4 replies to this topic

[HadeerK]

Hi everyone,

  I am doing a project on production of syngas from rice husk gasification. the gasifier design has been done. now i have to design a heat exchanger to lower the temperature of syngas to 55 C. 

 

I previously simulated a shell and tube heatx on aspen. The syngas enters the exchanger at 800 C and leaves at 55 C. the cooling fluid is water (in shell side) entering at 25 C and leaving at 100C with 0.46 Vapor fraction. The exchanger has 51 tubes in three passes with an area of 4.6 sqm. 

 

I want to know if the said shell and tube heatx is feasible? or should i consider using 2 or 3 exchangers in series. Or should i use Kettle Reboiler to cool down syngas? 

 

I couldn't find any informative source to help me learn Kettle Reboiler design using aspen plus software.

 

Thanks

[Pilesar]

I will assume you a student doing this project for a class. If that is correct, you should post in the Student section so others can better understand your knowledge level. The process you describe is not very energy efficient for a commercial-scale plant. You will want to use more than one exchanger for cooling the syngas. Think of your process effluent as a resource you can use to provide heat to other streams. Are there process streams you have to heat up? Perhaps feeds to the gasifier? Consider using those feed streams to help cool the gasifier effluent. Does the plant use higher pressure steam? Then pump the water to a higher pressure and use the hot effluent to generate higher pressure steam and then to superheat it! Order your exchangers so that you can use the effluent at the highest temperature you can. By using 800 C effluent to heat water to 100 C, you are giving away much temperature driving force that could probably be used for better purposes. Cold streams are streams you need to heat up. In general, you want the hottest cold stream matched to the hottest hot stream. Figure out which hot and cold streams can best be matched together before you even try to design the heat exchangers. If your flow rates are large, you can justify spending capital to save energy.

[Pilesar]

I just paid attention to the exchanger area you sized. This is a dinky exchanger (50 ft2). I think it might be helpful if you supplied more details about your project such as gasifier flow rate and how you plan to use this steam/water mix.

[HadeerK]

I just paid attention to the exchanger area you sized. This is a dinky exchanger (50 ft2). I think it might be helpful if you supplied more details about your project such as gasifier flow rate and how you plan to use this steam/water mix.

syngas is leaving gasifier at 46 kg/hr. temperature is 800C.. water flow rate in exchanger is set to 179kg/hr at 25C

[Bobby Strain]

You really should use a quench cooler for this laboratory size process.

 

Bobby