Waste heat-driven circulative heat-carrying gas methanation technology and device

Abstract

The invention relates to waste heat-driven circulative heat-carrying gas methanation technology. Waste heat of cooled and condensed product gas at the temperature of below 250 DEG C in a shell pass is used for driving a part of raw material gas to moisten simultaneously so as to achieve the steam / gas ratio of 3.0 to 4.0 while performing falling film temperature raising in a tube pass through an evaporation / condensation coupled heat exchanger under the normal pressure of between 0.15 and 3.0MPa and a pressurization range; due to the heat-carrying capability of the product gas, the exit temperature of the product gas in a first-section methanation heat-insulated reactor does not surpass 680 DEG C; after the heat of the product gas is released in a high-pressure steam over-heater to reduce the temperature, the product gas is mixed with another part of raw material gas at normal temperature and undergoes all reactions in a second-section methanation heat-insulated reactor, so that the exit temperature of the product gas does not surpass 680 DEG C; the high-temperature sensible heat of the product gas is recycled through a high-pressure steam boiler and the over-heater, the low-temperature waste heat of the product gas at the temperature of below 250 DEG C is recycled through the evaporation / condensation coupled heat exchanger and the product gas is cooled and condensed water is separated out by raising the temperature of the raw material gas and evaporating circulating water; and the condensed water is delivered into the tube pass of the evaporation / condensation coupled heat exchanger by using a circulating water pump and mixed with the raw material gas to undergo film falling evaporation so as to form an evaporation / condensation cycle. The waste heat is evaporated once again by raising the temperature so as to moisten, save power repeatedly, increase byproduct electric power output and enhance energy utilization ratio by at least more than 6 percent.

Description

technical field [0001] The invention belongs to the field of coal-based natural gas production, and in particular relates to a coal gas methanation technology and device. Background technique [0002] Coal-to-methane gas (or alternative natural gas, referred to as SNG) is an important way to convert coal into high calorific value gas fuel, which is beneficial to pit mouth processing, long-distance transportation and on-site capture and emission reduction of CO. 2 . [0003] The key step for coal to substitute natural gas is to contain high concentrations of CO and H 2 Catalytic reaction of gas methanation [0004] ΔH 0 =-206.4kJ mol -1 (CH 4 ) [0005] h 2 For coal gas with / CO=3, every time 1% of CO is converted, the gas adiabatic temperature rises by 70-100°C (increases with the increase of reaction depth). In the industry, two processes, the tubular external cooling isothermal catalytic reactor and the inter-stage cooling multi-stage adiabatic catalytic reactor,...

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Problems solved by technology

However, the power consumed by the circulating compressor is equivalent to more than 6% of the calorific value of the product, which directly reduces the energy conversion efficiency and economic benefits of the process

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