EP2666845A1

EP2666845A1 - Gas producing apparatus

Info

Publication number: EP2666845A1
Application number: EP12169260.2A
Authority: EP
Inventors: Murat Dogru
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-05-24
Filing date: 2012-05-24
Publication date: 2013-11-27

Abstract

A gas production apparatus (2) is disclosed. The apparatus comprises a receptacle (4) for receiving and processing carbonaceous material and or carbonaceous solid fuel and or fuel containing hydrocarbon(s)passing therethrough, the receptacle defining a flaming pyrolysis zone (34) in which carbonaceous material is heated in the presence of partial oxygen to generate volatile gases, and a gasification zone (42) in which carbonaceous material is to generate volatile gases and char-ash. A first agitator has a stirrer (16) and blades (18) for agitating carbonaceous material in the flaming pyrolysis zone and a hollow air pipe (28) for introducing air into the flaming pyrolysis zone. A second agitator has rotating double shaft (46) and hallow blades (50) for grinding and moving fused char and for introducing air and or water to the gasification zone (42)via air and water pipes (54). Gas discharge pipes (40) enable removal of volatile gases from the receptacle 4.

Description

The present invention relates to a gas producing apparatus, and relates particularly, but not exclusively, to a gas producing apparatus for producing flammable gases from carbonaceous combustible wastes and biomasses.
Gas producing apparatus are known for the production of flammable synthesis gases via thermochemical flaming pyrolysis (i.e. thermal decomposition of organic molecules), partial oxidation and gasification of combustible organic material such as biomass materials and combustible domestic and industrial wastes. The resulting raw gases produced by the gas producer are then cooled and cleaned and used for the production of energy in the form of electrical power and heat by means of gas engine generators, dual fuel converted diesel engine generators, gas, steam or oil turbines and high temperature fuel cells. The cooled and cleaned gasses can also be converted to liquid fuels such as methanol, ethanol, ammonia and FT-diesel by means of processing in catalytic converters. Pyrolysis and gasification of biomass or waste materials using sub-stoichiometric oxygen in air as an oxidising agent can generate a high yield of clean product gas known as producer gas or synthesis gas. Pyrolysis consists of thermochemical decomposition of carbon based compounds to produce char, tar and volatile compounds.
However, the resulting tar and char can impair the quality of the product gas. Also, conventional gas producers generally operate in batch mode as a result of difficulties encountered in continuous ash/clinker removal, overheating, fuel bridging or channelling and excessive tar production. Due to high temperature operation of conventional gas producers, clinkers are formed, and melted clinkers fuse together to form bridges in the base of the gasifier reactor which then cause discontinuous gas and fuel flow, as a result of which the resulting product gas has a high tar content. The increased tar content of the produced gas as a result of conditions in the start up, ramp up and low temperature phases resulting from intermittent use of the gasifiers causes tar to accumulate in the gas treatment sections and in internal parts of power generators utilising the product gas, as a result of which the various parts of the gas treatment equipment and the engine power generators require frequent cleaning and maintenance, which in turn increases maintenance costs. This limits the range of materials which can be used in the gas producing process. In addition, because of the relatively high local temperatures in the partial oxidation region in the course of the gasification process, melted cinders cannot be fully discharged, as a result of which congestion occurs in the system.
A continuous operation catalytic gasifier is disclosed in WO 2005/047435 . However, this arrangement suffers from the disadvantage that the perforated catalytic element can become blocked with deposition of carbon soot particles at the surface of catalyst whilst raw gas is passing through, limiting the extent to which the apparatus can be used continuously. In addition, large clinkers formed due to fused ash and char in the high temperature zone accumulate in the bottom of the gasifier over a period of operation time which then causes bridge formation, blocking the continuous fuel movement in the reactor and ash/char extraction from the gasifier.
Preferred embodiments of the present invention seek to overcome one or more of the above disadvantages of the prior art.
According to an aspect of the present invention, there is provided a gas production apparatus comprising:-
