Date:13/12/2021 DAPCE 3171307

Definitions:

1. Relaxation Time:

   Relaxation time refers to the time it takes for a system to return to equilibrium after being perturbed. In various contexts, it represents how quickly a physical property or state of a system approaches its equilibrium value after a disturbance.

2. Can Velocity:

   The can velocity, also known as free-stream velocity, is the speed of the fluid flow that surrounds a body, such as an aircraft or a vehicle, in an undisturbed environment. It's a crucial parameter in aerodynamics and fluid dynamics studies.

3. Filter Drag:

   Filter drag, often referred to as form drag or pressure drag, is the component of drag that arises due to the shape of an object moving through a fluid. It's caused by the pressure difference between the front and rear surfaces of the object.

4. Saltation Velocity:

   Saltation velocity is the minimum velocity required for small particles, like sand or dust, to be lifted off the ground and moved through the air in a jumping or bouncing motion. This term is often used in the context of wind erosion and sediment transport.

Comparison: High Velocity vs. Low Velocity Systems

Aspect	High Velocity System	Low Velocity System
Speed	Operate at high speeds, often supersonic.	Operate at low speeds, typically subsonic.
Examples	Supersonic aircraft, rockets.	Most everyday vehicles, slow-moving machinery.
Fluid Behavior	Compressibility effects are significant due to high speeds.	Compressibility effects are minimal.
Drag	Wave drag is a prominent form of drag.	Form drag is the dominant drag component.
Engineering Challenges	Thermal management, shock waves, and aerodynamic heating.	Steady airflow and efficient energy consumption.

Flue Gas Density Calculation at NTP

Given Composition (by % volume):

• CO2 = 14%
• N2 = 40%
• SO2 = 0.05%
• H2O = 45%
• O2 = 1.5%

Assuming ideal gas behavior and using molecular weights:

• CO2: Molecular Weight = 44 g/mol
• N2: Molecular Weight = 28 g/mol
• SO2: Molecular Weight = 64 g/mol
• H2O: Molecular Weight = 18 g/mol
• O2: Molecular Weight = 32 g/mol

Using the ideal gas law: density = (mass of gas) / (volume of gas)

At NTP, T = 273.15 K, P = 1 atm = 101325 Pa

Calculations:

        CO2:    Density = (0.14 * 44 g/mol) / (22.414 L/mol) = ... g/L
        N2:     Density = (0.40 * 28 g/mol) / (22.414 L/mol) = ... g/L
        SO2:    Density = (0.0005 * 64 g/mol) / (22.414 L/mol) = ... g/L
        H2O:    Density = (0.45 * 18 g/mol) / (22.414 L/mol) = ... g/L
        O2:     Density = (0.015 * 32 g/mol) / (22.414 L/mol) = ... g/L
        
        Total Density = Sum of densities of individual gases
        
        Total mass = Sum of (Volume % * Molecular Weight) for each gas
        Total volume = 22.414 L/mol (1 mole of ideal gas at NTP)
        Total Density = Total mass / Total volume
    

The calculated density of the flue gas at NTP is ... g/L.

Pyramid Hopper Height Calculation

Given Parameters:

• Valley Angle (θ) = 60 degrees
• Top Dimension (A) = 5 m
• Bottom Dimension (B) = 0.3 m

Using trigonometry to calculate the height (H) of the pyramid hopper:

H = (B - A) / (2 * tan(θ/2))

Calculations:

        H = (0.3 m - 5 m) / (2 * tan(60 degrees / 2)) = 2.684 m
    

The calculated height of the pyramid hopper is 2.684 meters.

Definitions and Equations:

1. (i) Migration Velocity:

   Migration velocity refers to the velocity at which charged particles move in response to an electric field in a fluid or gas. It's a critical parameter in processes like electrostatic precipitation.

   Design Equation: Vm = μ * E

   Where Vm is the migration velocity, μ is the mobility of the charged particle, and E is the electric field strength.

2. (ii) Resistivity:

   Resistivity is the measure of a material's opposition to the flow of electric current. It's a property used to characterize the electrical behavior of materials.

   Design Equation: R = ρ * (L / A)

   Where R is the resistance of the material, ρ is the resistivity, L is the length of the material, and A is the cross-sectional area.

3. (iii) Electrical Sectionalization:

   Electrical sectionalization refers to the division of an electrical system into separate sections to improve safety, control, and maintenance. It prevents the spread of faults and minimizes downtime.

   No specific design equation applies to this term.

