Dual-heat-source dual-purpose gasification system and working method thereof

Abstract

The present application relates to the field of energy saving, and discloses a dual-purpose gasification system of double heat sources and a working method thereof, the dual-purpose gasification system comprises a gasifier, an inlet of the gasifier is connected with an inlet water pipeline, an outlet of the gasifier is connected with an outlet water pipeline, a first valve is arranged on the inlet water pipeline, and a fifth valve is arranged on the outlet water pipeline; a water pump and a fourth valve are arranged on the inlet water pipeline in sequence along a seawater flow direction; a second branch pipeline and a third branch pipeline are arranged on the inlet water pipeline, a second valve is arranged on the second branch pipeline, a third valve is arranged on the third branch pipeline, and the second branch pipeline and the third branch pipeline both extend into a water storage pool. The present application solves the problem that the existing gasifier system cannot work at full load under the condition of double heat sources with different temperatures, and saves energy.

Description

Technical Field

[0001] This invention belongs to the field of energy conservation, specifically relating to a dual-use gasification system with two heat sources and its working method. Background Technology

[0002] Commonly used gasifiers typically use seawater as a heat source, with a minimum design temperature of 6.85 degrees Celsius and environmental requirements mandating an inlet-outlet temperature difference of less than 5 degrees Celsius. In heat exchange calculations, due to the small temperature difference (less than 5 degrees Celsius), a large water flow rate is required. In practical applications, when the gasification rate is 210 t / h, the water flow rate reaches approximately 9,000 tons per hour, requiring a 1500 kW water pump, resulting in significant operating costs.

[0003] With the rapid development of my country's LNG industry, energy conservation and environmental protection have become the focus of my country's natural gas development. How to achieve energy conservation and environmental protection while gasifying has become the main direction of the industry's development.

[0004] Natural gas is currently recognized worldwide as a green and environmentally friendly energy source. However, natural gas is usually in liquid form and needs to be vaporized before use. Currently, the main types of large-scale gasifiers in operation in my country are as follows:

[0005] (1) Open-frame vaporizer (2) Submerged combustion vaporizer (3) Intermediate medium vaporizer. Intermediate medium vaporizers mostly use propane as the intermediate medium and utilize seawater or hot water from nearby plants as the heat source. The primary heat source heats the intermediate medium, and then the intermediate medium vapor is used to heat the LNG, which can greatly improve the impact of icing. Its initial investment is large, but the operating cost is low. The requirements for the heat source seawater are also relatively low, making it suitable for sea areas with relatively turbid water quality (turbid seawater is defined as suspended sediment greater than 80 mg / L). Under the condition of having a continuous and stable waste heat source, the heat exchange equipment can greatly save energy through relevant design. However, sometimes the external heat source is discontinuous. Under the two conditions of discontinuous (with / without) heat source operation, the vaporization system may not be able to work at full load. On the other hand, when switching to the condition without a heat source, the minimum inlet temperature may be lower than the previous inlet design temperature, causing the equipment to malfunction. Summary of the Invention

[0006] To address the problem of existing vaporizer systems being unable to operate at full capacity under dual heat source conditions with different temperatures, thus wasting energy.

[0007] The specific solution adopted in this invention is as follows: a dual-purpose gasification system with dual heat sources, the dual-purpose gasification system including a gasifier, the inlet of the gasifier being connected to a water inlet pipe, the outlet of the gasifier being connected to a water outlet pipe, a first valve being installed on the water inlet pipe, and a fifth valve being installed on the water outlet pipe; a water pump and a fourth valve are sequentially installed on the water inlet pipe in the direction of water flow; a second branch pipe and a third branch pipe are installed on the water inlet pipe, a second valve is installed on the second branch pipe, and a third valve is installed on the third branch pipe, both of the second and third branch pipes extending into a water storage tank; a connecting pipe is installed on the water inlet pipe, the end of the connecting pipe being connected to one end of a heat exchanger, and the other end of the heat exchanger being connected to the water inlet pipe, the connection point of the heat exchanger and the water inlet pipe being located on the water inlet pipe between the second and third branch pipes, and in front of the water pump; a control system is installed on the connecting pipe.

