IT202300003249A1 - PLANT FOR THE RECYCLING OF LIQUID PRODUCTION RESIDUES WITH RELATIVE CONVERSION INTO THERMAL ENERGY - Google Patents

Description

TITLE: PLANT FOR THE RECYCLING OF LIQUID PRODUCTION RESIDUES WITH RELATIVE CONVERSION INTO THERMAL ENERGY

DESCRIPTION

The present invention relates to a system for the recycling of liquid production residues which involves converting them into thermal energy.

Every industrial activity involves the generation of a predefined quantity of residues (and/or waste) that must be disposed of.

For the disposal of industrial waste, companies often have to bear significant costs due to the need to resort to disposal plants with very expensive operating costs.

Some types of waste can be directly recycled (reintroduced into the production cycle), while others require waste-to-energy processes, i.e. their use as fuel in a specific incinerator that converts the heat generated by the combustion of waste into thermal energy that can be used for numerous purposes.

Many industrial wastes are directly combustible, while in others combustion is hindered by the formation of inert substances that interrupt the process and require numerous and complex cleaning operations.

This discussion refers to liquid production residues consisting mainly of carbon (in a percentage between 45% and 65%, preferably with values close to 54%-56%), and also including oxygen (in a percentage between 30% and 50%, preferably with values close to 38%-39%), hydrogen (in a percentage between 3% and 10%, preferably with values close to 6%-6.5%), nitrogen (in a percentage below 0.1%) and any other elements in variable proportions (relative to the missing portion to reach 100%).

From an analysis of the liquid residue which is the subject of this paper, it was found that it has a high calorific value (the lower calorific value is between 20,000 KJ/Kg and 30,000 KJ/Kg; the value detected on a specific sample was approximately 25,500 KJ/Kg) and a low ash content (approximately between 0.03% and 3%; the value detected on a specific sample was approximately 0.3%).

Through direct combustion, which involves the pulverization and/or nebulization of the residual liquid in a combustion chamber, the rapid formation of a sticky foam was observed which solidified after cooling, causing the occlusion of the delivery nozzles and the coating of the entire surface of the combustion chamber, rendering it unusable.

Even by diluting the liquid residues with specific solvents (such as methanol) a reduction of the phenomenon is observed, which however still puts the combustion chamber out of service (although after longer times).

These problems, given the current state of the art, make it impossible to use a liquid processing residue of the type described for its conversion into thermal energy through thermal splitting processes such as gasification, pyrolysis and the like.

The main task of this invention is to solve the problems described above, by proposing a plant for the recycling of liquid production residues with relative conversion into thermal energy that can operate, even continuously, for long periods.

Within the scope of this task, an object of the invention is to propose a plant for the recycling of production residues with relative conversion into thermal energy suitable for treating residues comprising Carbon (in a percentage between 45% and 65%, preferably having values close to 54%-56%), Oxygen (in a percentage between 30% and 50%, preferably having values close to 38%-39%), Hydrogen (in a percentage between 3% and 10%, preferably having values close to 6%-6.5%), Nitrogen (in a percentage less than 0.1%) and any other elements in variable proportions (relative to the missing portion to reach 100%) made liquid by means of at least one respective solvent.

Another purpose of the invention is to propose a system for the recycling of liquid production residues with relative conversion into thermal energy compliant with current regulatory requirements.

Another purpose of the invention is to propose a plant for recycling liquid production residues with relative conversion into thermal energy having high conversion efficiency. Another purpose of the invention is to propose a plant for recycling liquid production residues with relative conversion into thermal energy with low operating costs.

A further purpose of this invention is to create a plant for recycling liquid production residues with relative conversion into thermal energy at low cost, of relatively simple practical construction and safe application.

This task and these goals are achieved by a plant for the recycling of liquid production residues with relative conversion into thermal energy, characterised by the fact that it includes ? a warehouse configured to house biomass of vegetal origin chopped into small fragments,

<? >a tank configured to contain a liquid processing residue,

<? >a first dryer configured for the removal of water from predefined quantities of biomass fragments of plant origin, said first dryer being excludable in the case that said biomass has a moisture content lower than a predefined threshold value,

<? >a mixer configured for the impregnation of dried plant biomass fragments with said processing residue in the liquid state according to a predefined reciprocal dosage,

? a second dryer configured for the removal of volatile substances from said biomass fragments impregnated with said processing residue in the liquid state;

? an apparatus, of the type chosen between a gasifier and a pyrolyzer, configured for the conversion of biomass fragments impregnated with said processing residue in the dried liquid state into fuels of a type chosen between gaseous, liquid and solid, ? a combustor configured for the complete thermal degradation of the gaseous fuels previously obtained and the generation of thermal energy.

