Upgrading reactor and biomass gasification process

Abstract

The invention provides a biomass gasification process which comprises the following steps: (1) pulverizing biomass through a high-shear pulverizer, and mixing the pulverized biomass with water to prepare original slurry with proper concentration; (2) pressurizing the original slurry, and feeding the pressurized original slurry into an upgrading reactor for hydrothermal upgrading; (3) reducing the pressure of the upgraded slurry, feeding the slurry into a modification tank, and adding a modifier for modification; (4) the modified slurry enters a cyclone, and redundant water is separated out; and (5) obtaining concentrated finished product biomass slurry at an outlet at the bottom of the cyclone, buffering the concentrated finished product biomass slurry through a slurry tank, pressurizing the concentrated finished product biomass slurry through a diaphragm pump, and feeding the pressurized slurry into an entrained-flow bed gasifier to be converted into synthesis gas. After the biomass is subjected to hydrothermal upgrading and modification, the pulping concentration can be changed from 1t of the original biomass to 1t of the original biomass; the biomass gasification efficiency is improved from 40% to 50% or above, so that the biomass gasification has relatively high economical efficiency.

Description

Technical Field

[0001] The invention belongs to the field of biomass chemical industry, and in particular relates to an upgrading reactor and a biomass gasification process. Background Art

[0002] At present, chemical production mainly uses fossil fuels (coal, oil, natural gas) as raw materials, but fossil fuels cause huge carbon emissions, and other countries in the world have restrictions on carbon emissions. Biomass is increasingly valued as a potential raw material for chemical production. However, the low energy density and complex types of biomass are quite different from the needs of large-scale chemical production, which are the main obstacles restricting biomass as a chemical raw material.

[0003] Due to the complexity of biomass types, if biomass can be converted into synthesis gas (H2, CO) first, various bio-based chemicals can be produced using the currently mature coal chemical downstream industrial synthesis route. Referring to coal gasification technology, there are three types of coal gasification processes: fixed bed, fluidized bed, and entrained bed. The entrained bed process has become the mainstream process of coal gasification due to its large production capacity, high conversion efficiency, and no pollutants. There are two feed forms for coal gasification entrained beds, namely coal powder feed and coal slurry feed; analogy applied to biomass gasification, biomass is crushed into dry powder, which has poor fluidity and low powder density compared to coal powder, and the properties of different types of biomass powders vary greatly, making it difficult for the economy and stability of biomass dry powder feed to meet industrial production requirements; if the biomass is crushed and water is added to make slurry, the biomass has an extremely high oxygen content and the biomass slurry concentration is too low (forcibly increasing the concentration will make the slurry unable to flow), and a large amount of water is carried into the gasifier, seriously affecting the economic efficiency of gasification.

[0004] The above problems have resulted in the fact that although a large amount of research has been carried out on the use of biomass as a gasification raw material, its industrial application has always been difficult to implement. Summary of the invention

[0005] The present invention provides a quality-improving reactor and a biomass gasification process, which can make biomass into slurry with a concentration of >52% and meet the requirements of gasifier feed for slurry fluidity, so that biomass can be converted into synthesis gas through slurry feeding and fluidized bed gasification.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides a quality upgrading reactor:

[0008] An upgrading reactor comprises a shell and internal parts, wherein the shell comprises a straight cylinder section and spherical heads at both ends;

[0009] The reactor inlet is arranged at the bottom of the lower head, the reactor outlet is arranged at the top of the upper head, and the side exhaust port is arranged at the top of the straight section, which is used to regularly discharge the non-condensable gas in the corresponding part to prevent the formation of gas blockage;

[0010] The internal part is located in the straight section and the lower head area, and the interior of the upgrading reactor is divided into three connected areas by the internal part, namely, the annular gap area, the reaction area and the discharge area, wherein the annular gap area is located between the shell and the internal part, the reaction area is inside the internal part (the outer area of ​​the downcomer), and the discharge area is located in the upper head area; the annular gap area is connected to the reaction area through the downcomer, and the reaction area is connected to the discharge area through the upcomer;

[0011] The downcomer is generally DN25-DN32, and the specific number is determined by the required heat exchange area;

[0012] Magnetrons arranged in a ring are installed at the bottom of the reaction zone.

