Download - 14_Unit Pemantauan Dan Kontrol
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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