Hot Heated Tanks eBook

8/18/2019 Hot Heated Tanks eBook

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If your facility uses storage tanks to keep chemical liquids at a certain

temperature or uses tanks to cool down petrochemical materials, your facility will

need to report any emissions from your hot and heated tanks.

Emission calculations from hot and heated tanks are different than standard

fixed or floating roof tanks. This short guide will explain the best practice

procedure for reporting hot/heated tank emissions, whether you are doing

calculations manually or using a reporting tool.

Hot and heated tanks present a challenge because there are few tools designed to

handle hot & heated tank emissions. The EPA standard TANKS 4.09D is not

considered accurate for these types of emissions any more, since it

underestimates emissions based on an annual average temperature.

This guide will cover:

The five main factors in hot/heated tank emissions.

The basics of standing and working losses from storage tanks, and how hot

& heated tanks differ.

Why TANKS 4.09 doesn’t work and how you can avoid that issue in your

own reporting.

Best practices and links to resources that you can use.

An important note about this guide: this ebook examines hot & heated tanks

specifically. If you are also looking on information about other types of tanks,

ERA has written a guide for emission estimations for floating and fixed roof

tanks, as well as mobile sources (loading operations). You can download it here:

http://lando.era-environmental.com/the-science-of-tanks-emissions .

http://lando.era-environmental.com/the-science-of-tanks-emissionshttp://lando.era-environmental.com/the-science-of-tanks-emissionshttp://lando.era-environmental.com/the-science-of-tanks-emissions


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In general there are 5 main categories of factors that influence the quantity of

reportable emissions generated by hot and heated tanks. These are:

Tank parameters and physical properties (i.e. roof type, shell condition,

etc.)

Chemical makeup of the liquid being stored/processed

Stored temperature of the liquid in the tank

Amount of liquid moving through the tank (throughput) Timeframe of the liquid’s standing time

Here’s a brief explanation of each factor and how it affects hot and heated tank

emissions:

The physical characteristics of a tank have an enormous impact on the quantity of

emissions released.

There are numerous characteristics within this category. Tanks can be horizontal,

vertical, floating roof, fixed roof, domed roof, have vents and hatches, decks and

deck seams… all of these are accounted for in the emission calculation or create

type-specific emission events (such as roof landing emissions for floating roof

tanks).

For perfectly insulated hot and heated tanks, physical properties that affect heat

absorption are not as important (because these tanks are designed to stay a

relatively same temperature), but poorly-insulated hot and heated tanks should

take into account physical properties like shell color.

The type of liquid stored in your tank is also a major factor in the type of

emissions generated.


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Generally, heated tanks are used for petroleum products or other materials that

are temperature-sensitive in some way, and hot tanks are used to let a hotproduct come to a lower temperature.

Many types of petroleum products, like asphalt or crude oil, come in batches for

which you may not know the exact chemical composition. In this case, you may

need to provide the distillation slope and the RVP of the product, in order to

calculate the True Vapor Pressure (TVP) and emissions of the batch in your tank.

If partial compositions are known, they can be used to calculate the partial

speciations after the emission calculations.

For more information about partial speciation, refer to section titled “PartialSpeciation Method for Vapor Pressure and Emission Determinations”.

Some of the information you might need to know about your liquid’s chemical

makeup include:

%by Weight Chemical Composition of the liquid

Molecular weight

Chemical density

Molecular weight of product, vapor and liquid (Petroleum products)

Distillation slope (Petroleum products)

RVP (Petroleum products)

Unlike other tanks, which are greatly affected by ambient temperature changes,

hot and heated tanks are generally unaffected by ambient temperature because

they are generally already kept at a hotter internal temperature and are more

well-insulated than other types of tanks.

For a well-insulated tank one can assume that ambient temperature has no effect

on emission generation. However, some state agencies are investigating the

impact of heating cycles and ambient temperature on breathing losses for

insulated hot and heated tanks. If you use a poorly-insulated tank anywhere on

site, you should be tracking ambient temperature conditions, since if ambient


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temperature gets higher than the stored liquid temperature of the tank breathing

losses will occur.

You will also need to know the liquid height of the liquid stored in your tank and

how many times the tank was filled or emptied (turnovers) for the period that you

are accounting emission for. It is more accurate to know the exact liquid height at

any given moment, but you are usually able to calculate emissions using the 2/3

height of tank for the reporting period if the exact data is unknown.

