How to convert a coal power plant into a biomass plant

Four years after its closure, Ence has “resurrected” the Elcogás thermal plant giving it a new use. The company headed by Ignacio Colmenares, has become the first company to transform a coal-fired thermal power plant located in Spain into a renewable energy generation plant with biomass. The new facility, inaugurated on January 9, becomes the eighth biomass plant for Ence. Follow all the news of the energy sector in the Energy Economist

This type of project, considered by the company as a “magnificent example of contribution to the just energy transition”, becomes a sustainable solution to give a second life to the dozens of coal plants that will no longer be operational in our country in June of this year, having not undertaken the necessary investments in denitrification to reduce the impact of its polluting emissions, according to the regulations of large combustion facilities.

The truth is that some of its owners, such as Endesa, have been analyzing the possibility of using biomass in two of its plants to avoid its closure: As Pontes (A Coruña) and Carboneras (Almería). However, as they point out from the electricity company, the results have not been satisfactory, which, for the moment, makes this option unfeasible. But what requirements are needed for this type of plant to replicate the Ence project?

The first thing to do, says Felipe Torroba, General Director of Energy at Ence, “is to identify if there is sufficient biomass potential in the area where the facility to be converted is located.” It is true that in some countries like the United Kingdom, some companies such as the English Drax, have been making complete reconversion of coal to biomass for several years. However, Torroba points out, “this seems an aberration.”

The biomass consumed by these plants (mainly pellets) is brought from the US and, to produce it, we must use wood that has other uses of greater added value. In fact, explains the head of Energy of Ence, “we were seeing opportunities to invest in biomass projects in the United Kingdom, but all we saw (both new plants and to convert) were based on importing biomass from South America or North America and, to us, that doesn't seem sustainable. ”

In his opinion, “that sensitivity of using local biomass in other parts of the world is not being applied. The same does not happen in our case.” Previous analyzes carried out at the Elcogás plant before its acquisition, located in Puertollano (Ciudad Real), indicated that the amount of biomass available was sufficient to power a 50 MW plant, which is the power that Biollano has, the name it receives the new installation (the original installation had 320 MW).

The plant, which has been built in a record time of 16 months, will consume around 238,000 tons per year of biomass, mainly from agricultural by-products: 50% of pomace and 50% between vine shoots, pruning of olive groves and woody forest and agricultural remains , which will allow a strong reduction of uncontrolled burning of agricultural stubble. The use of this type of biomass will allow the plant to produce about 325,000 MWh of electricity per year, equivalent to the energy needs of more than 60,000 people. All this biomass, says Torroba, “complies with the Decalogue for the Sustainability of Biomass as a Fuel of Ence, a pioneering initiative that prevents us from using fuel that is outside a certain range of action.”

Another aspect to take into account when carrying out this type of project, says Torroba, “is the price of biomass.” Ence has conducted an analysis of all coal plants that are operational in Spain and, in conclusion, there are very few that have biomass availability at reasonable prices. The cost of biomass that exists, for example, in the Cantabrian coast and in Asturias where some of these plants are located, “planting is very high and would not make them competitive,” Torroba explains. They could be reconverted, he adds, but the production cost of the megawatt would not be reasonable. In this sense, the general director of Energy of Ence states that a large part of the owners of coal plants in Spain “have approached the company to see the feasibility of making the transition to a biomass plant and currently, we are analyzing the possibility of replicating the model in some other central “.

Converting a coal-fired power plant to biomass is economically more expensive than making a new wind or photovoltaic plant; However, as the General Director of Energy of Ence points out, “a biomass plant is manageable renewable generation, it can operate 24 hours a day, 365 days a year and deliver megawatt hours when demanded by the system.” The Ence spokesman explains that, although it is true that PNIEC is very focused on supporting wind and photovoltaic generation, this creates a very large manageability problem in the system with the coal coming out and, what will remain, is the regulating gas Therefore, “these types of projects are great to displace gas and have a clean energy that can manage that gap left by wind and photovoltaics,” says Torroba.

The Biollano plant has required an investment of approximately 100 million euros and its facilities have been projected following the best available techniques recommended by the sector to have a very high efficiency, which translates into lower biomass consumption per ton per hour, as well as taking advantage of a series of equipment and installations of the old site that, with respect to a new plant in a virgin site, means a saving of 10% of the cost of the investment.

These improvements include the installation of a regenerative steam water cycle with overheating, which will allow operating with high efficiency, which will reduce the consumption of biomass, and the installation of a nitrogen oxides (NOx) reduction system called ' selective non-catalytic reduction '. Also, closed silos have been built, covered systems will be used for the transport of biomass, and an efficient filter for the purification of combustion gases at the boiler outlet has been installed. The 70-meter chimney also exceeds the recommended characteristics for these installations. In addition, the plant amply meets the environmental parameters required in Spain and in Europe.

The activity of the Puertollano plant will contribute to the maintenance of more than 1,300 jobs, including direct, indirect and induced, most of them in rural areas. These jobs will be added to the 500 direct jobs generated by the plant during its construction.

Currently, Ence has a fairly advanced project in process in Almería, whereby they will solve an environmental problem by taking advantage of all the by-products of the greenhouses, using them as fuel for that future biomass plant that they have been managing for almost two years. “If there were auctions shortly, Torroba explains, and we understand that with the new government this should be so, by the end of this year we could have this project ready to begin construction.” The company also has another biomass project in Córdoba, but it is a less advanced state of processing.