In the manufacturing of carbon fiber-based energy storage cell felt, a critical component for advanced energy storage systems, various environmental pollutants are generated during production. This study, from my perspective as a researcher, aims to analyze the sources and components of exhaust gases and evaluate the feasibility of control measures. The energy storage cell felt is produced from polyacrylonitrile (PAN)-based fibers through processes like non-woven needling, pre-oxidation, carbonization, and graphitization, resulting in a material with high flatness, porosity, bulk density, specific surface area, and conductivity. Its applications span wind power energy storage devices, insulation in monocrystalline silicon furnaces, manufacturing of aviation engine single-crystal blades, and electrochemical water treatment in thermal power plants, highlighting its importance in the energy storage cell sector. During production, pollutants such as exhaust gases, wastewater, noise, and solid waste are emitted, with this research focusing specifically on exhaust gas treatment.
The production of energy storage cell felt involves multiple thermal treatment stages, each contributing to exhaust gas emissions. I analyzed these stages in detail to understand the gas composition and sources. The key processes include oxidation, carbonization, graphitization, and purification, all of which release gases due to chemical reactions and thermal decomposition. For instance, during oxidation, PAN-based fibers undergo structural changes, releasing small molecules like CO, CO2, CH4, H2, HCN, and NH3. Similarly, carbonization and graphitization involve nitrogen-protected heating, leading to the evolution of gases such as HCN and NH3, while purification at high temperatures emits CO, CO2, H2O, and H2. To summarize, I compiled the exhaust gas components from each process in Table 1.
| Production Process | Temperature Range | Main Gas Components | Key Pollutants | Remarks |
|---|---|---|---|---|
| Oxidation | Ambient to 300°C | CO, CO2, CH4, H2, HCN, NH3 | HCN, NH3 | Air as oxidant, electric heating |
| Carbonization | 200–1000°C | HCN, NH3, trace CO, CO2 | HCN, NH3 | Nitrogen protection, intermittent heating |
| Graphitization | 200–2000°C | CO, CO2, CH4, H2 | None | Nitrogen protection, electric heating |
| Purification | 2400–2500°C | CO, CO2, H2O, H2 | None | High-temperature sublimation under nitrogen |
From my analysis, the primary pollutants of concern are HCN and NH3, which arise mainly from oxidation and carbonization. These gases pose significant environmental and health risks, necessitating effective treatment. The production of energy storage cell felt, especially for energy storage cell applications, requires stringent control to minimize emissions. To quantify these emissions, I used analogical methods based on industry data. For example, in PAN-based carbon fiber production, approximately 207.9 g of HCN and 7.3 g of NH3 are released per kilogram of product. For an annual production of 600 tons of energy storage cell felt, the total emissions can be calculated using the formula:
$$ \text{HCN}_{\text{produced}} = 600 \times 10^3 \, \text{kg/a} \times 207.9 \, \text{g/kg} \times 10^{-3} = 124.74 \, \text{t/a} $$
$$ \text{NH}_3_{\text{produced}} = 600 \times 10^3 \, \text{kg/a} \times 7.3 \, \text{g/kg} \times 10^{-3} = 4.38 \, \text{t/a} $$
These values represent the baseline emissions before treatment. The collection efficiency for gases from oxidation and carbonization furnaces is high due to negative pressure designs, with 99% collection in heating zones and 98% in preparation and cooling zones. Thus, the collected amounts are:
$$ \text{HCN}_{\text{collected}} = 124.74 \, \text{t/a} \times 0.99 + (124.74 \, \text{t/a} – 124.74 \, \text{t/a} \times 0.99) \times 0.98 = 124.72 \, \text{t/a} $$
$$ \text{NH}_3_{\text{collected}} = 4.38 \, \text{t/a} \times 0.99 + (4.38 \, \text{t/a} – 4.38 \, \text{t/a} \times 0.99) \times 0.98 = 4.379 \, \text{t/a} $$
The uncollected emissions are minimal, at 0.02 t/a for HCN and 0.001 t/a for NH3, highlighting the effectiveness of containment measures in energy storage cell felt production.
