B51GH Mechanical Engineering Assignment Sample

 Section 1

1. What are the major global sources of anthropogenic CO2?

Answer 1: The major global sources of anthropogenic CO2 include the following:

• Chemical Production
• Transportation
• Industrial sources
• Production of petroleum
• Burning fossil fuels
• Deforestation
• Land use changes

2. If emissions to the atmosphere are ~40 GtCO2 per year, what is the expected annual increase in the concentration in the atmosphere? Current increases is atmospheric CO2 are approximately 2.5 ppm per year. Why is there a difference between the predicted and actual change in atmospheric CO2 concentration?

Answer 2: CO2 increase predicted will be 18.78 ppm per year.

3. Provide a short description for the following CO2 separation techniques.

(a) Chemical looping.

(b) Temperature-Pressure Swing Adsorption.

Answer 3:

• Chemical Looping: Chemical looping is a process used for combustion of fuel which is very highly efficient in separating carbon dioxide by making use of solid oxygen as carrier which helps in the conversion of the fuel.
• Temperature-Pressure Swing Adsorption: The Temperature-Pressure Swing Adsorption system works by adsorbing all the light gases from a fixed bed of adsorbents such as CO2, H2-. It is technique used to separate some species of gas from a mixture of gases under pressure keeping in mind features such as molecular characteristics.

4. What are the key steps in undertaking a life-cycle assessment?

Answer 4:

 The key steps in undertaking a life-cycle assessment are:

• Extracting the raw materials
• Processing the raw materials and manufacturing
• Transportation of the final goods
• Retail of the goods and its usage
• Disposal of any waste generate
• Analyzing the life cycle inventory
• Assessing the life cycle impact
• Interpreting the results

5. Why are oxyfuel processes used for carbon capture and storage?

Answer 5:

Oxyfuel processes are used for carbon capture and storage because the same is considerate as an optimal option being one of the leading technologies. Where required the modern technology can also be converted to conventional furnaces. It also provides for a more complete combustion, where by purer form of gas is separated from the mixture of gases.

6. What are the key criteria for selecting suitable geological storage sites for CO2?

Answer 6:

 The key criteria for selecting suitable geological storage sites for CO2 includes:

• Proper depth of the reservoir where CO2 is to be store
• The thickness of the storage
• The porosity and permeability of the storage site
• Standard of water mineralization

7. Explain the differences between ‘ex-situ’ and ‘in-situ’ mineralization.

Answer 7:

“The in-situ method is when the carbon dioxide is stored underground when a reaction takes place between carbon dioxide and the reactive material, trapping the carbon dioxide as carbonate materials, whereas the ex-situ reaction is the same as in situ but occurs above ground in a chemical processing plant.”

8. How might Biomass Energy Carbon Capture and Storage result in net negative emissions?

Answer 8:

“Some of the carbon in the biomass is converted to CO2 or biochar which can then be stored by geologic sequestration or land application, respectively, enabling carbon dioxide removal (CDR) and making BECCS a negative emissions technology (NET).”

9. Describe a biochemical conversion process for converting CO2 into a useful product.

Answer 9:

 Biochemical conversion makes uses of the enzymes of micro-organisms such as bacteria to break down biomasses. Different processes such as fermentation, composting and anaerobic digestion are involved in biochemical conversion.

Anaerobic digestion is where the bacteria break down the organic matter in the absence of any oxygen in order to produce biogas. This process takes places in sealed vessels which are known as reactor which come in different shapes and sizes and are specifically designed for the complex purpose of biochemical conversions.

10. Describe one meth of incentivising carbon solutions

Answer 10:

 While finding carbon solutions is the right thing to do, incentivising the same can be extremely helpful. One example is landfill tax. It is tax charged on disposing materials at landfills or even in unauthorised waste locations. It is used as tool to encourage to reduce the production, use and disposal of waste and encourages options like composting, recycling, etc.

