RU2701446C1 - Material for environmental protection from hydrogen sulphide and derivatives thereof from solid household waste landfills - Google Patents

Abstract

FIELD: waste processing and disposal.

SUBSTANCE: invention relates to material intended for treatment of solid domestic waste landfills in order to protect environment from action of hydrogen sulphide and its derivatives extracted from such dumps. Material contains zeolite and magnesium-containing silicate. Feature of the material is that it contains a zeolite in form of natural clinoptilolite, previously converted into an ionic form of Fe (II), and the magnesium-containing silicate is natural serpentinite, and further contains anhydrous spent activated sludge, with the following weight ratio (in terms of dry ingredients, excluding dried activated sludge): natural clinoptilolite pre-converted to ionic Fe (II) / natural serpentinite from 1:0.5 to 1:1.5; dehydrated spent activated sludge / natural clinoptilolite previously converted into Fe (II) ion form – from 0.4:1 to 0.6:1.

EFFECT: technical result is higher efficiency of absorption of hydrogen sulphide and mercaptans in order to enable a lesser repetition of treatment of solid household waste polygon without using compounds of transition metals, including iron (III) compounds, but not excluding use of iron (II) compounds; Besides, task of recycling spent active sludge without cleaning it from heavy metals is solved.

1 cl

Description

The invention relates to the field of ecology, more specifically to the disposal of existing landfills for storage of solid household waste (MSW), and in particular to a material intended for the processing of landfills for solid waste in order to protect the environment from exposure to hydrogen sulfide and its derivatives released from such landfills.

Known technical solutions for this purpose, in which a protective layer of gas-tight material is applied to the surface of the MSW landfill (see, for example, RF patent No. 2014164, publ. 06/15/1994 [1], US patent No. 8403598, publ. 03/26/2013 [2] )

The disadvantage of such solutions is that they only isolate the waste from the environment. Neutralization of the waste mass when using such solutions does not occur. At the same time, since it is almost impossible to guarantee the gas tightness of the protective layer over the entire surface of the landfill, the gases formed under this layer in an ever-increasing amount will inevitably penetrate the environment. Even if the protective layer was initially hermetic, its integrity is almost impossible to maintain during the further operation of the landfill, in particular, due to the need to move equipment, including heavy ones, along its surface.

It is known the use of zeolites for adsorption of hydrogen sulfide and mercaptans (USSR author's certificate No. 1109183, publ. 08.23.1984 [3]). However, the method [3] is applicable only in a production environment for the purification of methane from hydrogen sulfide and mercaptans.

From the patent of the Russian Federation No. 2310076 (publ. 10.11.2007 [4]) it is also known to use zeolites to neutralize toxic gases due to their absorption. The method according to this patent is aimed at preventing the entry of such gases into the environment from rock dumps saturated with aggressive brines, but is not intended for use in landfills;

In the technical solution for US patent application No. 20120024157 (publ. 02.02.2012 [5]), zeolite is used to separate hydrogen sulfide and mercaptans from landfill gas in a special device for processing such a basin.

The technical solution according to US patent No. 8100605 (publ. 24.01.2012 [6]) provides for the use of coating material for the surface of a solid waste landfill containing zeolite (preferably in the form of clinoptilolite), which is capable of not only retaining, but also absorbing hydrogen sulfide and other harmful gases and neutralize them, including due to ion-exchange properties, in particular, due to the use of zeolite in the said material in ionic form Zn. However, the absorption capacity of such a material is so small that this solution is focused on daily updating of the coating after the accumulation of another layer of waste that is insignificant in thickness, which limits the attractiveness of this technical solution. In addition, the use of zinc to trap landfill gases is unreasonably expensive.

The technical solution according to the patent [6] can be attributed to an alternative group, which is formed by decisions aimed at the selective absorption or neutralization of environmentally hazardous gases directly at landfills. The proposed technical solution also belongs to this group.

Closest to the proposed is the technical solution of the indicated group according to US patent No. 7056537 (publ. 06.06.2006 [7]). This technical solution provides for periodic filling of the surface of the MSW landfill with material in the form of a composition comprising a carrier material, which is used as “Fuller’s earth”, metal compounds and organic flavorings. According to the patent [7], "Fuller’s land" may consist of aluminosilicates, or magnesium silicates, or mixtures thereof, or from natural materials containing such silicates. For example, natural zeolite can be used as aluminosilicate. As metal compounds, nitrates or sulfates of silver, copper, zinc or iron (III) can be used, for example, iron sulfate Fe ₂ (SO ₄ ) ₃ . The proportion of this component of the material according to the patent [7] is in the range from 70 to 85 percent by weight, and the proportion of metals is up to 5000 ppm (0.5%). Filling ensures the absorption of hydrogen sulfide and other environmentally harmful gases, in particular organic derivatives of hydrogen sulfide - mercaptans.

