This document provides information about troubleshooting catalytic reactors. It begins with definitions of key terms like catalyst, activity, selectivity, and sintering. It then discusses common symptoms of issues like higher than expected pressure drop, rapid decline in conversion, and temperature runaways. For each symptom, it lists possible causes such as catalyst degradation, poisoning, maldistribution of gas flow, and inadequate heat transfer. It also covers mechanisms of catalyst deactivation like thermal sintering, chemical poisoning, and mechanical fouling. Overall, the document concisely outlines how to diagnose problems in catalytic reactors based on observable symptoms and their potential root causes.
Troubleshooting in Distillation Columns
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 FLOW DIAGRAM FOR TROUBLESHOOTING
5 GENERAL APPRAISAL OF PROBLEM
5.1 Is the Problem Real?
5.2 What Is the Magnitude of the Problem?
5.3 Is it the Column or the Associated Equipment which is Causing the Problem?
6 PROBLEMS IN THE COLUMN
6.1 Capacity Problems
6.2 Efficiency Problems
7 PROBLEMS OUTSIDE THE COLUMN
7.1 Effect of Other Units on Column Performance
7.2 Column Control System
7.3 Improper Operating Conditions
7.4 Auxiliary Equipment
8 USEFUL BACKGROUND READING
9 BIBLIOGRAPHY
FIGURES
1 FLOW DIAGRAM FOR TROUBLESHOOTING
2 DETERMINATION OF COLUMN CAPACITY
VULCAN Series VSG-Z101 Primary Reforming
Initial Catalyst Reduction
Activating (reducing) the catalyst involves changing the nickel oxide to nickel, represented by:
NiO + H2 <==========> Ni + H2O
Natural gas is typically used as the hydrogen source. When it is, the catalyst reduction and putting the reformer on-line are accompanied in the same step.
Distillation Towers (Columns) presentation on Types, governing Equations and ...Hassan ElBanhawi
Based on my 8 years of experience in Oil & Gas industry I can claim that you can find here All what you need to know about Columns. This is an introduction to understand more about their:-
-Types
-Basic Principles and equations
-Distillation System
-P&ID Symbols
-Worked Example
You can find also more at:
http://hassanelbanhawi.com/staticequipment/columns/
All the data and the illustrative figures presented here can be found through two reference books:-
ENGINEERING DATA BOOK by Gas Processors Suppliers Association
Process Technology - Equipment and Systems by Charles E. Thomas
Thank you.
Calculation of an Ammonia Plant Energy Consumption: Gerard B. Hawkins
Calculation of an Ammonia Plant Energy Consumption:
Case Study: #06023300
Plant Note Book Series: PNBS-0602
CONTENTS
0 SCOPE
1 CALCULATION OF NATURAL GAS PROCESS FEED CONSUMPTION
2 CALCULATION OF NATURAL GAS PROCESS FUEL CONSUMPTION
3 CALCULATION OF NATURAL GAS CONSUMPTION FOR PILOT BURNERS OF FLARES
4 CALCULATION OF DEMIN. WATER FROM DEMIN. UNIT
5 CALCULATION OF DEMIN. WATER TO PACKAGE BOILERS
6 CALCULATION OF MP STEAM EXPORT
7 CALCULATION OF LP STEAM IMPORT
8 DETERMINATION OF ELECTRIC POWER CONSUMPTION
9 DETERMINATION OF THE TOTAL ENERGY CONSUMPTION OF THE AMMONIA PLANT ISBL
10 ADJUSTMENT OF ELECTRIC POWER CONSUMPTION FOR TEST RUN CONDITIONS
11 CALCULATION OF AMMONIA SHARE IN MP STEAM CONSUMPTION IN UTILITIES
12 CALCULATION OF AMMONIA SHARE IN ELECTRIC POWER CONSUMPTION IN UTILITIES
13 DETERMINATION OF THE TOTAL ENERGY CONSUMPTION OF THE AMMONIA PLANT OSBL
14 DETERMINATION OF THE TOTAL ENERGY CONSUMPTION OF THE AMMONIA PLANT
Reactor and Catalyst Design
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 CATALYST DESIGN
4.1 Equivalent Pellet Diameter
4.2 Voidage
4.3 Pellet Density
5 REACTOR DESIGN
6 CATALYST SUPPORT
6.1 Choice of Support
TABLES
1 CATALYST SUPPORT SHAPES
2 SECONDARY REFORMER SPREADSHEET
FIGURES
1 GRAPH OF EFFECTIVENESS v THIELE MODULUS
2 VARIATION OF COSTS WITH CATALYST SIZE
3 VARIATION OF COSTS WITH CATALYST BED VOIDAGE
4 VARIATION OF COSTS WITH VESSEL DIAMETER
Distillation is one of the widely used separation method in most of the chemical process industries. Improper design
/operation & maintenance leads to various troubles like reduced plant capacity, poor quality of separated products,
high energy (utility) consumption, etc.
