BR102013005295A2 - Pyrolysis process of an organic matrix material - Google Patents

Abstract

Pyrolysis Process of an Organic Matrix Material The present invention relates to a process for pyrolysis of a carbon, or at least partially carbon, material such as that derived from biomass or organic waste and mixtures of various origins. In particular, the present invention relates to Figure 1.

Description

Pyrolysis process of an organic matrix material.

Description The present invention relates to a process for the pyrolysis of carbon-based, or at least partially carbon-based materials, such as those derived from biomass or organic waste and mixtures of various origins. Pyrolysis is a process of thermochemical conversion of organic matrix materials into combustible end products, which is performed in the absence of oxygen, or with a very limited presence thereof, in order to avoid oxidation reactions responsible for the formation of compounds such as dioxins and furans. Compared to combustion furnaces commonly used for waste incineration, pyrolysis reactors are much safer and do not require sophisticated oxidation control systems which, in the event of damage, could be dumped into the atmosphere. and furans with great health and environmental risk.

Pyrolysis products are gaseous, liquid or solid, in proportions that depend on the pyrolysis methods, the reaction parameters and the materials with which the pyrolysis reactors are fed. With respect to a direct combustion process, pyrolysis technology allows to transfer to the products, whether gaseous, liquid or solid, the energy content of the starting material in a low environmental impact process. In the experimental studies referred to in both literature and industrial practice, it is observed how the pyrolysis process has traditionally been employed to maximize the production of coal (carbon) or even more that of pyrolysis oil. The low attention paid so far to the production of gaseous fuel should be attributed to the low gas yield characteristic of conventional pyrolysis technology, which is typically less than 40% by weight of the starting material.

There is a huge variation in the processes and products that can be obtained, determined by the wide possibility of acting on the parameters governing the process reactions (temperature, dwell time, heating speed, pressure, feed material particle size). This leads to the fact that several classifications of existing pyrolysis technologies have been made, the most common of which being based on process temperature and reaction speed.

Depending on the temperature at which they are conducted, pyrolysis processes are distinguished by low (400 - 600 ° C), medium (600 - 1000 ° C) and high temperature (1000 - 2000 ° C) pyrolysis. The pyrolysis processes at low and medium temperature (450 - 1000 ° C) are distinguished in turn by the reactor typology in which they are conducted: 1. the vertical furnace, in which the organic material is fed from above, dried and pyrolysate being processed from top to bottom countercurrent to hot gases. Residues are recovered in the low section of the reactor, while gases are evacuated from the top. 2. The rotary kiln, similar to the vertical kiln, which is characterized by more efficient heat transport and better mixing of the fed organic material in view of its rotation. In contrast, pyrolysis conducted in a rotary reactor is a more delicate process due to the risks associated with the possibility of air entering the rotating joints. 3. the vertical cylindrical fluid bed furnace in which the organic material to be treated, which requires grinding and screening pretreatments, is held in suspension by an upward gas flow. An inert, usually silica sand, is placed inside the reactor to promote thermal exchange and to provide the system with sufficient thermal inertia. Such ovens are very complex and difficult to drive.

Products which are generated by processes conducted in the ovens described above are generally; • powders, composed predominantly of carbon powders. They are easily treatable compared to those produced during incineration as they comprise larger particles due to the lower exercise temperature. Moreover, these are more concentrated given the larger volume of gas phase produced. • Gas, consisting essentially of hydrogen (H2), carbon monoxide (CO) and inert gases due to infiltration. It is a gas with a calorific value between 12,500 and 20,900 kJ / Nm3. It does not contain nitrogen oxides due to moderate temperature and the strongly reducing atmosphere in which the process is conducted. • Pyrolysis oil, consisting mainly of partially oxidized organic compounds (acids, alcohols, esters). It is a fuel that must undergo a purification process due to the corrosive chlorine and sulfur products contained therein. It can be used for the endothermic supply necessary to carry out the pyrolysis reactions or be sold separately. • Pyrolysis solid waste or coke, which contains a mineral substrate from the inorganic fraction of the scrap and an organic carbon substrate. Such a residue may be used as solid fuel downstream of scrubbing treatments, or transformed into active charcoal. High temperature pyrolysis (about 2000 X) is performed at a high reaction rate (flash pyrolysis) and is characterized by a high thermal demolition yield of the waste in a reducing atmosphere and by minimization of tree gas or agricultural gas. synthesis with a very high yield.

