Claims:We Claim:

1) A method of reducing degradation of a chelate during process of hydrogen sulphide removal comprising of, contacting a hydrogen sulphide containing gas stream with an aqueous solution comprising of a metal chelate in the range of 0.1 to 10 % (W/V) and at least one stabilizer,
wherein the stabilizer is selected from a group of phenolic compounds consisting of phenol, catechol, resorcinol, hydroquinone, pyrogallol or combination thereof

2) The method as claimed in claim 1, wherein the amount of stabilizer is in the range of 0.005 % to 2% (W/V).

3) The method as claimed in claim 1, wherein the aqueous solution further comprises of at least one anti-oxidant in the range of 0.1 to 10% (W/V)

4) The method as claimed in claim 1, wherein the aqueous solution has a pH in the range of 8-11.

5) The method as claimed in claim 1, wherein the metal ion in said metal chelate is selected from a group consisting of Fe, V, Cu, Mn, preferably Fe3+.

6) The method as claimed in claim 1, wherein the cheating agent in said metal chelate is selected from group consisting of monoaminopolycarboxylic acids, polyaminopolycarboxylic acids, polyaminoalkyl polycarboxylic acids, polyaminohydroxyalkyl polycarboxylic acids, such as, ethylene diamine tetraacetic acid (EDTA), 2- hydroxyethyl ethylenediamine triacetic acid (HEDTA), nitrilo triacetic acid (NTA), diethylene triamine pentaacetic acid (DETPA); 1,2-diamino cyclohexane N,N-tetraacetic acid, and 1 ,2-phenylenediamine-N,N-tetraacetic acid.

7) The method as claimed in claim 1, wherein the molar ratio of metal to chelate in the metal chelate 1:1 to 1:3.

8) The process as claimed in claim 3, wherein the antioxidant is selected from a group consisting of alkali thiosulphate, in particular potassium thiosulphate or sodium thiosulphate.

Dated this 24 Day of July 2020
-Digitally Signed-
Vrinda Kaul
IN/PA-2078
Agent for the Applicant
, Description:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
THE PATENTS RULES, 2003
As amended by the Patents (Amendment) Rules, 2006

COMPLETE SPECIFICATION
(See section 10 and rule 13)

TITLE OF THE INVENTION
Method Of Reducing Degradation Of Chelate In Hydrogen Sulphide Removal Process

APPLICANTS
Aditya Birla Science and Technology Company Pvt Ltd
of address
Aditya Birla Centre, 2nd Floor, ‘C’ wing, S.K. Ahire Marg, Worli,
Mumbai 400025, Maharashtra, India

