Technological method for producing coal-derived synthetic natural gas

Technical Field

The invention relates to a process for the generation of the natural gas, can be used for large-scale coal-made natural gas projects.

Technical background

Coal gasification technology is to achieve clean coal, high-efficiency, comprehensive utilization of the key, is also an important means of coal conversion. Some low grade, the reserves is abundant and is not suitable for the long distance transportation of natural gas by gasification of the coal is made, is to solve the contradiction in an effective way to natural gas supply and demand.

With the traditional synthesis gas compared to catalytic systems, natural gas, coal hydrogenation gasified system natural gas flow and is more simple, the reaction can be carried out in a gasification furnace, the methanation reactor of the traditional process, thereby the overall higher efficiency, lower investment cost. Coal and hydrogen under the action of the catalyst under the reaction is carried out at a relatively low temperature, at the same time in preparing natural gas (SNG), the added value can be obtained by very high aromatic oil compounds. Coal hydrogenation gasification in the source of hydrogen can be obtained by the multi-nozzle coal gasification technology, can also be obtained by catalytic steam coal and water, or such as through a hydrogen network. The research programme prepared by catalytic hydrogenation of the coal gas product, not only solves the problem of shortage of natural gas, but also realizes the cleaner use of coal.

Main reaction: C+H₂ =CH₄

Coal hydrogenation systems natural gas process almost no CO₂ discharge, is green, the technical environment.

Content of the invention

The purpose of this invention is to the reaction under the hydrogen atmosphere, to produce high-quality of the natural gas and the high economic value of BTX, PCX, naphtalenes ancillary product. Coal hydrogenation reaction process in the mid-temperature, medium-pressure conditions, the temperature the 600-1000 between [...] (preferably the 750-900 [...]), pressure in the 1.0-10.0 MPa (preferably 2.0-5.0 MPa), coal through the catalyst effect gasification temperature is greatly reduced, improving the carbon conversion, coal is deep cracking, the generating rate of the methane is also very high. Heat exchange in the reaction process, by-product high-grade steam, can be used to supplement the water washing process of the catalyst recovery unit, or for steam turbine power generation, or is used for the preheating of raw materials. Coal hydrogenation of natural gas process gasified system CO₂ discharge, not only solves the problem that the shortage of natural gas, but also realizes CO₂reduces the platoon to gather , is an economic, environmental protection, flexible process flow.

The embodiment of the invention in the scheme provided by the, coal hydrogenation catalyst of methane in the process can be divided into a monocomponent and composite catalyst. Typical single-component catalyst is alkali metal, alkaline earth metal and a transition metal. Composite catalyst is in the single-component catalyst on the basis of adding rare earth metal, trace elements or different single component catalyst mixing. Plural composite catalyst because of low melting point, is in a liquid state at the gasification temperature, therefore apt to diffusion, a plurality of the active site, the best catalytic effect. Because the catalyst is mixed with the coal, consumption is relatively large, therefore, the process also includes catalyst recovery unit. After washing of the coal gasification method of is mad the slagging to recover most of the water-soluble catalyst active component, and a small amount of non-water-soluble catalyst active component, the alkali absorption method for the recovery. The catalyst recovery of coal hydrogenation systems natural gas process, saves the cost, it has certain economic benefits.

The process of the invention specific method comprises the steps as follows:

(1) mixing sample of coal and catalyst through the screw feeder or pump enter the gasification furnace and, in the lower part of the gasification furnace of hydrogen gas is, under the action of the catalyst for hydrogenation reaction of the methane. From a thermodynamic perspective, temperature rise is not conducive to CH₄ generation, but the actual control of the process dynamics need to be taken into account, from the 700 [...] is added to the 1000 [...] in the course of, reaction of a significant increase in average gasification rate; when the temperature is higher than the 800 [...] , the increase of the carbon conversion rate is not too noticeable. When the temperature is 700 the [...] , pressure is 2.5 MPa condition, the reaction gas products are primarily methane (> 90%, molar percentage quantity), accompanied by a small amount of CO₂, CO and CnHm, mainly in the coal hydrogenation gasification and depc, secondary reaction of tar produced in the process.

(2) CO₂ gas absorption is by alkaline solution of alkali metal carbonate, and this portion of the carbonate after crystallization can be used for coal hydrogenation reaction catalyst of the process, part of the remaining CO₂ can be sealed in order to reduce the emission of greenhouse gases;

(3) the gasification of coal hydrogenation of the tail gas contains very high heat of reaction, this part of the heat of gasification furnace can be connected through the heat exchange device can be recovered. Steam and low-temperature water in the heat exchanger a high-temperature reaction gas to convect heat get overheated steam, can be used for preheating the coal, also can be used for steam turbine power generation, or catalyst recovery unit water washing process.

(4) after is mad the slagging in coal gasification contain a large number of catalyst active component can be utilized, by washing the filter, a large amount of dust is reduced, on the other hand the catalyst is soluble in aqueous solution, through evaporative crystallization can be reused; a portion of the catalyst with the ash forming the non-water-soluble silicate, can access Ca (OH)₂ solution, alkali solution to the replacement thereof. Alkali wash process than response mole to be determined and the appropriate pH value of the solution. Washing solution after the atomic absorption spectrometer for analysis of the ion concentration of the active component, the active component of the catalyst is calculated by the amount of recovery, optimizing the recovery conditions.

Description of drawings

Chart 1' for this invention natural gas process flow chart.

