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Chemical Engineering
Chemical Engineering is the branch of engineering that deals with the technology of large-scale chemical production and the manufacture of products through chemical processes. Today, the field of chemical engineering is a diverse one, covering areas from biotechnology and nanotechnology to mineral processing.
1,464 Questions
What is critical flow and sub critical flow of fluids?
Critical flow is the special case where the froude number (dimensionless) is equal to 1. i.e. The velocity divided by the square root of (gravitational constant multiplied by the depth) =1.
Sub critical flow i has a froude number less than 1, and is therefore characterised by slow moving deep water.
Supercritical flow is defined as having a froude number greater than 1 and is therefore characterised by shallow fast moving flows.
How many liters in a squared meter?
None.
A litre is a measure of volume in 3-dimensional space while a square metre is a measure of area in 2-dimensional space. The two measure different things and, according to basic principles of dimensional analysis, conversion from one to the other is not valid.
Difference of Sodium and calcium lignosulfonate in concrete application?
Calcium lignosulfonate in concrete action and dosage - Stone Refractories
I. Calcium lignosulfonate water reduction in concrete reinforced role
Calcium lignosulfonate and sodium lignosulfonate reducing agent is a surface-active agent, added to the concrete, due to the orientation of hydrophobic groups adsorbed on the surface of cement particles, so that the cement with a negative charge. Cement particles have the same charge in the charge repulsion exclusion from each other under the action of dispersion of cement in water the initially-formed into a dispersion structure floc structure, flocculation cohesion body of free water is released, so as to achieve the purpose of reducing agent. Observations show that lignin added to the concrete after mixing for 5 minutes more than 80% of the reducing agent is adsorbed, clearly visible under the electron microscope, the center point of significantly increased hydration, hydration evenly distributed, hydrated crystal fibers longer various microscopic characteristics.
Thus, the adding of calcium lignosulfonate, leaving the pores free water evaporation is small, dense internal structure, that is, reduction of the porosity is clearly beneficial to increase the strength of concrete, cement improves the size and distribution of the pore structure conditions, the crystal growth rate slow, crystal growth more fully, and thus get more fibrous crystals interspersed with each other to form a strong network structure, so that the concrete strength significantly increased.
Therefore, in concrete mixed with lignin superplasticizer, concrete mixture can reduce water consumption and reduce water-cement ratio, improved workability, is conducive to pumping, improve concrete strength, density and durability.
Second, the lignin water reducer in concrete dosage and key performance indicators
1, to improve concrete performance: When the same amount of cement, concrete slump similar to the blank can reduce water consumption by 10-15%, 10-20% increase in 28-day strength, a strength of about 10%.
2, saving cement consumption: When the concrete strength and slump similar, can save about 10% of cement, use one ton of cement water reducing agent can save 30-40 tons.
3, to improve the workability of concrete: When the amount of cement concrete and water consumption constant, low plasticity of concrete slump can be increased about twice (by a 3-5cm up to 8-18cm), early strength and undoped who was close.
4, lignin retarding effect: 0.25% lignin superplasticizer mixed after the slump in keeping basically the same, the initial setting time 1-2 hours delay ordinary cement, slag cement 2-4 hours, and finally 2 hours setting time of portland cement, slag cement 2-3 hours, if not reduce water consumption and increase the slump, or when the slump while maintaining the same amount of cement used to save, then the setting time delay greater extent than less water greater.
5, can reduce early hydration heat: exothermic peak are longer than the delay undoped, about 3 hours of Portland cement, slag cement about 8 hours, 11 hours or more concrete dam, the exothermic peak maximum temperature and not miserable by comparison, ordinary cement is slightly lower, slag cement and cement dam were lower than 3 ℃
6, concrete air content increased: blank concrete air content of about 1%, 0.25% lignin mixed concrete air content of 2.3 percent.
7, the bleeding rate decreased: in concrete slump basically the same case, the doped lignin bleeding rate than those who are not doping can be reduced more than 30%, while maintaining the same water-cement ratio, increasing slump situation , it is also due to the introduction of air lignin hydrophilic and other reasons, the bleeding rate.
8, shrinkage performance: initial (1-7) days compared with non-water-reducing admixture, was close to or slightly decreased, 28 days and late (except saving cement above), a slight increase, but the increase values did not exceed 0.01% (0.01mm / m).
9, to improve the density of concrete, improve concrete impermeability. By the B = 6 grade up to B = 12-30 level.