[0013] In the present invention, after the biomass slurry enters the reactor from the reactor inlet, it flows upward in the annular gap area between the pressure-resistant shell and the internal parts, and absorbs the heat transferred by the internal parts, thereby keeping the reactor pressure-resistant shell at a state close to room temperature and reducing material and manufacturing requirements. In order to fully absorb heat, the width of the annular gap area should not be less than 50mm, preferably 50-100mm. At the same time, in order to reduce the heat transferred from the internal parts to the outside, a 3-5mm glass bead insulation coating is applied to the internal parts facing the annular gap area;

[0014] After the slurry passes through the annular gap area and rises to the upper part of the straight tube section, it enters the reaction zone through several downcomers. In the downcomers, the unreacted slurry exchanges heat with the reacted slurry through the tube wall. The microwaves generated by the annularly arranged magnetrons at the bottom of the reaction zone are absorbed by the water in the slurry to generate heat, which serves as a heat source for the quality improvement reaction;

[0015] Furthermore, the microwave frequency is 2.4-2.6 GHz, and the microwave intensity is adjusted so that the temperature of the slurry at the bottom of the reaction zone after being heated is 300-360°C, 1m 3 / h processing capacity slurry corresponding to the heating power of 70-120kW;

[0016] The heated high-temperature slurry rises in the reaction zone and undergoes a quality-improving reaction. At the same time, it exchanges heat with the unreacted slurry in the downcomer to gradually cool down, and enters the discharge zone through the riser, and finally leaves the reactor through the reactor outlet.

[0017] A second aspect of the present invention provides a biomass gasification process, comprising the following steps:

[0018] (1) The biomass is crushed by a high shear mill and mixed with water to form a raw slurry of appropriate concentration;

[0019] (2) pressurizing the original slurry and sending it to the aforementioned upgrading reactor for hydrothermal upgrading;

[0020] (3) The upgraded slurry enters the modification tank after decompression, and a modifier is added for modification;

[0021] (4) The modified slurry enters the cyclone to separate excess water, and the concentrated finished biomass slurry is obtained at the bottom outlet of the cyclone;

[0022] The separated water can be used for pulping in step (1), and the insufficient part can be supplemented with fresh water or other wastewater;

[0023] (5) After the finished biomass slurry is buffered in the slurry tank, it is pressurized by a diaphragm pump and enters the fluidized flow gasifier to be converted into synthesis gas.

[0024] In the present invention, in step (1), the biomass may be wine dregs, bamboo chips, wood chips, straw, etc., which are relatively concentrated and easy to collect;

[0025] The biomass was crushed by a high shear mill to a median particle size of <200 μm and a maximum particle size of <500 μm;

[0026] The water can be fresh water or wastewater containing certain organic matter generated by other devices in the chemical park;

[0027] After biomass is crushed and pulped, the maximum pulp concentration that can be achieved by different biomasses varies to a certain extent. The slurry viscosity should be ensured not to exceed 500mPa.s and the concentration should be in the range of about 20-40%.

[0028] The temperature of the original slurry is from room temperature to 80°C.

[0029] In the present invention, in step (2), the pressure is increased to 20-23 MPaG to ensure that water does not vaporize during the upgrading reaction;

[0030] The residence time of the slurry in the reaction zone of the upgrading reactor is preferably 1-2 hours, and the total residence time inside the upgrading reactor is preferably 2-3 hours;

[0031] After the slurry after the upgrading reaction exchanges heat with the unreacted slurry in the downcomer, the temperature is reduced to below 100° C. when leaving the reaction zone.

[0032] In the present invention, in step (3), the slurry after the upgrading reaction leaves the upgrading reactor and is depressurized to normal pressure before entering the modification tank;

[0033] The modification tank adopts a series of full mixing kettles, preferably 2-3 stages of full mixing kettles are connected in series;

[0034] The modifier is an alkyl ketene dimer or a silane coupling agent, and the silane coupling agent can be A151, A172, etc.;

[0035] The amount of the modifier added is 1-3% of the dry weight of the biomass;

[0036] Preferably, in the biomass modification process, the average residence time of the biomass slurry in the modification tank is about 0.5-2 h, the reaction temperature is about 70-90° C., and the pressure is 0-0.5 MPaG.

[0037] In the present invention, in step (4), the concentration of the concentrated finished biomass slurry varies according to the biomass, and is about 45-55%.