Coal (13) after grinding by crushing, and catalyst (12) in the mixing device (4) mixing, through the spiral feeder (or pump) enter the gasification furnace (1), the bottom of the hydrogen from the gasification furnace into the gasification furnace. In the gasification furnace, coal under the action of catalyst and hydrogen hydrogenation reaction occurred, generating CH₄ discharged at the top of from the gasification furnace, through a waste heat boiler (5) the H₂ O (14) enter the product after the heat exchange the separation device (6). Rich in after separating CH₄ gas through the purification system (7) processing into the natural gas pipe network (8), a small amount of pure CO₂ (9) can be used for industrial products for sale, the remaining unreacted hydrogen (15) through a compressor (11) is pressurized and then with fresh hydrogen reaction is carried out in the gasification furnace. Some of the steam generated by the waste heat boiler can enter into the room (2), by a water washing recovering most of the soluble catalyst active component, the non-dissolubility the activity of the catalyst component can be using lye (16) in the room (3) for recycling, the remaining is the drog (17). The active component of the recovered catalyst through the drying device (10) after drying, enter into the mixing device with a fresh, recycle.

Specific embodiments

Embodiment 1

The annual yield of the 4 billion nm³ process flow of natural gas.

Carbon content is about 80% coal through crushing, ball mill, and then mixed with the catalyst, into the gasification furnace by the screw feeder,   H₂ enter the gasification furnace from the bottom of the reactor, the 8 combination of a gasification furnace in parallel. Which a coal feeding quantity with the catalyst for the 960 tons/hour, the hydrogen flow rate is 1.964 × 10⁵ standard cubic meters/hours. In the 800 [...] , 4.0 MPa conditions, gasification furnace in the coal of mixed with catalyst H₂ atmosphere through hydrogenation reaction under gasification to methane, in the air outlet each group content minute mole : CH₄ 32.30%, CO₂   0.58%, CO   0.11%, the reaction end of the can is not hydrogen. A portion of the coal will also hydrogenation pyrolysis, generating aromatic hydrocarbon, heterocyclic compound, aliphatic hydrocarbon, such as phenols. Through the separation of the unit to remove a small amount of oil in the tail gas, high economic value of this part of the gas-liquid separation device of the oil can be recovered. Gas separated by low-temperature distillation method CH₄, high-quality natural gas (CH₄ gas molar content is 97.3%)is delivered to the natural gas pipeline network, H₂ the circulation again returned to the gasification furnace.

Coal hydrogenation gasification, and comprises a fluidized bed and a gasification by circulating pump and the heat exchanger and the like. Fluidized bed gasification furnace and a slag bucket co-contained in a cylindrical housing with, coal and hydrogen has a high sliding speed, the gas-solid two-phase fully mixed, enhance the mass transfer process, enhance the gasification efficiency. In the process of hydrogenation reaction, catalyst coal through the dry powder mix solid pump enter the gasification furnace, the coal particles are suspended in a stream of hydrogen, , pulverized coal under the action of the catalyst with the hydrogen energy affrettando to produce methane. Exhaust gas through the CO₂ trap, discharged from the vent port, the purification and separation of the high-quality natural gas, is conveyed into a city network through a pipeline, H₂ is returned to the hydrogenation of recycling of the gasification furnace.

The temperature of the gasification gas after hydrogenation is relatively high, this part of the heat energy to recover and utilize the heat exchanger. The heat exchange process shell-and-tube high temperature heat recovery device, heat exchange element material to a novel silicon carbide engineering ceramic, it can resist high temperature and thermal shock, as the coefficient of heat conductivity of stainless steel and has good corrosion resistance. The heat exchange mode adopts convection heat exchange, one end of the clothing, and falling steam, another the high-temperature and high-pressure exhaust gas. The recovery of water vapor the 250-650 within the range of temperature of [...] , can be directly into the catalyst recovery unit. Exhaust gas waste heat after heat exchange for evaporating the solution after washing the catalyst recovery, solution through evaporation, crystallization to obtain the activity of the catalyst component, mixed with the coal the catalyst used for hydrogenation process. The process of directly reducing the cost of the catalyst, the economic efficiency is increased.

Embodiment 2

Years-off 5 billion nm³ process flow of natural gas.

Carbon content is about 64% coal through crushing, ball mill, and then mixed with the catalyst, through the spiral feeder enter the gasification furnace and, H₂ enter the gasification furnace from the bottom of the reactor, the 12 combination of a gasification furnace in parallel. Correspondingly with the catalyst which a coal to 1500 tons/hour, the hydrogen flow rate is 2.455 × 10⁵ standard cubic meters/hours. In the 850 [...] , 4.0 MPa conditions, gasification furnace in the coal of mixed with catalyst H₂ atmosphere through hydrogenation reaction under gasification to methane, in the air outlet each group content minute mole : CH₄ 33.86%, CO₂   0.67%, CO   0.17%, the reaction end of the can is not hydrogen. A portion of the coal will also hydrogenation pyrolysis, generating aromatic hydrocarbon, heterocyclic compound, aliphatic hydrocarbon, such as phenols. Through the separation of the unit to remove a small amount of oil in the tail gas, high economic value of this part of the gas-liquid separation device of the oil can be recovered. Gas separated by low-temperature distillation method CH₄, high-quality natural gas (CH₄ gas molar content is 97.1%)is delivered to the natural gas pipeline network, H₂ the circulation again returned to the gasification furnace.

is mad the slagging gasification reaction of the obtained after washing and filtering, the catalyst active component dissolved in the wash liquid in K, through the appropriate after drying, is mixed with the coal, is used for hydrogenation the gasification process. Also a portion of the insoluble KAlSiO₄ adopts Ca (OH)₂ alkaline washing treatment solution, alkali presses the cauldron can be carried out in the, first using N₂ purging of the kettle, the temperature is increased to 150 the [...] , boost pressure to 1 MPa, reaction 1h, natural cooling to room temperature, filter and separate and retain the alkaline solution.