Simulasi Proses Kimia 1st

Simulasi Proses KimiaSTT Indocement

2013

Tujuan

• Mampu menjelaskan perbedaan streams dalam proses

• Menjelaskan maksud singkatan-singkatan standar dan simbol yang digunakan dalam proses flowsheet

• Menuliskan deskripsi proses flowsheet• Menggambarkan proses flowsheet dari deskripsi

tertulis.

Introduction

• Apa itu Proses?• Suatu proses adalah beberapa operasi yang dilakukan

untuk memodifikasi input(s) menjadi output(s) berdasarkan perubahan fisik dan/atau kimia

ProcessInputs

“feeds”

Outputs

“products”

1. Spesifikasi peralatan, material, dan penataan urutannya ke dalam proses yang mengontrol operasi fisik/kimiawi untuk memperoleh output yang diinginkan.

2. Analisis operasi proses kimia atau fisik yang ada untuk proses operasi untuk mencapai hasil yang diinginkan.

Process design vs. Process analysis

Peran dalam proses kimia

Kedua masalah membutuhkan fungsi analisis dan desain.

Contoh:Suatu boiler dalam suatu oil refinery tidak menghasilkan jumlah steam yang diinginkan. Seorang engineer pertamakali menganalisis boiler untuk menentukan sifat masalahnya (seperti suatu diagnosis, ini adalah suatu analisis).

Kemudian engineer mengusulkan solusi yang mungkin melibatkan beberapa desain. Jadi misalnya, jika kinerja buruk disebabkan oleh kekurangan pasokan udara untuk pembakaran, engineer akan menentukan jumlah udara yang benar, dan untuk memasok jumlah udara ia mungkin harus mendesain (atau menentukan) blower udara baru.

Menjelaskan Proses dengan

• Diagram input – output

• Diagram blok

• Diagram Proses Alir / Process Flow Diagram (PFD)

Process

ProductsRaw Materials

Diagram Alir Blok

Diagram Alir Blok

• Terdiri dari kumpulan blok unit proses yang terhubung • Garis dengan panah menghubungkan blok-blok dan

menggambarkan arus proses• Raw material masuk pada bagian kiri• Produk keluar pada bagian kanan

• 4 jenis unit “proses”:MixersReactorsSplittersSeparators

Mixer

mentega

C12H22O11

flour

eggs

NaCl

NaHCO3

Chocolate chips

Raw chocolate chipCookie dough

Baked chocolate chipCookiesReactor (Oven)

Raw chocolate chipCookie dough

Splitter

4 dozen cookies75% choc chip25% peanut butter



Separator


3 dozen cookies97.5% choc chip2.8% peanut butter

1 dozen cookies8.3% choc chip91.7% peanut butter

Flowsheets

Langkah pertama dalam setiap design atau analisis proses adalah mengkonstruksi flowsheet yang menunjukkan aliran material dan langkah-langkah pemrosesannya.

– simbol flowsheet yang umum–singkatan-singkatan yang umum

•Flow sheet memungkinkan visualisasi dan kuantisasi proses yang lebih baik. “A picture is worth a thousand words.”•Proses flowsheet terdiri dari unit-unit, yang digambarkan melalui bentuk sederhana seperti lingkaran atau persegi panjang.

Beberapa simbol flowsheet yang umum

Pumps are used to increase a fluids pressure so the fluid will flow from highpressure to low pressure, or used to condense a fluid or increase the speed of a chemical reaction.Gas compressor – a different unit description is used as the fluid responds differently than liquid in a pump (ie increase in pressure causes gas to condense)

Gas expander or turbine is similar but with flows reversed.Valves are needed to control flows between various units.

• Combiner and splitter:

• Avoid crossing streams. If streams must cross, you need to indicate whether they mix or not.

streams cross without mixing

Ambiguous streams combine and split

Example

Klasifikasi ProsesSuatu seri operasi dimana material dan/atau energi dikonversi dari satu bentuk ke bentuk yang lain.