[0038] In the present invention, in step (5), the operation of converting the slurry into synthesis gas by entering the entrained flow gasifier is a conventional operation in the art, for example:

[0039] After the pressure is increased by a diaphragm pump to 1-1.5MPa higher than the operating pressure of the rear-end gasifier, it is fed into the gasifier through the gasifier burner and oxygen;

[0040] The reaction temperature in the entrained flow gasifier is 1200-1300°C. For biomass with a higher ash melting point, such as wine grains, flux needs to be configured according to the mineral composition of the ash.

[0041] By adopting the above technical solution, the present invention has the following positive effects:

[0042] Hydrothermal upgrading of biomass can effectively remove oxygen from biomass and partially carbonize biomass, thereby greatly increasing the concentration of biomass powder pulping and improving the gasification economy of biomass slurry. Compared with the fixed bed pyrolysis process (similar to the production of coke), the slurry of hydrothermal upgrading can be transported by pump, which is suitable for continuous industrial production and has a simple feeding method. Hydrothermal upgrading uses high pressure to avoid water vaporization in the slurry, which is more energy-efficient, and the slurry preparation is not sensitive to the water content of the biomass raw materials. Since biomass generally has a high water content (>20%), this part of the water will vaporize during fixed bed pyrolysis. The biomass needs to be dried for dry powder gasification, and the energy consumption is relatively high.

[0043] The effect of hydrothermal upgrading on the slurryability of biomass mainly depends on the reaction temperature, and the pressure inside the reactor is slightly higher than the saturated vapor pressure of water at the corresponding reaction temperature. In order to maximize the slurry concentration of biomass after upgrading, the upgrading reaction temperature is about 300-360°C (not higher than the critical temperature of water), corresponding to the saturated vapor pressure of water of about 9.5-20MPaG. If the pressure-resistant shell of the reactor is subjected to the above temperature and pressure at the same time, the difficulty and cost of manufacturing the reactor will be greatly increased. The shell of the upgrading reactor described in the present invention only bears pressure, and the high-temperature area is only confined to a smaller area inside, which is conducive to reducing material requirements. The reactor shell can be made of conventional alloy steel and can operate at a higher pressure, which can reach about 360°C; in contrast, a wastewater treatment reactor with a certain similarity in conventional structure and process (such as a cracking reactor for treating nitrification wastewater) can only reach 300°C at most, and the pressure in the reactor at this temperature is only 50% of that at 360°C.

[0044] In the present invention, the outer part of the inner part facing the annular gap area is coated with a glass bead insulation coating, which can reduce the heat conduction from the inner part to the outside. After the original slurry enters from the bottom of the reactor, it rises along the annular gap area between the pressure shell and the inner part, and cools the glass bead insulation layer. Since the thermal conductivity of the insulation coating is low, the slurry in the annular gap area basically does not experience temperature rise, which can ensure that the pressure shell works at room temperature.

[0045] After the original slurry reaches the top of the annular gap, it returns to the downcomer, where it absorbs heat for preheating. After the slurry reaches the bottom of the reaction zone, it absorbs microwave energy and further heats up to the reaction temperature. The reacted slurry rises slowly and transfers heat to the original slurry in the downcomer to achieve heat recovery.

[0046] After hydrothermal upgrading and modification of biomass, the pulp concentration can be increased from <40% of the original biomass to more than 50%, making biomass gasification more economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Schematic diagram of the biomass upgrading reactor of the present invention, wherein:

[0048] ① is the reactor inlet, where the original biomass slurry enters the reactor;

[0049] ② is the downcomer, the original slurry from the annular gap enters the downcomer to absorb heat for preheating, and then enters the reaction zone;

[0050] ③ is the riser, through which the slurry after upgrading and heat exchange with the original slurry in the downcomer leaves the reaction zone and enters the discharge zone;

[0051] ④ is the reactor outlet, where the upgraded slurry and the non-condensable gas generated during the upgrading process leave the reactor and enter the next step;

[0052] ⑤ is the side exhaust port, which is used to discharge the non-condensable gas accumulated in the corresponding parts from time to time to prevent the formation of gas blockage;

[0053] ⑥ is a magnetron, which is used to generate microwaves to provide heat for the quality improvement process. DETAILED DESCRIPTION

[0054] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0055] Example 1

[0056] Upgrading reactor:

[0057] The metal pressure-resistant shell of the upgrading reactor is made of carbon steel lining 316L, with an inner diameter of 2.2m and a straight section height of about 5m. The internal parts are made of 316L material, with an internal diameter of 2m (annular gap width of about 80mm), and the outside of the internal parts is coated with a 4mm thick glass bead insulation layer; 300 φ25 downcomers are installed inside, with a total heat exchange area of ​​about 140m 2 There are 8 magnetrons installed at the bottom of the internal parts, the operating frequency is 2.5GHz, and the power of each magnetron is about 100kW.

