VII BASIC CONCEPT OF CLEAN PROCESS TECHNOLOGY, PROCESS CONTROL SAFETY

  Dr.Eng. Yulius Deddy Hermawan Department of Chemical Engineering UPN “Veteran” Yogyakarta

  

VII

BASIC CONCEPT OF

CLEAN PROCESS TECHNOLOGY,

PROCESS CONTROL & SAFETY

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Outline

  1. Clean Process Technology

  

2. Introduction to Process Control

  

3. Introduction to Process Safety

  

VII.1.

CLEAN PROCESS

TECHNOLOGY

Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  

Two classes of waste from chemical process

(Smith R., 2005)

  1. The two inner layers of the onion diagram (the reaction and separation and recycle systems) produce process waste. The process waste is waste byproducts, purges, and so on

  2. The outer layers of the onion (the utility system) produce utility waste. The utility waste is fuel combustion, products of waste from the production of boiler feedwater for steam generation, and so on.

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  

Source of Waste for Chemical Production

(Smith R., 2005)

  

1. Reactors. Waste is created in reactors through the

formation of waste byproducts, and so on.

  

2. Separation and recycle systems. Waste is produced

from separation and recycle systems through the inadequate recovery and recycling of valuable materials from waste streams.

  

3. Process operations. The third source of process waste

can be classified under the general category of process operations. Operations such as start-up and shutdown of continuous processes, product changeover, equipment cleaning for maintenance, tank filling, and so on, all produce waste.

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Clean Process Technology for Chemical Reactor

  

Under normal operating conditions, waste is produced in reactors in

the following ways:

  

1. If it is not possible, for some reason, to recycle unreacted feed

material to the reactor inlet, then low conversion will lead to waste of that unreacted feed.

  

2. The primary reaction can produce waste byproducts, for example:

FEED1 + FEED2  PRUDUCT + WASTE (BYPRODUCT)

  

3. Secondary reactions can produce waste byproducts, for example:

FEED1 + FEED2  PRUDUCT

PRODUCT  WASTE (BYPRODUCT)

  

4. Impurities in the feed materials can undergo reaction to produce

waste byproducts.

  

5. Catalyst is either degraded and requires changing or is lost from

the reactor and cannot be recycled.

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  

Clean Process Technology for Separation & Recycle Systems

Waste from the separation and recycle system can be minimized in

five ways: 1. Recycling waste streams directly.

  2. Reduction of feed impurities by purification of the feed 3. Elimination of extraneous materials used for separation.

  

4. Additional separation of waste streams to allow increased

recovery.

  

5. Additional reaction and separation of waste streams to allow

increased recovery Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  

Waste minimization in separation and recycle systems

Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  

Clean Process Technology for Process Operations

Sources of waste in process operations

  

:

  1. Start-up/shutdown in continuous processes Reactors give lower than design conversions.

   Reactors at nonoptimal conditions produce (additional) unwanted

   byproducts. Separators working at unsteady conditions produce intermediates with

   compositions that do not allow them to be recycled Separators working at unsteady conditions produce products that do

   not meet the required sales specification

  2. Product changeover In continuous processes, all those sources of process waste associated

   with start-up and shutdown also apply to product changeover in multiproduct plants. In both batch and continuous processes, it may be necessary to clean

   equipment to prevent contamination of new product. Materials used for equipment cleaning often cannot be recycled, leading to waste.

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY Sources of waste in process operations :

3. Equipment cleaning for maintenance, tank filling and fugitive emissions.

  Equipment needs to be cleaned and made safe for maintenance When process tanks, road tankers, rail tank cars or barges are filled,

   material in the vapor space is forced out of the tank and lost to atmosphere. Material transfer requires pipework, valves, pumps and compressors.

   fugitive emissions occur from pipe flanges, valve glands and pump and compressor seals.

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  

Other ways to minimize waste from process operation are

Minimize the number of shutdowns by designing for high availability. Install

   more reliable equipment or standby equipment.

