Dear all,
I would like to know whether you know any standard or commonly used control solution for the following problem:
I have a quench tower where several kind of flue gases enter. Before leaving the system through the flare I would like to cool it down as much as possible with condensate water (in the quench tower).
I open the flow control valve and the flue gas is cooled and then released at the flare. Now the problem is that I don't know what type of gas is leaving, but I know that after a given control valve output the flue gas temperature is not decreasing anymore. It doesn't matter whether the valve is totally open or it stays just at the output (command) where the gas is not cooling down anymore. Of course, the more I open the valve, the higher condensate flow I obtain. I would like to control the system in that way that I do not waste condensate water anymore. I was thinking about a solution where I monitor the input/output ratio and at a given point I start to track the PID but this seems such a mother wit solution to me.Thank you for your ideas!I've also attached a picture for more understanding:http://kepfeltoltes.hu/141031/1366844895Untitled_www.kepfeltoltes.hu_.png
Best Regards,
Rachelle McWright: Business Development Manager, Dynamic Simulation: U.S. Gulf Coast
In reply to BC Spear:
Hi,
you could program a similar block like is used with solarpanels MPPT. The function ames to find the highest power point in a system. You could modify it so that it tracks where the gas doesn´t cool down any more.
You could use the output of this block as a setpoint for the PID controller..
Niklas Flykt
Klinkmann Oy
Key Account Manager safety products
nikfly@gmail.com
In reply to Niklas Flykt:
HI,
if you really want to save water, you should get the temperature of the flue gas below the dew point of the water.
When the water changes phase it will "suck" much more energy from the gas heat energy and you will get the water back to the process insted of "burning" it up.
you could impliment a heat recovery system after the "washer" to get the temperature down and get free energy [Y]
In reply to Rachelle McWright:
What kind of insights would be nice? Been looking for some good information but I have only found articles in Finnish..
Here in the picture you can see the amount of energy that is theoretically possible to harvest in the scrubber/heat recovery system.
You can see if you decrease the temperature to the dew point (savukaasun kastepiste) at the heat exchanger area you can recover a lot more energy than just cooling the flue gas down.
Savukaasun jäähtyminen = cooling of the flue gas
Savukaasun lauhtuminen= condesing of the flue gas
y-sclae is the flue gas recovered power
x-scale is temperature of flue gas
Hake= wood chips
Turve=Peat
The problem has been the district heating system temperature requirements.
In Finland we have e.g. one solution we install a Heat pump in the return line from the district heating.
The system cools down the temperature of the return line before entering the heat exchangers in the scrubber as much as 20 ´C, that will ensure that the temperature at the heat exchangers are below the dew point of the water vapor.
The heat pump returns the heat to line after the scrubber so nothing is wasted.
pesuri=scrubber, savukaasu= fluegas, LTO(lämpöpumppu) =heat recovery (heat pump), KL meno/paluu = district heating feed/return
What I have read in these articles you can get up ~ 30% more energy of a biomass plant compared to only using a scrubber.
They say the payback time for the installed system is around ~2,5-3 years? Might be just sell guys talking, but it will sure increase efficiency, save water and the environment.