[0058] In this embodiment, distiller's grains are used as biomass gasification raw material. The moisture content of the distiller's grains is about 60%, and the moisture content is reduced to 40% through high-pressure dehydration.

[0059] First, the wine lees are made into raw biomass slurry through a high shear pulverizer, with a solid content of about 38%, a viscosity of about 500 mPa.s, and a median particle size of biomass particles in the slurry of about 100 μm.

[0060] The original biomass slurry is heated to 50℃ by hot water in the plant area, and then pressurized by a pump before entering the upgrading reactor for upgrading. The processing capacity is 10m 3 / h, the upgrading reactor operating pressure is 23MPaG. After passing through the annular gap area, the biomass slurry enters the downcomer to recover the heat of the reacted slurry, and the temperature is raised to about 300°C, and further heated to 350°C by the magnetron, and flows upward in the reaction zone and undergoes a quality upgrading reaction. The reacted slurry transfers the heat to the feed through the downcomer and then cools down to about 90°C, and together with the gas generated by the reaction, enters the discharge zone through the riser and leaves the reactor. The average residence time of the biomass slurry in the reaction zone is about 1h.

[0061] The material leaving the upgrading reactor is separated from the gas and liquid, and the gas phase is water-cooled to room temperature for the second liquid separation. The liquid phase returns to the front-end biomass crushing and pulping step, and the non-condensable gas is sent for incineration. The upgraded slurry after gas separation enters the modification tank. The modification tank adopts a 2-stage full mixing kettle in series, the operating pressure is 0.3MPaG, the reaction temperature is about 85°C, and the modifier is alkyl ketene dimer. The addition amount is 3% of the dry mass of biomass, and the total modification reaction time is 1.5h. In order to ensure the stability of the slurry, an additive of 0.2% of the dry mass of biomass needs to be added to the modified slurry. The additive adopts a commercially available coal slurry additive (Xingguang Baoyi No. 2).

[0062] The modified biomass slurry is pressurized by a pump and enters the cyclone. The water phase separated at the top of the cyclone returns to the front-end crushing and pulping unit, and the concentrated biomass slurry is obtained at the bottom, with a concentration of about 54% and a viscosity of about 600mPa.s. In order to ensure the slag discharge of the gasifier, 1% of the dry weight of the biomass needs to be added as a flux.

[0063] The slurry is buffered in a storage tank and pressurized to 2.2MPaG by a pump before entering an entrained flow gasifier. The operating pressure of the gasifier is 1.1MPaG, the reaction temperature is 1280°C, and the H2+CO ratio of the crude synthesis gas at the outlet of the gasifier is 75%.

[0064] Example 2

[0065] This embodiment uses bamboo chips left over from processing as raw materials. The bamboo chips have a water content of about 35%. First, they are converted into powder using a crusher, and then sent to a mixing tank after screening to mix with waste liquid circulating in the back end and additional water to form a 35% concentration of original slurry, which is further dispersed by a homogenizing pump and used for quality improvement and modification.

[0066] The slurry was pressurized to 20 MPaG by a diaphragm pump and entered into an upgrading reactor for upgrading. The reactor used was the same as that in Example 1. The difference in operation was as follows:

[0067] The temperature of the material in the reaction zone after being heated by the magnetron is 320℃, the residence time in the reaction zone is extended to 1.25h, and the processing capacity is 8m 3 / h;

[0068] The upgraded bamboo chips are separated by gas and liquid and enter the modification tank. Silane coupling agent A151 equivalent to 2% of the slurry solid content is added at 75°C and 0.25MPaG and reacted for 1 hour. After the reaction, the concentration is increased to 50% through cyclone flow, and calcium oxide equivalent to 1% of the solid content is added as a flux.

[0069] Under the same conditions as in Example 1, the slurry was buffered and pumped to increase pressure before being sent to the gasifier. The H2+CO ratio of the crude synthesis gas at the outlet of the gasifier was 69%.

