Control of quality and operating costs

Everywhere in our lives the widespread use of glass and ceramics is apparent. In our homes, in industry, in buildings, in art - the applications are almost unlimited and the versatility and durability of these products is obvious. As with metals, the manufacture of ceramics and glass uses a great deal of energy for the firing and melting stages. However, each process stage can benefit through improved quality control and control of operating costs from the use of Promat´s insulation solutions.
Promat in ceramics manufacture
Sintering is the concluding stage in the production process for ceramic components. It involves the densification of the preformed material through the application of high temperature. The firing of clay products is done at just over 1000 °C. The sintering temperature for technical ceramics can be in excess of 1750 °C. In ceramics, the green particles sinter even before they actually begin to melt into a glassy state (vitrification). Correct selection of the sintering temperature will ensure the preferred properties of the ceramic components. As well as minimising energy losses, an insulation system from Promat allows more precise control of temperature at every stage of the process to optimise product quality.

Promat´s solutions in glass making
Although glass has the appearance of a solid it is actually a supercooled liquid. At the molecular level, the chains of molecules which form the glass interlink with each other when hot, then, as cooling occurs, the chains cannot untangle themselves in order to reach a stable crystalline structure. Whereas true solids melt sharply at a defined temperature, when glass is heated it progressively softens.

This characteristic of glass allows good control of viscosity when it is molten by close control of temperature and by minimizing any temperature gradients across the bulk of the molten glass. Promat´s engineered insulation solutions for the glass making industry have revolutionised quality control in high volume production processes.

The challenges in energy efficiency and control for ceramics and glass manufacture
  • Thermal management – energy loss control – design optimisation
  • Best possible control of heat loss

  • Resistance to thermal shock
  • Non-combustibility
  • Ensure thermal security of process for personnel safety
  • Design for continuous high temperature operation without deterioration. Longest possible working life essential for insulation without excessive shrinkage or other impairment of performance
  • Easy installation of insulation components
  • Fast ROI for insulation – cost effective system design for competitive low maintenance requirement

Energy conservation
Energy efficiency in furnaces and kilns is a major issue. Over 50% of all energy used in the industrial sector is used in thermal processes. Promat is committed to save energy in production processes and reduce heat losses by optimizing the application design while addressing all economical and ecological aspects. 

Application solutions in ceramics manufacture

Tunnel kilns and periodic kilns
These are commonly used for continuous ceramics sintering (firing).

In tunnel kilns the sintered parts move on kiln cars or rollers through different temperature zones. A typical tunnel kiln has three zones:
  • Preheat zone for removing lubricant and other organic materials
  • Sintering zone where the products are exposed to temperatures up to 1500 °C.
  • Cooling zone where the sintered parts cool down.

Long working lives up to 15 years, and low heat losses, have a major impact on the operating costs of these furnaces. Promat is well experienced offering engineering of the lining, materials, plus full installation, or supervision of the installation, when required.

Periodic kilns are very similar with the heating and cooling sintering stages controlled  according to a pre-set programme.
Batch kilns
As the name indicates, these offer batch sintering of ceramics rather than a continuous operation. They can offer temperatures up to around 1800 °C and can provide fast production rates with rapid heat up/cool down times. When insulated with a Promat system they also offer excellent energy savings.
Laboratory kilns
These are a specialised class of batch kilns and include dental kilns operating at temperatures up to 1800 °C. They are characterised by fast batch times, low energy consumption, and a long working life.

Application solutions in glass making

The largest use of glass around the world is in the manufacture of bottles with millions being made every day on automated plants. Tight quality control and consistent product size and weight are of paramount importance. Throughout these plants the control of heat losses will ensure the most efficient and cost effective manufacture. Insulation systems from Promat help to control the accurate viscosity of the molten glass leading to more consistent gob size and freedom from imperfections.

Efficiency of glass making is improved by:
  • Lowering scrap – increasing the proportion of good items produced.
  • Lowering the weight of glass used per item.

A Microtherm® insulation system allows feeder system design that will facilitate the precise control of glass temperature from melting tank through to discharge from the orifice ring.
The molten glass stream is conditioned for homogeneity in the forehearth. Microtherm® insulation on the cold face of a forehearth structure reduces weight, reduces energy losses, minimises temperature gradients in the molten glass, and reduces the surface temperature of the structure for safe personnel access.
Feeder bowl
The use of Microtherm® pre tailored insulation in a feeder bowl directly affects the quality and cost of the glass finished product. A more uniform temperature is maintained within the bowl giving an even glass flow through the orifice. The resultant glass gob will have a consistent size and a minimum weight.
Feeder bowl cover and orifice ring
The use of Microtherm® insulation in feeder bowl covers and around the orifice ring contributes further to the accurate control of temperature and glass gob size. Because of the versatility of shape and form in the Microtherm® range, customized components allow fast installation and a precise fit. Standard kits are held for all well known feeder bowl designs. The fast availability of insulation systems in an optimised size and form is critical for minimizing maintenance down time.
Hot air recuperator furnace
Also known as regenerator furnaces. With a hot air recuperator, it is important that heat loss from the piping system supplying hot air at typically around 750 °C to the burners is kept to an absolute minimum. All piping can be insulated with a combination of MICROTHERM® SLATTED panel and MICROTHERM® MPS (Moulded Pipe Section). In case studies, the temperature drop between the recuperator and the final burner has been measured at less than 30 °C. Weight of insulation is important as all piping is supported off the recuperator structure.

The Microtherm® system is both thinner and lighter than conventional insulation alternatives. A further benefit from the Microtherm® is the stability of the insulation over a long period of time with continuous high temperature exposure.
Float glass manufacture
With furnace temperature of up to 1550 °C and a discharge temperature into the float at around 1100 °C, flat glass manufacture is very energy intensive and control of heat losses is essential to control product quality. Promat systems have proven performance in this application leading to major savings in energy costs. 

A big furnace can hold 2,000 tonnes of molten glass and the compressibility of the bottom insulation layer becomes critical in order to maintain the thermal performance. Microtherm® insulation has excellent resistance to compressive loads and shows only slight compression without adverse effect on thermal performance in furnace installations. For example, a load of 100 KN/m2 results in just 5% compression.

Throughout glass making processes the careful control of loss of heat ensures optimised control of product quality, dramatically improved energy efficiency, and minimum harmful environmental impact.

The most effective way of containing heat is by the use of a Promat engineered insulation system.