FGD and DeNOx
NEWSLETTER       

                                                                                                                    February  2002
                                                                                                                          No. 286

Multi-Pollutant Control with a Chiyoda CT-121 FGD

N. Miyata and S. Kido of Chiyoda Corp., P. Honeycutt of Southern Company and D. Harris of Black & Veatch  report that Chiyoda’s CT-121 wet FGD system provides additional benefits for multi-pollutant controls. The high particulate removal capability may assist a marginally performing particulate control device in meeting PM₁₀ and PM_2.5 emission limits. Likewise the air toxics removal capability of the CT-121 process may assist in air toxics emission control.

Mercury balance testing was conducted at Southern Company Yates, which is equipped with a CT-121 FGD system. Forty-six percent of the mercury in the vapor phase was removed by the Jet Bubbling Reactor. Since 35 percent of the vapor phase mercury was elemental, the percent removal is expected to be greater when an SCR system is downstream of the FGD. The mercury was stabilized in the sludge by the addition of a chelating agent.

The CT-121 FGD is an advanced wet limestone process that offers high performance for a wide range of sulfur contents on coal- and oil-fired units. In the CT-121 process, the flue gas is sparged into a vessel of absorbent liquid using a jet bubbling reactor (JBR). The JBR incorporates all of the necessary steps for SO₂ absorption, oxidation, neutralization, crystallization, and dust removal in a single reactor module. The CT-121 FGD system has demonstrated very high SO₂ removal efficiency (up to 99 percent) and low outlet SO₂ emissions (below 10 ppm). 

An improved CT-121 plant has been operated and tested for two years at 100-MW power station "M" in Japan. Features of the improved CT-121 are summarized as follows:

·         25 percent reduction of JBR cross-sectional area.

·         10 percent reduction of construction cost due to increased superficial gas velocity.

·         No critical performance differences from the original CT-121 in the areas of SO₂ and air toxics removal efficiency. 

A CT-121 installation for a 220-MW coal-fired power station, incorporating these improvements in JBR design, will be commissioned and commercially operated beginning in February 2002. 

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