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Inert Gas Consumption for Tank Blanketing

Inert gas is used to blanket certain fixed-roof tanks for safety. Nitrogen is a common inert gas used for the purpose. In addition to safety of storage tank, the benefit of tank blanketing includes improved product quality and equipment life cycle.

Why nitrogen is commonly used in tank blanketing?

Nitrogen has inert properties, wide availability, and relatively low cost at any economic efficiency. Other gases, such as carbon dioxide or argon, are also sometimes used for certain application.

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Condensate RVP (Reid Vapor Pressure)

In 2014, I have involved in multi-billion dollars EPC project in Indonesia. The project handled gas and condensate. For condensate, it was stated that the quality shall meet certain RVP (Reid Vapor Pressure) value. In this post, I want to share what RVP is.

Definition of RVP (Reid Vapor Pressure)

Stabilized condensate generally has a vapor pressure specification. Its specification is usually identified by its Reid Vapor Pressure (RVP) or True Vapor Pressure (TVP).

Reid Vapor Pressure (RVP) is related to the vapor pressure of a petroleum product, which measures its inherent tendency to evaporate at 100oF with vapor:liquid ratio of 4:1 (ASTM D323). RVP is a function of hydrocarbon’s composition and is independent of operating temperature and pressure. The value of RVP lies below the true vapor pressure.

The higher the RVP, the more quickly the condensate or  oil will vaporize into the air. Read More

Characteristics of Piping Material

In previous post, we learned how select piping material. There are several considerations in selecting piping material, which are service life, code requirement, allowable stresses, design temperature, design pressure, corrosion, and economics. As a continuation of the post, we also need to understand characteristics of piping material. What are important characteristics of piping material?

Let’s find out.

 

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Piping Material Selection

During engineering projects, I usually face with usual fluid condition. Therefore, the piping material used is usually carbon steel. But this year my team handled fluids with high acidity, so that material selection for piping and equipment are quite challenging.

In this occasion, I want to share a post about piping material selection. The main purpose is to refresh my knowledge about piping material selection I got during 3rd year in college. I hope I find this post useful in my future projects.

For info, this post will be summary of what I read from several resources. I am not a master of piping. But I hope this post will give us a bit insight in how to select piping material as process engineers. Read More

The Difference between Gross Heating Value, High Heating Value, Net Heating Value, and Low Heating Value

One day I found a nice and short article about the difference between terminology used to express heating values: Gross Heating Value (GHV), High Heating Value (HHV), Net Heating Value (NHV), and Low Heating Value (LHV).

As mentioned in my previous post about how to convert high heating value (HHV) to low heating value (LHV), the difference between those terms is if energy used to vaporize water include in the value.

During combustion, fuel react with oxygen molecules to form carbon dioxide, water, and to release heat. The heat released is called heat of combustion. Some of the heat released are used to vaporize existing moisture in the fuel and the water product.

Because all combustion reactions occur at temperatures above water boiling point, both existing water in fuel and water product are in vapor state after combustion. In a bomb calorimeter, the water in vapor state (existing as fuel moisture and water product) is cooled and condensed to room temperature. Therefore, the heat of condensation is recovered. All the heat of combustion are measured by the bomb calorimeter. The total heat of combustion measured by a bomb calorimeter per unit mass is called “high heating value” (HHV) or “gross heating value” (GHV). Read More

Design of Air-Cooled Exchanger (Part 2)

This post is continuation of air-cooled exchanger design (part 1). In this post, I want to share free spreadsheet of air-cooled exchanger design. I used sizing procedures from GPSA engineering data book.

Please differentiate between heat load and motor power. I sometimes found young engineers confused heat load with motor power, especially when listing equipment load list.

I found many resources in internet about how to size air-cooled exchanger. We can size air-cooled exchanger easily by inputting necessary variables. For example, I used Checalc to calculate air-cooled exchanger. But, it is necessary to understand what we do.

The hardest part of sizing air-cooled exchanger by using spreadsheet is so many data to check in charts/graphs. For example, friction factor, physical property factor, and correction factor. I hope we can be patient to handle this.

Please check my spreadsheet about how to size air-cooled exchanger. I hope you find this post useful.

Air Cooled Exchanger

Design of Air-Cooled Exchanger (Part 1)

Air-cooled exchangers are used to cool fluids with ambient air. They should be considered when cooling water is in limited or expensive. Air-cooled exchangers are used for cooling and condensing.

Principle of air-cooled exchanger
Principle of air-cooled exchanger [1]
Air-cooled exchangers consist of banks of finned tubes over which air is blown or drawn by fans mounted below or above the tubes. Air-cooled exchangers are classified as forced draft when the tube section is located on the discharge side of the fan, and as induced draft when the tube section is located on the suction side of the fan. Read More

Recommended Safety Distance for Siting and Layout of Facilities

Facility layout is one of many document deliverables in a project. Do you know the philosophy to create facility layout? In this post, I want to share a siting and layout approach, as well as recommended safety distance for siting and layout of facilities by Center for Chemical Process Safety (CCPS) of the American Institute of Chemical Engineers (AIChe).

The siting philosophy begin with a review of the material and processing hazards, such as toxicity, flammability, explosivity, reactivity, or a combination of these hazards. Other potential hazards should also be considered since they may be unacceptable to their surrounding community, such as odors, loud noises, or the light from flares.

Once the type of hazards have been identified, their potential off-site and on-site impacts can be addressed. This step includes how the local terrains affects the release scenarios. At the same time, the layout of the process units and associated areas within the facility, such as storage tank areas or flares, should be arranged to reduce risks. The layout of the equipment, including both orientation and distance between them, may affect day-to-day operations. Therefore, it is important to address the balance between reduced or increased distances and the impact on accessibility when evaluating the on-site consequences. Read More

Gas Dehydration Design with Glycol Solutions

Natural gas contains many contaminants, one of them is water. When the gas is transmitted to the surface from processing and finally pipeline transmission, its pressure and temperature reduced naturally in the well string. This reduce the capacity of natural gas to hold water vapor and free water is condensed. The water vapor must be reduced to meet sales gas requirement, which is usually around 2-7 lb/MMscf.

For many years, glycol solutions have been used for natural gas drying. Early glycol dehydration units utilized diethylene glycol (DEG). Triethylene glycol (TEG) came into use around 1950 primarily because its higher boiling point thus gives better separation of water and greater dew point depression without causing thermal decomposition of the glycol. Tetraethylene glycol (T4EG) has been used in some specialized cases, but in majority, triethylene glycol is used.

In this post, I want to share preliminary design of gas dehydration unit using glycol solutions. Calculation and formulae used in this post can be accessed through this link. Read More

Conversion Higher Heating Value (HHV) to Lower Heating Value (LHV)

As a process engineer dealing with gas project, I usually involve in these terms, higher heating value (HHV) and lower heating value (LHV). Do you know the differences between these two?

In simple words, higher heating value (HHV) includes energy used to vaporize water. While lower heating value (LHV) excludes energy used to vaporize water.

Which water?

Water contained in the original energy form or created during the combustion process.

If we put them into equation, then it will be like this.

Relationship between HHV and LHV
Relationship between HHV and LHV

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