London Brick benefits as HMIP backs down on emission limits

The second and final drafts of six guidance notes which will determine what standards the minerals industries must meet under integrated pollution control (IPC) have been circulated by HM Inspectorate of Pollution (HMIP).1 Cement and fibre producers are pressing for more time to upgrade their existing plants, while lime manufacturers want to operate to the same emission standards as the cement industry. But the biggest issues have been raised by the softening of HMIP's stance to emissions by the Fletton brick industry.

The minerals sector will be the third to come within IPC after the fuel and power and waste disposal industries. Existing minerals plants will have to apply for IPC authorisations between 1 December 1992 and 28 February 1993.

First drafts of the guidance notes dealing with the various minerals processes were issued for consultation at the end of 1991. The second drafts followed in March.

One important conclusion which may be drawn from some of the revised drafts is that HMIP is allowing wider economic factors into its thinking when defining the best available techniques not entailing excessive cost (BATNEEC).

Several of the minerals processes supply the building industry and have been hard hit by the recession. HMIP is going some way to meet industry's arguments that it cannot afford the large capital investments which would be required to meet stringent emission limits for all prescribed substances.

HMIP's philosophy now appears to be to target only key pollutants. One consequence is that the proposed limits for sulphur and nitrogen oxides are relatively high, and should generally be achievable without resort to flue gas treatment. Measures such as the use of low-sulphur fuels, changes in raw material inputs and process modifications are being encouraged instead.

This approach reflects the industry view that its contribution to the total output of acid gases is relatively small - particularly when compared to the power generation industry.

The sectors concerned are as follows:

  • Ceramic processes: HMIP has backed off from the very tight release limits outlined in the first draft of the guidance note for this sector. And while most of the other mineral processes falling under IPC are expected to upgrade their existing plants by April 1997, the ceramics sector has won an extension to April 1999.

    Processes covered by the guidance note include the firing of clay or refractory goods in a kiln with a reducing atmosphere. In practice this is restricted to the production of Fletton bricks by the London Brick Company (LBC) at its six sites in Bedfordshire and the Peterborough area.

    LBC produces about half of the UK's annual output of six million bricks. The rest of the industry is regulated by local authorities under the air pollution control system created by the Environmental Protection Act 1990. HMIP appears to have been persuaded that the stricter release limits proposed in the first draft of its guidance would have damaged LBC's competitiveness against these Part B processes. The release limits in its second draft are now very similar to those already set for Part B processes (see table ).

    LBC is, indeed, the main beneficiary of HMIP's less stringent approach to SO2 and NOx. The initial draft spelt out the full range of available flue gas desulphurisation techniques, andthese would almost certainly have been needed to meet the limit of 150mg/m3 for new plant. The revised level of 1,500mg/m3 is much closer to that required for Part B brick-making processes, and should be relatively easy to meet by switching to low-sulphur fuels. The SO2 emission from the Fletton process is typically 1800mg/m3.

    An equally controversial change is the deletion of specific limits for organic sulphur compounds, hydrogen sulphide and volatile organic compounds (VOCs). One of the principal reasons why the Fletton process was brought under IPC was the history of complaints about the odours released from the brickworks. The Lower Oxford Clay used in the process contains 5% by weight of organic matter which is converted to foul-smelling mercaptans during the baking process.

    The only control of odour problems now comes in a clause prohibiting any offensive smell outside the works - a subjective approach modelled on that for Part B processes. HMIP's justification for the change is that the odours are caused by such low concentrations of organic sulphides that emission limits would be impossible to monitor accurately.

    HMIP's apparent climb-down over the Fletton industry's emissions raises questions not only about the meaning of BATNEEC. Last year, LBC, in association with the process engineering group Bechtel, carried out a study to define BATNEEC for the process. But although the study appears to have influenced HMIP, the company is unwilling to disclose its findings. Neither is any material available from HMIP about how it weighed the available technical options for controlling emissions against the economic implications for the industry.

    HMIP's approach contrasts with, say, that of the Health and Safety Commission, which now includes a cost-benefit appraisal in all its consultative documents. But although HMIP sets out the technical options for abating releases in its guidance notes, at no point does it make public any estimates of their costs. As in the past, the dialogue in this area is carried out in private between inspectors and industry.

