Utility experience with SCR in Germany
The selective catalytic reduction (SCR) technology was primarily developed by Japanese industry for the reduction of NOx concentrations from power plant flue gas emissions. The first commercial Japanese DeNOx plant began operation in 1980 while the first German high dust SCR plant started up in 1985 and the first German tail end SCR plant started up in 1986. Two German environmental resolutions (GFAVO of June, 1983 and UMK of April, 1984) enhanced the adaptation of the SCR technique in German power plants. From the end of 1984 to 1987 most German utility owners ran pilot plant studies in order to become acquainted with this technology and to determine whether there are special deterioration mechanisms. The first full-scale plant started operation at the end of 1985. Since then, around 120 SCR plants have been installed on coal, oil and gas fired utility power plants. SCR technology for NOx control has also been applied on waste-to-energy plants, wood fired boilers, chemical plants, hazardous waste incinerators, glass smelters, refinery crackers, stationary diesel generators and sewage sludge incinerators. In addition, a special catalyst was developed to control dioxin/furan emissions in waste-to-energy plants, hazardous waste incinerators, sewage sludge incinerators, crematoria, iron ore sintering plants, and other thermal processes requiring dioxin/furan control. The German NOx emission limit for utility power plants is 200 mg/Nm{sup 3} at 6% O{sub 2} for dry bottom boilers and 5% O{sub 2} for wet bottom boilers or about 117 ppmv NOx at 3% O{sub 2}. This is approximately 0.12 lbs/MMBtu. Many German SCR units achieve high online availability on an annual basis. In the following paper, the authors will emphasize some aspects of the SCR process: (a) The chemical and physical/chemical properties of the catalyst; (b) The chemical engineering design of the catalyst volume; (c) The deterioration of catalytic activity with time; and (d) The effect of NH{sub 3} slip (caused by catalyst deterioration or non-homogeneous NH{sub 3} distribution) and of side reactions. The basis of the SCR technique is described first and each of the above areas is then discussed. In extrapolating the German SCR experience to U.S. applications, one of the most significant factors will be catalyst deactivation due to the differences in some U.S. coals with high alkaline metals and others with high sulfur and SO{sub 3} contents. The loss of activity potential of SCR reactors, which is related to material activity constant (K-value) and the geometrically active surface area, can be caused by: Excessive heat; Erosion and pluggage; Pore blockage; Accumulation of catalyst poisons like arsenic and alkali metals; and Prevention of gas diffusion by the formation of blinding surface layers. KWH PreussenElektra has led many developments in the German SCR industry over the past 15 years. Some of the most relevant advancements include: Development of new derivative titanium based structures; Development of new erosive resistant materials; Optimization of the catalyst pitch; Development of regeneration programs; Institution of coal blending programs to extend catalyst life; Development of catalyst maintenance programs; and Development of improved flow-modeling techniques. These improvements have led to an extended catalyst life for many facilities. This paper will discuss the German SCR experience and how it is being extended to the U.S. power industry.
- Research Organization:
- KWH c/o Licata Energy and Environmental Consultants, Inc., Yonkers, NY (US)
- OSTI ID:
- 20082327
- Resource Relation:
- Conference: Sixteenth Annual International Pittsburgh Coal Conference, Pittsburgh, PA (US), 10/11/1999--10/15/1999; Other Information: 1 CD-ROM. Operating systems required: Windows 95/98; Windows 3.X, Macintosh; PBD: 1999; Related Information: In: Sixteenth annual international Pittsburgh Coal Conference: Proceedings, [2000] pages.
- Country of Publication:
- United States
- Language:
- English
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