Hydrogen technologies

Hydrogen production system from the organic part of the solid waste of the Odessa landfill

The proposed hydrogen production system consists of low-temperature waste pyrolysis, high-temperature gasification of pyrolysis products, as well as a unit for membrane separation of synthesis gas into pure hydrogen and carbon monoxide. High efficiency of the system we offer is achieved due to the accumulation of waste exothermic heat pyrolysis in materials with phase transitions, as well as combustion of carbon monoxide obtained during the separation of synthesis gas. It is shown that the use of waste heat accumulation blocks based on materials with phase transitions in systems for the production of electrical energy by hydrogen fuel cells also allows improve the efficiency of these systems. The Odessa landfill receives solid waste per year, depending on the season, from 2.5 million m3 to 3.0 million m3 of waste. Accordingly, up to 1.0 million m3 of carbon-containing (biologically degradable) waste. From this volume, according to the technology we offer, 15,700 tons of hydrogen can be obtained, annual income from the sale of which will be $ 62.8 million. Key words: hydrogen, solid domestic waste, accumulation, pyrolysis, gasification, organic Rankine cycle.

Determination of the volume of carbon-containing waste at the Odessa solid waste landfill

At the Odessa solid waste landfill, the company "Clear Energy" in 2019 began work on the installation of a degassing system capacity up to 3 MW. In total, the company has already installed degassing systems at 14 landfills in different regions of the country. In accordance with the concept outlined by the Director of Clear Energy, Andrey Grinenko, the second stage of work of the company at the Odessa solid waste landfill will be the construction of a sorting and waste processing complex. All valuable raw materials, namely paper, plastic, wood, metal and glass, after sorting will be processed into useful products with market value. In total, these fractions make up 60% of the volume of solid waste. Of the remaining 40% of waste, only 35% is recyclable for energy.

The annual volume of solid waste supplied to the Odessa landfill, depending on the season, ranges from 2.5 million m3 to 3.0 million m3. Accordingly, up to 1 million m3 or 157,000 tons of carbon-containing (biodegradable) waste is subject to energy processing.


Hydrogen production from waste

When choosing the best progressive technology for producing hydrogen from waste, it is necessary to proceed from integrated assessment of the technologies under consideration, taking into account economic, environmental and social aspects. The urgency of the problem of hydrogen production from waste and various types of biomass is confirmed by the presence a large number of research papers and patents for inventions on this topic. Publication growth activity by country in the field of hydrogen production in 1997-2017 (according to Scopus data) is shown in Fig. 1.



Fig. 1. Our analysis of the literature and a patent search shows that the most commonly used method of converting waste into gases is two-stage gasification. At the first stage, biomass is pyrolized, and at the second stage, the products obtained at the first stage are gasified. In the considered two-stage technologies [2,3,4,5,6,] the final product is synthesis gas, the main components of which are H2 (hydrogen) and CO (carbon monoxide). Depending on the composition of the waste, the ratio of CO: H2 in it varies from 1: 1 to 1: 3.


Highly efficient way of producing hydrogen from waste

Our two-stage highly efficient method of producing hydrogen from waste is different: - preservation and reuse of thermal energy obtained at the stages of converting waste into synthesis gas, which can significantly reduce the cost of the produced synthesis gas; - the presence of blocks for separating synthesis gas into hydrogen and carbon monoxide; - the presence of a gas boiler fueled by carbon monoxide and the use of this heat to obtain superheated steam, which eliminates the need for an external source of thermal energy. Thus, the efficiency of the proposed system is achieved due to the recovery of exothermic heat the process of pyrolysis and combustion of carbon monoxide obtained from waste. When developing a production system pure hydrogen from the organic part of MSW, we used the development of the authors of this article, given in [7,8,9]. Highly efficient system for producing hydrogen from waste by low-temperature pyrolysis and high-temperature gasification in the proposed method includes: equipment for grinding and drying waste, pyrolysis oven, gasifier, low-temperature heat recuperator on materials with phase change, high temperature heat recuperator, steam generator, coke separator, synthesis gas cooling and purification system, hydrogen recovery unit, gas boiler, storage systems hydrogen, ash and carbon dioxide. We propose to perform the separation of hydrogen from synthesis gas using membrane units [10]. This method of separation of gaseous mixtures allows hydrogen to be separated from gas mixtures with minimal losses. streams. The main advantages of membrane plants that allow concentrating hydrogen include low maintenance costs, simple hardware design and long membrane life. Figure 2 shows a flow diagram of the interconnection of the elements of the proposed system for hydrogen production. from waste.

