The production of 114 kton/a of 2,5-dimethylfuran for octane improvement from fructose as a renewable feedstock

Process Systems' Engineerirv. DeIftChem Tech

Faculty of Applied Scier •

Derft University of TechntJ, . - ~l::> /} < ~

P.O. Box 5045,2600 GA ~' ~ _ ~~ ~~

TheNetherlanctr:

LPD No.

~~

_

~~/~,I.;·3

'

.

~i

·

T

U

Delft

..,. ~~. ~d S~, ~~.,tc..e~

~t4-Conceptual Process Design

Chemical Process Technology

Subject

The production of 114 kton/a of 2,5

-

dimethylfuran

for octane improvement from fructose as a

renewable feedstock

Authors

E.Q.B.A. Nettl

J.M. Schouten

J.A. Wassenaar

M.J. Verwijs

Keywords

2,5-dimethylfuran 5-hydroxymethylfurfural

Assignment issued

Report issued

Assessment

Faculteit Technische Natuurwetenschappen

Telephone

01521 21 821

015

21 41 403

01521 34316

01524 15970

18 September 1998

23

December 1998

19 J anuary 1999

CD

CPDNo.

Conceptual Process Design

Chemical Process Technology

Subject

The production of 114 kton/a of 2,5-dimethylfuran

for octane improvement from fructose as a

renewable feedstock

Authors

E.Q.B.A. Nettl

J.M. Schouten

J.A. Wassenaar

M.J. Verwij s

Keywords

2,5-dimethylfuran 5-hydroxymethylfurfural

Assignment issued

Report issued

Assessment

Telephone

01521 21 821

015 21 41 403

01521 34316

015

2~'i5

970

18 September 1998

23 December 1998

19 January 1999

CPD3226

s

ÎI

~

l!Un~,

chicory,

~

starçh.,

~

. " '.' .. -~-t ~conceptu~l proce.ss design ~:

;::>

(CPD) only the

fructose

/

sy~p

available from sugar refineries is cODsidered,

~

price

i.

f]

~~

0.{

was

~et

at Dfl

~~.E

~r"

kg

.

~

<t-e..{?'

,

~ ~

he production of DMFu from fructose is a two step synthesis. In the first reac.tion

fÎt-t

~

t~

step, fructose is converted to, 5-hydroxYl!lethyf-furfural (HMF) in a s~ries of four T~

,

J9\

continuous stirred boiling liqu.id slurry tanJe

reac~ors.

In the second reactiQn step,

~

is converted to DMFu via two interrnediates in a monolithi re . Besides-the use

é

l

of a monolithic

re~çtor,

two membranes

~ere

,

used.

The

~s

.

~

q;;'pment and the

<)

ft

non-availability ofphysical data makes the process in~ive. ~/~ ..

3e.~~

r:

~

~

The product price was derived from the MTBE'pr~ce. ~ MT~.E cos s Dfl2.00 r~ }

q

and DMFu is twice as effective as octane enhance'r, its price was set t Dfl3.00 er kg ~~ ...

I

..

~

\

r

-for t~flr:elia;J,iaary -àesjgn. The analysis of the economical aspect.s result . a ~ ~ '-t..~ •

negative cashflow with these feedstock

anç!~uct

prices. The process becomes

~I'P' ~

profitable at a feed~tock price of 0.64 I?tYo'r'ffprod~ct price of 3.25

pfl./'(f

~ O'f.

(~à··

'tf'

I>·

~/~)

L?

r:r

~(e

3.

_tIta

Finally to improve the production

o

r

DMF~

from fructose

sy~p

some

Y;J

recomrnendations are suggested ..

In the first place it shou1d be checked whether one solvent can be used for both reactions. This would substan~ially limit the amount of equipment and w'astestreams, especially if water is the only solvent.

. In the second place it is me . oned that~ne reactor ~Q9H18 Q@ 1,1688 for both reactions.

~#~

A thorough kinetic research . . . . .

r~' - It should also be checked ho the convers ion of giucose can be increased. ~Iy

el

J;R.e-glucose converSiO.i ' 0 ly 16 '(0.

I'

~

.t,..

'

~

"

~

~

~

..J

tfJeiJ"

CPD3226 Acknowledgement

Acknowledgement

We would like to thank the following persons for their assistance and support:

Ir.e.P. Luteijn, Dr.ir. M.Makkee, Prof.dr.ir. H. van Bekkum, Prof.dr.GJ.Witkamp,

Dr.G. Luijkx, R.Downing.

~

~

(OfL

.

~

I,)

CPD3226 Table of contents

Table of contents

~~

1 Introduction ... 1

1.1 Reaction products ... 1

1.2 The product and feedstock market... ... 1

1.3 The production process ... 2

1.4 The availability of physical data ... 2

2 Process Options and Selection ... 3

2.1 The choice of the reaction path ... 3

2.2 The choice of the catal yst.. ... .4

2.2.1 Catalyst choice for the first reaction ... 4

2.2.2 Catalyst choice for the second reaction ... 4

2.3 The choice of the extractant for the first reaction ... 5

2.4 The choice of the reactor. ... 5

2.4.1 Reactor choice for the first reaction ... 5

2.4.2 Reactor choice for the second reaction ... 6

3 Basis of Design ... 7

3.1 Description of the design ... 7

3.2 Block scheme ... 7 3.3 Thermodynamic properties ... 8 3.4 Basic assumptions ... 8 3.4.1 Plant capacity ... 8 3.4.2 Location ... 8 3.4.3 Battery limit. ... : ... 8

3.4.4 Definition of all in and out going streams ... 9

3.5 Determination of the margin and the maximum allowable investment... ... 10

3.5.1 Ca1culation of the margin ... 10

3.5.2 Ca1culation of the maximum allowable investment... ... 11

3.6 Conclusions of the BOD ... 11

4 Thermodynamic Properties and Reaction kinetics ... 12

4.1 Operating windows for the different reaction sections ... 12

4.2 Thermodynamic models and data validation ... 12

4.2.1 The first reaction section ... 12

4.2.2 The second reaction section ... 13

4.3 Data accuracy ... 13

4.4 Reaction kinetics ... 13

4.4.1 The first reaction section ... 13

CPD3226 Table of contents

5 Process Structure and Description ... 15

5.1 The production of HMF using a continuous stirred boiling liquid tank reactor 15 5.2 The product i on of DMFu using a monolithic reactor.. ... 15

5.3 The use of equipment. ... 16

5.3.1 The choice of distillation columns ... 16

5.3.2 The use of flash vessels and knock-out drums ... 16

5.3.3 The use of settlers ... 16

5.3.4 The use ofmembranes ... 17

5.3.5 The pumps and compressors ... 18

5.3.6 The heat exchangers, reboilers and condensers ... 18

5.3.7 The use of a hydrocyclone ... 18

5.4 The process flow scheme ... 19

5.5 The process stream summary ... 20

5.6 The use ofutilities ... 20

5.7 The process yields ... 20

6 Process contro!. ... 21

6.1 The feed streams ... 21

6.2 The first reaction section ... 21

6.2 The second reaction section ... 22

6.3 The separation sections ... 22

7 Mass and Heat Balances ... 24

7.1 The mass balance ... 24

7.1.1 The mass balance for total streams ... 24

7.1.2 The mass balance for stream components ... 24

7.2 The heat balance ... 24

7.2.1 The heat balance for total streams ... 24

7.2.2 Heat integration ... 25

8 Process and Equipment Design ... 26

8.1 The process simulation ... 26

8.1.1 The use of calculation programs ... 26

8.1.2 The use of a process flowsheet simulator.. ... 26

8.2 The design of the slurry reactors for the HMF production ... 26

8.3 The design of the monolithic reactor for the production of DMFu ... 27

8.4 The design of the equipment... ... 30

8.4.1 Design of the distillation columns ... 30

8.4.2 Design of the flash vessels and knock-out drums ... 35

8.4.3 Design of the settlers ... 36

8.4.4 Design of the membranes ... 37

8.4.5 Design of the pumps and heat exchangers ... 39

8.4.6 Design of the heat exchangers, reboilers and condensers ... 40

8.4.7 Design of the hydrocyclone ... 42

9 Waste streams ... 44

9.1 Liquid wastes ... 44

9.2 Gaseous wastes ... 45

9.3 Solid wastes ... 45

CPD3226 Table of contents

10 Process safety ... 46

10.1 Genera!. ... 46

10.2 The HAZOP analysis ... 46

10.3 The Fire and Explosion Index ... 46

11 Economy ... 48

11.1 Determination of the investment costs ... 48

11.2 Determination of the operating costs ... 49

11.3 Determination of the income and the cash flow ... 49

11.4 The economie criteria ... '" ... 50

11.5 Negative cash flow ... 50

12 Conc1usions and recommendations ... 51

12.1 Conclusions ... 51

12.2 Recommendations ... 51

Literature list. ... 52

List of symbols ... 53 Appendices:

