Method and device for decontaminating hydrocarbon gas processing waste

Abstract

The invention is intended for decontaminating natural hydrocarbon gas processing waste, in the form of sour gases and a water-methanol solution, of methanol, hydrogen sulphide and hydrocarbon impurities during the production of natural fuel gas and liquefied natural gas, and can be used in the gas processing industry. What is proposed is a method for decontaminating natural hydrocarbon gas processing waste, which includes catalytically and / or thermally decontaminating waste, and a device for carrying out the proposed method. The technical result is that of optimizing a process of decontaminating natural hydrocarbon gas processing waste in the form of a stream of a water-methanol solution or methanol concentrate, which provides for reduced energy consumption during the production of natural fuel gas or liquefied natural gas through a combination of decontamination methods and the consumption of waste, renders the technical process more sustainable from the point of view of energy savings, and improves the environmental friendliness of production. A further technical result is the creation of a device for carrying out a combination of different waste decontamination methods in a single apparatus.

Description

[0001] METHOD AND DEVICE FOR NEUTRALIZING HYDROCARBON GASES PROCESSING WASTE

[0002] AREA OF TECHNOLOGY

[0003] A method and device for rendering harmless waste from the processing of natural hydrocarbon gases in the form of acid gases and a water-methanol solution from impurities of methanol, hydrogen sulfide, and hydrocarbons during the production of fuel and liquefied natural gas, ensuring the conversion of toxic impurities into substances that have a lesser impact on the environment, can be used in the gas processing industry.

[0004] Liquefied natural gas production in the Russian Federation is concentrated at several large-scale facilities and is a key export component of the country's economy. In 2022, liquefied natural gas (LNG) production amounted to 32.5 million tons (45.5 billion cubic meters). According to the state LNG production development program, in addition to existing LNG capacity, several additional projects are to be launched over the next decade, with LNG production planned to increase to 100 million tons by 2030.

[0005] PRIOR ART

[0006] Natural gas, the feedstock for LNG production, contains significant amounts of impurities that are unacceptable in the cryogenic LNG production process and must be removed before the main stage of LNG production—deep cooling of the gas to the methane condensation temperature of minus 161.5°C. These impurities primarily include carbon dioxide, hydrogen sulfide, and toxic methanol, which is intentionally added to natural gas before its transportation from the natural gas field to the processing plant via pipelines to prevent hydrate formation. The concentration of LNG production at plants producing 10-20 million tons of final product annually creates local sources of extractable impurities with a capacity of hundreds of thousands of tons, which must be converted into a less toxic form before being released into the environment.To date, a large number of methods have been developed for converting toxic impurities extracted from natural gas, as well as those unacceptable for cryogenic processes, into less toxic forms. A large number of unconventional methods for acid gas utilization have also been proposed at the research stage. These include:

[0007] • purification of low-sulfur gases by a liquid-phase oxidation process, based on the absorption of hydrogen sulfide by certain oxidizing solutions with the formation of, for example, sodium hydrosulfide from hydrogen sulfide, which is then oxidized to sulfur in the presence of sodium vanadate; the disadvantage of the method is the periodicity of the process due to the need for air oxidation of vanadium to the pentavalent state;

[0008] • dissociation of hydrogen sulfide previously extracted from natural gas into hydrogen and sulfur by a thermal method at 1500-2000 K or by the method of hydrogen sulfide radiolysis at 250 °C and γ-irradiation of 1.5 Mrad, however, the conversion of hydrogen sulfide in this process is only 7-9%;

[0009] • a method of plasma chemistry using plasma generators, however, the implementation of this process is multi-stage and ensures the processing of only 10 m 3 / h of gas flow per 1 m 3 plasma volume, which does not allow this method to be used on an industrial scale.

[0010] High energy consumption combined with low technological effectiveness hinder the widespread industrial use of these methods (Neutralization (utilization) of acid gases by non-traditional methods / / Universum: technical sciences: electron, scientific journal. Bobokulov F.B. et al. 2022. 2(95). [Electronic resource] URL: https: / / 7universum.com / ru / tech / archive / item / 13154, accessed 12.07.2024). A known method of purifying methanol water is using copper-containing oxide catalysts. This involves evaporating methanol water containing 5% methanol and then catalytically decomposing methanol at 300°C to a level of 99-99.5% (V.G. Shchankina, V.N. Novikova. Purification of methanol water, one of the products of synthetic gasoline production, using Cu-containing catalysts. Advances in Chemistry and Chemical Technology. 2010, Vol. 24, No. 11 (116), pp. 127-129). The disadvantage of this method is that the bulk of the energy consumption is spent on heating and evaporating the ballast component, water.

[0011] A method is known for the comprehensive purification of gas emissions containing harmful components, including the sequential passage of the gases to be purified through layers of filtering, adsorbing and catalytically active materials, wherein the gases are passed through the adsorbent-absorber layer to remove fluorine-containing compounds, followed by heating and feeding into the 1st catalytic layer to reduce nitrogen oxides with ammonia, then the purified gases are fed into the 2nd catalytic layer to oxidize unreacted excess ammonia, then into the 3rd catalytic layer to oxidize organic substances and carbon monoxide, then into the 4th catalytic layer to convert ozone into molecular oxygen (patent RU 2102124 C1, IPC B01D 53 / 75, filed on 30.01.1996, published on 20.01.1998).The disadvantage of the invention is the combination of adsorption and catalytic purification processes in one apparatus without taking into account that the catalyst can function without replacement for 1-2 years, while the adsorbent is saturated with the extracted impurity in a few hours, and the regeneration of the adsorbent is not provided for in the method.

