**1. Introduction**

Nowadays, cement manufacturing is an energy-intensive industry. The energy costs of cement industry are about 40% of the product cost that indicates that this sector is one of the biggest CO2 emitter. The global anthropogenic CO<sup>2</sup> emission of cement industry is approximately 5% [1].

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

The International Energy Agency reported in 2011 that the world cement production was 3635 Mt. with a forecast rising up to 4556 Mt. in 2020, 4991 Mt. in 2030 and 5549 Mt. in 2050 according to scenarios with high demands. In case of the same scenarios, by 2050, the cement manufacturers have to reduce the CO2 emissions by 15%, with a direct decrease of up to 913 Mt. [2].

a mortar manufacturing process without remaining its physical properties. As presented by Wang et al. [14], the exergy approach combining with an organic Rankine cycle (ORC) and Kalina cycle were made to estimate of cogeneration opportunities of a cement factory as well as the calculation of optimal conditions and maximum efficiency. Process integration methods may be used as well to decrease energy use and emissions as were summarized in the work of Professor Seferlis et al. [15]. Presented approaches are based on thermodynamics laws and have different applications in different processing sectors; this issue was reported by Boldyryev and Varbanov [16]. In order to employ the industrial low potential heat and improve a heat utility system of different users and suppliers, a total site integration (TSI) may be employed as shown by Klemeš et al. [17]. Later, a similar approach was developed by different authors. As an example, Chew et al. [18] expanded the content of a pinch approach of individual process changes to improve a TSI and adapted the plus-minus principle for process modification options to improve process efficiency. Grip et al. [19] used the mixed-integer linear programming (MILP) approach, exergy analysis and pinch analysis (PA). Experience and results of a multiple approach were presented and considered in literature by many authors. For instance, Baniassadi et al. [20] represented a technique for an industrial energy system analysis with the use of modified R-curve approach. This methodology estimates the use of the most efficient fuel type for the industrial utility system. Mian et al. [21] employed the pinch analysis and the process integration approaches for energy optimization of cement manufacturing with primary energy demands of 3600 MJ/t. Authors calculated the thermodynamically and exergy available amount of heat that can be utilized and summarized that the potential of thermal energy reduction is 30%. However, the authors did not propose the retrofit project design nor was the definition of a feasible temperature approach provided. Summarizing the abovementioned, the recent works were rarely supplemented with proper industrial applications of the methodology, especially for the new heat exchanger network (HEN) design and retrofit of existing ones. The analysis and application of different methodologies are usually faced with process features of different industries. In addition, there is a lack of industrial applications of process integration techniques in the cement manufacturing processes owing to its specific process features and process limitations, such as solid particles of process streams, solid-gas and solid-air heat exchange and fast cooling of gaseous streams. Such approaches can be analyzed and subsequently used in appropriate case studies to achieve a real efficiency of the cement manufacturing processes. Thus, this chapter is dedicated to energy efficiency and pathways toward maximization of feasible heat recovery and the concept design of heat exchange system at

Heat Integration in a Cement Production http://dx.doi.org/10.5772/intechopen.75820 95

The energy efficiency potential of a cement factory is estimated. The total energy consumption of the particular cement manufacturing was compared with the benchmark value. Nowadays, considering a best available technology (BAT), the one with the lowest energy consumption of cement production is the rotary kiln use, many cyclone preheaters and the calciner. This technology has energy demands of a cement factory at about 2.93 GJ/t. The same amount is now used for benchmarking point [22]. Present technologies that use the kiln process have total energy consumption at about 3.65 GJ/t of cement. As mentioned, there are still opportunities

to reduce the energy consumption of the particular cement factory.

the particular cement factory.

Hence, cement manufacturing has to implement more energy reduction to be more environmentally friendly. However, as there is a large amount of CO2 coming from the existing technology, it is important to estimate a renewable energy potential use in the cement production industry or even switch from conventional fuel to a new one with low CO2 emissions.

