* Author: Concepción Carracedo de Luis *
Over the course of my 12 years of experience working for Iberdrola, I’ve had the chance to take part in various R&D projects at the Velilla del Rio Carrión power plant (Palencia), one of Spain’s foremost thermal power plants. It is now undergoing a thorough improvement process to optimise performance and efficiency and reduce its impact on the environment.
Our main goal is to continue to advance in our compliance with the ever-stricter environmental regulations. In 2005, we started to implement improvements in the combustion process in order to reduce nitrogen oxides by over 67% (from 2400mg/Nm3 to 800mg/Nm3) at a very low cost. This initial measure gave us an insight into the potential for reducing emissions at the plant and into planning the various measures that could be taken. In 2008, we completed the construction and commissioning of the desulphurisation plant, which is renowned for its excellent performance in reducing emissions of sulphur dioxide and particles.
Looking ahead to the future, further reductions will be needed. Bearing this in mind, two entirely innovative pilot projects were carried out at Velilla, with the participation of the Agency for Innovation, Finance and Corporate Internationalisation (ADE) for the Castile and León region and the Centre of Industrial Technological Development (CDTI).
The first reduction tests were focused on SNCR (Selective Non-Catalytic Reduction) technologies and involved the addition of reagents in boilers: ammonia and urea, by the installation of a pilot plant. These tests were carried out at different boiler levels and gas volume percentages, as well as at local level. The areas with the best performance in the chemical reaction that transforms nitrogen oxides into molecular nitrogen and steam were then identified.
We then studied the behaviour of various fuel mixes with different volatile material contents, which enable combustion conditions that generate less nitrogen oxides. We took advantage of the existing advanced resources for regulating and monitoring the Generator 2 boiler, as well as new technologies for fuel input stratification.
We are now focusing on completing the construction of the pilot plant to treat 1% of the gas flow with various types of catalysts and ammonia injections. It is expected to be commissioned after the summer. The results of these tests will reveal the potential for reduction when all of the measures are being implemented in unison. If we can prove that it is feasible, it will become an international reference that would greatly simplify and reduce the cost of existing technologies for reducing emissions of nitrogen oxides.
These projects are intended to optimise low-cost measures for the plant, so that the need for other more expensive ones may be minimised or even eliminated. None of this work could have been done without the effort, courage and technical knowledge of the personnel at Velilla.
Implementing these experimental measures means undertaking an operational risk that we have been able to manage at all stages of the process, with satisfactory results. The collaboration of Iberdrola’s Innovation Department was key in completing these projects.
The efforts made and the technical knowledge acquired have been transferred to the Longannet thermal power plant in Scotland, and if necessary, the same may also be done in the case of the Lada facility. In the case of Longannet, implementing these measures is expected to improve uptime and reduce emissions, thereby avoiding expensive investments in retail systems and enhancing the operational experience at the plant.
