WO2018164654A1

WO2018164654A1 - The method of plasma-arc heating and pyrolysis of waste of complex substances

Info

Publication number: WO2018164654A1
Application number: PCT/UA2018/000023
Authority: WO
Inventors: Volodymyr KOLODOCHKA
Original assignee: Kolodochka Volodymyr
Priority date: 2017-03-10
Filing date: 2018-03-12
Publication date: 2018-09-13

Abstract

The present invention discloses a method of plasma-arc heating and pyrolysis for wastes of complex substances, including substances from high molecular compounds, comprising the following steps: providing a voltage and establishing a direct arc (3) between a hollow graphite electrode (11) and fine coke (17), placed in an active type porous heater (16), and regulating amperage, power and arc's length.

Description

THE METHOD OF PLASMA-ARC HEATING AND PYROLYSI S OF WASTE OF

COMPLEX SUBSTANCES

The invention itself relates to the field of electrical engineering, and more specifically to the method of plasma-arc heating of materials, and can be used in electrothermal

equipment for heating, pyrolysis and conversion of conductive and non-conductive materials, as well as of wastes of complex substances, in particular, including substances from high- molecular compounds .

To heat, pyrolyze and convert the wastes of complex

substances and substances from high-molecular compounds, the heat of low-temperature plasma, which is generated in plasma torches of indirect action, is used(Zhukov M. F . , Smolyakov V.Y., Uryukov B. A. Electric arc gas heaters (plasma torches). - M. ; Nauka, 1973. 232 p.; Donskoi A. V.·, Klubnikin V. S. Electric plasma processes and installations in mechanical engineering. - L.: Mechanical engineering, 1979. - 221 p.; Ganz S. N . , Melnik A. P., Parkhomenko V. D. Plasma in chemical industry. -Kharkiv. Communist. - -1969. - 178 p.; Experimental research of plasma torches. Edited by an associate member of the USSR Science

Academy Zhukov M. F. Novosibirsk. Science, 1977, - 385 p.;

Plasma usage in chemical processes. Edited by the professor L. S. Poloka. M. : yr. -1970, 255 p.; Karp E. . , Grinchenko N. . , Christophorovich B. G. and others. Research of arc discharge in flame and natural gas combustion outcomes: Sb. tr. - Kyiv:

Scientific idea, 1977. p. 7 - 13) .

However, the technological processes of heating, conversion and pyrolysis of substances from high molecular compounds, based on heating the materials that are processed in the form of

, liquid, powders or pieces of thermal energy of a low-temperature plasma jet, have significant disadvantages, the main of which are :

low temperature of the source of heat - a low-temperature plasma jet, and, as a consequence, a low overall process efficiency; low temperature and unevenness of the temperature field of the heat source of the plasma jet, the small area of heating and pyrolysis zone, which cannot achieve the complete

decomposition of the processed material into simple chemical elements and, as a result, completely neutralize harmful and poisonous substances at the reactor's outlet;

low temperature of plasmatrons' plasma jet of indirect action makes it difficult or impossible to maintain the optimal parameters of the reaction zone (temperature, heat capacity, mass exchange and others) , leads to increased energy

expenditure;

low efficiency of plasmatron of indirect action and, as a result, low efficiency of the pyrolysis process;

small exploitation term of plasma torches of indirect action and their limited capacity;

high voltage of arc discharge (over 1000 V) , which complicates the operation of installations in terms of safety;

complexity of the construction of indirect plasma torches and excessively high costs of cooling water;

difficulties in introducing the recycled materials into the high-heated zone.

