CN110385018B - Nondestructive drying method for post-circulation reaction gas in methane preparation of chloromethane - Google Patents
Nondestructive drying method for post-circulation reaction gas in methane preparation of chloromethane Download PDFInfo
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Abstract
The invention discloses a nondestructive drying method for postpositional circulating reaction gas in methane-process chloromethane, which comprises the circulating operation steps of adsorption, thermal regeneration treatment and cold regeneration treatment of each adsorption tower, wherein the dehydration depth reaches below 10ppm for the systematic moisture accumulation and corresponding accumulation of other inert impurity components caused by the circulating reaction gas which is used in large quantity in the manufacturing process, the thermal regeneration carrier gas and the generated thermal regeneration waste gas are obtained and recycled in a system, and the effective component methane is not lost while the circulating reaction gas is dried and dehydrated, and the cold and hot regeneration waste gases are recycled.
Description
Technical Field
The invention relates to the field of adsorption, drying and dehydration of natural gas and circulating reaction gas in the process of preparing chloromethane series products by a fine chemical methane method, in particular to a nondestructive drying method of post-circulating reaction gas in the process of preparing chloromethane by the methane method.
Background
Methyl Chloride (CMS) is a widely used basic chemical raw material and product, including methyl chloride, methylene chloride, trichloromethane and tetrachloromethane, and is mainly used for the production of organic silicon, methyl cellulose, tetramethyl lead, herbicide, butyl rubber, organic solvent, organic synthetic material and refrigerant, and the production process mainly includes methanol method and methane method. The methane method mainly uses natural gas as a raw material and reacts with chlorine under certain conditions to generate CMS.
In the process of preparing CMS by a methane method, the water content of the CMS product exceeds standard, for example, the water content of methane chloride exceeds 300-500 ppm, the water content of dichloromethane exceeds 200-400 ppm and the like, the water content of the best carbon tetrachloride generally exceeds 50-100 ppm, and the purity and the application of the CMS product are influenced; compared to the methanol process, all CMS products have less than 50ppm water. Therefore, the control technology of water content in the process of producing CMS by methane method is very important.
The main reason that the moisture content of the CMS prepared by the methane method exceeds the standard is that firstly, the raw material methane and the moisture contained in the circulating reaction gas are used as raw materials to produce methyl chloride, natural gas is the main raw material gas, the lower the pressure of the natural gas is, the higher the moisture content is, and the raw material natural gas needs to be dried and dehydrated to ensure that the moisture content is less than 10 ppm; meanwhile, CMS products formed by methane chlorination, hydrochlorination or oxychlorination reaction and process water generated by accumulation in the circulating reaction gas are directly heated, and water brought by CMS in the simple distillation recovery kettle liquid enters into a crude chlorination liquid and a system; secondly, neutralizing moisture introduced by the process pipeline by using raw material gas chlorine; thirdly, high boiling point substances generated in the preparation of CMS by the methane method mainly comprise impurity components such as tetrachloroethylene and hexachloroethane, most of the impurity components are high hydrocarbon exceeding of the above-carbon (C2+) component in raw material gas methane, or chlorination side reactions caused by cracking of partial CMS due to poor control of chlorination reaction parameters are increased, the impurities are gradually accumulated in a CMS rectifying tower to further form blockage of equipment such as a tower, and water or steam is required to be added to the rectifying tower, so that residual water is introduced into a system, especially, the equipment is corroded due to accumulation in crude chlorination liquid, the service life of the equipment such as the tower and a pipeline is shortened, and the quality is reduced due to increase of acidity in a product.
The methane process for preparing CMS controls the water content of the product and there are several approaches:
firstly, carrying out hydrocarbon removal, dehydration and purification on raw material gas methane, and carrying out temperature swing adsorption to ensure that the content of C2+ impurity components is less than 100-200 ppm and the moisture content is less than 10 ppm;
secondly, changing a chlorine raw material into liquid chlorine, and enabling the water content of the liquid chlorine to be less than 10-20 ppm through ultraviolet low-temperature liquid-phase photochlorination and the like;
thirdly, by utilizing the characteristic that CMS and water form an azeotrope, azeotropic distillation is adopted, so that the moisture in the crude chlorination solution is further reduced, a high-quality intermediate material is provided for downstream production, the moisture can be prevented from being introduced into a system, the energy consumption is further increased, and the production cost is greatly increased;
fourthly, the CMS product is directly dried and dehydrated by adopting an adsorption method, including liquid phase or gas phase adsorption or resin exchange. This method is to treat the final result, and because CMS contains trace or trace amount of high boiling substance and aqueous solution of hydrogen chloride, it has great negative effect on the efficiency of adsorbent usage including service life, and the dehydration depth of CMS is limited.
