CN1919986A

CN1919986A - Coal bed gas coke deoxidization technique

Info

Publication number: CN1919986A
Application number: CN 200610021720
Authority: CN
Inventors: 胡善霖; 廖炯; 曾健; 陈耀壮
Original assignee: Southwest Research and Desigin Institute of Chemical Industry
Current assignee: Southwest Research and Desigin Institute of Chemical Industry
Priority date: 2006-08-31
Filing date: 2006-08-31
Publication date: 2007-02-28

Abstract

The invention discloses the coal bed gas coke deoxidization technology, comprising the following steps: deoxidizing coal bed gas with coke and anthracite coal, keeping the temperature between 600-1000Deg.C, then dedusting, and cooling; adjusting the oxygen content in deoxidation reactor to 5-9%. The technology can keep reaction temperature, remove oxygen of coal bed gas, reduce methane cracking, and improve safety.

Description

Coal bed gas coke deoxidation process

Technical Field

The invention relates to a deoxidation process before comprehensive utilization of coal bed gas.

Background

Coal bed gasis commonly called as 'gas', the main component of the gas is methane, and the gas exists in coal beds in large quantity and belongs to unconventional natural gas; coal bed gas is one of the main causes of coal mine underground accidents. Actually, the coal bed gas is a new energy source with high heat value and no pollution, and can be used as power generation fuel, industrial fuel, chemical raw materials, resident living fuel and the like. If the energy is reasonably utilized, the energy shortage can be made up; meanwhile, the recycling of the coal bed gas is also beneficial to protecting the environment. Because the leakage of coal bed gas into the air with coal mining can exacerbate the global warming effect. However, because the content of methane in the coal bed gas is relatively low and the content of air is relatively high, direct utilization is relatively difficult, so that a large amount of coal bed gas cannot be well utilized for a long time, a large amount of resources are wasted, and environmental pollution is caused.

In order to fully utilize the resource of the coal bed gas and ensure the safe operation of the subsequent process, the oxygen in the coal bed gas must be removed firstly, so that the composition of the coal bed gas avoids the range of the composition of the explosive gas. For the coal bed gas of the mine with medium concentration, the product gas which meets the national urban gas standard after deoxidation and desulfurization can be directly used as the urban gas. If the product is further concentrated and purified by pressure swing adsorption or cryogenic method, methane (CH) is obtained₄) High quality gas with a content higher than 93% or concentrated gas with higher purity can be used as industrial raw material, fuel and civil fuel, Compressed Natural Gas (CNG) or liquefied natural gas (CNG), etc.

The inventor of the present invention applied a Chinese patent (CN85103557) named "pressure swing adsorptionmethod for enriching methane in coal mine gas" in 1985, and disclosed a method for separating and enriching methane from a gas mixture (coal mine gas) by using pressure swing adsorption technology, which can make good use of coal bed gas and save energy. However, in general, during the concentration and purification of methane, the oxygen content of the discharged waste gas is also concentrated and increased, and meanwhile, the waste gas inevitably contains 5-15% of methane gas, so that the composition of the discharged waste gas is in the range of explosive gas composition, therefore, the explosion danger exists in the waste gas discharge pipeline all the time, and the popularization and application of the technology are limited.

In order to reduce the explosion risk and promote the reasonable application of the coal bed gas, it is important to perform safe and effective deoxidation treatment before processing and utilizing the coal bed gas.