Fig. 2.
The technology for producing hydrogen from the biological part of municipal solid waste is implemented in the following stages:
⦁ Shredding and drying of waste;
⦁ Production of low-temperature and high-temperature superheated steam;
⦁ Pyrolysis of raw materials by low-temperature water vapor at temperatures of 5000C-8000C with the formation of synthesis gas, ash and coke;
⦁ Separation of ash and coke;
⦁ Recovery of heat generated by the pyrolysis system;
⦁ Gasification of synthesis gas and coke with high-temperature superheated steam at 12000C -16000C;
⦁ Purification and removal of harmful impurities from synthesis gas;
⦁ Membrane-adsorption separation of synthesis gas to produce hydrogen and carbon monoxide;
⦁ Production of thermal energy by combustion of carbon oxide in a gas boiler.
⦁ Storage of carbon dioxide.
⦁ Storage of hydrogen.

According to our proposed technology, 1 kg of synthesis gas can be obtained from 5 kg of biodegradable waste and, after separation, at least 0.5 kg of hydrogen. Accordingly, 15700 tons of hydrogen will be obtained from 157,000 tons of biodegradable waste. With a minimum selling price of hydrogen of $ 4 / kg, the annual income from the sale of 15,700 tons will be $ 62.8 million.


Accumulation and storage of hydrogen

A large number of publications deal with hydrogen storage technologies [16, 18]. The most important characteristic that determines the efficiency of hydrogen storage is its bulk and gravimetric density. From this point of view, as well as taking into account safety requirements, the most preferable method is storage and transportation of hydrogen in a bound state [17]. This is either storage in a chemically bound form (hydrides), or storage using controlled processes of sorption – desorption of hydrogen by some intermetallic compounds [19]. The prospects of this method are determined by the following features:
⦁ accumulation of hydrogen in the composition of hydrides used as an intermediate product during transportation and storage [21];
⦁ generating hydrogen directly at the place of its consumption;
⦁ using the principle of a battery with the possibility of multiple charging and discharging without replacing sorbents;
⦁ possibility of hydrogen storage without drainage practically unlimited in time;
⦁ relatively low pressure and temperature during operation.

Hydrides provide a high bulk density of accumulation: 100-150 g / l. For example, containers from Pragma Industries with a total weight of 350 grams store 20 liters of hydrogen. Such a compact, efficient and safe hydrogen storage is especially promising for systems using fuel cells.


Improving energy efficiency of electric power generation generated by fuel hydrogen cells

Hydrogen (methane) and oxygen entering the fuel cell is converted into electricity with the release of heat. Up to 60% of this energy is converted into electrical energy, the remaining 40% is released with heat. Applied in In the present work, the methods of utilization of waste heat [8,9] were also used by us to construct a system utilization of these 40% of heat. We propose to use this heat to generate additional electricity small power plants built on the principle of organic Rankine cycle (ORC). This makes it possible to raise the conversion efficiency of hydrogen power plants to 76%. Today, international the markets of the USA and Europe have already introduced fuel cell power plants of a large range of capacities, up to several megawatt in one unit. In practice, these systems are part of future mass power systems for environmentally friendly fuel. Based on hydrogen fuel cells stationary power plants more than 300 million kilowatt-hours of electricity have already been generated at more than 80 stations around the world [20]. Technological scheme for converting waste low-grade heat released by hydrogen fuel elements is shown in Fig. 3.

