Page 38 - Air Pollution Control Engineering

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18 Lawrence K. Wang et al.

extremely complex, even inadequate for the specific requirements. These, plus the
atmospheric problems of wind, precipitation, temperature, and humidity, often make
stack testing an unenviable occupation.
Stack or source testing usually requires obtaining the following minimum data:
1. Gas velocity
2. Gas temperature (dry and wet bulb)
3. Static pressure in the duct
4. Barometric pressure
5. Inside diameter or area of the duct
6. Concentration of desired pollutants, which may include size and size distribution of
particulate
7. Emission source, name, and location
8. Date and time
9. Wind speed and direction
10. Control system operating conditions (pressure drop, temperature, liquid flow rate, and type)
11. Process operating conditions, including charge rate
Two procedures should be evaluated before an actual source test is undertaken. If
the system is a typical classical operation, it may be possible to obtain an estimate of the
amount of emissions from a listing of emission factors (8). To supplement these data, it
may even be possible to obtain data on size and size distribution from other sources such
as the Scrubber Handbook (13) or the McIlvaine Company manuals (14). The second
procedure consists of making an opacity method using the Ringelmann Smoke Chart.
This old but valuable approximation procedure developed by Professor Maximilian
Ringelmann in 1897 uses five charts ranging from white to black to indicate the degree
of opacity. For example, a white chart with a 20% apparent grayness of a plume blends
with the apparent grayness of the chart. Charts and instructions for using this method are
given in a Bureau of Mines circular (15).
The source sampling problems noted suggest that sampling costs could be high.
However, there is no substitute for good emission data, especially if control equipment
must be specified and installed. The expenditure of several thousands of dollars at his
stage could save many times that amount in control equipment capital and operating
costs. In addition, the control system designed for a specific facility has a high chance
of working compared with “guesstimation” procedures.

6.3. Sample Locations
The sample ports in a typical full-sized installation can be simply constructed by
installing “close” 4-in.-diameter pipe nipples in the stack or duct at the point where the
samples are to be taken. The nipples should not protrude inside the stack or duct sys-
tems where they could disturb the gas flow patterns. The 4-in.-diameter nipples are
required to permit the installation of standard-size test devices. When not in use, they
can be sealed with an installing cap. Heavy-wall nipples should not be used because
some devices will not pass through them. The typical installation will require a mini-
mum of four nipples at equal distance around the stack.
Gas flow patterns inside a pipe are influenced by bends, openings, location of the
blower, and location of obstructions. It is important that the sample location be chosen
in such a manner as to minimize flow irregularities. An engineering rule of thumb is to