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Category Archives: W. N. Best

 

Pressure atomization depends on the oil pressure inside the nozzle tip to spray a fine mist of oil, very similar to a Windex spray bottle. The micronized oil droplets are flung into the burner head, where they are thoroughly mixed with the combustion air and ignited. As mentioned above, the pressure at the oil nozzle is the key factor in the atomization process; therefore, your oil pump and pressure regulator are the key components in this system. The pump needs to be able to meet the gallons per hour (gph) requirement for the burner/boiler to meet their load capacity. The pressure regulator is set in accordance to the firing rate which is normally between 100-300 (psi). The turndown ratio for a pressure atomizing burner is normally only 3:1 or 4:1.

However, Preferred has just designed and shipped our first high turndown, 6:1 guaranteed, pressure atomized API-AF burners.

These API-AF burners are UL listed for No. 2 oil firing, utilizing pressure atomization. We demonstrated a turndown of 8:1 on pressure atomized oil firing to the UL inspector, extending the normal turndown ratio which is usually only 3:1 or 4:1

 

by Joe Wallace

Oxygen trim (O2 Trim) is a system that constantly monitors your boiler’s combustion. Unlike your car, your boiler has the ability to run properly without it, so what are the upsides to it? This system can adjust your air fuel ratio based on what it’s supposed to be and triggers alarms or lockouts should the combustion deviate from proper levels. It also helps end users save on operational and maintenance costs.

Safety:

We have all seen slipping couplings, broken shafts, blocked intakes or other things that have created improper combustion and unsafe conditions. Oxygen trim can prevent those situations from turning into something far worse. When a burner is tuned with O2 Trim, an oxygen level is assigned to each curve point and is stored with that point as a safe oxygen level. While the oxygen sensor continually monitors your burner’s combustion, it can detect any “off-curve” oxygen readings during combustion and adjust for them within reason. Should the oxygen level have a large deviation from setpoint, the control system will alarm and/or shut down the burner before something bad happens. Another safety function of O2 trim is if a very high CO condition is present, the CO will also make the O2 cell read a lower oxygen level and alarm/lockout the boiler.

Maintenance Savings:

Preventative maintenance should always be done in your boiler room including boiler tuning, but O2 trim may help save you some money on these visits. Since O2 trim constantly monitors your burner’s emissions and makes small adjustments to ensure proper and safe combustion, some areas have only required tuning bi-annually or less. Your system still needs to be set up by a professional and is certainly not a replacement for your service company, but is a great way to ensure your boiler is running properly between their visits. Due to this continually monitoring, the burner is much less likely to be damaged during operation. Improper combustion can lead to very expensive repairs to your system such as burner component replacement due to being burned up, refractory repairs do to instability and impingement, or a catastrophic boiler explosion. Having oxygen trim drastically decreases the risk of these events for a small fraction of the cost.

Operational Savings:

While one can tune a boiler for the conditions that exist while they are on site, what happens when the conditions change? The temperature in your boiler room, the fuel quality, hysteresis of control valves or dampers, etc. can cause a variation in your combustion. Often a boiler is tuned with a safety factor to accommodate for these variations which leaves some efficiency on the table. With O2 trim, you don’t have to accommodate for these future variations, therefore allowing you to run your boiler more efficiently. Your return on investment is contingent on your fuel usage and there are several utilities incentivizing the installation of this equipment with rebates as it has been proven to reduce fuel usage.

Oxygen trim is best coupled with a linkageless control strategy. If you have a Preferred Utilities FlexFit or BurnerMate Universal system already installed, oxygen trim is easily added. The return on investment is dependent on your usage and incentive programs in your area and can often pay for itself within a single heating season.

Ask us how you can improve your boiler efficiency and start saving today.

 

Made in the U.S.A., one of two new API-Ranger burners and BurnerMate Universal controls upgrade for existing boilers on factory fire test chamber. This burner and controls package is capable of burning three (3) fuels like ENSYN Renewable Fuel oil, an 85% carbon neutral fuel, along with natural gas and #2 oil. On fire test the Ranger API easily achieved <9 PPM NOx on natural gas.

This innovative and Low-Cost combustion solution is designed to meet sustainability goals, emission reduction requirements, and efficiency improvements for Colleges, Universities, Hospitals, Office Campuses, Apartment Complexes, Manufacturing Facilities and more.

