English Seminar - Industrial Processes

Liquefaction of gases Formox process

Professor: Marcos Carnavale

Students: Rodolpho Guilherme Menezes Gama

Tais Xavier de Andrade

06/03/2011- Rio de Janeiro

Formox Process

• The Formox process produces formaldehyde. Formox is a worldwide registered trademark owned by Perstorp Specialty Chemicals AB, Sweden.

• Industrially, formaldehyde is produced by catalytic oxidation of methanol. The most commonly used catalysts are silver metal or a mixture of an iron oxide with molybdenum and/or vanadium. In the more commonly used Formox process using iron oxide and molybdenium and/or vanadium, methanol and oxygen react at 400°C to produce formaldehyde according to the chemical equation:

CH3OH + ½ O2 → H2CO + H2O.

Introduction

• The silver-based catalyst is usually operated at a higher temperature, about 650 °C. On it, two chemical reactions simultaneously produce formaldehyde: the one shown above, and the dehydrogenation reaction:

CH3OH → H2CO + H2

• Further oxidation of the formaldehyde product during its production usually gives formic acid that is found in formaldehyde solution, found in parts per million values.

Advantages of the Formox process

• - designed & supplied by someone with in-depth understanding of process, plants & catalysts

• - superior yield • - high formaldehyde concentration (above 55%) • - low MeOH content in the product • - high steam production • - high level of safety • - environmentally friendly • - simple, reliable operation • - low total operating costs • - quality equipment at a competitive price • - fast, on-time delivery • - strong technical support & service • - simple, reliable UFC adaptation

Process Steps

• Number of processes for preparing formaldehyde from methanol are known (see, for example, Ullmann's Encyclopaedia of Industrial Chemistry). The processes carried out industrially are predominantly the oxidation:

CH3 OH 1/2O2→CH.sub.2 O H2 O

over catalysts comprising iron oxide and molybdenum oxide at from 300° C. to 450° C. (Formox process) and the oxidative dehydrogenation (silver catalyst process) according to:

CH3 OH→CH2 O H2

H2 1/2O2→H.sub.2 O

• At from 600° C. to 720° C. In both processes, the formaldehyde is first obtained as an aqueous solution. Particularly when used for the preparation of formaldehyde polymers and oligomers, the formaldehyde obtained in this way has to be subjected to costly dewatering. A further disadvantage is the formation of corrosive formic acid, which has an adverse effect on the polymerization, as by-product.

• Various methods of carrying out this reaction have been proposed; thus, for example, DE-A-37 19 055 describes a process for preparing formaldehyde from methanol by dehydrogenation in the presence of a catalyst at elevated temperature. The reaction is carried out in the presence of a catalyst comprising at least one sodium compound at a temperature of from 300° C .to 800° C.

Liquefaction of gases

Introduction

• Liquefaction of gases is the process by which a gas is converted to a liquid. For example, oxygen normally occurs as a gas. However, by applying sufficient amounts of pressure and by reducing the temperature by a sufficient amount, oxygen can be converted to a liquid.

• Liquefaction is an important process commercially because substances in the liquid state take up much less room than they do in their gaseous state. As an example, oxygen is often used in space vehicles to burn the fuel on which they operate. If the oxygen had to be carried in its gaseous form, a space vehicle would have to be thousands of times larger than anything that could possibly fly. In its liquid state, however, the oxygen can easily fit into a space vehicle's structure.

• Liquefaction of a gas occurs when its molecules are pushed closer together. The molecules of any gas are relatively far apart from each other, while the molecules of a liquid are relatively close together. Gas molecules can be squeezed together by one of two methods: by increasing the pressure on the gas or by lowering the temperature of the gas.

• The liquefaction of gases is a complicated process that uses various compressions and expansions to achieve high pressures and very low temperatures; using for example turboexpanders.

• The liquefaction of air is used to obtain nitrogen, oxygen, and argon and other atmospheric noble gases by separating the air components by fractional distillation in an cryogenic air separation unit.

