Environmentally benign chemical

processes

Typical unit operations and equipments

Erika Vági, Edit Székely

BME, Department of Chemical and Environmental Process Engineering

Schedule6 Feb. E. Vági: Introduction, Refreshing the basics.

13 Feb. E. Vági: Green chemistry metrics

20 Feb. E. Vági: IPPC, BATs, production of nitric acid

27 Feb E. Vági: Vacuum technologies6 March M. Test 1 (20 minutes) + Johannsen: Supercritical fluids 1. 13 March M. Johannsen: Supercritical fluids 2.

20 March – SPRING HOLIDAY (DAY OFF)

27 March M. Johannsen: Supercritical water oxidation, waste water treatment

3 Apr E. Vági: Test 2 (20 minutes) + Waste water treatment, purification strategies

10 Apr M. Johannsen: Membrane technologies

17 Apr E. Vági: Distillation, azeotropes

24 Apr E. Vági: Test 3 (20 minutes) + Presentations of BATs

1 May – LABOUR DAY (DAY OFF)

8 May – Dr. András Kovács – Biodiesel

15 May – Final lecture, repetation of test

2

Requirements – during term

• Attendance: min. 70% at lectures;

• VOC /BATs presentation will be given by individually and accepted (if excellently done half mark extra is offered).

• 3 mid term tests (20 minutes each) – min 50% of 2 is required for the signature. Over an average 80% the final mark is offered (80-89% - 4; 90-100%- 5). 3

Requirements – during term

• Download the slides of the lectures time totime from the website: http://kkft.bme.hu/en/education/subjects/envchemproc

• Slides might be useful to structure your knowledge, but are not enough!

• Lecturers: Edit Székely, Erika Vági, Monika Johannsen (TU Hamburg-Harburg) and András Kovács

4

Requirements - exams

5

• Students having valid signature may take a written or oral exam during the examination period.

• Application for the exams is only possible via the Neptun system.

• In case of questions please contact Edit Székely (sz-edit@mail.bme.hu) or Erika Vági (evagi@mail.bme.hu)

Aim of the course, topics

• To gain a general overview how the decide between possible synthetic routes and processes taking into consideration the environmental aspects.

• To familiarize with innovative/modern technologies as membrane separations, supercritical fluids, vacuum and high pressure separations etc.

6

Unit operations

1. Mechanical separations

2. Heat transfer operations

3. Equilibrium mass transfer separations

4. Non-equilibrium stage separations

5. Chemical modifications

6. Biochemical modification

7

1. Mechanical separations

• Precipitation• Sedimentation• Filtration• Flotation• Centrifugation• Electrostatic separation• Emulsion separation• Magnetic separation• Mechanical expression• Etc.

12

Precipitation

13

Filter press

Treated stream

Settling tank

Balance tank

Solid for recovery

/disposal

pH adjustment and flocculant

addition Feed stream

Sedimentation

15

Sedimentation with cyclone

16DISA high-efficiency Cyclone

Air flotation

17

Filtration – conventional multi medium sand filter

18

Filtration

• Driving force is the pressure difference

• Various filtration media

• Typically a batch operation

19

Filtration – rotary vacuum filter

20

Centrifugation, decanter

21

Emulsion separation

• Demulsification: chemical or physical

22

Cold pressing

2. Heat transfer operations

• Heat exchangers

– Tube in tube (shell and tube)

– U-tube

– Spiral

– Plate

• Evaporators

– Robert evaporators

– Falling film evaporator

24

25

• in smaller plants• in case of high pressure

Shanghai Ritai Medicine Equipment Project Co., Ltd.

Heat exchangers

26http://www.answers.com

27

http://www.answers.com

Diabon

28

Spiral heat exchangers

http://www.alfalaval.com

• Compact,

• Big relative surface area,

• Less viscous liquids of

condensation.

29

Plate heat exchangers

Alfa-Laval - Canaley Process Equipments Co.

Evaporation, traditional

30

Evaporation, falling film

31

A feedB vapourC concentrateD steamE condensate

32

Multi-effect evaporator in vegetable oil production

3. Equilibrium diffusional separations

• Distillation, rectification

• Absorption

• Extraction

• Adsorption

• Evaporation

• Crystallization

• Drying

• Etc.33

Distillation, rectification

• Major separation process for homogeneous liquids of two or more components.

• Separation is based on the difference in boiling points (volatility).

• No additional chemicals are needed, but energy requirement is relatively high.

• In a large number of separation task it is the most economical option.

35

Bubble point – dew point curves and the equilibrium curve

mixture of benzene and toluene at atmospheric pressure

Batch distillation

Distillation column

Absorption

• Based on distribution ratio between gas and liquid streams

• Typical applications: gas washers, columns.

39

http://www.separationprocesses.com/Absorption/GA_Figures/Fig115a.gif

Liquid-liquid extraction

41mixer settler

Solid-liquid extraction, Crown model III

Adsorption

43

LES: length of equilibrium sectionLUB: length of unused bed

Drying

Three basic methods of heat transfer are used in industrial dryers in various combinations: convection, conduction and radiation.

Drying – fluidized bed dryer

45

Membrane separations

46

46

Schematic drawing of membrane separation (cross-flow filtration)

Feed

Permeate

Membrane

Retentate

Stirred tank reactors (Pfaudler, Germany)

• 300-15 000 gallon

(1-60 m3) volume

• Clamp top

• 5-500 gallon (0.02-2 m3) volume

Tubular reactors (UHDE, Germany)• Used in petrol industry

• First reactor (1955):- 24 mm Ø

- 1600 bar

- 10.000 tons/year

• Current reactors: - 70-90 mm Ø - 3600 bar

- 300.000 tons/year

Multi-tubular reactor (Oita, Japan)

Crystallisation

• Crystallisation is the formation of solid particles within a formerly homogeneous phase.

• Crystallisation from liquid solution is the most important industrially.

• Solidification from a liquid melt by freezing is also used for purifying some certain materials.

50

Formation of crystals

• In the formation of a crystal two steps are required: the birth of new particle called nucleation and growth of this particle to macroscopic size.

• The final particle size and particle size distribution of the product are largely affected by the degree of supersaturation and the crystallisation technique applied.

51

NaCl-crystal production

52J. H. ter Horst et al. Fundamentals of Industrial Crystallization (2015)

A cascade of three forced-circulation crystallizers in sequence, with external heat exchanger and circulation pump (with heat integration).

Thank you for your kind attention!

Notes for exams/ tests (from the website):

- Technologies.pdf

- Unit operations.pdf