Lecture 58: Stack Emission Monitoring using Isokinetic Sampling

Summary

This video script delves into stack emission monitoring, a crucial process for assessing air pollutants from industrial chimneys. It covers the necessity of isokinetic sampling to accurately measure particulate matter and gaseous pollutants, detailing the equipment and procedures involved. The script also discusses the calculation of emission rates and the importance of quality control in ensuring reliable environmental data for compliance and health risk assessments.

Takeaways

• 🌐 Stack emissions are crucial to monitor for particulate matter and gaseous pollutants, as they are significant point sources of pollution.
• 🔍 Isokinetic sampling is emphasized for accurate stack monitoring because it ensures that the sampling velocity and conditions match those in the stack.
• 🛠️ The equipment for stack monitoring includes a panel box, probes, thermocouples, impinger tubes, vacuum pump, and a sampling probe.
• 📍 Sampling location is critical and should coincide with the point of velocity measurement to ensure accurate particulate concentration readings.
• 🌀 Nozzle size selection is vital for maintaining a sampling rate between 40 to 60 liters per minute, ensuring representative sampling.
• ⚖️ The mass of particulate matter collected on filter paper is measured before and after sampling, with the difference indicating the concentration of pollutants.
• 🔥 The filter paper or thimble is heated to remove moisture, ensuring accurate measurement of particulate matter free from errors.
• 📉 The volume of gas sampled is calculated using parameters like pressure difference, temperature, and barometer pressure to apply necessary corrections.
• 📊 Dust emission rate is calculated by multiplying the concentration of pollutants by the flow rate, providing a measure of total emissions.
• 🧪 Gaseous pollutants like SO2 and NOx can be monitored using impingers and specific sampling and analytical methods, such as barium-thorium titration for SO2.
• 🔄 Quality control is essential in stack monitoring to ensure the accuracy and reliability of the data collected for environmental compliance and assessments.

Q & A

What is the primary purpose of stack emission monitoring?

The primary purpose of stack emission monitoring is to measure the levels of particulate matter and gaseous components, such as sulphur dioxide and NOx, that are emitted from large chimneys or stacks, ensuring that these emissions do not exceed the standards set by regulatory bodies like the CPCB or MOEF.

Why is isokinetic sampling emphasized in stack emission monitoring?

Isokinetic sampling is emphasized because it ensures that the velocity, temperature, and other kinetic parameters of the sampling process match those inside the stack. This method helps to accurately represent the actual conditions of the emissions being sampled.

What are the key components of the apparatus used for stack emission monitoring?

The key components include a panel box for pressure and flow rate measurements, probes for inserting into the stack, pilot tubes for guiding the probes, thermocouples for temperature readings, impinger tubes for gaseous components, a vacuum pump for extraction, and a sampling probe.

How is the sampling rate calculated in stack emission monitoring?

The sampling rate is calculated using parameters such as flow rate, absolute gas temperature, absolute temperature of the metering conditions, and barometer pressure. These parameters are input into a specific equation to determine the appropriate sampling rate.

What is the significance of the location of sampling in stack emission monitoring?

The location of sampling is significant because it should be done at the point where velocity measurements were carried out to ensure the accuracy of the particulate concentration measurements.

How is the sample recovered after the sampling process in stack emission monitoring?

After sampling, the filter paper or thimble, which has collected the particulate matter, is carefully collected to prevent contamination. It is then weighed, and the mass of the collected dust is determined after drying in an oven at 120 degrees Celsius for about 2 hours to remove moisture.

What is the role of the rotameter in maintaining isokinetic sampling conditions?

The rotameter is used to regulate the flow rate of the suction pump, ensuring that the velocity of the gas passing through the sampling probe matches the velocity of the emissions coming out of the stack, thus maintaining isokinetic sampling conditions.

How is the concentration of particulate matter calculated in stack emission monitoring?

The concentration is calculated by dividing the weight difference of the filter paper or thimble before and after sampling by the volume of gas sampled. This gives the weight of particulate matter per unit volume of gas.

What is the procedure for monitoring gaseous pollutants like SO2 during stack emission monitoring?

Gaseous pollutants are monitored by using impingers to collect samples through extraction from the sampling point in the stack. The collected sample is then analyzed in the lab, and the concentration of pollutants like SO2 is measured using specific titration methods.

Why is quality control important in stack emission monitoring?

Quality control is important to ensure that the monitoring values are accurate and consistent with real-world conditions. Without strict adherence to guidelines and protocols, the data collected may not reflect the true levels of pollution, leading to incorrect assessments and decisions.