treatment of waste water effluents from the azomures

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Treatment of Waste Water Effluents from the Azomures Nitrogen

Fertilizer Complex in Romania

N. ARION Arionex Wasseraufbereitung

Bodenmattstrasse 8, 4153 Reinach, Switzerland

Azomures is a compact nitrogen fertilizer complex located in the centre of Romania, in Transylvania. Hitherto the waste effluents discharged from the complex, containing ammonia and/or ammonium nitrate, have been treated by steam stripping, which removes only ammoniacal nitrogen. The stripped effluent containing nitrate (NO3

-) is discharged to the river after pH correction and dilution with raw water. The desorbed NH3/H2O gas is sent to the ammonium nitrate plant, where ammonia is neutralized with nitric acid.

On account of the high cost of this treatment and the penalties for discharging nitrates into the environment, Azomures has taken the decision to install a new, modern closed-system (zero-discharge) waste water treatment plant to recover all materials involved as valuable products, such as demineralised water, ammonia gas and ammonium nitrate for recycling to the process plants. The ammonia- and ammonium nitrate-containing waste water stream will be initially treated in by steam stripping to remove free ammonia in two modern stripping units. The stripped effluent, containing ammonium nitrate but only traces of ammonia, will be desalinated in two fully-automatic Fertarex ion-exchange demineralisation units, in which the exhausted cation resin is regenerated with 58-60% nitric acid and the exhausted anion resin is regenerated with 12-15% NH3. Because the plant will be fully automated, the operating staff requirement is eexpected to amount to only 1-2 persons per shift.

Arionex Wasseraufbereitun, with Iprochim (Bucharest) ass sub-contractor, is supplying know-haw, basic and detail engineering, special equipment, valves, instruments, electric and control panel, as well as the complete automation system. Construction began in September 2003, and the expected start-up date is April-May 2005. The total capital cost is estimated at €5 million EUR. Taking into account the value of recovered products and savings on the high cost of the existing treatment and penalties, the return on capital (ROC) is estimated to be less than 2½ years.

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Fertilizer plant waste effluents present a continuous threat to the environment on account of the relatively important amounts of nitrogen compounds, such as urea, ammonia (NH3) and ammonium nitrate (NH4NO3), along with rain and uncontrolled run-off waste water discharged from the process plants. Furthermore, depending on the technological level of the process plants and on the local operating and maintenance conditions, the nitrogen content of the waste effluents may represent a nitrogen loss of between 0.5% and 3% of the fertilizer production capacity, and occasionally more.

The Azomures fertilizer complex, located in the centre of Romania, in Transylvania near the Mures river and close near Târgu Mures city (approx. 335 km. far from Bucharest), was started-up in 1966. At present the complex comprises two ammonia plants (each 300,000 t/a), one urea plant (300,000 t/a), three nitric acid plants (each 240,000 t/a), 1 complex (NPK) fertilizer plant (100.000 t/yr), 1 (AN) ammonium nitrate plant (400.000 t/yr), one calcium ammonium nitrate (CAN) plant (450,000 t/a), one melamine plant (16,500 t/a), one power plant and complete lines of off-sites and utilities. Azomures produces more than 1.3 million t/a of different fertilizers such as urea, melamine, CAN , AN, complex fertilizer (NPK), liquid fertilizer, etc., which are exported abroad.

ENVIRONMENTAL PROTECTION RULES The existing Romanian environmental protection rules limit the concentration of nitrogenous products in the river to 2 mg/l ammonium ion (NH4

+) and 25 mg/l nitrate (NO3-). Under a special

agreement with the local environmental authorities, Azomures is at the moment allowed to discharge waste effluents with larger nitrogen concentrations into the river Mures as long as they do not exceed 20 mg/l NH4

+ and 120 mg/l NO3-, i.e. a max. of 50 mg/l total nitrogen. The discharge of

higher concentrations than the permitted limits is penalized by paying taxes per each supplementary amount (kg) of nitrogen. This arrangement, however, expires at the end of 2006.

EXISTING TREATMENT SYSTEM Installed in 1970-1971, the existing waste water treatment system removes only free ammonia and the ammoniacal nitrogen of ammonium nitrate. After treatment by NaOH alkalising, steam stripping and neutralizing with sulphuric acid, the discharged treated effluent, containing traces of ammonium sulphate and a large amount of NO3

- as sodium nitrate, is discharged to the river. For

the environmental control, pH-value, NH4+ and NO3

- concentrations in the discharged effluents are

continuously monitored.

