08 monoglyceride e

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U I CThe First Address in Short Path Distillation

Production of

High Concentrated Monoglyceride

by Willi Fischer

Lecture given on occasion of the

DGF-Symposium in Magdeburg / Germany

in October 1998


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c\daten\ausarb\publikat\monovort.doc2

Production of High Concentrated Monoglyceride

Willi Fischer, UIC GmbH, Alzenau Hrstein

Main consumer of Monoglyceride is the food industry and quantities required are so

high, that worldwide several companies have specialized on Monoglyceride as their

main production. Monoesters with C16/C18 acid groups are preferred. If a high amount of

unsaturated acids is present, e.g. if the iodine value is >80 the final product is a liquid or

a jelly at room temperature. If the iodine value is


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Starting from Acids, the chemical reaction is a direct Esterification, while starting from

Triglycerides, Interesterification is involved as shown in Pic. 2.

Pic.2

Monovort.xls

Reaction Formulas for Synthesis of Monoglyceride

Direct Esterification (Fatty acid plus Glycerine)

Main Reaction

1 RCO2H 1 RCO2C3H7O2+ 1 H2O+1 C3H8O3

Acid Glycerine Monoglyceride Water

Secondar Reaction

1 (RCO2)2C3H6O+ 1 H2O+1 RCO2H

Monoglyceride Acid Diglyceride Water

1 RCO2C3H7O2

Interesterification (Fat or Oil plus Glycerine)

Main Reaction

1 RCO2C3H7O2+ +1 C3H8O3

Triglyceride Glycerine Monoglyceride Diglyceride

Secondar Reaction

+ 1 C3H8O3

Diglyceride Glycerine Monoglyceride

1 (RCO2)3C3H5 1 (RCO2)2C3H6O

1 (RCO2)2C3H6O 2 RCO2C3H7O2

Secondary reaction of direct Esterification reduces the concentration of Monoglycerides

but cannot be avoided as it happens simultaneously.

Both types of synthesis lead to an equilibrium which is as more on the right side as

higher the temperature and as longer the reaction time is. To maintain a high quality in

the final product, the temperature is limited to approx. 240C and the residence time on

this temperature should not exceed half an hour. The concentration at the end of the re-

action is 40 60 %. It should be noticed, that water is created by direct Esterification.

To avoid uncontrolled foaming by too sudden water formation, the reaction speed must

be dampened while for Interesterification there is not such a limitation.


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The dominating part of the manufacturing cost is the price for the feed material. Acids

and Glycerin are more expensive than Triglycerides. Also only 0.67 mole of Glycerin is

required for one mole of Monoglyceride by Interesterification while direct Esterificationrequires one mole of Glycerin for one mole of Monoglyceride. Therefore manufacturing

costs for direct Esterification are higher and this method is done only if Monoglycerides

with a specified Acid distribution is required. Interesterification produces Monoglycerides

with the same Acid distribution as in the Triglyceride. Limited change is only possible by

blending of different Triglycerides and hydrogenation of the double bounds. Pic. 3

shows, that basically always Fat or Oil, is the feed material for both type of reaction.

Pic.3Monovort.xls

Interesterification

Transformation of Fat or Oil into Monoglyceride

Fat, Oil

Splitting

Fatty Acids Glycerine

Esterification

Monoglyceride

Fatty Acids

The reaction speed is forced by employment of a catalyst. In production plants soaps of

elements of the first and second row of the periodic system are used. Sodium and Po-

tassium soap can be removed easier after reaction, while Calcium soap shows a slightly

higher activity.

To push the equilibrium towards Monoglyceride by excess Glycerin, 73 wt% of fat and

27 wt% of Glycerin are recommended to add to a batch. The excess Glycerin is not


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complete soluble in the Fat and intensive mixing is required. Pic. 4 shows an overview

of product streams including recycling.

