Table of Contents INTRODUCTION ....................................................................................................................................... 2 DAP FERTILIZER ................................ ....................................................... ........................ ............................... ............................. .................... 2 Overview ................................................................................................................................................. 2 History ..................................................................................................................................................... 2 Introduction ............................................................................................................................................ 3 Structure ................................................................................................................................................. 3 Properties ................................................................................................................................................ 4 Color .................................................................................................................................................... 4 Density ................................................................................................................................................ 4 Solubility .............................................................................................................................................. 4 Kinetics ................................................................................................................................................ 4 Chemical formula: ............................ ......................... ............................... ............................ ................ 4 Molecular weight: ................................ .......................... .......................... ............................ ................ 4 Storage properties ............................................................................................................................... 4 Specification ............................................................................................................................................ 5 Uses ........................................................................................................................................................ 5 fertilizer ............................................................................................................................................... 5 Fire retardant ...................................................................................................................................... 5 Yeast .................................................................................................................................................... 6 Medicine.............................................................................................................................................. 6 DAP industries in Pakistan ....................................................................................................................... 6 Process of DAP......................................................................................................................................... 7 TVA PROCESS OF GRA NULATION....................................................... ........................ ............................... ................................................... ...................... ............................. 7 Jaccobs-Dorrco process ........................................................................................................................... 8 INTRODUCTION ................................................................................................................................... 8 THE JACOBS SLURRY PROCESS ................................................................................................................. 8 Dry Section .......................................................................................................................................... 8 Wet Section ......................................................................................................................................... 9 REFERENCE ............................................................................................................................................ 11
1
FERTILIZERS INTRODUCTION Fertilizers fall into three general categories; nitrogen (N) based, phosphorus (P) based, and Combined nitrogen-phosphorus (N-P) based. The majority of nitrogen based fertilizers are derived from ammonia. In the 1990s, over95% of all commercial nitrogen fertilizer was derived from synthetic ammonia. Worldwide, the annual production of synthetic ammonia is about 120 million tons, of which about 85% is used in fertilizers, including urea.
DAP FERTILIZER Ammonium phosphate, particularly Di-ammonium phosphate (D.A.P) is the most popular phosphate fertilizer on worldwide basis.
Overview Until the 1950s, fertilizer manufacturing facilities were relatively small and produced fertilizers tailored to the soil needs of area farmers, commonly within a 100-mile radius. Prior to 1950, only 4 million tons of primary nutrients ± nitrogen (N), phosphate (P) and potassium (K) - were produced yearly. But in the late 1940s this began to change. Domestic agriculture and industry, as well as European and Western Pacific markets devastated in World War II, increasingly requested these nutrients. In the 1960s, the Tennessee Valley Authority (TVA) and the Land Grant Colleges began to promote higher analysis fertilizers so that more phosphate could be delivered to the farmers at lower costs and changed the way fertilizers were produced. In the 1960s, more concentrated phosphates began replacing normal superphosphate as the primary fertilizer commodity, turning what had been strictly a mining business into chemical production. This was especially true in Florida, which produces approximately 75% of the phosphate rock mined in the U.S. Phosphate rock is no longer sold for fertilizer manufacture. It is exclusively used to make phosphoric acid, almost all of which is used in the production of phosphate fertilizers.
History A scientist named Hennig Brand discovered phosphorus in 1669. He found it inside his own urine! Gross!!! Phosphate comes from bones and fossils of ancient animals. When land came out of water after the ice-age bones and fossils became phosphate. 2
People started mining phosphate in England. They mined it because they discovered that phosphate can be used for fertilizers. In England, phosphate mining started about 1850s. In 1880, Dr. C.A. Simmons found some rock that had phosphate in Central Florida close to the city of Gainsville. he knew it had phosphate because he sent it to Washington D.C. for analysis. In 1883 dr. Simmons tried phosphate mining. But, it did not work out and he closed his mine soon after. In 1889 Albertus Vogt discovered huge deposits of phosphate near Dunellon in Marion County. This started the Florida phosphate mining boom! Mr. Vogt started the first mining company in Florida. He named it Marion Phosphate Company. In 1886 John C. Jones and Captain W. R. McKee who enjoyed their Florida hunting trip, found phosphate around Peace River between Fort Meade and Charlotte Harbor. This phosphate was not a rock. It was a pebble! They started the Peace River Phosphate Company. They did not mine the phosphate, but sold leand to people to mine on it! This was the first phosphate mining in the Bone Valley Area. The news spread of "Florida's Black Gold". Soon, thousands of people swarmed Flroida in search of their riches. It was like the gold rush in California. there were many prospectors looking to find their own mines. There were also thousands hoping to find a good job.By the end of century there were more than 215 mining companies in Florida.Railroads were very important for mining. Miners could send phosphate to port of Jacksonville. Today, Florida produces 75% of the United States and 25% of world's phosphate. It has lots of land that still can be mined. Phosphate mining is slowly moving south where there are deposits that haven't been mined yet. Mining is done by huge companies. There are four phosphate companies in Florida: IMC Phosphates Company, Cargill Fertilizer, Inc., PCS Phosphate ± White Springs, and CF Industries, Inc. In a few months IMC and Cargill will merge to form a new company. So from 215 to 3 main phosphate companies, Florida still remains one of the world's largest phosphate producers.
