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Bio Diesel » JATROPHA BIODIESEL MAKING
 
Plant Bio DieselThe SVO can be used directly in village machineries like Stationery engines/ tractors but to use it in Car/modern engines some modification are required.




Vegetable oils when used as diesel fuel have the following limitations:

High viscosity
Poor atomization • Poor volatility
Thermal cracking in diesel engines • Poor oxidation stability
Polymerization in combustion chamber leading to deposits
Injection fouling by deposits
Fuel line and filter clogging
Polymerization of triglycerides in lube oil

Hence, modification of vegetable oils is necessary for efficient and trouble-free engine operation. One way to modify vegetable oils to produce diesel is to transesterify them.

Pilot Plant Transesterification stage in which raw oil is transesterified to bio-diesel, which is methyl or ethyl ester based on whether methanol or ethanol is used in the production process. The capacity of the transesterification plant is dependent on the amount of raw oil that has to be transesterified into bio-diesel. The capital cost of the transesterification plant depends on its capacity

The molecular weight of Jatropha curcus oil with major chemical constituents was determined as 870 [Ramesh, 2004]. Since the oil also contains other minor constituents, the approximate molecular weight of Jatropha curcus oil was taken as 900.

As per the transesterification reaction, 3 moles of methanol were required to react with 1 mole of vegetable oil [Kavitha, 2003]. The molecular weight of methanol is 32 and hence 96 g of methanol were required for the transesterification of 1 mole (or 900 g) of Jatropha curcus oil, which amounted to 10.67 % methanol.

As per Tamil Nadu Agricultural University report:

The optimum concentration of methanol required for effective transesterification of Jatropha oil was 20 %. the optimum concentration
The NaOH required for effective transesterification was 1.0 %. the maximum ester
The maximum yield was obtained at 60ºC temperature.
The maximum ester yield of 98 % was obtained at 90 min of reaction time.

Processing of Oil

The quality of feed vegetable oil particularly FFA content plays an important role in identifying the suitable technology. The important factors to be considered for a biodiesel production plant include:

  • Process ability of variety of vegetable oils without or minimum modifications
  • Process ability of high free fatty acid (FFA) containing oils/feed-stocks
  • Must be able to process raw both expelled and refined oil
  • Process should be environment friendly with almost zero effluent
  The selection of appropriate technology for production of biodiesel calls for careful selection of processing steps, catalyst and downstream process integration.


BIODIESEL PRODUCTION PROCESS

The processing steps for the most commonly used method viz. base catalyzed transesterification would be as follows:

Generally following procedure can be followed to produce biodiesel from fresh SVO and methanol in a base catalyzed environment.

The Steps below is a very much summarized general guideline. Many tips and tricks and safety recommendations have been left out for the sake of compactness. It is good to read more about this before starting. If you would like to use used cooking oil, ethanol or another catalyst instead, many Internet sites can help you adapt the recipe. Please notice that the methanol and lye involved are quite dangerous chemicals. Be sure to know what you are doing, work in a well ventilated area and wear protective clothes and glasses!

The following resources are required (all quantities are expressed per liter of J OIL:

1liter of J Oil; 5 grams of lye (caustic soda; NaOH (> 95%) or KOH (> 85%)); at least 220 ml of methanol (> 99%).

  1. First dissolve the lye into the methanol. Shake or swirl until all the lye has dissolved.
  2. This may take 10 minutes. It is normal that temperature rises. This mixture is called sodium methoxide. Now make sure the J Oil is in a vessel large enough (at least 150% of its volume), preferably with a valve at the bottom, and heat it to about 60 °C, then stop heating. Then add the methoxide mixture and make sure it is mixed well for at least 10 minutes. Leave the vessel and let the different constituents separate by sedimentation
  3. The glycerin will settle out at the bottom. After 8 to 24 hours the sedimentation is complete and the glycerine can be drained off.
  4. What remains is raw biodiesel. If the reaction went well and the biodiesel is clear, it may be used straight, although its quality may be inferior because of impurities. Water washing will remove most of these impurities.
  5. Consult Our relevant Book   on the websites to gather more information about this.

Transesterification, also called alcoholysis, is the displacement of alcohol from an ester by another alcohol in a process similar to hydrolysis. Methanol is most commonly used for the purpose since it is the cheapest alcohol available. Ethanol and higher alcohols such as isopropanol, butanol etc. can also be used for the esterification. Using higher molecular weight alcohols improves the cold flow properties of biodiesel but reduces the efficiency of transesterification process. The reaction is as follows:

Transesterfication

Methods commonly used for producing biodiesel are batch and continuous processes. In general, smaller capacity plants and variable feedstock quality warrant use of batch systems. Continuous systems generally lead the operation on a 24x7 basis, requiring larger capacities to justify larger staffing needs and also requiring uniform feedstock quality.

The transesterification works well when the input oil is of high quality. However, quite often low quality oils are used as raw materials for bio-diesel preparation. In cases where FFA content of the oil is above 1%, difficulties arise due to the formation of soap, which promotes emulsification during the water washing stage. If the FFA content is above 2%, the process becomes unworkable.