Table 1: Amount and composition of existing waste water effluents

Contaminant Urea NH3 NH4NO3 Origin of the waste water effluent

Flow rate, m3/h

g/l kg/h g/l kg/h g/l kg/h Urea plant 14 - 19 0.1 - 0.5 4 90 - 100 1400 -- -- NH3 plants 0.8 –1.0 -- -- 160 - 190 140 -- -- NH4NO3 (AN+CAN) plants 50 - 60 0.0 0.0 2 - 4 150 4 - 7 360 Melamine plant 10 - 12 2 - 4 27 0.4 – 1.0 5 -- --

Figure 1 is a block flow diagram of the existing treatment system.

Current cost Owing to the high chemicals (NaOH, H2SO4) and steam consumption, the treatment cost for 2004 has been estimated to €2.0-2.2 million, of which approximately €1.15 million was incurred in the treatment of the effluents from the ammonium nitrate plants (equating to €2.6-2.9 per m3) and about €0.9 million in the treatment of the urea, ammonia and melamine plant effluents (€6.1-6.4 per m3).

Treatment of Waste Water Effluents from the Azomures Nitrogen Fertilizer Complex in Romania

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THE NEW EFFLUENT TREATMENT PLANT Because there is not much time before the special agreement with the local environmental authorities lapses, and on account of the high existing waste water treatment costs and the dual the economic burden resulting from the loss of approximately 2,300 t/a of nitrate discharged in the treated waste water and the from the concomitantly high environmental penalties, Azomures decided to install a new, modern waste water treatment plant working as a completely closed system without waste effluents (a zero discharge system).

Technical considerations When designing a fertilizer waste water treatment system, various factors, some time-related, influence the selection of the different treatment processes. It is obvious that before any definite proposals can be made, a study is required to determine the waste effluents to be treated, its normal and uncontrolled volume and composition, any possibilities for reducing volume and concentration before treatment; and available options for final disposal or recovery after treatment. The process should be able to ensure, on a continuous, uninterrupted basis, treatment according to specification of plant effluents and the recovery and return to the process plants of all valuable constituents of the effluents, including demineralised water, ammonia gas and ammonium nitrate solution. No single treatment process is capable of fulfilling this requirement universally. The final choice of the optimal treatment process or processes will depend on such things as the regulations issued by the Environmental Protection Authority, the reliability and economics of the process, and the ability of the main process plants to re-utilise the recovered materials safely and economically. All these factors have to be considered carefully to ensure that factors such as process requirements, capital and operating costs and amortisation period are reconciled.

A techno-economical study concerning the treatment of the Azomures waste water effluents, carried out in September 2002 by Arionex Wasseraufbereitung, Switzerland, selected a combination of two

FIG. 1: EXISTING WASTE WATER TREATMENT PLANT AT AZOMURES

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processes for the new waste water treatment system: a steam stripping process for removing free ammonia followed by demineralisation of the stripped effluents by a special ion-exchange system (the Fertarex process). The following are the main advantageous features of the selected processes.

Ammonia stripping process • A simple and reliable process for removal of NH3 from waste water effluents • High stripping efficiency (99.94 to 99.99%) • High concentration of ammonia in NH3/H2O overhead vapours • Low ammonia content in the stripped waste water (<100 mg/l NH3) • Use of existing residual low pressure steam, available at the site at low cost • Use of the existing connection lines for feed waste water, utilities, power supply, etc • Re-use of existing equipment, such as stripping column, heat exchangers, etc., after revamping • Use of existing know-how and experience of the steam stripping process.

Fertarex ion-exchange process • Very effective, safe and reliable process for removal of NH3 and NH4 NO3 from large flows of

contaminated effluents containing 25-100 eq/m3 NH4+ and 25-90 eq/m3 NO3.

• Use of minimum quantities of special ion-exchange resins owing to short-cycle operation. • Low salinity of treated water owing to counter-current operation of the ion-exchangers. • Regeneration of the ion-exchange resin with HNO3 and NH3, products which are locally

manufactured and therefore available at low cost. • Production of highly concentrated regeneration effluents (18-25% NH4NO3) owing to the

regeneration of the cation and anion resins with 58-60% HNO3 and 12-15% NH3 respectively and the selective fractionation of the cation and anion resin regeneration effluents.

• Safe cation resin regeneration system with 58-60% HNO3 due to special ion-exchange resins, the very short contact time between the nitric acid and the cation resin and the cooling of the cation resin regeneration system.

• Completely closed system, without waste effluents, with recycling of all materials involved back to the process plants, i.e. an absolute zero discharge system.

