VII BASIC CONCEPT OF CLEAN PROCESS TECHNOLOGY, PROCESS CONTROL SAFETY

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Department of Chemical Engineering - UPN “Veteran” Yogyakarta Page 1 of 29

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)

VII.1.

CLEAN PROCESS

TECHNOLOGY

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

(3)

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.

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.

(4)

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

(5)

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.

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.}

(6)

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.

(7)

VII.2.

INTRODUCTION TO

PROCESS CONTROL

Process Control Motivation

:

(Stephanopoulus, G., 1984)

Requirements during plant operation:

1. Safety

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

 Automatic process control should be implemented to maintain the

operating condition at its set point.

2.

Product specifications

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

3. Environmental Law

 Operating conditions (P, T, C, F) should be located in the range of

desired value. e.g. [SO₂]_max, water quality dispose to the river

4.

Operation Limits

 Tank: can’t be empty or overflow

 Reactor catalytic temperature should be kept lower than upper limit

5.

Economic

 Plant operation must agree with market conditions, e.g. raw

(8)

Liquid Level Dynamic in A Stirred Tank Heater

V-03 V-02 V-01

From the upstream unit

to the next unit

hsp liquid’s level set-point

Steam Condensate

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

(9)

Typical Heat Exchanger

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

Process

stream Heatedstream

Ti(t), f(t) T(t)

Steam

Condensate

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

Manual ? Or Automatic ?

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

(10)

Feedback Control of Heat Exchanger

TT : Temperature Transmitter (Sensor) thermocouple

TC : Temperature Controller 3 basic components_• _{Sensor/Transmitter} :

• Controller

• Final Control Element

3 Basic Operations: • 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.

Process

stream Heatedstream

T_i(t), f(t) T(t)

Steam Condensate TC 01 TT 01 SP

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.

Process

stream Heatedstream

T_i(t), f(t)

(11)

Feedback vs Feedforward

Warm water

Hot water (THconstants)

Cold water (TCvaries)

TC(t)

TH _T_H

Note: father’s left hand senses warm water temperature, and father’s right hand arranges the opening valve of hot water.

(A)

Note: father’s right hand senses the cold water temperature, and father’s left hand arranges the opening valves of hot water.

(B) Cold water

(TCvaries)

TC(t)

Hot water (THconstants)

Warm water

Combination of Feedback-Feedforward Control

TT : Temperature Transmitter (Sensor) _thermocouple

FT : Flow Transmitter

Process

stream Heatedstream

Ti(t), f(t)

T(t) Steam Condensate TC 10 TT 10 SP Feedforward controller TT 11 FT 11

(12)

Temperature Control in Heater Treater

HEATER TREATER

BURNER AT HEATER TREATER

HT’s Intrumentation

Temperature Indicator

(13)

Flow Control

FT 10 FC

10

FSP

F

FT 10 FC

10

FSP

F

FC Flow Controller FTFlow Transmitter

FTDifferential Pressure Cell (DP Cell)

(14)

Good Plumbing

plumbing

1

st

law:

PUT

VALVE

IN

DOWNSTREAM

AFTER CENTRIFUGALPUMP

plumbing

2

nd

law:

USE ONLY

ONE

VALVE

IN LIQUID PIPELINE

(15)

Good Plumbing

plumbing

3

rd

law:

DON’T

THROTTLE

DISCHARGE

OF COMPRESSOR

(16)

Pressure Control

PT

10 PC10

PSP

P

PC Pressure Controller PTPressure Transmitter

PTDifferential Pressure Cell (DP Cell)

Flash drum

Level Control

LT

10 LC10

h_SP

LC Level Controller LTLevel Transmitter

LTDifferential Pressure Cell (DP Cell)

F3

F2

F₁

(17)

Composition Control in mixing process

CC Composition Controller CTComposition Transmitter

CTComposition Analyzer gas chromatograph, spectroscopic

CT 10 CC

10

F1, C1

F2, C2

F3, C3

CSP

mixer

Composition Control in purging process

CC Composition Controller CTComposition Transmitter

CTComposition Analyzer - gas chromatograph, - spectroscopic

CT 10

CC 10

F1, C1

F2, C2

F3, C3

C_SP

splitter

Recycle

(18)

HDA Process with Energy Integration Alternative 1

From Terrill and Douglas (1987)

Pneumatic Valve

pressured air

liquid

(a) FO-AC

liquid

pressured air

(19)

Preparing of Vapor/Gas Feed

Develop the control configuration

Preparing of High Pressure Gas Feed

dry gas (FG)

coolant (FC)

condensate (FL)

SEPARATOR CONDENSOR

COMPRESSOR

flare (Fflare)

high pressure gas

gas feed (FF)

comp. suction

(Fsuct)

to oil pit

T, P

SPLITTER

(20)

VII.3.