Batch process: •has a definite end•material is put in, processed, and discharged•applies to more than just reactors (washing machine for example)

Continuous process •materials enter and leave in uninterrupted streams•periodic shutdown is required•Garden sprinkler

Semibatch or Semicontinuous•Some materials are charged/discharged at intervals while some enter/exit continuously•Biotechnology industry, to add nutrients

Contoh: apakah proses berikut termasuk batch, semibatch atau continuous? Apa raw material dan produknya?

1. A coffee maker

2. A home oil furnace

3. An oil refinery

4. A toaster

5. The kidney

Processes, plants and pipes

Proses operasi dilakukan dalam vessel yang didesain khusus (kolom destilasi, tanki, reaktor,dll)

Material dibawa ke dalam vessel melalui pipa atau ban berjalan. Hal ini disebut sebagai stream.

Garis menggambarkan pipa atau aliran material, persegi panjang menggambarkan banyak perubahan fisik, dan sangat mungkin terdiri dari multiple pieces of equipment.

feed

Net overhead

bottoms

*Directional arrows are important!

Process Flow Diagram

• A PDF or process flow diagram shows the basics without the inner workings of equipment or the control schemes.

• Konsep flowsheet dapat diaplikasikan untuk banyak industri

• Hal pentingnya adalah– The different operations that make up the process– The sequence in which these operations occur (ie the

relationship between the operations)

Contoh: flowsheet untuk pemanas udara di rumah dalam sistem forced circulation.

Cool air from house Warm air to house

oil Air

Gas buang ke cerobong

• Persegi panjang merepresentasikan oil burner• Dua aliran udara terpisah: - udara yang disirkulasikan ke rumah

- udara yang digunakan untuk pembakaran• Panah mengindikasikan input ke furnace dan output dari furnace• Garis kontinyu sirkulasi udara menunjukkan bahwa udara tersebut tidak

bercampur dengan fuel, udara dan produk pembakaran dalam furnace.• Anda dapat menggunakan flowsheet yang sama untuk merepresentasikan

fuel atau produk yang berbeda.

• Bagaimana memodifikasi flowsheet untuk menyertakan kipas yang mensirkulasikan udara ke rumah, pompa untuk oil, dan tanki penyimpanan oil?

• Modifikasi untuk menyertakan rumah?

Cool airWarm air to house

oil Air

Flue gas to chimney

Storage tank

pump

Fan/blower

Cool airWarm air to house

oil Air

Flue gas to chimney

Storage tank

pump

Fan/blower

house

• Untuk analisis proses: chemical engineer must take a complex flowsheet and reduce it to a description

• Untuk desain proses: you must draw a flowsheet from a process description.

Contoh:

Gambarkan flowsheet dari deskripsi sederhana berikut mengenai sintesis amonia:

Suatu campuran hidrogen dan nitrogen diumpankan ke reaktor katalitik dimana beberapa hidrogen dan nitrogen dikonversi menjadi amonia. Efluen reaktor disalurkan ke dalam kondenser dimana semua amonia dikondensasikan. Amonia terkondensasi dialirkan ke penampungan produk. Hidrogen dan nitrogen yang takterkondensasi didaur ulang dengan mencampurkannya dengan feed baru dengan komposisi yang sama. Campurannya masuk ke dalam reaktor.

