EVAPORATOR CONDENSATE COLOR MONITORING

INTRODUCTION

The detection of color changes in a liquid process stream is often a good indication of other process parameters that might effect the intermediate and/or final product. In the case of pulp mills, there is a definite advantage in monitoring the color of the condensate off the evaporator. The condensate is used in so many areas of the process that immediately catching an upset could eliminate equipment damage.

APPLICATION

In sulfite pulp mills, there is a widespread need to look for liquor contamination in the condensate. Since condensate is used throughout the mill in many capacities, it is imperative that it be clean and free of any red liquor. The contaminated condensate can cause extensive damage to the equipment and thereby increase maintenance and reduce efficiency throughout the plant. The detection of color changes has historically been done in the laboratory using human vision or the spectrophotometer. Visual comparisons of a liquid sample are made against standards established by each company or by APHA (American Public Health Association). Like all visual color tests, APHA color is limited by human subjectivity. This limitation is more pronounced in applications where the color changes are barely visible to the human eye, such as dark oils or apparent colorless fluids. (To the eye, clean condensate is clear where contaminated condensate has a reddish brown tint. This equates to approximately 100 APHA – an alarm point where the stream might be diverted to the sewer rather than used throughout the process. Acceptable readings average about 20 APHA.)

SOLUTION

In many areas within a mill, condensate monitoring is accomplished using inexpensive conductivity systems. However, the sulfite mill is different in that the condensate produced is quite acidic (conductive) to begin with and therefore traditional conductivity equipment won’t detect a change caused by liquor addition. Monitek provides a color monitor that can be installed in-line to continuously detect color changes in the condensate due to red liquor carryover. Any upset response will allow the operators to take immediate action to prevent downstream “disaster”.

ADDITIONAL COMMENTS

The Monitek unit can also be correlated to other standard color units such as ASTM and Saybolt. There is a need in many processes to immediately detect color changes in a liquid. These changes may be due to color addition, color removal or unwanted discoloration.

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