[0008] On the other hand, the present invention discloses a method for operating a dual-purpose gasification system with two heat sources, the method comprising the following steps:

[0009] (1) Open the water pump, the first valve, and the third valve. Seawater enters the reservoir through the seawater inlet, the first valve, the water pump, and the third valve.

[0010] (2) The control system shuts off the first valve and the second valve after the water level in the reservoir reaches the preset position;

[0011] (3) The control system opens the second valve and the fourth valve, and seawater enters the gasifier from the water storage tank through the gasifier inlet;

[0012] (4) Seawater enters the heat exchanger through the gasifier outlet and the sixth valve. After being heated, it enters the gasifier through the eighth valve, the water pump, the fourth valve, and the gasifier inlet to complete the cycle.

[0013] The method involves two calculation steps:

[0014] (1) Perform the first step of the calculation according to the working condition without high temperature heat source, assign values ​​to the seawater outlet temperature, intermediate temperature and propane working temperature respectively, and calculate the water flow rate and heat exchange area.

[0015] (2) After adding the heat exchanger, the calculation is performed again. The seawater becomes a high-temperature heat source after passing through the heat exchanger. The equipment inlet temperature is increased before entering the gasifier. The second step of reverse calculation is performed: the seawater inlet / outlet temperature is assigned a value, the water inlet / outlet temperature difference is gradually increased, the water consumption is reduced, so as to reduce the load on the water pump.

[0016] The present invention has the following beneficial effects:

[0017] This invention discloses a dual-purpose gasification system with two heat sources, including a gasifier. The inlet of the gasifier is connected to a water inlet pipe, and the outlet of the gasifier is connected to a water outlet pipe. A first valve is installed on the water inlet pipe, and a fifth valve is installed on the water outlet pipe. The dual-purpose gasifier system regulates the flow rate by controlling the water pump and the valves, thereby saving energy.

[0018] On the other hand, the present invention utilizes the waste heat of buildings such as power plants and steel plants near the receiving station to increase the inlet temperature of the gasifier water. By adding a water-to-water heat exchanger or a gas-to-water heat exchanger, the inlet temperature of the gasifier heat source water is increased, the water flow rate is reduced, and energy saving is achieved. It can still work normally after switching to the low-temperature heat source of natural seawater. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the system structure described in this invention;

[0020] Figure 2 This is a schematic diagram illustrating the working principle of the present invention when a heat source is present.

[0021] Figure 3 This is a schematic diagram of the working principle of the present invention when there is no heat source.

[0022] Symbol explanation:

[0023] In the diagram, 1-seawater inlet, 2-first valve, 3-second valve, 4-storage tank, 5-water pump, 6-third valve, 7-fourth valve, 8-inlet pipe, 9-gasifier, 10-control system, 11-outlet pipe, 12-fifth valve, 13-sixth valve, 14-seventh valve, 15-heat exchanger, 16-eighth valve, 17-second branch pipe, 18-third branch pipe, 19-connecting pipe. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0025] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0026] Example

[0027] This invention discloses a dual-purpose gasification system with two heat sources. The dual-purpose gasifier system includes a gasifier 9, whose inlet is connected to a water inlet pipe 8 and whose outlet is connected to a water outlet pipe 11. A first valve 2 is installed on the water inlet pipe 8, and a fifth valve 12 is installed on the water outlet pipe 11. A water pump 5 and a fourth valve 7 are sequentially installed on the water inlet pipe 8 in the direction of water flow. A second branch pipe 17 and a third branch pipe 18 are installed on the water inlet pipe 8. A second valve 3 is installed on the second branch pipe 17, and a third valve 6 is installed on the third branch pipe 18. Both the second branch pipe 17 and the third branch pipe 18 extend into a water storage tank 4. A connecting pipe 19 is provided on the water inlet pipe 8. One end of the connecting pipe 19 is connected to one end of a heat exchanger 15, and the other end of the heat exchanger 15 is connected to the water inlet pipe 8. The connection point between the heat exchanger 15 and the water inlet pipe 8 is located on the water inlet pipe 8 between the second branch pipe 17 and the third branch pipe 18, and is located in front of the water pump 5. A control system 10 is provided on the connecting pipe 19. In this invention, the control system is a conventional control system that controls the water pump and valves by detecting the temperature and flow rate of the fluid in the pipe.

