METHOD FOR REDUCING NOx DURING COMBUSTION OF COAL IN A BURNER BY OPTIMIZING COMBUSTION AIR FLOW

a combustion air flow and combustion method technology, applied in the direction of solid fuel combustion, combustion types, lighting and heating apparatuses, etc., can solve the problems of less efficient combustion, inability to reduce nox emissions, and settle out of heavier particulate fractions, so as to reduce the air/fuel ratio, reduce the output, and reduce the ash content

Inactive Publication Date: 2010-02-04
HEADWATERS ENERGY SERVICES CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0013]Embodiments of the present invention provides methods for reducing the output of NOx during coal combustion by (1) cleaning an initial coal feedstock to yield a refined coal product having reduced ash content and density, (2) pulverizing the refined coal product, (3) feeding the pulverized refined coal product of lower ash content and density into the primary combustion zone of a coal burner while reducing the amount of primary combustion air used to convey the coal

Problems solved by technology

Providing insufficient air velocity in the pipes results in settling out of the heavier particulate fractions.
When enough of the coal has settled out, the air velocity becomes high enough to pick up the laid-out coal, causing a slug of fuel to suddenly exit the pipe and enter the burner, which causes flame instabili

Method used

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  • METHOD FOR REDUCING NOx DURING COMBUSTION OF COAL IN A BURNER BY OPTIMIZING COMBUSTION AIR FLOW

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0094]A NOx emissions test of Wellington coal feedstocks and refined coal fuel products was performed. The combustion test was part of an ongoing program to evaluate the combustion performance and NOx emissions of refined coal products relative to their initial coal feedstocks. During these combustion tests, four samples from the Wellington coal refining facility (Utah) were evaluated. The primary Wellington coal feedstock contained 15.9% ash by dry basis weight and the primary refined product contained 8.5% ash by dry basis weight. The secondary Wellington coal feedstock contained 48.2% ash by dry basis. weight and the secondary refined product contained 14.9% ash by dry basis weight. The purpose of these combustion tests was to study the relationship between ash content and NOx emissions.

[0095]The operating conditions for this test series were designed to simulate, to the greatest extent possible, actual boiler conditions for a majority of the pulverized coal-fired boilers in the ...

example 2

[0103]A similar test as in Example 1 was performed using Alabama CEF #3 fine coal and refined products. The following conclusions were made from these tests:[0104](1) refining the CEF #3 feedstock from about 40% ash (dry basis) to about 20% ash (dry basis) and using no overfire air resulted in a NOx emissions reduction of about 50%;[0105](2) refining the CEF #3 feedstock from about 40% ash (dry basis) to about 20% ash (dry basis) and using 15% overfire air resulted in a NOx emissions reduction of about 50%.

[0106]The coal samples were analyzed in the same manner as the samples in Example 1. The results of this analysis are shown in Table 2 below, and are reported on as received and dry bases.

TABLE 2FeedstockProductPARAMETER20072007As Received BasisProximate (wt. %)Moisture1.721.63Volatile Matter15.4717.87Ash40.5418.17Fixed Carbon42.2762.33Ultimate (wt. %)Carbon49.9372.91Hydrogen3.374.32Nitrogen0.801.23Sulfur0.380.51Oxygen3.261.23Ash40.5418.17Heating Value (Btu / lb)844112591Mercury (pp...

example 3

[0107]NOx emissions tests were performed using an eastern bituminous secondary coal material from eastern Kentucky (Century Material). The results of these tests are graphically depicted in FIG. 7. The NOx emissions reductions were on average about 50%.

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Abstract

An initial coal feedstock comprised of primary or second coal is cleaned so as to reduce its ash content by at least about 20% in order to yield a refined coal product that produces fewer NOx emissions. The reduced NOx emissions result primarily from the ability to use less primary combustion air in order to maintain the pulverized refined coal in a suspended condition within the feeder pipes of a coal burner compared to the minimum quantity of air required to maintain pulverized coal from the initial coal feedstock in a suspended condition within the feeder pipes. Reducing the primary combustion air reduces the amount of oxygen in the primary combustion zone that would otherwise be available for converting fuel nitrogen into NOx. Instead, more of the fuel nitrogen is converted into N2. Reducing the primary combustion air also reduces the temperature of the core flame, reducing thermal NOx formation. Increasing the amount of secondary and/or tertiary combustion air to compensate for the reduced primary combustion air results in an overall decrease in NOx formation, as thermal NOx formation is reduced as combustion is completed in the cooler secondary and/or tertiary combustion zones.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]None.BACKGROUND OF THE INVENTION[0002]1. The Field of the Invention[0003]The present invention relates to a method for reducing NOx emissions during combustion of coal, more particularly to methods that utilize coal that has been cleaned to lower the ash while reducing the ratio of primary combustion air to fuel and compensating for such reduction with increased secondary and / or tertiary (or overfire) air.[0004]2. Related Technology[0005]Coal combustion is a major source of energy for the production of electricity throughout the world. Coal is a good source of energy because of its high energy to weight ratio and its great abundance. The use of coal, however, is increasingly under scrutiny because of environmental concerns. Among the known environmental difficulties with coal combustion is the production and emission of NOx compounds, such as NO, N2O, and NO2. NOx compounds can be very harmful to human health and are known to produce undes...

Claims

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Application Information

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IPC IPC(8): F23D1/00F23B50/10F23N3/00F23K1/00
CPCF23K2900/01001F23K1/00
Inventor MINKARA, RAFICHARDING, N. STAN
Owner HEADWATERS ENERGY SERVICES CORP
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