Fuel and Combustion By A Nirala

Assistant ProfessorGalgotias University

niralaiitk@gmail.com

SYNTHETIC FUEL

Includes:(A) Introduction(B)Methods of producing (a) Polymerisation (b)  Fischer– Tropsch process (c) Bergius Process

INTRODUCTION

Synthetic fuel or synfuel is a liquid fuel obtained from coal, natural gas, oil shale, or biomass. It may also refer to fuels derived from other solids such as plastics or rubber waste. It may also (less often) refer to gaseous fuels produced in a similar way. Common use of the term "synthetic fuel" is to describe fuels manufactured via Fischer Tropsch conversion, methanol to gasoline conversion, or direct coal liquefaction.

Methods of producing synthetic petrol:

• Polymerisation• Fischer- Tropsch method• Bergius process

Polymerisation:In this method, smaller molecules of hydrocarbons are combined to form heavier molecule resembling gasoline.It is of two type:(a)Thermal polymerisation(b)Catalytic polymerisation

(a)THERMAL POLYMERISATION:

Thermal polymerisation is carried out at temperature about500-600 oC and pressure about 70-350 kg/cm.cm

(b)CATAIYTIC POLYMERISATION: It is carried out at a lower temperature of 150-200 C ,in a low pressure and in presence of catalyst like posphoric acid. The rate of reaction is increased. The gasoline obtained is of improved quality andpossess high antiknock properties than the gasoline obtained from thermal polymerisation process.

The Fischer– Tropsch process (or Fischer– Tropsch synthesis) is a collection of chemical reactions that converts a mixture of carbon monoxide and hydrogen into liquid hydrocarbons. The process, a key component of gas to liquids technology, produces a synthetic lubrication oil and synthetic fuel, typically from coal, natural gas, or biomass. The F–T process has received intermittent attention as a source of low-sulfur diesel fuel and to address the supply or cost of petroleum-derived hydrocarbons.

Fischer- Tropsch process

Fischer- Tropsch process The water gas is varied with hydrogen and the combination is purified by transitory from side to side Fe2O3 and then into a mixture of Fe2O3+Na2CO3. The cleanse gas is dense to 5 to 25 atm and then led from side to side a converter, which is preserve at a temperature of 200 – 300oC. The converter is provided with a catalyst bed consisting of a mixture of 100 parts cobalt, 5 parts thoria, 8 parts magnesia and 200 parts keiselghur earth.

The outcoming gaseous mixture is led to a condenser, where the liquid crude oil is obtained. The crude oil is fractionated to yield gasoline and heavy oil. The heavy oil is used for cracking to get more gasoline.

http://en.wikipedia.org/wiki/File:Indirect_conversion_synthetic_fuels_processes.jpg

:Bergius processOne of the main methods of direct conversion of coal to liquids by hydrogenation process is the Bergius process.In this process, coal is liquefied by mixing it with hydrogen gas and heating the system (hydrogenation). Dry coal is mixed with heavy oil recycled from the process. Catalyst is typically added to the mixture. The reaction occurs at between 400 °C (752 °F) to 5,000 °C (9,030 °F)and 20 to 70 MPa hydrogen pressure. The reaction can be summarized as follows:

Bergius Process - Synthetic Petrol:

         In this process, the finely powdered coal is completed keen on a paste through heavy oil and a catalyst powder (tin or nickel oleate) is mixed with it. The paste is pumped along with hydrogen gas into the converter, where the synthetic paste is heated to 400 - 450°C under a pressure of 200 - 250 atm.         During this process hydrogen combines with coal to form saturated higher hydrocarbons, which experience additional decay at superior temperature to acquiesce combination of lesser hydrocarbons. The mix is led to a condenser, where the crude oil is attained. The crude oil is then fractionated to yield:(a)Gasoline (b)Middle oil (c)Heavy oil