Coal-to-ethanol device low-temperature heat combined utilization system

Abstract

The present application relates to the technical field of coal-to-ethanol, and discloses a low-temperature heat combined utilization system of a coal-to-ethanol device, which comprises a heat medium storage tank, a flash steam-gray water heat exchanger, a heat medium-flash steam heat exchanger, an ethanol refining tower body, an ethanol light component removal tower body and a methanol ester removal tower body, the heat medium storage tank is connected with the heat medium-flash steam heat exchanger through a heat medium booster pump, and the flash steam-gray water heat exchanger is connected with the heat medium-flash steam heat exchanger; the ethanol refining tower body is connected with an ethanol refining tower heat medium reboiler and an ethanol refining tower steam reboiler, the ethanol light component removal tower body is connected with an ethanol light component removal tower heat medium reboiler and an ethanol light component removal tower steam reboiler, and the methanol ester removal tower body is connected with a methanol ester removal tower heat medium reboiler and a methanol ester removal tower steam reboiler; and the heat medium storage tank, the heat medium-flash steam heat exchanger, the ethanol refining tower heat medium reboiler, the ethanol light component removal tower heat medium reboiler and the methanol ester removal tower heat medium reboiler form a closed loop.

Description

Technical Field

[0001] This invention relates to the field of coal-to-ethanol technology, specifically to a low-temperature thermal combined utilization system for coal-to-ethanol plants. Background Technology

[0002] Coal-to-ethanol refers to the process of producing ethanol from syngas (mainly composed of CO and H2) generated by coal gasification using different process routes. There are four main process routes for producing ethanol from syngas generated by coal gasification: 1) Syngas directly reacts with chemical catalysis to produce ethanol; 2) Syngas directly produces ethanol after anaerobic fermentation; 3) Syngas first reacts to synthesize methanol, then methanol is converted to acetic acid, and finally ethanol is produced by directly adding light to the acetic acid; 4) Syngas first reacts to synthesize methanol, then methanol is converted to methyl acetate, and finally methyl acetate is added with light to produce ethanol.

[0003] Ethanol plants consume large amounts of low-pressure steam during processes such as material heating, distillation, and reboiling, with initial heating temperatures mostly below 100°C. Using steam as a heat source results in high-quality but low-efficiency energy utilization. Furthermore, many units in coal-to-ethanol plants have heat sources with temperatures above 100°C that are cooled by air coolers and water coolers, leading to insufficient waste heat recovery. This does not comply with the principle of temperature-level matching and tiered utilization, nor with existing industry requirements for waste heat and pressure recovery. Summary of the Invention

[0004] The purpose of this invention is to provide a low-temperature heat co-utilization system for coal-to-ethanol plants to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a low-temperature heat co-utilization system for a coal-to-ethanol plant, comprising a heat medium storage tank, a flash steam-ash water heat exchanger, a heat medium-flash steam heat exchanger, an ethanol refining tower body, an ethanol light component removal tower body, and a methanol deesterification tower body. The heat medium storage tank is connected to the heat medium-flash steam heat exchanger via a heat medium booster pump, and the flash steam-ash water heat exchanger is connected to the heat medium-flash steam heat exchanger. The ethanol refining tower body is connected to an ethanol refining tower heat medium reboiler and an ethanol refining tower steam... The reboiler is connected to both the ethanol light-weight removal tower body and the ethanol light-weight removal tower steam reboiler. The methanol deesterification tower body is also connected to both the methanol deesterification tower heat medium reboiler and the methanol deesterification tower steam reboiler. The heat medium-flash steam heat exchanger is connected to the ethanol refining tower heat medium reboiler. The ethanol refining tower heat medium reboiler is connected to the ethanol light-weight removal tower heat medium reboiler. The ethanol light-weight removal tower heat medium reboiler is connected to the methanol deesterification tower heat medium reboiler. The methanol deesterification tower heat medium reboiler is connected to the heat medium storage tank.

[0006] Preferably, it also includes a heat medium-shifting gas heat exchanger, a shifting gas-demineralized water heat exchanger, and a demineralized water-crude methanol heat exchanger. The heat medium storage tank is connected to the heat medium-shifting gas heat exchanger via a heat medium booster pump. The heat medium-shifting gas heat exchanger, the shifting gas-demineralized water heat exchanger, and the demineralized water-crude methanol heat exchanger are connected in sequence.

