NEW APPROACHES to PLASMA GASIFICATION SYSTEMS

NRC “Kurchatov institute”Complex of Physical & Chemical Technologies

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

Sergey Korobtsev, Boris Potapkin, Dmitriy Medvedev, Alexandr Pereslavtsev

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

EXPERIMENTAL SET-UP

(Discharge Chamber)

coal steam reforming assisted by pulse barrier discharge (DBD):

С + Н2О → Н2 + СО

water

vapor

input

coal syn-gas

output

high

voltage

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.

0

200

400

600

800

1000

0 50 100 150 200 250

L ,mm

T,oC

1

2

Temperature distribution along reactor axis (1 – before and 2 – after

optimization)

Luminescence of pulse barrier discharge in the

bulk of coal grains.

4

HYDROGEN PRODUCTION in PLASMA ASSISTED PROCESS of COAL STEAM REFORMING

EXPERIMENTAL RESULTS

Syn-gas energy cost vs. reactor temperature

(vertical position, water – 45 g/h, discharge power – 20 W)

Amount and composition of syn-gas produced

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).

A B

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.

high temperature DBD reactor

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.

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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)

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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

Plasma-melt technology of waste/coal gasification

8

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

MAIN STAGES of the GASIFICATION PROCESS

BENEFITS of the TECHNOLOGY

CxHy + x/2 O2 х CO +у/2 H2

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.

Plasma-melt technology of waste/coal gasification

EXPERIMENTAL SET-UP

Experimental system - Inductive Melt Furnace

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Plasma-melt technology of waste gasification

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

EXPERIMENTAL RESULTS of the PROCESSING of HYDROCARBON-CONTAINING MATERIALS (Petroleum sludge and

Tar)

Petroleum sludge composition, wt %:

• mechanical impurities 50,6

• oil products 19,3

• mass fraction of water 25,9

Elemental composition of the samples

The synthesis gas content of the gaseous products is in good agreement with the inverse logarithmic dependence on the

consumption of sludge10

Time evolution of synthesis gas composition, rubber

gasification

Plasma-melt technology of waste gasification

A SUMMARY of the EXPERIMENTAL RESULTS

Synthesis gas composition (model mixture –

municipal solid waste)

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.

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Simulation of Plasma–melt Reactor

and Optimization of Process Parameters

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.

Flow lines and the absolute velocities of a liquid phase (m/s).

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.

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

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.

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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.

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

biomass

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).

Technology scheme of waste treatment plant

LOW TEMPERATURE PLASMA TECHNOLOGIES for TREATMENT of SOLID WASTES

• 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.

Products: syn-gas and inert

glasslike slag

Shaft furnace of the plant:

1 - loading unit; 2 - shaft; 3 - melter;

4 – box for receiving slag; 5 -

plasma torch; 6 - slag discharging

unit; 7 - output of gas.

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.

Complex for processing of low-activity waste (Novo-Voronezh Nuclear Power Plant)

The chamber of melter EDP-200 plasma torches

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

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.

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

with controlled temperature and gas composition and to carry out plasma

chemical reactions of waste treatment.

EDP-200

EDP-600

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• Microwave plasmatrons

• RF plasmatrones

• High voltage (high pressure) arc plasmatrons

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.

High voltage variant of Arc Plasma Torch

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 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

power - up to 50 kW

frequency - 915 MHz

Dragobytch,

Oil refinery plant

power - up to 500 kW

frequency - 915 MHz

Moscow,

NRC «Kurchatov institute»

power - up to 500 kW

frequency - 915 MHz

Orenburg,

Gas-processing plant

VARIANTS of POWERFUL MICROWAVE PLASMATRONS

(for industrial applications)

For technical realization of the hydrocarbon conversion technology19

PLASMA TECHNOLOGIES for GASIFICATION PROCESSES

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.

summary

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.