    HMIP's primary concerns are now to bring the industry's particulate and fluoride emissions under control. Particulate emissions from the Fletton industry are currently around 70mg/m3 and fluoride levels about 18mg/m3.

    The draft guidance identifies several techniques for fluoride abatement. These are dry absorption, such as packed bed or cloth filters, and condensation and wet scrubbing techniques. LBC is keen to avoid the capital cost of these measures, and is hoping to comply with the limits by reducing the proportion of Lower Oxford Clay - the source of the fluorides - in its raw material mix.

    The other process covered by the guidance note is salt glazing, which is similar to other firing processes in the ceramic industry but for the use of salt and borax in the kiln. In addition to the usual problems of fluorides, oxides of sulphur, odours and particulates, salt glazing emits hydrochloric acid due to partial dissociation of the salt under the high temperatures in the kiln.

    The draft note warns that any new salt glazing installation will almost certainly need to fit gas cleaning equipment such as scrubbers. Even so, the proposed chloride limit of 30mg/m3 will be easier to meet than the original figure of 5mg/m3.

  • Cement manufacture: The draft guidance for this sector has generated less controversy. The general view of the cement industry is that the standards are not unreasonable - but that the April 1997 deadline for upgrading existing plant will cause difficulties.

    The principal concern is the 50mg/m3 limit on particulate emissions for new and existing kilns from 1997. The current limit, laid down in an old "best practicable means" note, is 100mg/m3. The industry claims that most of the 30 or so kilns in operation are achieving levels down to 60mg/m3.

    Operators' concern is over how the 50mg/m3 limit will be interpreted. If HMIP accepts that excursions to 60mg/m3 are acceptable then many kilns fitted with modern electrostatic precipitators may already comply. But if, as seems likely, the standard is applied strictly then Blue Circle alone estimates that it will have to invest well over £10 million in improved particulate arrestors.

    Other standards proposed in the note will require limited changes. The SO2 limit of 750mg/m3 is already being achieved by most kilns as sulphur oxides are absorbed in the clinker. Those sites which exceed the limit will have to consider switching to low-sulphur fuels - or face the cost of installing flue gas desulphurisation.

    Emissions of NOx will be limited to 1200-1800mg/m3, the precise value depending on whether the process is dry, semi-dry or wet. In all cases the best way of meeting the limit is by careful control of temperature in the burning zone. On-line control systems, such as the Linkman expert system developed by Blue Circle, offer the easiest route and have the bonus of improving energy efficiency.

  • Lime manufacture:
    The lime industry views itself as an indirect competitor of the cement industry in several markets and is keen to be regulated to a similar standard. The first draft of the guidance notes took this line, with emission limits for particulates, SO2 and NOx being similar for both industries.

    But the second draft caused some dismay in the lime industry. The limit for SO2 was reduced from 750 to 200mg/m3, and that for NOx from 1800 to 800mg/m3. HMIP argues that the tighter levels are readily achievable, especially in view of the fact that in lime manufacture a powerful SO2 absorbent - calcium oxide - is inevitably present.

    The industry takes a different view. Of the several different process types, vertical shaft kilns tend to be found in the older and smaller factories and are efficient absorbers of SO2. In contrast, the larger rotary kilns are designed to prevent SO2 being absorbed by the clinker. This is particularly important for kilns supplying the steel industry, where high calcium sulphate contamination in the lime is undesirable.

    In the guidance note, HMIP describes three techniques to control SO2 emissions. These are to design the kiln to absorb the sulphur on the lime, fit flue gas desulphurisation equipment, or limit the sulphur content of the fuel and raw materials.

    It seems likely that the note will, if it remains unchanged, result in a shake-up in the industry. Some processes may become uneconomic if they are forced to use a low-sulphur fuel such as natural gas. The cost of complying with the original note has been estimated at several million pounds for each battery of kilns. The tighter SO2 limit can only increase this.

    Like the cement industry, the lime sector has a dust pollution problem. Similar abatement measures will be required to bring the emission of particulates down from 100 to 50mg/m3 for new kilns and for existing kilns by April 1997. A particular problem is the emission of dust particles from lime hydrators during the slaking process. The particles act as condensation nuclei, causing a persistent visible water plume. A wet scrubber, cyclone or water spray will be needed to keep emissions below 100mg/m3.