10, no chlorine salt, no corrosion of steel hazards.
Usage of lignosulfonates on the base of sodium, relating to the hydrofilizing plastificators, at the concrete manufacture and dry construction mixtures lets to reduce the consumption of components up to 10-15%. Demixing of the concrete mass reduces and its solidity rises, the speed of hardening slows down. They insert additives of lignosulfonates in the quantity of 0,15-0,20%, it is necessary to insert superplastificators from the mass of dry substance in the quantity of 0,5-2,0% from the mass of dry concrete. When replacing superplastificators by lignosulfonates the solidity of concrete rises up to 20-25%, freeze resistance - in 3-4 times and the cost of mixtures reduces cause of adding of small amount of lignosulfonates, what is connected with their adsorbtion on the surface of hard phase. Usage of lignosulfonates reduces humidity of raw mud if conserving its flow behavior, what rises the manufacture of stove and reduces specific flow volume to the burning of clinker. With the usage of intensifier on the base of lignosulfonates the production of grinding units rises and there is an opportunity to change expensive and deficit chemical products.
more information please visit:www.greenagrochem.com
Pipe that meets the requirements of sour gas service per NACE MR0175.
What are the different chemical agents and their effects?
3 blood agent: attacks the oxygen-carrying capacity of the body
4 Chokin agent: attacks the airways and lungs
1 nerve agent: attacks muscles of the body
2 blister agent: attacks the skin and lungs
3,4,1,2
Attacks the muscles of the body--------- Nerve agent
Attacks the skin and lungs----------- Blister agent
Attacks the airways and lungs------ Choking agent
Attacks the oxygen-carrying capacity of the body- Blood agent
Attacks the airway and lungs - Choking Agent
Attacks the muscles of the body - Nerve Agent
Attacks the oxygen-carrying capacity of the body - Blood Agent
Attacks the skin and lungs - Blister Agent
Attacks the airways and Lungs------ Choking agent
Attacks muscles of the body--------- Nerve agent
Attacks the oxgen-carrying capacity of the body--- Blood Agent
Attacks the skin and Lungs------ Blister Agent
Weight of 1m by 1m by 1m rubber?
It depends on the density of rubber. Different kind of rubber have different density so different weights. weight = volume X Density in your case the volume is 1cuM. Natural rubber - 920 Kg/cu M Neoprene Rubber - 1230 kg/ cu M Silicone Rubber - 1150 kg/cu M EPDM Rubber - 860 kg/cu M Ramki- India
Can carbon steel be used as pump material in Ammonium Chloride services?
As the pumps are used to transfer the liquid from one place to another place,not solid.
ammonium chloride is a crystalline solid.
if we make solution of ammonium chloride with the water it becomes slightly acidic,when this acidic solution passes through the carbon steel make pump,it will corrode the pump because the carbon steel is not resistant to corrosion.
also the oxide layer form is dissolved by the solution which causes the rate of corosion increases and ultimately the equipment damaged.
What is printed circuit heat exchangers?
Printed Circuit Heat Exchangers (PCHEs) are characterised as high integrity plate type heat exchangers. They are fabricated from flat metal plates (sheets) that have fluid flow channels chemically etched into them using the same process as printed circuit hence the product name.
The etched plates are stacked and diffusion bonded together to make the core of the heat exchanger(s). PCHEs can be made of one or several cores welded together to suit the duties required. Headers and nozzles are attached to the core(s) to complete the exchanger.
PCHE are highly compact, highly robust exchangers and can achieve high thermal effectiveness of over 98% depending on the process:
- PCHE are four to six times smaller than conventional shell and tube heat exchangers of the equivalent duty.
- They have a pressure capability in excess of 600 bar (9000 psi) and can cope with extreme temperatures, ranging from cryogenic to above 900°C (1650°F).
They are well established in the upstream hydrocarbon processing, petrochemical and refining industries. They can incorporate more than two process streams into a single unit. This design feature has space and weight advantages, reducing exchanger size together with piping and valve requirements.
Additional functions can be included in the exchanger design, such as chemical reaction, mass transfer and mixing, optimising the process considerably.