at least one receptacle for receiving and processing at least one first carbonaceous material passing therethrough, at least one said receptacle defining (i) at least one respective first zone in which at least one said first carbonaceous material is heated in the presence of oxygen to generate at least one volatile gas and at least one second carbonaceous material, and (ii) at least one respective second zone in which at least one said second carbonaceous material is at least partially combusted to generate at least one volatile gas and char;
first oxygen containing material introducing means for introducing at least one oxygen containing material into at least one said first zone;
first agitator means for agitating at least some of said first and/or second carbonaceous material in at least one said first zone;
at least one gas outlet for enabling at least partial removal of at least one said volatile gas from at least one said receptacle;
second oxygen containing material introducing means for introducing at least one oxygen containing material into at least one said second zone; and
second agitator means for mechanically reducing the size of char particles formed in at least one said second zone.
By providing first agitator means for agitating at least some of said first and/or second carbonaceous material in at least one said first zone, this provides the advantage of simplifying the construction of the apparatus, thereby reducing its cost, while also reducing the formation of fuel bridges, thereby enabling the apparatus to be operated continuously for longer periods, thereby increasing the efficiency of operation of the apparatus. In addition, by enabling the apparatus to be operated continuously for longer periods, this reduces the tar content of the resulting gas, as a result of which maintenance costs of gas and water cleanup downstream equipment and power generating apparatus using the resultant gas can be reduced. Furthermore, by providing second agitator means for mechanically reducing the size of char particles formed in at least one said second zone, this provides the advantage of minimising material blockage in said receptacle, thereby enabling the apparatus to be operated continuously for longer periods. This in turn reduces the tar content of the resulting gas.
The first oxygen containing material introducing means may be adapted to introduce fluid containing oxygen through at least one said agitation member.
This provides the advantage of enabling more compact construction of the apparatus.
At least one said gas outlet may be arranged between at least one said first zone and at least one said second zone.
This provides the advantage of enabling more compact construction of and more efficient operation of the apparatus.
At least one said receptacle may be arranged such that at least one said first carbonaceous material and/or at least one said second carbonaceous material and/or said char move therethrough under gravity.
This provides the advantage of enabling more simple construction of the apparatus thereby improving its efficiency and reliability and reducing its cost.
Said first agitator means may comprise at least one agitation member adapted to be rotated relative to a body of a respective said receptacle.
This provides the advantage of enabling more simple and compact construction of the apparatus, by enabling the agitation member to also assist in causing the first and/or second carbonaceous material to pass through the receptacle.
The second agitator means may comprise at least one pair of rotating members adapted to engage material therebetween.
The second oxygen containing material introducing means may be mounted to said second agitator means.
The second oxygen containing material introducing means may include a plurality of fluid introducing members mounted to at least one said rotating member of at least one said pair.
The apparatus may further comprise removal means for removing char and/or ash generated in at least one said second zone.
This provides the advantage of enabling the apparatus to be used continuously for longer periods.
At least one said receptacle may define at least one third zone for drying at least one said first carbonaceous material before entry thereof into at least one said first zone.
At least one said receptacle may define inner and outer walls having a gap therebetween.
This provides the advantage of enabling the introduction of temperature control or cooling fluid, thereby enabling the temperature of reactions inside the receptacle and exit gas to be controlled, thereby enabling efficiency of operation of the apparatus to be controlled.
According to another aspect of the present invention, there is provided a method of producing gas, the method comprising:

