WO2017179004A2

WO2017179004A2 - Process for generating electricity

Info

Publication number: WO2017179004A2
Application number: PCT/IB2017/052136
Authority: WO
Inventors: Nico Smit; Frans BEZUIDENHOUT
Original assignee: Advance Carbon Technologies (Pty) Limited
Priority date: 2016-04-15
Filing date: 2017-04-13
Publication date: 2017-10-19
Also published as: EP3443265A2; WO2017179004A3; ZA201806797B

Abstract

According to the present invention there is provided an electricity generating process, a water purification process and a combustion process utilizing a gas-liquid interface, in a pressurized reactor, the process including the steps consisting of preparing the reactor for continuous reaction, through an initial pressurization step to establish a pressure of between 10 to 30 Bar inside the reactor and introducing a source of water containing a source of carbon into the reactor and providing an activator for conditioning the reactor to achieve optimal conditions inside the reactor to enable the source of water containing carbon to reach boiling point. The process further includes the introduction of a source of oxygen at pressure and temperature to enable exothermic combustion to occur and further provides for a continuous source of water containing carbon and a source of oxygen to enable continuous exothermic combustion to occur and lastly utilizing both the flue gas and steam in a means for generating electricity or purifying water.

Description

PROCESS FOR GENERATING ELECTRICITY

TECHNICAL FIELD The invention relates to a process for generating electricity, purifying water and for combusting carbon-based materials. In particular, said process utilizes a gas-liquid interface inside a reactor.

BACKGROUND ART

Coal is one of the least expensive and most abundant resources in many countries making it an attractive fuel for electricity generation.

Conventionally, the state of the art comprises of processes wherein carbon is reacted with oxygen and the resulting energy is utilized in steam generation for use in electricity generation. The aforementioned processes may achieve efficiencies of up to 39% energy fed vs. energy generated.

The art further teaches of atmospheric fluidized-bed reactors and entrained fuel-type reactors, wherein a coal-water slurry is utilized as a fuel for generating electricity. More recently, there has been an increased focus in developing and using pressurized fluidized-bed type reactors utilizing a coal-water slurry as a fuel, wherein the hot flue gasses from the reactor are expanded through a gas turbine thereby generating electrical power.

A number of different pressurized fluidized-bed type reactor processes are known, in particular, United States Patent No. 5,067,317 hereinafter referred to as "the US patent", teaches of the use of a process wherein a coal-water slurry is fed to a pressurized fluidized bed reactor wherein the slurry is atomized and the coal is reacted with air to produce a mixture of flue gas, steam and particulates.

The US patent's process further includes the separation of particulates from the flue gas and steam downstream from the reactor, where after the flue gas is utilized in a turbine generator for the generation of electrical power. Moreover, the flue gas is cooled, prior to releasing the flue gas to the atmosphere, through a stack. A disadvantage associated with the aforementioned process is that the exothermic reaction has to occur in the gaseous phase, thereby necessitating the use of extremely high pressures and temperatures in the reactor, which reduces the overall efficiency of the US process when compared to the instant invention.

A further disadvantage of the US process pertains to the complexity of the US process whereby further downstream process equipment is needed in order to remove the particulate matter from the flue gas and steam which results in further heat loss and therefore a further reduction in overall efficiency when compared to the instant invention.

A yet further disadvantage of the US process is the need for the use of a stack for cooling the flue gas prior to releasing it in the atmosphere, which is necessitated by the high operating temperature inside the reactor of the US process.

Great Britain Patent Number 935,658 hereinafter referred to as "the GB patent", teaches of a process for producing steam, wherein a communicated solid fuel, an oxidising gas and water is introduced into a gas-fluidized bed of substantially non- combustible material which is maintained at a temperature above the minimum combustion temperature of the said fuel and at super-atmospheric pressure. The steam generated by this process is withdrawn together with the products of combustion.

A disadvantage associated with the aforementioned process, as with US Patent No. 5,067,317, is that the exothermic reaction has to occur in the gaseous phase, thereby necessitating the use of extremely high pressures and temperatures in the reactor, which reduces the overall efficiency of this process.