In summary, the prior art scheme for controlling the water content in the process of preparing CMS by methane method mainly processes raw material gas or final product, but does not have a corresponding processing scheme or an effective drying method for drying the circulating reaction gas and avoiding methane waste caused by drying for the systematic water accumulation and corresponding accumulation of other inert impurity components caused by the circulating reaction gas used in large amount in the manufacturing process.
Disclosure of Invention
The invention aims to: aiming at the problems of systematic moisture accumulation and corresponding accumulation of other inert impurity components caused by methane circulating reaction gas in the production process of preparing methyl Chloride (CMS) by a methane method, a corresponding processing scheme is not provided, and an effective drying method is not provided, so that the reaction circulating gas can be dried, and the problem of methane waste caused by drying can be avoided.
A nondestructive drying method for postpositional circulating reaction gas in methane-process chloromethane preparation comprises the circulating operation steps of adsorption, thermal regeneration treatment and cold regeneration treatment of each adsorption tower, and specifically comprises the following steps: gas-liquid separation, namely introducing the circulating reaction gas after methane chlorination into a first gas-liquid separator, discharging a small amount of water and water-soluble liquid flowing out of the bottom, and dividing the moisture into moisture I and moisture II, wherein the circulating reaction gas flowing out of the top is the moisture;
a) adsorbing, namely directly feeding the moisture I into the top of an adsorption tower which is formed by connecting in parallel through a pressure regulating valve and a first program control valve, wherein the adsorption tower is in an adsorption step, the adsorption operation temperature is 10-60 ℃, the adsorption operation pressure is 0.3-1.5 MPa, and discharging dried product gas from the bottom of the adsorption tower in the adsorption step through a second program control valve;
b) pre-adsorbing the regeneration gas, namely allowing moisture II or methane raw material gas required by the reaction of preparing methyl chloride by using a methane method to pass through a moisture pressure regulating valve and a third program control valve, allowing the moisture II or the methane raw material gas to enter a pre-adsorption drying tower for pre-adsorption drying, allowing the adsorption operation temperature to be 10-60 ℃ and the adsorption operation pressure to be 0.3-1.5 MPa, allowing the gas to flow out of the pre-adsorption tower through a two-way valve, allowing the gas to enter a heater for heating to 120-220 ℃, and taking the gas as the thermal regeneration carrier gas of the adsorption tower for completing the adsorption step;
c) performing thermal regeneration treatment, namely allowing the thermal regeneration carrier gas in the step c) to pass through a fourth program control valve, entering an adsorption tower in which the adsorption step is completed to perform thermal regeneration treatment from the adsorption tower, wherein the operation temperature of the thermal regeneration treatment is 120-220 ℃, the operation pressure is 0.3-1.5 MPa, then flowing out thermal regeneration waste gas from the adsorption tower, allowing the thermal regeneration waste gas to pass through a fifth program control valve, entering a cooler to be cooled to 10-60 ℃, then entering a second gas-liquid separator to perform gas-liquid separation, and flowing out from the top to obtain cold regeneration carrier gas;
d) cold regeneration treatment, namely returning the cold regeneration carrier gas in the step d) to the moisture after the pressure regulating valve, enabling the cold regeneration carrier gas to pass through a sixth program control valve, enabling the cold regeneration carrier gas to enter the adsorption tower after the heat regeneration treatment step to perform cold regeneration, enabling the cold regeneration carrier gas to flow out of the bottom of the adsorption tower at the operating temperature of 10-60 ℃ and the operating pressure of 0.3-1.5 MPa, and enabling the cold regeneration carrier gas to reversely enter a heater E through a seventh program control valve to be heated to 120-220 ℃ to obtain preheated regeneration carrier gas;
e) and (3) pre-adsorption heat regeneration, namely reversely feeding the pre-heated regeneration carrier gas into the pre-adsorption tower from the bottom of the pre-adsorption tower which is subjected to the pre-adsorption step for pre-adsorption heat regeneration, wherein the operating temperature of the pre-adsorption heat regeneration is 120-220 ℃, the operating pressure is 0.3-1.5 MPa, feeding the pre-heated regeneration waste gas flowing out of the top of the pre-adsorption tower into a cooler through an eighth program control valve, cooling to 10-60 ℃, then feeding the pre-heated regeneration waste gas into a second gas-liquid separator for gas-liquid separation, and feeding the cooled gas flowing out of the top of the pre-heated regeneration waste gas into moisture returned to a pressure regulating valve as cold regeneration carrier gas for recycling, so that the adsorption drying cycle operation is completed.