  • Asbestos processes: The asbestos industry is already closely regulated, and the new guidance is unlikely to entail major changes in abatement practices. Most of the industry is confident that it is already meeting the limit of 2 fibres/cm3 for emissions for existing plant.

    However, a major concern is the cost of monitoring equipment. Asbestos plants often have numerous vents to atmosphere to protect the internal environment. The draft guidance requires continuous monitoring of asbestos and particulate releases. The cost of each monitor is put at £15-20,000. With some sites having as many as 150 vents, the resulting bill could be hefty.

    Some asbestos suppliers are reorganising their activities to reduce the number of sites subject to IPC. Part A processes are those using raw asbestos fibre, whereas sites processing finished asbestos textiles are regulated under Part B and emission samples need be taken only once every six months. Raw asbestos handling is therefore being concentrated on fewer sites to escape the more stringent monitoring requirements of Part A.

    However, there is still some confusion over the dividing line between Part A and Part B, even though the deadline for Part B applications is 1 April 1992.

    One section of the industry which will need to invest in emission abatement equipment is the production of asbestos sheeting. A limit of 20mg/m3 for VOCs will apply to these processes, which emit solvent during the curing process.

  • Glass and non-asbestos mineral fibres: In its second draft for this sector, HMIP has acknowledged a natural split in the industry by setting separate release limits for melting processes and downstream processes.

    The initial melting process presents broadly the same problems as those encountered in the rest of the glass industry, which is regulated as a Part B process. The standards set under IPC for the melting process now closely follow those already in place for Part B.

    The new draft contains separate emission limits for the fairly complex downstream processes in which fibres are coated and treated. These include a particulate limit of 50mg/m3, including a maximum of 20mg/m3 for glass or mineral fibre. Total VOCs are restricted to 20mg/m3, with individual limits being set for some of the more common organic pollutants.

    Several processes are covered by the note, including the production of continuous, glass wool and mineral wool fibres. It is clear that substantial investment will be required to supply abatement equipment such as incinerators and filters for air treatment, as well as flocculation and biological treatment plant for liquid effluents.

    British Glass, the industry's trade association, estimates that fitting the full range of necessary pollution controls on an existing plant would cost £2 million. For a new plant on a greenfield site, it puts the cost of environmental protection measures at 20-25% of the total investment.

    The UK's fibres industry comprises seven plants. British Glass is unhappy that existing sites must be upgraded by April 1997, compared with the October 2001 deadline for Part B glass processes. The industry is pressing for more time to meet HMIP's demands. This, it argues, would allow investment in less polluting formulations and better control approaches than end-of-pipe clean-up measures.

  • Glass frit and enamel frit: In this sector HMIP's principal concern is to control emissions of particulates and heavy metals.

    Glass and enamel frit are produced by shattering fused raw materials by water quenching. The products are used in the production of enamel and ceramic glazes. The sector is characterised by a great diversity of processes and of scale.

    HMIP has recognised the fragmented nature of the industry by varying its proposed release limits according to emission rates. For particulates, the limit for both new and existing processes with an emission rate greater than 0.5kg/h is 50mg/m3, while for lower rates it is 100mg/m3. Fluoride emissions are limited to 5mg/m3 where the emission rate is above 50g/h.

    The high temperature in frit furnaces can volatilise many metals and salts which cool to form a sub-micron fume. This may contain compounds of lead, cadmium, arsenic or selenium, depending on the frit formulation. Limits for these metals are specified in the guidance note.

    The frit industry is hoping to tackle the sub-micron fume and particulate requirements with bag filters. Johnson Matthey and Cookson Minerals are looking at this technology already. An investment of roughly £500,000 is typical for a bag plant on the necessary scale.

    Other options are available, such as maintaining a reducing atmosphere in the kiln to reduce lead emissions and using electric furnaces to reduce particulates. A cheaper option will be careful choice of raw materials and avoiding the use of heavy metals.

    HMIP is likely to require equipment such as spray dryers to minimise fluoride emissions. But the limits for SO2 and NOx are high and in most cases are already being met.

  • Please sign in or register to continue.

    Sign in to continue reading

    Having trouble signing in?

    Contact Customer Support at
    or call 020 8267 8120

    Subscribe for full access

    or Register for limited access

    Already subscribe but don't have a password?
    Activate your web account here