Methanol production system and method based on the co-utilization of landfill waste and landfill gas

Abstract

This invention relates to a method for the co-utilization of existing landfill waste and landfill gas to produce renewable methanol. RDF (Regenerative Thermal Deposition Facility) is pretreated and then purified into high-temperature syngas through pyrolysis, plasma gasification, desulfurization, and steam reforming. This purified syngas is mixed with steam-reformed landfill gas and green hydrogen obtained from water electrolysis, and the ratio is adjusted to obtain a methanol reaction feedstock gas satisfying [H2 / (2CO+3CO2)=0.9-1.1]. The feedstock gas is then used to produce methanol through a methanol synthesis reaction. Under a recycle ratio of 0.6-0.8, the hydrogen-to-carbon ratio of the syngas is 0.89-1.01, the methanol production exceeds 17 tons / hour, the system energy efficiency exceeds 75%, and the CO2 equivalent emission reduction rate is 82.5-91.7%. This invention achieves complementary carbon source utilization and hydrogen-to-carbon ratio through the parallel use of landfill waste and landfill gas as dual gas sources, improving system load stability and heat cascade utilization efficiency, and providing a new solution for the co-resource utilization of waste and the large-scale production of renewable methanol.

Description

Technical Field

[0001] This invention relates to the field of environmental protection technology, specifically to a methanol production system and method based on the synergistic utilization of landfill waste and landfill gas. Background Technology

[0002] Sanitary landfill was once the primary method of municipal solid waste disposal, with numerous landfills built over the past few decades. With the increasing prevalence of more efficient and environmentally friendly treatment methods such as incineration and gasification, many landfills have entered the closure or remediation phase. Landfill extraction has emerged as a new concept, aiming to mitigate environmental risks and achieve the reuse of landfill resources. Landfill waste and landfill gas, as major byproducts, have the potential to be converted into waste-to-energy (WtE).

[0003] Methanol is a crucial raw material for the chemical industry, with demand continuing to grow. Currently, production primarily relies on fossil fuels such as coal and natural gas. Synthesizing renewable methanol using green hydrogen and CO / CO2 from biomass or derived fuels (RDF) is considered an important alternative to fossil methanol. Excavated waste and landfill gas, rich in carbon, can serve as ideal feedstocks for renewable methanol synthesis.

[0004] Landfill gas is mainly composed of methane (approximately 55%) and carbon dioxide (approximately 45%), and the resulting syngas after reforming is severely deficient in hydrogen. Methane can be converted to CO / CO2 through various pathways, including steam reforming, dry reforming, partial oxidation, and oxygen-enriched combustion. Double or triple reforming can be used to improve conversion rates when necessary. Considering the high CH4 and CO2 content in landfill gas, dry reforming is a suitable technical choice. Patent document CN114621053A (application number: 202110730850.7) provides a method for preparing methanol from landfill gas. This process mixes landfill gas with steam, converts it into hydrogen-poor syngas through a reforming reaction, and introduces hydrogen obtained from renewable energy electrolysis of water to adjust the hydrogen-to-carbon ratio of the syngas, thereby synthesizing methanol. Although this method has achieved the resource utilization of landfill gas, it still has obvious limitations: First, the amount of landfill gas produced is easily affected by site-specific factors and decay over time, resulting in large fluctuations in system operating load and difficulty in maintaining long-term stability; Second, when landfill gas is used for methanol synthesis, it requires a large amount of external electrolysis of hydrogen, which not only increases energy consumption and operating costs, but also further strengthens the dependence on renewable electricity.

[0005] In contrast, existing landfill waste (such as wood products, paper, textiles, yard waste, and low-value plastics rich in hydrogen) benefits from the higher hydrogen content of its organic components, producing syngas with a better hydrogen-to-carbon ratio (H2 / CO), making it an ideal "hydrogen-rich" feedstock. In recent years, plasma gasification (PGF) has been developed for the resource conversion of landfill waste. Its advantage lies in its ability to produce clean syngas that is virtually free of dioxins and tar under high-temperature conditions, while the byproduct glassy slag can be utilized in the building materials industry.

[0006] Existing methanol production technologies are mostly limited to the use of a single gas source. In contrast, by using landfill waste and landfill gas in parallel, complementary carbon source utilization and hydrogen-carbon ratio can be achieved, reducing external hydrogen consumption through electrolysis and alleviating the problem of unstable production capacity caused by insufficient landfill gas supply. Therefore, this invention proposes a new process for the co-utilization of landfill gas to produce renewable methanol, realizing the co-resource recovery of waste, balancing economic and environmental benefits, and providing a new solution for the large-scale production of renewable methanol. Summary of the Invention

[0007] The purpose of this invention is to address the problems in existing technologies by providing a methanol production system and method based on the co-utilization of landfill waste and landfill gas. This invention is a novel process for producing renewable methanol through the co-utilization of landfill waste and landfill gas. By using a "dual gas source" approach (landfill waste and landfill gas in parallel), it achieves complementary carbon source utilization and hydrogen-carbon ratio, improving system load stability and heat cascade utilization efficiency while reducing hydrogen consumption.

[0008] To achieve the above-mentioned objectives of this invention, the present invention adopts the following technical solution:

[0009] This invention provides a methanol production system based on the synergistic utilization of landfill waste and landfill gas, comprising: an RDF (Refuse Derived Fuel) purification system, a landfill gas reforming system, and a methanol synthesis system;

[0010] The RDF purification system includes a dryer D101, a pyrolysis decomposer R101, a distributor S101, a plasma gasification furnace R102, a second heat exchanger (waste heat exchanger) E102, a gas-solid separation device S102, a second compressor C102, a zinc oxide (ZnO) fixed bed reactor R103, a steam reformer R104, and a third compressor C103, connected in sequence.

[0011] The landfill gas reforming system includes a first mixer M101, a fourth heat exchanger E104, a reforming reactor R105, a fifth heat exchanger E105, a condenser E106, a fourth compressor C104, and a first flash evaporator V101 connected in sequence.

[0012] The methanol synthesis system includes a second mixer M102, a first-stage composite adsorber R106, a second-stage fine remover R107, a fifth compressor C105, a methanol reactor R108, a seventh heat exchanger E107, an eighth heat exchanger E108, and a second flash evaporator V102 connected in sequence.

[0013] The third compressor C103 in the RDF purification system and the first flash evaporator V101 in the landfill gas reforming system are both connected to the second mixer M102 in the methanol synthesis system.

[0014] As one embodiment of the present invention, the dryer D101 is provided with an RDF inlet and a high-temperature air inlet. RDF 101 and high-temperature air (hot air) 102 enter the dryer D101 from the RDF inlet and the high-temperature air inlet, respectively.

[0015] In one embodiment of the present invention, the dried RDF 103 obtained from the dryer D101 enters the pyrolysis decomposer R101. The pyrolysis product 104 obtained from the pyrolysis decomposer R101 enters the distributor S101.

[0016] The pyrolysis product 104 includes syngas and solid residue; wherein, the solid residue includes fixed carbon, ash and residual volatile matter; the syngas (RDF plasma gasification product components) includes 35%-40% H2, 35%-45% CO, 15%-20% CO2 and 0-2% N2 by volume, and the volume ratio of H2 to CO is 0.9-1.1:1.

[0017] In one embodiment of the present invention, the distributor S101 and the plasma gasification furnace R102 are connected by a gas pipeline and a solid pipeline (main pipeline), respectively; a first heat exchanger E101 is provided on the gas pipeline. The pyrolysis product 104 is separated in the distributor S101 to obtain pyrolysis gas 105 and solid residue 106. The pyrolysis gas 105 is preheated by the first heat exchanger E101 and then introduced into the plasma gasification furnace R102; the solid residue 106 directly enters the plasma gasification furnace R102 through the solid pipeline.

[0018] As one embodiment of the present invention, the plasma gasifier R102 is further provided with an oxygen inlet and a water inlet. The oxygen inlet is used to input oxygen 118 for the RDF purification system. The water inlet is used to input water. Water is pressurized by a booster pump P101, passes through a third heat exchanger E103, and enters the water inlet.

[0019] Oxygen 117 is passed through compressor C101 to obtain oxygen 118 for RDF purification system and oxygen 119 for landfill gas reforming system.

[0020] Industrial water can be selected as the water source. Industrial water 120 is pressurized by pump P101 to obtain pressurized industrial water 121, which is then passed through the third heat exchanger E103 to obtain first industrial water 122, which enters the water source inlet.

[0021] The industrial water is instantly vaporized at high temperatures inside the furnace to form steam, which acts as a gasifying agent to react with fixed carbon and volatiles in the RDF pyrolysis products in a high-temperature water-gas reaction (C + H2O → CO + H2). The main functions of introducing industrial water include: first, supplementing the hydrogen source, increasing the volume fraction of H2 in the syngas, and improving the basic H2 / CO ratio; second, utilizing the endothermic characteristics of the water-gas reaction, in conjunction with the exothermic oxidation reaction of oxygen, to synergistically regulate the furnace temperature and maintain it within the process range of 1200-1600℃; and third, utilizing the high reactivity of high-temperature steam to deeply convert solid carbon particles and tar, improving carbon conversion rate and inhibiting carbon deposition.

