Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Nitrogen or nitrogenous component
Patent
1991-02-27
1994-08-30
Straub, Gary P.
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Nitrogen or nitrogenous component
4232423, 4232427, 422168, C01B 2100, C01B 1700
Patent
active
053425928
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus which permits the introduction of a chemical agent into relatively confined areas of a utility boiler. Most preferably, the injected chemical agent is especially for the purpose of reducing the level of pollutants, such as nitrogen oxides (NO.sub.x) or sulfur oxides (SO.sub.x), in the effluent from the combustion of carbonaceous fuels and other organic matter. The apparatus comprises a lance-type injector, by which is meant an injector which extends to a significant extent into the interior of the boiler.
Carbonaceous fuels can be made to burn more completely, and with reduced emissions of carbon monoxide (CO) and unburned hydrocarbons, when the oxygen concentrations and air/fuel ratios employed are those which permit high flame temperatures. When fossil fuels are used in suspension fired boilers such as large utility boilers, temperatures above about 2000.degree. F. and typically about 2200.degree. F. to about 3000.degree. F. are generated. Unfortunately, such high temperatures, as well as hot spots of higher temperatures, tend to cause the production of thermal NO.sub.x, the temperatures being so high that free radicals of oxygen and nitrogen are formed and chemically combine as nitrogen oxides. NO.sub.x can also arise from oxidation of nitrogen containing compounds in the fuel. NO.sub.x can form even in circulating fluidized bed boilers which operate at temperatures which typically range from 1300.degree. F. to 1700.degree. F.
Nitrogen oxides are troublesome pollutants which are found in the combustion effluent streams of boilers when fired as described above, and comprise a major irritant in smog. It is further believed that nitrogen oxides contribute tropospheric ozone, a known threat to health, and can undergo a process known as photochemical smog formation, through a series of reactions in the presence of sunlight and hydrocarbons. Moreover, nitrogen oxides comprise a significant contributor to acid rain, and have been implicated as contributing to the undesirable warming of the atmosphere, commonly referred to as the "greenhouse effect".
Recently, many processes for reducing nitrogen oxides have been developed, which comprise the introduction into combustion effluents of chemical agents which reduce NO.sub.x by selective, free radical-mediated processes. Such processes are often referred to as selective non-catalytic reduction (SNCR) processes. SNCR processes are believed to be temperature sensitive and require the introduction of specific chemical agents into the boiler at specific temperature zones in order to be effective. Often, though, due to the geometry of the boiler, such temperature zones wherein desirable chemical agents should be introduced are in confined or otherwise inconvenient locations for introduction. For instance, in a typical utility boiler, there are areas between heat exchange tubes where desired temperature zones may exist. Such areas are generally less than 2 meters, often less than 1.5 meters, in the direction of effluent flow. Unfortunately, conventional injectors, which produce a spray pattern having a substantially conical shape, cause the chemical agent being sprayed into the effluent to impinge upon these heat exchange tubes. Because of the temperature differential between the effluent and the heat exchange tubes (and also the walls of the boiler), the chemical agent, when striking the relatively cool heat exchange tube or boiler walls, will not only be less effective at the reduction of NO.sub.x, but can in certain circumstances react to form additional NO.sub.x or other pollutants such as ammonia (NH.sub.3) or CO, depending on the chemical agent being utilized. In addition, impingement of liquid droplets on the tubes can result in rapid corrosion and failure of the tubes.
One method to avoid impingement is to use an injector that produces very small droplets which will evaporate rapidly. However, it is virtually impossible to achieve penetration of such small droplets in a direction perpendicular to the
REFERENCES:
patent: 3900554 (1975-08-01), Lyon
patent: 4131432 (1978-12-01), Sato et al.
patent: 4208386 (1980-06-01), Arand et al.
patent: 4325924 (1982-04-01), Arand et al.
patent: 4486398 (1984-12-01), Casperson
patent: 4719092 (1988-01-01), Bowers
patent: 4751065 (1988-06-01), Bowers
patent: 4770863 (1988-09-01), Epperly et al.
patent: 4777024 (1988-10-01), Epperly et al.
patent: 4780289 (1988-10-01), Epperly et al.
patent: 4803059 (1989-02-01), Sullivan et al.
patent: 4830839 (1989-05-01), Epperly et al.
patent: 4842834 (1989-06-01), Burton
patent: 4863704 (1989-09-01), Epperly et al.
patent: 4902488 (1990-02-01), Epperly et al.
patent: 4915036 (1990-04-01), DeVita
patent: 4950473 (1990-08-01), Flockenhaus et al.
patent: 4985218 (1991-01-01), DeVita
Grimard Francois X.
Peter-Hoblyn Jeremy D.
Fuel Tech Europe Ltd.
Straub Gary P.
LandOfFree
Lance-type injection apparatus for introducing chemical agents i does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Lance-type injection apparatus for introducing chemical agents i, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lance-type injection apparatus for introducing chemical agents i will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-28245