[0070] Example 3

[0071] This embodiment uses sugar waste bagasse as gasification raw material. Bagasse has a water content of about 60%, and is first dehydrated to 48% by high pressure plate frame, and then made into slurry with a solid content of 32% by wet mill (need to supplement the wastewater separated at the back end).

[0072] The above slurry is pressurized to 23MPaG by a diaphragm pump and enters the upgrading reactor for upgrading. The processing capacity is 15m 3 / h. The inner diameter of the pressure shell of the reactor used is 2.6m, the diameter of the inner part is 2.4m, the number of downcomers is increased to 420, the magnetron configuration is 125kW×10, the temperature of the material in the reaction zone after heating is 350°C, the residence time in the reaction zone is 1h, and the other reactor parameters are the same as those in Example 1.

[0073] The upgraded bagasse slurry is separated from the gas and liquid and enters the modification tank. Alkyl ketene dimer equivalent to 2.5% of the slurry solid content is added at 85°C and 0.35MPaG and reacted for 1.5 hours. After the reaction, the concentration is increased to 50% by cyclone.

[0074] Under the same conditions as in Example 1, the slurry was buffered and pumped to increase pressure before being sent to the gasifier. The H2+CO ratio of the crude synthesis gas at the outlet of the gasifier was 71%.

[0075] Comparative Example 1

[0076] This comparative example is similar to Example 1, except that after the distiller's grains slurry is hydrothermally upgraded, no further chemical modification is performed, but the same coal slurry additive and flux (1% iron oxide) as in Example 1 are added after direct cyclone dehydration. The final biomass slurry concentration is about 45%, and the H2+CO ratio in the outlet crude synthesis gas after being sent to the gasifier is 60%.

Claims

1. A quality upgrading reactor, comprising a shell and internal parts, wherein the shell comprises a straight section and spherical heads at both ends; in, The bottom of the lower head is provided with a reactor inlet, the top of the upper head is provided with a reactor outlet, and the top of the straight cylinder section is provided with a side exhaust port; The internal part is located in the straight section and the lower head area, and the interior of the upgrading reactor is divided into three connected areas by the internal part, namely, the annular gap area, the reaction area and the discharge area, wherein the annular gap area is located between the shell and the internal part, the reaction area is inside the internal part, and the discharge area is located in the upper head area; the annular gap area is connected to the reaction area through the downcomer, and the reaction area is connected to the discharge area through the upcomer; Magnetrons arranged in a ring are installed at the bottom of the reaction zone.

2. The upgrading reactor according to claim 1, wherein: The width of the annular gap zone is not less than 50 mm, preferably 50-100 mm.

3. The upgrading reactor according to claim 1 or 2, wherein: The inner part facing the annular gap area is coated with a 3-5 mm glass bead insulation coating.

4. The upgrading reactor according to any one of claims 1 to 3, wherein: The microwave frequency generated by the magnetron is 2.4-2.6 GHz.

5. A biomass gasification process comprising the following steps: (1) crushing the biomass and mixing it with water to form a raw slurry; (2) pressurizing the original slurry and sending it into the upgrading reactor according to any one of claims 1 to 4 for hydrothermal upgrading; (3) The upgraded slurry enters the modification tank after decompression, and a modifier is added for modification; (4) Separating excess water from the modified slurry; (5) The slurry enters the fluidized flow gasifier and is converted into synthesis gas.

6. The biomass gasification process according to claim 5, wherein: In step (1), the biomass includes at least one of wine lees, bamboo chips, wood chips, and straw; Preferably, the biomass is pulverized by a high shear pulverizer to a median particle size of <200 μm and a maximum particle size of <500 μm; Preferably, the temperature of the original slurry is from room temperature to 80°C.

7. The biomass gasification process according to claim 5 or 6, wherein: In step (2), the pressure is increased to 20-23 MPaG; Preferably, the temperature of the slurry at the bottom of the reaction zone after being heated is 300-360°C; Preferably, the residence time of the slurry in the reaction zone is 1-2 hours.

8. The biomass gasification process according to any one of claims 5 to 7, wherein: In step (3), the modifier is an alkyl ketene dimer and / or a silane coupling agent, and the silane coupling agent preferably includes at least one of A151 and A172; Preferably, the amount of the modifier added is 1-3% of the dry weight of the biomass; Preferably, the modification reaction temperature is 70-90°C and the pressure is 0-0.5 MPaG.

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