[0022] As one embodiment of the present invention, the high-temperature synthesis gas 107 obtained from the plasma gasification furnace R102 is passed through the second heat exchanger E102 to obtain low-temperature synthesis gas 108, which then enters the gas-solid separation device S102.

[0023] Carbon combustion reaction:

[0024]

[0025] Water vaporization reaction:

[0026] Water-gas shift reaction:

[0027] Tar and hydrocarbon cracking reaction: C+ .

[0028] In one embodiment of the present invention, the gas-solid separation device S102 is provided with a syngas outlet and connected to the second compressor C102. The gas-solid separation device S102 is also provided with an ash outlet. The low-temperature syngas 108 passes through the gas-solid separation device S102 and is separated into ash 123 and syngas 109, which are discharged through the ash outlet and the syngas outlet, respectively.

[0029] As one embodiment of the present invention, the synthesis gas 109 passes through the second compressor C102 to obtain compressed synthesis gas 110, which then enters the zinc oxide (ZnO) fixed bed reactor R103.

[0030] In one embodiment of the present invention, the zinc oxide (ZnO) fixed-bed reactor R103 is provided with an absorbent inlet, a purified gas outlet, and an absorbent liquid outlet. The purified gas outlet is connected to a steam reformer R104. The purified gas 113 obtained in the zinc oxide (ZnO) fixed-bed reactor R103 enters the steam reformer R104 through the purified gas outlet.

[0031] H2S absorbent 111 enters the zinc oxide (ZnO) fixed-bed reactor R103 through the absorbent inlet. The washing wastewater and H2S-rich absorbent liquid 114 generated by the reaction are discharged from the absorbent outlet at the bottom.

[0032] As one embodiment of the present invention, the zinc oxide (ZnO) fixed-bed reactor includes a fixed bed composed of zinc oxide particles.

[0033] The zinc oxide (ZnO) fixed-bed reactor R103 is designed to deeply remove sulfide impurities from syngas that are highly toxic to subsequent steam reforming and methanol synthesis catalysts. In this reactor, syngas 110 passes through a fixed bed composed of zinc oxide particles. Hydrogen sulfide (H2S) and carbonyl sulfide (COS) in the gas stream react chemically with the solid zinc oxide, converting it into solid zinc sulfide (ZnS) which is then fixed within the bed.

[0034] In one embodiment of the present invention, the steam reformer R104 is provided with a steam inlet. Steam 112 enters the steam reformer R104 through the steam inlet.

[0035] In one embodiment of the present invention, the reformed gas 115 obtained from the steam reformer R104 is passed through the third compressor C103 to obtain purified gas 116 vaporized from RDF. Methane steam reforming, water-gas shift reaction, and methane dry reforming occur simultaneously in the reforming reactor. The reformed gas is then passed through the third compressor C103 to obtain purified gas vaporized from RDF.

[0036] In one embodiment of the present invention, the first mixer M101 is provided with an oxygen inlet, a landfill gas inlet, and a steam inlet. The oxygen inlet is used to input oxygen 119 for the landfill gas reforming system. The landfill gas inlet is used to input landfill gas 144. The steam inlet is used to input pressurized steam 146 (steam 145 is pressurized by the second pressurization pump P102).

[0037] In one embodiment of the present invention, the landfill gas mixture 147 obtained from the first mixer M101 is passed through the heat exchanger E104 to obtain feed gas 148. The feed gas 148 passes through the reformer R105 to obtain high-temperature synthesis gas 149, passes through the heat exchanger E105 to obtain heat-exchanged synthesis gas 150, passes through the condenser E106 to obtain cooled synthesis gas 151, and then passes through the compressor C104 to obtain mixed gas 152.

[0038] As one embodiment of the present invention, the first flash evaporator V101 is provided with a mixed gas inlet, a syngas outlet, and a waste outlet. The mixed gas 152 enters the first flash evaporator V101 through the mixed gas inlet and undergoes flash separation. Under the action of gravity, the liquid waste 153 is discharged from the waste outlet at the bottom of the tank, while the landfill reforming gas 154 is discharged from the syngas outlet at the top of the tank.

[0039] In one embodiment of the present invention, the second mixer M102 includes a purified gas inlet, a hydrogen inlet, and a syngas inlet. Purified gas 116 from the RDF vaporization of the RDF purification system enters the second mixer M102 through the purified gas inlet. Landfill gas reforming gas 154 from the landfill gas reforming system enters the second mixer M102 through the syngas inlet. Hydrogen 124 enters the second mixer M102 through the hydrogen inlet.

[0040] The landfill gas reformed gas 154 passes through the first online gas analyzer T101 to obtain the analyzed landfill gas reformed gas 155, which then enters the second mixer M102.

[0041] RDF purified gas 116 passes through the second online gas analyzer T102 and enters the second mixer M102.

[0042] This analyzer is used to detect the instantaneous concentration and flow rate of key components (H2, CO, CO2) in two air streams in real time and continuously.

[0043] As one embodiment of the present invention, the mixed gas 125 obtained by the second mixer M102 passes through the first-stage composite adsorber R106 to obtain the first-stage purified gas 126, enters the second-stage fine remover R107 to obtain pure synthesis gas 127, and after passing through the fifth compressor C105, it obtains methanol synthesis gas 128.

[0044] As one embodiment of the present invention, methanol synthesis gas 128 passes through methanol reactor R108, and the resulting reaction mixture 129 passes through the seventh heat exchanger E107 and the eighth heat exchanger E108 to obtain methanol mixed product 130.

[0045] In one embodiment of the present invention, the second flash evaporator V102 is provided with a gas outlet and a crude methanol outlet. After the mixed product 130 enters the second flash evaporator V102, the unreacted gas mixture 131 and crude methanol 132 are discharged from the gas outlet and crude methanol outlet of the second flash evaporator V102, respectively.

[0046] In one embodiment of the present invention, crude methanol 132 enters the first distillation column V103 and the second distillation column V104 to obtain methanol 134. The second distillation column V104 is also provided with a wastewater outlet for discharging wastewater 135.

[0047] In one embodiment of the present invention, the gas outlet of the second flash evaporator V102 is connected to the second mixer M102. The unreacted gas mixture 131 passes through the circulating gas compressor C107, and part of the resulting gas is used as the recovered gas mixture 136, and part is used as the combustion gas mixture 138. The recovered gas mixture 136 passes through the sixth compressor C106 to obtain the compressed recovered gas mixture 137, which then enters the second mixer M102.

[0048] As one embodiment of the present invention, the gas outlet of the second flash evaporator V102 is also connected to the boiler R109.

[0049] In one embodiment of the present invention, the first distillation column V103 is provided with a light gas outlet at the top, which is connected to the boiler R109. The light gas 133 discharged from the light gas outlet enters the eighth compressor C108 together with the combustion gas mixture 138, and the resulting compressed combustion gas 139 enters the boiler R109 for combustion together with the fuel gas 143.

[0050] Fuel gas 143 is fuel gas after pressurization and heat exchange. It is obtained by passing the fuel gas through the third pressurization pump P103 to obtain compressed fuel gas 142, and then passing it through the ninth heat exchanger E109.

[0051] In one embodiment of the present invention, boiler R109 is provided with a steam outlet and a power generation output terminal 140. Combustion generates electricity, which is output from the power generation output terminal 140, and the generated steam 141 is discharged from the steam outlet.

[0052] This invention provides a methanol production method based on the co-utilization of landfill waste and landfill gas, comprising the following steps:

[0053] S1. Refuse-derived fuel (RDF) is pyrolyzed and plasma gasified to obtain high-temperature syngas 107. After cooling and gas-solid separation, the resulting syngas 109 is purified and reformed to obtain purified RDF gasified gas 116.

[0054] S2. Landfill gas mixture 147, obtained by mixing landfill gas with oxygen and water vapor, undergoes methane steam reforming, water-gas shift and dry reforming reactions in a reforming reactor to generate high-temperature synthesis gas 149, which is then flash-separated to obtain landfill gas reformed gas 154.

[0055] S3. The purified gas 116 obtained from the RDF gasification in step S1, the landfill reformed gas 154 obtained in step S2, and hydrogen are mixed and the proportions are adjusted to obtain a mixed gas 125 (methanol reaction feedstock gas). Pure synthesis gas 127 is obtained through a two-stage purification system. Methanol is prepared in the methanol reactor through methanol synthesis reaction under the catalysis of a catalyst.

[0056] In one embodiment of the present invention, in step S1, the Refuse Derived Fuel (RDF) is obtained through manual sorting, crushing, magnetic separation, air separation, hot air drying, and briquetting. The calorific value of RDF is 15-20 MJ / kg.