Reaction step(kg/batch)

Stream Name Fat Glycerine Recycle 1 Mix 1 Mix 2 Glycerine Low Mono

Stream no. 1 2 3 4 5 6 7

Total Quantity -- -- 3.770 7.615 7.618 510 7.108

Fat 2.773 -- -- -- -- -- --

Glycerine -- 1.072 587 1.094 1.094 485 609

Monoglyceride -- -- 449 3.561 3.561 15 3.546

Diglyceride -- -- 2.566 2.774 2.774 -- 2.774

Others -- -- 168 168 169 10 179

Distillation step (kg/h)

Stream Name Low Mono Strip. Dist. Strip. Bott. Recycle 2 High Mono

Stream no. 8 9 10 11 12

Feed/h 2.706 324 2.382 1.132 1.250Glycerine 272 264 8 0 8

Monoglyceride 1.328 30 1.289 138 1.160

Diglyceride 1.039 -- 1.039 961 78

Others 67 30 37 33 4

Pic.4

Monovort.xls

Distilla-

tor

Recycle

Tank Stripper

LoMo

Tank

Reactor

1

Reactor

2

Decan-

ter

Product Streams of Mono-Process(Interesterification of hydrogenated Tallow)

Batch operation Continuous operation

2

1

4 5 6 7

3

810 12

911

After reaction, 15 % of unreacted Glycerin is still left in the mixture.Only 6 - 7 % of Glyc-

erin is soluble in the Glyceride phase. 8 - 9 % Glycerin can be separated by settling.


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The Glyceride phase contains about 50 % Monoglyceride, 7 % free Glycerin, 40 % Di-

glyceride and 3 % of a mixture of Triglyceride, Diglycerine, free Acids and traces of

catalyst or decomposed catalyst.For some applications the separated Glyceride phase can be sold direct. For other ap-

plication the so called Low Mono with less than 1 % of Glycerin is required. The Glyc-

erin is stripped either in a flash column or better in a wiped film evaporator at some

mbar. Very often a concentration of >90 % Monoglyceride with low content of free Acids

and Diglycerine and free of Ash is required. For the production of this so called High

Mono the distillation of Low Mono is necessary. This can be done only by Short Path

Distillation at approx. 200C and 0.01 mbar or less.

Pic. 5 shows the sectional view of a distillation unit for a feed rate of 13 000 mt/a Low

Mono. The quantity of High Mono recovered from the Low Mono can vary from 40 55


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% of the total content depending on what concentration is required. Monoglyceride is

the distillate, Di- and Triglyceride remain in the residue.

In the Monoglyceride molecule the acid group is coupled with Glycerin either in - or in

position. The -Mono content is wanted as high as possible as it has a much higher

emulsifying effect as -Mono. Just after reaction, the -Mono portion can be 7 % of to-

tal. During storage some -Mono will be converted into -Mono and the content can be

as low as 2 % if conversion is completed. Therefore the specification of-Mono content

is not precise and is depending on the time when the sample is analyzed. In elder litera-

ture we find often the specification of-Mono while in our time total Mono content is

specified. Reason is, that the wet analysis which was used in former time can determine

only -Mono while the GC method now used measures the total Mono content.

The residue from the Mono concentrating is recycled to the reaction process and is fur-

ther converted into Monoglyceride. Approximately 50 % of the recycled residue is con-

verted into Monoglyceride at each recycle. After 6 recycles, about 98 % of the fat is con-

verted finally into Monoglyceride. As for each reaction batch fresh Fat and fresh Glyc-

erin is added the averaged residence time of the material in the process is between 2

and 3 passes. As longer the residence time of the material in the process as more

thermal degradation can happen. The acceptable number of recycles is determined by

the quality specs. of the final product and is influenced by the quality of the feed mate-

rial, but more by adequate equipment, precise operating conditions and proper storage.

E.g. nitrogen blanketing of material at elevated temperature shall be considered. Manu-

facturers told as that recycle rates ranging from 3 to more than 25 recycles are usual.Unlimited number of recycle is only theoretically a 100 % use of material. A small

amount of Glycerides is purged with the settled Glycerin after reaction. From the mate-

rial balance of an existing plant over an extended time of operation and with more than

20 recycles, the lost of fat was calculated in the range of 2-3 %.


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High excess quantity of Glycerin in the feed mixture is required for several reasons. It

was already mentioned, that excess Glycerin pushes the equilibrium to the right side of

the reaction formula. As the catalyst is promoting also the reaction backwards there is a

risk, that Monoglyceride is disproportioned during Glycerin stripping Therefore it is nec-

essary to deactivate the catalyst. The deactivation is done by adding Phosphoric Acid.

The Phosphate will be extracted from the mixture by the insoluble portion of Glycerin. It

is removed from the process together with the settled Glycerin. To avoid recycling of the

Phosphate in the process, the settled Glycerin must be distilled before it can be recy-

cled to the reactor.