• Tipe proses?– Reaktor dan kondenser adalah kontinyu– Tanki penyimpanan bersifat semikontinyu

• Reaksi: N2 + 3H2 2NH3

•Step 1, feed ke reaktor:

reactor“feed”N2

H2

“effluent” NH3

N2

H2


•Step 2, memurnikan produk:

reactor“feed”N2

H2“effluent” NH3

N2

H2

condenser

NH3

liquid


•Step 3, menyalurkan produk ke tanki penampungan

reactor“feed”N2


N2

H2

condenser

NH3

liquid

Storagetank


•Step 4, daur ulang feed yang blm bereaksi:

reactor“feed”N2


N2

H2

condenser

NH3

liquid

Storagetank

N2, H2

recycle

purge


Variabel Proses

Variable yang menjelaskan kondisi proses dibagi menjadi dua kategori:

• Extensive variables: bergantung pada ukuran/jumlah/size sistem (masa, volume)

• Intensive variables: tidak bergantung pada size of the system (T, p, , dan fraksi mol)

Seringkali dalam suatu flowsheet proses, kita perlu menentukan variabel prosesnya (misalnya ukuran dan suhu kondenser)

Flowsheet conventions

• Process flowsheet: menunjukkan bagian penting dari proses (operations and sequence). Kadang-kadang informasi mengenai energi dan aliran massa ditempatkan dalam flowsheet dekat streams atau dalam tabel tambahan yang berdampingan.

• Process Control Flowsheet: menunjukkan instrumentasi dasar yang dibutuhkan untuk mengkontrol proses dan keperluannya.

• Engineering flowsheets: suatu seri flowsheet yang menunjukkan semua data yang dibutuhkan untuk menentukan peralatan proses. Biasanya terdiri dari flowsheet-flowsheet terpisah:

– Piping flowsheet shows all pipes and equipment with sizes and other necessary specifications. This flowsheet contains one symbol for each piece of equipment in the process.

– Instrumentation flowsheet shows the relationship of every instrument to the process (often combined with piping flowsheet in a P&ID)

– Utility flowsheet shows the relationship of the utilities (steam, water, air electricity) to the process and specifies pipe sizes etc.

– Plot plan show a plan view of the plant giving the physical arrangement of the equipment.

Contoh Flowsheet

Instrumentation and Control

• Instruments are used to sense process variables and drive control valves.

• These are denoted on P&IDs by circles with letters:

• Valves are connected by solid lines to the point where variables are measured, and by dotted lines to the equipment they control

LC FRC

FRC

As 1st letter As 2nd letter As 3rd letter

A analyzer Alarm Alarm

C - controller controller

F flow - -

I - indicator -

L Level/liquid level -

P Pressure - -

R - Recorder -

T Temperature - -

V - - Valve

D Differential Differential -

r ratio ratio -

Instrumentation symbols

• First letter describes the variable sensed by the instrument: Pressure (P), Temperature (T), Flow (F), level or liquid level (L or LL), composition (A)

• The second and third letters describe the action taken: Record ( R), Indicate (I), Sound an alarm (A), or Control (C )

• Explain the symbols:

LC FRC

Description

• Main pieces of equipment are the column (C1), accumulator drum (D1), reboiler (E2) and condenser (E1).

• The distillation column (C1) separates the feed stream according to volatility into overhead and bottoms products.

• The heat exchangers (E1) and (E2) condense the overhead vapours and partially vaporize the liquid from the bottom of the column.

• The drum (D1) accumulates the condensed liquid and also accommodates surges in overhead product rate.

• Control elements are shown by circles and dashed lines.

Control elements

• The rate of bottoms withdrawal is controlled by the liquid level in the bottom of the column. When the level rises the valve is opened to increase the withdrawal rate and thus lower the level.

• The net bottoms flow is controlled by an analyzer (with recorder) which sets the flow controller on the steam to the reboiler to maintain the bottoms composition within specified limits.

• The net overhead is withdrawn from the drum on level control (ie when the level in D1 rises the valve is opened). This keeps the level in the tank within a preset upper and lower limits.

• The rate at which reflux is returned to the column is controlled by the Temperature at a particular point in the column, when this temperature rises the valve is opened and more reflux flows to the column. This instrument is an indicator as well as a controller so it sends a signal proportional to the temperature to a readout instrument in the control room.

• The column is feed controlled by an FRC.