This task and this purpose are also achieved by means of a process for the recycling of liquid production residues with relative conversion into thermal energy, characterised by the fact that it consists in the

? dry a predefined quantity of plant biomass fragments, extracting water, producing dried plant biomass fragments,

? impregnate said dried plant biomass fragments with liquid production residues according to a predefined reciprocal dosage, producing biomass fragments impregnated with liquid production residues,

? dry said biomass fragments impregnated with liquid production residues, extracting specific volatile substances and producing biomass fragments, impregnated with liquid residues, dried, <? >treat, through a method chosen between gasification and pyrolysis, said biomass fragments, impregnated with liquid residues, dried, generating fuels of a type chosen between gaseous, liquid and solid,

? subject said gaseous fuels to complete thermal degradation, generating thermal energy.

Further features and advantages of the invention will become clearer from the description of a preferred, but not exclusive, embodiment of the plant for recycling liquid production residues with relative conversion into thermal energy, illustrated by way of example and not by way of limitation in the attached drawings, in which:

Fig. 1 represents a block diagram of the system according to the invention.

With particular reference to these figures, the symbol 1 generally indicates a plant for the recycling of liquid production residues A with relative conversion into thermal energy.

The system 1 according to the invention comprises a warehouse 2 configured to house a biomass 3 of vegetal origin chopped into small fragments.

By way of example and not limitation, such warehouse 2 may consist of a biomass storage pit 3 made of concrete (preferably vibrated reinforced concrete). A possible pilot plant 1 may include an underground storage pit with the following dimensions: length 4.0 m, width 7.0 m and height 4.0, defining an overall capacity of approximately 60 m<3 >(corresponding to approximately 24 tons of biomass fragments 3).

Plant 1 also includes a tank 3 configured to contain the processing residue in the liquid state A.

The system 1 according to the invention also includes a first dryer 4 configured for the removal of water from predefined quantities of biomass fragments 3 of plant origin.

Biomass B can be extracted from warehouse 2, for example by means of a doser that is able to regulate the correct quantity to be transferred to the first dryer 4 which will reduce/stabilize its relative humidity. The installation of the first dryer 4 is planned as a precaution (for this reason it can be excluded from plant 1 if biomass B has a relative humidity value lower than a predefined threshold value), to avoid malfunctions of plant 1 due to excessive relative humidity of biomass B.

The first dryer 4 may be of the "static" type, with a cylindrical shape, with a diameter of approximately 3.2 m and a height of approximately 4 m. In this case it will be insulated externally to limit heat loss.

By way of example and not limited to, it is specified that the movement of the material present inside it can be achieved by means of a central rotating reel, suitable for moving at low speed on the fixed bottom. Drying will occur by blowing hot air (about 75/80 °C) from the bottom, which will be sucked into the upper central part to be sent to a dust filtering battery (made for example by means of sleeve filters). It will be explained below that the thermal energy for the production of the hot air necessary for the first dryer 4 can be recovered from the exhaust fumes C of the system 1 through appropriate air/water exchange batteries. The dried biomass B will be extracted from the lower part (hot zone) of the first dryer 4; with regard to a pilot system 1, illustrated solely by way of example and not limited to, a flow rate of about 350 kg/hour can be envisaged.

The plant 1 according to the invention also comprises a mixer 5 configured for the impregnation of the dried plant-origin biomass fragments B1 with the liquid processing residue A according to a predefined reciprocal dosage.

Mixer 5 is designed in a similar way to the first dryer 4 but with the internal installation of suitable sprayers to obtain the mixing of the liquid processing residue A with the dried biomass B1. The installed sprayers must allow for flow rate adjustment and cleaning of the nozzles during normal operation. The dried biomass B1 will be introduced into the upper part of mixer 5. Following impregnation, a dried biomass B impregnated with liquid residue A will be generated in the mixer which will be identified below as impregnated biomass D, which can be extracted from mixer 5 from the relative lower part.