PREAMBLE TO THE DESCRIPTION
The following specification particularly describes this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
[001] The invention relates to a method of removing hydrogen sulfide (H2S) from a gaseous stream. More particularly the invention relates to a method of reducing degradation of chelate during the operation of a hydrogen sulfide removal process.
DESCRIPTION OF THE BACKGROUND ART
[002] H2S (hydrogen sulphide) is produced along with coking coal gasification, oil exploration, refining, natural gas development, sewage treatment, waste composting and many other chemical industrial processes, such as, paper and pulp industry and viscose fibre manufacturing. Hydrogen sulphide (H2S) is a very toxic and corrosive gas. The permissible limit of H2S is 20 parts per million by volume (ppmv) as per regulation of Occupational Safety & Health Administration (OSHA, USA). The inhalation of 500-1000 ppmv of H2S may cause severe health hazards. Therefore, the amount of H2S must be reduced to acceptable levels before the discharge of a flue gas due to safety and environmental concerns. Economical removal of H2S from the industrial streams is not easy, and many processes have been explored and tested.
[003] The desulfurization by liquid redox sulphur recovery (LRSR) process using aqueous iron- chelate solution is well known in the art. The iron-chelate solution is contacted with the hydrogen sulfide containing gas to effect oxidation of the hydrogen sulfide to elemental sulfur and concomitant reduction of the iron from its ferric state to its ferrous state. The solution is regenerated for reuse by contacting it with an oxygen-containing gas, preferably air, to oxidize the iron from its ferrous state to its ferric state.
[004] U.S. Pat. No. 4,009,251 suggests to use a metal chelate catalyst solution for hydrogen sulfide removal which contains a salt of a non-oxidizing acid having a pK of 1.2-6, such as formic and benzoic acids, to inhibit the formation of acidic sulfur oxides and accelerate the reaction of hydrogen sulfide to form sulfur.
[005] U.S. Pat. No. 4,696,802 suggests to treat steam released during geothermal well drilling with an aqueous solution of ferric chelate and a water soluble cationic polymeric catalyst to remove hydrogen sulfide therefrom.
[006] U.S. Pat. No. 4,002,727 discloses an aqueous solution composition for removing hydrogen sulfide from a gas stream, in which the aqueous solution comprises iron in concentrations of 1-5000 ppm, possibly in the form of iron-EDTA.
[007] A problem associated with the use of chelating agents is that most chelating agents are expensive and are degraded during the hydrogen sulfide removal process.
[008] British Pat. No. 999,799 recommends close adjustment of pH to avoid breakdown of the chelate complex.
[009] U.S. Pat. No. 4,189,462 to Thompson indicates that restricting the molar ratio of EDTA to iron is an important consideration in avoiding breakdown of the chelate molecule.
[010] U.S. Pat. No. 4,278,646 to Lynn et al suggests the addition of selected amine salt stabilizers to achieve chelate stability at low pH levels.
[011] Later, it was found that, the degradation of chelating agent can be reduced by the addition of chemical stabilizers that retard the degradation of the chelating agents. The use of stabilizers substantially improves the economics of the hydrogen sulfide removal process. Various organic and inorganic materials were investigated as possible stabilizers, but only a few materials were found that displayed significant effectiveness.
[012] U.S. Pat. No. 4891205A discloses stabilized chelating agents for removing hydrogen sulfide. The stabilizers include aromatic compounds, bromide ions, iodide ions, cyanides, nitrites, amino acids, sugars, ascorbates, alcohols, polyols, aliphatic aldehydes, compounds having unsaturated carbon-carbon bonds, dimethyl sulfoxide, organic disulfides, alkyl amines, and formates.
[013] U.S. Pat. No. 5338778A recite a process for the removal of H2S from a fluid stream by utilizing an iron chelate, wherein the iron chelate is inhibited from degradation by the addition of an effective amount of an anionic polymer.
[014] U.S. Pat. Nos. 4,382,918, 4,388,293, and 4,400,368 propose the addition of various sulfur-containing and nitrogen-containing compounds as stabilizers to reduce the rate of chelate degradation, but the reported data show only a relatively modest improvement in the chelate loss.
[015] U.S. Pat. No. 4622212A recites a method of preventing excessive degradation of chelating agent during prolonged continuous operation of a hydrogen sulfide removal process using an aqueous chelated polyvalent metal catalyst solution by incorporating in the solution an effective amount of a stabilizing agent capable of retarding or preventing rupture of nitrogen-carbon bonds in the chelating agent during oxidative regeneration of the catalyst solution. Said stabilizing agent being selected from the group consisting of alkaline thiosulfates and dihydroxy alcohols having 2 to 3 carbon atoms.
