Based at Pederobba in Northern Italy, cement manufacturer Industria Cementi Giovanni Rossi S.p.A. has been producing cement and hydraulic binders for over 90 years. Sustainability and ecological practices are important values in the corporate philosophy of the Cementirossi Group. In line with this sustainable approach, Cementi Rossi uses technologies that combine production requirements with environmental concerns.

Stricter emissions limits
Until December 2022, Industria Cementi Giovanni Rossi S.p.A. used a SNCR system to reduce NOx as part of flue-gas cleaning measures. In January 2023, the rules on emissions limits at the Pederobba site in Italy became more strict, meaning it was no longer possible to observe the NOx limit values reliably. Flue-gas cleaning was previously achieved using SNCR. In order to reduce emissions, urea pellets were injected at the heat exchanger tower, meaning NOx was reduced without any catalytic reaction. To ensure the stricter emissions limits could be reliably met, it was necessary to find a new solution.

Custom solution
To achieve the required emissions limit values, environmental specialist Scheuch installed a custom SCR tail-end tower. Scheuch developed a concept that was precisely tailored to the customer’s requirements. In December 2020, the order for a SCR tail-end tower system to reduce flue gases was confirmed. From December 2020 to February 2022, Scheuch worked hard to plan and implement the exhaust gas cleaning solution, which was specially adapted to the cement manufacturer’s requirements. The system layout was defined together with the customer. The automation and visualization elements were implemented by the customer in exemplary fashion on the basis of a functional description provided by Scheuch.

Scheuch was able to develop the optimal solution by taking account of a host of relevant parameters, as well as the local conditions. The customer’s site is located in an earthquake zone and a nature conservation area. Glossy surfaces had to be avoided for reasons of environmental protection and animal welfare. Scheuch also implemented noise protection measures so that a sound pressure level of 65 dBA as a limit value was not exceeded at a distance of 1 metre.

This state-of-the-art system will also enable future emissions limits for nitrogen oxide (NOx) and ammonia (NH3) to be reliably met. The system makes it possible to reduce NOx, NH3 and TOC by up to 65 per cent. Moreover, the system is a significant addition to the Scheuch product range for exhaust gas cleaning.

 “I am particularly happy that we were able to successfully demonstrate our expertise in this technologically challenging project and gain another satisfied customer that, like Scheuch, places a high value on working in partnership. We undoubtedly benefited from our many years of experience in the implementation of SCR systems. The expertise we have built up in the cement industry over the decades enables us to always deliver solutions that meet the diverse requirements of the industry.”
Andreas Brandstetter – Team Leader, Project Management

Technical feat
The SCR tail-end tower can be isolated from the clinker brick firing process via a bypass circuit with its own SCR fan. The advantage of this approach is that the system can be started up and shut down in a way that is reliable and completely autonomous from the kiln process.

The kiln exhaust gas is collected downstream of the bag filter at a relatively low temperature. This is due to the heat recovery system, which the technologically innovative cement plant has operated for several years. To ensure that NOx can be separated reliably with simultaneously low NH3 emissions, it is necessary to maintain a minimum temperature at the catalyst.

Increasing this temperature in an economical way is the biggest challenge for all tail-end SCR solutions. In the project at Industria Cementi Giovanni Rossi S.p.A., a combination of plate heat exchanger and gas burner was chosen. The installation of a plate heat exchanger (REKUGAVO) ensures extremely economical re-heating of the exhaust gas. Both gases flow through the profiled plates – which are welded together – with a high specific capacity in the countercurrent. This design ensures that the gases flow through without any leaks. To counterbalance the unavoidable temperature losses through the system, two gas burners are also installed that can be controlled according to the initial SOx concentration. This minimizes the risk of corrosion at the inlet of the plate heat exchanger.

Compact design conserves resources: The reactor size or cross-section is influenced not only by the catalysts used, but also by the type of ammonia solution injection point. In order to achieve a compact design, it is not productive to rely on tried-and-tested direct injection via two-component nozzles. Even a conventional injection grid upstream of the first catalyst layer requires an appropriate installation height for the process-related distribution of ammonia over the surface. To achieve a compact design, Scheuch chose an alternative solution. The reagent is injected in the upward-flowing duct on the side of the reactor. To implement this version, exhaust gas is removed from the process before being subjected to intermediate heating and fed into the evaporator line, where the ammonia solution injection lances are located. Once the ammonia solution has been pre-evaporated in this way, a compact system configuration with a low installation height that conserves resources can be achieved.

Ensuring even gas distribution: In virtually all exhaust gas cleaning processes used in process engineering, the even distribution of gas upstream of or within a reactor plays a vital role. The trick is often to take the flow of exhaust gas from compact pipe diameters or ducts at speeds of ~ 20 m/sec within short overall lengths and expand it to large rectangular cross-sections. Using in-house flow analysis, models and installations were developed that were reverse-engineered and tested on a model scale in order to generate useful data for the large-scale system. The even temperature distribution at the reactor inlet, the low differential pressure and the stoichiometric factor of < 1 demonstrate that correct upscaling was applied to the selected models and the large-scale system can therefore be operated more efficiently. When it comes to the stoichiometric factor of < 1, the process benefits from the ammonia that is released during heating of the raw material in the heat exchanger tower and is ultimately implemented at the catalyst. This enables raw material-related NH3 emissions to be reduced to a minimum.

The system was commissioned between October and December 2022.

Technical specifications

• Task: exhaust gas cleaning
• Scheuch technology: SCR tail-end tower
• Target: reduction of NOx, NH3 and TOC (up to 65 %)
• Gas flow inlet: 340,000 to 380,000 Nm³/h
• Technical features: NH3 supply, external evaporation, perfectly designed gas distribution at catalyst, installation tailor-made for customer production conditions

Testing phase
The system underwent testing in January 2023. To ensure that emissions limits were observed, a performance test was carried out in which the electricity consumption, gas consumption, NOx separation, NH3 consumption and noise limits were monitored. The measurements taken during the performance test confirmed adherence to all guaranteed limit values. The performance test was completed in February 2023, immediately following the winter revision, which resulted in acceptance of the system being issued.

“Let me congratulate all the Scheuch team for the important achievement!
After an excellent job made together, we can say that the Low Dust SCR in Pederobba works fine and is state-of-the-art in the cement industry, worldwide. It was a pleasure working with the Scheuch team.”
Gennaro Verbaro – Direttore Tecnico – Industria Cementi Giovanni Rossi S.p.A.

SCR technology
To reduce harmful gases such as NOx, NH3 and organic compounds, Scheuch has achieved crucial further developments of SCR technologies, making them the optimal way to meet customer requirements. Different, technically sophisticated system types are available depending on the system configuration. In addition to high-dust applications like high-dust SCR, semi-dust SCR or catalytic filter candles (CCF), there are low-dust SCR systems such as regenox, deconox®, LT catalyst or – as described above – the SCR tail-end tower to choose from. These applications ensure a reliable reduction in NOx. SCR technology makes it possible to achieve extra-low NOx/NH3 emissions values with an economical stoichiometric ratio of one or less.

“In line with environmental protection goals, it is essential that the cement industry also follows a sustainable path. Combining environmental interests with those of industry will create complex future challenges for the cement industry. With its extensive product range in the field of industrial dedusting, as well as outstanding process expertise, Scheuch is the first point of contact when it comes to implementing complex systems for dust and exhaust gas cleaning in the cement industry. As an international technology leader in the environmental technology segment, Scheuch makes an important contribution to the prevention of air pollution for future generations.”
Alois Hermandinger – Director Sales