CN1955268B - Method for preparing synthetic gas or safety fuel gas using gas of coal mine - Google Patents

Abstract

The invention relates to a method for producing synthesis gas or safe fuel gas by using coal mine gas. The gas is mixed with a certain amount of oxygen-containing gas and water vapor and then input into a gas reformer. Methane is generated in the combustion zone at the top of the reformer. Partial oxidation reaction and combustion reaction with oxygen, the high-temperature reaction gas then enters the middle and lower catalyst beds for conversion/partial conversion reaction of methane and water vapor, and the converted gas obtained after the reaction is syngas or safe fuel gas. The method is used to treat the oxygen-containing gas extracted from underground coal mines to keep it out of the range of explosion, and the produced product gas can be used as synthesis gas required for the production of chemical products such as synthetic ammonia and methanol, or as safe civil or industrial fuel gas. To make full use of coal mine gas resources.

Description

A method for producing synthesis gas or safe fuel gas from coal mine gas

technical field

The invention relates to a method for producing synthesis gas or safe fuel gas from coal mine gas, which can be used to convert the easily explosive gas into synthesis gas that can be used as chemical raw material or safe fuel gas that can be transported over long distances .

Background technique

Coal mine gas is a common name for coalbed methane, which is an unconventional natural gas that is mainly in the state of adsorption and stored in coal-measure strata. Its composition is basically the same as that of conventional natural gas, the main component CH ₄ content is greater than 95%, and its calorific value is greater than 33890KJ/Nm ³ (8100kcal/Nm ³ ). It is a new type of clean energy that has emerged in the past 20 years.

The mining methods of coal mine gas are divided into surface extraction method and underground extraction method. The surface drainage method is to drill and extract from the ground before coal mining, and the concentration of the gas produced is more than 90%. Like natural gas, it is convenient for transportation and processing; the underground drainage method is closed drainage in the coal mine. The obtained gas is mixed with more air, and the concentration is only about 50%.

China is rich in gas resources with a buried depth of less than 2000m, with a total reserve of about 30-35 trillion m ³ , equivalent to the total amount of onshore conventional natural gas resources (about 30 trillion m ³ ), ranking second only to Russia and Canada, and ranking first in the world. three. However, my country's geological conditions are complex, and there are not many gas fields that can be extracted by industrial surface drilling. The amount of gas currently exploited is not only small, but most of them are extracted underground.

The gas extracted from downhole generally contains CH ₄ ~ 50%, O ₂ ~ 10%, N ₂ ~ 35%, CO ~ 2%, CO ₂ ~ 3%. Air, _CH4 content will decrease, and _O2 and _N2 content will increase. Due to the high content of _O2 , the gas extracted underground is prone to explosion during transportation. At present, it is mostly used near coal mines as domestic fuel or power generation fuel. Underperformed.

In China, the vast majority of coal mines still exhaust the gas to the atmosphere through the ventilation system, which not only wastes a lot of resources, but also seriously pollutes the environment (the greenhouse gas effect of CH ₄ is 21 times greater than that of CO ₂ ), and has caused numerous gas outburst accidents in coal mines. occur.

Contents of the invention

The purpose of the present invention is to convert easily explosive gas into synthetic gas or safe fuel gas that can be used in chemical production, so as to fully utilize coal mine gas resources and increase its use value.

In order to achieve the above object, the present invention provides a method for producing synthesis gas or safe fuel gas by using gas, the technological process of the inventive method is: the gas is mixed with oxygen-containing gas and steam and then input into the gas reformer, The partial oxidation reaction and combustion reaction of methane and oxygen occur in the top combustion zone of the gas reformer, and the high-temperature gas generated by the reaction then enters the middle and lower catalyst beds of the gas reformer for the separation of methane and water vapor. Reforming/partial reforming reaction, the reformed gas obtained after the reaction is synthetic gas or safe fuel gas.