After passing through a product gas buffer tank, or after being subjected to pressure regulation, the product gas serving as the circulating reaction gas directly returns to the CMS reactor for reaction, or returns to a natural gas pressure swing adsorption dealkylation purification system for dealkylation purification and then enters the CMS reactor for reaction, or enters a denitrification system for removing accumulated nitrogen and then enters the CMS reactor for reaction after being subjected to pressure regulation.
Preferably, the adsorbent filled in the adsorption tower is one or more of aluminum oxide, silica gel and molecular sieve, and forms a composite bed layer.
Preferably, the volume ratio of the moisture I to the moisture II is (5-4): (0 to 1).
Preferably, the adsorption tower comprises 3 adsorption towers and 1 pre-adsorption tower which are formed in parallel, namely an adsorption tower A, an adsorption tower B, an adsorption tower C and a pre-adsorption tower D, each adsorption tower is subjected to adsorption, pressure reduction, thermal regeneration treatment, isolation, cold regeneration treatment and pressure increase, specifically, when the adsorption tower A is in the adsorption step, the corresponding adsorption tower B is subjected to the three steps of isolation, cold regeneration treatment and pressure increase in sequence, and the corresponding adsorption tower C is subjected to the pressure reduction and thermal regeneration treatment in sequence and then is in the isolation step; after the adsorption step of the adsorption tower A is finished, the steps of pressure reduction and thermal regeneration treatment are carried out in sequence, then the adsorption tower A is in the isolation step, the corresponding adsorption tower B is in the adsorption step, and the corresponding adsorption tower C is subjected to the steps of isolation, cold regeneration treatment and pressure increase in sequence; when the adsorption tower A sequentially undergoes the steps of isolation, cold regeneration treatment and pressure rise, the corresponding adsorption tower B sequentially undergoes the steps of pressure reduction and heat regeneration treatment and is in the isolation step, and the corresponding adsorption tower C is in the adsorption step, so that the adsorption tower A, the adsorption tower B and the adsorption tower C cyclically perform temperature change operation and simultaneously perform pressure change operation, and the system continuously operates to flow out dried and dehydrated product gas.
Furthermore, in the cycle operation steps or cycle sequences of adsorption, pressure reduction, heat regeneration treatment, isolation, cold regeneration treatment and pressure increase performed by the adsorption tower a, the adsorption tower B and the adsorption tower C respectively, the adsorption tower a, the adsorption tower B or the adsorption tower C in the isolation step, a program control valve or a pressure regulating valve connected with the adsorption tower a, the adsorption tower B or the adsorption tower C are all closed, and a part of heat regeneration waste gas directly enters the pre-adsorption tower D through a bypass for heat regeneration.
Preferably, the nondestructive drying steps of the adsorption tower A, the adsorption tower B and the adsorption tower C can be cyclic operation steps of adsorption, depressurization, thermal regeneration treatment, cold regeneration treatment and pressurization. I.e. no isolation operation is performed.
Preferably, any two of the adsorption tower A, the adsorption tower B and the adsorption tower C are subjected to adsorption drying cycle operation, and one of the adsorption towers serves as a standby tower.
Preferably, the flow direction of the hot regeneration carrier gas in the adsorption column is the same as or opposite to the flow direction of the moisture i of the adsorption step in the adsorption column.