[0057] In one embodiment of the present invention, in step S1, the waste-derived fuel undergoes drying treatment after pyrolysis at a temperature of 150-300°C. The drying process involves mixing the waste-derived fuel with high-temperature air at 150-300°C and 0.1-0.3 MPa in a dryer. The high-temperature air contacts the RDF and evaporates moisture, thus achieving drying.

[0058] In one embodiment of the present invention, in step S1, the pyrolysis is performed under anaerobic conditions of 400-600°C and 0.1-0.5 MPa. The pyrolysis is carried out in a pyrolysis decomposer R101.

[0059] As one embodiment of the present invention, in step S1, the pyrolysis product 104 obtained by thermal decomposition is subjected to gas-solid separation to obtain pyrolysis gas 105 and solid residue 106. The pyrolysis gas 105 is heated to 650-750°C and then subjected to plasma gasification treatment together with the solid residue 106.

[0060] As one embodiment of the present invention, in step S1, the plasma gasification treatment involves mixing the heated pyrolysis gas 105 and solid residue 106 with oxygen and water, and carrying out a plasma gasification reaction at 1200-1600°C (the plasma arc region can reach >3000°C) and 0.2-0.6MPa to generate high-temperature synthesis gas 107.

[0061] As one embodiment of the present invention, in step S1, the high-temperature synthesis gas 107 obtained by plasma gasification is cooled to 600-900°C and then subjected to gas-solid separation to obtain synthesis gas 109.

[0062] In one embodiment of the present invention, in step S1, purification is achieved by passing syngas 109 through a zinc oxide (ZnO) fixed-bed reactor R103.

[0063] The zinc oxide (ZnO) fixed-bed reactor R103 is designed for the deep removal of sulfide impurities from syngas that are highly toxic to subsequent steam reforming and methanol synthesis catalysts. In this reactor, syngas 109 passes through a fixed bed composed of zinc oxide particles. Hydrogen sulfide (H₂S) and carbonyl sulfide (COS) in the gas stream react chemically with the solid zinc oxide, converting it into solid zinc sulfide (ZnS), which is then fixed within the bed. The main chemical reaction formulas are as follows:

[0064] ZnO + H2S → ZnS + H2O

[0065] ZnO + COS → ZnS + CO2.

[0066] In one embodiment of the present invention, in step S1, reforming involves reforming the purified gas 113 with water vapor to obtain reformed gas 115. The reforming temperature is controlled at 700℃-900℃, and the operating pressure is 0.5-0.7MPa. The reforming is carried out in a steam reformer.

[0067] During the reforming process, the molar ratio of water vapor to carbon is maintained at 3:1. The reaction equation for the reforming is as follows:

[0068] Methane steam reforming: CH4 + H2O CO + 3H2

[0069] Water-gas shift reaction: CO + H₂O CO2 + H2

[0070] Dry reforming of methane: CH4 + CO2 2CO + 2H2

[0071] In one embodiment of the present invention, in step S1, the reformed gas 115 is compressed to obtain purified gas 116 of RDF vaporization.

[0072] In one embodiment of the present invention, in step S2, the main components of the landfill gas are CH4, CO2, N2 and O2. The molar ratio of CH4 to CO2 is 1:(0.6-1.0).

[0073] In one embodiment of the present invention, in step S2, the temperature of the oxygen is 240-270°C and the pressure is 0.4-0.6 MPa.

[0074] As one embodiment of the present invention, in step S2, the molar ratio of CH4 to water vapor in the landfill gas is 1:(1.1-1.6).

[0075] In one embodiment of the present invention, in step S2, the landfill gas mixture 147 is preheated to 720-880°C and the pressure is maintained at 0.4-0.6 MPa before entering the reforming reactor.

[0076] In one embodiment of the present invention, in step S2, the operating temperature of the reforming reactor is controlled between approximately 720-880°C, and the operating pressure is maintained between 0.4-0.6 MPa.

[0077] As one embodiment of the present invention, in step S2, the high-temperature synthesis gas 149 undergoes heat exchange, condensation and compression to obtain a mixed gas 152 with a temperature of about 15-25°C and a pressure of about 5-7 MPa, which is then subjected to flash separation.

[0078] In one embodiment of the present invention, in step S2, flash separation is performed by separating the liquid and gaseous states under the action of gravity to obtain syngas 154.

[0079] As one embodiment of the present invention, in step S3, before the purified gas 116 from RDF vaporization and the reformed landfill gas 154 are mixed with hydrogen, they pass through online gas analyzers T101 and T102 respectively. These analyzers are used to detect the instantaneous concentration and flow rate of key components (H2, CO, CO2) in the two gas streams in real time and continuously.

[0080] In one embodiment of the present invention, in step S3, the first stage of the two-stage purification system is a composite adsorbent R106, which is filled with a composite adsorbent based on modified activated alumina or molecular sieve. The second stage is a second-stage fine remover R107, which is filled with a layered or mixed bed of high-precision copper-based desulfurizing agent and dechlorinating agent.

[0081] In one embodiment of the present invention, in step S3, the pure synthesis gas 127 is compressed to 5-7 MPa to obtain synthesis gas 128, which then enters the methanol reactor R108.

[0082] In one embodiment of the present invention, in step S3, the methanol synthesis reaction is carried out at 4-8 MPa and 220-280 °C.

[0083] As one embodiment of the present invention, in step S3, the mixture obtained from the methanol synthesis reaction is cooled to 50°C and then separated by flash evaporation. The crude methanol 132 obtained is passed through two distillation columns V103 and V104 to obtain high-purity methanol (99.8% purity).

[0084] As one embodiment of the present invention, in step S3, a portion (95%) of the unreacted gas mixture

[131] obtained by flash separation enters the second mixer M102 for methanol reaction, and a portion (5%) enters the boiler R109 for combustion together with the light gas 133 obtained from the first distillation column V103 and the fuel gas 143 (which is the fuel gas after pressurization and heat exchange, obtained by pressurizing the fuel gas to obtain compressed fuel gas 142 and then passing through the ninth heat exchanger E109).

[0085] The unreacted syngas mixture after purification is recovered; part of it is reused in the methanol reaction, and the other part is mixed with light gases from the distillation column and fuel gas before being fed into the boiler and generator unit for cogeneration. Crude methanol is then purified to obtain high-purity methanol through two-stage distillation.

[0086] In step S2 of this invention, oxygen is introduced into the landfill gas reforming system to construct a methane autothermal reforming process, overcoming the high energy consumption and catalyst carbon buildup problems caused by relying solely on steam reforming and dry reforming in existing technologies. Its mechanism of action lies in the fact that the addition of oxygen triggers a strongly exothermic partial oxidation reaction of methane (CH4 + 0.5O2). CO + 2H2, ΔH = -36 kJ / mol), the heat of reaction released by this reaction compensates in situ for the strongly endothermic reforming of methane vapor (CH4 + H2O). CO + 3H₂, ΔH = +206 kJ / mol) and dry reforming of methane (CH₄ + CO₂) The heat required for the reaction 2CO + 2H₂ (ΔH = +247 kJ / mol) achieves internal heat balance within the reactor, thus eliminating dependence on external high-energy-consuming heating equipment and improving heat transfer efficiency. Simultaneously, the present oxygen acts as a highly efficient carbon deposition inhibitor, promoting carbon deposition through the oxidation reaction (C + O₂). The continuous gasification of CO2 eliminates carbon precursors deposited on the active sites of the catalyst, significantly extending the single-pass service life and operational stability of the catalyst when treating complex landfill gas.

[0087] Compared with the prior art, the present invention has the following beneficial effects:

[0088] (1) This invention constructs two gas production paths—RDF plasma gasification and landfill gas reforming (R105)—through a "dual gas source parallel" approach. After manual sorting, crushing, drying, and briquetting, the RDF is fed into a plasma gasification furnace, where hydrogen-rich syngas is generated under high temperature, with the participation of oxygen and water vapor. Simultaneously, the landfill gas is mixed with water vapor and oxygen in the first mixer and reformed into syngas with insufficient hydrogen. The two gases are then heat-exchanged, compressed, and enter the second mixer, where they are combined with an appropriate amount of green hydrogen to adjust the hydrogen-to-carbon ratio, resulting in syngas suitable for methanol synthesis ([H2 / (2CO+3CO2)=0.9-1.1]) and methanol is synthesized.

