A methanol dehydration upgrading and consumption reduction recovery device for esterification section of coal-based synthetic gas to ethylene glycol process

Abstract

The utility model belongs to the field of coal chemical industry, concretely relates to a kind of methanol dewatering quality upgrading and consumption reducing recovery device of coal-based synthetic gas preparation glycol process esterification section, normal / pressure rectifying column, low-pressure rectifying column and pressurized rectifying column connected in turn;Normal / pressure rectifying column lower part is connected with normal / pressure rectifying column reboiler, and column top is connected with normal / pressure rectifying column overhead condenser, and the gas phase outlet of the low-pressure rectifying column is connected with the shell side or tube side inlet of the normal / pressure rectifying column reboiler by pipeline;The gas phase outlet of the pressurized rectifying column is connected with the shell side or tube side inlet of the low-pressure rectifying column reboiler by pipeline, and the low-pressure rectifying column kettle is connected with pressurized rectifying column by pressurized tower feed preheater.The utility model prevents light component to accumulate in glycol production process, improves the purity of methanol, while reducing steam consumption 40%-70%.

Description

Technical Field

[0001] This utility model belongs to the field of coal chemical industry, specifically relating to a methanol dehydration, upgrading, consumption reduction and recovery device in the esterification stage of a coal-based syngas to ethylene glycol process. Background Technology

[0002] The coal-based syngas to ethylene glycol process mainly consists of two parts: CO oxidative coupling to dimethyl oxalate (DMO) and catalytic hydrogenation of DMO to ethylene glycol (EG).

[0003] The synthesis of dimethyl oxalate (DMO) from CO oxidative coupling mainly involves two reactions.

[0004] First, methyl nitrite (MN) and CO undergo an oxidative coupling reaction under the action of a catalyst to generate DMO. The reaction equation is as follows:

[0005] 2CH3ONO + 2CO → (COOCH3)2 + 2NO

[0006] This step is completed in the synthesis reactor.

[0007] The generated NO then undergoes an oxidative esterification reaction with methanol and oxygen (O2) to produce methyl nitrite (MN). The reaction equation is as follows:

[0008] 2CH3OH+2NO+1 / 2O2→2CH3ONO+H2O

[0009] This step is completed in the esterification tower. The reaction product, methyl nitrite (MN), is returned to the synthesis reactor and combined with CO oxidant to form dimethyl oxalate (DMO). The bottom liquid of the esterification tower contains not only the reaction product water, but also the raw material methanol and various light components produced by the side reactions.

[0010] The synthesis of DMO produces dimethyl carbonate (DMC) as a byproduct. The DMO product generated in the synthesis reactor enters the DMO section and is absorbed by methanol spraying in the DMO absorption tower. The methanol absorption liquid containing DMO and DMC enters the DMO distillation tower, where methanol and DMC are separated and recovered. Numerous documents describe the methanol recovery process in this procedure.

[0011] In the catalytic hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG), the DMO purified by the DMO distillation column is mixed with H2 and then fed into the hydrogenation reactor, where it reacts to produce ethylene glycol (EG) and methanol. Some literature describes methanol recovery in the ethylene glycol synthesis unit, such as utility model patent CN105218305B, but this patent does not address methanol recovery from the esterification column.

[0012] As mentioned above, there are literature reports on methanol recovery in both the DMO and ethylene glycol processes.

[0013] Currently, there is little literature on methanol recovery from the bottom liquid of esterification towers. The bottom liquid phase of esterification towers contains a large amount of methanol, and the conventional method is to recover the methanol from a single tower. Patent CN204918418U mentions using a methanol recovery tower (single tower) to recover methanol from the esterification reaction tower, but this process consumes a lot of energy and does not remove the light components contained in the bottom liquid of the esterification tower, which will accumulate in the entire process system. Utility Model Content

[0014] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a methanol dehydration, upgrading, and energy-saving recovery device for the esterification stage of a coal-based syngas to ethylene glycol process. This device reduces the energy consumption of the entire ethylene glycol production process, improves the purity of recovered methanol, and enhances the economic and social benefits of enterprises.

[0015] The technical solution to achieve the purpose of this utility model is as follows:

[0016] This utility model provides a methanol dehydration, upgrading, energy saving and recovery device for the esterification stage of a coal-based syngas to ethylene glycol process, comprising: an atmospheric / vacuum distillation column, a low-pressure distillation column and a pressurized distillation column connected in sequence;

[0017] The lower part of the atmospheric / vacuum distillation column is connected to a reboiler, and the top of the column is connected to a condenser and a reflux tank.