This special ion exchange process, patented in 1968 in Romania, has been in use since 1976 without any mishaps in several fertilizer effluent treatment plants. A reference list is given in the Appendix.

DESIGN DATA Table 2 shows the design flow-rates and composition of the discharged waste water effluents.

Table 2: Effluent flow rates and compositions

Contaminants Urea NH 3 NH4 NO3 Origin of the waste effluent

Flow rate m3/h

Temper-ature

°C

Oil mg/l

Other salts meq/l mg/l kg/h g/l kg/h g/l kg/h

Waste condensate from NH4NO3 plants 70 max. 50 nil 0.01 --- --- 3.5 245

max. 4 - 6 420 max.

Waste effluents from urea and NH3 plants 23 max. 50 nil 0.05 30 0.5 155 2770

max. nil nil

Rain and/or uncontrolled run-off waste water 3 max. 18 0.1 1 – 3 10 0.03 --- --- 2 - 4 12

Total 96 0.53 3015 420

Treatment plant No. 1 (AN plant waste condensate) The design composition of 3.5 g/l NH3 (205.9 eq/m3 NH4

+) and 6 g/l NH4NO3 (75 eq/m3 NH4 NO3), together representing a very high ammonium (NH4

+) load of 280.9 eq/m3, make it impossible to treat the effluent economically by ion-exchange alone. Therefore free ammonia (3.5 g/l NH3 i.e.


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245 kg/h NH3) has to be removed in a preliminary steam stripping stage before the ion exchange treatment.

Ammonia stripping unit no. 1 Figure 2 is a diagram of the stripping units of the No. 1 and No. 2 treatment plants.

Pump P1/A feeds contaminated condensate at a rate of 70 m3/h, containing approximately 245 kg/h NH3 and 420 kg/h NH4NO3, from tank TK1 through pre-heater HE-1 and ejector EJM-1 to the top of stripping column A25. The feed liquid flows downwards across several separation slot trays, in countercurrent with low-pressure (144°C) steam, which is introduced into the column at the bottom. The stripped condensate, with a content of less 100 mg/l NH3, leaves the bottom of the column and passes through pre-heater HE-1 and then, via pump P1/B, through cooler HE-5, from which it passes at 35°C to ion-exchange unit no.1. The desorbed NH3/H2O vapour leaves column A25 as overhead and is partially condensed in condenser HE-3, after which the rest of the NH3/H2O vapour is separated from the condensate in separation vessel VS-1. The separated condensate, containing 4.5-5% NH3, is reintroduced, along with the feed water, through ejector EJM-1 into stripping column A25. The NH3/H2O-vapour from VS-1 is further condensed through final condenser HE-4 from which the resulted 12-15% NH3 solution is sent, for further treatment, to ammonia stripping unit no. 2.

Table 3 (overleaf) shows the technical data of ammonia stripping unit no.1.

Ion-exchange demineralisation unit no. 1 As shown in Fig. 3, the stripped condensate discharged from ammonia stripping unit no.1 contains at the most 5,900 eq/h NH4

+ and 5,300 eq/h NO3-. It is collected in tank TK2 and mixed together

with other waste water effluents recycled back from the ion exchange process with a content of approximately 300 eq/h NH4

+ and 370 eq/h NO3-.

FIG. 2: INTERCONNECTED STRIPPING SYSTEMS OF NOS 1 AND 2 TREATMENT PLANTS

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The mixed contaminated effluent, with an ionic burden of maximum 6,200 eq/h NH4+ and 5600

eq/h NO3-, is sent by pumps P2/A,B,C to ion-exchange demineralisation unit no.1. The ionic NH4

+ and NO3

- charge is continuously monitored by on-line analyser AIA NH4/NO3.

The demineralisation unit consists of three up-flow, packed-bed cation filters FC-1/A,B,C (two in operation, one in regeneration stand-by), three up-flow, packed-bed anion filters FA-1/A,B,C (two in operation, one in regeneration stand-by), two mixed-bed filters FPM/A,B (one in operation, one in regeneration/stand-by), a regeneration station, a chilled water cooling station, a motor control centre (MCC), several local control panels (LCP) and other facilities for the full-automatic operation and control of the ion-exchange process. The cation and anion exchanger are operated in parallel; therefore each cation filter can be connected with each anion filter. Because of the high NH4

+ and NO3- ionic load, the cation and anion exchangers have been designed for a short-cycle

system, with a service run of 160 minutes minimum for the cation filters and 180 minutes minimum for the anion filters. Regeneration takes 60 minutes maximum for the cation resin and 67-70 minutes for the anion resin. Because there are always two cation and two anion filters operating simultaneously, one cation filter and one anion filter have to be regenerated approximately each 80-

