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Gas Treating
Technologies |
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SPECIALTY AMINES VERSUS GENERIC: LOWER GAS TREATING COSTS |
Methyl Diethanolamine (MDEA) has become the amine molecule chosen
to remove hydrogen sulfide, carbon dioxide and other contaminants
from hydrocarbon streams. Amine formulations based on MDEA can significantly
reduce the costs of acid gas treating. Under the right circumstances,
MDEA based solutions can boost plant capacity, lower energy requirements
or reduce the capital required. The DOW Chemical Co. manufactures
Specialty Amine Solvents which are based on MDEA, but their formulation
includes other components that provide a higher level of performance
than MDEA alone. Most amine units can be readily converted to specialty
amines. The benefits of conversion can produce pay backs in less than
six months. It is therefore no surprise that hundreds of acid gas
treatment plants have converted from generic to specialty amines.
The term 'gas treating' covers many applications, each with its own
unique gas characteristics and with differing objectives for the treated
gas streams. Specialized MDEA based products were developed to answer
these needs. One key difference among the various specialty amines
is selectivity towards hydrogen sulfide, instead of removing both
hydrogen sulfide and carbon dioxide, as generic amines such as MEA
and DEA do, some products readily remove hydrogen sulfide to specifications,
but allow controlled amounts of carbon dioxide to slip through. |
Alternatively, products that are designed for carbon dioxide
removal are also available. For Example, DOW's Specialty Amines cover
the full range from the maximum carbon dioxide slip, to nearly complete
carbon dioxide removal.
Higher amine concentrations
Specialty amines can be used in concentrations of upto 50%. More corrosive
amines, such as MEA or DEA, are generally limited to a maximum of
15% and 30% respectively. With higher concentrations, the MDEA based
amines make more active amines available for acid gas removal. Therefore,
each gallon of solution has more gas treating capacity. As a result,
the gas treating ability of each plant is significantly increased.
This requires no plant expansion or expense in capital costs. Even
for plants that do not require expansion, specialty amines may still
be relevant. While maintaining current capacity, operating expenses
can be cut significantly, by reducing energy consumption. Each gallon
of solution has more gas treating capacity, Therefore operators can
reduce the circulation rate, and as a result, less power is needed
to operate the pumps. Energy savings also occur in the reboiler because
less energy is required to break the bonds between the acid gas and
the amine. This lower reaction heat requires less energy for regeneration.
The selectivity of MDEA based products can lead to more energy savings.
For example, allowing carbon dioxide to remain in the treated gas
reduces the amount of acid gas in the amine that needs to be regenerated,
thus reducing the amount of energy required.
New
plants require less capital
For Companies planning new plants, specialty amines can be used to
lower the capital investment required. When compared to generic amines,
companies can meet the same treated gas specifications for the same
volume of gas but with a much lower circulation rate. This allows
plant operators to use much smaller vessels, smaller pumps, smaller
pipes and smaller storage tanks. In addition, the lower corrosion
potential of MDEA can increase equipment life and reduce long term
maintenance costs.
If acid gas must be flared, incinerated, or otherwise processed for
sulfur recovery, the uses of specialty amines will often reduce treatment
costs. For example, using a selective amine product that allows carbon
dioxide to slip through the absorber yields reduced volumes of stripper
off-gas that are higher in hydrogen sulfide than gasses treated with
generic amines. Higher hydrogen sulfide concentrations and lower amount
of carbon dioxide in the stripper off-gas reduce fuel consumed in
flaring or incineration. In situations where the off-gas is processed
for sulfur recovery, this higher hydrogen sulfide concentration allows
more efficient Claus plant operation.
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