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Zero Liquid Discharge in PVA glue production

By 16 September 2016case, chemicals, pcr

The Client
The Client is one of the European branches of a Multinational Company leader in the production of adhesives having a wide range of industrial applications.

The challenge
The company carries out the mixing of basic adhesive ingredients in suitable reactors. The final product is sold in liquid form to the wood and furniture, graphic, textile and automotive industries. The wastewater coming from the production process is sent to disposal involving even higher costs.

The Solution provided
The plant as a whole is able to treat about 15 m3/day of wastewater. The initial phase consists of a heat pump vacuum evaporator with forced circulation PC F 12 to pre-concentrate the waste. The final phase aims to reach the required concentration through the heat pump scraped vacuum evaporator PC R 2 FF.

EVALED® evaporators exploit the combined effects of vacuum and heat pump to obtain a low temperature evaporation (35 °C or 95 °F) of water-based solutions. The evaporators are made of a ferritic austenitic alloy – SAF 2507 – that is resistant to possible pitting corrosion phenomena due to the presence of a high concentration of chloride.
The PC R 2 is equipped with scraping blades inside the boiling chamber that to keep the heat exchange walls clean.
The lower part of the boiling chamber is made by a heating jacket that provides necessary heat for evaporation of the liquid.

Results & Benefits
Analytical results confirmed the initial expectations about the end product quality: a constant density solution to be mixed with fresh glue as demanded by the market. Recycling the distillate coming from the treatment allows to reduce wastewater discharge to zero. What one time was disposed of, now it is reused in the production process.
As a result, the company eliminated several issues related to controls on discharge by the local authorities, and converted wastewater into an economic resource.

Parameters U.M. Effluent Distillate Concentrate
pH 3.5 3 3.8
Salt content (105 °C) % 3.34 0 31.13
Tensides mg/l >350 2.3
Chlorides mg/l 319 < 1
Ammonia mg/l 25 < 1
Boron mg/l 5.6 < 0.1
Iron mg/l 11.2 < 0.1