result is “a very green product”. The waste biomass qualifies for renewable fuel subsidies and meets the US Environmental Protection Agency’s (EPA) section 111D clean air standard as well as the Mercury and Air Toxics Standard (MATS).

“Some of these new renewable energy portfolios are trying to hit 30 per cent [renewable content]. With a mixture of one-third biomass and two-thirds coal fines you hit 33 per cent,” says Fritz.

“We are being a little picky in how we go to market” says Fritz

The company also processes agricultural waste such as corn stover, bagasse and rice hulls. In addition, Fritz notes that certain trees have become invasive species in parts of the US and elsewhere, and are being cleared and becoming waste streams. “Only 30 per cent of the tree is heart wood,” he notes; the rest is classified as waste. “This fuel stream is technically carbon-neutral, a major issue when a plant is faced with closing because of impending industry standards.”

Active Energy says it wants to partner with coal-fired power station owners and operators worldwide on converting their plants to burn a wide variety of materials.

“We have a commercial demonstration unit that is doing all kinds of testing of material – both internal and third-party testing,” Fritz says, adding that the results will be disclosed during the first quarter of this year. “The next big thing is to get into the marketplace.”

According to Fritz, the first Coalswitch units to be brought to market will be able to process 40 tonnes of biomass per hour, with an output of around 300,000 to 320,000 tonnes of fuel per year. The units can be run in parallel to achieve greater output, Fritz says, and they are skid-mounted so can be deployed in remote locations.

“One unit is around 12,500 square feet (1160 m2), so they need a little bit of space,” he notes, adding that he believes a selling point of Active Energy’s technology will be the ability to disassemble, transport and reassemble its manufacturing facilities at different locations when a raw material feedstock source is exhausted or a more productive source is identified.

Active Energy intends to bring its product to market using a tolling model. The firm will install, own and operate its units, with the client as the offtaker. In terms of market focus, Fritz says Germany is “an ideal market” and Canada is “extremely interested because there’s a lot of biomass there, and a new green government. Anybody that is polluting in a major way using coal is a candidate,” he continues: “India, China, the US.” The firm has filed patents, he says, “across 42 countries – all the major countries that have coal: most of the countries in Asia, the whole of the EU, all of North America, Brazil. We’re covering the locations that have a lot of coal and biomass.”

“We’re being extremely cautious and a little bit picky in how we go to market,” he adds. “We can’t solve the whole coal industry.” Instead, he says, “we’re looking to partner with the right people.”

Fritz hopes his firm’s potential partners will include “two or three major utilities” as offtake parnters, as well as a feedstock supplier with “a good supply”, whether of biomass, coal fines or coal. “We think this will help the coal industry too,” he says.

Coal economics

And he believes that the time is right to bring his product to market given the current economics of coal-fired power production. “In the US, 300 coal plants are being shut down over the next eight years, and maybe more now after [the climate talks in] Paris,” he says. “Some of those plants probably have another 20 to 30 years left if they could meet emissions standards but not have to spend billions of dollars on retrofits.”

He describes a US utility which operates a coal-fired plant: “Eleven years ago they had three stacks. They spent $1 billion dropping two stacks and putting a scrubber on the third stack to [meet the requirements of] the Clean Air Act. However, with the pressure against coal, three months ago they announced that they’re getting rid of that coal plant and are going to convert it to natural gas. It will cost another $1 billion to do that and will take four years. So, over a 15-year period, they will spend $2 billion to make this plant green. With us, all they’ll have to do is convert their supply and not do any of those retrofits.”

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