Venturi Scrubber Gas Velocity Calculation

Given Parameters:

• Flow of Flue Gas (Q) = 2.5 m³/Sec
• Diameter of Throat (D) = 150 mm = 0.15 m

Calculating Gas Velocity:

Using the continuity equation for incompressible flow:

Q = A * V

Where Q is the flow rate, A is the cross-sectional area, and V is the velocity.

For the throat of the venturi scrubber:

A = π * (D/2)^2

V = Q / A

Calculations:

        A = π * (0.15 m / 2)^2 = 0.01767 m²
        V = 2.5 m³/Sec / 0.01767 m² ≈ 141.22 m/Sec
    

Design Sketch:

        +-------------------+
        |                   |
        |                   |
        |                   |
        |                   |
        |                   |
        |         Throat    |
        |        ---------> |
        |                   |
        |                   |
        |                   |
        |                   |
        |                   |
        +-------------------+
    

The calculated gas velocity at the throat of the venturi scrubber is approximately 141.22 m/Sec.

Design Criteria for Various Parameters

1. (i) SCA (Specific Collection Area):

   SCA is the ratio of the total collection area of a filtration system to the total gas flow rate it handles. It's used to assess the efficiency of the filtration process.

   Design Criteria: Higher SCA values are desired to ensure effective particle collection and filtration efficiency. An optimal SCA should be selected based on the specific filtration requirements and the characteristics of the particulate matter.

2. (ii) Dielectric Constant:

   Dielectric constant (also known as relative permittivity) is a measure of a material's ability to store electrical energy in an electric field. It influences the electrical behavior of materials.

   Design Criteria: For insulating materials, a higher dielectric constant can be advantageous in applications such as capacitors. For other applications, the choice of dielectric constant depends on the desired electrical characteristics of the material, such as its ability to resist electrical breakdown or store charge.

3. (iii) A/C Ratio (Air-to-Cloth Ratio) for Shaking Bag House:

   A/C ratio represents the amount of gas flow (expressed in cubic meters per minute or other suitable unit) passing through a unit area of filter fabric in a baghouse system.

   Design Criteria: A suitable A/C ratio is chosen based on factors such as the desired filtration efficiency, dust loading, and cleaning mechanism. A higher A/C ratio may result in higher air velocities through the fabric, which can affect pressure drop and filtration performance. The A/C ratio should be balanced to achieve optimal dust collection while minimizing energy consumption and fabric wear.

Relationship between Resistivity and Migration Velocity

Resistivity and migration velocity are both important parameters that play a significant role in the behavior of charged particles in a fluid or gas. They are related in the context of electrostatic precipitation and particle collection.

Resistivity:

Resistivity (ρ) is a property of a material that measures its ability to resist the flow of electric current. It is often associated with the electrical conductivity of a material.

Migration Velocity:

Migration velocity (Vm) refers to the velocity at which charged particles move in response to an electric field in a fluid or gas. It determines how fast particles migrate towards collection surfaces in processes like electrostatic precipitation.

Relationship:

The relationship between resistivity and migration velocity can be understood as follows:

• Higher resistivity materials tend to have lower mobility of charged particles. This means that charged particles in higher resistivity materials may move more slowly in response to an electric field.
• Lower resistivity materials allow charged particles to move more easily and quickly in response to an electric field, resulting in higher migration velocities.
• Migration velocity is influenced by factors such as the magnitude of the electric field, the charge on the particles, and the gas properties. However, resistivity of the medium through which particles are moving can also significantly impact migration velocity.

Therefore, in systems involving charged particle collection (e.g., electrostatic precipitators), the resistivity of the gas or fluid can affect the migration velocity of the particles, which in turn influences their movement towards collection surfaces and the overall efficiency of the collection process.

Relationship between Resistivity and Migration Velocity

Aspect	Resistivity	Migration Velocity
Definition	Resistivity is the measure of a material's opposition to the flow of electric current.	Migration velocity is the velocity at which charged particles move in response to an electric field in a fluid or gas.
Influence	Higher resistivity indicates a material's poor conductivity.	Migration velocity is influenced by the mobility of charged particles and the strength of the electric field.
Relation	Higher resistivity can lead to slower migration of charged particles.	The migration velocity is directly proportional to the mobility of charged particles and the electric field strength.
Applications	Important in designing insulating materials, cables, and electrical components.	Relevant in electrostatic precipitators, particle separation, and charged particle movement in gases and liquids.

Design of Bag Filter System

Steps for Design:

1. Identify Requirements:

   Determine the specific needs of the filtration system, including flow rate (Q), particulate characteristics, efficiency requirements, and permissible pressure drop.

2. Select Bag Material and Design:

   Choose a suitable filter material based on the type of particulate matter, temperature, chemical compatibility, and filtration efficiency required.

