CN101613627B - Catalytic deoxidation process of oxygen-contained coal bed gas - Google Patents

Abstract

A catalytic deoxygenation process for oxygen-containing coalbed methane. The oxygen-containing coalbed methane and the returned coalbed methane product gas are mixed into a fixed-bed adiabatic catalytic reactor. The methane in the coalbed methane reacts with oxygen to generate carbon dioxide and water, thereby decomposing the The oxygen concentration in the product gas is reduced below 0.2%. The invention can effectively remove the oxygen in the oxygen-containing coalbed methane with an oxygen concentration of 1%-15%, the recovery rate of methane is close to the theoretical recovery rate calculated according to the complete conversion of methane and oxygen, and the low oxygen concentration in the product gas is completely eliminated The potential safety hazards in the subsequent coalbed methane separation (liquefaction, pressure swing adsorption, membrane separation, etc.) process were identified.

Description

A catalytic deoxidation process for oxygen-containing coal bed gas

technical field

The invention belongs to the field of chemistry, and in particular relates to a catalytic deoxidation process of oxygen-containing (O ₂ ) coal bed gas.

Background technique

Coalbed methane is a combustible gas adsorbed in coal seams, and its main component is high-purity methane (CH ₄ ). The existence of coalbed methane has brought great potential safety hazards to the safe production of coal mines. Therefore, it must be extracted or diluted before or during the coal mining process. Since coalbed methane usually does not contain sulfur, and does not contain carcinogenic toxic substances such as benzene, mercury, and lead, coalbed methane can replace conventional natural gas as a high-calorific value, pollution-free high-quality clean energy, and can be used as fuel for power generation and industrial fuel , vehicle fuel, chemical raw materials and residential fuel. At present, the utilization technology of coalbed methane with CH ₄ content above 60% is relatively mature; while coalbed methane with relatively low CH ₄ concentration and mixed with air can only be used on site, most of which are burned and vented. According to statistics, CH ₄ emitted from the coal mining industry in China reaches 19.4 billion m ³ every year, which causes a great waste of resources. In addition, _CH4 has 21 times the greenhouse effect of _CO2 . Therefore, if the medium and low concentration oxygen-containing coalbed methane can be processed, purified, transported and utilized, it will have significant economic and environmental benefits.

Coalbed methane purification technology refers to the separation of N ₂ or air from CH ₄ , so that the methane content in coalbed methane increases accordingly, thereby increasing the calorific value of coalbed methane and reducing transportation costs. CBM purification technologies mainly include low-temperature cryogenic separation, pressure swing adsorption and membrane separation. For pressure swing adsorption and membrane separation, high pressure is beneficial to the separation and purification of gases. However, the high operating pressure widens the explosion limit of methane, and the operation risk increases for the purification of such medium and low concentration oxygen-containing coalbed methane. Patents CN1952569A and CN1908559A disclose a low-temperature two-stage rectification liquefaction and separation process for air-containing coalbed methane. Both liquefaction and separation are carried out at low temperature, and the product purity of liquefied natural gas can reach more than 99%. However, during the separation process of this technology, as the concentration of methane increases, the oxygen content of the exhaust gas is also concentrated and increased. It is inevitable that there will be a stage that falls within the range of methane combustion and explosion, and there are great safety risks.

Therefore, a relatively safe separation and purification scheme is to remove the O ₂ in coalbed methane first and then carry out purification treatment. An effective deoxidation process is the safety guarantee for subsequent processes such as pressurized liquefaction and separation of coalbed methane. Currently available coalbed methane deoxidation methods mainly include catalytic deoxidation (ZL02113628.9, CN101139239A, etc.), coke combustion (ZL02113627.0, CN1919986A) and so on. Although the coalbed methane coke combustion method deoxidation process can effectively remove O ₂ in oxygen-containing coalbed methane, but this process uses coke as fuel (such as using anthracite instead of coke will bring SO ₂ emissions and other problems), and the energy consumption is high; The coke and dedusting process is also relatively complicated; the higher reaction temperature not only puts forward higher requirements on the material of the reactor, but also may lead to side reactions such as high-temperature cracking and reforming of CH ₄ , which reduces the recovery rate of CH ₄ in coalbed methane . All of these increase the cost of coke combustion deoxidation process.

