Seeking success with new sensors

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Save to read list Published by David Bizley, Editor World Cement, Wednesday, 19 July 2023 10:30 Dust Concentration Detector

Seeking success with new sensors | World Cement

Manish Patel, Leomi Instruments Pvt. Ltd India, discusses a new sensor technology that is unlocking further process optimisations in cement plants with new advancements in air and process gas flow monitoring.

The cement industry is crucial to the development of the global construction and infrastructure sector, with approximately 4.4 billion t of cement being produced across the world in 2021. The world’s largest cement producer is China accounting for more than 55% of global capacity, with India representing the second-largest producer with around 7%. After the outbreak of Covid-19 there was a sudden rise in demand from rural and urban infrastructural developments across the world and this demand spike was observed most acutely in underdeveloped countries. Initiatives such as the ‘Smart City’ project by India will stoke further long-term demand for cement products as well as the technological retooling of existing cement plants with upgrades directed at cost and energy optimisation.

The cement industry is one of the most energy intensive industrial sectors. Energy consumption represents 40 – 60% of the total production cost. Due to increasing demand, efficiency and optimisation will be the key criteria for today’s cement plant operators, and this will largely depend on the accurate and repeatable measurement of various process parameters such as temperature, pressure, and the flow rate/level.

Generally, in the cement industry pressure and temperature are used to calculate process gas flows in correlation with fan/blower speeds and power consumption. However, this is an assumption that generates significant uncertainties around the actual gas flow rate and energy consumption of prime movers such as fan/blowers.

There is an urgent need to achieve optimal air and process gas flow measurements in order to improve the overall quality of the cement and boost the efficiency and cost optimisation of the various processes involved in its manufacture.

Cyclone preheaters are used prior to the rotary kilns in cement plants to heat the raw mix and drive off carbon dioxide and water before it is fed into the kiln. The quality of the preheater in a cement plant directly affects the stability of the calcining temperature and the quality of the cement clinker in the kiln. By measuring the exhaust gas flow rate in the downcomer, operators can make use of the fine control of the ID Fan downstream to achieve the optimum control of O2 content in the kiln off-gas.

Exhaust gas flow measurement is generally challenging due to the large diameter of ducts, high dust concentration, and high temperatures around 350 – 400°C. Generally, velocity is measured temporarily by pitot tube with a high uncertainty for cross checking which does not contribute to the efficient control of the process.

The clinker cooler is a key device in the clinker production line which helps in quenching and transporting the hot clinker discharged from the rotary kiln, supplying hot air for the rotary kiln and preheater system. As the first piece of equipment where high-temperature clinker releases its heat, it plays an indispensable role in reducing coal and power consumption, increasing the secondary and tertiary air temperature, and improving the heat recovery rate.

A good clinker cooler can help cement plants reduce energy consumption by two means: one is by improving the cooling efficiency and reducing the power consumption of the clinker cooler itself; the other is to reduce the coal consumption of the rotary kiln and preheating systems by improving the heat recovery rate. Efficient control over the clinker cooler fan is vital to achieving both a high cooling rate, with respect to feed rate adjustment, as well as better energy efficiency. Measuring the continuous flow rate of cooling air plays an important role in optimising the operation of a clinker cooler.

The measurement of a clinker cooler fan is a challenging task due to the high concentration of highly abrasive clinker dust, meaning flow sensors need to be robust and highly resistant to abrasion. Currently this application has limited flow measurement solutions with a life expectancy of approximately 1 – 6 months.

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Seeking success with new sensors | World Cement