Introduction Diammonium phosphate (DAP) (chemical formula(NH 4)2HPO4, IUPAC name diammonium hydrogen phosphate) is one of a series of water-soluble ammonium phosphate salts which can be produced when ammonia reacts with phosphoric acid. Solid diammonium phosphate shows a dissociation pressure of ammonia as given by the following expression and equation: (NH4)2HPO4(s) NH4H2PO4(s)
NH3(g )
+
Structure
3
Properties Color Colorless clarity rhombic crystal or white powder.
Density The relative density is 2.338.
Solubility It is soluble in water and insoluble in ethanol, acetone and ammonia. It decompounds at 155 centigrade
K inetics It is easy to lose ammonium and becomes ammonium dihydrogen phosphate in the air. React with ammonia and form triammonium phosphate
Chemical formula: (NH4)2HPO4.
Molecular weight: 132.06.
Storage properties Good storage properties Total water soluble phosphoric acid helps plants to utilize moisture better and let roots grow stronger and deeper even in acidic soils Being non- hygroscopic, DAP stores well even in high rainfall areas High concentration of nutrients makes packing, storage and transport per unit cost of nutrient very low Nitrogen is present in an easily absorbed ammonical form, loss due to leaching is thus minimum
4
Specification Moisture % by wt. Max
1.5
Total Nitrogen % by wt. Min
18.0
Ammonical Nitrogen from % by wt. Min
15.5
Total N2 in form of Urea, % by Wt. Max
2.5
Neutral ammonium citrate soluble phosphates as (P 2O5) % by wt. Min
46.0
Water Soluble Phosphate (as P2O5), % by Wt. Min
41.0
Uses f ertilizer DAP is used as a fertilizer. When applied as plant food, it temporarily increases the soil pH, but over a long term the treated ground becomes more acidic than before upon nitrification of the ammonium. It is incompatible with alkaline chemicals because its ammonium ion is more likely to convert to ammonia in a high-pH environment.
Fire retardant DAP can be used as a fire retardant. It lowers the combustion temperature of the material, decreases maximum weight loss rates, and causes an increase in the production of residue or char. These are important effects in fighting wildfires as lowering the pyrolysistemperature and increasing the amount of char formed reduces 5
that amount of available fuel and can lead to the formation of a firebreak. It is the largest component of some popular commercial firefighting products.
Yeast
DAP is also used as a yeast nutrient in winemaking and brewing mead; as an additive in some brands of cigarettes purportedly as a nicotineenhancer; to prevent afterglow in matches, in purifying sugar; as a Flux for soldering tin, copper, zinc and brass; and to control precipitationof alkali-soluble and acid-insoluble colloidal dyes on wool.
Medicine It is use in medicine and radio tube, also used in phosphorus, nitrogen high efficient compound fertilizer. Low arsenic grade is mainly used as nutrient.