The essence of the catalytic deoxygenation process is the catalytic combustion of CH ₄ in a fuel-rich and oxygen-poor atmosphere. The main reaction in this process is CH ₄ (g)+2O ₂ (g)=CO ₂ (g)+2H ₂ O(g)- 802.32kJ/mol, which is a strong exothermic reaction; at the same time, it can be seen from the thermodynamic analysis of the reaction system that when the reaction temperature exceeds 650 ° C, the steam reforming reaction of CH ₄ and the cracking carbon deposition reaction are more likely to occur. Therefore, how to remove a large amount of heat released during the reaction and control the temperature of the catalyst bed at a relatively low level (such as within 650°C) to reduce the occurrence of side reactions is the key to the catalytic deoxygenation process. The use of an isothermal bed reactor with internal components will lead to a sharp increase in the cost of reactor equipment; if an adiabatic bed reactor is used, a circulating reactor and a part of the product gas circulation process are inevitable choices. Patent CN101139239A discloses a sulfur-resistant catalytic deoxidation process for methane-rich gas, which reduces the oxygen concentration and controls the reaction temperature by circulating the partially deoxygenated cooled gas. However, this process uses a manganese-based sulfur-resistant deoxidation catalyst. In order to maintain the activity of the catalyst to achieve the required deoxidation depth, a higher reaction temperature and a lower reaction space velocity must be adopted. A higher reaction temperature will increase the chance of side reactions of CH ₄ and reduce the recovery rate of CH ₄ ; a lower reaction space velocity will make the reactor equipment bulky and increase the cost of coalbed methane deoxygenation. In addition, the use of non-precious metal catalysts will make it difficult to start the catalytic deoxygenation reaction; granular catalysts increase the resistance drop of the bed, which is not conducive to the coalbed methane deoxygenation process with low inlet pressure. The above-mentioned problems all reduce the feasibility of the technical solution of the catalytic deoxidation process.

In view of this, it is necessary to develop a more efficient and practical coalbed methane catalytic deoxygenation cycle process to further improve the technical feasibility and reduce the deoxygenation cost in view of the process characteristics of large coalbed methane treatment capacity, low pressure head, and frequent and severe changes in oxygen concentration.

Contents of the invention

The purpose of the present invention is to provide a catalytic deoxidation process for oxygen-containing coalbed methane, which solves the potential safety hazards caused by the existence of _O2 in the process of coalbed methane liquefaction, storage and transportation, and can be applied to catalytic deoxidation of oxygen-containing coalbed methane and other Catalytic deoxygenation process of oxygen gas.

The invention provides a catalytic deoxidation process of oxygen-containing coal bed gas, including the low-temperature start-up process of the system, the process flow and process operation parameters;

details as follows:

By introducing a small strand of hydrogen preheated to 25-50°C into the oxygen-containing coalbed methane feed gas, it reacts with oxygen on the deoxidation catalyst, and the combustion exothermic preheats the catalyst bed to reach the light-off temperature of methane catalytic combustion; steady-state operation When the initial oxygen-containing coalbed methane and the recycled coalbed methane product gas are mixed into the fixed-bed adiabatic deoxygenation reactor equipped with a catalyst with a monolithic structure of precious metals, the methane in the coalbed methane reacts with oxygen under the action of the catalyst to form carbon dioxide and water, and the product gas After heat exchange/cooling to lower the temperature and remove the moisture contained in it, the qualified coalbed methane product gas is obtained; part of the product gas is returned to the inlet of the deoxygenation reactor at a certain circulation ratio and mixed with the initial oxygen-containing coalbed gas to control the inlet of the deoxygenation reactor The oxygen concentration of the coalbed gas; where:

(1-1) The volume percent concentration of oxygen in the oxygen-containing coalbed methane is 1%-15%;

(1-2) Oxygen volume percentage concentration in qualified coalbed methane product gas is less than 0.2% (preferably 0.1%);

(1-3) The operating pressure (gauge pressure) of the deoxygenation reactor is 0-10MPa, the inlet temperature of the catalyst bed is 250-450°C during steady state operation, and the outlet temperature of the catalyst bed is 450-650°C. The space velocity is 1,000-80,000hr ^-1 ; the preferred condition is that the operating pressure (gauge pressure) of the deoxygenation reactor is 0.01-0.03MPa, the inlet temperature of the catalyst bed is 285-325°C during steady-state operation, and the outlet of the catalyst bed The temperature is 550-650°C, and the volumetric reaction space velocity is 30,000-50,000hr ^-1 .

(1-4) The CBM product gas undergoes at least two stages of heat exchange/cooling to reduce its temperature to 30-50°C and remove its contained moisture;

(1-5) The ratio of the volume flow rate of the recycled coalbed methane product gas to the initial oxygen-containing coalbed gas is 0:1 to 6:1.

