Mckenzie Corp: Deaeration of Boiler Feedwater

Pour yourself a tall glass of cold water. Place it in front of you and read on.

The water you have just poured for yourself is much like the feedwater you may be sending directly into your boiler.

It contains among other things, dissolved gases such as oxygen and carbon dioxide that can be particularly destructive to feed lines, condensers and to your boiler.

The oxygen in this raw feedwater is released within the boiler as a result of heat and rises in the form of bubbles. These bubbles attach themselves to the boiler tubes, water legs and the sides of the boiler drum shell at the water line.

The oxygen along with the carbon dioxide attacks the iron and set up chemical musical chairs in which the steel in your system will always lose. This destructive game will continue until either all the oxygen is entirely removed from the water or the steel or iron is dissolved.

A deaerator will prevent the game from ever starting. This piece of equipment removes corrosive gases from boiler feedwater and preheats the water prior to entrance into the boiler.

A deaerator should be considered if any of the following situations occur:

- Your boiler plant operates at 75 psig or greater.
- Your boiler plant has limited standby capacity.
- Production depends on your continuous boiler operation.
- Your boiler plant uses 25% or more cold water makeup.

Now take a good look at that glass of water you poured earlier. Those little bubbles that have formed on the inside of the glass are just what we have been describing. Imagine the inside of your boiler system with high temperatures and high pressures. If you don't have a deaerator, maybe it is time to consider one.

COMMON WATER IMPURITIES

Impurity Source Effect
Algae organic growth fouling
Calcium mineral deposits scale
Carbon dioxide dissolved gases corrosion
Chloride mineral deposits corrosion
Free acids Indus. Wastes corrosion
Hardness mineral deposits scale
Magnesium mineral deposits scale
Oxygen dissolved gases corrosion
Silica mineral deposits scale
Suspended solids undissolved matter fouling/scale

There are five major problems directly associated with water quality that will effect boiler performance. These are:

- Scale formation
- Corrosion
- Fouling
- Foaming
- Embrillement

SCALE is a very hard substance that adheres directly to heating surfaces forming a layer of insulation. This layer of insulation will decrease heat transfer efficiency. Scale also results in metal fatigue/failure from overheating, energy waste, high maintenance costs and unnecessary safety risks. A one-sixteenth inch thickness of scale in a firetube boiler can result in a 12.5% increase in fuel consumption.

CORROSION is defined as the destruction of a metal by chemical or electromechanical reaction with its environment. The metal is eaten away in much the same manner as fender rusts on a car. Corrosion dramatically increases maintenance costs and can cause unnecessary safety risks. It will occur when levels of oxygen or carbon dioxide are high, where pH values are low, where contact occurs between dissimilar metals and in damp environment or corrosive atmospheres.

Corrosion is an electrochemical process in which electricity flows through a solution of ions between areas of metal. Deterioration occurs when the current leaves the negatively charged metal or anode and travels through the solution to the positively charged metal or cathode, completing an electrical circuit in much the same manner as a battery cell. The anode and the cathode can be different metals or areas of the same metal. Corrosion occurs when there is a difference in the electrical potential between them.

FOULING occurs when a restriction develops in piping and equipment passageways and results in inefficient water flow. The fouling of boiler room equipment directly impacts energy efficiencies and cost of operations.

FOAMING is a condition in which concentrations of soluble salts, aggravated by grease, suspended solids or organic matter, create frothy bubbles or foam in the steam space of a boiler. When these bubbles collapse it creates a liquid that is carried over into the steam system. Foaming degrades steam quality and in some cases can create a water slug that is discharged into the steam lines.

CAUSTIC EMBRITTLEMENT will occur when there is a high concentration of alkaline salts (a pH value of 11 or greater) that will liberate hydrogen absorbed by the iron in the steel. Caustic embrittlement will be more evident in high temperature areas of the boiler's waterside and manifests itself in the form of hairline cracks.

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Date: 2014.08.27 Category: Technology Comments (0) Trackbacks (0)

McKenzie Corp: Firetube or Watertube? What's the difference?

Boilers come in many different sizes, shapes and designs. This creates quite a challenge for those of us that do not purchase boilers on a regular basis. The choice between a firetube design and a water tube design can become very confusing for novice boiler buyers.

Advantages/Disadvantages

We thought a quick discussion on the advantages and disadvantages of these boiler designs might prove helpful.


FIRETUBE BOILERS

So What is a Firetube Boiler?
FireTube Boiler


The name firetube is very descriptive. The fire, or hot flue gases from the burner, is channeled through tubes that are surrounded by the fluid to be heated. The body of the boiler is the pressure vessel and contains the fluid. In most cases this fluid is water that will be circulated for heating purposes or converted to steam for process use.

Every set of tubes that the flue gas travels through, before it makes a turn, is considered a "pass". So a three-pass boiler will have three sets of tubes with the stack outlet located on the rear of the boiler. A 4-pass will have four sets and the stack outlet at the front.