 The factors affecting the transesterification process are

  1. Oil temp.
  2. Reaction temp.
  3. Ratio of alcohol to oil
  4. Catalyst type & conc.
  5. Intensity of mixing
  6. Purity of reactants

The approx. process constituents are listed hereunder:

JATROPHA OIL ALCOHOL(98%) CATALYST(SODIUM OR POTASSIUM HYDROXIDE GLYCERINE BIODIESEL
1050 liters 150 liters 3.8 kg 11kg 1000 liters

Transesterification: Industrial Practice - Lurgi Process

Lurgi’s process of transesterification is used most widely in the world. The process involves intensive mixing of methanol with the oil in presence of a catalyst and then separation of lighter methyl ester phase by gravity from the heavier glycerol. The process flow chart for production of biodiesel is illustrated in Figure below.

Oil, methanol and sodium methylate catalyst are mixed in the reactor and allowed to separate into two phases. The lighter methyl ester/oil phase is mixed with additional methanol and catalyst in the reactor (R-II) followed by gravity separation. This second reactor stage maximizes the biodiesel yield and quality. The lighter phase is washed with water to remove residual glycerol or methanol dissolved in the ester phase, followed by vacuum drying to yield biodiesel.

The denser glycerol phase from R-II containing excess methanol and catalyst is recycled to the front end of R-I. The denser glycerol phase leaving R-I still containing excess methanol is distilled for its recovery in the Methanol Recovery Column and sent back to R-I. The wash water from the Water Wash Column is used in the Methanol Recovery Column. Thus the entire methanol is consumed in the production of methyl ester. The heavier fraction from the Methanol Recovery Column is processed in the Glycerin Water Evaporation Column to recover crude glycerin (conc. 80-85%) as a byproduct. This can be further upgraded to pharmaceutical glycerin by distillation, bleaching, if required, and vacuum drying.

The key features of Lurgi’s biodiesel process are:

  1. Technology applicable to multiple feedstock’s
  2. Continuous process at atmospheric pressure and at 60?C
  3. Dual Reactor System operating with a patented Glycerin Cross  flow configuration for maximized conversion
  4. Recovery & recycling of methanol
  5. Closed loop water wash recycle to minimize waste water
  6. Phase separation by gravity process (no centrifuges necessary)

Almost all the biodiesel is produced using the base catalyzed transesterification process as it is the most economical one requiring only low temperatures & pressures with 98% yield.


Biodiesel: Physical Characteristics

Properties Values
Specific gravity 0.87 to 0.89
Kinematic viscosity@ 40°C 3.7 to 5.8
Cetane number 46 to 70
Higher heating value (Btu/lb) 16,928 - 17,996
Lower heating value (Btu/lb) 15,700 - 16,735
Sulphur wt % 0.00 - 0.0024
Cloud point °C -11 to 16
Pour point °C -15 to 13
Iodine number 60 - 135

Storage of Biodiesel

The efficient storage of biodiesel resources can provide energy security to the country. Adequate data are not available for long-term storage of biodiesel and blends. Based on the experience, biodiesel can be stored up to a max. 6 months.

As a mild solvent, biodiesel tends to dissolve sediments normally encountered in old diesel storage tanks. Brass, teflon, lead, tin, copper, zinc etc. oxidize biodiesel and create sediments. The existing storage facilities and infrastructure for petrol & diesel can be used for the biodiesel with minor alterations. For biodiesel storage, shelf life and how it might break down under extreme conditions assume importance. The following merit attention for storage of biodiesel:

  • Biodiesel has poor oxidation stability. Use of oxidation stability additives is necessary to address this problem.
  • Low temperature can cause biodiesel to gel, but on warming it liquefies quickly. Hence, insulation/jacketing of storage tanks and pipelines would need to be done at the low temperature zones.
  • To avoid oxidation and sedimentation of tanks with biodiesel, storage tanks made of aluminium, steel etc. are recommended for usage.

Small PlantTRANSESTERIFICATION PROCESS: CURRENT STATUS IN INDIA

  • A bench scale process was developed for catalyst free transesterification of jatropha seed oil, other vegetable oils, acid oil etc. at IICT, Hyderabad. The crude product is further processed to obtain biodiesel meeting ASTM specifications. IICT is working on the development of a green process for biodiesel using solid catalysts and enzymes.
  • The Department of Bio-energy, Tamil Nadu Agricultural University (TNAU) has studied different variations of methanol, sodium hydroxide, reaction time and reaction temperature to optimize the process conditions for maximum biodiesel yield for alkali-catalyzed transesterification of jatropha oil. An average biodiesel yield of 96% was obtained in an up-scaled biodiesel plant of TNAU. Their pilot plant of 250-litres/day capacity consists of a biodiesel reactor with heating & agitating devices, catalyst mixing tank, glycerol settling tanks and biodiesel washing tank. The properties of the biodiesel (free fatty acid, acid value) were found to be within specified limits.
  • Transesterification process has been optimized and patented by R&D Centre of IOCL. Technology know-how has been transferred to M/s. Venus Ethoxyethers, Goa for commercialization.
  • CSMCRI has developed a simplified process for biodiesel production from the oil complying with Euro-3 specifications for free fatty acid methyl ester. An important objective has been to identify outlets for by-products to enhance the overall value of the seed and thereby make jatropha cultivation more remunerative. While biodiesel conforming  to Euro-3 specs. is produced in Europe from rapeseed oil, this is the first time that such biodiesel has been made from jatropha oil. The biodiesel developed by CSMCRI has been evaluated at Daimler Chrysler AG and found to be matching all specifications. The cetane number has been established to be 58.5.
  • Delhi College of Engineering has established small capacities of 5, 10, 50 & 100 liters batch reactors. Studies on biodiesel from waste cooking oils and greases being carried under a project sponsored by PCRA
   
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