In the coalbed methane deoxidation catalyst provided by the present invention, the noble metal integral structure catalyst refers to containing one or more catalytically active components of platinum group noble metals Pd, Pt, Ru, Rh, Ir, and the carrier is cordierite honeycomb ceramics, molybdenum Catalysts for stone honeycomb ceramics, Al ₂ O ₃ honeycomb ceramics, metal honeycombs, metal foams and other inert materials with regular structures.

The coalbed methane deoxidation catalyst provided by the present invention, said heat exchange/cooling device includes at least one high-temperature gas-gas heat exchanger or waste heat boiler, and at least one low-temperature gas-liquid heat exchanger; high-temperature gas-gas heat exchanger or waste heat boiler The outlet gas temperature of the deoxygenation reactor can be cooled to 150-500°C; the low-temperature gas-liquid heat exchanger can cool the outlet gas temperature of the high-temperature gas-gas heat exchanger or waste heat boiler to 30-50°C.

In the coalbed methane deoxidation catalyst provided by the invention, the ratio of the volume flow rate of the recycled coalbed methane product gas to the initial oxygen-containing coalbed methane is 0:1 to 4:1. Gas circulation can be done in a number of ways. For example, the recycled coalbed methane product gas is the coalbed methane product gas after heat exchange/cooling and dehydration. This gas exchanges heat with the high-temperature reaction gas for preheating, and then mixes with the normal temperature raw material gas into the reactor. As another example, the recycled coalbed methane product gas is the high-temperature gas at the outlet of the deoxidation reactor, and this gas is mixed with the normal-temperature raw material gas and enters the reactor.

The coalbed methane deoxidation catalyst provided by the present invention has two methods for the low-temperature start-up process. One method is to directly introduce a small strand of _H2 accounting for 4-10% of the volume flow rate of the coalbed methane raw material gas into the initial coalbed methane raw material gas, Oxygen and hydrogen in the coalbed methane are burned on the deoxidation catalyst to exothermic and preheat the bed to 250-450°C to reach the light-off temperature of the catalytic combustion of methane; another way is to preheat to 30-50 Introduce small strands of H ₂ , which account for 4-10% of the volume flow rate of the raw material gas of CBM, into the initial CBM raw material gas at ℃, and the oxygen and hydrogen in the CBM are burned on the deoxidation catalyst to release heat and preheat the bed to 250-450℃, The light-off temperature for the catalytic combustion of methane is reached.

In the coalbed methane deoxidation catalyst provided by the present invention, the recycled coalbed methane product gas is the coalbed methane product gas after heat exchange/cooling and dehydration. The gas is mixed into the reactor; or the recycled coalbed methane product gas is the high-temperature gas at the outlet of the deoxidation reactor, and this gas is mixed with the normal temperature raw material gas into the reactor.

The process of the present invention can realize the ignition and start of the catalytic deoxidation reaction at low temperature, and can perform a stable and efficient deoxidation reaction under the conditions of low pressure, high space velocity and temperature less than 650°C, and finally deoxidize the volume percentage content of oxygen in oxygen-containing coalbed methane Divide to less than 0.2%. High catalyst activity, reaction space velocity, and low catalyst bed pressure drop increase the treatment capacity of oxygen-containing coalbed methane on the catalyst per unit volume, thereby reducing the cost of catalytic deoxygenation; low reaction temperature avoids the high reaction temperature of non-precious metal catalysts. The occurrence of secondary reactions such as cracking of CH ₄ into carbon and steam reforming improves the recovery rate of CH ₄ in coalbed methane. The process of the invention is particularly suitable for the catalytic deoxidation process of oxygen-containing coal bed gas with large processing capacity, low pressure head and frequent and severe changes in _O2 concentration.

Description of drawings

The drawings show the oxygen-containing coalbed methane circulation catalytic deoxidation process of the present invention, including two circulation modes.

Fig. 1 is part of the low-temperature circulation process of coalbed methane product gas, in which: 1 is the reactor; 2 is the circulation booster fan; 3 is the waste heat boiler or high-temperature heat exchanger; The returned coalbed methane product gas is the coalbed methane product gas after heat exchange/cooling and dehydration. The gas exchanges heat with the high-temperature reaction gas for preheating, and then mixes with the normal temperature raw material gas and sends it into the reactor by a low-temperature circulation fan; In some embodiments of the oxygen-containing coalbed methane catalytic deoxidation process described in the present invention, the normal-temperature raw material gas can also exchange heat with the high-temperature reaction gas in the high-temperature heat exchanger for preheating, and then mix with the circulating product gas and enter the reactor ;

Fig. 2 is part of the high-temperature circulation process of coalbed methane product gas, in which: 1 is the reactor; 2 is the circulating booster fan; 3 is the waste heat boiler or high-temperature heat exchanger; The returned coalbed methane product gas is the high-temperature gas at the outlet of the deoxidation reactor, which is mixed with the normal-temperature raw material gas and sent to the reactor by the high-temperature circulation fan.