[0012] A method for utilizing the still residue from methanol regeneration is known, characterized in that the still residue with a methanol content of no more than 50% is fed into a furnace, followed by combustion of the organic phase of the still residue and evaporation of water (patent RU 2593615 C1, IPC F23G 7 / 04, C07C 31 / 04, filed on 02.07.2015, published on 10.08.2016). The disadvantage of this invention is the high energy consumption of the method, associated with the low concentration of methanol in the still bottoms: taking into account that the heat of evaporation of methanol and water is 1084.4 and 2258.2 kJ / kg, respectively, and the heat capacity of their vapors is 2.16 and 4.3 kJ / (kg deg), the energy costs for heating, evaporation and superheating of water vapor exceed by 2 times the corresponding energy costs for methanol at its concentration in the still bottoms of 50% and by 8 times at a methanol concentration in the still bottoms of 25%.

[0013] A method is known for processing natural gas with an increased content of acidic components, which sequentially includes the following stages: a) separation and metering of the consumption of raw natural gas, b) absorption purification of the separated natural gas from acidic components and mercaptans with regeneration of the absorbent and obtaining sulfur-containing acidic gases, c) drying of the purified natural gas, d) obtaining elemental sulfur by the Claus method from sulfur-containing acidic gases, d) granulation and storage of commercial sulfur, e) metering of commercial natural gas sent to consumers, g) thermal disposal of waste, h) obtaining propane cold, while the content of acidic components in the raw natural gas is 19 mol.and more and the carbon dioxide:hydrogen sulfide ratio is greater than 1.7; stage (b) is carried out sequentially in two stages, wherein in the first stage hydrogen sulfide is selectively extracted from the separated natural gas, and in the second stage carbon dioxide and mercaptans; stage (c) is implemented by absorption drying or low-temperature separation of natural gas using stage (z); acid gases stripped from the condensate containing dissolved hydrogen sulfide isolated in stage (a), expansion gases of the first and second stages of stage (b), acid desorption gases formed during the regeneration of the absorbent in the second stage of stage (b), as well as weathering gases and condensate formed in stage (c) are additionally sent to stage (g), wherein water vapor formed in the waste heat boilers in stage (d) and the exhaust gas after-treatment furnace in stage (g) is used as.

[0014] 5 coolant for regeneration of absorbents at stages (b) and (c).

[0015] In this case, during the operation of stage (g), unreacted gases from sulfur recovery units 301 / 1 and 301 / 2 are sent for thermal utilization of waste in waste-heat boilers and exhaust gas afterburners through pipelines 36 and 37 to thermal utilization units 302 / 1 and 302 / 2. In addition, expansion gases obtained in the absorption units for cleaning natural gas from acidic components and mercaptans 201 / 1 and 201 / 2 of the natural gas cleaning units 200 / 1 and 200 / 2 are sent to thermal utilization units 302 / 1 and 302 / 2 of the sulfur recovery units 300 / 1 and 300 / 2 through pipelines 15 and 19, separated from the condensate in the sour stripping units

[0016] 15 drains 202 / 1 and 202 / 2 of natural gas purification units 200 / 1 and 200 / 2 acid gases through pipelines 14 and 18, flash gases through pipelines 17 and 21 and condensate through pipelines 16 and 20 from natural gas drying units 400 / 1 and 400 / 2, respectively (patent RU 2705352 C1, IPC BOID 53 / 00, filed on 26.06.2019, published on 06.11.2019). The disadvantage of this

[0017] 20 of the invention is the inefficiency of thermal utilization units 302 / 1 and 302 / 2 during the cold season, which is more than 7-8 months in northern regions, and 12 months in permafrost zones, when hundreds of kilograms of methanol are inevitably added hourly to the raw natural gas transported to the plant. This methanol will partially pass into expansion gases, which are then utilized in thermal utilization units 302 / 1 and 302 / 2, however, some of the methanol will end up in the condensate supplied through pipelines 16 and 20 from natural gas drying units 400 / 1 and 400 / 2, which, during thermal utilization of condensate in units 302 / 1 and 302 / 2, will lead to significant additional energy costs for heating and evaporating the condensate and heating its vapors to a temperature of about 1000 °C.In addition, some of the methanol will also end up in the condensate at the acid waste stripping units 202 / 1 and 202 / 2, which will lead to toxic pollution of the wastewater and significantly increase the costs of environmental protection measures.

[0018] Also known is the method closest to the claimed invention for removing undesirable impurities from process streams in the production of liquefied natural gas, comprising the stages: a) washing the original compressed natural gas with water to remove methanol with the formation of a stream of water-methanol solution; b) absorption removal of hydrogen sulfide and carbon dioxide from the compressed natural gas after stage (a), followed by regeneration of the absorbent with the formation of a stream of acid gases; c) adsorption removal of moisture from the compressed natural gas after stage (b), followed by regeneration of the adsorbent with the formation of a stream of desorption gases with an admixture of hydrocarbons; d) adsorption removal of moisture from the components of the refrigerant, which is used for cooling and / or liquefying natural gas, and / or supercooling liquefied natural gas, followed by regeneration of the adsorbent with the formation of a stream of desorption gases with an admixture of hydrocarbons, characterized in that,that the water-methanol solution after stage (a) is sent to the stage of methanol stripping (d) for mass-exchange stripping of methanol from the stream of water-methanol solution and its concentration in a distillation column with the formation of a stream of methanol concentrate, and the methanol concentrate formed in stage (d), the stream of acid gases in stage (b) and the streams of desorption gases in stages (c) and (d) are subjected to neutralization in the stage of thermal and / or catalytic oxidation (e) (patent RU 2820467 C1, IPC F25J 1 / 00, F25J 3 / 08, declared on 22.06.2023, published on 04.06.2024). The disadvantage of this invention is the high energy consumption associated with the need to use a significant amount of external fuel to heat the mixture of acid gases with air during catalytic and especially thermal neutralization; in addition, thermal and catalytic neutralization of exhaust gases of different composition and flow rate is usually carried out in different devices.The combined implementation of catalytic and thermal waste treatment in a single apparatus has not been developed. Typically, thermal waste treatment is implemented in pressurized furnaces, while catalytic waste treatment is carried out in reactors with a bulk catalyst bed or a catalytic film deposited on a plate or honeycomb metal base of varying spatial configurations.

