What Would You Want to Know About a Substance in Order to Determine Whether It Combusts

All substances incorporate varying amounts of convict energy depending on the substance and how it exists; that is, solid, liquid, or gas. The uniting of two substances to class other substances is chosen a "chemic reaction". Combustion is a chemic reaction. This reaction is for the purpose of releasing heat. As nosotros'll meet, oxygen will e'er be 1 of the substances in the reaction, and the other will be a hydrocarbon, mixtures of hydrogen, carbon, sulphur, etc.

Perfect combustion is simply a mixture of fuel and oxygen, with both beingness completely consumed in the burning process. The ideal situation would be to provide just plenty air in the combustion chamber to insure complete burning of the fuel. This would exist true if it were physically possible to bring each cantlet of fuel in direct contact with the amount of air required to consummate its combustion. To date, no method has been devised in a combustion chamber so that air and fuel come in consummate contact in just the correct proportions.

If we reduce the corporeality of oxygen, in a perfect mixture, we would have a fuel-rich status. Withal, if we increase the amount of oxygen, in a perfect mixture, we now have excess, which does not contribute to the called-for process. Having just the correct corporeality of oxygen (no more than, no less) is called the stoichiometric betoken, or stoichiometric combustion. The stoichiometric indicate is likewise called the 100% air signal.

Annihilation above the 100% point is chosen backlog. For example, we might use the term 20% excess air to describe a boiler's air/fuel mixture point. This means the excess air is running at the 120% level or 20% (higher than stoichiometric) above the perfect mixture bespeak.

Stoichiometric combustion is important since information technology is the reference indicate from which we tin can measure the efficiency of a heating unit. Air contains 20.9% oxygen and 79.ane% nitrogen. The air/fuel mixture tin be described simply as fuel + air. Keep in listen that air consists of two parts oxygen (0 2 ), forth with 7.52 parts nitrogen (Northward two ).

If we do a chemical/mathematical caption of a fuel using natural gas (methane CH 4 ), nosotros can see how various measurable compounds are formed that can be used to calculate how efficiently a heating unit of measurement is using its fuel.

A natural gas air mixture tin be expressed equally CH 4 + 20 2 + 7.52 N 2 . Allow's at present increase the corporeality of air past 20% over this perfect mixture bespeak:

20% excess air = 100% + 20% = 120% or 1.ii

Therefore, let'due south mix marsh gas (CH 4 ) with 1.2 times the normal 100% air

or CH iv + i.ii x 2 0 2 + 1.2 x seven.52 N 2

or CH four + 2.4 0 2 + nine N 2

At present, permit's burn this new mixture and show the chemical transformation :

CH 4 + 2.4 0 2 + 9 N 2 ® C0 2 + 2H 2 0 + .4 0 ii + 9 N two

Note that .iv parts of 0 ii be in the resultant flue gas because it was not used in the burning process; information technology was excess.

Let'southward practice a C0 2 analysis on a dry basis and too an 0 2 analysis on a dry out ground. In the flue, due to the called-for process, we now have:

1 role CO 2 + .4 part of 0 ii + ix parts of N 2

Therefore, ane + .four + nine = 10.4 total parts .

Notation: Nosotros drop the 2 H 2 0 term considering our analysis is on a dry basis .

% C0 2 = i part Co 2 x 100% = 1 = 9.61%

10.iv parts 10.four

% 0 2 = .4 part 0 2 x 100% = 3.8%

10.iv parts

Finally: Actual 0 2 - Theoretical 0 two x 100% = excess air

Theoretical 0 2

2.four - 2 10 100% = .4 x 100% = 20% excess air

two 2

Therefore, a C0 2 point of 9.61%, an 0 two point of three.8%, and an backlog air point of xx% all mean the same thing in describing the air/fuel mixture point in the combustion process.

For natural gas, we accept an ultimate or maximum C0 2 level of:

1 or 11.73%

1 + 0 + 7.52

This ways our excess air is ready to 0%, which as well means 0% 0 2 occurs in the flue, allowing the ultimate C0 2 level to be achieved .

Figure 1.

