Waste heat recovery type hydrogen production and methanol production system

Abstract

According to the waste heat recovery type hydrogen production and methanol production system, a plurality of preparation devices of an offshore platform can generate waste heat in the operation process, each preparation device is provided with a heat exchanger, a plurality of heat exchangers are sequentially connected through pipelines to form a waste heat recovery pipeline, and the generated waste heat is connected into the waste heat recovery pipeline through the heat exchangers; the preparation device comprises hydrogen production equipment and methanol production equipment. And one end of the waste heat recovery pipeline is connected with the evaporative fresh water generator through a high-temperature seawater branch and is connected with the seawater supply cabin through a low-temperature seawater branch. Seawater enters the seawater supply cabin and the reverse osmosis fresh water generator through the seawater supply pump, the seawater circulates in the waste heat recovery pipeline, and the seawater is heated by the exchanged waste heat. When hydrogen production and methanol synthesis are carried out, dependence on reverse osmosis fresh water preparation can be greatly reduced, waste heat resources can be fully utilized and are not wasted, and extra and excessive requirements on power load, arrangement space and cost on a platform are not generated when related functions are realized.

Description

Technical Field

[0001] The present invention belongs to the field of offshore green energy preparation, and particularly relates to a waste heat recovery hydrogen and methanol production system. Background Art

[0002] Hydrogen energy has core advantages such as being clean and efficient, storable and transportable, and having rich application scenarios, and is expected to become the most competitive carbon emission reduction solution. At the same time, in the energy and chemical industry, preparing methanol based on green hydrogen reaction is one of the important ways for efficient conversion and utilization of carbon dioxide and "carbon fixation with hydrogen".

[0003] The initial raw material for the above-mentioned green hydrogen or methanol production process is fresh water. On offshore hydrogen and methanol production platforms, since there is no direct supply of fresh water, seawater is usually desalinated to obtain raw material fresh water. This desalination process is achieved through large-flow watermakers (mainly reverse osmosis watermakers). However, due to the large desalination volume, the reverse osmosis membranes of such watermakers need to be frequently replaced, resulting in high costs. One method of making fresh water is to heat seawater and reduce the air pressure (evacuate) to make it evaporate rapidly, and fresh water is produced by distillation. In engineering, a vacuum evaporation watermaker is usually used to achieve this. Heating seawater requires a corresponding heat source. There are often a large number of heat exchanges in various functions and process flows of offshore production facilities, but the thermal energy in these processes has not been effectively utilized, resulting in a large waste of energy. If the waste heat can be recovered and reused and fresh water can be produced through an evaporation watermaker, the overall economy of the offshore hydrogen and methanol production process can be significantly improved.

[0004] For the waste heat that can be recovered and reused on offshore hydrogen and methanol production platforms, there is waste heat generated by the exhaust of generator sets, waste heat generated by the central fresh water cooling system for cooling various equipment on the ship (such as air compressors, HPUs, air-cooled equipment, etc.), waste heat generated during the hydrogen production process, waste heat generated during the methanol production process, etc. In view of the above situation, an offshore production platform can be designed to recover and utilize the above waste heat to produce fresh water and further produce hydrogen and methanol, so as to further improve the greenness and economy of the hydrogen and methanol production processes. Summary of the Invention

[0005] To solve the above problems, the present invention provides a waste heat recovery hydrogen and methanol production system, aiming to reuse the waste heat generated by various devices on the offshore platform and improve the greenness of hydrogen and methanol production. The technical solution adopted is as follows:

[0006] A waste heat recovery hydrogen and methanol production system, where the offshore platform is equipped with multiple preparation devices. During the operation of the multiple preparation devices, waste heat will be generated. Each preparation device is equipped with a heat exchanger, and the multiple heat exchangers are sequentially connected through pipelines to form a waste heat recovery pipeline. The generated waste heat is connected to the waste heat recovery pipeline through the heat exchanger; the preparation devices include hydrogen production equipment and methanol production equipment.

[0007] One end of the waste heat recovery pipeline is connected to the seawater supply tank, and the other end is respectively connected to the evaporative water maker through the high-temperature seawater branch and to the seawater supply tank through the low-temperature seawater branch. A low-temperature temperature control valve is provided on the low-temperature seawater branch, and a high-temperature temperature control valve is provided on the high-temperature seawater branch.

[0008] The evaporative water maker is successively connected to the hydrogen production equipment and the methanol production equipment. Before the waste heat recovery pipeline is divided into the low-temperature seawater branch and the high-temperature seawater branch, a seawater circulation pump and a temperature sensor are provided. The temperature sensor controls the high-temperature temperature control valve and the low-temperature temperature control valve.

