CN1172739C - Reversible desulfurizing absorbant based on the modification of biomass and its prepn. - Google Patents

Abstract

The present invention discloses a modified reversible desulphurization absorbent based on biotic matter and a preparation method thereof. The modified reversible desulphurization absorbent of the present invention adopts the additive agent of the biotic matter, wherein the biotic matter comprises the stems, the leaves, the roots, etc. of the crops of rice, wheat, grain, maize, grain sorghum, etc., and grass, tree leaves, wastepaper, wood, wooden powder, etc. The preparation method comprises the steps that the material of the biotic matter and the desulphurization absorbent are impregnated or soaked in water and dried. The additive agent for modifying in the present invention has low cost and is easy to obtain, and the modification has the advantages of simple method, low energy consumption and low cost; the speed and the efficiency of desulphurization can be enhanced to a large extent, and the absorbent after the desulphurization can be recycled.

Description

Reversible desulfurization absorbent based on biomass modification and preparation thereof

The invention belongs to the technical field of comprehensive development and utilization of biomass and reversible desulphurization absorbent, and particularly relates to a biomass modified reversible desulphurization absorbent applied to the technical field of flue gas desulphurization.

At present, the main absorbents used for flue gas desulfurization are the following two types:

(1)CaCO₃，CaO，Ca(OH)₂and (4) preparing the system. The desulfurization process is divided into a dry method, a semi-dry method and a wet method, wherein the desulfurization efficiency of the dry method is very low, the water consumption of the wet method is too large although the desulfurization efficiency of the dry method can reach more than 90%, and the semi-dry method is between the dry method and the semi-dry method. The generated calcium sulfate (gypsum) has no considerable development and utilization prospect, and is accumulated in a large amount to form white pollution.

(2)Na₂CO₃，MgCO₃And (4) preparing the system. Single Na without carrier₂CO₃Or MgCO₃System, under dry low temperature conditions, Na₂CO₃Or MgCO₃The utilization rate is only about 10-20%. The process adopts Al₂O₃When the catalyst is a carrier, the desulfurization efficiency is high. But is made of Al₂O₃The carrier is expensive, the source is limited, the preparation process is complicated, the energy consumption is high, and the treatment process of recycling is complex.

The invention aims to provide a method for preparing Na by taking an inexpensive, easily-obtained and disposable additive as a carrier₂CO₃，MgCO₃Modifying the absorbent system to obtain a modified reversible desulfurization absorbent, thereby increasing SO to a greater extent₂The method has the advantages of simplified process, reduced investment cost, no ash, full recovery, and no secondary white pollution.

The technical scheme of the invention is as follows:

the reversible desulfurization absorbent of the invention uses biomass as raw materialMatrix material supported (modified) Na₂CO₃，MgCO₃And the like, wherein the biomass comprises stems, leaves, roots and the like of crops such as rice, wheat, corn, sorghum and the like, and biomass such as grass, leaves, waste paper, wood powder and the like.

The preparation method of the (modified) reversible desulfurization absorbent loaded by biomass as a matrix material sequentially comprises the following steps:

(1) processing biomass into a shape suitable for mixing with a desulfurization absorbent to obtain a biomass material;

(2) soaking or immersing the biomass material and the reversible desulphurization absorbent in water to obtain a mixture;

(3) and (3) naturally drying, drying or drying in other modes to obtain the reversible desulfurization absorbent modified by the biomass.

The modification mechanism of the invention is that after the biomass is used, the surface morphology of the absorbent can be obviously improved, and the specific surface area of the absorbent is increased; adjusting the pore distribution of the absorbent and accelerating SO₂Diffusion in the product layer; elongation and SO₂The contact time of (2) and the reaction efficiency are improved. Thus, the following reactions are greatly facilitated to occur:

the additive adopted by the invention is cheap and easily available biomass, and the raw material source is convenient and economic; compared with the traditional method, the absorbent modification preparation process is simple and easy to implement and has low energy consumption (only soaking/dipping and drying are needed if hydrothermal treatment and stirring are not needed); the potential value of the biomass and the abandoned biomass can be reasonably utilized, and a series of practical biomass desulfurization processes are developed. Simultaneously, the desulfurization speed and the desulfurization efficiency can be improved to a greater extent, and Na obtained after desulfurization₂SO₃Biomass, MgSO₃SO released from biomass₂And can be recycled.

A comparative experiment proves that: each gram of Na modified by biomass straw₂CO₃100 percent removal of SO from desulfurizer₂Is about 33 hours per gram of unmodified Na₂CO₃100 percent removal of SO from desulfurizer₂The time of the reaction is only 14 minutes, and the desulfurizing agent SO modified by the biomass straw can be seen₂The 100% removal time is greatly extended. gamma-Al₂O₃Modified desulfurizing agent SO₂The 100% removal time is also greatly prolonged, but compared with the absorbent after biomass straw modification, the 100% removal of SO₂The time of (a) is much shorter, only 16 hours/g. In addition, Na₂CO₃The utilization rate of the method is improved to 85 percent from the original utilization rate of less than 10 percent. (see examples for relevant data)

Description of the drawings:

FIG. 1 shows wheat straw modified Na₂CO₃The desulfurization curve of the desulfurizing agent shows that the dosage of the desulfurizing agent is 1.065 g.

FIG. 2 shows wheat straw powder and unmodified Na₂CO₃Desulfurization curve diagram of desulfurizer;

wherein curve 1 is the desulfurization curve of the straw powder with the dosage of 0.1920 g, and curve 2 is the Na with the dosage of 0.5065 g₂CO₃Desulfurization profile of the desulfurizing agent.

