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Dismantling of a chlor-alkali electrolysis plant

Until a few years ago, the so-called amalgam method was often used for the technical implementation of chlor-alkali electrolysis. Although with this method mercury was used in large quantities, possible carryovers were extremely low because the metal was sealed in special cells.

The decommissioning of such facilities, however, is a particular challenge today. Mercury is a highly toxic heavy metal; depending on the contact both acute and chronic effects are possible. For the decontamination of the plant stricter occupational safety measures and carrying out the work in stages are essential:

Stage 1: emptying the mercury from the electrolytic cells.

Stage 2: rinsing the mercury-contaminated installation with an oxidising agent.

Stage 3: removal of the cells and disassembly of mercury-contaminated steel and plant components.

Stage 4: the steel has small pores in which the mercury is still present in trace amounts. The contaminated steel parts and surfaces are cleaned with sandblasting and a specially equipped installation with special filters.

Stage 5: for the recovery of the steel and the sand jet as well as disposal of waste, today the following options are available:
- Recovery: reprocessing of the contaminated steel in a specially equipped steelworks
- Recovery: thermal treatment of the sand jet in a special plant with mercury recovery
- Disposal of mercury-contaminated hazardous waste through special packaging and storage in underground storage.

During the dismantling of a chlor-alkali electrolysis plant (amalgam method) special occupational safety and health protection measures were taken.

Dismantling of electroplating plants

In electroplating the surfaces of workpieces are protected, refined or provided with special properties using metallic and other coatings. Because of the widespread use of cyanides, chromates and heavy metals, however, the method involves special requirements regarding environmental and health protection. Often operation was not discontinued in an orderly fashion. As a result, today these installations can only be cleaned up with considerable time and effort.

Electroplating facility before dismantling

Electroplating facility after dismantling

Chiresa AG has many years of experience with the dismantling of electroplating operations. The basic procedure is:

Disposal of the remaining baths and residues

Emptying and dismantling the electroplating baths and all product-conducting pipes

Removal and cleaning of tanks and basins

Analysis of the waste and subsequent recycling or disposal

Decontamination and handover of the rooms

Dismantling tanks with white phosphorus

Owing to developments in the chemical industry, new production methods are introduced and production sites shut down. The old operating sites must be prepared for new tasks. Therefore storage tanks must be emptied of hazardous raw material. A typical example is the disposal of large quantities of white phosphorus. This material contains a very high risk potential, as it can ignite spontaneously in air and thus releases highly toxic gases.

Opening a tank with white phosphorus

The dismantling of the storage tanks and the removal of phosphorus can only be done manually, since the material must be kept constantly under water because of the high risk of fire. This means very high requirements regarding occupational safety and health and environmental protection. The phosphorus residues must be disposed of in appropriate special incinerators.

Cleaning the tank with a high pressure water jet

The steel surfaces heavily encrusted with phosphorus are cleaned using high-pressure water jet technology. Increased occupational safety and protective measures are essential.

Canton of Valais (2006/2008).

As part of two contracts in Canton Valais, Chiresa AG dismantled disused tank containers with residues of white phosphorus. In both cases, the dismantling had to be carried out without significant interruptions of the nearby manufacturing plant. Safety concepts were developed with measures for immediate fire fighting, taking into account the in-house safety rules and site-specific circumstances.

Southern France (2007).

NFollowing closure of an operating facility in southern France several plants were left with residual white phosphorus. Chiresa AG was awarded the contract for the proper decommissioning of three "phosphorus tanks" with a capacity of up to 200 m3 and the complete emptying and cleaning of several collecting tanks. The remediation approach consisted of the following fundamental elements:

Inspection of facilities on site by our specialists

Development of a dismantling and remediation concept

Execution of remediation in precisely defined phases: dismantling / cleaning / emptying / packing.

Cleaning of the steel and concrete surfaces heavily encrusted with phosphorus using high-pressure water jet technology. Manual (cut and break up) dismantling of the tank.

Removal and transfer of the phosphorus residues in liquid-tested containers, largely manually. It was thus possible to carry out the work on the building site safely and to ensure the storage of the white phosphorus and its transport the disposal facility.

Incineration of the phosphorus residues in a specially equipped special incinerator.

Because of the potential danger of poisoning and fire, increased safety and organisational measures were implemented during the entire remediation operation.

