Introduction to heater and steam generation in oil and gas industries
Steam boilers in oil and gas industries:
Boilers and gas turbines are equipment commonly used to generate steam and electricity by burning fossil fuels.
Steam is the phase of water liquefied petroleum gas. When water absorbs heat at the pressure of one's deference, it starts to boil and produce steam by converting water into steam, its volume is approximately 1,600 times. And its internal energy increases at least 6 times in saturation mode.
The gas is compressible unlike liquid and can be compressed easily.
1- Reasons for the widespread use of steam in the chemical industry:
A) Abundance and cheap water
b) Availability and safeness of water
c) Heat transfer from steam to other objects is easily done
Like putting a coil inside or putting a thermal jacket around it
c) Easy to control the temperature of the steam if it is used for heating.
Such as installing a control valve to reduce or increase heat
d) High pressure steam can be done with the help of steam turbine.
Boilers (boilers) in the industry use to produce steam.
Boiler division:
Boilers are divided accordingly
Based on the way the water circulates:
A) Natural flow: The basis of water circulation in this type is the density difference resulting from the difference in temperature in the lower and rising pipes.
b) Forced circulation: performed by using a pump
2- Based on the type of mineral fuel
1- Gas fuel
2- Liquid fuel
3- Solid fuel
4- Combined fuel
3- Based on the contents of the pipes:
We'll look at it below.
4- Based on the smooth or curved pipes:
1- Steep
2- Vertical
5- Based on the type of source:
Fossil fuel (solid, liquid, gas)
with electrical
energy with atomic
energy 6-based on operating pressure:
1- Low pressure boiler (below 200 Psi)
2- Medium pressure boiler (200-500Psi)
3- High pressure boiler (500-200 Psi)
The most important criterion is the division of boilers based on the contents inside the pipe.
Subdivision of boilers based on the contents inside the pipes
Firetuber
type boilers are composed of a combustion chamber and boiler containing pipes that enter the f and the other side of the boiler space is occupied by the pipes and the rest of the space is intended for water . Heat transfer between the gases passing through the pipes and the water in the boiler causes the heating of the water and the production of steam.
2- Water Tube
These boilers are composed of combustion chambers, climbing and downward pipes, steam dram (water dram-mud…
These boilers can have different shapes that include a variety of structures based on the type of pipes, the number and manner of the placement of steam and sludge tanks.
Types of water tube boilers
Two-drum
drumboiler boilers (type o,D)
three drums (in the form of English A)
boilers of four or five drums
for steam production, first water enters a device called aerosol or Dearator to separate insoluble gases such as oxygen and carbon dioxide from it so as not to cause corrosion in the boiler.
After the weathering phase, the water is entered into the boiler feeding ring by pumps and then sent to each boiler.
Water recharging for each boiler, under flow control (FIC) by a pipe split from the main line, enters the preheater section (ECONO Maizer) and heats up.
The outlet water from the economy enters the steam drum. In the drum above, the inlet water to the boiler goes through the down comer tubes towards the water drum. From there, the flow of water enters the climbing pipes (Riser).
Climbing pipes make different parts of the combustion chamber. like walls , floors and ceilings .
Water in climbing pipes is exposed to heat and part of it becomes steam.
A mixture of water and steam re-enters the steam tank (high drum) where two phases of steam and water are separated by passing through the separation of water and steam stages.
The circulation flow from top to bottom and vice versa is due to density difference.
The vapor phase is separated from the water by passing through the separation of water particles from the steam and exits from the top of the steam tank (high drum) through a separate line. This steam is saturated. (Saturated steam)
To obtain super heated steam, they send wet steam to the superhid.
In the Super Heat, there are two types of tubes:
Secondary
secondary primary
tubes are injected under the corresponding TIC control of de-superhite water to adjust the output temperature and the final frequency of F to the output vapor of the primary tubes.
Finally, Hps steam is produced with an output pressure of 42 bar to 44 and temperature, and to supply all kinds of steam needed, it is sent to the Let Down station to produce the following types of vapors in this section.
Hps: 42 bar
Mps: 21 bar
Lps: 4.5 bar
LLps: 4 bar
The steam generated in the steam unit, after use in the operational units, is returned to the steam unit and after condensation, the steam production cycle is re-entered.
Reasons for purifying boiler water
Preventing the formation of vapor
quality protection deposits
to minimize corrosion in boiler and external vapor
systems, such as removal of suspension particles, insoluble gases, hardness of water is done.
Internal treatment of boiler water is done by injecting chemicals into boiler water.