Section B

14. Compare and contrast the key features, benefits and limitations of carbon capture processes.

Answer 14:

Carbon capture and storage processes are used as measures to mitigate carbon dioxide from various energy intensive sectors such as cement, petro-chemicals, etc. This is applied to traditional power plants to reduce atmospheric emissions by about 80-90%.  Carbon dioxide is captured using different methods such as oxyfuel, combustion and post-combustion processes. After the CO2 is captured, it is compressed to liquid state and transported through pipelines, tankers, etc and are eventually pumped underground. Three basic types of Carbon capture process and their characteristic features are noted below:

• Pre-combustion process: In a pre-combustion process fuel is converted into a gaseous mix of carbon dioxide and hydrogen. The HO2 that is separated can be burnt and the burning does not produce any carbon dioxide as the same has already been separated. The carbon dioxide that is separated is compressed and stored.
• Post-combustion process: In a post combustion process carbon dioxide is separated from exhaust gases. In this case, the CO2 is captured using a liquid solvent. Once the carbon dioxide is absorbed the liquid solvent, “the CO2 is released by heating to form a high purity CO3 stream”. This post-combustion process is very commonly used in the food and beverage industry.
• Oxyfuel combustion: The oxyfuel combustion process makes use of oxygen instead of air for combustion of fuel. In this process gas which mainly consists of water vapour is produced and the CO2 can be easily separated and used to form a high purity CO2 stream.

Limitations

One of the most substantial challenges entering the energy sector poses to CCS innovators is the complexity of its industrial processes. It is reasonable to assume that CCS would require significant increases in cost for this kind of system, especially when considering how much excess energy is required to catalyze most capture techniques. As a consequence, commodity products become less competitive, meaning businesses and the industrial sector as a whole are unlikely to choose to transition.

Moreover, there is insufficient evidence to prove that underground carbon dioxide storage is absolutely secure. Several scientists and experts suggest that these storage sites must be monitored very closely. The leakage of any of these gases in high quantities can proved to fatal in certain circumstances.

Advantages

Considering these disadvantages against the opportunity for deep decarbonization, it isn’t difficult to weigh their relative importance. Global climate change discussions are complicated, but their underlying advantages can be attributed to a successful CCS technology. If we fail to eliminate toxic carbon emissions, we will possibly damage our entire ecosystem.

15. Critically evaluate potential uses of carbon dioxide, and describe how this may make a meaningful impact on climate change.

Answer 15:

Carbon dioxide emission is one of the largest contributors to global warming. Yet carbon dioxide continues to form a major part of our industrial processes for hundreds of years now. It is used directly in may food and carbonated drinks, oil recovery, etc. indirectly it is used for chemical and biological transformation such as manufacturing of synthetic fuels, designer fuels. It is also used In manufacturing of chemicals and materials such as in organic chemistry and minerals.

It is also highly likely that carbon di oxide could possible be an alternative to several fuels and chemicals.

CO2 and Environment: As a green house gas, carbon dioxide absorbs and radiates heat. As the Earth’s surface is continually warmed by the sunlight, it emits thermal energy. Unlike gases like oxygen and nitrogen, carbon dioxide absorbs that heat and releases it over a period of time. Without this greenhouse effect, the temperature of earth would be 60 degrees Fahrenheit which is extremely chilling. But this has now crossed the usual level and trapped excessive heat leading to the rise in temperature. While carbon dioxide absorbs less heat per molecule in comparison to methane or nitrous oxide, it is larger in quantity and stays for a longer period of time. Another issue with the rise in carbon dioxide is the melting of the ocean. The carbon dioxide reacts with the H20 molecules and produce carbonic acids which reduces the PH level of the ocean and increases the acidity. This is known as ocean acidification.

References:

• (2020) Delaware Climate Action Plan Supporting Technical Greenhouse Gas Mitigation Analysis Report. Delaware Department of Natural Resources and Environmental Control. Available at: https://decaptransfer3.wpengine.com/wpcontent/uploads/2020/09/DNREC-Technical-Report_FINAL-9-3-20-CLEAN.pdf
• Governor’s Office of Coastal Activities. (2021) Louisiana Climate Initiatives Draft Partial Final Report. Office of the Governor Available at: https://gov.louisiana.gov/assets/docs/CCITaskforce/CITF_Draft.Partial.Final.Report.for.Public.Comment.pdf
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