Firetube Boilers are:

* Relatively inexpensive
* Easy to clean
* Compact in size
* Available in sizes from 600,000 btu/hr to 50,000,000 btu/hr
* Easy to replace tubes
* Well suited for space heating and industrial process applications


Disadvantages of Firetube Boilers include:

* Not suitable for high pressure applications 250 psig and above
* Limitation for high capacity steam generation



WATERTUBE BOILERS

What is a Watertube?
water.jpg


A Watertube design is the exact opposite of a fire tube. Here the water flows through the tubes and are incased in a furnace in which the burner fires into. These tubes are connected to a steam drum and a mud drum. The water is heated and steam is produced in the upper drum. Large steam users are better suited for the Water tube design. The industrial watertube boiler typically produces steam or hot water primarily for industrial process applications, and is used less frequently for heating applications.


Watertube Boilers are:

* Available in sizes that are far greater than the firetube design. Up to several million pounds per hour of steam.
* Able to handle higher pressures up to 5,000 psig
* Recover faster than their firetube cousin
* Have the ability to reach very high temperatures


Disadvantages of the Watertube design include:

* High initial capital cost
* Cleaning is more difficult due to the design
* No commonality between tubes
* Physical size may be an issue

The best gauge of which design to consider can be found in the duty in which the boiler is to perform. Fortunately most boiler sales agencies offer a number of boiler designs and can help you make the correct choice. Ask these professionals what they would recommend and have them explain why.
Date: 2014.08.13 Category: Industry Comments (0) Trackbacks (0)

Mckenzie Corp: Boiler Storage Tips

At some point in time you may wish take your boiler off line and store it for an extended period of time. Be very cautious. Boilers that sit idle will corrode leaving you with a quite a mess when you want to place the boiler back in service.

Here are two ways you can store your boiler.

The first is wet storage, which is generally better for shorter periods of time. In fact, we would recommend wet storage for anybody that needs a boiler for emergency stand-by. A word of caution, make sure the temperatures in your boiler room do not dip below freezing.

For wet storage we recommend the following steps:

• Inspect the boiler and clean it if needed
• Fill the boiler with deaerated feedwater to the normal levels
• Contact your water treatment company for the chemicals needed to condition the water
• An alternative would be using a nitrogen blanket throughout the entire boiler. Make sure the vents are closed and that the nitrogen pressure is greater than atmospheric pressure.

The dry storage method is preferred for boilers that will be out of service for an extended period of time or where the temperatures can go below freezing.

• Again, inspect and clean your boiler
• Drain all the water and make sure that the boiler is completely dried. Remember, any moisture left on boiler surfaces will eventually corrode
• Next make sure that moisture cannot enter the boiler. Close off any steam lines, feed lines and any points of entry for air
• Then place moisture absorbent material, such as quicklime or silica gel inside the boiler. This should be placed on trays inside the boiler. We suggest 2 pounds of quicklime or 5 pounds of silica gel per 30 cubic feet of boiler volume.
• Close up all manways and handholes
• Next place a sign on the boiler so that nobody makes the mistake of firing it without removing the absorbent material. This sign might read as follows:
• Attention - moisture absorbent material has been placed in the water side and furnace of this boiler. This material must be removed before water is placed in the boiler and before the boiler is fired.
• Finally, inspect the boiler every two or three months and replace the absorbent materials with new or regenerated materials.
Since 1946, P. C. McKenzie Company has been actively involved in the Natural Gas Industry, this experience combined with Ingersoll Rand, the leader in natural gas compression for the NGV market, makes us the ideal solution for your NGV station design.

Today, P.C. McKenzie Company is a leading supplier of compressed natural gas (CNG) equipment for vehicle fueling.

The rugged, prepackaged modular compressor systems are available in sizes ranging from 28 scfm up to 116 scfm.
Date: 2014.08.08 Category: Industry Comments (0) Trackbacks (0)

NBW Incorporated Boilers Mechanical Piping Pressure Vessels Burners

Burner Installations

The heart of any heating plant is the fuel burning equipment. Equipment compatibility, efficiency, reliability, and safety all must be considered and a balance maintained.

Burner Assemblies

From complete assemblies to individual components, NBW has years of experience with all major manufacturers. Whatever your heat requirements, we can offer you the most efficient and economical unit.

Our experienced personnel can handle all solid, liquid, gaseous, and waste fuel conditions. We will match the appropriate fuel train or fuel feed system, combustion air equipment, and combustion controls to meet your performance, capacity, and emissions requirements.

Combustion Controls

Boilers and furnaces require safe operation, monitoring, and control of the burner equipment and combustion process. Not only is the initial selection of equipment important, but proper upkeep is essential to maintaining safe and efficient operation.

From the burner flame safety management system to the combustion control system, as well as integrating these systems into a plants monitoring network, NBW can accomplish any goal by coordinating and implementing a plan that meets the customer’s needs and wants.

Low NOx

NBW has been involved in, and completed many Low NOx burner installations since the first regulations were put into practice. Maintaining a stable flame while preventing flame impingement and boiler vibration are vital components to a successful project.

Field Service

On site problem solving, equipment maintenance, and performance analysis are another example of our commitment to providing full service to our customers. Additionally, new pieces of equipment bring new questions from operating personnel. Our technicians will train your personnel and get them oriented and comfortable with the new operation.

Whatever time of the day or year, we have field service technicians on call to get your plant back in operation.Whether you are considering a retrofit of existing equipment, or purchasing new, let NBW help your company make an informed and intelligent decision.
Date: 2014.08.03 Category: Industry Comments (0) Trackbacks (0)