1 ~ process flow scheme

2 ~process stream summary

3 j)fl(utility summary

4 ~ structure forrnulas and reaction scheme 4.1 The structure formulas

4.2 The reaction scheme 5

~

quipment

data sheets

5.1 Equipment summary sheets 5.2 Equipment specification sheets 6 ~ HAZOP study

7 Membrane information

8 Calculations of the unit operations

8.1 The calculation of the CSTR reactors 8.2 The calculation of the distillation columns

8.3 The calculation of flash drums and knock out drums 8.4 The calculation of the membrane contactor

9 Economy 10 Heat integration 11 Thermodynamic data

-1

H3C~CH3

2,5-Dim~thyl Furan~

DMFu _{2-Methyl Furan: MF} Figure 1.1: Structure forrnulas of the octane boosters

CPD 3226 Introduction

1 Introduction

Because of the limited amounts of fossil oil, man is looking for renewable feedstocks.

One of the available feedstocks is fructose, aby:product from sugar refineries. From

fructose it is possible to produce 2,5-Dimethylfuran (DMFu) which can be used as an

octane booster in gasol,ine. Adding an octane booster to gasoline is necessary to \

improvy the performance of the engine. Jn the past, Tetra-alkyllead ,,:,ás use.d, but

~-.eL

..J

because of its severe polluting effects, it was rePlaced~ bethyl t-But~l Ether

>(MTBE). The advantage of DMFu over MTBE is its high r octane number. Besides,

DMFu is produced from renewable feedstocks whereas TBE is produced from

petroleum. _ .I _ ~ ~ _ ,

~~~J ~.~ .. . . !\.

1.1 Reaction produets

Beside 2,5-Dimethylfu~an (DMFu), also 2-Methylfu~an (MF) is produced. The

structure formulas are shown iq figure 1.l_l and in appendix 4 all structure formulas of

the components in vol ved are shown. In table 1.1 some physical properties of the products are given. In table 4.2 the physical properties 'of all the components are given.

T bI 1 1 Ph a e

..

ySlca pro rt . I Je les 0 fDMF u an dMF

component formula mole. octane boiling point melting point density

weight number (K, 1 bara) (K, 1 bara) (kg/m3)

DMFu C6HgO 96 215 366.7 246.4 888

MF CSH6

0

82 209 336-369 184.5 827

There is not much information about the thermodynamic properties in the literature, so most of these properties has to be estimated with a propêr model. For this, the

UNIF AC method and the Benson method were applied. The thermodynamic pToPerties are further specified in chapter 4.

1.2 The product and feedstock market

Actually there is no indusrrial production of DMFl!, so the only competitor is MTI3E an octane enhancer with an octane number of 120. The price of MTBE is Dfl2.00

[information obtained from Sh~ll]. The ~axim-wn aJlowablequantity of:MTBE in

gasoline is 5 Vo/,~. As DMFu hàs a higher octane number, the allowable quantity i's

less. T~e design is made to supply the Dutch gasoline market with octape-booster, and

to replace all MTBE. A production of 114 kton/a is necessary for this replacement, _. ~ ~ ,

with a purity above 99.5 %. W'I

Fructose can be obtaTned from ;e~ral sourees, suc

asf

uI ehi and tareh. A

k problem is that fructose is not fre available, but' quotat,ed. his is because fruct~se

is 40 times sweeter than glucos~. This quotation i lid f e f<?od-inqustry, 'so for

non-fo<?d purposes an exemption can be obt~ined. With this e)(,ç ion,-th1

CPD 3226 lntroduction

1.3 The production process

In literature, two reaction paths were found for the production of DMFu. The reaction

path chosen, is a h~drolys~~~~m~t~.fu.rfural (HMF)

followed by a hydrogenation to DMFu. The hydrolysis takes place in a series of four

tank reactors,

~y

extracti9n with

methyl

~

isobut

l-keton

(MIBK). The hydrogenation takes pI ace in a monoht ic tube reactor. In figure 2.1 the block scheme of the pr()cess is shown.

However the process is extremely hazardous according to the Dow Fire and Explosion Index, which is merely due to the use of hydrogen at 40 bara, hydrogenation reactions are widely used in chemical industry. These issues are further developed inchapter ~O.

1.4 The availability of physical data

From the pure component list presented in chapter 4, it follows that the physical properties of the products of rea~tion are not abund.ant. Therefore several diffe&ent estimation methods were us~d to determine properties such as the enthalpy of

formatton, enthaTpy of evaporation and heat capacity. · .

As for the thermodynamic properties little information was available, also little infonnation was available for reaction kinetics and phase equilibria.

~~~--~

.

The most important result of the lack of information is the use of different solvents,

-

--and a l~. The unknown kinetics resulted in the use of rules of

thumb such as a decrease in selectivity as the reaction temper~ture is increa§ed and an

in

~

rease

in reaction .ra!e as the.pressure is

incre~ed.

c---' "

-..

<strearn-number>, main compoDent(s), flow in kt/a, and (t/t) .<61> hydrogen

7.7 kt/a (0.07)

<45>+<53> MlBKlwater rec. ISI4 kt/a (16)

I

<Ol> diluted

fructose feed Reaction

407 kt/a (3.55~ Section I <26>+<29> <07> MlBK .... ~C» 2223 kt/a (l~

....

2.3 kt/a (0.02) 443 K 11 bara

~

I

Separation Section I f~/'No° 381-559 K 2-12bara I

<2S> catalyst recycle S.I kt/a (0.07) <57> buranol 3.3 kt/a (0.03) <104> decanol Nl'<" TotallN: 420 t/a (3.66 t/t)

Figure 2.1: Bloek scheme

(z,)

1'f~/A)lu+e.

FCOt

f~

·

~tlod

.

~~,

I

<102> butanol recycle 715 kt/a (6.23)

I

<56> Reaction <67>

165 kt/a (1.44~ Section 2 914kt/a(7.~

....

5J.(-/hf:>

...

327-339 K 40 bara

r-+

I

l

Separation Section 2 ~~ -l~" 300-556 K 1.5-38 bar. <106> purge NNF <93>+<97> water 47 kt/a (0041) --'" <SS>MF 9.7 kt/a (O.OS)--", <9O>DMFu 114kt/a(l~ <l03>EI~ 4.7 kt/a (0.04)

<6S>+<7S> hydrogen recycle 22.1 kt/a (0.19)

<55> water 244 kt/a 2.13 Total OlIT: 420 t/a (3.66 t/t) ) ~

CPD3226 Process options and selection

2 Process Options and Selection

In this chapter, different process options are compared to produce DMFu from

fructose. Besides different reaction paths, also several types of reactors can be used for this production. As the availability of data is poor, the selection criteria are mostly based on toxicity of the solven?and the information from experiments found in literature.