The most important reasons for chemical injection:
Regulating the pH and maintaining the alkalinity
of the inlet
water preventing the formation of sludge
from heated parts of the hot
water and preventing oxygen
corrosion preventing alkaline
fragility preventing the formation of protective film foam
to prevent corrosion
by condensed vapors
Boiler components and accessories:
1- Lpc,DM water supply unit
2- Heat exchangers, a shell of DM water
3- Inlet water ring to boiler
4- Twin filters of water inlet to airborne tanks
5- Airborne tanks
6- Feeding pumps
7. Economery
8- Steam dram (high drum)
9- Water dram (low drum)
10- Riser pipes (top winner)
11- Down comer pipes (bottom winner)
12- Dee Super Heater
13. Super Heat
14- Blow down (boiler water imagination)
15- Soot blower (soot)
16- Water and steam separators in high drum
17- Test pipe (test tube)
18- Silenser (silencer)
19- psv (pressure safety valves)
20- Chimney stack
21- Combustion Chamber
22- Purple and infrared rays (scaners)
23. Torches
24- Pilot torches
25- Fans
26- Air Preheater
27- Injection of chemicals
28- Sampling system
29- Fuel supply system to boiler
30- Pressure reducing station
31. Vans and Evacuations
32- Hps Steam Ring
33- Stop valve
34- Reng valve
Airborne tanks:
Airborne tanks are used to remove dissolved oxygen in the water, feed boilers and heat it. Each of these reservoirs is composed of two horizontal tanks located on each other, which are related by five communication tubes, three of which are embedded to lower the water and two tubes for increasing the vapors, two oxygen.
Mechanism of Work:
DM water after passing through the filter and also hot and cold distilled water (LPC) after passing through the filters from above enter the tank, the upper container has a number of separator plates and sprays that these sprays or nozzles pour water on the separator plates. LLPS steam is inserted from the bottom of the separator plates and inlet waters from the top of it at a pressure of 4 bar.
Due to the contact of water droplets with water vapor, oxygen and carbonic gas through the outlet paths, the upper vesel is removed. Vents and inlet water are heated and enter the main reservoir down through communication pipes. This reservoir also performs water storage for feeding pumps.
The pressure of the airborne tanks is controlled by LLp 4bar steam and as a result, the water temperature will be exhausted.
The output of the airborne tanks is injected to remove the residual oxygen and to regulate the pH of a substance called Helamin (H90) 90.
In the past, instead of this material, they used hydrazine and amines.
A) Economy
Boiler feeding water enters the water ring after aeration by feeding pumps, which for each boiler is taken a branch of the water ring that enters the boiler, in order to preheat the water, before entering the high drum, it passes through the economy, and thus the water temperature will reach from the combustion gases after passing through the displacement section through the channels. It enters the smokestack and enters the atmosphere through it. Due to the high temperature of these gases and the ejection of a lot of energy from the boiler outwards, this energy can be used to increase the boiler efficiency. For this reason, boilers have economes, which are essentially heat exchangers and tubes that are placed in the path of hot emission gases.
B) Steam drum (steam tank)
The inlet water to the boiler after passing the preheater (Economizer) first enters the steam drum and is transferred to the lower tank through the downward pipes.
Hot water and steam mixtures are also transferred to this tank by climbing pipes.
With the accumulation of steam in the steam tank, the steam pressure is increased and after reaching the required operational pressure and separating the water droplets from the steam, it is transferred out of the tank.
If the vapor and water phases are not separated well, two common phenomena occur in boilers.
Carry overCarry
underdece
carry over
If the droplets of water with steam go from the steam tank to the super heat, it is called carry over. This phenomenon causes problems in the super heaters section.
In this way, water droplets contain minerals that precipitate on the inner walls of super heat after evaporation of water in super heat. Due to the increase of these sediments, the problem of over-heating the pipes and subsequent destruction of them will be created.
Carry ounder phenomenon
If there is some steam in the inlet water to the lower pipes, it is called Carry under because of this problem, the amount of steam in the rising pipes is more than water and stays dry in parts of the pipe and the problem of overheating the pipes arises.
c) Boiler tubes
1- Downward pipes: (down comer)
Pipes that transfer inlet water to the low drum and are located in the boiler displacement section.
2- Climbing pipes: Riser
These pipes are essentially boiler combustion chambers. In these pipes, the water moves upwards with the heat of the view. Sometimes these pipes, also called evaporators, are located between two riser tubes, a plate to prevent gas from passing.
If the risers are in the wall, they are called Tube Wall and if they are on the floor, they are called Fcoor Tube.
c) Water and steam separators
In the past, dry pipe was used to separate water from steam in high drums. Today, however, to better separate, they use multi-stage separators that include the following steps:
The initial separation
of the riser is inserted into the high drum and into a global channel, on which a metal plate is installed and the mixture of water and steam from the climbing pipes enters the channel and overflows from it. And to pass, it is forced to change direction and due to this collision and mutation, another part of the water is separated with steam.
Drying or drying
is the result of the first step, it contains liquid particles, bubbles, foams or foams to separate them use filters and generally in the form of boxes that are attached to the output header from the top and blocked from the bottom by a metal plate.
On two side levels, metal plates are parallel. Steam passes through the layers of these metal plates and enters into the box and then goes from the top of the box to the output header.
Water particles are separated from steam in dealing with these metal plates.
In other types, porous membranes are used instead of these parallel metal plates. In some other tanks, silicon separators are used instead of canals and metal plates (in the initial separation phase).