Рис.3.
Diagram of the relationship of hydrogen fuel cells with the organic Rankine cycle The low potential thermal energy released by the hydrogen cell is stored in a storage tank with phase change and then converted into electricity produced using the organic cycle Rankine (ORC). The cycle uses an organic low-boiling working fluid to create steam, which can be used, for example, pentane (C5H12), which after a temperature of + 36˚С turns into a gaseous state. Examples of other organic low boiling liquids are hydrocarbons (butane, propane), freons (R11, R12, R114, R123, R245 + a), ammonia, toluene, diphenyl, silicone oil, etc. Initially low potential heat from the hydrogen cell enters the storage tank, where it heats the working fluid, converting it to steam. The use of phase change materials in the tank allows a long time maintain the same temperature, which creates the preconditions for the stable operation of the system (Fig. 4). The working area of ​​the cycle is between points D and F.



Fig. 4.
Graph of temperature change in a storage tank with heat storage material.
ORC units handle waste heat with low and medium thermal potential in the temperature range from 40 ° C to 90 ° C. Further, the steam of the organic liquid enters the steam turbine, where it does work, the generator, which is on the same shaft as the turbine, generates electricity. Thus, the incoming heat flux from the accumulator tank is transformed by the ORC into electrical energy with an efficiency of up to 25-26% and up to 75% of waste heat is also released. To increase the efficiency of the ORC, we propose the spent Waste heat turbines can also be used for preheating the organic working fluid. For this, a heat economizer (recuperator) is added to the cycle. Steam after extraction of heat from the cooling circuit the generator goes back to the evaporator, where it additionally heats and evaporates the working fluid. This makes it possible to additionally accumulate thermal energy in the tank and, accordingly, increase The efficiency of the Rankine cycle by at least another 10% and bring it to 35%.





Highly efficient system for the production of pure hydrogen from the organic part of solid waste.


⦁ Annotation.
The system consists of low-temperature waste pyrolysis, high-temperature gasification of pyrolysis products, and a membrane separation unit for synthesis gas into pure hydrogen and carbon monoxide. The high efficiency of our proposed system is achieved due to the recuperation of the exothermic heat of the process and the combustion of carbon monoxide obtained during the separation of synthesis gas. The Odessa landfill receives solid waste per year, depending on the season, from 2.5 million m3 to 3.0 million m3. Accordingly, up to 1.0 million m3 or 157,000 tons of carbon-containing (biodegradable) waste is subject to energy processing. With a minimum selling price of hydrogen of $ 4 / kg, the annual income from the sale of 15,700 tons will be $ 62.8 million.

⦁ Determination of the volume of carbon-containing waste at the Odessa solid waste landfill.
In accordance with the concept outlined by the Director of Clear Energy, Andrey Grinenko, the second stage of the company's work at the Odessa solid waste landfill will be the construction of a sorting and waste processing complex. All valuable raw materials, namely paper, plastic, wood, metal and glass, after sorting will be processed into useful products with a market value. In total, these fractions make up 60% of the volume of solid waste. Of the remaining 40% of waste, only 35% is recyclable for energy.
The morphological composition of the solid waste of the Odessa landfill is shown in Table 1. taken from the report of the Kharkiv LLC "Ukrainian Research Institute for the development and implementation of utility programs and projects" 2018 "On the provision of services for determining the morphological composition of solid waste in residential buildings in Odessa."


The annual volume of solid waste supplied to the Odessa landfill, depending on the season, ranges from 2.5 million m3 to 3.0 million m3. Accordingly, up to 1.0 million m3 or 157,000 tons of carbon-containing (biodegradable) waste is subject to energy processing. In order to implement the proposals set forth by you in the article "Why Ukraine can stimulate development of water" , we propose to recycle this volume of waste into hydrogen.

⦁ Production of hydrogen from waste.
When choosing the best progressive technology for producing hydrogen from waste, it is necessary to proceed from integrated assessment of the technologies under consideration, taking into account economic, environmental and social aspects. The urgency of the problem of hydrogen production from waste and various types of biomass is confirmed by the presence a large number of research papers and patents for inventions on this topic. Conducted by us analysis of the literature and patent search shows that the most commonly used method of converting waste to gases is a two-stage gasification. Table 2. a list of technology patents obtaining hydrogen from biomass. At the first stage, biomass is torrified, and at the second stage, gasification products obtained at the first stage.



