Sweet Gazoil
Solutions for the treatment of waste plastics and waste/used oils
SURFACE FLASH CRACKING
The Basics
Hydrocarbons are long molecules having a Carbon-Carbon backbone on which other types of atoms are bonded (such as Hydrogen, Oxygen, etc.). As an example, in a petroleum refinery, the various products are made from molecules (hydrocarbons) of various length (number of carbons in the backbone):
| Hydrocarbon product | Hydrocarbon chain lengths |
|---|---|
| Natural gas | 1 to 3 carbons |
| Gasoline | 5 to 12 carbons |
| Diesel | 8 to 24 carbons |
| Heavy fuel oils | 9 to 50 carbons |
One of the ways refineries produce gasoline from heavy oils is through cracking.
Cracking is the result from a pyrolysis reaction that breaks down long-chain hydrocarbons into smaller hydrocarbons. Using relatively high temperatures (400°C to 550°C) in the absence of oxygen, waste oils and/or waste plastics can be broken down into valuable hydrocarbon vapors, leaving behind solid material (coke), which gets deposited on the reaction sites.
There is a distinction to be made between slow and fast pyrolysis. A slow pyrolysis occurs when the feedstock is slowly heated to cracking temperatures (taking between 30 minutes to a few hours). Slow pyrolysis generally promotes the formation of solid and gaseous products, while minimizing oil yields.
A fast pyrolysis occurs when the feedstock is rapidly heated to cracking temperatures within seconds. This type of pyrolysis maximizes the oil product at the cost of solid and gaseous yields
Not all types of fast pyrolysis are equal. Depending on heat transfer, reaction temperature, residence time, entrainment of solids, and other factors, the degree of cracking and type/quality of products obtained will vary greatly.
For each of these types of pyrolysis, there are different ways of doing it (steam cracking, catalytic cracking, thermal cracking) which utilize different types of reactors (fluidized bed, auger reactor, rotating kiln reactor, stirred reactor), each having their advantages and disadvantages.
Surface Flash Cracking
Our patented anti-fouling rotating kiln reactor performs a type of ultrafast pyrolysis called Surface Flash Cracking, in which the feedstock reacts almost instantly as soon as it touches the heated reaction sites (metal plates).
This is achieved by having the material fed into the reactor in the form of small particles/droplets, which are sprayed onto the reaction sites. Since the droplets are very small, they react as if they were homogeneous and are transformed almost instantly. Being able to tightly control the temperatures of the reaction sites, each drop absorbs only the energy needed crack (without over-cracking) producing right-size hydrocarbon.
However, upon decomposition, some solid material forms on the reaction surfaces. This causes fouling in the reactor and reduces heat transfer, making it difficult to get a stable and fast reaction.
The Sweet Gazoil rotating kiln reactor is designed with patented anti-fouling technology which causes coke to be continuously scraped off the reactions surfaces and removed from the reactor. The plates in the reactor not only act as easily maintainable and cleanable reaction sites, but also protect the reactor walls from thermal shock, coke deposits, hot spots and failure.
The hydrocarbon vapors produced are rapidly swept out of the reactor to prevent further decomposition. Contrary to other pyrolysis reactors, through Surface Flash Cracking, the vapors do not travel through a liquid phase. This prevents them from cooling down and becoming saturated, ultimately making the removal of entrained solids (purification) much more effective. This is highly advantageous because the solids that are entrained by the vapors are very sticky, build up on the internal walls of the equipment and cause fouling which prevents the use a distillation column.
Upon exiting the reactor, the hydrocarbon vapors are purified, separated using a distillation column into gas, naphtha, diesel, and heavy oil. The gas is used as fuels on site, while the diesel is either sold/used as is or stabilized, the naphtha is combusted or sold, and the heavy oil is recycled into the process or sold as either a heavy fuel or specialty oil.
The coke produced in the reactor is mostly carbon and can contain metals and other impurities. For most feedstocks, it is a non-leachable hydrophobic powder that can either be combusted to supply heat/generate electricity or used to extend the life of asphalt or cement. The process produces no harmful by-products.
