Fer lizers

Introduc on

A fer lizer is a material that furnishes one or more of the chemical elements necessary for the proper development and growth of plants. The most important fer lizers are chemical or mineral fer lizers, manures, and plant residues.

Plant Nutrients

Chemical elements that are essen al for the proper development and growth of plants are typically referred to as plant nutrients. sixteen.

Expression Quan es or percentages of the primary nutrients in terms of elemental nitrogen (N), phosphorus penta oxide (P2O5), and potassium oxide (K2O).

Secondary nutrients and micronutrients usually are expressed on an elemental basis although calcium and magnesium some mes are expressed in the oxide form.

However, several countries express all plant nutrients on an elemental basis.

Introduc on

Introduc on

Fer lizer grade

All fer lizer labels have three bold numbers. The first number is the amount of nitrogen (N), the second number is the amount of phosphate (P2O5) and the third number is the amount of potash (K2O). A bag of 10-10-10 fer lizer contains 10 % N, 10 % P2O5 and 10% K2O

mixing two or more nutrient sources together to form a blend mixed fer lizers

Nitrogen sources include ammonium nitrate (33.5-0-0), urea (46-0-0), sodium nitrate (16-0-0) and liquid nitrogen (30-0-0). Phosphorus is provided as 0-46-0 and potash as 0-0-60 or 0-0-50

Introduc on

Terminology and Defini ons

Interna onal Associa on for Standardiza on (ISO) and Associa on of American Plant Food Control Officials (AAPFCO) Fer lizer (AAPFCO):

Contains important quan es of no more than one of the primary plant nutrients (N, P, or K). Has 85% or more of its plant nutrient content present in the form of a single chemical compound. Is derived from a plant or animal residue or by product or natural material deposit which has been processed in such a way that its content of plant nutrients has not been materially changed except by purifica on and concentra on.

Soil Condi oner Material added to soils, the main func on of which is to improve their physical and/ or chemical proper es and/ or their biological ac vity.

Introduc on

Liming Material containing one or both of the elements calcium and magnesium, generally in the form of an oxide, hydroxide, or carbonate, maintain or raise the pH of soil.

Straight Fer lizer: nitrogenous, phospha c, or potassic fer lizer having a declarable content of only one of the primary plant nutrients, i.e. nitrogen, phosphorus, or potassium.

Compound Fer lizer: A fer lizer that has a declarable content of at least two of the plant nutrients nitrogen, phosphorus and potassium, obtained chemically or by blending or both.

Granular Fer lizer: formed into par cles of a predetermined mean size.

Coated Fer lizer Granular fer lizer that is covered with a thin of a different material in order to improve the behavior and/ or modify the characteris cs of the fer lizer.

Fer lizer unit The unit mass of a fer lizer nutrient (in the form of the element or an oxide) generally 1 kg.

Plant Food Ra o The ra o of the numbers of fer lizer units in a given mass of fer lizer expressed in the order N P K.

Fer lizers

EECA (Russia and Ukraine)

West Asia (Iran, Qatar, Saudi Arabia)

Sr. No. Name Loca on Product

1 Fauji Fer lizer Company Limited Plant I Rahim Yar Khan Urea

Plant II Rahim Yar Khan Urea

Plant III Mirpur Mathelo Urea

2 Fauji Fer lizer Bin Qasim Limited Plant I Bin Qasim Urea

Plant II Bin Qasim DAP

3 Engro Fer lizer Limited Plant I Dharki Urea

Plant II Bin Qasim NPK

Plant III Dharki Urea

4 Dawood Hercules Chemicals Limited Sheikhopura Urea

5 Fa ma Fer lizer Company Limited (Pak Arab Fer lizer Limited)

Plant I Multan Urea

Plant II Multan NP

Plant III Multan CAN

6 Fa ma Fer lizer Company Limited Plant I Rahim Yar Khan Urea

Plant II Rahim Yar Khan CAN

Plant III Rahim Yar Khan NPK

7 Agritech Limited Mianwali Urea

8 Hazar Phosphate Fer lizers Limited Haripur SSP

9 Lyallpur Chemicals & Fer lizers Limited Jaranwala SSP

11 are in Punjab, 6 in Sindh and 1 in Khyber Pakhtunkhwa

Urea

Uses

Main N2 fer lizer Ca le feed supplement (protein food supplements) where it is cheap As an ingredient in the manufacture of melamine plas cs and various adhesives (Urea Formaldehye, urea melamine formaldehyde) in the manufacture of resins and coa ngs Tex les an -shrink agents and ion exchange resins intermediate in the manufacture of ammonium sulfamate, sulfamic acid and pthalocyanines.