Table 3: Ammonia stripping unit no. 1 Capacity and dimensions of main equipment

Technical characteristics Equipment

Flow-rate kg/h

Steam kg/h Type, area, internals Dimensions, mm

Pre-heater HE-1 70000 Plate heat exchanger S=147.6 m2 2000 x 800 x 1900 Stripping column A25 75400 7500 26 Kühni RF slit trays type BV Ø 2200 x 9700 Condenser HE-3 68500 Platular welded plate heat exchanger S=22.6 m2 2000 x100 x 600 Separation drum VS-1 4900 Cylindrical drum with conical bottom Ø 800 x 1000 Condenser HE-4 1917 Vertical tube/shell heat exchanger S=80 m2 Ø 600 x 5000 Cooler HE-5 75600 Plate heat exchanger S= 58.8 m 2 1200 x 800 x1900

FIG. 3: ION-EXCHANGE DEMINERALISATION UNIT NO. 1


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90 minutes. Therefore no filter is on stand-by for more than about 20 minutes. The mixed-bed filter has a service run of at least 140 hours and the regeneration of the mixed cation/anion resins takes 4 hours.

Operating cycle The feed water is fed at a rate of 60 m3/h, controlled by flow meter FIQ, to the bottom of each cation filter (FC-1). The water flows upwards through two cation resin (R-H) compartments, which remove NH4

+ ions. Afterwards the decationised effluent, containing HNO3 and NH4+ leakage,

leaves the cation filter at the top and is fed, across resin trap FR-1 and flow controller FIQC, into an anion filter FA-1 at the bottom. The acidic effluent flows upwards through two weak anion resin compartments (R•) which remove nitric acid. The treated demineralised water, containing traces of NH4NO3 leakage and with a conductivity of 5-30 µS/cm, leaves the anion filterat the top, via control valve FCV and resin trap FR-3. From anion filter FA-1 the demineralised water flow, mixed with the demineralised water flow from the parallel anion filter, is sent at a rate of 120 m3/h to mixed-bed filter FPM, via flow controller FIQC. Approximately 50 m3/h of demineralised water are recycled via control valve FCV to tank TK2. The rest (about 70 m3/h) is fed in at the top of the mixed-bed filter FPM and flows downwards across the mixed-bed (cation-anion) resin, which polishes it to a conductivity value of less 0.1 µS/cm. It flows thence to tank TK3, from which it is sent by pumps P3/A,B,C to consumers or for use as boiler feed water or process water. Part of the produced demineralised water is used as service water inside ion-exchange demineralisation units nos 1 and 2.

The demineralisation process is represented by the following equations:

Cation resin: NH3 + NH4NO3 + R-H ⇔ RNH4 + HNO3

Anion resin: HNO3 + R• ⇔ RH•NO3

During the demineralisation the quality of the decationised water after the cation filter FC-1 is monitored by a pH meter, while that of the demineralised water after the anion exchanger FA-1 is monitored by a conductivity- meter. When the cation resin in one of the filters becomes exhausted, the ammonia slip increases and so the pH value of the decationised water leaving the cation filter rises. Similarly, when the anion resin is exhausted, the amount of NO3

- ion and NH4NO3 leaking through increases and, with it, the conductivity of the demineralised water. When the pH value from the cation exchanger or the conductivity value from the anion exchanger exceeds a predetermined value, the automatic process control system (PLC) triggers the following operating sequence in the corresponding ion-exchange system:

• The stand-by (freshly regenerated) ion filter goes on load • The exhausted cation filter goes off load • Internal regeneration of the exhausted resin begins

During regeneration the exhausted cation resin (RNH4) and the exhausted anion resin (RH•NO3) are converted back into their initially activated state by regeneration of the cation resin with HNO3 and of the anion resin with NH3, according the following equations:

Cation resin : RNH4 + HNO3 ⇔ RH + NH4NO3 Anion resin RH• NO3 + NH3 ⇔ R• + NH4NO3

Resin regeneration procedures Cation resin regeneration comprises the following steps:

• Cooling by rinsing with cold demineralised water • Counter-current elution with cold 58% HNO3 • Rinsing with cold demineralised water; and • Selective fractionation of the cation resin regeneration effluent, as

follows:

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• Fraction 1, containing 2-3% of eluted NH4NO3, which is recycled back to tank TK2

• Fraction 2, containing 95-97% of eluted NH4NO3 and approximately two thirds of the surplus HNO3, is collected, as product, in the neutralisation drum.