For your Aggressive Sustainability Goals, choose a Preferred burner/controls upgrade to achieve emission / carbon reduction milestones while increasing combustion turn down, efficiency, and reducing electric consumption.

Features: 10:1 turn down on NG, 8:1 turn down on oil, <2.5% O2, 50-100% firing rate, <3.5% O2, 10-40% firing rate. <9 PMM NOx with <26% FGR.

Now that is a lot to be Joyful about!

 

A New York City Public School central heating plant and their consulting engineer made the decision to install 3 new low emissions burners with state of the art combustion control systems to meet Local Law 87 initiatives.

Compliant with Local Law 87, no fiber metal mesh heads or air filters required.

For sub 35 PPM NOx, burners maintain low O2 performance without FGR and ability to go to sub 9 PPM NOx with FGR– all without fiber metal mesh heads or air filters!

If dual fuel capabilities are added, they can have a sub 5-minute change over from natural gas to oil firing. Their new controls packages includes: BurnerMate Universal O2 Trim, Draft Indication & Control, Fuel Air Ratio Control, Flu Gas Temperature indication and alarm, Smoke Opacity, Flame Safeguard control, with VFDs.

These burners will reduce electricity consumption by 60% or more and allow for 8:1 turn down on oil firing. O2 ranges from sub 1.5% at 50-100% firing rate, to sub 3.5% 10-40% firing rate. The burners and controls package are made by skilled American tradesmen in our Danbury, CT, UL 508 / IBEW shop, and started up by our combustion field engineers.

Made in the U.S.A. for a Greener, more Sustainable and more Fuel Efficient future for NYC.

 

Our SECOND burner and controls retrofit for Bates College on one of their existing 700 HP Cleaver-Brooks™ boilers so they can burn ENSYN Renewable Fuel Oil (100% renewable fuel source derived from trees) as their primary heating source! With our help, Bates is on the verge of reaching their 2020 emissions and carbon reduction milestones while increasing combustion efficiency and reducing electric consumption.

Read the full story here.

 

 

An innovative, low-cost combustion solution to meet sustainability goals, emission reduction requirements, and extreme efficiency improvements.

This installation is at an American college with aggressive sustainability goals. Our solution for them–a burner and controls upgrade on one of their existing 700 HP Cleaver Brooks boilers to achieve their emission and carbon reduction milestones, while increasing combustion efficiency and reducing electric consumption. This upgrade will NOT require the removal of the Cleaver Brooks front or rear doors, but acts as a direct replacement “insert” for the existing Cleaver Brooks burner, while reusing the existing Cleaver Brooks combustion fan and making no cuts or modifications in the original front door.

This specialized API-Ranger burner and controls upgrade will allow the college to burn ENSYN Renewable Fuel Oil, an 85% carbon neutral renewable fuel, along with natural gas or #2 oil.

American made and supported, our technological advancements continue to out-pace the competition.

 

Most of us benefit from some sort of combustion every day. Whether for the release of heat or the expansion of gas to perform work, this special category of oxidation is probably the most widely-used chemical reaction in our daily lives. Like most chemical reactions, there are parameters that need to be present not only for the reaction to take place, but to be the most efficient.

For combustion, we follow the Three T’s…time, temperature, and turbulence.

The time of combustion refers to the rate of the reaction. The fuel (natural gas for example), is introduced to the furnace through injectors or pokers. These are usually pipes with a plate at the end with several holes (some call this a poker “shoe”). The volumetric rate, the size and the quantity of holes will result in a design gas velocity at each hole in the poker shoe. Remember also, most burners modulate, so as the firing rate changes so will the gas velocity. This range of gas velocities need to coincide with the rate of the combustion. Gas velocities too high result in the flame “leaving the zone” of combustion which can cause unburned fuel or flame outs. Gas velocities too low can result in “puffs” or a “punky” flame similar to when you shut the gas off to your grill (okay for barbecues, but not for your boiler).

The temperature of combustion is more intuitive. We all know we need to “ignite” the flame to start the reaction, but what does that mean? Simply, we are introducing heat with a spark or pilot flame at the point where air and fuel are mixed to start the reaction. Once the reaction is started, it provides the heat to maintain the temperature to keep the reaction going. Those familiar with gas pilots know adjusting the pilot gas pressure is key to making the pilot flame reliable. Make sure there is a separate pilot gas regulator to accomplish this.