For a graphical caption of excess air, refer to Figure 1. This graph shows a typical theoretical air curve, showing the relationship betwixt the combustion air setting on the banality and diverse fuels. The combustion setting, therefore, tin be expressed equally any i of the three terms: backlog air, 0 2 , or C0 ii .

Effigy ii.

Effigy 2 is known as a theoretical air curve. This curve is for the fuel natural gas and is intended to show % backlog air as information technology relates to being either fuel rich or fuel lean. The fuel lean side is a safe side.

Note: A C0 2 analysis solitary does not provide a safe indication of the combustion air/fuel setting. Additional measurements of either smoke or CO are recommended.

In other words, a given C0 2 value can occur on either side of the stoichiometric.

Excess air is the preferred term to describe the combustion setting on the safety side of the stoichiometric. In order to get in at the backlog air value, an 0 two measurement is performed .

Figure 3.

Effigy 3 is a theoretical air curve chart for fuel oil.

Over again, C0 two can appear on both the fuel rich and excess airsides of stoichiometric. This is a very important point worth repeating.

Alarm: When doing combustion testing, if yous only rely on C0 ii per centum alone, you can get high C0 ii readings and be on the fuel rich side of the stoichiometric. Avoid the fuel rich side since partially burned fuel will result in carbon monoxide (C0), a gas that in large enough concentration can kill!

See Figure 1 again. Note that testing for oxygen, 0 2 , insures being on the excess airside of combustion and correlates directly to C0 two readings, regardless of the fuel existence burned.

Note: Measuring 0 two in the flue gases is the preferred method for combustion analysis.

All modernistic electronic portable combustion analyzers use an 0 2 cell. They may be able to brandish C0 two , but it will exist calculated or computed from the 0 ii reading.

Now that we have a handle on what happens when we "burn down" something, how can this knowledge be put to use? It should be clear that we could test a heating unit with some instruments that tin can measure the products of combustion, and discover out how efficiently the unit of measurement is using its fuel. Nosotros could even "tune upwardly" a burner to burn more efficiently. A combustion analysis can also diagnose problems with the burner.

There is nothing mysterious about combustion efficiency. Information technology is but 100% minus the per centum of heating value lost through the stack. If stack losses are 25% of the heating value for a given fuel, then the combustion efficiency is 75%.

Combustion efficiency calculations start with assuming complete combustion and and then applying three bones factors:

1. The heating valve for a given fuel.
2. Net stack temperatures.
3. Percentage of oxygen past volume.

The Heating Value of a fuel is the stoichiometric air/fuel mixture, or put another way, the potential energy in the fuel. The Net Stack Temperature is the temperature that the gases are raised above the temperature of the master and secondary air, usually ambience air temperature. In some commercial-industrial applications, the main air will be pre-heated.

If we only want to know the efficiency of a particular burner, nosotros need simply an musical instrument to find percent 0 2 , a thermometer, and a combustion efficiency computer or chart for the fuel being used. Combustion efficiency calculators, such as the Bacharach x-5064, or combustion efficiency charts (run across Figure 4), take taken into consideration the heating value of a fuel, and so information technology is merely necessary to find the cyberspace stack temperature, per centum 0 2 , and insert these figures into the chart or calculator.

Figure iv.

As an example, a natural gas furnace with a net stack temperature of 350 o F and an 0 2 reading of seven 1/2% is 80% efficient (see Figure four). What this means, is that eighty% of the heating value of the gas is existence used to heat with and twenty% is wasted. Another way to look at it is to say that for near every dollar of fuel spent, 80 cents is returned as usable rut and 20 cents is going out the stack. At today's and future fuel prices, this is expensive. At today's toll of natural gas, by increasing a unit of measurement's efficiency from 80% to 85% will save most $7.00 per $100 of fuel toll.

A contractor tin use uncomplicated overall combustion efficiency to compare a customer's operating unit to a proposed modern high-efficiency unit and guess fuel toll savings to show payback. Information technology'south a useful selling tool, but is non truthful combustion analysis. For combustion analysis, nosotros desire to know more than only net stack temperatures and percent 0 2 . We also want to know C0 parts per million (PPM), draft, smoke (if oil), and for large industrial burners, sulfur dioxide (PPM) and oxides of nitrogen (PPM). With all that data, we can then properly analyze the burner's performance, diagnose problems, and tune the burner for optimum efficiency.

