Pakarab Fertilizers

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Background

PAKARAB FERTILIZERS PVT LTD MULTAN

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MANUFACTURING PROCESS

FERTILIZER PRODUCTS CAPACITY PRODUCTION

Calcium Ammonium Nitrate (CAN) 1500 (MTPD)

Nitro-phosphate (NP) 1015 //

Urea 280 //

The intermediate products are Ammonia and Nitric Acid. The company plant therefore has five units excludingPower Generation, Utility and Bagging & Shipping facilities. Production capacities of intermediate plants are

summarized below:

INTERMEDIATE PRODUCTS CAPACITY PRODUCTION

Ammonia 960 (MTPD)

Nitric Acid 1380 //

Nitric Acid (New plant) 1200 //

Nitric Acid Plant (Old) 180 //

Ammonia Nitrate Crystals. On demand.

Product specification

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Mr. Saleem Zafar


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NP:

N : 22 + 1 %

P2O5 : 20 + 1 %

Moisture : < 0.7 %

CAN:

N : 26 + 0.5 %

CN : < 1.1 %

Moisture : < 0.8 %

Urea:

N : 46 min. %

Biuret : < 1.2 %

Moisture : < 0.5 %

NH3 : < 300 Ppm

Pakarab Fertilizers Limited is an agriculture based company. The core business is manufacturing

of chemical fertilizers. Pakarab is the Pakistan's one of the largest producers of compound

fertilizer situated at Khanewal Road, Multan. The three main products of the company are:

CAN (Calcium Ammonium Nitrate)

NP (Nitro Phosphate)

Urea

Nitro PhosphateIt is unique combination of phosphoric and nitrogen, having balance proportion of nitrogen

(N) and phosphorus (P). It provides synergetic effect in terms of efficiency. It is only

compound N & P contains nitrate type of nitrogen. It is unique in shape and no body can

adulterate it with any other material. It is equally good for application at the time of sowing or

after sowing. It is the best source of early stage nutrient supplement in case of vegetables and

transplanted crops. Its chemically reaction is acidic having pH 3.5. This gives an edge over

other basal fertilizers. Pakistans most of soils are alkaline in reaction and its acidic reaction

makes it more favorable to plant to recover nutrient from soils. It is equally good for manual

or mechanical application. It has good storage capacity.

Calcium Ammonium NitrateIt is only nitrogenous fertilizer having synergetic combination of nitrate and ammonical type

of nitrogen. This makes it superior over urea. Its nitrate portion starts working right after

irrigation and ammonical source works later on. Its N is not lost thru volitization or

leaching as other fertilizers. It works in conditions when soil has very low moisture when noother nitrogenous fertilizer can be applied. It can be used when there is good dew on soil

surface in winter. It is neutral in pH hence farmers can use it with liberty at any stage of crop.

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It is safe and has no phototoxic effect on plant. It is free flowing and can be applied

mechanically or manually. It is technically proven to be the best source of nitrogen

supplement to the crop in case of saline and water logged (salt effected soils and water logged

soils). It works 20 % longer period than other source, means it is more in term of lasting

effects. It is free from adulteration. It contains 2% SOP, an ideal source of potassium and

sulfur supplement. This is also the best fertilizer for fertigation (application after dissolving it

in irrigation water).

In house products Nitric Acid

Ammonia

WATERTREATMENTINTRODUCTION

Water treatment is a very important process in any industry where water is used. Water treatment

is basically used to remove certain impurities or salts from water in order to avoid corrosion or

scaling in pipes or other parts of equipments. These are basic two types of impurities.

Physical Impurities

Chemical Impurities

PHYSICAL IMPURITIESPhysical impurities consist of taste, odor, color, turbidity etc. Taste & odor may be due to

presence of organic matter, industrial wastes etc. Color & turbidity (cloudiness) in water is mainly

caused by the suspended particles like clay, sand etc.

REMOVALOF PHYSICAL IMPURITIESPhysical impurities can be removed by applying sieves in order to separate sand & clay

particles. Physical impurities are removed by

Screening

Sedimentation or Settling

Coagulation

Filtration

CHEMICAL IMPURITIES

Chemical impurities are due to.

Dissolved Salts

These are Carbonates, Bicarbonates, Chlorides & Sulphates of Ca, Na, Mg, K etc.

