SUCCESSFUL REHABILITATION PROJECT FOR MINES COMPANY

By: Paul A. Smith

This report was not available at the time this book was prepared.

( PRAYON - RUPEL TECHNOLOGIES S.A. Ucensing Division rue Joseph Wauters 144, B-4480, ENGIS - BELGIUM Tel.: +32/41/73.93.41 Fax.: +32/41/75.09.09

SUCCESSFUL REHABIUTATION PROJECT

FOR

JORDAN PHOSPHATE MINES COMPANY

AT

AQABA,JORDAN

by

Mr. Paul A. SMITH

of

PRAYON - RUPEL TECHNOLOGIES, ENGIS, BELGIUM

Presented at the AIChE Clearwater Conference - May 1994 4

1

SUCCESSFUL REHABIUTATlON PROJECT for JORDAN PHOSPHATE MINES COMPANY at AQABA, JORDAN

Summary

The Phosphoric Acid Plant commissioned in Aqaba, Jordan in 1982, based on a Dihydrate Process incorporating a Single Reactor and a Single Filter, was unable to reach its nominal capacity due to several process and equipment deficiencies.

Due to the fact that this unit was an integrated part of the overall complex,

consisting upstream of two Sulphuric Acid Plants of 1800 mtpd [1980 stpd) H2SO. and down stream DAP facilities of two lines of 1150 mtpd [1265 stpd) product each, the shortfall in acid production seriously affected the operation and consequently the financial results of the complex as a whole.

In 1989 Jordan Phosphate Mines Company (JPMC), owner of the Fertilizer Complex, decided to rehabilitate the Phosphoric Acid plant to achieve the nominal capacity, product quality and yield. After reviewing several available options, JPMC chose to convert the plant to one based on the multl­ compartment PRAYON Mark 4 Process.

In this paper the performance of the Reaction, Fiftration, Concentration and Cooling Water sections of the plant before and after rehabilitation are reviewed along with the major boHle-necks encountered during the former years of operation, along with a description of the process modifications made and the results of the performance test.

The historical information on the original plant performance was provided by JPMC but additional information will be available when JPMC presents a paper in October at the IFA Technical Conference in , Jordan. 2

SECTION 1

PROCESS DESCRIPTION OF ORIGINAL ( PLANT AND REVIEW OF PROBLEMS

A flowsheet of the original plant design is attached as Figure 1 and a plan layout is shown in Figure 2.

Phosphate Grinding

The design specification for the phosphate feed to the reactor was 75% through 200#. Due to mill problems, some of the ball charge had to be removed in 1984 and from that time the ball mill has operated close to 65% through 200#, even though the throughput was lower due to capacity limitations caused by other operational problems.

Reaction

The single reactor, with a useful volume of 1250 m3 [330,200 US Gal], a specific volume of 3 1 m /mtpd P20 S [240 US Gal/stpd], is agitated by a single central agitator designed to incorporate the phosphate in the slurry and to homogenize the reactional mass. Screw type agitators act as surface coolers and some of them are also used to disperse the sulphuric acid through the slurry. As the available reactor surface was limiting for air cooling, additional cooling was provided by diluting the sulphuric acid down to

80% H2S04 and removing the heat of dilution in dilution coolers. The principal problems were the following .-

Poor performance of the dilution coolers (low capacity & scaling)

Insufficient cooling, requiring operation at a lower strength to prevent Hemihydrate

formation (26-27% P20 5 )

Poor crystal formation

Cake efficiency 93 - 94.4%, lower than design (95.5%)

Average capacity of 60-73% of nameplate capacity.

Filtration

The filter selected was a UCEGO N°12 with three washes but the poor quality of the gypsum meant that the water soluble losses were much higher than expected. The design wash cycle was once every two days but the high reaction temperature and the lack of maturation volume caused severe filter scaling, resulting in the need for frequent mechanical cleaning of the cloth support grids and frequent cloth changes. 3

Evaporation

The evaporator design basis was to concentrate 1250 mtpd [1375 stpd] P20S from 30 - 54%

P20 S in three parallel lines. Each line was fitted with one block heat exchanger and one flash chamber.

The units neither reached the design instantaneous capacity nor the design on-stream factor due to scaling problems in the blocks. In addition, the increased evaporation load due to the lower strength of weak acid aggravated the problem. The poor performance of the cooling water pond (see Cooling Water) meant that the design vacuum was difficult to obtain and this increased the problem of scaling even more.