Detailed ways

The following examples will further illustrate the present invention, but do not limit the present invention thereby.

Unless otherwise pointed out, all the numbers appearing in the specification and claims of the present invention, such as the inlet and outlet temperature ranges and pressure ranges of each unit equipment, and the volume percentages representing gas components should not be interpreted as absolutely accurate The value is within the error range understood by those skilled in the art and allowed by known techniques. The precise numerical values appearing in the specification and claims of the present invention should be construed as forming part of the embodiments of the present invention. While every effort has been made to ensure accuracy in the examples given herein, any measured value will inevitably contain errors necessarily resulting from the standard deviation found in various measuring techniques.

The reaction space velocity described in the present invention is defined as the volume flow rate of the reaction gas raw material (dry basis) entering the reaction system per hour divided by the volume of the catalyst. Expressed in GHSV, the unit is hr ^-1 .

The ignition and light-off temperature of the catalyst in the present invention means that under the reaction process conditions described in the specification of the present invention, when the catalyst bed reaches a certain temperature, the bed temperature suddenly rises sharply and finally the combustion of the catalyst can be stabilized. This temperature is defined as the catalyst ignition light-off temperature.

The de _-O2 conversion rate in the present invention is defined as the mole percentage of _O2 converted in the feed gas, that is, the mole percentage of the difference between the moles of _O2 in the feed gas and the product gas relative to the _O2 in the feed gas, and the unit is %.

The circulation ratio in the present invention refers to the ratio of the volume flow rate of the recycled coalbed methane product gas to the initial oxygen-containing coalbed gas, represented by R.

The essence of the CBM catalytic deoxidation process is the catalytic combustion of CH ₄ in a fuel-rich and oxygen-poor atmosphere. As we all know, CH ₄ molecule has a regular tetrahedral structure, which is a kind of organic compound that is difficult to activate. Therefore, how to realize the ignition and start of the catalytic deoxidation reaction of coal bed gas at a lower temperature is the primary problem to be solved in the technical solution of the present invention. Compared with various metal oxide, perovskite and hexaaluminate methane combustion catalysts, supported noble metal catalysts have higher catalytic activity, lower light-off temperature and better poison resistance. And it is widely used in the low-temperature light-off stage of CH ₄ catalytic combustion process.

The main reactions in the catalytic deoxidation process of coalbed methane are as follows:

CH ₄ (g)+2O ₂ (g)=CO ₂ (g)+2H ₂ O(g) (A)

This reaction is a strong exothermic reaction, and the heat release is 802.32kJ/mol. The concentration of O ₂ in oxygen-containing coalbed methane can sometimes be as high as 15%. According to thermodynamic calculations, if about 15% of O ₂ is directly removed, the adiabatic temperature rise of the gas will be about 1000°C, which may cause the temperature of the catalyst bed to reach 1300°C. ℃ or more. Such a high reaction temperature is unbearable for most catalysts and reactor materials. Therefore, how to remove a large amount of heat released in the reaction process is another key problem to be solved in the technical solution of the present invention. The use of an isothermal bed reactor with internal components will lead to a sharp increase in the cost of reactor equipment; if an adiabatic bed reactor is used, a circulating reactor and a part of the product gas circulation process are inevitable choices.

In addition to the above-mentioned main reaction (A) in the catalytic deoxidation process of coalbed methane, the following side reactions (B)-(F) may also occur within a certain temperature range:

CH ₄ +0.5O ₂ =CO+2H ₂ (partial oxidation of methane) (B)

CO+0.5O ₂ ＝CO ₂ (carbon monoxide combustion reaction) (C)

H ₂ +0.5O ₂ ＝H ₂ O (hydrogen combustion reaction) (D)

CH ₄ ＝C+2H ₂ (methane cracking reaction) (E)

CH ₄ +H ₂ O=CO+3H ₂ (steam reforming reaction of methane) (F)

