Analysis and economic evaluation of a unique carbon capturing system with ammonia for producing ammonium bicarbonate
Introduction
Climate change is heavily affected by human activities that produce harmful emissions, such as carbon dioxide (CO2), as the most widely emitted greenhouse gas which causes global warming (resulting in greenhouse effect) by retaining sunlight heat in the atmosphere. This heat build-up in the atmosphere has caused the average global temperature to rise and this is one of the reasons for some of the recent global disasters, such as large wildfires, sea level risings, and droughts [1]. To reduce these adverse effects on the habitat of humans and animals, it is important to decrease the net CO2 emissions released to the environment. Using renewable energy sources, such as solar cells and wind turbines, is not sufficient and fast enough to reach the targets of emissions reductions set by the Paris agreement to be achieved before 2050 [2]. For these reasons, carbon capture technologies and systems come as a transition solution from a fossil fuel-based economy to a completely renewable energy-based economy. Carbon capture technologies are defined as devices and systems that separate the CO2 from the flue gases emitted by power or chemical plants for later transport and storage or possible utilization. Several systems have been built to a pilot-scale and are currently tested [3]. Although these carbon capture systems hold great promise in capturing CO2 from flue gases with efficiencies exceeding 85%, the main challenge is the energy penalty caused by retrofitting these systems to current thermal power plants [4]. This is because a considerable amount of thermal energy is needed to separate the CO2 from the flue gases which is drawn from burning more fossil fuel and losing net electric power efficiency of the plant by around 8.6% [5]. This makes carbon capture systems unattractive to the power industry due to the economic implications of this energy consumption by the carbon capture systems. For this reason, a number of investigators have developed carbon capture systems that produce high purity CO2 or other chemical products to offset the economic losses incurred by such systems [6]. High purity CO2 has multiple applications in different industries. For example, CO2 can be used in Enhanced Oil Recovery (EOR) to extract fossil fuels and fill the vacuum with this CO2 [7]. Another application is in the food industry where carbon dioxide is used in making soda beverages. One other approach to offset the costs of carbon capturing is the use of waste heat recovery and solar cells to provide the energy needed to separate the CO2 from the flue gases without any consumption from the fossil-fueled power plant as investigated by Ye et al. [8]. In the recent literature, several CO2 capture methods have been investigated. For instance, Petrescu and Cormos [9] studied the environmental impact of using a chemical and calcium looping method for capturing carbon as part of an integrated coal gasification combined cycle (IGCC). Their results show that using the iron-based chemical looping method minimizes the global warming potential indicator compared to an IGCC without carbon capturing. In another interesting study by Zhou et al. [10], the authors surveyed and studied the potential of using ionic liquids in the application of carbon capturing. They conducted a systemic analysis on the selection and concentration of using these ionic liquids for chemically absorbing CO2 from the flue gases. Zhang et al. [11] modeled a membrane-based carbon capture system for absorbing CO2 from incoming flue gases. Their model was used to investigate how membranes behave under different operating conditions. Using ammonia (NH3) as a chemical absorbent has been demonstrated to be one of the effective ways to separate CO2 from flue gases and ammonia as an absorbent has three main advantages, high absorption rate compared to other methods and other absorbents, like monoethanolamine (MEA), low regeneration energy and temperature requirements, high thermal stability, and cheaper than other chemical absorbents [12].
