Do you think this Waste-To-Energy plant will work?

[chris767336]

Some people say it's ambitious, some people say its crazy and some people say it just won't work. What do you think?

[JAlberts]

Your thread on the Physics Forum was closed before I had a chance to respond and I am sorry that your exchange posts took a turn that was of no real benefit to you, so here is my feedback on your proposed system; and, I am willing to discuss its elements at more length if you so desire as well.
From my view, it is not a matter of "will it work", it is more a matter of "is this an efficient or more efficient way of converting the energy of waste gas and matter to an output form of energy i.e. electricity".
Viewing your diagram, basically each element will work but with a limited degree of performance and one main feature, water to steam to water circulation cycle is of no benefit. If the water tank and fired tube are viewed as a closed system, the water in the tank will circulate through the tube and be heated to steam as you propose due to the fact that the water column in the tank is denser than the steam in the heating tube; however, because keeping the output steam turbine running requires a constant outflow of steam from the system and therefore a constant inflow of water into the system, the water stored in the tank serves no real purpose. It is more efficient to simply feed the incoming water through a preheating section (as you have done) and then directly into the fire box tube and then directly to the steam turbine.
As discussed in the other thread, it is the steam pressure that provides the flow that drives the steam turbine and converting the energy from the waste burning to steam is simply a method of converting that energy to a form of energy (steam) that can used to turn the turbine and the higher the combined heat and pressure energy in the steam the more energy there is to drive the turbine.
Using the feed water system you show without a water supply pump means that the maximum amount of pressure you can maintain in your tank is only equal to the water head in the short feed tube you show in blue in the left upper corner of the diagram because if the pressure in the tank exceeds the weight of that short column then the tank pressure simply push the water back into the box; and 2 psi of pressure no matter how hot the gas (steam) from a 4 ft water column is simply not going turn a steam turbine.
Apart from those issues, yes, each the mechanical elements shown in your diagram will function, but taken as a complete system the unit there is no breakthrough element in the design that will allow it to generate an energy output (electricity) at any better efficiency than the direct water to steam to turbine systems now in operation using waste gas and matter as a boiler feedstock.

[chris767336]

JAlberts,

Thank you for your response,

My initial design was as you suggest: "It is more efficient to simply feedthe incoming water through a preheating section (as you have done) and thendirectly into the fire box tube and then directly to the steam turbine."However I changed it in the belief that this system would operate moreefficiently. I should put a pump and check valve before feed into thewater boiler/heater and also after the water turbine at the base of waterboiler/heater before piping it into the incineration chamber. This will preventany back flow. There would obviously be much more pressure in theincineration piping then that at the top of the waterboiler/heater. The water being feed into the incineration chamber is already at~100 C from the base of the water boiler/heater, which makes this plant quiteefficient I would say.

More input is needed to progress further with this diagram. I believe moreefficiency can be gained with the reburning of flue gas and with lookingat the condensate of the steam turbine.

What makes this Waste-To-Energy plant far more efficient and financiallylucrative is that the city will pay the plant to take all of its waste(municipal, industrial, sewage) and the plant will sell back electricity, waterand gas. The plant also produces its own fuels.


I have about 5 or 6 different methods of incineration.

[chris767336]

Apologies for the grammar and word linkages from the previous post. Posting from word into the forum isn’t very compatible.

So just to provide greater clarity. There will be numerous water piping tubes running through the incineration chamber from the water heater/boiler. The pressure in these water pipes/tubes being feed into the head of the water boiler/heater will be 2 to 3 times greater than the pressure accumulating at the head of the water heater/boiler from the multiple heating sources, that being the flue gas emissions, gas turbine exhaust and the bootstrap.

[JAlberts]

The key to an efficient delivery of the energy available from the waste (all sources) is primarily dependent upon effective incineration and then minimizing the loses that will occur as this energy is transferred from that source through its various stages until it is delivered to the gas turbine. In that respect, I agree that all attempts to recover the flu gas and turbine exhaust heat and recycle it back into the system are critical to the efficient operation of the system.

