Process for recovering and purifying ammonia to produce ultra-pure ammonia

Abstract

The application discloses a kind of ammonia recovery purification process for preparing ultra-pure ammonia, comprising the following steps: S1, ammonia raw material is prepared;S2, ammonia tank is pressurized;S3, preheater preheating;S4, after preheating, ammonia is transported to concentration column;S5, after condensation, part of liquid phase reflux, another part of industrial liquid ammonia is extracted for standby;S6, industrial liquid ammonia is transported to light removal column;S7, light removal column is pressurized and separated, and condensed;S8, after condensation, non-condensable gas is extracted;Liquid phase enters reflux tank and returns to light removal column;S9, liquid ammonia of light removal column enters heavy removal column;S10, heavy removal column is pressurized and separated, and heavy components are removed;S11, qualified ultra-pure ammonia product is extracted from heavy removal column;S12, filling, warehousing;The application realizes the whole production preparation of 7N ultra-pure ammonia from raw material, intermediate product to final product through a series of processes, greatly reduces the energy consumption of production, can better meet the product standard, and is beneficial to provide the productivity and competitiveness of enterprise.

Description

Technical Field

[0001] This invention relates to the field of ultrapure ammonia preparation technology, specifically to a process for recovering and purifying ammonia water to produce ultrapure ammonia. Background Technology

[0002] Ultrapure ammonia is a key material for silicon nitride and gallium nitride masking films in microelectronics. It is also an important raw material in the optoelectronics, semiconductor, and light-emitting diode industries. Its purity has a direct impact on the lifespan of devices, the electrical and optical properties of materials, and the increasing demand for electronic products, new energy-saving lighting devices, and clean energy from society as a whole, leading to increasingly higher requirements for the purity of ultrapure ammonia.

[0003] The production of ultra-high purity ammonia generally involves using industrial liquid ammonia to remove various light components, high-boiling substances, water, and metal impurities through physicochemical methods such as adsorption, distillation, and filtration. This process is relatively complex, consumes a lot of energy, and is not conducive to improving production efficiency or reducing production costs. To solve the above problems, a process for producing ultra-pure ammonia by recovering and purifying ammonia water has been developed. Summary of the Invention

[0004] The purpose of this invention is to provide a process for recovering and purifying ammonia water to produce ultrapure ammonia. This process realizes the complete production and preparation of ammonia water as raw material, industrial liquid ammonia as intermediate product, and 7N ultrapure ammonia as the final product. It simplifies the preparation process, greatly reduces energy consumption, and the 7N ultrapure ammonia can better meet product standards, which is beneficial to improving the productivity and competitiveness of enterprises.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A process for recovering and purifying ammonia water to produce ultrapure ammonia includes the following steps:

[0007] S1, Load the ammonia water raw material at room temperature and pressure into the ammonia water tank for later use;

[0008] S2, use a diaphragm pump to pressurize the ammonia in the ammonia tank to 20-24 bar;

[0009] S3, the pressurized ammonia water is sent to the preheater for preheating to 120-140℃;

[0010] S4, the preheated ammonia water is delivered to the concentration tower, the operating pressure at the top of the concentration tower is controlled at 17.1-17.5 bar, the operating temperature is controlled at 43-47℃; the operating pressure at the bottom of the tower is controlled at 17.2-17.5 bar, and the operating temperature is controlled at 200-210℃.

[0011] S5: After the gaseous phase of the material in the concentration tower is condensed by the condenser at the top of the tower, part of the liquid phase is refluxed and the other part of the qualified industrial liquid ammonia is collected for later use.

[0012] S6, pressurizes industrial liquid ammonia using a diaphragm pump and delivers it to the light-weight product removal tower;

[0013] S7, after industrial liquid ammonia is separated by pressure in the light-light-removal tower, it is then condensed in the top condenser of the tower;

[0014] S8, the non-condensable gas condensed at the top of the tower is taken out of the ammonia absorption system; the condensed liquid phase enters the reflux tank and is returned to the light condensate removal tower by gravity through the reflux tank.

[0015] S9, liquid ammonia containing heavy components is collected from the bottom of the light component removal tower and enters the heavy component removal tower through pressure difference;

[0016] S10, the heavy components in the liquid ammonia are separated by pressurization in the heavy components removal tower;

[0017] S11, the gas phase at the top of the heavy removal tower is condensed by the top condenser. After condensation, the liquid phase flows into the reflux tank of the heavy removal tower. Part of the liquid phase flows back into the heavy removal tower by gravity, while the other part, as qualified ultrapure ammonia product, is cooled by the product cooler and then filtered by 0.01um and 0.001um product filters to remove solid particulate impurities. The product is then divided into two paths: one path is directly filled into the packaging container, and the other path is stored in the product storage tank.

