RU2704836C1 - Material for environmental protection from hydrogen sulphide and derivatives thereof from solid municipal waste landfills (versions) - Google Patents

Abstract

FIELD: ecology.

SUBSTANCE: invention relates to three versions of material for protection of environment from action of hydrogen sulphide and its derivatives, extracted from solid municipal wastes. Material is a product of two or three components to be combined before consumption. According to the first version, the first component is zeolite in form of natural clinoptilolite mixed with magnesium-containing silicate in form of natural serpentinite, the second component is iron sulphate in form of iron sulphate – iron (II) sulphate. According to the second version, the first component is a zeolite in form of natural clinoptilolite, the second component is a magnesium-containing silicate in form of natural serpentinite in a mixture with iron sulphate in form of iron sulphate – iron (II) sulphate. According to the third version, the first component is a zeolite in form of natural clinoptilolite, the second component is a magnesium-containing silicate in form of natural serpentinite and the third component is iron sulphate in form of iron sulphate – iron (II) sulphate. Weight ratio in terms of dry ingredients of said components: natural clinoptilolite / natural serpentinite – from 1:0.5 to 1:1.5; natural clinoptilolite / iron sulphate – from 10:1.8 to 10:2.2.

EFFECT: high efficiency of absorbing hydrogen sulphide and mercaptans and enabling a lesser repetition of treatment of landfill SMW without using compounds of transition metals, including iron (III) compounds.

3 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 three options for the material intended for the processing of landfills for the purpose of protecting the environment from the effects of 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 sealed, 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 gas.

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 a technical solution to the specified 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 flavors. 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 proposed technical solution is represented by three versions of a material for protecting the environment from hydrogen sulfide and its derivatives, which are emitted from solid waste landfills, hereinafter also briefly referred to as protective material.

The invention for all three proposed options is aimed at achieving a technical result, which consists in increasing the efficiency of absorption of hydrogen sulfide and mercaptans in order to provide the possibility of more rare repetition of processing of solid waste landfill (but at time intervals for which the accumulating next layer of waste is still insufficient to create a danger to environment) without the use of transition metal compounds, including iron (III) compounds (but not excluding the use of unused in the method [7] of iron (II) compounds. Below, when disclosing the essence of the invention according to three options and its further discussion, other types of achieved technical result will be named.

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

To achieve the above technical result, the proposed protective material according to the first embodiment, in contrast to the closest known to it, is a two-component product, the components of which must be combined immediately before use. Moreover, it contains as the first component zeolite in the form of natural clinoptilolite mixed with magnesium-containing silicate in the form of natural serpentinite, and these natural materials are crushed to a particle size of not more than 5 mm, and as the second component, iron sulfate in the form of iron sulfate - sulfate iron (II), with the following weight ratios, calculated on the dry ingredients of the indicated components: natural clinoptilolite / natural serpentinite - from 1: 0.5 to 1: 1.5; natural clinoptilolite / iron sulfate - from 10: 1.8 to 10: 2.2.

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

To achieve the above technical result, the proposed protective material according to the second embodiment, in contrast to the closest known to it, is a two-component product, the components of which must be combined immediately before use. Moreover, it contains as the first component zeolite in the form of natural clinoptilolite, and as the second component - magnesium-containing silicate in the form of natural serpentinite mixed with iron sulfate in the form of iron sulfate - iron (II) sulfate, and these natural materials are crushed to particle size not more than 5 mm, with the following weight ratios, calculated on the dry ingredients of the indicated components: natural clinoptilolite / natural serpentinite - from 1: 0.5 to 1: 1.5; natural clinoptilolite / iron sulfate - from 10: 1.8 to 10: 2.2.

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

To achieve the above technical result, the proposed protective material according to the third embodiment, in contrast to the closest known to it, is a three-component product, the components of which must be combined immediately before use. Moreover, as the first component, it contains zeolite in the form of natural clinoptilolite, as the second component, magnesium-containing silicate in the form of natural serpentinite, and as the third component, iron sulfate in the form of iron sulfate - iron (II) sulfate, and these natural materials are crushed to a particle size of not more than 5 mm, with the following weight ratios, calculated on the dry ingredients of these components: natural clinoptilolite / natural serpentinite - from 1: 0.5 to 1: 1.5; natural clinoptilolite / iron sulfate - from 10: 1.8 to 10: 2.2.

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,%.

As you can see, in all three embodiments of the proposed protective material, the combination and ratio of the ingredients that make up the components of this material, combined before use, are the same. Therefore, for all these options, the "mechanism" of the protective material functioning with the achievement of the above technical result is the same and can be considered simultaneously.

Clinoptilolite and iron sulfate are part of the various components of the product, which is a protective material, so they cannot interact before using this material for its intended purpose. When using the proposed protective material immediately before processing it with a solid waste landfill as a result of the interaction of these two ingredients, which occurs when the components of the material are combined with mixing on water to the state of wet sand, clinoptilolite undergoes transition to the Fe (II) ionic form with the formation of R ₂ SO ₄ , where R is an insoluble clinoptilolite matrix.

