By Chris Duncan, Business Manager, Emerson Automation Solutions

Detecting flammable gas that has the potential to threaten people and property in areas where gas clouds easily disperse is a problem in many applications. This recent case history is a classic example.

A UKCS (United Kingdom Continental Shelf) operator was issued an improvement notice from the Health and Safety Executive after a large volume gas leak went undetected on one of their North Sea platforms. The release had not been picked up by the platform’s existing flammable gas detection system because the gas had been dispersing as soon as it escaped.

The company contacted Emerson for help. The solution was to provide the Incus, an ultrasonic gas leak detector that, while working in conjunction with the existing gas detection system, added another line of defense and provided an early warning when gas releases occurred. Most importantly, it increased the safety of platform personnel.

Ultrasonic gas leak detection uses acoustic sensors to identify fluctuations in noise that are imperceptible to human hearing within a process environment. The sensor and electronics are able to detect these ultrasound frequencies (25 to 100KHz), while excluding audible frequencies (0 to 25KHz).

Unlike traditional gas detectors that measure the accumulated gas, ultrasonic gas detectors “hear” the leak, triggering an early warning system. The sensors respond to sound generated by escaping gas at ultrasonic frequencies. Leak rate is mainly dependent on the size of the leak and the gas pressure. In most facilities, the majority of process noise is in the audible range, while limited ultrasonic noise is generated in normal operation. Highly pressurized gas releases produce ultrasound (25-100 kHz) which the sensors are able to pick up despite the presence of audible noise. Ultrasonic (acoustic) gas leak detection technology has several advantages over conventional gas sensor technologies: it does not have to wait until a gas concentration has accumulated to potentially dangerous concentrations; it does not require a gas cloud to eventually make physical contact with a sensor; and the response is instantaneous for all gas types.

The Incus is ideally suited for monitoring outdoor applications such as on an oil platform. The Incus has been engineered to withstand even the most extreme conditions. Performance is not affected by inclement weather, wind direction, leak direction or any potential gas dilution, with an instantaneous response to all gas types. It is an excellent addition to many safety systems adding another layer of detection to existing technologies.

The Health and Safety Executive subsequently inspected the platform and approved the solution provided, resulting in a very happy customer!

Do you have an application that might require the addition of ultrasonic detection? It might be worth a discussion. Contact us HERE today.

by Robin Hudson, Rosemount Level Product Manager, Emerson Automation Solutions

An interesting case history from a 600 kW coal fired power plant in China has implications for any safety-critical environment. This application involved drain pot alarms on super critical steam lines.

As you know, any liquid entering a steam turbine will cause damage. This is costly and even more important, can be dangerous to personnel due to the extreme temperatures and pressures involved in the steam turbine. Generally, steam pots (also called condensate traps or steam traps) are used on steam lines to drain off condensate before it can enter the turbine. These drain pots use level sensors to detect high levels of condensate buildup and then open valves to discharge it.

The problem that arises, however, is that the extreme temperatures and pressures in the steam lines can cause many level detection devices to fail. The plant in China had been using float switches but their performance was found to be unstable over 2900psi pressure and 932˚F. Components had to be replaced frequently. In addition, the devices had no self-diagnostics or status outputs so the operators couldn’t detect when the floats might fail or if they were working properly. This high and unpredictable failure rate increased maintenance which added costs and upped the chances of a significant accident.

To resolve the issue, the plant replaced all of their float switches on the supercritical steam lines with Mobrey Hydratect 2462 Water and Steam Detection Systems. Unlike most detection systems, the patented-design Mobrey Hydratect 2462 functions reliably in steam/water detection environments up to 4350psi pressure and 1,040˚F – easily accommodating the requirements of the Chinese plant. In addition, the electronic controller gives a visual indication and relay output to indicate steam, water or a fault condition. Extensive self-monitoring within the system assures that any component failure results in a fail-safe condition.