heating at least one first carbonaceous material in at least one first zone in the presence of oxygen to generate at least one volatile gas and at least one second carbonaceous material;
partially combusting at least one said second carbonaceous material in at least one said second zone to generate at least one volatile gas and char;
introducing at least one oxygen containing material into at least one said first zone;
agitating at least one said first and/or second carbonaceous material in at least one said first zone;
at least partially removing at least one said volatile gas;
introducing at least one oxygen containing material into at least one said second zone; and
mechanically reducing the size of char particles formed in at least one said second zone.

The method may further comprise removing char and/or ash generated in at least one said second zone.
The method may further comprise drying at least one said first carbonaceous material in at least one third zone prior to entry of said first carbonaceous material into at least one said first zone.
A preferred embodiment of the invention will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawing in which Figure 1 is a schematic side cross sectional view of a gas producing apparatus embodying the present invention.
Referring to Figure 1, a gas producing apparatus 2 embodying the present invention includes a receptacle 4 comprising an upper part 6 mounted to a lower part 8. The upper part 6 includes a fuel hopper 10 for feeding carbonaceous material such as biomass and/or organic waste material into an upper body 12 via a gate valve 14. A first agitator comprises a stirrer device 16 having blades 18 and an axle 20 mounted via bearings 22 to an upper part 24 of the upper body 12. The blades 18 are rotatable about a longitudinal axis of the axle 20 by means of a motor and gearbox assembly 26. The axle 20 contains a hollow air pipe 28 enabling oxygen containing material in the form of air with or without water mist to be introduced into a flaming pyrolysis zone 34 (described in greater detail below) through the interior of the upper body 12, and an air inlet pipe 30 is provided in an upper region of the upper body 12 to enable a limited amount of air distribution through diffusion in voids in material contained within the upper body 12.
The upper body 12 defines a fuel drying zone 32 in which organic material introduced via the hopper 10 and gate valve 14 is dried, and flaming pyrolysis zone 34 in which chemical decomposition of organic molecules in the presence of a limited or partial supply of oxygen in air occurs while the organic material is being agitated by the stirrer blades 18.
The upper body 12 of the receptacle 4 is mounted to lower body 8 such that an upper part 36 of the lower body 8 surrounds a lower cylinder 38 of the upper body 4 surrounding the flaming pyrolysis zone 34. Gas discharge pipes 40 are provided through the upper part 36 of the lower body 8 to enable removal of volatile gases generated in the flaming pyrolysis zone 34 and in a char gasification zone 42 located below the flaming pyrolysis zone 34. The lower body 8 has twin walls having a gap 44 therebetween so that chilled water can be circulated through the reactor walls to control the reaction temperature within the lower body 8 and the gas exit temperature.
In the char gasification zone 42, partial combustion of char generated in the flaming pyrolysis zone 34 and passing downwards through the receptacle 4 under gravity occurs. A second agitator 46 for mechanically breaking down char generated in the flaming pyrolysis zone 34 is located below the char gasification zone 42 and includes a pair of adjacently located parallel counter rotating shafts 48 (only one of which is shown in Figure 1) having cylindrical and or rectangular blades 50 extending radially outwardly therefrom. The shafts 48 are rotated by means of a motor and gearbox 52 mounted to first ends of the shafts 48, and the shafts 48 are hollow to enable oxygen containing material in the form of air to be introduced, with or without water mist or steam, by means of air pipes 54 at second ends of the shafts 48. The second agitator 46 facilitates char and ash mixture flow through the receptacle 4 by engaging and moving fused ash and unreacted fused char (clinker material) from the char gasification zone 42 and. The second agitator 46 then grinds and pushes such materials downwards to an char and ash removal zone 56 leading to an ash discharge auger system 58 located at the lower end of the gas producer 2.
The gas producing apparatus 2 operates as follows.
Biomass and or carbon containing waste material is introduced into the fuel drying zone 32 defined in the upper body 12 via the fuel hopper 10 and gate valve 14. The heat energy required for endothermic drying in the fuel drying zone 32 is provided from the flaming pyrolysis zone 34 via radiation and convection heat transfer, and the fuel drying zone 32 is operated at temperatures around 100°C to 300°C, preferably in the region of 200°C. The dried fuel is then agitated by means of the first agitator, the blades 18 of the agitator urging the fuel downwards into the flaming pyrolysis zone 34, while preventing formation of fuel bridges formed during the reaction in the flaming pyrolysis zone 34 and filling voids generated in the flaming pyrolysis zone 34.
The following main reactions occur in the flaming pyrolysis zone 34, which operated typically at temperatures above 950°C:

[1] C + ½ O2 → CO (-111 MJ/kmol)

[2] CO + ½ O2 → CO2 (-283 MJ/kmol)

[3] H2 + ½ O2 → H2O (-242 MJ/kmol)
Dried fuel in the flaming pyrolysis zone 34 is then converted into char and volatile gases, and carbon based char materials generated in the flaming pyrolysis zone 34 descend to the gasification zone 42. In the gasification zone 42, char is gasified by means of the following reduction reactions with the addition of further limited amount of oxygen in air and/or steam and/or water mist from nozzles of the blades 50 mounted to the rotating shafts 48:

[4] C + H2O ↔ CO + H2 (+131 MJ/kmol)

[5] C + CO2 ↔ 2CO (+172 MJ/kmol)

[6] C + 2H2 ↔ CH4 (-75 MJ/kmol)

[7] CO + H2O ↔ CO2 + H2 (-41 MJ/kmol)