[0018] The lower part of the low-pressure distillation column is connected to a low-pressure distillation column reboiler. The top vapor outlet of the low-pressure distillation column is connected to the shell side or tube side inlet of the atmospheric / vacuum distillation column reboiler through a pipeline for heating it.

[0019] The lower part of the pressurized distillation column is connected to a pressurized distillation column reboiler. The top vapor outlet of the pressurized distillation column is connected to the shell side or tube side inlet of the low-pressure distillation column reboiler through a pipeline for heating.

[0020] The reboiler of the low-pressure distillation column is connected to the feed inlet of the pressurized distillation column via a pressurized column feed preheater.

[0021] Furthermore, the bottom outlet of the low-pressure distillation column is connected to the feed inlet of the pressurized distillation column via a low-pressure distillation column bottom pump and a pressurized column feed preheater; the bottom outlet of the pressurized distillation column is connected to a wastewater discharge pipeline via the pressurized column feed preheater.

[0022] Furthermore, the feed inlet of the atmospheric / vacuum distillation column is located in the middle or lower part of the column, and a side outlet for collecting refined methanol is provided above the feed inlet.

[0023] Furthermore, the top of the atmospheric / vacuum distillation column is connected to the top condenser of the atmospheric / vacuum distillation column via a pipeline. The top condenser of the atmospheric / vacuum distillation column has a non-condensable gas outlet for extracting light components, and its liquid phase outlet is connected to the reflux tank of the atmospheric / vacuum distillation column via a pipeline. The bottom outlet of the reflux tank of the atmospheric / vacuum distillation column is connected to the top reflux port of the atmospheric / vacuum distillation column via a reflux pump. The bottom outlet of the atmospheric / vacuum distillation column is connected to the feed inlet of the low-pressure distillation column via a bottom pump.

[0024] Furthermore, the vapor outlet at the top of the low-pressure distillation column exchanges heat with the reboiler of the atmospheric / vacuum distillation column and is then connected to the reflux tank of the low-pressure distillation column via a pipeline; the bottom outlet of the reflux tank of the low-pressure distillation column is connected to the top reflux port of the low-pressure distillation column via a reflux pump of the low-pressure distillation column, and the outlet pipeline of the reflux pump of the low-pressure distillation column is provided with a collection outlet for collecting refined methanol.

[0025] Furthermore, the vapor outlet at the top of the pressurized distillation column exchanges heat with the reboiler of the low-pressure distillation column and is then connected to the pressurized distillation column reflux tank via a pipeline; the bottom outlet of the pressurized distillation column reflux tank is connected to the top reflux port of the pressurized distillation column via a pressurized distillation column reflux pump, and the outlet pipeline of the pressurized distillation column reflux pump is provided with a collection outlet for extracting refined methanol.

[0026] Furthermore, it also includes cooler one, cooler two, and cooler three. The inlet of cooler one is connected to the side outlet of the atmospheric / vacuum distillation column, and is used to cool the refined methanol collected from the side of the atmospheric / vacuum distillation column. The inlet of cooler two is connected to the refined methanol outlet of the reflux pump of the low-pressure distillation column, and is used to cool the refined methanol collected from the top of the low-pressure distillation column. The inlet of cooler three is connected to the refined methanol outlet of the reflux pump of the pressurized distillation column, and is used to cool the refined methanol collected from the top of the pressurized distillation column. The outlets of cooler one, cooler two, and cooler three are combined into a single high-purity methanol product output pipeline.

[0027] Furthermore, the atmospheric / reduced pressure distillation column, the low-pressure distillation column, and the pressurized distillation column are one or a combination of plate columns, bulk packed columns, or structured packed columns.

[0028] This utility model has the following beneficial effects:

[0029] Most literature does not address methanol recovery in the esterification stage of existing coal-based syngas-to-ethylene glycol processes. In actual production, methanol recovery consumes a huge amount of energy, and the accumulation of light components in the recovered methanol due to their non-removal throughout the entire unit is a significant problem. This invention can remove light components from the recovered methanol, preventing their accumulation throughout the ethylene glycol production process, thus improving methanol purity and reducing steam consumption by 40%-70%. This significantly reduces the energy consumption of the ethylene glycol production process, making the product highly competitive. Attached Figure Description

[0030] Figure 1 This is a diagram of the device of this utility model.

