first urea granulation plant in brazil...the granulation plant is designed to receive the molten...

IFA Technical Symposium Sao Paulo, 10-14 March 2008

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First Urea Granulation Plant in Brazil

-The highest product quality and the most energy saving process-

RENATO PEREIRA DA SILVA Fábrica de Fertilizantes Nitrogenados – Sergipe(FAFEN-SE) Petróleo Brasileiro S.A. (PETROBRAS)

EIJI SAKATA

Toyo Engineering Corporation

1. INTRODUCTION

Petroleo Brasilleilo S.A (PETROBRAS) started the commercial operation of first urea granulation plant in Brazil, which process is the Spout-Fluid Bed Urea Granulation Process owned by Toyo Engineering Corporation (TOYO).

This granulation plant has been constructed beside the existing urea plant of Fábrica de Fertilizantes Nitrogenados – Sergipe(FAFEN-SE) of PETROBRAS built by TOYO in 1982. The plant has been successfully commissioned and achieved the first production of granular urea in Nov. 2007.

TOYO is well known not only as a world leading engineering contractor but also as a major license owner of Urea Process Technologies since its establishment in 1961. The Spout-Fluid Bed Urea Granulation Process, to produce the large size urea product with the feature of the highest product quality and the most energy saving, is one of the Urea Process Technologies owned by TOYO. It has been applied for 17 urea plants from 50 MT/D to 3,250 MT/D production capacities in single train as a sufficiently proven and reliable process. (See Table-1) TOYO has been awarded a contract for this granulation plant in 2005.

This paper introduces the TOYO’s technology of Spout-Fluid Bed Urea Granulation Process and the project of the first granulation plant of PETROBRAS in Brazil.


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2. TOYO’s SPOUT FLUID BED UREA GRANUALATION PROCESS

TOYO started the establishment of a urea granulation process based on a Spouted Bed type urea granulator and expanded its own Technical range to provide a variety of urea fertilizer products since 1980’s in addition to the conventional Urea Prill Product and Urea Solution Product.

In late 1990's, TOYO further improved its design of the granulator by applying the Spout-Fluid Beds for the granulator, which is a combination of the spouted beds and fluidizing beds and reduces energy requirements and improves the quality of the product granules. (See Fig.-1)

In the granulator, spouting bed is formed by an upward stream of air introduced into the bottom of the granulator and fluidized bed is formed surrounding the spouting beds.

The air introduced into the spouting bed maintains that the particles remain in suspension. The droplets of urea solution fed to the bed through the spray nozzles are deposited on the surfaces of suspended seed particles. Thus the particles gradually grow up in layer-upon-layer.

Since air introduced for spouting and fluidizing has effects on cooling and drying, the spout-fluid bed granulator has functions of a cooler and a drier. By the drying function, 96% urea solution can be fed to the granulator to obtain a product with a moisture

Table-1: List of TOYO’s Urea Granulation Plant


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content of 0.3% or less. These functions with feeding urea solution give lower biuret product and lower utility requirement in the Granulation Plant than molten urea feeding case.

Droplet size of sprayed urea solution on seed particle in Granulator by spray nozzle is one of the key parameter to improve the drying function and the shape of product. The smaller droplet size of urea solution realizes the more surface area contacting with spouting hot air at the spouting pipe and more uniform and thinner film on seed particle surface. They will accelerate the vaporization of water in Urea Solution by efficient contact with spouting and fluidizing air. More uniform film will help to realize the sphericity (roundness) of product shape. And the smaller droplet size also eliminates the agglomeration of product.

The multi spray nozzle with four small nozzles is adopted in the granulator developed newly by TOYO. The multi spray nozzle realizes the smaller droplet size by more number of spray nozzles without increasing the size of granulator and the number of spouting pipe.

The droplet size of multi spray nozzle has been confirmed by water spray test and the result shows big improvement for droplet size without atomizing air from the conventional spray nozzles of full cone type with single outlet hole.