[0018] S12, Store and put the products into storage.

[0019] In a preferred embodiment, in step S1, the concentration of the ammonia raw material is selected to be 18-24%.

[0020] In a preferred embodiment, in step S2, the diaphragm pump pressurizes the ammonia in the ammonia tank to 21-23 bar.

[0021] In a preferred embodiment, in step S3, the heat source for the preheater is provided by the heat extracted from the bottom of the enrichment tower.

[0022] In a preferred embodiment, in step S4, the operating pressure at the top of the concentration column is controlled at 17.2-17.4 bar, and the operating temperature is controlled at 44-46℃; the operating pressure at the bottom of the column is controlled at 17.2-17.4 bar, and the operating temperature is controlled at 205-210℃.

[0023] In a preferred embodiment, in step S6, industrial liquid ammonia is pressurized to 19.5-21.5 bar by a diaphragm pump and then transported to the light-duty removal tower.

[0024] In a preferred embodiment, in step S7, the operating pressure of the light-removal tower is controlled at 18.5-19.5 bar.

[0025] In a preferred embodiment, in step S10, the working pressure of the deweight removal tower is controlled at 16-18 bar.

[0026] In a preferred embodiment, in steps S5, S7, and S11, the condenser at the top of the column is cooled by circulating water; the heat source for the reboiler at the bottom of the concentration column is provided by a heat transfer oil device, with the temperature controlled between 0 and 300°C, while the heat source for the reboilers at the bottom of the light and heavy removal columns is provided by hot water.

[0027] In a preferred embodiment, in step S11, the liquid ammonia containing water, oil, and heavy metals in the bottom of the heavy metal removal tower flows into the ammonia removal water absorption system by gravity through pressure difference.

[0028] Due to the application of the above technical solution, the beneficial effects of this application compared with the prior art are as follows:

[0029] This application provides a process for recovering and purifying ammonia to produce ultrapure ammonia. Through a series of process flows and corresponding supporting systems, it realizes the complete production process from raw ammonia, intermediate product industrial liquid ammonia to the final product 7N ultrapure ammonia. The process flow is relatively simplified. In the preparation process, more environmentally friendly and energy-saving circulating water is used for cooling. The heat source for the preheater is provided by the water extracted from the bottom of the concentration tower. The reboilers at the bottom of the light and heavy removal towers use hot water as a heat source. The energy of the products in the entire system is fully utilized for circulation, which greatly reduces the energy consumption and production cost. At the same time, the prepared 7N ultrapure ammonia can better meet product standards, which is conducive to improving the productivity and competitiveness of enterprises. Attached Figure Description

[0030] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the process for recovering and purifying ammonia to produce ultrapure ammonia according to the present invention. Detailed Implementation

[0032] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0033] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0034] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing the invention and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0035] Furthermore, in addition to indicating direction or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in certain situations to indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0036] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; 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, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this invention according to the specific circumstances.

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] Example 1

[0039] Please see Figure 1 This application provides a process for recovering and purifying ammonia water to produce ultrapure ammonia, comprising the following steps:

[0040] S1, put the ammonia water raw material with a concentration of 18-24% at room temperature and pressure into the ammonia water tank for later use;

[0041] S2, use a diaphragm pump to pressurize the ammonia in the ammonia tank to 21 bar;

[0042] S3, pressurized ammonia water is transported to the preheater for preheating to 120°C; the heat source for the preheater is provided by the bottom of the concentration tower.

[0043] S4, the preheated ammonia water is delivered to the concentration tower, and the operating pressure at the top of the concentration tower is controlled at 17.2 bar and the operating temperature is controlled at 44℃; the operating pressure at the bottom of the tower is 17.2 bar and the operating temperature is controlled at 200℃.

[0044] S5: After the gaseous phase of the material in the concentration tower is condensed by the condenser, a portion of the liquid phase is refluxed, and the remaining portion of qualified industrial liquid ammonia is collected for use as raw material for the subsequent process to prepare 7N ultrapure ammonia. The cold source for the bottom condenser is circulating water, and the heat source for the reboiler is provided by a 0-300℃ heat transfer oil device. The ammonia content in the wastewater at the bottom of the concentration tower is less than 100PPM. After exchanging heat with the feed to the preheater, the temperature reaches 48℃ before being discharged.