The turbulence of combustion is the “mixing” of the ingredients…fuel and air. Those who have seen the heads of burners know the multitudes of designs to create turbulence at the combustion zone. This creates good mixing and efficient combustion. Poor mixing can allow unburned fuel to create unwanted compounds in the flue gas like carbon monoxide. Burner designers also consider the size and shape of the furnace. A turbulence pattern that makes the flame too wide or too long can result in flame impingement.

Burner technicians use a stack gas analyzer and a sight glass at the back of the boiler to make their final adjustments for the most efficient combustion. They also do this when the furnace is at normal operating temperature as a “hot” furnace has different combustion characteristics than a “cold” furnace.

So next time you’re in the boiler room, take a peek at the flame and look for the Three T’s.

 

– Robert Frohock, PE

 

Preferred Featured in Today's Boiler

 

The Spring 2015 edition of Today’s Boiler magazine published Dr. Jianhui Hong’s article “NOx Emissions Reduction Strategies.” In the article Dr. Hong explains the importance of low NOx and provides solutions for complying with low NOx emissions regulations.

He explains that “NOx is a term used to include two important air pollutants: NO (nitric oxide) and NO₂ (nitrogen dioxide). These pollutants are sometimes called mono-nitrogen oxides…NOx is a term used to include two important air pollutants: NO (nitric oxide) and NO₂ (nitrogen dioxide). These pollutants are sometimes called mono-nitrogen oxides.”

NOx gases are harmful in a number of ways. Exposure to NOx gases is harmful to human health by irritating the mucous membranes and penetrating the lungs, “causing oxidizing damage to the tissues.”

When NOx reacts with water or water vapor, “it forms nitrous acid (HNO₂) and nitric acid (HNO₃). These acids in the rain can make ‘acid rain.’ Acid rain can damage plants and man-made structures such as buildings, bridges, and outdoor sculptures.”

In highly populated areas, “NOx emissions from combustion processes are primarily in the form of NO. In the air, NO reacts with oxygen to produce NO₂. In the presence of sunlight, NOx can react with hydrocarbons, especially VOC (volatile organic compounds) in the air to form ground-level ozone, which is an important ingredient of smog. The reddish brown color of the hazes hanging over the skies of some major cities comes from NO₂ gas… It can cause irritation to eyes, noses, throats, and lungs. It can even cause asthma and other chronic lung diseases such as emphysema and chronic bronchitis.” NOx can also combine with moisture in the air which “induces changes in phytoplankton and produces toxic brown or red algal blooms (i.e. “red tides”). The algal blooms can cause the death of other plants and marine animals in the water.

Thermal NOx, Fuel NOx, and Prompt NOx create the conditions for NOx emission.

Dr. Hong presented five solutions for the combustion community to reduce NOx emissions.

  • Flue Gas Recirculation “targets the thermal NOx by reducing the peak flame temperature and also oxygen concentration…The use of external FGR increases the requirements for the combustion fan” which “become a significant factor in the overall costs of the burners (including fixed costs and operating costs).”
  • Steam/water injection “works similarly to external FGR. It targets thermal NOx by reducing peak flame temperature and oxygen concentration.”
  • Ultra lean premixing “aims to reduce the flame temperature by staying away from stoichiometric condition. Ultra Lean Premixing, if used alone, has the downside of high oxygen level (up to 9%) in the flue gas, and the loss of fuel efficiency due to the very high excess air.”
  • Air Staging supplies combustion air in two or more stages. “The general goal is to reduce flame temperature, and create fuel rich conditions in the early stages, before the final stage of air is supplied.”
  • Fuel Staging supplies fuel in two or more stages. “The general goal again is to reduce peak flame temperature. This technique is often combined with Ultra Lean Premixing to overcome the efficiency issue of the latter.”

In conclusion, Dr. Hong cites that although NOx emissions can be controlled by the mentioned techniques, “the most cost-effective methods tend to be combustion modifications, especially using low NOx and ultra-low NOx burners.”

Dr. Hong’s greatest contribution to the combustion community is his ability to present solutions for common problems in the industry and the stringent regulations placed on emissions.

