WO2010036201A1

WO2010036201A1 - Toilet system

Info

Publication number: WO2010036201A1
Application number: PCT/SE2009/051081
Authority: WO
Inventors: Lars Ehnhage; Ingemar Fernkvist
Original assignee: COMBUTECH HOLDING AB
Current assignee: COMBUTECH HOLDING AB
Priority date: 2008-09-29
Filing date: 2009-09-29
Publication date: 2010-04-01
Anticipated expiration: 2011-03-29
Also published as: SE0802047L; SE532433C2; EP2328448A1

Abstract

A toilet system is provided comprising a combustion chamber with an electric combustion device comprising an electric heating coil (30). The toilet system is characterized in that the electric heating coil has the shape of a cone. By providing a cone-shaped heating coil, a turbulent air flow is created, which penetrates the electric heating coil along its entire length. No part of the electric heating coil will be in the “shadow” of the air flow and the heat transfer efficiency will be high.

Description

TOILET SYSTEM

FIELD OF INVENTION The present invention relates to a toilet system in which incineration of collected urine and faeces takes place in a separate combustion chamber by means of an electric heating coil.

BACKGROUND In the market there are today a number of different types of toilets without connection to the public sewage-system, and which have different solutions of collecting devices for urine and faeces. Many of these toilets have proved to be constructed in a most complicated way and are also expensive with a high operating cost. It has also proved to be complicated to carry out a simple and odour-free discharging of the contents when needed and in those cases that the toilet is of a kind where incineration of the faeces takes place it has been difficult to accomplish an efficient and economical incineration.

According to EP 1 748 715 there is a known toilet system, wherein urine and faeces are incinerated in a combustion chamber provided with a burner head. The toilet system is adapted for combustion using Liquefied petroleum gas (LPG) or the like.

The US patent No. 4,425,571 discloses a toilet system comprising a combustion chamber with an electric combustion device comprising an electric heating coil. SUMMARY OF THE INVENTION

An object of the present invention is to at least partly eliminate these problems in prior art and to provide a toilet system with improved electric combustion.

According to the invention there is provided a toilet system comprising a combustion chamber with an electric combustion device comprising an electric heating coil, which is characterized in that the electric heating coil has the shape of a cone.

By providing a cone-shaped heating coil, a turbulent air flow is created, which penetrates the electric heating coil along its entire length. No part of the electric heating coil will be in the "shadow" of the air flow and the heat transfer efficiency will be high.

In a preferred embodiment, the toilet system comprises a fan adapted to create an air flow, preferably downward into the combustion chamber, which transfers heat energy from the electric heating coil to the combustion chamber.

In a preferred embodiment, a the heat exchanger is adapted to heat the air flow before reaching the electric heating coil, whereby the efficiency of the toilet system is improved.

Further preferred embodiments are defined in the dependent claims.

BRIEF DESCRIPTION OF DRAWINGS

The invention is now described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a schematic overall view of a toilet system according to the invention,

Fig. 2 shows a view from above of the combustion chamber with an electric combustion device in accordance with a preferred embodiment of the present invention,

Fig. 3 shows a side view of the combustion chamber in section in the prior art toilet system of EP 1 748 715 and which can also be applied in the present invention and from which view is seen how the bottom of the combustion chamber is designed,

Fig. 4 shows a part view of the bottom of the combustion chamber in the prior art toilet system of EP

1 748 715 and which can also be applied in the present invention,

Fig. 5 shows a side view partly in section of the combustion chamber illustrated in 3,

Fig. 6 shows an end view of the combustion chamber illustrated in Figs. 3-5,

Fig. 7 is a detailed view of a cone-shaped electric heating coil adapted to provided in the combustion chamber of a toilet system according to the invention,

Figs. 8-12 show the combustion chamber and the heat exchanger of the toilet system according to the invention,

Fig. 13 exemplifies process control of combustion used with the toilet system according to the invention. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

In the following, a detailed description of a preferred embodiment of a toilet system according to the invention will be given.