Among them, the partial oxidation reaction and combustion reaction of _CH4 and _O2 consumes _O2 and releases a large amount of heat. The main chemical reaction formula is as follows:

The high-temperature gas generated by the reaction enters the middle and lower part of the nickel-based catalyst bed of the gas-to-gas reformer, where the conversion/partial conversion reaction of CH ₄ and water vapor occurs, and CH ₄ is converted into H ₂ , CO and CO ₂ , mainly The chemical reaction formula is as follows:

For the convenience of description, unless otherwise specified, the gas content mentioned below in the present invention all refers to the volume content under the standard state, and the mentioned gas usage ratio all refers to the volume ratio under the standard state.

Synthesis gas produced from coal mine gas by the method of the present invention mainly contains H ₂ (50-60%), N ₂ (17-25%) gas, followed by CO and CO ₂ , residual CH ₄ ≤0.5%, residual CH 4 O ₂ ≤0.2%, can be used as raw material gas for chemical products such as synthetic ammonia, methanol, soda ash, etc. If there are hydrocarbon gases or hydrogen-containing gases to be used nearby, such as natural gas, petroleum refinery gas, coke oven gas, etc., they can also be mixed with coal mine gas and enter the gas reformer to produce synthesis gas.

The safe fuel gas prepared from coal mine gas by the method of the present invention mainly contains CH ₄ (30-36%), N ₂ gas (40-50%), followed by CO, CO ₂ and H ₂ gas, and residual O ₂ ≤0.5%, calorific value 12000～15000KJ/Nm ³ (2868～3585kcal/Nm ³ ), can be used as civil fuel gas or industrial fuel gas. If there are other fuel gases nearby, such as natural gas, city gas, liquefied petroleum gas, etc., they can also be mixed with the fuel gas prepared by the method of the present invention, and then transported safely to users through a long-distance pipeline network.

The process conditions for the partial oxidation, combustion and conversion/partial conversion reaction of methane described in the above method are as follows: when producing syngas, the pressure is 1.0-6.5MPa(G), and the temperature is 950-1350°C; when producing safe fuel gas, the pressure is 0.2 ～4.0MPa(G), temperature 600～850℃. The temperature of the reformed gas at the outlet of the gas reformer is: 800-1050°C when producing synthesis gas, and 550-800°C when producing safe fuel gas.

The oxygen-containing gas described in the above method is air, oxygen-enriched air or oxygen. Oxygen or oxygen-enriched air is used to prepare syngas, and the amount of _O2 and water vapor to be added is based on the composition of the required synthesis gas for heat balance and chemical reaction balance. It is determined by conventional process calculations. Generally, the amount of _O2 added is gas 0.1 to 0.15 times the gas volume, the amount of water steam is determined according to the total carbon content ∑C in the gas, which is H ₂ O/∑C=2.5 to 3.5 (molecular ratio). At this time, the temperature in the gas reformer is generally 950 to 1350 ℃; air is used in the production of safe fuel gas, and the amount of air used is to make the temperature in the gas reformer reach 600-850°C and ensure that the _O2 content in the product gas is ≤0.5%. 0.2 to 0.3 times. The amount of steam added is 0.5-1.2 times of the total carbon content ΣC in the gas.

The gas described in the above method needs to be purified (dust removal, desulfurization) before entering the gas reformer. The total sulfur content in the treated gas should be removed to ≤1mg/Nm ³ when producing syngas; it should be removed to ≤20mg/Nm ³ when producing safe fuel gas.

The gas, oxygen-containing gas and steam described in the above method need to go through a preheating step before entering the gas reformer. Usually, the high-temperature reformed gas at the outlet of the gas reformer is used to preheat the gas entering the furnace. Preheat to 400-550°C when making gas, and preheat to 300-400°C when making safe fuel gas.

In the above method, the heat of the high-temperature reformed gas at the outlet of the gas-to-gas reformer is firstly used to by-produce steam from the waste heat boiler, and then to preheat the aforementioned gas, and the by-product steam can be input to the gas-to-gas reformer.

By adopting the method of the invention, the coal mine gas resource can be fully utilized, and its use value can be improved.