In the two-stage technologies discussed in Table 2, the final product is synthesis gas - the main components of which are H2 (hydrogen) and CO (carbon monoxide). Depending on the composition of the waste, the ratio of CO: H2 in it varies from 1: 1 to 1: 3.
⦁ Высокоэффективный способ производства водорода из отходов.
Our proposed two-stage highly efficient method for producing hydrogen from waste is different:
- preservation and re-recovery of thermal energy obtained at the stages of converting waste into synthesis gas, which can significantly reduce the cost of the produced synthesis gas;
- the presence of blocks for separating synthesis gas into hydrogen and carbon monoxide;
- the presence of a gas boiler operating on carbon monoxide and the use of this heat to obtain superheated steam, which makes it possible to abandon an external source of thermal energy.
Thus, the efficiency of the proposed system is achieved due to the recovery of the exothermic heat of the process and combustion of carbon monoxide obtained from the waste.
A highly efficient system for producing hydrogen from waste by low-temperature pyrolysis and high-temperature gasification in our proposed method includes:
- equipment for grinding and drying waste, pyrolysis furnace, gasifier, low-temperature heat recuperator, high-temperature heat recuperator, steam generator, coke separator, synthesis gas cooling and purification system, hydrogen extraction unit, gas boiler, ash and carbon dioxide hydrogen storage systems.
We propose to perform the separation of hydrogen from synthesis gas using membrane units. This method of separating gaseous mixtures allows hydrogen to be separated from gas streams with minimal losses. The main advantages of membrane units that allow hydrogen concentration are low maintenance costs, simple hardware design and long membrane life. Figure 1. the flow chart of the interconnection of the elements of the proposed system for producing hydrogen from waste is presented.




Где:
1. equipment for drying and grinding waste;
2. pyrolysis oven;
3. gasifier;
4. heat exchanger for cooling synthesis gas;
5. system for cleaning and removing impurities from syngas;
6. Compressor for compression;
7. hydrogen evolution unit;
8. hydrogen storage;
9. low temperature heat recuperator;
10. steam generator;
11. high temperature heat recuperator;
12.CO2 storage
13. gas boiler;
14. water source;
15. coke separator;
16. ash storage.
According to the technology we offer from 5kg. biodegradable waste can be obtained 1kg. synthesis gas and after separation not less than 0.5 kg of hydrogen. Accordingly, 157,000 tons of 15700 tons of hydrogen will be produced. With a minimum selling price of hydrogen of $ 4 / kg, the annual income from the sale of 15,700 tons will be $ 62.8 million.

The basis for this development was the work performed and implemented earlier:
- on the development of an effective technology for producing pure hydrogen from waste, Patent of Ukraine No. 141908 dated 04/27/2020 "Method for the production of hydrogen from agricultural waste";
- on the creation of thermal energy storage systems using storage materials with phase transitions Patent of Ukraine No. 115816 dated 25.04.2017, "Heat accumulator with phase transition";
- for heat recovery from flue gases of solid fuel heating boilers Patent of Ukraine No. 125300 dated 05/10/2018. "Economizer of solid fuel boilers flue gas".



A method for increasing the energy efficiency of electric power generation generated by fuel hydrogen cells.

The European Union has decided to make Europe a climate neutral continent by 2050. To this end, the reduction of harmful emissions into the atmosphere by 2030 should be 55%. Study consortium "Gas for Climate" [1] showed that this can be achieved only with complete decarbonization energy system of the EU. Hydrogen energy plays a decisive role in achieving this goal. One of main ways of development of hydrogen energy is the widespread use of hydrogen fuel elements (VTE). Globally, the hydrogen fuel cell industry continues to strengthen, confidently moving from investment technology projects to a full-fledged commercial industry. Hydrogen fuel cells are promising both for building distributed energy networks and organizing autonomous power supply of remote objects. The fuel for fuel cells can be not only hydrogen, but also methane, which significantly affects the efficiency. Table 1. some of the most common hydrogen fuel cells [2].