Producing other useful chemicals from the process of carbon capturing is also possible and has been investigated by researchers in the literature. Recently, a policy study of the carbon capture and utilization from power plants has concluded the need to support such value-producing carbon capture systems [13]. De Groot et al. [14] studied the production of dimethyl carbonate (DMC) using CO2 and methane as input gases. Economic feasibility studies and modeling of such a process were conducted in their work. The integration of this chemical process was later investigated by Sánchez et al. [15] to produce DMC in a sustainable way using renewable energy sources to first produce urea and methanol and then reacting these two substances to make DMC which has various applications and an economic value. At the same time, it stores the CO2 in a chemical form. The CO2 is proposed to come from thermal power plants or chemical plants that release CO2 as flue gases. The production costs of DMC using this route are 520 euros per ton and this is almost half what the typical costs are. This makes the carbon capture system both environmental and economic. In addition, Koohestanian et al. [16] proposed a novel process to produce urea using both the CO2 and nitrogen in the flue gases. Nitrogen had been ignored as a useful gas to produce any valuable chemicals. In their study, 2856 kg h−1 of urea can be made which has an economic value of 3.5 million USD a year. This is another case where it possible to capture the carbon dioxide and store it in a valuable chemical product to compensate for the energy penalty of carbon capturing systems. Ishaq et al. [17] introduced a carbon capture system that is powered by photovoltaic solar cells and wind turbines for the multigeneration of hydrogen (H2), urea, and power along with carbon dioxide capturing from a thermal power plant. Their simulation results show that the rate of power produced is 2.14 MW, and the hydrogen is produced at a rate of 518.4 kmol h−1, while the urea production is 86.4 kmol h−1. This system uses renewable energy sources to produce these three useful outputs and store the CO2 in the form of urea which has applications in the agriculture industry. This system has both economic and environmental advantages and does not suffer from the economic losses induced by the energy penalty of typical carbon capture systems. A recent extensive review was conducted by Al-Hamed and Dincer [18] that discusses the novel carbon capture systems proposed in the literature that focus on producing useful chemicals alongside carbon capturing from flue gases of thermal plants. One of the software pieces that are commonly used for simulating carbon capturing processes is ASPEN Plus. For example, Sheikh et al. [19] used this software to analyze an IGCC process with carbon capturing using the methods of techno-economic analysis. Another example, Feenstra et al. [20] employed ASPEN Plus in their simulation study of a diesel-based powering system featuring carbon capturing where the application of this powering system is marine vehicles. One more instance where ASPEN Plus was used is in a study by Bove et al. [21], where they simulated a carbon capturing process that is integrated with a molten carbonate fuel cell. These previous works show that using the Aspen Plus as the software for simulating carbon capturing systems is appropriate to understand the thermodynamics of the system.
In this work, a complete exergy analysis of an ammonia-based carbon capture system with the co-production of ammonium bicarbonate (NH4HCO3) is presented since the open literature has no work in this regard. Also, the present work offers a great economic potential in producing such a commercially valuable chemical to compensate for the economic losses of using more electricity and other material sources to produce the ammonium bicarbonate. This carbon capturing process will practically provide some economic incentives to the power industry to adopt such a system that produces value instead of simply consuming energy.
Section snippets
System description
This work considers a carbon capturing system that splits water (H2O) for hydrogen generation, then produces ammonia to react with the incoming CO2 stream from a thermal power plant to make ammonium bicarbonate. Ammonium bicarbonate has several applications, such as baking in the food industry, adhesives, farming, and cleaning products [22], [23]. While urea is mainly used in the agriculture industry. This chemical commodity is valuable and can be sold to potentially compensate for the
Analysis
This section will describe the analyses and models used to simulate the ammonia-based carbon capture system. The main assumptions of the thermodynamic model used to analyze the system are listed as follows:
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All components operate under the conditions of steady-state and uniform flow.
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The changes of potential energy and kinetic energy across each component of the system are considered small compared to the enthalpy values and the work and heat magnitudes [26].
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The pressure losses across the
Results and discussion
This section discusses the results of the models of the carbon capture system described above. The first thing to discuss is the input of the parameters of the model used. These parameters are listed in Table 4. After inputting these values into the model of the system, the output parameters resulting from the model are presented in Table 5. There are some points to be outlined from the results shown in this table. Firstly, the hydrogen production rate of the PEM electrolyzer is 0.08663 kg h−1,
Conclusions
In this paper, a thermodynamic analysis was conducted for the present carbon capture system using energy and exergy tools. The modeling of this system was mentioned in detail along with the assumptions made for this analysis. Some preliminary results have been found from the models implemented using the Aspen Plus software package and its modules. The first point found was that the PEM electrolyzer heat losses are the highest in the system. Secondly, this system requires almost 4.5 times more
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
References (46)
- et al.
Experimental study on capturing CO2 greenhouse gas by ammonia scrubbing
Energy Convers Manag
(2004) - et al.
Current status and challenges of the ammonia-based CO2 capture technologies toward commercialization
Int J Greenh Gas Control
(2013) - et al.
A parametric investigation of the Chilled Ammonia Process from energy and economic perspectives
Fuel
(Nov. 2012) - et al.
The economic value of CO2 for EOR applications
Energy Procedia
(2014) - et al.
Thermoeconomic evaluation of double-reheat coal-fired power units with carbon capture and storage and waste heat recovery using organic Rankine cycle
Int J Greenh Gas Control
(2021) - et al.
Environmental assessment of IGCC power plants with pre-combustion CO2 capture by chemical & calcium looping methods
J Clean Prod
(2017) - et al.
Thermodynamic modeling and rational design of ionic liquids for pre-combustion carbon capture
Chem Eng Sci
(2021) - et al.
Modeling of a CO2-piperazine-membrane absorption system
Chem Eng Res Des
(2018) - et al.
Current status and challenges of the ammonia escape inhibition technologies in ammonia-based CO2 capture process
Appl Energy
(2018) - et al.
Sustainable DMC production from CO2 and renewable ammonia and methanol
J CO2 Util
(2019)