Decomposition and reduction of N{sub 2}O over limestone under FBC conditions

Conference · Wed Dec 31 04:00:00 EST 1997

OSTI ID:357874

Johnsson, J E; Jensen, A; Vaaben, R; Dam-Johansen, K ^[1]

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1. Technical Univ. of Denmark, Lyngby (Denmark). Dept. of Chemical Engineering

The addition of limestone for sulfur retention in FBC has in many cases been observed to influence the emission of N{sub 2}O. The catalytic activity of N{sub 2}O over calcined Stevns Chalk for decomposition of N{sub 2}O in a laboratory fixed bed quartz reactor was measured. It was found that calcined Stevns Chalk is a very active catalyst for N{sub 2}O decomposition in an inert atmosphere, and the presence of 3 vol % CO increased the rate of N{sub 2}O destruction by a factor of 5 due to the catalytic reduction of N{sub 2}O by CO. The activity decreased with increasing CO{sub 2} concentration, and uncalcined or recarbonated limestone had negligible activity. Sulfation of the calcined limestone under oxidizing conditions lowered the activity, however sulfidation under reducing conditions showed that CaS is an active catalyst for the reduction of N{sub 2}O by CO. Without CO present a gas solid reaction between N{sub 2}O and CaS takes place and SO{sub 2} is released. Kinetic rate expressions for the decomposition and reduction of N{sub 2}O were developed and used to simulate the addition of Stevns Chalk to a 12 MW{sub th} CFBC burning bituminous coal. The rate of N{sub 2}O destruction was doubled when limestone was added at a Ca/S ratio of 1.8 with 90% desulfurization.

• OSTI ID: 357874
• Report Number(s): CONF-9705116--; ISBN 0-7918-1557-9
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
BITUMINOUS COAL
CALCIUM SULFIDES
CARBON MONOXIDE
CATALYTIC EFFECTS
DECOMPOSITION
FLUIDIZED-BED COMBUSTORS
LIMESTONE
NITROUS OXIDE
REDUCTION
SORBENT INJECTION PROCESSES