Troubleshooting in Distillation Columns
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 FLOW DIAGRAM FOR TROUBLESHOOTING
5 GENERAL APPRAISAL OF PROBLEM
5.1 Is the Problem Real?
5.2 What Is the Magnitude of the Problem?
5.3 Is it the Column or the Associated Equipment which is Causing the Problem?
6 PROBLEMS IN THE COLUMN
6.1 Capacity Problems
6.2 Efficiency Problems
7 PROBLEMS OUTSIDE THE COLUMN
7.1 Effect of Other Units on Column Performance
7.2 Column Control System
7.3 Improper Operating Conditions
7.4 Auxiliary Equipment
8 USEFUL BACKGROUND READING
9 BIBLIOGRAPHY
FIGURES
1 FLOW DIAGRAM FOR TROUBLESHOOTING
2 DETERMINATION OF COLUMN CAPACITY
VULCAN Series VSG-Z101 Primary Reforming
Initial Catalyst Reduction
Activating (reducing) the catalyst involves changing the nickel oxide to nickel, represented by:
NiO + H2 <==========> Ni + H2O
Natural gas is typically used as the hydrogen source. When it is, the catalyst reduction and putting the reformer on-line are accompanied in the same step.
Distillation Towers (Columns) presentation on Types, governing Equations and ...Hassan ElBanhawi
Based on my 8 years of experience in Oil & Gas industry I can claim that you can find here All what you need to know about Columns. This is an introduction to understand more about their:-
-Types
-Basic Principles and equations
-Distillation System
-P&ID Symbols
-Worked Example
You can find also more at:
http://hassanelbanhawi.com/staticequipment/columns/
All the data and the illustrative figures presented here can be found through two reference books:-
ENGINEERING DATA BOOK by Gas Processors Suppliers Association
Process Technology - Equipment and Systems by Charles E. Thomas
Thank you.
Calculation of an Ammonia Plant Energy Consumption: Gerard B. Hawkins
Calculation of an Ammonia Plant Energy Consumption:
Case Study: #06023300
Plant Note Book Series: PNBS-0602
CONTENTS
0 SCOPE
1 CALCULATION OF NATURAL GAS PROCESS FEED CONSUMPTION
2 CALCULATION OF NATURAL GAS PROCESS FUEL CONSUMPTION
3 CALCULATION OF NATURAL GAS CONSUMPTION FOR PILOT BURNERS OF FLARES
4 CALCULATION OF DEMIN. WATER FROM DEMIN. UNIT
5 CALCULATION OF DEMIN. WATER TO PACKAGE BOILERS
6 CALCULATION OF MP STEAM EXPORT
7 CALCULATION OF LP STEAM IMPORT
8 DETERMINATION OF ELECTRIC POWER CONSUMPTION
9 DETERMINATION OF THE TOTAL ENERGY CONSUMPTION OF THE AMMONIA PLANT ISBL
10 ADJUSTMENT OF ELECTRIC POWER CONSUMPTION FOR TEST RUN CONDITIONS
11 CALCULATION OF AMMONIA SHARE IN MP STEAM CONSUMPTION IN UTILITIES
12 CALCULATION OF AMMONIA SHARE IN ELECTRIC POWER CONSUMPTION IN UTILITIES
13 DETERMINATION OF THE TOTAL ENERGY CONSUMPTION OF THE AMMONIA PLANT OSBL
14 DETERMINATION OF THE TOTAL ENERGY CONSUMPTION OF THE AMMONIA PLANT
Reactor and Catalyst Design
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 CATALYST DESIGN
4.1 Equivalent Pellet Diameter
4.2 Voidage
4.3 Pellet Density
5 REACTOR DESIGN
6 CATALYST SUPPORT
6.1 Choice of Support
TABLES
1 CATALYST SUPPORT SHAPES
2 SECONDARY REFORMER SPREADSHEET
FIGURES
1 GRAPH OF EFFECTIVENESS v THIELE MODULUS
2 VARIATION OF COSTS WITH CATALYST SIZE
3 VARIATION OF COSTS WITH CATALYST BED VOIDAGE
4 VARIATION OF COSTS WITH VESSEL DIAMETER
Distillation is one of the widely used separation method in most of the chemical process industries. Improper design
/operation & maintenance leads to various troubles like reduced plant capacity, poor quality of separated products,
high energy (utility) consumption, etc.