A known method of electric arc heating and melting of materials (see Patent UA 61183 A MPK N05V 7/22/Zabarylo O.S., Melnyk CO., Kolodochka V.O. from November 17, 2003 (application dated July 30, 2001, February Π , 2003 bulletin No. 11), which is chosen as a prototype due to which the gas is supplied to the inner hollow electrode, the arcs between the internal and external electrodes, and the heated material are stimulated, amperage is regulated, furnace charge materials are supplied into the arc zone, the internal and external electrodes are moved as to each other and as to other materials, counting that the amperage of each arc burning between the hollow internal and . external electrodes is regulated due to the sequence of location of external electrodes on the circumference of disintegration within the range of 0.5-1.5 from the. rated value, and the amperage of each arc burning between the hollow inner and outer electrodes is regulated with a frequency of l*10^"z to 1* 10^"5 Hz.

The following goals are thus achieved:

even heating of furnace charge materials, melts of metal and slag, which prevents their overheating, selective

evaporation of ingredients and spraying; and finally, the high quality of the obtained material;

sensitive adjustment of heating temperature of the electrodes, reducing their erosion;

- an increase in the heat exchange οί· arc discharges with a heated material that burns throughout the area of electrodes' decomposition.

However, the abovementioned known method also has

imperfections. The regulation of the amperage of the arcs between the internal and external . electrodes in the sequence of their location on the circumference of disintegration within the range of rather wide limits (0.5-1.5) from -the rated value with a frequency of 10~² - 10~⁵ Hz results in:

heterogeneity, low temperature and low volume of heating zone of solid, liquid and gas materials that are being

processed.

violation of the optimal parameters required for pyrolysis reactions (temperature, heat capacity, speed and completeness of mass exchange) ;

- reduction of the main indicators of the final product - completeness of decomposition of the processed materials into simple chemical elements which are subject to neutralization.

In addition, the parameters stated in the prototype do not provide the compliance with the basic conditions - the choice of optimal current strength and arc length, which provide the necessary performance and completeness of processing the materials.

The prototype also does not take into account the influence of the mass of the processed material per unit time on- the heat capacity of the working area, which leads to large fluctuations in the temperature of the reaction zone and violation of the abovementioned optimal parameters of the technological process.

The object of the invention is to improve the known method of electric arc heating by choosing optimal process parameters:

the ratio of amperage of the active and porous active heaters multiplied by the voltage drop on their active supports to the processed material's performance;

the ratio of amperage of the current strength of the arc discharge multiplied by the voltage^' drop on the arc to the processed material's performance;

the ratio of the arc column's length to the processed material's performance. .

To avoid the abovementioned prototype's drawbacks:

heterogeneity, low temperature and small volume of heating zone of solid, liquid and gas processed materials; violation of optimal parameters (temperature, heat capacity, speed and completeness of mass exchange) required for pyrolysis reactions; the reduction of the main indicators of the final product - completeness of decomposition of the recycled materials into simple chemical elements that are subject to neutralization, the process of heating and pyrolysis is^' carried out in three - stage heating of the substance that is being processed.

At the first stage, the preheating of the material in the active type heater is carried out up to the temperature of 1800 - 2000°C by adjusting and maintaining the ratio of the amperage of the active type heater multiplied by the voltage drop on the active resistance of the heater to the processed material's performance (kg/h) within the limits of 1000-1370 (W^«h/kg) . Thus conversion of solid, powdered or liquid material into a gas state and destruction of weak chemical bonds are achieved.

At the second stage, the gaseous material is heated in a porous heater of the active type up to the temperature of 2200- 2300° C by adjusting and maintaining the ratio of active current heater's amperage multiplied by the voltage drop on the active resistance of the heater to the processed material's performance (kg/h) within 900-13350 W*h/kg. Thus maintaining the temperature of the gaseous product at a fairly high level before feeding it into the arc discharge, completing the introduction of the processed material into a high-temperature zone of the arc discharge and reducing the residence time of the material

necessary to heat it in the arc up to the temperature of 4500- 6000° C, as well as increasing the efficiency of heating the material in the' arc are achieved.

