ITPR20090048A1 - PROCEDURE AND PLANT FOR THE PRODUCTION OF BIOMASS SYNTHESIS GASES AND / OR WASTE IN GENERAL - Google Patents

Description

TITLE

PROCEDURE AND PLANT FOR THE PRODUCTION OF S INTES I GAS FROM B IOMASS AND / OR F IUT I IN GENERAL

DESCRIPTION

The present invention relates to a process and a plant for the production of synthesis gas

Several processes are already known for the production of synthesis gas, in the technical jargon defined SINGAS, which can be used as a fuel or for industrial uses such as for the production of methanol, methane and hydrogen.

In all the processes used up to now that involve the use of one or two reactors, the synthesis gases formed by CO (carbon monoxide) and H2 (hydrogen) are polluted by other highly harmful substances which must be separated and eliminated.

A process described in patent EP 153235 two reactors were used: in the first there is a gasification at medium-high temperature from 700 - 800 ° C lower than the melting temperature of the products introduced

In the second reactor, to increase the conversion temperature, the gas temperature was brought to a value between 3000 - 5000 ° C by passing said gas through a plasma torch placed at the outlet of the gas supply circuit. second high temperature reactor.

This process, with high energy consumption, does not solve the problem of eliminating polluting products

The purpose of the present invention is to obtain a synthesis gas practically free of pollutants and that is containing carbon monoxide, hydrogen and a modest percentage of nitrogen (around 0.1%) and carbon dioxide (around 2- 3%) with a lower calorific value of 11,400 Kj / Nmc.

The gas has the advantage of being free of sulfuric and sulfur dioxide, hydrochloric acid, chlorinated hydrocarbons, hydrogen cyanide and hydrofluoric acid, polycyclic aromatic hydrocarbons (PAHs) and dusty compounds of coke carbon.

Said objects and advantages are all achieved by the process and by the plant, both of which are the subject of the present invention, which is characterized by the provisions of the claims set forth below.

This and other characteristics will be better highlighted by the following description of an embodiment illustrated, purely by way of non-limiting example, in the accompanying drawing tables in which:

Figure 1 schematically illustrates the plant which also constitutes the block diagram of the process;

Figure 2 shows a detail of the radical reactor according to a longitudinal section;

figure 3 shows the detail of figure 2 sectioned along the plane B-B.

With particular reference to figure 1, the procedure provides for the pre-treatment of laceration and shredding 1 of the material to be processed to bring them to a uniform size not exceeding 50 mm, a first drying of the biomass, a second dehumidification in the radical reactor 2 for a more easy degassing of char.

Subsequently, the shredded product is demetallized 3 and placed in a dispenser 4 which mixes the shredded material with any glass waste for a correct vitrification of the ashes and aggregates.

Calcite (CaCO3) can also be added which, transformed into CaO at 500 ° C, has the property of binding in the high temperature reactor with any traces of sulfur and chlorine escaped from the capture of the radical reactor to transform into inert salts of CaSO4 (gypsum ) and calcium chloride (CaCl2).

The radical reactor 2 has the task of deaerating the material which generally incorporates about 1.8 m <3> of air per ton of bulk material.

In the first stage of the radical reactor, the evaporation of the water present in the processed material is also obtained, approximately 95%, which is extracted, realizing a significant energy saving.

The radical reactor also has the task of transferring the treated material to a high temperature reactor 5 while simultaneously absorbing a quantity of heat necessary to bring the mass of the material to a temperature of 600 ° C in a hydrogenating atmosphere (hydrocracking) at low pressure ( 5 bar).

For this purpose in the low temperature reactor the synthesis gas produced in the high temperature reactor circulates in countercurrent and with a helical trend, which indirectly transfers part of its sensitive heat to one or two augers 2a of large initial diameter which move in a slow but continuous the material processed.

The shaft 2b supporting the augers is partially hollow and provides for a plurality of holes 2c located in correspondence with the auger of intermediate diameter for the introduction of synthesis gas rich in hydrogen.

Hydrogen is added in order to activate the reactions of hydrodechlorination, hydrodesulfurization and hydrodealkylation.

The formation of a thin layer of carbon inside the jacket of the augers guarantees very limited wear.

Two conical reductions with subsequent chamber devoid of propellers act as plugs to avoid the return of gases towards the ends.

The radical reactor also has the function of removing all the percentage of water present in the material, the steam that escapes is condensed in 9 and sent to a water treatment plant 8 which can be used as make-up water in other plants.

In this way, decomposition reactions with a radical mechanism shifted towards desired compounds (hydrogenolysis) are obtained.

The nitrogen forms NH3; sulfur is transformed into H2S (idordesulfuration); chlorine is transformed into hydrochloric acid (hydrochlorination) thus avoiding the formation of hydrogen cyanide, sulfur dioxide, carbon sulphide and carbonyl sulphide, all highly polluting and harmful substances.