Catalyst Catastrophes in Syngas Production - II
Contents
Review of incidents by reactor
Primary reforming
Secondary reforming
HTS
LTS
Methanator
Reactor loading
Support media
Some general comments on alternative actions when a plant gets into abnormal operation
Steam Reformer Surveys - Techniques for Optimization of Primary Reformer Oper...Gerard B. Hawkins
Introduction
Background Radiation and Temperature Measurement
Reformer Survey Inputs
Other Troubleshooting Tools
Safety
Preparation
Onsite Data Collection
TWT Survey
Observation/Troubleshooting
Modelling and Analysis
Results/Outputs
Case Studies
Conclusions
Case Study 1
Case Study 2
Case Study 3
Conclusions
Theory of Carbon Formation in Steam Reforming
Contents
1 Introduction
2 Underpinning Theory
2.1 Conceptualization
2.2 Reforming Reactions
2.3 Carbon Formation Chemistry
2.3.1 Natural Gas
2.3.2 Carbon Formation for Naphtha Feeds
2.3.3 Carbon Gasification
2.4 Heat Transfer
3 Causes
3.1 Effects of Carbon Formation
3.2 Types of Carbon
4 What are the Effects of Carbon Formation?
4.1 Why does Carbon Formation Get Worse?
4.1.1 So what is the Next Step?
4.2 Consequences of Carbon Formation
4.3 Why does Carbon Form where it does?
4.3.1 Effect on Process Gas Temperature
4.4 Why does Carbon Formation Propagate Down the Tube?
4.4.1 Effect on Radiation on the Fluegas Side
4.5 Why does Carbon Formation propagate Up the Tube?
5 How do we Prevent Carbon Formation
5.1 The Role of Potash
5.2 Inclusion of Pre-reformer
5.3 Primary Reformer Catalyst Parameters
5.3.1 Activity
5.3.2 Heat Transfer
5.3.3 Increased Steam to Carbon Ratio
6 Steam Out
6.1 Why does increasing the Steam to Carbon Ratio Not Work?
6.2 Why does reducing the Feed Rate not help?
6.3 Fundamental Principles of Steam Outs
TABLES
1 Heat Transfer Coefficients in a Typical Reformer
2 Typical Catalyst Loading Options
FIGURES
1 Hot Bands
2 Conceptual Pellet
3 Naphtha Carbon Formation
4 Heat Transfer within an Reformer
5 Types of Carbon Formation
6 Effect of Carbon on Nickel Crystallites
7 Absorption of Heat
8 Comparison of "Base Case" v Carbon Forming Tube
9 Carbon Formation Vicious Circle
10 Temperature Profiles
11 Carbon Pinch Point
12 Carbon Formation
13 Effect on Process Gas Temperature
14 How does Carbon Propagate into an Unaffected Zone?
15 Movement of the Carbon Forming Region
16 Effect of Hot Bands on Radiative Heat Transfer
17 Effect of Potash on Carbon Formation
18 Application of a Pre-reformer
19 Effect of Activity on Carbon Formation
High Temperature Shift Catalyst Reduction ProcedureGerard B. Hawkins
High Temperature Shift Catalyst Reduction Procedure
The catalyst, as supplied, is Fe2O3. This reduces to the active form, Fe3O4, in the presence of hydrogen when process gas is admitted to the reactor.
1. The mildly exothermic reactions are:
3 Fe2O3 + H2 ========= 2 Fe3O4 + H2O
3 Fe2O3 + CO ========= 2 Fe3O4 + CO2
Getting the Most Out of Your Refinery Hydrogen PlantGerard B. Hawkins
Getting the Most Out of Your Refinery Hydrogen Plant
Contents
Summary
1 Introduction
2 "On-purpose" Hydrogen Production
3 Operational Aspects
4 Uprating Options on the Steam Reformer
4.1 Steam Reforming Catalysts and Tube Metallurgy
4.2 Oxygen-blown Secondary Reformer
4.3 Pre-reforming
4.4 Post-reforming
5 Downstream Units
6 Summary of Uprating Options
7 Conclusions
Furnaces in Refinery and Petrochemicals
Process furnaces
Crude distillation unit
Reaction Heaters
Reformer Heater
Heater Performance objectives
Reasons to save Energy
Heater Types
Radiant section
Convection section
Crossover section
Burners
Ammonia Plant Technology
Pre-Commissioning Best Practices
GBHE-APT-0102
PICKLING & PASSIVATION
CONTENTS
1 PURPOSE OF THE WORK
2 CHEMICAL CONCEPT
3 TECHNICAL CONCEPT
4 WASTES & SAFETY CONCEPT
5 TARGET RESULTS
6 THE GENERAL CLEANING SEQUENCE MANAGEMENT
6.6.1 Pre-cleaning or “Physical Cleaning
6.6.2 Pre-rinsing
6.6.3 Chemical Cleaning
6.6.4 Critical Factors in Cleaning Success
6.6.5 Rinsing
6.6.6 Inspection and Re-Cleaning, if Necessary
7 Systems to be treated by Pickling/Passivation
Pressure Relief Systems Vol 2
Causes of Relief Situations
This Volume 2 is a guide to the qualitative identification of common causes of overpressure in process equipment. It cannot be exhaustive; the process engineer and relief systems team should look for any credible situation in addition to those given in this Part which could lead to a need for pressure relief (a relief situation).