[0019] A reactor for catalytic purification of gaseous emissions is known, comprising a cylindrical body, the inner surface of which is covered with a catalyst with an infrared radiation source placed in the body, characterized in that the reactor additionally contains a tubular heat exchanger placed in the lower part of the body, a turbine mixing device located in the upper part of the body, and additionally a permeable cylindrical shell made of catalyst, installed in the upper part of the body so that the axes of symmetry of the shell and the body coincide, and the shell covers the mixing device, and the infrared radiation source is made in the form of a six-pointed star, installed in the middle of the body in such a way that its plane is perpendicular to the axis of symmetry of the reactor, the outlet pipe is communicated with the intertube space of the heat exchanger, and the feed pipe is located in such a way,to ensure heating of gaseous emissions by the heat of the reactor exhaust gases (patent RU 2267708 C1, IPC F23G 7 / 06, filed on 28.04.2004, published on 10.01.2006). The disadvantages of this invention are:

[0020] • low degree of purification of gaseous emissions due to the fact that the contact time of the emissions with the additional permeable cylindrical shell of the catalyst is short, and the catalyst applied to the inner wall of the reactor has virtually no effect on the purification of the emissions passing through the inter-tube space of the heat exchanger and contacting the catalyst only with the outer surface of the emission stream;

[0021] • uneven heat transfer from the flow of reaction products in the inter-tube space in the lower part of the reactor to the flow of purified emissions in the tube space due to an unsuccessful structure of the flow of reaction products, leading to the formation of stagnant zones in the form of a sphere under the tube sheet and a cone with an inclined base in the zone where the reaction products are removed from the reactor.

[0022] A large number of reactor designs for catalytic purification of exhaust gases are also known, with a fixed catalyst bed of thin thickness, shaped as a flat disk, cylinder, glass, cone, or system of cones, protected by a series of patents (Mukhutdinov R.Kh., Samoilov N.A. Theory and Practice of Catalytic Purification of Exhaust Gases. Ufa: Gilem Publishing House, 2002, 251 p.). A common drawback of these designs is the difficulty in ensuring the structural connection in a single common housing of the burner device, the catalytic section, and the heat exchange section, leading to a significant increase in the dimensions of the reactors, their metal consumption, and, as a consequence, to difficulties in repairing the apparatus and in unloading and loading operations when replacing the catalyst.

[0023] DISCLOSURE OF THE INVENTION

[0024] During the development of the claimed invention, the task was set to optimize the process of rendering harmless waste from the processing of natural hydrocarbon gases in the form of a stream of water-methanol solution formed at the stage of washing natural gas from methanol with water, and a stream of acid gases formed at the stage of absorption purification of natural gas with aqueous solutions of amines from carbon dioxide, hydrogen sulfide and traces of methanol, from impurities of methanol, hydrogen sulfide and hydrocarbons, ensuring a reduction in energy costs in the production of fuel and liquefied natural gas, allowing the disposal of waste streams by converting various toxic impurities into substances that have a less negative impact on the environment, and a combination of methods for rendering harmless and waste consumption, increasing the level of stability of the technological process from the standpoint of energy saving, as well as the creation of a device that implements various combinations of methods

[0025] 5 waste disposal units in one device.

[0026] The stated problem is solved due to the fact that a method for rendering harmless waste from the processing of natural hydrocarbon gases has been developed, including separate catalytic and / or thermal rendering harmless waste in the form of acid gases and a water-methanol solution from impurities of methanol, hydrogen sulfide, hydrocarbons, while the flow of water-methanol solution is divided into two parts, the first part of the flow of water-methanol solution is heated, evaporated, mixed with acid gases and air and subjected to catalytic rendering harmless, the second part of the flow of water-methanol solution is heated, evaporated, mixed with air and

[0027] 15 are subjected to thermal neutralization, the heating and evaporation of the first and second parts of the water-methanol solution flow is ensured by contactless heat exchange with the flue gases formed as a result of the oxidation of the impurities being neutralized and the combustion of external fuel in the process of catalytic neutralization, while the ratio

[0028] 20 between the first and second parts of the water-methanol solution flow is maintained within the range of 0.7-1.5, ensuring the minimization of external fuel consumption for the implementation of the method.

[0029] Even with a constant flow rate of incoming natural gas, the operation of an LNG plant is significantly complicated by the variable impurity composition of the feedstock, which can change both quantitatively and qualitatively. For example, when methanol is injected into natural gas during gas transportation from a field to an LNG plant, the amount of methanol injected is not constant but depends on the pressure and temperature of the transported gas. During gas pumping optimization, methanol flow rate can vary by 10-50%, and in summer, at the appropriate temperature, methanol injection is stopped. The content of impurities in natural gas, such as carbon dioxide, hydrogen sulfide, and mercaptans, depends on the reservoir characteristics of a specific section of the field being operated.

[0030] The placement of waste treatment equipment can also vary considerably: it can be located at a single production site in the form of high-capacity units processing multiple waste streams, or it can be located at specific process facilities in the form of smaller units processing a single waste stream. The solution to this problem is largely determined by the excess pressure reserve of the resulting waste, which allows for its transportation to the treatment zone without the use of additional pumps or compressors.

[0031] The distribution of the same impurity across different emission streams is also largely determined by the specifics of the LNG production technology at a particular facility. For example, methanol partially dissolves in the feed gas wash water, forming a methanol-water solution, and also partially converts into acid gases during absorbent regeneration.