In this description, the term "cone" is to be construed as any conical shape, including frusto-conical shape and a shape with diverging sides, whether having circular, square or other cross-sectional shape.

As shown in fig. 1 here is presented an embodiment of a toilet system according to the present invention, which comprises three main parts, namely a toilet unit 2, a holding tank 6 and combustion chamber 8 with economizer. The toilet unit 2 is equipped with a device 3 for macerating and transportation of the waste together with the flush water so called blackwater 4 in a first pipe 5 to the holding tank 6, which is directly or indirectly connected via a transportation tank, not illustrated on the drawings, to the combustion chamber 8 with the economizer via a second pipe 7.

The device 3 for macerating the faeces and transportation of the blackwater 4 through the first pipe 5 to the holding tank 6 comprises a pump 9 with a mace- rator known per se and/or with vacuum and the second pipe 7 is provided in this example with a dosage pump 10 for transportation of the blackwater 4 into the combustion chamber 8, from which flue gases are output via its specially designed bottom 11 through an outlet pipe 14 to the atmosphere. The combustion chamber 8 provided in a toilet system according to the invention is designed to ensure complete incineration of all solids, including faeces in said blackwater 4, that is dosed by the dosage pump 10 into the combustion chamber 8 from the holding tank 6 located up-stream in the system. With its unique bottom design incineration is achieved with high efficiency and thereby low fuel consumption. Also the size and weight of the combustion chamber 8 has been able to be limited thanks to the efficient utilization of the excess energy in the flue gases. The bottom design of the combustion chamber 8, see Figs. 2-6, consists in that its bottom 11 includes a wave-profile 12, where flue gases can pass below the entire combustion chamber bottom 11 in wave peaks 13, which are sealed downwards in order to constitute a number of parallel alongside running flue gas channels 12', through which the flue gases from the incineration pass and thereafter are guided out to the atmosphere through the outlet pipe 14. The flue gas channels 12' extend in the flow direction of the incineration gases at the same time as the excess of heat from the flue gases is brought back to the blackwater 4 located in wave troughs 13' , thereby a larger bottom surface is obtained in the combustion chamber 8 than otherwise, which in turn gives a higher efficiency. By the bottom design of the bottom 11 of the combustion chamber 8 the wave troughs 13' constituted by the wave-profiles 12 consist of a number of next to each other and all across the bottom extending V-formations for receiving the blackwater 4. By this design the excess heat in the flue gases are brought back to the blackwater 4, which is located in the wave troughs 13' at a flange- efficiency of 100 %. In order to secure that the heat transfer is performed in a uniform way all across the combustion chamber bottom 11, a flue gas shield 16, see Fig. 5, is mounted at the end of the flue gas channels 12' . This causes a narrowing at the centre of the bottom profile in order to force the flue gases to spread evenly over the entire cross section and in this way cold spots are avoided and the entire bottom surface is used efficiently.

An electric combustion device comprising an electric heating coil 30 in accordance with an embodiment of the present invention is mountable directly above the top 18 of the combustion chamber 8, alternatively in the same way on a flange 17 (see Fig. 5) in the prior art toilet system of EP 1748715, in such a way that the electric heating coil is protected from direct impact from both the blackwater 4 during pumping and also from water vapour during the incineration process itself. The flue gases together with the vaporized blackwater 4 leave the combustion chamber 8 in the way shown in Figs. 9-13 and corresponding description below. In order to give the flue gases a maximum of duration in the incineration space in the combustion chamber 8 the electric heating coil can be mounted as far away as possible from the flue gas opening 19. The flue gas opening 19 is designed in size after the capacity of the fan of the electric heating coil, i.e. flow and pressure. The flue gases are thereafter directed into a slot 21 at the rear end of the combustion chamber 8 in under the bottom 11 of the combustion chamber. The dimensions of the combustion chamber 8 are adapted to the output of the electric heating coil, which in turn is determined by the number of users or the number of connected toilet units. Thus, it is realized that a plurality of toilet units can be connected to one single combustion chamber 8.