[0007] Preferably, the heat medium-shifting gas heat exchanger is connected to the heat medium reboiler of the ethanol refining tower.

[0008] Preferably, valves are provided between the reboiler of the ethanol refining tower and the reboiler of the ethanol light-removal tower, and between the reboiler of the ethanol light-removal tower and the reboiler of the methanol deesterification tower.

[0009] Compared with existing technologies, the beneficial effects of this invention are: This invention can optimize or upgrade the heat recovery design of the entire coal-to-ethanol plant, improve the heat recovery rate and efficiency of the unit, and enable the recovered low-temperature heat to be used for one or more low-temperature heat traps in the ethanol unit. Without changing the original control scheme, the low-temperature heat medium can be utilized in stages, reducing the consumption of thermal utilities in the ethanol unit and the cold utilities load of other units in the plant. It breaks the traditional concept of independent design between units, achieves full recovery and utilization of low-temperature heat, realizes local energy saving and plant-wide efficiency improvement, and ultimately achieves the overall goal of energy saving and carbon reduction. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of the present invention;

[0011] Figure 2 This is a simplified flow chart of the high and low pressure flash steam heat recovery process of the gasification device in an embodiment of the present invention;

[0012] Figure 3 This is a simplified flow chart of the heat recovery process of the methanol-to-conversion device in an embodiment of the present invention;

[0013] The following are the labels in the diagram: 1. Heat medium storage tank; 2. Heat medium booster pump; 3. Flash steam-ash water heat exchanger; 4. Heat medium-flash steam heat exchanger; 5. Heat medium-shift gas heat exchanger; 6. Shift gas-demineralized water heat exchanger; 7. Demineralized water-crude methanol heat exchanger; 8. Ethanol refining tower body; 9. Ethanol refining tower heat medium reboiler; 10. Ethanol refining tower steam reboiler; 11. Ethanol light oil removal tower body; 12. Ethanol light oil removal tower heat medium reboiler; 13. Ethanol light oil removal tower steam reboiler; 14. Methanol deesterification tower body; 15. Methanol deesterification tower heat medium reboiler; 16. Methanol deesterification tower steam reboiler. Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] In the description of this invention, it should be noted that the terms "vertical," "upper," "lower," "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0016] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0017] Please see Figure 1-3 This invention provides a technical solution: a low-temperature heat co-utilization system for a coal-to-ethanol plant, comprising a heat medium storage tank 1, a flash steam-ash water heat exchanger 3, a heat medium-flash steam heat exchanger 4, an ethanol refining tower body 8, an ethanol light oil removal tower body 11, and a methanol deesterification tower body 14. The heat medium storage tank 1 is connected to the heat medium-flash steam heat exchanger 4 via a heat medium booster pump 2, and the flash steam-ash water heat exchanger 3 is connected to the heat medium-flash steam heat exchanger 4. The ethanol refining tower body 8 is connected to an ethanol refining tower heat medium reboiler 9 and an ethanol refining tower steam reboiler 10. The main body 11 of the alcohol light removal tower is connected to the ethanol light removal tower heat medium reboiler 12 and the ethanol light removal tower steam reboiler 13. The main body 14 of the methanol deesterification tower is connected to the methanol deesterification tower heat medium reboiler 15 and the methanol deesterification tower steam reboiler 16. The heat medium-flash steam heat exchanger 4 is connected to the ethanol refining tower heat medium reboiler 9. The ethanol refining tower heat medium reboiler 9 is connected to the ethanol light removal tower heat medium reboiler 12. The ethanol light removal tower heat medium reboiler 12 is connected to the methanol deesterification tower heat medium reboiler 15. The methanol deesterification tower heat medium reboiler 15 is connected to the heat medium storage tank 1.

[0018] Furthermore, it also includes a heat medium-shift gas heat exchanger 5, a shift gas-demineralized water heat exchanger 6, and a demineralized water-crude methanol heat exchanger 7. The heat medium storage tank 1 is connected to the heat medium-shift gas heat exchanger 5 through a heat medium booster pump 2. The heat medium-shift gas heat exchanger 5, the shift gas-demineralized water heat exchanger 6, and the demineralized water-crude methanol heat exchanger 7 are connected in sequence.

[0019] Furthermore, the heat medium-shifting gas heat exchanger 5 is connected to the ethanol refining tower heat medium reboiler 9.