One question I have is, what you are trying to achieve by heating the steam to the superheated condition if you are then only going to cool it and reduce the pressure feed to run the gas turbine? One of two things is going to occur over a sustained operating period, either you are going to keep raising the temperature of the water tank (which, no matter how well insulated is going to be a point of heat (btu's) loss and therefore a drain on your system efficiency) until it reaches the equilibrium of the boiler output temperature or you are going to have to reduce the steam flow through the heating tubes to the point that the gas turbine can carry the excess heat (as input energy to the turbine) to prevent the overheating of the water.
Keep in mind my above statement, the key to maximum efficiency is to get every btu of energy from the waste sources to the gas turbine with the least loss between those two points. Anything that is not included in your system that is not specifically targeted to that goal is really of no importance.
Just as a note, with regard to your bootstrap loop, I fully understand its system start up function; but, once the system is running then running that unit is a detriment to the total efficiency of the system because the system's efficiency = all output obtained at the gas turbine - any energy, other than that of the waste, input (i.e. any outside source of energy required to run the bootstrap turbine, fuel or power, reduces the total efficiency of the system).
I do understand that a certain minimum incineration temperature is required to effectively sterilize the flue discharge waste products; however, there is point at which excessive temperature itself can result in undesired combustion products such as nitrous oxides so there is a balancing point that can limit the degree of steam superheat you can attain.

Ultimately the best route to attaining your goal is to focus on the simplest method of efficiently burning the waste (which you understand), delivering those btu's to the gas turbine with the minimum heat (btu's) loss and then focusing on the best method(s) of returning to your heating system all of the turbine steam and flu gas exhaust heat possible (which is another point you fully understand).

[chris767336]

"One question I have is, what you are trying to achieve by heating the steam to the superheated condition if you are then only going to cool it and reduce the pressure feed to run the gas turbine?"

Fair point. The reasoning behind adding the superheated conditioned vapour to the head of the boiler before it runs through the steam turbine, is to significantly boost the steam pressure to the volume that will optimize the steam turbine performance and efficiency. This water boiler/heater isn't little, it is huge.

"Just as a note, with regard to your bootstrap loop, I fully understand its system start up function; but, once the system is running then running thatunit is a detriment to the total efficiency of the system"

The bootstrap on start-up will require assistance from the independent GasTurbine Engine. So in the bootstrap, air is heated by passing through the incineration chamber before passing through a compressor, then the air is cooled in the water boiler/heater before passing through a turbine, to then repeat the process in perpetuity. The compressor and turbine are on the same spool which in essence is a naturally thermodynamically perpetuating system.This compressor and turbine spool is assist and governed by a transfer drive from the Gas Turbine Engine. On start-up it will require some assistance from the Gas Turbine Engine, but once in full operation, little assistance and more governance is required as the system is mostly being run on the thermodynamic temperature differential. So the Gas Turbine Engine in the diagram is integral to the efficiency of the entire incineration plant as it:

- Assists and governs the bootstrap with little efficiency loss.
- Provides a significant boost to additional plant electricity generation.
- Provides significant water heating to the water boiler for further steam production from its exhaust heat.

The Gas Turbine Engine is an independent powerplant that is integrated into the overall design. I would like to run this Gas Turbine Engine on kerosene from the waste plastics collected at the plant.

"I do understand that a certain minimum incineration temperature is required to effectively sterilize the flue discharge waste products; however,there is point at which excessive temperature itself can result in undesired combustion products such as nitrous oxides so there is a balancing point that can limit the degree of steam superheat you can attain."

Yes much more work and detail is needed, however I believe it is possible and practical to achieve.

[JAlberts]

"Engine, but once in full operation, little assistance and more governance is required as the system is mostly being run on the thermodynamic temperature differential."

The booster loop can circulate similar to the major boiler operation to add heat to the tank (in that respect it simply and small short additional heating coil through the boiler) but I am doubtful it can provide significant additional power generation because a pressure differential is required to turn the turbine and I doubt that the small loop will be able to deliver much driving power to the turbine(s) based on the fact that it really simply a heat convection circulation loop.

[chris767336]

The bootstrap is naturally self-perpetuating from the significant thermodynamic temperature differential. The bootstrap itself wouldn't necessarily provide additional power generation, however it is a highly efficient method to heat a large volume of water. Such bootstraps are proven systems. Using a bootstrap that is assisted and governed by a Gas Turbine Engine makes this design extremely efficient.

[JAlberts]

As far as it being a good method of tank heating, I am in full agreement. It was the power generation part that I had a problem with.

[chris767336]

There will be some teething problems as with any engineering feat.

I will be on the next flight out of Sydney if John Cornyn and Ted Cruz are willing to move forward with such an initiative and the funding can be secured.

[chris767336]

This is better again.