Method of extracting pure hydrogen from tail gas of semicoke

    2022-03-29 15:50:14

The invention belongs to the applied technical field of semicoke tail gas, in particular to a method for extracting pure hydrogen by using blue carbon tail gas.
Technical background
Blue charcoal, also known as semi-coke, is a solid substance with high fixed carbon content produced by medium and low temperature distillation process with Jurassic non-stick coal and weak stick coal as raw materials. It is named for its blue flame when burning. At the same time the production of blue carbon by-product blue carbon tail gas and coal tar, currently each production of a ton of blue carbon about 700Nm3 tail gas, calorific value of 1700~2000 kcal. In 2010, the national output of blue carbon was about 10 million tons, that is, the by-product of blue carbon tail gas was about 7 billion Nm3. During the 12th Five-Year Plan period, China's orchid carbon market is expected to reach more than 50 million tons/year, that is, the exhaust volume of orchid carbon will reach 35 billion Nm3/ year.
Due to different coal quality and production process, the composition of blue carbon tail gas is also different. The composition of conventional blue carbon tail gas is shown in Table 1:
Table 1. Main components of tail gas of conventional typical blue carbon H2 CH4 CO CO2 CnHm N2 O2 H2O V %
20~28 7~10 14~18 8~12 1~3 37~43 0.1~0.

Saturated in addition, the tail gas of orchid also contains tar, benzene, naphthalene, phenol, dust, sulfide, ammonia, heavy metals and other impurities.
From the composition of carbon tail gas, hydrogen, methane and carbon monoxide in carbon tail gas are very valuable chemical raw materials. If the
On the one hand, it provides a new way for clean utilization of the tail gas of blue carbon, and on the other hand, it turns waste into treasure. The pure hydrogen produced can be used as a supplement of China's energy, which not only realizes the resource utilization of industrial emissions, but also optimizes China's energy structure.
Pressure swing adsorption technology (PSA) is the use of the adsorbent used for different components of the adsorption capacity with different pressure and different characteristics, so that hydrogen and other impurities to achieve separation. It with adsorbent porous solid matter) (internal surface on the basis of the physical adsorption of gas molecules, using adsorbent adsorption under the same pressure easily absorb under the high boiling components and pressure increase (adsorption) the characteristics of the feed gas under pressure from a certain adsorption by adsorbent bed, high boiling point impurity components by selective adsorption, Hydrogen with low boiling point is not easily adsorbed and can be separated from impurities through adsorbent bed. The adsorbent is decreasing
Regeneration is obtained by desorption of adsorbed impurity components under pressure.
There are a lot of impurities in the tail gas of blue carbon, and the composition is very complex. In addition to a large amount of N2, H2 and a certain amount of CH4, CO, CO2, O2, there are also a small amount of high-carbon hydrocarbons, naphthalene, inorganic sulfur and tar, etc. The latter are difficult to desorption components at room temperature. For the adsorbents used in psa, the adsorption capacity is so strong that it is difficult to desorption. Therefore, before entering the PSA process, high carbon hydrocarbons and other high boiling point impurities are removed through the main processes of detarring and naphthalene, desulfurization and PSA pretreatment to achieve the purpose of pre-purification of the PSA tail gas, and then 99% purity H2 is obtained through PSA process.
In view of this, the invention aims to provide a method for extracting pure hydrogen from the tail gas of blue carbon with low energy consumption, simple process, high product gas purity, high device automation and simple operation.
The invention content
The purpose of the invention is to provide a method for extracting pure hydrogen by using the tail gas of blue charcoal. Through the method of using the purification
Pure hydrogen with high purity was prepared from the treated and compressed blue carbon tail gas by pressure swing adsorption
The technical scheme of the invention is as follows:
A method for extracting pure hydrogen from the tail gas of blue charcoal is characterized in that it includes the following steps:
(1) crude purification: the blue carbon tail gas after crude purification treatment, removal of impurities including tar, naphthalene, dust, get crude purification
Blue carbon tail gas;
(2) Compression: use a compressor to pressurize the tail gas of crude purified blue carbon prepared in Step (1) to 0.6~ 2.15mpa;
(3) desulfurization: Desulfurize the compressed gas obtained in the previous step and remove hydrogen sulfide to a content less than 10mg/ cm2
(4) PSA pretreatment: the desulfurized purified gas is sent to the PSA pretreatment section, and the hydrocarbons are removed by the preprocessor
To obtain purification gas in accordance with the requirements of psa raw gas;
(5) PSA-H2 process: The pretreated gas enters the PSA-H2 system to obtain pure hydrogen with the volume percentage of H2 ≥ 99%.
In the above methods, a sulfur-resistant transformation stage can be added between steps (2) and (3) : The tail gas of ranchar, which is coarsely purified after being pressurized by the compressor in Step (2), is transformed into CO+H2O → H2+CO2 under the action of the catalyst, and the H2 content increases.
The CO content of the converter gas is reduced, and impurities including oxygen are removed, and the converter gas is then desulfurized in step (3).