Hydrogenation - Process and Product Quality Control

Hydrogen is a very complicated process as each unsaturated bonds in each chain may be hydrogenated at difference rate depending on the position of the double bond. During hydrogenation of fats and oils, three important reactions occur simultaneously namely saturation of double bonds, cis-trans isomerization of double bonds and migration of double bonds to new positions in the fatty acid carbon chain. The relative rates of each of the reaction can be controlled by the reaction conditions.

            There are 2 important parameters in a hydrogenation process namely activity and selectivity. Activity usually refers to the rate of reaction which means that how fast the hydrogenation reaction can proceed. On the other hand, selectivity defines as the relative rate of hydrogenation of the more unsaturated fatty acids when compared with that of the less saturated acids. The conditions used in hydrogenation process is the balance between the process quality (Trans fat, selectivity and activity) and the production cost (cost of catalyst, the apparatus for use of high temperature and pressure). When a catalyst is chosen to hydrogenate specific oil, the reaction parameters are temperature, pressure, catalyst concentration and agitation rate. All the parameter must be properly controlled because they influence both the rate of the reaction and the trans isomer selectivity.

            Trans isomerization occurs when the reaction is carried out at high reaction temperature, low pressure, low catalyst dosage and slow agitation rate. On the other hand, high reaction rate can be achieved by using high reaction temperature, high pressure, high catalyst concentration and high agitation rate. However, increasing the catalyst concentration will increase the production cost and might not effective when the solubility of hydrogen is the limiting factor. Hence, high pressure and fast agitation rate are applied in most hydrogenation process. The process conditions required to achieve high selectivity, high activity and low trans fat is summarized in table below:

Parameter	High Selectivity	High Activity	Low Trans-fat
Pressure	Low	High	High
Temperature	High	High	Low
Catalyst dosage	High	High	High
Catalyst	-	-	Ni
Agitation rate	Low	High	High

Hydrogenation - Introduction

In edible oils and fats industry, hydrogenation is used to produce a more oxidative stable product and change liquid oil into a semi solid or solid fat with the desired melting characteristics. Hydrogenation is a chemical reaction in which hydrogen is reacts with the double bonds found in triglycerides to form saturated bond. It usually performed batch wise in a pressurized stirred reactor with nickel as catalyst. In most cases, the oil is not fully hydrogenated as fully hydrogenated oil is too hard for some applications. Hence, partially hydrogenation is applied and this gives high trans fatty acid in the hydrogenated oil. It has been proven that trans fatty acid have negative effect on human health. As a result, future approach of hydrogenation is in the reduction of trans-formation.

First of all, feed oil is pumped into a buffer tank. This buffer tank is a multi function tank where it provide heating, degassing, drying and as a buffer tank. The feed oil is preheated by the out going hydrogenated oil followed by steam to 160 ^oC. After the measuring tank reached the pre-set amount and temperature, the oil will be drained to the hydrogenation reactor. At the same time, nickel catalyst in oil slurries is pumped into the reactor.

After the filling process completed, vacuum is applied to the reactor before the pressurized hydrogen is pumped in. This is to remove moisture and oxygen in the air which may cause hazard when mixed with hydrogen. The hydrogenation reaction proceeds as follow:

R₁CH=CHR₂ + H₂ à R₁CH₂-CH2R₂                                          

IV for the hydrogenated oil is checked from time to time. When the required IV is obtained, the hydrogenated oil is pumped to a drop tank.

This drop tank act as a buffer tank to hold the hydrogenated oil before it is used for heat recovery with the feed. After heat exchange, the hydrogenated oil is sent to another buffer tank to cool down to temperature below 100 ^oC prior sent to filtration process. This is to protect the cloth in the pulse tube filter. The filtered oil is sent to final polishing filter before pumped to storage tank. The schematic representation of hydrogenation process is shown below:

 

Fractionation - Process Quality Control

 Process and Product Quality Control

            In palm oil fractionation, olein fraction is the desired product and it is important to increase the olein yield, at the same time maintaining the oil quality. Important parameters for palm olein characterization are IV, cloud point and cold test. Normally, palm oil fractionation can give a yield up to 80 %. On the other hand, the desired product in PKO fractionation is the stearin fraction which can be used as CBS. Hence, the objective in PKO fractionation is to maximize the stearin yield. Important parameters for stearin are SFC (especially 30^oc), SMP and IV. A good quality stearin will have a steep SFC profile.

alm Oil Fractionation

High final crystallization temperature will produce larger and better crystal which is easier to filter. However, this will give low stearin yield and olein with low IV. At the same time, the stearin IV will be low and olein yield is high. On the other hand, low final crystallization temperature will produce lot of smaller crystal which is weaker. In this case, the olein produced is high IV with low yield. The stearin will be high IV and high yield.

