Reduction of hydrate formation in a natural gas stream by contacting with anit-freeze agent

Claim 2

In a process for reducing the moisture content of a moisture-containing Stream of natural gas without substantail moisture removal prior to introducing an antifreeze agent into said gas stream, wherein said gas, which is at an atmospheric temperature in the range 40*-125*F, is contacted in a first contacting zone with an amount of an aqueous liquid solution containing 51 to 90 weight percent of a low boiling (high vapor pressure) desiccant-antifreeze agent and 49 to 10 weight percent water at a temperature in the range 40*-125*F and pressure conditions sufficient to absorb a major portion of said moisture from said gas and simultaneously vaporize an amount of said agent into said gas which is sufficient to prevent solids formation in subsequent low temperature processing of said gas, said thus-treated gas is then chilled to a temperature sufficient to condense substantially all of the propane and heavier hydrocarbons therefrom leaving a residue gas rich in methane and ethane, and a liquid stream comprising said condensed propane and heavier hydrocarbons, water, and said agent, but at a temperature sufficiently above the eutectic freezing point for the water-agent solution to prevent freezing of the water-agent solution and formation of solids during said chilling, the improvement comprising the steps of: a. contacting said separated liquid stream with water in a countercurrent contacting zone under conditions sufficient to substantially extract said agent from said condensed propane and heavier hydrocarbons; b. recovering overhead essentially agent-free said condensed propane and heavier hydrocarbons from said countercurrent contacting zone; c. passing a bottoms stream comprising water and said agent from said countercurrent contacting zone to a fractionation zone; d. withdrawing an overhead stream comprising 51 to 90 weight percent of said agent and 49 to 10 weight percent of water from said fractionation zone; e. returning said overhead stream of step (d) to said first contacting zone as at least a portion of said agent used therein; f. withdrawing a bottoms stream comprising water from said fractionation zone; and g. adjusting the water content of said aqueous solution of said agent in said overhead stream by adjusting conditions in said fractionation zone of step (d) so as to control the water content of said withdrawn overhead stream of step (d).

Claim 3

IN A PROCESS FOR REDUCING THE MOISTURE CONTENT OF A MOISTURE-CONTAINING STREAM OF NATURAL GAS WITHOUT SUBSTANTIAL MOISTURE REMOVAL PRIOR TO INTRODUCING AN ANTIFREEZE AGENT INTO SAID GAS STREAM WHEREIN SAID GAS, WHICH IS AT AN ATMOSPHERIC TEMPERATURE IN THE RANGE OF 40*-125*F, IS CONTACTED IN A FIRST CONTACTING ZONE WITH AN AMOUNT OF AN QUEOUS LIQUID SOLUTION CONTAINING 51 TO 90 WEIGHT PERCENT OF A LOW BOILING (HIGH VAPOR PRESSURE) DISICCANT-ANTIFREEZE AGENT AND 49 TO 10 WEIGHT PERCENT WATER AT A TEMPERATURE IN THE RANGE 40*-125*F AND PRESSURE CONDITIONS SUFFICIENT TO ABSORB A MAJOR PORTION OF SAID MOISTURE FROM SAID GAS AND SIMULTANEOUSLY VAPORIZE AN AMOUNT OF SAID AGENT INTO SAID GAS WHICH IS SUFFICIENT TO PREVENT SOLIDS FORMATION IN SUBSEQUENT LOW TEMPERATURE PROCESSING OF SAID GAS, THUS-TREATED GAS IS THEN CHILLED TO A TEMPERATURE SUFFICIENT TO CONDENSE SUBSTANTIALLY ALL OF THE PROPANE AND HEAVIER HYDROCARBONS THEREFROM LEAVING A RESIDUE GAS RICH IN METHANE AND ETHANE, AND A LIQUID STREAM COMPRISING SAID CONDENSED PROPANE AND HEAVIER HYDROCARBONS, WATER, AND SAID GENT, BUT AT A TEMPERATURE SUFFICIENTLY ABOVE THE EUTECTIC FREEZING POINT FOR THE WATER-AGENT SOLUTION TO PREVENT FREEZING OF THE WATER-AGENT SOLUTION AND FORMATION OF SOLIDS DURING SAID CHILLING, THE IMPROVEMENT COMPRISING THE STEPS OF: A. CONTACTING SAID SEPARATED LIQUID STREAM WITH WATER IN A COUNTERCURRENT CONTACTING ZONE UNDER CONDITIONS SUFFICIENT TO SUBSTANTIALLY EXTRACT SAID AGENT FROM SAID CONDENSED PROPANE AND HEAVIER HYDROCARBONS, B. RECOVERING OVERHEAD ESSENTIALLY AGENT-FREE SAID CONDENSED PROPANE AND HEAVIER HYDROCARBONS FROM SAID COUNTERCURRENT CONTACTING ZONE; C. PASSING A BOTTOMS STREAM COMPRISING WATER AND SAID AGENT FROM SAID COUNTERCURRENT CONTACTING ZONE TO A FRACTIONATION ZONE; D. WITHDRAWING AN OVERHEAD STREAM COMPRISING 51 TO 90 WEIGHT PERCENT OF SAID AGENT AND 49 TO 10 WEIGHT PERCENT OF WATER FROM SAID FRACTIONATION ZONE; E. RETURNING SAID OVERHEAD STREAM OF STEP (D) TO SAID FIRST CONTACTING ZONE AS AT LEAST A PORTION OF SAID AGENT USED THEREIN; F. WITHDRAWING A BOTTOMS STREAM COMPRISING A WATER FROM SAID FRACTIONATION ZONE; AND G. ADJUSTING THE WATER CONTENT OF SAID AQUEOUS SOLUTION OF SAID AGENT IN SAID OVERHEAD STREAM BY ADJUSTING CONDITIONS IN SAID FRACTIONATION ZONE OF SAID STEP (D) SO AS TO CONTROL TH E WATER CONTENT OF SAID WITHDRAWN OVERHEAD STREAM OF STEP (D).

