SO2 emission reduced more than 97%
The Brevik plant explored various methods to reduce its SO2 emissions
To comply with the Gothenburg Protocol, an FLSmidth gas suspension absorber, FLS-GSA® semi-dry scrubber was installed at the Brevik cement plant (Norcem AS) in Norway as an alternative to a more expensive wet scrubber.
The objective
In the cement industry, many plants are looking for ways to reduce gaseous emissions to comply with new environmental regulations. Norcem AS, part of Heidelberg-Cement, wanted to reduce its gaseous emission of sulfur dioxide (SO2) by 400 tpy.
Defining the project
The Brevik plant explored various methods to reduce its SO2 emissions. The plant uses two different raw mixes to make three types of clinker. One of the raw mixes produces a negligible SO2 emission, while the other raw mix produces SO2 emission of up to 400 mg/Nm³ dry. Therefore, the plant required a technology that only needs to be used when operated with the raw mix producing high SO2. After reviewing potential solutions, the plant decided to install FLSmidth’s gas suspension absorber technology. Norcem AS was already familiar with this technology as in 1991 they purchased an FLS-GSA® semi-dry scrubber for installation at the Kjøpsvik plant.
The solution
As there are two separate gas streams from the kiln system, it had to be decided if two separate semi-dry systems were required. With one gas stream passing through the raw mill system, which is a natural SO2 scrubber, it was decided to only install a semi-dry scrubber system in the gas stream not passing through the raw mill.
The scope of the project includes the complete semi-dry scrubber system (see figure): reactor (1) cyclones (2) recirculation box (3) lime/water mixing tank (4) lime slurry spray nozzle system (5) pumps and compressors (6) water tank (7). Also, existing 60 tonnes silo (8) was reused for burnt lime storage. A new booster fan was installed to handle the extra pressure drop across the system. Based on the process design criteria, the reactor dimensions are 3.65m in diameter by 14.2m tall and the two cyclones are 4.0m in diameter.
Challenges
Due to the very limited space available for the GSA installation, it was a challenge to fit in the new equipment. Even with a GSA footprint at only 50 m2, the space available was fully utilised. The GSA system was erected while the cement plant was in operation. Only 17 days were required for system shutdown.
Result
The semi-dry scrubber system installed at the Brevik plant has exceeded its designed performance, achieving 97.3 percent reduction of SO2 emissions and 95.2 percent reduction of HCl emissions. It has proven that it can achieve reductions in SO2 and HCl emissions that are similar to what can be achieved in a more expensive wet scrubber system.
Emissions testing has shown that the GSA system also gives the plant the capability to reduce mercury (Hg) emissions by 90 percent.
Together with previous experiments, the results at Norcem Brevik have confirmed that the GSA system in most cement plants can fulfill the NESHAP requirements for removal of SO2, HCl, and Hg.
With this reference and three more on its way at Siam Cement, the GSA system has established itself well within cement as a competitive alternative to a wet scrubber.
Contact:Flemming Jensen