Stay on Top of Your Tanks

Emerson's Steve Attri

For storage tanks, controlling emissions is a high priority concern. A pressure vacuum relief valve (PVRV) is a critical component in managing pressure.

Knowing when and for how long it opens to release pressure also helps to determine what emissions occurred.

In this quick 1:52 video, PVRV with Smart Wireless Technology, Emerson’s Steve Attri, explains how wireless technology can help determine if the PVRV is working or not. The wireless PVRV solution uses a Rosemount wireless transmitter coupled with a Topworx proximity sensor. Together, these let operators know whether the PVRV is open or closed. Continue Reading

Adsorption Process to Separate Fluid Components

Control-Valve-Sourcebook-AdsorptionMany techniques are used to separate impurities in fluids. One common method is to use the process of adsorption. In an online document, Control Valve Sourcebook — Chemical Unit Operations, adsorption is defined as:

…a typical mass transfer operation used in process plants to remove or separate specific components of a liquid or gaseous mixture. The specific definition of adsorption is the adhesion of atoms, ions, or molecules to a solid surface.

How it differs from absorption is that:

…absorption consumes the particles, while adsorption is the binding of molecules or particles to a surface. This binding takes place primarily on the walls of the porous material. In a process known as regeneration, the sorbent, or material performing the adsorption is purged of particles that have adhered to the sorbent.

Three types of regeneration processes include:

  • Pressure swing adsorption (PSA)
  • Temperature swing adsorption (TSA)
  • Vacuum pressure swing adsorption (VPSA)

adsorption-bedsIn a dual bed arrangement, one adsorption bed can be adsorbing while the other is offline and regenerating. The article provides an example of an oxygen and nitrogen air separation process:

During the production step, air is pumped into a cylinder containing beads of adsorbent material at pressure. Adsorbent material is selected based on what component of the air is needed. As the air passes through the bed, the adsorbent material separates the unwanted air components and only allows the desired product to pass through. During the regeneration step, a small amount of product nitrogen or oxygen is used to flush the waste gas through an exhaust port, preparing the vessel for another production cycle.

Other examples where the adsorption process is used include:

  • Removal of sulfur compounds from natural gas
  • Removal of water content in cracked gas for ethylene production
  • Air separation units
  • Dehydration of ethanol
  • Clarification of sugar
  • Softening of hard water
  • Carbon dioxide (CO2) removal

Critical valves used in adsorption processes include switching valves, feed gas valves, dump/purge valves, purge supply valves, product/repressurization valves and equalization process valves. Sizing the valves correctly for the application depends on the regeneration process type as well as the process pressure, temperature and fluid materials.

For example, the:

TSA process the cycle time is around eight hours and much longer than the PSA and VPSA process. The PSA and VPSA switching process take between one to three minutes.

Since pressure changes more rapidly than temperature, controlling the pressure is important to avoid fluffing the beds. Technologies that can help include [hyperlinks added]:

Fisher and Bettis actuators can be used for fast switching and accurate control. Also, Fisher FIELDVUE DVC6200 digital valve controllers are used to ensure accuracy when opening the switching valves so they are not opened too quickly.

Read the control valve sourcebook article for examples and recommended valve and actuator selections for the other valves used in the adsorption and bed regeneration processes.

You can also connect and interact with other valve and actuator experts in the Actuators and Valves groups in the Emerson Exchange 365 community.

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Optimizing the Process of Purifying Natural Gas Liquids

Emerson's Chuck Miller

Author: Chuck Miller

It is no secret that the oil and gas producers attraction to the shale fields has been the high BTU wet gas that contains a significant volume of heavier hydrocarbons known as Natural Gas Liquids or NGLs. The purpose of the Natural Gas / NGL Recovery plant is to recover the methane and send it to interstate pipelines. However, its primary role is to maximize the recovery of high-value NGLs. In this two-part series, we’ll look at NGL Recovery plant operations and share the findings from a typical optimization study.

The natural gas liquids, sometimes known as Y-grade, must then be transported to fractionation facilities where the liquids can be mixed or separated into their base components as purity products. The NGL Fractionation facility separates the NGLs extracted from the raw gas feed stream into purity products based on their component boiling point ranges (also known as cut points).

Fractionation Distillation Columns

The distillation columns separating the NGL components perform the following functions:

  • T-301, the de-ethanizer, removes ethane from the feed stream.
  • T-302, the de-propanizer, separates propane product from the base of T-301.
  • T-303, the de-butanizer, separates butane from the base of T-302.
  • T-450, the butane splitter, separates the isomers of butane into two product streams.
  • T-350, the de-pentanizer, separates pentane from the base of T-303.
  • T-351, the pentane splitter, separates the isomers of pentane into an i-pentane stream and an n-pentane stream that is blended with the base of T-350.

Continue Reading

Improve It Turnaround Mindset

Emerson’s Marcelo Carugo

The mindset in most plant and production facility turnarounds is to get things fixed as fast as possible in order to get the facility back on line. At the American Fuel & Petrochemical Manufacturers (AFPM) Annual Meeting earlier this year, Emerson’s Marcelo Carugo teamed with a leading Latin American refiner to provide ideas on enhancing the turnaround planning mindset from “fix it” to also include “improve it”.

Turnarounds provide the opportunity to bring equipment closely back to original design effectiveness. They also provide the opportunity to increase ongoing mechanical availability and reduce operating costs through improved operations analysis and control. These investments to implement improvements are a small part of the overall turnaround budget but can have an extremely high incremental return on investment.

The key is to take a systematic examination of potential improvements very early in the turnaround planning process to get the actions identified, approved, budgeted and implemented during the shutdown window. Continue Reading

Accurate Multiphase Flow Measurement

Many industries, such as oil & gas production, require flow measurement for fluids with gas and liquid phases.

Emerson's Kevin Borden

In this quick 1:49 video, 5700 with Advanced Phase Measurement, Emerson’s Kevin Borden describes how advanced phase measurement (APM) technology provides multiphase Coriolis flow measurement for challenging gas or liquid applications. APM technology is available in the Micro Motion Model 5700 advanced field mount transmitter.

Kevin notes that this technology can provide accuracy of +/-3% for a gas void fraction up to 15%. The APM algorithm provides corrected mass and volumetric flow values when multiphase flow conditions are present. Gas void fraction is also calculated. Continue Reading