By-Pass Type Odorizer
The By-Pass odorization of a gas flow (Evaporation Absorption) involve establishing a small side flow of gas, saturating the small stream with odorant vapor and returning it to the main stream.
Consideration must be given to the flow control of the small stream, the temperature of the saturating vessel, and the type of odorant used.
This type of Odorizer used for Distributing Systems such as Pressure reducing gas stations with maximum capacity of ۱۰,۰۰۰ SCMH
Fig.1: By-Pass Odorizer
Principles of Operation
The evaporation-absorption (By-pass) Odorizer consists of a tank equipped with one or more wicks located on a by-pass gas line. The control for bypassing the gas through the tank is obtained by manually throttling a valve located on the main line.
Fig.2: By-Pass Odorizer Operation
Adjustment of the By-pass
The By-pass flow adjustment depends on solubility of the odorizing agent in gas, on the gas pressure and temperature. Below
diagram shows the solubility of mercaptan in methane vs. operating pressure & temperature .
Fig.3: Solubility Diagram
THBO –۲۵۰۰ – B- 60
Family Flow Rate (SCMH) Rating(Class) Min.Press.
|Shell||ASTM A516 GR.70|
|Heads||ASTM A516 GR.70/ASTM A105|
|Legs||ASTM A283 GR.C/St.37|
|Pipes||ASTM A106 GR.B|
|Stud Bolt& Nuts||ASTM A193-B7/ASTM A194 2H|
|Inlet pressure||Pi: up to 300 Psig|
|Main Gas flow rate||up to 10,000 SCMH|
|Operating temperature||-۲۰ °c to + ۶۰ °c|
|Acceptable gases||Natural Gas|
|Odorant Spec.||MERCAPTAN(Sulfide Comp.)|
|Throttling device||Orifice R ButterflyR|
|Design code||ASME Sec VIIII-Div.1|
|Min. inlet/outlet gas temperature||-۲۰°c /+50°c|
By-Pass Odorizer Installation and Maintenance Problems
In By-Pass odorant selection consideration must be given to the type of odorant. If a mixture of compounds with different boiling points is used rather than a single compound, the odorant will fractionate in the saturating vessel and allow the higher boiling compounds to accumulate. For that reason the odorant selected for By-Pass type odorizer should have a narrow boiling range. Install odorizer on a flat surface. if possible, take care that in event of leakage the odorant agent cannot penetrate into the earth (through or similar device).The fixing holes in the feet should be anchor bolted. Due to the fact that odorizing rate depends on parameters like temperature, the unit should be protected locally against extreme temperature variations and outside corrosion.
Install the unit as near the main gas line as possible; the shorter the piping, the less losses by internal resistance of piping and the more exact the proportional by-pass flow. Make sure that all valves keep closed Open butterfly valve in main gas line. Open valve in by-pass outlet , Open slowly valve in by-pass line inlet. wait a few seconds, until the Odorizer tank pressure is in equilibrium with the pressure in the main gas line. Open slowly valve “INLET”. Adjust now the throttle valve in the main gas line so that the desired amount of odorant flows through the by-pass.
Fig.4: By-Pass Odorizer Installation
The application of chromatographic equipment for analysis of minute concentrations of odoriferous sulfur-bearing compounds in combustible ducted at the American Institute of Gas Technology (I.G.T). It is the only method that allows individual chemical identification by instruments.
Fig.5: Odorization Effectiveness
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