Further features and advantages of the present invention will be more clearly apparent from the description of an exemplary and illustrative non-limiting embodiment hereinafter, with reference to the following figures: Figure 1 is a schematic view of a pyrolysis plant for actuating the invention. process of the invention; and Figure 2 is a sectional side view of the reactor according to the invention. The process of the invention enables a high pyrolysis gas yield to be obtained by combining three fundamental parameters: a) reaction rate; b) humidity; c) presence of catalysts in the organic matrix material to be subjected to pyrolysis. The reaction rate varies within the range of 0.5-1.5 hours, operating at a temperature of from 400 ° C to 600 ° C, more preferably from 400 ° C to 500 ° C. This is therefore a slow pyrolysis process. The amount of water is regulated as a function of the carbon content of the material to be pyrolyzed and is greater than that present in known pyrolysis processes. In general, the amount of water in the material to be pyrolised is about 30% by weight.

By the expression "about 30 wt.%" Referred to the water content of the material to be pyrolized is meant an aqueous content comprised between 25 wt% and 35 wt%.

The catalysts for the pyrolysis process of the present invention are cracking reaction catalysts, preferably chosen from iron, nickel or chromium based catalysts. Considering that an increase in catalytic properties in the order Fe <Ni <Cr is observed, the choice of the appropriate parent catalyst is made according to the reactivity of the starting material, which varies according to the order biomass> predominantly polymeric matrix organic waste. (plastics). Therefore, a less reactive catalyst for a more reactive substrate will preferably be employed.

Preferably such metals are found in powder form with a particle size of not more than 1 mm. Preferably between 100 and 300 mg of catalyst is used for each kg of starting material.

The scopes of the present invention are achieved by means of an installation and specifically a reactor as outlined below.

With reference to the figures, an installation according to the invention is indicated as a whole by the number 1. The organic matrix material (scrap, biomass, etc.) to be pyrolyzed is transferred from a bathtub 10 to a hopper. 3 through conveyor means 11, typically a helical conveyor. In the hopper 3 in the material to be pyrolyzed the pre-set catalyst is added via the metering device 2. Hopper 3 is arranged on a helical conveyor 4. Vacuum means, such as a vacuum pump or fan, make and remove air absorbed by the material. to be pyrolyzed to create within the reactor 5 of. pyrolysis, a vacuum of about 5-10 mm water column. The helical conveyor 4 carries the material to be pyrolyzed into the pyrolysis reactor 5. The reactor 5 comprises a reaction chamber 5a. Reaction chamber 5a is a rotating horizontal cylindrical chamber. Coaxially there is disposed a fixed combustion chamber 6. The combustion chamber 6 is preferably coated with refractory material. The reaction chamber 5a comprises a first preheating portion 7 arranged upstream with respect to the direction of advance of the material to be pyrolyzed and a second pyrolysis portion 8 disposed downstream of the first preheating portion 7. The preheating portion 7 comprises a helical fin 9 on its outer surface. The preheating of the material to be pyrolyzed also has the function of evaporating any excess water that may be present, bringing its content below 30 ° C. % by weight. the dehydration content is regulated by varying the speed of the helical conveyor 4 and thus the residence time in such a section 7. Even excessive or lower dehydration does not, however, lead to problems since in the successive portion of the reactor all the agia will be evaporated and available for reactions with the organic matrix cracking carbon. The combustion chamber 6 in turn has a first preheating portion 12, which surrounds the preheating portion 7 of reaction chamber 5a, and a second heating portion 13, which surrounds the pyrolysis portion. 8 of reaction chamber 5a. In said second heating portion 13 burners 14 are positioned. The burners 14 are disposed longitudinally along the entire heating portion 13 of the combustion chamber 6, typically at its bottom. The fuel for burners 14 may be propane, methane and diesel, part of the pyrolysis gas produced in the same reactor 5 (line 24). The distribution of the burners 14 longitudinally over the entire surface of the pyrolysis portion 8 of the reaction chamber 5a allows temperatures in the shell of the pyrolysis portion 8 of about 800 ° C to be achieved, optimizing the internal heating of the reactor. In this way the cracking performance is increased.

