Magnon Green Energy: Technology Reviving an Industry: Pulp Mill Reborn as World’s Largest Biomass Power Generation Plant | Technology
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If an industrial religion existed, the case of the pulp mill in Huelva would be a resurrection or a reincarnation, depending on the creed professed. Ence’s pulp factory, after half a century of activity and with a final direct workforce of 294 workers, announced its closure in 2014. Thanks to technology and an investment of 310 million euros, Magnon, a subsidiary of the original company, has Part of the 40-hectare factory has been converted into the largest energy-generating plant from biomass (vegetable remains) in Spain and one of the largest in Europe. It has 155 permanent workers, although it employs up to 800 in some phases, and it aspires to grow. This is how it works and these are its challenges.
Verónica Martínez is responsible for the production of one of the three power generation lines, the H50 or, as her colleague Roberto Romero, a process engineer, calls it, “the Ferrari” of the three available at the plant. Verónica Martínez shows detailed diagrams of the entire system, showing kilometers of pipes and structures, as well as dozens of production and control devices. Finally, reluctantly, she accepts a simplification of the complex to make it understandable: it is like a pressure cooker where the gas that comes out of the valve moves the turbines. “But our boiler is equivalent to a nine-story building,” she says.
It all starts in the field. “We obtain the biomass from nearby agricultural and forest residues. This means that we take advantage of one million tons of waste generated within a radius of 100 kilometers”, explains Diego Lamela, manager of the plant. This is one of the key elements of the sustainability of this technology, because only remains of pruning or transformations and other agricultural or forest cleaning activities are used. “It is not planted to produce biomass,” he says. In this way, it is guaranteed that the fields are neither imported nor transformed to cultivate exotic species with which to supply the factory and which could have an environmental impact.
The established distance range ensures that the transport of the raw material does not generate more pollution than is avoided. The one in the environment is enough. According to the Swedish University of Agricultural Sciences and Eurostat, the potential of Spanish biomass is equivalent to 6,754 tons of oil. The availability of this resource per million inhabitants places Spain as the third country in Europe, behind Finland and Sweden. In addition, the removal of waste from the fields prevents its uncontrolled burning and the risk of fires.
According to the Association of Renewable Energy Companies (Appa), biomass saves polluting emissions by replacing the use of fossil fuels, avoids spills and prevents fires. The estimated benefit in economic terms, of specific compensation for biomass technologies, exceeds 300 million euros per year. According to Magnon, its six plants (three in Andalusia, one in Extremadura and two in Castilla-La Mancha) prevent the emission of more than 335,000 tons of CO₂ into the atmosphere in one year.
The remains are separated from non-combustible material (earth debris, for example) and adapted to the size necessary to be used in combustion. They are stored in silos with a capacity of 10,000 tons and transported by belts to feed the plant, to maintain the fire of the gigantic pressure cooker. Rosario Maestre is responsible for the newest line, the H46, with three turbine bodies, and explains that the composition of the biomass is based on two main criteria: “its energy efficiency and the effect on maintenance”.
Both aspects are essential. The first because not all remains have the same energy potential (those from olive trees are the most efficient) and the composition of the mixtures must be calibrated to achieve the necessary temperature, between 800 and 900 degrees Celsius. In the case of the H50 line, where the combustion is generated on a fluid bed of sand (similar to a boiling piece of beach), any variation in temperature can compact these compounds until they turn into something similar to concrete, paralyzing the plant .
Maintenance is another crucial aspect and the three-week annual technical stoppage that is carried out for these tasks represents a cost of 3.25 million euros and the participation of 700 people from some 70 companies. Any preventive element that alleviates these functions represents considerable savings and any error generates unnecessary expense. “A deviation in the process, even for a minute, entails an analysis of the cause”, explains Roberto Moreno.
From combustion, the boilers generate 180 tons of steam per hour at 100 bars of pressure that move the turbines. “They can only be gases. If there were a tiny particle of something else, water, for example, at a pressure equivalent to 101 kilograms per square centimeter, it would destroy the rotor blades”, warns the engineer.
