CN103396835B - Method for simultaneously preparing clean gaseous fuel and adsorbent by sludge - Google Patents

Abstract

The invention provides a method for simultaneously preparing clean gas fuel and an adsorbent from sludge, the steps of which are: sequentially adding an iron-containing oxidant and a calcium-based regulator to sludge slurry, stirring and mixing, and performing mechanical dehydration to obtain dewatered sludge; The dewatered sludge is crushed and steam-gasified to produce a clean gas fuel rich in H ₂ , CO, and CH ₄ , and the solid product obtained from the gasification is the sludge ash-based adsorbent. From the perspective of integration of sludge treatment and resource utilization, the present invention implants the process of improving the gasification characteristics of sludge and enhancing the adsorption activity of solid products into the composite conditioning and dehydration process, and adopts a wet mixing method to make the iron-containing oxidant with catalytic activity and calcium-based regulators are more evenly distributed in the sludge particles, and the synergistic effect between the two can be used to increase the amount of gas fuel generated during the gasification process and the catalytic activity of solid products, and to inhibit the release of pollutants throughout the process, to achieve It realizes the utilization of sludge with low cost, low energy consumption, low pollution and high output.

Description

A method for simultaneously preparing clean gas fuel and adsorbent from sludge

technical field

The invention belongs to the field of sludge treatment and resource utilization, and in particular relates to a method for simultaneously preparing clean gas fuel and an adsorbent from sludge.

Background technique

Sludge is a by-product of sewage treatment. It is highly hydrophilic, and its organic matter content is usually as high as 40% to 80%. It is easy to rot and smell. In recent years, with the construction, renovation and expansion of a large number of sewage treatment plants across the country, the amount of sludge has increased sharply, and it is directly discharged into the environment, which is likely to cause serious secondary pollution. However, if appropriate measures are taken, sludge can "turn waste into treasure". In addition to achieving the goal of reducing, stabilizing, and harmless solid waste treatment and disposal, it can also realize its effective resource utilization.

At present, sludge resource utilization technology is developing rapidly, among which the preparation of gaseous fuel and carbon-based adsorbent can effectively convert sludge into high value-added products, so it has been widely researched and recognized. Chinese patents CN101775315A, CN102994152A, CN202705199U, CN202193763U, and CN202881204U all improve sludge gasification efficiency from the development of gasifier type. Chinese patent CN102557361A discloses a sludge gasification method. The flocculant is added and the sludge slurry after acid treatment is layered, and the sediment is sent to the gasification reactor, so that carbon-containing substances and supercritical water are gasified. reaction to obtain gaseous fuel.

In terms of the preparation of sludge-based adsorbents, the existing technologies start with the development of different activation methods, making full use of organic matter to prepare sludge activated carbon. For example, Chinese patent CN100418621C adopts ZnCl ₂ solution to mix with sludge, after pyrolysis and washing, wet sludge carbonization adsorbent is prepared. Chinese patents CN101559354B, CN101537342B, and CN101869825B respectively selected surfactants such as solid NaHCO ₃ , cetyltrimethylammonium bromide, and water-based polyurethane emulsion containing mercapto groups as chemical activators to improve the activity of sludge activated carbon. CN102728321A and CN102886247A mix municipal sludge with waste tires and alumina industrial red mud respectively, and then prepare adsorbents through subsequent impregnation, carbonization and other processes.

The unresolved problems of the prior art are:

(1) The sludge is prepared into gas fuel or adsorbent separately, and the organic and inorganic components in the sludge cannot be used at the same time to achieve maximum resource utilization;

(2) During the preparation process, especially in the stages of carbonization, pyrolysis or gasification, high temperature will cause the N and S in the sludge to be released in the form of sulfur- and nitrogen-containing gas pollutants. Harmony and unity have not been achieved.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for simultaneously preparing clean gas fuel and adsorbent from sludge with high yield, low energy consumption and low pollution.

In order to achieve the above-mentioned purpose of the invention, the technical solutions of the embodiments of the present invention are as follows:

A method for simultaneously preparing clean gas fuel and adsorbent from sludge, comprising the steps of:

Add iron-containing oxidants and calcium-based regulators to the sludge slurry in sequence, stir and mix, and perform mechanical dehydration to obtain dewatered sludge;

The obtained dewatered sludge is crushed and directly steam-gasified to produce a clean gas fuel rich in H ₂ , CO and CH ₄ , and the solid product obtained from the gasification is the sludge ash-based adsorbent.

Further, the iron-containing oxidant specifically includes the following components added in sequence according to the weight ratio of sludge dry basis: H ₂ SO ₄ or CH ₃ COOH is 0% to 3%; FeSO ₄ or Fe ₂ (SO ₄ ) ₃ or Fe ₂ (S ₂ O ₈ ) ₃ is 0.3% to 15%; H ₂ O ₂ is 0% to 3%.

