EP2421943A1

EP2421943A1 - Process for converting biomass to solid fuel

Info

Publication number: EP2421943A1
Application number: EP10727858A
Authority: EP
Inventors: Savino Sartori
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-04-24
Filing date: 2010-04-23
Publication date: 2012-02-29
Also published as: WO2010122525A1; ITVI20090090A1

Abstract

A process for the treatment of poultry droppings and similar biomasses, characterised in the production of solid fuel through heating of the poultry- droppings under vacuum, in a current of steam at a temperature between 250 0C and 4800C. This process being achieved by the use of a plant consisting of a reactor (10), supplied under vacuum through chambers divided by valves, and in that the plant comprises a stirrer with blades, which causes the mixing and infeed of the material from the entry point towards the exit point at a variable speed, according to the nature of the product and its humidity, and that the flows of steam are injected as required on the entry side by a steam generator (11) and extracted near the discharge point with the volatised substances passing through a condenser (12) and then to the vacuum system (13) with a scrubbing effect on the incondensable products.

Description

"PROCESS FOR CONVERTING POULTRY DROPPINGS TO SOLID FUEL

AND CONVERSION PIANT"

* * * * *

INTRODUCTION This invention concerns a process for the heat treatment of poultry droppings carried out in a continuous or discontinuous way in order to obtain solid fuel with separation of the organic fluid mixture.

The conversion process according to the invention makes it possible to achieve important results from the point of view of alternative fuel energy production, in particular energy produced from animal organic waste normally used for fertilization in the agricultural sector. According to the invention, the volatilization and decomposition temperature is achieved by means of controlled-temperature heating of the outer surface of a reactor, using an appropriate thermal vector, provided by a generator, such as diathermic oil or preferably an eutectic mixture of molten salts with a melting temperature starting from 135⁰C and which can be used up to a maximum of 480⁰C.

This invention can be applied in the sector for production of alternative fuel energy, in particular in the sector for the production of energy from animal organic waste, that is to say waste currently used for fertilization in the agricultural sector or at most for the production of gas by means of pyrolysis.

BACKGROUND ART

As known, poultry droppings are normally used as an organic fertiliser obtained by industrial treatment recycling of bird farm droppings. Due to their chemical features, these droppings are functionally classified in an intermediate position between organic fertilisers and chemical manure. It is also known that energy exploitation of agricultural biomasses in general and of poultry droppings in particular can be achieved by means of thermal processes. These are, briefly: incineration, isolated or with other biomasses or refuse-derived fuel; pyrolysis; use in the production of bricks and cement after drying.

Incineration is a possible form of use for agricultural biomasses and for poultry droppings, it is technically appropriate in large plants, but not very common in Italy due to the widespread diffidence of the population as regards incineration plants.

Pyrolysis/gasification, a known technology, has not been developed much, despite the fact that it allows good recovery of the energy contained in the organic matrix and considerably easy management of the gases produced.

The main reasons for the limited development of this technology can be found in the lack of simple and economic continuous processes for small plants, the difficulty of managing the process, since it is carried out on non-homogeneous products, and in the tendency to create a solid and tarry deposit during the gasification process, with severe soiling of the equipment and the need for heavy maintenance, which is not always easy to foresee and control.

Pyrolysis / gasification of poultry droppings is therefore a technology which, while on paper seems easy to apply, cannot be carried out in stable production conditions due to the variability of its features such as: variations in humidity and size, and difficulties in movement of the product when its humidity level is high. The resulting gaseous emissions cause concern due to the potential polluting gases such as: SO_x, NO_x, unburnt and burnt organic products, and fine dust.

The as yet unresolved objective naturally facing all operators in this sector is to have small-sized or at most medium-sized plants, which can be easily accepted by the authorities and the local population, with safe and reliable functioning and simple technologies, designed to be carried out as a complement to the main activity of agricultural and bird farms, which do not require agricultural sector operators to become specialists in electricity production or complex thermal-chemical plant management .

The current background art thus requires a different approach to the problem of disposal and exploitation of poultry droppings and biomasses from farms, which takes into account the insufficiency of the current processes and of the new Nitrates Directive, providing at the same time a financial contribution to the low profitability of animal farming in general.

DESCRIPTION OP THE PLANT

This invention proposes to provide a process for the heat treatment of poultry droppings which can eliminate or at least reduce the drawbacks described above. The invention also proposes to provide a process for the heat treatment of poultry droppings which is relatively easy to carry out in order not to excessively affect production costs. This is achieved by means of a process for the heat treatment of poultry droppings whose features are described in the main claim.

The dependent claims of the solution in question describe advantageous embodiments of the invention.

