One of the most asked questions in the oil & gas engineering company is, “What is the best way to process gas?” That’s a tricky question because every gas and customer is unique, but some proven best practices exist. In this blog, we’ll tell you what they are.
1. Condensate and Water Removal
Gas recirculated through the unit must be dried to remove any water vapor, which will condense in the refrigeration circuit. This step is accomplished by using a coalescer. A coalescer consists of a large vessel equipped with an internal grid or honeycomb structure. The honeycomb allows liquids to pass through into collection tanks while trapping larger particles within the honeycomb structure.
The condensed water from the system passes through a coalescer, where it is separated from the hydrocarbon gases by gravity. The hydrocarbon gas stream then enters a de-euthanized, separating ethane and heavier components from the methane stream. The ethane and heavier components are collected for use as fuel or for further processing into derivatives such as ethylene, propylene, and butadiene.
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Acid Gas Removal
Acid gas removal is a process used to remove sulfur dioxide, hydrogen sulfide, and carbon dioxide from natural gas or refinery products. The most common acid gas removal processes are Amine Treating and Lime Softening.
Amine treating uses amines to remove H2S, CO2, and SO2 from gases. Amine treatment is usually done in the field but can also be done at the refinery. Amines are chemicals that have been found to be very effective at removing hydrogen sulphide (H2S), carbon dioxide (CO2), and sulfur dioxide (SO2). The amine itself is not consumed in the process, but rather it forms stable complexes with the gases being removed, which are then removed by filtration or vacuum distillation.
Lime softening uses calcium hydroxide (Ca(OH)) to remove CO2 from gas streams by forming CaCO3. Lime softening is a commonly used process for removing CO2 from natural gas streams prior to pipeline transmission or storage because of its high efficiency and low capital cost relative to other technologies, such as cryogenic separation or adsorption processes.
Dehydration – Moisture Removal
The process of dehydration involves removing moisture from gas streams. The key purpose of dehydration is to reduce the volume of gas by increasing its temperature and pressure. Dehydration can be achieved by several methods, such as absorption, heat exchange, refrigeration, and membrane separation.
A wet gas stream contains water vapor that must be removed before it can be used in an industrial application. This is done by using a dehydration unit that increases the temperature and pressure of the stream while removing water vapor. Once removed, the water vapor can be condensed into liquid form, which is then stored until it can be disposed of or reused.
Mercury Removal
The process of removing mercury from gas streams is called mercury removal.
There are two main methods for mercury removal: activated carbon adsorption and ion exchange. Carbon adsorption is the most popular technique for removing mercury from industrial gas streams used in Oil and gas companies in Dubai. The principle behind this process is that the activated carbon acts as a “sponge” that binds with the mercury in the gas stream.
Activated carbon has small pores that allow other gases to pass through but trap impurities such as mercury. In order to regenerate the activated carbon, it must be heated to a high temperature (over 600 degrees Celsius) to burn off any trapped contaminants such as oil, acid, or water vapor. It does have some disadvantages, however: it requires frequent regeneration, which can be costly; it requires a constant supply of fresh activated carbon, and sometimes the activated carbon itself can become contaminated with organic compounds.
Nitrogen Rejection
Nitrogen rejection is one of the most important properties of gas processing plants. It is defined as the percent of nitrogen in the feed gas that is rejected in the product stream. In other words. It measures how much nitrogen is left behind in the product stream. How much has been removed by various processes in the plant.
The amount of nitrogen rejected depends on the nature of the process and its design parameters. For example, a low-pressure process with a low operating temperature usually has high nitrogen rejection. While a high-pressure process with high temperatures will have lower nitrogen rejection. Higher pressure also means less energy consumption, which can greatly affect your bottom line.
Nitrogen rejection also depends on what type of equipment you use for separation and where you place this equipment in your plant design. The key is to find that sweet spot where you can get maximum production without wasting too much energy on separation processes or increasing costs unnecessarily through additional equipment purchases.
NGL Recovery, Separation, Fractionation, and Treatment of Natural Gas Liquids
NGL Recovery: NGL recovery processes include cryogenic distillation, absorption, refrigeration absorption, water-wet cryogenic distillation, membrane separation, pressure swing adsorption (PSA), and selective catalytic reduction (SCR).
Separation: Separation processes include condensation, cooling, distillation, and fractionation. The most common separation techniques used in naphtha-cracking plants are distillation columns, flash drums, evaporators, and heat exchangers.
Fractionation: Fractionation processes include atmospheric distillation towers and vacuum distillation towers. Fractionation can also be achieved by freezing point depression or by using specific gravity differences between components (e.g., ethane/propane)
Conclusion:
When processing natural gas, all the components of the raw natural gas must first be separated and concentrated. So that they can be further processed.
Gas Processing involves the extraction of natural gas liquids or NGLs from wet natural gas feedstocks. It is a crucial operation for any natural gas processing facility since the NGL fraction. Especially ethane and propane, are very valuable, but their recovery from a wet gas stream is often difficult. Their recovery can be expensive to achieve. Several techniques and polymers are used in natural gas plants for different applications. The most common ones include pore conditioning, membrane separation mainly by pervaporation technology, cryogenic distillation. Liquid extraction using solvent blends and supercritical CO2, solvent extraction for propane/butanes recovery, and cryogenic extraction for extractable removal like the aromatics.