To treat the collected exhaust gases, I investigated several control technologies, focusing on incineration and scrubbing systems. The direct-fired incinerator operates at 850°C, oxidizing gases like HCN with an efficiency of 98.4%. This is followed by a spray absorption tower using a 1.5% sodium hydroxide and sodium hypochlorite solution, which further removes HCN at 94.9% efficiency and NH3 at 90% efficiency. The combined treatment efficiency for HCN can be expressed as:
$$ \eta_{\text{total, HCN}} = 1 – (1 – \eta_{\text{incinerator}}) \times (1 – \eta_{\text{scrubber}}) = 1 – (1 – 0.984) \times (1 – 0.949) = 0.9992 \text{ or } 99.92\% $$
This high efficiency ensures that emissions are significantly reduced. For particulate matter (PM), SO2, and NOx from the incinerator’s combustion of liquefied gas, wet scrubbing analogous to wet dust removal achieves removal rates of 87% for PM and 15% for SO2, while NOx remains untreated due to its formation mechanism. The incinerator uses 8 t/a of liquefied gas, with emission factors derived from analogous projects. I summarized the incinerator emissions in Table 2.
| Pollutant | Production Rate (kg/h) | Production Concentration (mg/m³) | Removal Efficiency | Emission Rate (kg/h) | Emission Concentration (mg/m³) |
|---|---|---|---|---|---|
| Particulate Matter (PM) | 0.072 | 2.4 | 87% | 0.0097 | 0.32 |
| Sulfur Dioxide (SO2) | 0.077 | 2.57 | 15% | 0.065 | 2.17 |
| Nitrogen Oxides (NOx) | 0.150 | 5 | 0% | 0.150 | 5 |
In addition to thermal processes, the cutting and finishing of energy storage cell felt generate particulate emissions. Based on material balance, dust production is estimated at 5% of waste edges, leading to an annual production of 0.35 t/a. With local dust collection at 70% efficiency, the emissions are reduced to 0.105 t/a. This step is crucial for maintaining air quality in facilities producing energy storage cell components.
To assess the overall feasibility, I computed the final emissions after treatment. The exhaust gases from oxidation, carbonization, graphitization, and purification, along with incinerator combustion gases, are treated in the spray absorption tower and discharged through a stack. With a fan capacity of 30,000 m³/h and annual operation of 7,200 hours, the emission concentrations for key pollutants are calculated as follows:
$$ \text{HCN emission concentration} = \frac{\text{HCN emission rate}}{\text{Volumetric flow rate}} = \frac{0.0142 \, \text{kg/h} \times 10^6}{30,000 \, \text{m}^3/\text{h}} = 0.47 \, \text{mg/m}^3 $$
$$ \text{NH}_3 \text{ emission concentration} = \frac{0.061 \, \text{kg/h} \times 10^6}{30,000 \, \text{m}^3/\text{h}} = 2.03 \, \text{mg/m}^3 $$
These values, along with others, are presented in Table 3, comparing them to regulatory standards. The energy storage cell felt production must comply with emissions limits to ensure environmental sustainability.
| Pollutant | Emission Rate (kg/h) | Emission Concentration (mg/m³) | Regulatory Standard (mg/m³) | Compliance |
|---|---|---|---|---|
| HCN | 0.0142 | 0.47 | 1.9 (GB 16297-1996) | Yes |
| NH3 | 0.061 | 2.03 | 4.9 (GB 14554-93) | Yes |
| PM | 0.0097 | 0.32 | 120 (GB 16297-1996) | Yes |
| SO2 | 0.065 | 2.17 | 550 (GB 16297-1996) | Yes |
| NOx | 0.150 | 5.00 | 240 (GB 16297-1996) | Yes |
The feasibility of the control measures is further supported by their alignment with best available techniques. According to technical guidelines, incineration combined with alkaline scrubbing is considered a viable technology for carbon fiber production, including energy storage cell felt. My analysis shows that the proposed system reduces HCN emissions to negligible levels, with overall removal efficiencies exceeding 99% for critical pollutants. This is essential for scaling up production of energy storage cell materials without compromising environmental goals.
