User:Rishabh186/sandbox

INTRODUCTION
Presently non-renewable resources such as, petrochemicals, natural gas and coal fulfill the world’s energy needs. As a result of continued increase in the demand these resources will be depleted in few years and the cost of petroleum based fuels and the present pattern of consumption. Biodiesel has emerged as a viable substitute for petroleum diesel. Biodiesel is a renewable fuel which is mono-alkyl esters (fatty esters) of long chain fatty acids (carbon ranging from C¬¬12-C20) is produced from natural and renewable sources such as variety of edible and non-edible vegetable oils and animal fats, but vegetables oils (mainly triglycerides) are the main feedstocks. Transesterification of vegetable oils using alcohol into alkyl esters in a catalytic environment is most commonly used method for producing biodiesel. Most existing biodiesel plants currently rely upon the use of a homogeneous catalyst in a continuous reactor system, using the transesterification of soyabean or rapeseed oil with methanol into alkyl esters. The alcohols used should be of low molecular weight being one of the most used ethanol for its low cost. However, greater conversions into biodiesel can be reached using methanol. Although the transesterification reaction can be catalyzed by acids or bases but the common means of production is base-catalyzed transesterification. This path has lower reaction times and catalyst cost than those posed by acid catalysis. However, alkaline catalysis has the disadvantage of its high sensitivity to both water and a fatty acid present in the oils. The vegetable oil esters are practically free of sulphur and have a high cetane number ranging from 46 to 60 depending upon the feedstock. Due to presence of oxygen, biodiesels have a lower calorific value than the diesel fuels. Biodiesel produced from pure vegetable oil costs much more than petroleum-based diesel. To minimize the raw material cost is the main concern in recent biodiesel research as a result overall cost will reduce. One effective way is to use waste cooking oil instead of virgin oil for the production of biodiesel also it can help to solve the problem of disposal of waste oil.

Transesterification
The overall reaction is given below. Triglycerides, as the main component of vegetable oil, consist of three long chain fatty acids esterified to a glycerol backbone. When triacylglycerol’s (Triglyceride) react with an alcohol (e.g., methanol), the three fatty acid chains are released from the glycerol skeleton and combine with the alcohol to yield fatty acid alkyl esters (e.g., fatty acid methyl esters or FAME). In this reaction glycerol is obtained as a by-product and about 95% conversion of oil (triglyceride) takes place. FAME formation is affected by reaction temperature, pressure, molar ratio, water content and also free fatty acid content. At subcritical state of alcohol, reaction rate is so low and gradually increased as either pressure or temperature rises. The yield of FAME increased with increasing the molar ratio of oil to alcohol.

Catalyst Removal
3 NAOH + H3PO4 ⎯→ Na3PO4 + 3 H2O Sodium hydroxide is used as the catalyst and is removed by adding H3PO4 and precipitate into Na3PO4. About 100% conversion of NAOH takes place.

Simulation
A simulation model is required that would perform calculations necessary to produce a mass and energy balance for their biodiesel plants based on user inputs. We have to supply a starting set of components (inputs) and physical property parameters for modeling processes of this type. The inputs depends on variables such as production rates, feedstock composition, plant location, etc. various simulation software can be used for biodiesel production here focus is on ASPEN PLUS simulation software. By using Experimental thermodynamic data and realistic operating conditions, the actual process behaviour can be simulated. Moreover, process simulation enables process engineers develop better processes by using tools such as sensitivity analysis, calculator block, optimization block, profitability analysis and design specification.

SIMULATION STEPS
Step 1: Identify the unit operations and the process streams that flow to and from them in the process flowsheet. Label all streams and connect them to the unit operation models.

Step 2: Identify the chemical components from the Aspen Plus databanks or define them in the process.

Step 3: Identify thermodynamic models built into Aspen Plus to estimate the physical properties of the components and mixtures in the process.

Step 4: Identify the thermodynamic conditions and the component flow rates of the input streams.

Step 5: Identify the operating conditions for the unit operation models.