The thermal power of the main burner can be calculated from production and heat consumption:
The thermal power of the main burner can be alternatively calculated from fuels:
The specific axial impulsion of the primary air can be approximated using the following formula (rule of thumb):
The required electrical power can be calculated as:
The total pressure increase p of a fan can be calculated as:
The volume flow depends on the fan speed as:
The static pressure depends on the fan speed as:
The electrical power requirement depends on the fan speed as:
DETERMINE THE SATURATED & SUPER HEATED STEAM VELOCITY/PRESSURE DROP & PIPE DIAMETER CALCULATION:
Some information about a common method for both saturated and superheated steam to determine velocity/pressure drop/ pipe diameter.
Before taking the next step for calculation, we should choose the calculation method and acceptable velocity range.
1- For short pipe up to 50 m, size the line based on velocity because the pressure drop is negligible.
2- For long runs, check the pressure drop as well as velocity.
The velocity:
1- Should be between 25 to 40 m/s (4920-7872 fpm) for saturated steam. Low velocity as low as 20 m/s (~4000 fpm) is acceptable and, also, higher velocity than 40 m/s would be acceptable providing that the line is short and straight, horizontal and well insulated to make sure the steam is dry.
2- Can exceed above limits for superheated steam, because it is dry and there would be no chance for errosion due to water droplets.
PRESSURE FACTOR METHOD:
What required:
1- Pipe Length (including straight length plus the equivalent lenght because of all fittings, valves, etc.)
Here, there are some shortcuts:
a) If straight length< 50 m —---> Pipe Length= 1.05* straight run
b) Longer than 50 m with a few fittings —---> Pipe length= 1.1 * straight run
c) Longer than 50 m with more fittings —---> Pipe length= 1.2* straight run
2- Inlet and outlet pressure
3- Actual flowrate (process flowrate plus the condensate flowrate). Some of the steam gets condensed due to natural heat transfer. Convection and radiation heat transfer should be calculated to know the condensate load. But, choose 3.5% condesate load per 100 m as a rough estimation. Please note that total pipe length MUST be used to calculate actual flowrate not only the length of straight run.
Example: How much is the actual flowrate when 100 t/hr steam flows through a 250 m straight run pipe with several bends to drive a turbine.
1.2* 250= 300 m
every 100 m produces 3.5% condensate:
(300/100)* 3.5%= 10.5%
Actual flowrate= 1.105* 100= 110.5 t/hr
It means although the turbine needs only 100 ton/hr to operate, boiler should supply to 110.5 t/hr. This is a rough estimation.
Pressure factor method employed one formula and two tables to give us the pipe diameter (internal diameter). The tables should be used to find factors for inlet and outlet pressures. Then, calculate pressure factor:
F= (P1-P2)/L
Where :
P1= factor for inlet pressure
P2= factor for outlet pressure
L= Actual Length
How to validate the result:
Check the velocity to see whether it is in the range?
If yes, enjoy it.
Otherwise, the piping should be modified.
Pressure factor method is good for the time that pressure drop is constant and maximum allowable pressure drop is already determined. So, the pipe length and diameter should be chosen such that velocity is in the allowable range.
This is the last part of velocity/pressure drop/sizing based on Spirax Sarco procedure.
NOMOGRAM METHOD:
There are two nomograms applicable to both saturate and superheated steam.
a) Pressure drop chart
What you have: Steam conditions, steam flowrate and inside pipe diameter
What yoy find: Pressure loss bar/100 m
so you don't need to know the steam velocity. Steam velocity should be validated to make sure it is in the allowable range.
b) Velocity Chart
What you have: Steam conditions, steam flowrate and steam velocity
What you find: Pipe diameter
****STEAM PIPELINE SIZING CHART****
DEMINERALIZATION:
Demineralization: removing ions
ION: Electrically charged atom;
can be positive (Cation) like:
Calcium (Ca++)
Magnesium (Mg++)
Iron (Fe+++)
Manganese (Mn++)
Sodium (Na+)
Hydrogen (H+)
Can be negative (Anion) like:
Chlorides (Cl-)
Sulfates (SO4=)
Nitrates (NO3=)
Carbonates (CO3=)
Silica (SiO2-)
Hydroxyl (OH-)
Demineralized Water is the only water source MUST be used to generate steam or be addd as an ingredient to the processes, because it has the least possible amount of impurities and, therefore, its electrical conductivity (The best indicator for impurities) is less than about 0.2 micro siemens/cm.
