SUPPLEMENTARY MEMORANDUM SUBMITTED BY
THE ENVIRONMENT AGENCY
IMPLEMENTING THE HAZARDOUS WASTE INCINERATION
DIRECTIVE (HWID) ON CEMENT AND LIME KILNS BURNING SUBSTITUTE LIQUID
1. For approximately twenty years cement
kilns have used coal and/or petroleum coke to generate the heat
needed to convert a mixture of limestone and shale to clinker,
the precursor to cement. Lime is manufactured in a similar way
except that shale is not used in the raw material feed.
2. In terms of concentration and/or volume,
both the fuels and the raw materials contain significant levels
of sulphur, chlorine and metals, which are either trapped in the
clinker or are converted to pollutants such as sulphur dioxide,
oxides of carbon and nitrogen, dioxins and hydrogen chloride.
The process also results in the release of large volumes of carbon
dioxide as calcium carbonate changes to calcium oxide (a process
known as calcination).
3. Over the last five to 10 years operators
have sought to reduce their fuel costs by replacing the conventional
coal and/or petroleum mix with substitute fuels. The Agency has
taken the decision that the substitute fuels that have been used
to date are waste, with some being classified as hazardous waste.
As a consequence of this decision cement companies burning hazardous
liquid waste must comply with the requirements of the HWID.
4. The HWID was adopted in 1994 and introduced
into UK law in 1998 through a Secretary of State's Direction and
Regulations. These required processes burning hazardous waste
to comply fully with the Directive's requirements by 30 June 2000.
5. The Direction required the Agency to
vary all Part A Integrated Pollution Control (IPC) authorisations
for processes burning hazardous waste to include conditions by
30 June 2000 that satisfy the Directive's requirements.
6. By the end of June 2000 the Agency had
varied all the authorisations for cement kilns burning hazardous
waste in accordance with the requirements of the HWID. This has
ensured that the Agency's regulation of hazardous waste burning
in cement kilns is in accordance with the minimum standards set
by EU legislation.
7. In applying the HWID to cement plants
burning hazardous waste, the Agency imposes the same emission
limits on the flue gas generated by hazardous waste as it would
if the waste was burned in a dedicated hazardous waste incinerator.
Emissions from a cement or lime kiln burning hazardous waste would
be apportioned between those emissions arising from the burning
of hazardous waste and those arising from the combustion of conventional
fuel: the HWID limits apply to the former, and the latter are
regulated in accordance with Best Available Techniques Not Entailing
Excessive Cost (BATNEEC). The method of doing this is prescribed
by Annex II of the HWID.
8. The HWID provides for limits to be based
on a "mixing" or "pro-rating" formula. For
cement and lime kilns the emission limit values set out in the
HWID were applied to the volume of flue gas generated by the hazardous
waste fraction and the existing cement plant limits were applied
to the remainder of the gas. This ensures that the emission limit
values in the HWID are applied to the gas generated by hazardous
waste burning irrespective of the type of combustion unit. The
rules for calculating the final emission limit values are complex.
9. Cement and lime kilns have a residence
time for the gases which is estimated to be around six seconds
and a gas temperature of at least 1500ºC. This compares with
the HWID's requirements of two seconds and 1100ºC as a minimum
for halogenated hazardous waste, eg wastes containing 1 per cent
chlorine. This should result in a very high level of destruction
of organic components in the hazardous waste. The atmosphere in
the kilns is highly alkaline, resulting in the absorption of acid
gases. The solids levels in SLF are low, and most would be incorporated
into clinker or would be captured by the air pollution control
equipment. Similarly, metals are also likely to be captured in
the same way.
(a) Gases generated by a cement or lime kiln
burning SLF arise from four principal sources:
(b) Breakdown of carbonates to release carbon
dioxidethe bulk of the gas comes from this source (a process
known as calcination);
(c) Combustion of the traditional fossil
fuelcoal and/or petroleum coke;
(d) Combustion of SLF; and
(e) Combustion of non-hazardous waste such
|Castle Cement Ketton
|Rugby Cement Barrington
|Castle Cement Clitheroe
SLF FOR CEMENT
10. The Agency's policy on what material can and cannot
be incorporated into SLF is set out in two documents:
11. The Environment Agency's response to the House of
Commons Environment Committee Report on the Environmental Impact
of Cement Manufacturing (June 1997); and
12. The Substitute Fuels Protocol for use on cement and
lime kilns (August 1999).
13. The first document is "high level" and
sets out in a general manner the policy of the Agency when it
regulates substitute fuels on kilns. It requires the exclusion
of certain materials from SLF and commits the Agency to defining
a specification for substitute fuels.
14. The policy outlined above was translated into practical
guidance in August 1999 by the Substitute Fuels Protocol which
requires that substitute fuel must conform to a specification
agreed with the Agency. No substitute fuels to which the following
substances have been deliberately added should be subject to trial-burning:
radioactive material or radioactive waste;
15. Although each case must be considered on its merits,
trials of substitute fuel containing the following substances
should not be permitted:
16. radioactive material or radioactive waste (as defined
in sections 1 and 2 respectively of the Radioactive Substances
Act 1993); and
17. explosives, including: propellants, cartridges, or
bombs, or explosive material extracted from them or explosive-contaminated
material from their manufacture or decommissioning.
18. Inspectors should seek to avoid the blending of waste
streams into substitute fuel which do not contribute to its performance
as a fuel. In addition, for SLF, solids content should generally
be less than 20 per cent. Operators should propose a specification
for substitute fuel to be burned in the trials and this should
cover at least the following parameters:
calorific value (gross);
content of individual halogens;
heavy metals content (as defined in IPC Process
Guidance Note S2 5.01);
suspended solids content (for SLF); and
19. If the Agency is satisfied with the outcome of trial-burning
of SLF, the authorisation that is eventually granted will contain,
as a minimum, a specification for SLF which:
20. sets maximum concentrations of the parameters listed
above (except CV where a minimum value will be set); and
21. lists the type of waste that may be incorporated
into the SLF and its associated six digit identification code
from the EU's Hazardous Waste List.
IPC processes are those designated for regulation by the Environment
Agency through Regulations made under Part I of the Environmental
Protection Act 1990. Back