Preferably, the flow direction of the cold regeneration carrier gas in the adsorption tower is the same as or opposite to the flow direction of the moisture i of the adsorption step in the adsorption tower.
Preferably, the flow directions of the hot regeneration carrier gas and the cold regeneration carrier gas are consistent and opposite to the flow direction of the moisture I.
Preferably, the product gas is connected with the hot regeneration waste gas, the cold regeneration waste gas and the preheated regeneration waste gas through discharge ports. So as to prevent safety problems caused by excessive accumulation of inert impurity components during the circulation, the regeneration waste gas is partially discharged directly, and the system operation is changed from lossless drying to a general drying system.
Furthermore, the wet gas feeding valve of the pre-adsorption tower is closed, the pre-adsorption tower is used as a regenerated waste gas dryer in the adsorption cycle operation process, the product gas is used as hot regenerated carrier gas after passing through a heater or directly used as cold regenerated carrier gas, and the regenerated waste gas is dried and dehydrated for cyclic utilization.
The technical scheme adopted by the invention is as follows:
in summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
(1) aiming at the problems that in the current methane method for preparing methyl Chloride (CMS), raw material gas or a final product is mainly treated, including the drying of the raw material gas methane or the drying of the final product CMS, and no corresponding treatment scheme exists for the systematic moisture accumulation and the accumulation of other corresponding inert impurity components caused by a large amount of used circulating reaction gas in the manufacturing process, the method makes up for the blank and ensures that the dehydration depth is less than 10 ppm;
(2) in the nondestructive drying scheme provided for preparing the circulating reaction gas in the methyl chloride by the methane method, the thermal regeneration carrier gas and the generated thermal regeneration waste gas are obtained and recycled in the system, and the effective component methane is not lost while the circulating reaction gas is dried and dehydrated, and the cold and hot regeneration waste gases are recycled;
(3) the invention can selectively arrange the flowing directions of the raw material gas, namely moisture, the regeneration carrier gas during heating regeneration and the regeneration carrier gas during cooling regeneration in the adsorption tower according to the composition of the circulating reaction gas and the drying degree of the product gas, so as to carry out lossless drying and save energy consumption;
(4) the pre-adsorption tower can be used for adjusting the circulation proportion of the circulating reaction gas and treating and recycling the regenerated waste gas;
(5) in the drying dehydration, desorption gas purified by methane PSA in the process of preparing CMS by a methane method can be used as regeneration gas, and dry regeneration tail gas can be used as regeneration gas through a pre-adsorption drying tower, so that 'lossless' drying is realized; not only can adopt four-tower operation, but also can adopt three-tower operation; meanwhile, reasonable matching of adsorption and desorption can be realized by adopting a way of pressure variation and temperature variation in a drying time sequence, so that the drying effect is better.
Drawings
The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a schematic flow chart of example 1 of the present invention;
FIG. 2 is a schematic flow chart of example 5 of the present invention;
FIG. 3 is a schematic flow chart of example 6 of the present invention.
Detailed Description
All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.
The present invention will be described in detail with reference to FIGS. 1 to 3 and tables 1 and 2.
