CN106833759B - Device and method for removing biomass gasification tar based on chemical chain reforming - Google Patents

Abstract

The invention discloses a device and method for removing biomass gasification tar based on chemical chain reforming, which comprises a first cyclone separator connected in sequence for separating and dedusting the crude gas of biomass gasification, A preheater for preheating biomass gasification crude gas, a reforming reactor for reforming the preheated biomass gasification crude gas with an oxygen carrier, and a reforming reactor for reforming the oxygen carrier An air combustion reactor for combustion reaction with air, a second cyclone separator for separating and dedusting the oxidized oxygen carrier is connected between the air combustion reactor and the reforming reactor, and the reforming reactor is also A third cyclone separator for separating and dedusting the reacted gas is connected. The invention utilizes the lattice oxygen and catalysis of the oxygen carrier to partially oxidize the tar macromolecules into CO, _H2 and other small molecular substances; the oxygen carrier is regenerated cyclically between the reforming reactor and the combustion reactor, and the regeneration of the oxygen carrier is simple.

Description

A device and method for removing biomass gasification tar based on chemical chain reforming

technical field

The invention relates to the technical fields of energy and chemical industry, in particular to a device and method for removing biomass gasification tar based on chemical chain reforming.

Background technique

Biomass is a resource-rich renewable energy source. The high volatile (about 70%) content of biomass determines that its gasification utilization method has economic and technical advantages. Biomass gasification technology can be connected with subsequent units of synthetic liquid fuels, power generation, heat supply, and production of chemical products, so as to achieve clean, efficient and diversified utilization of biomass resources. However, at present, whether it is biomass gasification technology using air, steam or oxygen, and fixed bed or fluidized bed reactor, the gas contains more tar by-products due to the high volatile content of biomass. Gaseous, and condenses to liquid below about 200°C. The existence of tar has a serious impact on biomass gasification and its utilization, such as reducing gasification efficiency, blocking pipelines, poisoning subsequent synthesis catalysts, and damaging gas utilization equipment, etc. It will also increase the difficulty of gas purification and cause environmental pollution. Therefore, the tar content in the gas is one of the decisive factors restricting the large-scale application of biomass gasification technology. How to eliminate the tar in the gasification process is the most urgent problem to be solved in the current biomass gasification technology. Although measures such as increasing the operating temperature can reduce the amount of tar produced during biomass gasification to a certain extent, even so, the tar content in the gas is still relatively high, and further removal is required to meet the downstream utilization requirements. The removal technology of tar in gas includes physical method and chemical method. The physical method is to remove the tar from the gas by washing with water or an absorbent. The method is simple but very easy to cause secondary pollution. The chemical method is to decompose the tar into small molecular gas through catalytic cracking, without secondary pollution, and at the same time, the tar is converted and utilized. It is the most studied tar removal method at present. The traditional catalytic cracking is divided into two ways: one is that dolomite, alkaline earth metal compounds and biomass are catalytically gasified together in the gasifier to reduce the production of tar; of tar. Coke and dolomite have the disadvantages of large dosage and low catalytic efficiency. Nickel-based catalysts have high activity and good tar cracking effect, but their surface is prone to coking and deactivation. Nickel-based catalysts are generally composed of nickel, additives and carriers. The catalyst needs to be reduced before use, and elemental nickel is the active site of the catalyst. Ni-MgO/HZSM-5 disclosed in patent (CN104549450A), NiO-MgO-CeO ₂ -WO ₃ -olivine disclosed in patent (CN102145292A), NiO-La ₂ O ₃ -CeO ₂ -MgO disclosed in patent (CN101693204B) -γAl ₂ O ₃ , the monolithic NiO-γAl ₂ O ₃ -cordierite and other biomass gasification tar catalytic cracking catalysts disclosed in the patent (CN100404135C) need to be reduced with H ₂ before use. After the above-mentioned nickel-based catalyst is deactivated by carbon deposition, it needs to go through a two-step regeneration process of carbon removal and reduction, which is complicated in process and high in cost. The industrial application of nickel-based catalyst for cracking tar is severely restricted by cost.

Therefore, the existing technology still needs to be improved and developed.

SUMMARY OF THE INVENTION

In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a device and method for removing biomass gasification tar based on chemical chain reforming, aiming to solve the existing tar removal technology that is easy to deposit carbon, requires pre-reduction and reproduction difficulties.