   Design Equation: A = Q / (V * t)

   Where A is the required filter area, Q is the flow rate, V is the air velocity, and t is the desired residence time.

3. Determine Number of Bags:

   Calculate the number of bags required based on the total filtration area needed and the available space in the filter housing.

   Design Equation: Total Bags = A_total / A_single

4. Calculate Pressure Drop:

   Estimate the pressure drop across the filter system to ensure it meets the system's constraints.

   Design Equation: ΔP = (K * Q²) / A²

   Where ΔP is the pressure drop, K is a constant, Q is the flow rate, and A is the filter area.

5. Design Fan and Airflow:

   Select an appropriate fan based on the pressure drop and airflow requirements.

   Design Equation: Fan Power = (ΔP * Q) / η

   Where Fan Power is the required power, ΔP is the pressure drop, Q is the flow rate, and η is the fan efficiency.

6. Consider Dust Disposal:

   Plan for efficient dust collection and disposal mechanisms such as hoppers, rotary valves, or bins.

7. System Integration:

   Integrate the bag filter system into the overall process, considering ductwork, supports, controls, and safety measures.

These steps ensure a comprehensive design for an efficient and effective bag filter system.

Comparison: Adsorption vs. Absorption

Aspect	Adsorption	Absorption
Definition	Adsorption is the process of molecules adhering to the surface of a solid or liquid substance.	Absorption is the process of a substance being uniformly distributed throughout the bulk of another substance.
Interaction	Adsorption involves surface forces like van der Waals, electrostatic, and chemical interactions.	Absorption involves the permeation of a substance into the structure of another, often through diffusion.
State Change	No change in the state of the adsorbent occurs.	The absorbent often undergoes a change in physical state, such as becoming a solution or swelling.
Examples	Activated carbon adsorbing gases, ions, or organic molecules on its surface.	Water being absorbed by a sponge or paper, or a solute dissolving in a solvent.
Surface Area	Higher surface area of the adsorbent enhances adsorption.	Uniform distribution and solubility of the absorbed substance are key factors.

Estimation of ESP Collection Efficiency

Given Parameters:

• Specific Collection Area (A/Q) = 0.984 m²/m³.min
• Actual Overall Efficiency = 97%
• Anticipated Specific Collection Area (A/Q) = 1.5 m²/m³.min
• Assumed Value (n) = 4

Using Deutsch Equation:

Estimated Collection Efficiency = 1 - exp(-A/Q)

Calculations:

        For given A/Q = 0.984 m²/m³.min:
        Estimated Efficiency = 1 - exp(-0.984) ≈ 0.6266 (as a decimal)

        For anticipated A/Q = 1.5 m²/m³.min:
        Estimated Efficiency = 1 - exp(-1.5) ≈ 0.7769 (as a decimal)
    

Using Hazen Equation:

Estimated Collection Efficiency = 1 / (1 + (A/Q)^n)

Calculations:

        For given A/Q = 0.984 m²/m³.min and n = 4:
        Estimated Efficiency = 1 / (1 + (0.984)^4) ≈ 0.6989 (as a decimal)

        For anticipated A/Q = 1.5 m²/m³.min and n = 4:
        Estimated Efficiency = 1 / (1 + (1.5)^4) ≈ 0.8418 (as a decimal)
    

Disadvantages of Bag Filters

• Dust Accumulation:

  Over time, collected dust can accumulate on the filter bags, leading to reduced airflow and efficiency. Regular maintenance and cleaning are required.

• Pressure Drop:

  As dust accumulates on the filter surface, it increases the pressure drop across the system, which may require increased fan power to maintain airflow.

• Blinding:

  Filter bags can become blinded or clogged due to sticky or hygroscopic particles, reducing their filtration efficiency and necessitating more frequent cleaning or replacement.

• High Operating Costs:

  Bag filters often require ongoing maintenance, filter replacement, and increased energy consumption due to pressure drop, leading to higher operational costs.

• Space Requirements:

  Bag filter systems can occupy a significant amount of space, making them less suitable for environments with limited available area.

• Chemical Incompatibility:

  Certain chemicals or aggressive gases can corrode or degrade filter bags, limiting their use in applications with chemically aggressive environments.

• Particle Re-entrainment:

  During bag shaking or pulsing, there's a possibility of releasing collected dust particles back into the air, reducing overall efficiency.

• Particle Size Limitations:

  Bag filters might not be effective for very fine or submicron particles due to their limited capture efficiency in this size range.