A further disadvantage associated with the process described in the GB patent is that the non-combustible material in the fluidized bed may be blown out of the reactor, especially at high oxidising gas velocities, into downstream equipment. The aforementioned circumstance, necessitates the use of further expensive downstream equipment to remove such impurities in the steam and flue gas. In addition to the above disadvantages, it is to be noted that the heating of the non- combustible materials in the fluidized bed would require a substantial amount of energy which results in a reduction of the steam generation process. In view of the foregoing discussion, it is apparent that there is a need in the art for providing a novel and improved process for utilizing carbon as a fuel source in electricity generation, which overcomes and/or addresses the shortcomings and disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

According to the present invention, there is provided an electricity generating process utilizing a gas-liquid interface, in a pressurized reactor, the process including the steps consisting of:

i. preparing the reactor for continuous reaction through an initial pressurization step to establish a pressure of between 10 to 30 Bar inside the reactor;

ii. introducing a source of water containing a source of carbon into the reactor; iii. providing an activator for conditioning the reactor to achieve optimal conditions inside the reactor corresponding to the boiling point of the source of water containing carbon;

iv. introducing a source of oxygen at a pressure and temperature to enable exothermic combustion to occur;

v. providing a continuous source of water containing carbon and a source of oxygen to enable continuous exothermic combustion to occur;

vi. utilizing both the flue gas and steam as a means for generating electricity and optionally, providing a catalyst to enhance the combustion reaction. According to a second aspect of the invention, there is provided a water purification process utilizing a gas-liquid interface, in a pressurized reactor, the process including the steps consisting of:

ii. introducing a source of water containing a source of carbon into the reactor; iii. providing an activator for conditioning the reactor to achieve optimal conditions inside the reactor to enable the source of water containing carbon to reach boiling point;

v. providing a continuous source of water containing carbon and a source of oxygen to enable continuous exothermic combustion to occur; and vi. utilizing the steam produced by the process as a source of water.

According to a third aspect of the invention, there is provided a combustion process utilizing a gas-liquid interface, in a pressurized reactor, the process including the steps consisting of:

v. providing a continuous source of water containing carbon and a source of oxygen to enable continuous exothermic combustion to occur.

In one embodiment of the invention, there is provided for an accumulator for controlling the pressure of the resultant flue gas and steam. In an embodiment of the invention, there is provided for a catalyst to enhance the combustion reaction.

In a further embodiment of the invention, the carbon source may be any one or more of a solid, a liquid and a gas. The carbon may be mixed with water in ratios of between 15 percent and 86 percent by carbon weight.

In an ideal embodiment of the invention, the source of carbon may be coal. In terms of the invention the coal particles may have a diameter of less than 1 .0 millimeter. Preferably, the coal particles may have a particle size of 0.5 millimeter. In yet a further embodiment the coal particles may have a 30.0 weight percentage of coal in the source of water containing carbon, said coal being in suspension.

The source of water may comprise of any one or more of potable water, gray water, mine acid drainage waste water, recycled water and salt water or combinations thereof. In one embodiment of the invention, the activator may be in the form of a burner heating potable water, said water being in fluid flow communication with the reactor. The water may be heated to between 180 °C and 520 °C and may be controllably fed at a temperature and pressure corresponding to the boiling conditions of the source of water containing carbon already present inside the reactor. The fluid flow communication between the activator and reactor may be disabled before the introduction of step (iv).

The invention yet further provides for the source of oxygen to be introduced into the reactor may be air. The air may be introduced into the liquid phase of the reactor to enable uniform distribution of the air inside the liquid phase. The pressure of the air being introduced into the reactor during step (iv) may be at a pressure range of between 100 and 200 Bar. In the ideal embodiment of the invention, the internal reactor temperature may be 280 °C and the internal pressure may be 100 Bar during step (iv) to step (vi) of the process.