[0089] (2) On the one hand, this invention fully develops the gaseous and solid carbon resources of landfills, achieving a complementary hydrogen-to-carbon ratio. It utilizes RDF-rich hydrogen syngas to compensate for the hydrogen shortage in landfill gas syngas, thereby reducing the dependence on external water electrolysis for hydrogen production. On the other hand, it constructs a system architecture that combines high-temperature RDF gasification with low-calorific-value gases from landfill gas. The parallel operation of the two gas sources not only improves the overall system's heat utilization efficiency but also effectively solves the problem of unstable system load caused by fluctuations in landfill gas production in traditional landfill gas-to-methanol processes. Attached Figure Description

[0090] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0091] Figure 1 This is a simplified process flow diagram for producing renewable methanol;

[0092] Figure 2 This is a process flow diagram for producing renewable methanol;

[0093] in,

[0094] Detailed Implementation

[0095] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0096] To address the unique technical challenges of mixing landfill waste and landfill gas using a "dual gas source" approach in this invention, a specific process design solves derivative problems that do not exist when treated separately. Firstly, the mixing of hydrogen-rich RDF gasification gas and hydrogen-poor landfill gas syngas faces a severe risk of salt crystallization blockage. This is because the pyrolysis of chlorine-containing substances (such as PVC) in RDF releases trace amounts of acidic hydrogen chloride (HCl), while landfill gas derived from anaerobic biomass fermentation contains alkaline impurities such as ammonia (NH3). While both gases are gaseous at high temperatures when present individually, the reaction NH3(g) + HCl(g) occurs when they are mixed and enter subsequent heat exchange / cooling or compression stages (such as compressor C105). NH4Cl(s) reacts to form solid ammonium chloride particles. These white crystals readily deposit on compressor impellers and pipeline valves, leading to surge, decreased heat exchange efficiency, and even system shutdown. To address this, this invention incorporates a two-stage purification system after the second mixer M102 and before the compressor C105. Specifically, the first-stage composite adsorbent (R106) utilizes a specific adsorbent to remove these two precursors before the mixed gas enters the low-temperature, high-pressure section, fundamentally preventing crystallization blockage. Secondly, addressing the complex impurity profile of the mixed gas source, this invention resolves the "synergistic poisoning" effect of sulfur and chlorine on the copper-based catalyst for methanol synthesis. The presence of chlorine accelerates the reaction rate between sulfur and copper or causes catalyst crystallization, resulting in an exponential decrease in catalyst lifetime. Therefore, this invention includes a second-stage fine remover (R107) employing a high-precision copper-based desulfurizer and dechlorinator bed to remove impurities to the ppb level, ensuring the stability of subsequent synthesis reactions.

[0097] Regarding improvements in process pathways and unexpected technical effects, this invention achieves highly efficient synergy between two pathways through targeted unit operation optimization. In the RDF processing pathway (step S1), this invention innovatively employs a decoupled process of "drying-pyrolysis-gas-solid separation-gas phase preheating-plasma gasification". Unlike traditional direct gasification, the pyrolysis gas is separated from the solid residue by a distributor S101 and a first heat exchanger E101, and the pyrolysis gas is preheated to 650-750°C before being fed into the plasma furnace. This improvement significantly reduces the arc energy required to maintain the plasma furnace at a high temperature of 1200°C, significantly reducing energy consumption, while simultaneously enabling independent adjustment of the gas-solid feed rate, effectively improving the load stability of furnace temperature control.

[0098] This invention breaks through the traditional, simple dry reforming process in the landfill gas treatment path (step S2) by employing a precise locking technology for "three-dimensional reforming" parameters. By strictly adjusting the feed molar ratio and introducing oxygen into reactor R105, the coupling of steam reforming, dry reforming, and water-gas shift conversion is achieved. The introduction of oxygen produces two unexpected effects: first, the exothermic reaction of partial oxidation of methane balances the strong endothermic effect of steam reforming, achieving heat self-sufficiency within the reactor; second, by utilizing the strong oxidizing properties of oxygen and precisely proportioned steam (H2O / CH4 = 1.1-1.6), the industry problem of catalyst coking (Boudouard reaction) caused by high concentrations of CO2 in landfill gas is effectively suppressed, significantly extending catalyst life.

[0099] Example 1

[0100] This invention provides a methanol production system based on the co-utilization of landfill waste and landfill gas, comprising:

[0101] RDF (Refuse-Derived Fuel) purification systems, landfill gas reforming systems, and methanol synthesis systems; Figure 1 )

[0102] The RDF purification system includes a dryer D101, a pyrolysis decomposer R101, a distributor S101, a plasma gasification furnace R102, a second heat exchanger (waste heat exchanger) E102, a gas-solid separation device S102, a second compressor C102, a zinc oxide (ZnO) fixed bed reactor R103, a steam reformer R104, and a third compressor C103, connected in sequence.

[0103] The landfill gas reforming system includes a first mixer M101, a fourth heat exchanger E104, a reforming reactor R105, a fifth heat exchanger E105, a condenser E106, a fourth compressor C104, and a first flash evaporator V101 connected in sequence.

[0104] The methanol synthesis system includes a second mixer M102, a first-stage composite adsorber R106, a second-stage fine remover R107, a fifth compressor C105, a methanol reactor R108, a seventh heat exchanger E107, an eighth heat exchanger E108, and a second flash evaporator V102 connected in sequence.

[0105] The third compressor C103 in the RDF purification system and the first flash evaporator V101 in the landfill gas reforming system are both connected to the second mixer M102 in the methanol synthesis system.

[0106] Specifically as follows ( Figure 2 ):

[0107] The dryer D101 is provided with an RDF inlet and a high-temperature air inlet. RDF101 and high-temperature air (hot air) 102 enter the dryer D101 from the RDF inlet and the high-temperature air inlet, respectively.

[0108] The dried RDF 103 obtained from dryer D101 enters pyrolysis decomposer R101. The pyrolysis product 104 obtained from pyrolysis decomposer R101 enters distributor S101.

[0109] The splitter S101 and the plasma gasifier R102 are connected by gas pipelines and solid pipelines (main pipelines), respectively; a first heat exchanger E101 is installed on the gas pipeline. The pyrolysis product 104 is separated in the splitter S101 to obtain pyrolysis gas 105 and solid residue 106. The pyrolysis gas 105 is preheated by the first heat exchanger E101 and then introduced into the plasma gasifier R102; the solid residue 106 enters the plasma gasifier R102 directly through the solid pipeline.

[0110] The plasma gasifier R102 is also equipped with an oxygen inlet and an industrial water inlet. The oxygen inlet is used to supply oxygen 118 for the RDF purification system. The industrial water inlet is used to supply the first industrial water 122.

[0111] Industrial water 120 is pressurized by pump P101 to obtain pressurized industrial water 121, and then passes through the third heat exchanger E103 to obtain first industrial water 122.

[0112] Oxygen 117 is passed through compressor C101 to obtain oxygen 118 for RDF purification system and oxygen 119 for landfill gas reforming system.

[0113] The high-temperature synthesis gas 107 obtained from the plasma gasification furnace R102 passes through the second heat exchanger E102 to obtain low-temperature synthesis gas 108, which then enters the gas-solid separation device S102.

[0114] The gas-solid separation device S102 is equipped with a syngas outlet and is connected to the second compressor C102. The gas-solid separation device S102 is also equipped with an ash outlet. The low-temperature syngas 108 passes through the gas-solid separation device S102 and is separated into ash 123 and syngas 109, which are discharged through the ash outlet and syngas outlet, respectively.

[0115] Synthesis gas 109 passes through the second compressor C102 to obtain compressed synthesis gas 110, which then enters the zinc oxide (ZnO) fixed-bed reactor R103.

[0116] The zinc oxide (ZnO) fixed-bed reactor R103 is equipped with an absorbent inlet, a purified gas outlet, and an absorbent outlet. The purified gas outlet is connected to the steam reformer R104. The purified gas 113 obtained in the zinc oxide (ZnO) fixed-bed reactor R103 enters the steam reformer R104 through the purified gas outlet.

[0117] H2S absorbent 111 enters the zinc oxide (ZnO) fixed-bed reactor R103 through the absorbent inlet. The washing wastewater and H2S-rich absorbent liquid 114 generated by the reaction are discharged from the absorbent outlet at the bottom.

[0118] A zinc oxide (ZnO) fixed-bed reactor comprises a fixed bed of zinc oxide particles.

[0119] The zinc oxide (ZnO) fixed-bed reactor R103 is designed to deeply remove sulfide impurities from syngas that are highly toxic to subsequent steam reforming and methanol synthesis catalysts. In this reactor, syngas 110 passes through a fixed bed composed of zinc oxide particles. Hydrogen sulfide (H2S) and carbonyl sulfide (COS) in the gas stream react chemically with the solid zinc oxide, converting it into solid zinc sulfide (ZnS) which is then fixed within the bed.

[0120] Steam reformer R104 is equipped with a steam inlet. Steam 112 enters steam reformer R104 through the steam inlet.

[0121] The reformed gas 115 obtained from the steam reformer R104 is passed through the third compressor C103 to obtain purified RDF gas 116. Methane steam reforming, water-gas shift reaction and methane dry reforming occur simultaneously in the reforming reactor. The reformed gas is passed through the third compressor C103 to obtain purified RDF gas.

