Consorci per al tractament de residus sòlids urbans del Maresme

Improvements in the Waste-to-Energy Plant

Compliance with the Directive 2000/76/CE

With the approval of the Directive 2000/76/CE, of 4th December, concerning the waste incineration, the requirements applicable to this activity within the waste management field for the EU were established. This Directive represented the introduction of significant changes with respect to the previous regulations, since it meant an important reduction of the limits of gas emissions, as well as a more accurate control of them by means of the continuous measurement of several of them, which was only to be periodical with the previous legislation.

Despite overly complying with the previous regulations concerning waste incineration, the new provisions coming into effect with the Directive 2000/76/CE made it necessary to plan for the future in order to ensure the adequacy of the facilities to the new legal frame.

Thus, financial help from the Cohesion Fund was requested in a joint project of adaptation of all the Catalan Waste-to-Energy facilities to the Directive 2000/76/CE.

The actions carried out in 2004-05 with the aim to ensure compliance with the Directive 2000/76/CE were:

• Implementation of a new system to reduce NOx (nitrogen oxide) based on a system of selective non-catalytic reduction (SNCR) with urea injection in the combustion chamber. The system consists of a sole storage tank of 45% urea, transport to the combustion chamber of each of the two lines, and a multilevel injection through several injecting spears into the points of the chamber which have the optimal conditions for the reduction reaction.

• Replacement of the electrostatic filters by fabric filters. These consist of two blocks of fabric filters with several compartments, to filter accurately the 70,000 Nm3/h of gas resulting from the combustion by line. In addition to the filtering effect, the filters act as chambers of post-reaction for the additives used in the treatment (lime and active carbon) since these are trapped in the fabric until they are consumed. The filters also have a pneumatic system of recirculation of the ashes in order to optimize the consumption of the additives contained.

• Incorporation of a contact reactor. It works with dry lime and it is placed between the neutralization reactor (which works with hydrated lime slurry) and the new fabric filters. This way, the best possible performance in the treatment of the acid gas is achieved, ensuring the compliance with the new limits on emissions.

• Modification of the active carbon injection system and implementation of a new silo for storing carbon.

• Implementation of new systems for measuring the gas emissions through the chimney in order to have the measurement results in a continuous way for the following pollutants: total particles, CO, HCl (same as to date); HF, COT, SO2 and NOx (new continuous measurements required by the Directive).

With the new infrastructures in the new Centre, work has been done to adapt and improve several aspects of the Waste-to-Energy plant. The actions carried out between 2010 and 2011 have been:

- Improvements in the combustion control system: new combustion control system FuzzEvent, installation of a thermal camera per line to see the combustion on the grate, installation of two pirometers IR per line to optimize the combustion process.

- Improvements in the boilers: installation of new refractory lining on the walls, new Inconel 625 cover of the boiler tubes, new tubes cleaning system.

- Improvements in the depuration system: implementation of a catalitic system for the reduction of NOx emission (SCR). The SCR system works with the previous injection of ammonia (NH3) as a reducing agent on the gas flow which then goes through a reactor containing catalyst blocks. Its efficiency reaches close to 95%. The old non catalytic system equipment is kept (SNCR) as back up when the new system needs to be stopped for maintenance.

- Improvements in the emission control system: installation of new multigas analyzers FTIR at the exit of each line’s boilers, installation of a new mercury (Hg) analyzer per line, installation of new multigas analyzers FT+FID integrated at the exit of each line’s chimneys.