There is further provided for the liquid phase to be a reaction zone wherein the exothermic combustion occurs between the coal and the oxygen inside the liquid phase, such that the energy released from the combustion reaction may cause the water of the liquid phase to undergo a liquid to gas transformation.

There is also provided for the accumulator to be in the form of a vessel to serve as a buffer between the reactor and the means for generating electricity.

There is yet further provided for the means for generating electricity to be in the form of a turbo generator. The catalyst may be in the form of any one or both of palladium and platinum.

According to a further embodiment of the invention, there is provided for a discharge mechanism for discharging particulate matter gravitationally collected from the liquid phase, whilst the reactor is in use. The discharge mechanism may be in the form of an air lock. According to a fourth aspect of the invention, there is provided for the use of a process according to the first aspect of the invention for electricity generation.

According to a fifth aspect of the invention, there is still further provided for the use of electricity obtained during the process of the first aspect of the invention.

According to a sixth aspect of the invention, a further feature is the use of flue gas, steam and energy obtained during the process of the first, second and third aspects of the invention

According to a seventh aspect of the invention, there is provided for the use of a reactor during the process of the first, second and third aspects of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS shows a reactor coupled with an accumulator in accordance with the first aspect of the invention;

Figure 2: shows a reactor in accordance with the second and third aspects of the invention; and

Figure 3: shows a schematic representation of process parameters which were obtained during a batch process run using the process described under Figures 1 and 2.

The presently disclosed subject matter will now be described more fully hereinafter with reference to the accompanying examples and figure, in which representative embodiments are shown. The presently disclosed subject matter can, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the embodiments to those skilled in the art. DETAILED DISCLOSURE OF THE INVENTION

Figure 1 shows the reactor setup (10), wherein the first step consists of preparing the reactor (14) for continuous reaction through an initial pressurization step (12) to establish a pressure of between 10 to 30 Bar inside the reactor. Figure 1 further shows the introduction of a source of water containing carbon (16) into the reactor (14) and shows an activator (18) for conditioning the reactor (14) to achieve optimal conditions inside the reactor (14) and to enable the source of water containing carbon (16) to reach boiling point. Figure 1 yet further shows the introduction of a source of oxygen (12) at a pressure and temperature to enable exothermic combustion to occur. Figure 1 also shows an outlet (20) to enable fluid flow communication between the reactor (14) and accumulator (22) for controlling the pressure of the resultant flue gas and steam. Figure 1 also depicts a means for generating electricity (24) in the form of a turbo generator (24).

Figure 1 further shows a liquid phase (26) wherein the exothermic combustion occurs between the coal and the oxygen inside said liquid phase, such that the energy released from the combustion reaction causes the water (26) of the liquid phase (26) to undergo a liquid to gas transformation. The reactor (14) further shows a gas phase (28).

Figure 1 further shows a discharge mechanism (30) for discharging particulate matter (32), gravitationally collected from the liquid phase (28), whilst the reactor is in use. Figure 2 shows the reactor setup (34), wherein the first step consists of preparing the reactor (38) for continuous reaction through an initial pressurization step (36) to establish a pressure of between 10 to 30 Bar inside the reactor. Figure 2 further shows the introduction of a source of water containing carbon (40) into the reactor (38) and shows an activator (42) for conditioning the reactor (38) to achieve optimal conditions inside the reactor (38) and to enable the source of water containing carbon (40) to reach boiling point. Figure 2 yet further shows the introduction of a source of oxygen (36) at a pressure and temperature to enable exothermic combustion to occur. Figure 2 also shows an outlet (42) from the reactor (38) for removing steam and flue gas from the reactor (38).

Figure 2 further shows a liquid phase (46) wherein the exothermic combustion occurs between the carbon source and the oxygen inside the said liquid phase, such that the energy released from the combustion reaction causes the water (46) of the liquid phase (46) to undergo a liquid to gas transformation. The reactor (38) shows a gas phase (48). Figure 2 shows a discharge mechanism (50) for discharging particulate matter (52), gravitationally collected from the liquid phase (46), whilst the reactor is in use.

