Production of carbon dioxide and carbon dioxide storage, carbon capture

CO2 Capture Technology Tool

CO2 Capture Rate (%): Select Technology: Post-Combustion Capture Oxy-Fuel Combustion Direct Air Capture Chemical Looping Combustion Membrane Separation Energy Penalty (GJ/ton CO2): Capital Cost ($/ton CO2 captured/year): Operational Cost ($/ton CO2 captured/year): Plant Lifetime (years): Discount Rate (%): CO2 Emission Cost ($/ton CO2 Avoided):

We see how carbon dioxide is changing the atmospheric conditions and we are one of the reasons for the increase of CO2 levels. We cannot control the carbon dioxide that emits from volcanoes, forest fires and other natural causes but we can handle the amount of carbon dioxide that our industries and automobiles produce. To do this we have to understand the sources of production of carbon dioxide, capture it, storing and use it in green technologies.

Industrial operations that produce carbon dioxide through byproduct and flue gas:

• Combustion operation (Power plants)
• Reforming operations (Refineries and chemical plants)

Carbon dioxide capturing:

• By chemical technology: Chemical and physical absorption

CO2 removal reaction using Potassium bicarbonate

• Plantation

Storage:

• Dry ice

Converting carbon dioxide by green technology:

• By converting it into methanol or dimethyl ether using the CO2 hydrogenation technique.

Let us know one of the technologies available to chemically absorb carbon dioxide from industrial gases in larger quantities.

Giammarco Vetrocoke Process Design Flow diagram for CO2  Capture 

Process flow diagram of CO2 absorption from Industrial gases

CO2 Absorption Process with Giammarco-Vetrocoke Technology: A Detailed Overview

Carbon dioxide (CO2) capture stands as a pivotal technology in mitigating greenhouse gas emissions and advancing sustainable industrial practices. This article delves into a core CO2 removal process widely utilized in various industrial applications: absorption using the Giammarco-Vetrocoke (GV) technology, particularly valuable in ammonia production where CO2 can undesirably react with ammonia to form urea, impacting product purity and process efficiency. The GV process, a proprietary solution, ensures optimal CO2 removal.

The Absorption Tower: Initiating CO2 Capture

The CO2 removal journey commences within the absorption tower, a meticulously designed vessel where the incoming process gas encounters a specialized absorbent: a heated potassium carbonate (K2CO3) solution. This solution, often maintained at elevated temperatures to enhance absorption kinetics, selectively captures CO2 from the gas stream. Packed beds, carefully arranged within the tower, facilitate a maximized contact area between the gas and liquid phases through a counter-current flow pattern. This configuration optimizes the mass transfer of CO2 from the gas phase to the liquid phase. The governing chemical reactions driving this absorption are:

CO2 + H2O ⇌ H2CO3 (Carbon dioxide reacts with water to form carbonic acid)

H2CO3 + K2CO3 ⇌ 2KHCO3 (Carbonic acid reacts with potassium carbonate to form potassium bicarbonate)

The resultant purified gas, characterized by a significantly reduced CO2 concentration (typically below 1000 ppm), is then directed to downstream processes.

GV Technology: Precision CO2 Removal

The Giammarco-Vetrocoke (GV) process represents a specialized, proprietary technology designed for the selective removal of carbon dioxide (CO2) from industrial gas streams. This process is particularly critical in ammonia production where CO2 can react with ammonia to form urea, compromising product quality. The GV solution, meticulously formulated with a specific concentration (28-30%) of potassium carbonate (K2CO3), is enriched with glycine (NH2CH2COOH), an amino acid that enhances CO2 absorption, and a corrosion inhibitor, vanadium pentoxide (V2O5), to protect equipment integrity. This specialized formulation enables the preferential absorption of CO2, ensuring efficient and reliable removal.

Methanator Section: Further Gas Purification

Post-absorption, the process gas undergoes further refinement. After passing through a knockout drum to remove any entrained liquids, the gas enters the methanator section. This critical step operates under specific conditions:

• Temperature: 65°C

• Pressure: 25.0 ksc (kilograms per square centimeter)

Under these conditions, the gas composition is as follows (mole %):

• H2: 72.72

• N2: 25.79

• CO: 0.44

• CO2: 0.1

• CH4: 0.64

• Ar: 0.31

Absorbent Regeneration: Restoring Capture Capacity

To maintain a sustainable and continuous CO2 capture process, the absorbent solution must be regenerated, liberating the captured CO2 and restoring the solution's capacity to absorb more. This regeneration occurs in a carefully orchestrated two-stage process:

1. Flashing: The CO2-rich solution undergoes a pressure reduction (flashing) to a low pressure, facilitating the release of a significant portion of the absorbed CO2.