Equilibrium Effects
- Methane Steam
- Water Gas Shift
Relationship of Kp to Temperature
Relationship of WGS Kp to Temperature
Effect of Temperature on Methane Slip
Approach to Equilibrium
Reaction Path and Equilibrium
Effect of Pressure Increase
Operating Parameters
- Pressure
- Temperature
- Feed Rate
- Steam to Carbon
Effect of Exit Temperature Spread
Useful Tools
Calculating ATM
Catalyst Catastrophes in Syngas Production - II
Contents
Review of incidents by reactor
Primary reforming
Secondary reforming
HTS
LTS
Methanator
Reactor loading
Support media
Some general comments on alternative actions when a plant gets into abnormal operation
Steam Reformer Surveys - Techniques for Optimization of Primary Reformer Oper...Gerard B. Hawkins
Introduction
Background Radiation and Temperature Measurement
Reformer Survey Inputs
Other Troubleshooting Tools
Safety
Preparation
Onsite Data Collection
TWT Survey
Observation/Troubleshooting
Modelling and Analysis
Results/Outputs
Case Studies
Conclusions
Case Study 1
Case Study 2
Case Study 3
Conclusions
Theory of Carbon Formation in Steam Reforming
Contents
1 Introduction
2 Underpinning Theory
2.1 Conceptualization
2.2 Reforming Reactions
2.3 Carbon Formation Chemistry
2.3.1 Natural Gas
2.3.2 Carbon Formation for Naphtha Feeds
2.3.3 Carbon Gasification
2.4 Heat Transfer
3 Causes
3.1 Effects of Carbon Formation
3.2 Types of Carbon
4 What are the Effects of Carbon Formation?
4.1 Why does Carbon Formation Get Worse?
4.1.1 So what is the Next Step?
4.2 Consequences of Carbon Formation
4.3 Why does Carbon Form where it does?
4.3.1 Effect on Process Gas Temperature
4.4 Why does Carbon Formation Propagate Down the Tube?
4.4.1 Effect on Radiation on the Fluegas Side
4.5 Why does Carbon Formation propagate Up the Tube?
5 How do we Prevent Carbon Formation
5.1 The Role of Potash
5.2 Inclusion of Pre-reformer
5.3 Primary Reformer Catalyst Parameters
5.3.1 Activity
5.3.2 Heat Transfer
5.3.3 Increased Steam to Carbon Ratio
6 Steam Out
6.1 Why does increasing the Steam to Carbon Ratio Not Work?
6.2 Why does reducing the Feed Rate not help?
6.3 Fundamental Principles of Steam Outs
TABLES
1 Heat Transfer Coefficients in a Typical Reformer
2 Typical Catalyst Loading Options
FIGURES
1 Hot Bands
2 Conceptual Pellet
3 Naphtha Carbon Formation
4 Heat Transfer within an Reformer
5 Types of Carbon Formation
6 Effect of Carbon on Nickel Crystallites
7 Absorption of Heat
8 Comparison of "Base Case" v Carbon Forming Tube
9 Carbon Formation Vicious Circle
10 Temperature Profiles
11 Carbon Pinch Point
12 Carbon Formation
13 Effect on Process Gas Temperature
14 How does Carbon Propagate into an Unaffected Zone?
15 Movement of the Carbon Forming Region
16 Effect of Hot Bands on Radiative Heat Transfer
17 Effect of Potash on Carbon Formation
18 Application of a Pre-reformer
19 Effect of Activity on Carbon Formation
High Temperature Shift Catalyst Reduction ProcedureGerard B. Hawkins
High Temperature Shift Catalyst Reduction Procedure
The catalyst, as supplied, is Fe2O3. This reduces to the active form, Fe3O4, in the presence of hydrogen when process gas is admitted to the reactor.
1. The mildly exothermic reactions are:
3 Fe2O3 + H2 ========= 2 Fe3O4 + H2O
3 Fe2O3 + CO ========= 2 Fe3O4 + CO2
Getting the Most Out of Your Refinery Hydrogen PlantGerard B. Hawkins
Getting the Most Out of Your Refinery Hydrogen Plant
Contents
Summary
1 Introduction
2 "On-purpose" Hydrogen Production
3 Operational Aspects
4 Uprating Options on the Steam Reformer
4.1 Steam Reforming Catalysts and Tube Metallurgy
4.2 Oxygen-blown Secondary Reformer
4.3 Pre-reforming
4.4 Post-reforming
5 Downstream Units
6 Summary of Uprating Options
7 Conclusions
Furnaces in Refinery and Petrochemicals
Process furnaces
Crude distillation unit
Reaction Heaters
Reformer Heater
Heater Performance objectives
Reasons to save Energy
Heater Types
Radiant section
Convection section
Crossover section
Burners
Ammonia Plant Technology
Pre-Commissioning Best Practices
GBHE-APT-0102
PICKLING & PASSIVATION
CONTENTS
1 PURPOSE OF THE WORK
2 CHEMICAL CONCEPT
3 TECHNICAL CONCEPT
4 WASTES & SAFETY CONCEPT
5 TARGET RESULTS
6 THE GENERAL CLEANING SEQUENCE MANAGEMENT
6.6.1 Pre-cleaning or “Physical Cleaning
6.6.2 Pre-rinsing
6.6.3 Chemical Cleaning
6.6.4 Critical Factors in Cleaning Success
6.6.5 Rinsing
6.6.6 Inspection and Re-Cleaning, if Necessary
7 Systems to be treated by Pickling/Passivation
Pressure Relief Systems Vol 2
Causes of Relief Situations
This Volume 2 is a guide to the qualitative identification of common causes of overpressure in process equipment. It cannot be exhaustive; the process engineer and relief systems team should look for any credible situation in addition to those given in this Part which could lead to a need for pressure relief (a relief situation).