[0009] Seawater enters the seawater supply tank and the reverse osmosis water maker through the seawater supply pump. The reverse osmosis water maker is successively connected to the hydrogen production equipment and the methanol production equipment. A waste heat return control valve is provided at the seawater inlet of the seawater supply tank, and a standby branch control valve is provided at the seawater inlet of the reverse osmosis water maker. Seawater flows in the waste heat recovery pipeline, and the exchanged waste heat heats the seawater.

[0010] The seawater supply tank is used to ensure the supply of circulating water. There are multiple heat exchangers in the waste heat return to collect various types of waste heat. There is a seawater circulation pump in the waste heat return to circulate the seawater in the circuit. The evaporative water maker is used to prepare raw material fresh water using waste heat. The temperature sensor controls the opening and closing of the high-temperature temperature control valve and the low-temperature temperature control valve.

[0011] For the above-mentioned waste heat recovery type hydrogen production and methanol production system, further, a stop check valve is provided at the position where the low-temperature seawater branch is close to the seawater supply tank.

[0012] For the above-mentioned waste heat recovery type hydrogen production and methanol production system, further, a stop check valve is provided at the connection between the seawater supply tank and the waste heat recovery pipeline, and a stop check valve is provided on the passage from the evaporative water maker to the hydrogen production equipment.

[0013] For the above-mentioned waste heat recovery type hydrogen production and methanol production system, further, the hydrogen production equipment is connected to a hydrogen external transmission device.

[0014] For the above-mentioned waste heat recovery type hydrogen production and methanol production system, further, the methanol production equipment is connected to a methanol external transmission device.

[0015] For the above-mentioned waste heat recovery type hydrogen production and methanol production system, further, the preparation device further includes a generator exhaust pipe, a central fresh water cooling system and other waste heat production equipment.

[0016] The beneficial effects of the present invention are as follows:

[0017] 1. When the present invention produces hydrogen and synthesizes methanol, it can greatly reduce the dependence on reverse osmosis fresh water production.

[0018] 2. The waste heat resources of the present invention can be fully utilized without being wasted.

[0019] 3. When the present invention realizes relevant functions, it does not impose excessive additional requirements on the power load, layout space and cost on the platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of the existing system;

[0021] Figure 2 is a schematic diagram of the system of the present invention;

[0022] Among them, 1 - seawater supply pump, 2 - reverse osmosis water maker, 3 - hydrogen production equipment, 4 - methanol production equipment, 5 - evaporative water maker, 6 - seawater supply tank, 7 - low-temperature seawater branch, 8 - high-temperature seawater branch, 9 - heat exchanger, 10 - temperature sensor, 11 - high-temperature temperature control valve, 12 - low-temperature temperature control valve, 13 - generator exhaust pipe, 14 - central fresh water cooling system, 15 - preparation device, 16 - stop check valve, 17 - seawater circulation pump, 18 - waste heat circuit control valve, 19 - standby branch control valve, 20 - waste heat recovery pipeline. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be further described in conjunction with the accompanying drawings.

[0024] A waste heat recovery type hydrogen production and methanol production system, as Figure 2 shown, first, the seawater supply pump 1 provides seawater for the production of raw fresh water, which is divided into two paths. When this set of system is just started, the main waste heat sources on the offshore production facilities, namely the hydrogen production equipment 3 and the methanol production equipment 4, do not have enough waste heat output, and the waste heat resources generated by other preparation devices are less. At this time, both the waste heat circuit control valve 18 and the standby branch control valve 19 are kept open, the high-temperature temperature control valve 11 is kept closed, and the low-temperature temperature control valve 12 is kept open. One path of seawater flows into the reverse osmosis water making unit 2 through the standby branch control valve 19 for the preparation of fresh water. The prepared fresh water enters the hydrogen production equipment 3 for the production of hydrogen. The produced hydrogen is mainly supplied to the downstream methanol production equipment 4 for the production of methanol. The produced methanol can be exported or used as energy to supply back to the offshore production facilities (depending on the actual application scenario of the facilities). The produced hydrogen can also be exported or used as energy to supply back to the offshore production facilities (depending on the actual application scenario of the facilities),

[0025] Another path of seawater enters the seawater supply tank 6 through the control valve 18, and then flows through a plurality of heat exchangers 9 in the waste heat recovery circuit 20 in sequence after flowing out of the seawater supply tank 6. The waste heat energy exchanged by the heat exchanger 9 and the preparation device or system that can generate waste heat is used to heat the seawater in this branch.