From an engineering perspective, I also evaluated the operational parameters of the treatment systems. The incinerator operates at 850°C to ensure complete oxidation, with energy recovery through heat exchangers to preheat incoming gases and provide energy for desorption processes. The spray absorption tower maintains a liquid-to-gas ratio of 1:5 to 1:9, with a residence time of 5–60 seconds, optimizing contact for gas absorption. The alkaline solution, continuously recirculated and periodically replenished, degrades cyanides and organic compounds through oxidation, achieving a closed-loop operation that minimizes wastewater discharge. This integrated approach is particularly beneficial for energy storage cell manufacturing, where resource efficiency is paramount.
Moreover, the unorganized emissions from furnaces are mitigated through enclosed building designs and localized ventilation. The oxidation and carbonization furnaces feature segmented structures with negative pressure in heating zones, reducing fugitive releases. For cutting operations, dust collection hoods and curtains capture particulates at the source, with an efficiency of over 70%. These measures collectively ensure that the production of energy storage cell felt adheres to stringent air quality standards.
In terms of environmental impact, the treated emissions pose minimal risk. The calculated concentrations for all pollutants are well below national standards, as shown in Table 3. For instance, HCN emissions at 0.47 mg/m³ are less than 25% of the allowable limit, while NH3 at 2.03 mg/m³ is under half the standard. This demonstrates the effectiveness of the treatment chain in safeguarding atmospheric quality around production facilities for energy storage cell components.
To enhance the analysis, I incorporated mathematical models to predict emissions under varying production scales. For energy storage cell felt output Q (in tons per year), the HCN production can be modeled as:
$$ \text{HCN}_{\text{produced}} (Q) = Q \times 207.9 \, \text{kg/t} $$
Similarly, after treatment with incineration and scrubbing, the emission E is given by:
$$ E_{\text{HCN}} = \text{HCN}_{\text{produced}} \times (1 – \eta_{\text{total}}) $$
Where ηtotal is the combined efficiency. This model allows for scalability assessments, crucial for expanding energy storage cell production to meet growing demand in renewable energy sectors.
Furthermore, I explored the chemical kinetics of gas formation during oxidation and carbonization. The release of HCN and NH3 is influenced by temperature and residence time. For example, in oxidation, the reaction rate for HCN formation can be approximated by an Arrhenius equation:
$$ k = A e^{-E_a / RT} $$
Where k is the rate constant, A is the pre-exponential factor, Ea is activation energy, R is the gas constant, and T is temperature in Kelvin. This explains why higher temperatures in carbonization (up to 1000°C) accelerate gas evolution, necessitating robust treatment. Understanding these kinetics helps optimize process conditions to minimize pollutant generation at source, complementing end-of-pipe treatments in energy storage cell felt manufacturing.
The economic feasibility of the exhaust gas treatment system is also considered. The incinerator and scrubber involve capital and operational costs, but these are offset by the environmental benefits and regulatory compliance. For energy storage cell projects, investing in such technologies ensures long-term sustainability and reduces potential liabilities from emissions. Additionally, energy recovery from the incinerator lowers fuel consumption, enhancing overall efficiency.
In conclusion, my comprehensive analysis confirms that the exhaust gas treatment measures for carbon fiber energy storage cell felt production are technically and environmentally feasible. The combination of incineration and alkaline scrubbing effectively reduces key pollutants like HCN and NH3 to levels compliant with national standards. The production of energy storage cell felt, vital for advancing energy storage technologies, can thus proceed with minimal environmental impact. Future work should focus on continuous monitoring and optimization of treatment parameters to further enhance performance. This study underscores the importance of integrated pollution control in high-tech manufacturing, particularly for energy storage cell applications driving the transition to a sustainable energy future.