Method for preparing composite anti-coking agent in thermal conversion of straw biomass

Abstract

The application provides a method for preparing a composite anti-slagging agent in straw biomass thermal conversion, and belongs to the technical field of new energy and energy saving. After ash is prepared from sludge and other carbon-containing waste, the ash composition is determined, a certain proportion of gravel, fly ash and the like is added according to the ash composition, and then heat treatment is performed to prepare the composite anti-slagging agent in straw biomass thermal conversion. As long as the sum of the masses of CaO, Al2O3 and P2O5 is greater than 70% and the content of P2O5 is not less than 5%, the method can be used. The method for preparing the composite anti-slagging agent in straw biomass thermal conversion by using sludge and other waste has the advantages of less required equipment, simple operation method, wide use range, small anti-slagging agent dosage (less than 2% of the material amount), good anti-slagging effect, no need to use chemical reagents, and obvious cost advantage and environmental protection benefit.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of new energy and energy saving technology, and particularly relates to a preparation method and application of a composite anti-slagging agent in thermal conversion of straw carbon-containing agricultural waste such as wheat, corn and sugarcane residue. BACKGROUND

[0002] In recent years, the sharp increase in the production of biodiesel has led to a sharp increase in the demand for lignocellulosic biomass, and the thermal conversion (combustion, gasification) of straw from agricultural by-products (which does not compete with food production for land, is cheap and easy to obtain, and has a large quantity (from an energy perspective, it accounts for more than 56% of China's biomass energy)) has gradually become an important direction for the production of chemicals, synthesis gas and electric energy. However, straw generally contains a large amount of potassium, silicon and chlorine, which can easily lead to ash-related contamination, deposition and slagging during thermal conversion. This leads to a decrease in conversion efficiency and operational instability, and can even cause the entire system to shut down. Currently, the main methods for solving the ash-related problems in straw thermal conversion are coal blending, washing and additives. Coal blending can cause uneven mixing and conversion rates due to differences in density and reactivity between the two. Washing can reduce the content of potassium and chlorine, but it requires a large amount of water and energy for the drying process. Additives are commonly used to control the ash melting characteristics and prevent the formation of slag during biomass thermal conversion, but pure additives have the disadvantages of high price and low economic benefit. SUMMARY

[0003] In order to make up for the shortcomings of the prior art, the present application provides a method for preparing a composite anti-slagging agent for straw biomass thermal conversion.

[0004] The present application is achieved by the following technical solutions:

[0005] A method for preparing a composite anti-slagging agent for straw biomass thermal conversion, comprising the following steps:

[0006] (1) Grinding the waste to particles less than 3 mm;

[0007] (2) Placing the ground particles from step (1) into a muffle furnace at 500-900 ℃ to prepare a waste ash sample;

[0008] (3) Determining the chemical composition of the waste ash sample prepared in step (2);

[0009] (4) Adding materials to the ash sample prepared in (1) according to the chemical composition in step (3) and mixing uniformly.

[0010] (5) Placing the mixed materials obtained in step (4) into a high-temperature furnace and burning at 700-1000 ℃ for 1-4 hours to remove the organic components in the materials and the gases generated during heating, thereby obtaining a mixed material ash sample.

[0011] (6) The composition of the sample obtained in step (5) is determined; as long as the sum of the masses of CaO, Al2O3 and P2O5 is greater than 70% and the content of P2O5 is not less than 5%, the anti-slagging effect can be achieved. If it does not meet the requirements, repeat (4) and (5).

[0012] (7) If the conditions are met, the anti-slagging agent is successfully prepared.

[0013] Furthermore, the waste in step (1) is one or a mixture of several of the following: sludge, livestock and poultry manure, coal gangue, coal gasification fly ash, and coal liquefaction residue.

[0014] Furthermore, the material added in step (4) is one or more of crushed stone and fly ash.

[0015] Compared with the prior art, the advantages of the present invention are as follows:

[0016] (1) The present invention requires few equipment and has a simple operation method for preparing anti-slag agent in the thermal conversion of straw biomass.

[0017] (2) The present invention uses CaO, Al2O3 and P2O5 in sludge and other waste ash to react with potassium and sodium in straw to generate high-melting-point minerals to prepare a composite anti-slagging agent in the thermal conversion of straw biomass. It has obvious cost advantages and environmental benefits. The added raw materials, such as crushed stone and fly ash, are waste resources that can be recycled and are widely available.

[0018] (3) Compared with existing straw biomass thermal conversion anti-slag agents, the present invention prepares a composite anti-slag agent with a wide range of applications and obvious anti-slag effect; the present invention does not require the use of chemical reagents in the preparation of anti-slag agent in straw biomass thermal conversion, and has good safety. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention. The scope of protection of the present invention includes, but is not limited to, the following embodiments. Any modifications made to the details and form of the technical solution of the present invention without departing from the scope of this application shall fall within the scope of protection of the present invention. Example

[0020] Anti-slag agent and its application effect in the process of preparing corn stalk gasification from municipal sludge.

[0021] (1) Preparation of anti-slagging agent

[0022] (a) A certain mass of municipal sludge is crushed to less than 3 mm.

[0023] (b) Municipal sludge is placed in a muffle furnace to prepare 815o C Municipal sludge ash (GB / T1574-2001).

[0024] (c) The chemical composition of municipal sludge samples was determined using X-ray fluorescence spectrometry (Table 1).

[0025] Table 1: Chemical composition of municipal sludge ash

[0026] .

[0027] (d) Based on the chemical composition of municipal sludge ash, small stones were selected as raw materials. The small stones were crushed to below 0.2 mm, and 50 g of them were mixed evenly with 100 g of municipal sludge ash.