An alternative which does not require a redistillation of the settled Glycerin each time is

the use of Calcium soap as a catalyst. Calciumphosphate is insoluble in Glycerin and

can be separated by filtration or with a centrifuge. However this is somewhat difficult

and there is a risk, that the ash content is higher in the final product. Also it has to be

considered that Diglycerine together with undistilled Glycerin is recycled and will in-

crease the content in the final High Mono.

On production scale, direct Esterification as well as Interesterification can be done con-

tinuously or batchwise. As today more than 90 % of Monoglyceride is produced by In-

teresterification only this route shall be further discussed.

For continuous reaction one equipment configuration can be a mixing vessel followed

by a pipe reactor.


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Pic.6Monovort.xls

Reflux

condenser

Liquid

ring

pump

Coolingwater

Cooling

water

Cooling

waterSteam

Batch Reactor System for Monoglyceride SynthesisEquipment Diagram

M M

Fat,

Glycerine,

Recycle-

mixture

Deactivatingchemicals

Catalyst Steam

Coolingwater

To hotwell

Steam ejectors

ScrubberDecanter

Reactor 2Reactor 1

Reflux

condenser

Precipitated

Glycerine

Glyceride

mixture

A simplified equipment diagram of a 3 stage batch reactor system is shown in Pic. 6.

Reactor 1 is a steam heated mixing vessel with a reflux condenser. In this vessel the

mixture is heated till the required concentration of Monoglyceride is reached. Then the

mixture is pumped into the second reactor and cooled as fast as possible, to minimize

reverse reaction. After catalyst deactivating the and settling is finished, Glycerin and

Glyceride mixture are pumped to separate storage tanks.

The total batch time is almost 9 hrs. However, in a 3 vessel reactor system as shown

the vessels are operated in an overlapping mode which allows to finish all 3,5 hrs an

other batch and nearly 7 batches can be made in 24 hrs. The batch volume has to be

considered carefully. Too small reactors cause higher specific manufacturing and oper-

ating cost. Too large reactors designed with a small l/d ratio are expensive again and

very powerful, high energy consuming agitators are required. If l/d is high, the muchheavier Glycerin phase is not carried quickly enough in the upper section and emulsion

equilibrium is not reached.


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Experience taught us, that reactors for a batch volume of 5 - 10 m are somewhat an

optimum. The design of the reactor system must also consider GMP rules and espe-

cially low thermal degradation. Heating with steam rather than with hot oil reduces tem-

perature overshooting. Recommended material of construction is Inox according to

German code 1.4571 or American code 316.

Pic.7Monovort.xls

Rect-

fication

ower

Condenser

Coolingwater

Diglyceride

Coolingwater

Hotoil

Liquid

ring

pump

Continuous Distillation System for High and Low MonoglycerideEquipment Diagram

M

Glyceride

Mixture

after

Reaction

Steam

Coolingwater

To hotwell

Steam ejectors

Scrubber

High Monoglyceride

M

StrippedGlycerine

Hotoil

Cooling

Glycerine

stripper

Monoglyceridedistillator

Cold trap

Oil

booster

um

Quench cooler Low Monoglyceride

Pic. 7 shows the simplified equipment diagram of a double stage distillation plant for

Monoglyceride. In the first stage Glycerin is stripped in a thin film evaporator with rectifi-

cation tower and an external condenser. Glycerin free Low Mono can be discharged via

a quench cooler from this step. For High Mono production, the bottom product is

pumped into the following Short Path distillator with internal condenser, where

Monoglyceride is concentrated in the distillate.


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Both evaporators are thin film evaporators indirect heated with thermal oil. Vacuum is

produced by an oil booster pump followed by a multiple stage steam ejector system and

a liquid ring pump. Driving fluid for the oil booster pump and the liquid ring pump is

Glycerin. This will avoid contamination with a non food grade auxiliary medium in case

of operating or plant failure.

Thin Film Evaporator Series RF Short Path Distillator Series KD

Pic. 8 shows the principle of thin film evaporators with and without internal condenser.

For economical reasons high availability of the distillation is essential. Modern plants

are operated with net distillation time of 8000 hrs/a. This is an uninterrupted operation

24 hours a day for 7 days a week all year round. Only one shut down per year for main-

tenance is necessary. To maintain the high quality specs for the final product, fouling on

the evaporator surface must be avoided. Experienced manufacturers of agitated film

evaporators deliver equipment with fine polished surface and optimal roller wiper sys-

tem to fulfill these requirements.