Agitation rate is another important parameter in a crystallization process. This is because crystallization is an exothermic process and oil is a rather poor heat conductor. If heat produced during crystallization process can not be removed effectively, it will melt some of the crystal causing uneven crystal formation. This will lead to difficult filtration. Hence, agitation is required to give intimate mixing of the oil for good heat transfer. On the other hand, high agitation rate tent to break the crystal causing secondary crystallization. Second crystallization will lead to uneven crystal formation. As a result, high agitation rate is used in cooling step and lower agitation rate is used in the crystal formation state.

Palm Kernel Oil Fractionation

In PKO fractionation, the important parameters that affect the product quality and yield are final slurries solid fats content, static crystallizer temperature and holding time. High final slurries solid fat content indicate that there are a lot of nucleus initiated and this will give a smaller crystal in cake formation steps. If the cake formed in static crystallizer is too soft, there are 2 possible reasons, namely temperature too high or holding time too short in static crystallizer. Soft cake will lead to low stearin yield and low stearin and kolein IV. On the other hand, hard cake will give higher stearin yield with high stearin and olein IV.

Fractionation - Process description

4.3.1 General Process flow

First, the feed oil will be preheated before entering the crystallizer to destroy all crystal memories. The oil will be cooled in the crystallizer according to the preset cooling profile depending on the feed oil quality and product quality required. For palm kernel oil fractionation, the crystallization section consists of two steps; dynamic crystallization and static crystallization. Dynamic crystallization process is performed in a crystallizer to initiate the nucleation while the static crystallization is performed in a statoliaser for cake forming. On the other hand, palm oil fractionation only has one crystallizer which is dynamic crystallizer. After crystallization, the slurries will be sent to membrane filter press to separate the olein (liquid fraction) and stearin (solid fraction). The schematic representation of the process is shown in below

Dry Fractionation - Fractionation Technologies

Dry fractionation

Dry fractionation is the simplest and cheapest separation technique. This is because no post treatment of the finished product is required as there is no chemical added in the process. The slurries will be fed into a membrane filter press to separate into olein and stearin. Some products need to fractionate in a special way. For example, palm kernel oil is solidified into cakes in the static crystallizer before feed into the membrane filter press.

Solvent fractionation

The crystallization is performed in dilute solutions with usually acetone or hexane is used as solvent. This process only requires a short crystallization time and provides rather easy separation. Hence, solvent fractionations give higher yield and higher purity of the finished products. As solvent fractionation required a very high production costs and capital investment, it is becoming less interest to the industry and only used in specialty fats production.

Detergent fractionation

In detergent fractionation, an aqueous detergent solution is added to the crystallized oil. The wetting agent, usually sodium lauryl sulfate, in combination with an electrolyte, usually magnesium sulfate allows the crystals to be suspended easily in the aqueous phase. The water phase and the oil phase are separated by means of centrifuge. The water phase is subsequently heated to melt the stearin which will be recovered in a second centrifugation step. After separation, the olein and stearin fractions are washed and dried to remove the detergent added. The high production costs and contamination with the detergent are the main disadvantages of this fractionation technique.

FRACTIONATION - Introduction

Among the various edible oil and fats modification processes, dry fractionation has gained the most interest in edible oil industry. It is now applied to many kinds of fats and oils such as palm oil, tallow, fish oil, cottonseed oil, sunflower seed oil, palm kernel oil, tallow butter fat and special fats. Dry fractionation is a pure physical and fully reversible process. Thus this replies to the increasing demand of oil processors for more cost efficient, environmental friendly and safer processes.

Dry fractionation separates the high melting triglycerides from low melting triglycerides by crystallization from the melt. It simply consists of a controlled crystallization of melted oil, conducted accordingly to a specific cooling program followed by separation of the solid from the liquid fraction. Apparently, it looks simple, but in practice, this physical process is completed by the fact that the formation of nuclei depends on the foreign particles, agitation, temperature, triglycerides composition and the type of pre-treatment followed by the oil and fats.

Crystallization is a 3 step process: controlled cooling of the melt, nucleation and crystal growth. The shape and size of the crystals are determined by the way the lipid material is cooled and agitated.