The association of chemical etching and diffusion bonding processes into a single product allow the use of a wide range of materials of construction enabling the use of a wide range of clean fluids in the heat exchanger, including corrosive ones.
zone as is made by Nature, and by Man. Nature uses ozone gas to protect Earth's surface from UV-B radiation (which damages DNA). Nature also uses ozone to moderate day / night temperature swings, and to couple nitrogen and oxygen temperatures to radiate away some of their heat (they cannot radiate in infrared, but ozone can). Nature makes ozone to fight infection / predation in organisms. Finally, Nature makes ozone with lightning and waterfalls, which helps purify the air. Man makes ozone for water treatment, chemical processes, medical and dental treatments, for purification of confined spaces (both air and food-prep / surgical surfaces), and directly and indirectly from exhaust products. Ozone made at Earth's surface does not survive to "reinforce the ozone layer".
Difference between bar and barg?
The 'g' added on to bar means 'gauge', as opposed to bara, meaning 'absolute'.
The 'zero' of a normal gauge is normally set at atmospheric pressure (things like tire pressure gauges, water gauges etc.) These gauges will read as "10 bar" but really mean that the absolute pressure is 10 bar + atmospheric pressure (~1.01325 bar).
Some gauges however are absolute gauges. These might include weather gauges, or gauges on closed processes.
bara = barg + atmospheric pressure
What is the working principle of orifice meter?
An obstruction (orifice) is placed in a pipe filled with fluid. The pressure of the fluid is measured at two different points: 1) just upstream of the orifice and, 2) close to the contraction of the fluid (vena contracta). The difference in these two pressures is known as differential pressure. The differential pressure across an obstruction (orifice) in a pipe of fluid is proportional to the square of the velocity of the fluid.
Many factors associated with the pipe, orifice and fluid affect the measurement. Satisfactory measurement requires steady-state, homogeneous, turbulent flowing fluids. Other properties which affect the measurement include: the ratio of pipe diameter to orifice diameter and the density, temperature, compressibility and viscosity of the fluid.
There are dfferent types of cooling towers available in Industry.
Some of the commonly is used cooling towers are
- Round Cooling Towers
- Square Cooling Towers
- Dry Cooling Tower
- Wooden Cooling Tower
- Cross Flow Cooling Tower
- Modular Cooling Towers
- Evaporative Cooling Towers
- Natural Cooling Towers
- Counter Flow Cooling Towers
Get a highly durable cooling tower according to your industry.
Compressibility factor of steam?
For an Ideal gas(steam), the compressibility factor is obviously unity under all conditions whereas for real gas(steam), the compressibility factor may be less or more than unity based on the actual conditions. With best regards, elavazhgan.
What is true about an electrolytic cell?
A.Oxidation occurs at the anode.B.Reduction occurs at the cathode.C.Electrical energy is converted to chemical energy.
The negative terminal of the voltage source is attached to the cathode.
What is the basic operating principle of a flash tank?
What You Should Know About Flash Tanks
by J. E. TROCOLLI • Sarco Co., Inc. • Allentown, PA (Actual Specifying Engineer/71)
High-pressure steam systems
require flash tanks -
here is a guide to determining sizes
Condensate temperatures in high-pressure steam systems
generally are only slightly less than the saturated
temperature of the steam. When hot condensates are discharged
into lower-pressure areas, condensate temperature
immediately drops to the saturated temperature of
the low-pressure area. As the result of the drop in temperature,
heat released evaporates a portion of the condensate,
generating flash steam.
To return condensate to the boiler or to discharge it to
the sewer, it is necessary to separate flash steam from
the condensate. This is accomplished by discharging condensate
through steam traps into a vented tank, referred
to as a flash tank.
Flash steam produced in the flash tank may be vented
to the atmosphere or piped to a low-pressure main. Condensate
remaining may then be returned to the boiler or
discharged to drain.
Tanks must be large enough to ensure dryness of the
released steam and to avoid carryover by the steam of
water in droplet form. When using horizontal flash tanks,
the required area is found by multiplying the diameter of
the tank by its length. This measures the tank's capacity
to handle condensate. Table 1 illustrates the required area
for each 1,000 lb. of condensate/hour with varying steam
and flash pressures.
How big a tank?
Problem:
An absorption machine condenses 12,000
lb. of steam/hr. Assuming the flash tank is vented to the
atmosphere, determine the size of the flash tank required
with a steam pressure of 12 PSIG.
Solution:
Enter table 1 at 12 PSIG steam pressure,
moving horizontally to 0 PSIG. Find .75, which is the number
of square feet required for each 1,000 lb. of condensate.
Since 12,000 lb. of steam are generated, it may be
determined that by multiplying 12 x .75, 9 sq. ft. of surface
will be required, or that the diameter of the tank in
feet times its length in feet must equal 9. Thus, a tank 2
ft. by 4.5 ft. may be used.