This set of data is important because the more empty air-filled space there is in a

tank, the greater the standing loss emissions. The liquid height will tell you how

much empty space is in your tanks for the reporting period. Working losses will

be affected by movement through the tank.

The longer your stored liquid stands in a tank, the more evaporation takes place

and generates air emissions. You will need to know how long a liquid was stored

before it was transferred into another tank, a product, or a package.

The next section will cover the basic science behind the emissions calculations

used for hot and heated tanks.


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Put simply, there is no singular equation for hot and heated tank emissions. The

equation you will need to use is based on the tank’s specific properties.

In general, the total losses from a storage tank is the sum of all working losses

and all breathing losses. In theory, a well-insulated hot or heated tank will not

produce breathing losses since it is kept at a stable temperature change.

Working losses are all the emissions from a tank that are the result of the

inflow of the liquid into the tank.

Standing losses, also known as breathing losses, are the result of evaporated

vapor escaping the tank due to the normal temperature fluctuations that occur

throughout the day. Hot & Heated tanks are specifically designed to counteract

standard ambient temperature fluctuations.

When calculating air emissions for any type of tank, the most basic logic at work

can be summed up in one equation, outlined in the U.S. document AP-42,

chapter 7 (available online at

http://www.epa.gov/ttnchie1/ap42/ch07/final/c07s01.pdf ):

Lt (Total losses) = Ls (Standing storage loss) + Lw (Working losses)

Lt, the total amount of product lost in the form of emissions is the combined

amounts of the losses due to standing evaporation in the tank (Ls) and the total

amount lost from forced expelling when the tank is being filled with liquid (Lw).

Depending on the type of tank you are using, the variables used to determine LSand L W will differ. There are over 30 variations on the base AP-42 equation, so

refer to that document to determine which calculation to use for your specific

tank.

http://www.epa.gov/ttnchie1/ap42/ch07/final/c07s01.pdfhttp://www.epa.gov/ttnchie1/ap42/ch07/final/c07s01.pdfhttp://www.epa.gov/ttnchie1/ap42/ch07/final/c07s01.pdf


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For hot and heated tanks, the base equation can be simplified to:

Lt (Total losses) = Lw (Working losses) + any breathing losses from

heating cycles and/or poor insulation.

Working losses can be calculated using the following equation:

Lw = 0.0010 x Mv x P vA x Q x K N x Kp

Where:

Mv is the molecular weight of vapor

*** A note about molecular weight: if you are unable to determine the

molecular weight of one or more chemical components of your liquid,

assuming an AVERAGE value of 150 will help avoid under-reporting

emissions. However, this assumption should only be made when absolutely

necessary. *** P VA is vapor pressure at stored liquid temperature. Vapor pressure is

considered one of the more complex variables to calculate for materials

stored in hot and heated tanks. For best practices, see the section

“Calculating Vapor Pressure”.

Q is the flow (amount of liquid processed)

K N is the working loss turnover factor

K P is the product factor for the specific liquid

This above core equation provides the basis for calculating air emissions from

tanks. However, each of the above variables will differ based on the 5 main

factors of tank emissions. You will need to calculate the unique values for each of

the basic variables for each tank before you can apply this general equation.

Breathing losses can be calculated using the following methodology:


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There’s no concrete equation provided by environmental regulatory agencies atthe time of this guide’s publication, but some official ruling on insulated tank

emissions is expected in the next few years. Until then we recommend following

these basic guidelines (based on a combination of TCEQ research and our own).

Breathing losses from an insulated tank are dependent the ambient temperature

range and how well insulated the tank is

A semi-insulated tank (either having an uninsulated roof or being overall

poorly insulated) means you should track the maximum and minimum ambient

temperature range. If the ambient temperature (either max or min) is higher than the tank’s liquid storage temperature then use the following equations to

determine Tmax and Tmin while applying the standard AP-42 breathing losses

equation appropriate for your tank :

Tmax = maximum of the two (Tmax-amb, Ttank)

Tmin = maximum of the two (Tmin-amb, Ttank)

If your tank is fully insulated, the TCEQ recommends that you modify the basic

AP-42 breathing loss equation for your tank following this logic:

Replace 365 days with the number of heating cycles.

Replace daily temperature range with the temperature range of the

stored liquid.