• Fraction 3, containing the rest of the eluted NH4NO3 and surplus HNO3, is collected in a tank. The diluted nitric acid solution is used for the anion resin conditioning.

Anion resin regeneration comprises the following steps :

• Conditioning with dilute nitric acid solution • Counter-current elution with 12-14% NH3 solution • Rinsing with demineralised water • Selective fractionation of the anion resin regeneration effluent, as

follows: • Fraction 1, containing 2-3% of the total eluted NH4NO3, is

recycled back to storage tank TK2. • Fraction 2, containing 80-90% of the eluted NH4NO3 and about

two thirds of the eluted NH3 surplus is collected in the neutralisation drum and mixed with fraction 2 of the cation resin effluent. The surplus HNO3 from the cation resin effluent reacts with the surplus NH3 in the anion resin effluent to produce supplementary NH4NO3.

• Fraction 3, containing approximately 10% of the eluted NH4NO3 and approximately one third of the NH3 excess, is collected in the regeneration drum, where ammonia gas is added in order to prepare a new ammonia solution for the next anion resin regeneration.

• Fraction 4, containing residual NH4NO3 and NH3 excess, is recycled back to TK2.

Table 4 shows technical data for ion-exchange unit no.1.

Resin backwash Backwashing of cation resin from FC-1/A,B,C and anion resin from FA-1/A,B,C is done externally by using cation resin backwash vessel CBV for the cation resin and anion resin backwash vessel ABV for the anion resin. When, during the demineralisation steps, the pressure drop across one of the resin beds inside cation filter FC-1 or inside the anion resin bed in FA-1 exceeds a pre-selected value, external backwash of this resin bed is required. It is estimated that this will be necessary once every six months. The resin is transported between ion-exchange filters FC-1/A,B,C and FA-1/A,B,C and the backwash vessels CBV and ABV hydraulically, using demineralised water.

Treatment plant no. 2 (urea and ammonia plant effluents) Ammonia stripping unit no. 2 The design for ammonia stripping unit No. 2 is shown in Fig. 2.

Waste water from the urea and ammonia plants flowing at a rate of 23 m3/h, along with 12% NH3 solution from stripping unit no. 1 containing approximately 2,770 kg/h NH3 and 234 kg/h NH3, are collected in tank TK11. Pump P1/A delivers solution form this tank to the pre-heater HE-11 and then, via ejector EJM-2, to the top of the stripping column A34. The feed liquid flows downwards across several high performance separation slot trays, in counter-current with secondary steam (130°C), generated by re-boiler RB-1, which is introduce into the column at the bottom. The


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stripped condensate, at a temperature of approximately 121°C and containing less than 150 mg/l NH3, leaves the column at the bottom, is cooled through pre-heater HE-11 and is then pumped by pump P11/B to ion-exchange unit no.2 across cooler HE-14. The desorbed NH3/H2O vapours leave column A34 at the top and are partially condensed through condenser HE-13, where the rest of NH3/H2O vapour is separated from the condensate in separation vessel VS-2. The separated condensate, containing approximately 19% NH3, is recycled to the inlet of ejector EJM-2 and thence to stripping column A34. The NH3/H2O-vapour from VS-2, with a content of approximately 3000 kg/h NH3 and 320 kg/h H2O, is sent to the ammonium nitrate process plant, where NH3 is neutralized with 58% HNO3. All equipment is made of stainless steel.

Table 5 shows the technical data of ammonia stripping unit no.2

Table 5: Ammonia stripping unit no. 2 Capacity and dimensions of main equipment

Technical characteristics Equipment

Flow-rate kg/h

Steam kg/h Type, surface S, internals Dimension. (mm)

Pre-heater HE-11 25000 plate heat exchanger S = 5.6 m2 900 x 600 x 300 Stripping column A34 27800 7400 32 pcs. Kühni RF slit trays type BV Ø 1300 x 7000 Condenser HE-13 6100 Platular welded plate heat exchanger S=32.4 m2 2000 x1500 x 600 Separatation drum VS-2 2780 cylindrical drum with conical bottom Ø 800 x 1000 Cooler HE-14 21700 plate heat exchanger, S= 24 m 2 1000 x 0.8 x1.9 Reboiler RB-1 30000 7300 plate heat exchanger S=131 m 2 1300 x 1100 x 2900

Ion-exchange demineralisation unit no. 2 Stripped condensate is discharged from ammonia stripping unit no. 2 at a rate of approximately 22 m3/h and, along with approximately 3 m3/h rain and/or uncontrolled run-off waste water filtered in gravel and activated carbon filters, is collected in tank TK-11 and mixed with waste water effluents recycled from the ion exchange process. The mixed contaminated effluent is sent by pumps P11/A,B-C to ion-exchange treatment unit No. 2.