The currently available deoxidation methods are mainly catalytic deoxidation (CN02113628.9) and coke combustionA method (non-catalytic combustion deoxidation, CN02113627.0) and the like, wherein the former causes coal bed gas to pass through a catalyst bed layer at a certain temperature, and the methane and oxygen are reacted at a higher space velocity to quickly deoxidize; the latter makes the coal bed gas enter into a reactor after being preheated, and the coal bed gas is deoxidized by a high-temperature coke bed layer in the reactor to generate CO and CO₂While generating a small amount of H₂And water. Compared with the coke combustion method, the coke combustion method is more economic and effective and simple to operate, does not need to use a catalyst, can reduce the oxygen content in the coal bed gas to below 1 percent, basically does not lose or has less loss of methane, saves resources such as water, electricity and the like, and basically has no adverse effect on the environment. However, the temperature control in the reaction process of the coke burning method is a difficult point, if the reaction temperature is too low, the coal bed gas is not completely deoxidized, and the coke is not completely burnt, so that the coke consumption is increased, and resources are wasted; if the reaction temperature is too high, the cracking degree of methane is increased, and energy is wasted. In addition, because the reaction between coke and oxygen, the reaction between methane and oxygen, and the like in the deoxidation process are strong exothermic reactions, and the coke deoxidation reactor is an adiabatic reactor, the temperature in the reactor is continuously increased along with the extension of the reaction time, and the reaction temperature is difficult to maintain in a required temperature range.

Disclosure of Invention

The invention aims to provide a novel coal bed gas coke deoxidation process, which can better control the reaction temperature, effectively remove oxygen in the coal bed gas, reduce methane cracking to the maximum extent, enable the loss of methane to be below 5 percent, reduce the explosion possibility in the deoxidation process and improve the safety.

The technical scheme adopted by the invention for solving the technical problems is as follows: a coal bed gas coke deoxidation process, the coal bed gas is deoxidized through a hot coke layer or a smokeless coal bed in a deoxidation reactor, the deoxidation reaction temperature is controlled at 600-; in the deoxidation process, the oxygen content of the reaction gas entering the deoxidation reactor is adjusted to 5-9%, preferably 7-8% by circulating part of the deoxidized and cooled coal bed gas into the coal bed gas before deoxidation.

The deoxidation process of the coal bed gas coke can be carriedout in a fixed bed reactor, and the fixed carbon content (mass fraction) of the coke is preferably not less than 80%; anthracite coal with high carbon content can also be used to replace coke.

In the coal bed gas deoxidation process, under the high-temperature condition, oxygen in the coal bed gas and carbon in coke or anthracite are subjected to chemical reaction; meanwhile, a small amount of methane is cracked to generate hydrogen and carbon, and the newly generated carbon reacts with oxygen, so that the aim of effectively removing the oxygen in the coal bed gas is fulfilled. The main chemical reactions that take place are as follows:

at the same time, a small amount of methane undergoes the following chemical reaction at high temperature:

the coal bed gas deoxidized by the method can be sent to the next step for subsequent processes such as concentration and purification after being treated by desulfurization and the like.

Compared with the prior art, the invention has the beneficial effects that: in the process of deoxidizing the coal bed gas coke, the invention adjusts the oxygen content of the reaction gas entering the deoxidation reactor to a proper range by circulating the partially deoxidized and cooled coal bed gas to the coal bed gas before deoxidation, can more effectively control the temperature of the deoxidation reaction to be in the proper range, and can prevent the reaction temperature from being too high to cause large cracking of methane in the coal bed gas, thereby not only effectively removing the oxygen in the coal bed gas and reducing the oxygen content in the coal bed gas to be below 0.5 percent, but also maximally reducing the cracking of the methane to ensure that the loss of the methane is below 5 percent, being beneficial to saving and utilizing the methane resource, simultaneously ensuring that the composition of the discharged waste gas is outside the range of the composition of the explosion gas, reducing the explosion possibility in the deoxidation process and improving the safety of the whole process.

Drawings

FIG. 1 is a flow chart of the coalbed methane coke deoxidation process of the invention.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments.

