Flash Separator

 

INTRODUCTION • 

A flash separator is a device or an equipment used in several industrial applications to separate a vapour- liquid mixture. It is performed to determine the product condition and phases. It is referred also to as flash drum or knock- out drums.

PROBLEM STATEMENT 

We have a stream containing 15% ethane, 20% propane, 60% i- butane, and 5% n- butane at 50°F and atmospheric pressure and a flowrate of 100lbmoles/hr. Th compressed to 50 psia, and then cooled to 32°F. The resulting vapour and liquid are to be separated as the two product streams. What the flowrates and compositions of these two streams?

Hysys Simulation of Pump

 Estimate the outlet temperature of n-hexane and note down 

the duty of the pump 

Use hysys to find solution   

ex: estimate n-hexane pressure in 3 atm to 10 atm 

 

Adding Material Streams

 

 Hysys simulation -

>Starting HYSYS 

>Simulation Basis Manager

>Creating A New Simulation

>Adding Components to the Simulation

>Selecting A Fluids Package 

>Selecting Thermodynamics Model 

>Enter Simulation Environment

>Adding Material Streams

>Review and Summary Problems

Hydrogen Recovery from Refinery Off-gases

Background 

Hydrogen is one of the main intermediate products largely utilized in oil and petrochemical industries.

 

• It is used as a raw material and obtained in some processes as a by-product.

 

• The off-gas streams contain considerable amount of hydrogen, which are

 

mostly incinerated in refinery flares as a waste gas.

 

>Hydrocarbons are converted into hydrogen reformers in order to produce

 

the hydrogen needed for hydrogen consuming processes.

 

>Separation of hydrogen from an existing refinery off-gas stream

 

represents an opportunity to achieve significant cost reductions in refineries

>Cryogenic Technology (CT)

 

Separation principle:

 

Cryogenic technology is based on the difference in the relative

 

component volatility at low temperatures.

 

Disadvantages:

 

Extra compressors to increase the pressure at least 20 bar. CO2 separation is necessary to avoid freezing the CO2 in line at low temperatures.

see simulation 

 

Design of Heat Exchanger using ASPEN Shell & Tube Exchanger

 example:

Design an exchanger to sub-cool condensate from a methanol condenser from 95°C to

40°C. Flow-rate of methanol 100,000 kg/h. Cooling water will be used as the coolant,

with a temperature rise from 25°C to 40°C.

1.

Determine the heat exchanger duty

In this example, since coolant is more corrosive, it is assigned to the tube side.

Specific heat capacity of methanol = 3.926kJ/kg°C

Heat Exchanger Duty

Q = mCp.(AT) =(100000/3600) × 3926 × (95 – 40) =

 5998.056 × 10³W = 5998.056kW

2.

Specific heat capacity of water[= 4.2kJ/kg°C

Mass flowrate of cooling water:

mwater= Q/Cp.water (Twater out-Twater.in)= (5998056/4200(40-25))= kg/S 95.21 = 342360 kg/hr

Using 1-2 Shell and Tube Heat Exchanger,

Log Mean Temperature Difference:

see simulation 

 

Refrigeration Cycle

Example:

A Refrigeration cycle utilizes propane as the working fluid is used in

the liquefaction of the NG. Propane is fed to an evaporator (Heater) the pressure drop-5 kPa, where it absorbed 1.50e+6 kJ/hr from the NG and leaves at the dew point (Vapor Fraction=1.0) at T= -15°C. The output of the evaporator is then compressed adiabatically with efficiency of 75%, and then it's condensed to reject heat. Inside the Condenser there is a pressure drop of 30 kPa, and leaves as saturated liquid at 45°C. Finally, the propane passes through a valve to return the pressure of the Evaporator.

Fluid Pkg: Peng Robinson

 

Plug Flow Reactor

PROBLEM STATEMENT

Consider the reversible aqueous phase esterification

of acetic acid shown below:

CH3COOH + C2H5OH = CH3COOC2H5 + H₂O

Reaction Kinetics:

Forward Reaction: 8 x 10-6m³ kmol-1s-1

Backward Reaction: 2.6 x 10-6m³ kmol-1s-1

Activate.

It is desired to produce 375kg/hr of ethyl acetate from a

feed stream consisting of 13mole% acetic acid, 35mole%

ethanol and 52mole% water. This feed stream is available

at 100,000kg/day. A single tube plug flow reactor with a

length of 10m and diameter of 1m is available for use in

an existing chemical plant. Determine if it is feasible to

achieve the desired product using this reactor, also find

the residence time in minutes.

Fluid Package: NRTL.

Feed Properties: 25°C, 1Bar.