PIPOC 2013

PIPOC 2013

Date: 19 - 21 Nov 2013

Venue: Kuala Lumpur Convention Centre, Malaysia

Organizer: Malaysia Palm Oil board (MPOB)

Website: www.mpob.gov.com

The Malaysian Palm Oil Board International Palm Oil Congress (PIPOC), is a biennial event organized by the Malaysian Palm Oil Board (MPOB). PIPOC will once again be held at the Kuala Lumpu Convention Center (KLCC), which offers a stimulating environment for conferences and exhibitions. PIPOC 2011 attracted more than 6000 participants and trade visitors from 58 countries and bore testimony to one of the world's largest palm oil technical and trade congregations.

PIPOC 2013 has five concurrent conferences to provide a strategic platform for interaction and in-depth deliberation on the many facets of the oil palm and the palm oil industry, ranging from innovations, latest developments, challenges and the way forward for the industry. A trade exhibition with more than 200 exhibition booths will also be held throughout the Congress. This would provide opportunities for delegates to view and discuss current technologies, state-of-the-art equipment and products related to the oils and fats industry. The exhibiton also provides excellent networking opportunities for buyers and sellers.

 

PIPOC 2013 is expected to draw more than 7000 participants and trade visitors comporising mainly CEOs, directors, researchers, policy makers, millers, traders and exporters and all who are involved either directly or indirectly in the palm oil industry.

 

PIPOC 2013 themed 'Green Opportunities from The Golden Crop' will focus on palm oil as the powerhouse in the oils and fats market. The remarkable performance of the Malaysian oil palm industry has contributed to the growth of the national economy and world oils and fats market. The dynamic development and advancement of the palm oil industry provide endless sustainable opportunities for the economic growth of the oils and fats business. PIPOC 2013 will focus on sustainable production, versatility of applications in both the edible and non-edible sectors, as well as being a formidable player in the global oils and fats market.

 

I therefore take this opportunity to invite you to join industry leaders and hear from notable and renowned speakers and learn their views, at this not-to-be-missed event - PIPOC 2013, from 19 - 21 November at the Kuala Lumpur Convention Centre.

Quote from Datuk Dr Choo Yuen May, An Invitation, http://pipoc.mpob.gov.my/

 

 

 

Chemical Refining Part 2

Process and Product Quality Control

There are a few process parameters that must be control properly to minimize oil loss while maintain the desired quality. They are caustic dosage in neutralization and sulfuric acid dosage in acidulation.

The selection of proper amount and strength of caustic is very important in neutralization process. It is customary to measure the strength of caustic for refining in terms of their specific gravity expressed in degree Baume.

First, the strength or concentration of caustic is determined by type of oil to be neutralized. Lower FFA feed will require lower concentration of caustic. After this, the amount or usually term as treat is determined as shown in equation below:

                                      

Where treat is the amount caustic added, 0.142 is ratio of molecular weight of sodium hydroxide and oleic acid, FFA is the percent of free fatty acid in crude oil, % NaOH is the strength of caustic and Excess is the excess sodium hydroxide selected. The oil loss due to neutralization process can be determined as follow.

            If the caustic is overdose, more soap will be produced. Hence, more sulfuric acid is required to convert the soap into fatty acid and salt. As a result, more acid oil which is a lower grade product will be produced. Sulfuric acid dosage plays another important role in the quality of the process. Excess sulfuric acid will cause problems in effluent plant where more caustic is required to neutralize the sulfuric acid. Low sulfuric acid will lead to incomplete conversion of soap to fatty acid.

 

 

Chemical Refining - Part 1

Introduction

 

Chemical refining usually refer to a neutralization process where alkali reacts with the free fatty acid (FFA) in the crude oil to form oil insoluble soap and water. Usually, seed oil with high FFA might need to go through this neutralization process before going for physical refining. This process can give almost complete removal of FFA and some of the impurities. Neutralization plant is a small plant but it may be the most complicated plant in vegetable oil refinery complex. This is because there are lots of parameters that must be control properly in order to get the neutralized oil quality and minimize the oil loss. 

            In recent year, researches have showed that phospholipase are able to perform the degumming process. Enzymatic degumming offers advantages of lower oil loss, eco friendly process. However, the expensive production cost is main concern.