Example 1
As shown in fig. 1, a nondestructive drying method of post-circulating reaction gas in methane production of methyl chloride comprises the following steps:
a) gas-liquid separation, namely, a circulating reaction gas formed by methane chlorination reaction is fed into a first gas-liquid separator 1 at the temperature of 20-40 ℃ and the pressure of 0.8-1.0 MPa, a small amount of water and water-soluble liquid flow out from the bottom and discharged, a wet circulating reaction gas (hereinafter referred to as 'wet gas') flows out from the top, the water content of the gas is 500-600 ppm, the water-soluble organic volatile matter is about 200ppm, 2.6 percent of nitrogen (volume ratio, the same below), 97.2 percent of methane, and the balance of trace carbon monoxide, carbon dioxide, oxygen, argon, helium and the like, and the flow rate is 6,560Nm3H, dividing the wet gas I and the wet gas II into two parts to enter the subsequent step;
b) adsorbing, wherein 80% of moisture from the first gas-liquid separator 1 directly passes through a moisture pressure regulating valve and a first program control valve A1 and enters the top of an adsorption tower A in an adsorption step in an adsorption tower A, B, C composed of three parallel connection bodies for adsorption drying, the adsorption operation temperature is 20-40 ℃, the adsorption operation pressure is 0.8-1.0 MPa, the dehydrated and dried dry gas flows out of the bottom of the adsorption tower A through a second program control valve A5 and a dry gas pressure regulating valve, the dehydration depth is less than 10ppm, and the dehydrated and dried dry gas serving as a product gas passes through a product gas buffer tank and then returns to a methyl Chloride (CMS) reactor as a circulating reaction gas for reaction;
c) the regeneration gas is pre-adsorbed, 20% of moisture from the first gas-liquid separator 1 directly enters the top of a pre-adsorption drying tower D through a third program control valve D1 for pre-adsorption drying, the adsorption operation temperature is 20-40 ℃, the adsorption operation pressure is 0.8-1.0 MPa, the moisture flows out of the bottom of the pre-adsorption tower D through a two-way valve and directly enters a heater E for heating to 160-200 ℃, and the moisture is used as heat regeneration carrier gas of an adsorption tower A for completing the adsorption step for heat regeneration treatment (hot blowing);
d) performing thermal regeneration treatment (hot blowing), feeding thermal regeneration carrier gas (hot blowing gas) from the pre-adsorption step into an adsorption tower A in a reverse direction (opposite to the feeding direction of the feeding gas in the adsorption step) from the bottom of the adsorption tower A completing the adsorption step through a fourth program control valve A4 to perform thermal regeneration or hot blowing, wherein the operation temperature of the thermal regeneration is 160-200 ℃, the operation pressure is 0.8-1.0 MPa, and the thermal regeneration waste gas flowing out of the top of the adsorption tower A enters a cooler F through a fifth program control valve A2 to be cooled to 20-40 ℃ and then enters a second gas-liquid separator 2 to perform gas-liquid separation;
e) cold regeneration treatment (cold blowing), discharging water and water-soluble liquid which flow out of the second gas-liquid separator 2, returning cooled gas which flows out of the top of the second gas-liquid separator as cold regeneration carrier gas (cold blowing gas) to moisture after the pressure regulating valve, enabling the cooled gas to enter the adsorption tower A which completes the hot regeneration step from the top of the adsorption tower A (the same as the feeding direction of the feeding gas in the adsorption step) in the forward direction through a fifth program control valve A3 for cold regeneration or cold blowing, enabling the cold regeneration operation temperature to be 20-40 ℃, enabling the operation pressure to be 0.8-1.0 MPa, enabling cold regeneration waste gas which flows out of the bottom of the adsorption tower A to reversely enter a heater E through a seventh program control valve A4, and heating the cold regeneration waste gas to 160-200 ℃;
f) and (2) performing pre-adsorption thermal regeneration, namely reversely feeding the regenerated waste gas generated in the cold regeneration step heated to 160-200 ℃ by a heater E into the pre-adsorption tower D from the bottom of the pre-adsorption tower D after the pre-adsorption step is finished, performing thermal regeneration in the tower in a reverse direction (opposite to the feeding direction of the feeding gas in the pre-adsorption step), wherein the operation temperature of the thermal regeneration is 160-200 ℃, the operation pressure is 0.8-1.0 MPa, feeding the hot regenerated waste gas flowing out of the top of the pre-adsorption tower D into a cooler F through a sixth program control valve D2, cooling to 20-40 ℃, then feeding the cooled waste gas into a second gas-liquid separator 2 for gas-liquid separation, discharging water and water-soluble liquid from the bottom of the separator, and feeding the cooled gas flowing out of the top into moisture after being used as a cold regeneration carrier gas (cold blowing gas) pressure regulating valve for recycling. Therefore, the adsorption tower A completes all steps of circulating reaction gas and drying without damage;
a step of drying the adsorption column B, C without damage, which corresponds to the step of the adsorption column a, in which the adsorption column a is in the adsorption step, the corresponding adsorption column B is in the cold regeneration step, and the corresponding adsorption column C is in the hot regeneration step; the adsorption tower A is in the thermal regeneration step, the corresponding adsorption tower B is in the adsorption step, and the corresponding adsorption tower C is in the cold regeneration step; the adsorption tower A is in a cold regeneration step, the corresponding adsorption tower B is in a hot regeneration step, and the corresponding adsorption tower C is in an adsorption step; meanwhile, the corresponding first gas-liquid separator 1 and second gas-liquid separator 2, the pre-adsorption tower E, the heater E and the cooler F respectively perform corresponding operations. Thus, the three adsorption columns A, B, C are operated circularly, the system is operated continuously to flow out the dried and dehydrated product gas, namely the circulating reaction gas, and the effective component methane in the dried circulating reaction gas is not lost and is returned to the CMS reactor for circulation and reaction.