Combustion analysis used to be done by taking tests the quondam-fashioned way that is with oristats, sometimes called "cocktail shakers". Tuning a burner using those devices was very time consuming. Modern electronic combustion analyzers allow yous run into the results of changes fabricated during a burner melody-upward immediately. They are accurate and much easier to utilize than oristats. A prime example of a mod analyzer is the Bacharach Model 300.

A fully equipped 300 can display on large LED readouts:

1. Stack temperature,
2. PPM C0
3. Percent 0 2
4. Percentage excess air
5. Percent efficiency
6. Percentage stack loss
7. Percent C0 2
8. PPM NOX
9. PPM S0 2

It tin print out the data and tin transfer the data to a figurer.

The 300 can do all this for seven selectable fuels:

1. Natural gas
2. Number ii fuel oil
3. Number half-dozen fuel oil
4. Propane
5. Coal
6. Forest
7. Bagasse.

With the improver of a smoke tester, draft judge, manometer, and oil pressure gauge, the service technician would have every instrument needed to do a complete combustion assay, tune-up, or diagnose bug of whatsoever burner.

Combustion efficiency gives us an overall view of a burner's performance. Using our instruments, these problems tin can exist isolated, and through interpreting the readings, the problems can exist corrected.

But the manufacturer of a piece of equipment knows what the recommended 0 2 , net temperature, draft, etc. should be. The design of the equipment will dictate what the "correct" settings, the optimum operating parameters, should be. If the manufacturer's specifications are not available, some general guidelines will take to be used, along with federal, country, and local codes. Authorities or utility regulators oftentimes prepare excess air settings and commanded C0 concentrations.

In general, near equipment will operate between 16% and 30% excess air, that'due south 3% to five% 0 two (see Effigy 1).

Over fire typhoon of .02 inches water column (Westward.C.) is acceptable with flue draft .02 to .04 inches W.C. greater than the over fire draft.

Internet stack temperatures vary according to the fuel used. Non-condensing units are not designed to withstand condensation, so the stack temperatures must exist maintained above the dew point.

Crude guidelines for minimum cyberspace stack temperatures are:

1. Natural gas 250 ° F
2. Number 2 fuel oil 275 ° F
3. Number five fuel oil 300 ° F
4. Coal 325 ° F
5. Forest 400 ° F.

A 0 PPM C0 reading is ideal, but not practical. No code or manufacturer specification allows 400 PPM or more C0. 1 tin can reasonably expect to achieve C0 readings below 100 PPM.

When "tuning up" a burner, the exact adjustments depend entirely on the equipment's pattern, size, and make. Every attempt should exist made to follow the manufacturer'due south specifications. A general procedure would be to complete all maintenance. Clean the heat substitution surfaces, oil equipment, supercede defective parts, etc.

For burners using heavy oils, bank check the preheat temperature. If unknown start at 250 o F and reduce the temperature until best combustion is achieved. Check and accommodate fuel input. Operate the burner for at least fifteen minutes. If a modulating burner, operate at high fire until the unit is at normal operating temperature. Check and set excess air settings. Check for C0 (and smoke, if an oil burner). Reset air settings until C0 and smoke are acceptable levels, cheque internet stack temperatures. On modulating burners, check all settings at depression fire and at several points over the firing range. Suit as necessary. If a dual fuel burner, repeat the procedures for both fuels.

The modulating boiler is a combustion organisation that adjusts its firing level and steam production to meet a changing output need. A process steam boiler is a practiced example of a organization that has this modulating or variable firing rate adequacy.

The Model 300 is capable of measuring combustion efficiency at each firing rate or combustion load point. To put information technology simply, the Model 300 measures all the necessary combustion process parameters and in turn automatically calculates and displays the actual combustion efficiency for each boiler operating betoken.