[0045] S6, industrial liquid ammonia is pressurized to 19.5 bar by a diaphragm pump and then transported to the light-duty removal tower;

[0046] S7, after industrial liquid ammonia is separated under pressure in the light component removal tower, the light component accumulates at the top of the tower, and the gas phase at the top of the tower is then condensed by a condenser; the working pressure of the light component removal tower is controlled at 18.5 bar.

[0047] S8, the non-condensable gases (including N2, H2, CH4, CO2, CO, NH3, etc.) condensed at the top of the tower are taken out of the ammonia absorption system; the condensed liquid phase enters the reflux tank and returns to the light condensate removal tower by gravity.

[0048] S9, liquid ammonia containing heavy components is collected from the bottom of the light component removal tower and enters the heavy component removal tower through pressure difference;

[0049] The reboiler at the bottom of the light-light-removal tower uses 70℃ hot water as a heat source to provide heat for the light-light-removal tower, while the condenser at the top of the light-light-removal tower uses circulating water as a cold source to provide cold source for the light-light-removal tower.

[0050] S10, the heavy removal tower pressurizes and separates liquid ammonia to remove heavy components such as water, oil, and metal ions; the working pressure of the heavy removal tower is controlled at 16.5 bar.

[0051] In S11, the vapor phase at the top of the heavy ammonia stripping tower is condensed by a condenser. The condensed liquid phase flows into the reflux tank of the heavy ammonia stripping tower. Part of the liquid phase flows back into the heavy ammonia stripping tower by gravity, while the other part is collected as qualified ultrapure ammonia product. After being cooled by a product cooler, the liquid phase is filtered for solid particulate impurities by 0.01µm and 0.001µm product filters and then split into two streams. One stream is directly filled into packaging containers, and the other stream is stored in a product storage tank with a moisture content of less than 30 ppb. The moisture content in the receiving tank at the top of the heavy ammonia stripping tower is less than 5 ppb. In addition, the liquid ammonia containing water, oil, and heavy metals in the bottom of the heavy ammonia stripping tower flows into the ammonia water absorption system by gravity through pressure difference.

[0052] The reboiler at the bottom of the deweight removal tower uses 70℃ hot water as a heat source to provide heat to the deweight removal tower, while the condenser at the top of the deweight removal tower uses circulating water as a cold source to provide cooling to the deweight removal tower.

[0053] S12, Store and put the products into storage.

[0054] Example 2

[0055] Please see Figure 1 This application provides a process for recovering and purifying ammonia water to produce ultrapure ammonia, comprising the following steps:

[0056] S1, put the ammonia water raw material with a concentration of 18-24% at room temperature and pressure into the ammonia water tank for later use;

[0057] S2, use a diaphragm pump to pressurize the ammonia in the ammonia tank to 22 bar;

[0058] S3, pressurized ammonia water is sent to the preheater for preheating to 130°C; the heat source for the preheater is provided by the reboiler at the bottom of the concentration tower.

[0059] S4, the preheated ammonia water is delivered to the concentration tower, and the operating pressure at the top of the concentration tower is controlled at 17.3 bar and the operating temperature is controlled at 45℃; the operating pressure at the bottom of the tower is 17.3 bar and the operating temperature is controlled at 205℃.

[0060] S5: After the gaseous phase of the material in the concentration tower is condensed by the condenser, a portion of the liquid phase is refluxed, and the remaining portion of qualified industrial liquid ammonia is collected for use as raw material for the subsequent process to prepare 7N ultrapure ammonia. The cold source for the bottom condenser is circulating water, and the heat source for the reboiler is provided by a 0-300℃ heat transfer oil device. The ammonia content in the wastewater at the bottom of the concentration tower is less than 100PPM. After exchanging heat with the feed to the preheater, the temperature reaches 48℃ before being discharged.

[0061] S6, industrial liquid ammonia is pressurized to 20 bar by a diaphragm pump and then transported to the light-duty removal tower;

[0062] S7, after industrial liquid ammonia is separated under pressure in the light component removal tower, the light component accumulates at the top of the tower, and the gas phase at the top of the tower is then condensed by the condenser; the working pressure of the light component removal tower is controlled at 19 bar.

[0063] S8, the condensed non-condensable gases (including N2, H2, CH4, CO2, CO, NH3, etc.) are extracted from the top of the tower by the ammonia removal water absorption system; the condensed liquid phase enters the reflux tank and returns to the light condensate removal tower by gravity through the reflux tank;

[0064] S9, liquid ammonia containing heavy components is collected from the bottom of the light component removal tower and enters the heavy component removal tower through pressure difference;

[0065] The reboiler at the bottom of the light-weight product removal tower uses 70℃ hot water as a heat source to provide heat for the light-weight product removal tower, while the condenser at the top of the light-weight product removal tower uses circulating water as a cold source to provide cold source for the light-weight product removal tower.