[0032] The choice of a technological method of neutralization is determined primarily by its energy consumption, taking into account the flow rates of contaminated streams, and it is necessary to form such a combined system for neutralizing the flows of removed impurities so that this system as a whole is less energy-consuming for the enterprise. In this regard, the neutralization of waste containing methanol is of particular importance, since methanol, when oxidized (combusted), becomes an energy carrier, that is, an internal fuel for the neutralization process, which allows saving external fuel supplied from the outside. The introduction of external fuel into the process is necessary for thermal neutralization to ensure a high process temperature (800-1200 °C with a small excess air coefficient of 0.05-0.35), and for catalytic neutralization of organics in gases at 150-350 °C (while the catalyst temperature rises to 450-500

[0033] 5 °C) due to the need for significant dilution with air or an inert flow to bring the concentration of organics in the gas to a level of several g / m3 3 To avoid a sharp rise in the catalyst's temperature, which would lead to its sintering and deactivation, a significant external fuel consumption is also necessary. A concentration that is sufficiently safe for the catalyst

[0034] 10 organics in the gas flow (in particular air) is 5-15 g / m3 3 Concentrating the impurity being neutralized in the purified gas stream by reducing gas dilution to achieve 100% gas purification increases process costs due to the need for an increased catalyst bed thickness (catalyst costs), an increased process temperature (fuel costs), and a reduction in gas flow rate (increasing reactor size and metal consumption). This situation requires an optimized approach to waste neutralization solutions.

[0035] The proposed separation of the water-methanol stream into two parts with

[0036] 20 mixing the first part with acid gases and air necessary for burning acid gas impurities, creates during catalytic neutralization a system in which the required concentration of methanol in the mixture is ensured at a level of 10 g / m3 3 , safe for the catalyst. This technique eliminates the need to introduce air into the system to dilute methanol vapor to the required level during catalytic cleaning, thereby reducing the need for external fuel.

[0037] In order to reduce energy consumption, it is advisable to first remove water from the initial water-methanol solution to obtain a methanol concentrate, since fractionation of, for example, a 10% methanol solution in water by rectification at a temperature of about 100 °C and heating the water will require 6-7 times less energy compared to heating, evaporation and superheating of water to 300 °C during catalytic purification of this solution.

[0038] It is advisable to obtain methanol concentrate by rectifying the initial water-methanol solution.

[0039] It is useful to implement catalytic waste disposal in a fixed bed of granular catalysts for oxidation reactions, which simplifies the hardware and technological design of the process.

[0040] It is advisable to use noble metals as catalysts for oxidation reactions while reducing the total contribution of the high cost of the catalyst and low fuel costs for the implementation of the low-temperature catalytic process to the cost of waste disposal.

[0041] Alternatively, it is advisable to use metal oxides, preferably transition metal oxides, as catalysts for oxidation reactions, while reducing the total contribution of the low cost of the catalyst and the high fuel costs for the implementation of the high-temperature catalytic process to the cost of waste disposal.

[0042] It is useful to use the original natural hydrocarbon gas or processed natural hydrocarbon gas as the external fuel, as they are the most readily available at a particular plant, while the water-methanol mixture or methanol concentrate is the internal fuel, leading to savings in external fuel.

[0043] Thermal neutralization of the second part of the water-methanol mixture or methanol concentrate can be achieved without the consumption of external fuel, provided that their preliminary complete evaporation is ensured.

[0044] It is desirable that during catalytic neutralization of the first part of methanol concentrate together with acid gases and air, the optimal amount of the first part of methanol concentrate, which allows for the concentration of methanol in the mixture to be maintained at a level of 10 g / m3 3 , was determined by equation (1):

[0045] GMKI = (V KG + V A ) / 95, (1) where GMKI is the optimal amount of the first part of methanol concentrate, kg / h;

[0046] VKG and VA are, respectively, the volume of acid gases and air required for the catalytic neutralization of acid gas impurities and combustion of fuel to heat the flow of acid gases and air to the temperature of catalytic neutralization, m 3 / h.

[0047] In this case, the catalytic neutralization of the optimal amount of the first part of the methanol concentrate leads to savings in external fuel costs, determined by equation (2):

[0048] AGF = (VKGPKGCKG + VAPACA)(1K - to) / (QF8) - GMKIQ KI / QF, (2) where AGF is the amount of saved external fuel, kg / h;

[0049] PKG and PA are the density of acid gases and air, respectively, kg / m3 3 ;

[0050] CKG and CA are the heat capacity of acid gases and air, respectively, in kJ / (kg-degree); tK and to are the catalytic neutralization temperature and the initial temperature of acid gases and air at the mixer inlet, respectively, in °C;

[0051] QF – net calorific value of external fuel, kJ / kg;

[0052] 8 - efficiency of fuel combustion in the device;

[0053] QMKI – heat of combustion of methanol, kJ / kg.

[0054] The proposed device for implementing a method for rendering harmless waste from the processing of natural hydrocarbon gases, including catalytic and thermal rendering harmless waste in the form of acid gases and a water-methanol solution from impurities of methanol, hydrogen sulfide, hydrocarbons, contains a cylindrical body with a bottom with a burner or a group of burners with a system for igniting a combustible mixture, installed on the bottom, and a cover connected to the body by a flange connection, nozzles for inlet of the flows to be rendered harmless, hatches for loading and unloading the catalyst, a system of control valves, by means of which the flow of water-methanol solution is divided into two parts, in the lower part of the body there is a zone of catalytic rendering harmless waste, in the upper part of the body there is a zone of thermal rendering harmless waste, in the zone of catalytic rendering harmless, along which the first part of the flow of water-methanol solution moves, a grate is installed, coupled with the body,on which a grid with a layer of ceramic packing and a layer of catalyst arranged sequentially along the height is placed, in the zone of thermal disposal of waste, through which the second part of the water-methanol solution flow passes, a second cylindrical body is placed coaxially to the body with a bottom with a burner with a system for igniting the combustible mixture, connected by the upper part with a perforated collector for collecting flue gases, connected to an exhaust pipe installed on the cover of the body, in the space between the two bodies, spiral heat exchange coils are installed for heating and evaporating, respectively, the first and second parts of the flow of water-methanol solution or methanol concentrate, a mixer of the evaporated first flow of water-methanol mixture or methanol concentrate, acid gases and air is installed on the outside of the bottom of the cylindrical body, connected to a burner or a system of burners inside the bottom,a mixer of the evaporated second flow of water-methanol mixture or methanol concentrate and air is mounted on the outside of the shell of the cylindrical body, connected to the burner of the second cylindrical body, wherein the outlets of the spiral heat exchange coils for heating and evaporating the first and second parts of the flow of water-methanol solution are connected to the corresponding mixers by pipelines located on the outside of the cylindrical body, the flows formed in the mixers are designed with the possibility of passing sequentially, the first part of the flow of water-methanol solution through the grate, mesh, ceramic packing layer and catalyst layer, the second part of the flow of water-methanol solution through the flare burner, respectively, thereby ensuring contactless heat exchange of the first and second parts of the flows of water-methanol solution in the spiral heat exchange coils with flue gases in the first and second bodies of the device,moving upward to the exhaust pipe through a perforated flue gas collection manifold, where the flue gas flows from the catalytic waste treatment and thermal waste treatment zones are combined and mixed in the perforated flue gas collection manifold, and then discharged into the atmosphere through the exhaust pipe.