Equilibrium Effects
- Methane Steam
- Water Gas Shift
Relationship of Kp to Temperature
Relationship of WGS Kp to Temperature
Effect of Temperature on Methane Slip
Approach to Equilibrium
Reaction Path and Equilibrium
Effect of Pressure Increase
Operating Parameters
- Pressure
- Temperature
- Feed Rate
- Steam to Carbon
Effect of Exit Temperature Spread
Useful Tools
Calculating ATM
Fouling, in technical language, it is the general term of unwanted material which is accumulating on surfaces, such as inside pipes, machines or heat exchanger.
It contains introduction, homogeneous, heterogenous, transition metal, organometallic, enzymatic and phase transfer catalysis part with certain aspect of greener approach.
It cover approximately all topic according to M.pharm Organic chemistry syllabus, not in advance but for general and basic purpose of understanding.
Introduction
Basis
Importance
Classification
Homogeneous catalysis
Mechanism
Example
Heterogeneous catalysis
Mechanism
Examples
Promoters
Catalytic Poisoning
Autocatalysis
Enzyme catalysis
Enzymes
References
Catalyst: -
The substances that alter the rate of a reaction but itself remains chemically unchanged at the end of the reaction is called a Catalyst.
The process is called Catalysis.
prop-
A catalyst cannot start the reaction by itself.
Catalytic activity increases as surface area of catalyst increases.
Catalysts are thermolabile, this effect is very well pronounced in enzymes.
Catalytic activity is maximum at a catalyst’s optimum temperature.
A catalyst does not alter the position of the equilibrium, instead it helps in achieving the equilibrium faster.
Catalysis Science & Technology covers both the science of catalysis and catalysis technology, including applications addressing global issues. The journal publishes research in the applied, fundamental, experimental and computational areas of catalysis. Contributions are made by the homogeneous, heterogeneous and biocatalysis communities.
Detailed Explanation of Heat Exchangers Failures Pillai Vishnu S
Awareness of how an Heat Exchanger failure occurs due to various leaks, Ruptures, and Tube chocking. These data is been taken from practical exposure that have occurred in some of the industries and most commonly occurred failure.
It shows the basic facts of catalyst along with its importance in industry along with its long last milestone,its characteristics & application in industry its reaction process and preparation of a solid catalyst.
Catalyst poisons & fouling mechanisms the impact on catalyst performance Gerard B. Hawkins
Primary Effects
Secondary Effects
Typical Poisons in hydrocarbon processing
Permanent Poisons
- Arsenic, lead, mercury, cadmium…
- Silica, Iron Oxide….
Temporary Poisons
- Sulfur, Chlorides, Carbon
Boiler Feed water impurities
Heavy Metals
Foulants
THE NATURE OF CARBON DEPOSITS FORMED ON CATALYSTS
- CARBON FORMATION
Type A, B, C
- FEEDSTOCK COMPOSITION EFFECTS
COMMERCIAL’ CARBON DEPOSITS
- CARBON BURNING IN AIR
- CARBON REMOVAL BY STEAMING
- CARBON BURN CONTROL METHODS
- CATALYST – REACTION WITH STEAM
- MAXIMUM OXYGEN CONCENTRATION
- TEMPERATURE OF THE CATALYST SURFACE DURING CARBON BURNS
- CONDITIONS TO BURN OFF CARBON COATED CATALYST
- EFFECT OF CARBON FORMATION
Austenitic stainless steels are extensively used in hydrotreating units of oil refineries because of their resistance to H2S+H2 attacks at high temperatures and pressures. However, during the shutdown period presence of metal sulfides leads to polythionic acid cracking. Polythionic Acid (PTA), (H2SXO6) is a complex acid formed by the reaction of sulfide of metals with water and oxygen during shutdown when the system is cooled, and oxygen and water can enter the system. The Polythionic Acid cracking is intergranular and occurs more readily in sensitized stainless steel.
