Objective
The aim of the project is to demonstrate the reburn technology using coal as reburn fuel as a means of achieving NOx reductions from large, coal, wall-fired, power station boilers, of the type which provide the bulk of coal fired generation in Europe. The demonstration will be conducted on a 320 MWe opposite wall-fired boiler, unit 4 of Vado Ligure power station (ENEL, Savona), and will complement the knowledge gained from the Longannet Project. Due to the fact that most of the partners of this project are the same as for Longannet, the two projects will have a strong synergy, allowing a group of European companies to have a detailed knowledge of the reburning technology in all its aspects, greatly improving their competitiveness in the world market. Using the technology developed in this demonstration, a consortium of European Partners will be formed to exploit the growing requirement for this technology in the world market.
In a coal fired boiler NOx is generated from high temperature processes which oxidise the nitrogen arising from fuel bound sources and from the combustion air. The reburn process is a fuel-staged process whereby three conceptual zones are created within the boiler. Approximately 80% of the original coal load is fired in the primary zone under near stoichiometric conditions. Coal is then injected above the primary combustion zone to provide the balance of the thermal input to the boiler. A fuel rich reburning zone is formed where NO is chemically reduced to molecular nitrogen. A burnout zone is achieved by introducing additional air further downstream to ensure complete combustion.
Coal reburning requires supply of the reburn fuels to the boiler through a system of pipework and valves. The system allows the addition of recirculated flue gas to increase the momentum and thus the mixing ability of the reburn fuel. Reburning coal will be of suitable fineness to promote both high ratesof devolatilisation and char burnout and will be supplied with a proper system in a micronised form. The flue gas will be provided by a flue gas recirculation fan and associated ductwork. Additional air will also be provided by fans, ductwork and ports. Control and monitoring equipment will form an integral part of the system. The system will be designed in order to allow also the use of oil as reburn fuel.
The main advantage of using coal as reburning fuel is the fact that this fuel is available at no operating cost increase. Therefore all the advantages that can be obtained in lowering NOx emissions become financial return to the investment. The possibility of using coal as reburning fuel is well established at research scale, although largely dependent on the type of coal to which the technology is applied. When using coal as reburning fuel the problem of unburned carbon (UBC) increase has a greater importance. When using gas as reburning fuel there is no problem with UBC increase, after the main combustion zone. It is therefore essential that, using coal as reburning fuel, the UBC coming from the main combustion zone is kept at a minimum. This is a major concern, since ashes with UBC grater than 7% cannot be sold to cement or brick-lining factories and therefore present a disposal problem. The process design selected is consistent with the previous know-how of the Proposers, but it needs to be proven and optimised at a sufficiently large scale. The result will be a system which allows compliance with the Italian Regulatory Limit by adding to reburn a low cost SCR system. It will also provide vital information to the utility partners who have yet to decide a course of action on further NOx abatement and to industrial partners who are looking to establish clear advantage in a competitive market. Whilst gas reburning over coal is a proven technology, coal reburning have, in fact, been less exploited.
Fields of science (EuroSciVoc)
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Topic(s)
Call for proposal
Data not availableFunding Scheme
DEM - Demonstration contractsCoordinator
00198 ROMA
Italy