[016] Before the present invention, the prior art has not provided an effective, environmentally acceptable, and inexpensive solution to the problem of chelate degradation.
SUMMARY OF THE INVENTION
[017] It is an object of the present invention to provide a more effective and economical process for removal of hydrogen sulphide from a gaseous stream.
[018] Another specific object of the invention is to provide an improved method of preventing excessive degradation of chelate in a process for removal of hydrogen sulphide.
[019] In an aspect, the present invention provides a method of reducing degradation of a chelate during process of hydrogen sulphide removal comprising of, contacting a hydrogen sulphide containing gas stream with an aqueous solution comprising of a metal chelate in the range of 0.1 to 10 % (W/V), more preferably 0.5 to 5% (W/V) and at least one stabilizer, wherein the stabilizer is selected from a group of phenolic compounds consisting of phenol, catechol, resorcinol, hydroquinone, pyrogallol or combination thereof.
[020] In an aspect, the method of the invention may further comprise of at least one anti-oxidant in the aqueous solution.
BRIEF DESCRIPTION OF THE DRAWINGS
[021] The foregoing summary, as well as the following detailed description of the invention will be better understood when read in conjunction with the appended drawings. For the purpose of assisting in the explanation of the invention, there are shown in the drawings embodiments which are presently preferred and considered illustrative. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown therein. In the drawings:
[022] FIG 1 is a flow chart illustrating process flow of H2S oxidation to elemental sulphur in aqueous Fe-chelate solution.
[023] FIG 2 shows the setup of hydrogen sulphide removal process.
[024] FIG 3 is a graph depicting the effect of stabilizer (phenol), on the chelate degradation during hydrogen sulphide removal process
DESCRIPTION OF THE INVENTION
[025] In describing and claiming the invention, the following terminology will be used in accordance with the definitions set forth below. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described herein. As used herein, each of the following terms has the meaning associated with it in this section. Specific and preferred values listed below for individual process parameters, substituents, and ranges are for illustration only; they do not exclude other defined values or other values falling within the preferred defined ranges.
[026] As used herein, the singular forms "a," "an," and "the" include plural reference unless the context clearly dictates otherwise.
[027] The terms “preferred” and “preferably” refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention
[028] As used herein, the terms “comprising” “including,” “having,” “containing,” “involving,” and the like are to be understood to be open-ended, i.e. to mean including but not limited to.
[029] As used herein, “chelating agent” refers to organic compounds that are capable of linking together with metal ions to form complex, ring-like structures. called metal chelate or chelate
[030] As used herein “chelate” refers to a complex, ring-like structure comprising a metal ion and a chelating agent.
[031] Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described. All publications and other references mentioned herein are incorporated by reference in their entirety. Numeric ranges are inclusive of the numbers defining the range.
[032] The desulfurization of hydrogen sulphide containing gaseous stream by liquid redox sulphur recovery (LRSR) process using aqueous iron-chelate solution is well known in the art. Figure 1 is a flow chart illustrating process flow of H2S oxidation to elemental sulphur in aqueous Fe-chelate solution. The process comprises the steps of (i) passing the gaseous stream containing H2S to a first column containing Fe-chelate, wherein H2S is oxidized to elemental sulphur and Fe3+-chelate is reduced to Fe2+-chelate (ii) the contents are conveyed to a second column, where Fe2+-chelate solution is oxidized to Fe3+-chelate through passing the air; (iii) the contents from second column containing suspended sulphur is filtered to separate the precipitated sulphur and the filtrate is conveyed back to the absorber column for reuse. The conveying of the aqueous Fe-chelate solution from first column to the second column and back to the first column after sulphur filtration is in such a way that levels of both the columns are constant.