The electric heating coil 30 is shown in detail in Fig.

7. The number of turns in the coil is preferably between 5 and 10. A first feeding portion 30a is connected to the innermost turn of the cone-shaped coil and the second feeding portion 30b is connected to the outermost turn of the cone-shaped coil.

The system according to the invention functions as follows: A low flush toilet unit 2 macerates the waste at flushing and pumps the waste to the holding tank 6. The flush water comes either from the ordinary pressure water system alternatively from a separate closed pressure water system, connected to the toilet. The holding tank 6 will contain so called blackwater 4, where all solids are finely-cut in a relatively homogenous solution. The holding tank 6 is designed to contain one to two days maximum usage of the toilet unit 2 and the holding tank 6 can be located anywhere it is suitable from a space point of view. There is no demand to locate the holding tank 6 in close connection to neither the toilet unit 2 nor the combustion chamber

8. At the outlet side of the holding tank 6 an ordinary membrane pump can be used for transportation of the blackwater to the combustion chamber. The membrane pump is extremely reliable and totally insensitive for clogging at the same time as it operates under high pressure . The combustion chamber 8 is heated by the top mounted electric heating coil 30. Electric heating coil output and size of the combustion chamber can vary and is designed after the number of users of the toilet unit and the number of connected toilets. The entire process is electronically controlled and supervised by a microprocessor 23.

According to one embodiment and in accordance with the prior art toilet system according to EP 1748715, the incineration of the blackwater 4 from the holding tank 6 is programmed to take place preferably at night-time but can be chosen to take place at optional occasion alternatively when the holding tank 6 is full. When incineration has been decided to start by clock or alternatively full tank the microprocessor 23 gives a signal to the dosage pump 10 to run for a predetermined number of seconds and to pump a first controlled amount or batch of blackwater to the combustion chamber 8. The electric heating coil starts and operates thereafter continuously without interruption during the entire incineration. When the fluid level has decreased to the top of the wave-profile 12 of the bottom 11, a new signal is given to the pump, which pumps a second amount or batch of blackwater into the combustion chamber 8. The vaporization goes on continuously at a constant rate and when the fluid level once again has decreased to the top of the wave-profile 12, a new signal is given to the pump for the third amount or batch of blackwater and so on. This dosage goes on until the holding tank 6 is empty. A difference from the prior art toilet system according to EP 1748715 is that a final combustion is initiated and conditional combustion can be performed in accordance with the present invention; see description below with reference to Figs. 9-13. This is performed to ensure complete incineration of all solids, mainly faeces. The temperature in the combustion chamber is increased hereby since no vaporization of fluids takes place and the time for final incineration can be varied dependent on operation conditions.

The electric supply can be adapted to 230 Volts.

The remains that result from the process are completely harmless. The ashes can be vacuumed out of the combustion chamber a few times a year and the emission to the surroundings through a chimney provided at the outlet pipe 14 consists, besides of flue gases from the electric heating coil 30, of 100% pure, odour-free water vapour.

In accordance to the above mentioned patent publication EP 1748715, the control of the incineration and the vaporization of the blackwater 4 in the combustion chamber 8 is performed by continuous registration of the change of temperature in the combustion chamber 8, which temperature is measured by a sensor 24 placed in a protective-casing 25, which is mounted in the combustion chamber 8. The location of this sensor 24 is of major importance in order to achieve fast and careful registration of the vaporization. The sensor 24 is located on the same side as where the flue gases leave the combustion chamber and is mounted directly on top of a wave peak 13 in accordance to fig. 4. The sensor 24 is connected to the microprocessor 23.