INTRODUCTION TO

PROCESS SAFETY

Illustration of Chemical Process System

CHEMICAL PROCESS SYSTEM

FEED PRODUCT

SAFETY SYSTEM

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

CC, …

UTILITY SYSTEM •WATER AND STEAM

•ELECTRICAL •PRESS AIR •REFRIGERANT

•INERT

OFFSITE SYSTEM •STORAGE

•HARBOR •RAILWAY •WASTE TREATMENT

(21)

CHEMICAL PROCESS

TECHNOLOGY

MORE & MORE COMPLEX

High

pressure

More

reactive

chemical

Exotic

chemistry

Needs sophisticated safety technology and chemical

engineer who understand safety concepts well

“care to fundamental things will safe;

otherwise, it is a disaster”

Terminologies

•

Safety or loss prevention

prevention to the accident by using adequate technology for

identifying chemical plant’s hazards and eliminate before it

happens

•

Hazard

A chemical or physical condition that has the potential for causing

damage to people, property, or the environment

•

Risk

(22)

Ingredients of successful safety program

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

fund

company

engineer

Profit

gives salary and

facilities

invest

able to minimize

the financial loss

and makes the

environment safe

and friendly for

employees and

peoples

(23)

Table 1-1. American Institute of Chem. Engineers Code of Professional Ethics

Engineers shall uphold and

advance the integrity, honor and dignity of the engineering

profession by

Engineers harus menegakkan dan meningkatkan integritas,

kehormatan, dan martabat profesi keteknikan

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

welfare

1. Menggunakan pengetahuan dan kecakapan untuk meningkatkan keselamatan manusia

2. being honest and impartial and serving with fidelity the public, their employers, and clients

2. Mengutamakan kejujuran dan kesetiaan kepada masyarakat, pekerja, dan klien

3. striving to increase the

competence and prestige of the engineering profession

3. Berjuang utk meningkatkan kompetensi dan prestise profesi keteknikan

Tabel 1-1. Continued Fundamental Canons Dasar Peraturan

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

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

2. Engineers shall perform services only in areas of

their competence 2. ST harus melakukan pelayanan hanya padakompetensi mereka 3. Engineers shall issue public statements only in an

objective and truthful manner 3. ST harus menyatakan persoalan publik secaraobjektif dan berbicara kebenaran 4. Engineers shall act in professional matters for each

employer or client as faithful agents or trustees, and shall avoid conflicts of interest

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

5. Engineers shall build their professional reputations on

the merits of their services 5. ST harus membangun reputasi profesional pd pelayanan yg baik 6. Engineers shall act in such a manner as to uphold

and enhance the honor, integrity, and dignity of the engineering profession

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

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

7. ST harus melanjutkan pengembangan profesionalnya melalui kariernya dan membuka peluang

(24)

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)

Acceptable Risk



We cannot eliminate risk entirely



Every chemical process has a certain amount of risk

Chemical

industry

Single

Process

Multi

Process

Certain risk

High risk >>

Multiple exposures

(25)

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

The three major accidents/hazards in process plant

Type of

Accident/hazard Probability of Occurrence Potential for Fatalities Potential for 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

(26)

Plant’s Accident Examples

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

(27)

Significant disaster example:

Flixborough England, on Saturday in June 1974

Cyclohexane (CH),

Similar to gasoline

Oxidation

155 °C; 7.9 atm

6 reactors in series

Caprolactam

70000 tons/year

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

vapor cloud, the cloud was ignited by unknown source about 45 second after the release 

explosion

20 inch

28 people died, 36 were injured, damge extended to 1821 nearby houses and 167 shops. Fire in plant burned for over 10 days.

R5 was found to be leaking, need to be repaired; bypass from R4 to R6 by pipe line 20 inch

28 inch

Design of Chemical Process Safety

•

Eliminate initiation step

•

Change propagation step to termination step

Prevent

accident

Practical:

ineffective and unrealistic to

eliminate all initiation steps

theoritical:

(28)

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

Type Typical Techniques

Minimise

(intensification) Change from large batch reactor to a smaller continuous reactor _{Reduce storage inventory of raw materials} Improve control to reduce inventory of hazardous intermediate chemicals

Reduce process hold-up Substitute

(substitution) Use mechanical pump seals vs. packing_{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

Inherent Safety Techniques

(

continued

)

Moderate (attenuation and limitation of effects)

Use vacuum to reduce boiling point

Reduce process temperatures and pressures Refrigerate storage vessels

Dissolve hazardous material in safe solvent

Operate at conditions where reactor runaway is not possible Place control rooms away from operations

(29)

Inherent Safety Techniques

(

continued

)

Simplify

(simplification and error tolerance)

Keep piping systems neat and visually easy to follow Design control panels that are easy to comprehend 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

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

VII BASIC CONCEPT OF CLEAN PROCESS TECHNOLOGY, PROCESS CONTROL SAFETY

Dr.Eng. Yulius Deddy Hermawan

CLEAN PROCESS

2. The outer layers of the onion

separation and recycle systems through the inadequate

cleaning for maintenance, tank filling, and so on, all produce

waste of that unreacted feed.

waste byproducts.

2. Reduction of feed impurities by purification of the feed

Clean Process Technology for Process Operations

Other ways to minimize waste from process operation are

INTRODUCTION TO

Product specifications

Economic

Implementation of Process Control for

Typical Heat Exchanger

Operator often sees (checks) the temperature of HE

Feedback Control of Heat Exchanger

Feedforward Control of Heat Exchanger

Feedback vs Feedforward

Combination of Feedback-Feedforward Control

HEATER TREATER

HT’s Intrumentation

Good Plumbing

plumbing

Level Control

mixer

Pneumatic Valve

SEPARATOR CONDENSOR

INTRODUCTION TO

CHEMICAL PROCESS SYSTEM

CHEMICAL PROCESS

Terminologies

Ingredients of successful safety program

3 systems to determine the effectiveness of safety program:

Process

Chemical plant designers who specify the acceptable risk are

cotton.

Plant’s Accident Examples

Cyclohexane (CH),

Design of Chemical Process Safety

Inherent Safety Techniques

Inherent Safety Techniques

Problems

exposure to all three units simultaneously?