THE ENERGY INDUSTRY TIMES - MAY 2017 Technology 15 Getting the drop on coal A new type of black pellet looks set to offer generators a true ‘drop-in’ biomass replacement for coal. Junior Isles reports. I n an effort to cut emissions, many coal fired plant operators are converting their plants to allow firing on biomass. The cost of conversion, however, can be substantial. And even for those that have made or are considering the conversion, there are often questions around the sustainability of the biomass used to replace the coal. But a solution may be on the way. UK-based company, Active Energy Group (AEG) is currently in the process of commercialising a revolutionary ‘drop-in’ biomass product which produces pellets only from waste timber (unlike the white pellets currently used), thereby ensuring that the whole tree is used during forestry operations rather than pieces of it being left to rot. According to AEG, its pioneering product, CoalSwitch, can be mixed at any ratio with coal, or completely replace coal in existing coal fired power stations globally without the need for retrofitting. The new fuel is certainly good news for coal fired generators, not just in terms of environment but also from an economic standpoint. The cost of converting three of the six coal fired boilers at the UK’s Drax power station for full firing on biomass has been well documented. The price tag for modifying fuel mills and boilers at the plant and the construction of storage facilities and conveyors for the wood pellets is estimated at around £700 million. It is a huge investment, which AEG believes could largely be avoided through a fuel like CoalSwitch. Brian Evans-Jones, Chief Financial Officer, Active Energy Group, argued: “In our view, the cost of the Drax conversion is rather scandalous. The UK government sort of nailed its covers to the biomass mast and Drax went off down that route. We had discussions with government almost two years ago and the opinion of the advisers to Westminster was that we were behind the curve on this and that white pellet was the future. I was staggered then, and remain absolutely staggered now. “The carbon footprint of that process is well documented and it is not the way forward in our opinion. What we are looking to do is use waste product or timber that has no decent commercial value.” CoalSwitch is based on a technology that had been under development in Utah, USA, for several years. Evans-Jones said: “The technology was brought to us in late 2015. We had a look at it and formed a joint venture to actually move it forward. This culminated in us bringing the whole business in-house through a CoalSwitch is a ‘black pellet’ that can be ground into a very fine powder, capable of being used by coal handling systems and does not have the corrosive elements contained in biomass share-swap last year so that CoalSwitch technology is now part of the group.” AEG says its emphasis has been on avoiding what has been happening in the white pellet market, where hardwood and very high quality wood is used to produce high calorific value biomass pellets. CoalSwitch is a “second generation” biomass that is produced entirely from waste material instead of cutting down trees. CoalSwitch is essentially a ‘black pellet’ but with some key differences, according to AEG. It can be ground into a very fine powder, capable of being used by coal handling systems in power plants and does not have the corrosive elements contained in biomass. “Once you get over 5-6 per cent of firing biomass in a coal fired plant, you start to experience issues,” said Evans-Jones. “Our process removes the salts – the chlorine, potassium, etc. Other black pellet production processes don’t actually remove any of the impurities that cause it to be a problem when it is burned in coal fired power systems. Our entire approach has been to focus on removal of impurities in biomass, thereby elevating the calorific value and allowing it to be fired in coal plants without affecting the boiler.” Testing of the pellets has been carried out as the fuel has evolved. Just over a year ago, AEG engaged with the University of Utah to run some tests at its highly accredited research facility. The test, led by Dr Andrew Fry, was on the original fuel developed at Utah University. Since then the fuel has been substantially improved, according to Evans-Jones. “We have invested a lot of money in the pilot plant in the interim. The goal is to increase the calorific value to between 9800 and 10 200 Btu/lb (22.8-23.3 MJ/kg).” This is the range that will allow a generator to maintain base load.” Commenting on this test, he said: “Not only have they burnt it, they have burnt it with coal. They have proved that we have taken the biomass material and raised it to a calorific value that is comparable with many coals.” In the co-firing element of the test, Evans-Jones notes that researchers also discovered that the pellets improved the efficiency of the burning of the coal. Following this test, the University performed another set of tests commissioned by Rocky Mountain Power. The utility, based in Salt Lake City, has 1.1 million customers and is looking to move into the biomass space to improve the environmental performance and sustainability of its generating fleet. It therefore, wanted to see if CoalSwitch burns like coal and whether it is truly a “drop-in” alternative to coal. Evans-Jones commented: “We believe this is the first drop-in alternative to coal because it can be pulverised down to powder for pulverised coal injection. This is done in a bore mill, and Rocky Mountain Power wanted to test to ensure there were no flashover issues or risk of fire.” The tests showed its handling characteristics were more or less identical to coal, with no issues identified during the bore mill test. Satisfied with the results, Evans-Jones says Rocky Mountain Power is now awaiting a 500 t sample and is one of 17 major power producers now looking for samples. AEG is currently able to produce about 1 t/day of CoalSwitch and is therefore raising capital to allow it to expand production capacity to the level needed by generators. “The biggest sample a utility has asked for to-date is 50 000 t to do a burn test, so it will take a while to produce this. I recently put together a fundraiser with the aim of getting the first commercial plant operating. The intention is to have that first reference plant operating before the end of this year.” AEG says it is in advanced negotiations with “a substantial partner” on the first commercial reference plant but has a number of alternatives for that, both in North America and Southeast Asia. With a commercial scale installation imminent, Evans-Jones is confident of the future outlook. “We have an endless stream of people looking to engage with us on the CoalSwitch technology. If we had a plant operating at the right level, I could sell on commercial terms a quarter of a million tons of pellets tomorrow to some of the world’s major power generators.” Improving black pellet production As the biomass industry comes under closer scrutiny with regards to the sustainability of the resources used to produce the fuel, industry players have been developing technologies to produce black pellets. In addition to being sustainable, these are claimed to be safer, more cost-efficient, and deliver more energy than conventional “white” biomass pellets. This is becoming increasingly important in a market where demand is growing rapidly. According to market consultants Hawkins Wright, total global biomass pellet demand is expected to nearly double in the next seven years, from 29 million tons in 2015 to 53 million tons in 2023. Large amounts of renewable woody biomass feedstock are widely available across the globe at competitive prices. However, this biomass feedstock is often inefficient to transport to its final end-users, largely due to its high moisture content. Valmet solves this problem through steam treatment of the woody biomass followed by rapid depressurisation. This process creates a low-moisture material that is suited for the production of durable, water-resistant pellets or briquettes. These black pellets can be transported safely and economically over long distances, allowing power generators to take advantage of the global abundance of raw biomass supply. According to Valmet, its black pellets can replace fossil coal up to 100 per cent in smaller units and up to 70 per cent in larger units. The powder produced by grinding has a relatively high bulk density and is free flowing, meaning that it is ideal as a feed material to entrained flow gasification systems as well. Valmet’s technology partner Zilkha Biomass has already completed nine full-scale tests of the final black pellet product at utilities across Europe and Japan, in units ranging from 80 MW to 500 MW in size. In total, over 9000 tons of black pellets have been tested by potential utility customers.
Energy Industry Times May 2017
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