[0028] The dual-heat-source gasification system provided in this invention utilizes waste heat from power plants, steel mills, etc., near the receiving station to increase the inlet temperature of the water in the gasifier. This is achieved by adding a heat exchanger (water-to-water or gas-to-water exchanger) to increase the inlet temperature of the heat source water in the gasifier, thereby reducing the water flow rate and achieving energy savings. It can still operate normally after switching to natural seawater, which lacks a high-temperature heat source. Its working principle is shown in the attached figure. Figure 2 (The solid line in the diagram represents the circulation without a high-temperature heat source, and the dashed line represents the circulation with an intermittent heat source): Waste heat can be used to increase the inlet temperature of the circulating water, achieving energy-saving goals. Its working principle when there is no heat source is shown in the attached diagram. Figure 3 The equipment will switch to a lower temperature seawater operating condition, which solves the problem of energy waste caused by the gasifier not being able to work at full load under the two operating conditions of discontinuous (high / low temperature) heat sources in the existing technology.

[0029] To save energy, this invention first performs calculations under conditions without a high-temperature heat source: assigning values ​​to the seawater outlet temperature, intermediate temperature, and propane operating temperature to calculate the water flow rate and heat exchange area. Specifically: using the natural gas inlet and outlet temperatures T1 and T2, the mass flow rate G, and based on the enthalpy difference ΔI between the inlet and outlet temperatures of LNG at a given pressure P, the water inlet temperature t1, and the specific heat capacity C under the corresponding conditions... p1 Given the conditions, assume the water outlet temperature t2 and the specific heat capacity C under the corresponding state. p2 The heat transfer coefficient k is obtained through the formula

[0030] Q×(t1×Cp1-t2×Cp2)=G×ΔI

[0031] 1 / k=1 / h+R+do / (2×λ)×LN(do / di)+(1 / h+R)×(do / di)

[0032] A = W / k / Δt

[0033] By assigning values ​​to relevant quantities and performing iterative calculations, the heat exchange area A, water flow rate Q, and theoretical heat transfer W of the water are calculated, thus determining the structure of the gasifier.

[0034] Then, calculations are performed based on the addition of a waste heat recovery structure (water heater) to convert it into a high-temperature heat source. Seawater passes through a heat exchanger, its inlet temperature is increased before entering the vaporizer, and a second step of reverse calculation is performed: values ​​are assigned to the seawater inlet / outlet temperatures (above the normal annual minimum seawater temperature) to gradually increase the inlet / outlet temperature difference, reducing water consumption and thus lowering the pump load to save energy. However, the temperature difference cannot be increased indefinitely, because as the temperature difference increases, the water flow rate decreases. Due to the reduced flow rate, the water velocity gradually decreases, leading to a decrease in the Reynolds number. When a certain value is reached, the water flow state changes from turbulent to laminar, and the heat transfer coefficient drops sharply. Therefore, repeated adjustments and trial calculations are needed to find the appropriate temperature difference, flow velocity, Reynolds number, water flow state, and suitable water flow rate, while also ensuring that the tube-side temperature is above zero degrees Celsius to prevent icing. In other words, using the inlet / outlet temperature, flow rate, pressure, and heat exchange area of ​​natural gas as known conditions, and through iterative calculations using the inlet / outlet temperature of the feedwater as a supplement, the appropriate inlet / outlet temperature difference and flow rate, among other relevant parameters, are determined to match the heat exchange area. Furthermore, it ensures that the Reynolds number, i.e., the fluid flow state, remains within the turbulent range, and that the heat exchange area is sufficient.

