What we can learn from Nepalese cement production

Make no mistake about it: producing cement in Nepal is a difficult task. Wedged between two giant neighbours, India and China, this landlocked country offers cement producers a long list of challenges – from the availability and quality of raw materials to the supply of fuel and skilled labour. Throw in the fact that its seismically-active location, high in the Himalayas, makes the production of consistently high-quality cement of particular importance. And top it off with a market situation on the cusp of severe overcapacity. It all leaves no doubt that cement companies have their work cut out.

Taking on these challenges with the latest technologies, Riddhi Siddhi Cement is a relative newcomer to the increasingly crowded Nepalese cement sector. Its new 2200 tpd fully-automated production line in Hetauda, south of the capital, Kathmandu, began production in 2019. Fully supplied by FLSmidth, Riddhi Siddhi Cement has registered a number of technological firsts for Nepal, including the first to begin operations with an automatic sampling and laboratory solution.

Obsessed with quality

It is no exaggeration to say that Riddhi Siddhi Cement’s primary focus in on quality. Through the production of high-quality of cement, it aims to improve the strength and resilience of local construction. In a country often rocked by earthquakes, this is literally a matter of life or death. The magnitude 7.8 earthquake that hit central Nepal in April 2015 killed about 9000 people and injured many thousands more; it also damaged or destroyed more than 600,000 structures.

As recently as June 2020, however, it was reported that two cement companies had had their production permits revoked by the Nepal Bureau of Standards and Metrology (NBSM) for selling products that did not meet standards. This followed a report last year by the NBSM that found the production of sub-standard cement to be a particular problem for the industry.

A particular challenge is posed by the raw materials in Nepal. Although limestone is widely available, it is high in magnesium oxide (MgO), which has a detrimental impact on the soundness of concrete that can affect the strength and durability of a structure. Controlling the levels of MgO in cement is therefore one of the major concerns of Nepalese cement producers.

Limestone is also sourced from opencast quarries with little control over quality – and from a variety of suppliers. Meanwhile, during the rainy season, supply is disrupted, forcing cement plants to store large reserves of both limestone and additives to allow plant operations to continue for long periods of time without resupply. All of this results in a highly-variable raw mix that must, nonetheless, be turned into cement of consistent quality.

At Riddhi Siddhi Cement, these difficulties have been overcome with the installation of the QCX® automatic sampling and analysis solutions from FLSmidth, QCX/Blend Expert, QCX/Auto Sampling and QCX/RoboLab.

By analysing the chemical conditions of the available raw materials, QCX/Blend Expert adjusts the set point of material and additive feeders to ensure that the final mix of raw materials, additives and corrective materials sent to the raw mill is of consistent quality. From the mill, a QCX/Auto Sampling system takes a sample of the raw mix, which is then sent via a transport pipe to the QCX/RoboLab for analysis. Two more QCX/Auto Sampling systems are located at key points on the production line, sampling kiln feed to the preheater and at the cement mill outlet. All of this occurs automatically, without the need for operator input.

The use of automatic sampling and laboratory analysis results in faster, more regular and more accurate insight into the quality of the raw mix and intermediate products than manual sampling and analysis could provide. While a normal manual sampling routine may take 4-5 hours to come up with results (and during the rainy season in Nepal, manual sampling may simply not happen), the use of QCX/Auto Sampling and QCX/RoboLab can provide analysis within half an hour of sampling. Any problems are therefore detected more quickly, allowing faster response and giving the plant much more control of the process to guarantee final product quality.

Control over the raw mix also allows Riddhi Siddhi Cement to utilise lower-quality limestone in an optimised blend with higher-quality materials. This conserves higher-quality reserves at its own quarries and also reduces the amount of high-grade limestone the company needs to source from third parties.

All of this results in lower overall cost per tonne of cement produced at Riddhi Siddhi – vital in an already competitive market that is facing a surge in capacity over the next two years. Total present market capacity is about 8 million tpa. But this is forecast to jump to about 14 million tpa, as a number of large-capacity plants come online in 2021 and 2022. With no real possibility to export, Nepalese cement companies are facing a potential price crunch that will favour only the most competitive producers.

This all means that guaranteeing the performance of the system is crucial. QCX modules can be monitored remotely by FLSmidth experts, who can connect at any time and from anywhere to provide support via the Go2FLS service. This helps keep the system operating at peak performance and reduces the risk of unexpected breakdown. When problems do occur, they can quickly be resolved them, limiting the impact on production. 

An environmental twist

A final area of benefit is seen in the sustainability of operations. For example, by enabling the use of lower-quality limestone in an optimised raw mix, QCX/Blend Expert helps lower the amount of material that needs to be extracted. This reduces the impact of quarry operations on the local environment, as well as reducing CO₂ emissions from both quarry operations and the trucking of limestone the often 30-40km from quarry to plant. Reducing the amount of coal used also has a positive impact on CO₂ emissions – both direct from the stack and indirectly, as a result of fewer truck journeys to bring the coal into the country.

Automatic sampling and analysis can also support higher rates of alternative fuel substitution, as process changes caused by variation in fuel quality can be more quickly identified and corrected. Although not widely used in Nepal at the moment, there is a developing interest with some plants looking into burning rice husks (a widely available material) and tyre chips. Meanwhile, production of clinker of consistent reactivity allows the addition of higher levels of supplementary cementitious materials (SCR), reducing the CO₂ generated per tonne of cement.

Conclusion

The laboratory at a cement plant may only be small, especially when compared to other parts of the production line. But it is by no means insignificant. Automating sampling and analysis with QCX/Auto Sampling and QCX/RoboLab, and combining with advanced quality control systems, such as QCX/Blend Expert, can have an outsized impact on plant operations, helping to ensure quality and reduce costs, as well as setting a foundation for more sustainable production. 

This article was first published in World Cement