DAP industries in Pakistan ENGRO fertilizer limited FFBL, Karachi
6
Process of DAP There are two processes for DAP manufacturing which are given below: TVA process Jaccobs-Dorrco process TVA
PROCESS OF GR ANULATION
The process developed in the TVA pilot plant involves partial ammoniation of phosphoric acid in a preneutrailzer and completion of ammoniation in a rotary ammoniator granulator. Granulation is controlled by recycling product fines to the drum. Addition of excess ammonia to the drum allows reaction to an NH 3:H3PO4 mole ratio of about 2.0, thereby decreasing the solubility of ammonia phosphates and improving control of granulation. The excess ammonia is recovered by scrubbing the gases from the drum with the feed acid before preneutralization. The granular material is dried and then screened to obtain a closely sized diammonium phosphate of 18-46-0 to 21-53-0 grade. N-P-K grades, such as 18-18-18, 15-15-15 and 14-35-14 and can be produced by adding other feed material. High analysis ammonium phosphate fertilizers are becoming more in demand as the trend toward production of higher analysis grades increases as a bulk blending increases in popularity. It is estimated that shipment of ammonium phosphate in 196061 was about 300,000 tons, or about 28% over 1959-60, and additional plant expansion is under way or planned. The tennesssee valley authority has developed on pilot scale a new and improved process for producing granular diammonium phosphate from ammonia and phosphoric acid. Much less recycle and drying of the product is required then in other ammonia phosphate granulation processes since the heat of reaction of ammonia and acid is used to evaporate the 80 to 90% of the moisture. The process can be used in a TVA type ammonia granulation plant by adding a scrubber and preneutrlizer. The product is of uniform size and has a very good storage and handling properties. At least three new commercial scale plants already have been built to use this process and other manufacturers are considering this process in their plants for entering the rapidly expanding market of granular ammonia phosphate. In the pilot plant work diammonium phosphate was used alone or with other fertilizer material to make a variety of grades. Satisfactory results were obtained with electric furnace or wet phosphoric acid and either gaseous or liquid ammonia. The grades of diammonium phosphate ranged from 21-53-0 to 18-46-0, depending on the amount of impurities in the acid. Grades such as 14-35-14 and 18-18-18 were made by adding potassium chloride and ammonia ammonium nitrate solutions.
7
Jaccobs-Dorrco process INTRODUCTION
No matter the industry, every company is looking for ways to reduce costs and increase profits. In the manufacture of diammonium phosphate fertilizer (DAP), there are many methods available to cut costs which are not being utilized as much as they should. This paper will focus on various design options that yield a high rate of return on investment. The design options that will be investigated are as follows: Granulator Pipe Reactor in conjunction with a Preneutralizer Dual Mole Scrubbing Recycling Dedust Gas to the Combustion Chamber Ammonia Vaporization using Tail Gas Scrubber Liquor Ammonia Air Chiller These options result in a reduction of fuel consumption in the Dryer, a reduction of citrate insoluble P2O5, and reduction in the amount of strong phosphoric acid needed which increases the amount of power that can be generated from sulfuric acid production. Each one of these options will be compared against a base case that does not contain any of these options to determine the rate of return of investment for each. Then a final case including all of the design options will be compared against the base case. In the case of a plant revamp the loss of profit from downtime will be considered as well. All the options described in this paper can also be applied to the production of MAP and ammonium phosphate based NPK¶s.
THE J ACOBS SLURRY PROCESS Dry Section A simplified process flow diagram for the Dry Section of the Jacobs Slurry Process can be seen on page 14. Phosphoric acid, gaseous ammonia, and scrubber liquor enter into the Preneutralizer where it is controlled at a specific gravity of 1.53 and a mole ratio of 1.5, which corresponds to a moisture content in the slurry of 18%. The mole ratio is the DAP Plant Optimization number of moles of nitrogen divided by the number of moles of phosphorous. The Preneutralizer is maintained at a mole ratio of 1.5 to ensure maximum solubility of the slurry. The ammonium phosphate slurry is pumped from the Preneutralizer to the Pipe Reactor where it is combined with strong phosphoric acid, and gaseous ammonia and sprayed onto the bed of the Rotary Granulator at a mole ratio of 1.5 and a moisture of 10%. Underneath the bed in the Granulator is the Ammonia Sparger that supplies liquid ammonia to raise the mole ratio of the fertilizer up to the desired value. The material leaves the Granulator and enters into the Rotary Dryer where the DAP is dried, using hot gases leaving the Combustion Chamber, to a moisture of 1.0-1.5% or even lower if 8
