Hazard and Operability Study PDF

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Summary

3 HAZOP ON FURNANCEFurnace or it can be referred to as a heater or direct fired heater is a heating unit used toprovide heat for an industrial process. This equipment typically provide heat higher than 400 ̊Cand serve as reactor which provides heats of reaction. Furnace are used in many application ...

Description

3.1 HAZOP ON FURNANCE Furnace or it can be referred to as a heater or direct fired heater is a heating unit used to provide heat for an industrial process. This equipment typically provide heat higher than 400˚C and serve as reactor which provides heats of reaction. Furnace are used in many application such as oil refining, steam cracking and glasswork. Furnace are mostly used as a major component of a central heating system and the most important equipment because this equipment define the product yield of the entire plant. In our process, there are two primary feed stocks for the production of propylene which are naphtha and natural gas such as ethane, propane, butane or others more. The feedstock is preheating by heat exchanger to 650˚C. The feedstock then vaporized with superheated steam and further heated to its incipient cracking temperature (750˚C - 900˚C). During the reaction, hydrocarbons in the feed are cracked into smaller molecules, producing propylene and co‐ products. This process is called as steam cracking. Steam cracking is the main process utilized to manufacture propylene from large hydrocarbon molecules. Steam cracking reaction is very highly endothermic and need high energy rates. The cracking coils is important part as it can optimize temperature and pressure in order to maximize the yield of desired products. Short residence times are also the most important as they increase the yields of primary products and can avoid secondary reactions. The cracked gas then go to the quench tower for the cooling process.

HAZOP Table on FURNACE Study Note Dilution Steam

Process Guide Deviation Parameter Word •Temperature •Less •Temperature is lower than normal

Possible Causes

Possible Consequences

Action Required

1. Control valve for steam failure. 2. Temperature indicator controller (TIC) malfunction. 3. Temperature sensor fail.

1. Cannot get and maintain desired thermal output. 2. No superheating of dilution steam. 3. Increase the time taken to crack the gas.

1. Install low temperature alarm (TAL). 2. Proper maintenance.

•Pressure

•Less

•Pressure lower than normal

1. Liquid indicator controller (LIC) malfunctions 2. Leaking in the vessel 3. Pressure indicator controller (PIC) malfunctions

1. Leads to low flow of superheated dilution steam 2. Upsets in operation

1. Install low pressure alarm (PAL) 2. Do maintenance regularly

•Flow

•Less

•Low feed flow of dilution steam than normal

1. Flow control valve failed to open 2. Pressure indicator controller (PIC) malfunctions 3. Leaking

1. Develop maintenance procedures 2. Install low flow alarm (FAL)

•Level

•Level

•Low water level in steam drum

1. Pump clogged 2. Leaking

1. Leads to low flow of superheated dilution steam 2. Upsets in operation 3. Reaction disturbance due to the insufficient amount of feed 1. Less water for cooling the reactor 2. Rapid increase of heat load 3. Runaway reaction in the reactor

1. Install low level alarm (LAL) 2. Provide safety relief valve

Study Note •Radiant coils inlet

Process Parameter •Flow

Guide Word •No

•More

Deviation

Possible Causes

Possible Consequences

•No oil feed flow

1. Supply failed 2. Pipe blocked 3. Blockage downstream of vaporizer

•No hydrocarbon feed flow

1. Supply failed 2. Pressure relief valve (PRV) failed to open 3. Pipe blocked 1. High pressure 2. Flow controller (FC) failure 3. Errors at set point of flow controller

1. No liquid/gas enter the furnace 2. Possible overheating 3. Vaporizer coil overheats and may fail 1. Process delay 2. Causing unvaporized liquid oil fed to the process 1. Oil with low temperature will delivered to the next process 2. May overload vaporizer

•More oil feed flow

Action Required 1. Install low flow alarm (FAL) 2. Provide preventive corrective in the system 1. Install low flow alarm (FAL) 2. Provide preventive corrective in the system 1. Provide bypass control valve 2. Provide high flow alarm (FAH)

•Temperature •Less

•Low temperature in furnace

1. Temperature indicator controller (TIC) malfunctions 2. Control valve for steam failure

1. No reaction occur as it can't lower the hydrocarbon partial pressure 2. Failed to produce a huge volume of cracked effluent gas in short time

1. Install low temperature alarm (TAL) 2. Increase the dilution steam

•Pressure

•Pressure is too high than normal

1. Pressure indicator controller (TIC) malfunctions 2. Level indicator controller (TIC) malfunctions

1. Possible overheating due to high pressure 2. Frequent leaking

1. Provide high pressure alarm (PAH) 2. Adjust the setting on pressure control valve (PCV)

•More

Study Note •Radiant coils outlet

Process Guide Deviation Parameter Word •Temperature •More •Temperature is too high

Possible Causes

Possible Consequences

Action Required

1. Temperature indicator controller failure 2. Wrong set point at temperature controller

1. Fail to achieve desired yield 2. Secondary olefin reactions will occur

1. Install high temperature alarm (TAH) 2. Operator should ensure the temperature sensor is in a good condition

3.2 HAZOP ON QUENCH Quench tower is an equipment used to prevent undesirable side reactions from taking place. This equipment also important components as production of propylene requires cooling for further fractionation and therefore the temperature is reduced or quenched. Usually, quench towers use one or more heat transfer sections or pump to remove heat from the column. The reason why heat transfer sections or pump is use because it is give better distribution of tower loads result than would be the case if all of the heat were removed in the tower overhead. The cracked gas mixture is subsequently quench in the transfer line exchangers to 550 650. These heat transfer activities can prevent degradation by the secondary reactions. The other reason is that it also generate high pressure steam for driving compressor. The transfer line exchanger effluent then will direct quenching in a quench fitting with cooled quench oil. Quenched effluent from two quench fittings is send to the fractionator for further fractionation.