Read the full article here.

 

 

Energy Savings Calculator

The Advanced Performance Inject-Aire burner blends the best of both worlds: high efficiency and low emissions. In a day and age where manufacturers compromise quality and effectiveness, Preferred Utilities prides itself in challenging the status quo. We don’t do cheap. We don’t do flimsy. We build our equipment to last—in fact, some of our burners built in the 1960s are still in operation in New York City. That’s dependability.

When it comes to decision time, many customers find themselves struggling to pick between low emissions and high efficiency—but why should you have to choose? As an added bonus, our burners can pay for themselves in just a year’s time.

So just how much energy can your application save with an API Burner?

Download our “EnergySaver Payback v8.3” to find out.

Download: Energy Savings Calculator

 

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Danbury, CT – A boiler system functions as a critical component to the continuous operation of a facility.  The loss of a boiler can cause disruption of operation and significant loss. Thus, it is important to maintain safe, reliable, and efficient operation while minimizing any downtime of the boiler system.

A boiler system consists of many sub-systems working in harmony, such as the boiler, the burner and its control, boiler control including feed water and draft control, fuel oil handling system (if burning oil is required), water treatment, fuel gas booster system (for areas with low supply gas pressure) etc.These sub-systems are sometimes procured from multiple sources.  In order to deliver the safe, reliable and efficient service that the end user expects, it is advantageous to adopt a “full system integration” approach.

Possible Problems

A boiler system in general could have many modes of failures.  Failures in water level control have serious implications on the longevity of the boiler and in safety (the sudden inrush of feedwater to a baked-dry boiler could lead to a steam explosion). Water treatment failures can decrease the longevity and efficiency of the boiler. Boiler operators need to understand these dangers. Among all sub-systems, the burner system is by far the most sophisticated subsystem in a boiler system. The burner system has many modes of failure that require extensive training and/or experience for the boiler operators to fully understand.

When a boiler system is not delivering satisfactory performance to the end user, it is sometimes difficult to pinpoint the exact cause of the problem. The following example is used to illustrate this difficulty. Sometimes a burner makes a low frequency noise, often called a combustion rumble. The rumble could be a nuisance or discomfort to the operators and residents nearby, or could even cause damage to property. Potential causes of the rumble include, but are not limited to:

  1. The burner has poor stability at certain firing rates; or the burner’s window of operation is too narrow. This could be related to the design or manufacturing of the burner.
  2. The air/ fuel ratio is improper due to poor commissioning or lack of maintenance.
  3. The servos used by the burner control may have poor accuracy or repeatability.
  4. The linkage between servos and dampers may be loose.
  5. The system does not have oxygen trim to ensure consistent excess air levels. Any variation in draft, ambient temperature, fuel gas composition, building ventilation (affecting building inside pressure vs. outside ambient pressure), or wind speed blowing on outlet of chimney, can affect the amount of combustion air supplied by the fan.
  6. Lack of draft control.  Severe draft variation may cause the air/fuel ratio to go out of range.  This is definitely a challenge if the system does not have an oxygen trim system; it can be a problem even with an oxygen trim if the draft variation is too severe for the oxygen trim to compensate.
  7. The “acoustic coupling” between the burner and the boiler’s fire chamber and the subsequent space the flue gas flows through.
  8. The fuel gas booster could surge and cause the gas pressure to oscillate, beyond the pressure regulator’s ability to regulate.
  9. The boiler room’s ventilation system could be improperly designed. When windows and doors are shut, a significant negative pressure can develop in the boiler room, causing a drop in combustion air supply and air/fuel ratio.
  10. Fuel gas supply pressure and composition can fluctuate, especially if the fuel gas is from an alternative fuel source, such as land fill gas or, to a lesser degree, digester gas.
  11. Burner components may not work well together. For example, the gas regulator may be over-sized for the flow rates of the burner.

Problems with the Multiple-Vendor Approach

Fully integrated custom controlsWhen the subsystems are procured from many different vendors piece-meal (by the general contractor or the end user) and no engineering firm takes responsibility for integrating these subsystems, it may be difficult to identify the party responsible for correcting the problem. This often results in blame shifting among different parties, ultimately frustration for the end user.

