Dynamic Adsorbents “DrysphereTM” activated alumina
and dessicant offers the best
drying and regeneration properties on the market today.
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What is DrysphereTM?
Dynamic Adsorbents has built upon excellence
in design and manufacturing by creating superior uniform alumina
spheres demanded for the drying of industrial liquids and gases.
These spheres offer superior drying and regeneration properties
and are known as DrysphereTM. These proprietary alumina
spheres are manufactured as specialized desiccant agents.
DrysphereTM is a form of activated alumina
manufactured by a novel production process. It works as a
desiccant through the process of adsorption. The superior
adsorption is achieved by the hydrophilic characteristics, the
design of the microporosity and the extent of the achieved
surface area.
What is Activated Alumina?
Activated alumina is manufactured from
aluminum hydroxide by dehydroxylating it in a way that produces
a highly porous material. This material yields a surface area of
between 120-250 square meters per gram of material. Activated
aluminas do not soften or disintegrate when immersed in liquids.
A high internal surface area through the presence of pores or
micropores is necessary to create adsorption sites.
What are Desiccants?
Desiccants and sorbents are specialized
moisture absorbing minerals or chemicals. Alumina, silica gel,
calcium sulfate, barium oxide, lithium chloride, perchlorates
(such as lithium, barium or magnesium perchlorate) and molecular
sieves such as zeolite are commonly used as desiccants. These
materials are used as desiccants because they possess both high
water adsorption capacities as well as favorable water
adsorption isotherm shapes. (discussed below) The water
adsorption capacity of these materials varies from 20 to 50 wt
%.
Desiccants attract moisture from gases and
liquids. The desiccant material becomes saturated as moisture is
adsorbed onto its surface. The best adsorbents will therefore
have the greatest surface area available for adsorption.
Superior adsorbents are designed to maximize the available
surface area for moisture removal. DrysphereTM by Dynamic
Adsorbents, Inc. is designed to increase surface area by
containing multiple channels and pores which dramatically
increase the available surface area for physical and chemical
interaction.
How are Desiccants and Sorbents Different?
Desiccants and sorbents are related
products, but differ. Sorbents recover liquids through
absorption, adsorption and chemically react with or otherwise
remove water. Absorbents retain liquid through the molecular
structure, causing more than 50% swelling. Adsorbents are coated
by a liquid on the surface (including pores) without swelling
more than 50%. Adsorption is a phenomenon which involves the
fixation of a material present in a fluid on a solid. A
selective mass transfer occurs between these two phases. Since
adsorption is a surface phenomenon the best adsorbents have
large surface areas per unit mass and high attractive forces for
the compounds they are adsorbing.
Desiccants and sorbents differ in how
performance is measured. One unit of desiccant will adsorb 3
grams of water vapor at 20% relative humidity, or 6 grams of
water vapor at 40% relative humidity at 77 C. To achieve very
dry air, a dehumidifier desiccant can be rotated through process
air and heated to remove moisture. Desiccants can be reactivated
using heat as the method to remove captured moisture, thus
allowing the desiccant to once again become fully activated.
Superior desiccant materials such as alumina break down slowly
and therefore can be used and regenerated multiple times.
How Does One Determine How Much Moisture Can Be Removed?
The water content of a gas is defined as the
weight or volume of water vapor per unit weight or volume of
gas. This is expressed as parts per million weight (ppmw) or
parts per million volume (ppmv). For any given temperature water
content can also be expressed by its relative humidity, which is
defined as the ratio of its partial pressure to its saturation
pressure.
The water adsorption isotherm relates the
equilibrium amount of water adsorbed onto a solid and the water
content in a fluid at any constant temperature and pressure. The
amount of water trapped on a solid at a given relative humidity
and temperature depends on its chemical affinity for the solid
and the number of available sites for interaction. The capacity
of a desiccant for water is expressed as the mass of water
adsorbed per mass of desiccant.
Water adsorption is a combined result of
three phenomena:
-
Chemisorption
-
Physisorption – hydrogen bonding
with some surface forces (Van der Waals’ forces) due to the
formation of multiple layers by hydrogen bonding in the
pores of the desiccant.
-
Capillary Condensation – growth
of multilayers of water (Kelvin’s law) where localized
condensation takes places at temperatures above that of the
bulk fluids dew point.
As the relative humidity begins to increase
the first step in the process of adsorbing a liquid or gas onto
a solid is chemisorption with a monomolecular layer forming on
the surface of the adsorbent. As the relative humidity
increases, the less active sites adsorb water more gradually,
with the monolayer completely bound when the relative humidity
reaches approximately 10%. At this point multilayers of water
vapor form, reflective of the fact that physisorption is taking
place. When the water vapor pressure (relative humidity) reaches
40% the pores begin to fill in by capillary condensation. When
the relative humidity of the inlet gas attains 100% and the bed
is in equilibrium there is no further adsorption through these
three mechanisms of adsorption and complete saturation occurs.