HAZOP Table on Quench Tower Study Note •Transfer Line Exchanger

Process Guide Deviation Parameter Word •Temperature •More •Temperature higher than the reaction temperature

Possible Causes

Possible Consequences

Action Required

1. Temperature indicator controller (TIC) malfunctions 2. Temperature sensor failure

1. Secondary olefin reactions will occur 2. Cannot restrict the polymerization reactions.

1. Install high temperature alarm (TAH) 2. Do maintenance regularly

•Less

•Temperature is too low than normal

1. Temperature indicator controller (TIC) malfunctions

1. Temperature controllability of water quench tower will be affected 2. Hard to remove pyrolysis oil and heavier hydrocarbons

1. Install high temperature alarm (TAH) 2. Make a regularly inspection

•Pressure

•Less

•Pressure lower than super high pressure

1. Temperature indicator controller (TIC) malfunctions 2. Low temperature

1. Fail to recovered heat 2. Fail to maximize the energy efficiency of the plant

1. Install low pressure alarm or indicator (PAL) 2. Technician must do the inspection regularly

•Flow

•Less

•Flow water lower than normal flow

1. Flow pipe blocked 2. Leaking

1. Slow cooling of hot gas 2. Secondary reaction occur

1. Proper inspection 2. Install low flow alarm (FAL)

•More

•Flow higher than normal flow

1. Overpressure

1. High pressure boiler feed water flow into process steam 2. Upset condition

1. Install high flow alarm (FAH)

Study Note •Boiler Feed Water

Process Parameter •Level

•Flow

Guide Deviation Word •More •Level water higher than normal level

Possible Causes

Possible Consequences

Action Required

1. Steam drum level drop 2. High pressure 3. Level controller malfunction

1. Level control valve of BFW open widely 2. Leaking

1. Install high level alarm (LAH) 2. Check valve regularly 3. Develop maintenance procedures

•Low

•Level lower than normal level

1. Pump leaking 2. Level indicator controller malfunction

1. Low level in steam drum a trip of the heater

1. Install low level alarm (LAL)

•Less

•Low flow of quench water circulation

1. Flow controller failed to open 2. Flow indicator controller (FIC) malfunction 3. Pump blocked

1. Dilution steam not fully condensed 2. Temperature controllability of water quench tower will be affected

1. Provide preventive corrective device 2. Provide low flow alarm (FAL)

•More

•High flow of quench water circulation

1. Flow indicator controller (FIC) malfunction

1. Leads to the low temperature of quench tower overhead

1. Provide preventive corrective device 2. Provide high flow alarm (FAH)

1. Emulsification problem in the decanter

1. Excessive amount of hydrocarbons being carried back to the quench water tower 2. Can cause severe fouling problem

1. Check maintenance procedure

•As •Hydrocarbon well as product

Study Note •Oil/Gas inlet

Process Parameter •Pressure

Guide Word •More

Deviation •High quench oil pressure

Possible Causes 1. Pressure indicator controller (TIC) malfunctions 2. Level indicator controller (TIC) malfunctions

Possible Consequences 1. Temperature in the transfer line exchanger rise rapidly 2. Loss of quench oil leads to the equipment damage

Action Required 1. Provide high pressure alarm (PAH) 2. Adjust the setting on pressure control valve (PCV)

3.3 HAZOP ON COMPRESSOR Centrifugal compressor or also known as dynamic compressor is a equipment used to compress air and are used for delivering large volume of refrigerant at low pressure. In this equipment, there are two main services where centrifugal compressors are utilized in ethylene plant which are cracked-gas compression and refrigeration. The process in this equipment start with cracked-gas compression. Turbine driven compressor is use to perform gas compression and it will be typically has two to five stages with intermidiate cooling. The number of stages use is depending the cracked gas composition. In this process, heat sometimes can suddenly increase. To reduce heat in the compressor, water injection is utilize to cool the gas stream. The gas is compressed is compress from in 5 stage centrifugal compressor. Condensate from stage 3 discharge drum recycled to stage 2 suction drum via stage 3 suction drum where hydrocarbon and water get condensed. At between stage 4 and stage 5 of the compressor, acid gas removal system is located. After stage 5, the charge gas is progressively cooled by refrigerant cooling. Then, it will flow to the dryer.