Dissolved Gases

These are N2, CO2, O2, SO2, & H2S etc.

HARDNESSOF WATERWater which on treatment with soap which produced lather is called hardness.

TYPESOF HARDNESSTEMPORARY HARDNESS

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Temporary hardness is caused by soluble bicarbonates of Ca & Mg such as Ca(HCO 3)2 &

Mg(HCO3)2. Temporary hardness of water is removed by boiling of water.

Ca(HCO3)2 CaCO3 + CO2 + H2O

Carbonates of Ca & Mg thus formed are insoluble & are deposited as scale at bottom of

container, & thus can be removed. No chemicals are used for removal of temporary hardness.

PERMANENT HARDNESS (NON-CARBONATE HARDNESS)This is due to presence of chlorides & sulphate of Ca, Mg, & other heavy metals. This is

not removed by boiling. Chemicals like Ca(OH)2, Na2CO3 are used to remove hardness. Different

process like hot & cold process are used. Hot methods are preferred because it also results in

removal of dissolved gases & capacity of plant in increased. Process of removing hardness of

water is called softening of water.

REMOVALOF CHEMICALIMPURITIESORREMOVALOF WATERHARDNESSThe presence of chemical impurities (dissolved impurities) result in hardness of water.

Removal of softening of water.

THEREAREFOURMETHODSFORWATERSOFTENING. Lime Soda Method

Zeolite Method

Demineralization Method or Ion Exchange Method

Reverse Osmosis

In the power house at Pakarab fertilizers factory we use demineralization method for the

water treatment.

DEMINERALIZATION METHOD.

All natural water contains dissolved salts, which dissociate in water & form charged

particles called ions.

Positively charged particles called cat ions (such as Ca++, Mg++) etc .

Negatively charged particles are called Anions (such as Cl-, SO4--) etc.

DEMIN WATERPLANT

GENERAL DESCRIPTIONThe boiler feed water treatment consist of:

- 3 Cat ion exchangers

- 1 Degasifying tower

- 3 Anion exchanger

- 3 Mixed beds exchangers

- Regenerating equipment for HNO3, NH4OH and NaOH regeneration

Specifications:Plant capacity (200 m3 design) but now a days plant is operated at a capacity of 160-170 m3.

3 Cation Filter

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- Diameter 2600 mm- Height on straight 3060 mm

- Operating pressure 2.54 kgf/cm2

- Design pressure 5.5 kgf/cm2

- Design temp max. 80 0C

- Capacity 1100 m3

- Volume of the cation resin 10,000 ltr Duolite C-20 A- Volume of an inert resin 1550 ltr

1 Degasifier tower

- Diameter 2000 mm- Straight side 4000 mm

- Material welded mild steel, internally rubber lined

- Wall thickness 6 mm

- Packing material 2" saddles, 7 m3 - 1.5" Rashing rings

- Air blowers 2 of Capacity 4350 Nm3/ hr, 5 HP motor, 2900 RPM

2 Degasifying water booster pump- Medium for transportation Cation water pH 2-3

- Specific gravity 1.0

- Capacity 232 m3/hr

- Pressure at inlet 0.1 kgf/cm2

- Pressure at outlet 3.8 kgf/cm2

- Operational temperature ambient

- Suction size 125 mm

- Discharge size 100 mm

- Motor 37 kw, 2900 RPM

3 Anion Filter- Diameter 2300 mm

- Height on straight 3060 mm

- Operating pressure 4 kgf/cm2

- Design pressure 5 kgf/cm2


- Capacity 990 m3

- Volume of the anion resin 3400 ltr Duolite A-368 PRD

3600 ltr Duolite A-368 DD

- Volume of an inert resin 1200 ltr

3 Mixed Bed Exchanger

- Diameter 1500 mm- Height on straight 2040 mm

- Operating pressure 4 kgf/cm2

- Design pressure 5 kgf/cm2


- Capacity 12000 m3

- Volume of the cation resin 800 ltr Duolite C-20 MB

- Volume of the cation resin 800 ltr Duolite A-101 D

PROCESS DESCRIPTION

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1. CATION FILTERS (C.I AND C.II)

Raw water run via a flow indicators and water meters to the cation filters and is distributes

at the top of the filters by a distributor over a whole filter surface.

