Plastic to Energy

Plastic can be used for energy in a few different ways. The most obvious way and one you’re probably quite familiar with is recycling. This saves tons of energy in the form of materials and labor used to harvest them. However, what I’m more concerned about for this article is converting plastic into oil and using synthetic oils to create plastic. Both of these are relatively new concepts that have only been tested in laboratory settings. Commercial scale operations are still quite a ways off. With the abundance of plastic that ends up in landfills and the ocean though this could be a great new alternative energy source. Especially if oil created from waste plastic could be refined to produce gasoline and other useful hydrocarbons.

First let’s talk about converting plastic into oil.
There are a handful of facilities that produce oil from waste plastics and they all use different techniques. One company is using catalytic pyrolysis to convert plastics. A single “module” or building unit can produce over 700 litres of oil out of every ton of plastic waste that is processed. The entire system can process between 200 and 400 tons in a month so there is a considerable amount of oil that can be obtained. If more plastic needs to be converted then additional buildings can be built. The system is designed to be self contained so additional units can be built for expansion.
Here is a video fly through of a waste plastics to bio oil facility located in Korea. Skip ahead to one minute where the actual facility part starts. Although it’s lacking descriptions it is pretty clear what the process is.

Creating plastic with synthetic oil or artificial oils.
This is a very new technique that is only just starting to be used for commercial development of oil and plastics. The idea behind it is actually quite simple. Biomass with specific bacteria added will break down into gasoline or diesel fuel. Overall the goal is to eventually be able to produce a variety of hydrocarbons which plastics could be made from. Right now the company that is bringing this into production plans to have products on the market by the second quarter of 2009.
In addition to creating plastic from synthetic oil there have been a variety of attempts to replace plastic with other materials. For example, a company is using wood sawdust chemically altered to produce a plastic like material. Cullulose has been used to create plastic bottles and bags that are also biodegradable. All of these technologies will have a place in replacing and updating our ideas of what plastic should be used for.

The Cynar Technology

Source : http://www.cynarplc.com/cynar_technology.asp#top

Current situation of recycling of plastics Pyrolysis Structure of the System Operations

The system uses liquefaction, pyrolysis and distillation of plastics. The system can handle almost all the plastic that is currently being sent to landfills.
A major advantage of the process is its high efficiency. Each plant can produce up to 19k litres of fuel from 20 tonnes of waste plastic.

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Current situation of recycling of plastics

Various methodologies have been tried and tested to process waste plastics for many years, with recycling becoming the most common method reflecting the needs of the time. Plastics that cannot be processed are handled by waste management companies by normal landfilling or incineration.
The building or expanding of incinerators has become difficult due to opposition from governments and community groups with environmental concerns, most notably the levels of emissions.
Liquefaction of plastic is a superior method of reusing this resource. These distillate products are excellent fuels and make the Cynar Technology one of the best, economically feasible and environmentally sensitive recycling systems in the world today.
The synthetic fuels produced, given their low sulphur and high cetane qualities, will most likely be blended into a larger pool for use in trucks, buses, trains, boats, heavy equipment and generators.

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Pyrolysis

Pyrolysis is a process of thermal degradation in the absence of oxygen. Plastic waste is continuously treated in a cylindrical chamber and the pyrolytic gases condensed in a specially-designed condenser system to yield a hydrocarbon distillate comprising straight and branched chain aliphatics, cyclic aliphatics and aromatic hydrocarbons. The resulting mixture is
essentially equivalent to petroleum distillate. The plastic is pyrolised at 370ºC-420ºC and the pyrolysis gases are condensed in a 2-stage condenser to give a low sulphur content distillate.
The essential steps in the pyrolysis of plastics involves:

1. evenly heating the plastic to a narrow temperature range without excessive temperature variations
2. purging oxygen from pyrolysis chamber,
3. managing the carbonaceous char by-product before it acts as a thermal insulator and lowers the heat transfer to the plastic
4. careful condensation and fractionation of the pyrolysis vapours to produce distillate of good quality and consistency

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Structure of the System

The system consists of stock infeed system, pyrolysis chambers, contactors, distillation, centrifuge, oil recovery line, off-gas cleaning, and residual contamination removal.
Waste plastics are loaded via a hot-melt infeed system directly into main pyrolysis chamber.
Agitation commences to even the temperature and homogenise the feedstocks. Pyrolysis then commences and the plastic becomes a vapour. Non-plastic materials fall to the bottom of the chamber.
The vapour is converted into the various fractions in the distillation column, the distillates then pass into the recovery tanks.
From the recovery tanks, the product is sent to a centrifuge to remove contaminants such as water or carbon.
The cleaned distillates are then pumped to the storage tanks.