2.1 The choice of the reaction path

In literature, two different reaction paths are described for the production of DMFu

-out of fructose, both reaction paths consists of a two step synthesis. The first reaction is with Chloro-methyl-Furfural (CMF) [10] as intermediate and the second reaction is with HMF as intermediate

[l0]

{

))H~r tbvcw-

'

r'-~

(

~

fW!~

The reaction of fructose with HCL to CMF is exc1uded for an industrial production process because chlorated by-products will have a serious effect on the environment. Special materials will be needed because of the corrosive effects of HCI.

The reaction of CMF to HMF is exc1uded for the same reasons as mentioned above. As the yield via both paths is the sa.me, 'DMFu will be produced from

fructo~e

with HMF as the int~rmediate. For the production of DMFu from HMF hydrogen is

= -

.

needed. There are several possible hydrogen donors, hydrogen and cyc10hexene are

---' "

known in literature. Due to the toxicity of CYc10hex~n)' e, hy'drog~n is chosen.

The reaction path from fructose via HMF towards D u is divided into two reaction

steps: - ,

~?

- The dehydrolysis of fructose to HMF.

\.uy

1 -

t

r

etase

-->

~o

+

HMF

11o~d

(443 K, 11 bam)

- The hydrogenation of HMF to DMFu.

~

c:

::::)L

J HMF + 3H, --> 2H,O +DMFu

~<C(j

(33~ K, 40 bara)

A bloc:k scheme of this process is shown

~re

2.}.

~s

these main reactions,

>'

also by-products are for:ned in the first re~ctIOn:1ne conversi~n of fructose to HMF i~> 91 % selective [Prof. van Be~um, TU Delft]. The rest of the fructose is ~onverted

into furtural (FE), ànd yields in the,second.reaction

MP

.

'

-For the production of HMF from

fructos~

'

several f.atáiysts can be used. In the next ) lil

paragraph the catalysts for both reactions will be chosen with respect to their selectivity, conversion, toxicity, and corrosivity. ' .

.

----~#

.... ~--'

...

--L

3

CPD3226 Process options and selection

2.2 The choice of the catalyst

2.2.1 Catalyst choice for the first reaction

For the dehydrolysis of fructose to HMF several catalysts can be used. In table 2.1 the catalyst are listed with the selection criteria. .

T bI a e 2 1 P OSSl e ca a ys s or e 1rs reac IOn an d th . 'bl t I t f th f t t e1r pe rf orrnance [12]

Catalyst Selectivity Convers ion Toxocitv Corrosivity

-H3P04

+

+

-- --.

Pyridine 1;-

+

.

-

.,

Ammonium salts

₊

+

-

--Zeolite (Si/Al)

++

+

+

+

Iodide Pyr~dine and H3P04 are exçluded because of their c~e behaviour.

Besides, they are also very toxic and hazardous for the environment. Ammonium salts _{--==r . .} are c;orrosive, and cause difficulties with separation and are therefore exc1uded. The best option to convert fructo~e is the use of a zeQlite. The conversion of the fructose is highly selectiye towards HMF due to the por~ size distrib~tion of the zeolite.

The zeolite used for this process is a H-mordenite. This zeolite has several advantages over the'homogeneous

~

id)

catalysis and also over i.sm

exsha~~sJu§.

The

advantages are: - Higher selectivity

\

-Higher operating temperature (than resins) favouring the formation of HMF - Easy regeneration

More information about the catalyst can be found in chapter 5.

2.2.2 Catalyst choice for the second reaction

For industrial hydrogenation reactions, mo~tly heterogeneous_catalysis is used. In literature however several articles were found about hOJ?ogeneous catàlysis b~t described the reaction with toxic and corrosive catalysts such as H3P04 and HCI [19]. Combining these 'results, a ,heterogeneous catalyst is chosen. A w~

largely used hydrogenation cata is a ~m ac~e Eha~n coal CPd/Ç) [19].

-CPD3226 Process options and selection

2.3 The choice of the extractant for the first reaction

The production of HMF from fr.uctose occurs in an aqueous medium (water). During the production of HMF, the product of reaction needs to be extracted as rapidly as possible from the reaction mixture to prevent further reactions such as polymerisation reactions. Several solvents can be used to extract the HMF from the reaction mixture. They are listed in table 2.2 with the selection criteria.

T bI 22 HMF a e .. extractants an d h t elr pe rf ormance .

Extractant Capacity ToXicity Costs

DMSO ++ --

--Toluene + -

--Higher alcohol's + +

+

MIBK + +

+

From table 2.2 alcohol's as weIl as MIBK seem to be good extractants. Due to ether formation of HMF with alcohol's, they are not suitable.

MIBK is therefore chosen as extractant in the first.reaction section.

2.4 The choice of the reactor

~ ~

2.4.1 Reactor choice for the ~t reaction )

The first reaction requires a three phase reactor

wit~i~

phases

an

~

§Qli2

phase. The reaction from fructose to HMF is highly exothermic which largely

influences the choice of the' reactor. For the purpose of the CPD, several options have been studied. In the first place a choice was made between a fixed bed reactor and a slurry reactor, below in table 2.3 the performances of both

op~e

listed.

~

Table 2.3: Performances of different reactors for the first reaction [18] Performances

Three phase fixed bed reactor Slurry reactor

Advantages Advantages

Immobilised cat,alyst The possibility of a good temperature

con trol in the reactor due to the possibility of solvent evaporation Multiple possible configurations

Disadvantages

_....

Disadvantages

Difficulty of regeneration of the c~talyst Mjlhli(sed catalyst

Possibility of formation of hot spots The cablyst needs to be separated from the reaction mixture

The impossibility of asseIJ1bling the zeolite grains ori a packing'_{. . .} ,known to be efficient in liquid-liquid èxtraction

Due to the highly exotherrnic reaction a slurry reactor is chosen.

" .

.

CPD3226 Process options and selection

....

.

In the second plac several slurry reactor configurations have been studied~

c..

_.ft. ..

- Pulsed column reactor: The major disadvantage of the pulsed reactor column is the

counter-current flow of water and MillK. At the top of the column, 'the MillK-rich

phase is brought in COnt'lct with the w,ater phase with les's

!IMF,

which implies a loss

in separ~tion efficiency. This loss coulçl be rninirnised using a bette;r solvènt, which is

not kno\\;'n at this time. Reactors that resemble$~his option, such as the Rotating

Disk Contactor Reactor and the Plate / Sieve tray Column Reactor, have bee,n dropped

for the same reason.

- Dispersion reactor: With a dispersion reactor the extraction problem is avoided due to the creation of a turbulent flow (good mixing). The disadvantage of a dispersion reactor is the flow regime restriction. In this regime the highest achievable conversion is lower than the conversion achievable in a CStR slurry reactor, therefore the

~n reactor is excll.lded.

- CSTR-Sluny reactor: The disadvantages that oc~ur in the above mentioned reactor

options do not occur in the CSTR Also there is abundant information about the CSTR operation therefore, a CSTR reactor is chosen. By operating the CSTR as a boiling

"

.

liquid reactor the heat transport is guaranteed, and a good c';>llversion can be a~hieved.

2.4.2 Reactor choice for the second rea ct ion

The second reaction consists of the selective partial reduction of HMF to DMFu with

hydrogen on a PdlC çatalyst and ~ol as solvent. Two different reactors can be

used, a Trickle Bed Reàctor (TBR) and a monolithic reactor (MR). In table 2.4 the properties of both reactors are listed.

Table 2.4: Performances of the different possible reactors, for the second reaction Performances

Trickle Bed Reactor Monolithic Reactor

High catalyst load High s~lectivity

La:r-ge experience Low pressure drop

Low cost Good catalyst shape

During the production of DMFu from Hl\1F, selectivity prob!ems occur together with

difficult kinetics (further re~ctions), a hi,gh pressure is ryq)lired, a monolitnic

reactor wi"ll be more attractive. .