Once its function has been fulfilled, neither the steam nor the excess heat is wasted. On the contrary, they are reincorporated into a closed cycle to continue reusing them. In the case of gases, up to 75% is re-incorporated into the generation circuit.
In the combustion process, particles are formed that, according to Moreno, “are reduced by up to 99%”. In other words, they are captured by two systems that the engineer also finally agrees to simplify: “One is like a coffee maker with a paper filter. The other is an electromechanical system that makes the particles stick to a panel and precipitate hitting it. These residues can be reused for landfill, as fertilizer or as a construction material. The dust generated throughout the process, one of the great challenges, is minimized with sprinklers that precipitate it. And in terms of emissions, the control systems monitor them permanently so that they are at least 20% below what is forecast by the environmental authority, which has access to data in real time.
The end result is 137 megawatt hours (MWh) in Huelva alone. The three Andalusian plants (the one in Huelva and those in Córdoba and Jaén) generate 876,000 MWh, enough to meet the energy needs of between 700,000 and 800,000 people, a population equivalent to that of the city of Seville.
Biomass generation is still the little sister of all generation systems. According to the Appa report from last March, “it represents 6% of the total final energy consumed in Spain”. However, if only that from renewable sources is considered, this percentage rises to 48%, if thermal generation and for transport are included.
There is room for more and better. Chinese researcher Gaoyang Hou, co-author of a study published in Journal of Renewable and Sustainable Energy, points out as “cleaner and more energetically efficient” the hybrid solar-biomass systems, the multigeneration that integrates photovoltaic-thermal energy sources and plant remains.
Tuomas Koiranen, a professor at the Finnish Technological University of LUT, also points to the possibility of producing by-products: “Countries with a high potential for wood waste and green electricity can be producers of acetic acid, which is hydrogenated to produce ethanol as a fuel. ”.
Magnon is in these lines. In the presentation of the results of its parent group (Ence), when a net profit of 13 million euros was announced in the first quarter of this year compared to the 9.6 million lost in the same period of 2021, the bet was maintained by biomass, photovoltaic energy, biofuels and biogas.
How to deal with the shadows
But not everything is lights. There are also shadows. Despite the advantages of using biomass, there are still misgivings about this system. Raymond Pierrehumbert, professor of Physics at the University of Oxford, doubts that the methods used to determine that they yield a zero or negative balance in emissions, the difference between the carbon added to the atmosphere and that removed, are correct. It largely depends on how you get [la biomasa] and that implies an intricate and difficult accounting of the emissions in the complete cycle”, he assures. It also warns of the problems that it can generate in biodiversity, alluding to deforestation or intentional production of plant species to supply the industry to the detriment of native forest masses or traditional and basic agricultural systems to supply the population. “The devil is in the details,” she warns.
In this regard, it points out how the Drax power station made the UK one of the world’s largest importers of pellets (wood particles smaller than two centimeters) and contributed to the growth of this industry, with a long and complex supply chain. “The source of the wood pellets being burned and the forestry practices involved in their production are crucial factors,” he says. He also warns of the problem of considering forest waste, vegetable remains that contribute to storing carbon or trees that are economically unviable, but ecologically valuable.
Researchers José R. Moreira, from Brazil, Roberto Bissio, from Uruguay, and Ethan B. Davis and Tom L. Richard, from the United States, believe it is necessary to analyze the benefits of energy production from biomass and the danger of dedicate arable land to it, which could “further undermine food security in the developing world.”
The Magnon plants overcome these misgivings with “new ways of working”, according to the manager of the Huelva plant. His formula is based on what would be the commandments of this new industrial religion: respect the natural environment; do not use wood of more than 10 centimeters in diameter, unless its only possibility of consumption is energy use, or that it comes from invasive species, unless expressly indicated by the competent administration; respect the priority uses of biomass (construction and manufacture of furniture); do not use that which competes in resources with food or with livestock uses; respect laws and human rights; minimize carbon emissions and resort to the best and most sustainable practices for the use, transport, treatment and storage of biomass, as well as in the production of energy.
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