Cooling Water

The cooling water return was fed to a cooling pond with surface sprays to increase efficiency. However the capacity was only 60% of the design and even at the reduced production rate the cooling water feed temperature was often as high as 45°C [113 oF] and not the 30°C [86 OF] as expected.

c 4

SECTION 2 ( PRAYON PHILOSOPHY

Flash-cooling

The PRAYON process, since its origins, has been characterised by a multi-tank design with flash-cooling, which has proved to have greater flexibility than air-cooling especially when cooling capacities above the nominal capacity are desired.

The low level flash-cooler, LLFC, was incorporated Into the Mark 4 design to enable the operation of the flash-cooler circuit without scaling and with a low energy consumption even at cooling rates above the design capacity. The high recirculation rate is ensured by a low head, high flowrate axial flow pump with a low power consumption and giving a aT of about 2°C [4°F] under design conditions.

Dilution cooling

Although the Mark 1 and 2 PRAYON designs had dilution of H2S04 to 50-60% H2S04 and removal of the heat of dilution in coolers, since the 1970's the PRAYON Mark 3 and subsequent Mark 4

designs have been characterised by the feeding of 98% H2S04• To attain this aim the Mark 3 design was specifically modified by the deletion of the dilution coolers and included the boosting of the flash-cooler

capacity to balance the total cooling load, this also enabled the feeding of phosphate slurry. The H2 S04 dilution cooling system previously used had a very bad image and many operators of Mark 1 and 2 units were well aware of the maintenance headaches that these units have caused.

Digestion Section

The Mark 3 units also heralded the provision of a digestion section to ensure full de­ supersaturation or maturing of the slurry prior to the filtration stage thus minimising filter scaling and down­ time, due to less frequent washing and cleaning. The normal standard split for a PRAYON reactor Is 66% for Attack and 34% for Digestion this is shown in Figure 3. By changing the point of introduction of the sulphuric acid the volume of, or the residence time in, the "Low Sulphate Zone" can be adjusted to be larger or smaller.

Obviously the original design at Aqaba did not incorporate this experience

As such the proposal for the Rehabilitation of the Aqaba unit required a great deal of creativity to Incorporate the existing equipment into a flowsheet that resembled a PRAYON unit and more importantly was able to perform as well as a PRAYON unit. 5

SECTION 3

PRAYON FEATURES INCORPORATED INTO THE REHABILITATION DESIGN.

The plan layout of the rehabilitation is shown in Figure 4 and the flexibility of the "Low Sulphate Zone" can be adjusted as in the PRAYON standard design, see Figure 5.

Reaction Volume

The reaction volume was increased, almost doubled, by the provision of five additional tanks, two in the AHack section and three in a newly created Digestion section. The final total volume was 3 3 2530 m [670,000 US Gal] giving a Specific Volume of 1.9 m /mtpd P20 5 [455 US Gal/stpd P20J. The final spilt of volumes was 67% for the AHack and 33% for the Digestion. Although the split follows the PRAYON standard the large size of the existing tank means that this is equivalent to a number of smaller compartments. An overall view of a 3-D computer layout is shown in Figure 6 - New Reaction Section.

Phosphate feeding

Two highly agitated square tanks were added each with a volume of 220 m3 [52,700 US Gal) both fitted with a three stage agitator, two PRAYON 4-PHT helicoidal sets of blades in the slurry and one PRAYON GTA at the surface, the agitator drawing 119 kW. The phosphate was diverted from the old reactor to the first of these tanks where it is was mixed with the cooled recycle flow from the flash -cooler. The return acid from the filter is fed to the first and/or second square tank pre-mixed in a Mixing Tee with part

of the 98% H2S04•

The slurry returns to the main reaction tank by two overflow channels. The layout of the New Attack Tanks is shown in Figure 7.

Main Reador

Very few changes were made to the main reactor except for the deletion of the dilution

coolers, the balance of the 98% H2 S04 being added to the dispersers fitted to three of the surface agitators. The suction pipe to the flash-cooler was inserted into this compartment and the flow to the flash cooler is effected by the suction of the vacuum in the flash body.

Flash Cooler

The low level flash cooler, LLFC, of approximately 7 metres [23 ft) diameter was installed between the main reaction tank and the two additional tanks. The recirculation pump was fiHed on the outlet and provides a large flow of 10,600 m3/h [42,300 US GPM] with an axial flow pump having a TDH of less than 0.9 metre [3 ft), absorbed power 91 kW. The vacuum system was oversized considerably compared with the standard quantity of non-condensibles expected in the multi-tank PRAYON reactor but even so, it was found that the gassing in the existing reactor was much greater than expected and the capacity of the vacuum system had to be increased to cope with the greater load of non-condensibles.

