Ion exchanger system, IAT circulation system

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An ion exchanger system can be used to recirculate industrially contaminated rinsing water in order to remove ionogenic contaminants (e.g. heavy metals, alkaline earth metals) from this water and return it to the industrial cycle. This reduces the production of avoidable wastewater, prevents the ion exchanger circulation water from being salinated, which would impair its quality, and complies with the regulatory requirements for system operation.

In aqueous ion exchanger circulation systems, a low conductance of the water is required in order to achieve the desired rinsing effects, such as stopping the chemical pre-processes and cleaning soiling in the sink. The required conductance is calculated according to the rinsing criterion, e.g. after pickling/decapsulation 1:1000, after electrolyte baths 1:10,000. The conductance increase in the circulation rinses is caused by carryover of the adhering liquid from the active baths or by make-up water. These are essentially cations (such as the undesirable hardness formers calcium and magnesium, but also heavy metals from metallic materials such as copper, nickel, zinc, lead and chromium) and anions (such as the undesirable corrosive chlorides or, where applicable, cyano complexes). The cation exchanger in an ion exchanger system removes the cations contained in the water and releases the hydrogen ion H+, the anion exchanger removes the anions contained and releases the hydroxyl group OH- or binds protons and an equivalent amount of anions. Together, H20 is therefore produced in the outlet of the system in exchange for the anionic and cationic inputs. By removing the ionogenic substances, this ensures a low conductivity value at the outlet of the system so that the water can be reused for rinsing. In addition, any organic matter and other apolar substances that may have entered are removed in further filter stages, if necessary.

A common application for an ion exchanger system is the circulation of rinsing water contaminated with heavy metals in aqueous processes using ion exchangers, e.g. in electroplating or industrial parts washing machines. In particular, carryover (concentrations < 10 mval/l) from upstream process steps are enriched in a bath with demineralized water, which is continuously cleaned by the ion exchanger system. Depending on the application, the circulation system consists of one or two lines, each with a strongly acidic cation exchanger, so-called SAC (sulphonic acid exchanger on styrene-divinylbenzene copolymer), a weakly basic exchanger, so-called WBA (tertiary amine exchanger on styrene-divinylbenzene copolymer) or a so-called “medium basic” exchanger, and possibly a strongly basic anion exchanger, so-called SBA (quaternary amine exchanger on styrene-divinylbenzene copolymer). In applications that require a low conductivity value, a mixture of a strongly acidic and a strongly alkaline exchanger is additionally connected downstream for external regeneration, so-called mixed bed resin or mixed bed exchanger (i.e. a demineralization cartridge), which can achieve a conductance of less than 0.1 µS/cm up to the lowest technically achievable conductance of 0.056 µS/cm or 18.18 MΩ-cm under optimum conditions.

Furthermore, depending on the application, an ion exchanger system may involve physical pre-filtration using a gravel filter or multi-layer filter or filter cartridges, denaturation of any interfering biology using UV light and/or removal of apolar or non-ionic substances using activated carbon or a scavenger resin as an exchange unit. For further purification of demineralized water to pure water or ultrapure water, additional mixed-bed polisher ion exchangers, i.e. a demineralization cartridge, can be used.

Fully demineralized water (VE-water) or demineralized or deionized water (DM water, DeMi water or DI water) is not defined separately as such, but its parameters are derived from the customer-specific process. The main aim is to avoid stains during subsequent use. Higher purity levels than demineralized water are the so-called pure water (1- 0.1 µS/cm) and ultra pure water (with < 0.1 µS/cm), which can be achieved with electrodeionization and/or mixed bed ion exchangers for external regeneration.

Typically, however, the following conductance values are required at the outlet of the system: Semiconductor < 0.1 µS/cm (0.06 µS/cm), hard chrome plating < 3 µS/cm, electroplating < 20 µS/cm, anodized < 30 µS/cm, hot-dip galvanizing < 50 µS/cm, forklift water or battery water during filling: < 30 µS/cm.

Consideration of the conductance alone is often not sufficient for a reliable design, as the slip phase of the ion exchanger begins as soon as the conductance rises for the first time. The anion exchanger in a demineralization process in particular starts early with the release of weakly bound substances, e.g. silicic acid, which hardly affects the conductivity, and of (corrosive) chlorides. Both substances are generally undesirable in the process and may require additional technical measures in the ion exchanger system.

As a rule, the VE- water produced by the demineralized water system is monitored by the conductance in [µS/cm] at the outlet of the ion exchanger system. Typical conductance values at the outlet of the ion exchanger system are between 30 µS/cm – 3 µS/cm depending on the system and expansion stage, with downstream further mixed bed exchangers and/or electrodeionization also lower down to 0.056 µS/cm, so-called ultrapure water.

