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ROUX ASSOCIATES, INC.ROUX ASSOCIATES, INC.

Environmental Consulting and ManagementEnvironmental Consulting and Management

www.rouxinc.comwww.rouxinc.com

International PetroleumEnvironmental Conference22

OUTLINE

Why quantify vapor recovery?

General methodology for estimating equivalent free-product recovery

Evaluation of methods for estimating thermal energycontent of process stream

Demonstrate that LNAPL plume volume is beingreduced by more than just liquid-phase extraction

Show remedial progress when liquid-phaseextraction begins to diminish

Provide option for reaching remedial endpoints

Purpose for Quantification

Cumulative Product Recovery Over Time

Recovery nearing asymptotic conditions

May need to show continued recovery

General Method

“Equivalent Free-Product” Definition:

Volume of free-product that would need to be burnedas fuel to produce the same amount of energy that isreleased by the combustion of the volatile gaseswithin a given volume of soil vapor extracted by thesystem

Conversion of gaseous SVE process air to flowrate in equivalent liquid free-product

Relates the energy content of the vapor and liquidphases

Steps in Calculation

Field measurements / samples

Energy content measured and/or estimated fromthe influent SVE process air

Vapor phase energy content converted toequivalent liquid phase energy content

Liquid phase energy content converted to anequivalent free-product recovery volumetric flowrate

Based on measured unit weight of the free-product

The energy in the vapor phase is proportionalto the energy in the liquid phase

The heating value of the SVE stream is notinfluenced by any external source

Leaking natural gas

Biodegradation of non-petroleum organic matter

The contribution of carbon dioxide to theoverall energy content of the SVE stream canbe neglected

Assumptions

Calculating Equivalent Recovery

Qfp,equiv = equivalent free-product recovery ingallons per day (gpd)

qSVE = measured / estimated heating rate of theinfluent SVE process stream in BTU/hour

Hc,fp = heating value / heat of combustion for theliquid free-product, in BTU/lb

γfp,v = unit weight of liquid free-product, in lb/gal

Heating Value of Vapor

Thermal Method

Using temperature measurements

Combustion Energy Method

Using lab analysis

Using screening equipment

Thermal method

Temperature set-point in oxidizer maintainschamber temperature by opening orclosing valve to control supplemental fuel

The amount of heat required to maintainset-point temperature is directlyproportional to the flow of process air beingheated

General Heating Rate Formula

q = heating rate input to the fluid to cause the desiredtemperature change;

Q = fluid volumetric flow rate;

cp = specific heat of the fluid being heated;

T2 = final temperature that the fluid is heated to (setpointtemperature);

T1 = initial temperature of the inlet stream.

AH = available heat factor

Thermal Energy Balance

qng is the heating rate of natural gas fedto the Flame-Ox in BTU/hr.

With known natural gas consumption,heating rate of SVE stream can bedetermined

Thermal Energy Method

Disadvantages

Advantages

Significant calibration andperformance testing required

Available heat factor not easilymeasured, variable tooperating conditions

Accuracy is limited whenenergy content of vapor streamis low relative to supplementalfuel

Inputs are easy to measure

No special samples need tobe collected and no specialmeasurements are requiredbeyond the process air flowrate, temperature and naturalgas usage

Combustion Method

Utilizes the concentrations of the majorcompounds present in the stream

molecular and energy data of these compounds

estimate the theoretical amount of energy releasedduring the combustion of those compounds

The theoretical amount of energy releasedduring the combustion of a flammablecompound is equal to the volume of thatcompound multiplied by the heat ofcombustion of that compound (typically inBTU/ft3 for a gas)