Solvent recovery systems

The Courtaulds semicommercial production system is iUustrated in Figure 8. Dissolving-grade woodpulp is mixed into a paste with NMMO and passes through a high temperature dissolving unit to yield a clear viscous solution. This is filtered and spun into dilute NMMO whereupon the ceUulose fibers precipitate. These are washed and dried, and finally baled as staple or tow products as required by the market. The spin bath and wash Uquors are passed to solvent recovery systems which concentrate the NMMO to the level required for reuse in dissolution. 

Gastak Solvent Recovery System, product Hterature, Kureha Chemical Industry Co., Ltd., New York, 1990. 

Put in the necessary hooding, ducting, and equipment for a solvent recovery system which will decrease the atmospheric pollution and also result in some economic solvent recovery,... 

In recent years, the use of solvent-borne adhesives has been seriously restricted. Solvents are, in general, volatile, flammable and toxic. Further, solvent may react with other airborne contaminants contributing to smog formation and workplace exposure. These arguments have limited the use of solvent-bome adhesives by different national and European regulations. Although solvent recovery systems and afterburners can be effectively attached to ventilation equipment, many factories are switching to the use of water-borne rubber adhesives, hot melts or 100% solids reactive systems, often at the expense of product performance or labour efficiency. 

Optimizing Solvent Recovery Systems in Potymer Processes... 

Figure 1. Simplified process flow diagram for the solvent recovery system.

An example of such a closed-loop system might include a closed solvent recovery system in which the dirty solvents are piped from the degreasing unit to a solvent still where the solvent is cleaned, and then piped back to the degreasing unit. 

Sodium hydrosulfite is produced through the Formate process where sodium formate solution, sodium hydroxide, and liquid sulfur dioxide reacted in the presence of a recycled stream of methanol solvent. Other products are sodium sulfite, sodium bicarbonate, and carbon monoxide. In the reactor, sodium hydrosulfite is precipitated to form a slurry of sodium hydrosulfite in the solution of methanol, methyl formate, and other coproducts. The mixture is sent to a pressurized filter system to recover sodium hydrosulfite crystals that are dried in a steam-heated rotary drier before being packaged. Heat supply in this process is highly monitored in order not to decompose sodium hydrosulfite to sulfite. Purging is periodically carried out on the recycle stream, particularly those involving methanol, to avoid excessive buildup of impurities. Also, vaporized methanol from the drying process and liquors from the filtration process are recycled to the solvent recovery system to improve the efficiency of the plant. 

It is important to identify the expensive steps, because it is here that research and development efforts should be concentrated. If the solvent recovery system is inexpensive, the prospective savings to be obtained by thoroughly studying it are small, and the cost of research may exceed any hoped-for saving. Conversely, should the reaction step be expensive, determining the kinetics of the reaction... 

ALMA [Alusuisse maleic anhydride] A process for making maleic anhydride by oxidizing -butane, using a fluid bed reactor and a special organic solvent recovery system. The catalyst contains vanadium and phosphoms on iron oxide. Developed jointly by Alusuisse Italia and ABB Lummus Crest. First licensed to Shin-Daikowa Petrochemical Company, Yokkaichi, Japan, in 1988. The world s largest plant plant was built for Lonza in Ravenna, Italy, in 1994. 

In-plant management practices may often control the volume and quality of the treatment system influent. Volume reduction can be attained by process wastewater segregation from noncontact water, by recycling or reuse of noncontact water, and by the modification of plant processes. Control of spills, leakage, washdown, and storm runoff can also reduce the treatment system load. Modifications may include the use of vacuum pumps instead of steam ejectors, recycling caustic soda solution rather than discharging it to the treatment system, and incorporation of a more efficient solvent recovery system. 

No drying on screens thus, screen cleaning is all but eliminated. Absence of solvents can eliminate the need for costly solvent recovery systems. 

Absence of solvents can eliminate the need for costly solvent recovery systems. 