[0055] The proposed device design enables the neutralization of emissions of various types and phases using thermal and catalytic methods in a single compact unit. The use of spiral heat exchangers increases the flow velocity within the spiral tube and indirectly increases the heat transfer coefficient from the tube wall to the methanol waste.

[0056] It is advisable to connect the outlets of the spiral heat exchange coils for heating and evaporating the first and second parts of the flow of water-methanol solution or methanol concentrate with the corresponding mixers by pipelines located on the outside of the cylindrical body, which simplifies the design of the device.

[0057] It is useful to equip spiral heat exchange coils with fins, which increases the heat exchange surface and intensifies heat transfer through the coil wall.

[0058] - It is recommended to equip mixers with perforated disc turbulators, which intensifies the mixing of flows of different streams by increasing the speed of local jets in the perforation zone.

[0059] It is useful to supply air to the corresponding mixers with an air blower, which is an economical device for moving gases under conditions of slight excess pressure (10-100 kPa), and the waste disposal device is essentially a small hollow apparatus with a thin layer of catalyst.

[0060] It is advisable that the burner or burner system inside the bottom be structurally designed as a panel and flameless, which avoids the risk of an open high-temperature flame during fuel combustion hitting the catalyst with its subsequent deactivation, reduces the distance between the burners and the catalyst bed and indirectly reduces the height and metal content of the apparatus, and equalizes the temperature profile of the hot neutralized gas at the entrance to the catalyst bed.

[0061] It is advisable that the burner of the second cylindrical body be structurally designed as a flare, which increases the residence time of the oxidized methanol in the high-temperature zone of the flare.

[0062] It is useful to install a heat exchange coil in the exhaust pipe to produce superheated water vapor, which allows for a lower temperature of the exhaust flue gases, an increase in thermal efficiency, and the generation of an additional coolant flow.

[0063] It is useful to use the resulting superheated water vapor as a heat carrier when obtaining methanol concentrate by rectification from the original water-methanol solution.

[0064] It is advisable to apply a layer of thermal insulation to the outer surface of the housing, which will reduce heat loss to the environment from the device housing and increase the thermal efficiency.

[0065] LIST OF DRAWINGS

[0066] The implementation of the claimed method for rendering harmless waste from the processing of natural hydrocarbon gases in the form of flows of acid gases and methanol concentrate is illustrated by the operation of the device, the basic diagram of which is shown in Figure 1 using the following designations:

[0067] 1 - cylindrical body;

[0068] 2 - bottom;

[0069] 3 - cover; 4 - flange connection;

[0070] 5 - catalytic waste disposal zone;

[0071] 6 - waste thermal disposal zone;

[0072] 7 - inlet fitting for the first part of the methanol concentrate flow;

[0073] 8 - nozzle for inlet of the second part of the methanol concentrate flow;

[0074] 9 - acid gas inlet fitting;

[0075] 10, 29 - air inlet fitting;

[0076] 11 - external fuel inlet fitting;

[0077] 12, 28 - mixers;

[0078] 13 - grate;

[0079] 14 - grid;

[0080] 15 - layer of ceramic packing;

[0081] 16 - catalyst layer;

[0082] 17 - catalyst loading hatch;

[0083] 18 - catalyst discharge hatch;

[0084] 19 - spiral heat exchange coil for heating and evaporating the first part of the methanol concentrate flow;

[0085] 20 - spiral heat exchange coil for heating and evaporating the second part of the methanol concentrate flow;

[0086] 21 - second cylindrical body;

[0087] 22 - flare burner;

[0088] 23 - flameless combustion panel burners;

[0089] 24 - perforated flue gas collection collector;

[0090] 25 - exhaust pipe;

[0091] 26, 27 - connecting pipelines.

[0092] BRIEF DESCRIPTION OF DRAWINGS

[0093] The proposed device implementing this method comprises a cylindrical body 1 with a bottom 2 and a cover 3 connected to the body by a flange joint 4. In the lower part of the cylindrical body 1 there is a zone of catalytic neutralization of waste 5, in the upper part of the cylindrical body 1 there is a zone of thermal neutralization of waste 6. On the cylindrical body 1 there is a nozzle for inlet of the first part of the methanol concentrate flow 7 and a nozzle for inlet of the second part of the methanol concentrate flow 8. On the outer part of the bottom 2 there is a system for inlet of flows into the zone of catalytic neutralization of waste 5, consisting of a nozzle for inlet of acid gases 9, a nozzle for inlet of air 10 and a nozzle for inlet of external fuel 11, united by a mixer 12.

[0094] In the catalytic waste treatment zone 5, a grate 13 is installed, connected to a cylindrical body 1, on which a grid 14 is placed with a layer of ceramic packing 15 and a layer of catalyst 16 placed sequentially along the height. The initial loading of the catalyst and its replacement is ensured by a catalyst loading hatch 17 and a catalyst unloading hatch 18, located on the cylindrical body 1.

