GB2635098A

GB2635098A - ThermoHybrid cycle

Info

Publication number: GB2635098A
Application number: GB2018248.1A
Authority: GB
Inventors: Israel Mayomi Tolulope
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-11-20
Filing date: 2020-11-20
Publication date: 2025-05-07
Also published as: GB202018248D0

Abstract

A process for generating electricity, hydrogen, sulphuric acid and hydrogen sulphide comprising the steps of i) combusting hydrogen sulphide with air/oxygen in a combustion chamber; ii) passing the products of the combustion to generate electricity by turning a turbine or to generate steam; ii) the separation of the products of the combustion using water to isolate the nitrogen and sulphur dioxide; iii) the passing of the sulphur dioxide into an electrolyzer, wherein the electrolysis of sulphur dioxide and water generates hydrogen and sulphuric acid; iv) the sulphuric acid is placed in a reactor with sulphate-reducing bacteria to produce hydrogen sulphide that subsequently used as the fuel of the process and combusted in a combustion chamber to restart the cycle. The nitrogen, hydrogen, and carbon dioxide that are produced during the process but are not used as part of the process are stored using conventional storage methods. The hydrogen sulphide may be produced by placing the sulphuric acid in a microbial reactor with sulphate-reducing bacteria.

Description

ThermoHybrid Cycle. Field of the Invention

This invention builds on the hybrid sulfur cycle for splitting water with a heat source of high temperature. The hybrid sulfur cycle henceforth abbreviated as HyS consists of 2 steps: One is the thermal decomposition of sulfuric acid (H2SO4) to sulfur dioxide (502), oxygen (02) and water.

H2SO4 (aq) = l-bo(g) + S02(g) + 0.502(g) The second step is the sulfur dioxide depolarised electrolysis of water to H2SO4 and H2.

502(g) + 2H20(1) = H2SO4(aq) + H2(g) E° = -0.156V Hys was patented in 1975 by Brecher and WU in US Pat No3,888,750 This invention also builds on the Salt cycle for hydrogen production which consists of a thermodynamic cycle, an electrochemical cycle and chemical reactions to produce hydrogen and electricity simultaneously.

Salt cycle for hydrogen production has a publication No US-2018-0119293-A1 and a publication date of 05/03/2018.

Background to the Invention

This invention relates to thermochemical cycles for hydrogen production such as the hybrid sulfur cycle or the sulfur-iodine cycle. This technology holds promise as a source of cheap and abundant source of hydrogen.

Statement of Invention

The present invention relates to a process that produces hydrogen and electricity simultaneously. The process of generating hydrogen and electricity simultaneously involves a thermodynamic process, an electrochemical process and the use of sulfate reducing bacteria simultaneously such that one or more products (either matter or energy) from each of the processes (thermodynamic, electrochemical or bacterial) mentioned above is either used up completely in the other processes or transformed into a different product. For example, sulfuric acid produced in the electrochemical process is converted by the sulfate reducing bacteria into hydrogen sulphide which is then used in the thermodynamic cycle to produce electricity.

An advantage of the present invention over current thermochemical cycles for producing hydrogen is the efficiency in the production of hydrogen. Currently, most thermochemical hydrogen production methods are in the range of 30% -50% efficient in producing hydrogen, while expressed in terms of the LHV of hydrogen. However, the present invention is more efficient at producing hydrogen.

The present invention is more efficient than previous thermochemical hydrogen production methods because unlike current thermochemical hydrogen production methods, the present invention produces electricity as well as hydrogen and some or all of the electricity produced in the thermodynamic process can be used to supply power for the electrolyzer, which produces the hydrogen. Hence, the present invention is more efficient when the efficiency of the process is calculated as the ratio of the energy output in terms of the LHV of hydrogen produced to the amount of power consumed in producing the hydrogen.

Another advantage of the present invention over thermodynamic cycles is that it produces both electricity and hydrogen simultaneously, unlike current thermodynamic cycles which produce only electricity as the end product.

The novelty of the present invention is that it integrates both a thermodynamic cycle and a process mediated by bacteria with an electrochemical process.

Other thermochemical cycles such as the hybrid sulfur cycle could be used to integrate a thermodynamic cycle (e.g. solar thermal plants for supplying the high temperature heat source requirement for the decomposition of concentrated sulfuric acid), with an electrochemical process mediated by a sulphur dioxide depolarised electrolyzer, however there is no thermochemical process, including the hybrid sulfur cycle which integrates any bacteria medium as a backbone for the overall hydrogen production process.