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The economical figures, especially the production of high concentrated Monoglyceride

which requires a higher investment shall be analyzed. Pic. 9 shows the annual key data

of 1994 of a production plant with a capacity of 10 000 mt/a.

Input

Unit price Quantity Annual cost Portion

US$ %

Hardened Soy Oil 930 US$/mt 8.319 mt/a 7.736.670 48,8

Glycerine 2.050 US$/mt 1.815 mt/a 3.720.750 23,5

Rework of settled Glycerine 105.000 0,7

Share of plant cost per year1)

1.400.000 8,8

Steam 40 barg 61 US$/mt 8.900 mt/a 542.900 3,4

Steam 12 barg 56 US$/mt 2.400 mt/a 134.400 0,8

Fuel 305 US$/MWh 750 mt/a 228.750 1,4

Electricity 82 US$/mt 880 MWh/a 72.160 0,5

Other utilities, instrument air, 150.000 0,9

nitrogen, cooling water,

waste disposal, etc.

Labor cost 50 US$/h 260.000 1,6

Overheads 1.500.000 9,5

Total2)

15.850.630 100,0

Output

Unit price Quantity Annual grosspro t

US$

High concentrated Mono 2.140 US$/mt 9.840 mt 21.057.600

1)Total Plant Investment is 7.000.000 US$. 20% of this sum covers depreciation, intrest rate,

insurance, etc. per year.2)

Cost do not include packing, transport and distribution and sales activity.

Pic.9Monovort.xls

Cost/Profit Break Out of Figures of 1994

Plant Capacity: 10.000 mt/a High Mono


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This plant makes good profit even if the additional distribution costs are considered. In-

teresting is a look on the cost increments. Feed material is almost 72 % of the total cost,

while 9% is overheads. Only the remaining 19 % of the cost can be influenced by engi-

neering and production management. Energy, maintenance, labor are small portions

and must not be analyzed furthermore. The remaining portion for plant investment with

less than 9 % is reasonable.

However as the investment is high, purchase departments tend to decide more on price

rather than on technical performance to save money. However this is not smart at all.

Due to strong competition amongst bidders for this type of plants the range for high and

low price bids are max. 10 %, which is only 1 % cost saving. If less investment would

reduce the yield by only 2 % this would increase the feed material cost portion by about

1.5 %. This shows the relation. The same is true for reduced maintenance efforts.

Another aspect is the minimum size where profit is made at all. As some cost factors

are constant, others linear and some reverse proportional, there is a minimum produc-tion where break even is reached. This is dependent on market situation, infrastructure,

environmental regulations, annual load etc.

To support the decision of potential investors, our company has developed an in-house

calculating program for quick calculation of economical key data. Pic. 10 shows several

cases of investigation of different sizes often requested in an early stage of investment

decision. It is astonishing, how much break even can differ depending on theconditions.


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P ro du ctio n c ap ac ity of h ig h P ro du ctio n c os t re la tiv e to gro ssco nce ntra ted M ono glyce rid e s ale s p rice

m t/a %

Case 11.300 1075.000 87

15.000 791.850 (Break even)

Case 21.300 985.000 81

15.000 701.230 (Break even)

Case 31.300 117

5.000 9515.000 86

3.500 (Break even)

Case 41.300 108

5.000 8715.000 74

2.030 (Break even)

C ase 1 2 3 4

N et. production tim e/year 7.500 8.000 6.400 8.000Source for raw m ateria l O utside Inhouse O utside O utsideFabrica tion program M onoglyceride O ther O leo- O ther O leo- M onoglyceride

only chem ica ls as chem ica ls as onlyw ell w e ll

Infrastructure M edium level H igh leve l M edium leve l H igh leve lEnv ironm etal regula tions H igh H igh Low H ighR eaction process Batchw ise B atchw ise B atchw ise C ontinuousN o. of R ecycles >6 >6 >6 >6

Pic.10Monovort.xls

Inf luence of Plant Size on Prod uct ion C ostCo mpa rison of different Scenarios

Summarized we can say, that the technology for the production of Monoglyceride has

reached a high level so far. Under the pressure of global competition plant manufactur-

ers as well as producers are forced to optimize the technology further. Based on todays

experience remarkable improvement of the distillation technique is not expected. How-

ever improvement of the synthesis and optimized operating conditions seem to have

room for further improvement in the near future. It will be interesting to see the results.

08 monoglyceride e

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