NEW APPROACHES to PLASMA GASIFICATION SYSTEMS

Sergey Korobtsev, Boris Potapkin, Dmitriy Medvedev, Alexandr Pereslavtsev

NRC “Kurchatov institute” Complex of Physical & Chemical Technologies

Kurchatov sq., 1, 123182 Moscow, RUSSIA www.nrcki.ru CONTENT

 Introduction

 Examples of plasma implementation to gasification processes:

 Coal steam reforming assisted by pulse barrier discharge

 Plasma-melt method of waste/coal gasification

 Plasma torch in combination with shaft furnace

 Plasma systems for waste/coal treatment

 Summary

2 PLASMA TECHNOLOGIES for GASIFICATION PROCESSES

The gasification of coal as well as of solid domestic and industrial wastes is an important task, as it allows not only to efficiently use solid hydrocarbons as energy or chemical raw materials, but also to fulfill high environmental standards and requirements set in energy technologies.

These plasma processes and/or plasma assisted processes can be a convenient tool to modernize the traditional and create completely new high-performance technologies to process hydrocarbon raw materials (including - carbonaceous wastes) and obtain an effective energy carrier – syn-gas (hydrogen) and then use it in the energy sector, chemical industry, etc.

Plasma processes are characterized by extremely high specific productivity (more than 100 times in comparison with catalytic processes), low metal capacity and absence of inertia, they are ecology friendly. HYDROGEN PRODUCTION in PLASMA ASSISTED PROCESS of COAL STEAM REFORMING Within this study, we investigate the possibility of increasing the efficiency of thermal gasification by generating active particles in cold plasma without an increase in the average temperature in the gasifier.

EXPERIMENTAL SET-UP (Discharge Chamber)

coal syn-gas coal steam reforming assisted by pulse barrier discharge (DBD): output С + Н2О → Н2 + СО

1000

800

600 C

water o

vapor T, 400 1 input 2

200

Luminescence of pulse barrier discharge in the 0 high bulk of coal grains. 0 50 100 150 200 250 voltage L ,mm Temperature distribution along reactor axis (1 – before and 2 – after optimization) 4 HYDROGEN PRODUCTION in PLASMA ASSISTED PROCESS of COAL STEAM REFORMING

EXPERIMENTAL RESULTS

Amount and composition of syn-gas produced A B depending on water vapor at the reactor input (vertical – A and horizontal - B position, temperature 720оС).

Amount of produced gas and water conversion degree depending on water flow rate at the reactor input (vertical position, temperature 720оС).

Syn-gas energy cost vs. reactor temperature (vertical position, water – 45 g/h, discharge power – 20 W)

5 HYDROGEN PRODUCTION in PLASMA ASSISTED PROCESS of COAL STEAM REFORMING

 In the process of steam gasification of coal stimulated by nonequilibrium plasma the concentration of hydrogen in the output reaches 60% when energy consumption for plasma generation is less than 0.5 kWh/m3.

 It is shown that by using plasma, the temperature of the gasification process falls to 100oC while maintaining the performance.

 The use of plasma allows to control the process of gasification (productivity, output gas content, working temperature) by changing electric parameters and geometry of the discharge.

high temperature DBD reactor

6 Plasma-melt technology of gasification of coal, solid and liquid hydrocarbons, biomass

The research is aimed at developing a process, where the gasification, vitrification and binding of neutral components, as well as purification of the gas of sulfur and other harmful impurities are carried out in a single step, wherein the gasification product is mainly syngas. Such process can be organized in a melt metal.

Simplified scheme of wasteless plasma melt conversion of solid municipal wastes into syn-gas (hydrogen)

7 Plasma-melt technology of waste/coal gasification

BENEFITS of the TECHNOLOGY

 high specific production rate;  pollution free;  production of pure syn-gas in ideal plug flow regime;  absence of problems with solid rest;  treatment of any type of hydrocarbon waste, coal and biomass;  binding of sulfur and other harmful substances

MAIN STAGES of the GASIFICATION PROCESS

 Chemical dissolution of О2 in the melt with Me oxides formation

 Hydrocarbons pyrolysis with production of Н2 and carbon diluted in the melt  Reduction of Me oxides by carbon and СО production

CxHy + x/2 O2 х CO +у/2 H2

8 Plasma-melt technology of waste/coal gasification

EXPERIMENTAL SET-UP

Functional diagram of the laboratory installation for the conversion of different types of carbon-containing raw materials (including solids, liquids, and gases) into synthesis gas: (1) air supply line, (2) water supply line, (3) solid raw material supply line, (4) liquid raw material supply line, (5) raw gas supply line, (6) heat-transfer agent (reaction medium) supply unit combined with a slag removal unit, and (7) reactor unit. Experimental system - Inductive Melt Furnace