!!~

III

~

~.f

~~~

?

. -fructose 407(3.55) <lJ1.:> <56> HMF 165 (1.44) butano1 3.3 (0.03) <57> decano1 NNF <104> Total IN: 420 kt/a (3.62 t/t) decanolrecycle 864(752) <91> 767 6.6

Figure 3.1: Extended bloek seheme of 2,5-dimethylfuran proeess Table wlth FIgure 3.1: EqUJpment list of figure 3.1

C03

448

503

115

I

coding equipment pressure

bara ROl

S05

4 boiling liquid reactors with 4 settlers for fructose conversion (R01-R04 and SOl-S04)

11

hydrocyclone for catalyst separation 11.5

A-(~ FO 1 flash for MIBK removal 2

+""

~Q, CO 1 HMF column 2

Áoq .I\~) C02 azeotropic waterlMIBK column 2

1\ Q}o C03 water recovery column 1l.5

C03 egulpment nr. 448 temp. top (K) 503 temp. bottom 11.5 pressure (bara <lJ1>sueam nr sue ams kt! a (tJt) 244(2.13) <55>water <106> purge NNF ~8>MF 9.7 (0.08) 445 (039) <93> water: <90>DMFu 114 (1.00) TotaIOUT: 420 kt/a (3.62 t/t) temperature (K) top bottom 443 443 388 384 559 381 406 448 503

Go

-

R05 monolith reactor for HMF conversion 40 333

2

t

....

MOl membrane contactor (hydrofobie) 38 300

~

'+

-

F02 flash for hydrogen removal 3 300

\

i~' i~

C04 furans column 3 404 556

i

IR

~

.

C05 DMFulMF column 1.5 341 383

I

Cl:t- \ ... M02 water membrane (hydrophilic) 36 300

J 4..(<1( I '(lt4 C06 waterlbutanol column 2 384 417

CPD3226 Basis of desi n

3 Basis of Design

I ./

,

3.1 Description of

'

he design

_./ /'

In chapter 2, two action paths are desérfbed. The reaction path chosen is the one with HMF as an interrned' e. The path is divid ä into two reactions, during the first reactión fructose is converted in HMF,

~d

during

th

~

se-eon reaction HMF is converted to DMfu. The

C"?

reactions e shown i~ figure 4.1 and 4.2. ~ 1>~ f:tA~4 ~ ~

~ '-~

.

'---

.,7', . . .

-

-Th first r action, - y rolysis eaëtion, takes plac~ i~ a ~nce of four tank reactop~e

rea wo ph ase ent, tlfe reaction medium water d the extracting agent,~

The catalyst is a zeolite,

<tCrP

orde

~

fter

each tank a settler is placed to separate tpe aqueous and organic laye?'tl e product HMF is extracted from the water phase and the catalyst remains in the water phase. Af ter ~he fourth settler, a hydrocycione is placed, to separate the catalyst from the water. The catalyst 'is recyc1ed to the first reactor.

In the first separation section HMF i.s separated from MIBK and water in a distillation column, to go to the second, reaction section. The solvent MIBK is recovered from the water in two distillation columns, and recyc1ed. The water is removed from the process, together

with unconverted fructose and glucose. ~ - I _

~ ~~~~

The

tfe

c~

reaction takes place in the fifth reactQr, a monolith reactor, in whicI iHMF,

~

but~

hydrogen flow co-current. Butanol is a solvent, which is also

i

~

ve~

in the/.

ti

conversion. The reaction proceeds in three st~ps.HMF is converted to

.§l9

,

aR8

lIoia E~ !yields DMFu. The mixture leaving the reactor is separated in a liquidJvapour separator and the hydrogep is recyc1ed to the reactor.

The second separation section consists of two membranes, a flash drum and four distillation

. ' .

colu~s. The membranes are a m~tact?r and a wat~brane. The

membrane contactor is hydrophobic with an extractipn fluid (decanol) at the permeate side.

The water selective membrane is o'nly perrneabl{( for w.ater. The d~canol is recover~d in a

Cf:?y

column and reçyc1ed,to the

'

membr~ne.

The butanol is also recovered in a

c?lui

~

m

and

recycled. The product DMFu is purified to 99.8

%

i,kf

C

D_7.

3.2 Block scheme

For the process, two levels of block schemes are made. The first block scheme is shown in

~re 2.1 and gives an overall view of the process. In the second block scheme, figure 3.1,.. the

1

process is shown in

mo~ith

all major equipment. The equipment coding and stream

numbers,

correspond

~

oding

and numbers used in the Process Flow Scheme (PFS),

CPD3226 Basis of design

3.3 Thermodynamic properties

For the successful design of a chemical process, reliable thermodynamic data are indispensable. As the production process involves several components that are hardly

described in literature, several estimation's were used to determine pr~perties such as heat of

vaporisation and phase eÇLuilibria. In the 'first reaction section, Jhe Unifàc. thermodynamic

model was used, together with the ~ model. The use of the Wilson model ,:"as justified

in the case of

~~IB!-

Ebase

eq~

.

i

l}

m.

J!l

the

secOI

lft.r.~~

c

y~~

ction

the

Peng-Robins2n equation was used.aill' the estimations

are

:ilili)

n

=

~~

c

~p

t

~~

The Benson

method which was used to estimate the heat of vapori~ation, estimates within 4 % (or

example.

'3

Û ,

(3.tw.1v~

- - - '

?

'

3.4 Basic assumptions

3.4.1 Plant capacity

The goal of the DMFu plant is to provide the entire

booster. To achieve this goal, a producrion of per year is required. The plant will

operate 8000 hla, therefore all streams are based on a production of 14.25 tonlh pMFu. In

figure 3; the in- and out going streams necessary for this production are shown. The plant life is taken 15 years.

\

.

te

For the productia of DMFu, two

ma

~

tants are

,

~eeded,

hydrogen and

fructos

,

~:

3.4.2 Location

/ /

./

•

These reactants ave to be supplied ~s the DMFu-plant easily. Hydrogen rnfght be

obtained from,oil refinery, otherwise a hydrogen plant has to bè built.

Besid

~

e

need for

hydrogen also solvents are required in the process. Considerin . èsëJactsl11è--location for the

DMFu plant is dderrnined. The DMFu plant is placed near t e refiner of Pemis'\rhe fructose

sJ:fl!P will be supplied by trucks fr0Il! the sugar

refine~

not r important adva.o,fage of Pemis is that most of the g11ine is produced tbere} tbe DMFu cano e e lvered to the

c1ients with a pipeline as we 1. ~ ~ j /

I.

9

LtPl:-lt-__

l

~

->

~

~

ju),

1J()r~~

.

3.4.3 Battery limit .;f • ~ ~yJ..J...

•

The feedstock of the process is fructose syrup. There are several possible suppliers of a fructose syrup. For the purpose of the CPD only fructose supplied by the sugar factory is considered. The syrup delivered has the specifications as shown in table 3.1.

CPD3226 Basis of desi n

The other streams that are needed, cross th ence of the battery limit at the conditions shown in table 3.2.

Table 3.2: Streams crossin limit:

Stream /

pr

~

Z7

r

Phase in component

I

/

ocess

r~ssure (bara) Fructose 2 / 11 MIBK 2 / 11 298/443 Butanol 2 / 40 298/333 / 11 298/443 <) 40. 298/333 ~ 40 298/333/

3.4.4 Definition of all in and out going stre~ms // r I .

...,./ tJfrl"~~

.

Feedstocks and products: e

The incoming streams ructose syrup, hydrogen gas, a butanol. The composition

of the fruct is 91 % fructose and 9% glucose on a dry base. he other inc.oming

ere are several outgoing streams. T outgo' streams can be sold,

~_. ~ e product streams have to be at least 99.5 % pure. ~. ?

For the production of 114 kton/a, in 8000 hours

-

e

a~

e ~ion

is

!i1:2.

tonlh is

required. To obtain this production a sugar feed f 3~.7 tonlh 0 a illYl!asis is required. The r /.l

feedstock of hydrogen has to be 0.97 tonlh.

~

p~

~~

.

?~~~at~~ .,tA!ut~

Processchemicais: ~- ~. ~

In the first reaction section MIBK is used to extract HMF from the reaction mixture. M t of

~

•

the MIBK is recQvered in the separation ~ection, but inevitable losses do occur. The MIBK _{. ,.} feed to the pr:ocess is 0.29 tonlh.

In the second reaction, the reaction from HMF to DMF occurs through two intermediates.

These are ~utoxy furans. B~ca~se of this loss the 'process require~.41 tonlh bwrnoilrn

chapter 5.5, a detailed stream summary is given. \ .

For the èxtraction ofDMFu and MF in the membrane contactor, decf.nol is necessary. The

column that recovers thè decanol for the recycle into the membrane is' esigned for total

CPD3226 _{Basis of design}

Catalysts:

In the first reaction a zee . ic catal st is used. The Si/Al ratio of the zeolite is 11. The particles

have aTameter of 1 , . The catalyst is suspensled In the boiJing liqu!d rèactors by mixing

with a stirrer and ga ubbling due to the boili{1g.

In the se~ond re ac ,the catalyst is a. Pd!C ~1?%) ~onoFth .. The ch~nnels. in the m9.JlG>.Iith.-....

