EQUIPMENT FROM EXHAUST FUMES

Description:

The purpose of the invention is to improve the heat recovery from heating appliances and internal combustion engines, and at the same time clean the exhaust fumes. Both functions are achieved by using a single wet scrubber and the only heat recovery of the exhaust fume energy is done by the washing liquid.

1- The existing technology

For industrial applications solutions have been found for a long time to clean and sometimes recover the latent heat of fumes from condensation. But as most industrial processes require heat at a higher temperature then 100°C, a single wet scrubber can't be used. Most of the time a simple solution is to use a tube heat exchanger and then a wet scrubber or an electrostatic filter.

The main example is the production of electricity by burning any carbon compound, which most of the time requires steam at above 200°C. Another important application is steam networks for heating purposes but it requires heat at above 100°C. The US patent 4,359,006 is an example of an industrial process using a wet scrubber as heat recovery, but the exhaust gas is first cooled by air injection and then the energy is used to dry waste before entering the washing tower. The Chinese patent 101445852 describes a wet dedusting system, but the gas is first cooled before entering the wet scrubber. For the industry simpler solutions haven't been found because usually the

temperatures required do not allow it.

For further explanation we should clarify the system efficiency. Usually in North America efficiency is expressed in Higher Heating Value, HHV, and so the maximum is 100% and that's what will be used later on. To understand it well, it should be compared to some values which are used in Europe, Lower Heating Value, LHV, where the maximum is around 110%. That strange value comes from the fact that latent heat from the water condensation was considered

unrecoverable and so there is the difference.

For domestic applications there are numerous suppliers but none of them offer a direct contact gas to liquid in a single stage heat recovery. The well known Dedietrich manufacturer supplies some condensation energy recovery systems but they are for second stage recovery and without direct contact gas to liquid. Suppliers such as Dedietrich produce some gas boilers with an efficiency around 93% HHV at maximum power when the water inlet is at 30°C. Because of the easy heat transfer with the direct contact gas to liquid, the invention allows an efficiency around 98% HHV in the same conditions.

Most of fuel oil boilers for domestic use have an efficiency around 92% HHV at maximum power when the water inlet is at 30°C. The invention allows an efficiency around 97% HHV in the same conditions and clean the smoke.

Famous wood boilers such as Eta or Hargassner have an efficiency around 84% HHV. The invention allows an efficiency around 96% HHV and captures around 99% of smoke particles. The invention requires one heat exchanger and one water circuit more than the standard design but regarding the complexity of the usual automatic heat exchanger scraping, it's nothing. Standard wood stoves have an efficiency around 70% HHV, with the new technique it will be around 95% HHV.

Globally the invention is much simpler than most of the industrial installations but can't be used in most of those cases. For domestic purposes the solution is more complicated than most of the existing systems but allows a better efficiency and the possibility to clean the gases at the same time.

2- Figure 1

The figure 1 just gives an idea of what a domestic wood heating appliance may look like. Most of the time it will be technically a mixture between figure 2 and figure 3.

3- Figure 2

This is the simplest arrangement for the invention. The fresh air 15 goes to the combustion area1. The hot gas 2 reaches the washing tower 3, where it's cooled and cleaned, and then escapes through the chimney 4. The liquid which has been heated into the wet scrubber 3 gets cooled in the radiator 12 (the radiator can be fitted with a fan to increase the liquid cooling effect and so increase the system efficiency) and then the pump 13 pushes the liquid back to the scrubber for a new cycle. In this example some liquid is stored at the scrubber bottom and in 14 we get an overflow and a sludge drainage valve. The overflow allows the excess liquid coming from the gas condensation to escape the system. By opening the drainage valve from time to time the sludge is sent to the sewage system. The overflow and drainage can end up in a removable tank, to be emptied daily for example if the surrounding doesn't offer another choice.

The production of sludge can be important if it's a wood heater, in case of charcoal, diesel or oil it will be less and nearly nonexistent in the case of a gas burner, so the drainage timing can be different. The excess liquid produced by the steam condensation can also be used to flush the ash if the combustion produces some, and so facilitating the maintenance by preventing dust.

4- Figure 3

Most of the wood log boilers will work on a similar principle. All the other boilers with an automatic fuel feed do not need the bypass valve 6. The fresh air j_5 goes to the combustion area1. The hot gas 2 reaches the washing tower 3, where it's cooled and cleaned, and then escapes through the chimney 4. If the pressure lost in the scrubber is too much for the existing chimney, a fan 5 can be installed to compensate. If the system is a stove and if an electricity shutdown happens, it would be useful to have a bypass valve 6 to preserved an emergency heating system.

The liquid which has been heated in the wet scrubber 3 arrives at the tank 16, then the pump 13 pushes it to the heat exchanger JJ. (usage can be for hot tap water, sorption cooler, sorption freezer and heating network) and then cooled again in the heat exchanger 10 (usage can be for lower temperature heating network, underfloor heating network or hot air blower) finally the liquid arrives back at the scrubber for a new cycle.

5- Figure 4

In the case of an internal combustion engine it's possible to get a co-generation, three- generation or quadri-generation system. Because it's possible to produce mechanical force or electricity, heat, cold and drinking water by distillation. The fresh air 1_5 goes to the combustion engine 1. The hot gas 2 (at that point as on a heater or a boiler, some urea can be injected to reduce the NOx concentration) reaches the washing tower 3, where it's cooled and cleaned, and then escapes through the exhaust pipe 4.

The liquid which has been heated in the wet scrubber 3 gets cooled in the heat exchanger 10 (heat exchanger 10 can be on the same line as the heat exchanger JJ_ but if the need of product supplied by the heat exchanger JJ_ is more important, then having 2 lines will be more efficient), then the liquid goes back to the scrubber. The heat delivered by the heat exchanger JJ. can for example be first used for a sorption cooler or freezer, then to a water distillation system. Before going back to the wet scrubber 3 the liquid may have been in contact with some limestone or some chemicals may have been injected to reduce the amount of sulfuric compound of the exhaust fumes. The same system as in this paragraph can be used on a boiler.

The engine cooling liquid can be used as a simple heater with the radiator 12, or can be used for water distillation as on some ships, or for multiple tasks as the heat exchanger JJ_.

Presently lots of electricity worldwide is produced by the combustion of gas or oil and in most cases the whole heat or the main part of it is wasted. At the same time personal heating appliances burn some fuel without producing any electricity One solution to improve this fact will be to have a co-generation or three-generation engine with around lto 5kW electricity power and 4 to 20kW heat power for personal supply. A mass production can make it not too expensive and the invention can make it thermally efficient and clean. The same application for an office or residential building will just be more powerful.

6- Conclusion

Lots of applications can be improved with the invention and some others developed. The few figures and explanations just show some technical arrangements and lots of solutions are possible.