Cost and Emissions Reduction in CO2 Capture Plant Dependent on Heat Exchanger Type and Different Process Configurations: Optimum Temperature Approach Analysis

The performance of a plate heat exchanger (PHE), in comparison with the conventional shell and tube types, through a trade-off analysis of energy cost and capital cost resulting from different temperature approaches in the cross-exchanger of a solvent-based CO2 capture process, was evaluated. The aim was to examine the cost reduction and CO2 emission reduction potentials of the different heat exchangers. Each specific heat exchanger type was assumed for the cross-exchanger, the lean amine cooler and the cooler to cool the direct contact cooler’s circulation water. The study was conducted for flue gases from a natural-gas combined-cycle power plant and the Brevik cement plant in Norway. The standard and the lean vapour compression CO2 absorption configurations were used for the study. The PHE outperformed the fixed tube sheet shell and tube heat exchanger (FTS-STHX) and the other STHXs economically and in emissions reduction. The optimal minimum temperature approach for the PHE cases based on CO2 avoided cost were achieved at 4 °C to 7 °C. This is where the energy consumption and indirect emissions are relatively low. The lean vapour compression CO2 capture process with optimum PHE achieved a 16% reduction in CO2 avoided cost in the cement plant process. When the available excess heat for the production of steam for 50% CO2 capture was considered together with the optimum PHE case of the lean vapour compression process, a cost reduction of about 34% was estimated. That is compared to a standard capture process with FTS-STHX without consideration of the excess heat. This highlights the importance of the waste heat at the Norcem cement plant. This study recommends the use of plate heat exchangers for the cross-heat exchanger (at 4–7 °C), lean amine cooler and the DCC unit’s circulation water cooler. To achieve the best possible CO2 capture process economically and in respect of emissions reduction, it is imperative to perform energy cost and capital cost trade-off analysis based on different minimum temperature approaches.

New Method of Materials Flow Calculation for Double-String SLCI Type Cement Plant (Part 2: Suspension Preheater and Calciners)

In many industries, energy auditing is important as the basis for controlling processes and designing additional equipment or modifying an existing plant. However, it requires detailed data of the materials flow, which often cannot be determined easily by direct measurement due to high-temperature limitations. This paper presents the second part of an integrated study to perform energy auditing in a separate line and in-line calciners (SLC-I) type cement plant. The second part of this study, as presented in this paper, focused on the materials flow calculation for eight separate cyclones and two calciners. The least square method was employed for solving the obtained overdetermined system equations. Using the operation data from Part 1 of the study, calculation of the detailed materials flow in each cyclone was executed. The results showed that the separation efficiency of cyclones 1A, 2A, 3A, 4A and 1B, 2B, 3B, 4B was 93.86%, 89.80%, 84.41%, 81.98% and 93.96%, 88.70%, 88.53%, 80.72% respectively and the estimated calcination percentage of kiln feed coming out of the ILC and the SLC was 85.3% and 56.3%, respectively. These values are impossible to be measured directly in the cyclones and calciners during plant operation.

The Effect of Excess Heat Utilization on the Production Cost of Cement

Industrial excess heat is a largely untapped resource that has the potential for external use that would be beneficial to the cement industry. Therefore, this work studied the excess heat utilization for the optimization of production cost in a cement plant within a period of three years. The study of plant layout in the selected plant in Nigeria (Ewekoro II Cement Plant of 200 tonnes/hour) was carried out to identify areas where excess heat is generated. The temperature and static pressure of precalciner, kiln, and cyclone were taken using a temperature probe, pitot tube, digital manometer, and light-emitting diode temperature reader. These parameters were used to obtain the mass flow rate and heat transfer needed for the heat energy analysis of the system. The kiln was maintained at constant tonnage per hour through a clinker truck weighed using the weighbridge. The result showed that the heat generated from the kiln was 577,640,260 MJ/hr. through excess air draft of 780,000 m3/hr (89.4%) at 250 °C and induced draft fan of 900,000 m3/hr at 350 °C. The result showed that excess heat can be utilized in pre-heater and air quenched cooler boilers, steam turbines and auxiliaries, and generators. The total estimated heat that could be saved amounted to 344,648,250 MJ with a total annual capacity of 2.25 million tonnes of cement. A saving of over two billion dollars could be achieved in production cost per year.

Combination of the Reduction Reaction in the Cement Plant DeNox by the Extended Precalciner Module and Intelligent SNCR System Upgradation

Nox emission is required to be less than 50 Mg/Nm3 for cement industry according to the environmental policies in some provinces. As Nox can be chemically reduced to N2 by reduction reaction, this paper will introduce a new method by the combination of two reduction reaction to reduce the Nox emission in cement plant. One reduction reaction is reducing the Nox by CO which is produced in the extended gasifier calciner. Another reduction reaction is reducing the Nox by ammonia which is produced by spraying the ammonia water in the pre-calciner outlet where temperature is between 850°C and 950°C which is considered as the best reaction temperature range for this reduction reaction. Also, the intelligent SNCR system is introduced in the reduction reaction to control the reaction amount of the ammonia water. The intelligent SNCR system can forecast the working situation by studying the clinker calcining system process data. In this way, Both the Nox emission and the ammonia consumption can be substantially reduced.

Ground and satellite monitoring of atmospheric pollution processes in urban areas

The results of the analysis of atmospheric pollution processes in the vicinity of the Chernorechensky cement plant and the Iskitim city were presented. Snow cover samples and high-resolution satellite images were used as research materials. The reconstruction of the fields of impurity concentration was carried out on the basis of low-parameter models. Statistical relationships were identified between ground-based and satellite observations.

Disposal of hazardous industrial waste in cement kiln – A pilot study of acid tar sludge

Acid tar sludge (ATS) is a hazardous waste generated in steel plants as a process by-product. ATS disposal is a major challenge for the steel industry around the world and specifically for developing nations. Hazardous wastes are usually disposed of in a dedicated expensive thermal treatment plant as per existing rules. Due to inadequate capacity of treating the total amount of hazardous waste, study of other economical options are required. India generates over 7.2 million metric tonnes of hazardous waste annually as per Central Pollution Control Board (CPCB), Government of India. Thus, co-processing of ATS in cement plant as an alternative means of disposal was studied based on a number of trials. During the five trials of 5 day each, feed rate of ATS was maintained at 0.4 tonne per hour (TPH) with an average coal feed rate of 10 TPH. No incremental variations in emissions were observed during the trials. The analysis further revealed insignificant impact on clinker quality, leach behaviour and cement property. The study also showed negligible impact on ambient air quality based on NO x, SO2, RSPM, SPM measurement at varying location around the cement plant. Thus, co-processing of hazardous waste such as ATS in cement plant can be an effective way to address the hazardous waste disposal problem in developing countries such as India.