Problem:
A dryer operating at 100 PSIG condenses
18,000 lb. of steam/hr. The flash tank is to discharge its
flash into a 5-PSIG heating main. Determine the size of
the flash tank required.
Solution:
Again, using table 1, enter at 100 PSIG
initial pressure. Move horizontally to the 5-PSIG column
and find 1.92.
Then:
18 x 1.92 = 34.6 sq. ft.
A flash tank 4 ft. by 9 ft. will be satisfactory for the
application.
Sizing vent lines
If flash steam is to be discharged to the atmosphere,
a properly sized vent line must be provided. To determine
the proper size, first find the area of the flash tank,
using the method described above.
Problem:
Determine the size of the vent line using
table 2. If, as in the first problem, tank size is 2 ft. by 4.5
ft. (9 sq. ft.), refer again to table 2, where 9 sq. ft. falls on
7.4-to-12 line. For this range, a 2-in. vent line would be
satisfactory.
Problem:
Determine the size of the vent line if the
flash tank size is 4 ft. by 9 ft. or 36 sq. ft. In table 2, 36 is
in the 27-to-36 line, and, in this case, a 3
1/2 in. vent would
be needed.
Figure 1 shows a typical flash-tank piping diagram
in which the flash is discharged to the atmosphere.
If it is desired to utilize the flash steam by discharging
it into a low-pressure main, refer to figure 2. In this
instance, it will be necessary to properly size the line
connecting the flash tank to the low-pressure main.
Using table 3, determine the percent of flash. Multiply
this percentage by the condensate load in lb./hr. to
determine the number of pounds of steam that are flashed.
Determine what steam velocity will be acceptable in the
line. If a low noise level is desired, a relatively low velocity
must be selected - 4,000 to 6,000 FPM.
Where noise is not a factor, a velocity of 12,000 FPM
or higher may be used. After velocity has been determined,
the required pipe size can be found in table 4.
Problem:
10,000 lb./hr. of condensate is discharged
into a flash tank from a 125-PSI steam system. Flash
steam is to be piped into a 10-PSIG low-pressure heating
main. Determine the size pipe required for connecting
the flash tank to the steam main.
Enter table 3 at 125-PSI initial pressure. Move horizontally
to the 10-PSIG column and find 12.2 percent
flash. Then the amount of flash steam/hr. is found this
way:
10,000 x 12.2 percent = 1,220 lb./hr.
SECTION ENG - PAGE 0100
FLASH TANKS
TABLE 1 FLASH TANK IN SQ. FT. = DIAMETER x LENGTH OF HORIZONTAL
TANK FOR 1,000 LB. CONDENSATE PER HOUR BEING DISCHARGED
TABLE 2 VENT LINE SIZE TABLE 3 PERCENT FLASH
FOR HORIZONTAL
FLASH TANKS
½"
FLASH TANKS
TABLE 4 STEAM VELOCITY CHART
FORM FLASH TANKS
Revised 4/04 SHIPCO® IS A REGISTERED TRADEMARK OF SHIPPENSBURG PUMP CO., INC.
SHIPPENSBURG PUMP COMPANY, INC.,
P.O. BOX 279, SHIPPENSBURG, PA 17257 • PHONE 717-532-7321 • FAX 717-532-7704 • WWW.SHIPCOPUMPS.COM
PRINTED IN THE U.S.A. • BEIDEL PRINTING HOUSE, INC., 717-532-5063 PERMISSION TO REPRINT BY SPIRAX SARCO INC.
Since low noise level is important, a velocity in the
4,000 to 6,000 FPM range must be selected. Enter table
4 at 1,220 lb./hr., moving horizontally to a flash-steam
pressure of 10 PSIG. Then move up to 4,000 to 6,000
FPM velocity. Here, the chart shows that a 3-in. pipe will
handle about 6,000 FPM, or a 4-in. line would handle
about 3,500 FPM.
When vent lines cannot be extended to discharge
outside the buildings, it is important that the condensate
be cooled below the dewpoint to prevent the exhaust
from condensing and wetting walls, machinery, floors and
so on.
Estimating temperature
Since the dewpoint depends on several factors, including
relative humidity and temperature (which are variable),
the temperature to which the condensate must be
cooled should be estimated for individual cases.