2. Steam Stripping: The solution is then subjected to steam stripping, where a counter-current flow of steam further removes the remaining CO2.

The resulting lean solution, now depleted of CO2, is cooled and recycled back to the absorption tower, completing the continuous absorption-regeneration cycle.

Optimizing Energy Efficiency in Regeneration

Energy efficiency is paramount in any industrial process. In this CO2 capture system, the process gas emanating from the low-temperature shift converter undergoes preheating prior to entering the reboilers. Here, steam is generated, providing the thermal energy necessary for stripping CO2 from the absorbent in the regeneration towers. To further enhance energy efficiency, the stripping process is implemented in two stages.

Two-Stage Stripping: Maximizing CO2 Removal and Minimizing Energy Input

The semi-lean solution from the regeneration towers undergoes flashing across level control valves and enters a second regeneration tower, operating at a significantly reduced pressure (0.1 ksc). In this stage, CO2 stripping is accomplished without the need for additional heat input, leveraging the energy-efficient flashing process. The final lean solution is then collected, cooled, and recycled back to the absorption tower, maximizing resource utilization.

CO2 Stream Processing: From Regeneration to Compression

The CO2-steam mixture exiting the regeneration towers is condensed, and the liberated heat is transferred to a demineralized water stream, promoting energy recovery. The condensate is then recycled back into the process. The resultant CO2 stream undergoes final cooling using cooling water, prior to being compressed and routed to a urea production unit or for other beneficial utilization.

Equipment Inventory for CO2 Absorption and Regeneration

The described CO2 capture system utilizes a range of specialized equipment to ensure efficient and reliable operation:

• Absorption Tower: The primary vessel for CO2 absorption.

• Reboilers: Generate steam for CO2 stripping in the regeneration towers.

• Regeneration Towers: Vessels where steam stripping removes CO2 from the absorbent.

• Steam Strippers: Enhance CO2 removal from the absorbent.

• Condensers: Cool the CO2-steam mixture from the regeneration towers.

• Pumps: Facilitate fluid transport throughout the system (including condensate and circulation pumps).

• CO2 Booster Compressor: Compresses the CO2 stream for downstream processes.

• Heat Exchangers: Recover heat and preheat streams (including economizers and demineralized water preheaters).

• Separators: Remove entrained liquids (including flash drums and knockout drums).

• Valves: Control fluid flow (including level control and block valves).

Energy Optimization: A Two-Stage Approach to Stripping

A key element of the GV process lies in its two-stage stripping configuration. The GV solution, now rich in CO2, is flashed to the top of the regenerator, typically operating at a pressure of 1.04 ksc. This pressure reduction facilitates the release of a significant portion of the absorbed CO2. The solution then trickles down packed beds, encountering a counter-current stream of steam vapor and CO2, which further strips CO2 from the solution. This process optimizes the consumption of energy.

The heat necessary for this stripping process is supplied by a process gas re-boiler and a dedicated steam boiler. The two-stage process, where the partly stripped rich solution is flashed into a second regenerator operating at 0.1 ksc (achieving stripping without additional heat input) is optimized for energy consumption.

Condensate Handling: Resource Recovery

The overheads from the two regenerators are sequentially cooled, first by a heat exchanger with demineralized (DM) water, and then by cooling water. The separated condensate is carefully collected in dedicated separators and subsequently pumped to the process condensate system for reuse as boiler feed water (BFW). A portion of this recovered condensate is strategically used as makeup water in the steam boiler and to maintain optimal water balance within the entire system.

CO2 Compression and Delivery

The CO2 produced within the regenerator at low pressure is compressed via a blower to achieve the pressure level of the regenerator operating under pressure. The combined CO2 stream, with an approximate purity of 58.5%, is then delivered to the urea plant, typically at a temperature of 40°C and a pressure of 0.6 ksc.

Process Condensate Stripper: Further Waste Stream Processing

To address potential environmental concerns, the system incorporates a process condensate stripper. The process condensate, generated from process gas cooling and the GV section, contains ammonia, methanol, and CO2. This stripper utilizes low-pressure steam to remove these volatile components. The stripped ammonia and methanol are recycled back into the ammonia production process, enhancing resource efficiency. The remaining condensate undergoes further treatment in a demineralization plant before being reused as boiler feed water. A series of solution storage and sump tanks, filters, and antifoam injection pumps are utilized to help maintain optimal solution conditions.