[033] The chemical reactions involved in this process is shown as below:
Absorption
H2S(gas) + H2O H2S(aq)
H2S(aq) + 2Fe3+ – Chelaten- S? + 2Fe2+ – Chelaten- + 2H+
Regeneration
O2(g) O2(aq)
O2(aq) + 4Fe2+– Chelaten- + 2H2O 4Fe3+ – Chelaten+ + 4OH-
[034] In this process, the chelating agent is selected from monoaminopolycarboxylic acids, polyaminopolycarboxylic acids, polyaminoalkyl polycarboxylic acids, polyaminohydroxyalkyl polycarboxylic acids, such as, ethylene diamine tetraacetic acid (EDTA), 2- hydroxyethyl ethylenediamine triacetic acid (HEDTA), nitrilo triacetic acid (NTA), diethylene triamine pentaacetic acid (DETPA); 1,2-diamino cyclohexane N, N-tetraacetic acid, and 1 ,2-phenylenediamine-N,N-tetraacetic acid.
[035] It is also known that progressive chemical degradation of chelating agents occurs by severance or rupture at weak positions, for example, ethylene moiety of EDTA during oxidative regeneration of metal chelate. The rupture is ascribed to the presence of hydroxyl radicals, which is produced from the re-oxidation of ferrous chelate product into active ferric chelate via a Fenton mechanism. Due to formation of hydroxyl radicals, there are two strong consequences on the process: (i) the loss of the chelate due to continuous regeneration of metal-chelate solution and (ii) the unwanted precipitation of iron, which cause the impurity in sulphur. In practice, the loss of the chelate turns out to be the most significant factor affecting the economic feasibility of large scale operations. It is well reported that chelated iron solutions are unstable, which may cause undesirable precipitation of iron compounds. The careful control of regeneration of metal-chelate solution have been recommended to avoid the over-oxidation of solution and resultant degradation of chelating agent.
[036] Many stabilizers have been reported to avoid the degradation of chelating agents, such as, thiosulphates, selected amine salts, various sulphur and nitrogen containing compounds, bromide ions, iodide ions, cyanides, nitrites, amino acids, sugars, catalase ascorbates, alcohols, polyols, aliphatic aldehydes, soluble organic compounds having unsaturated carbon-carbon bonds, dimethylsulfoxide, organic disulfides, alkyl amines, (poly)alkanol amines, formates and aromatic compounds, such as, sodium benzoate. However, only a few materials are available that are effective.
[037] It is also shown that aromatic compounds can retard the degradation of the original metal chelate solution by reducing the amount of free hydroxyl radicals in the solution and by later complexing with metal ions released by degraded chelating agents before the aromatic compounds are degraded by additional hydroxyl radicals.
[038] However, stabilizers known in the art have not provided an effective, environmentally acceptable, and inexpensive solution to the problem of chelate degradation. Most of the reported additives in literature are less effective in presence of thiosulphates, which is generated during the H2S absorption in alkaline solution of Fe-chelate as byproduct.
[039] Based on the foregoing mechanism of chelate degradation and as a result of intensive experiments, the inventors of the present application have found that certain stabilizers when incorporated in hydrogen sulphide removal process are effective in preventing the rupture of bonds that results in degradation of the chelating agent.
[040] In an embodiment, the invention provides a method of reducing degradation of chelate during process of hydrogen sulphide removal comprising of, contacting a hydrogen sulphide containing gas stream with an aqueous solution comprising of a metal chelate and at least one stabilizer.
[041] In an embodiment of the invention, the aqueous solution is maintained at a pH in the range of 8-11.
[042] In an embodiment, the stabilizer is selected from a group of phenolic compounds consisting of phenol, catechol, polyhydroxy benzene, resorcinol, hydroquinone, pyrogallol or combination thereof. In another embodiment, the amount of stabilizer is in the range of 0.005 % to 2% (W/V), preferably, 0.01 % to 1% (W/V).
[043] In another optional embodiment of the invention the aqueous solution further comprises of at least one anti-oxidant in the range of 0.1 to 10% (W/V). The antioxidant is selected from a group consisting of alkali thiosulphate, in particular potassium thiosulphate or sodium thiosulphate.
[044] In an embodiment, the amount of metal chelate in the aqueous solution is in the range of 0.1 to 10 % (W/V), preferably, 0.5 to 5 % (W/V). The molar ratio of metal to chelating agent in the metal chelate is in the range of 1:1 to 1:3 preferably 1:1 to 1:2.