Demineralization is done by several methods. Ion Exchange process is one of them that uses resins to remove non-desirable ions which may cause corrosion, deposition on boiler tubes, boiler malfunction, etc.
Resins are organic polymeric beads and able to exchange ions with the
cations and anions:
Cations are removed by cation resins . Hence, cation resines have negatively charged functional group.
Anions are removed by anion resins. Hence, anion resins have positively functional group.
There are two types of cation resins:
1-WAC WEAK ACID CATION
2-SAC STRONG ACID CATION
WAC is mainly used to decrease pH (Dealkalization), but SAC is the right choice for water demineralization.
There are two types of anion resins:
1-WBA WEAK BASE ANION
2-SBA STRONG BASE ANION
Both types are used for demineralization;
WBA can not remove Silica and Carbonates, only neutralize weak acids and produces water with pH less than 7, if used in a dual separate bed system.
SBA removes all anions and produces water with pH higher than 7, if used in a dual separate bed system.
SAC and SBA are mixed to make a mixed-bed for Ion Exchange process.
Different ions are attracted by different strengths. For example, Calcium with 2+ charges is attracted more strongly than Hydrogen ion with only one positive charge. Both Hydrogen and Hydroxyl ions are not attracted strongly and, therefore, can be exchanged easily with other stronger ions. This is the exact definition of Ion Exchange. As a result of these exchanges, Hydrogen and Hydroxyl ions are detached from the resins and combine to produce water.
But, resins have limited capacity . All their actives sites get occupied by stronger ions than Hydrogen and Hydroxyl ions. So they get saturated sooner or later.
Cation resines that already attracted cations MUST be regenerated by an Acid such as HCL or H2SO4. For example, Hydrogen ion in HCL is exchanged with Ca++ that was already attracted by the resines.
On the other side, Anion resins MUST be regenerated by a base like caustic( NaOH) to release negatively charged ions and reattract Hydroxyl ion.
After regeneration, they are ready to exchange Hydrogen and Hydroxyl ions with stronger ions again.
A question came to me:
Why resines are mixed during regeneration by air blower?
Ok. Let’s assume resines are not mixed in one vessel and there are two separate vessels, one of them is filled with cation resines and the other filled with anion resins.
Suppose dirty water flows through cation bed first and exchange its own cations with Hydrogen ion. For example, CaCl2 can exchange its Ca++ with H+. Therefore, Ca++ is attached on the resin, but the released H+ combine with Cl- to produce HCL. So, effluent is a water stream with less than 7 pH.
Then effluent passes through anion bed to exchange negatively charged ions with anion resins. Hydroxyl ions are released.
The gnerated HCL is exchanged Cl- with OH-. H+ is added to OH- to produce water.
You may say:
Ok, there is no issue.
But what if the dirty water had some Sodium ion (Na+)?
If you take a look at positive ions in previous post, you see both H+ and Na+ have only one positive chrge. It means, cation resins can’t exchange Sodium ion with Hydrogen well. So, the effluent of cation bed contains some Sodium that leakes to anion bed. It is called ‘Sodium Leakage’.
This Sodium combines with released OH- in next vessl to produce NaOH which increases electrical conductivity. Therefore, outlet stream of anion bed has high conductivity.
Sodium leakage has direct effect on Silica leakage. In anion bed, silica as an negative ion is attracted on anion resins. The produced caustic due to sodium leakage, regenerate attracted silica. Silica is released and final effluent silica analyzer shows Silica leakage and operating time is decreased significantly.