Due to great significance of the cement industrial sector and high environmental perception [3] last time, a lot of researches worldwide have shown the energy efficiency improvement of cement factories and pollution reduction. Most of the published researchers investigated the improvement of the cement technology and different varieties for CO<sup>2</sup> emission reduction. Pardo et al. [4] are trying to define the potential of energy efficiency improvement of the EU's cement sector and CO2 gaseous emission reduction by 2030. Liu et al. [5] have presented the retrofit and building of new cement factories in China, accounting different technologies. Chen [6] had defined the advantages of the clinkering process by compact internal burning of carbon inside a cement shaft kiln. This research demonstrated the competitiveness of the proposed measure with the existing one that uses the precalciner kiln process. The work published by Hasanbeigi et al. [7] points out the CO2 cost curves for the Thailand cement sector. An estimated potential and expenses of CO2 abatement were investigated taking into account the expenses and CO2 abatement for a variety of applications. As presented by Worrell et al. [8], an in-depth analysis of a US cement industry considering a potential for energy cost and CO2 emission decreasing by the national technologies database was done. It was found that one of the most effective pyro-processing cement manufacturing systems composed of a calciner, several preheaters and the rotary kiln. The data of observed factory for the analysis of the parameters influencing the energy usage of a rotary kiln were utilized in the research by Atmaca and Yumrutas. Their work highlighted that high-energy savings may be obtained by reduction of heat losses with use of insulation, decreasing the outlet gas temperature and heat transfer enhancement. Sheinbaum and Ozawa [9] have presented the energy demands and CO2 emissions of the cement sector of Mexico, summarizing, that the measures of a fossil fuel, CO2 and other pollutants reduction have to be focused on the use of environmentally friendly energy sources. These assumptions were also concluded by Mikulčić et al. [10]. With the use of real industrial data and combination of kinds and flow rates of alternative energy sources, the work [11] estimated the ecological impact of cement manufacturing process. It is concluded that the environmental impact of the cement manufacturing process could be lowered if a more energy-saving process of cement manufacturing is utilized along with alternative fuels.

Stefanović et al. [12] estimated the potential of CO2 emission reduction that may be lowered partly by use of cement with fly ash in the concrete. The research showed that the properties and quality of the new kind of concrete remain the same. Another work by Zervaki et al. [13] investigated the properties of the cement mortars manufactured by use of sludge water. It was examined that the sludge water, as well as a dry or wet sludge, may be employed in a mortar manufacturing process without remaining its physical properties. As presented by Wang et al. [14], the exergy approach combining with an organic Rankine cycle (ORC) and Kalina cycle were made to estimate of cogeneration opportunities of a cement factory as well as the calculation of optimal conditions and maximum efficiency. Process integration methods may be used as well to decrease energy use and emissions as were summarized in the work of Professor Seferlis et al. [15]. Presented approaches are based on thermodynamics laws and have different applications in different processing sectors; this issue was reported by Boldyryev and Varbanov [16]. In order to employ the industrial low potential heat and improve a heat utility system of different users and suppliers, a total site integration (TSI) may be employed as shown by Klemeš et al. [17]. Later, a similar approach was developed by different authors. As an example, Chew et al. [18] expanded the content of a pinch approach of individual process changes to improve a TSI and adapted the plus-minus principle for process modification options to improve process efficiency. Grip et al. [19] used the mixed-integer linear programming (MILP) approach, exergy analysis and pinch analysis (PA). Experience and results of a multiple approach were presented and considered in literature by many authors. For instance, Baniassadi et al. [20] represented a technique for an industrial energy system analysis with the use of modified R-curve approach. This methodology estimates the use of the most efficient fuel type for the industrial utility system. Mian et al. [21] employed the pinch analysis and the process integration approaches for energy optimization of cement manufacturing with primary energy demands of 3600 MJ/t. Authors calculated the thermodynamically and exergy available amount of heat that can be utilized and summarized that the potential of thermal energy reduction is 30%. However, the authors did not propose the retrofit project design nor was the definition of a feasible temperature approach provided. Summarizing the abovementioned, the recent works were rarely supplemented with proper industrial applications of the methodology, especially for the new heat exchanger network (HEN) design and retrofit of existing ones. The analysis and application of different methodologies are usually faced with process features of different industries. In addition, there is a lack of industrial applications of process integration techniques in the cement manufacturing processes owing to its specific process features and process limitations, such as solid particles of process streams, solid-gas and solid-air heat exchange and fast cooling of gaseous streams. Such approaches can be analyzed and subsequently used in appropriate case studies to achieve a real efficiency of the cement manufacturing processes. Thus, this chapter is dedicated to energy efficiency and pathways toward maximization of feasible heat recovery and the concept design of heat exchange system at the particular cement factory.