Further, the calcium-based regulator is one or a combination of CaO, Ca(OH) ₂ , and CaCO ₃ , and the dosage of the calcium-based regulator is 5% to 50% of the dry weight of the sludge.

Further, 30% to 80% of its mass of coal powder is also mixed into the calcium-based conditioner.

Further, short-time heat drying is performed on the dewatered sludge before crushing, the drying temperature is 45°C-200°C, and the drying time is 0min-30min.

Further, the steam vaporization temperature is 600°C-1000°C, and the water-carbon ratio is 1.2-2.2:1.

Further, the particle size of the crushed sludge particles is 0.045mm-5mm.

Further, the sludge slurry is municipal sludge and/or papermaking sludge and/or oily sludge, and its water content is 90%-99%.

Generally speaking, compared with the prior art, the above technical solutions conceived by the present invention have the following effects and advantages:

Because the invention implants the process of improving the sludge gasification characteristics and improving the adsorption activity of solid products into the compound conditioning and dehydration process. Compared with physical mixing, impregnation and ion exchange, the wet mixing method makes the substances with catalytic effect or calorific value increase and sludge particles mixed more fully and distributed more uniformly, so as to improve the gas production of sludge gasification more effectively rate, especially the rate of hydrogen production. Direct use of iron salts and calcium salts (or a mixture of calcium salts and coal powder) remaining in the mud cake can also reduce chemical and operating costs, and realize energy-saving and efficient resource utilization of sludge organic matter.

At the same time, the interaction between iron salts, calcium salts and sludge ash matrix can effectively increase the porosity and specific surface area of solid products, and increase the Ca content. The prepared sludge-based adsorbent has high adsorption activity and realizes High value utilization of inorganic residues.

In addition, during the entire gasification process, the thermochemical conversion products of iron salts and calcium salts can effectively fix sulfur in sludge, and promote the conversion of N in sludge to _N2 , reducing _SOx , _NOx and their precursors The generation of pollutants is effectively controlled, and the low-cost, high-yield, low-pollution sludge gasification and adsorbent preparation are realized.

Description of drawings

Fig. 1 is a schematic flow chart of the method of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

The invention provides a method for simultaneously preparing clean gas fuel and adsorbent from sludge. Raw sludge slurry includes municipal sludge, papermaking sludge and oily sludge, etc., with a moisture content of 90% to 99%. The process is shown in Figure 1:

Add iron-containing oxidants and calcium-based regulators to the sludge slurry for compound conditioning, and then use mechanical dehydration. After solid-liquid separation, iron-containing oxidants and calcium-based regulators exist in the solid mud cake in the form of iron salts (including ferrous salts) and calcium salts (or mixtures of calcium salts and modified coal powder).

There are two implementation paths from dehydration to gasification:

One is to dry the dewatered sludge at 45°C to 200°C for 5min to 30min, then crush it into sludge particles with a particle size of 0.045mm to 5mm, and then perform steam gasification. Due to the compound conditioning and modification process, the existing form of water in the sludge changes and is easily evaporated, so the drying process takes a short time and consumes low energy.

The other is to crush the dewatered sludge into sludge particles with a particle size of 0.045 mm to 5 mm, and then send them directly to the gasification furnace. Residual moisture can replace part of the gasification medium and reduce the consumption of water vapor. In addition, compared with the externally added water vapor, the evaporated water inside the particles is in closer contact with the sludge carbon matrix, and the gasification effect is better. The instantaneous evaporation of water at high temperature creates larger and more porous structures in the solid residue.

The steam gasification process is synchronized with the adsorbent preparation process, the water-carbon ratio is controlled at 1.2-2.2:1, and the reaction temperature is 600°C-1000°C. The iron-containing oxidants and calcium-based regulators remaining in the mud cake are evenly dispersed inside the sludge particles, increasing the content of Fe, Ca, C and other elements in the sludge, and working in three aspects:

In the production of gaseous fuels, iron salts can increase the reaction rate of sludge gasification, and the supplementary C source can increase the production of CO, CH ₄ , and hydrocarbon gases. Highly active CaO promotes the breakage of carbon-hydrogen bonds and carbon-carbon bonds on the surface of sludge particles, resulting in the decomposition of macromolecules into small molecules, and the formation of pore structures in the particles, increasing the specific surface area of sludge particles. At the same time, CaO can catalyze the cracking of tar and capture carbon dioxide water gas shift reaction steam gasification reaction and steam reforming reaction Moving to the right effectively increases syngas production, especially hydrogen production.