The mechanism of action of the material used in the patent [7] is not discussed in detail, but it can be assumed that it is based on physical adsorption, since the role of the porosity of the used carrier materials, as well as on the chemical interaction of hydrogen sulfide with metals and their compounds, is emphasized.

The main disadvantages of the method [7] are as follows:

- the use of transition metal compounds (except iron) for protection against hydrogen sulfide and gaseous mercaptans is not economically feasible; however, reducing the metal content in the composition does not solve this problem, because the amount of hydrogen sulfide retained for the entire duration of the household waste landfill is determined by the total number of metal compounds used during this time; on the contrary, their low content in the composition leads to additional operating costs associated with frequent updating of the coating, and additional capital costs associated with an unreasonably high content of silicates;

- the use of iron (III) compounds in the composition is technologically unjustified due to the fact that the iron sulfide Fe ₂ S ₃ obtained by interaction with hydrogen sulfide is an unstable compound that can be hydrolyzed in a humid environment with the return of hydrogen sulfide.

The present invention relates to a material for protecting the environment from hydrogen sulfide and its derivatives released from solid waste landfills (hereinafter also referred to as a protective material), aimed at achieving a technical result consisting in increasing the absorption efficiency of hydrogen sulfide and mercaptans in order to provide the possibility of more a rare repetition of processing a landfill without using transition metal compounds, c. including iron (III) compounds (but not excluding the use of iron (II) compounds not used in the method [7]). Below, when disclosing the essence of the invention and its further discussion, other types of achieved technical result will be named.

The proposed protective material, as well as the specified closest known material according to the patent [7], includes zeolite and magnesium-containing silicate.

To achieve the above technical result, the proposed protective material, in contrast to the closest known to it, contains zeolite in the form of natural clinoptilolite, previously converted to the ionic form Fe (II), as a magnesium-containing silicate - natural serpentinite, and these natural materials are crushed to particle size not more than 5 mm, and additionally dehydrated spent activated sludge, with the following weight ratios in terms of dry ingredients, with the exception of dehydrated Botan activated sludge: natural clinoptilolite previously converted into the ionic form of Fe (II) / natural serpentinite - 1: 0.5 to 1: 1.5; dehydrated spent activated sludge / natural clinoptilolite previously converted to the ionic form Fe (II) - from 0.4: 1 to 0.6: 1.

Mentioned recalculation means that the indicated mass ratios use the actual mass values of the ingredients, multiplied by a factor: 1 - W / 100, where W is the moisture content of the corresponding ingredient,%.

It is known that clinoptilolite is a natural ion exchanger that can be easily converted from one ionic form to another by treatment with a soluble compound of the corresponding ion (NF Chelishchev, VF Volodin, VL Kryukov. Ion-exchange properties of natural high-silicon zeolites. - M ., Science, 1988, ch. 2 [8]).

Dehydrated by commonly used non-thermal methods (filtration, flotation, centrifugation, sedimentation), spent activated sludge may contain, according to a number of sources, from 75% to 90% moisture (E.Yu. Bryazgina, RR Nasyrov, Z.A. Latypova , LR Khazimova. Method for the disposal and disposal of spent activated sludge. Electronic scientific journal "Oil and Gas Business", 2014, No. 3, P. 124-133, http://www.ogbus.ru [9]; A.G. Ushakov, Utilization of dehydrated excess activated sludge to obtain fuel granules, Bulletin of the Kuzbass State Technical University, 2010 , No. 5, S. 142-144 [10]; Aut. St. USSR No. 1623696, publ. 01/30/1991 [11]; RF patent No. 2421288, publ. 06/20/2011 [12]); A.E. Kuznetsov et al. Applied Ecobiotechnology, vol. 1. M., BINOM, Laboratory of Knowledge, 2012, S. 241 [13]).

Natural materials - clinoptilolite and serpentinite, used in powdered form, can have a very wide particle size distribution: from pulverized to particles no more than 5 mm in size (the use of larger particles would lead to a decrease in the intensity of chemical and sorption processes at the same time as which they participate).

Moreover, serpentinite in the composition of the proposed protective material can be used, in particular, after grinding by wet grinding, since the above characteristic of the proposed protective material contains ratios that depend on the amount of dry matter in the used natural materials, i.e. taking into account their actual humidity. Wet grinding is applicable to natural clinoptilolite, converted into the ionic form Fe (II) at the stage of obtaining the proposed protective material. At the same time, in the finished product, which is the proposed protective material, it is preferable to use serpentinite and clinoptilolite converted to the ionic form Fe (II) after drying, as this makes storage and transportation of the resulting product easier and cheaper.