According to the standard thermodynamic data of each reaction above, it can be calculated that in the temperature range of 250-1450 °C, the complete combustion reaction of CH ₄ (A) is dominant. When the temperature is lower than 650°C, the combustion reactions (C) and (D) of CO and H ₂ also account for a certain proportion; CH ₄ cracking carbon deposition reaction (E) and steam reforming reaction (F) basically do not react. When the temperature is higher than 650° C., reactions (E) and (F) may occur, and the rich CH ₄ atmosphere of the process of the present invention increases the chances of reactions (E) and (F) to occur. At the same time, the equilibrium concentrations of _H2 and CO increased and the yield of _CH4 decreased as the temperature increased. It can be seen that the lower reaction temperature helps to inhibit the occurrence of _CH4 cracking carbon deposition reaction and steam reforming reaction, reduce the _H2 and CO content in the deoxygenated coalbed methane product gas, improve the methane yield and the safety of operation sex. Another key point of the catalytic deoxidation process of the present invention is to control the temperature of the catalyst bed at a relatively low level (eg, within 650° C.) to reduce the occurrence of side reactions. The catalytic deoxidation process of the present invention will use a supported noble metal catalyst to achieve the above purpose.

In addition, in order to adapt to the gas source conditions of large flow rate and low pressure head of oxygen-containing coalbed methane, the catalyst bed must also have a low resistance drop. Compared with traditional granular catalysts, catalyst structures with regular geometric shapes, such as honeycomb catalysts, have advantages in obtaining lower catalyst bed resistance drop, so that the deoxygenation reaction can be operated at a higher volumetric reaction space velocity, The oxygen-containing coalbed methane treatment capacity of the catalyst per unit volume is increased, thereby reducing the cost of deoxygenation.

Based on the above considerations, the first aspect of the present invention provides a catalytic deoxygenation cycle process flow for oxygen-containing coalbed methane, see accompanying drawings 1 and 2. Accompanying drawing 1 and accompanying drawing 2 are only simple schematic diagrams of the technological process of the present invention, only disclose the most basic feature of the technological process of the present invention, wherein omit many details, for example automatic control system, sensor device, valve etc. Those skilled in the art can design more detailed integrated process drawings based on the basic characteristics of the process flow disclosed in the accompanying drawings.

According to the oxygen-containing coalbed methane catalytic deoxidation cycle process flow provided by the present invention, during steady-state operation, the oxygen-containing coalbed methane raw material gas and the coalbed methane product gas sent back by the pressurized circulation fan 2 are mixed into the deoxygenation reactor 1, and the coalbed methane The CH ₄ reacts with O ₂ under the action of a catalyst to generate CO ₂ and H ₂ O, and the product gas undergoes at least two stages of heat exchange/cooling to reduce its temperature to 30-50°C and remove its contained moisture to obtain O ₂ Qualified coalbed methane product gas with a concentration of less than 0.2% by volume; part of the product gas is returned to the inlet of the deoxygenation reactor 1 at a certain circulation ratio to mix with the initial oxygen-containing coalbed gas to control the oxygen concentration of the coalbed gas at the inlet of the deoxygenation reactor. In the above embodiment of the oxygen-containing coal bed gas catalytic deoxidation process, the heat exchange/cooling device includes at least one high-temperature gas-gas heat exchanger or waste heat boiler 3 and at least one low-temperature gas-liquid heat exchanger 4 . The high-temperature gas-gas heat exchanger or waste heat boiler 3 can cool the gas temperature at the outlet of the deoxidation reactor to 150-500°C. The low-temperature gas-liquid heat exchanger 4 can cool the temperature of the gas at the outlet of the high-temperature gas-gas heat exchanger or the waste heat boiler 3 to 30-50°C. Two ways can be used for gas circulation. For example, in some embodiments, the recycled coalbed methane product gas is the coalbed methane product gas after heat exchange/cooling and dehydration, and the gas exchanges heat with the high-temperature reaction gas for preheating , and then mixed with the normal temperature raw material gas into the reactor, that is, the product gas is circulated at low temperature; In other embodiments, the raw material gas at normal temperature is mixed with the circulating product gas, exchanged heat with the high-temperature reaction gas for preheating, and then enters the reactor.

The second aspect of the present invention provides a set of operating process parameters and conditions suitable for the above-mentioned oxygen-containing coalbed methane catalytic deoxygenation cycle process.

In the embodiment of the oxygen-containing coalbed methane catalytic deoxygenation cycle process described in the present invention, the deoxygenation reactor is a fixed-bed adiabatic reactor equipped with a noble metal monolithic catalyst, wherein the noble metal monolithic catalyst refers to a catalyst containing platinum group noble metals Pd, Pt , one or several catalytically active components in Ru, Rh, and Ir, and the carrier is a catalyst with structured inert materials such as cordierite honeycomb ceramics, mullite honeycomb ceramics, Al ₂ O ₃ honeycomb ceramics, metal honeycombs, and metal foams . For example, a preferred example of a supported noble metal monolithic catalyst is the platinum group noble metal Pd as the main catalytic active component, the CeO ₂ -La ₂ O ₃ binary composite oxide as the catalytic promoter, and the cordierite honeycomb ceramic as the physical support . However, in the deoxidation process described in the present invention, the catalyst can be, but not limited to, the above preferred examples, any noble metal monolithic catalyst with high low-temperature catalytic deoxidation activity and stability at a temperature lower than 650°C can be used It can be applied in the deoxidation process described in the present invention.