For example: in a piece-meal approach, the burner may be supplied by a burner company, the controls may be supplied by a company that is solely dedicated to burner controls and knows little about the combustion behaviors of the particular burner. The specifications do not call for a draft control or oxygen trim, when in reality one or both of those may be required for the site conditions and requirements. The booster, if there is one for the job, may be supplied by yet another vendor, the commissioning may be done by a contractor, the ventilation system of the boiler room may not have been designed properly to avoid high negative building pressure.  The troubleshooting process itself is further complicated by the diverging interests of the different parties involved.

Sole Source Responsibility

The most important advantage of the full system integration approach is that the integrator must accept sole source responsibility. If the burner system does not perform, the integrator is responsible for correcting the problem. There is no blame shifting among different suppliers.XPlus

A burner system supplier that adopts the full system integration approach is inclined to build a long term relationship whenever it sells a job. The supplier would look at the specific conditions and requirements of the customer, and look for the best solution tailored for the job instead of chasing the latest trendy requirement in specifications. For example, it may be tempting to ask for a 12:1 or higher turndown from the burner system, but can the non-condensing boiler operate at 12:1 or higher turndown without condensation and corrosion problems?  Is 10:1 or 8:1 turndown enough for the job? In another example, does the system require a draft control device to work? Can the burner deliver satisfactory performance without the draft system?

A supplier adopting the full system integration approach would look at total costs of ownership (the fixed costs and the operating costs) for the boiler system, instead of focusing on the fixed costs. In today’s corporate procurement practices, too often the one responsible for buying the boiler system is not the one paying the energy bill, hence there is less incentive to consider the total costs of ownership.

For example, a burner capable of operating at 1.5-2.5% oxygen during the majority of its operation time can lead to significant savings in fuel costs.  If a vendor offers a burner system without use of  oxygen trim, is the burner operating at consistent excess air levels all year round? Does the lack of oxygen trim mean conservatively high excess air levels? In another example, a fiber mesh burner may be used to meet 9 ppm NOx requirements without FGR, but the additional costs of fuel due to the very high excess air levels (typically 8-9% oxygen dry in flue gas) and the costs of replacing filters and fiber mesh combustion heads need to be factored in when purchasing a burner system. In another example, a burner constructed with flimsy, low grade sheet metals may need frequent service and replacement parts, while a burner constructed out of durable steel can provide years of service beyond the normal warranty periods.

The “full system integration” approach requires an integrator to have in-depth understanding and strong product offerings in all of the following areas:

  1. Boiler controls. The boiler controls ensure safe and smooth operation (water level control, burner firing rate based on temperature or pressure, draft control if necessary). It should have the capability to manage the lead-lag control of multiple boilers to ensure the boilers are operating at maximum efficiency.
  2. Fuel oil handling systems (main tank, day tank, pump sets, filtration, leak detection, etc.)
  3. Burners–especially those designed for both high efficiency and low emissions at the same time. The end user should not be forced to choose between high efficiency and low NOx.  High turndown (such as 10:1) helps avoid cycling of the boiler, and low excess air minimizes loss of heat to flue gas. Use of FGR is acceptable, but the incremental costs of running a larger motor due to FGR should be factored in. Advanced designs of burners can achieve mandated NOx emissions with less, little, or no FGR (depending on the NOx levels required).
  4. Burner controls.  The burner must be equipped with the latest Burner Management/ Combustion Control Systems (BMS/CCS) to assure that safety aspects are in accordance with the latest requirements of NFPA 85 and CSD-1. When high efficiency or tight emissions are required,  an oxygen trim system should be included, and parallel positioning or fully metered control should be used in lieu of jackshaft. The combustion control and the servos should be designed to modulate the controlled fluids (air, fuel, FGR etc.) in a coordinated manner.  For example, if the air servo cannot move fast enough to be in sync with the fuel servo, then the fuel servo needs to be slowed down in modulation, and vice versa.
  5. Commissioning and maintenance.  The burner system is commissioned and maintained by qualified service technicians that are knowledgeable about all the subsystems.
  6. Technical support and spare parts. These should be available from nearby locations.

Preferred Utilities Manufacturing Corporation has earned a reputation for accepting single-source responsibility. We firmly believe in the advantages of full system integration. Compared to the piece-meal approach, the benefits of full system integration make the choice clear. If you believe the same way, please contact us about your next project.