Urea produc on

Urea import

Companies

Engro Fer lizers Ltd (Engro UREA)

Fauji Fer lizer Company Ltd (Sona Urea)

Dawood Hercules (Bubber Sher) Fa ma Fer lizer Company Ltd (Sarsabz Urea)

Agritech Ltd (Tara Urea)

Urea

Engro 2plants FFC 4plants Fa ma 2plants Dawood 1plants Agritech 1plants

Produc on

Reac on of ammonia and carbon dioxide at high pressure forming ammonium carbamate, which is then dehydrated by applying heat, forming urea and water:

2 NH3 + CO2 NH2COONH4 CO(NH2)2+ H2O Both reac ons take place in the liquid phase in the same reactor and are in equilibrium. Reac on 1 is fast and exothermic and essen ally goes to comple on under the industrial reac on condi ons used Reac on 2 is slower and endothermic and does not go to comple on The conversion (on a CO2 basis) is usually in the order of 50 80 %. The conversion increases with increasing temperature and NH3/CO2 ra o and decreases with increasing H2O/CO2 ra o.

Produc on

Equilibrium reac ons are hydrolysis of urea:

CO(NH2)2 + H2O NH2COONH4 NH3 + CO2 The hydrolysis reac on takes place in the presence

of water. Acids or alkaline solu ons accelerate hydrolysis forma on of biuret:

2 CO(NH2)2 NH2CONHCONH2 + NH3 forma on of isocyanic acid:

CO(NH2)2 NH4NCO NH3 + HNCO

Urea Processes

Once Through

Par al recycle

Total recycle (All new plants)

Once through

The once through process is simplest and least expansive (both capital and opera ng cost) Least flexible and cannot be operated unless some provision is made to u lize large amount of ammonia and off-gas.

Par al recycle

Part of the off gas is recycled back to the reactor. The amount of ammonia is reduced to 15% to that of once through that must be used in other processes. Investment cost is somewhat lower than the total recycle process, this advantage apparently does not compensate the inflexibility arising from the necessity to operate a co-product plant with mutual interdependency problems.

Total recycle

At an economical conversion rate of NH3 and CO2 to urea, the process is designed to efficiently separate urea from the other reac on components, to recover excess NH3, and to decompose residual ammonium carbamate to NH3 and CO2 for recycling into the process.

This is usually realized by stripping (s ll at high pressure) and subsequent depressurisa on/hea ng of the urea solu on or combina ons of both.

Total recycle

Total recycling processes Conven onal processes without stripping

CO2 stripping processes, e.g. Stamicarbon

NH3 stripping processes, e.g. Snamproge

Isobaric Double Recycling process (IDR), applying stripping with NH3 and CO2, e.g. Montedison

Total recycle

Total recycle

All unconverted NH3 and CO2 is recycled back to the reactor (99% conversion). No nitrogen co-product is necessary.

Most flexible urea process as it depends only NH3 and CO2 supply. Most expensive in investment and opera ng cost.

Urea Finishing Processes

Urea solu on from the synthesis/recycling stages of the process is concentrated via evapora on or crystalliza on to a urea melt for conversion to a solid prilled or granular product for use as a fer lizer or technical grade.

Prilling: Spinning bucket, shower head or acous c vibrators

All prilling tower have dust problem Induced dra , forced dra or natural dra . Inline cooling or fluidized bed cooling.

Granula on: Less dust problem, uniform size, be er crushing and impact, transport and handling strength.

Ammonium nitrate (AN) & Calcium ammonium nitrate (CAN)

nitrogenous fer lisers ammonium nitrate containing 33.5 34.5 % nitrogen

calcium ammonium nitrate containing less than 28 % nitrogen.

The world produc on of ANs is es mated to be 40 45 Mtonnes per year.