(

'--'- -p- - ---_ ... ' -- -'- -- .... ~-- 6

Digestion Section

The existing filter feed pump was re-routed to feed a battery of three digestion tanks In line each with a useful volume of 280 m3 [74,000 US Gal). The level of agitation in these tanks required being solely that to ensure solids suspension, each tank was fitted with a one stage agitator with a power of 51 kW. The computer layout of the Digestion Section is shown in Figure 8.

The filter was converted to a two-wash design.

Concentration Units

These three units suffered the most radical changes, the original units had low circulation block heat exchangers with a high 8T and the conversion to Sigri carbon fibre reinforced tubes with a high recirculation meant that many changes had to be made. The circulation ducts had to be increased in size and this included the branches on the flash-chamber. In order to reduce the 8T to 3.3 °C [6 oF] the pump capacity had to be increased to 8,500 m3/h [37,400 US GPM) and the existing mixed-flow centrifugal pump was replaced with an axial flow design. The heat exchanger was fitted with 805 x 50/37mm [2/1.75 Inch) (id/od) tube of 7 metre length giving a total effective heat transfer area based on od of 870 m2 [9360 ffJ. The layout of the New shell and tube heat exchangers is shown in Figure 9.

Cooling Waler

The existing COOling pond was greatly undersized and also caused pollution problems within the complex due to the drift of the acidic water. As such it was decommissioned and a new 18 cell forced-draught cooling tower system was installed. 7

SECTION 4

PERFORMANCE OF THE PLANT AFTER REHABILITIATION.

The rehabilitation project was completed on time and a test-run was performed at the end of February 1994.

The performance of the plant was outstanding with all sections surpassing capacity, quality and efficiency guarantees, except for one item. The original sheets signed by the client and contractor are included in Annex 1 and show the level of performance attained.

Some comments on these results are required to fully understand the extent of the success of this project. The guarantee values are in brackets.

The main guarantee parameters were measured during a continuous 72 hour period, the capacity of the unit was tested during a 7 day period including one wash cycle (7 hours for the Reaction and Filtration (R&F) section and 12 hours for the Concentration section).

CAPACITIES

The following Table shows the performance of the Reaction & Filtration and Concentration Sections during the test run.

J I mtpd P205 I stpd P20 5 I Attained Guarantee Attained Guarantee

R&F

Insf. capacity 1371 1310 [15111 [1444]

Weekly capacity 9176 8750 [10115] [9645]

CONCENTRATION l?d~ 'J-t~-1)

Inst. capacity 4528 4290 (4991) (4729) I?D9 {:P '/'

Weekly capacity 9618 9310 [10600] [10260] \-;'1-1

Cooling Tower

Attained the design duty of 90 x 108 kCal/h [357 x 108 BThu/h, giving a cold water temperature of 29.8 °C [85.6°F], (guarantee 30°C [86°F] 8

QUAUTlES

Dilute phosphoric acid

The average P205 content was 28.13% (28) and the sulphate expressed as H2S04 was 2.15% (2), this value was slightly above design but in fact the 504 in the concentrated acid was below the guarantee value, see below.

Concentrated acid

The P20 5 was 52.53% (52) and the H2SOiP205 ratio was 0.0634 (0.0715) whilst the solids content was 2.38% (3.5).

Fluosiliclc Acid

The strength of the Fluosilicic Acid was 22.32% H2SiF8 (20) with a P20 5 content of less than 100 ppm (150).

YIELDS

Reaction and Filtration

On filter cake basis, the efficiency was 95.83% (95.5).

Concentration

The efficiency was over 99.99% (99.8). 9 SECTION 5 CONCLUSION

The challenge of a "fixed price turn-key" revamp is not an easy one to accept, particularly due to the unknown quality of equipment at the time of bidding. PRAYON along with their partners on this project, COPPEE LAVALIN and BOUYGES, managed to complete this difficult task, within schedule, whilst easily attaining the guarantee values. Our thanks must also go to the client who provided us with the chance to demonstrate the value of our technology.

The client JPMC, after the test, made a maximum performance trial and managed to obtain over 1500 mt [1650 stpd] P20 S in a 24 hour period, this whilst maintaining the acid strength above 28% P20 S and an efficiency over 95%. These values also show that JPMC should be well pleased with the future potential of this unit now converted to the PRAYON philosophy.

