Texaco gasification technology and process flow (sharing the information I collected earlier with everyone)

Thread Content

Texaco Inc. was founded in 1902 in Houston, Texas, United States. It was originally named Texas Company, and in 1959 its name was changed to Texaco. Texaco is one of the world’s renowned multinational oil companies, primarily engaged in the exploration, production, refining, transportation, and sales of oil and natural gas. The main subsidiaries of Texaco are as follows: TEXACO U.S.A. is responsible for exploration, production, refining, as well as the transportation and sales of oil and petroleum products in the United States. TEXACO.EUROPE is responsible for exploration, production, refining, and sales operations in Europe. TEXACO MIDDLE EAST FAR EAST is responsible for crude oil production and supply activities in Saudi Arabia, Indonesia, and other oil-producing countries in the region. Caltex Petroleum Corp. is responsible for oil refining and marketing operations in 55 locations across Asia, East Africa, and the Pacific region. It is a joint venture between Texaco and Chevron, with Texaco holding 50% of the shares in Caltex. TotalEnergies’ refining and marketing activities are spread across more than 60 countries, mainly in the region east of Suez. The main structure of the gasifier in the Texaco gasification technology is a single-nozzle bottom-fed coal water slurry type; most systems employ a water quenching process, although waste heat recovery processes are also used in IGCC power generation projects. The maximum capacity per furnace currently allows for a daily coal input of 2,000 tons. The operating pressures are mostly 4 MPa and 6.5 MPa; in a few projects, this pressure has reached 8.4 MPa as well. The first plant in China to adopt Texaco’s gasification technology was the Lunan Fertilizer Plant in Shandong, which began operations in 1993; to date, more than a dozen plants are using this technology. With 30 years of application experience, Texaco’s gasification technology has also been in use in China for over a decade; it is a relatively mature gasification technology. There are significant advantages in terms of technical proficiency and operational expertise, as well as in the localization of equipment and the production of supporting refractory materials. The main advantage of Texaco’s gasification technology lies in the water-coal slurry, which makes it easier to increase pressure. If the pressure in the gasification furnace of Nanhua reaches 8.4 MPa, it becomes possible to synthesize methanol directly without compression, thereby saving energy consumed for compression. The disadvantages of Texaco’s gasification technology are also related to coal water slurry; the presence of 40% water in coal water slurry reduces its calorific value. The requirements regarding coal quality have become stricter; coals with poor slurry-forming properties, high ash content, and high ash fusion points are less economical to use ； The gasification efficiency is relatively low, with a carbon conversion rate of about 95%. The specific oxygen consumption is the highest among various fluidized bed gasification processes, at around 400 standard cubic meters per thousand cubic meters (CO+H2) ； Heat-resistant furnace walls must be used; each batch of refractory bricks costs 500,000 dollars, while imported ones cost 1 million dollars, and their lifespan is less than 2 years. The nozzle, worth $150,000, only lasts about 2 months before it needs to be taken apart for repair. Texaco water gasification process flow 1. Slurry preparation system: The slurry preparation system is used for the production of water coal slurry. The raw coal is measured by a coal weighing feeder and then fed into the grinder; simultaneously, water, additives, limestone, and ammonia are added to the grinder, where it is ground into a coal-water slurry with an appropriate particle size distribution. The qualified coal-water slurry is pumped into the slurry tank using a low-pressure slurry pump. 2. In the syngas system, the water-coal slurry is pressurized by a high-pressure coal slurry pump and then mixed with high-pressure oxygen in a Texaco burner; this mixture is sprayed in a mist form into the combustion chamber of the gasifier, where complex gasification reactions take place. The resulting gas (known as syngas) and slag are cooled in the quenching chamber and downcomer of the gasifier. The cooled syngas enters the carbon scrubber through a nozzle washer, while the slag settles at the bottom of the quenching chamber to cool and solidify, after which it is removed periodically. In the carbon scrubbing tower, the syngas is further cooled and dedusted, and the water-gas ratio (i.e., the molar ratio of water vapor to dry gas) is controlled; thereafter, the syngas exits the carbon scrubbing tower and proceeds to subsequent processes. 3. Burner cooling system: The Texaco process burner is a key component of the gasification unit; it typically features a three-channel external mixing design. Within the burner, the coal slurry is thoroughly atomized by a high-speed stream of oxygen, which facilitates the gasification reaction. Since the Texaco burner is inserted into the combustion chamber of the vaporizer and exposed to high temperatures of around 1400°C, cooling jackets are installed on the outside of the burner to prevent it from being damaged. A water jacket is also provided at the burner head, and a separate system supplies cooling water to the burner; this system is equipped with complex safety interlocks. 4. The solid slag that falls to the bottom of the quenching chamber within the slag locking system is crushed by a slag crusher and then enters this system. The slag locking system is equipped with a complex automatic circulation control system for regularly collecting the slag. During slag discharge, the lock hopper is isolated from the gasifier; the cycle of the lock hopper consists of four stages: depressurization, cleaning, slag discharge, and pressurization. Each cycle lasts about 30 minutes, ensuring that slag is discharged regularly without interrupting the operation of the gasifier. The slag locking system mainly consists of a slag tank, slag locking valves, a slag discharge valve, as well as a flushing water tank. There are usually two slag locking valves and one slag discharge valve. When collecting slag, pressure needs to be applied to the slag tank; when the pressure in the tank approaches that of the gasification furnace, the slag locking valves are opened. After slag collection is complete, the slag locking valves are closed to relieve pressure in the tank. Once the pressure has returned to normal, the slag discharge valve is opened to discharge the slag. After slag discharge is finished and the tank has been flushed, the slag discharge valve is closed again, and pressure is applied to the tank, starting the cycle over. 5. Flash evaporation and water treatment system: The flash evaporation and water treatment system is primarily used for the recycling and treatment of water. The black water with a high solid content discharged from the gasifier and carbon scrubber tower is sent to the water treatment system for treatment before being reused. First, the black water is sent to a high-pressure, vacuum flash evaporation system for depressurized flash evaporation, in order to lower its temperature, release soluble gases, and concentrate it; the solid content in the black water after flash evaporation increases further. It is then sent to a sedimentation tank for clarification, and the clarified water is reused.