After passing the resin bed the water is collected in the bottom and runs to Co 2

degassifier The cation exchangers are equipped with pressure differential meters.

2. CO2 DEGASSIFIER. (T.I)

The cation water is fed into the top of the Co2 tower and by a distributor over the tower

surface. The water flows through the Rashing rings filling and is collected in the concrete sump in

the bottom of the tower. It is also possible to bypass the tower and to lead the cation water to the

degassed water sump. For the removal of the free Co2 out of the water, air is blown in the up flow

direction through the tower, by a fan. The air leaves the tower together with the free Co 2 at the top

of the tower. In the inlet of the tower the butter fly valve controlled by a level controller is

installed. The sump is equipped with level indicator and a level switch to stop the booster pump in

case of the low pump level.

3. BOOSTER PUMP (P.I AND P.II)The pump are fed with Co2 free cation water from the degassed water pump.

The pump deliver the water to the anion exchanger and are equipped with a pressure gauge in the

discharge line.

4. ANION FILTERS (A.I AND A.II)

The water from the booster pump flows to the anion exchanger via a flow indicators and is

distributed at the top of the filter over the whole surface. After passing the resin bed, the water is

collected in the bottom and flow to the mixed bed exchanger. The filters have pressure differential

meter. To control the effluent quality a conductivity meter is installed. A conductivity alarm is

provided in case of the too high effluent conductivity.

5. MIXED BED FILTERS (MB.I AND MB.II)

The water from the anion exchanger flows to the mixed bed exchangers where it is divided

by a distributor over the total surface. After passing the resin bed, the water is collected at the

bottom and runs via a security resins trap to the treated water tank. This resins trap is provided

with a pressure differential meters, which given an alarm at high differential pressure across the

trap. In the outlet line the water meter is installed by means of the which the treated amount of the

water can be checked. To control the effluent quality of the mixed bed filters, a conductivity

meter with the recorder is installed. A conductivity alarm is provided in case of the too highconductivity of the water.

BACK WASHING OR REGENERATION

1. Cation filters are regenerated with 7 7.5% conc.

2. Anion filters are regenerated with Ammonium hydroxide and casting soda.

IMPORTANT NOTES

1. Back wash of the cation unit can be carried out before or after acid injection.

2. If a back wash is carried out, a double quantity of acid has to be used for regeneration.

FEW DEFINITIONS IN CONNECTION WITH THE ION EXCHANGE

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1. Ion exchange material are synthetic copolymers of the styrene and divinyl benzene.

Reacted with the functional groups which provide the specific ion exchange

characteristics.

2. Free mineral acidity is the total amount or strong acid in effluent from hydrogen

exchanger

3. Total exchangeable ions; are these able to be removed from water by ion exchange. In

hydrogen cation units, it is usually the sum of the concentrations of Ca

++

, Mg

++

and Na

++

.In hydroxide anion units. It is usually the sum of HCo3, Cl, So4, NO3 and HSio3.

4. End point or break through occurs when an un exchanged ions in the effluent exceed a

present limit.

5. Exchange capacity is expressed as KG or ions removed per Cubic feet of resins before

break through.

6. Leakage devotes the steady appearance of unwanted ions in exchanger effluent.

7. Regerant level is no. of Kgs of Regerant chemical applied per cubic meter of resin

8. Regenration efficiency in Kgs of pure Regerant chemicals required per Kgs. of ion

removed .

9. The meaning of pH in water chemistry: the pH scale indicates the acidity or alkalinity of a

solution .

Definition of the pH is the logarithm of the reciprocal of the hydrogen ion concentration

Scale range is usually 0 14 MID point is 7.0 and solution with this pH is said to be neutral. High

value devotes alkalinity and lower value acidity.

CONDUCIVITY

The conductivity of aqueous solution is a function of the kind and quality of the % age of ions

present in the solution. For dematerialized water the conductivity is the straight line function of

the concentration of the any ion present. The conductivity of an aqueous solution is equivalent to

the sum of the conductance of individual ion present in that solution. The conductivity of the

solution is definitely affected by temp. which it is measured free carbon dioxide and ammoniawhen in solution appreciably affect the conductivity

GENERAL RESINS PROBLEMS

Physical degradation of the ion exchange resins may take place through any of the following

mechanism.