Natural highly porous materials included in the proposed protective material selectively and stably immobilize hydrogen sulfide and mercaptans not only due to physical adsorption, but also mainly due to chemical interaction with them.

The first ingredient - clinoptilolite in ionic form Fe (II) interacts with the harmful components of the MSW landfill in accordance with the reactions:

Here, R is an insoluble clinoptilolite matrix; the sign “...” means that poorly soluble reaction products remain in the clinoptilolite matrix, as if “immobilized” in it.

Thus, relatively stable slightly soluble compounds are formed - iron sulfides and their organic derivatives in the matrix of the mixed ionic form of hydrogen and iron. However, with a significant degree of clinoptilolite mining (which usually takes place after prolonged use), an unstable pure hydrogen form is formed.

Processes (1) and (2) by themselves are fast, especially in conditions of excessive wetting of solid waste landfills, which eliminates the breakthrough of harmful gas components. The capacity of the zeolite for hydrogen sulfide depends on the possible content of the ionic form Fe (II), which can be from 2 to 5% by weight of hydrogen sulfide in zeolite.

The second ingredient of the protective material - natural serpentinite contains 8-10% magnetite - a mixed oxide of Fe (II) and Fe (III), which itself interacts very slowly with hydrogen sulfide, but at the same time has an extremely large buffer capacity for acid (in this case, for hydrogen sulfide).

During the compaction of the solid body of the solid waste landfill under the influence of backfill of the protective material and the subsequent storage of a new layer of solid waste, serpentinite falls into the heated zone of putrefactive decomposition of waste, and the reaction of hydrogen sulfide with magnetite is accelerated:

In a mixture of serpentinite and clinoptilolite, the latter works more efficiently due to buffering:

As can be seen from the above reactions, in contrast to (1) and (2), the pure hydrogen form of clinoptilolite (R-H) is not formed here, which is unstable and collapses, but the magnesium form is obtained. Provided all reactions (1) - (4) are completed, a mixed hydrogen-magnesium form will be formed, which is significantly more stable than the pure hydrogen form.

It should be further emphasized in the analysis of chemical processes (1) - (4) that iron (II) in the ionic form of clinoptilolite and in metal oxide is not the same thing. In ionic form, it is more free and immediately (quickly) reacts with hydrogen sulfide, as opposed to iron in molecular form in the form of oxides, which slowly react with hydrogen sulfide.

The third ingredient of the proposed protective material - dehydrated spent activated sludge - creates the possibility of obtaining ready-to-use material in advance and its subsequent storage:

- it provides reducing conditions, reducing the rate of oxidation of iron (II) in clinoptilolite and the resulting iron (II) sulfide until, during the operation of the landfill, the backfill layer is under the next putrefactive layer of solid waste, creating further the necessary reducing conditions;

- it provides the necessary humidity for the effective operation of the entire mixed backfill, namely, the first two ingredients, regardless of their own moisture content, until during the operation of the landfill the backfill layer is under the putrid layer of solid waste, which creates further increased humidity.

Thus, only the combined use of the three considered ingredients of the protective material provides the possibility of both increasing its capacity for hydrogen sulfide and mercaptans, and the very possibility of storing and using pre-prepared material.

Moreover, the presence of dehydrated activated sludge in its composition also plays an important role in the following aspect related to the technical result provided by the invention.

It contains iron and manganese interacting with hydrogen sulfide, as well as heavy metals, which form even more stable insoluble compounds with hydrogen sulfide, entering into a reaction like:

where A is the anionic type organic component.

In addition, the use of dehydrated spent activated sludge as part of the proposed material contributes to the parallel solution of an important environmental and economic problem of utilizing the spent activated sludge itself without removing heavy metals (the presence of the latter, on the contrary, creates the additional environmentally useful technical result described above) and without heat treatment .

As for serpentinite, in addition to the noted extremely important buffer role of magnetite included in its composition and direct participation in the interaction with hydrogen sulfide, it has bactericidal properties, which reduces the intensity of bacterial decomposition and gas evolution.

The ratio of clinoptilolite in ionic form Fe (II) and serpentinite (1: 0.5-1: 1.5) by weight (in terms of dry ingredients) is selected based on the following considerations. For long-term exploited landfills (more than 30 years) almost all magnetite in the composition of serpentinite manages to be mined, and estimates based on taking into account the speed of the processes show the sufficiency of the ratio 1: 0.5. For landfills with a short period of operation (less than 10 years) more than the second ingredient is required, up to a ratio of 1: 1.5.