Various systems based on VTE for continuous and backup power supply have already been installed in 19 countries of the world. In 2018, the total number of WTE systems in the world totaled 1,127,560 installations. Total revenue forecast from sales of stationary systems at VTE in 2022 is 40 billion dollars. USA. Entering The fuel cell converts hydrogen (methane) and oxygen into electricity with the release of heat. From this up to 60% of energy is converted into electrical energy, the remaining 40% are released with heat. Single fuel the cells produce relatively small electrical potentials, about 0.7 volts. Therefore, for for the production of the required volume of electricity, WTE are collected in fuel hydrogen power plants. Have fuel cell power plants, among all existing types of hydrocarbon fuel power plants the lowest emissions: NOx emission - less than 0.5 ppm; CO2 50% less than gas-fired power plants with conventional technologies. In addition, fuel cell power plants have a number of the following advantages:

- High electrical efficiency;
- Low operating costs;
- High reliability
- Air cooling of the fuel cell power unit;
- Stable voltage;
- Combined production of electricity and heat;
- Insignificant volumes of installation and commissioning works;
- Small amount of service work;
- Convenience of service.
Today, there are already many manufacturers of ready-made integrated systems for VTE, which have proven themselves well in the world market. You can point to some:
- The ReliOn company has been manufacturing and supplying complex systems for VTE since 1995, which are used in more than 30 countries.
- The Danish company Dantherm Power develops and supplies systems for VTE, based on the fuel cells of the Bollard Power System.
- The German company FutureE, headquartered in Stuttgart, focuses on the development and supply of innovative, efficient hydrogen fuel cell systems.
- The Italian company "ACTA" has been supplying electrolysers since 2004, and since 2012 the company has begun to produce systems "ACTA POWER", based on fuel cells, working in conjunction with a hydrogen generator.


Energy recovery of waste heat.

In recent years, the desire to maximize the use of waste heat from various processes has been noticeable rose. The simplest option is to use waste heat for central heating systems. residential buildings and areas. But for this it is necessary that such a consumer is in close proximity to heat source. In addition, the temperature of the waste heat is often higher than that required by the systems. central heating, therefore, a significant portion of the energy is wasted. It is also very often necessary in heating is limited. For this reason, small power plants are being developed based on the principle organic Rankine cycle (ORC). If the waste heat from the fuel cell is disposed of and also generate electricity from it, then its efficiency can be increased to 76%. Therefore, in the proposed method waste thermal energy in the amount of up to 40%, released by fuel hydrogen cells used to generate additional 16% of electricity. Converting waste heat to electricity allows you to place power plants in any required place and transfer this energy to many consumers on high-voltage power grids. Based on hydrogen fuel cells stationary power plants have already generated more than 300 million kilowatt-hours of electricity for more than 80 stations around the world [5]. To date, the international markets of the USA and Europe have already been introduced power plants on fuel cells of a large range in terms of capacities, up to several megawatts in one unit. Hydrogen fuel cell primary power supply systems occupy a special place in the HFC industry. In practice, these systems are part of future systems of mass power supply on an environmentally friendly fuel. Already today, these systems make it possible to successfully solve energy supply problems in cases where it is difficult access to existing power grids, or in cases where there is no free capacity to connect new ones consumers. The following companies dominate the world market of primary autonomous energy supply:

- "FuelCell Energy" (RKTE / MCFC, 300 kW);

- Bloom Energy (SOFC / SOFC, 200 kW);

- "ClearEdge Power" (PAFC, 400 kW).

The technological scheme for converting waste low potential heat released by fuel hydrogen cells is shown in Fig. 1.



The low potential thermal energy released by the hydrogen cell is stored in the accumulator tank and beyond It is also converted into electricity produced using the organic Rankine cycle (ORC). The cycle uses an organic low-boiling working fluid (LWL) to create steam, which can be used, for example, liquid pentane С5Н12, which after a temperature of +36 ˚С turns into a gaseous state. Examples of other organic low boiling liquids are hydrocarbons (butane, propane), freons (R11, R12, R114, R123, R245 + a), ammonia, toluene, diphenyl, silicone oil, etc. At the beginning, low potential heat from the hydrogen cell enters the accumulator tank, where it heats the OHRG, converting it into steam. ORC units handle waste heat with low and medium thermal potential in the temperature range from 40 to 90 ° C. Further, the steam of the organic liquid enters the steam turbine, where it does work, while the generator located on the same shaft with the turbine, generates electricity. Thus, the incoming heat flow from the accumulator tank ORC is transformed into electrical energy with an efficiency of up to 25-26% and also releases up to 75% of waste heat. To increase the efficiency of the ORC, we propose the waste heat spent after the turbine to also be used for preheating the organic working fluid. For this, an economizer (recuperator) is added to the cycle. heat. After taking off the heat from the cooling circuit of the generator, steam is returned to the evaporator, where additionally heats and evaporates the OHRG. This makes it possible to additionally accumulate heat energy in the tank and accordingly, increase the efficiency of the cycle by at least another 10% and bring it to 35%. There are two technologies today recovery of heat taken after the generator. One technology provides for the use for this purpose intermediate heat carrier (for example, water), the second technology of direct recovery - without intermediate coolant. Efficiency of heat recovery systems of exhaust gases after the generator with the use of an intermediate heating medium is naturally lower than with direct heat recovery. On the other hand, with direct heating, the OHRF can be heated by the exhaust gases to higher temperatures, which can lead to its fire or degradation.