To sum up the benefits of using this type of detection system, the Mobrey Hydratect 2462 lets you –

  • Reliably detect water or steam in lines, columns, and condensate pots
  • Eliminate the need for routine testing through superior reliability
  • Prevent turbine water damage with Turbine Water Induction Protection (TWIP)
  • Saves time with self-checks that make routine testing unnecessary
  • Configurable steam/water thresholds adjustable according to water quality

The combination can significantly reduce maintenance costs, and even more important, greatly improve protection of people and property.

Do you deal with level measurement in a safety critical environment? What type of system do you use?

by Amanda Gogates, Cascade Global Product Manager, Emerson

Nitrogen oxides are powerful pollutants that can cause smog and acid rain and contribute to the development of tropospheric ozone. It’s critical to control nitrogen oxide (NOx) emissions to protect the environment and meet environmental regulatory requirements. NOx occurs as a result of combustion occurring in the presence of nitrogen and results from combustion processes in turbines, crackers, combustion engines, boilers, and other locations within a plant.

Ammonia can be used to react with NOx at high temperatures in order to turn it into molecular nitrogen and water vapor. Both selective catalytic and selective non-catalytic reduction (SCR and SNCR) are techniques used worldwide to remove NOx in DeNOx reactors.

However, this process can result in a byproduct of unreacted ammonia, or ammonia slip. Operators must use the precise amount of ammonia since either too much or too little can be problematic. Not enough ammonia will result in emissions, while too much ammonia can lead to waste.

As a result, continuous measurement and monitoring of ammonia slip is needed. However, such measurement can be challenging, especially in high-dust, high-temperature environments.

The video describes the Emerson DeNOx Optimization Solution, a unique system using the Quantum Cascade Laser. I think you’ll find this solution interesting and maybe a bit surprising.

For questions on how this system can both optimize DeNOx and maintain precise measurement of ammonia slip, please contact me at amanda.gogates@emerson.com. Or get more information on the Quantum Cascade Laser analyzer technology here.

by Lee Ju Young, Senior Account Manager, South Korea, Emerson Automation Solutions

Most of us know that conductivity is an excellent way to detect the interface between a non-conductive liquid, such as a hydrocarbon, and a conductive aqueous solution. Even more impressive, however, is hearing how this vital analysis is saving time and money for real companies. Here’s a great example.

Hanwha Total Petrochemical is headquartered in Seoul, South Korea, but operates a large petrochemical complex, consisting of 13 separate plants, at Daesan, in South Korea’s Chungnam Province. The company manufactures building block chemicals that go into the making of a host of other chemicals needed for various consumer products. It starts with a naphtha cracker, yielding propylene and ethylene, which are the raw materials in the production of many of polymers, like naphtha.

The naphtha is kept in storage tanks before use. During storage, water accumulates and sinks to the bottom of the tank. Because water interferes with the cracking process, it must be periodically removed. Conductivity is ideal for monitoring the drain. The water has a conductivity between 650 and 1000 uS/cm, and the naphtha has essentially no conductivity. As the water drains, the conductivity is high. When the water/naphtha interface is present, the naphtha in the interface, being non-conductive, causes the conductivity to drop. When naphtha alone is present, the conductivity is practically zero. Thus, by stopping the drain at the first sign of a conductivity drop, the operators are ensured that only water has been drained with minimum loss of naphtha.

Prior to Hanwha Total Petrochemical’s decision to use the conductivity analyzer, draining the tank of water was manual, requiring substantial human intervention. One person was positioned at the control valve at the tank outlet to watch the water drain. This person used a visual check to make sure that only water drained out.  If naphtha was observed, the person called to the DCS to close the valve in order to minimize the loss of naphtha.

The simple addition of a Rosemount 1066 conductivity analyzer and sensors has significantly reduced the personnel hour demands on the plant’s staff, and even more significantly, has dramatically reduced leakage of costly naphtha from the tank. In addition, naphtha in wastewater increases the load on wastewater treatment and makes it more difficult to comply with environmental regulations – possibly leading to fines.