The lack of satisfactory solvent recovery methods prior to 1930 prevented the use of selective solvents more suitable for lubricating oils. The major part of any solvent extraction plant is its complex solvent recovery system. Chemical engineering s contributions to distillation theory and process design resulted in the development of efficient solvent recovery techniques. In 1933, as illustrated by Figure 3, large commercial plants were... 

Figure 3 also illustrates the rapid growth of lubricating oil solvent extraction processes. From the point of view of popularity, furfural, phenol, and the Duosol processes are outstanding. Most of the recent developments have been improvements in the solvent recovery systems to minimize solvent consumption, to reduce costs, and in the treater sections, to increase raffinate yield. 

Furfural exhibits high selectivity at elevated temperatures (175° to 250° F.) this characteristic results in the benefits of reduced viscosity and high temperature gradient and permits operation on waxy stocks. At ambient temperatures, kerosenes and gas oils may be extracted. Water in furfural has a bad effect on its extraction efficiency therefore, solvent recovery systems must include dehydration facilities. From its chemical composition aldehyde furfural appears to be unstable. However, when handled in accordance with standard operating procedures, decomposition and polymerization are negligible. 

A flow diagram of an anhydrous phenol solvent extraction plant is shown in Figure 8. Raw distillate is passed through a tower in which it absorbs phenol from the recovery system vapor. The oil is then passed to the treating tower, generally a few sections above the bottom. Anhydrous phenol is introduced at the top of this tower. Phenolic water condensate from the solvent recovery system (about 9.5% phenol) is introduced at the bottom of the tower to effect reflux. A temperature gradient of 10° to 75° F. may be... 

There are several companies today which specialize in the manufacture of different distillation systems to recover solvents for further reuse within a pharmaceutical plant ]46, 47]. According to ProsGon , the major cost benefits that their customers realize when using their solvent recovery systems are reductions in solvent purchases, waste disposal costs, and transportation costs [46]. 

Also, successful implementation of a solvent recovery system will depend on the savings it will yield. Although solvent recovery systems can cut down on the purchasing of fresh solvents and waste disposal, they also require an input of energy to operate while producing wastes of their own. If a solvent system is... 

In order to test the laboratory data obtained, a small extractor system was used with those solvents having suitable properties, which were obtainable in sufficient quantities for testing, using natural waters or sodium chloride solutions. The extraction system consists of a 2-inch packed column approximately 4 feet high to which water and solvent were fed countercurrently. An analysis of the resulting extract feed and brine was made to determine the material balance for the system. The data obtained from this column using diisopropylamine as solvent are shown in Table I. The feed concentration was 2000 p.p.m. of sodium chloride. The product contained 490 p.p.m., of which part was the amine hydrochloride. In practice, this would be replaced in the solvent recovery system by an equivalent amount of sodium to give the total salt content indicated. Sufficient data have been obtained to indicate that the calculations... 

In the process, the vacuum residuum is brought to the desired extraction temperature and then sent to the extractor where solvent (straight run naphtha, coker naphtha) flows upward, extracting soluble material from the down-flowing feedstock. The solvent-deasphalted phase leaves the top of the extractor and flows to the solvent recovery system where the solvent is separated from the deasphalted oil and recycled to the extractor. 

The ROSE process is a solvent deasphalting process with minimum energy consumption using a super-critical solvent recovery system and the process is of value in obtaining oils for further processing. (Gearhart, 1980 Low et al., 1995, Hydrocarbon Processing, 1996 Northrup and Sloan, 1996). 

ROSE process a solvent deasphalting process (q.v.) that uses a super-critical solvent recovery system to obtain high-quality oils from heavy feedstocks (q.v.) for further processing. 

Solvent recovery systems would also necessitate the specification of condenser duties, distillation tower sizes, holding tanks, piping, and valves. It is important to note that the engineering design of an adsorption system should be based on pilot data for the particular system. Information can usually be obtained directly from the adsorbent manufacturer. The overall size of the unit is determined primarily by economic considerations, balancing the operating costs against the capital costs. 

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