1. osmotic shocks.

2. Thermal shocks.

3. Copper fouling.

4. Organic fouling.

5. Oil fouling.6. Micro biological fouling.

7. Mechanical strains.

8. Iron fouling.

9. Insoluble hardness fouling.

10. Calcium sulphates fouling.

11. Aluminum fouling.

12. Silica fouling.

ANALYSIS OF RAW WATER

Total hardness 150 170 ppm as CaCo3Ca++ 40 45

Mg++ 11 15

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Na+ 100 110

K+

Ca++ 40 45

Bicarbonates 268 317 ppm

Sulphates 90 115 ppm

Chlorides 12 20 ppmSilica 10 23 ppm

Total solids 440 480 ppm

Suspended solids 1 1.2 ppm

Free Co2 3 5 ppm

Conductivity 720 740 s / cm

pH 7.5 8.0

KMnO4 consumption 1 1.6 mg/l

COOLING TOWER

The cooling towers are used to provide an economical heat sink. Cooling towers are chosen

because they minimize heat rejection cost while water is being conserved. Water cooling is

generally takes place by evaporation and heat losses. Approximately 1000 BTU are lost from

water for every pound of water evaporated. The amount of the heat lost by the tower through the

sensible heat loss depends on the temperature rise of the ambient air before it leaves the cooling

tower This indicates that both the dry bulb and wet bulb temperature are of great importance. The

wet bulb temperature is the maximum temperature to which the water can be cooled by cooling

tower evaporation. It is not practical to design the cooling tower to bring the sump temperature

equal to the wet bulb temperature since the heat rejection is done primarily by the evaporation of a

portion of the cooling water, cooling towers are designed to bring into contact the maximum

air/water contact.

Types

1. Natural draft cooling towers

2. Mechanical draft cooling towers

Mechanical draft cooling tower

A mechanical draft cooling towers are further divided into two categories:

a). Forced circulation type.

b). Induced circulation type.

Induced draft cooling towers are further classified as below:

FORCED DRAFT COOLING TOWERThe forced draft system pushes the air into the tower where it is directed out form the

tower. The water trickles from the top and air passage is from the bottom thus causing a counter

flow.

COUNTER FLOW

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The counter flow provides the means of the more efficient heat transfer because coolest

water came in contact with the coolest air initially.

CROSS FLOWIn cross flow design air flow is normal to water movement more fill is required to transfer the

given amount of heat. The cross flow has the advantage of an easier path for the HP also the cross

flow has the lower air pressure drop.

HEAT TRANSFERUsually heat transfer occurs within the tower fill area, typically this consist of the wood, asbestos,

cement, plastic fills glasses polyester reinforced polyester grids for supporting the fill poured or

pre cast support beam and columns. Asbestos, Cement or PVC drift eliminators are used to

separate the droplets of the water and prevent them to escape. The selection of the packing

depends upon the installed design

There are two type of arrangement

1. Film Type

2. Splash Bars type

Film type packing are often used in the counter flow type cooling towers

Splash Bars are usually used in the counter flow type of cooling towers

CATEGORIZATION BY AIR-TO-WATER FLOW

Cross flow

Cross flow is a design in which the air flow is directed perpendicular to the water flow (see

diagram below). Air flow enters one or more vertical faces of the cooling tower to meet the fillmaterial. Water flows (perpendicular to the air) through the fill by gravity. The air continues

through the fill and thus past the water flow into an open plenum area. A distribution orhot water

basin consisting of a deep pan with holes ornozzles in the bottom is utilized in a cross flow tower.

Gravity distributes the water through the nozzles uniformly across the fill material.

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Counter flow

In a counter flow design the air flow is directly opposite of the water flow (see diagram below).

Air flow first enters an open area beneath the fill media and is then drawn up vertically. The water

is sprayed through pressurized nozzles and flows downward through the fill, opposite to the air

flow.

Common to both designs:

The interaction of the air and water flow allow a partial equalization and evaporation of

water.

The air, now saturated with water vapor, is discharged from the cooling tower.

A collection orcold water basin is used to contain the water after its interaction with the

air flow.

