|We are introducing new biocoagulants.
Aquero Company is introducing some fully biodegradable and environmentally
friendly coagulants for water clarification applications. Below is some information about coagulants and their use.
In oilfield recovery operations, water is used for many purposes. During many of these, a leftover stream of
produced water is generated. The produced water often occurs as a stable reverse (oil-in-water) emulsion that needs
to be cleansed prior to recycling and re-use.
The emulsified, micron and sub-micron sized oily droplets
in water are stabilized owing to their own partially ionic character, typically partially anionic. There are residuals
of many complex hydrocarbons that contain carboxylic groups and sometimes sulfated or sulfonated residues and the like.
They are too hydrophobic to be soluble, at least most of them are like this, and they don't separate well during the separation
of the product oil and the water, so they end up in the produced water stream. Usually, they are present along with
some micro clays and other solids like sand particles, as a few tenths of 1 % by weight, although sometimes the emulsified
oily solid content is a lot higher than this.
The emulsified oily phase is thought to consist of the anionic
groups facing outward toward the bulk phase of the water, with the hydrophobic parts inward, forming tiny micelles.
These are dispersed from one another via the anionic charge repulsion, and hence the stable emulsion.
A first step,
and often the only step in commonly encountered chemical treatment protocols, is to attempt to neutralize the charge repulsion
and thus destabilize the emulsion. This is what coagulants are supposed to do.
The most commonly used coagulants
in oilfield applications are polycationic, vinyl petro-polymers like the copolymer of epichlorohydrin and dimethyl amine
(polyEPI/DMA). If the right amount of a polycation is added to cover up enough of the anionic charges, the oily micelles
begin to be drawn toward each other through hydrophobic attraction. At this stage, the water begins to clarify with
micron-sized oily particulates as one phase and clearer water as another.
This is OK, but the solid phase is very
easily stirred, and can be re-emulsified if conditions are too turbulent in the process stream. This occurs because
the polycations normally only cover up a relatively small fraction of the anionic charges that are thought to be located at
the outer surface of the micelles. The interior of the micelles are not neutralized and can be re-exposed under shear
forces. This restores the reverse emulsion, only now it is more complex and harder to fix.
encountered problem is that the distribution of oily solids in water can be converted from an anionic dispersion to a cationic
dispersion if the dose of the polycationic coagulant becomes too high. A operator naturally has the tendency
to increase the dose if the water isn't responding very well for one reason or another, and often this is the wrong move.
Such a stable, reverse emulsion that has been "flipped" from anionically dispersed to cationically dispersed is
even harder to fix.
|SAGD produced water treated with 100% biodegradable coagulant
Another thing to keep in mind about polycationic coagulants is that the covering of cells and
cellular components (like cell walls, cell membranes, membranes of organelles) are almost invariably net-anionic in character.
This means that polycations tend to stick very nicely to living things, often disrupting cellular processes. In fact,
many biocides and biostats are polycationic for this reason.
This leads to concerns about over-use and release
of non-degradable polycations to the environment. Currently, there are ongoing debates about this, made more serious
in view of the very large scope of water use in the oil-sands region for example and in oilfield operations in general.
What are the unintended effects, if any, of the use of heavy doses of non-degradable polycations? What
is their fate
in the environment?
Aquero Company is offering alternative materials for this class of
chemicals. The Aquero polycats are being offered under the Aquial tradename. The compositions of matter, their
methods of synthesis, methods of commercial production, and uses are patent-pending.