Prior to leaving combustion chamber 6, combustion fumes having a temperature of about 1200 ° C pass through the preheating portion 12 along a spiral path determined by the helical fin 9, thereby maximizing contact time. with the wall of the preheating portion 7 of the reaction chamber 5a. The fumes are then eliminated through line 19 aspirated by suction means 20 and, after passing through heat exchange means 21 and appropriate purification means employing urea solutions in an SNCR 21a reactor, are discharged in one way. 22

In the heat exchange means 21 air is preheated which, through line 23, is injected into the burners 14 as oxidizing. Downstream of the reaction chamber 5a, the reactor 5 comprises a vertical axis chamber 15, open at the bottom from which carbon with the inert is discharged via automated gate valves. The inert and carbon are collected in a bathtub 16, from which they are transferred via a helical conveyor 17 to a water-cooled duct 18 and then to the carts for removal from the installation. A portion of these, always via the helical conveyor 17, may be sent to hopper 3 for recirculation and maximization of pyrolysis gas production.

In reactor 5, maintained at a temperature of between 400 ° C and 500 ° C, typically about 450 ° C, and in an oxygen-depleted atmosphere, the material undergoes a thermal decomposition process and the carbon thus produced reacts with water. to form the pyrolysis gas (hydrogen and carbon oxide) in a yield of about 80 wt%. Pyrolysis gas leaving reaction chamber 5a of reactor 5 is sent through line 25 to a cyclone separator 26 for disposal of powders. The cyclone separates the solid or liquid particles present in the gas flow taking advantage of the centrifugal force developed by the vortex movement imposed to said gas flow.

From cyclone 26 pyrolysis gases, free from most powders, are subjected to a quench phase of from about 450 ° C to about 40-60 ° C. In such phase the condensation of the acid gases (HCl, SO2) is obtained. The quench phase is performed by adding cold water to the temperature controlled gas. The gas at the outlet of cyclone 26 along line 27 is passed through a rapid cooling unit 28 preferably provided with a restricted section duct into which, by venturi effect, water is injected finely. disperses in gas. The gas thus cooled is sent to a washing unit 29. Such a washing unit preferably consists of a scrubber which comprises a vertical reservoir filled with inert material (spiralette). In such a reservoir, in countercurrent with the gas flow, the basic washing waters are fed to neutralize the acidic substances present in the pyrolysis gas. Such basic waters may advantageously consist of water mixed with quicklime milk.

Washing waters having a temperature of about 40-60 ° C are sent to a decanter 30 for separation of the clarified waters by the sludge. The sludge, through line 32a, is sent to the top of the installation in hopper 3.

The clarified waters are revived along line 32 to wash unit 29 and rapid cooling unit 28. Pyrolysis gas exiting from wash unit 29 along line 33 is forced to pass through one unit. condensation 31, in which the residual liquid particles condense and are then eliminated, yielding a high purity pyrolysis gas, which enables a high yield of energy transformation.

In one embodiment, the condensing unit 31 is comprised of a gas-coil recovery heat exchanger associated with a cooling group 31a, in which the refrigerant is, for example, comprised of a glycol solution. of ethylene.

At the outlet of the condensing unit 31, along line 34, the purified pyrolysis gas is routed through suitable pumping means 35 (e.g. rotary vane aspirators) to an accumulation lung 36 (membrane pressure accumulator). or gasometer).

As stated above, pyrolysis gas can be sent, in part and along line 24, to burners 14, while line 37 leads it to cogeneration group 38, typically consisting of an internal combustion engine. and an alternator connected to the main motor shaft.

In embodiments, the purified pyrolysis gas may be sent along line 39 to an emersion torch 40 in which the gas is burned prior to its emission into the atmosphere. This solution is useful both when production exceeds the capacity of accumulation lung 36 (gas is sent along line 41 rather than to accumulation lung 36), and where it is necessary to perform a forced exhaustion of the accumulating lung (line 42).