Claim 4

IN A PROCESS FOR REDUCING THE MOISTURE CONTENT OF A MOISTURE-CONTAINING STREAM OF NATURAL GAS WITHOUT SUBSTANTIAL MOISTURE REMOVAL PRIOR TO INTRODUCING AN ANTIFREEZE AGENT INTO SAID GAS STREAM WHEREIN SAID GAS, WHICH IS AT AN ATMOSPHERIC TEMPERATURE IN THE RANGE OF 40*-125*F, IS CONTACTED IN A FIRST CONTACTING ZONE WITH AN AMOUNT OF AN QUEOUS LIQUID SOLUTION CONTAINING 51 TO 90 WEIGHT PERCENT OF A LOW BOILING (HIGH VAPOR PRESSURE) DISICCANT-ANTIFREEZE AGENT AND 49 TO 10 WEIGHT PERCENT WATER AT A TEMPERATURE IN THE RANGE 40*-125*F AND PRESSURE CONDITIONS SUFFICIENT TO ABSORB A MAJOR PORTION OF SAID MOISTURE FROM SAID GAS AND SIMULTANEOUSLY VAPORIZE AN AMOUNT OF SAID AGENT INTO SAID GAS WHICH IS SUFFICIENT TO PREVENT SOLIDS FORMATION IN SUBSEQUENT LOW TEMPERATURE PROCESSING OF SAID GAS, THUS-TREATED GAS IS THEN CHILLED TO A TEMPERATURE SUFFICIENT TO CONDENSE SUBSTANTIALLY ALL OF THE PROPANE AND HEAVIER HYDROCARBONS THEREFROM LEAVING A RESIDUE GAS RICH IN METHANE AND ETHANE, AND A LIQUID STREAM COMPRISING SAID CONDENSED PROPANE AND HEAVIER HYDROCARBONS, WATER, AND SAID GENT, BUT AT A TEMPERATURE SUFFICIENTLY ABOVE THE EUTECTIC FREEZING POINT FOR THE WATER-AGENT SOLUTION TO PREVENT FREEZING OF THE WATER-AGENT SOLUTION AND FORMATION OF SOLIDS DURING SAID CHILLING, THE IMPROVEMENT COMPRISING THE STEPS OF: A. CONTACTING SAID SEPARATED LIQUID STREAM WITH WATER IN A COUNTERCURRENT CONTACTING ZONE UNDER CONDITIONS SUFFICIENT TO SUBSTANTIALLY EXTRACT SAID AGENT FROM SAID CONDENSED PROPANE AND HEAVIER HYDROCARBONS, B. RECOVERING OVERHEAD ESSENTIALLY AGENT-FREE SAID CONDENSED PROPANE AND HEAVIER HYDROCARBONS FROM SAID COUNTERCURRENT CONTACTING ZONE; C. PASSING A BOTTOMS STREAM COMPRISING WATER AND SAID AGENT FROM SAID COUNTERCURRENT CONTACTING ZONE TO A FRACTIONATION ZONE; D. WITHDRAWING AN OVERHEAD STREAM COMPRISING 51 TO 90 WEIGHT PERCENT OF SAID AGENT AND 49 TO 10 WEIGHT PERCENT OF WATER FROM SAID FRACTIONATION ZONE; E. RETURNING SAID OVERHEAD STREAM OF STEP (D) TO SAID FIRST CONTACTING ZONE AS AT LEAST A PORTION OF SAID AGENT USED THEREIN; F. WITHDRAWING A BOTTOMS STREAM COMPRISING A WATER FROM SAID FRACTIONATION ZONE; AND G. ADJUSTING THE WATER CONTENT OF SAID AQUEOUS SOLUTION OF SAID AGENT IN SAID OVERHEAD STREAM BY ADJUSTING CONDITIONS IN SAID FRACTIONATION ZONE OF SAID STEP (D) SO AS TO CONTROL TH E WATER CONTENT OF SAID WITHDRAWN OVERHEAD STREAM OF STEP (D).

Claim 5

A process according to claim 1 wherein said moisture-containing gas stream is contacted countercurrently with said aqueous agent in said first contacting zone, and a moisture-enriched stream of said agent is withdrawn from said first contacting zone and also introduced into said fractionation zone.

Claim 6

A process according to claim 1 wherein: said separated stream in step (a) is contacted countercurrently with said water; and said water is at least a portion of the water stream withdrawn from said fractionation zone in step (f).

Claim 7

A process according to claim 1 wherein said aqueous liquid desiccant-antifreeze agent comprises an aqueous solution of methyl alcohol.

Claim 8

A process according to claim 4 wherein: said moisture-containing gas stream is contacted countercurrently with said aqueous agent in said first contacting zone; a moisture-enriched stream of said agent is withdrawn from said first contacting zone and also introduced into said fractionation zone of step (c); and said separated stream of step (a) is contacted countercurrently with said water, and said water is at least a portion of the water withdrawn from said fractionation zone in step (f).

Claim 9

A process according to claim 5 wherein: said contacting in said first contacting zone is carried out at a pressure within the range of from 5 to 5,000 psig; said aqueous solution of methanol has a water content within the range of from 40 to 15 weight percent; and at least one of said water content and said temperature is adjusted so as to control the amount of methyl aLcohol vaporized and introduced into said gas stream.

Claim 10

A process according to claim 6 wherein said pressure is within the range of from about 100 to about 1,000 psig.