9 Plasma-melt technology of waste gasification

EXPERIMENTAL RESULTS of the PROCESSING of HYDROCARBON-CONTAINING MATERIALS (Petroleum sludge and Tar) Elemental composition of the samples Petroleum sludge composition, wt %: • mechanical impurities 50,6 • oil products 19,3 • mass fraction of water 25,9

Synthesis gas content of the output mixture on the conversion of slime as a function of feed rate: (1) dry slime (2) slime diluted with 10% water The synthesis gas content of the gaseous products is in good agreement with the inverse logarithmic dependence on the consumption of sludge 10 Plasma-melt technology of waste gasification

A SUMMARY of the EXPERIMENTAL RESULTS The experimental data indicate that, in the process of converting petroleum slimes and tar in melted metal the introduction of a desulfurizing agent (50% CaO, 40% SiO2, 10% Al2O3) into the melt reduced the amount of sulfur-containing substances in the melt and the gaseous products of the process. The composition of the hydrocarbon fraction of the effluent gas from the melt did not changed. It was established that, under the conditions of the experiments, only about 10% of sulfur was carried off with gas, whereas 90% of sulfur was absorbed by the desulfurizing slag. Thus, the experiments confirmed the technological efficiency of processing petroleum slimes and tar into syn-gas in melted metals (carbon steel and cast iron). The concentration of syn-gas in the gasification products (of the test samples of oil wastes in the experimental melt reactor) was as high as 95 % vol in the case of slime sinking to the depth of 8–10 cm under the melt surface. In this case, the products did not contain any soot, whereas the sulfur accumulated mainly in the slag above the melt.

Synthesis gas composition (model mixture – Time evolution of synthesis gas composition, rubber municipal solid waste) gasification 11 Simulation of Plasma–melt Reactor and Optimization of Process Parameters The calculation of the thermal characteristics of a medium-scale melt reactor and the optimization of process parameters (at this level of productivity) have been carried out. Thermophysical characteristics were calculated for a 50-ton melt reactor with bottom blowing. Under optimum operating conditions, this reactor can ensure productivity at a level of 30000–40000 m3/h (NTP) of syn-gas.

Geometric dimensions of the model of a 50-ton melt reactor. Sizes are given in meters. The walls of the reactor and eight bottom tuyeres are shown.

This optimization made it possible to determine a permissible range of the moisture content of the raw material, which ensures a total neutral energy balance, and to calculate the composition of the Flow lines and the absolute velocities of a liquid phase (m/s). syn-gas.

Composition of synthesis gas upon the tar gasification at thermoneutral points with complete recovery and without the heat recovery of waste gases. Pressure, 1 atm; temperature, 1600 K. 12 Plasma-melt technology of gasification of coal, solid and liquid hydrocarbons, biomass

The optimal process is steam-air (-oxygen) conversion when the ratio of air (oxygen) to steam provides a neutral thermal balance (consistency of the temperature in the oven), and an additional amount of the syn-gas (hydrogen) is produced. Prototyping experiments confirmed that virtually all the basic characteristics of the waste gasification process coincided with earlier results of model calculations. That is in particular true for the composition of the gas fraction - up to 95% of the syn-gas. Evaluation of specific productivity (up to 5000 m3/h syn-gas from 1 m3 of melt) is adequate to estimations of the chemical reactions rates in the gasification process of the solid organics in the melted metal. Experiments have also shown that the conversion products do not contain soot, and sulfur accumulates mainly in the slag over the melt.

The catalytic process of producing methanol or dimethyl ether from gasification products was also studied, an experimental reactor was built. INDUSTRIAL and SEMI-INDUSTRIAL SYSTEMS of PLASMA TREATMENT of SOLID WASTES

System for plasma treatment of radioactive waste (state enterprise “Radon”, Sergiev Posad city).

Pilot plant for plasma assisted solid waste treatment built in Israel (experimental plasma system with productivity 3500 ton per year).

Complex for plasma treatment of low-activity waste (Novovoronezh Nuclear Power Plant).

Low temperature plasma technologies may be applied for the treatment of different kinds of wastes (solid municipal wastes; industrial wastes; agricultural wastes; medical wastes; radioactive wastes). LOW TEMPERATURE PLASMA TECHNOLOGIES for TREATMENT of SOLID WASTES

Shaft furnace of the plant: 1 - loading unit; 2 - shaft; 3 - melter; 4 – box for receiving slag; 5 - plasma torch; 6 - slag discharging Products: syn-gas and inert unit; 7 - output of gas. glasslike slag Technology scheme of waste treatment plant

• The process of plasma treatment of solid wastes can be reduced to (1) gasification processes of organic part of waste and (2) oxidation of inorganic part of waste into glasslike slag. • Products of plasma treatment are glasslike (basaltiform) slag and syn-gas. Complex for processing of low-activity waste (Novo-Voronezh Nuclear Power Plant)