The system 1 may advantageously also include a second dryer 6 configured for the removal of volatile substances E from the impregnated biomass fragments D, so as to deliver, at the output, impregnated and dried biomass fragments D1.

Downstream of the second dryer 6, an apparatus 7 is foreseen, of a type chosen between a gasifier and a pyrolyzer, configured for the conversion of the dried impregnated biomass fragments D1 into fuels of a type chosen between gaseous G, liquid and solid.

A gasifier is a component suitable for implementing a gasification process.

Gasification is a process by which a fuel, solid or liquid, can be transformed into a gaseous mixture that can be used as a fuel or for chemical synthesis. The fuel is placed in contact with a quantity of oxygen lower than that required for stoichiometric combustion, and at high temperatures. The main product is syngas G, a gaseous mixture rich in hydrogen and carbon monoxide.

The quantities of CO2 released into the atmosphere following the aforementioned combustion are exactly the same as those stored during the life of plant biomass through photosynthesis. It is therefore a zero-emission renewable energy source (if only plant biomass is used as raw material).

In the case in question, the adoption of a gasifier 7 will ensure that it presents an extremely limited quantity of waste, consisting of F ash (which however determines a negligible environmental impact).

A pyrolyzer is a component suitable for carrying out a pyrolysis process.

Pyrolysis is a heat treatment process that can be used for the energy conversion of various organic materials as long as they have a low water content (< 15%). The process, also called dry distillation, consists of non-oxidative thermal decomposition, i.e. without the addition of oxygen from outside, except for that which may already be present in the biomass. Decomposition occurs in the temperature range of 400 - 800?C, and the molecules of the organic substances are transformed into simpler elements.

The reaction products consist of: a solid fraction equal to approximately 20 - 30% by weight of the initial material, carbon-based, with a good calorific value (8000 kcal/kg) that can be used as fuel; a liquid fraction equal to approximately 50 - 60% by weight, which can be considered as a bio-oil, containing paraffins, isoparaffins, olefins, aromatic hydrocarbons and numerous oxygenated, chlorinated and sulphurised substances, which has an energy content equal to approximately 22-23 MJ/kg on a dry basis and 16 - 18 MJ/kg with 20% water; a gaseous fraction which constitutes approximately 15 - 30% by weight, also called pyrolysis gas, composed mainly of hydrogen, carbon monoxide, carbon dioxide, light hydrocarbons, this fraction has a calorific value of approximately 15-22 MJ/kg and can be used as fuel. It can be used for various purposes such as drying the starting material, generating electrical power, or it can be stored and sold to third parties.

Downstream of the apparatus 7 (be it a gasifier or a pyrolyzer) there is a combustor 8 configured for the complete thermal degradation of the gaseous fuels G previously obtained and delivered by the apparatus 7 and the generation of thermal energy W.

The system 1 according to the invention can also comprise a duct for conveying the volatile substances E into the combustor 8 with consequent mixing of the same with the gaseous fuels G and the thermal degradation of the mixture G+E constituted by them.

The combustor 8, fed by the gaseous fuels G and the volatile substances E supplied by the second dryer 6, will ensure that the combustion air is supplied and regulated automatically to obtain the complete oxidation of the mixture G+E at a temperature of approximately 1,100 ?C. The thermal recovery of the exhaust gases will be carried out by means of a suitable boiler 9 with diathermic oil at 280 ?C which can be placed in parallel to an existing thermal energy supply network, adopting a suitable collector to be inserted on the same.

The pilot plant 1 currently under study (illustrated solely for illustrative and non-limiting purposes) will be able to have a nominal power P of approximately 3,000 kW.

At the outlet of the diathermic oil recovery boiler 9, a device configured for the recovery of the heat contained in the fumes F is foreseen: in this case, an air/water exchange battery will preferably be used for the production of hot water at approximately 80° to be sent to the mixer 5 and to the first dryer 4 (it is thus seen how the energy supply of these components can be obtained as a by-product of the system 1 itself). The fumes will be discharged into the atmosphere at a temperature of approximately 140°C to avoid the formation of condensation (which should in turn be disposed of).