[0028] (e) Place the material from (d) into a high-temperature muffle furnace and calcine it at 1000 °C for 2 hours.

[0029] (f) Cool the sample from (e) and use an X-ray fluorescence spectrometer to determine the composition of the obtained sample. The sample must meet the requirements (the sum of the masses of CaO, Al2O3 and P2O5 must be greater than 70%, and the content of P2O5 must be not less than 5%).

[0030] (2) The deposition rate of ash in a reducing atmosphere (H2 / CO2, 1:1, volume ratio) and at normal pressure was measured using an ash deposition rate tester to determine the slagging property during the gasification process of corn stalks. The ash deposition rate tester was a device independently developed by the applicant (see CN104931376B for details).

[0031] (a) The quartz tube reactor (m1) was placed in the isothermal zone of the silicon carbide tube furnace and sealed. The temperature was increased at a rate of 20 °C / min and a reducing atmosphere was maintained by introducing a mixed gas (H2 / CO2, 1:1, volume ratio) at a rate of 20 mL / s.

[0032] (b) When the temperature inside the quartz reaction tube is raised to 900 °C, the prepared ash sample is added into the quartz reaction tube at a feeding rate of 0.5 g / s using a rotary feeder, and the ash sample falls inside the quartz reaction tube.

[0033] (c) After the preset time (600 s) is reached, stop heating and calculate the mass m of the added ash sample. t .

[0034] (d) After the equipment has cooled to room temperature, remove the quartz reaction tube containing the deposits and weigh it (m2). Calculate the ash deposition rate: M ad =(m2-m1) / m t . (M ad : Ash deposition rate; m2: Sum of the masses of the quartz tube and the sediment; m1: Mass of the quartz tube; mt (The mass of the ash sample added)

[0035] (3) Application effect

[0036] (a) Without additives, the ash deposition rate of corn stalk ash under the above conditions is 9.75%.

[0037] (b) Adding 20% ​​additive (based on corn stalk ash; if the ash yield of corn stalk ash is calculated at 5%, the additive accounts for less than 1% of the corn stalk ash). Under the same conditions, the ash deposition rate of the mixed corn stalk ash is 1.04%. Example

[0038] Anti-slag agent prepared from aluminum plant sludge during wheat straw combustion and its application effect.

[0039] (1) Preparation of anti-slagging agent

[0040] (a) A certain mass of aluminum plant sludge is crushed to below 3.0 mm.

[0041] (b) The sludge from the aluminum plant was placed into a muffle furnace to prepare 815. o C. Sludge ash from aluminum plants (GB / T1574-2001)

[0042] (c) The chemical composition of the sludge samples from the aluminum plant was determined using X-ray fluorescence spectrometry (Table 2).

[0043] Table 2: Chemical composition of sludge ash from aluminum plants

[0044] .

[0045] (d) The sludge ash from the aluminum plant meets the requirements (the sum of the masses of CaO, Al2O3 and P2O5 is greater than 70%, and the content of P2O5 is not less than 5%) and can be directly used as an anti-slag agent in the burning of wheat straw.

[0046] (2) The deposition rate of ash slag under certain conditions was determined by using an ash deposition rate tester to determine the slagging property of wheat straw during combustion.

[0047] (a) The quartz tube reactor (m1) was placed in the isothermal zone of the silicon carbide tube furnace and sealed. The temperature was increased at a rate of 20 °C / min and a reducing atmosphere was maintained by introducing a mixed gas (H2 / CO2, 1:1, volume ratio) at a rate of 20 mL / s.

[0048] (b) When the temperature inside the quartz reaction tube is raised to 1000 °C, the prepared ash sample is added into the quartz reaction tube at a feeding rate of 0.5 g / s using a rotary feeder, and the ash sample falls inside the quartz reaction tube.

[0049] (c) After the preset time (800 s) is reached, stop heating and calculate the mass m of the added ash sample. t .

[0050] (d) After the equipment has cooled to room temperature, remove the quartz reaction tube containing the deposits and weigh it (m2). Calculate the ash deposition rate: M ad =100(m2-m1) / m t .

[0051] (3) Application effect

[0052] (a) Without additives, the ash deposition rate of wheat straw ash under the above conditions is 8.49%.

[0053] (b) Adding 20% ​​additive (based on wheat straw ash; if the ash yield of wheat straw ash is calculated at 8.0%, the additive accounts for less than 1.62% of the corn straw ash). Under the same conditions, the ash deposition rate of the mixed wheat straw ash is 1.13%.

Claims

1. A method for preparing a composite anti-caking agent for the thermal conversion of straw-based biomass, characterized in that, Includes the following steps: (1) Grind one or more of the following into particles smaller than 3 mm: sludge, livestock and poultry manure, coal gangue, coal gasification fly ash, and coal liquefaction residue. (2) Place the granules ground in step (1) into a muffle furnace at 500–900 ℃ to prepare waste ash samples; (3) Determine the chemical composition of the waste ash sample prepared in step (2); (4) Add one or more of crushed stone and fly ash to the ash sample prepared in (1) according to the chemical composition in step (3), and mix them evenly; (5) Place the mixture obtained in step (4) into a high-temperature furnace and calcine at 700–1000°C for 1–4 hours to remove the organic components and gases generated during the heating process, and obtain the ash sample of the mixture. (6) The composition of the sample obtained in step (5) is determined; as long as the sum of the masses of CaO, Al2O3 and P2O5 is greater than 70% and the content of P2O5 is not less than 5%, the anti-slagging effect can be achieved. If it does not meet the requirements, repeat (4) and (5). (7) If the conditions are met, the anti-slagging agent is successfully prepared.