At the third stage, the heating of the gaseous material up to the temperature of 4500 - 6000° C by adjusting and maintaining the ratio of the arc discharge' s amperage multiplied by the voltage drop on the arc to the processed material's performance (kg/h) is maintained and adjusted within 950-1250 (W^»h/kg) , as well as by adjusting and maintaining the ratio of the arc column's length (mm) to the processed material's performance (kg/h) in the range of 0.15-0.3 within 14.9-18.1 (mm^«h/kg) . Thus it leads to heating the material up to the temperature of 4500 - 6000° C, complete destruction of the chemical bonds of high - molecular compounds and obtaining a gaseous mixture of simple chemical elements,, as well as to the optimal time of material stay in the arc zone, under which the complete destruction- of all chemical bonds of complex compounds and obtaining gaseous mixture of simple chemical elements are achieved.

In contrast to the prototype, at plasma-arc heating and pyrolysis of waste of complex substances and substances from high - molecular compounds, the heating and pyrolysis of the processed materials are carried out not by simple regulation of arc current, but by regulation and maintenance of optimal technological parameters of the process: ^'

ratio of amperage of the active and porous active heaters multiplied by voltage drop on the active supports of the heaters to the processed material's performance;

ratio, of amperage of the arc discharge multiplied by voltage drop on the arc to the processed material's performance; ratio of arc column's length to the processed material's performance.

Maintenance of optimal, parameters of the process is carried out by regulation of:

efficiency of processing of substances from high- molecular compounds;

amperage of active and porous active heaters;

amperage of arc discharge;

arc column's length.

The optimal limits, of the abovementioned parameters are determined experimentally, because it is impossible to find them by calculation due to^' the complexity of the processes:

heat exchange in the zone of pyrolysis reactions; high-temperature physical and chemical pyrolysis reactions;

determination of the main parameters of the arc and dynamics of its combustion in multicomponent high-molecular gas mixtures.

The essence of this invention will be understood more clearly under consideration of examples of its implementation and the attached drawing .

Fig . 1 shows the main type of device for plasma-arc heating and pyrolysis of complex substances. The heating and pyrolysis of complex substances are carried out in a sealed two-chamber reactor. The lower (1.9) and upper (15) reactor chambers are coated with refractory material from the inside.

In the lower chamber there is an active type heater (1) , in which the fine coke or helix layer of a material with high electrical resistance (21) is used as an active resistance . The electric power of the heater of the active type is carried out from the source (22), whose current can be regulated in wide ranges. For the feeding the processed material, a mechanism with a bunker (2) is provided on the surface of the active type heater (1). The working space of the lower (19) and upper (15) chambers is separated by, a porous heater of active type (16), through which the gaseous mixture (20), which was formed as a result of heating in the heater (1), pass'es through. As an active resistance in a porous heater of active type, a^' layer of fine coke (17) is used. The power supply of the porous heater of , active type is carried out from the source (18), whose current can be regulated in wide range. The hollow graphite electrode (11) is located on the lid of the upper chamber (15) , in the mechanism of t,he device, in a water cooled electrode (13), which is insulated from the lid by an insulator (14). ^'The mechanism of installation of the electrode provides the possibility^' of

. adjusting the length of the arc in wide ranges. The arc

discharge (3) is stimulated between the graphite electrode (11) and fine coke (17) of the porous heater of the active type (16) . The electric power of the arc (3) is carried out from the source (4), whose current can be regulated in wide range. A gaseous mixture of simple chemical elements (12) formed as a result of its high temperature processing in arc discharge (3) is fed through a cavity of a graphite electrode to a filtering device (5) for hardening and cleaning it from solid particles.

' Neutralization of harmful and poisonous gases, which can be in a gaseous mixture of simple chemical elements, is carried out in the system of filters (6, 7, 8, 9),, -after which the products of pyrolysis are thrown into atmosphere through the. pipe (10) . The control over composition of the exhaust gas is provided by the appropriate device (such as a chromatograph or gas

chrpmatograph) .

