CERAMICS - PowerPoint PPT Presentation

CERAMICS

Group 8

Blanco González, José Manuel

Gómez Rojo, Vidal

Llorente Pérez, Cristina

Sanz Moral, Luis Miguel

• Water is used in all ceramic processes.
• It can be used:
• As a raw material
• For the body and its preparation (low quality water)
• For glazes (good quality water)
• As a washing fluid (good quality water)
• As a cooling medium (good quality water)

• Significant emissions to air arise in the firing process
• Emissions vary:
• From site to site depending on the different clay raw materials (geological and geographical variations)
• From country to country

• There are a number of mineral species called clay minerals, but the most important are:
• Kaolinite
• Montmorillonite
• Halloysite
• Advanced ceramic products:
• contain only a small fraction of clay or none at all
• Based on the following materials:
• Oxides
• Carbides
• Nitrides
• Borides
• Other metal ions

• At this point, we consider the techniques that havepotential for achieving a high level of environmental protection
• Management systems, process-integrated and end of pipe measures are included
• Other procedures:
• Re-use of materials and energy
• Prevention and control
• Minimisation and recycling

The principal techniques to consider are in the following fields:

• Reduction of energy consumption
• Emissions of dusts
• Gaseous compounds
• Process waste water
• Process losses or waste
• Noise

We can reduce energy by the following ways:

• Improved design of kilns and dryers.
• Recovery of excess heat from kilns.
• Cogeneration/Combined heat and power plants
• Substitution of HFO and SF by LEF.
• Modification of ceramic bodies.

It include techniques and measures to prevent diffuse and channeled emissions:

• Measures
• Separation/filter systems:
• Centrifugal separators
• Filters: bas or lamellar
• Wet dust separators
• Electrostatic precipitators

- Is very important to reduce the input of pollutant precursors:

• Oxides of sulphur
• Oxides of nitrogen
• Inorganic chlorine compounds
• Inorganic fluorine compounds
• VOC´S

- Addition of Calcium rich additives

- Process optimization, an example is: Reduction of vapour water levels in the kiln gases

• Sorption plants (adsorbers and absorbers)
• Afterburning

Water has in our case a lot of uses:

• raw material
• a scrubing agent
• a heat exchange vehicule
• a cleaning agent

Objetive is to reduce the use of process water.

To reach these, process optimisation measures and process waste water treatment systems are employed

We have two methods where we can improve the process of manufacturing ceramics:

• Sludge arising in the manufacture of ceramic products.

This could be recycling systems or re-use in other products

• Solid process looses/ solid waste

This solid process looses can be re-use as raw material.

Applying measures at the source of the noise:

• Enclosure the unit
• Build up noise protection walls
• Double walls
• Vibration insulation
• Use silencers

Secondary noise protection measures:

• Thicker walls
• Sound insulation of the windows

Obviously also gates and windows have to be closed

and cautiously driving reduces the noise emissions.

And last, there is a time-limiting of noise intensive work.

• ‘Best Available Techniques’ for a specific installation will usually be the use of one individual or a combination of the techniques.
• BAT AEL does not define and suggest emission limit values (ELVs) because they are related to installations.

‘Best Available Techniques’ can be divided in two groups:

• GENERIC Best Available Techniques.
• SECTOR SPECIFIC Best Available Techniques.

GENERIC Best Available Techniques refer to the following areas:

• Environmental management.
• Energy.
• Dust emissions.
• Gaseous compounds.
• Process waste water (emissions and consumption).
• Sludge.
• Solid process losses/solid waste.
• Noise.

BAT are defined for each of these areas.

• BAT is to reduce energy:
• Improved design of kilns and dryers.
• Recovery of excess heat from kilns.
• Applying a fuel switch in the kiln firing process.
• Modification of ceramic bodies.
• Reduce primary energy consumption by applying cogeneration/combined heat and power plants.
• BAT is to reduce diffuse dust emissions:
• Measures for dusty operations.
• Bulk storage area measures.
• BAT is to reduce the emissions of gaseous compounds:
• Reducing the input of pollutant precursors.
• Heating curve optimisation.
• Cascade-type packed bed adsorbers.
• Dry flue-gas cleaning with a filter (bag filter or electrostatic precipitator).