The method of the present invention will be described in detail below in conjunction with the accompanying drawings.

Description of drawings

Fig. 1 is a schematic process flow diagram of the method of the present invention.

Detailed ways

Example 1:

Referring to Fig. ¹ , the purified gas (containing CH ₄ 50%, N ₂ 35%, O ₂ 10%, CO ₂ 3%, CO 2%, total sulfur ≤ 1mg/Nm ³ ), the gas gas preheater exchanges heat with the reformed gas from the oxygen preheater and the gas/steam mixture preheater. G) Steam at a temperature of 225°C is mixed and enters the gas/steam mixture preheater to exchange heat with the reformed gas from the waste heat boiler. After being preheated to 480°C, it enters the burner gas mixer of the gas reformer.

Oxygen (containing O ₂ ≥99.6%) with a flow rate of 650Nm ³ /h and a pressure of 2.5MPa(G) is mixed with a small amount of protective steam, and then enters the oxygen preheater to exchange heat with the hot reformed gas from the waste heat boiler, and is preheated After reaching 400 ° C, it enters the gas mixer at the head of the gas reformer.

After the gas/steam mixture gas and oxygen are fully mixed in the gas mixer at the furnace head of the gas reformer, it is sprayed out through the nozzle of the mixer, and partial oxidation and combustion reactions of CH ₄ occur in the top space of the gas reformer, so that The temperature in the combustion zone reaches 900-1350°C, and then carries the heat downstream into the gas reformer and the lower catalyst bed for the conversion reaction of CH ₄ and water vapor. The reformed gas from the gas reformer has a pressure of about 2.35MPa(G) and a temperature of about 900°C. It first passes through the waste heat boiler to recover heat and by-product steam with desalinated water, and then divides into two streams, which pass through the oxygen preheater and the gas/gas/ The steam mixed gas preheater recovers heat, and the two air streams merge and then pass through the gas gas preheater to recover heat.

The reformed gas exiting the gas reforming unit is syngas, with a dry gas flow rate of about 12500Nm ³ /h, a pressure of about 2.2MPa(G), and a temperature of about 360°C. Its composition is: H ₂ 56%, CO 14%, CO ₂ 12%, N ₂ 17%, O ₂ ≤0.2%, (CH ₄ +Ar) 0.8%, sent to process chemical products such as synthetic ammonia or methanol (a small amount of N ₂ should be added when processing synthetic ammonia, and N ₂ should be removed when processing methanol Gas components), can process synthetic ammonia or methanol about 3500kg/h.

Example 2:

Referring to Figure 1, the purified gas (containing CH ₄ ⁵⁰ %, N ₂ 35%, O ₂ 10%, CO ₂ 3%, CO 2%, total sulfur ≤ 20mg/Nm ³ ), through the gas preheater and heat conversion gas from the air preheater and gas/steam mixture preheater, after preheating, the flow rate is 1450kg/h, the pressure is 0.6MPa ( G) Steam at a temperature of 158°C is mixed and enters the gas/steam mixture preheater to exchange heat with the reformed gas from the waste heat boiler. After being preheated to 400°C, it enters the burner gas mixer of the gas reformer.

Air with a flow rate of 1500Nm ³ /h and a pressure of 0.6MPa(G) (containing O ₂ 21%, N ₂ 79%) mixed with a small amount of protective steam enters the air preheater to exchange heat with the heat conversion gas from the waste heat boiler , is preheated to 400°C and enters the gas mixer at the head of the gas reformer.

After the gas/steam mixed gas and air are fully mixed in the gas mixer at the furnace head of the gas reformer, it is sprayed out through the nozzle of the mixer, and partial oxidation and combustion reactions of CH ₄ occur in the top space of the gas reformer, so that The temperature in the combustion zone reaches 600-850°C, and then the heat is carried downstream into the catalyst bed for the partial conversion reaction of CH ₄ and water vapor. The reformed gas from the gas reformer has a pressure of about 0.5MPa(G) and a temperature of about 600°C. It first passes through the waste heat boiler and uses desalted water to recover heat and by-product steam, and then divides into two streams, which pass through the air preheater and gas/steam respectively. The mixed gas preheater recovers heat, and the two air streams are combined to recover heat through the tile gas preheater, and then cooled to normal temperature through the desalted water preheater, water cooler, and gas-water separator (not shown in the drawings). The condensate is separated and sent out of the system.

