Sergei Sheptalin, JSC HC Sibcem, discusses the update of a rotary kiln at Krasnoyarsk Cement.

Introduction

Established in 2004, Sibirskiy Cement is an industrial, vertically integrated holding. It is among the leading Russian producers of cement and cement-based construction materials.

The company includes Topki, Krasnoyarsk, and Timlui cement plants, concrete producers Sibirskiy Beton, and the Volna plant, which produces chrysotile cement products. Due to the stable activity of its repair, sale, and transport departments, Sibcem controls each production and sale stage - from the extraction of raw materials to the delivery of products to customers. The company's enterprises produce cement, ready mix concrete, mortar mixtures, roof covering, flat sheets, and nominal pipes.

Among the company's priority development directions is the technical re-equipment of plants built in the middle of the 20th Century. In 2018 alone, Sibirskiy Cement's investments amounted to more than RUB1.2 billion. The company invested these funds in increasing efficiency, environmental and industrial safety levels, the implementation of resource-saving technologies, the provision of reliable operation for main and auxiliary equipment, and the automation of technological processes.

Update at Krasnoyarsk Cement plant

A mong the company's most ambitious investment projects in 2018 - 2019 was the update of rotary kiln five at Krasnoyarsk cement plant. This required the separation of a burner oil production section and the installation of a multi-channel PYRO-JET burner, manufactured by German company KHD Humboldt Wedag AG. The contractor, Sibcemstroi LLC, was responsible for the implementation of the project. Headed at the beginning of the work by Vladimir Petrovich Skakun, the plant's employees, KHD representatives, and plant experts developed a technical idea and decided what equipment it would be necessary to produce.

On the completion of the project, the company would be able to reduce environmental impact, ensure compliance with the requirements of Federal Law No. 7 (on environmental protection), and use more resource and energy saving technologies. In addition, the project would improve the technical and economic performance of the equipment.

Built and commissioned in 1974, rotary kiln five produces clinker for standard and special cement production. The unit is equipped with a single-channel, first generation oil burner, which is a metal cylindrical tube w ith a cone section (nozzle). Coal dust w ith the primary combustion air is supplied through the tube, while the secondary air is supplied from the clinker cooler. The position of the burning zone is regulated by the extension of the oil burner and by means of a telescopic device in the nozzle.

Operating a single-channel burner using oil combustion assumes that the coal mill and the kiln work in a closed circuit. In such conditions, it is more difficult to burn clinker than when using a multi-channel burner. The high-pressure blow down fan, which ventilates the mill and transports the ground coal, also serves as the impulse source for feeding coal dust into the rotary kiln. However, at the Krasnoyarsk Cement plant the volume of air entering the plant unit was too large and much higher than demand. It is difficult to adjust this figure because reducing air volume by lowering the fan power would lead to the coal mill not being ventilated. As a result, additional air is required from the clinker cooler. With such a technological scheme, the efficiency factor of the cooler is not optimal, due to the variable air flow entering the kiln.

In case of a direct connection between the kiln and the coal mill, if the latter stops, the coal supply will reduce sharply, the concentration of fuel in the rotary kiln will decrease, and, accordingly, the temperature in the kiln will fall rapidly. To avoid such a situation, the amount of coal in the air is increased by means of additional fuel supply through the coal feeder. At the same time, the kiln operator will not allow the excessive supply of coal dust because the dispropotionate heating of the kiln causes the formation of 'spalls' of hot clinker.

PYRO-JET multi-fuel burner

"In terms of size, the equipment of rotary kilns, built more than half a century ago, is less productive than modern units," said Vladimir Afanasin, Managing Director of Krasnoyarsk Cement. "However, engineering developments can solve this problem. A pilot project for the technical re-equipment of kiln five is being implemented at Krasnoyarsk Cement, specifically for this purpose. It will replace a single-channel coal burner with a multi-channel and w e will see both economic and environmental impacts. Operation of the PYRO-JET burner will ensure complete fuel combustion. As a result of this, its consumption will be reduced and emissions of gaseous substances into the atmosphere will decrease. If operation of the new equipment shows good results, then w e will update other kilns in the same way."

The multi-fuel PYRO-JET burner meets current requirements for cement plant equipment and is notable for its reliability. Depending on design, the PYRO-JET means it is possible to burn solid, liquid, and gas fuel simultaneously, or to shift modes in various ratios. Comparatively, for a single-channel burner only coal is suitable.