The technical scheme of the present invention is as follows:

A device for removing tar from biomass gasification based on chemical chain reforming, which includes a first cyclone that is connected in sequence for separating and dedusting crude gas from biomass gasification, A preheater for preheating fuel gas, a reforming reactor for reforming the preheated biomass gasification crude fuel gas and oxygen carrier, and a combustion reaction for the reformed oxygen carrier and air A second cyclone separator for separating and dedusting the oxidized oxygen carrier is connected between the air combustion reactor and the reforming reactor, and the reforming reactor is also connected with a second cyclone for separating and dedusting the oxidized oxygen carrier. The third cyclone separator for separation and dust removal of the latter gas.

A method for removing biomass gasification tar using the above-mentioned device, comprising the steps of:

Step A. After the biomass gasification crude gas is separated and dedusted by the first cyclone separator and preheated by the preheater, it enters the reforming reactor for reformation reaction with the oxygen carrier, and the reacted fuel gas is separated by the third cyclone separator. After dust removal, clean gas is obtained;

In step B, the oxygen carrier after the reforming reaction enters the air combustion reactor, and carries out combustion reaction with air. After the oxygen carrier is oxidized, it is separated and dedusted by the second cyclone and then enters the reforming reactor for recycling.

The method, wherein the oxygen-depleted air produced by the combustion reaction in the air combustion reactor is separated and dedusted by the second cyclone separator, and then enters the preheater to preheat the crude gas.

The method, wherein, in the step A, the mass ratio of the tar content in the crude fuel gas to the lattice oxygen of the oxygen carrier in the reforming reactor is 1:0.5-5.

In the method, in the step B, the excess coefficient of air combustion in the air combustion reactor is 0.5-1.5.

In the method, in the step A, the operating temperature of the reforming reactor is 550-950° C. and the operating pressure is 0.1 MPa.

The method, wherein, the operating temperature of the air combustion reactor is 850-1050° C., and the operating pressure is 0.1 MPa.

The method, wherein the active component of the oxygen carrier is one or more of Fe oxide, Cu oxide, Ni oxide, Ce oxide, Mn oxide, and Ca oxide, and the oxygen carrier is The inert component of the carrier is one or more of Al ₂ O ₃ , MgO, and ZrO.

In the method, the content of the active component is 30-80 wt %, and the content of the inert component is 20-70 wt %.

In the method, the particle size of the oxygen carrier ranges from 0.1 to 5 mm.

Beneficial effects: the present invention utilizes the lattice oxygen of the oxygen carrier to partially oxidize the tar macromolecules to CO, H ₂ and other small molecular substances at high temperature to remove, and at the same time, it can partially retain and utilize the energy of the tar, which is removed by the device. The tar content of the rear gas is less than 1g/Nm ³ , and the tar removal rate exceeds 90%; in addition, the circulation of the oxygen carrier integrates oxygen transfer, heat transfer and catalysis, which can make full use of the oxidation reaction heat of the oxygen carrier and the display of crude gas. In addition, the oxygen carrier regenerates and eliminates possible carbon deposits by circulating between the reforming reactor and the air combustion reactor. The oxygen carrier is easy to regenerate and eliminate carbon deposits, which is conducive to maintaining the continuous operation of the system.

Description of drawings

1 is a schematic diagram of a device for removing biomass gasification tar based on chemical chain reforming according to the present invention.

Detailed ways

The present invention provides a device and method for removing biomass gasification tar based on chemical chain reforming. In order to make the purpose, technical scheme and effect of the present invention clearer and clearer, the present invention is further described below in detail. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

With reference to Fig. 1, a schematic diagram of a device for removing biomass gasification tar based on chemical chain reforming of the present invention, as shown in the figure, includes a sequential connection for separating and dedusting the biomass gasification crude gas. A cyclone separator, a preheater for preheating the biomass gasification raw gas, a reforming reactor for reforming the preheated biomass gasification raw gas with an oxygen carrier, and a An air combustion reactor for combusting the reformed oxygen carrier with air, and a second cyclone separator for separating and dedusting the oxidized oxygen carrier is connected between the air combustion reactor and the reforming reactor , the reforming reactor is also connected with a third cyclone separator for separating and dedusting the fuel gas after the reforming reaction.

Based on the above-mentioned device, the present invention provides a method for removing biomass gasification tar by using the above-mentioned device, which comprises the following steps:

Step A. After the biomass gasification crude gas is separated and dedusted by the first cyclone separator and preheated by the preheater, it enters the reforming reactor for reformation reaction with the oxygen carrier, and the reformed gas is separated by the third cyclone. After separating and dedusting, clean gas is obtained;

In step B, the oxygen carrier after the reforming reaction enters the air combustion reactor, and carries out combustion reaction with air. After the oxygen carrier is oxidized, it is separated and dedusted by the second cyclone and then enters the reforming reactor for recycling.

