Distiller Chemical Industry: Conclusions

The waste heat recovery technology has been tested by these five different prototypes with different variations in power electronics, thermal collector contact surfaces, cooling system and the thermoelectric generators to configure the best option for each type of heat source.

Efficiency is one of the main parameters analysed in each project. This parameter shows how much energy is extracted from waste heat.

The efficiency of the prototype depends on the heat source, the heat collector type and the cooling system applied.

DISTILLER treats and manages industrial waste using distillation processes to recover solvents and treat contaminated aqueous solutions.

Thermal oil is used to supply the necessary heat to perform the distillation processes. Thus, the factory has thermal oil boilers to heat and recirculate the oil to different energy consumers through a close circuit.

The energy recovery system (Heat R-System) installed in industrial waste manage plant that Distiller has in Sta. Perpetua de la Mogoda (Barcelona) makes use of the waste heat generated in a WOGA thermal oil boiler.

The operating cycle of the dryer is 24 hours a day, 7 days a week, and the gas temperature varies from 130 to 220 ºC. The device must withstand ambient temperatures up to 40 ºC and sun exposure.

The recovery system that is installed is intrusive: the fins of the WHRU thermal collectors are installed inside the chimney to capture the maximum amount of heat from the gases. Although intrusive, this system does not affect the operation of the boiler, as it does not cause any pressure drop or condensation.

WHRU modules uses water heat-exchanger (water-block) for their cooling to obtain the maximum temperature difference between the two sides of the Peltier cells. The water is pumped from a well. The water-cooling temperature is 25 ºC.

In this project, the energy recovery system is based on a new type of WHRU:






  • Cooling system principle: Forced water convention
  • Cooling components Cold plate or water heat exchanger (waterblock).
  • Heat capture system principle Forced air convection – gas exhaust.
  • Thermal collector Intrusive convectional heat sink
  • Electrical energy generator Thermoelectric generator TEG – Peltier cell
  • Peltier cell number 36 cells 40 *40 mm


The main feature of this device is that it groups a set of 36 thermoelectric generators into a single unit. This design was created to group as many thermoelectric generators as possible in the smallest possible space, optimising the ratio of power generated per unit area.





Exhaust gas temperature 130 – 220 ºC
Generation area of two WHRU. 1705.7 cm2.
Mean power generated *54.72 W
Maximum power generated *96.50 W
Energy generated *479.30 kWh/year
Power density *565,80 W/m2
Heat flow in the exhaust gas
Heat flow through Heat R- System *2275 W
Efficiency 4.24 %



This device shares many similarities with the Goma Camps prototype in terms of heat collection and cooling system, except that Distiller’s WHRU device packs more Peltier cells into a smaller area. In other words, Distiller’s WHRU device is equivalent to six Goma Camps devices.

The prototype developed for the Distiller’s project has the highest efficiency with a theoretical efficiency of around 4.24 %.

In this way, forced water cooling system together with forced convective flow heat collection based on the installation of the heat collector in contact with the hot gases is the best configuration for achieving the best performance of the prototypes.

This type of thermal collection uses a forced convective flow, which increases the temperature of the Peltier cells.

In addition, the power density of this WHRU device is increased by grouping 36 Peltier cells in a smaller area.

On the other hand, the action of the forced-water cooling system results in a significant temperature differential between the two sides of the Peltier cells which translates into a higher electrical power generation.

-From the standpoint of the installation, the water-cooling system requires a hydraulic loop with a pump. It is essential to ensure a continuous supply of cooling water to avoid damaging the prototype by exceeding the maximum working temperatures of the components. Therefore, installing two pumps instead of one or automating the start-up of the pump when the process starts are options to ensure the water supply. It is also crucial to ensure that all valves are open in the hydraulic circuit.


On the other hand, the quality of the water supply is important. The water must be free of suspended solids to avoid possible clogging that could hinder or prevent the water supply and thus damage the equipment.

Distiller Chemical Industry: Prototype Implementation

All components of the heat recovery system are integrated and connected to generate the maximum amount of power from the waste heat source.

