SECTION 112.33. Calculation Methods

(a) Applicability. Determination of the net ground level concentration shall be performed in accordance with the procedures outlined in this section for hydrogen sulfide and §112.32 of this title (relating to Allowable Emissions--Other Property) for sulfuric acid.

(b) Determination of compliance with emission limits. In most cases downwind samples will suffice; however, if the sampled properties are suspected of being influenced by an upwind source of H₂S, then both upwind and downwind samples will be taken. The concentration of H₂S in the "downwind sample" less the concentration in the "upwind sample" shall be used in determining whether the emissions from the property comply with the requirements of §112.31 of this title (relating to Allowable Emissions--Residential, Business, or Commercial Property) and §112.32 of this title (relating to Allowable Emissions--Other Property). Calculated maximum allowable emission rates or ground level concentrations which are obtained by the method in subsection (b) of this section may be used in determining whether a property is in compliance with the emission limits specified.

(c) Calculations of H₂S concentrations from stack samples and measurements. The maximum allowable H₂S emission rate which may be made from a stack on a property to comply with the emission limit set forth in §112.31 of this title (relating to Allowable Emissions--Residential, Business, or Commercial Property) and §112.32 of this title (relating to Allowable Emissions--Other Property) may be calculated by Sutton's equation which has been modified to consider the critical wind speed and to correspond to a 30-minute air sample. Additional credit on stack emissions can be obtained if the distance from the stack to the property line is greater than 30 stack heights. Those properties with greater than 30 stack heights to the property line should contact the executive director to obtain the proper correction factor.

(1) For exit stack gas for temperatures of less than 125 degrees Fahrenheit. The following calculations shall be used for exit stack gas for temperatures of less than 125 degrees Fahrenheit.

(A) The H₂S ambient air level is 0.08 ppm for 30 minutes.

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(B) The H₂S ambient air level of 0.12 ppm for 30 minutes.

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(C) To plot Graph II, assume a basic stack height of 100 feet and plot

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(2) For exit stack gas for temperatures greater than 125 degrees Fahrenheit. The following calculations shall be used for exit stack gas for temperatures greater than 125 degrees Fahrenheit:

(A) the H₂S ambient air level is 0.08 ppm for 30 minutes:

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(B) the H₂S ambient air level is 0.12 ppm for 30 minutes:

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(C) to plot Graph III assume a basic stack height of 100 feet and an exit velocity of 20 feet/second. Let stack gas temperature vary with stack diameter:

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(3) Examples. The following are examples of stack emission calculations.

(A) Example 1. (Temperature of stack gas less than 125 degrees Fahrenheit.) How many pounds/hour of H₂S can be discharged from a 200 foot stack having a four foot exit diameter (ID) and a 30 feet/second exit gas velocity? The stack gases temperature is 100 degrees Fahrenheit and the distance to property line is 3,000 feet. Emissions under §112.31 of this title (relating to Allowable Emissions--Residential, Business, or Commercial). Solution:

(i) the ratio of stack diameter to 100 feet is 4/100 = 0.04;

(ii) enter ordinate of Graph II with 0.04; go horizontally to intersection of 30 feet/second velocity curve. At the intersection read on the abscissa 24 pounds/hour on the scale set forth in §112.31 of this title (relating to Allowable Emissions--Residential, Business, or Commercial). This is the permitted value for a 100 foot stack;

(iii) correct emissions for a 200 foot stack. Enter Graph I at 200 feet and obtain correction factor of 2.3. Thus the emissions become 24 x 2.3 = 55 pounds/hour.

(iv) Note: less than 30 stack heights to property line--no credit.

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(B) Example 2. (Temperature of stack gas greater than 125 degrees Fahrenheit.) How many pounds/hour of H₂S can be discharged from a 200 foot stack having a four foot exit diameter (ID) and a 30 feet/second exit gas velocity? The temperature of the exit gases is 400 degrees Fahrenheit. Emissions under §112.31 of this title (relating to Allowable Emissions--Residential, Business, or Commercial). Solution:

(i) enter ordinate of Graph III with 400; go horizontally to intersection of four foot diameter, read on the abscissa on the scale set forth in §112.31 of this title (relating to Allowable Emissions--Residential, Business, or Commercial) 36 pounds/hour emission. This is permitted value for 100 foot stack and exit velocity of 20 feet/second;

(ii) correct for stack height of 200 feet. This is direct ratio and becomes 200'/100' = 2. The emission now becomes 36 x 2 = 72 pounds/hour;

(iii) correct for stack exit velocity of 30 feet/second. This is a direct ratio and becomes 30/20 = 1.5; the allowed emission now becomes 72 x 1.5 = 108 pounds/hour.

(iv) Note: less than 30 stack heights to property line--no credit.

Source Note: The provisions of this §112.33 adopted to be effective January 1, 1976