~~~::t::~~~;yf

2

:u"

The

monOhili

-=~:

1:~n

~~

_

~~tIon

7

Wil~~~

G

f O"

~

d

Utilities:

Table 3.3: Utilities used for the procfuction of DMFu properties and prices / 7

~

~.#l

The utilities needed are described in chapter 5.6. The properties of the utilities used are shown

in table 3.3.

~

?

?

Utility Properties

-

...

TemjJerature

(KJ::::::

Price

Steam Low pressure (3 bara) 463' --(q ;::> _{30 Dfl / ton}

Medium pressure (lObara) 493 Q~ 0 30 Dfl / ton

High pressure (40 bara) 683 .LIto 35 Dfl / ton

Electricity

I

0.20 Dfl / kWh

Water Cooling water

M

-..,~ 293 - 313 Qo-=>'Lo 0.05 Dfl / mJ

Air Cooling

I

298 :2 ( 0

-f2/-rt-

oe

~

-Wastes:

'-

,, - r~~ D

~~

There are seven outgoing streams. Stream <88> and <90> are the product streams and can be --- -S ct\.

:>

~.

Stream <97> is an emergency purge, with normally no flow. The four

.remaini~s

~

.J

are considered as waste. Stream <103> contains organic components, it can be fed to a ..

--furnace. Stream <93> contains only water, at 28 bara. This water could be recyc1ed to the first

reaction section, but at these

~

on

di'

ions

it

is

favo

~

rible

to make pressurised steam.

Stream <97> and <55> are aque s streams with 'organic compounds. These streams need

special treatment.

' 9 ?

~~ W~.

3.5 Determination of the margin and maximum allowable investment

3.5.1 Calculation of the margin

The margin is the difference between income from sales and the ,fosts of the feedstock. For

this ca1culation the prices of the chemicals producea were estimated. The estimates are shown

in table 3.4. In the same table the prices of the solvents are pres~nted. '

Table 3.4: Estimated Chemicals DMFu MF .

---,

r

-

-

...

.

~--.

rices oXhe produced Chemical ': nd solve

Price (Dfl / k ) Solvents

3.00 MIBK*

2.00 Butanol*

-2.61 2.07 The prices marked with an asterisk are found in the Chemical market

CPD3226 Basis of design

In table 3.5 the margin per year has been ca1culated. In the determination of the margin the

(

- .

value of the waste streams was set to zero. Table 3.5: Margin per Year MDflIa

Total~~ 364.400

Total11*- 0

\.l

.,-

211.434

MARGIN 152.966

3.5.2 Calculation of the maximum allowable investment .

r

~ ~

y

~~

.

The maximum allowable investment was

detennin

~

ofthe

annual margin cash flow.

The annua) cash flow was corrected for an interest 10ss of 10% per year. On basis of this calculation th-e maximum allowable investment is 988 MDfl .. The detai1ed ca1culation is shown in table 3.6.

table 3.6: Calculation of the maximum allowable investment. Cash flow

Margin cumul. flow Interest Cash Flow

Years MDfl/a MDfl/a 10% MDflIa

~

.

~.t"~tt

9

1 1 2 0.909 3 153 153 0.826 126

L:fi

4 153 306 0.751 241 5 153 459 0.683 346 6 153 612 0.621 441 7 153 765 0.546 527 8 153 917 0.513 606 9 153 1071 0.467 677 10 153 1224 0.424 742 11 153 1377 0.386 801 12 153 1530 0.350 854 13 153 1683 0.319 903 14 153 1836 0.290 948 15 153 1989 0.263 _~ Total 13920 _{_(}

9S8

~

3.6 Conclusions

The DMFu plant with a production of 115 kton/a and a plantlife of 15 years has a maximum allowable investment of 988 million Dutch guilders. This amount is ca1culated considering the basic assumptions and the vailable facilities outside the battery limit.

a e . . IS 0 pure componen s

Tbl 42 L·t f t

PURE COMPONENT PROPERTffiS

Component Name Technological Data Medical Data

Formula Mol. Boiling Melting Density MAC LDso Notes/

System Weight Point Point ofliq. value Oral Design

(1) (1) (2) Names

[g/mol] [K] [K] [kg/m3] [mg/m3] [glkg]

l-Butanol C4HlOO 74.12 390.8 183.3 809.8 45 BuOH

2,5-Dimethy lfuran C6HgO 96.13 366.7 210.4 888.8 n.a. DMFu

5-H ydroxymethy lfurfural C6H603 126.11 553 304.7 1206.2 n.a. HMF

Fructose C6H I20 6 180.16 n.a. 423.2 1600 n.a.

Glucose C6H I20 6 180.16 n.a. 419 1562 n.a.

Hyd~ H2 2.02 20.3 13.9 0.088 n.a

(

~

aldehy

d9

CH20 3.03 253 n.a. 1000 n.a.

ÏFü

~

CS~02 96.09 435 236.7 1159.4 8 0.127 FF

Water _H20 18.02 373 273.2 1000 n.a.

Methyl-isobutyl-keton C6H120 100.16 390 188.5 801 104 MIBK

Methylfuran CSH6

0

82.102 338 184.5 827 n.a. MF

1-Decanol CIOH22O 158.3 504.3 280.05 829.7 n.a.

Ether lOl ClOH I603 184 598* n.a. n.a. n.a. ElO

Ether 112 ClOH I60 2 168 506* n.a. n.a. n.a. ElI

Remarks: All data from Handbook of Physical Properties, Vol 74, except *. * : from CHEMCAD

I: 2-hydroxymethyl-5-butoxymethyl-furan 2 _{: 2-methyl-5-butoxymethyl-furan} '

Table 4.3: Thermodynamic data

Component Enthalpyof Enthalpyof Heat capacity /

formation evaporation (at Tb)

liqU;

~

Llli_f 0 (kj/mol) ~Hvap (kj/mol) Cp (J 0 )

Fructose -1101* 2~, HMF -339* 168* DMFu -146* 153* FF -159* 122* MF -68 * 123* Water -286 44 75 MIBK 34.5 213 Decanol 78.2 373 1-Butanol 52.4 192 E10 -493** ElI -341 ** Remarks:

* :

estimated with Benson

CPD3226 Thennodynamic options and reaction kinetics

4 Thermodynamic properties and reaction kinetics

For the successful design of a chemical process, reliable therrnodynamic data and kinetics are indispensable. Therefore in this chapter the data useQ for the CPD are presented together with eventualliterature data to show their validity.

