Pyrolysis Pilot Plant Results for Various Feedstocks

2 PYROLYSIS PILOT PLANT RESULTS FOR VARIOUS FEEDSTOCKS 

The price of baled HDPE with up to 2% impurities has fluctuated from 7-10 cents/lb two years ago to about 30 cents/lb recently. If the plastic used in the pyrolysis process did not require this limit, the cost could be considerably lower. (Unseparated waste plastic can be valued as low as negative 2 cents/lb, which accounts for landfilling cost or tipping fee.) Consequently, the run with HDPE was repeated, except the plastic was 96 wt% HDPE and 4 wt% waste polyethylene terephthalate from soft-drink bottles. Pyrolysis yields are given in Table 13.1, showing a 385°C- - yield, based on plastic, of 42.4 wt%. 

In the pyrolysis run, C4- was again quite low (about 3 wt%), and the product contained no 538°C+ in the bottoms. Assuming all the C4- came from the plastic would indicate about 6 wt% of the plastic was converted to gas. 

Pyrolysis was carried out on a feed composed of a 50/50 mixture by weight of low-density polyethylene (LDPE) and hydrotreated FT wax. Yields are given in Table 13.2, showing a 385°C- - yield of 57.5 wt%. The yield for a broader lube feed, 343°C- -, was 66.0 wt%. While there was considerable 538°C- - in the feed to the pyrolyzer, there was little 538°C- - in the product, which is believed here to be advantageous for low cloud point. Oleflnicity in the pyrolysis overhead was 76 wt% by PONA analysis. The olefinic overhead liquids from the pyrolysis of both FT wax and LDPE/FT wax were analyzed using gas chromatography. This showed the cracked product to be almost entirely 1-normal olefins and normal paraffins. 

A portion of the pyrolysis bottoms was hydrotreated to reduce the nitrogen from 8 ppm to less than 1 ppm. This was then hydroisomerized to give a — 15°C pour point 3.8 cSt oil with a 150 VI (Table 13.3). The overall 343°C+ yield was 40 wt%, close to that estimated for unhydrotreated feed at the same pour point. 

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