By the term "line" in the present description is meant a pipe in which gas circulates, either naturally or forcedly through suitable pumping or suctioning means.

One embodiment, the installation is provided with a line 43, 44 for recirculation of an inert gas through reactor and cyclone 26. This line is activated at the start and stop phase of the installation. The inert gas, typically nitrogen, is heated inside reactor 5, then circulated along line 25, cyclone 26 and lines 43, 44 to heat the pipelines along the pyrolysis gas pathway in the reactor. reactor output. This prevents condensation of liquid hydrocarbons which could form at low temperatures in such pipelines, depositing on both the cyclone and the walls. Once the reactor is started or broken, the same temperature as the pyrolysis gases keeps the piping at a sufficiently high temperature to prevent the formation of liquid hydrocarbons. The pyrolysis plant according to the present invention may advantageously be integrated with a command and control unit operated by an algorithm which, using the inlet flow and the characterization of the organic matrix material fed into the feedstock as input. reactor and the characteristics of all incoming and outgoing system flows, both globally and in unit components, allow for material and energy balances. The facility is equipped with suitable temperature, pressure and composition detectors and / or sensors for chemical-analytical analyzes for both the pyrolysis gas and the fumes produced, which include a set of parameter values that is used as input. (input) to the command and control unit during all phases of the process. The mathematical algorithm, in particular, provides the following outputs: • The flow, average composition and physicochemical characteristics that reveal the pyrolysis gas produced, which temperature, viscosity, density, calorific value; • the flow rate of the carbon powder produced and its calorific value; • the flow and the composition of the combustion fumes; ■ the amount of inert to be assimilated; • the condensates produced; • the pyrolysis gas flow rate required to maintain the reactor at a temperature of about 450 ° C required to initiate pyrolysis reactions; • Excess air required for combustion of pyrolysis gas and auxiliary fuels in reactor burners. The pyrolysis process according to the present invention therefore generally comprises the following operational steps: (a) making available an installation as defined above; b) adding a cracking reaction catalyst, preferably chosen from nickel, iron or chromium based catalysts, to said organic matrix material; c) preheating said organic matrix material and regulating the water content by about 30% by weight; d) slowly pyrolysis of said organic matrix material and recovering pyrolysis gases comprising hydrogen and carbon monoxide; e) the rapid cooling phase of said pyrolysis gases; and f) washing phase of said cooled pyrolysis gases. Step c) of preheating and regulating the water content usually provides for excess water to evaporate to the desired amount, as the organic material typically has a water content of greater than 30%.

However, in the case of an organic material with a lower water content, the adjustment phase may provide for the addition of an amount of water to obtain a total content equal to the desired value.

In one embodiment, the procedure of the invention comprises a start or stop phase of the installation in which reactor 5 is recirculated along line 25 downstream of reactor 5 and in cyclone 26 a pre-inert gas. heating. The process of the invention has many advantages that have already been highlighted in part. The process can be applied to both agricultural and forest biomass, as well as to refuse of any kind, as long as it contains an organic matrix, such as plastics, paper, fabrics, rotting organic material, etc. The process also allows the maximization of the production of pyrolysis gas, useful source of energy. At the same time, there is minimal carbon production and a total absence of liquid fuels. The energy requirement of the installation is guaranteed by the pyrolysis gas produced. The helical fin 9 allows to increase the contact of the combustion fumes with the walls of the preheating portion 7 of the reaction chamber 5a. Preheating the pipes and cyclone through inert gas allows condensation of liquid hydrocarbons to be avoided. The longitudinal arrangement of the burners 14 increases the heating efficiency of the pyrolysis portion 8 of the reaction chamber 5a. Slow, wet catalyzed pyrolysis according to the present invention can therefore be considered as an innovation in pyrolysis processes as it enables the transformation of organic matrix material into synthesis gas with a higher final yield. that of conventional pyrolysis processes. Given its characteristics, the gas obtained can be converted into electrical energy through simple internal combustion engines, engines whose technology is already consolidated.