Both cross flow and counter flow designs can be used in natural draft and mechanical draft

cooling towers.

COOLING TOWER AS A FLUE GAS STACK

At some modern power stations, equipped with flue gas purification like the Power Station

Staudinger Grosskrotzenburg and the Power Station Rostock, the cooling tower is also used as a

flue gas stack(industrial chimney). At plants without flue gas purification, this causes problems

with corrosion.

Wet cooling tower material balance

Quantitatively, the material balance around a wet, evaporative cooling tower system is governedby the operational variables of makeup flow rate,evaporation and windage losses, draw-off rate,

and the concentration cycles:[4]

Sohaib Shamshad Ali
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M = Make-up water in m/hr

C = Circulating water in m/hr

D = Draw-off water in m/hr

E = Evaporated water in m/hr

W = Windage loss of water in m/hr

X = Concentration inppmw (of any completely soluble salts usually chlorides)

XM = Concentration ofchlorides in make-up water (M), in ppmw

XC = Concentration of chlorides in circulating water (C), in ppmw

Cycles = Cycles of concentration = XC / XM (dimensionless)

ppmw = parts per million by weight

In the above sketch, water pumped from the tower basin is the cooling water routed through the

process coolers and condensers in an industrial facility. The cool water absorbs heat from the hot

process streams which need to be cooled or condensed, and the absorbed heat warms the

circulating water (C). The warm water returns to the top of the cooling tower and trickles

downward over the fill material inside the tower. As it trickles down, it contacts ambient air rising

up through the tower either by natural draft or by forced draft using large fans in the tower. That

contact causes a small amount of the water to be lost as windage (W) and some of the water (E) to

evaporate. The heat required to evaporate the water is derived from the water itself, which cools

the water back to the original basin water temperature and the water is then ready to recirculate.

The evaporated water leaves its dissolved salts behind in the bulk of the water which has not been

evaporated, thus raising the salt concentration in the circulating cooling water. To prevent the salt

concentration of the water from becoming too high, a portion of the water is drawn off (D) for

disposal. Fresh water makeup (M) is supplied to the tower basin to compensate for the loss of

evaporated water, the windage loss water and the draw-off water.

A water balance around the entire system is:

M = E + D + W

Sohaib Shamshad Ali
http://en.wikipedia.org/wiki/Parts_per_notationhttp://en.wikipedia.org/wiki/Chloridehttp://en.wikipedia.org/wiki/Condenser_(steam_turbine)http://en.wikipedia.org/wiki/Evaporationhttp://en.wikipedia.org/wiki/Salthttp://en.wikipedia.org/wiki/Image:CoolingTower.pnghttp://en.wikipedia.org/wiki/Parts_per_notationhttp://en.wikipedia.org/wiki/Chloridehttp://en.wikipedia.org/wiki/Condenser_(steam_turbine)http://en.wikipedia.org/wiki/Evaporationhttp://en.wikipedia.org/wiki/Salt


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Since the evaporated water (E) has no salts, a chloride balance around the system is:

M (XM) = D (XC) + W (XC) = XC (D + W)

and, therefore:

XC / XM = Cycles of concentration = M (D + W) = M (M E) = 1 + [E (D + W)]

From a simplified heat balance around the cooling tower:

E = C T cp HV

where:

HV = latent heat of vaporization of water = ca. 2260 kJ / kg

T = water temperature difference from tower top to tower bottom, in C

cp = specific heat of water = ca. 4.184 kJ / (kg C)

Windage (or drift) losses (W) from large-scale industrial cooling towers, in the absence of

manufacturer's data, may be assumed to be:

W = 0.3 to 1.0 percent of C for a natural draft cooling tower without windage drift eliminators

W = 0.1 to 0.3 percent of C for an induced draft cooling tower without windage drift eliminators

W = about 0.005 percent of C (or less) if the cooling tower has windage drift eliminators

Cycles of concentration represents the accumulation of dissolved minerals in the recirculating

cooling water. Draw-off (or blowdown) is used principally to control the buildup of these

minerals.

The chemistry of the makeup water including the amount of dissolved minerals can vary widely.

