Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G21/00—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents
  • C10G21/06—Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents characterised by the solvent used
  • C10G21/12—Organic compounds only
  • C10G21/20—Nitrogen-containing compounds
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
  • C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
  • C10L3/10—Working-up natural gas or synthetic natural gas

Definitions

• This invention relates generally to the treatment of sour gas and liquid hydrocarbon streams to remove or reduce the levels of hydrogen sulfide therein.
• the invention relates to the treatment of sour gas and oil streams flowing in a flow line.
• the invention relates to the use of nonregenerative scavengers to reduce the levels of hydrogen sulfide in natural gas and liquid hydrocarbon streams.
• a regenerative system for treating sour gas streams In large production facilities, it is generally more economical to install a regenerative system for treating sour gas streams. These systems typically employ a compound used in an absorption tower to contact the produced fluids and selectively absorb the hydrogen sulfide and possibly other toxic materials such as carbon dioxide and mercaptans. The absorption compound is then regenerated and reused in the system.
• Typical hydrogen sulfide absorption materials include alkanolamines, PEG, hindered amines, and the like.
• nonregenerative scavengers for small plant hydrogen sulfide removal fall into four groups: aldehyde based, metallic oxide based, caustic based, and other processes.
• the scavenger reacts with the hydrogen sulfide to form a nontoxic compound or a compound which can be removed from the hydrocarbon.
• the reaction produces a chemical complex known as formthionals (e.g., trithiane).
• the present invention employs a nonregenerative scavenger which may be of the aldehyde type. These include low molecular weight aldehydes and ketones and adducts thereof. The low molecular weight aldehydes may also be combined with an alkyl or alkanolamine as disclosed in U.S. Patent 4,748,011. Other aldehyde derived scavengers include the reaction product of low molecular weight alkanolamines and aldehydes disclosed in U.S. Patent 4,978,512.
• an H2S sour gas or liquid hydrocarbons are treated with 1,3,5-trimethyl-hexahydro-1,3,5 triazine to reduce the level of H2S and mercaptans therein.
• the 1,3,5-trimethyl-hexahydro - 1,3,5 triazine may be represented by the following formula (FORMULA I):
• the triazine is preferably prepared by reacting trimethyl amine with formaldehyde.
• the product preferably contains ⁇ 1000 ppm formaldehyde.
• the method of the present invention involves adding the triazine scavenger described above to any gas or liquid hydrocarbon containing H2S and/or mercaptans in a sufficient quantity to effectively reduce the levels of reactive S therein.
• the method may also be employed by passing the sour gas through an absorption containing a solution of the scavenger.
• the method of the present invention may be used in the treatment of sour gas and oil production streams, as well as in petroleum (e.g. crude oil and refined products) contained in storage tanks, vessels, pipelines. etc.
• petroleum e.g. crude oil and refined products
• the scavenging composition useful in the method of the present invention is 1,3,5-trimethyl-hexahydro-1,3,5-triazine.
• triazine this compound will simply be referred to as "triazine” unless otherwise indicated to distinguish between other triazines.
• the triazine (Formula I) is prepared by the condensation reaction of a trimethylamine and formaldehyde:
• the formaldehyde may be in the form of formalin or paraformaldehyde, with the former being preferred.
• hydrocarbon solvents may be present in the final product. These include xylenes, aromatic naphtha and alcohols.
• an aqueous solution of methylamine is added slowly to a concentrated aqueous methanol-free solution of formaldehyde and the stoichiometry is maintained so that there is a slight excess of methylamine at the end of the reaction, maintaining a molar ratio of at least 1.01 (e.g. about 1.02 moles) of methylamine to 1.00 moles of formaldehyde for the overall process.
• Free formaldehyde is minimized to ⁇ 1000 ppm in the liquid.
• Slow addition is desirable to control the reaction temperature to below 140°F.
• methanol or other solvents can be added back without adversely affecting the formaldehyde level.
• an essentially quantitative yield of 1,3,5-trimethyl-hexahydro-1,3,5-triazine can be formed under conditions which minimize the presence of objectionable amounts of free formaldehyde.
• the triazine may also be manufactured by the reverse addition of formaldehyde to methylamine to produce the same result, provided the temperature is maintained below 105°F to minimize methylamine loss by evaporation and provided the stoichiometry of the overall process is as described above.