In terms of the influence on the performance of the adsorbent, consistent with the above principles, the remaining solid product has well-developed pores and is rich in highly active calcium oxide, which is especially suitable for the adsorption and removal of sulfur-containing gases.

In terms of pollutant control, a synergistic effect occurs between calcium salts and iron salts to react with N in sludge, thereby reducing the formation of _NOx and its precursors. In addition, calcium salts interact with trace S in sludge or S in iron-containing oxidants to generate CaSO ₄ , CaSO _{3 ,} etc., which inhibit the release of sulfur-containing gases.

The iron-containing oxidant specifically includes the following components added in sequence according to the weight ratio of sludge dry basis: H ₂ SO ₄ or CH ₃ COOH is 0% to 3%; FeSO ₄ or Fe ₂ (SO ₄ ) ₃ or Fe ₂ (S ₂ O ₈ ) ₃ is 0.3% to 15%; H ₂ O ₂ is 0% to 3%, and the above components can be combined arbitrarily.

The calcium-based regulator is one or a mixture of CaO, Ca(OH) ₂ , and CaCO ₃ , and the dosage of the calcium-based regulator is 5% to 50% of the dry weight of the sludge.

Now, the present invention will be further described in detail by taking a specific method for simultaneously preparing clean gas fuel and adsorbent from sludge as an example.

Example 1

Take municipal sludge with a moisture content of 99%, add solid FeSO ₄ to the sludge slurry in turn, the dosage is 11% of the weight of the sludge dry basis, mix well and add H ₂ O ₂ , the dosage is the sludge dry basis 0.9% by weight, stirred and reacted for 15 minutes; then added 30% CaO as a calcium-based regulator, and mixed well.

After dewatering with a plate and frame filter press, the obtained dewatered sludge is crushed into sludge particles with a particle size of 0.5 mm to 2 mm. Direct steam gasification with a gasification temperature of 800°C and a water-to-carbon ratio of 1.2:1.

The yields of H ₂ , CO, and CH ₄ were 500 mL/gDS, 350 mL/gDS, and 63 mL/gDS, respectively.

The prepared sludge ash-based adsorbent has a BET specific surface area of 182m ² /g and an active CaO content of 34%.

Example 2

Take papermaking sludge with a moisture content of 95%, add 0.5% H ₂ SO ₄ solution, 0.3% FeSO ₄ solution, and 0.6% H ₂ O ₂ to the sludge slurry in sequence, and stir for 10 minutes; then add 50% calcium-based regulator, mix well. The calcium-based conditioner is a mixture of CaO, CaCO ₃ and coal powder, and the amount of coal powder is 80% of the weight of the calcium-based conditioner.

Centrifugal dehydration is used, and the obtained dewatered sludge is dried at 45°C for 30 minutes, and then crushed into sludge particles with a particle size of 0.045 mm to 0.106 mm. Next, steam gasification is carried out at 1000°C with a water-to-carbon ratio of 2.2:1.

The yields of H ₂ , CO, and CH ₄ were 800 mL/gDS, 890 mL/gDS, and 160 mL/gDS, respectively.

The prepared sludge ash-based adsorbent has a BET specific surface area of 297m ² /g and an active CaO content of 10%.

Example 3

Take oily sludge with a moisture content of 90%, add 3% H ₂ SO ₄ solution, 15% FeSO ₄ solution, and 3% H ₂ O ₂ to the sludge slurry in sequence, and react for 30 minutes; then add 15% Ca(OH) ₂ , stir to mix.

A belt filter press is used for dehydration, and the obtained dewatered sludge is dried at 200°C for 5 minutes, and then crushed into sludge particles with a particle size of 0.180 mm to 0.250 mm. Next, steam gasification is carried out at 600°C with a water-to-carbon ratio of 1.7:1.

The yields of H ₂ , CO, and CH ₄ were 280 mL/gDS, 130 mL/gDS, and 68 mL/gDS, respectively.

The prepared sludge ash-based adsorbent has a BET specific surface area of 101m ² /g and an active CaO content of 11%.

Example 4

Take municipal sludge with a water content of 96%, add 0.5% CH ₃ COOH solution, 8% solid Fe ₂ (SO ₄ ) ₃ , and 1.5% H ₂ O ₂ to the sludge slurry in turn, and react for 15 minutes; Add 50% CaO and stir to mix.

The plate and frame filter press is used for dehydration, and the obtained dewatered sludge is crushed into sludge particles with a particle size of 2 mm to 5 mm. Next, steam gasification is carried out at 1000°C with a water-to-carbon ratio of 1.7:1.

The yields of H ₂ , CO, and CH ₄ were 550 mL/gDS, 396 mL/gDS, and 98 mL/gDS, respectively.