In the implementation of the oxygen-containing coalbed methane catalytic deoxidation process of the present invention, the volume _percent concentration of O in the oxygen-containing coalbed methane raw material can be changed between 1-15%, which is suitable for the _O2 concentration in the coalbed gas. great features. The operating pressure (gauge pressure) of the deoxygenation reactor is 0-10MPa, the inlet temperature of the catalyst bed is 250-450°C during steady state operation, the outlet temperature of the catalyst bed is 450-650°C, and the volumetric reaction space velocity is 1,000- 80,000hr ^-1 , low pressure and high space velocity are suitable for the characteristics of large coal bed methane raw gas treatment capacity and low pressure head, and can be operated at high load to reduce deoxygenation cost; and operation below 650°C can effectively eliminate CH ₄ cracking and steam reforming And other side reactions, improve CH ₄ recovery. In a preferred embodiment of the patent of the present invention, the operating pressure (gauge pressure) of the deoxygenation reactor is 0.01-0.03MPa, the inlet temperature of the catalyst bed during steady state operation is 285-325 ° C, and the outlet temperature of the catalyst bed is 550-650°C, the volumetric reaction space velocity is 30,000-50,000hr ^-1 .

In the embodiment of the oxygen-containing coalbed methane catalytic deoxidation process of the present invention, the ratio of the volume flow rate of the recycled coalbed methane product gas to the initial oxygen-containing coalbed methane is 0:1 to 6:1. In the preferred embodiment of the oxygen-containing coalbed methane catalytic deoxidation process of the present invention, the ratio of the volume flow rate of the recycled coalbed methane product gas to the initial oxygen-containing coalbed methane is 0:1 to 4:1, which should meet the requirements of Under the premise of using the catalyst, the cycle ratio should be reduced as much as possible to reduce the energy consumption of the booster fan.

The third aspect of the present invention provides a method for realizing the low-temperature start-up of the oxygen-containing coalbed gas catalytic deoxidation process system described in the present invention.

In order to realize the low-temperature start-up of the entire oxygen-containing coalbed methane catalytic deoxygenation process system, the present invention utilizes the characteristics of low ignition temperature of the hydrogen-oxygen catalytic combustion reaction, and introduces a small stream of hydrogen (H ₂ ) into the raw material gas of oxygen-containing coalbed methane to make the H ₂ React with O ₂ in the coalbed methane on the deoxidation catalyst, and the combustion exothermic preheats the catalyst bed to reach the light-off temperature of CH ₄ catalytic combustion, so that the whole deoxygenation system can be started smoothly, and the supply of H ₂ is stopped when the system is running stably. In some embodiments of the oxygen-containing coalbed methane catalytic deoxygenation process described in the present invention, the low-temperature start of the catalytic deoxygenation reaction is by directly introducing a small amount of 4-10% of the volume flow rate of the coalbed methane raw material gas into the oxygen-containing coalbed methane raw material gas. The H ₂ , O ₂ and H ₂ in the coalbed methane are burned on the deoxygenation catalyst to release heat and preheat the bed to 250-450°C, reaching the catalytic combustion light-off temperature of methane. In other embodiments, the low-temperature start-up of the catalytic deoxygenation reaction is by introducing a small stream of H ₂ accounting for 4-10% of the volume flow rate of the coalbed methane feedstock gas into the initial coalbed methane feedstock gas that has been preheated to 30-50°C. Oxygen and hydrogen in the deoxygenation catalyst are burned to release heat and preheat the bed to 250-450 ° C, reaching the light-off temperature of catalytic combustion of methane.

Example 1-Example 8

Embodiment 1-embodiment 8 has provided different coalbed methane product gas circulation modes and different coalbed methane raw material gas _O concentration, reaction bed inlet temperature, outlet temperature, inlet pressure, circulation ratio R, reaction space in the process of the present invention Influence of operating process parameters such as speed on the gas composition of the deoxygenated coalbed methane product, wherein Example 6 and Example 8 are comparative examples, which are not included in the protection of the present invention.

