WO2007012149A1

WO2007012149A1 - A method of converting organic wastes into fuels

Info

Publication number: WO2007012149A1
Application number: PCT/BG2006/000002
Authority: WO
Inventors: Chavdar Angelov
Original assignee: Chavdar Angelov
Priority date: 2005-07-29
Filing date: 2006-01-17
Publication date: 2007-02-01
Also published as: EA008270B1; EA200600429A1; UA79215C2; EP1969096A1; BG109245A

Abstract

The method is applicable to the utilization of organic wastes through their gasification into synthesis gas with subsequent catalytic conversion of synthesis gas obtained into liquid synthetic motor fuels and (or) valuable chemical products. The method includes a stage of treatment of the wastes with gasifying agent containing oxygen, water vapor and (or) carbon dioxide, at which synthesis gas is obtained, which is subsequently compressed, subject to deep purification from mechanical impurities and compounds of sulphur, nitrogen and heavy metals. Then synthesis gas or synthesis gas mixed with liquid organic wastes is fed into a reactor for synthesis of hydrocarbons and converted into liquid motor fuels and components of basic oils with help of a polyfunctional catalyst.

Description

A METHOD OF CONVERTING ORGANIC WASTES INTO FUELS

FIELD OF APPLICATION

The method for converting organic wastes into fuels is applicable to the utilization of these wastes by their gasification into synthesis gas with subsequent catalytic conversion of the synthesis gas obtained into liquid synthetic motor fuels and (or) valuable chemical products.

PRIOR STATE OF THE ART

A method of converting organic wastes, including their treatment with a gasifying agent - oxygen (air), water vapor and (or) carbon dioxide - is known. After this the gas mixture obtained is subject to decomposition at temperature 950 - 1,050 ⁰C for 1 s, which results in obtaining products of destruction that are immersed in water at temperature 200 - 800 ⁰C for their separation to synthesis gas and low-molecular compounds. The synthesis gas is treated in the presence of a catalyst and liquid hydrocarbons or alcohol compounds, gaseous hydrocarbons and CO₂ are obtained [RU2014346].

The method of converting oganic wastes, consisting in their treatment with a gasifying agent (oxygen, water vapor and (or) carbon dioxide) in the presence of fuel gas [RU2217199] is the closest to the invention and a prototype. Natural gas in the volumetric ratio of oxygen/natural gas from 0.01 to 0.5 is used as a fuel gas. The synthesis gas obtained after gasification is compressed and subject to deep purification from mechanical impurities, compounds of sulphur and nitrogen and heavy metals. Then the compressed and purified synthesis gas or the synthesis gas along with the liquid organic wastes is fed into a reactor for synthesis of hydrocarbons, where it is subject to conversion into liquid motor fuels or into liquid motor fuels and components of basic oils in the presence of a bifunctional catalyst containing oxides of zinc and chromium, or of zinc, chromium and copper, or pf iron, or of cobalt and ruthenium, in combination with an acidic component - a zeolite of the type ZSM-5, Beta, modernite or silicoaluminophosphate. The gasification of wastes is realized in a plasma-thermal way, and sludges from municipal sewage water, partially dewatered to residual humidity not exceeding 50 % of the mass, are used as organic wastes, the gasification of sludges taking place at mass ratio of the oxygen to the natural gas equal to 1:10. In example 2 of the prototype the sludges from municipal sewage water are dewatered to residual humidity 55 % of the mass, heated up to temperature 500 - 800 ⁰C, and fed along with the natural gas and oxygen at mass ratio BIO/natural gas/O₂ = 8:1:0.01 for gasification into a plasma reactor (plasmatron) at temperature 1,100 — 1,300 ⁰C, where a 99-percent decomposition of the organic compounds to CO, CO₂ and H2 is accomplished. The gas mixture obtained (synthesis gas) is cooled by heat recuperation, compressed and purified from mechanical impurities, compounds of sulphur and nitrogen and heavy metals. The synthesis gas purified from impurities is directed, at pressure 80 atm, into a reactor for synthesis of hydrocarbons, where conversion of the hydrogen and carbon oxides takes place at temperature 360 - 420 ⁰C with the help of a bifunctional catalyst containing oxides of zinc and chromium in combination with the acidic component - zeolite of the type ZSM-5. The products obtained are cooled and separated in a separator into gas, water and hydrocarbon fraction. The motor fuel obtained is petrol with octane number 92 and features a yield of 140 g per 1 nm³ of synthesis gas for conversion of the carbon oxides above 90 %. The gaseous by-products obtained at the stage of hydrocarbon synthesis are directed to the fuel system of the enterprise. This method has a number of disadvantages, namely:

- To maintain the energy-consuming process of gasification of the organic wastes requires the use of an additional energy source - natural gas or biogas, for which the mass ratio between organic wastes and natural gas in converting the sludges from municipal sewage water is 1/10, and this is connected with additional expenses and worsening of the economical parameters of the process.

