NEW MULTIFAB ENGINEERS PVT. LTD. MUSE CONSULTANTS PVT. LTD. 225, GALA COMPLEX, D. UPADHYAYA MARG, MULUND (W), MUMBAI - 400 080. INDIA. FAX: 91-22-25646325 TEL: 91-22-25613136 / 25611291 / 25650593 E - MAIL: sumarji@vsnl.com | dipaksheth@vsnl.com | shethdipak@hotmail.com Resi. Tel : 25694991 / 25681726 ( Mr. Dipak Sheth )

BACKGROUND : ZEOCAT has been promoted by chemical engineers and as the name suggests, the company primarily works on zeolites and catalysts.

ZEOLITES: Synthetic Zeolites or molecular sieves (including carbon molecular sieves) are very widely used for adsorption and catalytic processes. Molecular sieves are mainly used for drying, purification and separation of industrial gases and organic liquids. On many occasions, the expensive molecular sieves are discarded due to deficient process performance or heavy pressure drops. Pressure or vacuum swing adsorption (PSA or VSA) systems do not have any facility for thermal regeneration and therefore user industry has no option but to get rid of used molecular sieves and load a fresh charge. We have the facilities for regeneration and testing of such once-used molecular sieves. It is possible to obtain original performance by this economical route of regenerating used molecular sieves. In this regard, we also offer the following services.

(a) Study of design and operating data of existing adsorption system and recommendations for optimisation of performance.
(b) Retrofitting to improve capacity at economical costs.
(c) Testing of trial quantity of adsorbents and pilot scale dynamic testing.
(d) Study of feasibility of using a mixture of adsorbents to minimize the overall costs.
(e) Annual service contract for periodic monitoring of performance and suggesting remedial measures.

OTHER ADSORBENTS:
We are also in a position to regenerate other adsorbents such as activated aluminas and activated carbons.
Services outlined above can also be provided.

CATALYSTS :
In many catalytic applications, the catalyst is supplied by the manufacturer with the active metallic ingredient in an oxidized state. Such catalysts have to be reduced to obtain active metal in a nascent condition.
Facilities for such reductions, for certain applications are not generally available at user's plant since this work needs to be done only once in the lifetime of the catalyst. Moreover, considerable time and effort will be required for controlled and measured reduction at site and this can delay commissioning of the entire project. We presently offer catalyst regeneration services in certain applications wherever the reduced catalyst can be safely transported in some medium.

DECOKING:
Some catalysts and catalytic materials during usage get carbon laid down in the material body and this needs to be removed for regaining activity. We offer decoking services for such materials at our facilities.

Bergabau Forschung GmbH, Germany have developed a technology for separating nitrogen from atmospheric air at room temperature by application of pressure swing adsorption (PSA) over carbon molecular sieves (CMS). Standard plants in the wide range of nitrogen capacities (5 to 1000 Nm3/hr) and purities (97% to 99.5% N₂) are available.

Carbon molecular sieves (CMS) adsorbs moisture, carbon dioxide and oxygen faster than (and in preference to) nitrogen. Feed air at 5 to 6 Kg/cm²(g) pressure and ambient temperature contains saturated amount of water vapour (typically 1% by vol. at 6 kg/cm² g and 40^oC) and 300 to 400 p.p.m of carbon dioxide. Both water and CO2 are absorbed first at the inlet end of the adsorption column. A major part of the adsorbent bed is used for adsorption of oxygen so that unadsorbed nitrogen escapes from the top.

ADSORBENT - RELATED PROBLEMS:

Due to deficiencies in the design and/ or operation of free water removal equipment in feed air circuit additional free water sometimes enters the main adsorption columns. This and recurrent pressure shocks create two problems.

(a) Weakening of physical structure of CMS and consequent dusting and powdering.
(b) Extension of moisture removal zone and consequent reduction in the length of oxygen removal zone. Nitrogen purity of the product gas therefore, drops.
The effects of the above problems show up over a period of time. Sieves manufacturers usually recommend replacement of old sieves with fresh ones at substantial cost. However, it is possible to regenerate used CMS at Zeocat Products & Services at fraction of the fresh CMS cost.