The BET specific surface area of the prepared sludge ash-based adsorbent is 269m ² /g, and the active CaO content is 48%.

Example 5

Take municipal sludge with a moisture content of 95%, add 7% FeSO ₄ solution and 1.1% H ₂ O ₂ to the sludge slurry in sequence, and react for 15 minutes; then add 50% calcium-based regulator and mix well. The calcium-based conditioner is a mixture of CaO and coal powder, and the amount of coal powder is 30% of the weight of the calcium-based conditioner.

A plate and frame filter press is used for dehydration, and the obtained dewatered sludge is dried at 105° C. for 15 minutes, and then crushed into sludge particles with a particle size of 0.180 mm to 0.250 mm. Steam gasification is carried out at 800°C, and the water-to-carbon ratio is 1.7:1.

The yields of H ₂ , CO, and CH ₄ were 306 mL/gDS, 154 mL/gDS, and 72 mL/gDS, respectively.

The prepared sludge ash-based adsorbent has a BET specific surface area of 136m ² /g and an active CaO content of 31%.

Example 6

Take municipal sludge with a moisture content of 95%, add 11% solid FeSO ₄ and 0.9% H ₂ O ₂ to the sludge slurry in turn, and react for 15 minutes; then add 5% Ca(OH) ₂ and mix well.

A plate and frame filter press is used for dehydration, and the obtained dewatered sludge is dried at 105° C. for 15 minutes, and then crushed into sludge particles with a particle size of 0.180 mm to 0.250 mm. Next, steam gasification is carried out at 800°C with a water-to-carbon ratio of 1.9:1.

The yields of H ₂ , CO, and CH ₄ were 436 mL/gDS, 174 mL/gDS, and 83 mL/gDS, respectively.

The BET specific surface area of the prepared sludge ash-based adsorbent was 145m ² /g, and the active CaO content was 1%.

Example 7

Take municipal sludge with a moisture content of 94%, add 8% Fe ₂ (S ₂ O ₈ ) ₃ solution to the sludge slurry in turn, and react for 5 minutes; then add 35% CaO, and stir to mix.

A plate and frame filter press is used for dehydration, and the obtained dewatered sludge is dried at 45°C for 30 minutes, and then crushed into sludge particles with a particle size of 0.106 mm to 0.180 mm. Steam gasification is carried out at 1000°C, and the water-to-carbon ratio is 1.7:1.

The yields of H ₂ , CO, and CH ₄ were 663 mL/gDS, 352 mL/gDS, and 109 mL/gDS, respectively.

The BET specific surface area of the prepared sludge ash-based adsorbent is 268m ² /g, and the active CaO content is 39%.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (5)

1. mud prepares a method for clean air fuel and sorbent material simultaneously, comprises the steps:

In sludge slurry, interpolation contains ferroxidant and calcium base conditioning agent successively, is uniformly mixed and carries out mechanical dehydration to obtain dewatered sludge;

Directly steam gasification is carried out afterwards to the dewatered sludge fragmentation obtained, obtains and be rich in H ₂, CO, CH ₄clean air fuel, gasification gained solid product is sludge ash base adsorbent;

The described ferroxidant that contains specifically comprises the following several component by mud butt weight ratio added successively: H ₂sO ₄or CH ₃cOOH is 0% ~ 3%; FeSO ₄or Fe ₂(SO ₄) ₃or Fe ₂(S ₂o ₈) ₃be 0.3% ~ 15%; H ₂o ₂be 0% ~ 3%;

Described calcium base conditioning agent is CaO, Ca (OH) ₂, CaCO ₃in one or more mixing, the consumption of described calcium base conditioning agent is 5% ~ 50% of mud butt weight;

Described steam gasification temperature is 600 DEG C ~ 1000 DEG C, and steam/hydrocarbons ratio is 1.2 ~ 2.2:1;

Described dewatered sludge is broken into the mud granule that particle diameter is 0.045mm ~ 5mm.

2. method according to claim 1, is characterized in that, also mixes the coal dust of 30% ~ 80% of its quality to calcium base conditioning agent.

3. method according to claim 1 and 2, is characterized in that, before to dewatered sludge fragmentation, also carry out heat drying in short-term to it, and mummification temperature is 45 DEG C ~ 200 DEG C, and drying time is 5min ~ 30min.

4. method according to claim 1 and 2, is characterized in that, described sludge slurry is municipal sludge and/or paper mill sludge and/or oily sludge, and its water ratio is 90% ~ 99%.

5. what prepare according to method described in Claims 1 to 4 any one claim is rich in H ₂, CO, CH ₄clean air fuel and sludge ash base adsorbent.