[0122] In one embodiment of the present invention, the first mixer M101 is provided with an oxygen inlet, a landfill gas inlet, and a steam inlet. The oxygen inlet is used to input oxygen 119 for the landfill gas reforming system. The landfill gas inlet is used to input landfill gas 144. The steam inlet is used to input pressurized steam 146 (steam 145 is pressurized by the second pressurization pump P102).

[0123] The landfill gas mixture 147 obtained from the first mixer M101 is fed into the feed gas 148 after passing through the heat exchanger E104. The feed gas 148 is then passed through the reformer R105 to obtain high-temperature synthesis gas 149, which is then passed through the heat exchanger E105 to obtain heat-exchanged synthesis gas 150. After being cooled by the condenser E106, it is then compressed by the compressor C104 to obtain the mixed gas 152.

[0124] The first flash evaporator V101 is equipped with a mixed gas inlet, a syngas outlet, and a waste outlet. The mixed gas 152 enters the first flash evaporator V101 through the mixed gas inlet and undergoes flash separation. Under the action of gravity, the liquid waste 153 is discharged from the waste outlet at the bottom of the tank, while the landfill gas reforming gas 154 is discharged from the syngas outlet at the top of the tank.

[0125] The second mixer M102 includes a purified gas inlet, a hydrogen inlet, and a syngas inlet. Purified gas 116, from the RDF purification system (formed by RDF vaporization), enters the second mixer M102 through the purified gas inlet. Landfill gas reforming gas 154, from the landfill gas reforming system, enters the second mixer M102 through the syngas inlet. Hydrogen 124 enters the second mixer M102 through the hydrogen inlet.

[0126] The landfill gas reformed gas 154 passes through the first online gas analyzer T101 to obtain the analyzed landfill gas reformed gas 155, which then enters the second mixer M102.

[0127] RDF purified gas 116 passes through the second online gas analyzer T102 and enters the second mixer M102.

[0128] This analyzer is used to detect the instantaneous concentration and flow rate of key components (H2, CO, CO2) in two air streams in real time and continuously.

[0129] The mixed gas 125 obtained from the second mixer M102 passes through the first-stage composite adsorber R106 to obtain the first-stage purified gas 126, which then enters the second-stage fine remover R107 to obtain pure synthesis gas 127. After passing through the fifth compressor C105, it becomes methanol synthesis gas 128.

[0130] Methanol synthesis gas 128 passes through methanol reactor R108, and the resulting reaction mixture 129 then passes through the seventh heat exchanger E107 and the eighth heat exchanger E108 to obtain methanol mixed product 130.

[0131] The second flash evaporator V102 is equipped with a gas outlet and a crude methanol outlet. After the mixed product 130 enters the second flash evaporator V102, the unreacted gas mixture 131 and crude methanol 132 are discharged from the gas outlet and crude methanol outlet at the top of the second flash evaporator V102, respectively.

[0132] Crude methanol 132 enters the first distillation column V103 and the second distillation column V104 to obtain methanol 134.

[0133] The gas outlet of the second flash evaporator V102 is connected to the second mixer M102. The unreacted gas mixture 131 passes through the recirculating gas compressor C107, and part of the resulting gas is used as the recovered gas mixture 136, while part is used as the combustion gas mixture 138. The recovered gas mixture 136 passes through the sixth compressor C106 to obtain a compressed recovered gas mixture 136, which then enters the second mixer M102.

[0134] The gas outlet of the second flash evaporator V102 is also connected to the boiler R109.

[0135] The first distillation column V103 has a light gas outlet at the top, which is connected to the boiler R109. The light gas 133 discharged from the light gas outlet, together with the combustion gas mixture 138, enters the eighth compressor C108, and the resulting compressed combustion gas 139, together with the fuel gas 143, enters the boiler R109 for combustion.

[0136] Fuel gas 143 is fuel gas after pressurization and heat exchange. It is obtained by passing the fuel gas through the third pressurization pump P103 to obtain compressed fuel gas 142, and then passing it through the ninth heat exchanger E109.

[0137] Boiler R109 is equipped with a steam outlet and a power generation output terminal 140. The combustion generates electricity, which is output from the power generation output terminal 140, and the generated steam 141 is discharged from the steam outlet.

[0138] Example 2

[0139] This invention provides a methanol production method based on the co-utilization of landfill waste and landfill gas, comprising the following steps:

[0140] The first step involves pyrolysis and plasma gasification of Refuse-derived fuel (RDF) to obtain high-temperature syngas. The syngas is then cooled and separated into solid and gaseous components. After purification, the syngas is reformed to obtain purified gas from RDF gasification.

[0141] In the second step, landfill gas, oxygen, and water vapor undergo methane steam reforming, water-gas conversion, and dry reforming reactions in a reforming reactor to generate syngas. This syngas is then mixed with the purified syngas obtained in the first step and green hydrogen obtained from water electrolysis, and the proportions are adjusted to obtain methanol reaction feedstock gas.

[0142] In the third step, the feed gas is reacted in a methanol reactor under the catalysis of a catalyst to produce methanol through a methanol synthesis reaction. Unreacted gas mixtures are recovered; a portion is reused in the methanol reaction, and the remainder is mixed with light gas from the distillation column and fuel gas to enter the boiler and generator unit for cogeneration. Crude methanol is then subjected to two-stage distillation to obtain high-purity methanol.

[0143] Preferably, in the first step, the plasma gasification furnace operates at a temperature of 1200-1600℃ and an operating pressure of 0.2-0.6MPa; the reforming reactor operates at a temperature of 700-900℃ and an operating pressure of 0.5-0.7 MPa; and the water vapor:carbon molar ratio is 3:1.

[0144] The preferred operating temperature of the reforming reactor in the second step is 720-880℃; the operating pressure is 0.4-0.6 MPa; and the feed gas obtained by mixing the added hydrogen, purified gas and syngas satisfies [H2 / (2*CO+3CO2)=0.9-1.1].

[0145] The preferred operating temperature of the methanol reactor in the third step is 220-280℃, and the operating pressure is 4-8MPa.

[0146] The preferred first step employs a coupled pyrolysis and plasma gasification process, with a gas-solid separation and recycling unit incorporated in the pyrolysis product diversion stage to improve the utilization efficiency of raw material carbon. The syngas requires desulfurization and reforming processes.

[0147] The pyrolysis reactor is located downstream of the first dryer, and its outlet product enters the first heat exchanger. The first heat exchanger, located downstream of the pyrolysis reactor and upstream of the plasma gasifier, preheats the pyrolysis gas before it enters the plasma gasifier. The syngas exiting the plasma gasifier enters the second heat exchanger, located downstream of the plasma gasifier and upstream of the second gas-solid separator, to cool the high-temperature syngas. The second gas-solid separator, located upstream of the second compressor, discharges ash and slag from its lower section and outputs syngas from its upper section for subsequent purification stages. The ZnO fixed-bed reactor, located downstream of the second compressor and upstream of the reforming reactor, removes H2S from the syngas.

[0148] In the preferred second step, landfill gas is mixed with oxygen and water vapor in the first mixer, and the molar ratio of CH4 / CO2 / H2O is adjusted to 1:(0.6-1.0):(1.1-1.6).

[0149] In the preferred second step, the high-temperature syngas after reforming needs to undergo two stages of heat exchange and flash evaporation to remove water vapor and other liquid byproducts. The fifth heat exchanger is located downstream of the reforming reactor and upstream of the sixth heat exchanger. The sixth heat exchanger is located downstream of the fifth reactor and upstream of the fourth compressor. The first flash evaporator is located downstream of the fourth compressor and upstream of the second mixer.

[0150] The purified syngas obtained from RDF gasification in the second step is preferred. The landfill gas mixture needs to pass through an online gas monitoring device, and then it needs to be mixed and the proportion adjusted before entering the methanol synthesizer with the green hydrogen obtained from water electrolysis. The second mixer is located downstream of the first flash evaporator and the third compressor, and upstream of the fifth compressor.

[0151] The preferred two-stage purification system in the second step consists of a composite adsorber filled with modified activated alumina or molecular sieve as the substrate and a fine removal unit filled with desulfurizing and dechlorinating agents. It is located downstream of the second mixer and upstream of the fifth compressor and methanol synthesizer.

[0152] In the preferred third step, the crude methanol liquid and unreacted gases are separated through two-stage heat exchange and flash evaporation, maximizing the recovery of unreacted gases. The seventh and eighth heat exchangers are located downstream of the methanol reactor and upstream of the second flash evaporator, which is located upstream of the distillation column. The unreacted gas mixture separated from the upper part of the second flash evaporator is recovered by the seventh compressor, while the crude methanol flowing out from the bottom is purified into refined methanol through two-stage distillation.

[0153] Preferably, a portion of the unreacted gas from the third step is recycled as inlet gas for the methanol reaction in the second mixer, while the other portion is mixed with the purge gas from the upper outlet of the second distillation column, compressed by the eighth compressor, and then enters the boiler.

