Process to remove mercury from monoethylene glycol streams

Abstract

A process for removing mercury from a stream containing monoethylene glycol (MEG) in an oil or gas production process is provided. The method includes adding an additive to the stream containing the MEG and mercury. The additive is a component capable of coagulating the mercury, such as a dithiocarbamate derivative. The method further includes filtering the stream containing the MEG after adding the additive to the stream to remove the coagulated mercury. The filtering step is typically conducted in a hydrophilic filter having a pore size ranging from 0.45 micron to 30 microns, preferably 10 microns to 20 microns. After the filtering step, the stream typically includes less than 50 ppb of mercury.

1 . A process for removing mercury from a stream containing monoethylene glycol (MEG), comprising the steps of:
 in a hydrocarbon production facility:
 adding an additive to the stream containing MEG and mercury, wherein the additive coagulates, binds, and/or agglomerates the mercury; and 
 filtering at least some of the coagulated, bound, and/or agglomerated mercury out of the stream containing the MEG after adding the additive to the stream to produce a mercury-depleted stream. 
   
     
     
         2 . The process according to  claim 1 , wherein the additive is a dithiocarbamate derivative. 
     
     
         3 . The process according to  claim 1 , wherein the additive includes at least one of sodium chloride, sodium sulfide, and sodium hydroxide. 
     
     
         4 . The process according to  claim 1 , wherein the mercury in the stream is in particulate form. 
     
     
         5 . The process according to  claim 1 , wherein the stream includes the MEG in an amount of at least 40 wt. %, based on the total weight of the stream. 
     
     
         6 . The process according to  claim 1 , wherein the additive is added in an amount of 250 ppb to 1000 ppb. 
     
     
         7 . The process according to  claim 1 , wherein adding the additive to the stream containing MEG and mercury comprises adding the additive into a conduit containing the stream upstream of a vessel, the vessel being a flash drum or a storage drum. 
     
     
         8 . The process according to  claim 1  comprising mixing the additive with the stream for a period of time within a vessel. 
     
     
         9 . The process according to  claim 8 , wherein the mixing step includes mixing the additive and the stream for 10 minutes to 30 minutes. 
     
     
         10 . The process according to  claim 1 , wherein the filtering step is conducted using a filter having a pore size ranging from 0.45 micron to 30 microns. 
     
     
         11 . The process according to  claim 10 , wherein the filter pore size ranges from 10 microns to 20 microns. 
     
     
         12 . The process according to  claim 1 , wherein the filtering step is conducted using a hydrophilic filter. 
     
     
         13 . The process according to  claim 1 , wherein the mercury-depleted stream includes less than 50 ppb of mercury. 
     
     
         14 . The process according to  claim 1 , wherein:
 the mercury of the stream is in elemental or particulate form;   the stream is a rich stream and includes the MEG in an amount ranging from 40 wt. % to 80 wt. %, based on the total amount of the stream, and a balance of water;   the additive is in liquid form;   the additive is a dithiocarbanate derivative;   the additive is added in an amount of 250 ppb to 1000 ppb;   the filtering step is conducted in a filter having a size ranging from 10 micron to 20 microns;   the filter is a hydrophilic filter;   the additive is mixed with the stream for 10 minutes to 30 minutes before the filtering step; and   the mercury-depleted stream includes less than 50 ppb of mercury.   
     
     
         15 . A process for producing natural gas, comprising the steps of:
 adding an additive to a rich stream containing alkylene glycol and mercury, wherein the additive coagulates the mercury;   filtering at least some of the coagulated mercury out of the rich stream after adding the additive to the rich stream to produce a mercury-depleted rich stream;   distilling the mercury-depleted rich stream containing alkylene glycol to produce a lean stream containing alkylene glycol; and   combining the lean stream containing alkylene glycol with a natural gas stream to prevent hydrate formation in the natural gas stream.   
     
     
         16 . The process according to  claim 14  including separating the rich stream containing alkylene glycol and mercury from a mixture of the rich stream, natural gas, and hydrocarbons prior to adding the additive to the rich stream. 
     
     
         17 . The process according to  claim 14 , wherein the step of adding the additive to the rich stream occurs after the rich stream passes through a flash drum. 
     
     
         18 . The process according to  claim 14 , wherein the alkylene glycol in the rich stream is present in an amount ranging from 40 wt. % to 80 wt. %, based on the total amount of the rich stream, and a balance of water; and the alkylene glycol is present in the lean stream in an amount ranging from 60 wt. % to 90 wt. %, based on the total amount of the lean stream, and a balance of water. 
     
     
         19 . The process according to  claim 14 , wherein the additive is a dithiocarbamate derivative and is added in a total amount of 250 ppb to 1000 ppb. 
     
     
         20 . The process according to  claim 14 , wherein the filtering step is conducted in a hydrophilic filter having a pore size ranging from 10 microns to 20 microns.