Chapter Seventeen

P^P^ ederal and state regulations require emissions source W owners to minimize or reduce air emissions under a number of regulatory circumstances. Four basic types of regulatory structures govern emissions control efforts. As shown in Table 17-1, a source may be affected by more than one of these. Selection of a technology and its cost-effectiveness are largely functions of the following factors:

• Type of fuel burning process. Major categories include boilers, combustion gas turbines, internal combustion reciprocating engines, reheat furnaces, glass melting furnaces, kilns, and other industrial processes. Specific control options are applicable to each.

• Capacity. In each category of fuel-burning equipment, capacity sub-categories are generally considered.

iyjj\ u tro! Measures

Typically, a capacity-related distinction is made between industrial (and commercial) and utility equipment when emissions rules are established. Retrofits are typically more cost-effective in larger capacities.

Load factor. Actual pollution output depends on emissions rates under various load conditions. The cost-effectiveness of emissions controls improves when run time and load factor are high. Type of fuel. A major factor in emissions levels for nox, SO2, and PM, as well as other pollutants, is the chemical composition of the fuel. Critical factors in NOX and SO2 emissions are the levels of fuel-bound nitrogen and sulfur. Nitrogen- and sulfur-intensive fuels, such as coal and residual oils, need to achieve greater reductions in order to burn as cleanly as light

Table 17-1 Types of Control Requirements Leading to Use of Air Emissions Controls

Type of Control Requirement

Specific Examples

Technology Standards — A source is required to use a prescribed control technology, an equivalent control technology, or a more effective control technology.

• Required use of low-NOx burners on some NOx sources in specific ozone nonattainment areas

• BACT is predetermined as an emissions level achieved by a specific technology for some new source permit decisions

• MACT standards

Emissions Rate Limits — A source is required to meet an emissions limit, which can be an exhaust concentration or an emissions rate limit, e.g., parts per million (ppm), grams per hp—h (g/hp—h), or lbm per million Btu (lbm/MMBtu).

• LAER determinations and most BACT decisions under prevention of significant deterioration (PSD) requirements

Emissions Budgets — Sources, or a group of sources, are given a fixed mass of emissions (usually tons). Sources are allowed to exchange their emissions (usually in the form of allowances or emissions reduction credits or ERCs) as long as the total emissions limits are met.

• SO2 allowance program for utilities

• South Coast Air Quality Management District's "Reclaim" program for NOx/SOx

• Federal restrictions on ozone depleting chemicals (e.g., CFCs)

• The OTC NOx Budget Program

Air Quality Impact Restrictions — Emissions must be controlled to a level that shows compliance with a downwind air quality concentration goal. Source location and stack height can influence compliance.

• State air toxics requirements

• PSD increments protection


Emission - Factors


ppm (wet)

ppm (dry)

ppm (15% O2)

ppm (13% O2)

ppm (5% O2)

ppm (0% O2)




g/MJ input

g/kg fuel



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