To optimize efficiency at any boiler indicate is quite simple. Connect the Model 300's probe to the boiler'due south sampling location and adjust the air in steps of 10% excess air and measure the efficiency. Next, plot a curve (efficiency vs. excess air) and decide the mechanical position necessary for the ideal process set point. Repeat the process at various boiler load points over the normal operating range. The procedure merely consists of adjusting the boiler in order to obtain the maximum safe combustion efficiency. To assure connected maximum safe efficiency, regular tests are repeated to ensure proper treatment of the key parameter variations. Changes in relative humidity, variations in the fuel's heating value, and changing combustion air temperatures must always be considered as possible random parameter variables, which bear upon combustion efficiency. A random variation in the humidity, for instance, tin cause the concentration of oxygen in the air to vary from 20.nine% at 0% RH to 20.forty% at 100% RH (at an air temperature of 70 o F). This humidity factory will cause a variation in the oxygen measurement of .five% 0 ii , at a twenty% 0 2 ready signal. This difference will result in a corresponding change in combustion efficiency of .2% or more than.

Using the Model 300 to spot check these combustion parameters ensures that the process does not change and become unsafe. Knowing the amount of combustibles present, determining the operating conditions over a range of fuel compositions, noting ambient temperature variations, and knowing the current humidity will allow the boiler set points to be maintained.

The modulating boiler's right air/fuel ratio depends upon the particular demand (load) placed on the banality. The correct operating parameters must be determined at each load condition. This "profile", when completed, is mechanically locked in place to ensure repeatability. Graphing efficiency vs. backlog air, at each load point, enables the operator to locate and ready the process for the maximum efficiency over the entire boiler operating range.

In small (automated) control systems, a jackshaft is used for modulating command. A modulating motor controls each load position in order to automatically adjust to air and fuel linkage. A cam is used equally an adjustment to alter the air/fuel ratio and is considered part of the control mechanical linkage. Past placing the burner on "bypass", manually setting a physical load position and constructing the necessary graphs, the optimum set point can exist established. Here again, utilize the Model 300 to determine the correct operating conditions. This procedure is executed for each ten% and 20% load position. This process, in other words, is repeated for each desired load point.

On larger control processes, the operator switches to "manual" and adjusts the air/fuel ratio at each load position. A graph is nonetheless produced and a final set betoken is established. The set point data, obtained by utilizing the Model 300, is then programmed in to a controller. The "trim" controller has (by design) a limited operating range, since it corrects or trims the air and fuel linkage to compensate for the various parameters previously noted. One final note on automatic command systems; the trim command must non exist used to correct malfunctions in the boiler and must always have a slower response time than the primary or overall control loop. This express range adjustment capability, on working boilers, is to prevent large-scale changes, which can crusade major disruptions in the combustion process. The Model 300, therefore, is a necessary tool for all modulating boilers regardless of automatic command type or bones mechanical adjustment configuration. The 300 is needed to ensure correct operating conditions for combustion systems that must be readjusted for each and every output need.

For many years, the combustion efficiency rating for new furnaces and boilers was in the range of 75% to 82%. This average figure of 80% combustion efficiency was considered equally the optimum performance level. Times accept inverse. Now combustion efficiencies are typically in the ninety% plus range. There are many reasons for this overall major improvement in heating unit of measurement performance.

• The "condensing" blueprint enables the recovery of the latent heat lost in the high stack temperatures previously required to maintain h2o in a vapor form.

• The addition of "draft inducer" fans to provide a abiding typhoon and to eliminate natural draw after burner shutdown.

• Utilization of exterior air for combustion air thus reducing the need for using inside (living area) oxygen for combustion.

• Improved oestrus exchanger designs and better utilization of circulating air for more efficient scrubbing of the rut transfer surfaces in hot air applications.

• The emptying of the abiding airplane pilot flame by the incorporation of electronic ignition systems.

• The elimination of the unsafe hot stack by replacing with pocket-sized diameter "room temperature" tubing.

• Venting has been greatly simplified, thus reducing the possibilities of incorrectly sized venting and improper chimney size and summit. Installation, therefore, allows the heating unit of measurement to be free from previous installation and design restrictions.