It should be noted that the system 1 according to the invention can conveniently include transport lines for the biomass B of vegetal origin placed between the warehouse 2 and the first dryer 4, as well as between the first dryer 4 and the mixer 5; further transport lines for the impregnated biomass D are also provided, placed between the mixer 5 and the second dryer 6 and also between the second dryer 6 and the apparatus 7.

Such conveyor lines may profitably be of a type preferably chosen from conveyor belts, screw conveyors, auger conveyors, gear conveyors and the like.

For example, biomass B can be transported by means of an extraction screw placed on the doser (possibly also made up of several consecutive branches oriented in various ways, so as to follow the desired path) so that it can be introduced into the upper part of the first dryer 5.

In general, the lifting/transport of biomass B from warehouse 2 (the storage pit) through a series of horizontal/vertical/inclined augers. For example, this may include an extraction auger (placed horizontally on the bottom of warehouse 2 and designed to extract fragments of biomass B); downstream of this extraction auger, there will be a lifting auger, mounted vertically to lift the fragments of biomass B from the bottom of warehouse 2 (with reference to the example illustrated above, this bottom would be at an indicative height of approximately -4.5 m) up to the necessary height (for example a height of 4.5 m). At this point, downstream of the lifting auger, there will be an upper auger, mounted horizontally and above the doser to receive the fragments of biomass B, lifted by the lifting auger and transport them to the doser.

With particular reference to a solution of undoubted practical and applicative interest, the doser can be loaded through two loading mouths to have homogeneous distribution on specific transport rakes. The expected flow rate for the devices used to load the doser in the pilot plant 1 already partially illustrated above, can be in the order of approximately 20 m<3>/hour.

It is specified that the system 1 according to the invention can profitably include filtering stations for fumes C and volatile substances E: these filtering stations will be configured to block particulate matter with a granulometry greater than a predefined threshold. In particular, it is specified that filters with a filtering capacity such as to trap dust with a granulometry greater than 5 ?m may be used.

The filtration of the exhaust gases (therefore of the fumes C, of the volatile substances E and, optionally, also of the steam W emitted by the first dryer 4) is foreseen with fabric filters to obtain the necessary cleaning of the same and to avoid dust pollution. The filters to be used will preferably be the so-called "sleeve filters", dust removal equipment calibrated to trap dust with granulometry values higher than a predefined threshold value (in the case exemplified above 5 ?m). These sleeve filters will be equipped with an automatic compressed air device for their continuous cleaning with regulation of the pulse times and cycle times.

It is important to illustrate that the biomass B of vegetal origin can efficiently be of a type preferably chosen among lignocellulosic biomass, wood chips, pellets and similar. In particular, it is highlighted that the use of wood chips guarantees optimal results in terms of efficiency of the plant 1 and thermal energy production efficiency P.

As previously indicated, the system 1 will comprise at least one heat exchanger configured for heating, using a thermal energy chosen between that generated by the combustor 8 (thermal energy H) and that of the fumes C delivered by the combustor 8, a carrier fluid intended to feed a device such as a diathermic oil boiler 9, an electric energy generator, an industrial machine and a combination of the same.

It is specified that, with particular reference to a particularly interesting application of the invention, the liquid production residues A are constituted by a substance T in the solid state at room temperature, treated with a solvent S chosen from methanol, ethanol, butanol, isopropyl alcohol, esters, ketones and ethers.

Such substance T in the solid state at room temperature will comprise Carbon, in a percentage between 45% and 65%, preferably having values close to 54%-56%, Oxygen, in a percentage between 30% and 50%, preferably having values close to 38%-39%, Hydrogen, in a percentage between 3% and 10%, preferably having values close to 6%-6.5%, Nitrogen in a percentage less than 0.1% and other possible elements in variable proportions.

Such substance T, in the case of primary applicative interest, could be a dark-coloured solid consisting of hydrocarbons and free carbon.

This substance S could be extracted from a wide variety of organic materials through a destructive distillation process.

Of particular interest will be the use of a substance S consisting of "distillation residues" or "distillation tails" (defined in English with the term "distillation residue").