The following is the recommended procedure:
Calculate the size of the flash tank in the method
described above:
Estimate the dewpoint, assuming unfavorable conditions,
and, when making the estimate, take ventilation into
account - it is a factor in determining relative humidity:
Once the dewpoint is known, estimate the quantity
of cooling water that will be required and finally:
Determine the pipe size and size of temperature
regulator valve required. A self-contained regulator with
a normally closed valve to open when the temperature
rises is recommended. All such controls have an ample
range over and under the calibration point so that setting
may be adjusted after installation.
Problem:
Calculate the quantity of cooling water required
to cool condensate in a flash tank vented to an
enclosed space, assuming the following data:
Steam pressure is 100 PSIG;
Condensate is entering the flash tank at 1,550 lb./hr.
at 335°F;
Ambient temperature of the space into which vent
discharges is 75°F; and
Cold water temperature is 50°F.
Assuming that ventilation at the above temperature
will be sufficient to have not more than 70 percent relative
humidity, the dewpoint will be 64.5°F (determined
from psychrometric chart).
To allow 1°F for safety, condensate should be cooled
from 338°F to 63.5°F. When the installation is completed,
further adjustment can be made by resetting the regulator.
The heat to be extracted from the condensate is equal
to:
1,500 lb./hr. x (338-63.5)°F = 410,000 BTUH
The quantity of cooling water required:
410,000 BTUH
(63.5 -50)°F
= 30,500 lb./hr.
or 3,670 GPH = 61 GPM
A 1.5-in. pipe to supply the water and a 1.25-in. temperature
regulator are recommended for this application.
Flash tanks separate flash steam from the condensate
by venting the flash steam to the atmosphere or
piping it to a low-pressure main, while returning the remaining
condensate to the boiler or discharging it to the
drain. If flash steam is discharged to the atmosphere, a
flash tank and a properly sized vent line must be determined;
if discharged to low-pressure mains it is necessary
to calculate the correctly sized line connecting the
flash tank to the low-pressure main. Also, the proper temperature
for cooling the condensate must be determined
for projects in which vent lines cannot be extended to
discharge outside the buildings.
Different situations require individual solutions to determine
the correctly sized flash tank, connecting pipe
and cooling temperature needed, but the calculation examples
offered here provide the means to determine the
necessary installations and accessories required.
Figure 1
A typical flash tank piping
diagram discharging to atmosphere.
NOTE: Omit trap if condensate is
discharged into vented pump receiver.
Figure 2
A typical flash tank piping
diagram with flash discharging to lowpressure
steam system.
Figure 3
This diagram depicts a
combination flash tank installation with
subcooling condensate.
VENT
PRESSURE
RELIEF VALVE
VENT IF
DESIRED
TO LOW
PRESSURE MAIN
HIGH PRESSURE
FROM
CONDENSATE
HIGH PRESSURE
SYSTEM
FLASH TANK
STRAINER
FLOAT AND
THERMOSTATIC
TRAP
FIN TUBE
COOLING LEG
REQUIRED
TO LOW PRESSURE
RETURN LINE OR
DRAIN
VENT TO
ATMOSPHERE
HIGH PRESSURE
FROM
CONDENSATE
HIGH PRESSURE
SYSTEM
FLASH TANK
STRAINER
FLOAT AND
THERMOSTATIC
TRAP
FIN TUBE
COOLING LEG
REQUIRED
TO DRAIN
CONDENSATE
FROM HIGH
PRESSURE
STEAM SYSTEM
TEMPERATURE
REGULATOR
STRAINER
COLD WATER
SUPPLY
VENT TO
T ATMOSPHERE
WATER LEVEL
COIL
DRAIN
TO SEWER
FLASH TANKS
Where are lanthanides located?
The lanthanide series comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium. These fifteen elements, along with the chemically similar elements scandium and yttrium, are often collectively known as the rare earth elements.
In the Group 3, Period 6 slot, After Barium and prior to Hafnium.
Applications of induction motor?
A single phase induction motor is mainly used in fans.It is capacitor start capacitor run induction motor.In three phase induction motor squirrel cage induction motor is mainly used in elevators,lifts,cranes.slip ring induction motor is mainly used in electrically driven ships.
What is positive isolation in plant?
Positive isolation is a method of Isolation where there is Zero potential of energy at the workplace.
- All Hazardous Energy has been identified
- All are isolated at the source
- Residual Energy has been eliminated.
eg. Electrically Isolated at the Transformer, earth applied, and fuses removed.
eg. Mechanically Isolated at the Pump, valve closed, blanked-off. Line drained, purged, etc