Disadvantages of Bag Filter

Disadvantage	Explanation
High Pressure Drop	As dust accumulates on the filter bags, the pressure drop across the system increases, requiring frequent cleaning or replacement.
Limited Temperature Range	Bag filters may not be suitable for high-temperature applications, as the filter material and sealants can degrade or melt.
Particle Erosion	High-velocity dust particles can cause wear and tear on the filter bags, leading to reduced filtration efficiency and shorter lifespan.
Chemical Compatibility	Some chemicals or corrosive gases can damage the filter material or affect its performance, necessitating careful material selection.
Space Requirements	Baghouses can occupy significant space, especially if a large number of bags are required for high filtration efficiency.
Complex Maintenance	Cleaning or changing bags requires shutdowns and maintenance work, impacting production schedules and adding labor costs.
Condensation Issues	In applications with temperature fluctuations, condensation can occur, leading to wetting of filter media and decreased performance.
Initial Investment	Bag filter systems can have relatively high upfront costs due to equipment, installation, and maintenance expenses.

Estimation of New Cut Diameter

Given Parameters:

• Initial Cut Diameter (Dcut) = 5 µm
• Flow Rate Increase = 30%

Estimating New Cut Diameter:

New Cut Diameter = Initial Cut Diameter * (1 + Flow Rate Increase)

Calculations:

        New Cut Diameter = 5 µm * (1 + 0.30) = 5 µm * 1.30 = 6.5 µm
    

The estimated new cut diameter is 6.5 µm.

Calculation of Flow Rate Ratio

Given Parameters:

• Initial Efficiency = 98%
• Final Efficiency = 93%

Calculating Flow Rate Ratio:

Flow Rate Ratio = (Initial Efficiency / Final Efficiency)

Calculations:

        Flow Rate Ratio = 0.98 / 0.93 ≈ 1.0538
    

The flow rate ratio is approximately 1.0538.

Operation and Maintenance Issues of Cyclone Separator

Aspect	Operation	Maintenance
Efficiency	Efficient at separating larger particles from a gas stream due to centrifugal force.	Efficiency can decrease for smaller particles and at high gas velocities.
Pressure Drop	Generates moderate pressure drop across the system.	Pressure drop can increase over time due to particle accumulation, requiring cleaning.
Particle Re-entrainment	Particles can be re-entrained into the gas stream, reducing efficiency.	Regular inspection and maintenance of internal surfaces can mitigate re-entrainment.
Particle Buildup	Particles collect in the bottom cone and need periodic removal.	Frequent cleaning of the cone, as well as seals and gaskets, is essential.
Maintenance Frequency	Generally requires less frequent maintenance compared to some other systems.	Regular inspections, cleaning, and occasional replacement of worn components are needed.
Material Erosion	High-velocity gas streams can cause abrasion of cyclone walls.	Choosing durable materials and monitoring erosion is crucial.
Temperature Limitations	Can handle high temperatures for many applications.	Extreme temperatures may affect cyclone components, necessitating appropriate materials.
Design Consideration	Relatively simple design, suitable for a wide range of industries.	Design modifications may be required for specific applications, impacting performance.

Selection Criteria for Fans

Criteria	Explanation
Flow Rate (Q)	The required air or gas volume that the fan must handle.
Pressure Drop (∆P)	The resistance the fan needs to overcome in the system.
Efficiency	The ratio of mechanical output power to the electrical input power.
Static Pressure	The difference in pressure between the fan's inlet and outlet.
Speed	The rotational speed of the fan's impeller, measured in revolutions per minute (RPM).
Operating Conditions	Consideration of temperature, humidity, corrosive or abrasive materials, and other factors that affect fan operation.
Noise Level	The acceptable level of noise produced by the fan.
Space Limitations	The available space for the installation of the fan.
System Integration	Compatibility with other components and systems in the application.
Certifications	Meeting industry standards and safety regulations.
Budget	The cost of purchasing, installing, and operating the fan.

Effects of Changes in Cyclone Design and Exhaust Gas Properties

Aspect	Changes in Cyclone Design	Changes in Exhaust Gas Properties
Efficiency	Increased cyclone length and cone angle can improve efficiency.	Higher particle loading or changes in particle size distribution can impact efficiency.
Pressure Drop	Modifications to inlet shape and dimensions can affect pressure drop.	Higher gas flow rates or density changes can alter pressure drop.
Collection Capacity	Changes in the number and size of cyclone chambers can affect capacity.	Higher particle concentrations can impact the ability to handle larger loads.
Particle Re-entrainment	Redesigning vortex finder and cone can minimize re-entrainment.	Changes in gas velocity or particle characteristics can influence re-entrainment.
Wear and Erosion	Using abrasion-resistant materials can reduce wear on internal surfaces.	Higher particle velocities or abrasive content can increase wear.
Gas Flow Distribution	Changes in inlet design can influence the uniformity of gas flow distribution.	Gas flow rate changes can impact uniformity and distribution of particles.
Material Separation	Modifications to cyclone geometry can affect separation efficiency for specific materials.	Particle properties, such as density, can influence material separation.
Space and Installation	Redesigning cyclone size and orientation can impact space requirements.	Changes in exhaust gas volume or temperature can influence installation considerations.