[0095] In the catalytic waste treatment zone 5, a spiral heat exchange coil for heating and evaporating the first portion of the methanol concentrate stream 19, a spiral heat exchange coil for heating and evaporating the second portion of the methanol concentrate stream 20 and a second cylindrical body 21 for thermally neutralizing the second portion of the methanol concentrate stream with a flare burner 22 are arranged. In the bottom 2, flameless combustion panel burners 23 are installed, communicating with a mixer 12. The second cylindrical body 21 is connected by its upper part to a perforated flue gas collection collector 24, connected to an exhaust pipe 25, installed on the cover 3 of the cylindrical body 1. The outlet of the spiral heat exchange coil for heating and evaporating the first portion of the methanol concentrate stream 19 is connected to the mixer 12 by a connecting pipeline 26.The outlet of the spiral heat exchange coil for heating and evaporating the second part of the methanol concentrate flow 20 is connected by a connecting pipeline 27 to a mixer 28 with an air inlet nozzle 29. The method for rendering harmless waste from the processing of natural hydrocarbon gases in the form of flows of acid gas and methanol concentrate is carried out as follows: the flow of methanol concentrate is divided into two parts using a system of control valves (not shown in Figure 1) in a ratio between the first and second parts within 0.7-1.5, the specific value of which is determined by the amount and composition of the waste, while the amount of the first part of methanol concentrate is determined by equation (1):.

[0096] GMKI = (VKG+ V A ) / 95, (1) where GMKI is the optimal amount of the first part of methanol concentrate, kg / h;

[0097] VKG and VA are, respectively, the volume of acid gases and air required for the catalytic neutralization of acid gas impurities and combustion of fuel to heat the acid gas flow to the temperature of catalytic neutralization, m 3 / h.

[0098] The flow of the calculated quantity of the first part of the methanol concentrate through the inlet nozzle of the first part of the methanol concentrate flow 7 enters the spiral heat exchange coil for heating and evaporation of the first part of the methanol concentrate flow 19, then the methanol vapors through the connecting pipeline 26 enter the mixer 12, into which the flows of acid gases, air and external fuel are fed respectively through the inlet nozzle of acid gases 9, the inlet nozzle of air 10 and the inlet nozzle of external fuel 11.The mixture of input flows formed in the mixer in the flameless combustion panel burners 23 is partially oxidized, heating up to a catalytic oxidation temperature of 150-450 °C (depending on the type of catalyst used) and then passes sequentially through the grate 13, mesh 14, ceramic packing layer 15 and catalyst layer 16, completing the complete deep oxidation of the combustible components of the waste to CO2, H2O and SO2 (if there are sulfur-containing substances in the waste - hydrogen sulfide, mercaptans).The resulting flue gases, passing through the annular space between the cylindrical body 1 and the second cylindrical body 21, provide heating and evaporation of the first part of the methanol concentrate flow in the spiral heat exchange coil for heating and evaporation of the first part of the methanol concentrate flow 19 and heating and evaporation of the second part of the methanol concentrate flow in the spiral heat exchange coil for heating and evaporation of the second part of the methanol concentrate flow 20.

[0099] The flow of the calculated amount of the second part of the methanol concentrate through the inlet nozzle of the second part of the methanol concentrate flow 8 enters the spiral heat exchange coil for heating and evaporation of the second part of the methanol concentrate flow 20, then the methanol vapors enter the mixer 28 through the connecting pipeline 27, into which the air flow is supplied through the air inlet nozzle 29. The mixture of the input flows formed in the mixer burns in the flare burner 22 at a thermal oxidation temperature of 900-1100 °C with complete deep oxidation of the combustible components of the waste to CO2, H2O and SO2 (in the presence of sulfur-containing substances in the waste - hydrogen sulfide, mercaptans).

[0100] The flue gas flows from the catalytic waste treatment zones 5 and the thermal waste treatment zones 6 are combined and mixed in the perforated flue gas collection collector 24 and discharged into the atmosphere through the exhaust pipe.

[0101] To evaluate the efficiency of the method for neutralizing waste from natural hydrocarbon gas processing in liquefied natural gas production and compare its effectiveness with other waste neutralization methods, several calculations were performed using identical input data for both waste quantity and composition. The analysis included an acid gas stream obtained after absorbent regeneration during amine purification of natural gas containing 2.3% by weight of organic components and a methanol concentrate after fractionation of water-methanol solutions containing 99.8% by weight of methanol (Table 1).

[0102] Example 1. Catalytic waste treatment at 400 °C and thermal waste treatment at 1100 °C up to 100% waste purification level are considered for both separate and combined purification of acid gas flows and methanol concentrate.

[0103] The calculation results are shown in Table 2.

[0104] As Table 2 shows, only thermal oxidation of methanol concentrate can neutralize methanol concentrate waste without external fuel consumption. However, this method consumes the maximum amount of fuel for acid gas neutralization at high temperatures. Catalytic oxidation of 72 kg of methanol concentrate requires slightly more external fuel consumption than 4.1 tons of acid gas due to the need for 100-fold dilution of methanol vapor with air to protect the catalyst from sintering and deactivation. The lowest external fuel consumption—46.7 kg / h—is achieved with combined catalytic neutralization of acid gas and methanol concentrate streams in a single unit.

[0105] Example 2. A variant of combined waste disposal according to the prototype (patent RU 2820467 C1, IPC F25J 1 / 00, F25J 3 / 08, filed on 22.06.2023, published on 04.06.2024) is considered, where the flow of acid gases is subjected to catalytic disposal at 400 °C, and the methanol concentrate is subjected to thermal disposal of waste at a temperature of 1100 °C up to 100% of the waste purification level.

[0106] The calculation results are shown in Table 3.

