Patent Application
20250179381
This disclosure relates to a process for removing mercury from a stream containing monoethylene glycol (MEG), such as a stream used to prevent hydrate formation in a pipeline during the transportation of natural gas.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
During the production and transportation of oil and gas, such as natural gas, hydrates oftentimes form due to low temperatures and conditions in the pipelines and wells. Hydrates can be problematic as they can plug pipelines used in the production and transportation process. To avoid formation of the hydrates, monoethylene glycol (MEG) can be injected into the pipelines and wells. During the production process, the production fluid, for example the fluid containing the natural gas, the injected MEG, and water travel through a slugcatcher. After leaving the slug catcher, the fluids pass through a stabilizing feed separator and to a flash drum to separate gas and hydrocarbon liquids from the monoethylene glycol (MEG) and water mixture. The mixture of MEG and water is referred to as “rich MEG.” The gas and hydrocarbons are transferred to shore for further processing while the MEG and water mixture continues on. Water is then removed from the mixture to produce “lean MEG,” and the lean MEG is reused later in the production process.
One challenge associated with the production process is that the monoethylene glycol (MEG) stream can become contaminated with mercury associated with the produced hydrocarbons. Several techniques have been developed in an attempt to remove mercury from the MEG, but improved processes are desired.
A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.
One aspect of the disclosure provides a process for removing mercury from a stream containing monoethylene glycol (MEG). The process includes 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.
Another aspect of the disclosure provides a process for producing natural gas. The process includes adding an additive to a rich stream containing alkylene glycol and mercury, wherein the additive coagulates the mercury. The process also includes 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.
The process according to the present disclosure is able to more efficiently remove a significant amount of mercury from the monoethylene glycol (MEG) stream, compared to other techniques and processes used to remove mercury from monoethylene glycol (MEG) streams. According to example embodiments, the process can efficiently reduce the amount of mercury present in a rich monoethylene glycol (MEG) stream to an amount of less than 50 ppb.
The drawing described herein is for illustrative purposes only of selected embodiments and is not intended to limit the scope of the present disclosure. The inventive concepts associated with the present disclosure will be more readily understood by reference to the following description in combination with the accompanying drawing wherein:
The disclosure generally relates to a process for removing mercury from a stream containing an alkylene glycol, such as monoethylene glycol (MEG), for example during the production or transportation of hydrocarbons (e.g., oil and/or gas). The process for removing mercury will be described in the present disclosure with reference to a natural gas production process that uses MEG, although the process could be applied to another type of oil or gas production process and/or another process that uses another glycol such as tri-ethylene glycol (TEG).
The transportation of natural gas typically occurs in pipelines which are at very low temperatures. Due to the low temperature, hydrates can accumulate in the pipelines, which can clog the pipelines and impede the flow of the production fluid, which contains the natural gas. In order to inhibit hydrate formation, an alkylene glycol, for example MEG can be injected into the pipelines.
As indicated above, the MEG can become contaminated with mercury (Hg), which is typically in the form of particulates but can be in elemental form as well. To remove the mercury, in accordance with certain embodiments an additive 17 can be injected into the rich MEG stream 10b at various injection points 18 in the system. Example injection points 18 are shown in
The additive 17 includes a component which is able to coagulate, bind, and/or agglomerate the mercury present in the rich MEG stream 10b. According to example embodiments, the additive 17 is a dithiocarbarnate derivative. For example, the additive 17 can be a derivative of polyethyleneimine from the condensation polymer prepared from ethylene-dichloride and ammonia, or a dithiocarbamate CS2-functionalized polymer. The additive 17 is typically added to the rich MEG stream 10b in an amount effective to reduce mercury down to a desired level, for example less than 100 ppb, less than 75 ppb, less than 50 ppb, or less than 25 ppb. As a non-limiting example, the additive 17 may be added to the rich MEG stream 10b in an amount of 250 ppb to 1000 ppb, and preferably about 500 ppb. The additive 17 is also typically in liquid form. By way of example, the additive 17 may be prepared as a concentrated solution (to a concentration of interest), and is subsequently injected at any one of a combination of the injection points 18. The addition of the additive 17 may be controlled by, for instance, a metering pump to control the flow rate of the additive 17.
As depicted in
After mixing the additive 17 with the rich MEG stream 10b, the rich MEG stream 10b moves through a pump 22 and to a filter 24 which removes the coagulated mercury from the rich MEG stream 10b and produces a mercury-depleted MEG stream 10c. The filter 24 has a pore size and material construction selected to remove the coagulated mercury from the rich MEG stream 10b. By way of non-limiting example, the filter 24 may have a nominal pore size ranging from 0.45 micron to 30 microns, and preferably 10 microns to 20 microns. The filter 24 is preferably a hydrophilic filter. In some embodiments, prior to the filtering step, the rich MEG stream 10b includes more than 50 ppb of mercury. After the filtering step, by way of non-limiting example, the mercury-depleted MEG stream 10c includes less than 50 ppb of mercury, which typically meets required standards.
After the filtering step, the mercury-depleted MEG stream 10c continues on in the process. The mercury-depleted MEG stream 10c is typically transferred to a distillation column (not shown) wherein water is removed from the mercury-depleted MEG stream 10c to produce a lean MEG stream (not shown). At this point, the lean MEG stream typically includes the monoethylene glycol (MEG) in an amount ranging from 60 wt. % to 90 wt. % and a balance of water, based on the total weight of the lean MEG stream. The lean MEG stream can be reused for hydrate prevention or in another process. For example, the lean MEG stream can be combined with natural gas for dehydration or other purposes.
The specific embodiments described above have been shown by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms, and can also be used in any appropriate combination. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure.