[0031] T1 is an atmospheric / vacuum distillation column, T2 is a low-pressure distillation column, T3 is a pressurized distillation column, V1 is a reflux tank for the atmospheric / vacuum distillation column, V2 is a reflux tank for the low-pressure distillation column, V3 is a reflux tank for the pressurized distillation column, E101 is a reboiler for the atmospheric / vacuum distillation column, E102 is a top condenser for the atmospheric / vacuum distillation column, E103 is cooler one, E201 is a reboiler for the low-pressure distillation column, E202 is cooler two, E301 is a reboiler for the pressurized distillation column, E302 is a feed preheater for the pressurized column, E303 is cooler three, V1 is a reflux tank for the atmospheric / vacuum distillation column, V... 2 is the reflux tank of the low-pressure distillation column, V3 is the reflux tank of the pressurized distillation column, P101 is the reflux pump of the atmospheric / vacuum distillation column, P102 is the bottom pump of the atmospheric / vacuum distillation column, P201 is the reflux pump of the low-pressure distillation column, P202 is the bottom pump of the low-pressure distillation column, P301 is the reflux pump of the pressurized distillation column, 1 is the feed, 2 is the light component, 3 is the side-collected refined methanol of the atmospheric / vacuum distillation column, 4 is the bottom liquid of the atmospheric / vacuum distillation column, 5 is the bottom liquid of the low-pressure distillation column, 6 is the refined methanol collected from the top of the low-pressure distillation column, 7 is the refined methanol collected from the top of the pressurized distillation column, 8 is the wastewater, and 9 is the high-purity methanol. Detailed Implementation

[0032] The following detailed description, in conjunction with specific implementation examples, provides a methanol dehydration, upgrading, energy-saving, and recovery device for the esterification stage of a coal-based syngas to ethylene glycol process. The following examples are descriptive only and not limiting, and should not be construed as limiting the scope of protection of this utility model.

[0033] like Figure 1 The methanol dehydration, upgrading, and energy-saving recovery device shown is used in the esterification stage of a coal-based syngas to ethylene glycol process. It includes an atmospheric / vacuum distillation column T1, a low-pressure distillation column T2, and a pressurized distillation column T3 connected in sequence. The lower parts of the atmospheric / vacuum distillation column T1, the low-pressure distillation column T2, and the pressurized distillation column T3 are respectively connected to an atmospheric / vacuum distillation column reboiler E101, a low-pressure distillation column reboiler E201, and a pressurized distillation column reboiler E301.

[0034] Raw material 1 is introduced into atmospheric / vacuum distillation column T1 for preliminary separation. Light component 2 is collected from the top of the column, refined methanol is collected from the side stream, and atmospheric / vacuum distillation column bottom liquid 4 is obtained from the bottom of the column. The atmospheric / vacuum distillation column bottom liquid 4 is introduced into low-pressure distillation column T2 for further separation. Refined methanol is collected from the top of the column, and low-pressure distillation column bottom liquid 5 is obtained from the bottom of the column. The low-pressure distillation column bottom liquid 5 is introduced into pressurized column T3 for final separation after exchanging heat with the wastewater 8 from the bottom of pressurized column T3 via pressurized column feed preheater E302. Refined methanol is collected from the top of the column, and wastewater 8 is discharged from the bottom of the column. The vapor phase from the top of pressurized column T3 is used to heat the reboiler E201 of the low-pressure distillation column, and the vapor phase from the top of low-pressure distillation column T2 is used to heat the reboiler E101 of the atmospheric / vacuum distillation column.

[0035] The atmospheric / vacuum distillation column T1 produces gaseous or liquid refined methanol via a side stream above the column's feed inlet. The atmospheric / vacuum distillation column T1 is connected to the feed inlet for raw material 1 in the middle or lower part.

[0036] The top of the atmospheric / vapor distillation column T1 is connected to the overhead condenser E102 via a pipeline. The overhead condenser E102 also extracts the non-condensable light component 2. The overhead condenser E102 is connected to the reflux tank V1 via a pipeline. The bottom of the reflux tank V1 is connected to the top of the atmospheric / vapor distillation column T1 via a pipeline through the reflux pump P101. The bottom of the atmospheric / vapor distillation column T1 is connected to the bottom pump P102 and the low-pressure distillation column T2 via pipelines, and the bottom liquid 4 of the atmospheric / vapor distillation column is pumped into the low-pressure distillation column T2.

