chemical industry

INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

Case Study # 82

1. Headline: Different technical measures were taken to

reduce the polymer residues in the process waste water

from a chemical process industry that manufactures

acrylate dispersions used as binding agents in water-based

inks.

2. Background: Rohm and Haas Nordic is a chemical process

industry that manufactures acrylate dispersions which are

used as binding agents in water-based inks. Rohm and Haas

as an international company has a central programme that

includes a "Waste Reduction Policy". The programme

originated from the rather strict environmental demands

placed on Rohm and Haas in the United States by the

American environmental authorities. Another contributing

factor to the formulation of the central environmental

programme was the bad will which the international

chemical industry got after several serious accidents.

The company's products are classified based on their

hazardousness and restrictions have been established for

each class. Other areas of emphasis include the intention

to limit landfilling, the requirement of catchment dams

to protect against discharges directly to fresh water,

and groundwater analysis to discover leakages. The company

also has the goal of reducing the polymer content in the

waste water (white water). The internal programme of

environmental measures is to some extent considerably more

far-reaching than the Swedish authorities requirements.

The company is part of the multinational concern Rohm and

Haas Co. The plant in Landskrona has about 50 employees

and the turnover in 1993 was US$ 26.9 million. Some 50

different products were manufactured with a total weight

of 27,500 tons. Case study was performed in 1990.

3. Cleaner Production Principle: Process modification

4. Description of Cleaner Production Application:

Process/equipment modification: The polymer binding

agents are made in batches, one product a time. The

production time for a product can be up to 24 hours. The

process stages during the manufacturing of polymer

products before accomplished changes of equipment:

In the pre-emulsifying tank the base chemicals,

principally acrylate monomers, are mixed with additive

chemicals for emulsifying the monomers. The mixture is

transferred to a reactor vessel where polymerization

takes place after the addition of catalysts and

activators. Then the product is tapped to a mixing vessel

where the final consistency is achieved. At this stage,

neutralization and preserving also takes place. The

product is then filtered to remove larger particles. The

final polymer product is a 50% water dispersion and is

pumped to a storage tank from which it is delivered either

in bulk or in a barrel or container.

The quality demands on the products are high. Therefore a

thorough cleaning of the process equipment after every

manufactured batch is necessary. The generated process

waste water is centrally collected in a sludge tank.

Certain treatment is carried out such as pH-adjustment and

test of the water which must be free from monomers before

discharge to the municipal waste water treatment facility.

Earlier reactor vessels in glass enamelled steel were

replaced with stainless steel reactor vessels which also

had a 50% larger volume. The increased capacity in

relation to each produced batch reduced the need for

cleaning. The surrounding equipment was also changed;

among other things, modern control equipment was added

permitting an increased automatic control as well as a

more effective and water saving high pressure wash of the

reactor. After emptying the reactor, the first rinse water

was transferred from the rotating nozzles to be used as

dilution water in the blending tank. These various

measures have lessened the role of the reactor as a

source of product loss as well as reduced the need for

cleaning.

The filtering of a product is done at several different

stages in the process. The product loss was greatest in

the filtering which takes place between the blending tank

and storage tank. The filters were replaced with others

with smaller volume. As a result product loss could be

reduced from the earlier 40 kg to 2-3 kg at every filter

replacement. It has been estimated that product loss

during the filter replacement amounted to around 100 tons

(50% polymer product). The quantity has now been reduced

by 80%. Dedicated pipelines have been installed to all

storage tanks for finished products. In this way, there is

no need to empty the system between every bulk unloading.

The dedicated pipelines system also makes it possible to

limit the product loss, cleaning needs and water

consumption. The preventive measures will save nearly 160

tons of polymers (50 % polymer product) which otherwise

would have left the facility with the waste water. A

waste reduction audit showed that this amount corresponds

to 30 percent of the total product loss.

Losses arose earlier in the transport pipeline between the

plant and the tank farm when product in the pipes was

rinsed away. The losses have been about 40 tons of

polymers a year (50% polymer product). To take care of

this loss a new line with the possibility for spiking was

installed. Spiking involves emptying a system by pushing a

plug of foamed plastic through with compressed air. The

spiking system reduced the product loss by up to 90% as

well as the water consumption and the amount of polymers

in the white water could be reduced.