Water vapor is present in the flue gases produced past the combustion of all fossil fuels. The combustion procedure needs an air/fuel mixture, and this mixture already contains water vapor, merely as the air nosotros breathe contains a certain amount of h2o vapor, depending on the relative humidity. In addition, water is a production of combustion for whatever fuel containing hydrogen or hydrocarbons. Fuels such every bit marsh gas and propane comprise large amounts of hydrogen, but even coal contains some hydrogen in the form of entrapped hydrocarbons. Information technology takes energy to heat and thus raise the temperature of all this water vapor in flue gas. This energy is latent heat. If hot flue gases are allowed to cool, energy is released. If water vapor is allowed to cool to the indicate where it condenses into a liquid (the dew bespeak temperature), a not bad deal of energy is released. This free energy is the latent heat of evaporation. A "condensing" furnace or boiler recaptures this latent heat (associated with both the raising of water temperature until it is fully vaporized and cooling the water vapor until information technology is fully condensed), and uses it to heat the boiler water or furnace air.

The amount of energy required to vaporize water (or conversely, the energy released when water vapor condenses) is staggering. At atmospheric pressure, it takes simply 142 BTU to raise the temperature of one pound of water from 70 ° F to its boiling betoken, 212 ° F. However, once this pound of water reaches 212 ° F, it takes almost 1000 BTU to convert it from a liquid to a vapor, the latent rut. Condensing furnaces recapture this heat. A conventional furnace lets this heat escape upwardly the stack.

The theoretical maximum heating value is the total estrus, which can be obtained from the combustion of a specific amount of a given fuel, mixed with the correct amount of combustion air (at the stoichiometric signal). With the combustion starting temperature at sixty ° F, the combustion process is allowed to completely take identify, and finally the flue gases (products of complete combustion) are allowed to cool back to threescore ° F. The heat released due to combustion is measured over this unabridged range.

Considering condensing furnaces allow the flue gases to cool to the condensing bespeak, the flue or exit temperature is typically effectually 100 ° F. In the non-condensing units, information technology is important to prevent condensation past keeping stack temperature in a higher place minimum values. For instance, stack temperatures must be at to the lowest degree 75 to 100 ° F higher than steam temperature in steam boilers or the water temperature for hot water boilers and heaters. If the water temperature is 180 ° F, for example, the stack temperature must be at least 250 ° F. The chief point is not-condensing units are not designed to withstand condensation. Therefore, the stack temperature must be maintained above the dew point.

Depending on the fuel and other weather condition. the increase in efficiency due to condensing is in the range of 5% to almost 20%. This is the gain due to recapturing the latent oestrus.

In condensing units, the key measurement is stack temperature. If the stack temperature is around 100 o F, we have a condensing unit, which should yield an comeback in combustion efficiency equally compared to non-condensing furnaces and boilers. Net stack temperatures (above ambient) of twoscore, thirty, xx, or even 10 ° F are possible.

The 2nd betoken of give-and-take is on the use of electrical fans to induce a typhoon. The purpose of a draft inducer is really twofold. Its commencement purpose is to pull flue gases evenly through the heat exchanger. Its second advantage is to eliminate the need for a chimney. The flue gases can at present be blown through a sidewall vent system.

Efficiency is actually helped past a few percentage points considering of two typhoon inducer effects. First a stable and constant flow of flue gases is achieved over the rut exchanger and secondly, the stand-by heat loss is reduced, since at that place will exist no suction through the heating unit of measurement, caused past a chimney "draw" during burner-off periods.

The primal measurement, in this instance, is the flue gas sample (either C0 2 or 0 2 ) taken at the same location every bit stack temperature. This volition exist at a positive force per unit area of around 0.three" of h2o, depending on the particular furnace or boiler. The typhoon-inducer's fan typically develops effectually one.5" of h2o negative pressure level for its function of drawing the flue gases through the rut transfer mechanism. Sometimes flue sampling may involve dealing with a condom device used to shut off the fuel supply in the consequence of draft-inducer failure. This rubber device is unremarkably in the form of a pressure switch.