Design continuous processes for flexible operation, for example, high

   turndown rate rather than shutdown.

Consider changing from batch to continuous operation. Batch processes, by

  

their very nature, are always at unsteady-state, and thus difficult to

maintain at optimum conditions.

Install enough intermediate storage to allow reworking of off-specification

   material

Changeover between products causes waste since equipment must be

  

cleaned. Such waste can be minimized by scheduling operation to minimize

product changeovers .

Install a waste collection system for equipment cleaning and sampling

  

waste, which allows waste to be segregated and recycled where possible.

This normally requires separate sewers for organic and aqueous waste,

collecting to sump tanks and recycle or separate and recycle if possible. Reduce losses from fugitive emissions and tank breathing

   Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

VII.2.

   Operating conditions ( P, T, C, F ) should be located in the range of desired value. e.g. [SO

  5. Economic

   Reactor catalytic temperature should be kept lower than upper limit

   Tank: can’t be empty or overflow

  4. Operation Limits

  , water quality dispose to the river

  2 ] max

  3. Environmental Law

  

INTRODUCTION TO

PROCESS CONTROL

Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

   plant product (quantity and quality) meets the market conditions

  2. Product specifications

   Automatic process control should be implemented to maintain the operating condition at its set point.

   P, T, C, F should be stayed at its desired condition

  1. Safety

  Requirements during plant operation:

  

Process Control Motivation

:

(Stephanopoulus, G., 1984)

  

Plant operation must agree with market conditions, e.g. raw materials availability must balance with the product Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Liquid Level Dynamic in A Stirred Tank Heater

  V-03 V-02 V-01

  From the upstream unit

  From the upstream unit to the next unit

  h

  sp

  liquid’s level set-point

  Steam Condensate Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  Implementation of Process Control for 

Suppress push down press the outside disturbances’ effect

(variation of T, P, F, C )

   Ensure the stability of chemical process  Optimize the chemical process performances Types of Process Control 

  Feedback Control  Feedforward Control  Combination of Feedback and Feedforward

• Purpose : maintain T at its desired value (set point)

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Typical Heat Exchanger

  The outlet temperature of process stream varies with the disturbance load changes

  Process stream Heated stream

  T i (t), f(t) T(t)

  Steam Condensate

  Manual ? Or

  Automatic ?

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Three weaknesses of manual control by operator:



  

Operator often sees (checks) the temperature of HE

 Different Operator gives different decision about how to handle the valve control of steam

   Most chemical plants consist of many controlled variables, it thus needs so many operators

  

Automatic process control should be implemented

  Smith, A., and Corripio, A.B., (1997)

• Sensor/Transmitter
• Controller • Final Control Element

01 TT

• Measurement (M)
• Decision (D)
• Action (A) The main goal is to maintain the outlet temperature of HE at its set-point by manipulating the steam flowrate, even though the disturbances enter the process.

  11

  TT

  Feedforward controller

  10 SP

  Condensate TT

  T _i (t), f(t) T(t) Steam

  Process stream Heated stream

  

Feedforward Control of Heat Exchanger

TT : Temperature Transmitter (Sensor)  thermocouple FT : Flow Transmitter

  The main goal is to measure the disturbance changes and make compensation before the controlled variable (The outlet temperature of HE) deviates form its set-point.

  01 SP Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  Condensate TC

  T _i (t), f(t) T(t) Steam

  Process stream Heated stream

  3 Basic Operations:

  3 basic components:

  TT : Temperature Transmitter (Sensor)  thermocouple TC : Temperature Controller

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Feedback Control of Heat Exchanger

11 FT

  

Feedback vs Feedforward

Cold water Cold water (T C varies) (T C varies)

  Warm water Warm water T C (t) T (t) _C T _H

  T H Hot water Hot water (T constants) _H

  (T constants) _H Note: father’s left hand senses warm water Note: father’s right hand senses the cold water temperature, and father’s right hand arranges the temperature, and father’s left hand arranges the opening valve of hot water. opening valves of hot water. (A)

  (B) Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Combination of Feedback-Feedforward Control

  Steam SP

  Feedforward controller

  TC

  10 TT FT TT

  10

  11

  11 T(t) Heated Process T (t), f(t) _i stream stream

  TT : Temperature Transmitter (Sensor)  thermocouple Condensate

  FT : Flow Transmitter

  Feedforward overcomes the main disturbance, while Feedback overcomes the other disturbances. .. what does it mean??