The history of the process

• Since the 1600s, chemists have known that temperature can determine whether a substance exists as a gas, liquid, or solid. Flemish chemist Jan van Helmont (1579-1644), who coined the term gas to describe carbon dioxide, used the term vapors to describe substances that became gaseous only when heated, such as water. During the late 1700s, scientists learned that when a gas is cooled, its volume is reduced by a predictable amount.

• Cooling slows down the motion of the gas molecules, so they take up less space. Similarly, pressurizing a gas, or forcibly squeezing its molecules closer together, reduces its volume. Eventually, through cooling and compression, the volume of a gas can be reduced by so much that its molecules collapse upon each other and come into contact, changing into a liquid. Compression and cooling soon became the twin tools of scientists attempting to liquefy gases.

• The first scientist to liquefy a substance that normally exists as a gas was Gaspard Monge (1746-1818), a French mathematician, who produced liquid sulfur dioxide in 1784. However, most gases were not liquefied until the mid-1800s, beginning in 1823 when English chemist Michael Faraday (1791-1867) liquefied chlorine. Faraday pressurized chlorine gas inside a curved glass tube that was submerged at one end in a beaker of crushed ice.

• Under pressure, the gas changed into liquid chlorine when cooled by the ice near the end of the tube. Faraday also liquefied carbon dioxide, hydrogen sulfide, and hydrogen bromid e in a similar manner. More than 20 years later, after pursuing other research, Faraday returned to gas liquefaction. By then, more effective cooling agents had been developed.

Critical temperature and pressure

• Two key properties of gases are important in developing methods for their liquefaction: critical temperature and critical pressure. The critical temperature of a gas is the temperature at or above which no amount of pressure, however great, will cause the gas to liquefy. The minimum pressure required to liquefy the gas at the critical temperature is called the critical pressure.

Methods of liquefaction

• In general, gases can be liquefied by one of three general methods:(1) by compressing the gas at temperatures less than its critical temperature; (2) by making the gas do some kind of work against an external force, causing the gas to lose energy and change to the liquid state; and (3) by using the Joule-Thomson effect.

(1)Compression

• In the first approach, the application of pressure alone is sufficient to cause a gas to change to a liquid. For example, ammonia has a critical temperature of 271°F (133°C). This temperature is well above room temperature. Thus, it is relatively simple to convert ammonia gas to the liquid state simply by applying sufficient pressure. At its critical temperature, that pressure is 112.5 atmospheres.

• A simple example of the second method for liquefying gases is the steam engine. A series of steps must take place before a steam engine can operate. First, water is boiled and steam is produced. That steam is then sent into a cylinder. Inside the cylinder, the steam pushes on a piston. The piston, in turn, drives some kind of machinery, such as a railroad train engine.

• As the steam pushes against the piston, it loses energy. Since the steam has less energy, its temperature drops. Eventually, the steam cools off enough for it to change back to water.

Making a gas work against an external force

• This example is not a perfect analogy for the liquefaction of gases. Steam is not really a gas but a vapor. A vapor is a substance that is normally a liquid at room temperature but that can be converted to a gas quite easily. The liquefaction of a true gas, therefore, requires two steps. First, the gas is cooled. Next, the cool gas is forced to do work against some external system. It might, for example, be driven through a small turbine. A turbine is a device consisting of blades attached to a central rod. As the cooled gas pushes against the turbine blades, it makes the rod rotate. At the same time, the gas loses energy, and its temperature drops even further. Eventually the gas loses enough energy for it to change to a liquid.

• This process is similar to the principle on which refrigeration systems work. The coolant in a refrigerator is first converted from a gas to a liquid by one of the methods described above. The liquid formed then absorbs heat from the refrigerator box. The heat raises the temperature of the liquid, eventually changing it back to a gas.

• There is an important difference between liquefaction and refrigeration, however. In the former process, the liquefied gas is constantly removed from the system for use in some other process. In the latter process, however, the liquefied gas is constantly recycled within the refrigeration system.

(3)Using the Joule-Thomson effect.