[0037] After the top gas of the low-pressure distillation column T2 is heated relative to the reboiler E101 of the atmospheric / vacuum distillation column, it is connected to the reflux tank V2 of the low-pressure distillation column through a pipeline. The bottom of the reflux tank V2 is connected to the top of the low-pressure distillation column T2 through the reflux pump P201 of the low-pressure distillation column via a pipeline. Moreover, refined methanol is also collected from the outlet of the reflux pump P201. The bottom of the low-pressure distillation column T2 is connected to the bottom pump P202 of the low-pressure distillation column, the feed preheater E302 of the pressurized column, and the pressurized distillation column T3 through pipelines, and the bottom liquid 5 of the low-pressure distillation column is pumped into the pressurized distillation column T3.

[0038] After the top gas of the pressurized distillation column T3 is heated relative to the reboiler E201 of the low-pressure distillation column, it is connected to the pressurized distillation column reflux tank V3 through a pipeline. The bottom of the pressurized distillation column reflux tank V3 is connected to the top of the pressurized distillation column T3 through the pressurized distillation column reflux pump P301 via a pipeline. Furthermore, refined methanol is also collected from the outlet of the pressurized distillation column reflux pump P301.

[0039] The methanol 3 collected from the side of the atmospheric / vacuum distillation column, the methanol 6 collected from the top of the low-pressure distillation column, and the methanol 7 collected from the top of the pressurized distillation column are cooled by cooler E103, cooler E202, and cooler E303 respectively, and then combined into high-purity methanol 9 as a product for reuse.

[0040] The atmospheric / reduced pressure distillation column T1, low-pressure distillation column T2, and pressurized distillation column T3 are selected from one or a combination of plate columns, bulk packed columns, or structured packed columns.

[0041] Example 1

[0042] use Figure 1 The process flow diagram shows that the raw material is fed into the feed inlet of atmospheric / vacuum distillation column T1 at a rate of 41516 kg / h, containing 0.61 wt% methanol, 0.356 wt% water, 0.014 wt% light components, and 0.02 wt% dimethyl carbonate. The operating pressure of atmospheric / vacuum distillation column T1 is 105 kPa absolute, the reflux rate is 0.85 times the feed rate, and the theoretical plate number is 50. The operating pressure of low-pressure distillation column T2 is 300 kPa absolute, the reflux ratio is 1.6, and the theoretical plate number is 50. The operating pressure of pressurized distillation column T3 is 800 kPa absolute, the reflux ratio is 2.2, and the theoretical plate number is 50. The recovered refined methanol 9 has a methanol purity of 96.4 wt%, a water content of 34 ppm, a DMC content of 3.3 wt%, and a light component content of 0.3 wt%. The energy consumption of the entire process is 6.98 gcal / h.

[0043] Comparative Example

[0044] Using a traditional single-tower process with 70 theoretical plates, methanol is collected from the top of the tower at a feed rate of 41,516 kg / h, containing 0.61 wt% methanol, 0.356 wt% water, 0.014 wt% light components, and 0.02 wt% dimethyl carbonate. The recovered methanol has a purity of 94.69 wt% and a light component content of 2.1 wt%, with an energy consumption as high as 14.51 gcal / h.

[0045] The comparison revealed that, compared to the current process of the comparative example, Example 1 consumed only 48.1% of the energy of the comparative example, saving 51.9% of energy. The methanol purity of 96.4% was much higher than the 94.69% of the current process, and the content of light components dropped sharply to 0.3%, which was only 14.3% of the original.

[0046] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the utility model, and these all fall within the protection scope of the present utility model.

