THE
COMPANY
Grupo
Primex began its operations in 1968 and has occupied
an international market position since 1983. It is
a part of AXA-Yasaki, a large Mexican industrial conglomerate
currently made up of 18 companies, with a total of 27
production plants and distribution centers operating
in Mexico, the United States, Argentina and Brazil.
Grupo
Primex currently has four process plants for polyvinyl
chloride (PVC) resins and compounds, phthalic anhydride,
dioctyl phthalate plastifiers (DOP) and trioctyl trimethylate
(TOTM), with an annual production of 450,000 tons.
Its petrochemical complex is located at Altamira in
the southern part of the State of Tamaulipas, and it
is considered to be the largest company of its kind
in Mexico. It is the domestic market leader and exports
40% of its annual production to the United States, England,
Germany, Italy, Japan, South Africa and Australia.
The
vision Grupo Primex has is:
- To
be a generator of wealth with worldwide leadership
in satisfying its customers;
- To
be the lowest price producer and to maintain an international
focus in managing its business; and
- To
be a company that is committed to its statements and
principles.
THE
PROJECT
Grupo
Primex found out that its DOP plastifier was picking
up an odor during the manufacturing process. Since
its main use is in food packing and specifically in
the manufacture of plastic cap liners, this is an undesirable
feature in DOP because it contaminates the packed food.
For this reason, a project was begun for obtaining a
food grade DOP, which means that it must be odorless
and flavorless. The DOP also needed to have certain
physical features such as a percentage of humidity of
0.05 or less, and less than 150 ppm of alcohol.
DESCRIPTION
OF THE PROCESS
The
manufacturing process for DOP plastifier consists of
the following stages:
1)
Raw Material Loading. This consists of loading the
raw materials (phthalic anhydride and alcohol) into
the reactor.
2)
Heating up to Catalyst Loading Temperature. Here,
heat is transferred to the reaction through a coil and
jacket in the reactor to enable the catalyst to work.
3)
Reaction. This is the chemical reaction between
the phthalic anhydride, alcohol and catalyst for making
the plastifier.
4)
Cooling of Plastifier. Heat is removed from the
reaction product by running steam through the reactor
coil.
5)
Neutralization. A chemical base (pH over 7) is
added to eliminate final acidity in the product.
6)
Unloading Reactor. This consists of sending the
product from the reactor to a treatment tank (tank Blow
Down).
7)
Alcohol Recovery. Vacuum pressure is applied in
the tank itself, which causes the temperature to rise
to 176 ºC. This causes the alcohol to evaporate, which
is exhausted through a pipe to a storage tank for use
in a prior stage.
8)
Distilling. This stage consists of running steam
through the plastifier to pull the remaining alcohol
out of the product. This is accomplished in a two hour
period and uses approximately 4,000 kg/hr of steam at
maximum vacuum.
9)
Cooling. This is accomplished by condensing in
which the plastifier is cooled down to 115 °C, then
demineralized water at low temperature is run through
the coil.
10)
Washing. This is accomplished by running two tons
of demineralized water through the plastifier for removing
impurities from it.
10)
Drying. Drying is done by heating the product to
145 °C at maximum vacuum to remove moisture from it.
It should be emphasized that according to staff from
the PRIMEX production department, this heating encourages
oxidation in the plastifier, thus causing an odor to
be generated in the resulting DOP.
11)
Tank Unloading. Product is removed by tank Blow
Down at 145 °C and it is sent to a treatment tank where
additives are put in and it then goes to filtering.
12)
Filtering. The product is run through a porous
medium to remove solid residue. This system consisted
of filtering in an uncovered tank (in contact with the
atmosphere), either through a valve or by venting.
DOP
Manufacturing Flowchart
Finished
product 
ECOEFFICIENCY
STRATEGY APPLIED
After
studies were made by the company, process changes were
put in place that brought about a significant decrease
in carbon dioxide (CO2) emissions to the
atmosphere, which shows the environmental tack taken
by this project developed by the company. It is important
to mention that there was no need for making any initial
investment, because the only thing that was done was
to make process changes that did not cost anything.
Process stages were changed to be as follows:
- Recovery:
Recovery temperature was changed to 178 °C and vacuum
pressure was increased.
- Distilling:
This stage was not changed at all, and it is still
accomplished in two hours by using approximately 4,000
kg/hr of steam at maximum vacuum..
- Cooling:
Condensing through the reactor coil is still being
used, but it is now being cooled to 125 °C. Washing
is performed by using the same amount of demineralized
water.
- Drying:
Heating is no longer used for drying. Cold nitrogen
is now being used (approximately 87 cubic meters at
105 °C, because that is its temperature after washing)
to carry off moisture and discourage product oxidation
as was happening before, and also by using maximum
vacuum at this stage.
- Unloading:
Unloading is now done at 95 °C, which is the temperature
at which the product comes out after drying, because
the nitrogen also cools the product in addition to
drying it.
- Filtering:
There is currently a hatch sealing the tank and leading
to a pipeline to keep the system inert, and in this
way contact between the product and oxygen in the
environment is avoided and thus, oxidation of the
product.
With
these changes, a significant improvement in CO2
emissions was achieved as a result of making steam in
the process by using a boiler with 80% efficiency, which
brought about a natural gas (CH4) use decrease
of 569,400 cubic meters. This also resulted in avoiding
the emission of an approximately 55,235 cubic meters
of CO2 into the atmosphere, which is the
main cause of global heating on the planet.
Daily
nitrogen consumption increased from 740 a 800 cubic
meters, but unlike natural gas, nitrogen use in drying
does not have any adverse impact on the environment.
FINANCIAL
BENEFITS
The
financial benefit is mainly from the savings represented
by decreased steam generation and by replacing this
with the use of nitrogen in the drying stage for the
plastifier, and the following cash flow benefit has
been achieved on an annual basis:
|
Raw
Material
|
Cost
(US $/year)
|
Saved
(US$/year)
|
|
|
Methane
|
|
44,800
|
|
|
Nitrogen
|
8,200
|
|
Total
Savings
|
|
|
|
|
36,600
US$/year
|
CONCLUSIONS
Results
achieved with this project were better than expected.
The original aim was to obtain odorless DOP. A study
was done with this goal in mind, and the DOP that was
desired was obtained with zero investment. Costs were
also substantially decreased, thus providing a significant
annual cost savings. This ecoefficiency program was
also positive in its results because in addition, this
savings in methane gas brought about a substantial decrease
in carbon dioxide emissions into the atmosphere.
GLOSSARY
Plastic
Cap Liners: Used as lining inside caps for bottles,
jars, etc.
Coil
: Coiled tubing installed around the center paddle
shaft of the tank and reactor but not touching it, used
for running fluids through it to either cool or heat
the product in the container through a convection process.
Blow
Down tank: Multiple treatment tank where the finished
product acquires its final characteristics.
CONTACT
Ing.
Martín Conde Carreño
Safely
& Environmental Superintendent
km
4.5 Autopista Altamira - Tampico
Nuevo
Puerto Industrial
Altamira,
Tamaulipas, Mexico
Tel.
(52 1) 229 0115
Fax.
(52 1) 260 0066
e-mail:
mconde@gpoprimex.com