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Temperature Control in Heater Treater

  HEATER TREATER BURNER AT HEATER TREATER

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY HT’s Intrumentation

  Temperature Indicator Temperature Set Point Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Flow Control

  FT

  10 F SP

  F

  FT

  10 FC

  10 F SP

10 FC

  F

  FC 

  Flow Controller FT 

  Flow Transmitter FT 

  Differential Pressure Cell (DP Cell) Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  

Plumbing Illustration in a process system

(Luyben, W.L.) Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Good Plumbing

plumbing 1 st law:

PUT VALVE IN DOWNSTREAM AFTER CENTRIFUGALPUMP

plumbing 2 nd law:

USE ONLY ONE VALVE IN LIQUID PIPELINE

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Forbidden Plumbing

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Good Plumbing

plumbing 3 rd law:

DON’T THROTTLE DISCHARGE OF COMPRESSOR

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Forbidden Plumbing

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Pressure Control

  10

  1

  2 F

  3 F

  F

  Differential Pressure Cell (DP Cell)

  Level Transmitter LT 

  Level Controller LT 

  SP LC 

  h

  10 LC

  PT

  LT

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Level Control

  Differential Pressure Cell (DP Cell) Flash drum

  Pressure Transmitter PT 

  Pressure Controller PT 

  PC 

  P

  10 P SP

  10 PC

  h

10 F

10 CC

  2

  Composition Analyzer

  CT

  10 F

  1

  , C

  1 F

  , C

  Composition Controller CT 

  2 F

  3

  , C

  3 C SP splitter

  Recycle stream

  Purge

  Composition Transmitter CT 

  CC 

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Composition Control in mixing process

  1

  CC 

  Composition Controller CT 

  Composition Transmitter CT 

  Composition Analyzer gas chromatograph, spectroscopic

  CT

  10 CC

  , C

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Composition Control in purging process

  1 F

  2

  , C

  2 F

  3

  , C

  3 C SP mixer

• gas chromatograph,
• spectroscopic

Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

HDA Process with Energy Integration Alternative 1

  From Terrill and Douglas (1987)

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Pneumatic Valve

pressured air liquid

  (a) FO-AC liquid pressured air

  (b) FC-AO Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Preparing of Vapor/Gas Feed

  Develop the control configuration Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  

Preparing of High Pressure Gas Feed

dry gas (F G ) coolant (F C ) c ondensate (F _L )

  

SEPARATOR

CONDENSOR COMPRESSOR flare (F _flare ) high pressure gas gas feed (F F ) comp. suction

  (F _suct ) to oil pit T, P

  SPLITTER Develop the control configuration

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

VII.3.

  

INTRODUCTION TO

PROCESS SAFETY

Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  

Illustration of Chemical Process System

CHEMICAL PROCESS

SYSTEM

FEED

  PRODUCT SAFETY SYSTEM CONTROL SYSTEM FC/ FRC, TC/ TRC, LC, PC,

  CC, …

  ENERGY

IN/ OUT

UTILITY SYSTEM

• WATER AND STEAM
• ELECTR>HARBOR
• RAI>PRESS AIR
• REFRIGE
• WASTE TREATMENT
>INERT OFFSITE SYSTEM
• STORAGE

  

CHEMICAL PROCESS

TECHNOLOGY

MORE & MORE COMPLEX

  