In Distiller, the heat recovery system aims to capture the maximum flow of waste heat through the WHRU heat collector inserted inside a chimney.


Figure. Heat collector in contact with the gas

Distiller Chemical Industry: Prototype Design


The building of the boiler room where the chimney is located has a height of approximately 12 m. The chimney can be accessed by a cat ladder, but the floor next to the chimney must be considered as not practicable as part of the ceiling of the boiler room.


Design decisions

It is proposed to install 2 WHRU modules that will penetrate one of the WOGA boiler gas outlet chimneys.

The WHRU units will be installed one on each side of the chimney 600 mm wide.

WHRU modules will be equipped with waterblocks for water cooling.

The cooling water distribution installation will be provided with traps to avoid the presence of air in the water circuit.

Each WHRU unit will consist of 6 waterblocks. Each waterblock will cool the cold face of 6 peltier cells. Therefore, each WHRU unit will consist of 36 peltier cells (6 waterblock x 6 peltier cells).

To maximize the effect of temperature on the WHRU collectors, a deflector will be installed inside the rectangular chimney.

For monitoring the correct functioning of the prototype, 3 types of sensor nodes will be installed:

Type 1-Temperature Node: Th, Tc and Tgases output.

Type 2-Node Wattmeter to measure the power generated by the system. Said node will be installed inside the electrical panel.

2 units will be installed. of type 1 sensor nodes (one for each WHRU module) and 1 unit of type 2 node.

A LoRa Gateway will be installed to collect all the data sent by the sensors. The Gateway will be installed inside the boiler room right next to the existing electrical panels. The Gateway will be powered from one of the existing boxes.


Distiller Chemical Industry: Technical visit

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 Distiller Company (Sta. Perpetua de la Mogoda, Barcelona) on May 9th, 2018.

Heat Source

After analyzing all the heat generation points of the facilities it was decided to explore several points, specially the WOGA oil boiler.



Below you can see the results obtained

Oil boiler Point 1

Name Average Min Max Emissivity Standard Deviation
Oil boiler Point 1 39,3°C 5,8°C 110,2°C 0,98 22,0ºC
Oil boiler Point 2


Name Average Min Max Emissivity Standard Deviation
Oil boiler Point 2 20,4°C 2,6°C 101,0°C 0,98 22,0ºC
Internal duct

Name Average Min Max Emissivity Standard Deviation
Internal duct 60,6°C 28,0°C 112,8°C 0,98 22,0ºC
Pipe WOGA oil boil point 1

Name Average Min Max Emissivity Standard Deviation
WOGA oil boil point 1 23,7°C 6,9°C 124,0°C 0,98 22,0ºC
Pipe WOGA oil boil point 2

Name Average Min Max Emissivity Standard Deviation
WOGA oil boil point 2 64,6°C 9,3°C 172,9°C 0,98 22,0ºC
Pipe WOGA oil boil point 3

Name Average Min Max Emissivity Standard Deviation
WOGA oil boil point 3 77,1°C 16,2°C 225,7°C 0,98 22,0ºC
Pipe WOGA oil boil point 4

Name Average Min Max Emissivity Standard Deviation
WOGA oil boil point 4 32,5°C 8,7°C 125,8°C 0,98 22,0ºC


According to the visit made, it is considered that the chimney of the output gases of the WOGA boiler can be a suitable place for the placement of the WHRU units.

The temperature display on the electrical panel of the boiler indicates a temperature of the WOLGA boiler outlet gases of 270ºC but the real range is about 200ºC.

Flue gas outlet duct dimensions and sheet thickness will be requested.

WHRUs must be installed in the upper part of the flue gas outlet duct. We should have water at that point. According to what was discussed with Head of the Plant Maintenance,  there will be no problem in having a continuous amount of water to help dissipate the heat and achieve a greater temperature differential and thus obtain higher yields from our equipment. The flow, pressure and temperature data of the cooling water must be available.

The client uses the use of his WIFI for communication with the outside.

Working hours of the plant: from Sunday at 10pm until Friday at 10pm (120h / set. For 220 days / year).


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