[045] In an embodiment, the metal ion in said metal chelate is selected from a group consisting of Fe, V, Cu, Mn, preferably Fe3+. In another embodiment the chelating agent in said metal chelate is selected from group consisting of monoaminopolycarboxylic acids, polyaminopolycarboxylic acids, polyaminoalkyl polycarboxylic acids, polyaminohydroxyalkyl polycarboxylic acids, such as, ethylene diamine tetraacetic acid (EDTA), 2- hydroxyethyl ethylenediamine triacetic acid (HEDTA), nitrilo triacetic acid (NTA), diethylene triamine pentaacetic acid (DETPA); 1,2-diamino cyclohexane N,N-tetraacetic acid, and 1 ,2-phenylenediamine-N,N-tetraacetic acid.
[046] Figure 2 shows the setup of hydrogen sulphide removal process. During operation H2S containing gas stream (1) and air (2) is mixed in a gas mixer (3) to maintain the H2S concentration of 100 ppm to 10000 ppm in air. The H2S containing air is passed to the absorption column (4) at the rate of 5 litre per minute to 20 litre per minute through a sparger. The absorption column contains aqueous solution comprising Fe-chelate, at least one stabilizer and optionally at least one anti-oxidant.
[047] Prior to passing the H2S containing gas stream, the aqueous solution in the absorption column (4) are air oxidized to maintain the Fe3+/Fe2+ ratio to be more than 1.5. The pH of the aqueous solution is maintained at pH 8-11, preferably at pH 10, and the pH is measured by pH sensor (11).
[048] In the absorption column (4), Fe3+-chelaten- oxidize H2S to be precipitated as elemental sulphur and Fe3+-chelaten- itself reduced to Fe2+-chelaten-. The contents from absorber column (4) is conveyed to a regeneration column (5) via a circulation pump (6) at the rate of 50 ml per minute to 500 ml per minute.
[049] The regeneration column (5), also contains an aqueous solution of the same composition as in the absorption column. Air is passed into the regeneration column through a sparger at the predetermined rate to oxidize the Fe2+-chelaten- to Fe3+-chelaten-. The aqueous solution in regenerated column is conveyed to the absorption column through a circulation pump (7).
[050] The precipitated sulphur is recovered by filtration via centrifuge filtration or press filter (8) to obtain the sulphur cake (9). The sulphur cake (9) is melted and separated through layer separation at above 120oC to obtain elemental sulphur.
[051] A condenser (12) is installed in both the absorption and regeneration column, to avoid the evaporation of aqueous solution. At outlet of absorption column, H2S sensor (13) is installed to measure its concentration in ppm to evaluate the H2S absorption efficiency of the solution, before venting the treated gas to atmosphere or scrubber (14).
[052] The sample of aqueous solution containing metal chelate was taken periodically, i.e., at each hour from the sampling point (15) from regeneration column to measure the chelate degradation in the aqueous Fe-chelate solution using HPLC method.
[053] The application of phenol and their hydroxyl derivatives as additive/stabilizer showed 60-80% reduction in the chelate degradation due to their affinity towards hydroxyl radicals. Since the chelate degradation is mainly due to hydroxyl radical catalysed reaction, the results indicate that phenol and their hydroxyl derivatives act as efficient hydroxyl radical scavengers in the process. Additionally, around 80% reduction in the chelate degradation also cause approximately 20% reduction in chemical oxygen demand (COD) in the effluent stream generated due to the process.
WORKING EXAMPLES
The following specific examples are illustrative and explanatory of the present invention but are not to be construed as limiting the scope of the invention.
EXAMPLE 1: BASELINE EXPERIMENT
[054] To prepare the iron-chelate solution, ferrous sulphate heptahydrate (96.6g, 0.35 mol) and EDTA tetrasodium dihydrate (159.0 g, 0.38 mol) was added in 10 litre of water and mixed together to dissolve. To this solution was added sodium thiosulphate pentahydrate (760g, 3.06 mol, 4% (W/V) in the solution) and stirred for dissolution. The solution was further stirred for 1h and their volume was maintained at 12 litre by further addition of water. The resulting iron chelate solution was divided in two equal parts and transferred to absorption and regeneration column reactors. Both the absorption and regeneration column reactors are attached with sparger, inlet for chemicals addition, condenser, pH sensor, H2S sensor, temperature sensor and outlets. The reactors are also interconnected through tubes and circulation pumps to transfer the solution from one reactor to another and vice versa to make the process continuous. Air was passed to the absorption and regeneration column through sparger at the flow rate of 10 litre per minute for 2 h to oxidize the Fe-chelate solution and achieve the Fe3+/Fe2+ ratio more than 1.5. The pH of the solution was maintained at 10 through the addition of 30% (W/V) aqueous solution of Na2CO3 from the inlet at regeneration column. The temperature of the process was maintained at 25oC.