The advantage of integrating a sulfate reducing bacteria into the process is that there is no high temperature heat requirement for the decomposition of sulfuric acid; a requirement found in the hybrid sulfur cycle and other thermochemical cycles.

A big disadvantage of integrating a high temperature heat source is that it limits the application of the cycle as it cannot be integrated into current thermodynamic cycles. For example, the hybrid sulfur cycle requires next generation nuclear and solar power plants to produce the high temperature heat sources required for thermal decomposition of sulfuric acid.

Brief description of the drawings

Fig 1 is a flow chart of the overall process called the Thermo Hybrid Cycle

Detailed description

As shown in Fig 1, the current invention consists of a thermodynamic process, an electrochemical process and reactions facilitated by bacteria.

As shown in Fig 1, the current invention involves the generation of electricity (in the thermodynamic process) and hydrogen simultaneously.

As shown in Fig 1, several other products are also generated in addition to electricity and hydrogen such as sulfur dioxide, sulfuric acid and hydrogen sulfide. As shown in Fig 1, there are several separation steps that exist to transfer products generated at each process to another process.

The thermodynamic process in the current invention can be modelled as a brayton cycle, as it comprises of three components: a compressor, a mixing chamber, and a turbine.

Ambient air is drawn into a compressor and is compressed. Pure oxygen can also be used instead of ambient air, but it usually leads to a reduction in the overall efficiency of the thermodynamic process due to the amount of energy required to separate oxygen from air. Overall the pressure ratio in the compressor is anywhere from 10:1 to about 20:1 with a higher pressure ratio generally leading to an increase in the electricity generated at the turbine.

The compressed air is then passed into the mixing chamber where it is mixed with hydrogen sulfide gas. The mixture is then ignited with sulfur dioxide, water vapor and heat produced as a result of the combustion. Overall, these products are at about 1200°C -1500°C The products of the combustion in the mixing chamber are then passed into a turbine where they are used to turn turbine blades and produce electricity. The products leave the turbine at atmospheric pressure at about 400°C -500°C The thermodynamic process is efficient with efficiency figures in the range of 35% -40% using the LHV of hydrogen sulfide.

In order for sulfur dioxide gas produced in the mixing chamber and released at the turbine to be used in the electrochemical process, it has to be separated from the other products of the combustion of the hydrogen sulfide with air.

The main gas at the exit of the turbine in the thermodynamic process is nitrogen, however in the present invention, it serves no real practical purpose.

Nitrogen can be separated from the other gases at the turbine exit due to the fact that it has a far lower boiling point than sulfur dioxide and water. The boiling point of water at 1 atm is 100°C, while nitrogen has a boiling point of -195.8°C at 1 atm, and sulfur dioxide has a boiling point of -10°C at 1 atm.

Therefore, the separation process for the gases coming out of the turbine consists of two stages. The first stage involves passing the gases through a heat exchanger which cools the gases to about 25°C. The net result is that water vapor changes to liquid water which can be easily removed from the other products.

The second stage involves cooling the remaining gaseous products which are nitrogen and sulfur dioxide to about -9°C so that gaseous sulfur dioxide turns into a liquid which can be easily separated from the nitrogen gas.

In addition to the separation method outlined above, alternative separation methods can be used for separating the various gaseous products from the turbine. For example, the products could be separated due to their differences in solubility in sulfuric acid or they could be sent to the anode of the electrolyzer where nitrogen would come out as an unused product in the reaction.

The liquid sulfur dioxide is then passed through a heat exchanger where it is heated back to about 25°C and passed to the anode of the electrolyzer in the electrochemical process. An alternative is to pass sulfuric acid liquid saturated with sulfur dioxide gas to the electrolyzer.

The reaction that takes place in the electrochemical process is carried out in an electrolyzer and is shown below: 2H20( I) + SO2( g)-H2 SO4 (aq) + H2( g) E° = -0.158V at 25°C The power for the electrolyzer can be supplied from the electricity generated at the turbine or form an external source of power.

Various electrolyzer types can be used in the electrochemical process such as a Proton exchange membrane electrolyzer or an alkaline electrolyzer The sulfuric acid produced by the electrolyzer varies and can be very dilute or extremely concentrated. However, the power requirements for the electrolyzer increases significantly as the concentration of sulfuric acid produced increases.

For optimal conditions which for the current invention involves the lowest possible power requirement for the electrolyzer, dilute sulfuric acid is produced at the electrolyzer. Dilute sulfuric acid is also preferred because it is requires less water to dilute further before it is sent to the sulfate reducing bacteria should this be required.