In hydroprocessing units, the Polythionic Acid Stress Corrosion Cracking often occurs sometimes during shutdowns or turnaround. The reason is that during normal operation of the hydroprocessing unit, Iron or Chromium Sulfide layers are formed on austenitic stainless steel. These sulfide scales react with O2 and liquid water forming the polythionic acid that ultimately cracks the metals. The cracking initiates during the shutdown but then propagates to failure during startup or operation. The reaction of moisture and oxygen in the air with the sulfide scale form polythionic acid (H2SxO6), which then attacks the metal. Polythionic Acid can be formed in the presence of FeS through this reaction;
4FeS + 5.5O2 + H2O → 2Fe2O3 + H2S4O6 (Tetrathionic acid)
Polythionic Acid Formation
There are higher chances of Polythionic Acid attack if the austenitic material is sensitized. Sensitization of austenitic stainless steel means the precipitation of chromium carbide at the grain boundaries when they are in operation at high temperatures for a long duration. This precipitation happens because the carbides are insoluble at these temperatures. Carbide precipitation takes chromium from the surrounding metal and creates a chromium-depleted zone around the grain boundaries. The sensitized alloy is highly susceptible to polythionic acid attack due to weak grain boundaries and loss of metal strength. The temperature ranges of sensitization are given in Table 1.0
For an on-stream hydrotreating unit, all equipment and piping made of austenitic stainless steel should be considered to contain a layer of iron sulfide scale. There is always the risk of polythionic acid attack even if the sulfur content in the feed is low and the layer of metal sulfide scale is very thin. The stainless steels are at high risk of Polythionic Acid attack, especially in the areas of residual tensile stresses, heat-affected zones adjacent to welds, and sensitized steels.
Reactor Section of Hydroprocessing Unit susceptible to Polythionic Acid Attack
Techniques to Avoid Polythionic Acid Attack
Polythioninc Acid Attack can be avoided by removing one of the items in the triangle, the Iron Sulfide Scale, Oxygen, and Water. Elimination of water or oxygen will prevent the formation of Polythionic Acid.
Various techniques are followed to avoid PTA as follows;
Removal of water or oxygen by applying
To promote intimate contact between the vapor and liquid, the distillation column contains internal devices. The internal devices may be grouped into two general categories: Tray-type and Packing-type.
The most widely applied trays in process industries are 1. Bubble cap trays, 2. Sieve trays and 3. Valve trays.
The crude oil assay is the collection of the results of physical tests that are performed to determine the key properties (boiling point, density, viscosity, heteroatom contents, acid number, etc.) of crude oil and its fractions. It is the procedure based on laboratory and pilot plant testing for determining the general distillation and quality characteristics of crude oil. Crude oil assay is important for determining the value and processability of crude oil. This is the preliminary step before processing the crude oil in the refinery. . In order to utilize the crude oil assay data, it is necessary to understand the results and significance of some of the laboratory tests.
Naphtha catalytic reforming process is the key process in oil refining to meet the demands of gasoline fuel specifications and hydrogen gas for hydrotreating and isomerization units. But one bottleneck of high aromatics content in gasoline may restrict the naphtha reforming process due to strict environmental regulations.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
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Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
1. Trouble Shooting of Catalytic
Reactors
BY: NASIR HUSSAIN
PROCESS OPERATIONS ENGINEER REFINERY
CONTACT: NASIR.MUGHAL3010@GMAIL.COM
2. Introduction
Catalyst: “A catalyst is a substance that changes the rate of chemical reaction
without itself appearing in the products.” A catalyst changes the rate of a
reaction by altering the free energy of activation (or activation energy) without
altering the thermodynamic aspects of the reaction.
3. Catalysts at My Refinery
Sr. No Area Catalyst Process Reactions
01 Hydrocracker Ni Mo/Co Mo Hydrocracking
02 Platforming Platinum, R134 Naphtha Reforming
03 DHT Ni Mo/Co Mo Hydro treating
04 Isomerization Platinum Isomerization
4. Important Terms
1. Catalyst
2. Activity
3. Selectivity
4. Sintering
5. Channeling
6. Temperature runaway
7. Chemisorption
8. Cocking or carbon laydown
5. Definitions
Activation Energy: Activation energy, in chemistry,
the minimum amount of energy that is required to
activate atoms or molecules to a condition in which
they can undergo chemical transformation.
2.Activity: It is the extent to which the catalyst
influence the rate of reactions as measured by the
disappearance of the reactions. It is often expressed
as rate per unit volume.
3. Selectivity: It is the ability to promote the
particular reaction while minimizing the production
of unwanted compounds.
4. Catalyst Life: It is the period during which the
catalyst provide the required product at required
degree of selectivity and activity.
6. Catalyst Sintering:
Sintering is the process of compacting and forming a solid mass of material by
heat or pressure without melting it to the point of liquefaction. The atoms in
the materials diffuse across the boundaries of the particles, fusing the
particles together and creating one solid piece. Thermally induced loss of
catalytic surface area, support area, and active phase–support reactions.
Sintering on bulk catalysts is normally physical (Thermal) rather than
chemical phenomena. Sintering is strongly temperature-dependent. The rate
of sintering increases exponentially with temperature. Sintering may
result; Agglomeration, the sticking of particles to one another or to solid
surfaces, is a natural phenomenon. For powders and bulk solids,
agglomeration can be unwanted, resulting in uncontrolled buildup, caking,
bridging, or lumping.
7. Catalyst Channeling
It is the formation of specific flow path by process fluid through the catalyst bed.
