QandA with Nishat Mills Technical Director, Hafeez-ur-Rehman Siddique.
Nishat Mills Limited has commissioned Unitop Caustic recovery plant. Please tell what is your motivation to invest in another Caustic recovery plant
As you may already know Nishat Mills in Lahore, had already invested quite early in a CRP unit, which is still working at the mill, but we needed to extend the evaporation amount in weak-liquor, and therefore, we were looking into an additional unit. In this context, for the last three years we have been comparing various methods and technologies of the first class suppliers, among those Unitop was also one of the suppliers.
The decision to invest in Caustic Recovery plant was not made overnight. The need to caustic recovery plant is initiated in order to save cost and resources (caustic/water/acid). Nishat has seen a steady growth in the production of mercerized fabrics and therefore we have been looking into various systems and solutions, where we can make sustainable savings in energy (steam), raw material (caustic soda) and other inputs (water and space).
Thanks to the continuous visits and technical information provided by Mr. Mondry, Adviser for International Sales, Unitop together with their agency ATC, we had a chance to look into various options. The most relevant benefit in my opinion is the savings in the steam consumption as well as the quality of the hot condensate, which will be retuned as wash water for the mercerizing at around 70C.
Another interesting aspect as reported by Unitop is the fact that with the help of this caustic recovery plant and especially with steam recovery the difference in steam economy can lead to the savings of more than US $100,000 per year in operation.
Why did Nishat consider Unitop-Aquacare as their supplier, knowing that they are an Asian supplier, when there are many suppliers from Europe
Unitop Aquacare offers Caustic Recovery Plant technology, and depend- ing on the process conditions, they design proper circuitry to deal with corrosion conditions. In case of Nishat, Unitop has designed several tailor made systems to suit individual needs of Nishat and the local conditions like fuel prices, quality of water and even the space constraints.
Energy is not only costly but also limited in availability in Pakistan. Thus, we at Nishat are always taking the energy consumption into account which has lead us to the conclusion that the CRP of Unitop-Aquacare, is the most economical solution, if you calculate the ratio of investment and future utility costs.
Another important aspect is timely service and technical support by Unitop, as we understand that their service team comprises of more than 30 service personnel and the fact that Unitop has trained local engineers of their agency ATC gives us the confidence to invest in their technology.
Last but not the least, we value their vast experience in the field of CRP manufacturing in combination with their capability to even serve European and Japanese customers. I was told that Unitop is a ISO 9001:2008 and TUV Nord approved company.
Can you please elaborate on the general working principle of a CRP and some of the technical benefits gained from Unitop expertise
Caustic Recovery Plant is based on the principle of Multi Effect Evaporation. There are three Stages and Condensers. The vacuum is applied to condenser by water ring pump (vacuum Pump). The advantage of applying the vacuum can be explained from the fact that under the vacuum conditions the boiling point of the water reduces and it also facilates the flow of caustic lye from first stage to the last stage due to the pressure difference. Hence no intermediate transfer pump between the stages is required.
The weak lye generated from mercerizer is stored in the tank and then it is passed through Preheater 2 Preheater 1 through Feed Pump. After preheating the weak lye enters Heater 1 (in the Tube Side) and then steam is applied on the Shell Side, which will heat the weak lye. Subsequently, this Weak Lye then enters Flash Vessel 1, where some water present in the weak lye is converted into vapors.
These vapors are then fed to Heater 2 which acts as steam for this stage. It is important to note that since some water is removed in form of vapors, which allows concentration of the weak lye.
The above process gets repeated in Flash Vessel 2 and Flash vessel 3, and at the last stage i.e. in Flash Vessel 3 the desired concentration of the lye is achieved.
At the same time the vapors generated from Flash Vessel 3 are fed into the condensers on shell side. The cooling water is fed in the tube side of the condenser to condense this vapors and this way the water is heated and again fed back to process.
The Unitop technology offers two fold advantage: (i) Firstly, it ensures that the output from CRP plant gives Caustic at the desired concentration. (ii) Secondly, the hot condensate is used as wash water and returned to the mercerizer at around 75C whereas the cooling water is available as pure hot water which can be used in further wet finishing processes.
I also appreciate that Mr. Mondry although from sales, knows about the technology and the working principle of the CRP plant. I understand that each system is customized and the individual technologies are adapted to achieve savings in steam and caustic recovery, which are different for each manufacturer. Therefore, in order to suit the requirements of Nishat, Unitop has developed their CRP system to maximize the savings in steam, perfect lye purification as well as caustic recovery.
Unitop has over 38 years of experience and with installation of almost 300 CRP units: What is the most important aspect which was considered by Nishat
As I mentioned before, the Caustic Recovery Plant is based on the principle of Multi Effect Evaporation. Unitop offers customized and individual technologies to achieve this effect, which are often very different from each customer. One of the reason that Nishat has considered Unitop as the supplier of the CRP plant, can be attributed to lowest steam thus energy consumption.
In Pakistan energy savings is the most important parameter to determine the efficiency and profitability for a large textile processing mill such as Nishat. A very important indicator hereto is the ratio of how many litres of water can be evaporated with 1 Kg of steam: with Unitop it can be said that 1 Kg steam can evaporate more than 4 litres of water.
Another important aspect is the Lye Purification system: Can you highlight how this has been achieved in terms of Unitop technology
The Lye purification entails taking out the remains of the starch based size and to reduce color of the recovered caustic (product). This product is mixed with a small amount of peroxide, which is a strong oxidation agent, and due to the subsequent chemical reaction, the cellulose particle are transformed as oxi-cellulose.
The oxi-cellulose is floated as foam stage, which is taken off and the solid impurities, which could be not filtered, are deposited at the bottom of the LPS, which can be easily purged once necessary. I have been informed that Unitop is even working on a method which can remove the indigo dye out of the weak-lye, which would be again an innovation and additional advantage when it comes to the caustic recovery in a textile wet processing plant.
Last, but not the least, one has to mention that the hot condensate which will be available as wash water for mercerizer at 75 Centigrade is of exceptional quality. This not always the case if one talks about the caustic recovery installation. This is an environment friendly and sustainable technology which is one step towards zero discharge of waste water and effluents.
What are key improvements initiated by Unitop, when it comes to an automation at the CRP plant
Unitop`s CRP are equipped with the state of the art automation systems, such as Siemens touch screen control units. With the advanced automation Unitop can offer various tools to control the actual flows for product, feed, steam and condensate. In addition to above, an overall performance control of the plant at any time can be monitored and real time" data as well as archives are now possible with SCADA/DAS System.
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|Title Annotation:||recovery plant designed|
|Publication:||Pakistan Textile Journal|
|Date:||Aug 31, 2015|
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