The treatment unit consists of two up-flow, packed-bed cation filters FC-2/A,B and two down-flow operated anion filters FA-2/A-B The cation and anion exchanger are operated in parallel; therefore each cation filter is connected with each anion filter.

Table 4: Data for ion exchange unit no. 1

Pos Feature Units Cation filter FC1/A-C Anion filter FA1/A-C Mixed bed FPM/A,B 01 Total filters pcs 3 3 2 02 Filter in operation pcs 2 2 1 03 Filter in regener./stand by pcs 1 1 1 04 Flow rate each filter m3/h 60 60 70 05 Volume of treated water m3/cy approx. 160 approx.. 180 approx. 11170

eq/h 8289 as NH4+ 8450 as NO3- 4.2 as NH4NO3 06 Total ionic charge / filter eq/m3 51.8 47 0.05

07 Operation (service) length min /h approx. 160 approx. 180 approx. 140 hours 09 Diameter mm 1600 1600 1200 10 Cross section m2 2.0 2.0 1.13 11 Total height mm 6470 8700 5880 12 Material Stainless steel W.I 4541 13 Lewatit resin type SAC - K 2629 WBA - S 4428 SAC-S100/SBA- M510 14 Regeneration chemicals 58% HNO3 12% NH3 6% H2SO4 , 4% NaOH 15 Regeneration time min max. 64 max. 67 max. 240 16 Regeneration frequency min / h each 80 min. each 90 min. 136 h 17 Stand by time min /h 18 - 20 23 -25 136 h

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Operating cycle The feed water is fed at a rate of 20-35 m3/h via flow controller FIQC into cation filter FC-2, at the bottom. The water flows upwards through the cation resin compartment (R-H), which removes NH4

+ ions. Afterwards the decationised effluent, containing Cl-, NO3-, etc, and NH4

+ leakage, leaves the cation filter at the top and is fed across resin trap FR-1 into the top of an anion filter FA-2. The acidic water flows downwards through the weak anion resin bed (R•), which removes first SO42- ions, then NO3

- and Cl- ions. The partially-demineralised effluent, containing traces of NH4NO3 and NaCl leakage, with a conductivity of 15-30 µS/cm, leaves the bottom of the anion filter and is collected, via resin trap FR-2 and control valve FCV, in tank TK5. The produced partially-demineralised water, with a conductivity of 20-30 µS/cm, may be used as make-up water for the cooling tower system or as process water.

During the demineralisation step the quality of the decationised water after cation filter FC-2 is monitored by a pH-meter and that of the demineralised water after anion exchanger FA-2 is monitored by a conductivity meter. When the cation resin is exhausted, sodium (Na+) and ammonia (NH3) begin to slip through and, consequently, the pH value in the decationised water increases. When the anion resin is exhausted, the chloride (Cl-) and nitrate (NO3

-) slip increases and the conductivity of the demineralised water rises. The automatic process control system (PLC) triggers regeneration of the cation resin when the pH value exceeds 4.5 and of the anion resin when the conductivity exceeds 100 µS/cm. Once again, the sequence at the start of regeneration of either cation or anion filters is:

• The stand-by (freshly regenerated) ion filter goes on load • The exhausted cation filter goes off load • Internal regeneration of the exhausted resin begins

During regeneration the exhausted cation resin (RNH4) and the exhausted anion resin (RH•NO3) are reactivated elution with, respectively, nitric acid and caustic soda.

Table 6: Characteristics and operating conditions for ion-exchange unit no. 2

Pos Feature Unit Cation filter FC2/A-C Anion filter FA2/A-C 01 Total filters pcs 2 2 02 Filter in operation pcs 1 1 03 Filter in regener./stand by pcs 1 1 04 Flow rate each filter m3/h 20-35 20-35 05 Volume of treated water m3/cy min. 185 min. 190

eq/cy 344 as NH4+ 1200 as NO3- 06 Total ionic charge / filter

eq/m3 approx. 13.9 approx. 6.3 07 Operation (service) length min /h approx. 462 /7.6 approx. 462 /7.6 08 Diameter mm 1200 1200 09 Total height mm 4230 4590 10 Material Stainless steel W.I 4541 11 Resin type SAC- Lewatit K 2629 WBA - Lewatit MP64 12 Regeneration chemicals 58% HNO3 4% NaOH 13 Regeneration time min max. 95 max. 111 14 Regeneration frequency min each 370 each 340 15 Stand-by time min approx. 370 approx. 340

Resin regeneration The cation resin regeneration and selective fractionation procedures are identical with the procedures used in the No. 1 plant, with the exception that, since there is no nitric acid conditioning step in the anion resin regeneration, fraction 3 is recycled back to tank TK2.

