WO2016189031A1

WO2016189031A1 - Scrubber wash water electrolytic treatment

Info

Publication number: WO2016189031A1
Application number: PCT/EP2016/061797
Authority: WO
Inventors: Rasmus Andreas Kunø TARP; Uffe WILKEN; Casper Ryborg SIMMELSGAARD
Original assignee: Gas2green
Current assignee: Gas2green
Priority date: 2015-05-25
Filing date: 2016-05-25
Publication date: 2016-12-01
Anticipated expiration: 2017-11-25

Abstract

The invention provides a method and apparatus for treating waste scrubber liquid from a wet scrubber. The method comprises subjecting the waste scrubber liquid to electrolysis, thereby providing concentrated waste scrubber liquid and at least one fuel, which is typically hydrogen. A power plant, waste disposal facility, ship or vehicle comprising the apparatus or using the method of the invention is also provided.

Description

SCRUBBER WASH WATER ELECTROLYTIC TREATMENT FIELD OF THE INVENTION

The present invention relates to an apparatus and method for treating and/or utilizing waste scrubber liquid that is discharged from a wet scrubber. The invention uses electrolysis to split waste scrubber liquid into its main elements and concentrated wastes, and to make the waste scrubber liquid into a resource for use in other situations.

BACKGROUND OF THE INVENTION

A wet scrubber is an air pollution control device which removes pollutants, such as uncombusted fuel or soot particles, from a gas stream. The gas stream is typically an exhaust gas stream from a combustion process, e.g. from an internal combustion engine. Wet scrubbers function by contacting the gas stream with a scrubber liquid, which can dissolve soluble pollutants and capture solid particulates in the gas stream.

Wet scrubbers are typically used in marine environments to remove pollutants from ship engines. Waste scrubber liquid (i.e. scrubber liquid that has been in contact with the gas stream) contains soluble pollutants such as sulfur compounds and particular pollutants such as soot, and is typically discharged at sea.

Electrolysis is used in several situations for treating liquids and gasses that are contaminated, polluted and/or unclean. However the use of electrolysis together with a wet scrubber, especially in the situation where the polluted and/or unclean product is utilized and reused as a resource is not known.

OBJECT OF THE INVENTION

With increasing environmental concern and legislation, it is of interest to reduce the volume of waste scrubber liquid produced by wet scrubber processes. Additionally, it is of interest to convert pollutants in the waste scrubber liquid to useful materials, such as fuels. The purpose of the invention is to reuse various waste/residual products as a resource, thus increasing the efficiency/utilization of the combustion facility or likewise. This allows for a more efficient utilization of the product of combustion (the fuel) where less energy is lost through waste products such as but not limited to exhaust gases, and residual combustion products such as sulfur and heat.

Firstly, the process used through the various stages of the invention allows for a higher economic efficiency since the products and the energy stored in for example, exhaust gases is transferred from the gas to the scrubber liquid. The products and the energy are then secondly, converted in an electrolytic process. The converted products can now lastly, be stored for sale, cooling, later use through combustion or through a fuel cell thus utilizing more of the chemical energy bound in the process of combustion and from the combustion products. SUMMARY OF THE INVENTION

The invention provides an apparatus and a method, which allow the utilization of more energy from products which were otherwise considered waste products and thereby increase a given plants/installation/ship/facility's overall efficiency or provides the possibility of using the end product of the electrolytic process elsewhere, in addition to decreasing the ouput of potentially harmful products/substances to the environment.

This hereby achieves the use of a product which otherwise would be released/discharged into the environment, in a way where it instead becomes a valuable fuel itself. The product of this process can be used, either to increase the efficiency in relation to the input of energy from fossil fuels, for cooling, or for utilizing the stored energy from the electrolysis elsewhere such as, but not limited to engines or fuel cells.

The utilization of the invention happens through various processes which form the basis of the invention. The first process happens in the scrubber, where exhaust gasses are cleaned. The second process is the splitting of the scrubber liquid in the electrolytic cell/bath. The third process is storage. The fourth and last process is consumption or combustion of the products produced through the electrolytic process.

So, in a first aspect, a method for treating waste scrubber liquid from a wet scrubber is provided, said method comprising the step of subjecting said waste scrubber liquid to electrolysis, thereby providing concentrated waste scrubber liquid and at least one fuel, typically hydrogen. An apparatus for treating waste scrubber liquid is also provided, said apparatus comprising; (a) a wet scrubber, and (b) an electrolytic cell arranged so as to receive waste scrubber liquid from said wet scrubber and to subject it to electrolysis, thereby providing concentrated waste scrubber liquid and at least one fuel.