[0035] Its energy-saving effect can be seen from Formula 1: When we increase the heat exchange temperature difference ΔT, with the total heat exchange Q remaining unchanged, the flow rate W will decrease. This allows us not only to use the gasifier normally, but also to reduce the amount of seawater used.

[0036] Formula 1: Q=CM△T

[0037] Q: Heat exchange

[0038] C: Specific heat

[0039] M: Traffic

[0040] △T: Heat exchange temperature difference

[0041] As can be seen from Formula 2, the power of a water pump is directly proportional to its flow rate. When the flow rate W is reduced by half, the power it consumes will also be reduced by nearly half.

[0042] Formula 2: P = 2.73 * W * H / η

[0043] P: Power

[0044] W: Traffic

[0045] H: Head

[0046] η: Efficiency

[0047] This invention discloses a method for operating a dual-purpose vaporizer with two heat sources, the method comprising the following steps:

[0048] This working method uses two different vaporizer inlet temperatures alternately, which can ensure normal vaporization of the vaporizer while greatly improving the energy-saving effect of the system.

[0049] (1) Open the water pump, the first valve, and the third valve. Seawater enters the reservoir through the seawater inlet, the first valve, the water pump, and the third valve. (2) The control system shuts off the first valve and the second valve after the water level in the reservoir reaches the preset position. (3) The control system opens the second valve and the fourth valve. Seawater enters the gasifier through the gasifier inlet from the reservoir. (4) Seawater enters the heat exchanger through the gasifier outlet and the sixth valve. After being heated, it enters the gasifier through the eighth valve, the water pump, the fourth valve, and the gasifier inlet to complete the cycle.

[0050] In the absence of a heat source, during the heat source circulation process, seawater enters the vaporizer through the first valve, the water pump, and the fourth valve; it is then discharged directly into the sea through the vaporizer outlet and the fifth valve, completing the second cycle.

[0051] Beneficial effects of the operating method: 1. When there is an external high-temperature heat source such as a power plant or steel plant heating network, the new system saves energy while ensuring the vaporization rate during heat exchanger operation. 2. When there is no external heat source, it can be switched to operating with ambient temperature seawater without changing the vaporization rate, thus achieving energy savings.

[0052] The method described in this invention involves two calculation steps:

[0053] (1) Perform the first step of calculation under the condition of no high temperature heat source, assign values ​​to the seawater outlet temperature, intermediate temperature and propane working temperature respectively, and calculate the water flow rate and heat exchange area; (2) After adding the water heat exchanger (under the condition of having a high temperature heat source), perform the calculation again. After the seawater passes through the water heat exchanger, the equipment inlet temperature is increased before entering the gasifier. Perform the second step of reverse calculation: assign values ​​to the seawater inlet / outlet temperature respectively, gradually increase the water inlet / outlet temperature difference, reduce the water consumption, so as to reduce the load on the water pump.

[0054] The two-step calculation is mainly to ensure that the heat exchange area remains unchanged after the first step, and the parameters that match it are obtained through the second calculation, thus fully guaranteeing that the equipment can be used for different inlet parameters at the same heat exchange area.

[0055] Economic benefit analysis:

[0056] Based on the original design of a 1500KW water pump, one unit can save energy per year.

[0057] Energy saving = (1-1800 / 9700)*1500 kW*24 hours*200 days ≈ 5.8 million RMB.

[0058] Additional project expenses (cost of laying pipelines from available waste heat sources to the receiving station):

[0059] 1. Material used for auxiliary pipelines: DN600*8 steel pipe (excluding roads).

[0060] Cost per kilometer from heat source to site: 620,000 RMB

[0061] Pipeline length: calculated at 20 kilometers

[0062] Total cost = 62 * 20 = 12.4 million yuan

[0063] 2. Heat exchanger (water-to-water heat exchanger or gas-to-water heat exchanger):

[0064] Estimated: 1 million yuan

[0065] 3. Single unit payback period = (1240 + 100) / 580 = 2.31 years

[0066] The above estimates are based on the energy-saving effect and payback period of a single unit. It can be seen that although the new system increases investment in heat exchange equipment and connecting pipelines, the investment can be recovered in just over two years.