Example 2
Based on example 1, as shown in fig. 1, the moisture flowing out of the top of the first gas-liquid separator 1 is all fed into the adsorption step, and the feed gas of the pre-adsorption step is the methane feed gas required for CMS reaction, instead of 20% of the moisture flowing out of the top of the first gas-liquid separator 1, thereby increasing the proportion of the recycled reaction gas.
Example 3
Based on the adsorption, thermal regeneration and cold regeneration cycle operation steps or cycle sequence of the three adsorption towers A, B, C shown in table 1 in example 1, the steps are further optimized to be adsorption, depressurization, thermal regeneration, isolation, cold regeneration and pressurization, wherein the steps of depressurization to normal pressure and pressurization to 0.8-1.0 MPa, the temperatures of thermal regeneration and cold regeneration are respectively 160-200 ℃ and 20-40 ℃, the specific cycle sequence is that when an adsorption tower a is in the adsorption step, the corresponding adsorption tower B undergoes the three steps of isolation, cold regeneration and pressurization in sequence, and the corresponding adsorption tower C undergoes the steps of depressurization and thermal regeneration in sequence and is in the isolation step; after the adsorption step of the adsorption tower A is finished, the steps of pressure reduction and thermal regeneration are carried out in sequence, then the step is in an isolation step, the corresponding adsorption tower B is in an adsorption step, and the corresponding adsorption tower C is subjected to the steps of isolation, cold regeneration and pressure increase in sequence; when the adsorption tower A sequentially undergoes the steps of isolation, cold regeneration and pressure rise, the corresponding adsorption tower B sequentially undergoes the steps of pressure reduction and heat regeneration and is in the isolation step, and the corresponding adsorption tower C is in the adsorption step, so that the three adsorption towers A, B, C perform pressure swing operation while performing temperature swing operation in a circulating manner, the system continuously operates to flow out dried and dehydrated product gas, namely circulating reaction gas, and effective component methane in the dried circulating reaction gas is not lost and returns to the CMS reactor for circulating use to perform reaction.
Table 1 schematic flow chart of example 3 of the present invention
Example 4
Based on examples 1 and 3, as shown in table 2, the cyclic operation steps or the cyclic timing sequence of the adsorption, pressure reduction, thermal regeneration, isolation, cold regeneration and pressure increase of the three adsorption columns A, B, C are further optimized to be the cyclic operation steps or the cyclic timing sequence of the adsorption, pressure reduction, thermal regeneration, cold regeneration and pressure increase.
Table 2 is a schematic flow chart of example 4 of the present invention
Example 5
Based on example 1, as shown in fig. 2, in the circulation operation step of the three adsorption towers A, B, C, the flow direction of the hot regeneration carrier gas and/or the cold regeneration carrier gas in the adsorption tower and the flow direction of the feed gas or the moisture in the adsorption tower in the adsorption step can be adjusted to be the same as the flow direction of the hot regeneration carrier gas and the cold regeneration carrier gas in the present case, and opposite to the flow direction of the moisture, that is, the moisture enters the adsorption tower from the top of the adsorption tower A, B, C, and enters the adsorption tower from the bottom of the hot cold regeneration carrier gas adsorption tower and flows out from the top of the adsorption tower in the direction corresponding to the flow direction of the moisture flowing out from the bottom of the adsorption tower. The flow direction of the moisture in the pre-adsorption tower is consistent with the flow direction of the moisture in the adsorption step. Under the condition, the adsorption time is adjusted to be shorter than that of the example 1, and the fluctuation of the water content in the moisture is not large, so that the water content of the product gas can be controlled below 10 ppm.
