Task Group EnergyThe study at ZhongTai was carried out jointly with the Xinjiang Academy of Environmental Protection Sciences (XJAEPS) as part of cleaner production audits that are mandated by the Xinjiang Department of Environmental Protection (XDEP). The energy and mass-flow of the ZhongTai plants were modeled using the software Umberto® 5.5. In this course the Chinese partners were trained in the method of a comprehensive energy and material-flow analysis and a Sino-German cooperation base for industrial efficiency was established in July 2011.
Together with partners from the XJAEPS and the Heidelberg-based Institute for Eco-Industrial Analyses (IUWA), IFEU scientists carried out a clean production evaluation for Zhongtai’s factory in Midong, the Huatai Industrial Park.
As a result, a total of 68 improvements were identified, most of which were implemented. For example, the manual collection of used mercury catalyst will be discontinued, acetylene losses were reduced and stricter temperature control was implemented. Carbide and fresh water consumption per unit of product decreased. These interventions reduced the need for cooling or steam in many specific locations and thus achieved considerable economic benefits of about 71 million RMB (8.6 million €) and resulted in CO2 emission reductions of 150,000 tonnes per year. Additional reductions will be achieved once acetylene loss reduction is further reduced.
It was demonstrated in the RECAST Urumqi project that a mass and energy-flow analysis of a complex industrial facility is a helpful tool to determine technological options to improve energy efficiency and environmental-performance of companies in China and that a great potential for improvement among large-scale PVC producers is given.
Modeling of the flow of acetylene gas at the Midong plant with Umberto® 5
For future plant expansions, two major PVC production technologies are currently under consideration: the petroleum derived, ethylene-based process ‘Petroleum-to-Ethylene (PtE)’ and the coal-based, carbide process using acetylene as input for VCM production. In addition, the third and, not yet, commercially-available PVC production process ‘Coal-to-Ethylene (CtE)’ is also a viable option. This process involves the gasification of coal for the production of ethylene and, like the PtE process, using it as an intermediate feedstock.
A great advantage of both the, CtE and PtE process, compared to the carbide process is the avoidance of mercury as a catalyst. This is of paramount importance as the rapid growth of the PVC industry in China may escalate mercury mining due to the fact that mercury-free catalysts are currently not readily-available for large-scale application.
The carbide process, which requires the use of a mercury catalyst, results in emissions of twelve tonnes of CO2-eq/tonne of PVC if produced in Xinjiang. This is a factor of 3.8 higher than for PVC from the PtE process.If CtE would be adopted, the CO2-eq emissions would be 20% lower than in the case of the carbide process but still quite substantial.
Our analysis suggests that if Xinjiang’s PVC industry switches from the carbide process to ‘CtE’ the CO2 (and mercury) reduction goals intended by China’s central government can be achieved. Furthermore, ZhongTai Chemical Company could remain independent from raw material imports.
In order to offer viable options to further reduce the energy-demand and greenhouse gas emissions from PVC production, one has to consider that the carbide process currently is the most profitable option. Strong economic incentives or regulatory decisions are needed to trigger investments into alternative production methods (PtE or CtE). A carbon tax and a regulatory requirement to phase out mercury catalysts would be suitable instruments.
PVC production alternatives
CO2 emissions for the three options for PVC production in China, Xinjiang and Europe
Download 2-page factsheet on the ZhonTai modelling