[0154] The method for co-producing methanol from landfill waste and landfill gas according to the present invention comprises the following steps:

[0155] RDF (Reactive Fuel Dioxide) is produced through sorting, crushing, drying, and briquetting. It then undergoes pyrolysis and plasma gasification to convert into syngas. After gas-solid separation, cooling, and desulfurization purification, it is combined with steam and fed into a steam reformer for methane steam reforming, water-gas shift reaction, and dry reforming to obtain purified syngas. Simultaneously, landfill gas, oxygen, and steam are mixed in a first mixer with adjusted molar ratios and then converted into syngas in a reformer. After cooling, compression, and flash separation, usable syngas is obtained. The two syngas streams are coupled and compressed with externally produced hydrogen from water electrolysis in a second mixer. The hydrogen-to-carbon ratio is stabilized within the optimal range for methanol synthesis by adjusting the hydrogen incorporation amount. The resulting syngas is fed into a methanol reactor to synthesize methanol under the action of a copper-based catalyst. The reaction products are cooled and flash separated to obtain unreacted gas and crude methanol. 95% of the unreacted gas is recycled, and 5% is sent to the boiler for combustion as purge gas. The crude methanol is purified by dual-tower distillation to obtain 99.8% high-purity methanol. The process utilizes high-temperature gas from the reactor outlet for feed preheating and process water heat exchange to generate medium-pressure steam as a source of steam.

[0156] (1) Syngas preparation:

[0157] After manual sorting, crushing, magnetic separation, air separation, hot air drying, and briquetting, RDF with a calorific value of 15-20 MJ / kg is obtained

[101] . RDF is fed into dryer D101 by the feeding system, and high-temperature air of 150-300°C and 0.1-0.3 MPa is introduced from below

[102] to contact RDF and evaporate moisture. The dried RDF

[103] enters pyrolysis decomposer R101 and decomposes under oxygen-deficient conditions of 400-600°C and 0.1-0.5 MPa. The pyrolysis products

[104] enter the separator S101 to obtain gas-solid two phases, and then the pyrolysis gas

[105] is preheated to 650-750°C by heat exchanger E101 and introduced into plasma gasification furnace R102. Solid residue

[106] enters plasma gasifier R102 along the main pipeline, while oxygen

[118] pressurized by compressor C101 and first industrial water

[122] from pressurized pump P101 are introduced into gasifier R102. Gasifier R102 undergoes plasma gasification reaction at 1200-1600°C (>3000°C in plasma arc region) and 0.2-0.6 MPa to generate high-temperature synthesis gas

[107] . After being cooled to 600-900°C by waste heat exchanger E102, it enters gas-solid separation equipment S102 to remove ash

[123] . The ash is transported off-site for treatment via a conveying system. Syngas

[109] is cooled and compressed by compressor C102

[110] and then fed into zinc oxide (ZnO) fixed-bed reactor R103. The syngas passes through a bed of H2S absorbent

[111] composed of solid zinc oxide particles and undergoes a gas-solid reaction (ZnO + H2S → ZnS + H2O) at 200-400°C, converting hydrogen sulfide into solid zinc sulfide and fixing it in the adsorbent, thereby removing hydrogen sulfide (H2S). The purified gas flows out from the top of the reactor, and the exhausted solid adsorbent is periodically discharged through the discharge port or replaced by switching reactors online.

[0158] The zinc oxide (ZnO) fixed-bed reactor R103 is designed to deeply remove sulfide impurities from syngas that are highly toxic to subsequent steam reforming and methanol synthesis catalysts. In this reactor, syngas

[110] passes through a fixed bed composed of zinc oxide particles. Hydrogen sulfide (H2S) and carbonyl sulfide (COS) in the gas stream react chemically with the solid zinc oxide to form solid zinc sulfide (ZnS), which is then fixed within the bed. The main chemical reaction formulas are as follows:

[0159] ZnO + H2S → ZnS + H2O

[0160] ZnO + COS → ZnS + CO2

[0161] The purified gas

[113] and water vapor

[112] are fed into the steam reformer R104. The operating temperature of the reformer R104 is controlled at 700℃-900℃ and the operating pressure is 0.5-0.7MPa. Methane steam reforming, water-gas shift reaction and methane dry reforming occur simultaneously in the reformer R104. The reformed gas

[115] passes through the third compressor C103 to obtain purified gas

[116] of RDF gasification. The water vapor:carbon molar ratio is maintained at 3:1 in the steam reformer.

[0162] The reaction equation is as follows:

[0163] Methane steam reforming: CH4 + H2O CO + 3H2

[0164] Water-gas shift reaction: CO + H₂O CO2 + H2

[0165] Dry reforming of methane: CH4 + CO2 2CO + 2H2

[0166] The landfill gas

[144] consists mainly of CH4, CO2, N2 and O2, which is mixed with oxygen

[119] at a temperature of about 240-270°C and a pressure of 0.4-0.6 MPa and pressurized steam

[146] (steam 145 is pressurized by a second pressurizing pump P102) in the first mixer M101, and the molar ratio of CH4 / CO2 / H2O is adjusted to 1:(0.6-1.0):(1.1-1.6). The landfill gas mixture

[147] is preheated by heat exchanger E104 to obtain feed gas

[148] at a temperature of about 720-880°C and a pressure maintained at 0.4-0.6 MPa. Subsequently, the feed gas

[148] enters the reforming reactor R105, and the reactor operating temperature is controlled between about 720-880°C and the operating pressure is maintained at 0.4-0.6 MPa. In this reactor, methane steam reforming, water-gas shift reaction, and methane dry reforming are carried out simultaneously. The high-temperature syngas

[149] obtained from the reaction outlet is heat-exchanged syngas

[150] through heat exchanger E105, cooled syngas

[151] through condenser E106, and then compressed by compressor C104 to obtain a mixed gas

[152] with a temperature of about 15-25℃ and a pressure of about 5-7 MPa. This mixed gas

[152] enters the first flash evaporator V101 for flash separation. Under the action of gravity, the liquid waste

[153] is discharged from the bottom of the tank, while the syngas

[154] is discharged from the top of the tank.

[0167] (2) Dual gas source mixing and purification:

[0168] Purified gas

[116] from RDF gasification and reformed landfill gas

[154] are respectively passed through online gas analyzers T101 and T102, which are used to detect the instantaneous concentration and flow rate of key components (H2, CO, CO2) in the two gas streams in real time and continuously. Then, they are mixed with green hydrogen

[124] obtained from water electrolysis in the second mixer M102 to obtain mixed gas

[125] . By adjusting the amount of hydrogen

[124] , the hydrogen-to-carbon ratio in the mixed gas

[125] is adjusted to the optimal hydrogen-to-carbon ratio required for methanol synthesis [H2 / (2*CO+3CO2)=0.9-1.1]. In order to solve the problem of cross-reaction of pollutants and synergistic poisoning of catalysts that do not exist in a single gas path due to the difference in the composition of the two gas sources, the mixed gas

[125] is sequentially processed by a two-stage purification system. The first stage is a composite adsorbent R106, which is filled with a composite adsorbent based on modified activated alumina or molecular sieve. Trace amounts of hydrogen chloride (HCl) remaining from RDF gasification gas and trace amounts of ammonia (NH3) remaining from landfill gas are simultaneously adsorbed here, thus preventing them from reacting in subsequent cryogenic equipment to generate corrosive and clogging ammonium chloride solid (HCl+NH3→NH4Cl), protecting downstream heat exchangers and compressors. The gas after primary purification

[126] enters the secondary fine removal unit R107, which is filled with a layered or mixed high-precision copper-based desulfurizing and dechlorinating agent bed. This bed utilizes the reaction of copper oxide with hydrogen sulfide at room temperature or low temperature (CuO+H2S→CuS+H2O) and the strong chemical adsorption of chloride by a special adsorbent to deeply remove residual ppb-level sulfides and chlorides in the gas. This measure aims to solve the synergistic poisoning effect on downstream methanol synthesis copper-based catalysts caused by the coexistence of trace sulfur and chlorine, which will cause the catalyst deactivation rate to far exceed the expectation when a single impurity is present, greatly shortening its service life. The pure syngas obtained after two stages of deep purification

[127] is compressed to 5-7 MPa using a C105 compressor to obtain syngas

[128] .

[0169] (3) Methanol synthesis and tail gas recycling:

[0170] The obtained synthesis gas

[128] is used to synthesize methanol in methanol reactor R108. The methanol synthesis reaction is carried out on a copper-based catalyst at 4-8 MPa and 220-280 °C. After methanol synthesis, the reaction mixture

[129] first enters heat exchanger E107 to exchange heat with the low-temperature feed gas. While recovering heat, the temperature is initially reduced. Then, it enters the eighth heat exchanger E108 and is further cooled to 35-40 °C by circulating cooling water, so that methanol and water are fully condensed to obtain a gas-liquid mixture

[130] . ​​The mixture

[130] passes through the second flash evaporator V102, and the unreacted gas mixture is separated from the upper part

[131] and crude methanol flows out from the lower part

[132] .