It is evident that only one particular embodiment of the present invention has been described, and that one skilled in the art is able to provide all modifications necessary for its adaptation to particular applications, without however escaping the scope of protection of the present invention.

Claims (18)

A plant for the pyrolysis of an organic matrix material, comprising: - a reaction chamber (5a) subdivided into a preheating portion (7) and a pyrolysis portion (8) downstream of said portion of preheating (7); - a combustion chamber (6) coaxial and external to said reaction chamber (5a), said combustion chamber (6) being subdivided into a preheating portion (12) which surrounds said portion (7) of the combustion chamber (5a), and in a heating portion (13) which surrounds said pyrolysis portion (8) of the reaction chamber (5a), said heating portion ( 13) of the combustion chamber (6) hosting burners (14), characterized in that: - said reaction chamber (5a) is rotatable along a horizontal axis within said combustion chamber (6), and The outer surface of the preheating portion (7) of the reaction chamber (5a) comprises a helical fin (9) which creates a spiral path for the flue gas generated by the burners (14). Plant according to Claim 1, characterized in that said burners (14) are arranged longitudinally along the entire length of the heating portion (13) of said combustion chamber (6). Installation according to Claim 1 or 2, characterized in that it comprises heat exchange means (21) for the combustion chamber evacuated combustion smoke (6), and in said heat exchange means (21). passes a line (23) which directs air to the burners (14) Plant according to any one of claims 1 to 3, characterized in that a cyclone (26) is disposed downstream of the reactor (26) to remove dust from the pyrolysis gas. Installation according to Claim 4, characterized in that downstream of cyclone (26) a rapid cooling unit (28) is provided for cooling pyrolysis gases to a temperature of 40 ° C to 60 ° C. ° C. Installation according to Claim 5, characterized in that said rapid cooling unit (28) comprises a restricted cross-section for finely dispersed water injection. Installation according to claim 5 or 6, characterized in that a washing unit (29) is arranged downstream of said rapid cooling unit (28). Installation according to Claim 7, characterized in that said washing unit (29) comprises a vertical reservoir filled with inert material for backwashing the gas with a rain of water. Installation according to Claim 7 or 8, characterized in that a condensing unit (31) is provided downstream of said flushing unit (29) for residual pyrolysis gas liquids. Installation according to Claim 9, characterized in that said condensing unit (31) is a gas-coil recovery heat exchanger associated with a refrigeration group (31a), the refrigerant being It is preferably comprised of an ethylene glycol solution. Plant according to any one of claims 1 to 10, characterized in that it comprises a line (43, 44) for the recirculation of a heated inert gas through the reactor (5) and the cyclone (26) during the start and stop phase of the installation. A slow pyrolysis process of an organic matrix material, comprising the following steps: (a) disposing of an installation as defined in any of the preceding claims; b) adding a cracking reaction catalyst, preferably chosen from nickel, iron or chromium based catalysts, to said organic matrix material; c) preheating said organic matrix material and regulating the water content by about 30% by weight; d) conducting slow pyrolysis of said organic matrix material and recovering pyrolysis gases comprising hydrogen and carbon monoxide; e) rapidly cooling said pyrolysis gases; and f) flushing said cooled pyrolysis gases. Process according to Claim 12, characterized in that said slow pyrolysis is conducted for a time between 0.5 and 1.5 hours and at a temperature between 400 ° C and 500 ° C, or then at about 450 ° C. Process according to Claim 12 or 13, characterized in that said cracking reaction catalyst is added in an amount of 100-300 mg per kg of organic matrix material. Process according to any one of claims 12 to 14, characterized in that said pyrolysis gases, prior to being subjected to dota rapid cooling phase e), undergo a depulverization treatment. Process according to any one of claims 12 to 15, characterized in that said rapid cooling step e) is carried out by injecting water into said temperature controlled pyrolysis gases. Process according to any one of claims 12 to 16, characterized in that it comprises a start and / or stop phase of the installation in which the reactor (5) is recirculated along the line ( 25) downstream of reactor (5) and cyclone (26), a preheating inert gas, said inert gas being preferably nitrogen. Process according to any one of claims 12 to 17, characterized in that said pyrolysis gases are used in a power / heat cogeneration facility.