More deliveries in bulk are now done with a corresponding

reduction in tapping from barrels and other containers.

This reduces the need for cleaning and water consumption.

In 1987 the distribution between the different forms of

delivery was 72% by bulk, 21% by barrel, and 7% by other

types of containers. The corresponding values for 1993

were 75% by bulk, 5% by barrel, and 20% by other types of

containers.

Earlier, the process water inhalted polymer products. An

installation of ultrafiltration equipment has now made it

possible to separate all polymer residues from the waste

water. The dry substance content is 40% for the recycled

polymer material.

Furthermore, the recovered product has a sufficiently high

quality and could be used as a simple binding agent.

Process and Waste Information: Rohm and Haas Nordiska AB

is a chemical process industry that manufactures acrylate

dispersions which are used as binding agents in water-

based inks. The environmental load was concentrated to

the process waste water which contained polymer residues;

the so called white water. A change of reactor vessels

lessened the role of the reactors as a source of product

loss as well as reduced the need for cleaning.

As a result of the new filters with smaller volume the

product loss could be reduced from the earlier 40 kg to

2-3 kg at every filter replacement. Dedicated pipelines to

every storage tank for finished products made it possible

to eliminate 160 tons of polymers from the process waste

water. The cleaning needs and water consumption could also

be reduced and there is no need to empty the system

between every bulk unloading. Ultrafiltration is used to

separate the polymer residues from the process water. The

recovered product has a dry content of 40% and such a

sufficiently high quality that it could be used as a

simple binding agent.

Scale of Operation: The plant has 50 employees and the

turnover in 1993 was US$ 26.9 million. Some 50 products

were manufactured with a total weight of 27,500 tons.

Year Process waste water Production Total dry content

in the waste water**

(tons) (tons) (kg/ton produced)

1986 156 12,000 12.7

1987 180 15,400 11.8

1990 250 26,400 9.5

1991/92* - - 6.6

1993 - 27,500 6.0

* Calculated from one year ahead from the middle of 1991

** Before ultrafiltration

The technology is fully implemented and commercially

available.

Material/Energy Balances and Substitution:

Material Category Quantity Before Quantity After

1986 1993

Waste Generation 12.7 kg/ton 6.0 kg/ton

Feedstock Use N/A N/A

Water Use N/A reduced

Energy Use equivalent

5. Economics

Investment costs include the installation of the dedicated

pipeline system within the tank farm: US$ 253,000, and the

installation of spiking system: US$ 16,900.

Payback Time: Based on the sales value the payback time

was 1.1 years for the tank farm and three to four months

for the dedicated pipelines system

6. Advantages

Reduction of the loss of finished products, reduced need

for cleaning and reduced volume of polymers in the process

waste water were obtained. The recovered product had a

sufficiently high quality and could be used as a simple

binding agent. The driving force behind the accomplished

changes at the company was a central programme which Rohm

and Haas had as a multinational company that included a

"Waste Reduction Policy". The programme originated from

the rather strict environmental demands placed on Rohm and

Haas in the United States by the American environmental

authorities. Another contributing force was the badwill

which the international chemical industry got after

several serious accidents.

7. Constraints: Not reported.

8. Contacts

Lars Siljebratt & Claes Nilon

Foundation of TEM

Asumsgatan 38 275 37

Sjobo Sweden

TEL: +46-(0)416-273 00

FAX: +46-(0)416-273 12

Rohm and Haas Nordiska AB

Ringvogen 163

Box 45

261 22 Landskrona

Sweden

Tel: +46-(0)418-240 90

9. Keywords: Sweden, chemicals, acrylate, process

modification, ink, water-based inks, polymers, binding

agent, spiking system, ultrafiltration.

10. This case study was translated from Swedish and submitted

by the Swedish Foundation of TEM to UNEP IE. It was

edited by UNEP IE in July 1995, but has not undergone a

formal technical review.