With reference to FIG. 1 , the above-mentioned method for removing tar from biomass gasification of the present invention will be described in detail below.

In step A, the crude gas containing tar from the biomass gasification system is separated and dedusted by the first cyclone separator, and then preheated with the high-temperature tail gas (oxygen-depleted tail gas) from the air combustion reactor in the preheater, and then enters the equipment containing the tar. The reforming reactor of metal oxides (oxygen carrier), the macromolecular tar substances in the crude gas and the lattice oxygen of the high temperature oxygen carrier undergo a partial oxidation reaction, after the conversion of CO, _H2 and other small molecular substances, the oxygen carrier is reduced, and the reaction After the gas is separated and dedusted by the third cyclone separator, clean gas is obtained. The invention utilizes the lattice oxygen of the oxygen carrier to partially oxidize the tar in the biomass crude fuel gas into small molecular substances such as CO and H ₂ to remove it, and at the same time, it can partially retain and utilize the energy of the tar.

In step A, the tar content in the crude fuel gas and the lattice oxygen mass ratio of the oxygen carrier in the reforming reactor are 1:0.5-5, preferably, the mass ratio is 1:1-3, for example, the mass ratio is 1:1, 1:2 or 1:3

In step A, the operating temperature of the reforming reactor is 550-950° C., and the operating pressure is 0.1 MPa. The heat required for the temperature of the reforming reactor of the present invention is provided by the sensible heat of the crude fuel gas and the high-temperature oxygen carrier, and the sensible heat of the high-temperature tail gas of the air combustion reactor.

In step B, the reduced oxygen carrier (which may have some carbon deposits on its surface) after the reforming reaction enters the air combustion reactor, and undergoes a combustion reaction with air, and the oxygen carrier is completely or mostly oxidized to regain crystals. Lattice oxygen, surface carbon is completely oxidized to _CO2 and eliminated, the oxygen carrier is heated by the heat generated by combustion at the same time, after oxidation, the high temperature oxygen carrier enters the reforming reactor for recycling.

In step B, the air combustion excess coefficient in the air combustion reactor is 0.5-1.5, and the air combustion excess coefficient refers to the ratio of the actual air amount to the theoretical air amount for complete oxidation of the reduced oxygen carrier.

The operating temperature of the air combustion reactor is 850-1050° C., and the operating pressure is 0.1 MPa. The heat required for the temperature of the air combustion reactor of the present invention is provided by the heat of oxidation reaction between the reduced oxygen carrier and the oxygen in the air.

The above two steps of step A and step B form a cyclic process.

The invention utilizes the lattice oxygen of the oxygen carrier to partially oxidize the tar in the biomass crude fuel gas into small molecular substances such as CO and H ₂ to remove it, and at the same time, it can partially retain and utilize the energy of the tar. The method does not require pre-reduction of the oxygen carrier, and can continuously regenerate the oxygen carrier lattice oxygen and eliminate carbon deposits through the circulation of the oxygen carrier between the reforming reactor and the air combustion reactor.

Specifically, the high-temperature tail gas (oxygen-depleted air) produced by the combustion reaction in the air combustion reactor of the present invention is separated and dedusted by the second cyclone separator and then enters the preheater to preheat the crude gas to recover heat. Part of the oxygen-depleted air after heat recovery can enter the air combustion reactor as required to adjust the air combustion excess coefficient.

Specifically, the active components of the oxygen carrier in the present invention may be one or more of Fe oxides, Cu oxides, Ni oxides, Ce oxides, Mn oxides, Ca oxides, etc. The inert component of the carrier may be one or more of Al ₂ O ₃ , MgO, ZrO, and the like. The invention adopts non-precious metal oxide as the oxygen carrier, which reduces the running cost. Preferably, the content of the active component is 30-80 wt %, and the content of the inert component is 20-70 wt %. The particle size of the oxygen carrier is in the range of 0.1-5 mm, preferably in the range of 0.15-2 mm, for example, the particle size is 0.18 mm.

Compared with the prior art, the present invention has the following advantages:

(1) The lattice oxygen of the oxygen carrier is used to partially oxidize the tar macromolecules to CO, H ₂ and other small molecular substances at high temperature, and at the same time, it can partially retain and utilize the energy of the tar;

(2) The circulation of the oxygen carrier integrates oxygen transfer, heat transfer and catalysis, making full use of the oxidation reaction heat of the oxygen carrier and the sensible heat of the crude gas;

(3) The oxygen carrier regenerates and eliminates possible carbon deposits by circulating between the reforming reactor and the air combustion reactor. The oxygen carrier is easy to regenerate and eliminate carbon deposits, which is conducive to maintaining the continuous operation of the system;

(4) The use of non-precious metal oxides as oxygen carriers reduces operating costs.