4.1 Operating windows for the different reaction sections

/I ti

The production of DMFu is a two step synthesis. In the second reaction the conditions are more severe than in the first reaction , table 4.1 shows the operating windows for

the two

r~lOn

sections. .• --_.r.')

~c..

t-t~ ~

?

T bI 4 1 0 a e . . peratmg WIn . d ows In t e h d1 ·n erent sectlons Reaction Temperature ( K) Pressure (bara)

(1) 443 ~:;.o 11

-(2) 333

±

6 ~o 40 . ,..

In table 4.2, some pro.perties of the pure components are specified. Together with the

data in t~ble 4.~ these are the data used for the C~D. The heat capacities and the ~

of forrnation were estimated with the Benson method or were taken from Chemcad.

- - -

'

-The heat of evaporatiqri of water and MIBK was corrected for the temperatl,lre at

-"--

-"'""-which evaporation takes place [17]. '

4.2 Thermodynamic models and data validation

4.2.1 The first reaction section

In

th~eaction

secJi2,n, three different therrnodynamic models were used. The

over~nnodynamic

model is the Unifac model,

WfiïêFï

iSä

~

ibution

model. The use of this model is qjlowed(in tne operating window of the fir~t reaction

section. '

In

t

tl'~e12aration s

~

cti

p

n,

several distillation columns and flash drums separate

wate

~

MIBK. In 'these cases the Wilson model is used. For the design of the

~~nt

,the Non

Ra~dom~

Liquids

~odel

iliRTL) was

u~ed.

In table 4.4, the binary interaction parameters from the simulation program (Chemcad) of the watèr-MIBK system are presented together with those found In the pechema

data series [9] .

HO OH

H

Fructose J HO OH H Fructose

o

(

(=

'3

y

1-1..1

S y

Q/.0

11

H

b

H /

H

K.

H

lO

f

~

/

H

H

,~

"

t - -Of(

() H

Furfural: FF .

CPD3226 Thermodynamic options and reaction kinetics

Table 4.4: Comparison of thermodynamic data for the first section [5]

Thermodynamic model Water-MIBK Chemcad Literature

Wilson A12 2561 2781

A21 IS74 1254

NRTL _{A 12}' _15.50. 2857

A21 562 7~7'

The data seeml not very

r~liable..~ere

pos si bie, the values from literature were used.

4.2.2 The second reaction section

In the second reaction section, there are two different thermodynamic models that

were used. The overall model in this

sec~

is not Unifac because hydrogen is present

in the system and Unifac is a group ~ontribution~. As watèr i~nt in most

of the sec~ion together V(ith an a1cohol,.the equation used to desc.ribe the phase equilibrium is the Peng-Robinson equation [9].

As water is present with an alcohol, theYlilson equation is used in one distillation

column, C02. .

In table 4.5, the binary interaction parameters of the water-MIBK system are presented

together with those found in the Dechema data series [5] ,

, .

T bI 45 C a e . . ompanson 0 f h t ermo ynarruc ata or tesecon d . d f h d

Thermodynamic model Water fBuOH Chemcad

Wilson A12 1435

A₂₁' ₁₉₇₆

These data are more reliable tpan the data for the first section.

~

4.3 Data accuracy

sectlon Literature 1361 2121

As very littl~ information was available ~b_QULthe reaction products, almost all data

for these components were esÜmate . These estimatl s were performed with the

Benson method which has less th;

~

--.J

~

4.4 Reaction Kinetics

t

'

~

-A complete reaction scheme with structure formulas of all components is showh in appendix 4.

4.4.1 The first reaction section

The dehydration of fructo occurs simultaneously with the formation of

furfural [11] as shown in igure 4.1. T e conversion of fructose can be described by a first order reaction at the onditl sed in this design (443 K; ~ 1 bara). The reaction

)

I

'

.

~

. 0 H₃C HMF

C

~ Hb

D~

o

l

-h

"

P:::-

I

(

~r"'?'

.JL

ï (

)

/~

~P"-

o

~,.

/

\

I

~~

/

/ "

~O

-r

tt,<-~o

/

----

-r rgure

---

4.3: Taylor flow in a monolithic channel

~ H3C

rr

CH₃ DMFu

C!b

k~o

~

LrCH3

H

!I-t

MF

(!;r

'<

,

f)-CPD3226 Thermodynamic options and reaction kinetics

constant (kF) was

det~rmined

by fitting a

fir

Ç.ff

eren

:::~a

found in literature [11].

~

.

, ...

This results in : . /

-[FJ=[FJo·e-kF·/

L

y"'bJ..

__

(4.1)

...

~~ ~

with:

h~O

.

024

[min"']

#I ___

~

d"",,,,,-

J

~~ ~

e.

-'"

The formation of HMF can therefore be described with the following

equati

~

.

-

~

?

(4.2)

This equation was also fitted with experimental data [11] and as a final result kH was

determined. This results in kH

=

0.022 [min-I] ( .

S>

~

.

Itl

W

~-I- ~ïC

•

ëïHf

The second reaction, see igure 4.2, t es place in a monolithic r~actor and is

hydrogen limited. Durin the mode ng of the monolithic reactor, i~ was found that

the reaction is hydrogen liffil e and therefore HMF conversion ;iepen on the

transport of H₂ to the catalytic1y active monolith wall, see als chapter 8

För the determination of the hydrogen transfer, first the transf . cients were

determined. In a monolithic reactor there are three transfer coefficients:

kgs : Mass transfer coefficient from gas to wall

C

9;-

~J...)

kgl : Mass transfer coefficient from gas to liquid

kis : Mass transfer coefficient from liquid to wall

~J.

)

(m2/s) (m2/s) (m2/s)

In figure 4.3 the transfer coefficients are represented graphi~~lly in a monolithic

channel ope~ating in a Taylor flqw regime [J3]. Th~ transfer coefficients are

determin~d with the Sherwoo~ number. From the ~ values of the transfer Jo(

coefficients it follows that the mass transfer from the liquid Ehas~ to the wall is

ne ctible. Therefore it is assumed th at a constant hydrogen concentration is present

in the liquid phase, and the HMF conversion can b~ described with transfer of

drogen to the wal!.

"

~';2~f"

-

.!:

~

~

(molis) (4.3)

, 3 . /

/ / /

In chapter 5 the

monolithiC

\

r~actor

will be further discussed.

CPD3226 Process structure and description

/> .4

A

!

5 Process structure and Description

~/' ~

('t.T'

,'"

In this chapter the process design criteria will be deliivéd and the equipment used to

achieve these criteria will be specified. '

~

---sing a continuous stirre slurry boiling

~ 'S

5.1 The

Iiqui

./ . .,t

As mentioned in chapte{ 2, the reaction is highIy exothermal and a CSTR is used to achieve sufficie~~at transport. To achieve the required cooling, the extracting agent (MIBK) is c muousi eva orated in azeotro ic mixture with water. The mixture is

condensated a then retumed to the reactor. The tanlè operates at a temperature of

