**3. Process integration in cement production**

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 network, but in this case, it is difficult due to manufacturing issues. The existing process design presumes a hot meal heating inside the kiln by flue gases that cannot be executed by another stream owing to the technology. Another problem is a hot clinker, which is from the kiln. The clinker must be cooled down rapidly, and that is done by fresh ambient air. The level of technology that is used now has several restrictions for process changes. They have to be taken into account when the retrofit of HEN is made. The methodology stages were updated and are presented later to obtain the more feasible solution of an efficient heat exchanger network design.

of the reduced total cost of the new design with the use of reduced operating and investment

Heat Integration in a Cement Production http://dx.doi.org/10.5772/intechopen.75820 99

The next step is performed by the analysis of the waste heat potential in the retrofitted cement production. As was identified by grand composite, there is waste heat utilization potential, and its possibility should be analyzed additionally. The appropriate integration and efficient placement of heat engines is used by grand composite, which shows the available energy, the supply and demand temperatures of heat engines and a heat source. The waste heat utilization that is discarded by cooling capacity, along with attempts to derive energy from low-potential heat sources, has motivated the use of heat engines, for example, by the organic Rankine cycle (ORC) [24] or utilization of wide site cooling and heating

An additional intermediate stream may utilize the heat from process streams to site heating capacities. This may be steam of different pressure, hot water, thermal oil and so on. The selection of the intermediate utility stream is mainly dependent from its start and target temperatures. The T-H diagram represents a total site sink and source profiles by employing individual ΔTmin specifications of heat transfer between process streams to show the real stream temperatures [25]. Total site targets of heating and cooling, heat engine capacity and produced emissions are considered by Sun et al. [26]. The use of multiple intermediate utilities of heat recovery and modified total site targets is represented by Boldyryev [27] and methodology advances are discussed. All computations were performed by the HILECT software [28] applying integrated process design with technological restrictions mentioned

This case study was previously introduced by Boldyryev et al. [29, 30]. The energy expertise of the cement factory was conducted during the summer operation mode. The steady-state devices and portable equipment were used. The historical data of process monitoring were collected and analyzed. There are two operation modes of the particular cement factory. The first one is when the raw mill is under operation and, in this case, the cooling water flowrate at the cooling tower is 3 t/h. A hot gas from the kiln is fed into the raw mill and a raw material is heated. The second operation mode presumes that the raw mill is out of operation. In this case, the cooling water flowrate greatly increases and it is 11 t/h. At the same time, the waste heat with hot gases from the kiln is also increased. There are 18 process streams, which may be included to the heat integration of a particular cement factory. There is a heat recovery of an inspected cement plant and a necessary process heat is provided by the fuel combustion while a cooling capacity is delivered by ambient air that is pumped by air fans. **Table 1** has all

necessary thermophysical parameters of process streams under analysis.

**3.6. Utilization of waste heat in cement production**

cost [23].

demands [16].

earlier.

**4. Representative case study**

**4.1. Data collection and reconciliation**

#### **3.1. Data extraction by energy expertise execution**

An audit expertise of a particular cement factory was conducted to verify energy and mass balances. A measurement of temperatures, flow rates and fuel burning efficiency is accomplished. The composite curves approach and balanced grand composite are employed for the estimation of energy targets, heat recovery and the operation condition of heat transfer equipment, taking into account the cross-pinch heat exchange. Inefficient heat transfer is identified, and process restrictions and forbidden matches between heat transfer equipment are determined.

#### **3.2. Targeting**

Considering the next step, the composite curves of cement production are constructed to obtain the energy target and pinch point position of the existing and improved process. At this step, process restrictions are not considered, and only thermodynamically available heat recovery is obtained.

#### **3.3. New concept of heat exchanger network**

Based on the previous stages, the heat exchanger network is built taking into account the process restrictions. It is shown that the cross-pinch heat transfer still exists and it cannot be avoided in this production process due to features. Process streams with limitations are not excluded from the considerations to show the actual heat recovery and the real energy efficiency potential of cement manufacturing. The heat exchanger network was built for the range of ΔTmin from 1 to 300°C with step 1°.

