1. Reduce heating demand
Reduce energy waste
In companies, thermal energy waste can be avoided by implementing simple measures. Some examples:
- a check makes it possible to avoid overheating in the manufacturing processes;
- regular maintenance to ensure good sealing and clean heat-recovery systems in order to avoid heat loss in boilers and furnaces;
- in the building sector, the means of action against heat loss are now known: improving the insulation of roofs, floors, walls and windows, as well as improving air tightness;
- for high-ceilinged industrial halls, radiant heaters are recommended instead of warm air heating systems. Radiant heating reduces draught losses and is not susceptible to the phenomenon of stratification, whereby warm air rises and is trapped at the ceiling without providing any useful effect at ground level.
Improve thermal processes
- energy is a production cost that needs to be controlled by applying temperature levels, processing times and other manufacturing methods accurately and without excess
- avoid operating installations (ovens, dryers, furnaces, etc.) at idle or partial load, as the fixed heat losses (cooling, exhaust) then become predominant over the useful effect.
Reduce distribution losses
These simple measures produce significant and lasting energy savings:
- effective thermal insulation of pipes and machine doors and walls
- elimination of heat carrier leaks: water, oil, steam.
2. Improve the efficiency of heat production
Minimum boiler efficiency requirements are defined by national legislation. Modern condensing boilers can achieve high thermal yields of up to 98%!
- On existing installations: recovering the heat lost through the flue gases makes it possible to preheat the combustion air or the make-up water, which improves the efficiency of the installation.
- Changing the carrier of useful heat can be advantageous: for example by replacing steam, which is energy-intensive and costly to maintain, with hot water or direct heating if the end uses allow it.
Modernise the burners and their control
- The traditional "all or nothing" mode of regulation is not always the most effective. Each time a burner is ignited, the combustion chamber is flushed with cold air, resulting in heat loss. Multi-stage burners help to reduce these losses.
- Sensors measuring the oxygen concentration in the flue gases permit precise adjustment of the combustion parameters of the burners even when the calorific value of the fuel varies.
Regular cleaning of the economisers and heat exchangers ensures optimum performance, as their efficiency decreases with the level of fouling.
In some cases, the implementation of water treatment in boilers and systems can provide benefits:
- improved heat transfer by preventing limescale deposits;
- reduced purge flow and related heat losses in steam boilers;
- avoidance of potential damage caused by aggressive water;
- filtration of filings and abrasive debris that damage the interior of pipe systems.
3. Recover heat
Large amounts of heat are lost along the flow of energy and materials through the company.
Where are the potential heat recovery solutions?
Each piece of equipment often rejects its excess heat as simple waste. Some examples:
- air compressors reject up to 96% of the electrical power absorbed in the form of heat;
- reheating furnaces used in metallurgy have an efficiency rate of approximately 60 to 75%: the energy losses are through the flue gases or the cooling water;
- on older boilers, the flue gas temperature can be used to preheat the combustion air or make-up water, which increases efficiency. Modern boilers offer high levels of efficiency (≥90%), which leaves little available potential;
- refrigeration installations also produce waste heat from their condensers;
- baking ovens and reactors, drying ovens, printing dryers, melting baths, etc. release varying amounts of thermal energy by convection or radiation;
- manufactured products often have to be force-cooled before being packaged or delivered.
These solutions must be carefully studied from the point of view of supplies and final needs according to:
- the amount of energy available and demanded by a possible use;
- the temperature levels available and necessary for use;
- the simultaneity of supply and demand;
- technical constraints such as distance and the technical possibility of recovering heat and installing pipes
The high exhaust temperatures available from furnaces and other heat-using machines mean significant heat recovery potential and make it possible, for example, to:
- pre-heat or dry raw materials;
- prepare steam or heat thermal oil or water;
- generate electricity using, for example, a steam turbine or an ORC cycle (Organic Rankine Cycle);
- prepare domestic hot water;
- provide additional heating at low temperatures, e.g. modern buildings with underfloor heating and a sufficient level of insulation.