There are many other cost savings besides these concrete figures, that could be expected following the philosophy of PRAYON, but could not be guaranteed being difficult to quantify. The reduction in down-time and Increase in overall efficiency, due to the extension to weekly washing of the filter means that the annual capacity will be increased and the production cost will be decreased. The consumption of filter cloths also shows signs of being at least a half and probably a third of the previous figure. The concentration units designed by COPPEE also show that they are capable of running at a washing cycle of almost double the design figure of once/week and will of course also give reduction in maintenance costs due to the integrity of this design of exchanger.

JPMC is now equipped with the tools in phosphoric acid production to make the most of the other units on their complex and are at present implementing a programme to revamp their sulphuric acid units to match the increased performance of their phosphoric acid units and a project to increase their granulation capacity. 11

ANNEX 1

OFFICIAL TEST RUN RESULTS

( REHABILITATED PHOSPHORIC ACID PLANT CLAUSE 26.3 PERFORMANCE GUARANTEES Sheet: 1/2

SUMMARY OF RESULTS OBTAINED OURJNG THE TEST RUN

Test Run period: from the 2310211994 at 10:30 h to the 02103/1994 at 10:30 h. I I -

L- 26.3.1 Cacacities Guarantee , Obtained ,Units I ,I , Dilute onosohonc ac:d , , a P2CS instantaneous ProduCllon , , Date : 25i02l1994 , RlJnI1lO9 time: 24 , 24 ,consecutive hours Production : 1310 1371 ;M T P205 b P,os :lroguc:ion Calla9£'! , , I , Date · , 2:1/02 to 02103194 , ~. Runnrng time : 161 , 161 'consecutive hours Washing time : 7 , 7 ,hours Production : 8750 9176 'M T P205 Concentrated ohosohonc .aCid , , a P20S ,nstantaneous Production Date : , 26 to 28/02194 , . _.. _------.-----r------, ---.. ~unnrng dme : 72 , 72 ,consecuti'Je hours " ProdUcbon · 4290 ' 4527.8 'MTP20S--- P2CS :lrOCUc:Jon C.J!2ac~ I , I " Dare I 2"3/02 :0 0210:3/94 I Runmng arne . 156 , 15-6 ,consecutive hours Washlll9 time : --,-_12 , 12 ~urs ____•• _ ProdUction . 9310 , 9618 1M T P20S Coolina rower ( 5 hours test I , , Heat removal cacacrty NLT 90 GGO 000 I 90 000 000 'kCal/h F!lr dry bUlb temc. 45 , 45 ," C , Y;-C wer bulb temc. 24 24 , I , I 26.3.2 Qualities , I a Dilute ohosohoric acfd , I , I ( on solids free basis) I I P205 NLT 28 I 28,13 101. wlw Free H2S0" NMT 2 , 2.15 ,% wlw b Concentraced ohosohoric aCid ( on solids free basis) P20S NLT 52 : 52.53 ;% wlw H2SO4 I P'Z05 NMT 0.0715 , 0,0634 , R2031 P20S NMT 0.027 I 0.016 ,I MgO I P205 NMT 0.015 I 0,006 ( as such) , , Solids content NMT 3.5 -. 2.38 '% w/w

SiW1atures Emolover ~~ con:rnct~ .0 .~. 0. Qr~ . 1 .. ___e=z- n y6 _ "F?'? $'."" • - llOU YGUES - COPPEE LAV ALIi ...... J.P.M.~. Aqaba - Jurdail REHA81LJTA TED PHOSPHORIC ACID PLANT -- CLAUSE 26.3 PERFORMANCE GUARANTEES Sheet: 212 SUMMARY OF RESU~TS OBTAlNED DURING THE TEST RUN

--- Test Run period: from the 23/0211994 at 10:30 h to the 02103/1994 at 10:30 h.

Guarantee I Obtained I Units I ,I ,I , b Fiucs/fic:c add , , F asH2SiF6 NLT 20 , 22,32 '0/0 wtw n05 NMT 150 I 99.67 ,pom c Water at the coolina tower outlet Temo!!ratlJre ( eXlr.!OOiaie I 30 I 29.8 IQ C --• <: I I ,I .. -- 26.3.3 Yieids { P205 Recoveru I a· Dilute acid NLT 95,5 , 95.83 1~/o -_.- • I' , b- Concentrated acid NLT 99.8 99.996 ,10,<, .-- ,I , 26.3.4 Raw Materials and Utilities consumotion L L LP Steam on concentration NMT 2 , 1.9 'T I T produced P205 r-- , , Industnal waler NMT 7 , 6,95 I TIT prodUced P2C6 .-- E!ec:ncal Power NMT 63 , 49.82 'KWH I T oroduced P20S , , 26.3.5. Effluents , , .. - a- In the Stacks , , I F NMT 10 9.63 9 I T ?'205 led b- From the cooling tower , , Onttlosses NMT 0,02 , 0.0004 ; % 01 c:rcula1inq ~ow