Operation and Maintenance Issues of Venturi Scrubber

Operation:

• Operates on the principle of using a high-velocity gas stream to create a pressure drop, which causes particles to be captured and removed from the gas stream.
• Efficiently removes both particulate matter and certain gases from industrial exhaust streams.
• Works well for controlling submicron particles and fine mists.
• Gas enters the narrow throat of the venturi, creating a high-velocity stream that atomizes and captures particles.
• Scrubbing liquid (usually water) is injected into the gas stream, capturing particles through impaction, interception, and diffusion.

Maintenance Issues:

• Nozzle Clogging: The scrubbing liquid nozzles can become clogged with particles or deposits, affecting efficiency. Regular cleaning is required.
• Pump Maintenance: The pumping system for delivering scrubbing liquid needs maintenance to ensure consistent flow and proper atomization.
• Corrosion and Erosion: The high-velocity gas stream and wet conditions can lead to corrosion and erosion of internal components. Material selection is crucial.
• Scaling: Minerals in the scrubbing liquid can lead to scaling on internal surfaces, reducing efficiency. Cleaning and chemical treatments are needed.
• Residue Buildup: Captured particles and solids from the gas stream accumulate in the scrubber's liquid reservoir. Regular draining and cleaning are essential.
• Slurry Handling: Disposing of the captured particulate-laden scrubbing liquid requires proper handling and treatment to prevent environmental impact.
• Efficiency Variability: Efficiency can be affected by changes in gas flow rates, particle characteristics, and scrubbing liquid properties. Monitoring and adjustments are necessary.
• Nozzle Wear: High-velocity gas can cause wear on nozzle tips. Regular inspection and replacement are needed to maintain optimal atomization.

Hood System and Explanation

Simplified Hood System Drawing:

       +-------------------------+
       |       Airflow           |
       |    +------------+       |
       |    |    Hood    |       |
       |    +------------+       |
       |                         |
       +-------------------------+
    

Explanation:

A hood system is a component used in industrial processes to capture and control airborne contaminants, such as dust, fumes, gases, or vapors, at their source of generation. The system consists of the following components:

• Hood: The hood is a device placed over the source of contaminants to capture them. It can come in various shapes, such as enclosures, canopies, or ducts, depending on the application. The hood design ensures that the airborne contaminants are effectively directed towards the capture area.
• Airflow: The airflow is created using a fan or an exhaust system. The airflow carries the captured contaminants away from the source and into the ventilation system for further treatment or disposal.

The primary purpose of a hood system is to minimize the dispersion of contaminants into the surrounding environment or workspace, ensuring the safety of workers, compliance with regulations, and preventing contamination of products or processes.

The efficiency and effectiveness of the hood system depend on factors such as the hood's design, placement, capture velocity, and the nature of the contaminants. Proper maintenance and regular inspection are essential to ensure that the system continues to perform optimally.

Concepts of Static Pressure, Velocity, and Total Pressure

Static Pressure:

Static pressure refers to the pressure exerted by a fluid (liquid or gas) when it is at rest. It is the pressure measured in a fluid that is not in motion. Static pressure is exerted uniformly in all directions within the fluid. In a gas or air system, static pressure is typically measured using pressure gauges, and it is a key parameter in ventilation, fluid dynamics, and engineering applications.

Velocity:

Velocity is a measure of the speed and direction of fluid flow. In a fluid system, velocity is the rate at which a fluid moves through a given cross-sectional area. It is a vector quantity, meaning it has both magnitude and direction. Velocity can vary at different points in a fluid system, and it is typically measured using flow meters or by calculating the change in position of particles within the fluid over time.

Total Pressure:

Total pressure, also known as dynamic pressure, represents the combined effects of static pressure and velocity pressure. It accounts for both the pressure exerted by a fluid due to its motion (velocity) and its rest (static pressure). Total pressure is crucial in fluid dynamics, as it helps describe the energy distribution in a moving fluid. In fluid systems, total pressure is often measured using pressure probes or devices.

These concepts are fundamental in various fields, including fluid mechanics, aerodynamics, and HVAC engineering, where understanding pressure and velocity interactions is essential for designing efficient systems.