Process Description

In general, the crude soft oils will be going through a degumming process before going to chemical refining. The crude soft oil will be mixed with phosphorous acid in a shear mixer at 80 – 100 ^OC to convert the non-hydratable phospholipids to hydratable phospholipids. After this, the crude degummed oil is sent to the caustic neutralization process where a base is added in to neutralize the FFA in the crude oil. In most cases, caustic soda (NaOH) is used as the neutralizing agent. This is because it is much more effective compared to other weaker alkali. However, it has a disadvantage of saponifying the neutral oil. Saponification process is the reaction of a metallic alkali (base) with a fat or oil to form soap.  Equation below shows the chemical reaction of neutralization process.

RCOOH + NaOH à RCOONa + H₂O                                

There are two common technologies in neutralization process namely short mix and long mix process.  Long mix process is usually used in United State while short mix process used widely in Europe and many other areas worldwide. Long mix process usually applied to good quality crude oil with low FFA which allows the neutralization process to occur at a much lower temperature, lower caustic dosage and longer retention time. Long mix process will reduce the caustic consumption but will give higher oil lost to soponification if the caustic dosage is not control properly. This is because of the longer contact time. On the other hand, Short mix process requires a higher concentration of caustic, higher temperature and shorter resident time. In return, short mix process gives advantages of eliminating the potential of large losses and suitable for poor quality crude oil with high FFA.

            The mixture with neutralized oil, gum and soap stock is sent to a separation process consists of centrifugation and water washing. First, the mixture is sent to a centrifuge to separate soap stock (heavy phase) from neutralized oil (light phase). Hot water is added in to the light phase to further reduce the soap in oil content. The neutralized oil is fed into the vacuum drier for drying the moisture level to 0.05-0.1 % before sending to storage. After neutralization process, NSBO, NRSO will be send to physical refinery while NMZO and NSFO will go through a dewaxing process before send to physical refinery.

            The soap stock from the centrifugation process will go through acidulation process. The soap stock is mixed with sulfuric acid in a splitting tank and agitated with steam or air. After this, the mixture is left for cooling and separation. Acid oil will be collected at the top while acid water is collected fro the bottom of each splitting tank. Acid water will be sent to effluent plant.  

RCOONa + H₂SO₄ à RCOOOH + NaSO₄         

 

    

Physical Refinery Part 2

Process and product quality control

 

In physical refining process, there are two critical control points which is at the deodorizer and final polishing filter. The temperature in the deodorizer must be maintains above 260 ^oC for palm oil and 220 ^oC for soft oil while final polishing filter is the last protection before deliver the RBD palm oil to customer. Beside Deodorization temperature, the bleaching earth dosage is another parameter that must take into consideration in order to maintain refined oil quality and minimize oil loss. Table below showed the common quality issue with possible reasons and corrective action.

 

Quality	Possible reasons	Corrective actions
High FFA	Low deodorizer temperature Low vacuum in deodorizer Retention time in deodorizer too short Low sparging steam to oil ratio	Check deodorizer temperature and pressure Recalibrate deodorizer temperature and pressure Use longer cycle time Check sparging steam rate and pressure
High color	Insufficient bleaching earth dosage Short retention time in bleacher	Use proper amount of bleaching earth Run the plant within the design capacity
High PV
High oil loss	Deodorizer temperature too high High bleaching earth dosage	Check deodorizer temperature and pressure Recalibrate deodorizer temperature and pressure Use proper dosage of bleaching earth
High moisture	Leakage in final product cooler	Check oil quality before and after the cooler. Change the gasket

Physical Refinery part 1

Crude vegetable oils contain a wide variety of materials including fatty acids, glycerides, phosphatides, sterols, tocopherols, hydrocarbons, pigments (gossypol and chlorophyll), stearol glucosides, protein fragments and mucilaginous material. Refinery process is designed to remove undesirable constituents in crude oils with minimal oil loss. Physical refinery usually refers to a process that removes FFA in the crude or degummed oil by evaporation rather than being neutralized in alkaline refining process.

            Deodorization is the major section in the physical refinery process. In the industry, the crude oil is usually pre-treated before entering deodorizer. The pre-treatment sections include degumming and bleaching. For seed oil with high FFA content, an alkaline refining process may be required. Degumming process is designed to remove phosphatides and mucilaginous material from the oil. Bleaching is the process to remove color bodies from the crude oil by adsorption onto the bleaching earth. Lastly, deodorization is designed to remove the relative volatile odoriferous compounds from the crude oil.