[0066] S10, the heavy separation tower pressurizes and separates liquid ammonia to remove heavy components such as water, oil, and metal ions from the liquid ammonia; the working pressure of the heavy separation tower is controlled at 17 bar.

[0067] In S11, the vapor phase at the top of the heavy ammonia stripping tower is condensed by a condenser. The condensed liquid phase flows into the reflux tank of the heavy ammonia stripping tower. Part of the liquid phase flows back into the heavy ammonia stripping tower by gravity, while the other part is collected as qualified ultrapure ammonia product. After being cooled by a product cooler, the liquid phase is filtered for solid particulate impurities by 0.01µm and 0.001µm product filters and then split into two streams. One stream is directly filled into packaging containers, and the other stream is stored in a product storage tank with a moisture content of less than 30 ppb. The moisture content in the receiving tank at the top of the heavy ammonia stripping tower is less than 5 ppb. In addition, the liquid ammonia containing water, oil, and heavy metals in the bottom of the heavy ammonia stripping tower flows into the ammonia water absorption system by gravity through pressure difference.

[0068] The reboiler at the bottom of the deweight removal tower uses 70℃ hot water as a heat source to provide heat to the deweight removal tower, while the condenser at the top of the deweight removal tower uses circulating water as a cold source to provide cooling capacity to the deweight removal tower.

[0069] S12, Store and put the products into storage.

[0070] Example 3

[0071] Please see Figure 1 This application provides a process for recovering and purifying ammonia water to produce ultrapure ammonia, comprising the following steps:

[0072] S1, put the ammonia water raw material with a concentration of 18-24% at room temperature and pressure into the ammonia water tank for later use;

[0073] S2, use a diaphragm pump to pressurize the ammonia in the ammonia tank to 23 bar;

[0074] S3, pressurized ammonia water is sent to the preheater for preheating to 140°C; the heat source for the preheater is provided by the reboiler at the bottom of the concentration tower.

[0075] S4, the preheated ammonia water is delivered to the concentration tower, and the operating pressure at the top of the concentration tower is controlled at 17.4 bar and the operating temperature is controlled at 46℃; the operating pressure at the bottom of the tower is 17.4 bar and the operating temperature is controlled at 210℃.

[0076] S5: After the gaseous phase of the material in the concentration tower is condensed by the condenser, a portion of the liquid phase is refluxed, and the remaining portion of qualified industrial liquid ammonia is collected for use as raw material for the subsequent process to prepare 7N ultrapure ammonia. The cold source for the bottom condenser is circulating water, and the heat source for the reboiler is provided by a 0-300℃ heat transfer oil device. The ammonia content in the wastewater at the bottom of the concentration tower is less than 100PPM. After exchanging heat with the feed to the preheater, the temperature reaches 48℃ before being discharged.

[0077] S6, industrial liquid ammonia is pressurized to 21.5 bar by a diaphragm pump and then transported to the light-duty removal tower;

[0078] S7, after industrial liquid ammonia is separated under pressure in the light component removal tower, the light component accumulates at the top of the tower, and the gas phase at the top of the tower is then condensed by the condenser; the working pressure of the light component removal tower is controlled at 19.5 bar.

[0079] S8, the condensed non-condensable gases (including N2, H2, CH4, CO2, CO, NH3, etc.) are extracted from the top of the tower by the ammonia removal water absorption system; the condensed liquid phase enters the reflux tank and returns to the light condensate removal tower by gravity through the reflux tank;

[0080] S9, liquid ammonia containing heavy components is collected from the bottom of the light component removal tower and enters the heavy component removal tower through pressure difference;

[0081] The reboiler at the bottom of the light-weight product removal tower uses 70℃ hot water as a heat source to provide heat for the light-weight product removal tower, while the condenser at the top of the light-weight product removal tower uses circulating water as a cold source to provide cold source for the light-weight product removal tower.

[0082] S10, the heavy removal tower pressurizes and separates liquid ammonia to remove heavy components such as water, oil, and metal ions; the working pressure of the heavy removal tower is controlled at 17.5 bar.