Fig.1: Illustration for Spout-Fluid Bed Granulator

Optimal Arrangement of Multi-stage Spouted Bed– Round and Uniform Product– High Drying Efficiency

Recycle Seed

Urea Solution

Fluidizing AirSpouting Air Product

Fig.-2: Conventional Spray Nozzle and Multi Spray Nozzle


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3. PROCESS DESCRIPTION

Fig.-3 shows the process flow of TOYO’s Granulation Process configured this Spout-Fluid type granulator. The urea solution or molten urea is fed on the spouting urea seeds through the multi spray nozzles to enlarge the recycle particles (seeds) in the granulator. The water in the feed urea solution is evaporated by spouting air on the spouted beds in the granulator to produce the urea granules. The enlarged granules are cooled to a suitable temperature by fluidizing air on the internal fluidized beds in the granulator. Coarse urea granules produced in the granulator are screened to separate the product size granules from over and under size granules through the double deck screen. Small sized granules are recycled back to the granulator as the seed and over sized granules are crushed through the double roller type crusher and recycled back to the granulator together with the under sized granules as the seeds. Exhaust air from the granulator and cooler is scrubbed in the wet type dust scrubber to recover the urea dusts in the exhaust air. Recovered urea dusts through the dust scrubber are recycled back to the urea plant for the recovery.

Fig.-3: Process Flow Diagram


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4. PROCESS FEATURE

The features of TOYO Urea Granulation Process are given below:

(1) High Energy Efficiency (2) High Product Quality (3) Low Emission TOYO Urea Granulation Process was developed to meet the current demand for high quality urea product and energy saving.

(1) High Energy Efficiency

TOYO Urea Granulation Process requires less utilities consumption than other granulation processes.

Almost all of energy for Granulation Process is consumed as the power normally for Air fan, blower, Pump and the transportation equipment. 80% of total power is utilized for air fan and blower. Therefore, the reducing the power consumption for air fan and blower is the most important point for energy saving.

TOYO has succeeded to minimize the head and flow rate of air fan and blower by following features.

a) No compressed air for atomization.

TOYO’s Urea Granulation Process utilizes single (liquid) phase spray nozzle with spouting air. The compressed air for atomization is not required. The less pressure drop for spouting air saves the power for blower.

b) Optimal bed depth minimizes pressure loss in the granulator;

The combination of spouted bed and fluid bed is the feature of TOYO’s Urea granulation Process. The solution is sprayed in the spouted bed and fluid bed has the functions of conveying and cooling the particles. It is not necessary to keep high level for fluid bed, which leads low power consumption of fluidizing air blower.

c) Smaller pressure drop dust scrubber.

Packed bed type dust scrubber designed by TOYO realizes the both of the low pressure drop and the high efficiency for dust reduction. The low pressure drop through dust scrubber leads low power consumption of induced fan.


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Following Table-2 shows the typical energy consumption of TOYO’s Urea Granulation Process.

Table-2 Utility Consumption (typical)

Steam 0.01 MT/MT *1)

Power 23 kWh/MT *2)

Cooling Waterｒ Nil

Note*1) Depend on ambient condition and concentration of urea solution feed.

Note*2) Depend on Plant Capacity and process scheme. In case Bulk Flow Cooler is applied instead of Fluidizing cooler for product cooling, the power consumption can be reduced to 19 kWh/T.

(2) High Product Quality

TOYO Spout-Fluid Granulation Process produces the highest quality product, owing to the following functions:

(a) Cooling – low biuret formation

As the granulator cools dries and solidifies the urea solution or molten urea feed rapidly, biuret formation is negligibly small.

(b) Drying – low moisture and high hardness

The granulator dries the granules so that the moisture content in the product become low enough to have sufficient hardness.

(c) Suspending – round and uniform product

Rounder and more uniform product is obtained, compared to other granulation processes, because the seed particles are suspended in the spouted bed during the granulating process.

As a result of the above three functions, the granular urea product is quite resistant against fracture and caking during storage and transportation.


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Following Table-3 shows the typical product specification of TOYO’s Urea Granulation Process.

Total Nitrogen 46.3 wt.%

Biuret 0.8 wt.%

Moisture 0.2 wt.%

Formaldehyde 0.45 wt.%

Size 2 - 4 mm 95 wt.%

Hardness 3.5kg/granule for 3 mm

Various sizes of granular urea product in accordance with market demand and applications, is produced simply by changing the screen mesh sizes as shown in Photo-1.