Alumina and other materials used as
desiccants have water adsorption isotherms that are concave to
the pressure axis, particularly at low pressure, which helps in
forming short, sharp mass transfer zones.(see below) These
materials are polar, and as such they selectively adsorb polar
molecules like water and alcohol, even though they adsorb all
liquid and gases to some extent. For example, water as a polar
compound is more strongly adsorbed than hydrocarbons.
How Much Desiccant is Required for Any Given Job?
The amount of desiccant required depends on
several factors including the amount of water present, the
capacity of the selected desiccant to take up water, and the
presentation of the desiccant relative to the components
containing water. Stream conditions such as pressure,
concentration and molecular weight of the molecules, temperature
and site competing molecules affect the efficiency of
adsorption.
What is the Adsorption Capacity?
Adsorption capacity is defined as the
accumulation of the solute molecules at the surface of a solid.
This capacity is directly proportional to the area of the
surface exposed and is dependent on the solute partial pressure
and the temperature.
An increase in temperature reduces the
adsorption capacity of activated alumina as the adsorption of
water on alumina is exothermic.
Adsorption capacity depends on the surface
site reactivity and is measured by the volume of adsorbed water
per unit of surface area. Water in the air actually sticks to
the alumina itself in between the tiny passages as the air
passes through them. The water molecules become trapped so that
the air is dried out as it passes through the filter. This
process is reversible, and when the alumina desiccant is heated
to between 350-600 F (177-316 C) it releases all of the water
stored inside it. The process of heating the activated alumina
is called regenerating the desiccant.
When a gas is compressed the partial
pressure of the water present increases. At a constant
temperature the adsorptive capacity for water increases with
increasing water partial pressure (and relative humidity).
Desiccants are manufactured to meet
standards such as “Standard Methods of Testing Sorbent
Performance of Absorbents” published by ASTM International, as
well as other US government standards.
Water removal from ambient air is the
important first step in the production of nitrogen enriched gas
from nitrogen containing gas mixtures such as air. This need for
water removal is essential for all gas separating processes
including cryogenics, membrane permeation and adsorption
techniques.
DrysphereTM is the
Superior Dessicant.
DrysphereTM is the superior dessicant for
the following industrial applications:
-
Purification of gases and liquids.
Water removal is necessary for efficient processing, storage
and transportation of fluids
-
Drying of organic liquids such as LPG,
butane, steam cracked liquid, aromatics, cyclohexane,
gasoline, chloro and fluoro hydrocarbons and aromatic
solvents
-
Drying of air and gases such as steam
cracked gases, catalytic reforming recycle gas, natural gas
and carbon dioxide
-
Desiccants which can be used in
compressed air dryers include activated alumina, silica gel and
molecular sieves. Compressed air dryers utilize activated
alumina as desiccant agents to remove moisture from compressed
air. The compressed air first passes through an aftercooler, air
receiver and coalescing filter before reaching the desiccant
drying site. At each point water is removed from the compressed
air via drain valves. The compressed air enters the compressed
air dryer and comes in contact with the desiccant in the
desiccant chamber. The desiccant removes the moisture from the
compressed air via adsorption. Once downsteam of the compressed
air dryer the compressed air’s dew point is generally – 40 F.
(The dew point is the measure of the amount of water contained
in the air). Particle filters downstream of the desiccant dryer
capture any desiccant fines and dust before the compressed air
enters production.
-
Catalyst for Claus conversion in sub dew
point processes in the purification and drying of compressed air
-
Natural gas in production and compression plants – liquid
petroleum gas, liquid nitrogen gas
-
Drying agent for aromatics, naphtha
cuts and cracked gas in petrochemical industries
Substances commonly dried with DrysphereTM
include:
Gases
-
Acetylene Ethane Hydrogen chloride Oxygen
-
Air Ethylene Hydrogen sulfide Propane
-
Ammonia Furnace Gas Methane Propylene
-
Carbon Dioxide Helium Natural Gas Refrigerants
-
Chlorine Hydrogen Nitrogen Sulfur dioxide
Liquids
-
Benzene Ethyl acetate Lubricating oils Refrigerants
-
Butane Gasolines Naptha Styrene
-
Butene Heptane Nitrobenzene Toluene
-
Butyl acetate Hexane Pentane Transformer oil
-
Carbon tetrachloride Hydraulic oils Pipeline products Vegetable
oil
-
Chlorobenzene Jet fuel Propane Xylene
-
Cyclohexane Kerosene Propylene
-
Drying of hydrogen, oxygen, nitrogen and
carbon dioxide
Uniform ball size (spheres of consistently
standard sizing) are essential in high pressure gas dehydration
where it is important to minimize pressure drop, such as in a
packed bed. Dynamic Adsorbents, Inc.’s DrysphereTM activated
alumina, being carefully quality controlled, provides low
pressure drops, and in so doing minimizes channeling while
liquids and gases travel through the packed bed adsorbent
chamber. Uniform sphere design maximizes the ability to use the
entire packed adsorbent bed to maximum efficiency
What are the Benefits in Using DrysphereTM
for Your Desiccant Needs?
