Land Contamination: Technical Guidance on Special Sites: Acid Tar ...

6.2.6 Thermal based systems• Thermal based systems can be divided into those utilising thermal desorption andthose which involve incineration;• the nature of the contamination (i.e. the sheer mass of tar) generally means that, forpractical purposes, incineration is the only viable thermal based option.Incineration• Incineration is an ex situ treatment that destroys the contaminants by thermaloxidation;• the systems available for remediation include direct fired and indirectly firedincinerators, fluidised bed incinerators and infra red incinerators;• acid tars are likely to require physical pre-treatment (drying) prior to incineration andthe residue from the incineration process is likely to require appropriate disposalmeasures;• incineration has been carried out in the past, and is currently the favoured option in theUK for treatment of acid tars from refinery processes, with 6,500 of the 8,000 tonnesproduced annually in the UK being incinerated;• there are a number of problems associated with this option, however, as follows:−−−−wide variation in terms of properties of the tar leading to variation in the efficiency ofincineration;high sulphur content of the tar and the resulting need for scrubbers to remove sulphurdioxide from the waste stream;presence of heavy metals, which have strict emission controls; andpresence of additional contaminants in the tar, including physical objects such asbuilding materials (especially bricks) and drums, and neutralising materials such aslime.• Cement kilns have considerable potential for acid tar incineration due to the longresidence time and high temperatures together with their capacity for sulphur dioxideabsorption. Whilst this technology has been successfully used for this purpose inEurope, in particular in Germany, incinerators/cement kilns are closely controlledunder the Prescribed Process Regulations in the UK. An IPC authorisation (in duecourse a PPC consent) would have to be modified to allow acid tars to be disposed ofat a particular facility. It is unlikely that a commercial incinerator facility would go tothe extent of attempting to modify its authorisation unless a substantial volume ofmaterial was to be provided for disposal.R&D <strong>Technical</strong> Report P5-042/TR/04 38