Page 181 - CW E-Magazine (19-9-2023)

Special Report Special Report

Water management in the fertiliser industry power generation and drying of pro- of lamella clarifi ers, as well as ultra- ground water. The rain water is collected
fi ltration (UF) and reverse osmosis and treated and being used as cooling
ducts.
(RO) technologies for the treatment tower make-up water.
ater is the most important reuse/recycle wastewater generated ARVIND CHAUDHARY In case of complex fertiliser plants, of trade effl uent. RO reject water is
and critical natural resource from the process after treatment. Plants Director General various methods of recycle and reuse of directly used in venturi scrubber of Monitoring of water consumption
Wfor sustaining life and human have also implemented measures to Fertiliser Association of India effl uents from plant discharge through reaction section in complex fertiliser Monitoring of water consumption is
activities. It is also an important reduce consumption of water by im- E-mail: dg@faidelhi.org the balance pond into the plant through plants. In urea plants, the RO permeates a prerequisite for effi cient water manage-
resource for various industrial acti- proved/modifi ed processes and using surge pond are in practice. This has not are used as cooling tower makeup. The ment. The digital fl ow meters with
vities. Though, 71% of the Earth’s turbines that consumes less steam. condensate stripper, while urea plants only reduced the water consumption RO rejects are further treated in multiple- totalisers in place of analogue meters
surface is covered with water, only have employed hydrolyser and stripper per tonne of product, but also improved effect evaporators (MEE), where water provide more accuracy. For effi cient
0.3% of it is usable and the other 99.7% With the concerted efforts of the to treat its condensate. P O recovery effi ciency. Use of cooling vapours are condensed and this water water management, it is also important
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is in oceans, soils, icecaps and the industry, water consumption in ammonia- tower blow-down, scrubber bleed-off is used as cooling tower makeup water. to understand the water distribution
atmosphere. urea integrated plants have reduced Steam is used as motive force to in the process areas and treated trade network, identify points of water
from 12.0-m /tonne urea in 1990-91 drive large compressors and pumps. effl uents are used for cake wash in Sewage treatment plants (STPs), consumption, leakages and wastages.
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Globally, about 20% of water is to 6.2-m /tonne urea in 2020-21 and The steam used for driving the turbines phosphoric acid plant itself. The washings/ installed for treating sewages in town-
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used by the industrial sector. In ferti- in case of complex (NP/NPK) plants in the process plants are condensed wash water in the phosphoric acid plant ships, can also serve as source of water. Water audit is an important tool,
liser plants, water is used for process, it reduced from 11.4-m /tonne P O to after use. It normally does not get conta- is neutralised with lime, if required, and A plant has been sourcing the sewages which helps to identify the areas where
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heating and cooling, steam genera- 4.5-m /tonne P O over the same period. minated with any process materials. the neutralised wash water is reused in from a city, treating it in STP and wastage of water is taking place and
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tion, fi refi ghting, drinking, cleaning, This translates to reduction of about Hence, steam condensate from turbines the phosphoric acid plant. Switching returning treated water back to the measures can be undertaken to plug the
deashing and sanitation. The source 50% in ammonia-urea plants and 60% require minor treatment like activated from wet gypsum stacking to dry municipality. Many plants have up- leakages. A number of fertiliser plants
of water in the fertiliser plants is both in case of complex fertiliser plants. carbon fi lters and basket strainer to gypsum stacking also helps in conserving graded and deploy technologies like have undertaken water audit.
ground and surface water. A few plants remove foreign particles in the deminera- water. membrane bio reactor (MBR), which
are sourcing sewage from nearby city Water consumption in ammonia/urea lisation (DM) plant. The treated water makes the treated water from STP The Central Ground Water Autho-
municipalities and treating it and using plants after polishing is reused as boiler feed Water use in cooling towers and suitable to be reused as cooling tower rity (CGWA) Guidelines on ground water
this treated water as raw water. In some Ammonia is the major intermediate water. Thus, recovery and reuse of boilers make-up water. restricts withdrawal of ground water
fertiliser plants, rain water is stored in for production of urea and all other condensate save considerable amount The rejection of heat to atmosphere and use for commercial and industrial