Figure 3 shows a schematic representation of process parameters as obtained during a batch process run wherein molasses containing 50 wt% carbon, together with water was fed to the reactor setup (38) of Figure 2. The total volume of molasses and water fed to the reactor setup (38) was 270 litres and the flow rate of air (the source of oxygen) (36) varied between 800 and 1200 litres/minute.

The x-axis label of the schematic representation of Figure 3 shows the time in the format hours:minutes:seconds. The y-axis of the schematic representation of Figure 3 shows the temperate in degrees Celsius and the pressure in Bar.

Figure 3 shows the purging of the reactor from time 12:00:01 to time 12:24:01 , during which time the valve (not shown in Figure 2) (labelled as "Valve Position" on Figure 3) which is located in the outflow (42) is in an open condition.

At time 12:24:01 , as shown in Figure 3, the above-mentioned valve is closed, where after the reactor (38) undergoes the initial pressurization step. The initial pressurization step continues until time 12:33:37, where after the molasses and water mixture is introduced into the reactor (38).

The reactor (38) has three temperature probes (not shown in Figure 2) which measures the temperature inside the reactor (38) at three regions thereof corresponding to a "bottom", "middle" and "top" region. The temperature readings of the afore-mentioned temperature probes are shown in Figure 3 as "Bottom Temperature", "Top Temperature" and "Dome Temperature", respectively.

Figure 3 further shows the conditioning (increasing the temperature and pressure inside the reactor) of the reactor via the activator from time 12:33:37 to time 13:20:25. During this time, as shown on Figure 3, the steam produced by the activator reaches a temperature of more than 250 °C, which is then fed to the reactor (38) to heat the molasses and water mixture, and the liquid phase (46) contained therein.

As shown by the "Bottom Temperature" and "Top Temperature" data in Figure 3, the liquid phase (46) reaches boiling point during the afore-mentioned conditioning of the reactor.

Figure 3, at time 13:20:25, shows the shutdown of the activator (42) whereby the temperature and pressure of the said activator (42) drops significantly. At time 13:20:25, the source of oxygen (36) is introduced to the reactor (38) and the valve (not shown in Figure 2) located on the outflow (42) is opened in a step-wise fashion, where after the combustion reaction inside the reactor (38) occurs. Evidence of this combustion reaction can be seen by the sharp increase in the readings of the "Dome Temperature" probe from time 13:20:25 and the initial increase of the reactor's (38) pressure.

Turning to the advantages associated with the present invention, a first advantage associated with the present process is the use of moderate pressures and temperatures inside the reactor, which results in an exothermic reaction occurring in the liquid phase and thereby increasing the heat transfer between the combustion reaction and water, thereby increasing the overall efficiency of the instant process up to 64 percent energy fed vs. energy gained. In addition, the use of said moderate pressures and temperatures alleviates the need for increased apparatus specifications such as wall thickness of the reactor and accumulator. Furthermore, a substantial cost saving in terms of process equipment will occur when compared to, inter alia, the patents described under the background of this specification.

A further advantage over the processes discussed under the background of this specification pertains to the simplicity of the design when compared to the US process, such as the redundancy of further downstream process equipment needed to remove the particulate matter from the flue gas and steam before it can be fed to the electricity generating means, thereby resulting in further cost savings.

A yet further advantage of the instant process resulting from the lower operating temperatures of the present invention when compared to the processes described under the background of this specification, is the absence of a stack whereby the flue gas is cooled prior to releasing it to the atmosphere.

Claims

An electricity generating process utilizing a gas-liquid interface, in a pressurized reactor, the process including the steps consisting of:

ii. introducing a source of water containing a source of carbon into the reactor;

iii. providing an activator for conditioning the reactor to achieve optimal conditions inside the reactor to enable the source of water containing carbon to reach boiling point;

v. providing a continuous source of water containing carbon and a source of oxygen to enable continuous exothermic combustion to occur; and vi. utilizing both the flue gas and steam as a means for generating electricity.