(3) Reduction of Urea Dust Emission

Urea dust in the exhaust air from the granulator and the product cooler is a major concern of air pollution in a urea plant. Optimal air velocity for spouted bed and through free board area of granulator minimizes the dust formation in the granulator.

Table-3: Product Quality (Typical)

Photo-1: Various Size of Urea Product


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And the Uniquely designed (Packed Bed type) low pressure-loss dust scrubber reduces urea dust to less than 30 mg/Nm3. Dust scrubber is located on the ground level as standard design. In case there is the limitation for available area, dust scrubber is provided on Granulator.

5. GRANULATION PLANT of PETROBRAS in BRAZIL

(1) Project Outline of first granulation plant in Brazil of PETROBRAS

Fábrica de Fertilizantes Nitrogenados – Sergipe(FAFEN-SE) of Petróleo Brasileiro S.A. (PETROBRAS) has started the production of 1100MTPD of prilled urea in 1982, which process has been TOYO’s Total Recycle-C Process. And the capacity has been increased to 1800MTPD in 1982. PETROBRAS has decided to produce the granular urea of 600MTPD with TOYO’s Spout-Fluid Bed Granulation Process in 2005.

Fig.4: Dust Scrubber (Packed Bed Type)

Fig.5: Urea Product of FAEN-SE


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Project outline for PETROBRAS’s Granulation Plant is summarized as Table-4.

Table-4 Project Data of PETROBRAS’s Granulation Plant

Plant Capacity: 600 MTPD Location: Laranjeiras,Sergipe Province, Brasil Process: TOYO Spout-Fluid Bed Granulation Process Scope of Work:

TOYO License & BDP Supply Critical Equipment Supply

CMM *1) Detail Engineering PETROBRAS Procurement, Construction and Commissioning

*1) CMM: Engineering Company in Brazil Project Milestone (actually achieved after contract effectuation)

2005 Feb. Project Started May Basic Design Package(BDP) was issued by TOYO 2006 Feb. Detail Design completed. 2007 Apr. Operation training in Germany. 2007 Oct. Mechanical Completion 2007 Nov. First Production of granular urea

Photo-2: Urea Granulation Plant of FAEN-SE, PETROBRAS


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(2) Outline of Process The Granulation Plant is designed to receive the molten urea from the top of existing prilling tower in urea plant. The molten urea equivalent to 600MTPD of urea granule is once stored in tank and pumped up to granulation plant. The process scheme in granulation plant is same as standard one described in Para. 3.

The existing storage house was extended to store the urea granule in addition to urea prill product.

Fig.-5: Process Scheme of FAEN-SE, PETROBRAS

Photo-3: Extended New Storage House for Urea Granule Product


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(3) First Production and Operation

The granulation plant has been commissioned smoothly and achieved first production and 100% operation successfully on Nov. 2007.

There were no significant problems during commissioning. The wire mesh of Screen was replaced several times to make the product size distribution better and finally achieved more than 95% for 2-4mm.

(4) Process Performance

Its performance has been confirmed by demonstration run conducted from Dec.21 to Dec.23 2007. Table-5 shows the results of demonstration run. The granulation plant has shown excellent performances, and they have fulfilled the requirement of product specification. Table-5 Performance Test Result of Granulation Plant

Item Unit The Result of performance evaluation

1.Production Capacity MTPD 601 2. Product Specification a) Nitrogen Content Wt％. 46.3 b) Biuret formation ｗｔ％ . 0.21 c) Moisture ｗｔ％ 0.3 d) Size Distribution （2-4mm）ｗｔ％ 95 3. Utility Consumption a) Power kWh/t-urea 28 b) Steam mt/t-urea 0.08

Photo-4: First Production of Urea Granule


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6. CONCLUSION

1. TOYO’s Urea Granulation Process is sufficiently proven and reliable. Already 17 plants has been applied in the world. The plant capacity reached to 3250MTPD with single train.

2. TOYO’s Spout-Fluid type Urea Granulation Process has the feature of the highest product quality and the most energy saving process.

3. First Granulation Plant in Brazil has commissioned successfully with excellent performance.

first urea granulation plant in brazil...the granulation plant is designed to receive the molten...

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