Kinetic Inhibitors are a new and evolving technology of a class of Low Dosage Hydrate Inhibitors (LDHI) that are
polymers
A polymer (; Greek '' poly-'', "many" + ''-mer'', "part")
is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic an ...
and
copolymers
In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are some ...
(or a mix thereof). The most common of which is
polyvinylcaprolactam (PVCap).
[ Kelland, Malcolm et al. A New Class of Hydrate Inhibitor. 2000. http://www.iris.no/internet/student.nsf/199f312efd2a0cacc125680e00635b85/b58dcb01591e3feac125768f004f4a66/$FILE/Fagernes%20paper.pdf] These inhibitors are primarily utilized to retard the formation of
clathrate hydrates. This problem becomes most prominent in
flow lines
Flow may refer to:
Science and technology
* Fluid flow, the motion of a gas or liquid
* Flow (geomorphology), a type of mass wasting or slope movement in geomorphology
* Flow (mathematics), a group action of the real numbers on a set
* Flow (psych ...
when hydrocarbons and water flow through a line. The pressure and cold temperatures that could be exposed to the flow lines provides an environment in which clathrate hydrates can form and plug up the flow line. The inhibitors generally slow the formation of the hydrates enough so the fluid reaches storage without causing blockage.
Structure
There may be variations on the types and structure of the polymer used as the inhibitor. However, in general, while the gas hydrate is forming, the cavity where the hydrocarbon usually resides. Instead, the
alkyl
In organic chemistry, an alkyl group is an alkane missing one hydrogen.
The term ''alkyl'' is intentionally unspecific to include many possible substitutions.
An acyclic alkyl has the general formula of . A cycloalkyl is derived from a cycloa ...
group penetrates the cavity followed by the
carbonyl
In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containi ...
group of the
amide
In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula , where R, R', and R″ represent organic groups or hydrogen atoms. The amide group is called a peptide bond when it i ...
group
hydrogen bonding to the surface of the hydrate, thus preventing the formation of hydrates.
Uses
These inhibitors chemically retard the formation of clathrate hydrates. Dosage of such inhibitors in the fluid is usually .3% to .5% by weight of the fluid, compared to 10% to 50% by weight for
thermodynamic inhibitors for prevention of clathrate formation.
Due to this and other factors, kinetic inhibitors are more cost effective than thermodynamic inhibitors. However, if the fluid is in a static environment (i.e.
packer fluid), kinetic inhibitors will have limited effect as hydrates will still form over sufficient time.
[Frostman, Lynn. Anti-Agglomerant Low Dosage Hydrate Inhibitors. 2000. http://www.coqa-inc.org/add20010531LDHI.pdf] At this point the only viable option is thermodynamic inhibitors.
References
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Fluid mechanics