Use Ultra-Sonic Flowmeter in FLARE Gas Header for emission monitoring

Increasing greenhouse effect and global warming has resulted environment changed dramatically. Signing of Kyoto protocol is part of the cumulative effort to minimize global warming. Rules and regulations becoming stricter and demands for continuous flare gas measurement and recording has become one of the mandatory requirements.

“Within the United States, the Environment Protection Agency (EPA, www.epa.gov) has enforced emission levels of NOx (Nitrous Oxides) and highly reactive volatile organic compounds (HRVOC) through individual states with allocations and fines. In Texas, California, and New Jersey the ozone depletion has led to stricter total emissions and monitoring of HRVOCs.. In Texas, the Texas Commission of Environmental Quality (TCEQ, www.tceq.state.tx.us) Chapter 115 Regulation has set the levels for each flare stack. The new regulations require a flare gas flowmeter to be specified to have +/- 5 percent inaccuracy at 30, 60, and 90 percent of range under its installed condition”

Calculating flare gas has gone into history. One of the biggest challenges of measuring flare gas is large TURNDOWN. Flare gas flow can ranged from low fuel gas purge during normal operation to large flow during emergency relief and/or total plant blowdown.

Common flowmeter type such as differential-pressure, vortex-shedding, and insertion thermal mass meters, etc are unable to meet such low turndown requirement. Ultra-sonic flowmeter is generally used in flare gas measurement & recording. See some features and benefits of an Ultra-Sonic Flowmeter HERE and HERE

Apart from large turndown capability (from 0.03 m/s to 85 m/s), ULTRA-SONIC flowmeter also has the following advantages in flare gas application :

- Extremely low pressure drop (virtual zero pressure drop)
- No internal, insertion and moving parts which potential create partial blockage of flare line
- Tolerate some condensed liquid
- Can take higher operating temperature (upto 260 degC)
- No affected by gas composition
- No maintenance

Thus, stringent authority requirements on flare gas measurement, ULTRA-SONIC flowmeter would be one of the best offers.

Further reading

• FLARE combustion efficiency
• The Future of Flare Gas Measurement
• Industrial Flares, Section 13.5. Sept. 1991
• How much do you flare? How to measure flowrates of flare gas accurately and reliably.
• Regulation 12, Rule 11: Flare Monitoring at Petroleum Refineries
• Point Source Monitoring to Identify and Reduce HRVOC Emissions

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MultiChannel Heat Exchanger

CLIMETAL - Multichannel heat exchanger has been used successfully in the automotive industrial. It is high efficiency & performance with compact unit has gained a lot attention from industrial. The following video clip describes in brief benifits / advantages, filtering feature (built-in) and flexibility of MultiChannel Heat Exchanger.

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ECI – Operation & Maintenance Engineers - Don't miss FREE articles (>40) related to HX Fouling & Cleaning (Part 2)

Last post <<ECI – Operation & Maintenance Engineers - Don't miss FREE articles (>40) related to HX Fouling & Cleaning (Part 1) >> has listed 3 articles.

1. Heat Exchanger Fouling & Cleaning - Fundamentals and Applications
2. Fouling During the Use of Seawater as Coolant - The Development of a User Guide™
3. Physical Water Treatment for the Mitigation of Mineral Fouling in Cooling-Tower Water Applications

This post i will only recommend some articles which are common to engineers in design & engineering and operation/maintenance in plant. I have left out other articles which are rather conceptual and research oriented. For those who are interested, please see HERE.

1. Crystallisation Fouling Of Mixed Salts During Convective Heat Transfer And Sub-Cooled Flow Boiling Conditions.
2. A Comparison of the Operating Characteristics of Two Cooling Water Systems using Chlorine and Chlorine Dioxide Biocides
3. Analysis of Fouling Data Based on Prior Knowledge
4. Challenges in Cleaning: Recent Developments and Future Prospects
5. Fouling of Some Canadian Crude Oils
6. Preheat Train Crude Distillation Fouling Propensity Evaluation by the Ebert and Panchal Model
7. Retrofitting Crude Oil Refinery Heat Exchanger Networks to Minimise Fouling While Maximising Heat Recovery
8. Chemical Cleaning of Oil Refinery Heat Exchangers -- The Need for a Joint Effort
9. Analysis and Steps to Mitigate Heat Exchanger Fouling in an Aromatics Plant
10. Fouling Characteristics of a Light Australian Crude Oil
11. Development of a Data-Based Method for Performance Monitoring of Heat Exchangers
12. Fouling Enhancement under Flow Boiling at Elevated Steam Qualities
13. Improvements and New Developments in Self-Cleaning Heat Transfer Leading to New Applications
14. The Practical Application and Innovation of Cleaning Technology for Heat Exchangers
15. Fouling Mitigation Using Helixchanger Heat Exchangers

Further Reading

• ECI – Operation & Maintenance Engineers - Don't miss FREE articles (>40) related to HX Fouling & Cleaning (Part 1)
• What type of heat exchanger can be used to handle fluid with solid ?
• FAYF - Heat Transfer - Useful Heat Transfer Equation
• Do Not Overspecified Fouling Factor s for PHE
• Why Lower Fouling in Plate Heat Exchanger ?
• Heat Exchanger Fouling Mechanism, Prevention and Treatment

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ECI - Operation & Maintenance Engineers Don't miss FREE articles (>40) related to HX Fouling & Cleaning [Part 1]

ECI - Engineering Conferences International Symposium Series

Engineering Conferences International (ECI) is a global engineering conferences program, originally established in 1962, that provides opportunities for the exploration of problems and issues of concern to engineers and scientists from many disciplines. ECI is a not-for-profit partnership between the Engineering Conferences Foundation (ECF) and Polytechnic University.