Clinoptilolite in ionic form Fe (II) interacts with harmful components of the MSW landfill in accordance with the reactions:

(the sign means that sparingly 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 hydrogen sulfide zeolite capacity depends on the possible content of the ionic form Fe (II) in it and can be from 2 to 5% by weight of hydrogen sulfide in zeolite.

The third ingredient of the protective material prepared for use (the composition mentioned above) is natural serpentinite containing 8-10% magnetite - a mixed oxide of Fe (II) and Fe (III), which itself very slowly interacts with hydrogen sulfide, but possesses 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, which converted to the ionic form of Fe (II), the latter works more efficiently by 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.

In addition to the markedly important role of serpentinite, it is necessary to indicate its bactericidal properties, which reduces the intensity of bacterial decomposition and gas evolution.

It should be noted the presence of strong bactericidal properties also in iron sulfate, which can be realized by its part, which was not used in ion exchange with clinoptilolite when converting it to the ionic form Fe (II).

It is additionally necessary to emphasize 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.

Thus, only the joint use of all the considered ingredients of the protective material in any of the three options provides the possibility of increasing its capacity for hydrogen sulfide and mercaptans. Moreover, the belonging of iron sulfate and clinoptilolite in any of the options to different components, to be combined only immediately before using the protective material, provides the possibility of arbitrarily long storage of the previously prepared two- or three-component product in the form of which the proposed protective material is made.

The ratio of the first two ingredients that make up the components of the proposed protective material - clinoptilolite and serpentinite (from 1: 0.5 to 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 component is required, up to a ratio of 1: 1.5.

The mass ratio of clinoptilolite and iron sulfate (referring to the dry ingredients in the components of the proposed protective material) is selected in the range from 10: 1.8 to 10: 2.2, taking into account the fact that with a smaller proportion of iron sulfate the excess amount of clinoptilolite does not go into the form of iron (II) and therefore is not used for purification from hydrogen sulfide, and with a greater proportion of iron sulfate, its excessive amount does not increase the purification efficiency.

Natural materials - clinoptilolite and serpentinite, used in powdered form, can have a very wide particle size distribution: from pulverized to granules no larger than 5 mm (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, these natural materials in the composition of the components 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 mass ratios in terms of dry ingredients in the composition of its components, i.e. taking into account their actual humidity. It is preferable to use crushed natural materials after drying, since the storage and transportation of the resulting protective material are facilitated and cheapened.

Used and spent natural sorption materials can be left at the place of storage of solid waste, and the surface of the landfill 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 from the proposed protective material according to any of the options. 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 a content of 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 therefore impractical.

With the above ratios of ingredients, this corresponds to an average specific consumption of clinoptilolite and serpentinite of the order of 500-1250 tons / ha. The specific average consumption of iron sulfate in this case is about 250 tons / ha. The flow rate during the construction of a permeable barrier around the territory of the solid waste landfill for liquid effluents (filtration water) has the same order.

Thus, the use of the proposed material in any of the described options 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.

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.

Claims (3)

1. Material for protecting the environment from hydrogen sulfide and its derivatives released from solid waste landfills, including zeolite and magnesium-containing silicate, as well as iron sulfate, characterized in that it is a two-component product, the components of which must be combined immediately before use, when this it contains as a first component zeolite in the form of natural clinoptilolite mixed with magnesium-containing silicate in the form of natural serpentinite, and these natural materials crushed to a particle size of not more than 5 mm, and as the second component, iron sulfate in the form of iron sulfate - iron (II) sulfate with the following weight ratios in terms of the dry ingredients of these components: natural clinoptilolite / natural serpentinite - from 1: 0 5 to 1: 1.5; natural clinoptilolite / iron sulfate - from 10: 1.8 to 10: 2.2. 2. Material for protecting the environment from hydrogen sulfide and its derivatives released from solid waste landfills, including zeolite and magnesium-containing silicate, as well as iron sulfate, characterized in that it is a two-component product, the components of which must be combined immediately before use, when this it contains as the first component zeolite in the form of natural clinoptilolite, and as the second component - magnesium-containing silicate in the form of natural serpentinite mixed with sulfate ohm of iron in the form of vitriol - iron (II) sulfate, and these natural materials are crushed to a particle size of not more than 5 mm, with the following weight ratios in terms of the dry ingredients of these components: natural clinoptilolite / natural serpentinite - from 1: 0, 5 to 1: 1.5; natural clinoptilolite / iron sulfate - from 10: 1.8 to 10: 2.2. 3. Material for protecting the environment from hydrogen sulfide and its derivatives released from solid waste landfills, including zeolite and magnesium-containing silicate, as well as iron sulfate, characterized in that it is a three-component product, the components of which must be combined immediately before use, when this, as the first component, it contains zeolite in the form of natural clinoptilolite, as the second component - magnesium-containing silicate in the form of natural serpentinite, and as a third the first component is iron sulfate in the form of iron sulfate - iron (II) sulfate, and these natural materials are crushed to a particle size of not more than 5 mm, with the following weight ratios in terms of dry ingredients of these components: natural clinoptilolite / natural serpentinite - from 1 : 0.5 to 1: 1.5; natural clinoptilolite / iron sulfate - from 10: 1.8 to 10: 2.2.