[0171] E107, as a "gas-to-gas heat exchanger" (heat recovery unit), uses the high-grade waste heat of the high-temperature mixture at the reactor outlet

[129] to preheat the low-temperature raw gas entering the reactor in a countercurrent manner. While initially reducing the product temperature, it realizes the cascade utilization of heat inside the system, significantly reducing the overall energy consumption of the system. E108, as a "water-cooled condenser" (phase change separation unit), is located downstream of E107. It mainly uses external circulating cooling water to remove the latent heat of the fluid and forces the gas after initial cooling to be cooled to below the dew point of methanol and water (usually 35-40℃). This ensures that the gaseous methanol and water vapor in the gas phase are condensed and liquefied to the maximum extent, providing the necessary phase conditions for efficient gas-liquid separation in the subsequent second flash evaporator V102.

[0172] The unreacted gas mixture

[131] is recovered by the circulating gas compressor C107, and 95% of the gas

[137] is re-entered into the second mixer M102 by the sixth compressor C106 for methanol reaction. The remaining 5% of the gas

[138] is mixed with the light gas

[133] in the subsequent process, compressed to 3-5 MPa by the compressor C108

[139] , and then entered the boiler R109 for combustion together with the fuel gas

[143] (which is the fuel gas after pressurization and heat exchange, which is obtained by passing the fuel gas through the third pressurization pump P103 and the resulting compressed fuel gas

[142] is obtained by passing through the ninth heat exchanger E109). The crude methanol stream

[132] containing impurities such as dimethyl ether (DME) and alcohols passes through two distillation columns V103 and V104, and methanol with a purity of 99.8% is distilled from the top of the second distillation column V104

[134] .

[0173] Example 3

[0174] This embodiment is a further preferred embodiment of embodiment 2, and the specific steps and parameters are as follows:

[0175] First, landfill waste briquettes, after sorting, crushing, magnetic separation, air separation, and hot air drying, are precipitated to obtain RDF with a calorific value of approximately 17 MJ / kg. The RDF is further dried in hot air at 200 °C and 0.2 MPa until the moisture content is less than 5%, and then pyrolyzed under anoxic conditions at 500 °C and 0.3 MPa. The products separate into gas and solid phases. The gas is preheated to 700 °C and then enters a plasma gasifier, while the solid residue is simultaneously fed into the gasifier. The gasification reaction is carried out at 1400 °C and 0.4 MPa, with oxygen and pressurized industrial water introduced. The generated high-temperature syngas is cooled to 800 °C and ash residue is removed. The purified gas is further compressed and enters a zinc oxide fixed-bed reactor to remove hydrogen sulfide. Then, it is mixed with steam at a ratio of H₂O:C = 3:1 and enters a reformer for methane steam reforming, water-gas shift, and dry reforming at 850 °C and 0.6 MPa to obtain hydrogen-rich syngas.

[0176] Simultaneously, landfill gas (component ratio CH4:CO2:N2:O2 = 55:35:7:3) is mixed with oxygen and steam at 250 °C and 0.5 MPa, adjusting the molar ratio to CH4 / CO2 / H2O = 1:0.8:1.4. After preheating to 800 °C, the mixture enters a reforming reactor, where it reacts at 0.5 MPa to generate hydrogen-lean syngas. This gas is then cooled, compressed to 6 MPa, and flash-separated to obtain purified gas and a small amount of liquid waste.

[0177] Two streams of syngas are mixed with hydrogen produced by water electrolysis and then sequentially processed through a two-stage purification system. The first stage is a composite adsorbent R106, filled with a composite adsorbent based on modified activated alumina or molecular sieves. The gas purified in the first stage enters the second-stage fine desulfurizer R107, which contains a layered or mixed bed of high-precision copper-based desulfurizer and dechlorinator. The resulting gas is compressed to 6 MPa and the hydrogen-to-carbon ratio is adjusted to 1.02. The mixed gas is then used to synthesize methanol over a copper-based catalyst at 250 °C and 5 MPa. The product is cooled to 50 °C and condensed, and then flash-distilled to obtain crude methanol and unreacted gas. 80% of the unreacted gas is refluxed to the synthesis step, and the remaining 20% ​​is burned as purge gas. The crude methanol is further subjected to two-stage distillation to finally obtain methanol product with a purity of 99.8%.

[0178] Simulation results show that under the condition of a recycle ratio of 0.8, the hydrogen-to-carbon ratio of the syngas is 1.01, the methanol production reaches 17.92 tons / hour, the system energy efficiency is 84.63%, and the CO2 equivalent emission reduction rate is 91.78%.

[0179] Comparative Example 1

[0180] This comparative example is basically the same as Example 3, except that there is no pyrolysis step, and the RDF is directly subjected to plasma vaporization treatment after drying.

[0181] This comparative example is basically the same as Example 3, except that the pyrolysis, diversion, and preheating steps in step S1 are removed. Specifically, after the RDF is dried in dryer D101, it is fed directly into plasma gasification furnace R102 via a screw feeder without passing through pyrolysis decomposer R101 and diverter S101. To maintain the reaction temperature inside the gasification furnace, the input power of the plasma torch is increased.

[0182] Simulation and experimental results show that, while maintaining the same feed rate as in Example 3, the power consumption per ton of feed in the plasma gasification furnace increased by 34.5% due to the direct absorption of heat by a large amount of cold solid feed. Simultaneously, the lack of decoupling regulation of the flow rates of pyrolysis gas and solid residue led to an expansion of the furnace temperature field fluctuation range to ±140℃, resulting in decreased stability of the syngas components. Ultimately, the system energy efficiency decreased to 71.25% (compared to 84.63% in Example 3), the carbon conversion rate decreased from 98.5% to 91.2%, and the methanol production decreased to 15.83 tons / hour.

[0183] Comparative Example 2

[0184] This comparative example is basically the same as Example 3, except that the first-stage purification treatment of the composite adsorber is not performed.

[0185] This comparative example is basically the same as Example 3, except that the first-stage purification process in step S3 is removed. Specifically, the mixed gas 125 obtained from the second mixer M102 bypasses the composite adsorber R106 and directly enters the second-stage fine removal unit R107 and subsequent compression stage. Simulation and experimental results show that the system's operating parameters are normal in the initial startup phase, and the methanol production is the same as in Example 3. However, after 56 hours of continuous operation, the pressure drop at the inlet filter of the fifth compressor C105 increases exponentially from an initial 0.01 MPa to 0.15 MPa, causing the compressor to experience a surge alarm and triggering an interlock shutdown. Disassembly and analysis of the pipelines and filters revealed white crystalline solid deposits on the inner walls of the pipelines and at the filter elements, which were confirmed by testing to be ammonium chloride (NH4Cl). This result indicates that the lack of first-stage purification prevents the system from meeting the requirements for continuous long-term operation of more than 72 hours.

[0186] Comparative Example 3

[0187] This comparative example is basically the same as Example 3, except that the second-stage purification process of the fine remover is not performed.

[0188] This comparative example is basically the same as Example 3, except that the second-stage purification treatment in step S3 is removed. Specifically, the gas treated by the first-stage composite adsorber R106 is directly fed into the fifth compressor C105 for compression without passing through the second-stage fine remover R107, and then enters the methanol reactor R108. At this point, the sulfur content in the gas entering the methanol synthesis tower is approximately 0.5 ppm, and the chlorine content is approximately 0.1 ppm.

[0189] Simulation and experimental results show that during the initial operation (0-100 hours), the methanol production was 17.88 tons / hour, basically consistent with Example 3. However, after 500 hours of operation, the methanol production showed a significant downward trend, dropping to 16.10 tons / hour; after 1000 hours, the production further decreased to 13.45 tons / hour. Calculations showed that the space-time yield of the catalyst decreased by 24.8% within 1000 hours, while the decrease rate in Example 3 was only 1.2% during the same period. Catalyst characterization results showed obvious sulfur-chlorine synergistic poisoning at the active sites, confirming the necessity of deep purification for maintaining catalyst lifetime.

[0190] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the substantive content of the present invention.

