Refineries use a significant amount of steam in the process of distilling gasoline, diesel and other hydrocarbon products. The refinery design will collect and return as much steam as possible to save on energy, water consumption and sewering costs. For some refineries 50% of the steam can be recovered. Because the return steam can be contaminated by hydrocarbon leaks in the heat exchangers, refineries often will install a monitoring system to alert operators when a hydrocarbon leak has occurred.
Refineries located near a large body of water, like a lake, river or ocean, can use this water source to make up for lost boiler water. Plant operators need to differentiate between contamination from the water source and any contamination introduced by the heat exchangers. A total organic carbon (TOC) analyzer can indicate the natural organics concentration from the lake, but a second measurement method is required for petroleum hydrocarbons.
A UV fluorescence monitor with a proper optical kit is ideal for isolating the response to only petroleum hydrocarbons and has no response to natural organics.
The data shown in the graph was collected from a refinery that is using both a TOC and UV fluorescence monitor in the boiler feed water. By comparing the measurement of the two monitors, boiler operators can determine whether contamination is coming from the refinery or the lake. In the graph, the green data shows TOC from the lake. The Red data shows the UV fluorescence monitor measurements. In the first half of the data, only the TOC measurement is changed by the presence of natural organics in the lake water. In the second half of the graph, the TOC and UV fluorescence monitor are indicating an increase in petroleum organics from the refinery.
When plant boiler operators can determine whether the contamination is natural organics or petroleum hydrocarbons, they are able to take the correct action to prevent boiler fouling. For petroleum hydrocarbon contamination, the steam return line is turned off to protect the boilers, and the operators can search for the leaking heat exchanger. When natural organics are detected, an oxidizing agent can be added to the water.
The TD-4100XDC, TDHI’s closed-cell online monitor is perfectly suited for detecting hydrocarbons in steam condensate. It offers the lowest available detection limits, low maintenance, long-term calibration stability and is internationally certified for hazardous areas. The TD-4100XDC is also available with custom configurations and wetted materials.