Example 6
Based on example 1, as shown in fig. 3, the three adsorption columns A, B, C are switched to two adsorption columns A, B to perform adsorption drying cycle operation, the adsorption column C is used as a spare column, and the pre-adsorption column D is used as an adsorption drying column for regeneration waste gas, so that the circulation ratio of the circulating reaction gas can be adjusted to be small.
The above description is only a preferred embodiment of the present invention, and not intended to limit the present invention, and the scope of the present invention is defined by the appended claims, and all changes that come within the meaning and range of equivalency of the specification are therefore intended to be embraced therein.
Claims (10)
1. A nondestructive drying method for postpositional circulating reaction gas in methane-process chloromethane is characterized in that the nondestructive drying step comprises the circulating operation steps of adsorption, thermal regeneration treatment and cold regeneration treatment of each adsorption tower, and specifically comprises the following steps:
a) gas-liquid separation, namely introducing the circulating reaction gas after methane chlorination into a first gas-liquid separator, discharging a small amount of water and water-soluble liquid flowing out of the bottom, and dividing the moisture into moisture I and moisture II, wherein the circulating reaction gas flowing out of the top is the moisture;
b) adsorbing, namely directly feeding the moisture I into the top of an adsorption tower which is formed by connecting in parallel through a pressure regulating valve and a first program control valve, wherein the adsorption tower is in an adsorption step, the adsorption operation temperature is 10-60 ℃, the adsorption operation pressure is 0.3-1.5 MPa, and discharging dried product gas from the bottom of the adsorption tower in the adsorption step through a second program control valve;
c) pre-adsorbing the regeneration gas, namely allowing moisture II or methane raw material gas required by the reaction of preparing methyl chloride by using a methane method to pass through a moisture pressure regulating valve and a third program control valve, allowing the moisture II or the methane raw material gas to enter a pre-adsorption drying tower for pre-adsorption drying, allowing the adsorption operation temperature to be 10-60 ℃ and the adsorption operation pressure to be 0.3-1.5 MPa, allowing the gas to flow out of the pre-adsorption tower through a two-way valve, allowing the gas to enter a heater for heating to 120-220 ℃, and taking the gas as the thermal regeneration carrier gas of the adsorption tower for completing the adsorption step;
d) performing thermal regeneration treatment, namely allowing the thermal regeneration carrier gas in the step c) to pass through a fourth program control valve, entering an adsorption tower in which the adsorption step is completed to perform thermal regeneration treatment from the adsorption tower, wherein the operation temperature of the thermal regeneration treatment is 120-220 ℃, the operation pressure is 0.3-1.5 MPa, then flowing out thermal regeneration waste gas from the adsorption tower, allowing the thermal regeneration waste gas to pass through a fifth program control valve, entering a cooler to be cooled to 10-60 ℃, then entering a second gas-liquid separator to perform gas-liquid separation, and flowing out from the top to obtain cold regeneration carrier gas;
e) cold regeneration treatment, namely returning the cold regeneration carrier gas in the step d) to the moisture after the pressure regulating valve, enabling the cold regeneration carrier gas to pass through a sixth program control valve, enabling the cold regeneration carrier gas to enter the adsorption tower after the heat regeneration treatment step to perform cold regeneration, enabling the cold regeneration carrier gas to flow out of the bottom of the adsorption tower at the operating temperature of 10-60 ℃ and the operating pressure of 0.3-1.5 MPa, and enabling the cold regeneration carrier gas to reversely enter a heater E through a seventh program control valve to be heated to 120-220 ℃ to obtain preheated regeneration carrier gas;
f) and (3) pre-adsorption heat regeneration, namely reversely feeding the pre-heated regeneration carrier gas into the pre-adsorption tower from the bottom of the pre-adsorption tower which is subjected to the pre-adsorption step for pre-adsorption heat regeneration, wherein the operating temperature of the pre-adsorption heat regeneration is 120-220 ℃, the operating pressure is 0.3-1.5 MPa, feeding the pre-heated regeneration waste gas flowing out of the top of the pre-adsorption tower into a cooler through an eighth program control valve, cooling to 10-60 ℃, then feeding the pre-heated regeneration waste gas into a second gas-liquid separator for gas-liquid separation, and feeding the cooled gas flowing out of the top of the pre-heated regeneration waste gas into moisture returned to a pressure regulating valve as cold regeneration carrier gas for recycling, so that the adsorption drying cycle operation is completed.