In accordance to the above mentioned patent publication EP 1748715, the principle for control is in accordance to the following: At start of operation a first fixed amount of blackwater 4 is pumped into the combustion chamber 8 and this volume is exactly as much to fill all wave troughs 13' in the profile bottom and to give a fluid surface or head a few millimetres above the wave peaks 13. The sensor 24 is hereby located in the blackwater and registers the fluid temperature. The electric heating coil starts and heats thereafter the blackwater 4 to 100⁰C, whereupon vaporization is initiated. When the fluid level has decreased to the wave peaks 13 the sensor 24 is located in air and the temperature rises immediately. When the sensor 24 registers approximately 120⁰C a new signal is given to the dosage pump 10, which pumps a second fixed amount of blackwater 4 into the combustion chamber 8. The sensor 24 is once again located in the blackwater 4 and obtains the same temperature as the blackwater during the moment of pumping. The temperature of the fluid rises rapidly to 100⁰C, which value is registered by the sensor 24. The temperature is registered in the microprocessor 23 until the surface of the fluid once again has decreased to the wave peaks 13, whereupon the sensor 24 rapidly registers an increasing temperature. When the temperature once again passes 120⁰C a signal is given to the pump to pump a third fixed amount of blackwater 4 into the combustion chamber 8. The process is repeated until the holding tank 6 is empty. The advantage with this control is that it always takes place a maximum heat transfer from the hot flue gases to the cold fluid (100⁰C) . If the surface of the fluid is allowed to decrease below the wave peaks 13 the heat transfer is reverted and the higher temperature in the combustion chamber heats the flue gases while passing through the flue gas channels 12' in the bottom 11. Hereby it is continuously secured during the entire vaporization process that the flange-efficiency is 100 %.

A difference from the prior art toilet system according to EP 1748715 is that final incineration is initiated and that conditional final incineration can be performed in accordance with the present invention, see description below in connection with Figs. 8-13.

The electric combustion device according to the invention and a combustion process which can be used with the electric combustion device will now be described in more detail with reference to Figs. 9-13.

Electric combustion

The electric heating coil 30 is used as an energy source and an air flow transfers the heat energy to the combustion chamber. The velocity of the air flow is varied by means of a fan 32 in an air inlet 33 conducting air to the electric heating coil 30 and onward to the combustion chamber 8. The fan 32 is adapted to provide:

a) Optimum heat transfer to the fluids during the vaporization phase. b) "Storage" of heat in the heating coil at the end of the vaporization phase.

c) Later intense heat transfer to the dried and thickened blackwater during the ignition phase.

The electric heating coil 30 is designed as a cone in order to create a turbulent air flow which penetrates the electric heating coil along its entire length. No part of the electric heating coil must be in the "shadow" of the air flow.

The combustion chamber is designed as a box which can be pulled out sideways with maintained functionality as regards returning of heat energy from flue gases by means of a V-shaped bottom to the fluids in the combustion chamber.

The flue gases pass through a heat exchanger 34 provided directly on the outlet pipe 14 (chimney) on the combustion chamber 8. This is an air/air heat exchanger. The secondary air is heated to approximately 50° C. This heated secondary air is conducted to the fan 32 and is returned to the combustion chamber 8. In this way part of the heat energy in the flue gases is recycled and the efficiency is increased.

The opening 38 of the inlet pipe 36 has increased dimension so that blackwater is "free falling" down into the combustion chamber from a point of the inlet pipe where drying in place cannot take place. The precise level of the point for "free fall" is defined by the lower diameter of the inlet pipe 36 and the combustion temperature in the combustion chamber. The combustion temperature is determined by the output of the electric heating coil as described above.

Process control

Blackwater divides into three different fractions in the holding tank 6:

a) One fractions floats and is successively dried when the physical thickness thereof increases. This fraction is the last one to leave the holding tank during the combustion process, which means that the inlet pipe 36 will be filled with this fraction when the combustion process is finished.

b) One fraction sinks and has a thickened structure.

c) One intermediate fraction consists of fluids.