Plasma-arc heating and pyrolysis of waste of complex substances are carried out in the following way. Before starting the process, fine coke layer (21) and (17), respectively, is loaded into the active. type heater (1) and the porous heater of the active type (16) . The feeder (2)· of the processed material gets the loaded material, after which the feeder is sealed. The lower (19) and upper (15) chambers are also sealed. Electric power supply (22) of the active type heater (1) is switched on, regulating the amperage and power of the heater (1) . The power source (18) of the porous heater of active type (16) is switched on, regulating the amperage and power of the heater (16) . The electric supply of arc discharge (4) is switched on, the arc discharge (3) between the surface of the fine coke (17) and the graphite electrode (11) is stimulated by contacting the

electrode (11) with fine coke's surface (17), adjusting the arc's length, amperage and arc's strength (4). The processed material from the feeder is supplied to the surface of the fine coke (21) of the active type heater (1) .

The processed material is heated in a heater of active type (1) up to the temperature of 1800-2000°C, at which it passes into the gaseous state_. (20) . This process is accompanied by a rupture of weak chemical bonds and an increase in the pressure of gases in the lower chamber (19) . The gaseous mixture (20) passes through the cavities of the porous heater of active type (16) under the action of the high pressure and is heated up to the temperature of 2200-2300°C, increasing in volume. The gas mixture heated to this temperature under the action of the high pressure of gases in the upper chamber passes through the arc (3) and is heated up to the temperature of 4500 - 6000°C. This process is accompanied by a rupture of all chemical bonds, resulting in a gaseous mixture of simple substances (12) which, under the action of the high pressure of gases in the upper chamber, flows through the cavity of the hollow electrode (11) into a filter device (5) for its hardening and purification from solid

particles . After the device (5), the gas mixture is sent to the filters (6, 7, 8, 9), in which the chemical cleaning of the gas mixture from harmful and poisonous gases is carried out. The gas mixture is released into the atmosphere purified from harmful and poisonous gases.

Further, the invention is depicted by description of the specific implementations.

Example

The proposed method of plasma arc heating and pyrolysis of wastes of complex substances - polyvinylchloride in particular- was tested experimentally. The device itself was a sealed two- . chamber reactor, coated with refractory material from inside.

In the lower chamber there was an active type heater (1) , in which an 85 mm thick fine coke layer was used as an active resistance. The dimensions of the working surface of the heater (fine coke layer) were the following: width - 200 mm and length - 300 mm. The power supply of the active type heater was carried out from a transformer with a regulated voltage in the range of 35-67 V, and regulated amperage within 300-800 A. As a material to be processed, polyvinyl chloride was used, which in the form of pieces 30·30·5 mm was fed to the working surface of the active type heater from the sealed hopper of the feeder' s

mechanism. The working space of the lower and upper chambers was separated by a porous heater of the^" active type, in which an 85 mm thick fine coke layer was used as an active resistance, with the width of the working surface at 180 mm, the length at 250 mm. The power supply of the porous heater of the active type was carried out from the same transformer used to power the active type heater .

A hollow graphite electrode with a diameter of 75 mm, with an aperture of 12 mm in diameter, was placed on the lid of the upper chamber in a water-cooled electrode separated from the lid by an insulator. The electric power of the arc was carried out from a source with an- idle voltage of 120- 360 V, the current strength of which could be regulated within 100-500 A. The mechanism of electrode's installation allowed adjusting the length of the arc within 0-150 mm during the process.

Cooling and cleaning of the gas mixture from solid

particles, as well as chemical purification of the gas mixture, ^" from chlorine and hydrogen chloride in particular, were carried out in the following filters:

In. a water type one, the water of which interacts with chlorine, producing hydrogen chloride and hypochlorous acid, which can later be used in various industries; a water solution of limestone or quicklime; these solutions actively interact with hydrogen chloride and

hypochlorous acid, forming calcium salts, which can further be used in various industries;

carbon tetrachloride in which there is well-soluble chlorine.