[0026] Process a): A temperature sensor 10 is equipped on the waste heat recovery loop 20. When the temperature of the seawater in this branch reaches the allowable water production temperature of the evaporative water maker (40 - 50 °C) due to the heating of waste heat, the temperature sensor 10 controls the high-temperature control valve 11 to open and the low-temperature control valve 12 to close through signals, and controls the standby branch control valve 19 to close. Then, the seawater with qualified temperature will flow into the evaporative water making unit 5 through the high-temperature seawater branch 8 for preparing fresh water. The produced fresh water enters the hydrogen production equipment 3 for subsequent production of hydrogen and methanol. At this time, the reverse osmosis water making unit 2 on the standby branch does not work due to the closing of the control valve 19, and the raw fresh water of the entire production system is only provided by the evaporative water making unit 5 in the high-temperature seawater branch 8.

[0027] Process b): When the temperature of the seawater in the waste heat recovery loop 20 does not meet the standard (below 40 °C), the temperature sensor 10 keeps the high-temperature temperature control valve 11 closed and the low-temperature temperature control valve 12 open through signals, and at the same time keeps the standby branch control valve 19 open. Then, the seawater with unqualified temperature will flow back to the seawater supply tank 6 through the low-temperature seawater branch 7. The seawater circulation pump 17 equipped in the waste heat recovery loop 20 makes the low-temperature seawater keep circulating in the waste heat recovery loop 20 and continue to be heated by the heat exchanger until it meets the standard and then transfers to Process a). Before the temperature meets the standard, since the standby branch control valve 19 is open, the reverse osmosis water making unit on the standby branch keeps working to provide raw fresh water for the production system.

[0028] Among them, low-level (20%) and high-level (95%) liquid level switches are set in the seawater supply tank 6 to control the opening and closing of the waste heat circuit control valve 18 when the liquid level is insufficient or too high.

[0029] Stop check valves 16 are installed on the waste heat recovery loop 20, the low-temperature seawater branch 7, and the high-temperature seawater branch 8 to prevent mutual interference between hot and cold seawater.

Claims

1. A waste heat recovery type hydrogen and methanol production system, characterized in that, The offshore platform is equipped with multiple preparation devices. During operation, these multiple preparation devices generate waste heat. Each preparation device is equipped with a heat exchanger. The multiple heat exchangers are sequentially connected through pipelines to form a waste heat recovery pipeline. The generated waste heat is connected to the waste heat recovery pipeline via the heat exchanger. The preparation device includes a hydrogen production device and a methanol production device. One end of the waste heat recovery pipeline is connected to the seawater supply tank, and the other end is respectively connected to the evaporative water maker through a high-temperature seawater branch and connected to the seawater supply tank through a low-temperature seawater branch. A low-temperature temperature control valve is provided on the low-temperature seawater branch, and a high-temperature temperature control valve is provided on the high-temperature seawater branch. The evaporative water maker is sequentially connected to the hydrogen production device and the methanol production device. Before the waste heat recovery pipeline is divided into a low-temperature seawater branch and a high-temperature seawater branch, a seawater circulation pump and a temperature sensor are provided. The temperature sensor controls the high-temperature temperature control valve and the low-temperature temperature control valve. Seawater enters the seawater supply tank and the reverse osmosis water maker through a seawater supply pump. The reverse osmosis water maker is sequentially connected to the hydrogen production device and the methanol production device. A waste heat return control valve is provided at the seawater inlet of the seawater supply tank, and a standby branch control valve is provided at the seawater inlet of the reverse osmosis water maker. Seawater circulates in the waste heat recovery pipeline, and the exchanged waste heat heats the seawater.

2. The waste heat recovery type hydrogen production and methanol production system according to claim 1, wherein A stop check valve is provided near the seawater supply tank on the low-temperature seawater branch.

3. The waste heat recovery type hydrogen and methanol production system according to claim 1, characterized in that, A stop check valve is provided at the connection between the seawater supply tank and the waste heat recovery pipeline, and a stop check valve is provided on the passage from the evaporative water maker to the hydrogen production device.

4. The waste heat recovery type hydrogen and methanol production system according to claim 1, characterized in that The hydrogen production device is connected to a hydrogen external transportation device.

5. The waste heat recovery type hydrogen and methanol production system according to claim 1, characterized in that, The methanol production device is connected to a methanol external transportation device.

6. The waste heat recovery type hydrogen and methanol production system according to claim 1, characterized in that, The preparation device also includes a generator exhaust pipe and a central fresh water cooling system.

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