|
Kinetic Properties |
|
30 minute exposure to 97% |
| |
Weight % Gain |
| DrysphereTM |
3.5% |
| P2O5 |
3.0% |
| CaSO4 |
2.6% |
| Silica Gel |
2.3% |
| Alumina |
1.6% |
|
Kinetic
Exposure Tests |
| |
Relative Humidity |
| Static @ 11% |
12 |
|
Adsorption @ 58% |
22 |
| Weight @ 97% |
36 |
|
Physical
Properties |
| Abrasion Loss (wt%) |
0.1 |
| Crush Strength (lb) |
30 |
| Bulk Density
(lbs./ft3) |
48 |
High crush strength
The advantage of
having high crush strength is that this allows for rapid
pneumatic loading, and in so doing allows the dessicant to
dehydrate acid containing gases and liquids such as C02 for long
operating life. DrysphereTM is manufactured with very high
resistance to attrition and crushing. These goals are attained
by the specifications of the manufacturing process and the
spherical shape of the beads.
Acid Removal
Transformer oils, lubricating
oils and refrigerants form degradation acids. DrysphereTM
removes these acids during use. In the manufacture of chlorinated
and/or fluorinated hydrocarbons, removal of these residual
halides and water is essential for non corrosive final products.
Packaging
DrysphereTM is easy to pack and
very convenient to use.
Dust-free
DrysphereTM is provided in a
dust-free configuration. They will not contaminate gas/liquid
streams with particulates. The same material can be scaled up
from lab and pilot to full industrial process applications.
High Capacity
Adsorbs 36% of its own
weight, three times more than standard alumina, 20% more than
silica, and 32% more than competitive products. DrysphereTM also
obtains drier samples, faster, for a longer period of time,
reducing downtime in the industrial production of gases and
liquids.
Wide Scope
As noted above DrysphereTM
is
indicated for use with a wide spectrum of gases and liquids.
They dehydrate acidic gases and liquids without softening or
breakage.
Adsorptive Properties
DrysphereTM cleans organcs while it dries and preferentially adsorb high polarity
impurities.
Example for the Industrial Usage of DrysphereTM
The following example is provided for the
use of DrysphereTM for petrochemical purification
Halogenated butyl rubbers were essential for
the development of the tubeless tire. In the manufacture of
halogenated butyl rubber residual amounts of isoprene and
isobutylene monomer are also halogenated. When the halogenation
is carried out in a solvent, the organic halides become
concentrated in the solvent and ultimately the concentration of
organic halides in the final rubber product increases. One
particular halide produced during the manufacture is MDBCP
(methyl dibromo chloro propane) which is highly toxic,
potentially carcinogenic and causes male sterility. This can be
removed by contacting the hydrocarbon solvent with an activated
alumina such as DrysphereTM.
While a wide variety of compounds will
remove halides to some extent from a hydrocarbon stream
activated alumina has been demonstrated to be the most effective
adsorption medium. The hydrocarbon stream is pumped through a
vertical bed of activated alumina. Halides can be removed from
the liquid hydrocarbon stream in a single pass through a bed of
alumina at a flow rate of one volume of hydrocarbon to one
volume of alumina per hour. Increasing the temperature speeds up
the rate of halide removal.
A superior method for removing the halides
from process streams is by gas phase adsorption in a packed bed
of activated alumina DrysphereTM. The
adsorption is carried
out at about – 50 C to about 20 C. The adsorbed halides are
stripped from the adsorption stage at about 100 – 400 C.
Another example for using DrysphereTM lies
in the production of methyl chloride and methylene chloride by
the oxy chlorination of methane. The chlorides are recovered by
gas phase adsorption in beds of activated alumina.
Under the proper operating conditions, the
pore size distributions and surface chemistry of activated
alumina is ideal for the adsorption of hydrocarbons. Dynamic
Adsorbents, Inc. can help you in designing the ideal desiccant
chamber design and surface chemistry characteristics for your
hydrocarbon requirements.
To address industrial needs Dynamic
Adsorbents has developed DrysphereTM which is a novel, dust
free, spherical activated alumina manufactured and designed to
optimize desiccant performance.
What are the Sizing Recommendations for
Alumina Sphere?
Spheres measuring 4-6 mm are recommended for
vapor phase dehydration applications where one desires high
water adsorptive capacity yet pressure drop must be kept to a
minimum
Spheres smaller than 3 mm are recommended
for liquid dehydration and other mass transfer limited
adsorption applications
DrysphereTM Material Safety Data Sheet
Click here to view the Material Safety Data
Sheet in PDF format.
Download Brochure - English (PDF) |
Spanish Version (PDF)