• Gases also can be made to liquefy by applying a principle discovered by English physicists James Prescott Joule (1818–1889) and William Thomson (later known as Lord Kelvin; 1824–1907) in 1852. The Joule-Thomson effect depends on the relationship of volume, pressure, and temperature in a gas. Change any one of these three variables, and at least one of the other two (or both) will also change. Joule and Thomson found, for example, that allowing a gas to expand very rapidly causes its temperature to drop dramatically. Reducing the pressure on a gas accomplishes the same effect.

• To cool a gas using the Joule-Thomson effect, the gas is first pumped into a container under high pressure. The container is fitted with a valve with a very small opening. When the valve is opened, the gas escapes from the container and expands quickly. At the same time, its temperature drops.

• In some cases, the cooling that occurs during this process may not be sufficient to cause liquefaction of the gas. However, the process can be repeated more than once. Each time, more energy is removed from the gas, its temperature falls further, and it eventually changes to a liquid.

Important liquefied gases

This list shows the most important liquefied gases.

• liquid nitrogen• liquid oxygen• liquid argon• Liquid hydrogen• liquid helium• LNG• Liquefied petroleum gas

Applications

• Chemical industry• Cryogenics• Cutting and welding• Environmental

protection• Food processing• Metrology &

measurement• Laboratory and

instrumentation• Gases for breathing• Gases for safety

and inerting

•Glass, ceramics, other minerals•Medical gases•Metallurgy•paintball•Rubber, plastics, paint•Semiconductor industry•Water treatment•Welding

Practical applications

• The most common practical applications of liquefied gases are the compact storage and transportation of combustible fuels used for heating, cooking, or powering motor vehicles. Two kinds of liquefied gases are widely used commercially for this reason: liquefied natural gas (LNG) and liquefied petroleum gas (LPG). LPG is a mixture of gases obtained from natural gas or petroleum that has been converted to the liquid state. The mixture is stored in strong containers that can withstand very high pressures.

• Liquefied natural gas (LNG) is similar to LPG, except that it has had almost everything except methane removed. LNG and LPG have many similar uses.

• In principle, all gases can be liquefied, so their compactness and ease of transportation make them popular for a number of other applications. For example, liquid oxygen and liquid hydrogen are used in rocket engines. Liquid oxygen and liquid acetylene can be used in welding operations. And a combination of liquid oxygen and liquid nitrogen can be used in Aqua-Lung™ devices (an underwater breathing apparatus).

• Liquefaction of gases also is important in the field of research known as cryogenics (the branch of physics that deals with the production and effects of extremely low temperatures). Liquid helium is widely used for the study of behavior of matter at temperatures close to absolute zero, 0 K (−459°F; −273°C).

Industry Chemicals: (industrial gases)Founded: 1907

Headquarters: Danbury, ConnecticutKey people: Steve Angel - Chairman,

President and CEORevenue: US$ 9 billion (2009)

Employees: 27,000 (2009)Web site: http://www.praxair.com

• Praxair, Inc. is the largest industrial gases company in North and South America and one of the largest worldwide. The company supplies atmospheric, process and specialty gases as well as high-performance coatings and related services to a wide diversity of customers around the world. Praxair has operations in over 30 countries and approximately 3,000 patents.

• Praxair serves a wide range of industries including: metals, health care, food & beverage, energy, aerospace, chemicals, electronics, manufacturing, and others.

• Praxair rooftop nitrogen storage tank at meat processing facility, Detroit, Michigan

• Praxair's primary products are:• Atmospheric gases—oxygen, nitrogen, argon

and rare gases (produced when air is purified, compressed, cooled, distilled and condensed).

• Process & specialty gases—carbon dioxide, helium, hydrogen, semiconductor process gases, and acetylene (produced as by-products of chemical production or recovered from natural gas).

• Applications technologies that help customers increase productivity and yield, reduce energy consumption and operating costs, and/or improve environmental performance.

• The company also designs, engineers and constructs cryogenic and non-cryogenic supply systems.