BACKGROUND
Volatile organic compounds such as methylene chloride, benzene, toluene, THF, hexane, rubber solvent acetone, methanol etc. are emitted into the surrounding atmosphere in many industrial activities. The well known industries in this category are pharmaceuticals, inks, gaskets, magnetic tapes. printing shops etc. These emissions are usually removed by activated carbons in two (or more) column systems. Apart from removing the pollutants these systems enable recovery of these valuable compounds. This is achieved by passing steam through the exhausted bed and condensing the vapours coming out. Process liquid and water are separated by gravity separation (if immiscible) or distillation (if miscible). Some typical results of solvent recovery plants are given in Table -1.

When activated carbon bed is regenerated with live steam all the absorbed vapours are not desorbed from the carbon. This happens due to two reasons:

(a) For economical and consistent operations, it is desirable to operate at working loadings that are 30% to 60% of the break through loadings.

(b) Some organics with boiling points higher than the steam temperature will not come out of the bed. Thus base level adsorption loadings keep rising with use.

Hence, a time comes when the available loadings drop considerably and the usual practice is to load fresh carbon. It is now possible to get another lease of life from such used carbons by sending them to Zeocat products & Services for regeneration. Regenerated carbons have been reused with more than 90% capacity in comparison to fresh carbons.

BACKGROUND :
There are two types of plants for generation of oxygen gas with 90 to 94% (by vol.) purity at room temperature.

(1) PSA i.e. Pressure Swing Adsorption in Twin Column System:

Compressed air 4 to 6 kg/cm²(g) pressure and 30 to 400^o C temperature is passed through an adsorption column, which is filled with a special molecular sieve (type 5A or 13X). The other adsorption column is kept under regeneration by purging with product gas at nearly atmospheric pressure and ambient temperature. PSA systems are economical in the range of 5 to 100 Nm3/.hr of product gas capacity.

(2) VSA i.e. Vacuum Swing Adsorption in Three (or more) Column System:

Atmospheric air very low pressure (e.g.2000mm WC) and 10 to 40^oC temperature is passed through an adsorption column. The other adsorption columns are under different stages or regeneration i.e.evacuation, vacuum holding and repressurisation. Typical vacuum levels reached are 650 mm Hg (25.5" Hg). VSA systems are economical in the range of 100 to 3000 Nm³/hr of product.

In both the above systems, adsorption of various components from feed air takes place in the following sequence from bottom to top.

(a) Moisture : Feed air is usually saturated with moisture at the operating temperature and pressure. This moisture is almost completely removed at inlet end of the bed.
Some length of the bed (typical 40 to 60 cm) is therefore earmarked for this duty. In VSA systems, moisture load is expected to be much higher due to low pressure adsorption and therefore, a cheaper adsorbent like activated alumina is used for this purpose.
(b) Carbon dioxide: Feed air contain 300 to 400 ppm (by vol.) of CO2 and the same is almost completely removed by molecular sieves. A small section of the bed is utilized for his purpose.
(c ) Nitrogen: A major part of the absorbent bed (exceeding 75%) is used for adsorption of nitrogen so that unadsorbed oxygen (and argon) escape from the top.

ADSORBENT - RELATED PROBLEMS :
Due to deficiencies in design and / or operation of free water removal equipment in feed air circuit, additional water sometimes enters the adsorption system. This and pressure shocks create two problems.

(a) Weakening of physical structure of zeolite molecular sieves and consequent dusting and powdering.
(b) Extension of moisture removal zone and consequent reduction in the length of nitrogen removal zone. Oxygen purity of the product gas, therefore, drops.

The effects of the above two problems manifest over a period of time depending on the amount of extra water entering the adsorption system. It is now possible to get another lease
of life from such adsorbents.