A water purification process utilizing a gas-liquid interface, in a pressurized reactor, the process including the steps consisting of:

3. A combustion process utilizing a gas-liquid interface, in a pressurized reactor, the process including the steps consisting of:

4. The process of any one of claim 1 , claim 2 or claim 3, wherein an accumulator for controlling the pressure of the resultant flue gas and steam is provided.

5. The process of any one of claim 1 , claim 2 or claim 3, wherein a catalyst is provided to enhance the combustion reaction.

6. The process of any one of claim 1 , claim 2 or claim 3, wherein the carbon source is any one or more of a solid, a liquid and a gas.

7. The process of any one of the proceeding claims, wherein the weight percentage of the source of carbon in water is between 15 and 86 percent.

8. The process of any one of claim 1 , claim 2 or claim 3, wherein the carbon source is coal particles.

9. The process of claim 8, wherein the coal particles have a diameter of less than 1 .0 millimeter.

10. The process of claim 8, wherein the coal particles have a particle size of 0.5 millimeter.

1 1 . The process of claim 8, wherein the coal particles have a 30.0 weight percentage of coal in the source of water containing carbon.

The process of claim 8, wherein the coal particles are in suspension.

The process of any one of claim 1 , claim 2 or claim 3, wherein the source of water comprises of one or more of potable water, gray water, mine acid drainage waste water, recycled water salt water and combinations thereof.

The process of any one of claim 1 , claim 2 or claim 3, wherein the activator is in the form of a burner which heats potable water, said water being in fluid flow communication with the reactor.

The process of claim 14, wherein the water is heated to between 180 °C and 520 °C and is controllably fed at temperature and pressure corresponding to the boiling conditions of the source of water containing carbon already present inside the reactor.

16. The process of claim 14, wherein the fluid flow communication between the activator and reactor is disabled before the introduction of step (iv).

17. The process of any one of claim 1 , claim 2 or claim 3, wherein the source of oxygen to be introduced into the reactor is air.

18. The process of claim 17, wherein the air is at ambient temperature and is introduced into a liquid phase of the reactor to enable uniform distribution of the air inside the liquid phase.

19. The process of claim 17, wherein the pressure of the air being introduced into the reactor during step (iv) is at a pressure range of between 100 and 200 Bar.

20. The process of any one of claim 1 , claim 2 or claim 3, wherein the internal reactor temperature is 280 °C and the internal pressure may be 100 Bar during step (iv) to step (vi) of the process.

21 . The process of claim 18, wherein the liquid phase is a reaction zone and wherein the exothermic combustion occurs between the coal and the oxygen inside the liquid phase, such that the energy released from the combustion reaction causes the water of the liquid phase to undergo a liquid to gas transformation.

22. The process of any one of claim 1 , claim 2 or claim 3, wherein an accumulator is also provided.

23. The process of claim 22, wherein the accumulator is in the form of a vessel to serve as a buffer between the reactor and the means for generating electricity.

24. The process of claim 1 , wherein the means for generating electricity is in the form of a turbo generator.

25. The process of claim 5, wherein the catalyst is any one or both of palladium and platinum.

26. The process of any one of claim 1 , claim 2 or claim 3, wherein a discharge mechanism is provided for discharging particulate matter, gravitationally collected from the liquid phase, whilst the reactor is in use.

27. The process of claim 26, wherein the discharge mechanism is in the form of an air lock.

28. Use of the process of claim 1 for electricity generation.

29. Use of electricity as obtained during the process of claim 1 .

30. Use of flue gas, steam and energy as obtained during the process of any one of claim 1 , claim 2 or claim 3.

31 . Use of a reactor during the process of any one of claim 1 , claim 2 or claim 3.

32. The process of claim 1 , substantially as herein described with reference to Figure 1 and Figure 3.

33. The process of claim 2 or claim 1 , substantially as herein described with reference to Figure 2 and Figure 3.

34. The use of claim 28 or 29, substantially as herein described with reference to Figure 1 and Figure 3.

35. The use of claim 30 or claim 31 , substantially as herein described with reference to Figure 2 and Figure 3.