The third and last indicate deals with furnaces and boilers, which utilize outside air for combustion air. The major advantage of bringing in outside air is the elimination of the adventure of depleting breathing air by using heated inside air for combustion purposes.

The net stack temperature (the difference between the inlet air temperature and the exhaust gas temperature) is very important to the efficiency of non-condensing furnaces , merely has little effect on the efficiency of condensing furnaces. In condensing furnaces, the relationship of the actual stack (frazzle gas) temperature to the dew point of the exhaust is the more than important factor, because of the very large amount of heat liberated when the stack gas is cooled below the dew point.

Dealing with the measurement aspects of new high-efficiency furnaces and boilers is quite simple. First cull an instrument that can measure, calculate, and display combustion efficiency to 99.9% and too ane that can automatically take primary air temperature into consideration. Remember, the outlet temperature must be around 100 o F and volition be under a slight positive pressure when dealing with draft inducers. A safety switch must be dealt with on certain units. Always cheque the particular manufacturer for measurement locations and procedures. Finally, combustion efficiency figures seem to run 1% or two% higher than the manufacturers' rating numbers. If a certain furnace or boiler has a rating or AFUE (Annual Fuel Utilization Efficiency) number 92%, the combustion efficiency will be around 93.5%.

The concept of having stack temperatures beneath the dew betoken, eliminating the need for a chimney, and bringing in outside air creates a challenging instrumentation need.

The Bacharach hand held Fyrite Ii is the platonic musical instrument for testing condensing furnaces and boilers. The Model 300 can too be used. Figure v and Figure vi show the difference in the location of the sampling bespeak for typical condensing (Figure 6) and non-condensing (Effigy 5) units.

Figures 5 and 6.

Location of the sampling holes to take the various measurements is very of import. For residential and light commercial or industrial equipment, the following recommendations are applicable.

Oil Gun Burners : Locate the sampling point as close the furnace breaching equally possible, and at to the lowest degree six inches upstream from the furnace side of the typhoon regulator.

Gas Burners : Locate the sampling hole at to the lowest degree six inches upstream from the furnace side of the draft diverter or hood, and every bit close to the furnace breaching equally possible. A probe can also be inserted downward in the flue through a draft diverter or hood.

For Larger Equipment : Locate the sampling betoken downstream from the concluding rut substitution device (such as an economizer, recuperate, or like device). Locating the point subsequently the last heat exchanger ensures that the net temperature will provide an accurate indication of the effectiveness of the exchangers. Withal, the further the point is from the terminal exchanger, the more heat will be lost through the duct or stack to the atmosphere and the greater the gamble of dilution from air leakage, reducing the accuracy of the exam.

Turbulence of the flue gases tin can sometimes cause samples taken from a sure portion of the duct to be misrepresentative of the flue gases. Ordinarily, going 8.5 duct diameters downstream of an elbow or other crusade of turbulence will eliminate this effect. To brand certain that the sample taken from larger ducts or stacks is representative; it is generally a good idea to accept several measurements with the probe inserted at diverse depths into the duct or stack. If the indications at these various points differ, take their average for calculations.

Be very conscientious of air leakage into the duct or stack that can adversely bear upon the accuracy of the percent oxygen by book indications. This will increase the oxygen percentage beyond that acquired by excess air.

Another sampling hole to measure over fire draft should exist made so that a draft gauge sampling tube with a few feet of 1/4" OD copper tube will be centered approximately a foot above a combustion chamber. This pigsty should exist sealed afterwards employ.

Previously, the Bacharach Model 300 combustion analyzer's general specifications were given. At present that we are more familiar with combustion analysis and what can be achieved with good analysis, the Model 300's features will be discussed in depth.

The Model 300'due south 23-foot long cablevision allows connection to large systems, and so the user is shut to the 300, not close to the probe insertion location. The large readouts permit the user brand adjustments and scout the displays to see the results of those adjustments.