Such a substance S is solid at room temperature and can be kept liquid only by the use of a solvent (for example any of those mentioned above, among which methanol is one of the most likely applicable). From the chemical point of view, substances S are condensation products obtained in reaction and by thermal degradation in distillation.

The protection offered by this invention also extends to a process for the recycling of liquid production residues A with relative conversion into thermal energy P, which consists of a series of consecutive phases.

In a first phase I, it is necessary to dry a predefined quantity of biomass fragments B of vegetal origin, extracting water W.

Subsequently, during a second phase II, it is necessary to impregnate these dried biomass fragments B1 with liquid production residues A according to a predefined reciprocal dosage, obtaining an impregnated biomass D.

A third phase III then involves drying the impregnated biomass D, extracting specific volatile substances E, obtaining a dried impregnated biomass D1.

In a fourth phase IV, the impregnated and dried biomass fragments D1 will be gasified, generating fuels of a type chosen from gaseous G, liquid and solid (the last two exclusively in the case in which the apparatus 7 is constituted by a pyrolyser). These gaseous G, liquid and solid fuels, possibly also mixed with the volatile substances E extracted in the third phase III, may be subjected, during a fifth phase V, to complete gaseous thermal degradation, generating thermal energy H.

The process 1 according to the invention comprises at least a sixth heat exchange phase VI for heating at least one carrier fluid which will have a nominal power P.

Depending on the requirements of the quantity of waste A to be treated and the thermal energy H that must be produced to have the required nominal power P, the plant 1 according to the invention may be built in different sizes or may consist of a parallel of single plants 1 that may operate simultaneously or separately depending on the specific momentary needs.

It should be noted that for the present invention numerous experimental tests have demonstrated the undoubted practical efficiency, even on an industrial scale, in the case in which the apparatus 7 consists of a gasifier; in the case in which the apparatus 7 is a pyrolyzer, the tests conducted mainly on a laboratory scale have demonstrated undoubted effectiveness (for this reason it is believed that this version will also be implemented industrially).

It is specified that the ratio between the liquid production residues A and the biomass B can preferably be such that the residues constitute a share between 20% and 70% of the impregnated biomass D, preferably between 30% and 60%, even more preferably between 35% and 45%.

Advantageously, the present invention solves the problems previously described, proposing a plant 1 for the recycling of liquid production residues A with relative conversion into thermal energy H that can operate, even continuously, for long periods.

According to the invention, the system 1, not being subject to accumulation of substances inhibiting the reactions foreseen therein, can operate for very long periods without the occurrence of malfunctions or breakdowns.

Conveniently, the plant 1 according to the invention is suitable for treating residues comprising Carbon (in a percentage between 45% and 65%, preferably having values close to 54%-56%), Oxygen (in a percentage between 30% and 50%, preferably having values close to 38%-39%), Hydrogen (in a percentage between 3% and 10%, preferably having values close to 6%-6.5%), Nitrogen (in a percentage less than 0.1%) and any other elements in variable proportions (relative to the missing portion to reach 100%) made liquid by means of at least one respective solvent.

Profitably, the system 1 according to the invention complies with the current regulatory requirements.

Favorably, the system 1 according to the invention has high conversion efficiency.

Usefully, plant 1 according to the invention has low operating costs (in particular, by providing that biomass B is made up of wood chips, it has been calculated that operating costs will be much lower than the savings due to the lack of purchase of methane gas for the production of thermal energy and the elimination of waste disposal costs A).

Validly, the plant 1 and the process according to the invention are relatively simple to implement in practice and have low costs: these characteristics make the plant 1 and the process according to the invention innovations of certain application.

The invention, thus conceived, is susceptible to numerous modifications and variations, all of which fall within the scope of the inventive concept; furthermore, all the details may be replaced by other technically equivalent elements.

In the illustrated examples of embodiment, individual characteristics, reported in relation to specific examples, may in reality be interchanged with other different characteristics, existing in other examples of embodiment.

In practice, the materials used, as well as the dimensions, may be any according to the needs and the state of the art.

