Xylene Recovery in the Toner Manufacture

Project Title:
Pollution Prevention at Nashua Corporation
Wilburn M. Miller
Home Phone: 603-654-2083
56 Robbins Road
Wilton, NH 03086
Nashua Corporation
44 Franklin St.
Nashua, NH 03061
Contact Person:
Pete Walsh
Project Engineer
Phone: 603-880-2482
Pete Walsh
Daryl Secrist
Lisa Grigg
Dave Shea
Executive Summary: Nashua Corporation wanted to reduce the
amount of waste it generates and prepare for future environmental
regulations. Nashua had three main projects: To obtain an
alternate outlet for recovered solvent which can not be reused,
investigate the production of waste in the developer
manufacturing process and research the current technologies
available to control the emissions from a particle coating
Background: Nashua Corporation has been trying to reduce its
production of waste solvent for several years. In the past they
have qualified the re-use of solvent into the processes where
possible and recently tried distillation in an attempt to purify
the solvents so they could be re-used within the company.
Unfortunately they were unable to achieve the needed quality to
allow for re-use and the project was terminated. Nashua would
like to continue trying to reduce the amount of solvent it ships
as waste and would like to explore other options available.
Nashua Corp has also been trying to reduce the amount of raw
material which becomes waste. They have already set up a system
to follow the production of toner. This allows Nashua to know the
product yield and more accurately determine the cost of toner
manufacturing. They would like to set up a similar system for
the developer manufacturing group.
It is important for Nashua Corporation to remain in
compliance with all EPA and DES regulations. Currently Nashua
does not operate any equipment which falls under EPA or DES VOC
emission restrictions, but they do have one machine that could
some day fall under such restrictions. If this equipment does
fall under regulation, Nashua anticipates to be held to the
industry standard of 95 percent emission reduction. With this in
mind Nashua Corp. wanted to know the current technologies
available that would meet the standard.
Objective: It was the goal of this project to find ways to
reduce the generation of waste at Nashua Corporation and help
them prepare for future environmental regulations. Most of these
projects could be accomplished using the pollution prevention
methods of reduce, reuse and recycle.
Approach: In order to reduce the amount of solvent waste
generated it was necessary to track where in the plant the
solvent was being used. Once the solvent usage was determined,
tests were run on the recovered solvent in an attempt to
determine the composition. Since the solvent is recovered from a
batch process, the exact composition of each barrel of recovered
solvent can not be determined unless it is tested, although it is
hoped that the solvent will have a statistically representative
composition. Once the general composition of the solvent is
known. What to do with the solvent can be addressed.
To track the generation of junk steel an understanding of
the various process involved in developer manufacturing was
needed as well as a history of the amount of junk steel produced.
The history of the generation of junk steel should provide some
information on where the waste is generated and if it has been
increasing. Once the analysis of past junk generation has been
done then certain parts of the process must be focused upon to
generate a mass balance. If needed the entire process can
evaluated using a mass balance.
Researching the current technologies to control the
emissions on the particle coating process involves knowing what
is in the emissions. It is essential to know the composition of
the exiting gas stream which is to be treated. When the
composition, flow rate and temperature of the exit stream is
known then the search for emission control can start. This is
done through contacting the manufacturer of the fluid bed to get
their input to solve the problem as well as other related
Chemical Usage/Equipment Needs/Releases/Waste Generated: The
solvents involved in the coating process are primarily MEK,
Toluene and Xylene. They are used as resin carriers to deliver
the resin coating to steel shot. Nashua uses two different
coating machines. The first coater is a fluidized bed coater
where the steel particles get fluidized in a stream of hot air.
The coating is sprayed onto the fluidized particles then the
carrier solvent is vaporized and released to the atmosphere. The
second coater mixes the coating and steel together in a bath then
vaporizes the solvent. The vaporized solvent is then recovered
by condensing the vapors. The first coater is the machine that
may fall under environmental regulations someday and is the
subject of the emissions control technology research. The second
coater is the source of the recovered solvent which becomes
waste. This waste is then declared hazardous waste and is
shipped to a fuel blending site for energy recovery.
In the developer manufacturing process steel shot is put
through many different steps. The amount of waste generated from
each step is unknown but over all it has been estimated that some
where between eight and twelve percent of the of the steel shot
that enters the process becomes waste.
Work Accomplished: The usage of solvent was reviewed throughout
the plant. It turned out that there were only two places in the
entire plant where solvent is used. The processes that use the
solvent are the two coater machines which are part of the
developer manufacturing process. In the developer coating
process steel shot is covered with a coating. The coating is
applied as a liquid with the aid of a carrier solvent and then
the carrier solvent is vaporized leaving the resin on the shot.
