PVC Coating/Synthetic Leather

Gas Cleaning › Indirectly Heated Oven Fume Filtration System

PVC / VINYL COATING – Indirect heated oven and no lacquer or chlorinated additives

PROCESS INFORMATION

Most common manufacturing applications are Synthetic Leather ( car upholstery, bags, shoes etc.), vinyl coated and linoleum flooring, vinyl coated wallpaper, laminated sheets ( special films, belts, tarpaulins ) and foam products.

Polyvinyl-chloride (PVC) is a thermoplastic and is mixed to additives which improve its properties and enable it to be processed more easily.

Most common major additives are:
plasticizers to provide elasticity i.e. DOP (Dioctyl Phthalate)
stabilizers to prevent degradation i.e. PB salts
lubricants (solvents) to prevent plugging on cylinders of the calendering machine
charges i.e. silicium
pigments i.e. anthraquinones

Typical formulation : PLASTICIZERS : 50% + SOLVENTS : 48% + OTHERS : 2%

The emulsion (polymer + additives) is spread coated and heat cured or calenderized in ovens. PVC emulsion is fed to ovens with successive steps of curing/calendering and cooling sections. Gas is extracted from curing/calendering sections and cooling sections.

Exit gas from curing ovens (180 – 150 °C) which has been indirectly heated.

Depending upon formulation, 500 to 5,000 mg/m³ of plasticizers are present in the exhaust gas. Solvents and other products are also entrained.

PROBLEMS TO SOLVE

Air pollution.

As an average, industrial sites regulations specify a maximum emission of 20 mg/m³ of plasticisers ( = invisible ), or 50 mg/m³ total carbon, or an odour related limit. More stringent levels, e.g. 2 mg/m3 of DOP plasticiser are now sought.

Recovered plasticizer and solvent could be re-used.

DESIGN SOLUTION

DOP BHT2 SERIES CANDLES

There are 4 main feature components in this system design :
An efficient prefilter (type BECOIL) is installed to collect large particles and insolubles, to give maximum protection to the downstream components to maximise their life and minimise maintenance.
It is usually necessary to fit a water fed fin & tube heat exchanger cool down the gas to 35°C to ensure all plasticizers and the less volatile solvents are in liquid phase.
High efficiency filters Type HT(2) TGW15, giving the ultimate in sub-micron fume collection.
Bag liners are fitted inside each candle filter to give final added protection to the fibre ( which is the most expensive component )

Additional benefit features are :
Pre-filter and Bag Liners can be cleaned and reused when pressure loss indicates solids blockage.
Pre-filter fitted via a drawer system, for easy access.
Candle Filters are fitted via removable flat roof sections for easy access to the Candle Filters and  Bag Liners.
Hot water heat recovery from the Heat Exchanger can be used in the plant.

Options :
Horizontal pre-filter housing and cooler for smaller air volumes or downward flow vertical pre-filter housing and cooler for larger air volumes.
Candle Filter lengths from 1,220 mm to 3,660 mm, to suit available height above vessel, or to minimise system footprint.
For some installations where the highest possible efficiency is demanded, we have installed an Xtra-Pure concentric double fibre bed candle filter design, which can achieve 5 to 10 mg/Nm3 exit.
If no corrosive components are present, cooler will be Copper tubes & Aluminium fins. Alternatively, Carbon Steel or Stainless Steel tubes can be used.