#### **3.4. Heat recovery improvement**

Based on the previous step, energy targets and pinch point location are defined for different ΔTmin, and maximum heat recovery was found. This procedure determines the heat exchanger network temperature approach, cross-pinch heat transfer and topology heat matches in the heat network.

#### **3.5. Economic analysis**

All topologies of heat exchanger network are compared with the base case taking into account operation cost, investment for new networks, operation time, tax rate and other economic prerequisites. Economic results of retrofit execution are defined based on the determination of the reduced total cost of the new design with the use of reduced operating and investment cost [23].

### **3.6. Utilization of waste heat in cement production**

network, but in this case, it is difficult due to manufacturing issues. The existing process design presumes a hot meal heating inside the kiln by flue gases that cannot be executed by another stream owing to the technology. Another problem is a hot clinker, which is from the kiln. The clinker must be cooled down rapidly, and that is done by fresh ambient air. The level of technology that is used now has several restrictions for process changes. They have to be taken into account when the retrofit of HEN is made. The methodology stages were updated and are presented later to obtain the more feasible solution of an efficient heat exchanger

An audit expertise of a particular cement factory was conducted to verify energy and mass balances. A measurement of temperatures, flow rates and fuel burning efficiency is accomplished. The composite curves approach and balanced grand composite are employed for the estimation of energy targets, heat recovery and the operation condition of heat transfer equipment, taking into account the cross-pinch heat exchange. Inefficient heat transfer is identified, and process restrictions and forbidden matches between heat transfer equipment

Considering the next step, the composite curves of cement production are constructed to obtain the energy target and pinch point position of the existing and improved process. At this step, process restrictions are not considered, and only thermodynamically available heat

Based on the previous stages, the heat exchanger network is built taking into account the process restrictions. It is shown that the cross-pinch heat transfer still exists and it cannot be avoided in this production process due to features. Process streams with limitations are not excluded from the considerations to show the actual heat recovery and the real energy efficiency potential of cement manufacturing. The heat exchanger network was built for the

Based on the previous step, energy targets and pinch point location are defined for different ΔTmin, and maximum heat recovery was found. This procedure determines the heat exchanger network temperature approach, cross-pinch heat transfer and topology heat matches in the heat network.

All topologies of heat exchanger network are compared with the base case taking into account operation cost, investment for new networks, operation time, tax rate and other economic prerequisites. Economic results of retrofit execution are defined based on the determination

network design.

98 Cement Based Materials

are determined.

**3.2. Targeting**

recovery is obtained.

**3.1. Data extraction by energy expertise execution**

**3.3. New concept of heat exchanger network**

range of ΔTmin from 1 to 300°C with step 1°.

**3.4. Heat recovery improvement**

**3.5. Economic analysis**

The next step is performed by the analysis of the waste heat potential in the retrofitted cement production. As was identified by grand composite, there is waste heat utilization potential, and its possibility should be analyzed additionally. The appropriate integration and efficient placement of heat engines is used by grand composite, which shows the available energy, the supply and demand temperatures of heat engines and a heat source. The waste heat utilization that is discarded by cooling capacity, along with attempts to derive energy from low-potential heat sources, has motivated the use of heat engines, for example, by the organic Rankine cycle (ORC) [24] or utilization of wide site cooling and heating demands [16].

An additional intermediate stream may utilize the heat from process streams to site heating capacities. This may be steam of different pressure, hot water, thermal oil and so on. The selection of the intermediate utility stream is mainly dependent from its start and target temperatures. The T-H diagram represents a total site sink and source profiles by employing individual ΔTmin specifications of heat transfer between process streams to show the real stream temperatures [25]. Total site targets of heating and cooling, heat engine capacity and produced emissions are considered by Sun et al. [26]. The use of multiple intermediate utilities of heat recovery and modified total site targets is represented by Boldyryev [27] and methodology advances are discussed. All computations were performed by the HILECT software [28] applying integrated process design with technological restrictions mentioned earlier.