X

~~~-. ~s the reaction takes pI ace in th'e Iiquid phase, the pressure in 'the reactor is maintained at

~

a

,

the vapor

pressure

~

I...[ 4. '\ ..

~

.

(

(

?'Oc

C ')

,

To achieve areasonabie convèrsion of fructose, 4 eSTR's in serie are used. This way a convers ion of 98.5 % is achieyed.

The catalyst passes through the four reactor~ whiie remaining in the water ph~se, and is recyc1ed af ter the fourth r~actor. .

The catalyst in the first reaction:

The catalyst chosen for the first reaction is the ,!!-mordenite zeolite. The acidity of the zeolite has an optimum with respect to HM,F productiop

at

a Si/Al-ratio of 11. The shape of the catalyst is important. In the zeolite many

microp

~

esopores

>

----

... ""'-'

,

are present. As the nlJmber of mesopores increases, more by-products WIll be formed. Micropores will not allow the polymerisation re'actio~or exampIe, which

represents an i~e in se~ctiv~ty. ~";)

90?

.

5.2 The production of DMFu using a monolithic reactor

Due to the selectivity problems in the hydrogenation reaction of HMF to DMFu, a monolithic reactor is chosen. The monolithic' reaétor consists of 45 bIo~ks

of

1m (standard length), with inierstage coaling due to the heat of reac~ion. The temperature in the reactor

v:af

i

-e~

33~K.

Every two blocks the flow is coo1ed. The pressure to achieve

r

~

onabie hydrogen transfer rates, is set at 40 bàra. Due to

.x

the relativel slow kinetics, he reactïon is hydrogen trànsfèr Iimitated, the length of the monolitH 's 45 m: Th ' ressure could

b

~

h

êi1 ~

electivity

wouid be less favourao e an inevitabie loss of product.

The catalyst used for this reaction is 10 w % Pd on coal. This kind of catalyst is frequently used in hy rogenation reacti~ns.

CPD3226 Process structure and description

5.3 Th&r

equipment

5.3.1 The choice of distillation columns

For the production of DMFu from fructose 7 distillation col mns are needed. This is essentially due to the use of several solvents. Over ?O % gfth~ distillation columns

are necessary to recover solvent. ~ .

All the distilIation columns are sieve tra

X

columns. The choice was mostly influenced from an economical point of view. For the production of DMFu no difficult

separations are required therefore the cheapest possible separation equipment is used.

The choice of sieve tray columns is favourable due t1he~xperience wi~~th~e -.L

X.

~columnl

~frv.

~~

~~T.h(

""

~

The" sequence of the columns is based on the geuristics mentioned by Douglas [3]. In the first reaction section the HMF stre~m is first separat~d from the other components (largest stream) 'after which the solvent (MIBK) is recovered. In the second reaction section again the largest str~am is separated'from the pro'c!uct stream first, af ter which the products óf reaction (DMFu & MF) are separated. In two other columns the lightest component (azeotropic mixture of water and butanol) is separated af ter which the solvent (BuOH) can be recovered.

The columns that separate solvent from water are all designed with an other

thermodynamic model than the overall model. As column CO 1, C02, C03 and C06 all separate between water and either MIBK or butanol, these columns were designed and simulated with the Wilson model.

5.3.2 The use of flash drums and knock-out drums

In the first reaction section one

convention<>~h

;U~l!Sed

to separate the azeotropic mixture (MIBK/water) from

the~iDn..~re

.

Wh en tlie four product streams from the four reactors are mixed together, the pressure is still 11 bara. By flashing-off nie azeotrope, the mixture is more easily separated in a distillation _,

column (less volume). I/h _ s-eP~

In the second reaction section, after the monolith, a

knot~out

drum is used to

~ "

separate the excess hydrogen from the product stream. .

" .

The second flash vessel is placed after the membrane to separate the dissolved

hydrog~n in the'liquid flow. ' . , . , .

5.3.3 The use of settlers

In the first r~aftion section after each CSTR a settler is placed. To.extr.~1be HMli,.

from the water .phase, MIBK is added to the reactor and due to the difference in density, the two liquid phases will separate in a settler. The HMF rich ph ase (MIBK phase) is at the top of the settler and the water phas~~with fruçtosejs ~t the bottom

of the vessel. . "

In fi ure 5.1 ~he temary diagram of ~K is shown which was. used to dete ne the equilibrium. .

CPD3226 Process structure and description

5.3.4 The use of membranes

Af ter the DMFu is formed, it has to be separated from the solvent and the other

~~

-products of re,action. As little inform~tion is known about the phase equilibria, thV

separation of the products of reaction from the solvent and the reaction mixture is by a

ac.

membrallé~. The great aclvantages of a membrane a~e besides the high selectivity a

large surface area per volume and low energy. reguirements. Two membranes are used

in the second separation section. ...

The first membrane is used io separate the roducts reaction MF and DMFu from

the solvent and

otherfPro~ucts:;

reactiO!}, the second mem

r~ne

is used to

separ~

,

te

water from butanol.

The first membrane is based on polarity. This membrane consists of a hydrophobic

poly~ene

layer, therefore pol~ponents are retarded, while non-polar

components can pass. In such a membrane rhass transfer-occurs by diffusion, so the superficial velocity of the extraction fluid influences the diffusion rate. Hollow-yber modules give a well defined flow, so the diffuslon and mass transfer óm be

ca1culated. For this rriembrane, hollow fiber modules are cHosen.

As the mass transfer occurs by

d~

force is not the pressure as in

reversed osmosis or convection as i~ ultrafiltra!ion. However limitations exist for the \)

transmembrane pre~sure. The transmembrane pressure must ngt k2>ceed a critical , '( ( value, to prev~nt retentate penetrati~n ("breakthrough") and contaminatl<?n enne ~ ~ permeate.

The membrane contactors are available in modules. When the surface area is not large

enough, several modules can be put in

~l.

Ce,lgard, à

mem~er

of the

Hoechst Group, sells modul~s with contacti~g membranes, called Liqui-Cel®. The large&t: is suitable for the separation, the specifications are given in table 5.1.

appendix 7 m re specific data are given. _{. ,} - ,

T bI SIS a e . : )pecl lca lons 'f t' 0 f one mem b rane mo u e d I

module size (m) 0.25xO.7

surface area (m2) 1~5'

area/volume (m2/m:) 3900

max temperature (K) 333

flow regime (m3/h) 10 - 48

max transmembrane pressure (bar) 8.4

The second membrane is used to separate water from a butanol. New techniques are

devel-;P~d

to separate a liquidJIiqui'd mixtu~embrane. In the

membrane, ihe water will pass and heavier corpponents are ret~rded. The use of the selective membranes is favourable over columns., because it can pass over the azeotropic compositÎon. Already in industry these membranes are used to separate

water-ethanol mixtures [14].

-MosTOfthèS~eparatîons take place in plate operation. The plates (sheets) can be spirally wound to form modules. There are no standard industrial modules available, because these have to be d~omised and produced for the process specifically. In this

><

design, the performance of a membrane from literature [10] is taken to' calculate the required surface area

---

. The -d~tailed design is left for the membrane manufacturer.

.

'"

.

,

CPD3226 Process structure and description

5.3.5 The pumps and compressors

All pumps are centrifugal pumps. These pumps are widely used in the process

industry and can be used for tbe operating conditions of this process. The slurry pump, used for the cat~ recycle stream, was designed in the same way as all other pumps.

For all pump spares re present. .

The compressors used are centrifugal compressors. The operating conditions of this process do not require the use of -!eciproc~ting or other high co st compression

~. '\

equipment.

5.3.6 The heat exchangers, reboilers and condensers

Heat exchangers: Three different

~~t

exchangers are used for the proce.ss design. The weIl known shell and tube is mostJy used. For heat exchangers where high temperature differences occur, floating,head and U-tube exchary.gers are used. They are

also easier to clean. '

Condensers: Due to the lJ.igh temperatures of the condensers in the distillation colqrnns cooling water can not be used for cooling. At the temperatures required the rate of fo~ling would be to high. Therefore, alÎ condensors will be air-cooled. _{. , . ::.} Reboilers:

Therrnosyphon reboilers are the most economical type for most applications, but not suitable for high viscosity fluids. In the process design therrnosyphon reboilers are therefore mostly used. In two cases however, fired heaters were used because of the high boiling point of the mixtures.

5.3.7 The use of a hydrocyclone