Channeling can either result in an increase in DP or a decrease in DP depending on what
is causing it. If there is coking in the bed, then flow will be forced through paths that are
not coked. The reduction in flow area will cause a net increase in DP. If there are voids
in the catalyst bed due to poor loading of the catalyst into the reactor, then the void
spaces in the bed provide more open channels for flow. Flow takes the path of least
resistance and much of the catalyst bed is effectively bypassed.
If you have coking going on you will see a higher than expected reactor DP. It may or
may not be accompanied by erratic radial temperature profiles and/or difficulty
meeting product specs (if coking is uniform across the top of the bed then it may only
show up as higher than expected DP). If you have channeling due to poor catalyst
loading it will show up as lower than normal DP, difficulty meeting product sulfur specs,
and likely an erratic radial temperature profile.
8. Channeling
Channeling may be confirmed by checking radial temperature variations across reactor at
various levels. If the temperature variation is more than 6-10 deg C, there is a channeling. On
the question of “how to tell,” a well-designed pattern of radial bed thermocouples and the luck
of having them read accurately throughout the run are the best means of determining
channeling .
9. Definitions
Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved
solid to a surface.[1] This process creates a film of the adsorbate on the surface of
the adsorbent. This process differs from absorption, in which a fluid (the absorbate)
is dissolved by or permeates a liquid or solid (the absorbent), respectively.
Adsorption is a surface phenomenon, while absorption involves the whole volume of
the material. The term sorption encompasses both processes, while desorption is the
reverse of it.
Chemisorption is a kind of adsorption which involves a chemical reaction between
the surface and the adsorbate. New chemical bonds are generated at the adsorbant
surface. Examples include macroscopic phenomena that can be very obvious, like
corrosion, and subtler effects associated with heterogeneous catalysis. The strong
interaction between the adsorbate and the substrate surface creates new types of
electronic bonds.
10. Definitions:
Temperature runaway: Thermal runaway occurs in situations where an increase in temperature
changes the conditions in a way that causes a further increase in temperature, often leading to a
destructive result. It is a kind of uncontrolled positive feedback.
In other words, "thermal runaway" describes a process which is accelerated by increased
temperature, in turn releasing energy that further increases temperature. In chemistry (and chemical
engineering), it is associated with strongly exothermic reactions that are accelerated by temperature
rise. Typical causes of temperature runaway;
1. Loss of quench gas
2. uncontrolled firing in feed heater
3.Loss of cooling media
4. Sudden change in feed quality
5. Maldistribution of flows across the reactor causing hot spots.
11. Catalyst Deactivation
The loss overtime of catalytic activity or selectivity of the catalyst is called
deactivation. Loss in catalytic activity due to chemical, mechanical or thermal
processes.
Catalyst deactivation, the loss over time of catalytic activity and/or selectivity, is
a problem of great and continuing concern in the practice of industrial catalytic
processes.
Typically, the loss of activity in a well-controlled process occurs slowly. However,
process upsets or poorly designed hardware can bring about catastrophic
failure.
13. Thermal
Thermally induced loss of catalytic surface area, support area, and active phase–
support reactions. Thermal degradation is the catalyst deactivation due to high
temperatures. This include normal or routine deactivation due to aging and also
due to plant upsets or thermal shocks. Following are the types of Thermal
degradation;
1. Sintering
2. Coking
14. Mechanical
Physical deposition of species (metals) from fluid phase onto the catalytic
surface and in catalyst pores. In addition, loss of catalyst surface or any other
problem due to high velocity of fluid is mechanical loss.
Moreover, any damage due to mechanical parts problem also comes in this
category.
1. Fouling due to heavy metals
2. Attrition/Crushing
15. Chemical
Deactivation of catalyst due to chemical reactions on the catalyst surface is
Chemical deactivation. It can permanent or temporary. Following are examples of
Chemical deactivations;
1. Poisoning
2. Chemical reactions; and Phase transformations
3. Coking can also come in this category.
18. Poisoning
Poisoning basically involve chemisorption of reactants or products or feed
impurities on the active sites of the catalyst surface, thereby decreasing
the number of active sites available for catalytic reactions. Since poisoning
involves chemisorption, it is known as chemical deactivation. This process
can be reversible or irreversible. Compound of sulphur and other
materials are frequently chemisorbed on nickel, copper and Pt catalysts.
In reversible poisoning, the strength of adsorption bond is not great and
activity is regained when the poison is removed from the feed. When the
adsorbed material is tightly held on the active sites, poisoning is
irreversible and permanent.
19. Troubleshooting of catalytic Reactors
Symptoms Causes
DP higher>design Catalyst degradation/ instrument error/ high gas flow/ sudden coking/ problem left in from
construction or revamp, internal damage.