FIG. 3 is Al₂O₃Carry Na₂CO₃The desulfurization curve of the desulfurizing agent shows that the dosage of the desulfurizing agent is 0.5 g.

In all figures, the abscissa represents SO₂Adsorption time, ordinate represents SO at the reactor outlet₂And (4) concentration.

Example (b): modified Na with wheat straw₂CO₃Preparation of desulfurization absorbent and comparative experiment

Na modified with wheat straw₂CO₃Preparation of the desulfurization absorbent: pulverizing biomassstraw as additive to obtain straw powder (hereinafter referred to asCalled wheat straw powder). Collecting 4g wheat straw powder and 16g Na₂CO₃Adding into 80ml water, soaking for a certain time, taking out, and naturally air drying in air to obtain modified Na₂CO₃A desulfurizing agent. Na in modified desulfurizing agent₂CO₃80.0 percent of wheat straw powder and 20.0 percent of wheat straw powder.

Separately treating pure Na in the same manner₂CO₃And straw meal were subjected to the following blank desulfurization experiment.

(II) with pure Na₂CO₃Comparison of desulfurization experiments for desulfurization absorbent

And (3) desulfurization conditions: at a temperature of 80 ℃ and SO₂Has a concentration of 2000ppm and the carrier gas is N₂The reactor is a fixed bed reactor.

The gas detection method was FT-IR spectrometer (Vector Brouker).

The experimental results are as follows:

as shown in FIG. 1, the amount of the desulfurizing agent modified with wheat straw was 1.065 g, wherein Na is contained₂CO₃80% in terms of weight, i.e. 0.852 g, 100% of which has been freed from SO₂Is about 28 hours, then per gram of Na₂CO₃After the desulfurizer is modified by wheat straws, 100 percent of SO is removed₂Is about 33 hours.

Referring to FIG. 2, curve 1 shows the desulfurization curve of wheat straw powder used in 0.1920 g, and curve 2 shows Na used in 0.5065 g₂CO₃Desulfurization profile of the desulfurizing agent. Unmodified Na₂CO₃100% removal of SO₂Only for about 14 minutes; 100% removal of SO from wheat straw powder₂The time isalmost 0.

Thus, straw-modified Na₂CO₃100 percent removal of SO from desulfurizer₂The time is greatly prolonged, and the absorbent modified by the wheat straw is proved to be a quick desulfurizer, which is beneficial to the desulfurization of flue gas flowing quickly in a reactor. In addition, Na₂CO₃The utilization rate of the method is improved to 85 percent from the original utilization rate of less than 10 percent. It follows that wheat straw is an ideal medium.

(III) with Al₂O₃Na as a carrier₂CO₃Comparison of desulfurizing agents

Preparation of the absorbent: with gamma-Al₂O₃Grinding to below 200um as carrier. Taking 4g of gamma-Al₂O₃And 1g of Na₂CO₃Adding into 5ml water, dipping, drying, grinding to obtain the desulfurizer. Na in modified desulfurizing agent₂CO₃20.0% of gamma-Al₂O₃Accounting for 80.0 percent. 0.5 g of the desulfurizing agent was taken out as a sample to conduct the following experiment.

And (3) desulfurization conditions: at a temperature of 80 ℃ and SO₂Has a concentration of 1958ppm and the carrier gas is N₂The reactor is a fixed bed reactor.

The gas detection method was FT-IR spectrometer (Vector Brouker).

The experimental results are as follows:

0.5 g of prepared gamma-Al as shown in FIG. 3₂O₃Na as a carrier₂CO₃Desulfurizing agent, 100% removing SO₂Is about 1.6 hours, wherein Na₂CO₃The content was 20.0%, i.e. 0.1 g. Therefore, with gamma-Al₂O₃Prepared as carrier per gram of Na₂CO₃100 percent removal of SO from desulfurizer₂Is about 16 hours, compared with unmodified Na₂CO₃In contrast, gamma-Al₂O₃Modified desulfurizing agent SO₂The 100% removal time is also greatly prolonged, but is comparable to the modified straw per gram Na₂CO₃100 percent removal of SO from desulfurization absorbent₂Time of 33 hours compared, 100% removal of SO₂Much shorter times. As can be seen, the modified wheat straw has Na₂CO₃The desulfurizing agent is more favorable for desulfurizing flue gas flowing fast in the reactor. Meanwhile, the wheat straw is cheap and easily available, has wide sources, is simple and convenient in preparation and modification processes, does not need complex processes with large energy consumption, such as grinding, stirring and the like, has absolutely low investment cost, and obtains higher and more ideal desulfurization effect.

Claims (2)

1. A modified reversible desulfurizing absorbent for removing SO from flue gas₂Gas, characterized in that the desulfurization absorbent consists of Na₂CO₃、MgCO₃One or more of the above-mentioned materials and biomass used as modifying additive are mixed, and the described biomass is selected from one or more of stem, leaf, root, grass, leaf, waste paper, wood and wood powder of crops.

2. A process for the preparation of a reversible desulfurization absorbent modified according to claim 1, comprising the following steps in sequence:

(1) processing one or more biomass selected from crop stem, leaf, root, grass, leaf, waste paper, wood, and wood powder into suitable for mixing with Na₂CO₃、MgCO₃One or a mixture of several of them to obtain a biomass material;

(2) mixing biomass material with Na₂CO₃、MgCO₃One or more of them is/are soaked or soaked in water to obtain a mixture;

(3) and (3) naturally drying, drying or drying in other modes to obtain the reversible desulfurization absorbent modified by the biomass.