HAZOP Table on Compressor Study Note •Cracked-gas compression

Process Parameter •Temperature

•Flow

Study Note

Process Parameter

Guide Word •Less

Deviation

Possible Causes

Possible Consequences

Action Required

•Temperature lower than normal

1. Decrease in temperature of inlet superheated pressure steam 2. Temperature indicator controller (TIC) failure

1. Potential difference over saturation

1. Provide low temperature alarm (TAL) 2. Make a regularly inspection

•More

•Higher temperature than normal

1. Possible high temperature at top of exhaust

1. Increase the tendency for polymerization of cracked gas 2. Possible high temperature on exhaust hood

1. Provide high temperatur alarm (TAH) 2. Inject wash gasoline into the suction line of each stage

•Less

•Flow lower than normal

1. The main oil pump failure 2. Tube leaking

1. Compressor or turbine bearing damage

1. Provide requirement for auto start of turbine and pump 2. Provide anti surge protection

•More

•Flow higher than normal

1. Flow controller failure 2. Pressure control valve (PCV) malfunctions

1. Potential more flow of lube oil to compressor bearing

1. Provide high flow alarm (FAH) 2. Review to up rate the pipe line 3. Provide anti surge protection

Possible Causes

Possible Consequences

Action Required

Guide Word

Deviation

•Pressure

•More

•Pressure is too high

1. Pressure valve malfunction

1. Overpressure can result catastrophic vessel failure due to brittle fracture

1. Provide high pressure alarm (PAH)

•Level

•Less

•Liquid level it too low

1. Pump pipe failure 2. Level control valve (LCV) malfunctions

1. Level control valve pass gas back to a lower pressure causing unnecessary losses.

2. Provide high level trip interlock systems

3.4 HAZOP ON FRACTIONATION COLUMN Distillation column is a process that involving other equipment which are condenser and reboiler. This process is the most important part because this process will produce main product. Distillation column is an equipment use to separate a feed stream into light ‐component and heavy‐component product. The lighter components boil at a lower temperature compare to the heavier components. Therefore, when the reboiler at the bottom supply heat to the column, the lighter materials are vaporized and rise to the top of the column. The overhead vapors are cooled until the components condense and become a liquid again. In this production of propylene, there are 3 fractionation column use, which is the primary fractionation, distillation column for demethanizer, distillation column for deethanizer acetylene hydrogenation and distillation column for depropanizer and C3 splitter. At the primary fractionation column, the cracked gas as a product from the furnace will flow into column. Gasoline and the lighter are taken out at the top of the column as an overhead vapor and sent to the centrifugal column while the pyrolysis fuel oil will be collect at the bottom of the column. At the distillation column for demethanizer, the cracked gas separate methane as an overhead components. Meanwhile the heavier components at the bottom is fed to the second column. For the second distillation column at top of deethanizer , the light component which is ethylene is removed

from the overhead.

The heavier components then fed to the third

distillation column. At the third distillation column, the process in this equipment is depropanizer. At the top of the column, propane is obtained while the heavier component will remove at the bottom. Propane will further process in the splitter to produce propylene.

HAZOP Table on Fractionation Column Study Note •Reboiler

Process Parameter •Flow

•Temperature

Guide Word •No

Deviation

Possible Causes

Possible Consequences

Action Required

•No flow

1. Oil circulating pump defective 2. Pipe blocking and leaking 3. Control valve shut

1. No operating 2. Reflux rate become erratic 3. Possible dangerous concentration

1. Provide high flow alarm (FAH) 2. Emergency plant shut down 3. Make bypass

•Less

•Flow lower than normal flow

1. Flow controller failure 2. Tube blocking 3. Pump failure

1. Product quality change 2. No flow of feed accumulation of heavier components 3. Column dry out

1. Install high flow alarm (FAH) 2. Check maintenance procedure and schedule 3. Make bypass

•More

•Flow higher than normal flow

1. Increase pumping capacity 2. Control valve is fully opened

1. Changes in product quality 2. Flooding in the column 3. Rise in bottom

1. Install high flow alarm (FAH) 2. Check maintenance procedure and schedule

•Less

•Temperature lower than normal

1. Temperature indicator controller (TIC) malfunction 2. Control valve for steam failure

1. Poor separation 2. Temperature desired may not achieve

1. Install low temperature alarm (TAL) 2. Schedule inspection and maintenance 3. Increase reboiler duty

•More

•High temperature than normal

1. Temperature indicator controller (TIC) malfunction 2. Control valve for steam failure

1. Vapor not condenser rapidly 2. Lead to poor purification

1. Install high temperature alarm (TAH) 2. Install thermal expansion relief on valve section

Study Process Note Parameter •Condenser •Pressure

Guide Word •Low

•More

Deviation •Pressure lower than normal

•Pressure higher than normal

Possible Causes 1. Pipe leaking 2. Pressure indicator controller (PIC) malfunction 1. High temperature cooling medium flowing across condenser 2. Steam malfunction

Possible Consequences

Action Required

1. Efficiency drop 2. Poor quality of product

1. Increase condenser duty 2. Inspection and maintenance regularly

1. Overheating and explosion due to overpressure 2. Poor quality of production

1. Install high pressure alarm (PAH) 2. Lower condenser duty...