[0107] As follows from the calculation results, by separate waste treatment using the most efficient technological methods for each of them, it was possible to reduce fuel consumption from 46.7 to 33.9 kg / h, i.e., by 27.4%. Example 3. A waste treatment option according to the claimed invention is considered, dividing the methanol concentrate flow into two parts, wherein the first part of the methanol concentrate is introduced into the acid gas flow and used as internal fuel, thereby reducing external fuel consumption, and the second part of the methanol concentrate is subjected to thermal treatment without external fuel consumption. The amount of the first part of the methanol concentrate is determined by equation (1):

[0108] GMKI — (VKG + VA) I 95, (1) where GMKI is the optimal amount of the first part of methanol concentrate, kg / h;

[0109] VKG and VA are, respectively, the volume of acid gases and air required for catalytic neutralization of acid gas impurities, m 3 / h. With an acid gas flow rate of 4156 kg / h, their volume is 2099 m 3 / h, then the consumption of the first part of methanol concentrate will be:

[0110] GMKI = (V KG + V A ) / 100 = (2099 + 1382) / 95 = 36.64 kg / h, and the second part of the methanol concentrate is (72 - 34.81) = 35.36 kg / h, that is, the ratio between the first and second parts of the methanol concentrate is 1.036 and is within the acceptable range of 0.7-1.5.

[0111] Example 4. A number of waste treatment options according to the claimed invention are considered, with various divisions of the methanol concentrate stream into two parts. The first portion of the methanol concentrate is introduced into the acid gas stream and used as internal fuel, thereby reducing external fuel consumption, while the second portion of the methanol concentrate undergoes thermal treatment without external fuel consumption. The results of calculating the external fuel consumption for the catalytic treatment process are presented in Table 4; no external fuel is consumed for thermal treatment.

[0112] Calculations have shown that the dependence of external fuel consumption on the amount of introduction of the first part of methanol concentrate into the catalytic neutralization zone is extreme in nature with a minimum at the introduction of the second part of methanol concentrate of about 36 kg / h, which is in good agreement with the GMKI value theoretically determined in example 3. =36.64 kg / h. Fuel consumption with the introduction of 36 kg / h of methanol concentrate into the acid gas decreased from 33.9 to 19.9 kg / h, a 41.3% reduction compared to the prototype, thereby reducing operating costs for environmental protection measures.

[0113] Figure 2 shows the dependence of the main parameters of waste disposal - external fuel consumption in kg / h (row 1), air in m 3 / h - 10' 2 (row 2) and external fuel savings in kg / h (row 3) from the amount introduced for catalytic conversion of methanol concentrate. As follows from Figure 2, introducing more than 65 kg of methanol concentrate for catalytic conversion together with acid gases is unacceptable, since in this case, external fuel consumption begins to increase due to the need to introduce additional ballast air to ensure the methanol concentration in the gas mixture being converted at a level of 10 g / m3. 3 .

[0114] Figure 3 shows the dependence of external fuel consumption on the ratio between the first and second portions of the methanol concentrate flows. The central dashed section of the curve corresponds to the zone of the most efficient operation of the proposed method in terms of external fuel savings, and the highlighted section in this zone, with a ratio between the first and second portions of the flows in the range of 0.7-1.5, characterizes the stability of the process in terms of energy conservation, since external fuel consumption, within the measurement error, becomes virtually self-similar to the amount of methanol concentrate introduced into the catalytic conversion zone.

[0115] Example 5. A feasibility study was performed for the claimed invention for the neutralization of waste from the processing of natural hydrocarbon gases in the form of acid gases and methanol concentrate during the production of liquefied natural gas. When processing 23 billion m 3 / year of natural gas with a carbon dioxide concentration of 4.05% by weight, it is necessary to neutralize 930,000 t / y of acid gases and 14,400 t / y of methanol concentrate. The waste composition corresponds to the data in Table 1. Half of the methanol concentrate, together with the acid gases, is neutralized by a catalytic method, the other half - by a thermal method. Waste neutralization according to the invention, compared to separate neutralization of acid gases by a catalytic method and methanol concentrate by a thermal method, will reduce external fuel consumption and save 3.5 million m 3 / year of external fuel natural gas worth 21 million rubles / year, thereby reducing environmental protection costs. Furthermore, by reducing external fuel consumption, carbon dioxide emissions into the atmosphere are reduced by 7,700 tons / year, thereby improving the environmental friendliness of production.

[0116] Thus, the claimed invention solves the problem of optimizing the process of rendering harmless waste from the processing of natural hydrocarbon gases in the form of a flow of water-methanol solution or methanol concentrate, ensuring a reduction in energy costs in the production of fuel and liquefied natural gas by combining methods of rendering harmless and waste consumption, increasing the level of stability of the technological process from the standpoint of energy conservation, improving the environmental friendliness of production, and also creating a device that implements a combination of various methods of rendering harmless waste in a single apparatus.

Claims

CLAUSES OF THE INVENTION 1. A method for rendering harmless waste from the processing of natural hydrocarbon gases, including catalytic and / or thermal rendering harmless waste in the form of acid gases and a water-methanol solution from impurities of methanol, hydrogen sulfide, hydrocarbons, characterized in that the flow of water-methanol solution is divided into two parts, the first part of the flow of water-methanol solution is heated, evaporated, mixed with acid gases and air and subjected to catalytic rendering harmless, the second part of the flow of water-methanol solution is heated, evaporated, mixed with air and subjected to thermal rendering harmless, the heating and evaporation of the first and second parts of the flow of water-methanol solution are ensured by contactless heat exchange with flue gases formed as a result of the oxidation of impurities to be rendered harmless and the combustion of external fuel in the process of catalytic rendering harmless, while the ratio between the first and second parts of the flow of water-methanol solution is maintained within the range of 0.7-1.5,ensuring the minimization of external fuel consumption for the implementation of the method, 2. The method according to paragraph 1, characterized in that water is first removed from the initial water-methanol solution to obtain a methanol concentrate.

3. The method according to paragraphs 1 and 2, characterized in that the methanol concentrate is obtained by rectification of the initial water-methanol solution.

