Heating Hazardous Area Process Gases – Top 4 Reasons To Heat Gases

Published 09 Feb 2017

Heating Hazardous Area Process Gases

Heating Hazardous Area Process Gases

T&D, a leading UK distributor for industrial and hazardous area Gas Detection Equipment, present a Guest Article by Debra Hall, Sales & Marketing Director of Control Instruments Corporation.

Control Instruments Corporation’s mission is to engineer and manufacture high quality solutions to gas detection problems. From simple to complex cases, Control Instruments Corporation ensure safety is a top priority.

In today’s guest post, Debra explains the top 4 reasons to heat industrial and hazardous area process gases.

Heating Industrial & Hazardous Area Process Gases

Industrial processes operate at various temperatures, using a wide variety of different gases, solvents and background constituents (i.e. tars, resins, salts, plasticisers, water vapor, etc). It is important to keep these process gases heated. Would you like to know why?

Read on to learn the top four reasons …

What are Process Gases?

Process gases consist of hazardous gases and solvents that are used in industrial processes. Industrial processes are those operations, which are typically enclosed, heated spaces that require an active sample drawing system.

These have an intentional release of process gases at all times. In fact these processes are often optimized for speed and performance by safely releasing more process gases, not less; as they often operate near legal limits for combustible gas concentrations.

These process gases are seen in production plants (chemical, automotive, painting, printing, pharmaceuticals) as well as used as non-traditional fuels for energy savings and sustainability, such as SYNGAS to turbine engines.

Some examples include,

  • Industrial dryers for printing, coating, or laminating that may be designed to operate at solvent concentrations above 25% LFL.
  • Or the measurement of process gases going into Amine Treaters for pollution control, where there are not only combustibles, but also toxic sulfides.

This means the precise concentration of process gases must be measured with a level of accuracy for safety, health and energy savings. Since the environment of the process gas stream can be a challenge, it is essential to keep them heated to a temperature above their dew point. The process stream must hence be heated from the sample pickup point all the way to the gas sensing analyzer.

Here are the Top 4 Reasons to Heat Hazardous Area Process Gases

1 – Avoid Condensation

The most common sampling problem is condensation (vapor returning to liquid during sampling). Condensation creates two problems: sample drop-out and clogging. When sample drops out due to condensation, the reading taken by the sensor is lower than actual. And clogging increases downtime and maintenance costs.

The temperature needed to avoid condensation can be found by looking up the Flash Point temperature for each compound in the sample (see table of common gases). The flash point is that temperature at which a solvent produces sufficient vapor to propagate a flame. Generally, the sample must be kept at or above the flash point temperature to remain in the vapor state during sampling.

Pictured : % Gas v Temperature : A Flash Point Temperature Graph 

A Flash Point Temperature Graph

Click here to view free Gas Monitoring Guide.

An essential guide for process and plant engineers concerned with gas detection and solvent vapour monitoring (including hydrocarbons and both flammable and toxic gases).

Data includes : CAT: Catalytic FTA: Flame Temperature Analyzer FID: Flame Ionization Detector ECM: ElectrochemicalFP: Flash Point LFL:  % Lower Flammable Limit PEL-TWA: Permissible Exposure Limit Time Weighted Average (ppm)

Table of Gases

2 – Ensure Accurate Readings

Keeping all sample-wetted parts of the sampling system and analyzer at the appropriate temperature will ensure that combustible vapors are properly measured with confidence.

  • Flammability changes as a function of temperature. Small changes in temperature can have a large effect on the flammability readings. Near the Flash Point of the combustibles, the vapor pressure tends to double for every 10°C rise in temperature. Small changes in temperature can have a large effect.  There could also be sample drop out if the process sample is cooled. Alcohols are water soluble and will blend with any water condensation, giving false low LFL readings.
  • Calorific Value Measurements taken on partially dried samples have large errors on their heating values. At atmospheric pressure, saturated water vapor can constitute up to 20% of the mixture’s volume at 60ºC (140ºF), but only 2% at 20ºC (68ºF). If a sample saturated with water vapor is taken at 60ºC and is allowed to cool to 20ºC prior to measurement, 18% of the sample volume turns to liquid, creating false readings than in the true 60ºC mixture

3 – Minimize Unnecessary Maintenance & Downtime

Tars, resins and other sample components can become a maintenance nightmare to the process and/or analyzers if it is allowed to cool. Tars will clog sample ports making them useless. This leads to costly downtime. Resins can cool to an almost glass-like substance. In this case, analyzers may not be able to be cleaned, they must be replaced.

4 – Enjoy Longer Corrosion-Resistance Life

High moisture and humidity can promote corrosion, leading to shorter life of the gas measuring system. Keeping all parts of the sampling system and analyzer properly heated to at least 250ºF (120ºC) prevents condensation of water vapor, which is the main component in causing corrosion.

It is however, very important to consider not only water vapor but also all constituents of the sample, including solvents, poisons, salts, resins, and other high-molecular-weight compounds present in the sample, this can be as high as 250ºC.

Summary

When designing a gas measurement process, it is important to take these four (4) points into consideration, because in no way should the high temperatures of the application impede your process’ operation. Look for a heated analyzer system that:

Has a corrosion-resistant, heated sample delivery train – The heat eliminates condensation and withstands corrosive elements, leaving you with an accurate representation of your process.

What temperature is right for you? Feel free to contact Control Instruments Corporation to assist you in solving the common challenges associated with higher temperature process gas monitoring applications.

Should you require any assistance achieving accurate levels of heat to industrial or hazardous area process liquids or gases, please contact T&D to discuss our heated hoses, drum heaters or heat tracing systems

gas detection blogs
Invitation – network, engage, promote

Thorne & Derrick are inviting you to join LinkedIn’s fastest growing Discussion Group – Process & Hazardous Area Industries : Heat Tracing, Gas Detection, Fluid Control & Flow Measurement. News, projects, videos, promotions, whitepapers, jobs, webinars, press plus much more. Instrumentation, Mechanical, Heating, Metering, Process, Flow Control - Hazardous Areas

Thorne & Derrick

ABOUT USOil & Gas

Thorne & Derrick International are your single-source supplier of Electrical, Mechanical, Process & Instrumentation Equipment. T&D provide an outstanding service to UK and international customers – we are highly customer responsive and absolutely committed to providing a world-class service.

T&D supply utilities, power, renewable energy, construction, rail, manufacturing, food/beverage, mining, oil, gas and petrochemical industries – distributing 100,000+ products from 100+ manufacturers from multi-million pound stocks. Since 1985 we have established a solid reputation based on service, integrity and trust.