Fa ma Fer lizer Company Limited (Pak Arab Fer lizer Limited) Plant III Multan

Fa ma Fer lizer Company Limited Plant II Rahim Yar Khan

Ammonium nitrate

AN is produced by neutralizing 50 70 wt-% aqueous HNO3 with gaseous NH3

NH3 + HNO3 NH4NO3

The reac on is highly exothermic and proceeds rapidly. The heat produced is o en used to generate steam. The obtained AN solu on can be concentrated by evapora on. Most applied produc on processes comprise three main opera ons: neutralisa on, evapora on and solidifica on (prilling or granula on).

Ammonium nitrate

Neutralisa on is carried out in a two-stage neutraliser operates with

low pH in the first stage (acidic condi ons) neutral pH in the second stage.

The equipment can operate at a variety of opera ng pressures and temperatures. Pressure, temperature and concentra ons in most neutralisers are linked by the boiling point characteris cs of the AN solu ons, with only two of these variables being independent.

Ammonium nitrate

The thermal instability of AN requires:

small reactor volume pure (chloride-free) nitric acid avoidance of an excess of acid

Post treatment : AN is highly hygroscopic a apulgite, kieselguhr or clay are used

single-stage or two-stages

Calcium ammonium nitrate

CAN is a valuable source of nitrogen. As a fer lizer it can be applied for all types of soil and all plants. It is a nitrogen fer lizer supplying nutri ve elements (N as NH4+ and NO3-, Mg and Ca as carbonates). It is suitable for blending with other granulated fer lizers Commonly used on fruit, process and vegetable crops

Calcium ammonium nitrate

ammonium nitrate solu on with powdered limestone

CAN is preferred to ammonium nitrate in acid soils Calcium ammonium nitrate is obtained by

reac on of lump limestone with concentrated nitric acid addi on of ammonia to neutralize excess of acid

evapora on of the resul ng solu on prilling or flaking the melt

The resul ng product is a double salt, Ca(NO3)2NH4NO3 called calcium ammonium nitrate calcium ammonium nitrate granules are coated with thin layer of soap stone powder, which; acts as a protec ve coa ng and prevents the absorp on of moisture during storage and transporta on

Calcium ammonium nitrate

NH3 + HNO3 NH4NO3

CaCO3 + 2HNO3 Ca(NO3)2 + CO2 + H2O __________________________________________________

CaCO3 + NH3+ 3HNO3 Ca(NO3)2 + NH4NO3 + CO2+H2O

Prilling process 1 to 3 % China clay, kieselghur or calcined fuller's earth is used to

condi on the prilled CAN. Granula on process

Pug mill process Drum process

Cold spherodizer pro

Single supper phosphate (SSP)

Hazar Phosphate Fer lizers Limited Haripur

Lyallpur Chemicals & Fer lizers Limited Jaranwala

Produc on

SSP is an excellent source of three plant nutrients.

Phosphorous, Sulfur and Calcium

The manufacturing process depends on reac ng phosphate rock with sulfuric acid and the fer lizer contains about (16- 20 %) P2O5.

The net reac on proceeds as follows:

Ca3(PO4)2 + 2H2SO4 + H2 2PO4)2.H2O + 2CaSO4

Produc on

It is generally agreed that the reac on proceeds in two stages:

sulfuric acid reacts with part of the rock, forming phosphoric acid and calcium sulfate The phosphoric acid formed in the first step reacts with more phosphate rock, forming monocalcium phosphate.

Two reac ons take place concurrently, but the first stage is completed rapidly while the second stage con nues for several days or weeks.

Produc on

Step 1 Finely ground phosphate rock (34% P2O5 content) is mixed with sulfuric acid. The acid usually is diluted to 68% - 75% H2SO4 before it is mixed with the rock. When concentrated sulfuric acid is diluted, much heat is generated; many plants cool the acid in heat exchangers to about 70°C before use.

Step 2 The fluid material from the mixer goes to a den where it solidifies. Solidifica on results from con nued reac on and crystalliza on of monocalcium phosphate. The superphosphate is excavated from the den a er 0.5 - 4.0 hours. At this me it is s ll somewhat plas c, and its temperature is about 100°C.

Produc on

Step 3 The product is removed from the den and conveyed to storage piles for final curing, which requires 2 6 weeks, depending on the nature and propor ons of the raw materials and the condi ons of manufacture.

During curing, the reac on approaches comple on.

The free acid, moisture, and unreacted rock contents decrease, and the available and water-soluble P2O5 contents increase.