It's worth noting that these modifications assume that all heating cycles will be

uniform - it means your final emission estimation will be skewed based on the

difference between your real world heating cycles and the assumed average. It's

possible to use a better system that individually tracks the heating cycles and uses

this more accurate data instead of averaging.

Hot and heated tanks can become difficult to manage if you have constantly

changing stored liquids and are constantly changing the temperature at which

they are stored. The key in this situation is careful recordkeeping and keeping

your emission estimations on the right schedule – if you see daily

product/temperature changes you’ll need daily records of all those variables to

ensure you have the data you need to report properly.


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That’s one main reason why many users of hot and heated tanks are using

sophisticated emissions management systems and monitoring devices to keepthem ahead of all this data management.


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In many cases you will need to calculate the vapor pressure of a mixture in a hot

or heated tank yourself. If no vapor pressure data was supplied to you by a

supplier, use the following methodologies to calculate vapor pressure. Be sure to

use the stored temperature of the product instead of atmospheric temperature.

Total vapor pressure can be estimated to be the sum of all the partial vaporpressures of all components within the stored mixture. Use Raoult’s Law .

a.

If the component’s Antoine constants (A, B, and C) are known, use the

Antoine Equation:

log10(P) = A – (B / (T + C))

b.

If that data is not available, check if the Riedel constants A, B, C, D and N,

are available. If so, use the Riedel Equation:

ln(P) = A + B/T + C ln(T) + D TN

c.

If that data is not available, use published or empirical data, like copies ofthe MSDSs or SDSs containing the pure component measurement at a

given location.

d. If that data is unavailable approximate using this set of assumptions:

All substances that are salts are assigned a vapor pressure of 0 psia.

All substances that are polymers and copolymers are assigned a

vapor pressure of 1 mm Hg (0.01938158 psia).

All remaining unknown components are assigned a vapor pressure of

0 psia.


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AP42 section 7 provides a specific equation to use for determining the Vapor

Pressure of petroleum products. Instead of Raoult’s Law use equation 3-24:

Where A and B are calculated from the equations displayed in figure 3-5 of the

same AP42 section. To use this equation you must know the S (distillation slope)

and RVP (Reid Vapor Pressure):

http://www.epa.gov/ttnchie1/ap42/ch07/bgdocs/b07s01.pdfhttp://www.epa.gov/ttnchie1/ap42/ch07/bgdocs/b07s01.pdfhttp://www.epa.gov/ttnchie1/ap42/ch07/bgdocs/b07s01.pdf


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The vapor pressure of crude oil products is determined using the equation in

AP42 section 7 figure 3-1b. To use this equation you must know the liquid’s Reid

Vapor Pressure (RVP) variable:

For Further Help with Vapor Pressure Data

The American Petroleum Institute (API) has compiled documentation and data

about various select petroleum and crude oil products and their properties. Table

2 “Typical Properties of Selected Petroleum Liquids” of API Chapter 19.4

provides vapor pressure constants, molecular weight, TVP, etc.

It is available for purchase from the API at www.api.org.

http://www.api.org/http://www.api.org/http://www.api.org/http://www.api.org/


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In the petrochemical industry there are many instances when you will not know

100% of the chemical components of the liquid in your tank. This is often the case

with materials like crude oil or asphalt.

The partial speciation method can be applied to these types of mixtures to

estimate the emissions from the specific chemicals for which you have a weight

fraction provided. It means that you don’t need to know everything about yourstored liquid, just the criteria chemicals in your stock.

You will need to know the following variable, or have the raw data available to

calculate the following:

The stock’s True Vapor Pressure (TVP). This can be extrapolated from

other available chemical data (Reid Vapor Pressure and distillation slope)

The stock’s liquid molecular weight

The stock’s vapor molecular weight

If you do not have enough information about your stock you will need to perform

testing/analysis. If you have a high turnover rate, testing every batch will be time

consuming and costly. Instead, we recommend improving the quality of your

EH&S database to avoid gaps in your knowledge.

The American Petroleum Institute (API) offers tables and guidance documents

that provide accepted TVP and molecular weight values for basic liquids like

crude oil. You can refer to it for TVP data when you have no other options for

finding out the TVP of your material. The API tables are a pay-for-access service

but are an acknowledged tool in the Oil & Gas industry.

