Instruction Manual

HAS60E-IM-HW

June 2007

NGA 2000 CLD

12.Close valve MV1. The NO concentration should be equal to or greater than the reading in Step 7. This indicates whether the NO contains any NO2.

13.Calculate the efficiency of the NO converter by sub- stituting the concentrations obtained during the test in the equation below:

 

 

 

 

 

%efficiency = 1 +

(b-a)

x 100

(c-d)

 

 

 

 

 

 

 

Where:

a = recorded concentration in Step 10 b = recorded concentration in Step 11 c = recorded concentration in Step 8 d = recorded concentration in Step 9

In the example in figure 3-23the following calculations would apply:

 

 

 

 

 

%efficiency = 1 +

(80-85)

x 100 = 92%

 

(80-20)

 

 

 

 

 

 

Efficiency checks should be made on each analyzer range, using an NO span gas concentration appropriate to the instrument range.

NOTE

In the initial measurement, after lowering the temperature setpoint in Step 2, the efficiency will normally be less than 92 %

14.Reset converter temperature setpoint 20 °C higher, wait 15 minutes for temperature equilibration, and measure conversion efficiency by repeating Steps 3 through 13.

Conversion efficiency should be improved.

15.Repeat Step 14 until:

a)95 % to 98 % efficiency is attained or

b)the final 20 °C converter temperature adjust- ment yields an increase in efficiency of less than 1 %.

16.Reset converter temperature setpoint 5 °C lower. Converter temperature is now set to the front edge of the plateau on the efficiency-vs.-temperature curve (see figure 3-23).This setting should pro- vide the optimum combination of high conversion efficiency and low ammonia interference.

17.Wait 15 minutes for temperature equilibration, and check converter temperature. Compare present temperature with original value. Normally, converter temperature should be in the range of 300 °C to 400 °C (572 °F to 752 °F).

c.Subnormal Conversion Efficiency

If measured conversion efficiency of between 95 % and 98 % is unobtainable within the normal temperature range, the most probable cause is depletion of the catalytic material within the converter.

However, before concluding that the converter is defec- tive, ensure that the conversion efficiency measurement is accurate. Though the measured efficiency is less than the 95 % to 98 % range, the actual efficiency may be somewhat higher.

An apparent subnormal efficiency can be due to a problem external to the Analyzer Module, perhaps located either within the test setup or between it and the Analyzer Module. Check the following:

1.Leakage

2.Loss of NO2 between test setup and Analyzer Module. Such loss can occur by reaction with a rubber diaphragm in a pressure reagulator or flow controller. Stainless steel diaphragms are pre- ferred. Loss can also occur during passage through filter media.

Emerson Process Management GmbH & Co.OHG

Operation 3 - 15