The present invention will be described in detail below through examples.

Example 1

Taking the removal of biomass downdraft fixed bed air gasification crude gas tar as an example to illustrate.

The crude gas from biomass downdraft fixed bed gasification is 10.0 Nm ³ /h, the tar content is 2.35g/Nm ³ , and the temperature is 450℃. The reactor reacts with the high-temperature oxygen carrier (CuO-NiO/Al ₂ O ₃ , 6kg/h) from the second cyclone, the oxygen carrier is reduced, the tar macromolecules in the crude gas are partially oxidized, and catalytically reformed to CO The tar content of the gas obtained after separation and dedusting by the ^{third cyclone separator is 0.07g/Nm 3} _, and the removal rate of tar in the crude gas is 97%;

The reduced oxygen carrier (there may be carbon deposits on the surface) enters the air combustion reactor, and the air excess coefficient that controls the combustion reaction of the oxygen carrier is 0.95. The reduced oxygen carrier is completely oxidized by air to regain lattice oxygen, and the surface area carbon is oxidized to CO ₂ is eliminated, and the oxidized oxygen carrier is separated and dedusted by the second cyclone separator and then enters the reforming reactor for recycling.

The temperature of the reforming reactor is 850°C and the pressure is 0.1Mpa, the temperature of the air combustion reactor is 900°C and the pressure is 0.1Mpa; the active components of the oxygen carrier are CuO and NiO, the inert components are Al ₂ O ₃ , and the three The mass ratio of the oxygen carrier is 2:2:1, and the particle size of the oxygen carrier ranges from 0.15 to 0.84 mm.

The implementation results of this method are as follows in Table 1:

Table 1. Implementation results

Example 2

Taking this method to remove biomass downdraft fixed bed oxygen-enriched (50v% oxygen) gasification crude gas tar as an example to illustrate.

The crude gas from biomass fixed bed oxygen-enriched (50v% oxygen) gasification is 10.0 Nm ³ /h, the tar content is 1.02g/Nm ³ , and the temperature is 480℃. Then it enters the reforming reactor and reacts with the high temperature oxygen carrier (Mn ₂ O ₃ -NiO/Al ₂ O ₃ , 5kg/h) from the second cyclone separator, the oxygen carrier is reduced, and the tar macromolecules in the crude gas are partially removed. Oxidation and catalytic reforming are converted into small molecular substances such as CO and H ₂ , and the tar content of the gas obtained after passing through the third cyclone separator is 0.05g/Nm ³ , and the removal rate of tar in the crude gas is 95%;

The reduced oxygen carrier (there may be carbon deposits on the surface) enters the air combustion reactor, and the air excess coefficient that controls the combustion reaction of the oxygen carrier is 0.8. The reduced oxygen carrier is completely oxidized by air to regain lattice oxygen, and the surface area carbon is oxidized to CO ₂ is eliminated, and the oxidized oxygen carrier is separated and dedusted by the second cyclone separator and then enters the reforming reactor for recycling.

The temperature of the reforming reactor is 900°C and the pressure is 0.1Mpa, the temperature of the combustion reactor is 1000°C and the pressure is 0.1Mpa; the active components of the oxygen carrier are Mn ₂ O ₃ and NiO, and the inert component is Al ₂ O ₃ , the mass ratio of the three is 4:5:1, and the particle size of the oxygen carrier ranges from 0.35 to 1.40 mm.

The implementation results of this method are as follows in Table 2:

Table 2. Implementation results

Example 3

Taking this method to remove crude gas tar from biomass fluidized bed air gasification as an example to illustrate.

The crude gas from biomass fluidized bed gasification is 5.0 Nm ³ /h, the tar content is 11.72 g/Nm ³ , and the temperature is 520 °C. Reaction with the high temperature oxygen carrier (Fe ₂ O ₃ -NiO/Al ₂ O ₃ , 5.4kg/h) from the second cyclone, the oxygen carrier is reduced, the tar macromolecules in the crude gas are partially oxidized and catalytically reformed It is converted and removed for small molecular substances such as CO and H ₂ , and the tar content of the gas obtained after separation and dust removal by the third cyclone separator is 0.92g/Nm ³ , and the removal rate of tar in the crude gas is 92%;

The reduced oxygen carrier (there may be carbon deposits on the surface) enters the air combustion reactor, and the air excess coefficient that controls the combustion reaction of the oxygen carrier is 0.85. The reduced oxygen carrier is completely oxidized by air to regain lattice oxygen, and the surface area carbon is oxidized to CO ₂ is eliminated, and the oxidized oxygen carrier is separated and dedusted by the second cyclone separator and then enters the reforming reactor for recycling.