[0083] In S11, the vapor phase at the top of the heavy ammonia stripping tower is condensed by a condenser. The condensed liquid phase flows into the reflux tank of the heavy ammonia stripping tower. Part of the liquid phase flows back into the heavy ammonia stripping tower by gravity, while the other part is collected as qualified ultrapure ammonia product. After being cooled by a product cooler, the liquid phase is filtered for solid particulate impurities by 0.01µm and 0.001µm product filters and then split into two streams. One stream is directly filled into packaging containers, and the other stream is stored in a product storage tank with a moisture content of less than 30 ppb. The moisture content in the receiving tank at the top of the heavy ammonia stripping tower is less than 5 ppb. In addition, the liquid ammonia containing water, oil, and heavy metals in the bottom of the heavy ammonia stripping tower flows into the ammonia water absorption system by gravity through pressure difference.

[0084] The reboiler at the bottom of the deweight removal tower uses 70℃ hot water as a heat source to provide heat to the deweight removal tower, while the condenser at the top of the deweight removal tower uses circulating water as a cold source to provide cooling capacity to the deweight removal tower.

[0085] S12, Store and put the products into storage.

[0086] This application provides a process for recovering and purifying ammonia to produce ultrapure ammonia. Through a series of process flows and corresponding supporting systems, it realizes the complete production process from raw ammonia, intermediate product industrial liquid ammonia to the final product 7N ultrapure ammonia. The process flow is relatively simplified. In the preparation process, more environmentally friendly and energy-saving circulating water is used for cooling. The heat source of the preheater is provided by the reboiler at the bottom of the concentration tower, light product removal tower, and heavy product removal tower. Using hot water as a heat source, the energy of the entire system itself is fully utilized for circulation, which greatly reduces the energy consumption of production. The system energy consumption is 1.7 kW, that is, the energy required to produce 1 kg of ultrapure ammonia is 1.7 kW, which reduces the production cost. At the same time, the prepared 7N ultrapure ammonia can better meet product standards, which is conducive to improving the productivity and competitiveness of enterprises.

[0087] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for the production of ultra-pure ammonia by recovery and purification of ammonia water, characterized in that, It comprises the following steps: S1, ammonia raw material with concentration of 18-24% at normal temperature and pressure is loaded into ammonia tank for standby; S2, diaphragm pump is used to pressurize ammonia in ammonia tank to 20-24 bar; S3, pressurized ammonia is delivered to preheater for preheating, and the temperature is preheated to 120-140℃, and the heat source of the preheater is provided by the material collected from the bottom of the concentration column; S4, the preheated ammonia is delivered to the concentration column, the operating pressure at the top of the concentration column is controlled to be 17.1-17.5 bar, and the operating temperature is controlled to be 43-47℃; the operating pressure at the bottom of the column is controlled to be 17.2-17.5 bar, and the operating temperature is controlled to be 200-210℃; S5, the gas phase in the concentration column is condensed by the overhead condenser, part of the liquid phase is refluxed, and the other part of the industrial liquid ammonia with qualified purity is collected for standby; S6, the industrial liquid ammonia is pressurized to 19.5-21.5 bar by a diaphragm pump and then delivered to the light removal column; S7, the working pressure of the light removal column is controlled to be 18.5-19.5 bar, and the industrial liquid ammonia is separated after being pressurized and then condensed by the overhead condenser; S8, the non-condensable gas condensed by the overhead condenser is collected from the top of the column and sent to the ammonia absorption system; the liquid phase after condensation enters the reflux tank and returns to the light removal column by itself; S9, the liquid ammonia containing heavy components is collected from the bottom of the light removal column and enters the heavy removal column by pressure difference; S10, the working pressure of the heavy removal column is controlled to be 16-18 bar, and the liquid ammonia is pressurized and separated to remove heavy components in the liquid ammonia; S11, the gas phase in the heavy removal column is condensed by the overhead condenser, and the liquid phase after condensation flows into the reflux tank of the heavy removal column, part of which returns to the heavy removal column by itself, and the other part is cooled by the product cooler, filtered by 0.01μm and 0.001μm product filters to remove solid particle impurities, and then divided into two paths, one of which is directly filled into the packaging container, and the other is stored in the product storage tank; S12, the product is stored and warehoused.

2. The process for recovering and purifying ammonia to produce ultra-pure ammonia according to claim 1, wherein In steps S5, S7 and S11, the overhead condenser is cooled by circulating water; wherein the heat source of the column reboiler of the concentration column is provided by a heat conducting oil device, and the heat source of the column reboiler of the light removal column and the heavy removal column is provided by hot water.

3. The process for recovering and purifying ammonia to produce ultra-pure ammonia according to claim 1, wherein In step S11, the liquid ammonia containing water, oil and heavy metals in the column of the heavy removal column is self-flowed into the ammonia absorption system by pressure difference.

Images