Conductivity analysis is one of the most used liquid measurements – for good reason. A simple addition of instrumentation can significantly improve the process efficiency, quality, and reliability.

by Sara Wiederoder, Product Manager, Rosemount Combustion Products, Emerson

Hello. My name is Sara Wiederoder and I’m your Analytic Expert for today. I’d like to share an interesting and innovative waste-to-energy application in which a number of Emerson products are used including the Rosemount OCX8800. The company in this application is Sustainable Waste Power Systems (SWPS) and they’re building a garbage in/power out (GIPO) system, or more specifically, a two-stage, wet, thermal conversion of wet carbon-based waste into synthesis fuel gas (SynFuel). In the system, a devolitization stage reduces the wet feedstock into a bio-char and light volatiles. A large pressure drop between the stages causes fluidization and pulverization of the flow. Gasification completes the fuel synthesis through the water-gas shift and cooling of hot oil and process systems provides thermal power to the customer.

One of the key challenges of the system is to provide stable burner and air control. In general, it can be said that the concentration of excess oxygen is one of the best indicators of how efficient a combustion process is. Industry quickly discovered that if you do not have excess oxygen in your flue gas (indicating there is too much fuel), there is a good chance your boiler will explode, so excess air/oxygen is required. Adding too much air/oxygen will cool down the combustion process, which is undesirable since combustion is being used to produce thermal energy, and the more you cool it, the less heat you can get out of it. Typically, combustion processes are controlled between 2-5% excess oxygen. The actual value varies upon the type of fuel. Gaseous fuels combust very efficiently and quickly, so there is less excess oxygen required for optimal efficiency. However, solid fuels don’t combust as well, so adding extra oxygen ensures the solid particles are fully combusted. Having a continuous measurement of oxygen, and inputting this data into a control system that automatically controls air flow to the combustion burner, ensures the combustion process is operating at optimal efficiency.

The Rosemount OCX8800 Combustion Flue Gas Transmitter provides a continuous, accurate measurement of not only the oxygen, but also the combustibles remaining in flue gases from a combustion process. The renowned zirconium oxide sensor is the basis for the oxygen measurement. This, combined with the combustibles sensor, detects oxygen and combustibles concentrations in flue gases with temperatures up to 2,600°F (1,427°C).

For this application, complete and efficient combustion within a very tight set point was crucial. So in addition to oxygen, carbon monoxide (CO) measurements give greater detail into the current condition of a combustion process. CO is an indicator of un-combusted fuel. When processes are short on oxygen it’s usual to see a lot of CO, but it’s normal to have small concentrations of CO right near the optimal combustion set point. Right around the point of greatest efficiency, it’s typical to see trace amounts of CO around 200 ppm. Using both CO and oxygen measurements gives the user greater control over their combustion process.

The solution in the SWPS application included:

  • A burner safety control panel that utilizes a pass-through 4-20mA signal once safety sequences are complete
  • Configuration of PID for fuel valve with furnace temperature as process variable feedback
  • Configuration of PID for air valve with O2 sensor as process variable feedback
  • Using the easy “manual track” feature in the built-in PID loops, which made the changeover to automatic control seamless
  • Feed forward adjustment to air valve output as factor times change in fuel valve output
  • A burner system that is very stable without the need for air or fuel mass-flow instrumentation

Ultimately, the commercial scalability of the GIPO was proven including:

  • High Total Carbon Conversion Efficiency > 90%
  • High Quality SynFuel Gas – 80% Fuel Gas Fraction
    • 16-30% CO2 (maximum)
    • 10-20% Methane
    • 30-45% Hydrogen
    • Balance Carbon Monoxide
    • No Tar Production

While your application may not resemble this unique GIPO system, talk to our analytic experts about achieving efficient combustion in your demanding applications.