过程质谱仪在线检测。The catalysts used in the experiment in Example 1-Example 8 are all honeycomb ceramic monolithic catalysts with a weight percent composition of 0.2%Pd/15%CeO ₂ -5%La ₂ O ₃ /79.8% cordierite. CH ₄ , N ₂ , CO ₂ , CO and H ₂ in raw gas and product gas are detected by gas chromatography thermal conductivity detector; O ₂ in raw gas and product gas is detected by PROLINE

Process mass spectrometer online detection.

During the experiment, H ₂ , ^which accounts for 6% of the total flow rate of the above-mentioned feed gas, was first introduced into the raw material gas of coalbed methane. ₂ and O ₂ in coalbed methane start to react on the catalyst, and the combustion exothermic preheats the catalyst bed to reach the light-off temperature of CH ₄ catalytic combustion, so that the whole deoxygenation system starts smoothly, and the system stops supplying H ₂ when it is running stably. The experimental data of stable operation under various conditions are listed in Table 1 below. Wherein, the product gas circulation mode of embodiment 1-embodiment 6 is low-temperature circulation, and the circulation mode of embodiment 7 and embodiment 8 is high-temperature circulation.

As can be seen from Table 1, except embodiment 6 (comparative example 6) and embodiment 8 (comparative example 8), the embodiment that operates according to the process parameter of the present invention has all obtained better deoxidation effect, and coalbed methane product gas The O ₂ content in the gas is less than 1000ppm, that is, the de-O ₂ conversion rate is greater than 98.5%; at the same time, the H ₂ and CO content in the product gas is low, and the CH ₄ loss is small, which is close to the calculation based on the complete conversion of CH ₄ and O ₂ The theoretical recovery rate, thus ensuring a high _CH4 recovery rate. Comparing Comparative Example 6 and Comparative Example 8, it can be seen that although the _O2 content in the CBM product gas is also less than 1000ppm, due to the high operating temperature of the deoxidation reactor, side reactions such as _CH4 cracking carbon deposition and steam reforming are intensified , resulting in higher _H2 and CO content in the CBM product gas, which increases the difficulty of the subsequent CBM liquefaction process. It can be seen that the key point of the process of the present invention is to control the operating temperature of the deoxidation reactor within 650° C. by adjusting the circulation ratio of the coalbed methane product gas.

Table 1 Stable operation experimental data under various conditions in embodiment 1-embodiment 8

Example 9-Example 12

Embodiment 9-Example 12 give a comparison of the ignition and start-up performance of the catalytic deoxygenation reaction process system under different conditions. The catalyst used in the experiment is a honeycomb ceramic monolithic catalyst with a weight percent composition of 0.2%Pd/15%CeO ₂ -5%La ₂ O ₃ /79.8% cordierite, and the volume space velocity of the ignition gas source is 5,000hr ^-1 . It can be seen from the experimental data in Table 2 that, for the raw material gas of oxygen-containing coalbed methane (comparative example 12), under the conditions of this experiment, the deoxidation reaction can only be started if it is preheated to above 280°C. Adding a preheater to preheat the reaction raw materials before the deoxidizer undoubtedly increases the complexity of the deoxidation process. By introducing a certain amount of H ₂ into the raw material gas of coal bed methane, H ₂ and O ₂ in the coal bed methane start to react on the catalyst, and the combustion exothermic preheats the catalyst bed to reach the light-off temperature of CH ₄ catalytic combustion, which can make The whole deoxidation system started smoothly at a lower temperature.

Table 2 Ignition and start performance of catalytic deoxygenation reaction process system under different conditions

Claims (14)

1. a coalbed methane containing oxygen catalytic deoxidation process comprises system hypothermia starting process, technical process and process operation parameter;

Specific as follows:

Be preheating to 25-50 ℃ shallow bid hydrogen through in the coalbed methane containing oxygen virgin gas, introducing, with oxygen reaction, burning heat release preheating catalyst bed reaches the combustion initiation temperature of methane catalytic combustion on dehydrogenation catalyst; During steady state operation; Initial coalbed methane containing oxygen is mixed into the fixed bed adiabatic deoxidation reactor that the precious metal integer structure catalyst is housed with the coal-seam gas product gas that circulation is returned; Methane in the coal-seam gas and oxygen react under catalyst action and generate carbonic acid gas and water; Product gas to lower the temperature and to remove its contained moisture, obtains qualified coal-seam gas product gas through heat exchange/cooling; Portioned product gas is back to the deoxidation reactor inlet with certain recycle ratio and mixes the coal-seam gas oxygen concn with control deoxidation reactor inlet with initial coalbed methane containing oxygen; It is characterized in that:

(1-1) concentration of volume percent of oxygen is 1%-15% in the coalbed methane containing oxygen;

(1-2) in the qualified coal-seam gas product gas oxygen concentration of volume percent less than 0.2%;

(1-3) working pressure of deoxidation reactor is 0-10MPa, and the temperature in of beds is 250-450 ℃ during steady state operation, and the temperature out of beds is 450-650 ℃, and the volumetric reaction air speed is 1,000-80,000hr ^-1

(1-4) coal-seam gas product gas makes its temperature reduce to 30-50 ℃ and remove its contained moisture through two-stage heat exchange at least/cooling;

(1-5) the coal-seam gas product gas that returns of circulation is 0: 1 to 6: 1 with the ratio of the volumetric flow rate of initial coalbed methane containing oxygen.