As a mobilised catalyst is used in the first reaction section, the catalyst particles need to be separated from the liquid mixture and recovered in order to recycle the catalyst. For this purpose a hydrocyclone is used. The diameter of the catalyst particles is chosen in such a way that the hydrocyclone can recycle a l / i e l e s.

k~~-:t

~~Ä?

CPD3226 Process structure and descri tion

0

,.-

~

-

Q-

'

--~-_

...

5.4 The process flow sc me

e.

In the first reactor (ROl) the reactant stream <6> is mixed with cat~lyst <28>, and preheated extractant <8> and <49>~ The reacto~ operates at the azeotropic boiling point of water and MIBK. On top of the reactor, a condenser is placed (EOS) to provide the necessary cooling. After the mixture ieaves the reactpr <10>, the water-organic mixture is separated in a settler (S,O~). Before each settler a pump is p,laced to keep the pressure constant in the reacto~s. There a~e four reactors in series, and therefore four pumps and four settlers.

The advantage of the four reactors is the i.ncrease in conversion, and a lower heat production (exothermic reaction ) 1?er reactor. From the four reactors four product streams <12>, <16>, <20> and <24> are iitixed and lead to the first separation section. The remaining water is lead to a hydrocyclone (SOS) where the catalyst is separated and recycled to the first reactor <28>. From the remaining water stream, MIBK and water are recovered in a distillation column (C03).

The product recovery (HMF) occurs in two steps. In the first step, the water-MIBK azeotrope is separated from HMF in a flash drum (F01), and retumed to the first reactqr <31>. The product stream leaving the flash <3~> is lead to a distillation column (COl) where the high boiling

HMF

is separated from th.e wateJ MIJ3K stream. The product stream <37> then ~~he second reaction ~ection. The water M~K

stream passes through a second d~stillation colump (C02), which is an ~eotropic

distillation c.clJJmn. The azeotrope is recovered overhead <42> and mixed with the other MIBK-water streams <S3>. The MIBK stream is d' ided intofour streams and divided over the four reactors.

The HMF stream which goes to the second reaction section passes through a buffer _{. ,} vessel (V04) to anticipate fluctu~tions. Before theHMF stream enters the, mOI)olithic reactor of the second reaction section, a new solvent i added, qutanol ~S9>. The

conditions in the second reaction section

a40~ s.:.ye~:

.. e

~

in the first sectiop, 40

~

.[;)

C

f bara and 333 K. The mixture is fed to the

r~dórtä'iè'tFfë'f"with

hydrogen, which i;=

needed

fot

the partial reduction of HMF to DMFu. As in the first reaction: the reaction is highly exothermic and therefore requires cooling. The monolith (ROS) consists of 45 units, each unit is 1 meter 10n,$.ITo achieve the required cooling without

'enormeous temperature differences, every two blocks the mixture is cooled. The product stream leaving the reactor, <67> is separated from the hydrogen,in a knock out drum (VOS), after being cooled. Although this cooling is inefficient (two phase stream) it is necessary to avoid product recyclin to the r~actor. ..

The hydrogen

IS

mixed together with fresn .. ydrogen and re~med to the react9r <64>. The product stream is led to. a membrane, (MO 1) where the pr:oduct is recovered as permeate <70> together with MP. In the second,flash drum (P02) the remaining hydrogen is separated 'trom the product stream and mixed with the other hydrogen recycle stream ->65>. The liquid stream is fed to a distillation column where tbe solvent, which was needed in the membrane, is completely recovered. The top stream

CPD3226 Process structure and descri tion

<76> is separated fr the remaining hydrogen due to a partial condens er, and leaves for a final distillat' n column. In this column ,(COS) the two octane bQosters are separated, MF I yes over the top <88> as DMFu leaves over the bottom <90>. The result is 99.8 % pure DMFu.

Two additional columns (C06 and C07) are required to recover butanol the solvent,

-and separate the water formed in the reaction.

~.~~

5.5 The process stream summary

As the process flow sheet, the process stream summary is an important tooI for the design of a chemical process. Due to the large number of streamS"it"is~ed in the appendices. The process stre~m summary can be found ·~ppendix 2 ) ,

-.;.--....:...' ...;'~- ' ' . ,../

---"-~,.,.~,...

5.6 The use of utilities

For the production of DMFu enormeous quantiti~.s of utilities are used becallse of the separation ~f large amounts of solvent. Large amounts of air are used because of the high temperatures in the conden,sers of the reactors and the distillation colu.mns. Due

to tube fouling by the formation-'of limestone caused by water ~vaporation, the use of

q

~ at these high temperatures.

As ~ the reactions are exotll.euual, much cooling is required. The exotht::rmicity of Q..

both reactions exclude the effective use of pinch technology betw~en heat flows.

~

two

reboiler~

a

f~mace

is required to reach the required temperatures.

Y

In appendix 3 a utility summary is presented.

5.7 The process yields

In the block scheme of figure 2.1, already some yields are presented. In this paragraph, the yields will be further specified to make it possible to compare this process with other processes. In table 5.2 the yields are shown.

Table 5.2 Y Ie s or e pro ld f th d uc IOn t' 0 fDMF f u rom f ruc ose t

Yields ton / ton product

Feed 2.1 ~.~_"--~-"" .... ,.-,

~.-~ ~~" ,"

proces~ca~

_-

_oo

_~

- MIB wate Vdec,anol

- tanol .03

Utilities MW/ton ~5000 l" ~

-

,;

Wastes L,58

In table 5.2 the internal recycle streams are not mentioned. From this point the waste streams seem important. This is mostly.due to the formation of 5 moles water per moIe DMFu produced. In paragraph 5.6 the use of utilities is already specified.

CPD3226 Process control

6 Process control

In order to operate the process confonn demands, the process needs to be controlled. The demands are, product specification, process condition boundaries, safety and environmental operation. The control system has three duties;

*

to protect the demands against extemal disturbances

*

to assure stability within the process

*

to optimise the process

The con trol system is shown in the process flow sheet in appendix 1.

6.1 The feed streams

The feed streams are controlled by flow controllers (FC) with a control valve (CV). This makes it possible to operate the pumps at a constant (ideal) power. The fructose syrup <01> is wanned up in a heat exchanger (HE)(E01), to make the syrup less viscous. This is done with a hot stream <82>. The temperature of the syrup is controlled with a temperature controller (TC), and a CV in the by-pass of the hot stream <82>. Af ter the syrup is mixed with the MIBK recycle, it is further heated. This is do ne in two heat exchangers (E02 anó:Ë03). The temperature after E02 is not measured and controlled, because aft er E02, in both streams <06> and <82> there is an additional HE to control the final temperature, so fluctuations are covered with utilities in that HE. Af ter E03, a TC controls the temperature of the fructose-MIBK stream entering the first reactor, with a CV in the by-pass of stream <37>. This is possible, because stream <38> is further cooled with an additional HE using cooling water. The fresh MIBK and fresh butanol are not heated before they enter the reactors,

because these streams are small in comparison with their recycle streams. The MIBK

feed stream <08> is controlled by a FC and CV in the feed and flow recorders (FR) in the recycle streams <45> and <53>. This is because the solvent stream in the reactor has to be constant. The butanol stream in the fifth reactor has to be constant too. Therefore a FC is placed in the feed and a FR in the recycle. The FC controls the CV in the feed. The hydrogen feed stream <61> is controlled by a FC, which controls the power of compressor KOL The FC is connected with the FR's in the recycle streams <68> and <78>, to have a constant hydrogen flow through the monolithic reactor ROS. The last feed steam is the decanol feed stream <105>, which has nonnally no flow, because column C04 is designed for total recovery of decanol. Therefore, the feed of decanol is controlled with a level controller (LC) in the bottom of column C04.

6.2 The first reaction section

The reactors are boiling liquid reactors. Therefore the pressure in the reactors can be held on the setpQint by controlling the condensers on the reactors. By setting the temperature, the pressure is also set. In the first reactor the cooling fluid is stream <43>. The pressure in the reactor is controlled with a CV in the by-pass of stream <43>. The other boiling liquid reactors are air-cooled. The pressure in the reactors is controlled with a PC, which controls the power of the air-blowers. To prevent