The first process that became of interest was one which was done
on the coater that recovers the solvent. The process that was
focused on used xylene as the resin carrier. The use of
recovered xylene in other developer projects has not been
qualified by Nashua Corp because the contaminants are feared to
cause problems in other xylene based coatings. The other
solvents that are used in this machine have been effectively
reused on the fluidized bed coater. The only declared waste of
these solvents are from cleaning and flushing operations. The
process was studied and it was found that the main source of
solvent was the resin which is purchased as a solution. The
resin solution composition is 80% xylene which accounts for
almost 80% of the total xylene used it the process. The other
20% of the xylene used in the process is virgin xylene which is
used to flush the system clean. The flush xylene used in this
process must be of very high quality to remove the catalyst from
the system. Since the main source of xylene entering the
facility is within the resin, which is a standard formulation
from a chemical company, then it is not feasible for Nashua to
try and recycle all of the xylene within the company. For this
reason the choice was made to try and sell the xylene to a
company who can use the xylene in its present state. The
manufacturer of the resin was consulted to get more information
on the contents of the recovered solvent and to see if they would
buy back the recovered xylene. They do not participate in a
solvent return program but they offered some help in determining
the composition of the recovered xylene. The Pollution
Prevention Division of the DES was then contacted for help to
find a market for the waste xylene. The DES provided the names
of several waste exchange organizations through which a solvent
broker was contacted. The broker came up with a company who is
interested in buying the recovered xylene.
This company must be
investigated and a statistical analysis of the impurities must be
completed before the xylene can be sold.
The other coating machine was the subject of the emission
control search. This process is similar to the first coating
machine except that the steel shot is fluidized in a stream of
hot air. The fluidized steel shot is then sprayed with the
coating and the solvent is vaporized leaving the coating on the
steel. The vaporized carrier solvent is then vented to the
atmosphere. This release of vaporized solvent is what could
someday become restricted under environmental regulations. To
prepare for this it is important to know what the composition of
the exit stream is and to what the expected reduction standards
are going to be. It is expected that the required reduction in
emissions is going to be 95% which is the industry standard for
VOC emission reduction. The theoretical composition of the exit
stream was calculated for each product and the concentrations of
the VOCs determined. Once the stream composition was known the
DES pollution prevention center and various vendors were
contacted to find out what the best equipment would be to achieve
the needed VOC reduction. There are several choices available to
reduce VOC emissions, they include: Condensation, Activated
Carbon, and Oxidizers. The choices were narrowed down by using
the conditions of the exiting gas stream. Condensation was not a
viable choice because of the low VOC concentration. Activated
Carbon was ruled out when it was considered that the carbon would
be recovering many different kinds of solvent which would make
the recovery of useful solvent impractical. A second thing to
consider about activated carbon was if there happened to be any
coating carry over from the coating process, the coating would
cover the carbon and decrease its effectiveness. Oxidization
(Incineration) became the most practical choice because of the
conditions in the gas stream. There are two types of
incineration, catalytic and non-catalytic. Catalytic incineration
was ruled out because, as before with activated carbon, if there
happened to be any coating in the gas stream, then the coating
would cover the catalysis and proper incineration would not
occur. For these reasons it was determined that the most
practical technology available at this time was non-catalytic
thermo-Oxidization. When this was done a collection of vender
names, who manufactured incinerators, and contacts was compiled
so that if needed the decision of whom should manufacture the
incinerator can be quickly made.
To analyze the generation of junk steel all the available
records over the past few years on the production of developer
and waste were used. The records showed that over the last three
years there has been a 34,000 pound increase in junk steel
generation. The records also showed that the manufacturing rate
of developer over the past three years was declining. This means
that the junk steel generated per pound of developer produced has
increased. Once this was found an attempt was made at discerning
where the increase in the generation of junk steel has come from
using all the records. The data suggested that the increase came
from the separation of over and under sized steel particles. A
material balance is pending over the developer manufacturing
process to try and locate exactly where the excess waste is
Project Benefits: These projects have numerous environmental and
economic benefits. The recycling of the recovered solvent
reduces the amount of money and effort involved in shipping and
disposing of hazardous wastes. This practice also increases the
life of the solvent, which reduces the amount that is used. This
is an environmental benefit. The reduction in steel waste
produced in the developer manufacturing will increase output and
efficiency while reducing the amount of raw materials purchased.
This could have substantial financial benefits because the cost
of the raw materials and labor which is put into making
developer. The goal of finding technology to reduce the
emissions on the fluid bed coater will not result in a direct
economic benefit but it will help keep Nashua Corp. in compliance
with state and federal environmental regulations which will be
environmentally and politically friendly.