- When domestic waste or sludges from sewage water are used as wastes to be converted, their conversion in a mixture with combustion materials selected from the following groups: masout, waste oils, heavy petroleum residues, or coal slurry, will be possible only if natural gas or biogas is used as an energy source, which is not cost-effective.

- The process of gasification of organic wastes from domestic waste and sludges from municipal sewage water is carried out in a plasma reactor at temperatures 1,100 - 1,300⁰C, which increases significantly the content of undesirable impurities, including oxides of nitrogen and sulphur, in the synthesis gas, and this requires an additional stage of purification.

- The process of gasification of organic wastes from domestic waste and sludges from municipal sewage water is carried out at high temperatures 1,100 - 1,300⁰C, which leads to considerable energy consumption and more rigorous requirements for the materials of the gasification reactor. This means more expensive equipment.

The conversion of the synthesis gas, obtained through gasification of organic wastes (domestic waste or sludges from municipal sewage water) at the stage of hydrocarbon synthesis, is realized by using a bifunctional catalyst containing copper, zinc and chromium oxides in combination with zeolite of the type ZSM-5, or oxides of cobalt and ruthenium in combination with zeolite of the type ZSM-5, or oxides of iron in combination with the acidic component of the zeolite of the type ZSM-5. Using the acidic component of the zeolite of type ZSM-5 in all the catalysts has the following disadvantages:

- Relatively high price of the zeolite of type ZSM-5;

- Short operational period of the catalyst with a carrier of the zeolite ZSM-5;

- Low coefficient of thermal conductivity of the catalyst with a carrier of the zeolite ZSM-5, typical for all oxides of the elements participating in the composition of zeolites. This leads to considerable release of heat, namely 11 - 12 MJ per kilogram of obtained liquid hydrocarbons. Such a release of heat complicates the installations, especially those of the systems for removal of the heat released, which is difficult to realize with the low thermal conductivity of catalyst and carrier. [Radchenko M. N., Kagan D. N., Krechetova G. A., Synthetic Liquid Hydrocarbon Motor Fuel from Natural Gas. Moscow, IVTAN, 1993, p. 223].

The presence in the synthesis gas obtained of considerable quantity of chemical impurities from compounds of nitrogen and sulphur, which are undesirable components at the following stage of catalytic synthesis of liquid hydrocarbons from the synthesis gas, requires an additional stage of purification of the synthesis gas from the compounds mentioned.

All the indicated disadvantages of the prototype do not permit performing the conversion of the organic part of domestic waste and sludges from municipal sewage water with high economical effectiveness.

The task of the invention consists in creating a method of converting the organic wastes into fuels with increased quality of the synthesis gas obtained, increased effectiveness of the synthesis of liquid hydrocarbons and optimized utilization of the catalyst in simplified equipment for the implementation of the method.

TECHNICAL ESSENCE OF THE INVENTION

This task is solved by creating a method of converting organic wastes into fuels, including a stage of treating the wastes with a gasifying agent containing oxygen, water vapor and (or) carbon dioxide, where a synthesis gas is obtained, which is subsequently compressed, subject to deep purification from mechanical impurities and compounds of sulphur, nitrogen and heavy metals. Then, the so purified synthesis gas or the synthesis gas mixed with liquid organic wastes is fed into a reactor for synthesis of hydrocarbons and converted with the help of a polyfunctional catalyst into liquid motor fuels and components of basic oils. It is characteristic that the first stage of gasification is realized at volumetric ratio of the organic wastes/activating gas in the range from 5 to 30 and at temperature 600 - 1,000 ⁰C under the action of modulated high-frequency fields in the frequency range from 1 MHz to 50 MKb at modulation frequency in range from 0.5 KHz to 100 KHz. Af the second stage the gasification is carried out under the action of no less than two single-electrode high-frequency discharges generated permanently in the central and upper parts of the reactor. The synthesis gas obtained after the gasification is subject to purification in the presence of non-homogeneous variable electromagnetic fields and non-equilibrium plasma and converted into liquid motor fuels with the help of polyfύnctional catalyst containing oxides of iron, zinc and molybdenum in combination with a carrier, namely aluminium, its oxides and phosphates.