[8] CH4 + H2O ↔ CO + 3H2 (+206 MJ/kmol)
Carbon monoxide and hydrogen gases are mainly generated in the gasification zone 42 and move upwards towards gas discharge pipes 40. The blades 50 mounted to the rotating shafts 48 provide a limited supply of air for partial combustion, and/or steam and/or water mist generally uniformly distributed to the char gasification zone 42, and residue char material gasified while the gases are generated in the gasification zone 42 by means of endothermic water gas shift reactions and char is further partially converted to gases and char with inert ashes. The lower part of the gasification zone 42 operate at temperatures of around 600°C to 900°C, but an operation temperature in the region of 800°C is preferred.
The blades 50 of the rotating shafts 48 also function to hold and support the fuel bed like a grate and grind clinker material (fused ash and fused char) and convey such material to the ash removal auger system 58 at the lower end of the receptacle 4. This also serves to convey clinker materials downwards to the ash removal auger system 58.
Operation of the gas production apparatus 2 is assisted by forming a negative pressure at gas outlet pipes 40 by means of a gas suction blower (not shown) which removes volatile gases from the system while enabling entry of a limited amount of air through air intake pipes 28, 30, 54.
It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only, and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims.

Claims

A gas production apparatus comprising:-
at least one receptacle for receiving and processing at least one first carbonaceous material passing therethrough, at least one said receptacle defining (i) at least one respective first zone in which at least one said first carbonaceous material is heated in the presence of oxygen to generate at least one volatile gas and at least one second carbonaceous material, and (ii) at least one respective second zone in which at least one said second carbonaceous material is at least partially combusted to generate at least one volatile gas and char;
first oxygen containing material introducing means for introducing at least one oxygen containing material into at least one said first zone;
first agitator means for agitating at least some of said first and/or second carbonaceous material in at least one said first zone;
at least one gas outlet for enabling at least partial removal of at least one said volatile gas from at least one said receptacle;
second oxygen containing material introducing means for introducing at least one oxygen containing material into at least one said second zone; and
second agitator means for mechanically reducing the size of char particles formed in at least one said second zone.
An apparatus according to claim 1, wherein said first oxygen containing material introducing means is adapted to introduce fluid containing oxygen through at least one said agitation member.
An apparatus according to claim 1 or 2, wherein at least one said gas outlet is arranged between at least one said first zone and at least one said second zone.
An apparatus according to any one of the preceding claims, wherein at least one said receptacle is arranged such that at least one said first carbonaceous material and/or at least one said second carbonaceous material and/or said char move therethrough under gravity.
An apparatus according to any one of the preceding claims, wherein said first agitator means comprises at least one agitation member adapted to be rotated relative to a body of a respective said receptacle.
An apparatus according to any one of the preceding claims, wherein said second agitator means comprises at least one pair of rotating members adapted to engage material therebetween.
An apparatus according to any one of the preceding claims, wherein said second oxygen containing material introducing means is mounted to said second agitator means.
An apparatus according to claims 6 and 7, wherein said second oxygen containing material introducing means includes a plurality of fluid introducing members mounted to at least one said rotating member of at least one said pair.
An apparatus according to any one of the preceding claims, further comprising removal means for removing char and/or ash generated in at least one said second zone.
An apparatus according to any one of the preceding claims, wherein at least one said receptacle defines at least one third zone for drying at least one said first carbonaceous material before entry thereof into at least one said first zone.
An apparatus according to any one of the preceding claims, wherein at least one said receptacle defines inner and outer walls having a gap therebetween.
A method of producing gas, the method comprising:
heating at least one first carbonaceous material in at least one first zone in the presence of oxygen to generate at least one volatile gas and at least one second carbonaceous material;

partially combusting at least one said second carbonaceous material in at least one said second zone to generate at least one volatile gas and char;

introducing at least one oxygen containing material into at least one said first zone;

agitating at least one said first and/or second carbonaceous material in at least one said first zone;

at least partially removing at least one said volatile gas;

introducing at least one oxygen containing material into at least one said second zone; and

mechanically reducing the size of char particles formed in at least one said second zone.
A method according to claim 12, further comprising removing char and/or ash generated in at least one said second zone.
A method according to claim 12 or 13, further comprising drying at least one said first carbonaceous material in at least one third zone prior to entry of said first carbonaceous material into at least one said first zone.