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Operations

The heart of the pyrolysis system is the prime chamber, which performs the essential functions of homogenisation, controlled decomposition and outgassing in a single process. The process requires minimal maintenance apart from carbon residue removal, and produces consistent quality distillate
from mixed and low-grade plastic waste.
The key to an efficient pyrolysis process is to ensure the plastic is heated uniformly and rapidly. If temperature gradients develop in the molten plastic mass then different degrees of cracking will occur and products with a wide distribution of chain lengths will be formed.
Another important aspect of pyrolysis is to use a negative pressure (or a partial vacuum) environment. This ensures that oxidation reactions are minimised and that gaseous pyrolysis vapours are quickly removed from the process chamber thereby reducing the incidence of secondary reactions and the formation of undesirable by-products.
The polymer is gently 'cracked' at relatively low temperatures to give predominantly straight chain aliphatic hydrocarbons with little formation of by-products. These hydrocarbons are then selectively condensed and cleaved further catalytically to produce the average carbon chain length required
for distillate fuel.

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A New Way to Turn Plastic Into Fuel?

By MATTHEW L. WALD

 

Envion Envion, a Washington, D.C., start-up, aims to turn plastics into fuel — with minimal mess.

Entrepreneurs have been trying for years to turn low-value wastes into high-value products. Waste plastic is among the lowest in value, and gasoline or diesel fuel the highest, but machines that carry out that conversion usually consume a lot of energy and get gummed-up by leftover materialthat they cannot convert.

Now a company in Washington, D.C., is trying out a new way — heating the plastic to a very carefully controlled temperature range, with infrared energy.

The company, Envion, is expected to cut the ribbon on Wednesday morning on a $5 million plant that it says will annually convert 6,000 tons of plastic into nearly a million barrels of something resembling oil. The product can be blended with other components and sold as gasoline or diesel.

“We are the world’s largest oil consumer and the world’s biggest producer of waste,’’ said Michael Han, chairman and chief executive of the company.

This process will convert one to the other for about $10 a barrel, he said.

Montgomery County, just north of Washington, D.C., apparently agrees, at least to the extent that it is giving Mr. Han a free supply of plastic and a spot at its waste transfer station to set up shop.

Gov. Martin O’Malley of Maryland was scheduled to speak at a ceremonial opening on Wednesday.

A day earlier, Mr. Han pointed out bales of plastics waiting to be shredded and fed into his machine, including planters, McDonald’s large-sized beverage cups, margarine containers and other materials typical of what suburban residents put out in blue bins once a week for pick-up.

His machine can digest the blue bins, too, he said.

Indeed, the machine will take everything except PET (the bottle with the “1’’ on the bottom) because those have a higher value on the recycling market, he said.

He will process the caps, though.

(Nationwide, 50 million tons of plastic waste are generated annually, according to the company.)

The finished product looks like a slightly murky lemonade and smells somewhere between gasoline and diesel fuel. One company has already agreed to buy the material for blending into motor fuel, and Mr. Han said he is in discussion with others. Envion would like to license its technology for use around the world.

Mr. Han and other company officials were a little vague on some details, which they said were proprietary, but the plant essentially consists of a two-story-high chemical reactor with an internal agitator (for mixing up the soup) and heating elements that give off infrared energy.

Another trick is to limit the amount of oxygen.

Because the process is driven by electricity and not with an open flame, the temperature can be tightly controlled, so most of the material — about 82 percent, according to the company — becomes liquid fuel.

Company executives predicted that they would have to shut down to clean out leftover sludge two to four times a year (conventional processes get clogged much faster).

The sludge can be burned for energy too, but it has much lower value.

Production depends on the plastic used as feedstock, but each ton of waste will produce 3 to 5 barrels of product, according to Envion. Producing a barrel consumes between 59 and 98 kilowatt-hours — two or three days’ worth of electricity for a typical house. The price of electricity per gallon comes to 7 to 12 cents, the company says.

Todd Makurath, the director of global brand management at the company, said that because it was all electric, it could be monitored over the Web, with just two employees on site, one to use a front-end loader to dump shredded plastic into the intake hopper and another to “watch for red lights” on the alarm system.

“This could be transformational in how we handle plastics,’’ Mr. Makurath said.