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ENVIRONMENTAL IMPROVEMENT RESULTING FROM OXYCOMBUSTION TECHNOLOGY USE IN THE GLASS INDUSTRY LOCATED IN SACCA SERENELLA (MURANO ISLAND, VENICE)

Introduction

One of the main environmental impacts due to this type of manufacturing activity are the emissions of pollutants in the atmosphere.

The production cycle of artistic glass is based on different operational phases; with regard to the environmental impact one of the most important steps is the blending of the vitreous solutions and by the following processing of formed glass.

Fusion of glass is responsible for about the 60% of energy consumption and 90% of solid and gaseous emissions deriving from the whole production cycle.

The aim of the project is the replacement of traditional techniques of glass fusion with techniques that lead to a lesser environmental impact and a lesser consumption of energy.

The furnaces for glass fusion are presently stoked by methane and the combustion is air/methane driven. Since a long time, experimental tests have been underway in order to evaluate the possibility of introducing different fusion techniques that could have relevant benefits also vis-à-vis energy consumption. Among them, the “oxycombustion” technique is one of the most promising.

Oxycombustion use in the glass industries located in Sacca Serenella (Murano Island, Venice) is foreseen as part of an experimental test that aims to reduce the environmental impact of the artistic glass production sector with regard to both, atmospheric emissions (i.e. carbon dioxide) and energy consumption.

The initiative has the support of the City of Venice, Artambiente (Craftsmen Association), SAPIO Spa (Private Company that produces oxygen), Confartigianato di Venezia and is to be enacted by glass craftsmen and the Glass Experimental Station (Laboratory for emissions analyses).

Environmental problems deriving from artistic glass production

Emissions in the atmosphere are caused by the raw materials themselves, the temperatures reached during the fusion phase and the combustion system.

Specifically they are made up of:

- by-products of methane combustion during the production cycle (carbon dioxide, and NO_X due to air oxidisation);

- by-products of the decomposition of the raw materials used to form the vitreous mixture (NO_X due to nitrates decomposition, CO₂ to carbonates);

- by-products of evaporation phenomena and possible re-condensation of volatile substances present into the vitreous mixture (PM, Heavy metals, chlorides and gaseous fluorides).

Oxycombustion replaces traditional methane/air combustion with a methane/oxygen driven combustion. In this way, the calorific value of the fuel increases because the presence of nitrogen, that at high rates in regular air combustion(about 80%), is almost completely removed. The result is a flame with higher temperatures so that a better diffusion of heat to the furnace and to the glass is obtained.

There are five glass industries involved in this experimental oxycombustion test.. They have a similar production cycle and a typology of product.

SAPIO Spa is charged with the detailed designs of all structural intervention necessary to run the experimental test both inside and outside the glassworks. Artambiente has to identify the glassworks that will be involved. The City of Venice Administration finances and establishes structural installations necessary for the experimental test as part of its urbanization intervention in Sacca Serenella. Upon the completion of the structural installations, the testing will last at least two years.

It is also expected to make use of the oxygen production potential in Porto Marghera industrial area and to link Murano through an underwater pipeline. Time needed for the pipeline completion is 12-18 months (upon receipt of the requisite authorisation release). To facilitate local distribution an arrival terminal for the pipeline will be built, from where a local distribution network will originate.

Potential energy consumption reduction

A relevant reduction of combustion consumption is due to experimental tests run on furnaces for artistic glass. Their combustion scheme has been modified from the methane/air to methane/oxygen mixture system.

The following table sums up specific consumptions checked during many tests:

¹ The value is given as the sum of energy spent for combustion and oxygen production equal to 2,3MJ/Kg of glass (2,1 mc O₂/kg glass; 0,3 kWh/mc O₂)

² A conventional factor of 2200 Kcal/KWh has been used.

At the moment in the Murano Island district a methane consumption of 4,4 million cubic metre has been recorded.

In terms of primary energy, consumption corresponding to the considerable introduction of the oxycombustion technique is reported into the following scheme:

Fuels consumption (basically natural gas) for house heating is about 148.000 tep.

Potential reduction of atmospheric emissions

The following scheme sums up the change of CO₂ global emissions corresponding to alternative configurations, both for unit of glass worked and as resulting from a considerable introduction of the oxycombustion technique.

Total reduction of equivalent CO₂ results in about 45.000 tons.

Other benefits

The main benefits derived from oxycombustion, besides the lower energy consumption and the reduction in emissions of greenhouse gases can be summed up in the following points:

1. reduction of nitrogen oxide emissions (lack of nitrogen to oxidize);

2. reduction of solid and gaseous emissions during production cycle (less frequent phenomena of evaporation/re-condensation)

3. reduction of smoke volume to be shifted by fan;

4. reduction of noise emissions (no air compressor is needed).

Inclusive costs

Costs corresponding to production of the distribution system is estimated to be about €10 million. This is broken down as follows:

- €4 million to build the oxygen pipe;

- €4 million to build the network of local distribution;

- €2 million to adapt the fusion furnaces.

Current and new technology working costs are also estimated as follows:

- €8,2 million to buy methane in the current methane/air blend;

- €6,8 million to buy methane and oxygen in the new methane/oxygen blend.

Last Updated

13th January 2005