At Krasnoyarsk Cement, the PYRO-JET burner primarily operates with pulverised coal fuel (PCF). It is planned to switch to liquid and gaseous fuels only during the firing of the rotary kiln.

The working element of the burner is concentrically arranged pipes. Through these, fuel nozzles are supplied with substances hat are necessary for combustion: primary air, coal dust, and fuel oil. They form channels and are numbered in sequence from internal to external.

Channel one is formed by three supporting bodies, namely a supporting body for the gas supply steam, a supporting body for a pilot burner, and a supporting body for a flame-checking relay. Supporting bodies are laid and centred with stiffening plates in the inner burner body.

Channel two transports the swirl air and connects to the outlet of the burner nozzle with a swirler, using position welding to support cartridge bodies.

Channel three transports primary air with PCF and closes at the outlet of the burner nozzle with a conic annulus opening outwards. In order to reduce rapid wear, the burner cone angle of the PCF is reduced.

An external plate with oil burners is welded to the pipeline for PCF, which separates the channels for the fuel and jet-type air. An internal nozzle for the PCF is screwed into the inner pipeline with oil burners, which, in connection with the inner burner body, separates channels two and three. The inner body is laid and centred with stiffening plates in the pipeline for PCF.

PCF is then fed to channel three through a pipe that is installed diagonally. It has an inspection hatch with a cover, through which it is possible to inspect the PCF feed area.

The walls of channel three in the PCF feed zone are protected against wear by a ceramic lining, consisting of glued wear-resistant plates. Ceramic lining for the protection of an outer section of channel three is attached to the inner sides of the half of the pipeline that is inserted into the PCF pipeline. The halves are welded by position welding to a closing flange in channel three, which makes it possible to prevent them from turning and slipping. Ceramic lining for the protection of an outer section of channel three is glued to the surface of the burner inner body. Its condition can be checked through an inspection hatch in the pipe for PCF. There is a special refinement for the surface of parts of the PCF unloading system that are subjected to wear.

Channel four transports jet-type air. It closes at the outlet of the burner nozzle via a disc with an atomizer burner welded to the PCF feedline, supporting the body of the burner. The disc has nozzle holes for jet-type air supply.

Channel five continuously transports cooling air through an external cooling air channel to protect the main parts of the burner and extend their service lifetime. It ends in the outer annulus of the burner nozzle outlet.

During operation, burner bodies expand in different ways, depending on the thermal effect. Thermal expansion is reduced by an axial compensator, for which appropriate pre-tension is provided during burner assembly.

Flame length in the kiln is reduced according to the design data after the update. Due to intensive air agitation and swirling in a short section of the burning zone, there will be as much oxygen as is necessary for the complete combustion of fuel in a short time. The oxygen will be completely consumed in the combustion process. In this case, there will be no chemical underburning of the coal. By reducing the amount of the 'cold' primary air passing through the burner, the required amount of oxygen for optimal coal combustion will come from the Volga 35 cooler, through the clinker layer, and will also be heated. According to the calculations of KHD experts, it will allow coal fuel of approximately 49 kcal/kg of clinker (or 9 kg/t of clinker) to be saved.

Conclusion

To effectively maintain the new equipment, technicians will reconstruct the coal compartment of kiln five. They will separate the section of burner oil preparation and mount a bag filter and a ventilation fan. KHD, which has worked with Sibirskiy Cement since 1989, will supply all necessary units. The basic equipment will be manufactured in Germany, while the ancillary equipment will be manufactured in Russia. The preliminary works, which do not affect the operation of the kiln, started in summer 2018, while the main work will be done in 1Q19. The new equipment will be commissioned in April.

About the author

Sergei Sheptalin is Executive Vice President of JSC HC Sibcem. He graduated from the Krasnoyarsk Institute of Non-Ferrous Metals with a degree in the engineering of metallurgy. After serving in the army, he was employed at the Achinsk alumina refinery plant, where he worked his way up from the burner of the rotary kiln to the head of the burning workshop. He has also held the role of Deputy Head of Production Management for main production at Achinsk alumina refinery plant, after which he worked as a manager of the operations control department at RUSAL-Management Co. He has been the Operation Support Director at OJSC RUSAL Achinsk and the General Director of Achinsk Cement. He has worked at JSC HC Sibcem since June 2015 and, in July 2016, he was appointed to his current role. In 2012, he was awarded the title Honourable Constructor of Russia.