Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
  • C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
  • C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
  • C07C29/86—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by liquid-liquid treatment

Definitions

• the present invention relates to a method for regeneration and reclamation of Mono 5 Ethylene Glycol.
• Hydrate inhibitors such as Mono Ethylene Glycol (MEG) are used in hydrocarbon gas and/or condensate pipelines e.g. in gas fields, to absorb moisture and prevent hydrate forming in the pipeline.
• MEG Mono Ethylene Glycol
• the MEG is injected into the upstream0 end of the pipeline and is separated from the hydrocarbon flow at downstream end.
• the separated MEG (approximately 50 % MEG, 50 % water), denoted as rich MEG, carries the absorbed water.
• This rich MEG is re-concentrated by a water removal process to produce "lean MEG" (approximately 90 % MEG, 10 % water) for re-use.
• the MEG is also contaminated with other components from the well and5 the pipeline. Pipeline corrosion products, scale and other contaminants such as hydrocarbons, salts from formation water or production chemicals are present, and those impurities are fully or partially removed in the reclamation process.
• WO 2007/073204 a process and a plant is described for regeneration of glycol from a mixture comprising glycol , water and salts, the salts comprising carbonate0 and/or bicarbonate ions.
• the mixture is flash distilled to obtain a salt- free solution of glycol and water. This solution is condensed and distilled to obtain glycol with reduced water content.
• the salts are concentrated in the vacuum boiler and removed from a sub-stream taken out of a return circuit to the vacuum boiler.
• US 2005/0072663 disclose a method of regenerating a glycol solution containing5 water, hydrocarbons and salts.
• the glycol solution is expanded in a drum, then distilled in a column.
• the concentrated glycol collected at the level of a reboiler is placed under vacuum to vaporize the water and to precipitate the salts.
• the salts are separated from the glycol in a separation device.
• the concentrated glycol feed of the salts is stored in capacity. 0
• two main types of systems are commonly used for MEG reclamation and re-concentration: the Full Stream concept and the Slip Stream concept. These two concepts are schematically shown in figures 2A and 2B respectively.
• WO 2007/073204 and US 2005/0072663 referred to above are specific examples of these two main systems respectively.
• re-concentration is meant concentrating the rich MEG to lean MEG, and by reclamation is meant removing contaminants as salts and corrosion products.
• Slip Stream as used herein is meant that the MEG is only partly reclaimed.
• all the rich MEG (C) first enters the reclamation part (A), wherein all the rich MEG is evaporated by vacuum boiling and all the salts (D) are removed in a single step.
• the evaporated rich MEG is then re-concentrated (B) to lean MEG (F) downstream the reclamation part by means of distillation under vacuum.
• the MEG reclamation and re-concentration are energy demanding processes and reducing the energy consumption would lead to large savings.
• Figure 1 is a schematic illustration of an embodiment of the present invention.
• Figure IA is a schematic illustration of an embodiment of the present invention.
• Figure 2A is schematically showing state of the art Full Stream concept
• Figure 2B shows the Slip Stream concepts.
• Figure 3 is a table showing the electrical power consumption (work) in the real case simulation in the Example.
• Figure 4 is a table showing the heating medium consumption in the real case simulation in the Example.
• Figure 5 is a table showing the cooling medium consumption in the real case simulation in the Example. DETAILED DESCRIPTION OF THE INVENTION
• the present invention concerns a method for re-concentration and reclamation of Mono Ethylene Glycol comprising the steps of a) re-concentrating the rich MEG to lean MEG by water boiling; and b) reclaiming a part of the lean MEG, wherein both the re-concentration and the reclamation step is performed at conditions below atmospheric pressure.
• the re-concentration and reclaiming steps are performed in separate units and the step of re-concentration of rich MEG to lean MEG is carried out at a temperature below the evaporation temperature of pure MEG. Salts are removed from part of the lean MEG, the Slip Stream, in a reclamation unit.
• the temperature in step a) is below the evaporation temperature of pure MEG at said pressure.
• water is evaporated at a pressure below atmospheric pressure and at a temperature below the evaporation temperature of MEG at said pressure.
• the operating temperatures in both step a) and b) are below the degeneration temperature of MEG.
• the concept according to the invention provides an energy effective system for large capacities.
• the whole inlet stream, rich MEG is evaporated under vacuum. This is a process with high energy demand as the total inlet flow, i.e. water and MEG, has to be evaporated.
• the whole inlet stream, rich MEG is re-concentrated by atmospheric water boiling; i.e. only water, not MEG, is boiled off from the main stream.
• the boiling is done at atmospheric pressure, i.e. at higher pressure than in Full Stream, the boiling temperature of the liquid is higher then in Full Stream and the energy savings by boiling off water only may be relatively small.
• the full rich MEG (3) stream is first re-concentrated (1) to lean MEG (6) in that water (5) is boiled off.
• the re- concentration unit is connected to vacuum and the boil off is performed at conditions below atmospheric pressure.
• water is boiled off under vacuum the boiling temperature is lowered and the energy needed for boil off of water is considerable reduced. This will allow the building of high capacity trains with very low energy demand as only the water is boiled off at low pressure and temperature.
• the reclamation unit is connected to vacuum and the reclamation is performed by vacuum boiling.
• the amount of lean MEG sent as Slip Stream part to the reclamation unit is regulated such that the salt concentration in the full lean MEG stream is kept below a certain maximum level which is acceptable for subsea processing.
• the re-concentration and reclamation parts may be connected to separate or common vacuum systems.
• the reclamation unit may be off line. The energy savings is even more considerable when the reclamation unit is put off line.
• the acceptable salt concentration for subsea processing varies from system to system, but would be about 50 g/L maximum, but varies for each case. Acceptable salt concentrations varies in a range from 0 g/L to a maximum of 20-30g/L or as high as 40-50 g/L depending on the system.
• Figure IA illustrates a particular embodiment of the present invention wherein the rich MEG (3) stream is first re-concentrated to lean MEG (6) in a re-concentration unit (1) where water (5) is boiled off under vacuum.
• the re-concentration unit is connected to vacuum and the boil off is performed at conditions below atmospheric pressure.
• the reclamation unit is connected to vacuum and the reclamation is performed by vacuum boiling.
• the tables in figures 3, 4 and 5 are base on real case simulations, looking at electrical power consumption (work), heating medium consumption and cooling medium consumption.
• the re-concentration process (1) is typically performed at a pressure of 15-20 kPa absolute and an operating temperatures are typically in the range of 84-91 °C for the re-concentrated (lean) MEG and 51-58 °C for the separated water phase.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Nitrogen Condensed Heterocyclic Rings (AREA)
• Heat Treatment Of Water, Waste Water Or Sewage (AREA)

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Cited By (21)

Citations (2)

• 2009
  • 2009-01-08 NO NO20090115A patent/NO332854B1/no not_active IP Right Cessation
• 2010
  • 2010-01-07 WO PCT/NO2010/000006 patent/WO2010080038A1/en not_active Ceased

Patent Citations (2)

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