It is possible that the gaseous hydrocarbons, obtained in the process of synthesis of motor fuels from synthesis gas, are subject to oligomerization for obtaining liquid hydrocarbons, this being realized in the presence of a molybdenum-containing catalyst.

An advantage of the method of converting organic wastes into fuels is the increased quality of the synthesis gas obtained, the increased effectiveness of the synthesis of liquid hydrocarbons and the optimized utilization of the catalyst, which simplifies the equipment for the implementation of the method.

EXEMPLARY EMBODIMENT

AND OPERATION OF THE INVENTION

The method is realized with known standard installations, including a stage of high-frequency gasification by treating the wastes with modulated high- frequency fields and a stage of plasma-chemical gasification, realized by means of an action exercised upon the wastes by strongly non-equilibrium plasma from single-electrode high-frequency discharges that are generated directly in the vapor medium. In such a way, a gas mixture of synthesis gas and solid inorganic products is obtained, the synthesis gas being subsequently subject to catalytic conversion into gaseous and liquid hydrocarbons. In this case the gasifying agent contains oxygen, water vapor and (or) carbon dioxide. The synthesis gas obtained is subject to purification from mechanical impurities, compressed and subject to high- frequency plasma-chemical purification from contents of nitrogen, sulphur and heavy metals through the action of modulated high-frequency fields and plasma from single-electrode high-frequency discharges generated in different areas of the purification apparatus. The so purified synthesis gas is directed into a reactor for synthesis of hydrocarbons and subject to conversion into liquid motor fuels or into liquid motor fuels and components of basic oils with the help of a polyfunctional catalyst containing oxides of iron, zinc and molybdenum in combination with a carrier of aluminium, its oxides and aluminium phosphate. In this the organic component of the domestic waste or of the sludges from the municipal sewage system is used as a converted material.

The process is carried out for a mass ratio of active gas/wastes in the interval 10/4. Further on, the synthesis gas, at pressure 30 - 50 atm (3 - 5 MPa), is directed into the reactor for synthesis of hydrocarbons, where, at temperature 220 - 340 ⁰C, the conversion of the hydrogen and carbon oxides into liquid motor fuels and (or) components of basic oils is performed in the presence of a polyfunctional catalyst. The gaseous by-products, which are obtained at the stage of hydrocarbon synthesis, are directed into a reactor for catalytic oligomerization in order to produce high- octane additions.

The distinguishing features of the invention are:

- The gasification of organic wastes by using an agent that represents a mixture of oxygen, water vapor and (or) carbon dioxide at the first stage is realized under the action of modulated high-frequency fields in the frequency range from 1 MHz to 50 MHz at modulation frequency in the range from 0.5 KHz to 100 KHz.

- The subsequent process of gasification of the organic wastes is carried out under the action of high-frequency fields and plasma from single-electrode high- frequency discharges, which are permanently generated in different areas of the reactor.

- The conversion of the synthesis gas in synthetic motor fuels takes place in the presence of a polyfunctional catalyst containing oxides of iron, zinc and molybdenum in combination with a carrier of aluminium, its oxides and aluminium phosphate.

Choosing the conditions of gasification of wastes is made empirically, the objective being maximum conversion of the organic components of solid domestic wastes.

Another important factor in determining the optimal conditions of gasification is the production of a synthesis gas, the composition of which, namely the ratio H₂/CO, is the most favorable for the further synthesis of hydrocarbons. At that the conditions of gasification, which favor the maximal conversion of the organic components of solid domestic wastes, may not correspond to the conditions, under which synthesis gas with optimal composition is obtained. For instance, raising the temperature of gasification increases the depth of conversion of the organic wastes, but at temperatures higher than 1,000 ⁰C an increase in the quantity of formed by-products is observed, in particular nitrogen oxides, which are undesirable impurities in the final product - the synthesis gas.

