Removing diamondoid components from natural gas at reduced temperatures
A process for separating diamondoids and water from a gas stream that is being cooled to below atmospheric temperature is disclosed. The multi-component gas stream is contacted with a diamondoid solvent and a water solvent (glycol) simultaneously. The feed gas can be cooled to temperatures of at least −40° F. without formation of water-based or diamondoid solids. Downstream equipment is protected from large accumulations of diamondoid solids or liquids. The feed gas may be natural gas, coal seam gas, associated gas, or other naturally occurring gases. The rich solvent with diamonoids may be regenerated or simply recirculated with make-up of fresh solvent and a purge of rich solvent. The rich glycol and rich diamondoid solvent streams are each separated from the feed gas after cooling. The lean glycol and lean solvent can be mixed using static mixers in order to inject with a single set of nozzles.
1. A process for separating diamondoids from a vapor phase of a multi-component gas stream, the process comprising:
contacting the multi-component gas stream with a lean solvent;
cooling the gas and lean solvent mixture to less than 0° F. in one or more heat exchangers; and
separating therefrom a diamondoid rich solvent from the vapor phase,
wherein the vapor phase comprises less than 1 pound/MMscf diamondoids.
2. The process of claim 1 , wherein the multi-component gas stream comprises methane.
3. The process of claim 1 , wherein the multi-component gas stream comprises one or more components selected from the group consisting of hydrogen, nitrogen, helium, argon, methane, ethylene, ethane, heavier saturated and unsaturated hydrocarbons and mixtures thereof.
4. The process of claim 1 , wherein the multi-component gas stream is contaminated with water, and ethylene glycol solvent is injected into the gas to prevent hydrate and ice formation.
5. The process of claim 4 , wherein the ethylene glycol and lean solvent are mixed prior to injecting into the multi-component gas.
6. The process of claim 1 , wherein the lean solvent is diesel solvent, kerosene solvent, aromatic solvent, paraffinic solvent, or naphthenic solvent.
7. The process of claim 1 , wherein the multi-component gas stream is natural gas, coal gas, refinery gas, or gas from chemical plants, or other hydrocarbon containing gases.
8. The process of claim 1 , wherein the lean solvent is regenerated by distilling or stripping diamondoids from the diamondoid rich solvent.
9. The process of claim 1 , wherein the diamondoid rich solvent is recirculated without regeneration, and a purge/make-up arrangement is used to control diamondoid concentration in the solvent.
10. The process of claim 1 , wherein the heat exchangers are shell and tube exchangers, and the multi-component gas is fed to the tube side.
11. The process of claim 10 , wherein the lean solvent is injected into the mulicomponent gas stream using one or more spray nozzles located at the entrance of the heat exchanger or in the head of the exchanger.
12. The process of claim 1 , wherein the heat exchangers are plate-fin exchangers, and the lean solvent is introduced into each channel of the exchanger.
13. The process of claim 1 , wherein the lean solvent is the same solvent used for an upstream diamondoid removal system operating at higher temperature.
14. The process of claim 8 , comprising a solvent regeneration system shared between an upstream system and the process for separating diamondoid components.
15. The process of claim 1 , further comprising contacting the vapor phase with a lean solvent in a multistage absorption tower.
16. The process of claim 15 , wherein the multistage absorption tower is operated at conditions below atmospheric temperature but above the coldest point of the multi-component gas stream cooling.
17. The process of claim 1 , where in the gas and lean solvent mixture is cooled to less than −25° F. in one or more heat exchangers.
18. The process of claim 1 , wherein the separation of the diamondoid rich solvent from the vapor phase occurs in a three-phase separator.
19. The process of claim 1 , wherein the one or more heat exchanger is a plate-fin aluminum or stainless steel exchanger.