[055] Separately, air at the flow rate of 10 litre per minute was mixed with H2S gas in a gas mixer to obtain required H2S concentration, i.e. 100 ppm to 10000 ppm. The flow rate of the air and H2S was measured and controlled by glass tube rotameters or mass flow meters.
[056] Once the Fe-chelate is oxidized, the absorption column was passed through the air containing 3000 ppm H2S at flow rate of 10 litre per minute via sparger, installed at the bottom of the reactor. At the same time, the regeneration column was passed through only air at flow rate of 10 litre per min via sparger, installed at bottom of the reactor. In the steady state of reaction, the solution from the absorption column was transferred to the regeneration column at the flow rate of 200 ml per minute through a circulation pump. At the same time, the solution from the regeneration column was transferred to the absorption column at the same flow rate as that from absorption column to regeneration column to maintain the level of both the reactor at constant. The reaction was continued for 20 hours. H2S sensor is installed at the outlet of the absorption column to measure the unabsorbed H2S concentration in vent air to evaluate the absorption efficiency. The pH of the solution was measured by pH sensor and maintained at pH 10 through addition of Na2CO3 in the regeneration column throughout the process. The sample of Fe-chelate solution was taken from the sampling point at every hour to determine the degradation of chelating agent by HPLC.
EFFECT OF ADDITIVES ON THE CHELATE DEGRADATION
EXAMPLE 2
[057] Same as the example 1, wherein additionally phenol as stabilizer is added to maintain its concentration of 0.1 gpl to 2 gpl in aqueous solution of Fe-chelate. The effect of phenol on the EDTA degradation is shown in Figure 3. The reductions in chelate degradation due to phenol at 15 h were found to be >80% with respect to the experiment without phenol.
EXAMPLE 3
[058] Same as the example 1, wherein Na2S2O3 is not used and additionally phenol as stabilizer or additive is added to maintain its concentration of 0.1 gpl to 2 gpl in aqueous solution of Fe-chelate.
EXAMPLE 4
[059] Same as the example 1, wherein instead of 40 gpl Na2S2O3, 80 gpl Na2S2O3 is used and additionally phenol as stabilizer or additive is added to maintain its concentration of 0.1 gpl to 2 gpl in aqueous solution of Fe-chelate.
EXAMPLE 5
[060] Same as the example 1, wherein additionally o-catechol as stabilizer or additive is added to maintain its concentration of 0.1 gpl to 2 gpl in aqueous solution of Fe-chelate.
EXAMPLE 6
[061] Same as the example 1, wherein additionally 1,4-hydroquinone as stabilizer or additive is added to maintain its concentration of 0.1 gpl to 2 gpl in aqueous solution of Fe-chelate.
EXAMPLE 7
[062] Same as the example 1, wherein additionally pyrogallol as stabilizer or additive is added to maintain its concentration of 0.1 gpl to 2 gpl in aqueous solution of Fe-chelate.
EXAMPLE 8
[063] Same as the example 1, wherein HEDTA is used as the chelating agent instead of EDTA and additionally, phenol as stabilizer or additive is added to maintain its concentration of 0.1 gpl to 2 gpl in aqueous solution of Fe-chelate. .
EXAMPLE 9
[064] Same as the example 1, wherein NTA is used as the chelating agent instead of EDTA and additionally, phenol as stabilizer or additive is added to maintain its concentration of 0.1 gpl to 2 gpl in aqueous solution of Fe-chelate.
EXAMPLE 10
[065] Same as the example 1, wherein molar ratio of iron to chelate is varied from 1.1 to 1.6 and additionally phenol or its hydroxy derivative as stabilizer or additives is added to maintain its concentration of 0.1 gpl to 2 gpl in aqueous solution of Fe-chelate.
EXAMPLE 11
[066] Same as the example 1, wherein H2S gas concentration is varied from 100 ppm to 10000 ppm and additionally phenol or its hydroxy derivative is added as stabilizer or additive to maintain its concentration of 0.1 gpl to 2 gpl in aqueous solution of Fe-chelate.
EXAMPLE 12
[067] Same as the example 1, wherein the pH of the reaction solution is maintained in the range of 8 to 11 by addition of 30% (W/V) Na2CO3 and additionally phenol or its hydroxy derivative is added as stabilizer or additive to maintain its concentration of 0.1 gpl to 2 gpl in aqueous solution of Fe-chelate.
[068] The foregoing description of the invention is illustrative and explanatory thereof. Various modifications will become apparent to those skilled in the art in view of the present disclosure. It is intended that all such variations which fall within the scope and spirit of the appended claims be embraced thereby.