The main emissions from a flat glass furnace come from the combustion of fuel and the decomposition of the carbonate and sulphate raw materials. The raw materials are melted at a very high temperature so the process is extremely energy-intensive.
Emissions to air
The most significant pollutants from a glass furnace are: nitrogen oxides formed from the nitrogen and oxygen in the air at high temperature; sulfur oxides from the refining agent (and from oil fuel if that is used); and particulate matter derived from compounds volatilized from the molten glass. Carbon dioxide comes from both the decomposition of carbonates and from combusted fuels.
We are tackling pollutant air emissions with a range of primary and secondary abatement techniques. Primary methods, such as special burners or carefully-chosen raw materials, including more cullet (recycled glass), reduce pollutant formation and can also improve the thermal performance of the furnaces.
Secondary abatement removes the pollutants from the furnace waste gases before they are emitted through the chimney.
Until recently, the furnace emission pollution control plants in operation around NSG Group have all been based on standard technology. This removes the pollutants from the waste gases in three stages: alkali is injected into a scrubber to remove acid gases, the resultant reaction products and particulate emissions are then collected in an electrostatic precipitator, and finally nitrogen oxide is removed using ammonia injected into a selective catalytic reduction unit. However, the latest pollution control plant built by NSG Group uses a novel technique called a catalytic ceramic filter, or CCF.
■ Air Emissions
Please refer to the data
Novel pollution control plant installed at Ottawa
The abatement plant just installed on NSG Group's OT1 furnace in Ottawa, USA, is a CCF unit purchased from McGill AirClean. The system is based on thousands of ceramic filters, or "candles", in a single unit. Alkali, in this case lime, is added to the waste gas and the resultant reaction products and primary particles are collected by the filter. The novelty of the process is that the fibers of the filters are coated with a metal catalyst so when the gases pass through the structure nitrogen oxides are also removed. It is expected that CCF technology will become the standard for new furnace pollution control plant throughout NSG group.
Monitoring and reducing carbon emissions
In 2019, NSG Group was responsible for the emission of 3.8 million tonnes of CO2e. This is a six percent decrease on the previous year due to a combination of reduced production output, increases in the proportion of renewable electricity use and many proactive operational energy and CO2 saving initiatives as described in the energy use section.
Our scope 1 emissions were 3.0 million tonnes. These direct emissions occur from a combination of the combustion of fossil fuels within the manufacturing process, transportation of product and the decompisition of carbonate raw materials in the glass melting process.
Our scope 2 emissions (market based approach) were 0.8 million tonnes of CO2e. Scope 3 emissions were estimated at 2.5 million tonnes of CO2e.
In the operation of our float plants, heavy oil to natural gas conversion has helped to reduce carbon emissions by around 50 percent over the past 40 years and a combination of design and operational innovations has made further progress.
We aimed to reduce CO2e emissions per tonne of equivalent product by one percent per year until FY20, using FY15 as a baseline performance. This target was achieved every year until FY20. The target was not achieved in FY20 due to a reduction in product output associated with deteriorating market conditions.
Moving forwards, NSG Group has already committed to a Science Based Target verified by the SBTi. This target is an absolute reduction of Scope 1 and Scope 2 CO2e emissions by 21% compared to a baseline year of 2018. In addition, we have introduced a revised target for CO2e emission per tonne of equivalent product, with the new target being an 8% improvement in this metric by end of FY24 compared to FY20 baseline.
Recycled glass to improve efficiency and reduce emissions
Glass for recycling is a valuable resource. Wherever quality allows, we recycle any glass off-cuts or cullet within our own glass melting lines. Glass from our downstream operations and from our customers represents a potentially useful resource to us. We gain a double benefit from the use of such cullet: its use to make glass reduces the requirement for raw materials and avoids disposing of what would otherwise be a waste material and closes the recycling loop.
Ten percent cullet use saves three percent furnace energy and leads to reductions in CO2 emissions. One of our sites has manufactured glass using only cullet.
Cullet return projects are ongoing to try to minimize the need for virgin raw materials. Landfill is the least favored disposal option.
If glass is produced that cannot be remelted on-site, it is sent, where practicable, for external recycling.
New pollution control unit at San Salvo
A new NOx control unit (SCR technology) is being retrofitted downstream the existing pollution control plant of San Salvo line 1 (SS1). The NOx abatement plant was purchased from the German company GEA, a well-known firm in the pollution control field. Once the installation is complete and the SCR unit started up, this will be the last step in the control of SS1 Float furnace pollutant emissions. In addition to the obvious beneficial effects on the environment, the new unit will give SS1 Float furnace additional flexibility in the combustion control, with potential benefits in the glass final quality.