The control of volumetric percent of chlorine content at the output from the second chamber is carried out by a

chromotograph .

Pyrolysis of polyvinyl chloride was performed in the form of pieces of 30·30·5 mm.

Before starting work the processed material was loaded to the feeder's bunker. The lower and upper chambers, as well as the feeder, were sealed. The power sources of the active type heater and porous heater of active type were switched on. The current strength of the active type heater and the porous heater of active type were regulated within the limits of 400-1100 A and 500-1500 A respectively. The arc discharge source was switched on and the arc was stimulated by contacting the

electrode with the surface of the porous heater of the active type with the following separating and adjusting the arc's length within 20-70 mm. The processed material was supplied to the surface of the active type heater with a productivity of 3θ^' kg/h, with its following performing heating and pyrolysis in the active type heater, the porous heater of the active type and in the arc discharge. In the process, the force of the current of the heaters and the arcs was regulated within the optimum, smaller and larger values of the ratios indicated in the

invention's formula. The arc's length was also adjusted within the optimum, smaller and larger values of the ratios indicated in the claims. In the process of experiments on plasma arc heating and pyrolysis of polyvinyl chloride, the electrical parameters of the heaters (current strength and voltage drop on active supports) , the strength of current and the voltage drop on the arc, the temperature of the gas mixtures, the efficiency of the fed processed material, the volume content of chlorine in gases after' processing them in an arc discharge, - were

measured.

Data on the measurement of technological and energy

parameters of the process of plasma-arc heating and pyrolysis of polyvinyl chloride in the four variants of changing parameters are presented in tables 1 - 4.

As it can be seen from the data presented, the high

efficiency of the process, the percentage of the processed material's transformation (polyvinyl chloride) into the gaseous state, the optimum values of temperatures of the gaseous product after heating it with the active type heater and temperature of the gaseous product before entering it into the arc discharge after the porous active type heater match the following

regulation limits:

the ratio of the active type heater' s amperage multiplied by the voltage drop on the active resistance of the heater to the productivity of the processed material;

the ratio of the active type porous heater's amperage ^' multiplied by the voltage drop on the active resistance of the heater to the productivity of the processed material;

the ratio of the arc discharge's amperage multiplied by the voltage, drop on the arc to the productivity of the processed material;

- the ratio of the length of the arc column to the efficiency of the processed material in the degree of 0.15-0.3.

The proposed method of plasma-arc heating and pyrolysis of complex substances can be used for the processing and conversion of industrial, household and medical waste. Table 1. Energy and technological parameters of plasma-arc heating and pyrolysis of polyvinyl chloride

Table 2. Energy and technological parameter^'s of plasma-arc heating and pyrolysis of polyvinyl chloride

Table 3. Energy and technological parameters of plasma-arc heating and pyrolysis of polyvinyl chloride

Table 4. Energy and technological parameters of ^'plasma-arc heating and pyrolysis of polyvinyl chloride

Claims

The method of plasma-arc heating and pyrolysis of waste of complex substances, under which the voltage between hollow graphite electrode and the material to be heated is provided, the arc of direct action between the hollow graphite electrode and the material to be heated is stimulated, the amperage, power and arc's length are regulated, characterized that the power is supplied to the active type heater, and the ratio of the active type heater's amperage multiplied by the voltage drop on the active resistance of the heater to the productivity of the material, is maintained and regulated within 1000-1370 (W»h/kg) , the power is supplied to the active type porous heater, counting that and the ratio of the porous active-type heater's amperage multiplied by voltage drop on the active resistance of the heater to performance of the processed material is supported and regulated within -900 -1350 (W^«h/kg)., and the ratio the arc discharge's amperage multiplied by^' the voltage drop on the arc to performance of the processed material is supported and regulated within 950-1250 (W'h/kg), and the ratio of the arc column's length to performance of the processed material in the degree of 0.15-0.3 is maintained and regulated in the range of 14.9-18.1 (mmh/kg) .