Claims

1. A methanol dehydration, upgrading, energy-saving, and recovery device for the esterification stage of a coal-based syngas to ethylene glycol process, characterized in that: include: The atmospheric / vacuum distillation column (T1), the low-pressure distillation column (T2), and the pressurized distillation column (T3) are connected in sequence. The atmospheric / vacuum distillation column (T1) is connected to a reboiler (E101) at the bottom and to a condenser (E102) and a reflux tank (V1) at the top. The lower part of the low-pressure distillation column (T2) is connected to a low-pressure distillation column reboiler (E201). The vapor phase outlet at the top of the low-pressure distillation column (T2) is connected to the shell side or tube side inlet of the atmospheric / vacuum distillation column reboiler (E101) through a pipeline for heating it. The lower part of the pressurized distillation column (T3) is connected to a pressurized distillation column reboiler (E301). The vapor phase outlet at the top of the pressurized distillation column (T3) is connected to the shell side or tube side inlet of the low-pressure distillation column reboiler (E201) through a pipeline for heating it. The bottom of the low-pressure distillation column (T2) is connected to the feed inlet of the pressurized distillation column (T3) via the pressurized column feed preheater (E302).

2. The apparatus according to claim 1, characterized in that, The bottom outlet of the low-pressure distillation column (T2) is connected to the feed inlet of the pressurized distillation column (T3) via the bottom pump (P202) and the feed preheater (E302); the bottom outlet of the pressurized distillation column (T3) is connected to the wastewater (8) discharge pipeline via the feed preheater (E302).

3. The apparatus according to claim 1, characterized in that, The feed inlet of the atmospheric / vacuum distillation column (T1) is located in the middle or lower part of the column, and a side outlet for collecting refined methanol is provided above the feed inlet.

4. The apparatus according to claim 1, characterized in that, The top of the atmospheric / vacuum distillation column (T1) is connected to the top condenser (E102) of the atmospheric / vacuum distillation column via a pipeline. The top condenser (E102) of the atmospheric / vacuum distillation column has a non-condensable gas outlet for extracting light components (2), and its liquid phase outlet is connected to the reflux tank (V1) of the atmospheric / vacuum distillation column via a pipeline. The bottom outlet of the reflux tank (V1) of the atmospheric / vacuum distillation column is connected to the top reflux port of the atmospheric / vacuum distillation column (T1) via the reflux pump (P101) of the atmospheric / vacuum distillation column. The bottom outlet of the atmospheric / vacuum distillation column (T1) is connected to the feed port of the low-pressure distillation column (T2) via the bottom pump (P102) of the atmospheric / vacuum distillation column.

5. The apparatus according to claim 1, characterized in that, The vapor outlet at the top of the low-pressure distillation column (T2) exchanges heat with the reboiler (E101) of the atmospheric / vacuum distillation column, and is then connected to the low-pressure distillation column reflux tank (V2) via a pipeline. The bottom outlet of the low-pressure distillation column reflux tank (V2) is connected to the top reflux port of the low-pressure distillation column (T2) via a low-pressure distillation column reflux pump (P201), and the outlet pipeline of the low-pressure distillation column reflux pump (P201) is equipped with a collection outlet for collecting refined methanol.

6. The apparatus according to claim 1, characterized in that, The vapor outlet at the top of the pressurized distillation column (T3) exchanges heat with the reboiler (E201) of the low-pressure distillation column, and is then connected to the pressurized distillation column reflux tank (V3) via a pipeline. The bottom outlet of the pressurized distillation column reflux tank (V3) is connected to the top reflux port of the pressurized distillation column (T3) via a pressurized distillation column reflux pump (P301), and the outlet pipeline of the pressurized distillation column reflux pump (P301) is provided with a collection outlet for collecting refined methanol.

7. The apparatus according to claim 1, characterized in that, It also includes cooler one (E103), cooler two (E202) and cooler three (E303). The inlet of cooler one (E103) is connected to the side outlet of the atmospheric / vacuum distillation column (T1) and is used to cool the side-collected methanol (3) of the atmospheric / vacuum distillation column. The inlet of cooler two (E202) is connected to the methanol outlet of the reflux pump (P201) of the low-pressure distillation column and is used to cool the methanol collected from the top of the low-pressure distillation column (6). The inlet of cooler three (E303) is connected to the methanol outlet of the reflux pump (P301) of the pressurized distillation column and is used to cool the methanol collected from the top of the pressurized distillation column (7). The outlets of cooler one (E103), cooler two (E202) and cooler three (E303) are combined into a high-purity methanol (9) product output pipeline.

8. The apparatus according to claim 1, characterized in that, The atmospheric / reduced pressure distillation column (T1), low-pressure distillation column (T2), and pressurized distillation column (T3) are one or a combination of plate columns, bulk packed columns, or structured packed columns.

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