Unit Monitor dan Kontrol

IGS Budiaman

Metoda Monitor dan Kontrol

Satu-satunya cara yg baik untuk memonitor kinerja cat cracking adl dg mensurvei scr periodik neraca massa dan panas pada unit

Memahami operasi cat cracker juga memerlukan pengetahuan yg dalam thd unit-unit neraca panas

Setiap perubahan kualitas feedstock, kondisi operasi, katalis, atau konfigurasi mekanik akan berdampak pada neraca panas

Neraca panas adl alat utama dalam memprediksi dan mengevaluasi perubahan yg akan mempengaruhi kuantitas dan kualitas produk FCC

Metoda Monitor dan Kontrol (cont.)

Pada akhirnya, sebelum unit dapat memproduksi satu barrel produk, unit harus mensirkulasi katalis secara lancar

Topik utama yang didiskusikan dalam bab ini

Neraca massa

Neraca panas

Neraca tekanan

Instrumentasi proses kontrol

Neraca Massa

Koleksi data lengkap harus dilakukan mingguan

Karena perubahan dlm unit scr kontinyu, diperlukan survei reguler antara pengaruh feedstock, katalis, dan kondisi operasi

Dalam tiap perhitungan neraca massa, langkah pertama adl mengidentifikasi aliran masuk dan keluar

Biasanya, digambarkan suatu envelope disekitar aliran masuk dan keluar seperti pd Figure 5-1 (contoh 2 envelope)

Uap keluaran reaktor berisi gas-gas HC, steam, dan inert

Neraca Massa

HC dalam aliran puncak reaktor sama dengan umpan segar ditambah recycle dikurangi umpan yg diubah menjadi coke

Asal usul steam dalam uap reaktor adl.: uap keatas dalam pipa tegak, atomisasi uap dalam nozel umpan, kubah steam, dan pelucutan steam

Tergantung pada tekanan reaktor, hampir 25% sampai 50% pelucutan steam terbawa dalam spent catalyst mengalir ke regenerator harus dikurangi

Gas-gas inert spt N2 dan CO2 masuk riser terbawa oleh katalis yg diregenerasi

Kuantitas gas-gas inert langsung dihubungkan dengan kecepatan sirkulasi katalis

Neraca Massa

Produk FCC biasanya dilapporkan dalam inert-free basis sebagai fraksi volume atau berat dalam umpan segar

Konversi didefinisikan sebagai persen volume atau massa umpan dikonversi menjadi gasolin dan produk-produk lebih ringan termasuk coke

Neraca Panas

Neraca panas disusun

disekitar stripper-

regenerator dan

disekitar reaktor

seperti terlihat dalam

gambar

Pressure balance deals with the hydraulics of catalyst

circulation in the reactor/regenerator circuit.

The pressure balance starts with the static pressures

and differential pressures that are measured.

The various pressure increases and decreases in the

circuit are then calculated.

The object is to:

Maximize catalyst circulation

Ensure steady circulation

Maximize the available pressure drop at the slide valves

Minimize the load on the blower and the wet gas compressor

Neraca Tekanan

Produk FCC

Perengkahan katalitik mengkonversi minyak gas nilai rendah menjadi produk bernilai lebih

Tujuan utama unit FCC adl untuk memaksimalkan konversi gas oil menjadi gasolin dan LPG

Hasil-hasil perengkahan katalitik adalah: Dry Gas

LPG

Gasoline

LCO

HCO

Decanted Oil

Coke

Mengatasi Masalah

(Troubleshooting)

In particular, the following FCC-related problem areas are addressed in detail: areas are addressed in detail:

Catalyst Circulation

Catalyst Loss

Coking/Fouling

Flow Reversal

High Regenerator Temperature

Afterburn

Hydrogen Blistering

Hot Gas Expander

Products Quality and Quantity

Guidelines for effected

troubleshooting

successful troubleshooting assignment

will require someone to:

good listener

historical background

Evaluate "common" and "uncommon"

causes of problems

Examine goals and constraints to verify the

applicability of the

CATALYST CIRCULATION

Catalyst circulation is like blood circulation to the human body.

Without "proper" catalyst circulation, the unit is dead.

Troubleshooting circulation problems requires a good understanding of the pressure balance around the reactor-good understanding of the pressure balance around the reactor-regenerator circuit and the factors affecting catalyst fluidization.

cyclones, lowering the differential pressure

across the slide valves. This causes the

Higher catalyst circulation usually requires opening the regenerated and spent catalyst slide (or plug) valves

Higher circulation increases the pressure drop in the riser and in the reactor cyclones, lowering the differential pressure across the slide valves

This causes the valves to open further, until the unit find the new balances

Evidences of catalyst losses are:

An increase in the ash and BS&W content of the slurry oil

An increase in the recovery of catalyst fines from the electrostatic precipitator or the tertiary separator

An increase in the opacity of the precipitator stack gases

A decrease in the 0 to 40 microns fraction of the equilibrium catalyst or an increase in average particle size

A gradual loss of the catalyst level in the reactor stripper and/ or in the regenerator

Causes of Catalyst Losses

Common causes of catalyst losses

include:

Changes in catalyst properties

Changes in operating conditions

Changes in the mechanical condition of the

unit

Changes in operating parameters also

affect catalyst losses. Examples are:

An increase and/or decrease in catalyst loading to the cyclones

Overloading the cyclones, even at a constant/or higher efficiency, will result in higher catalyst losses

An increase in the feed atomizing and/or stripping steam, causing catalyst attrition and generating fines

An addition of a large amount of steam to regenerator, causing catalyst attrition

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