Removal of PCB-containing coatings

Polychlorinated biphenyls (PCBs) are synthetic compounds with versatile applications. Because of their good insulation properties they were often used in capacitors and transformers. PCBs were also widely used as an additive in paints and lacquers, including for metallic components. Despite their good properties PCBs are polluting substances and harmful to health. They are poorly degradable and at high temperatures, highly toxic dioxins and furans develop.

When the ewz power station at Wettingen was renovated there were large areas with PCB-coated steel parts. Because in this form they could not be directly recycled, in 2006 Chiresa AG was contracted with the legally and environmentally compliant removal of the PCB-containing paints and lacquers. The work was carried out on site in a tent set up for this purpose and supplemented by various environmental protection measures. Thus a special filter system was used to minimise PCB-polluted dust emissions. Moreover, soil samples were taken before and after the work, and subjected to laboratory analysis. The paint layer contaminated with PCBs was separated mechanically by sandblasting and under safe working conditions.

Structural steel surface after the removal of the PCB-containing coating

The PCB-contaminated sand was disposed of as hazardous waste. The cleaned steel could then be sent for recycling without any further measures.

Asbestos removal in a pharmaceutical company

Chiresa AG is a SUVA approved asbestos removal company.

In the autumn of 2010 our specialist team carried out asbestos removal in a pharmaceutical company in the Basel area. In addition to the removal of Eternit panels with firmly bound asbestos the focus of the work was on the removal of PVC floor coverings, various soft asbestos sheets and several metres of asbestos cords around pipes with loosely bound asbestos. For the work (covering several storeys in the building), increased safety measures were introduced. Among other things, these measures included the establishment of cleanup zones with a system of locks, air-vacuum conditions and a filter system. The asbestos-containing waste was packed and labelled in accordance with the regulations, and then disposed of by Chiresa AG in an environmentally sound manner.

The cleaned up areas were only released after air measurements had been carried out, whereby the air quality controls were performed by an independent environmental services office.

Feasibility study for the disposal of chemical waste in Prishtina (Kosovo)

In 2008/2009, on behalf of Kosovo's energy company KEK and under the management of the World Bank, Chiresa AG carried out a feasibility study for the environmentally sound disposal of approximately 20,000 tonnes of toxic production residues from a decommissioned lignite-powered gasworks.

Feasibility study for the disposal of chemical waste

Based on extensive field and laboratory investigations, Chiresa AG has shown that the majority of the production residues – especially phenol-containing wastewater – can be detoxified on-site using chemical and physical methods. The particularly hazardous waste fractions must be disposed of in disposal facilities abroad.

In carrying out its study Chiresa AG provided the following services:

Feasibility study for the safe handling and transport as well as the environmentally sound disposal of 20,000 tonnes of hazardous production residues in liquid, paste or solid form.

Environmental management plan

Environmental impact statement

Occupational safety and health protection plan

Tender documents for the execution of the remediation work taking into account the World Bank requirements.

In 2010 the contract for the disposal of the production residues was awarded under an internationally tendered competition and the work is expected to be completed in 2011.

The feasibility study was conducted in conjunction with the office of Dr. Henry Jäckli AG, which dealt with the hydrogeological characterisation of the site and with contaminated site investigations.

Decontamination and demolition of a military flare measurement facility

In 2010 Chiresa AG was commissioned by the Swiss Army to decontaminate and demolish a facility for testing flares.

Decontamination and demolition of a military flare measurement facility

Burning flares left behind heavy metal deposits which could largely only be removed using water jet technology. Through the decontamination of the polluted parts of the plant and the subsequent total demolition a highly valuable area was recovered.

The wastewater resulting from the water jet technology was treated in our physico-chemical plant. The solid waste was packaged separately and disposed of in special incinerators (e.g. filters). The decontaminated steel parts and the demolished concrete parts were recycled.

Dismantling of a heat exchanger

The decommissioning of industrial plants contaminated with hazardous substances places high demands on occupational safety and environmental protection. In this connection Chiresa AG has suitable premises and technical equipment that ensure the safe handling of complex deconstruction projects and can be targeted to specific customer needs.

Dismantling of a heat exchanger

In early 2011 Chiresa AG dismantled a disused heat exchanger in which residues containing nitrosyl sulphuric acid had been deposited after years of operation. The toxic and chemically reactive gases evolving during the dismantling were extracted directly where they occurred and cleaned in our modern exhaust air purification system. The technical measures were supported with extensive organisational and personal protection measures.

Dismantling of a heat exchanger


For more information:

Chiresa AG

Landstrasse 2
-5300 Turgi/AG, Switzerland

Telefon +41 056 201 70 80
Telefax +41 056 201 70 81