Reducing ammonia content from emissions

The Challenge

Coventry & Solihull Waste Disposal Company (CSWDC) is an independent waste management company firing black bag waste.

To meet the new BREF regulations for waste combustion which imposed for the first time a limit on ammonia emissions, RJM was tasked by CSWDC to devise a robust and cost-effective solution to see how ammonia reagent usage could be optimised whilst still enabling the plant to meet its NOx emission limits.  

RJM Solution

A detailed site survey carried out at the beginning of the project confirmed that temperatures at the SNCR level were not sufficiently high for efficient ammonia reagent reaction to take place, resulting in reagent not reacting within the system and being emitted to atmosphere. This was compounded by the fact that when reagent was reduced to limit ammonia emissions, NOx emissions increased. Following detailed investigation by RJM, the OFA was identified as the root cause, resulting in a biased flue gas flow up the rear wall and causing non-uniform temperatures at the SNCR level. CFD analysis of the combustion process allowed an in-depth assessment of the installed OFA system and the development a new set of differently-sized OFA nozzles.

RJM’s 4.4 million cell CFD analysis of the furnace and the grate confirmed that an upgraded design of the OFA nozzles would enable NOx to be better distributed and removed more easily due to the higher temperature. 

Results

Following installation of the new set of OFA nozzles, the desired increase and even distribution of combustion temperatures at the SNCR level was achieved.  RJM then worked with the site to re-optimise the SNCR system for the new temperatures at the SNCR level which reduced the amount of ammonia slip, thereby enabling the plant to a) meet the new BREF limits on ammonia emissions and b) ensure that NOx emissions were still able to stay within regulations. All three units at CSWDC are now  emissions-compliant since the RJM upgrade works.

Ongoing work

RJM continues to work with the team at CSWDC, helping to resolve other combustion-related issues and supporting with other emissions optimisation initiatives.