Raising the content of oxygen in the vapor-gas mixture used in the gasification leads to an increase in the content of carbon dioxide in the synthesis gas obtained with simultaneous diminishment of the hydrogen content.

Adding carbon dioxide increases the content of carbon monoxide in the synthesis gas obtained.

In the process of gasification of the organic components of solid domestic wastes, when using of a mixture of oxygen, carbon dioxide and water vapor as a gasifying agent, a synthesis gas with low content of hydrogen (15 - 50 volume %) and high content of carbon monoxide (30 - 50 volume %) is obtained. Such a composition of the synthesis gas is not optimal for being used in the production of hydrocarbons by applying the Fischer-Tropsch reaction (the optimal ratio hydrogen/carbon monoxide is 2:2.5). In the prototype, to increase the content of hydrogen in the synthesis gas obtained, energy is additionally transferred into the gasification reactor and natural gas is additionally fed in. Using water vapor instead of oxygen requires additional transferring of heat to the gasification reactor. In the prototype this is achieved at the expense of introducing energy-carrying additions as natural gas, masout, coal or wood shavings in the reactor. Using a plasma-thermal method for gasification at temperatures 1,200 - 1,300 ⁰C is proposed for the transfer of additional energy to the reactor. In this situation the rate of conversion of the organic wastes attains 96 - 99 %.

However, the realization of the gasification process at such high temperatures is obligatorily accompanied by the formation of a considerable quantity of by-products in the synthesis gas, which decreases the conversion rate of the organic wastes.

In addition, the gasification conditions depend significantly on the composition of the organic part of solid domestic wastes. In its turn, the composition of the organic part depends on the specificities of transporting, sorting and storing the wastes.

The facts presented above indicate that choosing the optimal conditions of gasification is made empirically for the various types of domestic wastes and the different regimes of the gasification process.

Example 1: The organic wastes are dewatered to residual humidity of 50 - 60 %, heated up to temperature 500 - 600 ⁰C and fed for gasification, where they are treated with a mixture of water vapor, oxygen and carbon dioxide in the following ratio: wastes/H₂O/CO₂/O₂ = 20/2/0.5/0.5. The process of gasification takes place at temperature 800 ⁰C in two stages: at the first stage an action is exerted by means of modulated high-frequency fields with carrier frequency 1.76 MHz and modulation frequency 0.5 KHz, and at the second stage an action is exerted by means of two permanently generated single-electrod high-frequency discharges in the central and upper parts of the reactor. At that, 90 percent of the organic components of domestic wastes are decomposed to CO, CO₂ and H₂. The synthesis gas obtained after the gasification is subject to purification in the presence of non-homogeneous variable electromagnetic fields and non-equilibrium plasma, after which it is cooled, purified from mechanical impurities, compressed and directed into the reactor for synthesis of hydrocarbons at temperature 300 ⁰C and pressure 30 atm. The synthesis of liquid hydrocarbons is carried out in the presence of a polyfunctional catalyst containing oxides of iron, zinc and boron in combination with a carrier of aluminium and its oxides. The yield of the motor fuels produced is 190 g/nm³ of synthesis gas for conversion of the carbon oxides equal to 98 %.

Example 2: The organic wastes are dewatered to residual humidity of 50 - 60 % and fed for gasification, where they are treated with a mixture of water vapor, oxygen and carbon dioxide in the ratio of wastes/H₂O/Cθ₂/O₂ = 30/2/0.5/0.5. The process of gasification takes place in conditions analogous to those of Example 1. At that, 80 percent of the organic components of domestic wastes are decomposed to CO, CO₂ and H₂. The synthesis gas obtained after the gasification is subject to purification from mechanical and chemical impurities, compressed and directed into the reactor for synthesis of hydrocarbons at temperature 300⁰C and pressure 30 atm. The synthesis of liquid hydrocarbons takes place in the presence of a polyfunctional catalyst containing oxides of iron, zinc and molybdenum in combination with a carrier of aluminium, its oxides and phosphates. The yield of the motor fuel produced is 190 g/nm³ of synthesis gas for conversion of the carbon oxides equal to 98 %.

