Condensate Return

Over the last couple months, we’ve been focusing on boilers; specifically, we’ve talked about boilers based on fuel options, and we’ve also discussed determining capacity needed.  Today I want to talk about improving your boiler’s efficiency, and one way to do that is to monitor the condensate returned to the boiler with a goal of maintaining a return temperature of around 180 degrees.

Let’s dive into specifics.  One type of energy steam contains is latent energy or latent heat.  According to mobile-dictionary.reverso.net, latent heat is the heat evolved or absorbed by unit mass or unit amount of substance when it changes phase without change of temperature.  In a dry cleaning plant, when steam is supplied to a process, the steam releases latent energy to supply the piece of equipment with the steam it needs to function and then condenses to a liquid condensate.  That condensate still has energy, and if pumped back into the boiler, makes the boiler run more efficiently.  How?  First, less new make-up water is required, which helps keep water costs down.  Second, that water is already hot, so less energy is required to heat the water.  Third, most of the corrosive dissolved Oxygen has been removed from the water, reducing system corrosion.

Do these three things to make sure your plant is set up properly:

• Always T upwards off of the supply and return header to the equipment connections
• Always put a check valve after every steam trap
• Confirm that all steam traps are in good working condition

This last point is exceptionally important as equipment will not work properly without steam supply and as a result, it’s constantly blowing steam by heating the condensate return system above the 180 degree target temperature.  Then the pump can’t pump water into the boiler at over around 200 degrees so it takes longer to fill the boiler which equals more cost to run the pump longer. Also, remember that increased return water temperature equals malfunctioning steam traps that allow steam to blow through the trap and heat the return water.  This can result in more than 14% flash steam loss.  It’s basically like you’re putting a brick on the steam pedal of a puff iron, and its blowing steam all the time the boiler is up to pressure.  Double utility cost hit when the steam is blowing by heating the return water which causes the pump to run longer using more electricity and the boiler to cycle more often because the pressure is being lost through the malfunctioning steam trap. All this can be detected by checking the return tank water temperature, if you are regularly running over 185 degrees.

What Size Boiler Do I Need?

Last month we discussed the different fuel source options for commercial boilers, showing the cost savings and other benefits of choosing natural gas or propane over other options.  Obviously based on last month’s post, Tri-State Laundry Equipment prefers natural gas boilers, and we want to continue the boiler conversation focusing on what size natural gas boiler best fits your business.  To determine this, we’re going to talk in terms of BHP (boiler horsepower), which is a boiler’s capacity to produce steam.  One BHP is the amount of energy required to produce 34.5 pounds of steam per hour at pressure and temperature of 0 psig and 212 degrees Fahrenheit.

When I try to determine boiler need, I use two sources: first, a spec sheet from Unipress that provides finishing equipment technical specifications (all pieces of dry cleaning and laundry equipment have a BHP number), and second, years of experience.  For instance, I know that a dry cleaning utility press is rated at 1 BHP as is a dry cleaning legger or any other dry cleaning press that uses steam to heat and steam emitted for finishing.  Pants toppers with a form and emit steam to condition are rated at ¾ BHP, where form finishers which are any bag form that finishes dresses and tops and blows air and steam are rated at 2 BHP.  I tend to rate puff irons at ¼ BHP regardless of whether they are single or triples because they don’t emit steam all the time, and they consume a very small amount when at rest.

We all have our own unique set of talents, and mine is knowing all these numbers off the top of my head.  But for the remainder of the population, pressing equipment manufacturers provide a BHP number for all their laundry, shirt laundry, and dry cleaning pressing equipment as well as for dry cleaning machines and washers and dryers.  Sometimes a little digging might be required, but this is an important number to know when outfitting a new plant or when purchasing a single piece of equipment simply for an upgrade.  Once you have all your BHP numbers, figure in about 5% for header heat loss but be careful not to oversize unless the customer demands it.  And when it’s time to replace your boiler, don’t simply replace it with your current size.  Instead, run through this exercise to see if a larger size is necessary.

Determining your required boiler size can feel a bit complicated and overwhelming, but an experienced boiler system sales and design person can come up with a really close calculation.  And of course, Tri-State Laundry Equipment is always here to help whether is it’s dry cleaning or laundry boilers or dry cleaning or laundry equipment.

Choosing the Right Boiler Based on Fuel Type

While there are a number of fuel options for boilers, with some of them being quite unusual or messy (think biomass or coal), we’re going to focus on three for several practical reasons.  First, the last thing you want is an employee shoveling pulverized coal into your boiler and then heading over to press white shirts.  Second, it can be difficult to round up burnable plant material and debris from wood construction.  You get the idea.  For our purposes, let’s talk about the following three:

• Gas Fired – Gas fired boilers burn Natural Gas.  Natural Gas is chiefly Methane, but when it is removed from the ground, it may also contain Butane, Ethane, Pentane, and Propane.  These other products are stripped out before the Natural Gas is sent down the pipeline.  Natural Gas is one of the most efficient fuels to use for boiler operations because it is relatively inexpensive, energy efficient, dependable, and environmentally friendly.  While Propane is used in similar ways, it is quite different from Methane.  For instance, a smaller amount of Propane is required to produce the same amount of heat.  The good news is that it is easy to compare costs because both are done based on BTU ratings.  To learn more on how to compare costs, click here.  There is a down side to installing gas – the initial investment can be rather costly depending on your current set up.  We suggest bringing in a qualified technician to provide an accurate estimate of what is involved so that you can take the initial cost into consideration. 
• Oil Fired – Oil fired boilers are particularly popular for homes and businesses that are not connected to gas mains.  There are several downsides to going with oil.  For instance, the cost of oil can vary greatly.  You need to have an oil tank onsite or nearby and have oil delivered.  Finally, oil fired boilers require more maintenance and attention because of dirt and soot buildup.
• Electric – Compared to gas or oil boilers, electric boilers are more efficient because there’s no need for an exhaust flue for waste; therefore, no heat escapes from the system.  They also tend to take up less room than other boilers and can be more cost effective to install.   Plus on top of all of that, they are quiet.  On the downside, electricity is more expensive in most parts of the United States. 

Let’s do some cost comparing.  Our benchmark is Natural Gas which will give us 1,075,000 BTU’s per 1,000 cubic feet at a cost of approximately $3.87.  Propane will give us 91,000 BTU’s per gallon at approximately $.86 per gallon, which calculates to 11.8 gallons of Propane for a cost of $10.14.  Oil is our next fuel choice at 138,500 BTU’s per gallon priced currently at $1.59 per gallon, which translates to 7.8 gallons of fuel oil at a cost of $12.40.  Our last option of electricity requires 1-KW to produce 3,413 BTU’s at an average cost of $.1031 per KW and that translates to $37.80.

Summary:

To create the same quantity of steam, it costs

Natural Gas    $3.87

Propane    $10.14

Oil        $12.40

Electricity    $37.80

When you take a look at all the factors, not only is there a big difference when it comes to costs, keep in mind that Natural Gas is clean burning, and oil requires burner adjustments and maintenance to keep it in proper tune.  While there are some positives to electricity, the high cost makes it impractical.  Even though everyone doesn’t have access to Natural Gas, it would be beneficial to find a location that has it or petition your local gas company to expand into your area. 

If you need help choosing a boiler, feel free to contact Tri-State Laundry Equipment Company.  We are always glad to help.