Example 1

The coalbed methane coke deoxidation process comprises the following steps:

a reactor having a diameter of 32mm was charged with 200ml of metallurgical coke at 0.5M under normal pressure³Flow rate per hr and volume composition O₂10.5％、N₂39.5％、CH₄50% of the raw material coal bed gas can be heated to about 1008 ℃ along with the continuous reaction, and the temperature is higher; the composition of the deoxidized coal bed gas (volume percentage, dry basis) is determined as follows: CH (CH)₄42.98％、N₂39.8％、O₂0％、CO₂5.10％、CO 6.52％、H₂5.6％。

In this embodiment, part of the deoxidized and cooled coal bed gas is not circulated into the raw coal bed gas before deoxidation, and the oxygen content in the raw coal bed gas entering the deoxidation reactor is higher, so that the temperature in the reaction process is higher than an ideal temperature range, and the methane cracking loss in the reaction process is larger.

Example 2

The coalbed methane coke deoxidation process comprises the following steps:

a reactor having a diameter of 32mm was charged with 200ml of metallurgical coke at 0.5M under normal pressure³Flow rate per hrThe material coal bed gas is obtained by circulating part of deoxidized and cooled coal bed gas into the raw material coal bed gas before deoxidation, and adjusting the oxygen content of the reaction gas entering into the deoxidation reactor to ensure that the volume composition of each component is O₂7.14％、N₂26.86％、CH₄66 percent, along with the continuous reaction, the reaction temperature can be controlled to be about 780 ℃, which is a relatively ideal reaction temperature; the composition of the deoxidized coal bed gas (volume percentage, dry basis) is determined as follows: CH (CH)₄64.69％、N₂26.86％、O₂0％、CO₂4.11％、CO 2.84％、H₂1.5％。

Example 3

The coalbed methane coke deoxidation process comprises the following steps:

a reactor having a diameter of 32mm was charged with 200ml of metallurgical coke at 0.5M under normal pressure³Introducing raw coal bed gas at a flow rate of/hr, circulating part of deoxidized and cooled coal bed gas to the raw coal bed gas before deoxidation, and adjusting oxygen content of reaction gas entering a deoxidation reactor to make volume composition of each component be O₂6.3％、N₂23.7％、CH₄70 percent, along with the continuous reaction, the reaction temperature can be controlled to be about 670 ℃, which is a relatively ideal reaction temperature; the composition of the deoxidized coal bed gas (volume percentage, dry basis) is determined as follows: CH (CH)₄68.25％、N₂23.7％、O₂0.46％、CO₂5.08％、CO 1.93％、H₂0.58％。

In the embodiment 2 and the embodiment 3, the oxygen content in the raw material coal bed gas entering the deoxidation reactor is proper by circulating part of the deoxidized and cooled coal bed gas to the raw material coal bed gas before deoxidation, the temperature in the reaction process is controlled in a more ideal range, and the methane cracking loss is small.

As can be seen from the above examples 1-3, too high oxygen content in the raw coal bed gas before the reaction may result in a higher deoxidation reaction temperature, a higher methane cracking loss, and a methane cracking product H₂And an increase in the amount of CO; in a proper oxygen content range, the deoxidation reaction temperature is easily controlled to be properIn the range, the loss of methane cracking is small, and the product H of methane cracking is generated₂And the amount of CO is low.

Claims

1. A coal bed gas coke deoxidation process is characterized in that coal bed gas is deoxidized through a hot coke layer or a smokeless coal layer in a deoxidation reactor, the deoxidation reaction temperature is controlled to be 600-1000 ℃, the pressure is normal pressure, and then waste heat recovery-dust removal-cooling treatment is carried out, wherein the process comprises the following steps: in the deoxidation process, the oxygen content of the reaction gas entering the deoxidation reactor is adjusted to 5-9% by circulating part of the deoxidized and cooled coal bed gas into the coal bed gas before deoxidation.

2. The coalbed methane coke deoxidation process of claim 1, characterized in that: the deoxidation reaction temperature is 700-800 ℃.

3. The coalbed methane coke deoxidation process of claim 1, characterized in that: in the deoxidation process, the oxygen content of the reaction gas entering the deoxidation reactor is adjusted to 7-8% by circulating part of the deoxidized and cooled coal bed gas into the coal bed gas before deoxidation.