26.4 . Exoected frigures Expected I Obtained 'Units Fiucsilic:'c ac:d , I --'- I , a- CdOBClty ,I · - H2SiF5 100 ~{, 81 149.5 'M T per 24 hou~ I , , I b- Cua/ity Fe20J 70 ,I 9,94 ,ppm 504 1000 7,61 'ppm CI 3500 I 3053 'ppm

[~ I .- r Signatures I . EmQlo~er Contrac1n ~ , J . ,-- y\ ..g. (j)r~ , ~- . , ,..---, r--J I . . "i1ifJi~~;, ~-.. ~-. "':ri:..u. ')1',/r"l~ "'i'l' " , J L L L L r - ! . rl J' .~. , '... . ':: " ~ n I,--, ,- : ~ L \ , \ I-I \ r II II , ~ \ n I!

UOUYGlJES - COJ'I'EE LAVAUN J.P.M.C. Aqaba i PHOSPHORIC ACID PLANT ITEST RUN

SUMMARY OF PRODUCTION CAPACITIES DILUTE ACID CONCENTRA TED ACID H2SiF6

Duralian Prodllctian Ouralian Production >. at Run Capacity of Run Capacity RJ Dale: ------IP205)---- ,_(:~~51_[ __ _C_ap~c~~ ___ 0 hours %w/w ------melric Ions P205 ------hours %w/w melric Ions P205 ------lTIetric Ions H2SiF6

23/02/1994 18:30 1044,1 52,48 1 ------_. ._----- ... _ ..... _.. --. ... . ??!~7. " . ~97~,7 ...... ~~!t?~ ... . _ ..

2 24/02/1994 24:00 27.75 1377,8 52,26 . 1~9t?!~ .. . 1~1,4~ . __ ...... , 3 25/02/1994 24:00 28,45 1371,5 52,84 1489,2 . '" ... 11~1~? ......

4 26/02/19994 .. ... 23:45 5?- !57 . 14~~P -----._---_. _ - _...... ?~,?9 1~?1 ! ~ ". 1?~,?~ .... "

5 27/02/1994 23:40 ~? , 28 138,20 I ... _--_._- .------.,.- _... - . ?~I~? l~~Q!? .. 14~~.~ . , , ' • .. - '...... • ...... I

23:29 52.70 15445 8 28/02/1994 ?~I~ 1 1~37!B , ... ' - -- '--'- --_._-_ .. - ' --" --'-- ~ ...... 1~?,?'9

_L... _ ... ___ Q.1!Q~! ~~1. .... _. ___ .. ~4~Qq . . ~~,Q~ 1~88,7 ~2,56 .11~?1~ ...... 1?9t~~ ...

02/0311994 0:24

Total 161 :48 28,13 9222 156:00 52,53 9618 972

7 day8 production: Reaction filtration 161 9176 .. _... _.... J~f._1~.! .. h~.':!.~.~... ~~~.h!.f.1.9 ...... , ...... Concentration 7)l24 • 12 h washing: 156 • 9618 972

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lULU. RID EVAPORATOR SlOlA6EIAHK FlUOSIlltlt ACII QtU'4l~'f JORDAN PHOSPHATE MINES CO. LTD. AClABA CHEMICAL INDUSTRIES COMPLEX AAU4 - JO"DAH D_ 5.... U_ D.J." ·PHOSPHOlIC ACID P20- , e" flOW DIAGRAM FIGURE 1- A~ cess tAU blolCO. ENG- PRo-020 Figure 2

Gas to scrubbers

Orlglna' Reaction System. Aqaba Prayon

L::, ,":' I Low Sulphate Figure 3

'iiWM Optional Sulphate III High Sulphate #2 #1 #6 ~ Digestion v

#3 #4 #5

PAyon "'ade 314 •• Compartments (2 of Digestion) Prayo n Figure 4 - Layout

Gas t .... "'",rllhh"'r..

Phosphate

Phosphate Attack Section Digestion Section Modlfled Reaction System - Aqaba Prayon

QLOwsulPhate Figure 5 - Sulphate Profile Mi:it4 Optional Sulphate

• High Sulphate

&I Digestion

Phosphate

Phosphate Attack Section Digestion Section g.SO f./r~ Modified Reaction System - Aqaba Prayon :2 "c t-- c.J w en z "c -t- c.J

rn a: w f.Q 2 c:c :c c.J ~ w u.a a2 := I- ~ ....I .....~ :c U) 3: w :2

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