Draft IPC guidance for inorganic chemical processes

A second round of consultation has been initiated by HM Inspectorate of Pollution (HMIP) on guidance notes covering inorganic chemical processes.1 Industries affected include the production and use of ammonia, numerous inorganic chemicals processes, cadmium electroplating, and the manufacture of batteries, fluorescent lights, semiconductors, electrical components and instruments.

The processes covered by the guidance will come under integrated pollution control (IPC) on 1 May 1994. Operators of existing processes will have to apply for authorisation by 31 July 1994, and will be expected to upgrade to new plant standards by 1 May 1998.

As with earlier guidance, the upgrading deadline has remained unchanged since the first draft. So far HMIP is showing no sign of responding to industry pressure to ease the impact of IPC by postponing upgrading deadlines.

The latest versions are substantially unchanged from the first drafts, which were issued for consultation in April. The principal alteration is the addition of greater details on the techniques used in the manufacture of various metals and their compounds. However, as with previous guidance, the notes focus on process descriptions and are rarely prescriptive.

Responses to the current consultation are due by 17 September. The impact of the standards set out in the notes is difficult to evaluate, because of the wide range of industries covered. Some of the main points are:

  • Dilution of process releases: HMIP's policy for handling effluents on complex sites has now been made more explicit. The notes state that "the dilution of aqueous process effluent by mixing with general site effluent or the mixing of process streams from different processes to achieve co-dilution is generally not considered to represent BATNEEC (the best available techniques not entailing excessive cost)." Any company wishing to deal with liquid waste in this way must demonstrate that it is the "best practicable environmental option" (BPEO) compared to treatment of the concentrated process stream.

    Aqueous streams containing high levels of cadmium or mercury should always be segregated and BATNEEC used to recycle or minimise the release, the notes say.

    Similarly, "the dilution of process vents by mixing with general extract air is not generally considered to be BATNEEC" and must be justified as the BPEO.

    However, where plant is enclosed to protect staff safety, particularly for processes involving cyanides, hydrogen sulphide or mercury, the large volumes of extracted air may not lend themselves to abatement. HMIP says that firms should consider using total plant enclosure with low extraction volumes going to an abatement plant. Operators should demonstrate that abatement would entail excessive cost and that "suitable dispersion" is achieved.

  • Cadmium processes: These include cadmium electroplating, smelting, and manufacture of pigments and ceramic glazes. Most will be hardest hit by the proposed 50µg/l limit on cadmium releases to water. This compares to the standard limit of 10µg/l set for processes where cadmium is not a significant raw material.

    HMIP notes that for some cadmium processes, such as electroplating and ceramic glazing, technology now exists to segregate, treat and completely recycle aqueous streams - in these cases "releases are essentially zero or only occasional". According to the Metal Finishers Association (MFA), however, only a few cadmium platers are using this new technology. The remainder employ some form of precipitation, but this can reduce cadmium levels to only 500-1,000µg/l.

    Upgrading to the tighter standard will require treatment with electrochemical, ion exchange or membrane techniques, and the MFA claims that this could cost o50-100,000 for a typical plateshop. Over half of the 50 or so existing cadmium electroplating shops are already expected to shut as a result of new restrictions on the use of cadmium. The MFA claims that the further IPC requirements could drive all but 5-10 firms out of the cadmium plating business.

    Some sectors will also be hit by the proposed limit of 0.05mg/m3, expressed as cadmium, for releases to air of cadmium and its compounds. Fabric filters backed up by high efficiency particulate arrestors (HEPA) are generally considered to be BATNEEC for the abatement of particulates from these processes. Wet scrubbers are less effective, but may be acceptable where a large air flow is necessary for safety reasons.

  • Mercury processes: This note covers a particularly wide range of small industrial uses of mercury, including the manufacture of soaps, creams, fungicides, some batteries, fluorescent discharge lamps, thermometers and other instruments.

    Under the IPC regulations, all processes using mercury or its compounds may be prescribed for IPC. HMIP notes that "many processes only use very small amounts of mercury at ambient conditions with no planned releases to any environmental medium." Inspectors should consider such cases for exception on the grounds of triviality - "confirmation of a high degree of cleanliness and control in compliance with HSE guidance should be an important factor."

    Many of the affected industries - such as manufacturers of small button batteries - are already under pressure to move to mercury-free alternatives. The IPC requirements are likely to provide another spur. As with cadmium processes, the 0.05mg/m3 limit on releases to air of mercury and its compounds will require fabric and HEPA filters. The 10µg/l limit on mercury releases to water will also be hard to achieve using precipitation systems alone.

    However, manufacturers of fluorescent discharge lamps - particularly the low-energy compact lamps - face no easy alternative to the use of mercury and may need to invest heavily in abatement equipment.

  • Processes involving other metals: In contrast to its willingness to exempt small mercury processes, HMIP is reluctant to treat processes in the microelectronics industry as "trivial". It notes the small scale of processes using semiconductors for circuit manufacture, but says "this is compensated for by the highly toxic and polluting nature of many of the materials used and the complexity of the plant installations." For these processes, and others involving lead, antimony, platinum and semiconductors, abatement with HEPA filters will be needed to meet the tight emission limits.

    However, for processes using compounds of chromium, magnesium, manganese, nickel and zinc, abatement by fabric filters on their own may suffice.

  • Ammonia production and use: The key release limit for ammonia manufacture is one of 30mg/m3 for ammonia releases to air. To achieve this, either wet scrubbing or condensation is HMIP's preferred abatement technique.

    HMIP says that the use of a non-fired primary reformer represents best practice for new plants using the steam reforming option. However, the guidance notes that adaptation of existing plants "would be very expensive and problematical".

    For processes which use, release or recover ammonia a limit of 15mg/m3 has been set on the gas. This would apply to the Solvay ammonia process and the production of sodamide and ammonium salts.

  • Processes involving hydrogen cyanide and hydrogen sulphide: Release limits to air have been set at 5mg/m3 for hydrogen cyanide, hydrogen sulphide and inorganic cyanide dust, and at 1mg/m3 for cyanogen chloride. However, no limits have been set for releases to water and HMIP has not specified BATNEEC for abatement of releases to either medium.

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