The temperature of the reforming reactor is 880°C and the pressure is 0.1Mpa, the temperature of the combustion reactor is 950°C and the pressure is 0.1Mpa; the active components of the oxygen carrier are Fe ₂ O ₃ and NiO, and the inert components are Al ₂ O ₃ , the mass ratio of the three is 4.5:4.5:1, and the particle size of the oxygen carrier ranges from 0.25 to 1.19 mm.

The implementation results of this method are as follows in Table 3:

Table 3. Implementation results

In summary, the present invention provides a device and method for removing biomass gasification tar based on chemical chain reforming. The method of the present invention does not require pre-reduction of the oxygen carrier, and the oxygen carrier reacts with combustion in the reforming reactor through the oxygen carrier. The cycle between devices can continuously regenerate the oxygen carrier lattice oxygen and eliminate carbon deposits. In addition, the high-temperature crude gas from the gas outlet of the gasifier can directly enter the reforming reactor, and at the same time, the high-temperature crude gas and the sensible heat carried by the oxygen carrier are used to provide the high-temperature environment required for the partial oxidation reaction and improve the energy utilization efficiency. In addition, the lattice oxygen of the oxygen carrier is used to partially oxidize the tar in the biomass crude gas into small molecular substances such as CO and H ₂ for removal, which can make full use of the energy of the tar. After being removed by this method, the tar content of the fuel gas is lower than 1 g/Nm ³ , and the tar removal rate exceeds 90%. The method of the invention is a novel method for efficiently removing biomass gasification tar.

It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above descriptions, and all these improvements and transformations should belong to the protection scope of the appended claims of the present invention.

Claims (3)

1. A device for removing biomass gasification tar based on chemical chain reforming is characterized by comprising a first cyclone separator, a preheater, a reforming reactor and an air combustion reactor, wherein the first cyclone separator is used for separating and dedusting biomass gasification crude gas, the preheater is used for preheating the biomass gasification crude gas, the reforming reactor is used for reforming the preheated biomass gasification crude gas with an oxygen carrier, the air combustion reactor is used for carrying out combustion reaction on the oxygen carrier and air after the reforming reaction, a second cyclone separator is connected between the air combustion reactor and the reforming reactor and is used for separating and dedusting the oxidized oxygen carrier, and the reforming reactor is also connected with a third cyclone separator which is used for separating and dedusting the reacted gas;

the temperature of the reforming reactor is 900 ℃ and the pressure is 0.1 Mpa;

the temperature of the combustion reactor is 1000 ℃ and the pressure is 0.1 Mpa;

the oxygen carrier active component is Mn₂O₃NiO, inert component Al₂O₃The mass ratio of the three is 4:5:1, and the particle size range of the oxygen carrier is 0.35～1.40mm；

The mass ratio of tar content in the biomass gasification crude fuel gas to lattice oxygen of an oxygen carrier in the reforming reactor is 1:2, and the air excess coefficient of the air combustion reactor is 0.8.

2. A method for removing biomass gasification tar by using the apparatus of claim 1, comprising the steps of:

step A, after the biomass gasification crude gas is separated and dedusted by a first cyclone separator and preheated by a preheater, the biomass gasification crude gas enters a reforming reactor to carry out reforming reaction with an oxygen carrier, and the reacted gas is separated and dedusted by a third cyclone separator to obtain clean gas;

b, enabling the oxygen carrier after the reforming reaction to enter an air combustion reactor to perform combustion reaction with air, and enabling the oxygen carrier after being oxidized to enter the reforming reactor for recycling after being separated and dedusted by a second cyclone separator;

the temperature of the reforming reactor is 900 ℃ and the pressure is 0.1 Mpa;

the temperature of the combustion reactor is 1000 ℃ and the pressure is 0.1 Mpa;

the oxygen carrier active component is Mn₂O₃NiO, inert component Al₂O₃The mass ratio of the three components is 4:5:1, and the particle size range of the oxygen carrier is 0.35-1.40 mm;

the mass ratio of tar content in the biomass gasification crude fuel gas to lattice oxygen of an oxygen carrier in the reforming reactor is 1:2, and the air excess coefficient of the air combustion reactor is 0.8.

3. The method of claim 2, wherein the oxygen-depleted air generated by the combustion reaction in the air combustion reactor is separated and dedusted by the second cyclone separator and enters the preheater to preheat the raw fuel gas.

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