The International Energy Agency reported in 2011 that the world cement production was 3635 Mt. with a forecast rising up to 4556 Mt. in 2020, 4991 Mt. in 2030 and 5549 Mt. in 2050 according to scenarios with high demands. In case of the same scenarios, by 2050, the cement manu-

Hence, cement manufacturing has to implement more energy reduction to be more environ-

nology, it is important to estimate a renewable energy potential use in the cement production

Due to great significance of the cement industrial sector and high environmental perception [3] last time, a lot of researches worldwide have shown the energy efficiency improvement of cement factories and pollution reduction. Most of the published researchers investigated

tion. Pardo et al. [4] are trying to define the potential of energy efficiency improvement of the

the retrofit and building of new cement factories in China, accounting different technologies. Chen [6] had defined the advantages of the clinkering process by compact internal burning of carbon inside a cement shaft kiln. This research demonstrated the competitiveness of the proposed measure with the existing one that uses the precalciner kiln process. The work pub-

an in-depth analysis of a US cement industry considering a potential for energy cost and CO2 emission decreasing by the national technologies database was done. It was found that one of the most effective pyro-processing cement manufacturing systems composed of a calciner, several preheaters and the rotary kiln. The data of observed factory for the analysis of the parameters influencing the energy usage of a rotary kiln were utilized in the research by Atmaca and Yumrutas. Their work highlighted that high-energy savings may be obtained by reduction of heat losses with use of insulation, decreasing the outlet gas temperature and heat transfer enhancement. Sheinbaum and Ozawa [9] have presented the energy demands

emissions of the cement sector of Mexico, summarizing, that the measures of a fossil

and other pollutants reduction have to be focused on the use of environmentally

friendly energy sources. These assumptions were also concluded by Mikulčić et al. [10]. With the use of real industrial data and combination of kinds and flow rates of alternative energy sources, the work [11] estimated the ecological impact of cement manufacturing process. It is concluded that the environmental impact of the cement manufacturing process could be lowered if a more energy-saving process of cement manufacturing is utilized along with alter-

partly by use of cement with fly ash in the concrete. The research showed that the properties and quality of the new kind of concrete remain the same. Another work by Zervaki et al. [13] investigated the properties of the cement mortars manufactured by use of sludge water. It was examined that the sludge water, as well as a dry or wet sludge, may be employed in

mentally friendly. However, as there is a large amount of CO2

industry or even switch from conventional fuel to a new one with low CO2

the improvement of the cement technology and different varieties for CO<sup>2</sup>

emissions by 15%, with a direct decrease of up to 913 Mt. [2].

gaseous emission reduction by 2030. Liu et al. [5] have presented

abatement for a variety of applications. As presented by Worrell et al. [8],

cost curves for the Thailand cement sector. An

emission reduction that may be lowered

abatement were investigated taking into account the

coming from the existing tech-

emissions.

emission reduc-

facturers have to reduce the CO2

94 Cement Based Materials

EU's cement sector and CO2

expenses and CO2

and CO2

fuel, CO2

native fuels.

lished by Hasanbeigi et al. [7] points out the CO2

Stefanović et al. [12] estimated the potential of CO2

estimated potential and expenses of CO2

The energy efficiency potential of a cement factory is estimated. The total energy consumption of the particular cement manufacturing was compared with the benchmark value. Nowadays, considering a best available technology (BAT), the one with the lowest energy consumption of cement production is the rotary kiln use, many cyclone preheaters and the calciner. This technology has energy demands of a cement factory at about 2.93 GJ/t. The same amount is now used for benchmarking point [22]. Present technologies that use the kiln process have total energy consumption at about 3.65 GJ/t of cement. As mentioned, there are still opportunities to reduce the energy consumption of the particular cement factory.