The fraction a) is the most difficult to process in a reliable and repetitive way and is preferably treated in the following way:

- An extended first input pumping time in order to safeguard that a sufficient amount of the fraction according to a) and "new" blackwater are pumped into the combustion chamber. The thicker fraction in the inlet pipe 36 leads to increased pumping resistance in turn resulting in less pumping volume per time unit.

- An extended last input pumping time in order to minimize the amount of the fraction according to a) remaining in the inlet piping. A membrane pump adapted to pump air is used to "blow clean" and "loosen" the fraction in the piping. - Specialized continuous monitoring of the head in the holding tank is required in order to define the last input pumping occasion.

In order to ensure control and regulation of the combustion process, the amount of non-incinerated organic substances in the combustion chamber be continuously monitored. The amount of non-incinerated organic substances affects the sensitivity and the reaction speed of the temperature sensing. When the sensitivity and the reaction speed have been affected to a defined extent (a combination of time and lowering of temperature after input pumping) , a program step called "conditional final incineration" is performed. This part of the combustion process means that input pumping of new blackwater stops and an elevation of the combustion temperature is initiated whereby all non- incinerated organic material is burnt. After cooling of the combustion chamber, the process returns to "normal" combustion process with batch wise input pumping of blackwater. When the sensitivity and reaction time of the temperature monitoring again indicate that the conditions for "conditional final incineration" are met, then this program step is performed as described above. Depending on which of the fractions a), b) or c) is pumped into the combustion chamber, the program step "conditional final incineration" occurs with different intervals .

An example of the process control as described above is illustrated in the diagram of Fig. 13 showing the temperature versus time in the combustion chamber. The process is performed in two stages: a "vaporization step" which means that vaporization of fluids at 100° C (boiling) , and a "combustion step" which means combustion of solid particles wherein the temperature is increased to 575° C in order to ignite the material once more. In order to keep the efficiency of the process high, it is desired not the have a frequent combustion step. The dryness of the input pumping water is therefore monitored by monitoring the lowering of temperature that takes place during input pumping. The higher dryness, the slower temperature lowering.

A preferred embodiment of a toilet system according to the invention has been described. However, the person skilled in the art realizes that this can be varied within the scope of the appended claims without depart- ing from the inventive idea.

Claims

1. A toilet system comprising:

a combustion chamber (8) with an electric combustion device comprising an electric heating coil (30),

characterized in that

- the electric heating coil has the shape of a cone.

2. The toilet system according to claim 1, comprising a fan (32) adapted to create an air flow which transfers heat energy from the electric heating coil to the combustion chamber.

3. The toilet system according to claim 2, wherein the fan is adapted to create an air flow downward into the combustion chamber.

4. The toilet system according to any of claims 1- 3, comprising:

- an air inlet (33) connected to the combustion chamber,

- an outlet pipe (14) provided on the combustion chamber, and

- a heat exchanger (34) provided directly on the outlet piping so that flue gases pass through the heat exchanger,

- wherein the air inlet (33) passes through the heat exchanger.

5. The toilet system according to claim 4, wherein the heat exchanger (34) is adapted to heat the air flow before reaching the electric heating coil (30).

6. The toilet system according to claim 5, wherein the heat exchanger (34) is adapted to heat the air flow before reaching the electric heating coil (30) to a temperature of about 50° C.

7. The toilet system according to claim 1, comprising an air inlet pipe provided on the combustion chamber, wherein the opening of the inlet pipe is wider than the rest of the air inlet pipe.

8. The toilet system according to any of claims 1- 7, comprising at least one toilet unit (2), wherein each of said at least one toilet unit comprises:

- a holding tank (6),

- a device (3) for macerating and transportation of blackwater (4) to a holding tank (6), and

- a dosage pump (10) for transportation of blackwater from the holding tank and into the combustion chamber (8).

9. The toilet system according to any of claims 1-8, wherein the electric heating coil is adapted to be used as an energy source.