The reformed gas exiting the gas reforming device is safe fuel gas, its dry gas flow rate is about 7200Nm ³ /h, the pressure is about 0.4MPa(G), the temperature is normal temperature (≤40°C), and its composition is: CH ₄ 35%, H ₂ 8%, CO 4%, CO ₂ 7%, N ₂ 45.5%, O ₂ ≤ 0.5%, its low calorific value is about 13900KJ/Nm ³ (3300kcal/Nm ³ ), and it is sent to the fuel gas tank or directly to the fuel Tracheal network.

Finally, it should be noted that the above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that the present invention can still be modified and/or equivalents without departing from the spirit and scope of the invention.

Claims (6)

1. method of utilizing coal mine mash gas to produce synthetic gas or safety fuel gas, it is characterized in that input coal mine gas converter after coal mine gas and oxygen-containing gas and the vapor mixing, the partial oxidation reaction and the combustion reactions of methane and oxygen take place in combustion zone, described coal mine gas converter top, the high-temperature gas that reaction generates enter then described coal mine gas converter in, the lower catalyst bed layer, carry out the conversion/part conversion reaction of methane and water vapor, the reforming gas that obtains after the reaction is synthetic gas or safety fuel gas;

Described oxygen-containing gas adopts oxygen or oxygen-rich air when producing synthetic gas, according to volume ratio, add O ₂Amount is 0.1～0.15 times of gas tolerance, and the water vapor consumption is 2.5～3.5 times of total carbon ∑ C molar weight in the coal mine gas; Adopt air when producing fuel gas, according to volume ratio, add air capacity and be 0.2～0.3 times of gas tolerance, the steam add-on is 0.5～1.2 times of total carbon molar weight in the coal mine gas.

2. the method for utilizing coal mine mash gas to produce synthetic gas or safety fuel gas according to claim 1, it is characterized in that described partial oxidation of methane, burning and conversion/part conversion reaction carries out under following processing condition: pressure 1.0～6.5MPa (G) when producing synthetic gas, 950～1350 ℃ of temperature; Pressure 0.2～4.0MPa (G) when producing safety fuel gas, 600～850 ℃ of temperature; The temperature of the reforming gas of described coal mine gas converter outlet is: when producing synthetic gas 800～1050 ℃, and when producing safety fuel gas 550～800 ℃.

3. the method for utilizing coal mine mash gas to produce synthetic gas or safety fuel gas according to claim 1, it is characterized in that described coal mine gas handles through dedusting, desulfurizing and purifying before entering described coal mine gas converter, handle the total sulfur content in the after gas gas, when producing synthetic gas, be removed to≤1mg/Nm ³When producing safety fuel gas, be removed to≤20mg/Nm ³

4. the method for utilizing coal mine mash gas to produce synthetic gas or safety fuel gas according to claim 1, it is characterized in that described coal mine gas, oxygen-containing gas and steam, the reforming gas preheating that before entering described coal mine gas converter, exports with described coal mine gas converter; When producing synthetic gas, be preheated to 400～550 ℃, when producing safety fuel gas, be preheated to 300～400 ℃.

5. the method for utilizing coal mine mash gas to produce synthetic gas or safety fuel gas according to claim 1, after it is characterized in that described coal mine gas and other hydrocarbon gas or hydrogen-containing gas mixing, enter described coal mine gas converter more together, be used to produce synthetic gas.

6. the method for utilizing coal mine mash gas to produce synthetic gas or safety fuel gas according to claim 5 is characterized in that described hydrocarbon gas is Sweet natural gas, petroleum refinery's gas or coke(oven)gas.

Images