More

High Exotic

reactive

pressure chemistry

chemical

  Needs sophisticated safety technology and chemical engineer who understand safety concepts well “care to fundamental things will safe; otherwise, it is a disaster”

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Terminologies

• prevention to the accident by using adequate technology for identifying chemical plant’s hazards and eliminate before it happens

  Safety or loss prevention

• A chemical or physical condition that has the potential for causing damage to people, property, or the environment

  Hazard

• A measure of human injury, environmental damage, or economic loss in term of both the incident likelihood the magnitude of the loss or injury

  Risk

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  

Ingredients of successful safety program

(Crowl, D.A., and Louvar, J.F., 2011)

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

fund

invest Profit

company

able to minimize gives salary and the financial loss facilities and makes the environment safe and friendly for employees and

engineer

peoples

responsible to his/herself, family, people, and his/her profession

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Table 1-1. American Institute of Chem. Engineers

Code of Professional Ethics

  2. ST harus melakukan pelayanan hanya pada kompetensi mereka

  7. Engineers shall continue their professional development throughout their careers and shall provide opportunities for the professional development of those engineers under their supervision

  6. ST harus bertindak sedemikian utk menegakkan dan meningkatkan kehormatan, integritas, dan martabat profesi

  6. Engineers shall act in such a manner as to uphold and enhance the honor, integrity, and dignity of the engineering profession

  5. ST harus membangun reputasi profesional pd pelayanan yg baik

  5. Engineers shall build their professional reputations on the merits of their services

  4. ST harus bertindak profesional ke pada tiap pekerja atau klien seperti orang kepercayaan untuk menghindari konflik kepentingan

  4. Engineers shall act in professional matters for each employer or client as faithful agents or trustees, and shall avoid conflicts of interest

  3. ST harus menyatakan persoalan publik secara objektif dan berbicara kebenaran

  3. Engineers shall issue public statements only in an objective and truthful manner

  2. Engineers shall perform services only in areas of their competence

  Engineers shall uphold and advance the integrity, honor and dignity of the engineering profession by

  1. Sarjana teknik (ST) lebih mementingkan keamanan, kesehatan, dan keselamatan publik dalam tugas- tugas profesional

  1. Engineers shall hold paramount the safety, health, and welfare of the public in the performance of their professional duties

  Fundamental Canons Dasar Peraturan

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Tabel 1-1. Continued

  3. Berjuang utk meningkatkan kompetensi dan prestise profesi keteknikan

  2. Mengutamakan kejujuran dan kesetiaan kepada masyarakat, pekerja, dan klien 3. striving to increase the competence and prestige of the engineering profession

  1. Menggunakan pengetahuan dan kecakapan untuk meningkatkan keselamatan manusia 2. being honest and impartial and serving with fidelity the public, their employers, and clients

  1. using their knowledge and skill for the enhancement of human welfare

  Engineers harus menegakkan dan meningkatkan integritas, kehormatan, dan martabat profesi keteknikan

  7. ST harus melanjutkan pengembangan profesionalnya melalui kariernya dan membuka peluang pengembangan profesional bagi ST dibawah supervisinya

  3 systems to determine the effectiveness of safety program:

  1. OSHA (occupation safety and health administration) incidence rate

  2. Fatal accident rate (FAR), and

  3. Fatality rate or deaths per persons per year Mostly used by British Chemical Industries:

  (Crowl, D.A., and Louvar, J.F., 2011)

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Acceptable Risk

   We cannot eliminate risk entirely  Every chemical process has a certain amount of risk

  Single Certain risk Process Chemical industry Multi

  High risk >> Process Multiple exposures are additive

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  

Public Perceptions

 The general public has great difficulty with the concept of acceptable risk.  Chemical plant designers who specify the acceptable risk are assuming that these risks are satisfactory to the civilian living near the plant.  There is a suggestion that eliminating chemical hazards by

