DISTILLATION COLUMN PIPING

I. INTRODUCTION

The distillation is separation of the constituents of a liquid mixture via partial

vaporization of the mixture and separate recovery of vapor and residue. Various kinds of devices

called plates or trays are used to bring the two phases into intimate contact. The trays are stacked

one above the other and enclosed in a cylindrical shell to form a Distillation Column.

The feed material, which is to be separated into fractions, is introduced at one or more

points along the column shell. Due to difference in gravity between liquid and vapor phases, the

liquid runs down the column, cascading from tray to tray, while vapor goes up the column

contacting the liquid at each tray. The liquid reaching the bottom of the column is partially

vaporized in a heated reboiler to provide reboil vapor, which is sent back up the column. The

remainder of the bottom liquid is withdrawn as the bottom product. The vapor reaching the top

of column is cooled and condensed to a liquid in the overhead condenser. Part of this liquid is

returned to the column as reflux to provide liquid overflow and to control the temperature of the

fluids in the upper portion of the tower. The remainder of the overhead stream is withdrawn as

the overhead or distillate product.

II. PIPING AND INSTRUMENTATION DIAGRAM

Piping and instrumentation diagram/drawing (P&ID) is a diagram in the process industry

which shows the piping of the process flow together with the installed equipment and

instrumentation.

A diagram which shows the interconnection of process equipment and the

instrumentation used to control the process. In the process industry, a standard set of symbols is

used to prepare drawings of processes. The instrument symbols used in these drawings are

generally based on International Society of Automation (ISA) Standard S5.

Figure 1 shows the piping and instrumentation diagram of distillation column. The

reporter will be discussing the left side half and right side half of the system.

Figure 1 Piping and Instrumentation Diagram of a Distillation Column

Figure 2 shows the left half of the system which includes the stripper, pump, reboiler

valves and instrumentations.

Figure 2 P&ID of the left haft of the system

A. Piping

Piping is a system of pipes used to convey fluids (liquids and gases) from one location to

another. The engineering discipline of piping design studies the efficient transport of fluid.

1. RV-100-4” – RV for relief valve and 100 as the designated code which has a diameter

of four inches. It is used to convey overheated steam from the stripper as shown in Figure

3.

Figure 3 RV-100-4"

2. P-102-6” – P for pressurized and 102 as the designated code which has a diameter of

six inches. It is used to convey the inlet feed of fluid to the stripper as shown in Figure 4

Figure 4 P-102-6”

3. P-104-10” - P for pressurized and 104 as the designated code which has a diameter of

ten inches. It is used to convey the fluid outlet in the reboiler as shown in Figure 5.

Figure 5 P-104-10”, P-103-10”, S-100-6” & C-100-4”

4. P-103-10” - P for pressurized and 103 as the designated code which has a diameter of

ten inches. It is used to convey the fluid inlet in the reboiler as shown in Figure 5.

5. S-100-6” - S for steam and 100 as the designated code which has a diameter of six

inches. It is used to convey the steam inlet into the reboiler as shown in Figure 5.

6. C-100-4” - C for and 103 as the designated code which has a diameter of ten inches. It

is used to convey the fluid inlet in the reboiler as shown in Figure 5.

7. P-105-6” - P for pressurized and 105 as the designated code which has a diameter of

six inches. It is used to convey fluid from the bottom of the stripper to the bottom pumps

as shown in Figure 6.

Figure 6 P-105-6” & P-106-4”

8. P-106-4” - P for pressurized and 106 as the designated code which has a diameter of

four inches. It is used to convey fluid form the bottom pump to the bottoms or

reprocessing as shown in Figure 6.

B. INSTRUMENTS

1. Stripper

The Stripper is used to heat fluid and turn to steam to distill the fluid. Steam distillation is

also widely used in petroleum refineries and petrochemical plants where it is commonly referred

to as "steam stripping”.

Figure 7 Steam Distillation Stripper

2. Pump

The pump, specifically bottom pump is used to pump the fluid at the bottom of the

stripper for reprocessing. A pump is a device that moves fluids (liquids or gases), or sometimes

slurries, by mechanical action. Pumps can be classified into three major groups according to the

method they use to move the fluid: direct lift, displacement, and gravity pumps.

Figure 8 Bottom Pump

3. Reboiler

The reboiler in the system is used in reboiling the excess fluid the penetrated the stripper.

The reboiler is used to increase the efficiency of the system. Reboilers are heat exchangers

typically used to provide heat to the bottom of industrial distillation columns. They boil the

liquid from the bottom of a distillation column to generate vapors which are returned to the

column to drive the distillation separation.