[0020] Furthermore, valves are provided between the ethanol refining tower reboiler 9 and the ethanol light-removal tower reboiler 12, and between the ethanol light-removal tower reboiler 12 and the methanol deesterification tower reboiler 15. Example

[0021] Take a factory with an annual methanol production capacity of 600,000 tons and an annual ethanol production capacity of 500,000 tons as an example.

[0022] 1) Main heat source

[0023] The coal gasification unit of the plant consists of a gasification system, a scrubbing tower, and a high- and low-pressure flash evaporation system. The flash vapor at the top of the high- and low-pressure flash tanks of the high- and low-pressure flash evaporation system is mostly water vapor, with only a small portion being recovered by the gasification ash water. Most of the high-temperature steam is cooled by circulating water, which wastes valuable high-temperature steam heat and consumes a large amount of circulating water.

[0024] The heat recovery process of the converter unit in this plant uses cold demineralized water for cooling at the end. After the cold demineralized water temperature is increased, it is sent to the boiler deaerator. The temperature at the end of the heat recovery process in this plant is between 170℃ and 175℃, while the temperature of the demineralized water supply is generally between 55℃ and 60℃, with a flow rate of 500t / h. There is a large temperature difference between the two for heat exchange, and the effective energy efficiency of the heat exchange process is less than 60%, resulting in a large effective energy loss.

[0025] The methanol plant utilizes the reaction heat of the methanol reactor to produce a large amount of steam as a byproduct. However, after the reaction products exchange heat with the reaction feed, they enter the cooling section (crude methanol air cooler and crude methanol water cooler). Before entering the cooling section, the temperature is between 155℃ and 160℃. Due to the large reaction cycle, the cooling load is huge, the consumption of cooling utilities is huge, and the heat recovery rate of the reaction product stream is less than 30%.

[0026] The above analysis shows that the main heat sources of the plant are the high and low pressure flash steam streams from the gasification unit that are cooled by circulating water, the shift gas streams from the heat recovery process of the shift unit that are cooled by demineralized water, and the reaction product streams from the methanol unit reactor outlet that are cooled by air coolers.

[0027] 2) Main heat sink of the ethanol plant

[0028] The main low-temperature heat sinks (partial) of the plant's ethanol unit are as follows:

[0029] The above-mentioned steam-consuming users require a heat load of 62MW, equivalent to a steam consumption of 104t / h. In order to achieve energy conservation and carbon reduction for the entire plant, based on the principles of temperature matching and energy cascade utilization, the low-temperature heat sources of the methanol unit, gasification unit, and conversion unit can be organically matched with the low-temperature heat trap of the ethanol unit.

[0030] 3) Brief description of the process

[0031] 1. Heat recovery process of gasification unit

[0032] A new heat medium-flash steam heat exchanger 4 is added. Approximately 200t / h of heat medium at 90℃ exchanges heat with flash steam through the heat medium-flash steam heat exchanger 4, raising the temperature of the heat medium to 150℃. After exiting the heat medium-flash steam heat exchanger 4, the flash steam is sent to the flash steam circulating water heat exchanger for cooling.

[0033] 2. Methanol-to-conversion unit heat recovery process

[0034] The converter unit adds a heat exchanger 5 for the heat transfer medium and a heat exchanger 6 for the heat transfer gas and demineralized water. The methanol unit adds a heat exchanger 7 for demineralized water and crude methanol connected in parallel with the crude methanol air cooler. Approximately 400 t / h of heat transfer medium at 90°C exchanges heat with the 170°C heat transfer gas at the end of the heat recovery section of the converter unit. After its temperature rises to 150°C, it is sent to the ethanol unit. The heat transfer gas exiting the heat transfer medium-converter gas heat exchanger 5 enters the heat exchanger 6 for the heat transfer gas and demineralized water, where it exchanges heat with the cold demineralized water before being sent to the circulating water cooler. The cold demineralized water is heated to 75-80°C by the heat transfer gas and then sent to the methanol unit's demineralized water and crude methanol heat exchanger 7, where it exchanges heat with the 150°C reaction products from the methanol unit. After its temperature rises to 125-130°C, it is sent to the boiler deaerator. This scheme requires a temperature control system for the methanol unit to control the flow rate of the reaction product stream entering the heat exchanger by controlling the temperature of the demineralized water at the cold end outlet of the demineralized water and crude methanol heat exchanger 7.