The hydrogen and sulfuric acid produced are separated due to the fact that the hydrogen produced is in the gaseous phase and the sulfuric acid is produced as a liquid. After separation, the hydrogen gas is then stored.

There are several methods for storing hydrogen and they include but are not limited to metal hydrides, compression or cryogenic technologies.

The sulfuric acid produced in the electrolyzer is passed onto the biological reactor where with the activity of sulfate reducing bacteria, it is reduced to hydrogen sulfide.

Sulfuric acid produced in the reactor will inhibit the activity of the sulfate reducing bacteria as even dilute sulfuric acid (lOwt%) is too acidic for the bacteria. Sulfate reducing bacteria usually require at least a PH of 4.0 in order to carry out their biological activities.

Therefore, before the sulfuric acid is sent to the reactor, it can be neutralized using alkaline residue produced from industrial activities. Alkaline residue such as steelwork slags or Fly ashes are produced on a massive scale globally, thus it can be used to lower the PH of the sulfuric acid produced in the electrolyzer. By mixing the sulfuric acid produced in the electrolyzer with alkaline residue, sulfates can also be produced, which can also be used by the sulfate reducing bacteria in the reactor.

In addition to the liquid sulfuric acid passed into the biological reactor, an energy source such as lactate, acetate, etc. is needed in order for the reduction of sulfuric acid to hydrogen sulfide to be completed.

The energy source, for example acetate, can be supplied from an external source or from other bacterial species in the reactor. In such a case where the energy source is from a microbe, then such a process may be known as microbial electrosynthesis.

In microbial electrosynthesis, a cathode is used to supply electrons to bacteria, which in conjunction with some compounds, also supplied to the bacteria, are used to produce new compounds. For example, the carbon dioxide produced by the sulfate reducing bacteria can be used by other bacterial species in the reactor in addition to electricity to produce organic compounds for the sulfate reducing bacteria.

In such a situation, there is a symbiotic relationship between the various species of bacteria in the reactor. Alternatively, the bacteria involved in microbial electrosynthesis may be placed in a separate reactor if they are unable to coexist in the same reactor as the sulfate reducing bacteria.

The activity of the sulfate reducing bacteria produces hydrogen sulfide, carbon dioxide gas or acetate and water. The carbon dioxide gas if not used by other bacterial species, is not needed in any other process in the invention, therefore it is separated from the hydrogen sulfide gas.

Several separation processes exist for separating the two gases and they include but are not limited to: Ionic liquids, liquefaction, use of alkinolamines such as N-methyldiethanolamine (MDEA), differences in water solubility at various temperatures and pressures, membrane separation, etc. After both gases are separated, the hydrogen sulfide gas is sent to the mixing chamber to be used to produce electricity in the thermodynamic process.

Carbon dioxide gas is pumped and stored in underground caverns. It can also be used in oil exploration sites or for any other economic activity. Subsequently, it can even be reacted with hydrogen to produce methane through the Sabatier reaction

