Conversion Factors for Source Emission …

1 Conversion Factors FOR Source Emission MEASUREMENTS OF INCINERATOR FLUE GASES A. MARSHALLA G. CRAWFORD Joseph Coder Incinerators Elk Crove Village, Illinois ABSTRACT Since there are two basic units in which Source emis sion concentration of dustloading may be expressed, formulas are presented for their comparison. Furthermore, to standardize procedures and to elim inate some of the variables of dustloading tests, certain standards of correction have been agreed upon. Formulas are presented to facilitate these corrections.

2 INTRODUCTION As more state and city agencies pass air pollution codes and as existing codes become more stringent, the need for incinerator dustloading values has become critical. Since there are two basic units of dustloading, the need for con version formulas is obvious. Furthermore, the initial results of dustloading test are meaningless without applying the appropriate correction; both a 50 percent excess air and a 12 percent CO2 cor rection standard are in widespread usage. Formulas must be standardized for the application of these corrections.

3 BASIC ASSUMPTIONS In any dustloading test some of the variables which must be taken into consideration are the type of refuse or fuel being consumed, atmospheric conditions, such as temperature and pressure, and the components of the flue gas. While the formulas presented in this paper take these 176 variables into account, certain assumptions and simplifi cations have been made to make their derivation possible. All formulas presented have been derived on the basis that the fuel or refuse being burned is of the general form: ex Hy Oz.

4 However, the formulas are not dependent upon the specific values of the x, y, and z's. If the refuse being burned has a substantial quantity of elements other than carbon, hydrogen, and oxygen, as indicated above, it would be necessary to derive new formulas. Furthermore, all formulas have been derived on a dry basis; that is, all moisture content, whether resulting from oxidation of the refuse or ambient air of combustion has been neglected. One further simplification has been made. Since the percentage of carbon monoxide (CO) is normally zero or very small in a proper incinerator operation, its effects on the Conversion and correction formulas have been neg lected.

5 Conversion FORMULAS The dustloading is usually expressed in pounds of dust per 1,000 pounds of flue gas or grains of dust per standard cubic foot, where 7,000 grains is equal to one pound. Since the dustloading is first determined at sampling con ditions of temperature and pressure, the required correc tion to standard conditions of 68 F and inches Hg (ASME Standards) is t + 460 Dl = Do 68 + 460 P (1) where Dl = the dustloading in grains per standard cubic foot(gr/SCF), Do = the dustloading in grains per cubic foot (gr/CF), t = sampling temperature in degrees Fahren heit, P = atmospheric pressure in inches of Hg.

6 To convert from gr/SCF to pounds of dust per thou sand pounds of flue gas (lbs dust/1,000 lbs flue gas) we have D _ (1544) z-D1 (2) where M = the molecular weight of the flue gas Dz = the dustloading in lbs dust/1,000 lbs flue gas. By combining formulas (1) and (2) we may proceed directly from gr/CF (Do) at sampling conditions to lbs dust/1,000 lbs flue gas (Dz). The required formula is _ [ (t + 460)J Dz -DO M xP (3) The inverse of the above formula required to convert from lbs dust/1,000 lbs flue gas (Dz) to gr/CF (Do) is [.]]

7 320M xpJ DO = Dz (t + 460) (4) In many cases, including the T-6 Testing Method [1] the temperature of the flue gases, the molecular weight of the flue gases, and the barometric pressure are either not taken or are unknown to the person making the conver sions. In this case, formulas (3) and (4) are impossible to compute, so we offer the following alternate Conversion method which is reasonably accurate based on the assump tion of standard barometric pressure of in. Hg and an average molecular weight of at the listed tempera ture.

8 For computing gr/CF at temperatures other than those listed below use formula (4), inserting the desired temperature along with the above values for molecular weight and pressure. TABLE I Given Value In lbs dust/1 ,000 lbs flue gas lbs dust/1,000 lbs flue gas lbs dust/l,OOO lbs flue gas lbs dust/1,000 lbs flue gas Multiply By .574 .535 .533 .294 Resultant Value gr/ft3 @ 32 F gr/ft3 @ 68 F gr/ft3 @ 70 F gr/ft3 @ 500 F 177 A dustloading value presented in w/CF is meaningless if the temperature at which it was computed is not specified.

9 Therefore, formula (3) cannot be used to convert gr/CF to lbs dust/1,000 lbs flue gas if the temperature is unknown. However, if the temperature is known and the molecular weight and barometric pressure are not, the formula may still be used with reasonable accuracy by substituting the assumed values above. All these Conversion formulas while presented without derivation merely represent a density Conversion based on the universal gas law with the appropriate numerical fac tors for the Conversion of units. CORRECTION FORMULAS Two standards of correction are now utilized by most air pollution agencies.

10 The first correction standard to be considered is the 50 percent excess air correction. The need for such a standard is obvious. When any fuel or refuse is oxidized, there is some minimum air require ment for combustion which may be determined stoichio metrically from the refuse composition. However, in most incinerator processes, far more air is supplied than is actually required. The percentage of excess air then is defined to be p = 100(lbs air supplied/lbs refuse _ 1) lbs air needed/lbs refuse where P = the percentage of excess air.