• BAT is to reduce solid process losses/solid waste:
• Feedback of unmixed raw materials.
• Feedback of broken ware into the manufacturing process.
• Use of solid process losses in other industries.
• Electronic controlling of firing.
• Applying optimised setting.
• BAT is to reduce noise:
• Enclosure of units.
• Vibration insulation of units.
• Using silencers and slow rotating fans.
• Situating windows, gates and noisy units away from neighbours.
• Sound insulation of windows and walls.
• Closing windows and gates.
• Carrying out noisy (outdoor) activities only during the day.
• Good maintenance of the plant.

SECTOR SPECIFIC Best Available Techniques refer to the following areas:

• Bricks and roof tiles.
• Vitrified clay pipes.
• Refractory products.
• Expanded clay aggregates.
• Wall and floor tiles.
• Table- and ornamental ware (household ceramics).
• Technical ceramics.
• Sanitaryware.
• Inorganic bonded abrasives.

Of the same way, BAT are defined for each of these areas.

• BAT is to reduce the emissions of gaseous compoundsby addition of calcium rich additives, if the quality of the end-product is not affected.
• BAT is to reduce the emissions of volatile organic compoundsby applying activated carbon filters or thermal afterburning either in a one or a three chamber thermoreactor.
• BAT is to reduce channelled dust emissionsby applying bag filters, sintered lamellar filters, electrostatic precipitators or wet dust separators.
• BAT is to reduce the amount of solid process losses/solid waste by applying one individual or a combination of the following measures:
• Replacing plaster moulds by polymer moulds.
• Replacing plaster moulds by metal moulds.
• Us of vacuum plaster mixers.
• Re-use of used plaster moulds in other industries.

1 Radiant tube burners

2 Microwave assisted firing and microwave dryers

3 New type of drying system for refractory products

4 Advanced process waste water management with integrated glaze recovery

5 Lead-free glazing of high quality table porcelain

• Reduction of water vapour levels → usually results in lower emission rates for HF as well as of SOx.
• Technicaly difficult→that water is produced by the fossi fuels used tohead the kiln.
• Solution→ radiant-tube burners

Heat transfer is carried by thermal radiation.

Applied in roller hearth kilns and shuttle kilns, not yet proven for tunnel kilns.

• Heat transfer from the outside to the middle of the setting and into the centre of individual bricks is difficult. → Temperature gradients can lead to thermal stresses and damaged products
• Solution; microwave energy heats the product directly – including the centre of the units. microwave energy has been used in combination with conventional heating such as gas or electrical energy.

• Benefits
• minimisation of thermal stresses throughout the firing cycle
• reduction of solid process losses/solid waste
• reduced emissions based upon less energy consumption and higher production output

→can also be used for drying ceramic ware

• The drying of large size refractory building components is very time consuming and energy intensive.
• By placing heat resistant stainless steel foils or carbon fibres as the heating element →As drying takes place from the inside out, the water moves in the same direction as the temperature front. This reduces drying times considerably and reduces the energy requirement even 90%.

• An innovative model waste water treatment system →reductions in pollutants and savings in the manufacture.

The new process waste water system has five modules:

• Microfiltration.
• treatment of a tributary process waste water stream.
• inclusion of existing sedimentation tanks.
• construction of a new central process waste water treatment plant.
• separation of rainwater.

• Cost advantages

• reduction of personnel costs to 20 % of the original number of staff required through automation

• reduction of energy costs

• reduction in chemical additives

• recovery of re-usable glaze

• reduction of landfill costs.

• Potential disadvantages:
• energy costs for the filtration technology
• incorrect design of the microfiltration plant
• long phase of research into the use of recovered glaze
• high technical competence is necessary regarding the overall system
• redundancy measures have to be taken into account in the planning phase.

• Lead glazes have been used in the past mainly for high quality table porcelain.

→lead-free glaze formulations based on alkali boron silicates have been developed by a tableware producer.→annual savings in lead oxide of 60 tonnes. A higher energy requirement is needed for the treatment and recovery of process waste water