In order to start a thermoelectricity project, it is important to have a physical visit to the facilities in order to determine the waste heat ranges and the temperature in addition to the installation of the WHRU system. The technical visit was made at the Cementos Molins (St. Vicenç del Horts, Barcelona) on Juny 29th, 2018.
Heat Source
In Cementos Molins there is a big variety of heat points. The points analyzed are shown below:
Measurements
Below you can see the results obtained
| Name | Average | Min | Max | Emissivity | Standard Deviation |
| Rotary Oven Hopper | 186,84°C | 93,00°C | 276,38°C | 0,98 | 37,76ºC |
| Name | Average | Min | Max | Emissivity | Standard Deviation |
| Rotary Oven Point 1 | 368,86°C | 58,13°C | 398,59°C | 0,98 | 36,14ºC |
| Name | Average | Min | Max | Emissivity | Standard Deviation |
| Rotary Oven Point 2 | 367,08°C | 343,46°C | 388,50°C | 0,98 | 9,57ºC |
| Name | Average | Min | Max | Emissivity | Standard Deviation |
| WOGA oil boil point 1 | 175,17°C | 33,77°C | 362,51°C | 0,98 | 80,92ºC |
| Name | Average | Min | Max | Emissivity | Standard Deviation |
| Rotary Oven Chimney | 18,43°C | -6,00°C | 62,53°C | 0,98 | 15,34ºC |
| Name | Average | Min | Max | Emissivity | Standard Deviation |
| Industrial processing 1 | 127,85°C | 35,52°C | 799,40°C | 0,98 | 122,47 ºC |
| Name | Average | Min | Max | Emissivity | Standard Deviation |
| Industrial processing 2 | 132,45°C | 18,25°C | 838,23°C | 0,98 | 148,06ºC |
| Name | Average | Min | Max | Emissivity | Standard Deviation |
| Gas outlet chimney | 34,49°C | -3,06°C | 93,19°C | 0,98 | 21,17ºC |
| Name | Average | Min | Max | Emissivity | Standard Deviation |
| Heating pipe | 27,69°C | -5,67°C | 127,933°C | 0,98 | 16,94ºC |
Conclusion
After the visit to CIMENTS MOLINS, different potential heat recovery points have been identified, although not all of them are suitable.
Most pipes in the installation have an inner ring of refractory material having to withstand very high temperatures.
There are some pipes in the installation without refractory material inside that conduct gases at about 300ºC. The identified pipes are heat insulated and have a non-commercial diameter (greater than the standardized pipe diameter). This fact, together with the high height of these pipes, makes it impossible to place WHRU modules, from the point of view of their installation.
The manufacturing process of calcium aluminate cement (molten) is another point to consider the installation of WHRU units.
The installation of WHRU modules at this point is not suitable for several reasons:
• Dirty environment (with dust and vapors) and corrosive.
• Very high ambient temperature.
Another point to consider the installation of WHRU modules is in the rotary oven.
The rotary oven has an internal temperature of 1000 ºC. For this reason, the furnace is covered with refractory material that causes the outer temperature of the furnace surface to be around 390 ° C.
On the other hand, the available area existing at one end of the rotary kiln together with the ease of bringing cooling water to this point, makes it possible to consider the placement of WHRU modules that take advantage, by radiation, of the heat that emerges from the surface of the rotary oven.
The cooling water would come from the cooling towers. Said water leaves at about 25 ° C from the cooling towers. In the rotary oven, the cooling water is used to cool the rollers that move the oven. Very close to the area proposed for the installation of the WHRU modules, there is a roller and, consequently, availability of cooling water.
The Head of Engineering and Maintenance informs us that he would send us the cooling water to the WHRU installation point and return it to cooling towers through the return water network at his exit from the waterblocks.
Therefore, it is established that the installation of WHRU modules for the use of residual heat by radiation from the surface of the rotary oven would be the prototype to be proposed in this installation.