The use of the above method, or the above apparatus in a power plant, waste disposal facility, ship or vehicle is also provided. Similarly, a power plant, waste disposal facility, ship or vehicle comprising the above apparatus is provided.

LEGENDS TO THE FIGURES

Fig. 1 shows a schematic overview of the method and apparatus of the invention with the following references:

1. Scrubber

2. Exhaust gas (Flue Gas)

3. Water supply

4. Scrubber Discharge Pump

5. Circulation tank

6. Scrubber Circulation Pump

7. Electrolytic Cell Supply Pump

8. Electrolytic Cell

9. Supply of energy (electricity)

10. Supply of heat or supplements (like CO or C0₂)

11. Sludge tank

12. Sludge Discharge

13. Production tank Supply pump

14. Production tank

15. Production tank Discharge pump

16. Fuel Cell (or combustion chamber / Cooling system)

17. Energy output (electric energy)

18. Heat emission

DETAILED DISCLOSURE OF THE INVENTION Method

A method for treating waste scrubber liquid from a wet scrubber is provided. The scrubber (1) absorbs pollutants from exhaust gases (2) in water droplets supplied to the scrubber (3) and by recirculating previously-used water. The scrubber wash water from the flue gas purification is pumped (4) to a circulation tank (5) from where it can recirculate back to the scrubber once again (6) or be supplied to (7) the electrolytic cell (8). The cell itself will be powered by electricity (9) and can be supplied with excess heat (heat recovery) or other substances (10) depending on the product desired from the process. The water in the cell will be split into its elements through electrolysis, thereby creating hydrogen and oxygen in the process, where sulfur will remain and will be removed separately as sludge. The sludge will be accumulated in a sludge tank (11) for later disposal (12). The hydrogen fuel will then be pumped (13) to a production tank (14), where it is stored for later use. The hydrogen can be led (15) from said production tank (14) to a fuel cell (16) which will produce electricity (17), heat and water (18). The fuel cell can be used as a heat exchanger for optimal efficiency, however this is optional and the purified water can also be discharged directly.

As illustrated, the waste scrubber liquid is subjected to electrolysis. This is obtained by the scrubber liquid being led to the electrolytic cell(s) wherein the liquid is split into the products (main elements) that make up the liquid composition. These elements, such as hydrogen and oxygen are then stored in separate tanks. The products can then be used in other situations such as for cooling or, but not limited to, producing electricity through consumption of hydrogen (H₂) in a fuel cell.

Electrolysis is an electrochemical process which takes place by leading electricity via electrodes or by membranes through a medium/substance/solution. The two electrodes (anode and a cathode) or the membranes, have a respectively positive and negative charge. The voltage results in an ionization of the medium/substance/solution into, but not limited to, hydrogen and oxygen-ions. The positively charged hydrogen-ions (H⁺) are attracted to at the negatively charged cathode and the negatively charged oxygen-ions (0^2~) are attracted to the positively charged anode. During electrolysis, water in the waste scrubber liquid decomposes into oxygen (0₂) and hydrogen (H₂). The electrolysis step suitably takes place in an electrolytic cell. The electrolytic cell is not limited to a certain type. Several different types of cell can be utilized, such as Solid Oxide Electrolysator Cell (SOEC), Proton exchange membrane electrolysator cell (PEMEC), catalytic cells and electrolytic baths (galvanic). All can be used depending on the requirements, design or function of the installation. Use of seawater as the scrubber liquid provides advantages in the electrolysis process, due to the presence of salts such as sodium and lithium salts, which increase the conductivity of the waste scrubber liquid, and thus its susceptibility to electrolysis.

The product of the electrolysis step is concentrated waste scrubber liquid and at least one fuel. The fuel is typically hydrogen or other gasses. Commonly, the fuel is hydrogen (H₂), being the direct product of electrolysis of water. It is possible, in the production phase, where electrolysis is occurring, to mix in other products (additives) such as for example C0₂, and then produce hydrogen and CO which through industrial processes can be made into butane (C4H10) or methane instead of hydrogen and thereby make a product for consumption in combustion, rather than leading it back to a fuel cell.

Storage of the electrolytic products will vary depending on the specific product. The invention can be adapted to suit the demands that might be put forth as per specification. If, for example, the invention is to produce hydrogen, then this is normally produced as a gas but can be stored as a liquid and/or in/as solids if needed.