The main advantages of this solution concern the fact that the process and the plant according to the invention satisfy the conditions necessary to solve the problem of disposal of the poultry droppings and their exploitation, that is to say with the following features:

- It must be applicable to all types of poultry droppings (or excrement biomass) , regardless of the content of humidity;

- There must be no atmospheric emissions of any molecule harmful to man (furans, dioxins, fine dust, odours) ;

- It must provide by-products that can be used in agriculture, possibly within the same business that produces the biomass; - It must return water, air and solids to the environment without impact and respecting the relative regulations;

- It must be energetically compatible and independent;

- It must cover the costs of the production cycle and, if possible, produce a profit;

- It must consist of plants that can be dimensioned according to the requirements of the user business. The production process according to the invention differs from those currently in use for the following reasons: it is a process that removes - under vacuum and without emissions - all the free water, obtaining a component-enriched biomass; it is a process that separates - under vacuum, without emissions and at a higher temperature - the compounds which are volatile in themselves or as a result of the partial or total decomposition of the molecules and their structural arrangement; it is a process that transforms the biomass into charcoal, increasing the specific calorific power, this charcoal being defined as biochar, practically free of volatile substances, with total removal of the nitrogen and its compounds and having only a mineral base incorporated; it is a process that allows the storage of the odour-free produced charcoal, which can be easily moved without any environmental risk; - it is a biochar which can be easily gasified with known stoichiometry and without any risk of producing NOx, furans or dioxins; it is a process in which the gasification of biochar makes it possible to supply a cogeneration unit, with production of electricity, using endothermic motors or gas turbines or ORC generators, with easy heat recovery from the gasification gases and from the combustion products, in order to use this thermal energy for the same processes of drying and gasification; - it is a process in which the residual thermal energy after gasification and cogeneration allows selective evaporation which separates the process water from the oil produced by evaporation and molecular restructuring; it is a process in which the separated water is treated to remove the ammonia that it contains, with production of ammonium salts that can be used as fertilizers; it is a process in which the evaporated ammonia- stripped water is biologically oxidated for discharge and agricultural spreading, within the limits imposed by current legislation; it is a process in which the recovered oil, with a molecular ratio of nitrogen/charcoal of 1:10, can be used to supply plants producing biogas or salification products for fertilization; it is a process in which the ash produced has concentrations of potassium and phosphorus and heavy metals suitable for agricultural spreading, according to current legislation and, if disposed of, has a mass which is ten times less than the original mass.

The plant according to the invention substantially consists of a reactor, generally having a horizontal or sub-horizontal axis, supplied with vacuum by means of chambers divided by valves, with pre-vacuum between subsequent and continuous inputs, while in the case of discontinuous loads the vacuum is applied on completion of the load. The mixing and infeed of the material from the entry point towards the discharge point is controlled by a stirrer with variable speed blades, according to the nature of the product and its humidity.

Steam is injected as required at the entry side by a steam generator and extracted near the discharge point with the volatised substances passing through a condenser and then to the vacuum system with a scrubbing effect on the incondensable products.

The chamber outside the reactor is fed from a generator with the diathermic fluid for heating, typically a mixture of eutectic salts heated with traditional systems such as electricity, hot combustion gases, or combustion of the produced charcoal, in which the generation of eutectic salts is also accompanied by production of the transport steam.

The water/oil mixture is separated with conventional evaporation techniques in an evaporator, with separation of the oil and transfer of the excess water to conventional water treatment processes of aerobic/anaerobic biological fermentation or to partial recycling for steam generation.

DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will become clear on reading the description given below of one embodiment of the invention, provided as a non- binding example, with the help of the accompanying drawings in which: figure 1 is a block diagram showing the process for the conversion of poultry droppings to solid fuel according to the invention; figure 2 is a schematic view of a continuous flow type plant for conversion of poultry droppings to solid fuel; figure 3 is a. schematic view of a discontinuous flow type plant for conversion of poultry droppings to solid fuel.

DESCRIPTION OF ONE EMBODIMENT OF THE INVENTION

The plant according to the invention consists of a reactor 10, generally with a horizontal or sub-horizontal axis, supplied with vacuum by means of chambers divided by valves, with pre-vacuum between subsequent and continuous inputs, while in the case of discontinuous loads the vacuum is applied on completion of the load.

A stirrer with blades mixes and feeds the material at the entry point towards the discharge point with variable speed, according to the nature of the product and its humidity.

Steam is injected as required at the entry side by a steam generator 11 and extracted near the discharge point with the volatised substances passing through a condenser

12 and then to the vacuum system 13 with a scrubbing effect on the incondensable products.

The chamber outside the reactor is fed from a generator 14, with the diathermic fluid for heating, typically a mixture of eutectic salts in the range from 135 to 480⁰C, heated with traditional systems such as electricity, hot combustion gases, or combustion of the produced charcoal; the generation of eutectic salts is also accompanied by production of the transport steam.