large storage ponds and used after treat- nitrogen bearing fertilisers. Its production of raw water. is carried out in cooling towers, which Developments in water treatment activities falling under over-exploited
ment. Surface water is treated before is highly water intensive as steam is are major consumers of water. Evapora- chemistry assessment areas. The plants located in
use as raw water to remove suspended also required for the process, apart from Water consumption in complex ferti- tive loss of water takes place from the There has been continuous deve- such areas and relying only on ground
solids and other undesirable impurities. other industrial use. liser plants cooling tower, and this is the major lopment in water treatment chemistry. water have to put lot of efforts to reduce
The characteristic of raw water varies Water consumption level in complex reason for high water consumption. Better and environment friendly chemi- fresh water consumption. One such ferti-
from source to source and location to Ammonia and urea production fertiliser plants varies for plants with Continuous blowdown is carried out cals help in reduction in use of chemi- liser plant is exploring an innovative
location and also plays an important processes are highly exothermic in or without captive acid production. In from cooling tower to maintain the cals, as well as improving the quality of method of collecting moisture present
role in water management and design- nature, and water is used as medium for captive acid plants, water is consumed Total Dissolved Solids (TDS) in the wastewater and circulating water. This in atmosphere by condensation on air
ing raw water & effl uent treatment absorbing the exothermic heat of reac- in sulphuric acid production as process circulating water. Make-up water is results in increase in reuse of treated chilling coils. This has great potential
plants. The quantity of water consumed tions. Cooling of process gas containing water where it is used to absorb sulphur required to compensate for the evapora- water in process and improved cycle of of recovery during the humid seasons
in the fertiliser manufacturing process steam results in condensation of steam trioxide gas to produce sulphuric acid tion losses and blowdowns. To reduce concentration in cooling water circuit. or in plants located at coastal areas.
depends upon the process technology, in condensers. The process conden- and to generate steam from waste heat the consumption of raw water, effl uents
characteristics of water and raw mate- sate so generated contains constituents of the exothermic reactions. are treated and this water is being used Other initiatives Zero liquid discharge
rials used. of the reactions and are separated in as cooling tower make-up. Blowdowns Raw water is sourced in large quan- All ammonia and urea plants commis-
condensers. The process condensate Water is also consumed for prepa- take place during boiler operations to tity and stored in ponds. Evaporation sioned recently have been given the
Water conservation – a focus area in from ammonia plants carry some ring a slurry of rock phosphate, which maintain the quality of DM water. The loss from these ponds is quite substan- condition of zero liquid discharge. The
fertiliser industry dissolved impurities in form of ammonia, reacts with sulphuric acid in reactor, in quality of boiler blowdowns is suitable tial. Efforts are being made to reduce existing plants are also working to fully
Fertiliser manufacturing is water- methanol and carbon dioxide. In urea phosphoric acid plants. for use as cooling tower make-up water. the evaporation losses from the storage recycle and reuse the treated wastewater
intensive. Therefore, water conserva- production, process condensates gene- During regeneration of DM plant, effl uent pond. In a recent scheme, a plant imple- and achieve zero liquid discharge.
tion has been a focus area in fertiliser rated from different sections of the urea Water is also used for scrubbing of generated is of quality that can be used mented fl oating solar panels on its reser- Reduction in water consumption for
industry. Fertiliser plants have adopted plant contain impurities like ammonia, gases and dust from processes in the for cooling tower makeup. voirs, thus reducing evaporation losses production of fertilisers is an ongoing
the principle of reduce, reuse and carbon dioxide and urea. As a part of complex and single superphosphate as well as generating renewable power. process.
recycle while implementing various reuse of wastewater, each plant has its (SSP) fertiliser plants. In addition, water Water from effl uent treatment systems
water conservation schemes. A number own treatment system. The ammonia is consumed in utilities for generating Fertiliser plants are upgrading their Rain water harvesting has been [Indian Journal of Fertilisers, 19(6),
of schemes have been implemented to plant condensates are treated in process steam, which in turn, is used for effl uent treatment systems by installation adopted by many plants for recharging 530-531, June 2023]

180 Chemical Weekly September 19, 2023 Chemical Weekly September 19, 2023 181

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