Advantages of installing Economizer in Boilers

Every 6C rise in your Boiler feed water temperature there is a 1% decrease in fuel.

Your 7 Tph steam generation by the boiler is rated only at 100C feed water temperature. An Economizer will save between 3.5% to 5% gas/fuel and minimize thermal shocks inside the boiler increasing boiler life.

the data collected from site shows that feed water temperature is 60C where as you have mentioned 100C.plese specify thanks

So your boiler is generating 6.5 Tph at 60 C feed water + damage to tubes and Increased gas bill by over 6.5% Please try to increase feed water temperature by returning maximum condensate. How old is your boiler? The effeciency you gave is not boiler efficiency but combustion efficiency .What is your process: Textiles/Tannery etc? Are you in Pakistan? then communicate at my email duconems@yahoo.com.

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4) Quantity of steam generator per hour 570kg/hour.

So your boiler efficiency is between 67% to 70% thats because of radiation losses and operating at 7 bar instead design 10 bar.

thnks for your detail explanations.we are carrying out electrical energy audit for automobile industry in pakistan.the boiler is 10years old.will it be possible to pass on the details how you have calculated the boiler efficiency thnks

Is it with Mr.Sajid Lakhan of SMEDA?

No. As per our contract with the automobile industry we are not suppose to disclose the name of the industry to any one without thier prior permision I will try my best to get the permision from them. In case i am not successful please do not mind. Still waiting for the answer regarding my Question how you have calculated boiler efficiency.

Mr.Salahuddin Zia - After having gone through all your threads it seems that you are out there on Energy Audits (particularly electricity) and it seems that you have little experience in this"Energyv Audit" field and practically none in the boiler/steam field. You are out requesting electricial data / reports from members on hatchery/gum/etc., and very recently you started a couple of inter-related energy efficiency threads. Basically you are getting your homework done from us.

Who are you? What is the name of your Company?

I will appreciate you being really honest in your reply before anyone of us proceed further.

If you do not wish to disclose the name of your Company then it will not be difficult to find out too.

With a properly installed economizer, you will save fuel.

You must ensure that your boiler feed pump is sized to take tha additional pressure drop of the ecomonizer and, be forewarned that you may have to include additional support steel for the unit..

As long as you are burning natural gas, you probably wont have problems with corrosion on the economizer surfaces.

If you install a bypass on the feedwater piping around the new economizer, be sure that a properly sized relief valve is installed on the bypass piping.

Please let us know what your final decision is......

thanks for your suggestions.we are carrying out electrical energy audit of automobile industry.will add your suggestions in our final recommendations .

Dear salahuddin zia

You have mentioned several datii (plural of data) ,

1) Design capacity 7 Tonnes/hr at 169 C, working at 3-4 Tonnes/hr at 169 C.

2) Quantity of Gas used per hour 825K Cal. 3) Gross colorific value of gas 901 K Cal

4) Quantity of steam generator per hour 570kg/hour 5) Temperature of feed water 60 C

6) Design pressure 10kg/cm2(square) working at 7kg/cm2(square) 7) Boiler combustion efficiency 85%

But you have not mentioned about the following. Pl. indicate the following.

1. Chimney. Is it steel chimney or RCC chimney and height of the chimney.?

2. Draught of ID and FD Fans, to know whether margin for the pressure drop across the economizer is available.?

3. Blow-down quantity in terms of percentage, and TDS of Feed Water and blow-down water maintained.?

4. Whether the heat from the Blow-down water is recovered.?

5. What is the NPSH available.?

6. Fuel analysis indicating H2 and O2 in the fuel since will determine the DEW POINT Temp., leading to the condensation and corrode the chimney if the chimney is made of MS.?

7. Feed water pump pressure – to verify whether (in the present pump) the margin is available for the pressure drop in the economizer. ?

8. In your point no. 2 the figure 825 should be Kilograms. Not 825 K Cal. Pl. confirm.

Several CR4 Members have posted/replied in a very good manner. Now my views/suggestions are as follows.

1. Take steps to increase the feed water temp, from 60 Deg.C to comfortably to 110 to 120 Deg. C (or even 130 deg. C which will have a margin of 40 Deg.C with respect to the Saturation Temp. at 7 Kg/cm^2) before entering the steam drum. This can be done by 2 steps, a) Install a small heat exchanger recover the heat from the outgoing blow-down water by the boiler water before pumping by feed water pump, this calls for adequate NPSH, then by the new economizer to be installed to recover the heat from the flue gas. b) Instal an economizer

2. This economizer should be necessarily after the air pre-heater (if already exist) other wise the exit air temp. leaving the air pre-heater will be less and furnace temp. will be less and this is vicious circle.

3. If the economizer to be installed the draught of the ID fan should be suitably high amd may call for replacement with higher draught fan.

4. The condensate recovery should be maximum and used.

5. However it is worth to install an economizer in your case, since to form the steam it requires about 100 Kcal. of additional heat per Kg. of steam source being the fuel at the cost of more fuel cost.

DHAYANANDHAN.S