Anion resins are much expensive and more susceptible to fouling by cations. Cation bed should be installed first to exchange cations and act as a filter to remove suspended impurities for anion bed. Therefore, there is no advantage to install an anion bed before a cation one.
All in all, resins should be mixed, because having them in very close proximity makes a stronger driving force for released Hydrogen ion to attract released Hydroxyl ion and produce water.
Order of selectivity
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| Synchronous motor |
In large industries, these motors serve the two-purpose of driving mechanical loads as well as power factor improvements. These motors can run at the leading electrical factor with an increase in excitation power. The main feature of a synchronous motor is its constant speed operation. The motor operates at a constant synchronous speed given by the supply frequency and multiple poles in the stator winding.
Construction
 |
| Synchronous Motors |
Stator: - The stator is made of silicon steel lamination of the desired diameter and stacked to a suitable stator length. The motor kW rating depends on the air gap and core length on the diameter of the core. Radial ventilation ducts are provided at a regular distance of 70 to 80 mm for forced air cooling of the motor. The stator is wound with a three-phase winding with a suitable number of poles, depending on the speed of the motor. High voltage winding is used for motors above 500 kW rating. The voltage is usually 6.6 kv or 11 kv depending on the parameters of the supply system. The stator is fixed in the motor body. The body is made of steel with box-type fabricated construction.
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| Motors Construction |
1 Smooth Cylindrical Rotor - It is used in India for machines with 3000 RPM for 50 Hz. The smooth cylindrical rotor has slots on the periphery that distribute the winding to produce a sinusoidal magnetic field.
2 main polar rotor - It is used in motors with 1500 RPM and low RPM.
Main pole rotor- The number of poles in the rotor depends on the number of poles in the stator winding. For example, if a motor in the stator winding has 4 poles, the rotor will also have 4 poles and the 4 poles must be wound for DC winding. In the silent pole rotor, the spider is mounted on the shaft. The rotor poles are fixed on spiders with a detail or tee slot. The rotating leads are connected to two slip rings mounted on a shaft. The rotor is given a low voltage 24 volts to 50-volt high ampere DC supply to synchronize the motor. This rotor is currently 300 to 500 amp for a 1 MW motor. In addition to this DC excitation winding, there is a squirrel cage fastener winding on the face of the rotor pole. This damper provides starting torque to the winding motor which makes the motor self-starting.
Pedestal bearings: - There are two pedestal bearings to support the motor shaft. Bearings are made of Babylon metal. An oil cooling system is used for the cooling of the bearings.
Heat Exchanger: - A heat exchanger is used in a forced-air cooling circuit to transfer cooling air from cooling air.
Exciter: - The exciter is a low voltage high current DC generator connected to the main motor shaft. The DC supply generated in the exciter is used for the excitation supply of the main motor.
Synchronous motors are not started at any load, so firstly all the gates of the airline are completely closed. The motor is given three-phase power by closing the main OCB (oil circuit breaker). As the three-phase supply is rotated a rotating magnetic field is established in the stator core which induces torque in the damper winding and the rotor starts rotating. It is like a simple induction motor starting. Gradually the motor speed increases and approaches the synchronous speed, the DC contactor is automatically lifted and the DC excitation supply is switched on the rotor circuit through the carbon brush and slip ring. This excitation magnetizes the supply rotor poles that pull the rotor poles to the stator poles and then the stator and rotor poles are magnetically locked as the motor is synchronized. Then the rotor excitation current is controlled according to the load and power factor requirement. Now the sponge can be opened as per requirement.
Calculation | Heat Requirement (kJ) | Steam Requirement (kg) | |
Steam jacketed kettles | 4387 X 0.62 X 30 | 81,598.2 | 39.47 |
Oil heating | 30 X 900 X 2 X 30 | 1,620,000 | 783.74 |
Agitators heating | 251 X 0.5 X 30 | 3765 | 1.82 |
Total | 825.03 |
Calculation | Heat Requirement (kJ) | Steam Requirement (kg) | |
Oil heating | 30 X 900 X 2 X 30 | 1,620,000 | 783.74 |
Total | 783.74 |