The main goal of this chapter is to identify the potential of feasible energy recovery and to suggest pathways for a new concept design of heat exchange system avoiding the process traps and limitations. The maximum heat recovery of the particular cement manufacturing was obtained, and the updated heat exchange system was proposed. The author concluded that the energy consumption of the particular cement plant may be lowered by 30%. Thus, the features of the cement production process forced a methodology update to suggest feasible retrofit pathways with the objective of achieving the optimal temperature approach of the heat exchange system. There are different streams and processes that contain solid particles, gaseous phase and fast cooling down; these facts make a solution more complicated by the special construction of the process equipment, which causes impossible a heat transfer between some process streams.

with a capacity of 170 t/h and appropriate raw meal is produced. The storage of current raw

The prepared raw meal from the silos is supplied to the kiln. The kiln has an operation capacity of 90 t/h and upper bound of 110 t/h. A total of 57 t/h of the clinker is produced inside the kiln. For the heating of the raw mill, kiln raw meal, and a coal mill, hot flue gases from the kiln are deployed. Gases exit from a preheating tower with a temperature at about 370°C. Flue gases have be cooled down at the cooling tower because the filter bags cannot operate at the temperature higher than 140°C. The flue gases at the cooling tower are cooled

perature from 175 to 105°C, fans are used to pump the ambient air. Flue gases go to the stack

At the kiln outlet side the temperature of the clinker is approximately 1450°C. At this stage, to preserve the clinker mineral structure, that is, its quality, the clinker has to be cooled very quickly to a temperature of approximately 150°C. A large amount of ambient air is introduced through seven clinker cooler fans to achieve the target temperature outlet. The ambient air is heated up to 290°C. After that, a small amount of this air is employed as an additional oxygen source in the kiln and a bigger part is supplied for cement mill heating if it is under operation. The operation mode with disabled cement mill envisages air cooling down before the filter bags. The gas has to be cooled to 105°C prior to the clinker cooler filter bags, after the gas is

The hot gases are needed for the cement grinding process. The hot air is taken to the separator where materials (clinker, limestone/slag and gypsum), pre-grinded on the roller press, are heated to extract moisture and prepare the resulting material for filter bags. They can be delivered from the clinker cooler or, in the case when the kiln does not operate, generated by a hot gas generator (HGG) with use of light oil as a fuel. It is the expensive option but it is used only in several weeks when the kiln overhauls. The consumption of the light oil is about 200 l/h.

A material mixture is kept in a bin with a capacity of 70 t that is supplied by a cement ball mill. Dust and fly ash are supplemented after the ball mill depending on the required kind of cement. The cement is then transferred through a bucket elevator to the next separator.

The methodology is grounded on the thermodynamic analysis of the heat energy system by composite curves of process streams. The general issues are based on process integration aspects. The pinch analysis (PA) for optimal process structure synthesis is well illustrated by Klemeš et al. [23]. It provides a solution that is very close to the global optimum in a simply and understandable way. The methodology produces the result of potential savings, capital cost and payback period prior to the flow-sheet design. Often, a super targeting procedure is employed to obtain the optimal temperature approach (ΔTmin) of the heat exchanger

after filtration, and further, they are discharged into the environment.

Particles comprise the final product that is supplied to the cement silo.

of cooling water. To further reduce the flue gas tem-

Heat Integration in a Cement Production http://dx.doi.org/10.5772/intechopen.75820 97

meal has two silos with a capacity of 2200 t each.

eliminated to the stack by four rows of four blowers.

**3. Process integration in cement production**

to a temperature of 175°C by 10.5 m3