The most common way to store hydrogen currently is in steel- or aluminium cylinders, at a pressure of 200-250 Bar (as a compressed gas). Compressed gas has a superior energy density compared to other storage forms however, liquid hydrogen can be stored at "normal" atmospheric pressure, and is therefore more commonly used in industrial situations. Fuel from the electrolysis is therefore suitably collected in one or more fuel storage containers.

Storage of hydrogen in solid form involves a chemical reaction between the hydrogen and a metal with a negative enthalpy which in means that it will merge into an exothermal metal hybrid. If the product of the electrolysis is something else than hydrogen, for example, but not limited to, biodiesel, then this can be stored in commonly-known tanks, as per other similar fuels.

The electrolysis also provides oxygen (again, being a direct product of water electrolysis). Oxygen from the electrolysis may be collected in one or more oxygen storage containers.

As a further step, the method, may further comprise a step of producing electricity from said fuel. Suitably, a fuel cell is used to produce said electricity from said fuel. The fuel cell (16) is in essence a reverse electrolytic cell (16), with the reverse polarity. This unit can produce electricity without any emission of C0₂ or other harmful particles. This is possible when, for example, hydrogen is used as a fuel in the cell. The fuel - hydrogen - is led to the fuel cell (16) in addition to oxygen. Then a reaction takes place, inside the cell, between the hydrogen and the oxygen, during which water is produced as well as free electrons which are led into an electrical circuit. The fuel cell typically consists of an ionic conducting material (an electrolyte) which has been encapsulated, with an ionic conducting cathode on one side and an anode on the other which are then supplied with oxygenated gas (air) and hydrogen containing gas (fuel).

The cell is made up of a row of cells/membranes, stacked together to obtain the desired voltage.

The cells active area determines the voltage which a stack can deliver. The fuel cell system can be modular and built up from several stacks and is therefore very flexible in terms of desired size and function. This allows for the design to be fitted to any design.

A fuel cell has the advantage of not losing any efficiency regardless of size, which is not the case for normal combustion engines and turbines using similar fuels.

The fuel cell can be adapted to suit other fuels than hydrogen. It can for example be adapted to use natural gas or diesel. However, some fuel cells' electrodes are sensitive to various residual substances from supplied products and therefore needs a reformer which is able to reform the fuel or supplied product into a form (liquid, gas or solid) which the cell can then use without deterioration.

Since a fuel cell produces direct current, a system of this sort has to have an inverter which translates the fuel cells DC into alternating current (AC) with the correct voltage and frequency as needed to supply an electrical circuit/system. Electricity produced from said fuel may be used to power the electrolysis process and/or the scrubber process. A "Smart Grid" system will be in control of maintaining a balance between production and consumption of electricity. This system is a communications technology with the purpose of regulating production and consumption automatically in relation to the circuit/system. If excess electricity is present, from for example sustainable energy sources, from production or through a power management system, then this will be stored as hydrogen by transferring it through the electrolytic cell (16) .

The reverse is then the case whenever a demand for more electricity might occur or the hydrogen can be used in other instances as described earlier.

Apparatus The invention also provides an apparatus for treating waste scrubber liquid, said apparatus comprising; a. a wet scrubber; b. an electrolytic cell arranged so as to receive waste scrubber liquid from said wet scrubber and to subject it to electrolysis, thereby providing concentrated waste scrubber liquid and at least one fuel.

All preferred features of the method of the invention apply equally to the apparatus of the invention. For instance, the apparatus may additionally comprise at least one fuel storage container arranged to collect said at least one fuel from said electrolytic cell. The apparatus may additionally comprise means for receiving said at least one fuel from said electrolytic cell or said fuel storage container and producing electricity from said fuel. The apparatus may also comprise one or more storage tanks for waste scrubber liquid located between said wet scrubber and said electrolytic cell. In particular, the preferred fuel is hydrogen.

In a particular embodiment, the apparatus comprises; a. a wet scrubber, said wet scrubber comprising at least one gas inlet, at least one scrubber liquid inlet, at least one chamber in which gas from said gas inlet and scrubber liquid from said scrubber liquid inlet are mixed, and at least one outlet from said at least one chamber for waste scrubber liquid; b. an electrolytic cell arranged so as to receive waste scrubber liquid from said wet scrubber via said waste scrubber liquid outlet and subject it to electrolysis, said electrolytic cell comprising at least one electrolysis chamber, at least one cathode, at least one anode, at least one power supply connected to said at least one cathode and at least one anode, at least one fuel outlet and at least one concentrated waste scrubber liquid outlet. As above, the preferred scrubber liquid is seawater.