The Model 300 directly measures and displays flue gas oxygen content in the range 0.0 to 25.0% 0 2 , carbon monoxide content in the range of 0 - 3000 PPM C0, and the actual main or flue gas temperature in a range 0 ° to 2100 ° F. It also computes and displays combustion efficiency (0 to 99.9), C0 2 content (0 to xx%), excess air (0 to 250%), and stack loss (0 to 99.9%).

Recollect our dry gas assay did not take into account the water vapor (H 2 0)? Well, the Model 300 measures C0, relates this C0 value to C0, H 2 , and H 2 0, and includes this measured parameter in the combustion efficiency calculation. The Model 300 not only eliminates the need to graph combustibles along with combustion efficiency, only also performs the necessary subtraction operation based on a family of combustibles curves. The Model 300 determines and displays combustion efficiency with combustibles nowadays--automatically!

Process work and heating flavor applications are of no real consequence to the Model 300. Process boilers and furnaces similar hot water heaters in homes are used year-circular. Therefore, applications exist yr-round, regardless of climate. The Model 300 is probably less seasonal for the reason of heavy usage in industrial process piece of work.

Consider the length of time the combustion procedure will be analyzed. In other words, how long with the instrument be sampling and measuring in the stack or flue? If a boiler is being studied over fourth dimension (five, 10, 20, 45, 60 min., etc) the Model 300 is the choice. The Model 300 is a short-term monitor, which can be fastened to an industrial size boiler for a given period of time.

Nearly one-half of all the natural gas consumed in the United States can be attributed to the industrial sector, which includes both boilers and industrial furnaces. The industrial furnace is actually an instance of a high temperature flue gas application. The sample must be cooled below the upper temperature rating of the analyzer and, of course, the efficiency readings volition not be correct. Combustion efficiency must be achieved using actual net stack temperatures and, therefore, cooling to a lower value is just for determining an excess air indication.

In the industrial sector, that of the industrial furnace, the temperature range is 400 ° F to 4,000 ° F. The aforementioned relative improvement nosotros observe in the banality sector is possible. However, instead of dealing with improving a boiler's efficiency from, say 72% to 77%, or decreasing the boiler'southward 0 2 level from seven% to 2%, the improvement is achieved by reducing the furnace's excess air from 50% to 10%. Since the full fuel usage potential is similar to the banality market, the fuel savings possibilities are too similar. The 300 tin can handle up to 2100 ° , but if stack temperature exceeds 2100 ° F, it's easy to brand upward your ain custom high-temperature sampling and cooling assembly. Just cull tubing that closely matches a detail analyzer's probe dimensions. Measure the stack diameter, at the desired sampling location, and cut a new high-temperature probe to equal this measurement. Experience has shown that when a probe has 50% of its overall length left exposed to ambient temperature, the cooling caused by the heat-sink effect is quite large. Next attach a user-friendly length of rubber tubing to the one end, insert the new probe halfway into the stack, and attach the other cease of the rubber tubing to the flue gas analyzer's probe tip. Allow the analyzer to describe a flue gas sample through the new probe and hose associates and mensurate the percentage of backlog air. Finally, e'er lookout the analyzer'south temperature indication to preclude exceeding its own upper temperature limit. Make certain the tubing makes a leak-free seal on both probe tips. If the rubber covering the high temperature probe tip becomes hardened, but snip off this pocket-sized portion and re-attach it to the remaining soft portion of the probe. Most analyzers tin can accommodate up to ten feet of extension (probe and rubber tubing) without causing excessive drag on a sampling motor.

Do non forget the industrial furnace awarding. Fifty-fifty though the temperatures are quite high, equally compared to boilers, usually the temperature is already beingness measured and is known. The application, for the 300, is to merely measure the oxygen level (excess air) and in the procedure utilize plenty sampling line or probe extension to cool the flue gases to within the temperature specification of the analyzer. The combustion efficiency indication or its calculation is not correct; even so, the excess air measurement is right.

The main bespeak is that a significant savings is possible by but tuning a burner while using the right combustion analyzer, the Bacharach Model 300.

copelandwhoubson.blogspot.com

Source: https://www.industrialcontrolsonline.com/training/online/everything-you-need-know-about-combustion-chemistry-analysis

Share this post