The API provides a 12-step process for the partial speciation method, which is

available for purchase from the API website. We can't share it with you here due

to intellectual property regulations but we believe so strongly in the API's process

that we use it ourselves. The API provides full and detailed instructions on the

process, and we recommend using the API documents whenever possible.

http://www.api.org/http://www.api.org/http://www.api.org/http://www.api.org/publications-standards-and-statisticshttp://www.api.org/publications-standards-and-statisticshttp://www.api.org/publications-standards-and-statisticshttp://www.api.org/publications-standards-and-statisticshttp://www.api.org/publications-standards-and-statisticshttp://www.api.org/publications-standards-and-statisticshttp://www.api.org/publications-standards-and-statisticshttp://www.api.org/


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Because Tanks 4.09D was found to be inadequate for hot and heated tank

emission determinations, Environmental Managers have been forced to find

alternative methodologies for their reporting.

There are a few important best practices that will help any manufacturer using

hot and heated tanks. We’ll examine them below:

A core reason why reporting emissions from tanks is difficult is because of the

high number of detailed variables that need to be tracked and referenced for

emission estimations. This includes chemical data, tank characteristic data, and

data from suppliers.

If this information is scattered across multiple documents it will only slow down

your reporting. Likewise if you have a spreadsheet storing all that data –

spreadsheets don’t have the intelligence to search for the specific information you

need and tend to get overwhelmingly large when tracking more than one tank.

There are multiple tank and chemical database systems available to

petrochemical sites, and depending on the complexity of your operations,

possible to build your own.

If you often find your estimations using stand-in default values from API or other

sources instead of being able to reference your own records, it might be sign that

you aren’t getting the best possible data from your suppliers.

This is often the result of not having a good system in place for sharing data. Your

suppliers should feel secure in giving you as much data as possible about the

materials they send you, which often means an electronic and password-

protected portal for data uploads.


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At the 2015 4C Conference for Oil & Gas EH&S professionals, a representative

from the TECQ noted that reporters should strive to avoid using default values

whenever possible, unless lab analysis has proven that the default values are

actually representative of your specific stored liquid.

Avoiding default values means having accurate data about your own materials

and getting better information from your suppliers. It underscores the theme of

prioritizing data quality as a reliable method of improving reporting and

reducing how long it takes to estimate emissions.

The current environment offers EH&S specialists a wide array of tools and

spreadsheets that could be used. The key is to find a tool that encompasses all

your tank emission reporting needs: if you end up using a different tool for hot

and heated tanks, then another for inventory tracking, and another for floating

roof tanks… you end up with the same problem of scattered and decentralized

data.


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ERA Environmental Management Solutions is the leader in environmental

management and air emissions monitoring solutions and software. ERA’s EH&S

software is the only solution that has been designed by experienced

environmental scientists, created specifically for busy EH&S Managers that have

to track, monitor, and report their air emissions from a wide range of different

sources.

ERA’s software is used extensively by the petrochemical industry to manage

emissions and compliance reports, including tanks, pipes, flares, transport vehicles, and other downstream, midstream, and upstream processes. Businesses

using ERA software include some of the world’s greenest and award winning

Fortune 500 manufacturers, as well as small manufacturing businesses that want

to make the most of their resources.

ERA believes that your time is better spent on improving processes rather than

chasing down data from across your sites. That’s why we save 80% off of your

reporting time by automating your data collection and quickly generating reports

from the market’s largest library of over 400 state and federal reports.

We believe so strongly that ERA software will revolutionize the way you manage

your air, water, wand waste emissions that we are the only solution that comes

with a satisfaction guaranteed implementation and round the clock support from

our team of trained scientists.

Learn more about how ERA can help you achieve your environmental goals by

visiting:

www.era-environmental.com or by calling us at 1-866-493-6409.

Disclaimer: All information contained in this fact sheet is as accurate as ERA could

make it during the time of writing (July 2015). ERA accepts no liability for the contentof this fact sheet, or for the consequences of any actions taken on the basis of the

information provided. ERA has taken all actions to ensure the data contained in any

additional resources and websites is accurate, but accepts no liability for the content of

these resources. To ensure the accuracy of the information provided, please contact the

EPA. For a more recent revision of this document, please contact ERA at 1-866-493-

6409.
http://www.era-environmental.com/http://www.era-environmental.com/http://www.era-environmental.com/

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