The chamber of melter EDP-200 plasma torches

Plasma processing of radioactive waste provides a number of significant advantages in comparison with other methods of disposal of radioactive waste. This is primarily waste volume reduction of 50 - 80 times and essentially lower a leakage probability of radioactive elements and vitreous slag ingress into the environment. In some cases, it is possible to obtain a synthesis gas by gasifying the organic component of radioactive waste. Tests have shown that the plasma technology for processing waste of a nuclear power plant improves the economic and environmental efficiency of the management of radioactive waste. Plasma technology solves the problem of radioactive waste resulting from the operation and decommissioning of nuclear power plants, provides processing of previously accumulated radioactive waste. PLASMATRON SYSTEMS for WASTE or COAL TREATMENT The technology of plasma waste treatment based on the use of DC arc plasma torches as a source of heated gas (up to temperatures of 5000 - 8000°C).

Air or CO2 are used as a working gas. This allows to create a high temperature environment in insulated volume EDP-200 with controlled temperature and gas composition and to carry out plasma chemical reactions of waste treatment.

Unique plasma equipment was created in the NRC "Kurchatov Institute" for plasma treatment of waste - EDP-200 arc plasma torches as well as power supply and control systems. Arc discharge is powered by a controlled current source with pulse width modulation performed on IGBT transistors. The control system provides control parameters and controlling the plasma torch operation in a manual or automatic mode, including start-up, work under given parameters and switching off the plasma torch.

EDP-600

17 Plasma torches developed by NRC "Kurchatov Institute"

One of the most significant disadvantages of arc plasma torches is a small life time of the electrodes and a possible contamination of the reaction products by the electrode materials. To overcome these disadvantages other plasmatrons systems have been developed, in the first place - electrodeless.

• Microwave plasmatrons

• RF plasmatrones

• High voltage (high pressure) arc plasmatrons

High voltage mode of arc discharge - transient nonstationary form of gas discharge (close to gliding-arc and glow discharges) characterized by extremely small electrodes erosion. Electrodes life time ~ 10000 hours Power of channel - up to 1 kW Non-cooled Working pressure - 10 bar and higher Volt-ampere and Power-current characteristics of plasma torch in conventional arc mode (1) and in optimized mode (2) - High Pressure Glow Like Discharge.

High voltage variant of Arc Plasma Torch VARIANTS of POWERFUL MICROWAVE PLASMATRONS (for industrial applications)

power - up to 50 kW power - up to 500 kW power - up to 500 kW frequency - 915 MHz frequency - 915 MHz frequency - 915 MHz Dragobytch, Moscow, Orenburg, Oil refinery plant NRC «Kurchatov institute» Gas-processing plant

For technical realization of the hydrocarbon conversion technology 19 PLASMA TECHNOLOGIES for GASIFICATION PROCESSES

summary Most important problems of gasification technologies to be solved: P1. Energy efficiency of the process and energy cost of products; P2. (a) Syn-gas purity and dust content in output gases and (b) toxicity of solid rest; P3. Resistance of a refractory coat and high temperature materials of the reactor/heat exchanges.

Plasma technologies mentioned in this report can help to solve these problems:

Nonequilibrium plasma of DBD discharge helps in: P1. – due to combined character of the process, i.e. plasma assisted water steam reforming of coal; and P3. – lower process temperature due to the use of cold plasma. Plasma melt technology helps in: P1. – by combining partial oxidation and steam reforming processes; P2. – the melt serves as absorber of the dust and the slag as a sulfur absorbent; P3. – the technology allows to reduce the temperature due to the use of special alloys (or, for example, lead) as melt. Plasma in combination with shaft furnace helps in: P1. – due to counter-flow heat exchange; P2(b). – due to solid rest vitrification, but fails to resolve problem 2(a)., i.e. output gas purity. Conclusion

 Thus, the above examples showed that plasma processes or plasma assisting processes can be a convenient tool to modernize traditional and create completely new high-performance technologies to process hydrocarbon raw materials (including – gasification technologies) and obtain an effective energy carrier – syn-gas (hydrogen) to be used in the energy sector, chemical industry, etc.

 Different variants of plasma torches (and accompanying plasma equipment) are currently designed and manufactured for various industrial applications.

 However, the task of improving the plasma technology and adapting it to specific industrial tasks is still relevant, most of all it is necessary to increase the lifetime of the electrodes of arc plasma torches, to increase working pressure, to enhance the efficiency of power supplies, etc.

 Further research and development should be undertaken for the development of an advanced gasification reactor design.

This work was supported by the Ministry of Education and Science of the Russian Federation (state contract no. 14.607.21.0077 of October 20, 2014). Unique identifier of the project: RFMEFI60714X0077. Thank you for your attention !

This work was supported by the Ministry of Education and Science of the Russian Federation (state contract no. 14.607.21.0077 of October 20, 2014). Unique identifier of the project: RFMEFI60714X0077.