Claims (10)

CLAIM S 1. Plant for the recycling of liquid production residues (A) with relative conversion into thermal energy, characterised by the fact that it comprises ? a warehouse (2) configured to house a biomass (B) of vegetal origin chopped into small fragments, ? a tank (3) configured to contain a processing residue in a liquid state (A), <? >a first dryer (4) configured for the removal of water (W) from predefined quantities of biomass fragments (B) of vegetal origin, said first dryer (4) being excludable in the case that said biomass (B) has a humidity content lower than a predefined threshold value, <? >a mixer (5) configured for the impregnation of dried plant origin biomass fragments (B1) with said liquid state processing residue (A) according to a predefined reciprocal dosage, ? a second dryer (6) configured for the removal of volatile substances (E) from biomass fragments impregnated with said liquid state processing residue (D); <? >an apparatus (7), of the type chosen between a gasifier and a pyrolyser, configured for the conversion of biomass fragments impregnated with said dried liquid state processing residue (D1) into fuels of a type chosen between gaseous (G), liquid and solid, <? >a combustor (8) configured for the complete thermal degradation of previously obtained gaseous fuels (G) and the generation of thermal energy (H). 2. System, according to claim 1, characterised in that it comprises a duct for conveying said volatile substances (E) into said combustor (8) with consequent mixing of the same with said gaseous fuels (G) and the thermal degradation of the mixture (G+E) constituted by them. 3. Plant, according to one or more of the preceding claims, characterised in that it comprises transport lines for said biomass (B, B1) of vegetal origin placed between said warehouse (2) and said first dryer (4), between said first dryer (4) and said mixer (5) and transport lines for said biomass of vegetal origin mixed with said liquid production residues placed (D, D1) between said mixer (5) and said second dryer (6) and between said second dryer (6) and said apparatus (7), said transport lines being of a type preferably chosen from conveyor belts, screw conveyors, auger conveyors, gear conveyors and the like. 4. System, according to one or more of the preceding claims, characterised in that it comprises filtering stations for fumes (C), volatile substances (E) and vapours (W), configured to block particulate matter having a granulometry greater than a predefined threshold. 5. Plant, according to one or more of the preceding claims, characterised in that said biomass (B) of vegetal origin is of a type preferably chosen from lignocellulosic biomass, wood chips, pellets and the like. 6. System, according to one or more of the preceding claims, characterised in that it comprises at least one heat exchanger configured for heating, using thermal energy chosen from that generated by said combustor (8) and that of the fumes (C) delivered by said combustor (8), a carrier fluid used to feed a device (9) of the type of a diathermic oil boiler, an electric energy generator, an industrial machine and a combination thereof. 7. Plant, according to one or more of the preceding claims, characterised in that said liquid production residues (A) are constituted by a substance (T) in the solid state at room temperature, treated with a solvent (S) selected from methanol, ethanol, butanol, isopropyl alcohol, esters, ketones and ethers, said substance in the solid state (T) at room temperature comprising Carbon, in a percentage between 45% and 65%, preferably having values close to 54%-56%, Oxygen, in a percentage between 30% and 50%, preferably having values close to 38%-39%, Hydrogen, in a percentage between 3% and 10%, preferably having values close to 6%-6.5%, Nitrogen in a percentage less than 0.1% and any other elements in variable proportions. 8. Process for the recycling of liquid production residues (A) with relative conversion into thermal energy (H), characterised by the fact that it consists in <? >dry a predefined quantity of biomass fragments (B) of plant origin, extracting water (W), producing dried biomass fragments of plant origin (B1), ? impregnate said dried plant biomass fragments (B1) with liquid production residues (A) according to a predefined reciprocal dosage, producing biomass fragments impregnated with liquid production residues (D), ? dry said biomass fragments impregnated with liquid production residues (D), extracting specific volatile substances (E) and producing biomass fragments, impregnated with liquid residues, dried (D1), ? treat, through a method chosen between gasification and pyrolysis, said biomass fragments, impregnated with liquid residues, dried (D1) generating fuels of a type chosen between gaseous (G), liquid and solid, ? subject said gaseous fuels (G) to complete thermal degradation generating thermal energy (H). 9. Process, according to claim 8, characterised in that in correspondence with said thermal degradation phase, said gaseous fuels (G) are mixed with said volatile substances (E) extracted in the second drying phase. 10. A process according to at least one of claims 8 and 9, characterised in that it comprises at least one heat exchange phase for heating at least one carrier fluid.