Claims

1. A methanol production system based on the co-utilization of landfill waste and landfill gas, characterized in that, include: RDF purification system, landfill gas reforming system, methanol synthesis system; The RDF purification system includes a dryer (D101), a pyrolysis decomposer (R101), a distributor (S101), a plasma gasifier (R102), a second heat exchanger (E102), a gas-solid separation device (S102), a second compressor (C102), a zinc oxide fixed bed reactor (R103), a steam reformer (R104), and a third compressor (C103) connected in sequence. The dried RDF (103) obtained from the dryer (D101) enters the pyrolysis decomposer (R101); the pyrolysis product (104) obtained from the pyrolysis decomposer (R101) enters the splitter (S101). The splitter (S101) and the plasma gasifier (R102) are connected by gas pipelines and solid pipelines respectively; a first heat exchanger (E101) is provided on the gas pipeline; the pyrolysis product (104) is separated in the splitter (S101) to obtain pyrolysis gas (105) and solid residue (106); the pyrolysis gas (105) is preheated by the first heat exchanger (E101) and then introduced into the plasma gasifier (R102); the solid residue (106) enters the plasma gasifier (R102) directly through the solid pipeline. The gas-solid separation unit (S102) is equipped with a synthesis gas outlet and is connected to the second compressor (C102); The high-temperature syngas obtained from the plasma gasification furnace (R102) is passed through the second heat exchanger (E102) to obtain low-temperature syngas (108), which then enters the gas-solid separation device (S102). The gas-solid separation unit (S102) is equipped with a synthesis gas outlet and is connected to the second compressor (C102); Syngas (109) passes through the second compressor (C102) to obtain compressed syngas (110), which then enters the zinc oxide fixed-bed reactor (R103). The purified gas (113) obtained in the zinc oxide fixed-bed reactor (R103) enters the steam reformer (R104) through the purified gas outlet. The steam reformer (R104) is equipped with a steam inlet; Methane steam reforming, water-gas shift reaction, and dry methane reforming occur simultaneously in the reforming reactor. The reformed gas is then passed through the third compressor (C103) to obtain purified RDF gas. The landfill gas reforming system includes a first mixer (M101), a fourth heat exchanger (E104), a reforming reactor (R105), a fifth heat exchanger (E105), a condenser (E106), a fourth compressor (C104), and a first flash evaporator (V101) connected in sequence. The methanol synthesis system includes a second mixer (M102), a first-stage composite adsorber (R106), a second-stage fine remover (R107), a fifth compressor (C105), a methanol reactor (R108), a seventh heat exchanger (E107), an eighth heat exchanger (E108), and a second flash evaporator (V102) connected in sequence. The third compressor (C103) in the RDF purification system and the first flash evaporator (V101) in the landfill gas reforming system are both connected to the second mixer (M102) in the methanol synthesis system. The plasma gasification furnace (R102) is also equipped with an oxygen inlet and a water inlet. The zinc oxide fixed-bed reactor (R103) is provided with an absorbent inlet, a purified gas outlet, and an absorbent outlet; the purified gas outlet is connected to a steam reformer (R104); the purified gas (113) obtained in the zinc oxide fixed-bed reactor (R103) enters the steam reformer (R104) through the purified gas outlet; the zinc oxide fixed-bed reactor includes a fixed bed layer composed of zinc oxide particles. The first mixer (M101) is equipped with an oxygen inlet, a landfill gas inlet, and a steam inlet. The landfill gas mixture (147) obtained from the first mixer (M101) is fed into a feed gas (148) after passing through a heat exchanger (E104). The feed gas (148) is fed into a high-temperature synthesis gas after passing through a reformer (R105), and then passes through a heat exchanger (E105) to obtain a heat-exchanged synthesis gas (150). After being cooled by a condenser (E106), it is cooled into a cooled synthesis gas (151), and then compressed by a compressor (C104) to obtain a mixed gas (152). The first flash evaporator (V101) is provided with a mixed gas inlet, a syngas outlet and a waste outlet; the mixed gas (152) enters the first flash evaporator (V101) through the mixed gas inlet and is flash separated. Under the action of gravity, the liquid waste (153) is discharged from the waste outlet at the bottom of the tank, while the landfill gas reforming gas (154) is discharged from the syngas outlet at the top of the tank. The second mixer (M102) includes a purge gas inlet, a hydrogen inlet, and a synthesis gas inlet; Purified gas (116) from RDF vaporization in the RDF purification system enters the second mixer (M102) through the purified gas inlet; reformed gas (154) from the landfill gas reforming system enters the second mixer (M102) through the syngas inlet; hydrogen (124) enters the second mixer (M102) through the hydrogen inlet. The mixed gas (125) obtained from the second mixer (M102) passes through the first-stage composite adsorber (R106) to obtain the first-stage purified gas (126), which enters the second-stage fine removal unit (R107) to obtain pure synthesis gas (127), and after passing through the fifth compressor (C105) to obtain methanol synthesis gas (128). Methanol synthesis gas (128) passes through methanol reactor (R108), and the resulting reaction mixture (129) then passes through the seventh heat exchanger (E107) and the eighth heat exchanger (E108) to obtain methanol mixed product (130). The second flash evaporator (V102) is equipped with a gas outlet and a crude methanol outlet; after the mixed product (130) enters the second flash evaporator (V102), the unreacted gas mixture (131) and crude methanol (132) are discharged from the gas outlet and crude methanol outlet of the second flash evaporator (V102) respectively. Crude methanol (132) enters the first distillation column (V103) and the second distillation column (V104) to obtain methanol (134). The first-stage composite adsorber (R106) is filled with a composite adsorbent based on modified activated alumina or molecular sieves, where trace amounts of hydrogen chloride remaining from RDF gasification gas and trace amounts of ammonia remaining from landfill gas are simultaneously adsorbed. The second stage is the second-stage fine removal unit (R107), which is filled with a layered or mixed high-precision copper-based desulfurizing and dechlorinating agent bed to deeply remove residual ppb-level sulfides and chlorides from the gas.

2. The methanol production system according to claim 1, characterized in that, The dryer (D101) is provided with an RDF inlet and a high-temperature air inlet; RDF (101) and high-temperature air (102) enter the dryer (D101) from the RDF inlet and the high-temperature air inlet, respectively.

3. A method for producing methanol using the methanol production system as described in claim 1, characterized in that, Includes the following steps: S1. The waste-derived fuel is pyrolyzed and plasma gasified to obtain high-temperature syngas. After cooling and gas-solid separation, the obtained syngas (109) is purified and reformed to obtain purified gas (116) of RDF gasification. S2. The landfill gas mixture (147) obtained by mixing landfill gas with oxygen and water vapor undergoes methane steam reforming, water-gas shift and dry reforming reactions in the reforming reactor to generate high-temperature synthesis gas, which is then flash-separated to obtain landfill gas reformed gas (154). S3. The purified gas (116) obtained from the RDF gasification in step S1, the landfill reformed gas (154) obtained in step S2, and hydrogen are mixed and the ratio is adjusted to obtain a mixed gas (125). Pure synthesis gas (127) is obtained through a two-stage purification system. Methanol is prepared by methanol synthesis reaction in methanol reactor (R108) under the catalysis of a catalyst.

4. The methanol production method according to claim 3, characterized in that, In step S1, the waste-derived fuel undergoes drying treatment before pyrolysis, and the drying treatment temperature is 150-300℃; And / or, in step S1, the pyrolysis is performed under anaerobic conditions at 400-600°C and 0.1-0.5 MPa; And / or, in step S1, the pyrolysis product (104) obtained by thermal decomposition is subjected to gas-solid separation to obtain pyrolysis gas (105) and solid residue (106). The pyrolysis gas (105) is heated to 650-750°C and then subjected to plasma gasification treatment together with the solid residue (106). And / or, in step S1, the plasma gasification treatment involves mixing the heated pyrolysis gas (105) and solid residue (106) with oxygen and water, and carrying out a plasma gasification reaction at 1200-1600°C and 0.2-0.6 MPa to generate high-temperature syngas. And / or, in step S1, the high-temperature syngas obtained by plasma gasification is cooled to 600-900℃ and then subjected to gas-solid separation to obtain syngas (109).

5. The methanol production method according to claim 3, characterized in that, In step S2, the main components of landfill gas are CH4, CO2, N2 and O2; the molar ratio of CH4 to CO2 is 1:(0.6-1.0); And / or, in step S2, the temperature of the oxygen is 240-270℃ and the pressure is 0.4-0.6 MPa; And / or, in step S2, the molar ratio of CH4 to water vapor in the landfill gas is made up to 1:(1.1-1.6); And / or, in step S2, the landfill gas mixture (147) is preheated to 720-880°C and the pressure is maintained at 0.4-0.6 MPa before entering the reforming reactor; And / or, in step S2, the operating temperature of the reforming reactor is controlled between 720-880℃, and the operating pressure is maintained between 0.4-0.6 MPa; And / or, in step S2, the high-temperature synthesis gas undergoes heat exchange, condensation, and compression to obtain a mixed gas (152) with a temperature of 15-25℃ and a pressure of 5-7MPa, which is then subjected to flash separation.

6. The methanol production method according to claim 3, characterized in that, In step S3, the first stage of the two-stage purification system is a composite adsorber (R106), which is filled with a composite adsorbent based on modified activated alumina or molecular sieve; the second stage is a second-stage fine remover (R107), which is filled with a layered or mixed high-precision copper-based desulfurizing agent and dechlorinating agent bed. And / or, in step S3, the pure syngas (127) is compressed to 5-7 MPa to obtain syngas (128), which then enters the methanol reactor (R108); And / or, in step S3, the methanol synthesis reaction is carried out at 4-8 MPa and 220-280 °C.

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