In special cases, requirements are not only placed on the sum parameter conductance in [µS/cm], but other parameters in the treated effluent water are also important: e.g. pH value, residual concentrations of substances that only have a minor effect on the conductance, e.g. substances with a low degree of dissociation such as silicic acid, silicates, cyanides or salts of organic acids. Therefore, deionized water produced with the help of an ion exchanger system has different residual substances than the permeate from a reverse osmosis system.

When purchasing a demineralization system, the fundamental question is whether an ion exchanger demineralization system or a membrane process based on reverse osmosis, a so-called reverse osmosis system should be purchased. Both typically achieve this conductivity value, but differ in the process and the composition of the demineralized water produced. If only the conductance is required as a sum parameter, the main differences can be summarized as follows: A chemical-physical wastewater system is required for the demineralized water system, but not usually for the reverse osmosis system . Both systems do not require a WHG (Water Resources Act) permit on their own up to 10m³/week of wastewater production (the municipal monitoring values nevertheless apply; copper in particular can be problematic here due to the limit values in the Drinking Water Ordinance of 2.0 mg/L compared to the monitoring values in the Wastewater Ordinance of 0.5 mg/L (or 1.0 mg/L in most drainage regulations for discharges < 10 m³/week). The reverse osmosis system constantly produces waste water via the concentrate discharge, whereas the ion exchange system only produces waste water during regeneration. Cost considerations can be made over the entire period of use, in which the generally higher acquisition costs for the demineralized water system can be weighed up against the lower operating costs, see example operating cost comparison for reverse osmosis system demineralized water system.
Circulation ion exchanger systems type KR 30-250
Circulation ion exchanger systems type KR 30-250
Circulation ion exchanger systems type KR 30-250

Depending on the design of the system for the customer process, an ion exchanger system is equipped with an automatic regeneration station or can be regenerated externally in the central regeneration station in 92348 Berg as part of the ion exchanger regeneration service.

With a circulating water requirement of between 2.5 and 20 m³/h and an adequate ion load, an ion exchanger system with its own on-site regeneration station is generally a useful option. The ion exchangers used in the system in the various columns are regenerated with acid and alkali, usually with hydrochloric acid (HCl) and caustic soda (NaOH). The regenerates from the system are then treated in the company’s internal wastewater system. Please note that the system is subject to notification under water law and that an existing indirect discharge permit may have to be adapted.

For a flow rate of up to 2.5 m³/h or a very low ion load, an externally regenerated ion exchanger system is a useful alternative. This means that the ion exchanger cartridges are loaded at the customer’s premises during the customer process and then sent to the central regeneration station in 92348 Berg. This means that no wastewater from the system itself is produced on site. After regeneration, the cartridges are returned to the customer. The cartridge size can vary depending on throughput and capacity and is typically between 30 – 1500L resin volume.

Expansion options for ion exchanger systems:

  • Customer-specific design to suit the process (e.g. also water containing chromate and cyan) and the budget, starting from a semi-automated, functional simplex basic design through to an automated and remotely monitored duplex design.
  • Adaptation to any existing control technology and connection to a process control system and the existing structural conditions at the location or the entry to the location (e.g. through limiting doors)
  • Preliminary examinations and optional test plant provisions/technical center possible
  • Fulfillment of the legal requirements for water-saving measures acc. to the annexes of the Wastewater Ordinance and the best available techniques (BAT) for IED plants in accordance with the IE Directive 2010/75/EU or the 4th BImSchV.
  • Fulfillment of customer requirements for industrial rinsing processes (e.g. in the TSA process)
  • Siemens PLC circuit with/without touch display and with the option of external access
  • Duplex version for uninterrupted 24/7 operation optional
  • Stainless steel or plastic frame construction for corrosive environments
  • Pressure tanks in PE/GfK, PVDF/GfK or coated steel
  • Ion exchange resin from LANXESS Lewatit or Purolite or according to customer requirements
  • Piping and fittings in PVC, PP, PE or PVDF from the manufacturers GF, GEMÜ (pneumatic or electric) or according to customer requirements; otherwise design with standard industrial components without special elements where possible.
  • Temperature design up to 70°C possible, higher temperatures on request
  • Internal recirculation to avoid counterion re-dissolution effects
  • System design for operation in compliance with occupational safety requirements, even in the event of typical misuse
  • Disinfection option for the resin bed
  • Possibility of pre-acceptance and trial operation in our own workshop
  • Modular, maintenance-friendly design according to customer requirements with various optional expansion options, e.g. with storage tanks, chemical storage tanks as dosing stations or as AwSV LAU systems, drip pans, simple feeding to redundant FU duplex pressure boosting stations, pressure difference display, actual consumption and production data recording, separate resin change connections, system access control, valve position feedback, separate silica cleaning and external automatic fresh water feed option, e.g. by a reverse osmosis system.
  • Designed as an ion exchanger system to be regenerated externally with exchange cartridges (without wastewater generation on site) for the external ion exchanger regeneration service or as a system with its own regeneration station (with wastewater to be treated on site).
  • An ion exchanger system in the chemical-physical wastewater treatment plant is usually a selective exchanger system.

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