needed. After exiting the Dryer the material enters into the Primary Elevator to be distributed over the Oversize Screens. The Oversize Screens are double deck screens where the oversize is sent to the chain mills, the undersize falls onto the Recycle Belt along with the crushed material, and the product size material is sent to the Product Screen Elevator for distribution on the Product Screens. The purpose of the Product Screens is to remove the remaining fines that were not removed by the Oversize Screens. The fines fall onto the Recycle Belt and the on spec material enters into the Fluidized Bed Cooler or is recycled for control of the recycle ratio. The air entering into the Fluidized Bed Cooler can be chilled using the Ammonia Air Chiller which will be discussed later. Once leaving the Fluidized Bed Cooler the material enters into the Product Elevator and is distributed onto the Polishing Screens. The on spec material then enters into the Coating Drum and is then conveyed to the storage building. The gases leaving the Dryer, Product Cooler, and Dedust system are each sent through a separate set of cyclones. After the dedust gas exits the cyclones it is sent through a Baghouse to be sent to the Combustion Chamber. If this method of recycling dedust gases is not in place then the gases are sent to the RG Scrubber. The gases leaving the Dryer Cyclones go to the Dryer Scrubber and the gases leaving the Cooler Cyclones go the Tail Gas Scrubber. Wet
Section
A simplified process flow diagram for the Wet Section of the Jacobs Slurry Process can be seen on page 15. Ammonia laden gases exiting the Preneutralizer and Granulator first enter into the Prescrubber where they are scrubbed with a liquor at a mole ratio of 1.4 where 60-70% of the ammonia is absorbed. Once exiting the Prescrubber the gases enter into the Reactor Granulator Scrubber (RG Scrubber) where the gases are scrubbed with a liquor at a mole ratio of 0.7. The gases exiting the Dryer go through a cluster of cyclones and enter into the Dryer Scrubber where the gases are scrubbed with the same liquor that is used in the RG Scrubber. The liquor that is used in the RG Scrubber and the Dryer Scrubber is circulated from the Scrubber Tank. Gases from the RG Scrubber and Dryer Scrubber along with the gases that exit the Cooler Cyclones enter into the Tail Gas Scrubber and then exit into the atmosphere. The circulating liquor in the Tail Gas Scrubber is sent through a kettle type heat exchanger to vaporize ammonia. The purpose of the Pipe Reactor is to supply ammonium phosphate slurry at a low moisture content thereby reducing fuel requirements in the drying step. The Pipe Reactor mixes high strength phosphoric acid, gaseous anhydrous ammonia, and reactor slurry from the Preneutralizer and sprays it onto the bed of the Granulator. The reason the Pipe Reactor can operate at such a low moisture is because of the high temperature and pressure which keeps the slurry fluid. Under atmosphere pressure the slurry reaches a minimum moisture content of 18% and in the Pipe Reactor it can be as low as 10%. The moisture content in the Pipe Reactor is reduced by vaporizing water from the high heat of reaction of phosphoric acid and ammonia.
9
Another reason why the Pipe Reactor is economical is because it reduces citrate insoluble P2O5. Citrate insoluble P2O5 increases with increased retention time, and since the retention time of a Pipe Reactor is very low there is virtually no citrate insoluble P2O5 produced in the Pipe Reactor. The average citrate insoluble P2O5 can be reduced by 0.2% when a Pipe Reactor is used. The Preneutralizer mixes phosphoric acid, ammonia, and scrubber liquor to be sent to the Pipe Reactor or directly to the Granulator. The phosphoric acid and scrubber liquor are fed through the top of the reactor while the gaseous anhydrous ammonia is fed through spargers located at the bottom. Jacobs uses the reduced retention time Preneutralizer where the diameter at the bottom of the tank is smaller than the top. The advantage of this design is that the citrate insoluble losses are decreased while still maintaining the liquid level necessary to absorb ammonia and to not entrain liquid in the exiting gas. The citrate insoluble losses increase with increased retention time so it is necessary to minimize the liquid volume in the Preneutralizer. The Preneutralizer is much simpler to operate than the Pipe Reactor and when used in conjunction with the Pipe Reactor it gives the plant a stable baseline and increased controllability. Using a Preneutralizer reduces the amount of water that is vaporized in the Granulator by the Pipe Reactor. If less water is vaporized in the Granulator then less air is needed to keep the gas leaving the Granulator below the saturation point. For a 130 stph plant, the required airflow in the Granulator when a Pipe Reactor and Preneutralizer are installed is 44,000 ACFM and when there is only a Pipe Reactor present is 88,000 ACFM. This reduced airflow reduces the size of the Granulator, Prescrubber, RG Scrubber, RG Fan, Scrubber Pump and the Tail Gas Scrubber and Pump. The overall capital to install a Preneutralizer is less than the capital needed to upgrade all the equipment previously mentioned.
10
REFERENCE http://www.gsfclimited.com/di_ammonium_phosphate.asp?mnuid=3 http://chem.chemicalrawmaterials.com/phosphate/19079-diammonium-phosphate-dap-nh4-
2hpo4-products.html http://sxtermei.com/Details1312.html http://www.indexmundi.com/commodities/?commodity=dap-fertilizer¤cy=pkr http://en.wikipedia.org/wiki/Diammonium_phosphate
11