Rapid decline in
conversion
unfavorable shift in equilibrium at operating temperature, for exothermic reactions/
[sintering]*/ [agglomeration], poisons in feed, temperature runaway
Gradual decline in
conversion
Sample error/ analysis error/ temperature sensor error/ [catalyst activity lost]*/
[maldistribution]*/ [unacceptable temperature profiles]*/ [inadequate heat transfer]*/ wrong
locations of feed, discharge or recycle lines/ faulty design of feed and discharge ports/ wrong
internal baffles and internals/ faulty bed-voidage profiles
Temperature runaways Change in feed composition, furnace controlled firing, uncontrolled reactions. feed
temperature too high/ [temperature hot spot]*/ cooling water too hot, failure of cooling
media
Local high
temperature/hot spot
[misdistribution of gas flow]*/ instrument error/ extraneous feed component that reacts
exothermically
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20. Troubleshooting of catalytic Reactors
Local low temperature within the
bed
[maldistribution of gas flow]*/ instrument error/ extraneous feed
component that reacts endothermic ally
Exit gas temperature too high instrument error/ control-system malfunction/ fouled reactor coolant
tubes.
Temperature varies axially across
bed
[maldistribution}
Symptom: Soon after startup, temperature of tubewall near top>usual and increasing and perhaps Dp increase
and less conversion than expected or operating temperatures>usual to obtain expected conversion
Cause: inadequate catalyst regeneration/ contamination in feed; for steam reforming sulfur
concentration>specifications/ wrong feed composition; for steam reforming: steam/CH4<7 to 10
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21. Troubleshooting of catalytic Reactors
Symptoms Causes
conversions<standard Reduction faulty, bad batch of catalyst/ preconditioning of catalyst faulty/
temperature and pressures incorrectly set/ instrument error for pressure or
temperature
poor selectivity bad batch of catalyst/ preconditioning of catalyst faulty/ temperature and
pressures incorrectly set/ instrument error for pressure or temperature
Dp<expected and conversion<standard maldistribution and axial variation in temperature/ larger size catalyst.
conversion<standard and Dp increasing maldistribution and axial temperatures different]*/ feed precursors present
for polymerization or coking
Dp for this batch of catalyst>previous batch catalyst fines produced during loading/ poor loading
conversion<specifications per unit mass of
catalyst and more side reactions
maldistribution/ faulty inlet distributor/ faulty exit distributor
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22. Troubleshooting of catalytic Reactors
increased side reactions and
conversion<specification
Catalyst loading not the same in all tubes.
Active species volatized [regeneration faulty]*/ faulty catalyst design for typical reaction temperature/
[hot spots]*.
Agglomeration of packing or catalyst
particles
[temperature hot spots
Carbon buildup inadequate regeneration]*/ [excessive carbon formed]*. [Catalyst selectivity
changes]*: [poisoned catalyst]*/ feed contaminants/ change in feed/ change
in temperature settings
Catalyst activity lost carbon buildup]*/[regeneration faulty]*/ [sintered catalyst]*/ excessive
regeneration temperature/ [poisoned catalyst]*/ [loss of surface area]*/
[agglomeration]*/ [active species volatized
Excessive carbon formed operating intensity above usual/ feed changes/ temperature hot spots.
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23. Troubleshooting of catalytic Reactors
Symptoms Causes
Dust or corrosive products
from upstream processes
in-line filters not working or not installed/ dust in the atmosphere brought in with air/ air
filters not working or not installed.
Loss of surface area [sintered catalyst]*/ [carbon buildup]*/ [agglomeration
Maldistribution faulty flow-distributor design/ plugging of flow distributors with fine solids, sticky byproducts
or trace polymers/ [sintered catalyst particles]*/ [agglomeration of packing or catalyst
particles]*/ fluid feed velocity too high/ faulty loading of catalyst bed/ incorrect flow collector
at outlet.
Poisoned catalyst Poisons in feed/ flowrate of “counter poison” insufficient/ poison formed from unwanted
reactions.
Reactor instability Control fault/ poor controller tuning/ wrong type of control/ insufficient heat transfer area/
feed temperature exceeds threshold/ coolant temperature exceeds threshold/ coolant
flowrate<threshold/ tube diameter too large
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24. Case Study
At 0200 hours on April 2, one of the six continuous
polymerization reactors experienced a temperature runaway.
That is, the reactor temperature rose exponentially from a
normal temperature of 150 to 175 ° F in a 30 – minute period.
Polymerization is an exothermic reaction that generates a signifi
cant amount of heat for each pound of polymer produced. The
heat of reaction is removed by circulating cooling water.
Polymerization reaction rates generally double with every 20 ° F
increase in temperature. When the reactor in question reached
175 ° F, the reaction was terminated by injection of a quench
agent.
25. Case Study
All the other reactors were operating normally. The temperature
control system on the reactor was such that an increase in
temperature caused an immediate increase in the cooling water
supply fl owIt was known that a small increase in catalyst rate
occurred right before the temperature began increasing. However in
the past, catalyst rate increases of this magnitude only resulted in a
slight temperature increase. Following this slight increase, the
reactor temperature very quickly returned to normal as the cooling
water control system responded. The heat exchanger that is used to
remove the heat of polymerization is periodically removed for
cleaning. OnApril 1, the exchanger seemed to be “ ok ”.