Today, a number of companies are known that are engaged in the research and serial production of installations operating on ORR. These include the Italian Turboden srl, the American Ormat Technologies Inc, the German ADORATEC GmbH, GMK GmbH, the Russian company BPC Engineering, a distributor of Capstone Turbine Corporation (USA).

Capstone Turbine Corporation manufactures ready-made ORC turbine units with a unit capacity of 50 and 125 kW (WHG50, WHG125) for autonomous power generation systems. Figure 2 shows a general view of the Capstone ORC turbine [3].




The purpose of the technology we propose was to develop an effective and reliable way to accumulate waste heat energy at all stages of its conversion into electrical energy. In our proposed method, the utilization of low potential heat is carried out two times:

- for the first time due to the accumulation in the tank of 40% of all external energy supplied to the hydrogen fuel cells, which makes it possible to increase the efficiency of electricity generation by the ORC by 6%.
-vtoroy raz za schet rekuperatsii tepla posle turbiny/generatora, chto pozvolyayet povysit' effektivnost' vyrabotki elektroenergii OTSR yeshche na 10%. - the second time due to heat recovery after the turbine / generator, which allows increasing the efficiency of electricity generation by the ORC by another 10%. In total, the proposed method can bring the utilization rate of the primary energy entering the hydrogen cell up to 76%. Capital investments in 1 kW of installed capacity of a power plant with ORC are about 1-2.5 thousand US dollars
The key element of such systems for converting the low potential heat of hydrogen fuel cells into electrical energy is a thermal energy storage tank based on a heat storage material with phase transitions. It, firstly, actually accumulates thermal energy, and secondly, due to the heat-accumulating material with a phase transition, it maintains a constant temperature of the carrier for a long time (Fig. 3), which allows the turbine of the OPC cycle to operate stably. The working area of ​​the cycle is between points D and F.

Fig. 3. Graph of temperature change in a storage tank with heat storage material.



The technology we propose belongs to the field of heat engineering and can be used in heat exchange systems designed for the recovery and use of waste waste heat from various sources. It is based on the use of patents of the authors and the results of their implementation:
- UA 115816 from 25.04.2017 "Heat accumulator with phase transitions";
- UA 125300 dated 05/10/2018. "Economizer of solid fuel boilers flue gas".
- v 3 kvartale 2019 goda nami byla vvedena v ekspluatatsiyu v detskom sadike sela Kagarlyk, Belyayevskogo rayona, Odesskoy oblasti «Innovatsionnaya energosberegayushchaya sistema otopleniya i konditsionirovaniya». - in the 3rd quarter of 2019, we put into operation in the kindergarten of the village of Kagarlyk, Belyaevsky district, Odessa region "Innovative energy-saving heating and air conditioning system."
The central element of this system is the phase change storage tank.
- The design of the flue gas economizer developed by us was introduced in the production of solid fuel boilers at the plant Metallist-Shabo Plant LLC.



A common method for recovering and utilizing the waste heat of fuel cells involves heating the water in a hot water tank through a heat exchanger to recover heat and using the heated water for heating systems.

The fuel cell system includes a fuel cell unit 21 housing a fuel cell 7, a recuperative heat exchanger 4, and a hot water storage unit 22 housing a hot water storage tank 1.