The water/oil mixture is separated with conventional evaporation techniques in an evaporator 15, with separation of the oil and transfer of the excess water to conventional water treatment processes of aerobic/anaerobic biological fermentation or to partial recycling for steam generation.

According to the invention, the plant is envisaged in two versions: a first continuous process version (fig. 2) and a second discontinuous process version (fig. 3). DESCRIPTION OF THE PIANT (CONTINUOUS PROCESS)

DIAGRAM FIGURE 2

The continuous process plant consists of a biomass storage silo 20 from which a screw feeder 21 transfers the poultry droppings or similar biomass (bovine or pig excrement / biological sludge / biogas digestate / solid urban waste from separated collection) through an input valve 22 in a reactor 23, consisting of a horizontal cylindrical body with elliptical bottoms and a heating jacket, equipped with a stirrer with blades 24 scraping the heating surface, which continuously moves the biomass contained inside the reactor. The stirrer is controlled by a gear motor 25. The gear motor allows movement in both directions, to allow transfer towards the discharge or retention of the biomass in movement.

The jacket of this reactor is heated with low temperature diathermic fluids 26, circulated in the jacket by a pump and consisting of hot water, superheated water, steam or diathermic oil or hot air. The reactor heating energy is supplied by an external source.

The heating of the product fed into the reactor releases water which migrates towards the condenser - consisting of an exchanger 27, a vacuum pump and Venturi system 28. The dried biomass flows towards a second reactor 29, similar to the first one, but heated with a high temperature diathermic fluid such as diathermic oil, but more efficiently by an eutectic salt generator 30, in the range between 250 and 480°C. From the generator 30, the eutectic salts are pumped into the jacket of the reactor 29 by means of a pump 31.

The atmosphere in the reactors 23 and 29, mounted in series to allow the flow to move from the entry point towards the exit, is kept under pressure by the vacuum system 28, while steam is injected into the reactor 29 to allow steam cracking (similar to a petrochemical process) without oxygen. In addition to contributing to the process of molecular dissociation and recombination, the steam acts as a gas for transport of the molecules which form by degradation and recombination, and, passing through the reactor 23, flows towards the dust separator 32 to reach the condenser 27, cooled with water or air. The combination of the condenser system 27 and the vacuum system 28 guarantees condensation of the steam and the by-products without significant atmospheric emission. The biochar produced is discharged through the slide valve 33. The flow of condensate collected after drying / charcoalization is transferred to separation of the nonvolatile organic components for evaporation of the water using the vacuum evaporator consisting of a heat exchanger 37, an evaporator body 34, a condenser 35 and a vacuum unit 36. The water separated from the liquid, consisting of non-volatile components, is condensed in the exchanger 35. The separated oil and the biochar produced have extremely favourable features determined by specific analyses.

DESCRIPTION OF THE PLANT (DISCONTINUOUS PROCESS)

DIAGRAM FIGURE 3

The discontinuous process is carried out when the mass of poultry droppings or alternative biomass does not justify the construction of a complex plant, achieving the same transformation result but with a lower yield of heat use for energy production purposes.

Similar to the previous version, the storage silo 20 equipped with a screw feeder 21 feeds the poultry droppings or similar biomass (bovine or pig excrement / biological sludge / biogas digestate / solid urban waste from separated collection) through an input valve 22 into a reactor, consisting of a horizontal cylindrical body 23 with elliptical bottoms and a heating jacket, equipped with a stirrer with blades 24 scraping the heating surface, which continuously moves the biomass contained inside the reactor. The stirrer 24 is controlled by a gear motor 25. The gear motor allows movement in both directions, to allow transfer towards the discharge or retention of the biomass in movement.

The jacket of this reactor is heated with low temperature diathermic fluid, consisting of eutectic salts generated in the boiler 30 in the temperature range from 150 to 480⁰C.

The salt is pumped from the boiler to the reactor by means of a circulation pump 31.

Steam is injected into the reactor 24 to allow steam cracking (in similar to a petrochemical process) without oxygen. In addition to contributing to the process of molecular dissociation and recombination, the steam acts as a gas for transport of the molecules which form by degradation and recombination, and, passing through the reactor 23, flows towards the dust separator 32 to reach the condenser 27, cooled with water or air. The combination of the condenser system 27 and the vacuum system 28 guarantees condensation of the steam and the by-products without significant atmospheric emission. The flow of condensate collected after drying / charcoalization is transferred to separation of the nonvolatile organic components for evaporation of the water using the vacuum evaporator, consisting of a heat exchanger 37, an evaporator body 34, a condenser 35 and a vacuum unit 36.

The separation of the water from the liquid, condensed in the exchanger 35, produces an oil which has very favourable features of oily phase nitrogen and biochar analysis. The "biochar" produced is discharged through the valve 33.