If you are engineer working in plant and experiencing Heat Exchnager fouling problem...huh...here is the place where you may find your answer.

There are many FREE articles (>40) related to fouling and cleaning of Heat Exchanger available for download from ECI.

1. Heat Exchanger Fouling & Cleaning - Fundamentals and Applications

2. Fouling During the Use of Seawater as Coolant - The Development of a ‘User Guide’

3. Physical Water Treatment for the Mitigation of Mineral Fouling in Cooling-Tower Water Applications

[More]

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Rule-of-thumb For Minimum Flow Recycle

Display problem ? Click HERE

"Is there a rule of thumb used in determining the flow required through the recycle line on the pump discharge in case of minimum flow problem in pump? If yes, what percentage of the pump flow is considered to flow through the recycle line."

Strainght forward answer...

PUMP FLOW = RECYCLE FLOW + DELIVER FLOW

Percentage can ranged from 10% to 50% (or even 60%) of PUMP FLOW may be considered during design phase. I am recommending 30%-40%...However, this figure shall always be checked & confirmed with actual selected pump when they are manufactured.

There are at least four (4) main factors possibily determining pump MINIMUM RECYCLE flow. There are :

a) Fluid temperature rise
b) Minimum stable flow
c) Internal recirculation
d) Thrust capacity

Fluid temperature rise
As fluid enters pump suction chamber, pump impeller will spin the fluid and energy from shaft / impeller is transferred into fluid. However, there are mechanical losses within the pump in the energy transferring process. The mechanical losses will be transformed into acoustic energy (e.g. noise) and thermal energy (e.g. fluid temperature rise). Acoustic energy may transfer to fluid, pump casing and piping and it is further emitted to atmosphere as noise. Similarly thermal energy will also transfer to fluid, pump casing and piping. However, pumping process is a rather “fast” action and in general there is “insufficient time” for heat transfer from fluid to pump casing and piping. Thus, majority of the thermal energy will stay in the fluid and eventually cause fluid temperature rise (and/or liquid flashing). Reduce fluid passing pump results less heat “carrier” and higher temperature rises and high potential of liquid flashing. Thus a minimum flow can be established from fluid temperature rise. A process engineer may needs to establish minimum flow of a pump from temperature rise perspective. The principle is rather simple where

Energy loss to fluid = fluid thermal heat gain

Above has considered acoustic energy is zero.

Fluid temperature rise,

Where
h = pump head
g = gravity acceleration
e = pump shaft efficiency
Q = pump flow
Cp = fluid specific heat

Minimum system stable flow
Sometime a pumping system may shows two stable flows at certain pump head. As a result, it ”hunts“ or ”shuttles“ between these two flows and potentially damage the pump and other equipment within the pumping system. For example, gas trapped in the discharge line pocket. Trapped gas will reduce liquid flow path and increase line pressure drop. Pump head increase push trapped gas towards downward piping. As trapped gas move into the downward piping, liquid flow path increases and reduce the pump head. Trapped gas will form smaller bubble due to fluid turbulence and it will rise in the downward piping and finally back to the high pocket again. Similar cycle occurs again and pump oscillate in two flows. A process engineer shall always piping system to avoid pump operate in the oscillation region.

Internal recirculation
As flow rate decreases in the pump chamber, flow reversal will occur at the pump suction and discharge vanes. Recirculation vortex will form at both ends and potentially damage pump. Thermal heat gain within vortex will further increase pump fluid temperature and potential flashing occurs.

Axial thrust load
Axial thrust in a pump increases rapidly as flows are reduced and head increased. A minimum flow needs to be maintained so the thrust developed by the pump does not impair bearing life.

Related Topic

• Understand Meaning of "Pump Head"
• Pump Pressure Versus Head
• Why Centrifugal pump NPSH required increases with flow ?
• Tips for Centrifugal Pump
• Consider energy saving by optimizing the pump control

COLLECTION of Typical Overall Heat Transfer Coefficient (U-factor)

Many of us are very familiar with this fundamental equation in heat transfer.

Q = U.A.ΔT

For a given heat transfer service with known mass flow rates and inlet and outlet temperatures the determination of Q is straightforward and ΔT can be easily calculated if a flow arrangement is selected (e.g. logarithmic mean temperature difference for pure countercurrent or cocurrent flow). This is different for the overall heat transfer coefficient U. The determination of U is often tedious and needs data not yet available in preliminary stages of the design. Therefore, typical values of U are useful for quickly estimating the required surface area. The literature has many tabulations of such typical coefficients for commercial heat transfer services. The links below tabulates U values for different applications and heat exchanger types.

DELTA T (CheResources, Built-It-Solar)

The Engineering Tool Box
Engineering Page

If you aware of any site have similar information, i would be happy to include them here for the benefits of ALL within our community.

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Rule-of-thumb to gage suitability of Plate-Heat-Exchanger in Fluid-Contains-solid or Slurry

Plate Heat Exchanger having narrow channel most probably "not recommended" for fluid contains solid and/or slurry services. However, there are still many success story of using PHE in abovementioned services.

There are some rule-of-thumbs to gage if a plate heat exchanger suitable for fluid contains solid or slurry :

i) 80% of the particles are less than 70% of the interplate gap on the heat exchanger.

ii) 100% of the particles are less than 90% of the interplate gap

iii) Flowing velocity is below erosional velocity (causes premature plate failure)

iv) The minimum wall temperature is above a point where crystal growth is expected.

Further reading

• What type of heat exchanger can be used to handle fluid with solid ?
• FAYF - Heat Transfer - Useful Heat Transfer Equation
• Do Not Overspecified Fouling Factor s for PHE
• Why Lower Fouling in Plate Heat Exchanger ?
• Heat Exchanger Fouling Mechanism, Prevention and Treatment

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