  “returning to the nature”, for example to eliminate synthetic fibers produced by chemicals and use natural fibers such as cotton.  Statistic shows ( by Kletz ):

• – FAR for chemical industry = 4.0
• – FAR for agriculture = 10.0

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

The three major accidents/hazards in process plant

  Type of Probability of Potential for Potential for Accident/hazard Occurrence Fatalities Economic Loss

  Fire High Low Intermediate Explosion Intermediate Intermediate High Toxic Release Low High low

  “Human error” frequently causes losses

• almost accident (except caused by nature), can be related with human error
• e.g. imperfect maintenance (due to human error ) results mechanic damages
• Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Plant’s Accident Examples

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Most Accidents follow three step sequence:

  

Initiation

(the event that starts the accident )

  

Propagation

(the event or events that maintain or expand the accident )

  

Termination

(the event or events that stop the accident or diminish it in size ) Significant disaster example: Flixborough England, on Saturday in June 1974

Oxidation

Cyclohexane (CH),

  Caprolactam

155 °C; 7.9 atm

Similar to gasoline

  70000 tons/year

6 reactors in series

28 people died, 36 were injured, damge extended to

  28 inch

  1821 nearby houses and 167 shops. Fire in plant burned for over 10 days.

  Size of bypass pipe of was reduced (28”  20”) causes v >>  pipe ruptured  30 ton CH volatile  vapor cloud, the cloud was ignited

  20 inch

  by unknown source about 45 second after the release  R5 was found to be leaking, need to be repaired; explosion bypass from R4 to R6 by pipe line 20 inch

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Design of Chemical Process Safety

• Eliminate initiation step
• Change propagation step to termination step

  theoritical: Can be avoided by eliminating initiation step Prevent accident Practical: ineffective and unrealistic to eliminate all initiation steps

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  (Crowl, D.A., and Louvar, J.F., 2011) Inherent Safety Techniques

  Type Typical Techniques Minimise Change from large batch reactor to a smaller continuous reactor (intensification)

  Reduce storage inventory of raw materials Improve control to reduce inventory of hazardous intermediate chemicals Reduce process hold-up

  Substitute Use mechanical pump seals vs. packing (substitution)

  Use welded pipe vs. flanged Use solvents that are less toxic Use mechanical gauges vs. mercury Use chemicals with higher flash points, boiling points, and other less hazardous properties Use water as a heat transfer fluid instead of hot oil

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY ( )

  

Inherent Safety Techniques continued

  Type Typical Techniques Moderate Use vacuum to reduce boiling point (attenuation and

  Reduce process temperatures and pressures limitation of effects) Refrigerate storage vessels Dissolve hazardous material in safe solvent Operate at conditions where reactor runaway is not possible Place control rooms away from operations Separate pump rooms from other rooms Acoustically insulate noisy lines and equipment Barricade control rooms and tanks

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

  ( )

Inherent Safety Techniques continued

  Type Typical Techniques Simplify Keep piping systems neat and visually easy to follow (simplification and

  Design control panels that are easy to comprehend error tolerance) Design plants for easy and safe maintenance Pick equipment that requires less maintenance Pick equipment with low failure rates Add fire- and explosion-resistant barricades Separate systems and controls into blocks that are easy to comprehend and understand Label pipes for easy "walking the line" Label vessels and controls to enhance understanding

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY

Problems

  

1. An employee works in plant with a FAR of 4. If this

employee works a 4-hr shift, 200 days per year, what is the expected deaths per person per year?

2. Three process unit are in a plant. The units have FARs of 0.5, 0.3, and 1.0, respectively.

  a. What is the overall FAR for the plant, assuming worker exposure to all three units simultaneously?

b. Asuume now the units are far enough apart that an accident in one would not affect the workers in another.

  If a worker spends 20% of his time in process area 1, 40% in process area 2, 40% in process area 3, what is his overall FAR?

  Dr. Eng. Y. D. Hermawan – ChemEng - UPNVY