The content of dehydrated spent activated sludge and clinoptilolite in the ionic form Fe (II) is selected based on the fact that when the ratio (in terms of dry clinoptilolite) of 0.4: 1, the necessary humidity is already provided for the clinoptilolite to work as an ion exchanger (regardless of its own moisture, due to the fact that dehydrated spent activated sludge always has a moisture content in the range of 75-90%) and the necessary reducing conditions, and with a ratio exceeding 0.6: 1, the efficiency of the specified sorbent stops growing (speed spine and sorption capacity for hydrogen sulfide).

Used and spent natural sorption materials, including together with spent activated sludge, can be left at the place of solid waste storage, and the landfill surface can be reclaimed by known methods. On the other hand, these materials are agro-ore: ameliorants and fertilizers, and after a long aging time, they can be removed together with compost and humus formed from solid waste after their complete decomposition. In this case, oxidative treatment of sulfides to sulfates is required.

To solve the problems of liquid effluents (filtration water) from solid waste landfills, permeable artificial geochemical barriers around their territories can be implemented using backfill using the proposed protective material. Such barriers can block the spread of soluble forms of harmful substances, including residues of hydrogen sulfide and its derivatives, heavy metals, radionuclides and other toxic components.

The technology using the proposed protective material does not require the mandatory use of high-quality natural materials with a high content of clinoptilolite. For the purposes of immobilizing hydrogen sulfide, low-quality tuffs with up to 50% natural zeolite are suitable. As for serpentinite, a number of its rich deposits are located in areas of good transport accessibility.

When periodically filling (for example, once a year) the surface of the MSW landfill during its operation, it is advisable to create a layer 15–35 cm thick. If the layer is less than 15 cm thick, periodic “breakthroughs” of hydrogen sulfide are possible, but the layer thickness increases over 35 cm increases only the consumption of material and is impractical.

With the above ratios of ingredients, this corresponds to an average specific consumption of clinoptilolite, serpentinite and activated sludge of the order of 500-1250 tons / ha. The flow rate during the construction of a permeable barrier around the solid waste landfill for liquid effluents (filtration water) has the same order.

Thus, the use of the proposed material allows us to solve the problem of protecting the environment from hydrogen sulfide and its derivatives released from solid waste landfills both directly in gaseous form and as part of liquid effluents, while simultaneously contributing to the solution of the problem of utilizing spent activated sludge without cleaning it from heavy metals.

Information sources

1. RF patent No. 2014164, publ. 06/15/1994.

2. US patent No. 8403598, publ. 03/26/2013.

3. USSR Author's Certificate No. 1109183, publ. 08/23/1984.

4. RF patent No. 2310076, publ. 11/10/2007.

5. Patent application US No. 20120024157, publ. 02.02.2012.

6. US Patent No. 8100605, publ. 01/24/2012.

7. US patent No. 7056537, publ. 06/06/2006.

8. N.F. Chelishchev, V.F. Volodin, V.L. Hooks. Ion-exchange properties of natural high-silicon zeolites. - M., Science, 1988, 128 p.

9. E.Yu. Bryazgina, R.R. Nasyrov, Z.A. Latypova, L.R. Khazimov. The method of disposal and disposal of spent activated sludge. Electronic scientific journal "Oil and Gas Business", 2014, No. 3, P. 124-133 (http://www.ogbus.ru).

10. A.G. Ushakov, Disposal of dehydrated excess activated sludge to obtain fuel granules. Bulletin of the Kuzbass State. Tech. University, 2010, No. 5, pp. 142-144.

11. Copyright certificate of the USSR No. 1623696, publ. 01/30/1991.

12. RF patent No. 2421288, publ. 06/20/2011.

13. A.E. Kuznetsov et al. Applied Ecobiotechnology, vol. 1. M., BINOM, Laboratory of Knowledge, 2012, 629 pp.

Claims (1)

Material for protecting the environment from hydrogen sulfide and its derivatives emitted from solid waste landfills, including zeolite and magnesium-containing silicate, characterized in that it contains zeolite in the form of natural clinoptilolite, previously converted to the ionic form Fe (II), and as magnesium-containing silicate - natural serpentinite, moreover, these natural materials are crushed to a particle size of not more than 5 mm, and, in addition, additionally contains dehydrated spent activated sludge, in the following ratios p about the mass in terms of dry ingredients, with the exception of dehydrated spent activated sludge: natural clinoptilolite, previously converted to the ionic form Fe (II) / natural serpentinite - from 1: 0.5 to 1: 1.5; dehydrated spent activated sludge / natural clinoptilolite previously converted to the ionic form Fe (II) - from 0.4: 1 to 0.6: 1.