[0067] Each large receiving station is typically equipped with ten gasifiers. Therefore, we can expect that if a receiving station is operating at full capacity, after deducting the additional investment cost of more than ten million yuan, it can save about forty million yuan (RMB) in electricity per year.

[0068] The system in this invention saves energy while maintaining normal vaporization under conditions with a high-temperature heat source. When no high-temperature heat source is available, switching to seawater as the heat source also ensures the same vaporization rate.

[0069] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be permuted and combined. Those skilled in the art can exhaust all possibilities based on the mathematical knowledge of permutation and combination. Therefore, the present invention will not describe the technical solutions after permutation and combination one by one, but it should be understood that the technical solutions after permutation and combination have been disclosed by the present invention.

[0070] This embodiment is merely an exemplary description of this patent and does not limit its scope of protection. Those skilled in the art can make partial changes to it, as long as they do not exceed the spirit and essence of this patent, they are all within the scope of protection of this patent.

Claims

1. A working method of a dual-heat-source dual-purpose gasification system, which is based on a dual-heat-source dual-purpose gasification system, the dual-heat-source dual-purpose gasification system including a gasifier (9), the inlet of the gasifier (9) being connected to a water inlet pipe (8), the outlet of the gasifier (9) being connected to a water outlet pipe (11), a first valve (2) being installed on the water inlet pipe (8), and a fifth valve (12) being installed on the water outlet pipe (11); a water pump (5) and a fourth valve (7) are sequentially installed on the water inlet pipe (8) in the direction of the water flow; a second branch pipe (17) and a third branch pipe (18) are installed on the water inlet pipe (8), the second branch pipe (17) A second valve (3) is installed on the upper part of the third branch pipe (17), and a third valve (6) is installed on the third branch pipe (18). Both the second branch pipe (17) and the third branch pipe (18) extend into the water storage tank (4). A connecting pipe (19) is installed on the water inlet pipe (8). The end of the connecting pipe (19) is connected to one end of the heat exchanger (15), and the other end of the heat exchanger (15) is connected to the water inlet pipe (8). The connection point between the heat exchanger (15) and the water inlet pipe (8) is located on the water inlet pipe (8) between the second branch pipe (17) and the third branch pipe (18), and is located in front of the water pump (5). A control system (10) is installed on the connecting pipe (19). Its features are, The method includes the following steps: (1) Open the water pump, the first valve, and the third valve. Seawater enters the water storage tank through the seawater inlet, the first valve, the water pump, and the third valve. (2) The control system shuts off the first valve and the second valve after the water level in the reservoir reaches the preset position; (3) The control system opens the second valve and the fourth valve, and seawater enters the gasifier from the water storage tank through the gasifier inlet; (4) Under the condition of a high-temperature heat source, seawater enters the heat exchanger through the gasifier outlet and the sixth valve. After being heated, it enters the gasifier through the eighth valve, the water pump, the fourth valve, and the gasifier inlet to complete the cycle. In the absence of a high-temperature heat source, during the heat source circulation process, seawater enters the vaporizer through the first valve, the water pump, and the fourth valve; it is then discharged directly into the sea through the vaporizer outlet and the fifth valve, completing the second cycle, with the vaporization volume remaining unchanged. The described working method involves two calculations: (1) Perform the first step of the calculation according to the working condition without high temperature heat source, assign values ​​to the seawater outlet temperature, intermediate temperature and propane working temperature respectively, and calculate the water flow rate and heat exchange area. (2) After adding the heat exchanger, the calculation is performed again. The seawater becomes a high-temperature heat source after passing through the heat exchanger. The inlet temperature of the equipment is increased before entering the gasifier. The second step of reverse calculation is performed: the heat exchange area remains unchanged, and the seawater inlet / outlet temperature is given a value. The temperature difference between the inlet and outlet of the water is gradually increased, and the water consumption is reduced in order to reduce the load on the water pump.

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