US 5,325,796 A · Process for decreasing N.sub.2 O emissions from a fluidized bed reactor

Abstract

Emissions of nitrous oxide (N.sub.2 O) are lowered in a fluidized bed reactor utilizing two-staged combustion. A lower region of the furnace section is operated under substoichiometric conditions so that combustion in the lower region is incomplete, thereby inhibiting formation of N.sub.2 O and nitrogen oxides (NO.sub.x). An upper region of the furnace section is operated under oxidizing conditions to promote further combustion. An amount of particulate material is present in the upper region, and this amount of particulate material in the upper region is controlled to maintain a temperature in the upper region for destroying N.sub.2 O formed during combustion. The amount of particulate material present in the upper region may in turn be controlled by controlling the particulate material entrained from the lower region to the upper region. The temperature is also preferably controlled within a range to permit sulfur capture by sorbent particles so that emissions of N.sub.2 O, NO.sub.x, and oxides of sulfur (SO.sub.x) may be simultaneously lowered.

Claims30

Dependent claims

A method of operating a fluidized bed reactor to simultaneously lower emissions of N.sub.2 O, NOx and SOx comprising:

(a) providing a furnace section having a bed of particulate material comprising nitrogen-containing fuel particles for combustion and sorbent particles for sulfur capture;
(b) introducing a primary, oxygen-containing gas into said lower region at a fluidizing velocity sufficient to fluidize said particulate material;
(c) operating a lower region of said furnace section under substoichiometric conditions such that combustion of said fuel particles is incomplete;
(d) operating an upper region of said furnace section above said lower region under oxidizing conditions to complete combustion of said fuel particles in said upper region;
and
(e) maintaining said lower region at a temperature below approximately 1600.degree. F. to lower emissions of NOx;
and
(f) controlling said fluidizing velocity to control passage of said particulate material from said lower region to said upper region to maintain a temperature substantially within a range of 1650.degree. to 1800.degree. F. in said upper region for lowering emissions of N.sub.2 O formed during combustion while permitting efficient sulfur capture to lower emissions of SOx.

5 more elements

A method of operating a fluidized bed reactor to simultaneously lower emissions of N.sub.2 O, NOx and SOx comprising:

(a) providing a furnace section having a bed of particulate material comprising nitrogen-containing fuel particles for combustion and sorbent particles for sulfur capture;
(b) introducing a primary, oxygen-containing gas into said lower region at a fluidizing velocity sufficient to fluidize said particulate material;
(c) operating a lower region of said furnace section under substoichiometric conditions such that combustion of said fuel particles is incomplete;
(d) operating an upper region of said furnace section above said lower region under oxidizing conditions to complete combustion of said fuel particles in said upper region;
and
(e) maintaining said lower region at a temperature below approximately 1600.degree. F. to lower emissions of NOx;
and
(f) passing said particulate material from said lower region to said upper region;
and
(g) controlling the ratio of relatively five particulate material to relatively coarse particulate material passed from said lower region to said upper region to maintain a temperature substantially within a range of 1650.degree. to 1800.degree. F. in said upper region for lowering emissions of N.sub.2 O formed during combustion while permitting efficient sulfur capture to lower emissions of SOx.

7 more elements

A method of operating a fluidized bed reactor to simultaneously lower emissions of N.sub.2 O, NOx and SOx comprising:

(a) providing a furnace section;
(b) introducing nitrogen-containing fuel particles for combustion and sorbent particles for sulfur capture into said furnace section;
(c) combusting said fuel particles to form gaseous and solid products of combustion, said solid products of combustion mixing with said fuel particles and said sorbent particles to form particulate material;
(d) introducing a primary oxygen-containing gas into a lower region of said furnace section at a first level to support combustion of said fuel particles and to fluidize said particulate material to form a lower dense bed of said particulate material and an upper dispersed bed of said particulate material above said dense bed;
(e) operating said lower region at substoichiometric conditions so that said combustion of said fuel particles is incomplete;
(f) maintaining said lower region at a temperature below approximately 1600.degree. F. to lower emissions of NOx;
(g) introducing a secondary oxygen-containing gas into said furnace section at a second level above said first level to create oxidizing conditions in said upper region of said furnace section;
(h) passing said particulate material from said lower region to said upper region;
and
(i) controlling the ratio of relatively fine to relatively coarse particulate material passed from said lower region to said upper region to maintain a temperature substantially within a range of 1650.degree. F. to 1800.degree. F. in said upper region for destroying N.sub.2 O while permitting efficient sulfur capture to lower emissions of SOx.

7 more elements

Dependencies are inferred from the claim text.

Process for decreasing N.sub.2 O emissions from a fluidized bed reactor

Life of this patent

Process for decreasing N.sub.2 O emissions from a fluidized bed reactor

Life of this patent

Abstract

Claims30