• the scavenging composition is added to the gas or oil stream in a concentration sufficient to substantially reduce the levels of H2S and/or mercaptans therein.
• gas generally from 0.01 to 0.12, preferably from 0.02 to 0.10, most preferably from 0.04 to 0.08 gallons of scavenger product (34.5% active) per MMSCF (1,000,000 standard ft2 of gas) for each ppm of H2S removed will be sufficient for most applications.
• the treatment may also be based on weight of H2S in the gas. From .05 to 1.0, preferably 0.1 to .4 pounds of triazine per MMSCF per ppm H2S removed will normally be required.
• the scavenging compound contained in a solvent such as water or alcohol
• a solvent such as water or alcohol
• the injection may be in the flow lines or the gas may be passed through an absorption tower containing a solution of the triazine.
• the chemical formulations may also contain other compounds such as ethoxylated alcohols, ethoxylated phenols, sulfates of ethoxylated alcohols and phenols, quaternary amines, corrosion inhibitors, and the like.
• the preferred scavenger formulation comprises 10-50 wt% actives (triazines).
• the H2S scavenging ability of the 1,3,5-trimethylhexahydro-1,3,5 triazine is believed to be due to its reaction with hydrogen sulfide to produce sulfur containing organic compounds such as dithiazines.
• the scavengers used to treat the facility were as follows:
• the treatment with the Commercial Scavenger involved continuous injection into the pipeline at a rate of 75 gallons per day, and a 55 gallon slug treatment twice a week.
• the treatment with the Formula I Product involved injection into the 6'' pipeline at a rate of 73 gallons per day with no need for any slug treatments.
• the use of the Formula I Product limited the H2S content of the gas to 4 ppm. In a four month treatment, only one cleanout was required.
• the procedure was as follows: A 2-liter absorption column was used. Three milliliters of the Formula I Product were diluted in 500 milliliters of distilled water. The inlet concentration of H2S was determined, the cylinder was filled, and the flow rate of the natural gas stream was set at 3.0 liters of gas per minute. The flow rate was checked every 7 to 8 minutes and the outlet H2S concentration was determined every 15 minutes. The test was continued until the outlet H2S concentration was near the inlet level. The results are presented in Table I.
• a second side stream bubble tower test was performed at a second commercial facility.
• the procedure was as follows: A 2-liter absorption column was used. Fifty milliliters of Formula I Product were diluted in 400 milliliters of distilled water. The inlet concentration of H2S was determined, the cylinder was filled, and the flow rate was set at 3.0 liters of gas per minute. The flow rate was checked every 10 minutes and the outlet H2S concentration was determined every 15 minutes. The test was continued until the outlet H2S concentration was approximately forty percent (40%) of the inlet level. The test results are presented in TABLE II.
• a side stream bubble tower test was performed at the commercial facility tested in Experiment 2 to determine the absorption efficiency and capacity of the commercial scavenger used in the Field Test described above except the active triazine was between 45 and 50 wt%.
• a 2-liter absorption column was used.
• the cylinder was charged with 100 milliliters of the commercial scavenger and 500 milliliters of water.
• a gas flow rate of 4.0 liters per minute was passed through the cylinder.
• H2S hydrogen sulfide
• test results for the two tests are presented in TABLES III and IV.
• TABLE III Elapsed Time (Hours) H2S Inlet (ppm) H2S Outlet (ppm) Test Comments .00 55000 0 Test Started .17 55000 0 Added 0.5 ml .25 55000 0 antifoam agent .50 55000 10 .75 55000 600 Ended Test
• composition of the Commercial Scavenger is 45.0% to 50.0% by weight of 1,3,5-tri(2-hydroxyethyl)-hexahydro-1,3,5-triazine and the Formula I Product is 34.4% by weight of 1,3,5-trimethyl-hexahydro-1,3,5-triazine.
• the manufacture and use of the scavenger in accordance with the present invention offers the advantage that it is ecologically acceptable since it is substantially free of formaldehydes.

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• Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
• Treating Waste Gases (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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• 1994
  • 1994-06-09 CA CA 2125513 patent/CA2125513A1/fr not_active Abandoned
  • 1994-06-24 NO NO942415A patent/NO942415L/no unknown
  • 1994-07-15 EP EP94305225A patent/EP0636675A3/fr not_active Withdrawn

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