4. The method according to paragraph 1, characterized in that the catalytic neutralization is carried out in a fixed layer of granulated catalysts for oxidation reactions.

5. The method according to paragraphs 1 and 4, characterized in that noble metals are used as catalysts for oxidation reactions.

6. The method according to paragraphs 1 and 4, characterized in that metal oxides, preferably transition metal oxides, are used as catalysts for oxidation reactions.

7. The method according to paragraph 1, characterized in that the original natural hydrocarbon gas or processed natural hydrocarbon gas is used as the external fuel.

8. The method according to paragraph 1, characterized in that water is first removed from the initial water-methanol solution to obtain a methanol concentrate, and the water-methanol mixture or methanol concentrate is used as an internal fuel, leading to savings in external fuel.

9. The method according to paragraph 8, characterized in that the thermal neutralization of the second part of the water-methanol mixture or methanol concentrate is ensured without the consumption of external fuel.

10. The method according to paragraph 8, characterized in that during the catalytic neutralization of the first part of the methanol concentrate together with acid gases and air, the optimal amount of the first part of the methanol concentrate is determined according to equation (1): GMKI = (VKG+ V A) / 95, (1) where GMKI is the optimal amount of the first part of methanol concentrate, kg / h; VKG and VA are, respectively, the volume of acid gases and air required for the catalytic neutralization of acid gas impurities and combustion of fuel to heat the acid gas flow to the temperature of catalytic neutralization, m 3 / h.

11. The method according to paragraph 10, characterized in that the catalytic neutralization of the optimal amount of the first part of the methanol concentrate leads to savings in external fuel costs, determined by equation (2): AGF = (VKGPKGCKG + VAPACA)(1K - to) I (QF2) - GMKIQMKI / QF, (2) where AGF is the amount of saved external fuel, kg / h; PKG and PA are the density of acid gases and air, respectively, kg / m3 3 ; CKG and SD are the heat capacity of acid gases and air, respectively, kJ / (kg-degree); 1k and to are, respectively, the temperature of catalytic neutralization, the initial temperature of acid gases and air at the inlet to the mixer, °C; QF – net calorific value of external fuel, kJ / kg; 2 - efficiency of fuel combustion in the device; QMKI – heat of combustion of methanol, kJ / kg.

12. A device for implementing a method for rendering harmless waste from the processing of natural hydrocarbon gases, including catalytic and thermal rendering harmless waste in the form of acid gases and a water-methanol solution from impurities of methanol, hydrogen sulfide, hydrocarbons, containing a cylindrical body with a bottom with a burner or a group of burners with a system for igniting a combustible mixture, installed on the bottom, and a cover connected to the body by a flange connection, nozzles for inlet of the flows to be rendered harmless, hatches for loading and unloading the catalyst, a system of control valves by means of which the flow of water-methanol solution is divided into two parts, in the lower part of the body there is a zone of catalytic rendering harmless waste, in the upper part of the body there is a zone of thermal rendering harmless waste, in the catalytic rendering harmless zone, along which the first part of the flow of water-methanol solution moves, a grate is installed, connected to the body,on which a grid is placed with a layer of ceramic packing and a layer of catalyst arranged sequentially along the height, in the zone of thermal disposal of waste, through which the second part of the flow of water-methanol solution passes, a second cylindrical body is placed coaxially to the body with a bottom with a burner with a system for ignition of a combustible mixture, connected by the upper part with a perforated collector for collecting flue gases, connected with an exhaust pipe installed on the cover of the body, in the space between the two bodies, spiral heat exchange coils are installed for heating and evaporation, respectively, the first and second parts of the flow of water-methanol solution or methanol concentrate, on the bottom of the cylindrical body outside there is installed a mixer of the evaporated first flow of water-methanol mixture or methanol concentrate, acid gases and air, connected to a burner or a system of burners inside the bottom, on the shell of the cylindrical body outside there is installed a mixer of the evaporated second flow of water-methanol mixture or methanol concentrate and air, connected to a burner of the second cylindrical body, wherein the outlets of the spiral heat exchange coils for heating and evaporating the first and second parts of the flow of water-methanol solution are connected to the corresponding mixers by pipelines located on the outer side of the cylindrical body, the flows formed in the mixers are designed with the ability to pass sequentially, the first part of the flow of water-methanol solution through a grate, a mesh, a layer of ceramic packing and a layer of catalyst,the second part of the water-methanol solution flow through the flare burner, respectively, thereby ensuring contactless heat exchange of the first and second parts of the water-methanol solution flows in the spiral heat exchange coils with the flue gases in the first and second housings of the device, moving upward to the exhaust pipe through the perforated flue gas collection collector, where the flue gas flows of the catalytic waste treatment and thermal waste treatment zones are combined and mixed in the perforated flue gas collection collector, then discharged into the atmosphere through the exhaust pipe., 13. The device according to paragraph 12, characterized in that the outlets of the spiral heat exchange coils for heating and evaporating the first and second parts of the flow of water-methanol solution or methanol concentrate are connected to the corresponding mixers by pipelines located on the outer side of the cylindrical body.

14. The device according to paragraph 12, characterized in that the spiral heat exchange coils are provided with fins.

15. The device according to paragraphs 12 and 13, characterized in that the mixers are equipped with perforated disk turbulators.

16. The device according to paragraph 12, characterized in that the air supply to the corresponding mixers is provided by an air blower.

17. The device according to paragraph 12, characterized in that the burner or system of burners inside the bottom is structurally designed as a panel and flameless.

18. The device according to paragraph 12, characterized in that the burner of the second cylindrical body is structurally designed as a flare.

19. The device according to paragraph 12, characterized in that a heat exchange coil is installed in the exhaust pipe to obtain superheated water vapor.

20. The method according to paragraph 19, characterized in that the resulting superheated water vapor is used as a heat carrier in obtaining methanol concentrate by rectification from the initial water-methanol solution.

21. The device according to paragraph 12, characterized in that a layer of thermal insulation is applied to the outer surface of the housing.

Images