Anion resin regeneration comprises the following steps:


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• Co-current elution with 4% NaOH solution • Rinsing with demineralised water and discharge of the alkaline regeneration effluent to the

neutralizing tank, where NaOH excess is neutralized by 6% H2SO4.

Table 6 shows the technical data of ion-exchange unit no.2.

Cooling station The 58% HNO3 nitric acid, resin rinse and cooling water used in the cation resin regeneration are cooled in plate heat exchangers in counter-current with chilled (5°C ) demineralised water produced by a fully automatic cooling system with a capacity of approximately 550 kW. The cooling system, using refrigerating liquid R 407, consists of one chilled water buffer tank, three recycling pumps, three screw compressors, each with 54.1 kW motor, one stainless steel evaporator and three condensers with copper tubes. The total power consumption of approximately 163 kW will be supplied by the power and control cabinet LCP-11.

Fig. 4 is a block flow diagram of the entire new treatment plant.

Power supply, control and automation Power will be supplied by two transformers, each rated at 1,000 kVA, connected by copper bars to the Motor Control Centre (MCC) by a double feed system, each 1,600 kVA. The MCC is provided with an intelligent motor management system, SIEMENS Simcode and two PLC SIEMENS Simatic S7-400. The control and automation system is based on the following independent control panels equipped each with SIEMENS PLC system, such as ET 200, Simatic S7-400 or Simatic 315.

1) MCP - Main Control Panel 2) LCP01 - Stripping unit no.1 3) LCP02 - Stripping unit no.2 4) LCP03 - Ion-exchange unit no.1 - cation filters

FIG. 4: NEW WASTE WATER TREATMENT SYSTEM

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5) LCP04 - Ion-exchange unit no.1 - anion filters 6) LCP05 - Ion-exchange unit no.1 - mixed bed filters 7) LCP06 - Ion-exchange unit no.2 - pretreatment filters 8) LCP07 - Ion-exchange unit no.2 - cation + anion filters 9) LCP08 - Regeneration station 10) LCP09 - Cooling station 11) LCP11 - On-line-analyser + 1 heating system

The local panels LCP-01 to LCP-08 are each provided with a mimic diagram with push buttons, which allows the semi-automatic operation of the pneumatic valves from the site. Communication between the MCC, MCP and the local panels LCP 01-11 will be achieved by Profibus connection. The visualising of all process units will be performed by Swiss system VISCONTROL operated by 2 PC and 2 visual displays with 19" flat monitors.

ECONOMIC ASPECTS In May 2003 the Swiss company Arionex Wasseraufbereitung, located in Reinach, won the contract to supply license, know-how, basic and detail engineering, special equipment (pumps, heat exchangers, condensers, etc), valves, instruments, electric and control panels and also for the automation system. The Romanian company Iprochim SA, Bucharest, as subcontractor, has supplied the basic engineering for the stripping unit, the detail engineering for equipment and piping lay-out, foundation, civil work, electric, cabling, etc.

The total capital cost is estimated at €5 million. Due to recovery of valuable products, such as demineralised water and ammonium nitrate, estimated at more than €1 million per year, the savings of the existing treatment cost, estimated at approximately 2 million per year, and avoid of payment of taxes and penalties to the local environmental authority, the return on capital (ROC) may be estimated to less than 2.5 years.

Construction of the plant began in September 2003. The expected start-up date of the various units is April-May 2005. Operating staff is estimated at 1-2 persons/shift.

References 1. Roland, L. D.: (Foster Wheeler Ltd): “The recovery of ammonium nitrate from fertilizer factory wastes”.

Physicochemical Methods for Water and Waste Water Treatment - Second International Conference, Lublin, Poland (Jun 1979).

2. Arion, N. (to IPRAN): “Procedeu pentru epurarea si valorificarea condensatelor bazice din instalatiile de fabricare NH4NO3 si uree”. RO 52205 (Sep 1967).

3. Arion, N. (to IPRAN): “Regeneration of ion-exchange resins”. GB 1331948 (Oct 1969). 4. Arion, N.: (IPRAN): “Traitement des eaux ammoniacales par échangeurs d’ions”. Informations Chimie No.