            Generally, the crude oil is heated to about 105 ^oC before sent to the drier or degasser to remove moisture and dissolved gas. The dried oil will be mixed with phosphoric acid before entering a retention vessel. This retention vessel is designed to provide time for the coagulation of gums to occur. Here is the place where degumming process occurs and it is accomplished by hydrating the phosphatides and similar materials to make them insoluble in oil. Then, the oil slurries are sent to bleacher where bleaching earth is added in to adsorb the color bodies in the oil. The degummed-bleached oil is sent to a leaf filter to separate the oil from bleaching earth. Pre-coating is done by circulating oil in pre-coat tank to the leaf filter. This is to provide better filtration of bleaching earth as the cake form on the surface of the filter. the filtered oil is sent to a buffer tank. From buffer tank, the filtered oil is further refined in the deodorizer.

            There are many type of deodorization plant available in the market including continuous packed column, semi continuous tray and many others type. Normally deodorization column will be design with heat recovery whereby the hot oil leaving from the column bottom will be used to pre-heat the oil feed into the Deodorizer column. Deodorization column temperature will be depending on type oil. During deodorization, FFA and other volatile component is vaporized and sucked out by the vacuum. The RBD oil is further cooled down by heat exchanger before sent to a polishing filter prior to storage. The vapor phase from deodorizer is sent to scrubber to recover the FFA and is collected as fatty acid distillate, FAD. Below is the simplified process flow diagram for a normal physical refinery plant.

Palm Oil Processes

Vegetable oils and their derivatives have a wide range of application not only in food industry but also play an important role in non-edible industry such as oleochemical production. The food application may include frying oils, margarines, and shortenings, confectionery lipids, cooking oils, salad oils, emulsifiers and animal food. For non-edible application, it may cover fatty acid production, fatty alcohol production, soaps, detergents, glycerine, biofuel, lubricants, and hydraulic fluids, pharmaceutical and cosmetic application.

However, the native form of vegetable oils has limited applications due to the various components in the oil. Generally, vegetable oil consist of a wide range of triglyceride with different fatty acid composition, monoglyceride, diglyceride, phospholipids, FFA, moisture and other impurities depending on type of toil.

As a result, refinery process is needed to remove impurities from the vegetable oil. Conventional refinery process consists of bleaching and deodorization step. Seed oils with high FFA may need to undergo a chemical refinery to neutralize the FFA prior to physical refining. Besides this, wide ranges of oils and fats modification process are used to modify the physical properties of vegetable oil. These modifications include interesterification, hydrogenation and fractionation.

Composition Comparison

Fatty Acid	Carbon no	Coconut oil	Palm kernel oil	Palm oil	Soybeen oil
Caprylic acid	C8:0	5~10	3~6
Capric acid	C10:0	5~10	3~5
Laulic acid	C12:0	45~53	40~52
Myristic acid	C14:0	15~21	14~18	0~2
Palmitic acid	C16:0	7~11	6~10	38~48	7~12
Palmitoleic acid	C16:1
Stearic acid	C18:0	2~4	1~4	3~6	2~3
Oleic acid	C18:1	6~8	9~16	38~44	20~30
Linoleic acid	C18:2	1~3	1~3	9~12	45~58
Linolenic acid	C18:3				4~10
Arachidic acid	C20:0			< 1	0~3
Gadoleic acid	C20:1				< 1
Behenic acid	C22:0
Erucic acid	C22:1
Iodine value		8~12	14~23	44~54	120~140
Saponification value		250~264	245~255	194~206	190~195
melting point	oC	20~26	24~26	27~50	-23~-20

Fatty Acid	Carbon no	Rapeseed oil	Olive oil	Sunflower oil	Beef tallow
Caproic acid	C6:0
Caprylic acid	C8:0
Capric acid	C10:0
Laulic acid	C12:0
Myristic acid	C14:0	< 1	< 1		1~6
Palmitic acid	C16:0	2~5	7~16	3~10	20~37
Palmitoleic acid	C16:1			< 1	1~9
Stearic acid	C18:0	0~3	1~3	1~10	15~30
Oleic acid	C18:1	11~60	65~85	14~65	20~50
Linoleic acid	C18:2	12~24	4~15	20~75	0~5
Linolenic acid	C18:3	6~15	1~15	< 1	0~3
Arachidic acid	C20:0	0~2	< 1	< 1
Gadoleic acid	C20:1	0~14
Behenic acid	C22:0	0~1		< 1
Erucic acid	C22:1	2~52
Lignoceric acid	C24:0	< 1
Iodine value		95~108	80~88	120~140	35~55
Saponification value		170~190	188~196	186~194	190~200
melting point	oC	-9	-	20~28	40~50