Exercise: Using the flowsheet and description for production of methyl methacrylate and answer the following questions.1. How many reactors are there?2. How many heat exchangers are shown?3. How is the temperature controlled in the hydrolysis kettle?4. How many pumps are shown?5. Why is the inhibitor added?6. Which streams are bypass streams (indicate by stream number)7. Which streams are recycle streams (indicate by stream number)8. The bottoms from the CH3Oh recovery column is water. Where

did this water enter the process?9. What are the main species present in the extraction column

bottoms?10. Is the first reaction endothermic or exothermic? How do you

know?11. How is the heat required for the second reaction supplied?

Methyl methacrylate is a mononomer used in the production of polymeric materials.It is manufactured in a 2 step chemical process starting with acetone cyanohydrin and 98% sulfuric acid:

Acetone cyanohydrin and concentrated sulfuric acid are pumped into a cooled hydrolysis kettle to make the intermediate.

The stream leaving the kettle is dehydrated at steam temperature.

After cooling it goes to an esterification kettle where it is reacted with methanol continuously. To prevent polymerization inhibitors are added at various points in the process.

The esterified stream is pumped to the acid stripping column. Methyl methacrylate methanol and some water come overhead while the residue, made up of sulfuric acid, ammonium bisulfate, and water, is sent to the ammonium sulfate plant.

• The overhead stream from the acid stripping column enters a rectifier column where methyl methacrylate with some methanol comes over the top, is condensed, and sent to the wash column.

• The bottoms from the rectifier, containing methanol and water are sent to a methanol recovery column. Recovered methanol is recylced to the esterification kettle.

• The water solution leaving the bottom of the column, containing some methyl methacrylate and methanol, is recycled to the rectifier column for recovery.

• Crude methyl methacrylate (free from methanol) comes off the top of the wash column. This crude material is shipped to another plant for further purification by distillation.

• The inhibitor introduced in processing is sufficient for shipment of crude methyl methacrylate.

1. How many reactors are there?• 2 reactors: hydrolysis kettle and esterification kettle

2. How many heat exchangers are shown?– 5 (not including the steam jacket and reflux condenser)

3. How is the temperature controlled in the hydrolysis kettle?– Some of the kettle contents are removed, cooled and returned to the

kettle

4. How many pumps are shown?– 8

5. Why is the inhibitor added?– To prevent polymerization

6. Which streams are bypass streams (indicate by stream number)– None

7. Which streams are recycle streams (indicate by stream number)– 15,5,12,17

8. The bottoms from the CH3Oh recovery column is water. Where did this water enter the process?– Water enters in extraction column, acid stripping column and

CH3OH column, stream 6 and stream 2 if the acid is not 100%.

9. What are the main species present in the extraction column bottoms?– Water, methanol, methyl methacrylate

10. Is the first reaction endothermic or exothermic? How do you know?– Exothermic. Cooling is provided for the hydrolysis kettle

11. How is the heat required for the second reaction supplied?– By the condensation of steam.

Checklist of Data Normally Included on Flowsheets (detailed diagrams)

1. Process lines (bypass essential to an understanding of the process)

2. All process equipment. Spaces are indicated by letter symbols or notes

3. Major instrumentation essential to process control and understanding of the flowsheet

4. Valves essential to understanding the flowsheet.5. Design basis, including a stream factor6. Temps, pressures and flow quantities7. Weight and/or mole balance showing compositions,

amounts and other properties of principal streams8. Utilities requirements summary

9. Data for particular equipment:a) Compressors – SCFM (60F 14 psia), P, # stagesb) Drives – connected HP, utilitiesc) Drums and tanks – ID or OD, length, impt, internalsd) Exchangers- ft2, Btu/hr, T and flows, Shell, Tube e) Furnaces – kBtu/hr, T in and out, fuelf) Pumps – gpm, P, HP, type, driveg) Towers - # and type of plates, H and type of packing,

info on trays where fluids enter and leave, ID or OD, length

Simulasi Proses Kimia 1st

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