1. Twin screw reactor

The Entropic pyrolysis process uses a continuous, co-rotating twin screw extruder to convert organic solid waste materials into synthetic coal. The reactor consists of a drive unit, which may be either an electric motor or a steam turbine; a gearbox which reduces the speed of shaft rotation, and the extruder, consisting of two overlapping augur screws which are enclosed in a rectangular "barrel". Solid waste is introduced into the end of the barrel nearest to the gearbox, and is discharged at the other end, transformed into synthetic coal. The process, which takes about 90 seconds, operates in the absence of oxygen, and utilizes the friction of mixing to provide the heat required for pyrolysis.

2.Screw open for maintenance

This figure illustrates how the two augurs within the Entropic reactor are fully accessible for maintenance. Top and bottom of the barrel open to expose the augur elements.

3.Open screw with coal

In this view the Entropic reactor has been temporarily stopped and opened to show the progressive transformation of RDF (light colored) to Syncoal (Black).

4. Very large screw twin reactor.

The twin screw reactor is extremely versatile, and has wide application in industries as diverse as food processing, epoxy resins,
propellants, plastics and thermal processing. This single reactor, if applied to MSW, could process up to 100 tons per hour of solid waste.

5. Process description pyrolisis

In a standard 800 ton/day Entropic plant, pyrolysis is carried out by three 300mm diameter reactors operating in parallel. RDF enters each reactor at a rate of up to 8 tons/hour. Fully processed Syncoal is discharged hot from the reactor, cooled by a water-cooled conveyor, and directed to coal storage. Pyrolysis vent gases are used to fuel a boiler, producing roughly 40 tons/hr of steam. The steam is used to power the extruder reactors, either directly through steam turbine mechanical drives, or indirectly through a steam turbine generator set and electric motor.

6. RDF Dryer on waste analyzed

When MSW has a very high moisture content, the Entropic process can be modified to include a pre-drying step. A rotary dryer, such as the one shown here, reduces RDF moisture content to 10% or less. The moisture should modify the process energy dates.

7. Plant isometric view

This drawing shows an Entropic plant modified to process high moisture MSW. Waste is delivered to the tipping floor, where it is conveyed to RDF separation. A pair of trommel screens sort the MSW by size, sending oversized materials to the shredders. Shredded RDF is dried in three rotary driers, is air classified, then pyrolized in one of three Entropic reactors. Heat for the dryers is provided by the exhaust from three 10MW gas turbine generator sets, yielding nearly 30MW of power for sale to the utility grid.

8. Exterior plant view

The Entropic plant closely resembles a warehouse or light industrial facility. This facility, modified for high moisture waste, would have roughly 180,000 square feet under roof, and could process roughly 1,600 tons/day of MSW.

9. Entropic pyrolysis schematic

This slide illustrates the mass and energy flows that describe the Entropic process with very high moisture MSW. RDF separation reduces the quantity of landfilled materials to less than 10% of the original waste stream. Drying reduces the MSW stream to roughly one third of its original mass flow, while retaining nearly all its energy content. Pyrolysis concentrates the energy content of the RDF by releasing additional moisture and CO2. Byproduct oil vapors are recycled back into the process. Overall yield of Syncoal is roughly 22% by weight, containing roughly two thirds of the total energy content of the original waste stream.

10. Product composition

This bar graph illustrates the steps in conversion of high moisture MSW to Syncoal. For 3300 tons/day of MSW, RDF separation greatly reduces the content of moisture and mineral matter, recovering ferrous and non-ferrous metals. The pyrolysis step reduces moisture content still further, while also driving off CO2 and light oils. The resulting Syncoal yield averages about 750 tons/day.