Claims

Claims That which is claimed: 1. A process for producing hydrogen and electricity comprising all of the steps of: Combusting hydrogen sulfide at any temperature and pressure with air or oxygen to produce sulfur dioxide, water vapor and heat if oxygen is used or sulfur dioxide, water vapor, nitrogen, argon and heat if air is used, the combustion reaction can be complete or incomplete; Passing sulfur dioxide gas to the electrolyzer in the electrochemical process where in addition to water, it is used to produce sulfuric acid and hydrogen gas; Passing Sulfuric acid in addition to organic or inorganic compounds to a reactor containing sulfate reducing bacteria, with hydrogen sulfide gas and other compounds produced as a result of the activity of the sulfate reducing bacteria; 2. A process for producing hydrogen and electricity comprising some of steps below, where the steps which are optional are steps that are not listed in the first claim: Combusting hydrogen sulfide at any temperature and pressure with air or oxygen to produce sulfur dioxide, water vapor and heat if oxygen is used or sulfur dioxide, water vapor, nitrogen, argon and heat if air is used, the combustion reaction can be complete or incomplete; Using the combustion of hydrogen sulfide with oxygen or air to generate steam in a boiler; Using the products of the combustion of hydrogen sulfide with oxygen or air to generate electricity inside a gas turbine; Using the products of the combustion of hydrogen sulfide with oxygen or air which has been used inside a gas turbine to generate steam in a heat exchanger; Using the steam to generate electricity or for any other activity; Using the steam generated from the combustion of hydrogen sulfide to generate electricity in a steam turbine or for any other activity; Passing the products of the combustion of hydrogen sulfide with oxygen or air respectively, which has been used to turn a turbine through a heat exchanger where the temperature of the products reduces; Separating water from the other products of the combustion of hydrogen sulfide with oxygen or air which has passed through a heat exchanger due to the phase difference of water from the rest of the products at a specified temperature and pressure; Separating Sulfur dioxide gas from the other products of the combustion of hydrogen sulfide due to the difference in the boiling point of sulfur dioxide from the other remaining combustion products such as nitrogen and argon; Separating the Sulfur dioxide gas from Nitrogen gas which has passed been used to generate electricity in a gas turbine, and or has been passed through a heat exchanger to generate steam due to their differences in solubility in sulfuric acid; Passing the liquid Sulfur dioxide separated from the other products of the combustion of hydrogen sulfide gas through a heat exchanger where it is consequently turned into a gas; Passing the unused products of separation into the air, the remaining product of separation is mostly nitrogen gas; Passing the sulfur dioxide gas produced and separated as stated above to the electrolyzer in the electrochemical process where in addition to water, it is used to produce sulfuric acid and hydrogen gas; Using some or all of the electricity generated in either the steam or gas turbine from the previous steps or from an external source to power the electrolyzer; Storing the hydrogen for any use in any activity; Passing the Sulfuric acid produced in the electrolyzer as stated above in addition to organic or inorganic compounds to a reactor containing sulfate reducing bacteria, with hydrogen sulfide gas, carbon dioxide or acetate and water produced as a result of the activity of the sulfate reducing bacteria; Passing the Sulfuric acid produced in the electrolyzer as stated above in addition to organic or inorganic compounds to a reactor containing a cathode, sulfate reducing bacteria and other microorganisms, such that the sulfate reducing bacteria produce hydrogen sulfide gas, carbon dioxide or acetate and water and the other microbes consume the carbon dioxide produced by the sulfate reducing bacteria and in conjunction with the electrons flowing through the cathode, produce organic compounds such as acetate for the sulfate reducing bacteria; Supplying some or all of the electricity generated in either the steam or gas turbine from the previous steps or from an external source to the microbes used in conjunction with the sulfate reducing bacteria; Separating the hydrogen sulfide gas from the carbon dioxide gas, acetate or water which are produced by the sulfate reducing bacteria in the reactor; Storing the Carbon dioxide and water produced by the sulfate reducing bacteria, creating new compounds by reacting the carbon dioxide with other elements or using the Carbon dioxide and water produced for any other activity; 3. A process for producing hydrogen and electricity comprising all the steps of: Combusting hydrogen sulfide at any temperature and pressure with air or oxygen to produce sulfur dioxide, water vapor and heat if oxygen is used or sulfur dioxide, water vapor, nitrogen, argon and heat if air is used, the combustion can be complete or incomplete; Passing the products of the combustion of hydrogen sulfide with oxygen or air respectively, which has been used to turn a turbine or to generate steam and has been through a heat exchanger into an electrolyzer to generate hydrogen and sulfuric acid; 4. A process for producing hydrogen and electricity comprising some of the steps of, where the steps which are optional are steps that differ from the steps in the third claim above: Combusting hydrogen sulfide at any temperature and pressure with air or oxygen to produce sulfur dioxide, water vapor and heat if oxygen is used or sulfur dioxide, water vapor, nitrogen, argon and heat if air is used, the combustion reaction can be complete or incomplete; Using the products of the combustion of hydrogen sulfide with oxygen or air to generate electricity inside a gas turbine; Using the products of the combustion of hydrogen sulfide which have been used to generate electricity to generate steam through a heat exchanger; Using the steam to generate electricity or for any other activity; Using the combustion of hydrogen sulfide with oxygen or air to generate steam in a boiler; Using the steam generated from the combustion of hydrogen sulfide to generate electricity in a steam turbine or for any other activity; Passing the products of the combustion of hydrogen sulfide with oxygen or air respectively, which has been used to turn a turbine or to generate steam, through a heat exchanger where the temperature of the products reduces; Passing the products of the combustion of hydrogen sulfide with oxygen or air respectively, which has been used to turn a turbine or to generate steam and has been through a heat exchanger into an electrolyzer to generate hydrogen and sulfuric acid; Passing the products of the combustion of hydrogen sulfide with oxygen or air respectively, which has been used to turn a turbine or to generate steam and has been through a heat exchanger and remains unused after the reaction in the electrolyzer into the atmosphere; Using some or all of the electricity generated in either the steam or gas turbine from the previous steps or from an external source to power the electrolyzer; Storing the hydrogen for use in any activity;