Makeup waters low in dissolved minerals such as those from surface water supplies (lakes, rivers

etc.) tend to be aggressive to metals (corrosive). Makeup waters from ground water supplies

(wells) are usually higher in minerals and tend to be scaling (deposit minerals). Increasing the

amount of minerals present in the water by cycling can make water less aggressive to piping

however excessive levels of minerals can cause scaling problems.

As the cycles of concentration increase the water may not be able to hold the minerals in solution.

When the solubility of these minerals have been exceeded they canprecipitate out as mineral

solids and cause fouling and heat exchange problems in the cooling tower or the heat exchangers.

The temperatures of the recirculating water, piping and heat exchange surfaces determine if and

where minerals will precipitate from the recirculating water. Often a professional water treatment

consultant will evaluate the makeup water and the operating conditions of the cooling tower and

recommend an appropriate range for the cycles of concentration. The use of water treatment

chemicals, pretreatment such as water softening,pH adjustment, and other techniques can affect

the acceptable range of cycles of concentration.

Concentration cycles in the majority of cooling towers usually range from 3 to 7. In the United

States the majority of water supplies are well waters and have significant levels of dissolvedsolids. On the other hand one of the largest water supplies, New York City, has a surface supply

quite low in minerals and cooling towers in that city are often allowed to concentrate to 7 or more

cycles of concentration.

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Besides treating the circulating cooling water in large industrial cooling tower systems to

minimize scaling and fouling, the water should be filtered and also be dosed withbiocides and

algaecides to prevent growths that could interfere with the continuous flow of the water. [4] For

closed loop evaporative towers, corrosion inhibitors may be used, but caution should be taken to

meet local environmental regulations as some inhibitors use chromates.

Ambient conditions dictate the efficiency of any given tower due to the amount of water vapor theair is able to absorb and hold, as can be determined on a psychrometric chart.

Cooling towers and Legionnaires' disease

Another very important reason for using biocides in cooling towers is to prevent the growth of

Legionella, including species that cause legionellosis orLegionnaires' disease, most notablyL.

pneumophilia[5]. The variousLegionella species are the cause ofLegionnaires' disease in humans

and transmission is via exposure to aerosolsthe inhalation of mist droplets containing the

bacteria. Common sources ofLegionella include cooling towers used in open recirculating

evaporative cooling water systems, domestic hot water systems, fountains, and similar

disseminators that tap into a public water supply. Natural sources include freshwater ponds andcreeks.

French researchers found thatLegionella spread through the air up to 6 kilometres from a large

contaminated cooling tower at a petrochemical plant in Pas-de-Calais, France. That outbreak

killed 21 of the 86 people that had a laboratory-confirmed infection.[6]

Drift (or wind age) is the term for water droplets of the process flow allowed to escape in the

cooling tower discharge. Drift eliminators are used hold drift rates typically to 0.001%-0.005% of

the circulating flow rate. A typical drift eliminator provides multiple directional changes of

airflow while preventing the escape of water droplets. A well-designed and well-fitted drift

eliminator can greatly reduce water loss and potential for Legionella or other chemical exposure.

Sohaib Shamshad Ali
http://en.wikipedia.org/wiki/Scalinghttp://en.wikipedia.org/wiki/Foulinghttp://en.wikipedia.org/wiki/Filter_(water)http://en.wikipedia.org/wiki/Biocidehttp://en.wikipedia.org/wiki/Algaecidehttp://en.wikipedia.org/wiki/Corrosion_inhibitorshttp://en.wikipedia.org/wiki/Chromatehttp://en.wikipedia.org/wiki/Legionellahttp://en.wikipedia.org/wiki/Legionellosishttp://en.wikipedia.org/wiki/Particulatehttp://en.wikipedia.org/wiki/Scalinghttp://en.wikipedia.org/wiki/Foulinghttp://en.wikipedia.org/wiki/Filter_(water)http://en.wikipedia.org/wiki/Biocidehttp://en.wikipedia.org/wiki/Algaecidehttp://en.wikipedia.org/wiki/Corrosion_inhibitorshttp://en.wikipedia.org/wiki/Chromatehttp://en.wikipedia.org/wiki/Legionellahttp://en.wikipedia.org/wiki/Legionellosishttp://en.wikipedia.org/wiki/Particulate


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Nitric Acid Plant

Introduction:The nitric acid plant is designed in two parallel lines: the capacity of each line is 600

metric ton per day.

