Methanol injection in the oil and gas industry with LEWA skids and packages

Methanol is mainly used for dehydration and de-icing in the oil and gas industry.

Methanol is injected both continuously and intermittently. It prevents the formation of hydrates, mainly in offshore sources, and lowers the freezing point of water percentages during the oil and gas transport.

A high degree of safety and reduced energy costs from the LEWA pumps and systems mean they pay for themselves in a short time.

Solutions for methanol injection with packages by LEWA

Advantages of LEWA packages for methanol injection:

  • Reliable and leak-free for pressures up to 1,200 bar
  • Very good suction capability of the spring-loaded diaphragm return M900 pump head
  • Long service life of diaphragms (proven 10,000 hours and more)
  • Reliable, fast diaphragm monitoring system for maximum process reliability in extreme pressure ranges
  • Simple and swift diaphragm replacement
  • All movable parts of the pump head are protected in an oil bath
  • Special LEWA design easily overcomes high suction pressures and shut downs at high discharge pressures
  • Extremely low maintenance requirements and reliable monitoring, therefore it is:

    1. Suited for both manned and unmanned operation
    2. Designed for continuous as well as intermittent operation in low/medium and high pressure injection applications

  • Avoiding expensive production interruptions by using a sandwich diaphragm: The pump does not have be shut down immediately; operation can be continued until the maintenance team is on-site or the repair fits into the work flow

Other advantages

  • Compact, modular design, allows installation in space available (e.g. on FPSOs)
  • Flow rates from several hundred (continuous injection) up to several thousand liters per hour (intermittent metering) possible
  • Precise phase-shifted multiple pumps make a low-pulsation and uniform metering possible even without a pulsation damper
  • No separate lubeoil pumps with control and monitoring instruments are needed, since the crankcase has immersion lubrication and splah lubrication

Background for methanol injection

Methanol is a by-product of refining processes.

Properties of methanol:

Methanol is highly flammable and burns with a bright flame. It is barely visible in daylight, making it extremely dangerous. Flammable gas/air mixtures can form, and electrostatic combustion is possible (even at concentrations as low as 25%) Its decomposition products are carbon dioxide, carbon monoxide and formaldehyde.

Methanol itself is not toxic, but the enzymes that capture it in the human body form formaldehyde and formic acid. These products are highly reactive (formaldehyde) or extremely acidic (formic acid). Its reaction time in the body is 15 hours or more, so the actual cause of the poisoning often can no longer be determined. Methanol must therefore be handled with extreme caution and processed as leak-tight and leak-free as possible.

Use of LDHI:

In rare cases a methanol substitute is used, so-called LDHIs (Low Dosage Hydrate Inhibitors). This is the case when the later refining process does not tolerate methanol, since the last water preparation step is carried out biologically. The microbes that are used for the final removal of oil residues are killed by methanol. Since LDHIs are more expensive than methanol, they are only used if actually specified.

During use it must be taken into account that LDHI injection quantities are significantly lower, normally only 1/10 or 1/20 the quantity of the methanol. In addition, at high pressures (>350 bar) they can crystallize and become very abrasive and, for example, require the use of tungsten carbide valves.

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