The invention is described above with reference to a preferred embodiment. It is nevertheless clear that the invention is susceptible to numerous variations which lie within the scope of its disclosure, _in the form of technical equivalents.

Claims

1. A process for the treatment of poultry droppings and similar biomasses, characterised in that the production of solid fuel through heating of the poultry droppings under vacuum, in a current of steam at a temperature between 250⁰C and 480⁰C, this process being achieved by the use of a plant consisting of a reactor (10) , supplied under vacuum through chambers divided by valves, and in that the plant comprises a stirrer with blades, which causes the mixing and infeed of the material from the entry point towards the exit point at a variable speed, according to the nature of the product and its humidity, and that the flows of steam are injected as required on the entry side by a steam generator (11) and extracted near the discharge point with the volatised substances passing through a condenser (12) and then to the vacuum system (13) with a scrubbing effect on the incondensable products.

2. A process for the treatment of poultry droppings and similar biomasses according to the foregoing claim, characterised in that the chamber outside the reactor is fed with the diathermic heating fluid from a generator (14), this fluid typically being a mixture of eutectic salts in the range from 135 to 480⁰C heated with traditional systems such as electricity, hot combustion gases, or combustion of the produced charcoal; the generation of eutectic salts is also accompanied by production of the transport steam.

3. A process for the treatment of poultry droppings and similar biomasses according to either of the foregoing claims, characterised in that the water/oil mixture is separated with conventional evaporation techniques in an evaporator (15) , with separation of the oil and transfer of the excess water to conventional water treatment processes of aerobic/anaerobic biological fermentation or to partial recycling for steam generation.

4. A process for the treatment of poultry droppings and similar biomasses according to any of the foregoing claims, characterised in that the plant can be constructed to function with a continuous process or a discontinuous process.

5. A process for the treatment of poultry droppings and similar biomasses according to any of the foregoing claims, characterised in that the continuous process plant consists of a biomass storage silo (20) from which a screw feeder (21) transfers the poultry droppings or similar biomass (bovine or pig excrement / biological sludge / biogas digestate / solid urban waste from separated collection) through an input valve (22) in a reactor (23), consisting of a horizontal cylindrical body with elliptical bottoms and a heating jacket, equipped with a stirrer with blades (24) scraping the heating surface, which continuously moves the biomass contained inside the reactor, the stirrer being controlled by a gear motor (25) , and in that the gear motor allows movement in both directions, to allow transfer towards the discharge or retention of the biomass in movement.

6. A process for the treatment of poultry droppings and similar biomasses according to any of the foregoing claims, characterised in that the jacket of the reactor is heated with low temperature diathermic fluids (26) , circulated in the jacket by a pump and consisting of hot water, superheated water, steam or diathermic oil or hot air, the reactor heating energy being supplied by an external source, and in that the product fed into the reactor releases water which migrates towards the condenser - consisting of an exchanger (27), a vacuum pump and Venturi system (28) and that the dried biomass flows towards a second reactor (29) , similar to the first one, but heated with a high temperature diathermic fluid such as diathermic oil, but more efficiently by an eutectic salt generator (30) , in the range between 250 and 480⁰C, the eutectic salts being pumped from the generator (30) into the jacket of the reactor (29) with a pump (31) .

7. A process for the treatment of poultry droppings and similar biomasses according to any of the foregoing claims, characterised in that the atmosphere in the reactors (23, 29) , mounted in series to allow the flow to move from the entry point towards the exit, is kept under pressure by the vacuum system (28), while a flow of steam is injected into the reactor

(29) to allow steam cracking (similar to a petrochemical process) without oxygen; in addition to contributing to the process of molecular dissociation and recombination, the steam acts as a gas for transport of the molecules which form by degradation and recombination, and, passing through the reactor (23), flows towards the dust separator (14) to reach the condenser (27), cooled with water or air; the combination of the condenser system (27) and the vacuum system (28) guarantees condensation of the steam and the by-products without significant atmospheric emission; the biochar produced is discharged through the slide valve (33) .

8. A process for the treatment of poultry droppings and similar biomasses according to any of the foregoing claims, characterised in that the flow of condensate collected after drying / charcoalization is transferred to separation of the non-volatile organic components for evaporation of the water using the vacuum evaporator consisting of a heat exchanger (37), an evaporator body (34), a condenser (35) and a vacuum unit (36) ; the water separated from the liquid, consisting of non-volatile components, is condensed in the exchanger (35) , while the separated oil and the biochar produced have the features of the attached analyses (oily phase nitrogen analysis; biochar analysis) .

9. A process for the treatment of poultry droppings and similar biomasses according to any of the foregoing claims, characterised in that the discontinuous process plant differs from the continuous process plant in the fact that the plant is fed with subsequent loads and the vacuum is applied on completion of the load.