The formation of halogenated olefin compounds, responsible for the formation of dioxins and furans, is also avoided.

Aromatic hydrocarbons such as toluene, xylene, phenol, cresol are transformed into benzene while olefins are transformed into paraffins (hydrodealkylation).

The pyrolytic gas leaving the radical reactor will be sent to the fractional condensation 6 from which saturated hydrocarbons, tars and pyroligneous liquid will be obtained which will be sent to the high temperature reactor 5

More precisely, the cooling of the pyrolytic gas leads to the fractional condensation 6 from first of the tar oils and subsequently of the condensables (acids, alcohols, etc.) from which, by means of a separator 7, chloride salts are extracted by precipitation, fluoride and ammonium sulfide.

H2S hydrogen sulphide is desulfurated in 10.

The first radical reactor is therefore of the forced fluid bed type heated with synthesis gas at 800 ° C in countercurrent and helically moved

The high temperature reactor 8 is of the vertical type and in the lower part provides start-up burners 11 with oxymethane and lances for the introduction of oxygen for the partial oxidation of the CHAR, that is, of the semi-coke which it was formed in the radical reactor, according to the reaction C 1⁄2 O2 = CO; the partial oxidation of the separated tar in fractional condensation with a mixture of oxygen and steam according to the steam-reforming reaction:

Cn H2n + 2 + n H2O = nCO (2n 1) H2

Cn H2n + 2 + 1⁄2 O2 = nCO (n + 1)

Partial oxidation of carbon with CO2

C CO2 = 2CO

previously formed in the radical reactor.

This last reaction, endothermic and peripherally implemented in the hottest part of the reactor, allows a longer life of the refractories.

In conclusion, three different types of oxidants are used in the high temperature reactor: oxygen, water and carbon dioxide

In the upper area of the H.T. the definitive liberalization of the volatile hydrogen present in the Char is completed.

The feeding of the semicoke into the high temperature reactor takes place from the top and on two sides through two conical augers and the height of the charge varies between 1-3 m, while the axial length of the reactor is proportional to the potential of project.

The SINGAS which is taken from the high temperature reactor to heat the pyrolytic reactor is dedusted by means of a cyclone 12 and the powders are reintroduced into the high temperature reactor.

The SINGAS that comes out of the radical reactor, after having crossed it in countercurrent, has a temperature of about 300 ° C and undergoes a further cooling to be filtered, as a necessary condition to be used in a gas turbine and subsequent steam turbine for the electricity generation.

Claims (10)

CLAIMS 1. Process for the production of synthesis gas from biomass and / or waste in general characterized by providing for: - a first phase of gasification by means of a low-temperature radical reaction at about 550 - 600 ° C to obtain semicoke, pyrolytic and condensable gas; - a second step of gasification by means of a high temperature reaction (about 1700 - 2000 ° C) of said semicoke and condensates; - a step for removing the pollutants present in the pyrolytic gas downstream of the first low temperature gasification step and upstream of the second high temperature gasification step. 2. Process according to claim 1 characterized in that for the removal of the polluting products the fractional condensation of the pyrolytic gas is provided from which: saturated hydrocarbons are obtained; tars and pyroligneous liquid and various salts of chloride, fluoride and ammonium sulphide and others that are easy to remove. 3. Process according to claims 1 and 2 characterized in that the sulfur of the hydrogen sulphide produced in the radical reactor is separated from the carbon dioxide in a desulphurisation plant (7). 4. Process according to claim 1 characterized in that the heating in the first phase is obtained by means of the synthesis gas produced in the second phase at a high temperature in countercurrent with respect to the advancement of the processed material. 5. Process according to claim 1 characterized in that the oxidation in the second phase at high temperature is obtained by introducing more gasifiers (oxygen, CO2, H2O) into the lower part of the reactor 6. Plant for the production of synthesis gas from biomass and waste in general characterized by the fact that it includes: - a first low-temperature radical reactor about 550 -600 ° C which is fed with comminuted and demetallized material; - a second high temperature reactor about 1700-2000 ° C in which semicoke from the first reactor is sent; - a device for the fractional condensation of the pyrolytic gas produced in the first reactor 7. Plant according to claim 1 characterized in that the radical reactor is of the type with auger feeding. 8. Plant according to claim 1 characterized in that the radical reactor comprises one or two augers with variable diameter helices. 9. Plant according to claim 1, characterized by the fact that singas coming from the second reactor is made to pass in countercurrent on the outside of the screw propellers. 10. Plant according to claim 1 characterized in that the augers have a hollow rotation shaft with a plurality of holes to send inside, in a determined area, gas rich in hydrogen throughout the mass.