103 (Dec 1971). 5. Arion, N. (to IPRAN): “Process for treating and recovering waste water from fertilizer manufacture”. US

4,002,455 (Jul. 1975). 6. Arion, N. (to IPROCHIM): “Moving bed ion-exchange apparatus and operating method thereof”. US

3,969,243 Jul. 1976). 7. Pawlowski, L.; Bacicki, T.: “Stability of ion-exchangers in nitric acid solution”. Physicochemical

Methods for Water and Wastewater Treatment – 2 nd International Conference, Lublin (Jun 1979). Pergamon Press

8. Arion, N.; Ladendorf, P. (to Bran & Lübbe GmbH): “Verfahren und Vorrichtung zum Ionenaustauch in Flüssigkeiten”. EU 0013912 (Jan. 1980).

9. Calmon, C.: “Explosion hazards of using nitric acid in ion-exchange equipment” Chemical Engineering (17 Nov. 1980).

10. Arion, N. (to Christ AG): “Quasi-kontinuierliches Verfahren zum Behandeln von Flussigkeiten mittels multipler Aktivmassenbetten sowie Vorrichtung zur Durchführung des Verfahrens” CH 658796 (May 1983).


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11. Arion, N.; Uebersax, H. (Christ AG): “Récuperation des engrais azotés et de l’eau dans les effluents des usines d’engrais”. Informations Chimie No. 247 (Mar 1984).

12. Arion, N.; Jagust, J; Dzendo, Z. (INA Kutina, Croatia): “Fertilizer plant waste water treatment by ion exchange- application at the INA-Kutina complex”. Nitrogen (163) (Sep-Oct 1986).

13. Arion, N. (Christ AG): “Ion exchange process for the treatment of fertilizer waste waters”. IFA Technical Conference, Port el Cantaoui, Tunisia (Oct 1986).

14. Arion, N. (Christ AG): “Fertilizer plant waste water treatment – Application at the fertilizer complex Peti-Nitrogen Müvek, Hungary” 6th Annual Water Treatment Technology Conference, Abu-Qir, Egypt (May 1988).

15. Diehl, L. (BASF AG): “Nitrophosphate and fertilizer plants: The recycling concept for minimizing pollution of air and water”. IFA Technical Conference, Edmonton, Canada (Sep 1988).

16. Arion, N. (Christ AG): “Recyclage total des effluents pollués sortant des usines d’engrais azoté et recuperation du nitrate d’ammonium”. Symposium Technologie des Eaux, Annaba, Algeria (Jul 1990).

17. Orphanides, D.: “Optimum treatment of vapours and/or condensates from ammonium nitrate plants” AFA Technical Conference, Alexandria, Egypt (Jun 2001.).

APPENDIX

Ion-Exchange Effluent PurificationReference List

Treatment capacity Name and location Contractor Engineering

company FERTAREX

treatment system Regeneration data Flow m3/h

NH3/ NH4 eq/h

NO3 eq/h

Start up

Amonil, Slobozia Romania

MICh Romania

Ipran Bucharest Romania

Discontinous down- flow ion-exchange

Up-flow - counter-current with 10% HNO3, for cation resin + 10 % NH3 for anion resin 50 6,000 4,000 1974

Doljchim. Craiova Romania

MICh Romania


Continous up-flow ion-exchange

Down-flow counter-current with 47% HNO3 for cation resin + 15 % NH3 for anion resin 100 7,000 5,000 1976

Ch.C.Arad Romania

MICh Romania


Continous up-flow ion-exchange

Down-flow counter-current with 47% HNO3 for cation resin 80 5,500 - 1978

INA-Petrokemjia Kutina Croatia

Kellog Amsterdam NL

Christ AG Aesch - Switzerland

Short cycle, up-flow ion-exchange


Nitrogénmüvek Petfürdo -Hungary

Nitrogénmüvek Hungary

Brann & Lübe -DE Christ AG -CH



Deepak Fertilizer India

Humphreys & Glasgow UK

Arionex CH-4153 Reinach


Down-flow counter-current with 30% H2SO4, for cation resin + 12 % NH3 for anion resin 80 5,000 4,500 1990

Down-flow counter-current with 58% HNO3 for cation resin + 12 % NH3 for anion resin 70 19,662 5,250 Azomures SA

Târgu Mures, Romania

Azomures SA Romania

Arionex CH-4153 Reinach

NH3 steam stripping + short cycle, up-flow ion-exchange Down-flow counter-current with 58% HNO3

for cation resin + 4 % NaOH for anion resin 25 163,167 225 2005

treatment of waste water effluents from the azomures

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