Figure 9 Reboiler and Diagram

4. Strainer

Strainer in the system is used to remove the solid contaminants of the bottom fluid that

will pass through the bottom pump. Strainers are important components of piping systems to

protect equipment from potential damage due to dirt and other particles that may be carried by

the process fluid.

Figure 10 Strainer and Diagram

C. ISA Symbology

The ISA symbols present in the diagram are all field mounted measuring instrument with

identification letters and tag numbers.

Figure 11 ISA Symbologies in the P&ID

1. Flow Rate Control Valve

Figure 12 Flow Rate Control Valve Symbology and Location

In the diagram, it is used to regulate the steam flow in the reboiler. A flow control valve

regulates the flow or pressure of a fluid. Control valves normally respond to signals generated by

independent devices such as flow meters or temperature gauges.

Figure 13 Flow Rate Control Valve and Diagram

2. Flow rate Sensor

Figure 14 Flow Rate Sensor Symbology and Location

The flow rate sensor is working with the flow rate control valve which measure the flow

in to the system and trigger the control valve if necessary. The function is feed forward. A flow

sensor is a device for sensing the rate of fluid flow. Typically a flow sensor is the sensing

element used in a flow meter, or flow logger, to record the flow of fluids. As is true for all

sensors, absolute accuracy of a measurement requires a functionality for calibration.

Figure 15 Flow Rate Sensor

3. Pressure Transmitter

Figure 16 Pressure Transmitter Symbology and Location

The pressure transmitter in the system is used to monitor the pressure in the stripper

preventing over and under pressure. A pressure transmitter or pressure sensor is a device that

measures pressure in a liquid, fluid, or gas. Pressure transmitters are commonly used to measure

pressure inside of industrial machinery in order to alert the user before a catastrophe occurs.

They have many different uses, most of which are industrial or automotive in nature. A pressure

transmitter is easily recognized as it is a round gauge with various colors that represent different

pressure levels. While pressure transmitters are similar to other gauges, they are essential to

many of the applications they are used for.

Figure 17 Pressure Transmitter

4. Temperature Sensor

Figure 18 Temperature Sensor Symbology and Location

The temperature sensor in the system monitors the temperature of steam in the stripper to

know evaluate the quality. A temperature sensor is a device, typically, a thermocouple or RTD,

that provides for temperature measurement through an electrical signal. A thermocouple (T/C) is

made from two dissimilar metals that generate electrical voltage in direct proportion to changes

in temperature.

Figure 19 Temperature Sensor

5. Level Controller

Figure 20 Level Controller Symbology and Location

The level controller acts as a valve which regulates the flow of liquid and automatically

opens and close when necessary. Liquid level controllers are instruments which monitor liquid

levels in vessels, and send out either pneumatic (typically 6 – 15 psig) or electric (e.g. 4 – 20mA)

signals to either the main control system, a local control system, or directly to an automated

control valve.

Figure 21 Level Controller

6. Level Glass or Sight Glass

Figure 22 Level Glass or Sight Glass Symbology and Location

The level glass is coupled to the level controller which is used to verify the level

controller action and visually notify the operator. A sight glass or water gauge is a transparent

tube through which the operator of a tank or boiler can observe the level of liquid contained

within

Figure 23 Level Glass or Sight Glass

7. Relief Valve Temperature indicator

Figure 24 Temperature Relief Valve Symbology and Location

Relief valve temperature indicator is used to release heat inside the stripper when it is

overheating. Relief Valve that will open to inject liquid to desired temperature

Figure 25 Temperature Relief Valve

8. Relief Valve

Figure 26 Relief Valve Symbology and Location

The relief valve coupled to the relief valve temperature indicator as the actuator of the

sensor. The relief valve (RV) is a type of valve used to control or limit the pressure in a system

or vessel which can build up for a process upset, instrument or equipment failure, or fire. The

pressure is relieved by allowing the pressurised fluid to flow from an auxiliary passage out of the

system.Figure 27 Relief Valve

9. Temperature Indicator Control

Figure 28 Temperature Indicator Control Symbology and Location

The temperature indicator control is used to control the steam from the stripper whether it

has reached the required temperature. This is a common term used to refer to the Remote

Setpoint Input signal. V indicates a voltage signal while SET indicates its purpose: control

system setpoint. It can also be called MOD, MOD IN or ANALOG IN.

Figure 29 Temperature Indicator Control

10. Pressure Indicator Control

Figure 30 Pressure Indicator Control Symbology and Location

Pressure indicator control is use in the pump to maintain constant pressure of the pump. it

also prevents over pressure. Pressure indicators usually have a sensing element (sensor) and

transmitting and recording devices.

Figure 31 Pressure Indicator Control