2. according to the said coalbed methane containing oxygen catalytic deoxidation process of claim 1, it is characterized in that: the oxygen concentration of volume percent is less than 0.1% in the said qualified coal-seam gas product gas.

3. according to the said coalbed methane containing oxygen catalytic deoxidation process of claim 1; It is characterized in that: said precious metal integer structure catalyst is meant one or more catalytic active component that contain among platinum family precious metals pd, Pt, Ru, Rh, the Ir, and carrier is cordierite honeycomb ceramic, mullite ceramic honey comb, Al ₂O ₃The catalyzer of ceramic honey comb, metal beehive, some compound with regular structure inert materials of metal foam.

4. according to the said coalbed methane containing oxygen catalytic deoxidation process of claim 1; It is characterized in that: the working pressure of said deoxidation reactor is 0.01-0.03MPa; The temperature in of beds is 285-325 ℃ during steady state operation, and the temperature out of beds is 550-650 ℃, and the volumetric reaction air speed is 30; 000-50,000hr ^-1

5. according to the said coalbed methane containing oxygen catalytic deoxidation process of claim 1, it is characterized in that: said heat exchange/refrigerating unit comprises at least one pyritous gas-gas heat exchanger or waste heat boiler, and at least one cryogenic gas-liquid heat-exchange.

6. according to the said coalbed methane containing oxygen catalytic deoxidation process of claim 1, it is characterized in that: the coal-seam gas product gas that said circulation is returned is 0: 1 to 4: 1 with the ratio of the volumetric flow rate of initial coalbed methane containing oxygen.

7. according to the said coalbed methane containing oxygen catalytic deoxidation process of claim 1; It is characterized in that: said cold-starting process is through directly in initial coal-seam gas virgin gas, introducing shallow bid hydrogen; Oxygen in the coal-seam gas and hydrogen burn heat release preheating bed to 250-450 ℃ on dehydrogenation catalyst, reach the combustion initiation temperature of the catalyticcombustion of methane.

8. according to the said coalbed methane containing oxygen catalytic deoxidation process of claim 1; It is characterized in that: said cold-starting process is through in through the initial coal-seam gas virgin gas of well heater preheating, introducing shallow bid hydrogen; Oxygen in the coal-seam gas and hydrogen burn heat release preheating bed to 250-450 ℃ on dehydrogenation catalyst, reach the combustion initiation temperature of the catalyticcombustion of methane.

9. according to the said coalbed methane containing oxygen catalytic deoxidation process of claim 1; It is characterized in that: the coal-seam gas product gas that said circulation is returned is through the coal-seam gas product gas after heat exchange/cooled dehydrated; This strand gas and high-temperature reacting gas heat exchange are mixed into reactor drum with the normal temperature virgin gas then to carry out preheating.

10. according to the said coalbed methane containing oxygen catalytic deoxidation process of claim 1, it is characterized in that: the coal-seam gas product gas that said circulation is returned is the high-temperature gas of deoxidation reactor outlet, and this strand gas and normal temperature virgin gas are mixed into reactor drum.

11. according to the said coalbed methane containing oxygen catalytic deoxidation process of claim 5, it is characterized in that: said high temperature gas-gas heat exchanger or waste heat boiler are that the deoxidation reactor Outlet Gas Temperature is cooled to 150-500 ℃.

12. according to the said coalbed methane containing oxygen catalytic deoxidation process of claim 5, it is characterized in that: said low temperature gas-liquid heat-exchange is that high temperature gas-gas heat exchanger or waste heat boiler Outlet Gas Temperature are cooled to 30-50 ℃.

13. according to claim 7 or 8 said coalbed methane containing oxygen catalytic deoxidation process, it is characterized in that: the said amounts of hydrogen that infeeds is the 4-10% of initial coal-seam gas feed gas volume flow.

14. according to the said coalbed methane containing oxygen catalytic deoxidation process of claim 8, it is characterized in that: the preheating temperature of said initial coal-seam gas virgin gas is 30-50 ℃.

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