The material hardens and cools.

A er curing, the product from storage is fed to a disintegrator, usually of the hammer mill or cage mill type. The product from the mill is discharged onto an inclined screen of about 6-mesh size.

The material that fails to pass the screen is returned to the mill for further grinding.

Step 4 If granular superphosphate is desired, the product is granulated either before or a er it is cured. Granula on before curing has the advantage that less water or steam is required.

A er granula on, the product is dried in a direct contact dryer and screened; the fines are returned to the granula on unit.

Advantages

The process is simple, requiring li le technical skill and small capital investment. The economies of scale are minor; thus, small plants can be economical. Since the process is not capital intensive, there is li le advantage of a high percentage u liza on of capacity. In fact, many SSP plants operate on a planned seasonal schedule. The fer lizer effec veness of SSP is unques oned. In fact, it is a standard of comparison for other phosphate fer lizers. SSP supplies two secondary elements, sulfur and calcium, which are some mes deficient in the soil.

H2SO4 (NH4)2SO4 20%Nammonium sulfate

HNO3 NH4NO3 33%Nammonium nitrate

CO2 (NH2)2CO 45%Nurea

H3PO4 NH4H2PO4 11-18%Nammoniated phosphates11-48-018-46-0

HNO3/rock phosphate nitric phosphates

NH3 +

Monoammonium phosphate (MAP) & Diammonium phosphate (DAP)

Uses of MAP and DAP

Used as non-chloride N, P compound fer lizer

Used in manufacturing of yeast, vinegar, yeast foods, and bread improvers

Used as a fire preven on agent for fabric, mber and paper, as well as a fire preven on

coa ng, and dry powder for fire ex nguisher

For food grade, it is mainly used as a fermenta on agent, nourishment agent

Produc on of MAP and DAP

Ammonium phosphates are manufactured by reac ng anhydrous NH3 with H3PO4. Types of ammonium phosphate which are

monoammonium phosphate (MAP, NH4H2PO4)

diammonium phosphate (DAP, (NH4)2HPO4)

Produc on of MAP and DAP

Monoammonium phosphate (MAP) NH3 with H3PO4 gives MAP. It is a fer lizer or

fer lizer intermediate with high P2O5 content of about 55% and nitrogen content 11-12%.

Diammonium phosphate (DAP)

With more ammonia, technical grade DAP containing 16 -18% nitrogen and 46% P2O5 is formed.

Produc on of MAP and DAP

The two principal steps are Neutraliza on

Granula on

Reac ons

NH3 + H3PO4 NH4H2PO4

NH3 + NH4H2PO4 (NH4)2HPO4

TVA Process

Produc on of MAP and DAP

Neutraliza on

Quan es of NH3 with H3PO4 in the neutraliza on step are different for MAP and DAP.

To manufacture MAP, NH3 / H3PO4 ra o is 0.6 in the neutralizer and then 1.0 in the granulator.

While for DAP, NH3 / H3PO4 ra os are 1.4 and 1.0 in the neutralizer and granulator respec vely.

Produc on of MAP and DAP

Neutraliza on The exothermic reac on heats the slurry nearly to the boiling point (130°C). Unreacted and excess NH3 vapor is collected from the top and recharged for reducing NH3 losses (less than 3%). The hot slurry containing about 16 to 20% water is pumped into the granulator, where more ammonia is added to increase the molar ra o to approximately 2.0.

Produc on of MAP and DAP

Granula on Slurry from neutralizer is mixed with KCl and absorbed in a bed of dry recycle fer lizer moving through a rota ng drum granulator. This provides a tumbling ac on to coal recycle material with a slurry film. Drier reduces the moisture to less than 1%, with 10 minute contact

me with air ini ally at 1500C. Dried product is separated into three frac ons on a double deck screen.

A por on of the product from the deck of the lower screen is sent to bagging opera ons. The balance, together with pulverized oversize and fines, is returned to the granulator.

Major engineering problem

Ammonia losses Ammonia loss should be kept below 3%. It can be achieved by using mul stage reactors along with efficient recycling mechanism of collec ng the vapour of ammonia from top of the neutraliza on tower and recycle back to the process.

Corrosion Use of corrosion resistance material like SS316 for hot acid and fumes ducts, carbon steel for granula on, drying and screening