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Category Archive: Thermal Fluid Heating SYstems

The Importance of Effective Heating for Natural Gas Purification in Amine Plants

We are in the midst of a U.S. shale revolution: advancements in shale oil and gas extraction techniques have led to greater natural gas production levels and a renewed demand for natural gas in industrial and power applications. Because of the increased level of competition in the industry, process efficiency is paramount. Bringing natural gas to market cost effectively hinges on the optimal design and operation of the natural gas sweetening process.

STeBookNatural gas produced from reserves in almost never pure; rather, it contains acid gases such as carbon dioxide and hydrogen sulfide. One way to remove these impurities is amine gas treatment. An amine plant (also known as a sweetening plant) is used to remove the carbon dioxide and hydrogen sulfide from the gas solution so that pure natural gas can be efficiently transported to end users via pipeline.

Our latest white paper, Effective Heating Helps Amine Plants Purify Natural Gas, describes how to improve the natural gas purification process with effective heating. It also reviews the optimal conditions and system settings for controlling the amine regeneration temperature and optimizing the efficiency of the process.

The process works like this: the natural gas mixture and amine are combined in an absorber, where the carbon dioxide and hydrogen sulfide are removed. Pure natural gas exits from the top of the vessel and the amine is sent to a regeneration system (consisting of a still and a boiler) where it is filtered for reuse.

Usually, control and bypass valves are used to maintain a constant flow through the thermal fluid heater in the regeneration process. Moreover, the temperature of the system is typically controlled using overhead temperature measurements in the reboiler. There are a few problems with this standard procedure, which are described in detail in the eBook. If these problems are not addressed in the design of the control scheme, the process will not run optimally and the control systems could destabilize.

Using thermal oil as an indirect heat source can significantly increase the life of the amine solution and increase process efficiency. Typically, system operators manually set the flow of thermal oil through the reboiler. This is a convenient solution that prevents any need for frequent fine-tuning, but this conservative approach wastes energy. The eBook discusses the thermal fluid system specifications required to optimize the operation of amine plants.

Sigma Thermal has a long history of providing highly engineered process heating systems and fine-tuning services for existing systems. To learn more about Sigma Thermal’s expertise with amine reboilers, visit our website.

Download your free copy of the full eBook here or click on the button below.

Learn more about Thermal Fluid Heaters in Amine Plants

Retrofitting with Sigma Thermal: Two Case Studies

Retrofitting equipment can be a frustrating process if not planned and executed properly. Sigma Thermal has worked on a variety of retrofitting projects, including heater coil replacements, heater modifications, custom thermal system solutions and much more. To learn how Sigma Thermal can help you with your equipment, read on.

Case Study 1: Replacement and Repair of Thermal Fluid Heating System at a Biomass Mill

Specifics: J14090 

thermal-fluid-heating-case-study-photothermal-fluid-case-study-2

This project consisted of replacing 3 convection style tube bundles for a wood-fired thermal fluid system. Parts of the system were destroyed in a fire at a biomass mill.
Sigma Thermal has done a lot of work for this client before, so they had confidence we could deliver within the timeframe needed.

What We Did

Sigma Thermal engineered a temporary blind while still giving them access to the damaged equipment so it could be replaced. This allowed the customer to run half of their process and maintain
production with the other half of their system. 

Case Study 2: Replacement of Two Natural Draft Burners

Specifics: J14099 

This project consisted of replacing 2 natural draft burners with 2 forced draft burners, along with all the required supporting parts required to make the change. Once the project was installed, the service group went on site to fine tune the new burners. This change greatly reduced the start-up time for the heaters – as the purge time for a natural draft burner is near 15 minutes – where the forced draft is closer to 2 minutes.

What We Did

Sigma Thermal made required modifications to the heater lid, fuel train, electrical system, and controls, all of which were included in this project.

Learn More about Sigma Retrofits

Fire Safety and Thermal Fluid Heating Systems

Fire safety is an ever-present concern for operators of thermal oil heating systems. To understand the scope of the problem, let’s review the salient facts.

First and foremost, this is a relatively rare and well-understood threat to users of thermal oil heating systems. Plant owners and operators have been dealing with fire prevention issues for the better part of a century, according to an article in Chemical Processing magazine. So there are a lot of best practices in place to address this specific risk within the industry.

HC1_Thermal_Oil_Heater_-_Gas_ProcessingTo discuss the parameters of fire safety in this context, experts rely on three measurements that describe fire phenomena: flash point, fire point, and autoignition temperature. Flash point is the temperature at which vapor from a fluid will temporarily burst into flame (or flash) when exposed to an ignition source. It’s measured by two tests approved by the American Society for Testing and Materials: ASTM D92 and D93. Fire point is the temperature at which such a temporary flame continues to burn the available fuel source. Fire point is typically 40-100°F above the flash point. Both flash point and fire point depend on the presence of an ignition source, such as a spark. Autoignition temperature marks the point at which no ignition source is necessary (as described by ASTM E659-78).

While the physical parameters described are important in understanding the fire risk of thermal fluids, they are actually more helpful to scientists in a laboratory than to plant managers and engineers in an actual chemical processing operation. According to the Chemical Processing article, “Relatively few fires have originated in thermal fluid systems.” Rather, the culprit in most cases is not the overheated thermal fluid but the equipment and systems conveying it. Specifically, blame can commonly be placed on poor choice of insulation materials, loss of flow, cracked heater tubes, or uncontained leakage.

What practical advice is there for such hazards? The complete answer is detailed in the article above, and in well-known industry installation guidelines such as FM 7-99, but here are a few highlights:

  • Follow an industry accepted and widely used guideline, such as FM 7-99, to guide system design and installation decisions.
  • Most good hot oil system manufacturers and hot oil fluid suppliers have published guidelines for installation and design that should be consulted as well.
  •  “The most effective precaution against insulation fires is the identification of all potential leak points and the specification of high-temperature closed-cell insulation or no insulation at these points.”  Open cell insulation, such as fiberglass, will wick oil away from leak points and can potentially saturate hundreds of feet before a problem is seen.
  • “To avoid incidents resulting from loss of flow, low-flow shutdown should be included in the burner safety interlock. . . ..”
  • Use a low level alarm in your expansion vessel to notify an operator and shut down the system in the event that oil level in the system is falling below normal levels.
  • Centralize major equipment and install containment berms in those areas to contain spills and isolate possibly incident locations when possible
  • “To prevent excessive thermal cycling of the heater tube bundle, oversized heaters should be derated by the manufacturer.”
  • “To prevent leaks, plants should: Allow expansion joints and flexible hoses to move along their axes, never sideways. Maintain lubrication systems for rotary unions and supply these systems with the correct lubricating oils. Install valves with their stems sideways so any leaks run down the stem and away from the piping.”

For more information on fire prevention practices for thermal fluid heating systems, contact one of our knowledgeable representatives or Application Engineers. We’ll be happy to answer your questions.

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