2. The method for the nondestructive drying of the post-circulation reaction gas in the preparation of methyl chloride by using the methane method according to claim 1, wherein the adsorbent filled in the adsorption tower is one or more of aluminum oxide, silica gel and molecular sieve, and forms a composite bed layer.
3. The method for nondestructively drying the post-circulation reaction gas in the preparation of methyl chloride by the methane process according to claim 1, wherein the volume ratio of the moisture I to the moisture II is (5-4): (0 to 1).
4. The method for nondestructively drying the post-circulating reaction gas in the preparation of methyl chloride by using the methane method according to claim 1, wherein the adsorption towers comprise 3 adsorption towers and 1 pre-adsorption tower which are connected in parallel, namely the adsorption tower A, the adsorption tower B, the adsorption tower C and the pre-adsorption tower D, each adsorption tower is subjected to the steps of adsorption, pressure reduction, thermal regeneration treatment, isolation, cold regeneration treatment and pressure increase, specifically, when the adsorption tower A is in the adsorption step, the corresponding adsorption tower B is subjected to the three steps of isolation, cold regeneration treatment and pressure increase in sequence, and the corresponding adsorption tower C is subjected to the steps of pressure reduction and thermal regeneration treatment in sequence and then is in the isolation step; after the adsorption step of the adsorption tower A is finished, the steps of pressure reduction and thermal regeneration treatment are carried out in sequence, then the adsorption tower A is in the isolation step, the corresponding adsorption tower B is in the adsorption step, and the corresponding adsorption tower C is subjected to the steps of isolation, cold regeneration treatment and pressure increase in sequence; when the adsorption tower A sequentially undergoes the steps of isolation, cold regeneration treatment and pressure rise, the corresponding adsorption tower B sequentially undergoes the steps of pressure reduction and heat regeneration treatment and is in the isolation step, and the corresponding adsorption tower C is in the adsorption step, so that the adsorption tower A, the adsorption tower B and the adsorption tower C cyclically perform temperature change operation and simultaneously perform pressure change operation, and the system continuously operates to flow out dried and dehydrated product gas.
5. The method for nondestructively drying the post-cycle reaction gas in the preparation of methyl chloride by using a methane process according to claim 4, wherein the nondestructively drying steps of the adsorption tower A, the adsorption tower B and the adsorption tower C comprise cyclic operation steps of adsorption, depressurization, thermal regeneration treatment, cold regeneration treatment and pressurization.
6. The method for nondestructively drying the post-cycle reaction gas in the preparation of methyl chloride by using a methane process according to claim 4 or 5, wherein any two of the adsorption tower A, the adsorption tower B and the adsorption tower C are subjected to adsorption drying cycle operation, and one of the adsorption towers is used as a preparation tower.
7. The method for the nondestructive drying of the post-circulating reaction gas in the production of methyl chloride by a methane process according to claim 1, wherein the flow direction of the heat regeneration carrier gas in the adsorption column is the same as or opposite to the flow direction of the moisture i in the adsorption step in the adsorption column.
8. The method for the nondestructive drying of the post-circulating reaction gas in the production of methyl chloride by a methane process according to claim 1, wherein the flow direction of the cold regeneration carrier gas in the adsorption column is the same as or opposite to the flow direction of the moisture i in the adsorption step in the adsorption column.
9. The method for the nondestructive drying of the post-circulation reaction gas in the preparation of methyl chloride by the methane method according to claim 1, wherein the flow directions of the hot regeneration carrier gas and the cold regeneration carrier gas are consistent and opposite to the flow direction of the wet gas I.
10. The nondestructive drying method for the post-circulation reaction gas in the preparation of methyl chloride by the methane method according to claim 1, wherein the process flow is characterized in that the product gas is connected with a hot regeneration waste gas, a cold regeneration waste gas and a preheated regeneration waste gas through discharge ports.
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