The process selected for the plant is the medium pressure process. This provides significant

advantages compared with other process as high ammonia conversion efficiency low platinum

losses. Thus allowing 4 6 months operating intervals between catalyst changes, high reliability,

low operating and maintenance costs.

Ammonia and air are the raw materials. NH3 is taken from the storage tank of ammonia and air

from the atmosphere.

1. Ammonia SeparatorIn the ammonia separator, the ammonia is separate by heating from the liquid. Almost 38

% ammonia is evaporated in this loop.. The liquid ammonia is evaporated in evaporator 50% of

liquid ammonia is evaporated in the main evaporator at a temperature of 15 20 C 0 and pressure

is 6 kg/cm2. Ammonia gas stream from both the ammonia separator and evaporator are combined

and heated upto 60 C0 by steam heating in the ammonia heater to avoid carrying over of a liquid

ammonia droplet or mist.

2. Ammonia filtersAfter heating the ammonia, the gas is filtered in the ammonia filters, which is equipped

with filters candles from special ceramics to retain all impurities which might contaminate

through catalyst gausses.

3. Air CompressorsThe process air is taken from air compressor. First the air is filtered through air filters. The

air compressors is driven by steam turbine at one shaft end and by tail gases expander turbine at

the other end of the shaft. The hot air leaving the compressor is cooled down before using in

process in the tail gas heater.

4. Tail gas heaterIn the tail gas heater, the air is separated in to two systems, primarily air which is cooled to

244 0C and used for ammonia oxidation and the secondary air which is further cooled to 100 0C in

the same exchanger. This secondary air is used to bleach the nitric acid product in the bleaching

tower. The tail gas heated from 19 0C 153 0C

5. Ammonia air mixerPrimarily air enters the ammonia air mixer (here it is also heated and filtered) in to which

the heated and the filtered ammonia is introduced and then mixed with air. The mixture contain

10% by volume of ammonia and it leaves the mixer at a temperature of 203 0C.

6. Ammonia burner

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The mixture enters the burner and passes through the catalyst bed consisting of 14 layers

of Platinum and Rhodium silk fine gausses. This alloy consist of 90% Pt. 10% Rh. The burner bed

is equipped with circular bottles and perforated plates to provide uniform distribution of the

mixed gases. Over the total exposed catalyst area of optimum conversion efficiency. The reaction

of ammonia oxidation, initiated by the catalyst, rises the gas temperature up to 890 0C. The hot

burner gases is now passed through the waste heat boiler, by which the most of the heat reaction is

used to generate steam of 41.5 kg/cm

2

. Now the gas is cooled to 490

0

C. This steam is used todriver air compressor and the balanced is exported to utility plant. The reaction involved in this

process is given below.

4NH3 + 5O2 4NTQ + 6H2O

2NO + O2 2NO2

3NO2 + H2O 2HNO3 + NO (g)

The ammonia burner provided gas leaves the W.H.B (waste heat boiler) at a temperature of 2400C and passes through the tail gas heater where it exchanges heat. There are two tail cooler

condensers in parallel with the split flow gases inlet on one end. In the condenser the product gas

is cooled from 205 0C to 50 0C where almost all of the gas is separate from water by condensation,forming a weak HNO3 with approximate 38% HNO3 is pumped into the absorption towers on a

trays with nearly the same acid strength

7. Absorption towerThe process gases leave the condenser and enter in to the absorption column. There are

two A.T in series equipped with 73 sieve trays on which the nitrous oxides are absorbed in the

process water, introduced on the last tray in counter flow to the gas stream.

In the absorption tower first 40 trays are cooled with cooled water while other are cooled

with ammonia in order to maintain gas temperature of approximate 20 0C to achieve the emission

of NOX less then 500 ppm

8. BleachingThe acid product of first absorber is fed to the bleaching tower by using the pump where it

is fed over the rashig rings packing to free from the dissolved colored compounds

The final product, water clear HNO3 with 60% strength and a temperature of 460C enters

the storage tank from where it may be pumped by product acid pump.

OVERALL REACTION

NH3 + 2O2 + H2O HNO3(g) + H2O

Sohaib Shamshad Ali

Pakarab Fertilizers

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