Example 3: The organic wastes are dewatered to residual humidity of 60 %, heated up to temperature 800 ⁰C and fed for gasification, where they are treated with a mixture of water vapor, oxygen and carbon dioxide in the ratio of wastes/H₂O/CO₂/O₂ = 20/2/0.5/0.5. The process of gasification takes place in two stages: at the first stage an action is exerted by means of modulated high-frequency fields with carrier frequency 30 MHz and modulation frequency 50 KHz, and at the second stage an action is exerted by means of two permanently generated single-electrode high-frequency discharges in the central and upper parts of the reactor. At that, 96 percent of the organic components of domestic wastes are decomposed to CO, CO₂ and H₂. The synthesis gas obtained after the gasification is subject to purification in the presence of non-homogenous variable electromagnetic fields and non-equilibrium plasma, after which it is cooled, purified from mechanical impurities, compressed and directed into the reactor for synthesis of hydrocarbons at temperature 300 ⁰C and pressure 30 atm. The synthesis of liquid hydrocarbons takes place in the presence of a polyfunctional catalyst containing oxides of iron, zinc and molybdenum in combination with a carrier of aluminium, its oxides and phosphates. The yield of the motor fuels produced is 190 g/nm³ of synthesis gas for conversion of the carbon oxides equal to 98 %. The gaseous hydrocarbons that are obtained in the process of synthesis of motor fuels from the synthesis gas are directed for oligomerization, which is performed at temperature 240 ⁰C and pressure 5 atm in the presence of a catalyst containing molybdenum and a carrier of aluminium and its oxides. The obtained mixture of liquid hydrocarbons (oligomers) with octane number 90 is used as a high-octane addition to the motor fuels.

Example 4: The organic wastes are dewatered to residual humidity of 60 %, heated up to temperature 800 ⁰C and fed for gasification, where they are treated with a mixture of water vapor, oxygen and carbon dioxide in the ratio of wastes/H₂O/CO₂/O₂ = 20/2/0.5/0.5. The process of gasification takes place in two stages: at the first stage an action is exerted by means of modulated high-frequency fields with carrier frequency 50 MHz and modulation frequency 90 KHz, and at the second stage an action is exerted by means of two permanently generated single-electrode high-frequency discharges in the central and upper parts of the reactor. At that, 92 percent of the organic components of domestic wastes are decomposed to CO, CO₂ and H₂. The synthesis gas obtained after the gasification is subject to purification in the presence of non-homogeneous variable electromagnetic fields and non-equilibrium plasma, after which they are cooled, purified from mechanical impurities, compressed and directed into the reactor for synthesis of hydrocarbons at temperature 300 ⁰C and pressure 30 atm. The synthesis of liquid hydrocarbons takes place in the presence of a polyfunctional catalyst containing oxides of iron, zinc and molybdenum in combination with a carrier of aluminium, its oxides and phosphates. The yield of the motor fuels produced is 190 g/nm³ of synthesis gas for conversion of the carbon oxides equal to 98 %.

Claims

PATENT CLAIMS

1. A method of converting organic wastes into fuels, including a stage of treatment of the wastes with a gasifying agent containing oxygen, water vapor and (or) carbon dioxide, at which a synthesis gas is obtained, which is subsequently compressed, subject to deep purification from mechanical impurities and compounds of sulphur, nitrogen and heavy metals, after which the so purified synthesis gas or synthesis gas mixed with liquid organic wastes is fed into a reactor for synthesis of hydrocarbons and converted into liquid motor fuels and components of basic oils with the help of a polyfunctional catalyst, characterized by the fact that the first stage of gasification is realized for volumetric ration of organic wastes/activated gas within the interval from 5 to 30 and at temperature 600 - 1,000 ⁰C under the action of modulated high-frequency fields in the frequency range from 1 MHz to 50 MHz at modulation frequency in the range from 0.5 KHz to 100 KHz, and at the second stage the gasification takes place under the action of no less than two single-electrode high-frequency discharges generated permanently in the central and upper parts of the reactor, where the synthesis gas obtained after the gasification is subject to purification in the presence of non-homogeneous variable electromagnetic fields and non-equilibrium plasma and converted into liquid motor fuels with the help of a polyfunctional catalyst containing oxides of iron, zinc and molybdenum in combination with a carrier of aluminium, its oxides and phosphates.

2. A method according to claim 1, characterized by the fact that the gaseous hydrocarbons obtained in the process of synthesis of motor fuels from synthesis gas are subject to oligomerization for producing liquid hydrocarbons, this being performed in the presence of a molybdenum-containing catalyst.