[0035] 3. Heat medium circulation system process

[0036] The 600t / h of 90-95℃ heat medium from the self-heating medium storage tank 1 is pressurized by the heat medium booster pump 2 and then split into two streams. One stream, with a capacity of 200t / h, enters the heat medium-flash vapor heat exchanger 4, where the heat medium temperature rises to 150℃. The other stream, with a capacity of 400t / h, enters the heat medium-shifting gas heat exchanger 5, where the heat medium temperature rises to 150℃. After both streams reach 150℃, they merge and are first sent to the ethanol refining tower in the higher-temperature ethanol unit. Boiler 9 replaces 65%~70% of the low-pressure steam. After the temperature of the heat medium drops to about 110℃, the heat medium is sent to the ethanol light removal tower heat medium reboiler 12, which has a relatively low temperature, replacing 60%~65% of the low-pressure steam. After the temperature of the heat medium drops to about 105℃, the heat medium is sent to the methanol deesterification tower heat medium reboiler 15, replacing 80%~85% of the low-pressure steam. After the temperature of the heat medium drops to 90℃, the heat medium is sent to the heat medium storage tank 1 for recycling.

[0037] Note 1: The number and series / parallel connection of the heat medium reboilers are not limited to the examples shown above. The number and series / parallel connection of the heat medium reboilers in the ethanol unit can be flexibly matched according to the heat and temperature level recovered by the heat medium to realize the cascade utilization of the low-temperature heat medium.

[0038] Note 2: The addition of a heat medium reboiler does not require any changes to the original control scheme, provided that the original steam reboiler and control scheme are retained.

[0039] After adopting this optimization scheme, the plant can reduce the low-pressure steam consumption of the ethanol unit by about 70 t / h. Based on an annual operating time of 8,000 hours, it can save 52,800 tons of standard coal and reduce CO2 emissions by 143,000 tons per year. At 1,000 yuan per ton of standard coal, the annual economic benefit of this scheme is 52.8 million yuan.

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low-temperature heat co-utilization system for a coal-to-ethanol plant, characterized in that: The system includes a heat medium storage tank (1), a flash steam-ash water heat exchanger (3), a heat medium-flash steam heat exchanger (4), an ethanol refining tower body (8), an ethanol light component removal tower body (11), and a methanol deesterification tower body (14). The heat medium storage tank (1) is connected to the heat medium-flash steam heat exchanger (4) via a heat medium booster pump (2), and the flash steam-ash water heat exchanger (3) is connected to the heat medium-flash steam heat exchanger (4). The ethanol refining tower body (8) is connected to an ethanol refining tower heat medium reboiler (9) and an ethanol refining tower steam reboiler (10), and the ethanol light component removal tower body (11) is connected to an ethanol refining tower body. The light-light removal tower heat medium reboiler (12) and the ethanol light-light removal tower steam reboiler (13) are connected to the methanol deesterification tower body (14), and the methanol deesterification tower heat medium reboiler (15) and the methanol deesterification tower steam reboiler (16) are connected to it; the heat medium-flash steam heat exchanger (4) is connected to the ethanol refining tower heat medium reboiler (9), the ethanol refining tower heat medium reboiler (9) is connected to the ethanol light-light removal tower heat medium reboiler (12), the ethanol light-light removal tower heat medium reboiler (12) is connected to the methanol deesterification tower heat medium reboiler (15), and the methanol deesterification tower heat medium reboiler (15) is connected to the heat medium storage tank (1).

2. The low-temperature thermal co-utilization system for coal-to-ethanol production according to claim 1, characterized in that: It also includes a heat medium-shifting gas heat exchanger (5), a shifting gas-demineral water heat exchanger (6), and a demineral water-crude methanol heat exchanger (7). The heat medium storage tank (1) is connected to the heat medium-shifting gas heat exchanger (5) through a heat medium booster pump (2). The heat medium-shifting gas heat exchanger (5), the shifting gas-demineral water heat exchanger (6), and the demineral water-crude methanol heat exchanger (7) are connected in sequence.

3. The low-temperature thermal co-utilization system for coal-to-ethanol production according to claim 2, characterized in that: The heat medium-shifting gas heat exchanger (5) is connected to the heat medium reboiler (9) of the ethanol refining tower.

4. The low-temperature thermal co-utilization system for coal-to-ethanol production according to claim 1, characterized in that: Valves are provided between the ethanol refining tower reboiler (9) and the ethanol light removal tower reboiler (12), and between the ethanol light removal tower reboiler (12) and the methanol deesterification tower reboiler (15).

Images