Reduction of nitrogen oxides by injection of urea in the freeboard of a pilot scale fluidized bed combustor

The ‘thermal deNOx’ process using urea has been investigated in a 1 MW fluidized bed combustor. NOx reductions of up to 76% were obtainable by using this method. The experimental results show that urea is at least as active as NH3, which is commonly used in this application, but which is far more toxic and corrosive. Emission levels of 200 mg m−3 for NOx could be achieved by injecting the urea at a height of 2 m above the distribution plate in a molar ratio urea:NOx = 1.5. The SO2 emission value also appeared to be reduced when the urea was injected at a urea: NOx molar ratio > 4

Reversed combustion of waste in a grate furnace - an experimental study

Most widely used concept for municipal solid waste (MSW) incineration is combustion on a moving grate with energy recovery. In MSW incinerators fresh waste stacked on a grate enters the combustion chamber, heats up by radiation from the flame above the layer and ignition occurs. Ignition front propagates downwards producing heat for drying and devolatilisation of the fresh waste below until it reaches the grate. The present project is investigating the so called reversed combustion of waste on a grate. In this new concept the fuel layer is ignited by means of preheated air from below without any external ignition source. As a result a combustion front will be formed close to the grate and will propagate upwards. In order to investigate reversed combustion an experimental set-up that is able to simulate a real moving grate furnace is designed. Experimental study was conducted to determine the influence of different factors (amount of primary air, fuel moisture content etc.) on process parameters. In this paper, the detailed description of setup, as well as the results from experiments will be presented