Use

The apparatus and method of the invention can be used in a power plant, waste disposal facility, ship or vehicle. The invention thus provides a power plant, waste disposal facility, ship or vehicle comprising the apparatus according to the invention.

The invention is not limited to, but can be used in relation to power plants, waste disposal facilities, ships, transportation vehicles and in similar instances where a scrubber is attached as a part of a combustion facility or likewise such as, but not limited to, combustion engines, boilers (oil, coal, gas, biomass), incinerators, inert gas systems and combustion

compartments.

The invention is constructed as an addition to the scrubber and consists (besides the scrubber, which cleans exhaust and/or gasses) pumps to transport the discharged liquid, storage tanks for the liquid as well as for the post treatment waste product (after

electrolysis), electrolytic cell(s)/bath(s) to split the scrubber waste, storage tanks in which the collected product of the electrolytic cell/bath can be stored, such as but not limited to hydrogen (H₂) and biofuels.

The apparatus is powered by electricity. This can come from but is not limited to, sustainable energy, excess energy from a power management system or from general electricity production.

The supply of electricity can in all the above cases be controlled by a smart grid system as to accommodate a balance between production of H₂ by consumption of electricity and the other way around by production of electricity by consumption of H₂.

Claims

I. A method for treating waste scrubber liquid from a wet scrubber, said method comprising the step of subjecting said waste scrubber liquid to electrolysis, thereby providing concentrated waste scrubber liquid and at least one fuel. 2. The method according to claim 1, wherein said fuel is hydrogen or a biofuel, preferably hydrogen.

3. The method according to any one of the preceding claims, wherein the fuel from the electrolysis is collected in one or more fuel storage containers.

4. The method according to any one of the preceding claims, wherein said electrolysis also provides oxygen.

5. The method according to claim 4, wherein the oxygen from the electrolysis is collected in one or more oxygen storage containers.

6. The method according to any one of the preceding claims, wherein said electrolysis step takes place in an electrolytic cell. 7. The method according to any one of the preceding claims, wherein one or more additives are introduced to the waste scrubber liquid, before or during electrolysis.

8. The method according to claim 7, wherein said one or more additives is ammonia.

9. The method according to any one of the preceding claims, further comprising a step of producing electricity from said fuel. 10. The method according to claim 9, wherein the electricity produced from said fuel is used to power the electrolysis process.

II. The method according to any one of claims 9 or 10, wherein a fuel cell is used to produce said electricity from said fuel.

12. The method according to any one of the preceding claims, wherein the waste scrubber liquid originates from seawater.

13. An apparatus for treating waste scrubber liquid, said apparatus comprising; a. a wet scrubber; b. an electrolytic cell arranged so as to receive waste scrubber liquid from said wet scrubber and to subject it to electrolysis, thereby providing concentrated waste scrubber liquid and at least one fuel.

14. The apparatus according to claim 13 additionally comprising at least one fuel storage container arranged to collect said at least one fuel from said electrolytic cell.

15. The apparatus according to any one of claims 13-14, further comprising means for receiving said at least one fuel from said electrolytic cell or said fuel storage container and producing electricity from said fuel.

16. The apparatus according to any one of claims 13-15, further comprising one or more storage tanks for waste scrubber liquid located between said wet scrubber and said electrolytic cell.

17. The apparatus according to any one of claims 13-16, wherein said fuel is hydrogen. 18. The apparatus according to any one of claims 13-17, comprising; a. a wet scrubber, said wet scrubber comprising at least one gas inlet, at least one scrubber liquid inlet, at least one chamber in which gas from said gas inlet and scrubber liquid from said scrubber liquid inlet are mixed, and at least one outlet from said at least one chamber for waste scrubber liquid; b. an electrolytic cell arranged so as to receive waste scrubber liquid from said wet scrubber via said waste scrubber liquid outlet and subject it to electrolysis, said electrolytic cell comprising at least one electrolysis chamber, at least one cathode, at least one anode, at least one power supply connected to said at least one cathode and at least one anode, at least one fuel outlet and at least one concentrated waste scrubber liquid outlet.

19. The apparatus according to claims 18, wherein the scrubber liquid is seawater.

20. Use of the method according to any one of claims 1-12, or the apparatus according to any one of claims 13-19, in a power plant, waste disposal facility, ship or vehicle.

21. A power plant, waste disposal facility, ship or vehicle comprising the apparatus according to any one of claims 13-19.